1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2018 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2018 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2018 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument, if you want
878 to debug a running process:
881 @value{GDBP} @var{program} 1234
885 would attach @value{GDBN} to process @code{1234} (unless you also have a file
886 named @file{1234}; @value{GDBN} does check for a core file first).
888 Taking advantage of the second command-line argument requires a fairly
889 complete operating system; when you use @value{GDBN} as a remote
890 debugger attached to a bare board, there may not be any notion of
891 ``process'', and there is often no way to get a core dump. @value{GDBN}
892 will warn you if it is unable to attach or to read core dumps.
894 You can optionally have @code{@value{GDBP}} pass any arguments after the
895 executable file to the inferior using @code{--args}. This option stops
898 @value{GDBP} --args gcc -O2 -c foo.c
900 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
901 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
903 You can run @code{@value{GDBP}} without printing the front material, which describes
904 @value{GDBN}'s non-warranty, by specifying @code{--silent}
905 (or @code{-q}/@code{--quiet}):
908 @value{GDBP} --silent
912 You can further control how @value{GDBN} starts up by using command-line
913 options. @value{GDBN} itself can remind you of the options available.
923 to display all available options and briefly describe their use
924 (@samp{@value{GDBP} -h} is a shorter equivalent).
926 All options and command line arguments you give are processed
927 in sequential order. The order makes a difference when the
928 @samp{-x} option is used.
932 * File Options:: Choosing files
933 * Mode Options:: Choosing modes
934 * Startup:: What @value{GDBN} does during startup
938 @subsection Choosing Files
940 When @value{GDBN} starts, it reads any arguments other than options as
941 specifying an executable file and core file (or process ID). This is
942 the same as if the arguments were specified by the @samp{-se} and
943 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
944 first argument that does not have an associated option flag as
945 equivalent to the @samp{-se} option followed by that argument; and the
946 second argument that does not have an associated option flag, if any, as
947 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
948 If the second argument begins with a decimal digit, @value{GDBN} will
949 first attempt to attach to it as a process, and if that fails, attempt
950 to open it as a corefile. If you have a corefile whose name begins with
951 a digit, you can prevent @value{GDBN} from treating it as a pid by
952 prefixing it with @file{./}, e.g.@: @file{./12345}.
954 If @value{GDBN} has not been configured to included core file support,
955 such as for most embedded targets, then it will complain about a second
956 argument and ignore it.
958 Many options have both long and short forms; both are shown in the
959 following list. @value{GDBN} also recognizes the long forms if you truncate
960 them, so long as enough of the option is present to be unambiguous.
961 (If you prefer, you can flag option arguments with @samp{--} rather
962 than @samp{-}, though we illustrate the more usual convention.)
964 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
965 @c way, both those who look for -foo and --foo in the index, will find
969 @item -symbols @var{file}
971 @cindex @code{--symbols}
973 Read symbol table from file @var{file}.
975 @item -exec @var{file}
977 @cindex @code{--exec}
979 Use file @var{file} as the executable file to execute when appropriate,
980 and for examining pure data in conjunction with a core dump.
984 Read symbol table from file @var{file} and use it as the executable
987 @item -core @var{file}
989 @cindex @code{--core}
991 Use file @var{file} as a core dump to examine.
993 @item -pid @var{number}
994 @itemx -p @var{number}
997 Connect to process ID @var{number}, as with the @code{attach} command.
999 @item -command @var{file}
1000 @itemx -x @var{file}
1001 @cindex @code{--command}
1003 Execute commands from file @var{file}. The contents of this file is
1004 evaluated exactly as the @code{source} command would.
1005 @xref{Command Files,, Command files}.
1007 @item -eval-command @var{command}
1008 @itemx -ex @var{command}
1009 @cindex @code{--eval-command}
1011 Execute a single @value{GDBN} command.
1013 This option may be used multiple times to call multiple commands. It may
1014 also be interleaved with @samp{-command} as required.
1017 @value{GDBP} -ex 'target sim' -ex 'load' \
1018 -x setbreakpoints -ex 'run' a.out
1021 @item -init-command @var{file}
1022 @itemx -ix @var{file}
1023 @cindex @code{--init-command}
1025 Execute commands from file @var{file} before loading the inferior (but
1026 after loading gdbinit files).
1029 @item -init-eval-command @var{command}
1030 @itemx -iex @var{command}
1031 @cindex @code{--init-eval-command}
1033 Execute a single @value{GDBN} command before loading the inferior (but
1034 after loading gdbinit files).
1037 @item -directory @var{directory}
1038 @itemx -d @var{directory}
1039 @cindex @code{--directory}
1041 Add @var{directory} to the path to search for source and script files.
1045 @cindex @code{--readnow}
1047 Read each symbol file's entire symbol table immediately, rather than
1048 the default, which is to read it incrementally as it is needed.
1049 This makes startup slower, but makes future operations faster.
1052 @anchor{--readnever}
1053 @cindex @code{--readnever}, command-line option
1054 Do not read each symbol file's symbolic debug information. This makes
1055 startup faster but at the expense of not being able to perform
1056 symbolic debugging. DWARF unwind information is also not read,
1057 meaning backtraces may become incomplete or inaccurate. One use of
1058 this is when a user simply wants to do the following sequence: attach,
1059 dump core, detach. Loading the debugging information in this case is
1060 an unnecessary cause of delay.
1064 @subsection Choosing Modes
1066 You can run @value{GDBN} in various alternative modes---for example, in
1067 batch mode or quiet mode.
1075 Do not execute commands found in any initialization file.
1076 There are three init files, loaded in the following order:
1079 @item @file{system.gdbinit}
1080 This is the system-wide init file.
1081 Its location is specified with the @code{--with-system-gdbinit}
1082 configure option (@pxref{System-wide configuration}).
1083 It is loaded first when @value{GDBN} starts, before command line options
1084 have been processed.
1085 @item @file{~/.gdbinit}
1086 This is the init file in your home directory.
1087 It is loaded next, after @file{system.gdbinit}, and before
1088 command options have been processed.
1089 @item @file{./.gdbinit}
1090 This is the init file in the current directory.
1091 It is loaded last, after command line options other than @code{-x} and
1092 @code{-ex} have been processed. Command line options @code{-x} and
1093 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1096 For further documentation on startup processing, @xref{Startup}.
1097 For documentation on how to write command files,
1098 @xref{Command Files,,Command Files}.
1103 Do not execute commands found in @file{~/.gdbinit}, the init file
1104 in your home directory.
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1117 @cindex @code{--batch}
1118 Run in batch mode. Exit with status @code{0} after processing all the
1119 command files specified with @samp{-x} (and all commands from
1120 initialization files, if not inhibited with @samp{-n}). Exit with
1121 nonzero status if an error occurs in executing the @value{GDBN} commands
1122 in the command files. Batch mode also disables pagination, sets unlimited
1123 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1124 off} were in effect (@pxref{Messages/Warnings}).
1126 Batch mode may be useful for running @value{GDBN} as a filter, for
1127 example to download and run a program on another computer; in order to
1128 make this more useful, the message
1131 Program exited normally.
1135 (which is ordinarily issued whenever a program running under
1136 @value{GDBN} control terminates) is not issued when running in batch
1140 @cindex @code{--batch-silent}
1141 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1142 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1143 unaffected). This is much quieter than @samp{-silent} and would be useless
1144 for an interactive session.
1146 This is particularly useful when using targets that give @samp{Loading section}
1147 messages, for example.
1149 Note that targets that give their output via @value{GDBN}, as opposed to
1150 writing directly to @code{stdout}, will also be made silent.
1152 @item -return-child-result
1153 @cindex @code{--return-child-result}
1154 The return code from @value{GDBN} will be the return code from the child
1155 process (the process being debugged), with the following exceptions:
1159 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1160 internal error. In this case the exit code is the same as it would have been
1161 without @samp{-return-child-result}.
1163 The user quits with an explicit value. E.g., @samp{quit 1}.
1165 The child process never runs, or is not allowed to terminate, in which case
1166 the exit code will be -1.
1169 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1170 when @value{GDBN} is being used as a remote program loader or simulator
1175 @cindex @code{--nowindows}
1177 ``No windows''. If @value{GDBN} comes with a graphical user interface
1178 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1179 interface. If no GUI is available, this option has no effect.
1183 @cindex @code{--windows}
1185 If @value{GDBN} includes a GUI, then this option requires it to be
1188 @item -cd @var{directory}
1190 Run @value{GDBN} using @var{directory} as its working directory,
1191 instead of the current directory.
1193 @item -data-directory @var{directory}
1194 @itemx -D @var{directory}
1195 @cindex @code{--data-directory}
1197 Run @value{GDBN} using @var{directory} as its data directory.
1198 The data directory is where @value{GDBN} searches for its
1199 auxiliary files. @xref{Data Files}.
1203 @cindex @code{--fullname}
1205 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1206 subprocess. It tells @value{GDBN} to output the full file name and line
1207 number in a standard, recognizable fashion each time a stack frame is
1208 displayed (which includes each time your program stops). This
1209 recognizable format looks like two @samp{\032} characters, followed by
1210 the file name, line number and character position separated by colons,
1211 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1212 @samp{\032} characters as a signal to display the source code for the
1215 @item -annotate @var{level}
1216 @cindex @code{--annotate}
1217 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1218 effect is identical to using @samp{set annotate @var{level}}
1219 (@pxref{Annotations}). The annotation @var{level} controls how much
1220 information @value{GDBN} prints together with its prompt, values of
1221 expressions, source lines, and other types of output. Level 0 is the
1222 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1223 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1224 that control @value{GDBN}, and level 2 has been deprecated.
1226 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1230 @cindex @code{--args}
1231 Change interpretation of command line so that arguments following the
1232 executable file are passed as command line arguments to the inferior.
1233 This option stops option processing.
1235 @item -baud @var{bps}
1237 @cindex @code{--baud}
1239 Set the line speed (baud rate or bits per second) of any serial
1240 interface used by @value{GDBN} for remote debugging.
1242 @item -l @var{timeout}
1244 Set the timeout (in seconds) of any communication used by @value{GDBN}
1245 for remote debugging.
1247 @item -tty @var{device}
1248 @itemx -t @var{device}
1249 @cindex @code{--tty}
1251 Run using @var{device} for your program's standard input and output.
1252 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1254 @c resolve the situation of these eventually
1256 @cindex @code{--tui}
1257 Activate the @dfn{Text User Interface} when starting. The Text User
1258 Interface manages several text windows on the terminal, showing
1259 source, assembly, registers and @value{GDBN} command outputs
1260 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1261 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1262 Using @value{GDBN} under @sc{gnu} Emacs}).
1264 @item -interpreter @var{interp}
1265 @cindex @code{--interpreter}
1266 Use the interpreter @var{interp} for interface with the controlling
1267 program or device. This option is meant to be set by programs which
1268 communicate with @value{GDBN} using it as a back end.
1269 @xref{Interpreters, , Command Interpreters}.
1271 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1274 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1275 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1276 @sc{gdb/mi} interfaces are no longer supported.
1279 @cindex @code{--write}
1280 Open the executable and core files for both reading and writing. This
1281 is equivalent to the @samp{set write on} command inside @value{GDBN}
1285 @cindex @code{--statistics}
1286 This option causes @value{GDBN} to print statistics about time and
1287 memory usage after it completes each command and returns to the prompt.
1290 @cindex @code{--version}
1291 This option causes @value{GDBN} to print its version number and
1292 no-warranty blurb, and exit.
1294 @item -configuration
1295 @cindex @code{--configuration}
1296 This option causes @value{GDBN} to print details about its build-time
1297 configuration parameters, and then exit. These details can be
1298 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1303 @subsection What @value{GDBN} Does During Startup
1304 @cindex @value{GDBN} startup
1306 Here's the description of what @value{GDBN} does during session startup:
1310 Sets up the command interpreter as specified by the command line
1311 (@pxref{Mode Options, interpreter}).
1315 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1316 used when building @value{GDBN}; @pxref{System-wide configuration,
1317 ,System-wide configuration and settings}) and executes all the commands in
1320 @anchor{Home Directory Init File}
1322 Reads the init file (if any) in your home directory@footnote{On
1323 DOS/Windows systems, the home directory is the one pointed to by the
1324 @code{HOME} environment variable.} and executes all the commands in
1327 @anchor{Option -init-eval-command}
1329 Executes commands and command files specified by the @samp{-iex} and
1330 @samp{-ix} options in their specified order. Usually you should use the
1331 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1332 settings before @value{GDBN} init files get executed and before inferior
1336 Processes command line options and operands.
1338 @anchor{Init File in the Current Directory during Startup}
1340 Reads and executes the commands from init file (if any) in the current
1341 working directory as long as @samp{set auto-load local-gdbinit} is set to
1342 @samp{on} (@pxref{Init File in the Current Directory}).
1343 This is only done if the current directory is
1344 different from your home directory. Thus, you can have more than one
1345 init file, one generic in your home directory, and another, specific
1346 to the program you are debugging, in the directory where you invoke
1350 If the command line specified a program to debug, or a process to
1351 attach to, or a core file, @value{GDBN} loads any auto-loaded
1352 scripts provided for the program or for its loaded shared libraries.
1353 @xref{Auto-loading}.
1355 If you wish to disable the auto-loading during startup,
1356 you must do something like the following:
1359 $ gdb -iex "set auto-load python-scripts off" myprogram
1362 Option @samp{-ex} does not work because the auto-loading is then turned
1366 Executes commands and command files specified by the @samp{-ex} and
1367 @samp{-x} options in their specified order. @xref{Command Files}, for
1368 more details about @value{GDBN} command files.
1371 Reads the command history recorded in the @dfn{history file}.
1372 @xref{Command History}, for more details about the command history and the
1373 files where @value{GDBN} records it.
1376 Init files use the same syntax as @dfn{command files} (@pxref{Command
1377 Files}) and are processed by @value{GDBN} in the same way. The init
1378 file in your home directory can set options (such as @samp{set
1379 complaints}) that affect subsequent processing of command line options
1380 and operands. Init files are not executed if you use the @samp{-nx}
1381 option (@pxref{Mode Options, ,Choosing Modes}).
1383 To display the list of init files loaded by gdb at startup, you
1384 can use @kbd{gdb --help}.
1386 @cindex init file name
1387 @cindex @file{.gdbinit}
1388 @cindex @file{gdb.ini}
1389 The @value{GDBN} init files are normally called @file{.gdbinit}.
1390 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1391 the limitations of file names imposed by DOS filesystems. The Windows
1392 port of @value{GDBN} uses the standard name, but if it finds a
1393 @file{gdb.ini} file in your home directory, it warns you about that
1394 and suggests to rename the file to the standard name.
1398 @section Quitting @value{GDBN}
1399 @cindex exiting @value{GDBN}
1400 @cindex leaving @value{GDBN}
1403 @kindex quit @r{[}@var{expression}@r{]}
1404 @kindex q @r{(@code{quit})}
1405 @item quit @r{[}@var{expression}@r{]}
1407 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1408 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1409 do not supply @var{expression}, @value{GDBN} will terminate normally;
1410 otherwise it will terminate using the result of @var{expression} as the
1415 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1416 terminates the action of any @value{GDBN} command that is in progress and
1417 returns to @value{GDBN} command level. It is safe to type the interrupt
1418 character at any time because @value{GDBN} does not allow it to take effect
1419 until a time when it is safe.
1421 If you have been using @value{GDBN} to control an attached process or
1422 device, you can release it with the @code{detach} command
1423 (@pxref{Attach, ,Debugging an Already-running Process}).
1425 @node Shell Commands
1426 @section Shell Commands
1428 If you need to execute occasional shell commands during your
1429 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1430 just use the @code{shell} command.
1435 @cindex shell escape
1436 @item shell @var{command-string}
1437 @itemx !@var{command-string}
1438 Invoke a standard shell to execute @var{command-string}.
1439 Note that no space is needed between @code{!} and @var{command-string}.
1440 If it exists, the environment variable @code{SHELL} determines which
1441 shell to run. Otherwise @value{GDBN} uses the default shell
1442 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1445 The utility @code{make} is often needed in development environments.
1446 You do not have to use the @code{shell} command for this purpose in
1451 @cindex calling make
1452 @item make @var{make-args}
1453 Execute the @code{make} program with the specified
1454 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1457 @node Logging Output
1458 @section Logging Output
1459 @cindex logging @value{GDBN} output
1460 @cindex save @value{GDBN} output to a file
1462 You may want to save the output of @value{GDBN} commands to a file.
1463 There are several commands to control @value{GDBN}'s logging.
1467 @item set logging on
1469 @item set logging off
1471 @cindex logging file name
1472 @item set logging file @var{file}
1473 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1474 @item set logging overwrite [on|off]
1475 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1476 you want @code{set logging on} to overwrite the logfile instead.
1477 @item set logging redirect [on|off]
1478 By default, @value{GDBN} output will go to both the terminal and the logfile.
1479 Set @code{redirect} if you want output to go only to the log file.
1480 @kindex show logging
1482 Show the current values of the logging settings.
1486 @chapter @value{GDBN} Commands
1488 You can abbreviate a @value{GDBN} command to the first few letters of the command
1489 name, if that abbreviation is unambiguous; and you can repeat certain
1490 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1491 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1492 show you the alternatives available, if there is more than one possibility).
1495 * Command Syntax:: How to give commands to @value{GDBN}
1496 * Completion:: Command completion
1497 * Help:: How to ask @value{GDBN} for help
1500 @node Command Syntax
1501 @section Command Syntax
1503 A @value{GDBN} command is a single line of input. There is no limit on
1504 how long it can be. It starts with a command name, which is followed by
1505 arguments whose meaning depends on the command name. For example, the
1506 command @code{step} accepts an argument which is the number of times to
1507 step, as in @samp{step 5}. You can also use the @code{step} command
1508 with no arguments. Some commands do not allow any arguments.
1510 @cindex abbreviation
1511 @value{GDBN} command names may always be truncated if that abbreviation is
1512 unambiguous. Other possible command abbreviations are listed in the
1513 documentation for individual commands. In some cases, even ambiguous
1514 abbreviations are allowed; for example, @code{s} is specially defined as
1515 equivalent to @code{step} even though there are other commands whose
1516 names start with @code{s}. You can test abbreviations by using them as
1517 arguments to the @code{help} command.
1519 @cindex repeating commands
1520 @kindex RET @r{(repeat last command)}
1521 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1522 repeat the previous command. Certain commands (for example, @code{run})
1523 will not repeat this way; these are commands whose unintentional
1524 repetition might cause trouble and which you are unlikely to want to
1525 repeat. User-defined commands can disable this feature; see
1526 @ref{Define, dont-repeat}.
1528 The @code{list} and @code{x} commands, when you repeat them with
1529 @key{RET}, construct new arguments rather than repeating
1530 exactly as typed. This permits easy scanning of source or memory.
1532 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1533 output, in a way similar to the common utility @code{more}
1534 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1535 @key{RET} too many in this situation, @value{GDBN} disables command
1536 repetition after any command that generates this sort of display.
1538 @kindex # @r{(a comment)}
1540 Any text from a @kbd{#} to the end of the line is a comment; it does
1541 nothing. This is useful mainly in command files (@pxref{Command
1542 Files,,Command Files}).
1544 @cindex repeating command sequences
1545 @kindex Ctrl-o @r{(operate-and-get-next)}
1546 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1547 commands. This command accepts the current line, like @key{RET}, and
1548 then fetches the next line relative to the current line from the history
1552 @section Command Completion
1555 @cindex word completion
1556 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1557 only one possibility; it can also show you what the valid possibilities
1558 are for the next word in a command, at any time. This works for @value{GDBN}
1559 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1561 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1562 of a word. If there is only one possibility, @value{GDBN} fills in the
1563 word, and waits for you to finish the command (or press @key{RET} to
1564 enter it). For example, if you type
1566 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1567 @c complete accuracy in these examples; space introduced for clarity.
1568 @c If texinfo enhancements make it unnecessary, it would be nice to
1569 @c replace " @key" by "@key" in the following...
1571 (@value{GDBP}) info bre @key{TAB}
1575 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1576 the only @code{info} subcommand beginning with @samp{bre}:
1579 (@value{GDBP}) info breakpoints
1583 You can either press @key{RET} at this point, to run the @code{info
1584 breakpoints} command, or backspace and enter something else, if
1585 @samp{breakpoints} does not look like the command you expected. (If you
1586 were sure you wanted @code{info breakpoints} in the first place, you
1587 might as well just type @key{RET} immediately after @samp{info bre},
1588 to exploit command abbreviations rather than command completion).
1590 If there is more than one possibility for the next word when you press
1591 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1592 characters and try again, or just press @key{TAB} a second time;
1593 @value{GDBN} displays all the possible completions for that word. For
1594 example, you might want to set a breakpoint on a subroutine whose name
1595 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1596 just sounds the bell. Typing @key{TAB} again displays all the
1597 function names in your program that begin with those characters, for
1601 (@value{GDBP}) b make_ @key{TAB}
1602 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1603 make_a_section_from_file make_environ
1604 make_abs_section make_function_type
1605 make_blockvector make_pointer_type
1606 make_cleanup make_reference_type
1607 make_command make_symbol_completion_list
1608 (@value{GDBP}) b make_
1612 After displaying the available possibilities, @value{GDBN} copies your
1613 partial input (@samp{b make_} in the example) so you can finish the
1616 If you just want to see the list of alternatives in the first place, you
1617 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1618 means @kbd{@key{META} ?}. You can type this either by holding down a
1619 key designated as the @key{META} shift on your keyboard (if there is
1620 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1622 If the number of possible completions is large, @value{GDBN} will
1623 print as much of the list as it has collected, as well as a message
1624 indicating that the list may be truncated.
1627 (@value{GDBP}) b m@key{TAB}@key{TAB}
1629 <... the rest of the possible completions ...>
1630 *** List may be truncated, max-completions reached. ***
1635 This behavior can be controlled with the following commands:
1638 @kindex set max-completions
1639 @item set max-completions @var{limit}
1640 @itemx set max-completions unlimited
1641 Set the maximum number of completion candidates. @value{GDBN} will
1642 stop looking for more completions once it collects this many candidates.
1643 This is useful when completing on things like function names as collecting
1644 all the possible candidates can be time consuming.
1645 The default value is 200. A value of zero disables tab-completion.
1646 Note that setting either no limit or a very large limit can make
1648 @kindex show max-completions
1649 @item show max-completions
1650 Show the maximum number of candidates that @value{GDBN} will collect and show
1654 @cindex quotes in commands
1655 @cindex completion of quoted strings
1656 Sometimes the string you need, while logically a ``word'', may contain
1657 parentheses or other characters that @value{GDBN} normally excludes from
1658 its notion of a word. To permit word completion to work in this
1659 situation, you may enclose words in @code{'} (single quote marks) in
1660 @value{GDBN} commands.
1662 A likely situation where you might need this is in typing an
1663 expression that involves a C@t{++} symbol name with template
1664 parameters. This is because when completing expressions, GDB treats
1665 the @samp{<} character as word delimiter, assuming that it's the
1666 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1669 For example, when you want to call a C@t{++} template function
1670 interactively using the @code{print} or @code{call} commands, you may
1671 need to distinguish whether you mean the version of @code{name} that
1672 was specialized for @code{int}, @code{name<int>()}, or the version
1673 that was specialized for @code{float}, @code{name<float>()}. To use
1674 the word-completion facilities in this situation, type a single quote
1675 @code{'} at the beginning of the function name. This alerts
1676 @value{GDBN} that it may need to consider more information than usual
1677 when you press @key{TAB} or @kbd{M-?} to request word completion:
1680 (@value{GDBP}) p 'func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) p 'func<
1685 When setting breakpoints however (@pxref{Specify Location}), you don't
1686 usually need to type a quote before the function name, because
1687 @value{GDBN} understands that you want to set a breakpoint on a
1691 (@value{GDBP}) b func< @kbd{M-?}
1692 func<int>() func<float>()
1693 (@value{GDBP}) b func<
1696 This is true even in the case of typing the name of C@t{++} overloaded
1697 functions (multiple definitions of the same function, distinguished by
1698 argument type). For example, when you want to set a breakpoint you
1699 don't need to distinguish whether you mean the version of @code{name}
1700 that takes an @code{int} parameter, @code{name(int)}, or the version
1701 that takes a @code{float} parameter, @code{name(float)}.
1704 (@value{GDBP}) b bubble( @kbd{M-?}
1705 bubble(int) bubble(double)
1706 (@value{GDBP}) b bubble(dou @kbd{M-?}
1710 See @ref{quoting names} for a description of other scenarios that
1713 For more information about overloaded functions, see @ref{C Plus Plus
1714 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1715 overload-resolution off} to disable overload resolution;
1716 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1718 @cindex completion of structure field names
1719 @cindex structure field name completion
1720 @cindex completion of union field names
1721 @cindex union field name completion
1722 When completing in an expression which looks up a field in a
1723 structure, @value{GDBN} also tries@footnote{The completer can be
1724 confused by certain kinds of invalid expressions. Also, it only
1725 examines the static type of the expression, not the dynamic type.} to
1726 limit completions to the field names available in the type of the
1730 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1731 magic to_fputs to_rewind
1732 to_data to_isatty to_write
1733 to_delete to_put to_write_async_safe
1738 This is because the @code{gdb_stdout} is a variable of the type
1739 @code{struct ui_file} that is defined in @value{GDBN} sources as
1746 ui_file_flush_ftype *to_flush;
1747 ui_file_write_ftype *to_write;
1748 ui_file_write_async_safe_ftype *to_write_async_safe;
1749 ui_file_fputs_ftype *to_fputs;
1750 ui_file_read_ftype *to_read;
1751 ui_file_delete_ftype *to_delete;
1752 ui_file_isatty_ftype *to_isatty;
1753 ui_file_rewind_ftype *to_rewind;
1754 ui_file_put_ftype *to_put;
1761 @section Getting Help
1762 @cindex online documentation
1765 You can always ask @value{GDBN} itself for information on its commands,
1766 using the command @code{help}.
1769 @kindex h @r{(@code{help})}
1772 You can use @code{help} (abbreviated @code{h}) with no arguments to
1773 display a short list of named classes of commands:
1777 List of classes of commands:
1779 aliases -- Aliases of other commands
1780 breakpoints -- Making program stop at certain points
1781 data -- Examining data
1782 files -- Specifying and examining files
1783 internals -- Maintenance commands
1784 obscure -- Obscure features
1785 running -- Running the program
1786 stack -- Examining the stack
1787 status -- Status inquiries
1788 support -- Support facilities
1789 tracepoints -- Tracing of program execution without
1790 stopping the program
1791 user-defined -- User-defined commands
1793 Type "help" followed by a class name for a list of
1794 commands in that class.
1795 Type "help" followed by command name for full
1797 Command name abbreviations are allowed if unambiguous.
1800 @c the above line break eliminates huge line overfull...
1802 @item help @var{class}
1803 Using one of the general help classes as an argument, you can get a
1804 list of the individual commands in that class. For example, here is the
1805 help display for the class @code{status}:
1808 (@value{GDBP}) help status
1813 @c Line break in "show" line falsifies real output, but needed
1814 @c to fit in smallbook page size.
1815 info -- Generic command for showing things
1816 about the program being debugged
1817 show -- Generic command for showing things
1820 Type "help" followed by command name for full
1822 Command name abbreviations are allowed if unambiguous.
1826 @item help @var{command}
1827 With a command name as @code{help} argument, @value{GDBN} displays a
1828 short paragraph on how to use that command.
1831 @item apropos @var{args}
1832 The @code{apropos} command searches through all of the @value{GDBN}
1833 commands, and their documentation, for the regular expression specified in
1834 @var{args}. It prints out all matches found. For example:
1845 alias -- Define a new command that is an alias of an existing command
1846 aliases -- Aliases of other commands
1847 d -- Delete some breakpoints or auto-display expressions
1848 del -- Delete some breakpoints or auto-display expressions
1849 delete -- Delete some breakpoints or auto-display expressions
1854 @item complete @var{args}
1855 The @code{complete @var{args}} command lists all the possible completions
1856 for the beginning of a command. Use @var{args} to specify the beginning of the
1857 command you want completed. For example:
1863 @noindent results in:
1874 @noindent This is intended for use by @sc{gnu} Emacs.
1877 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1878 and @code{show} to inquire about the state of your program, or the state
1879 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1880 manual introduces each of them in the appropriate context. The listings
1881 under @code{info} and under @code{show} in the Command, Variable, and
1882 Function Index point to all the sub-commands. @xref{Command and Variable
1888 @kindex i @r{(@code{info})}
1890 This command (abbreviated @code{i}) is for describing the state of your
1891 program. For example, you can show the arguments passed to a function
1892 with @code{info args}, list the registers currently in use with @code{info
1893 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1894 You can get a complete list of the @code{info} sub-commands with
1895 @w{@code{help info}}.
1899 You can assign the result of an expression to an environment variable with
1900 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1901 @code{set prompt $}.
1905 In contrast to @code{info}, @code{show} is for describing the state of
1906 @value{GDBN} itself.
1907 You can change most of the things you can @code{show}, by using the
1908 related command @code{set}; for example, you can control what number
1909 system is used for displays with @code{set radix}, or simply inquire
1910 which is currently in use with @code{show radix}.
1913 To display all the settable parameters and their current
1914 values, you can use @code{show} with no arguments; you may also use
1915 @code{info set}. Both commands produce the same display.
1916 @c FIXME: "info set" violates the rule that "info" is for state of
1917 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1918 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1922 Here are several miscellaneous @code{show} subcommands, all of which are
1923 exceptional in lacking corresponding @code{set} commands:
1926 @kindex show version
1927 @cindex @value{GDBN} version number
1929 Show what version of @value{GDBN} is running. You should include this
1930 information in @value{GDBN} bug-reports. If multiple versions of
1931 @value{GDBN} are in use at your site, you may need to determine which
1932 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1933 commands are introduced, and old ones may wither away. Also, many
1934 system vendors ship variant versions of @value{GDBN}, and there are
1935 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1936 The version number is the same as the one announced when you start
1939 @kindex show copying
1940 @kindex info copying
1941 @cindex display @value{GDBN} copyright
1944 Display information about permission for copying @value{GDBN}.
1946 @kindex show warranty
1947 @kindex info warranty
1949 @itemx info warranty
1950 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1951 if your version of @value{GDBN} comes with one.
1953 @kindex show configuration
1954 @item show configuration
1955 Display detailed information about the way @value{GDBN} was configured
1956 when it was built. This displays the optional arguments passed to the
1957 @file{configure} script and also configuration parameters detected
1958 automatically by @command{configure}. When reporting a @value{GDBN}
1959 bug (@pxref{GDB Bugs}), it is important to include this information in
1965 @chapter Running Programs Under @value{GDBN}
1967 When you run a program under @value{GDBN}, you must first generate
1968 debugging information when you compile it.
1970 You may start @value{GDBN} with its arguments, if any, in an environment
1971 of your choice. If you are doing native debugging, you may redirect
1972 your program's input and output, debug an already running process, or
1973 kill a child process.
1976 * Compilation:: Compiling for debugging
1977 * Starting:: Starting your program
1978 * Arguments:: Your program's arguments
1979 * Environment:: Your program's environment
1981 * Working Directory:: Your program's working directory
1982 * Input/Output:: Your program's input and output
1983 * Attach:: Debugging an already-running process
1984 * Kill Process:: Killing the child process
1986 * Inferiors and Programs:: Debugging multiple inferiors and programs
1987 * Threads:: Debugging programs with multiple threads
1988 * Forks:: Debugging forks
1989 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1993 @section Compiling for Debugging
1995 In order to debug a program effectively, you need to generate
1996 debugging information when you compile it. This debugging information
1997 is stored in the object file; it describes the data type of each
1998 variable or function and the correspondence between source line numbers
1999 and addresses in the executable code.
2001 To request debugging information, specify the @samp{-g} option when you run
2004 Programs that are to be shipped to your customers are compiled with
2005 optimizations, using the @samp{-O} compiler option. However, some
2006 compilers are unable to handle the @samp{-g} and @samp{-O} options
2007 together. Using those compilers, you cannot generate optimized
2008 executables containing debugging information.
2010 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2011 without @samp{-O}, making it possible to debug optimized code. We
2012 recommend that you @emph{always} use @samp{-g} whenever you compile a
2013 program. You may think your program is correct, but there is no sense
2014 in pushing your luck. For more information, see @ref{Optimized Code}.
2016 Older versions of the @sc{gnu} C compiler permitted a variant option
2017 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2018 format; if your @sc{gnu} C compiler has this option, do not use it.
2020 @value{GDBN} knows about preprocessor macros and can show you their
2021 expansion (@pxref{Macros}). Most compilers do not include information
2022 about preprocessor macros in the debugging information if you specify
2023 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2024 the @sc{gnu} C compiler, provides macro information if you are using
2025 the DWARF debugging format, and specify the option @option{-g3}.
2027 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2028 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2029 information on @value{NGCC} options affecting debug information.
2031 You will have the best debugging experience if you use the latest
2032 version of the DWARF debugging format that your compiler supports.
2033 DWARF is currently the most expressive and best supported debugging
2034 format in @value{GDBN}.
2038 @section Starting your Program
2044 @kindex r @r{(@code{run})}
2047 Use the @code{run} command to start your program under @value{GDBN}.
2048 You must first specify the program name with an argument to
2049 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2050 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2051 command (@pxref{Files, ,Commands to Specify Files}).
2055 If you are running your program in an execution environment that
2056 supports processes, @code{run} creates an inferior process and makes
2057 that process run your program. In some environments without processes,
2058 @code{run} jumps to the start of your program. Other targets,
2059 like @samp{remote}, are always running. If you get an error
2060 message like this one:
2063 The "remote" target does not support "run".
2064 Try "help target" or "continue".
2068 then use @code{continue} to run your program. You may need @code{load}
2069 first (@pxref{load}).
2071 The execution of a program is affected by certain information it
2072 receives from its superior. @value{GDBN} provides ways to specify this
2073 information, which you must do @emph{before} starting your program. (You
2074 can change it after starting your program, but such changes only affect
2075 your program the next time you start it.) This information may be
2076 divided into four categories:
2079 @item The @emph{arguments.}
2080 Specify the arguments to give your program as the arguments of the
2081 @code{run} command. If a shell is available on your target, the shell
2082 is used to pass the arguments, so that you may use normal conventions
2083 (such as wildcard expansion or variable substitution) in describing
2085 In Unix systems, you can control which shell is used with the
2086 @code{SHELL} environment variable. If you do not define @code{SHELL},
2087 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2088 use of any shell with the @code{set startup-with-shell} command (see
2091 @item The @emph{environment.}
2092 Your program normally inherits its environment from @value{GDBN}, but you can
2093 use the @value{GDBN} commands @code{set environment} and @code{unset
2094 environment} to change parts of the environment that affect
2095 your program. @xref{Environment, ,Your Program's Environment}.
2097 @item The @emph{working directory.}
2098 You can set your program's working directory with the command
2099 @kbd{set cwd}. If you do not set any working directory with this
2100 command, your program will inherit @value{GDBN}'s working directory if
2101 native debugging, or the remote server's working directory if remote
2102 debugging. @xref{Working Directory, ,Your Program's Working
2105 @item The @emph{standard input and output.}
2106 Your program normally uses the same device for standard input and
2107 standard output as @value{GDBN} is using. You can redirect input and output
2108 in the @code{run} command line, or you can use the @code{tty} command to
2109 set a different device for your program.
2110 @xref{Input/Output, ,Your Program's Input and Output}.
2113 @emph{Warning:} While input and output redirection work, you cannot use
2114 pipes to pass the output of the program you are debugging to another
2115 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2119 When you issue the @code{run} command, your program begins to execute
2120 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2121 of how to arrange for your program to stop. Once your program has
2122 stopped, you may call functions in your program, using the @code{print}
2123 or @code{call} commands. @xref{Data, ,Examining Data}.
2125 If the modification time of your symbol file has changed since the last
2126 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2127 table, and reads it again. When it does this, @value{GDBN} tries to retain
2128 your current breakpoints.
2133 @cindex run to main procedure
2134 The name of the main procedure can vary from language to language.
2135 With C or C@t{++}, the main procedure name is always @code{main}, but
2136 other languages such as Ada do not require a specific name for their
2137 main procedure. The debugger provides a convenient way to start the
2138 execution of the program and to stop at the beginning of the main
2139 procedure, depending on the language used.
2141 The @samp{start} command does the equivalent of setting a temporary
2142 breakpoint at the beginning of the main procedure and then invoking
2143 the @samp{run} command.
2145 @cindex elaboration phase
2146 Some programs contain an @dfn{elaboration} phase where some startup code is
2147 executed before the main procedure is called. This depends on the
2148 languages used to write your program. In C@t{++}, for instance,
2149 constructors for static and global objects are executed before
2150 @code{main} is called. It is therefore possible that the debugger stops
2151 before reaching the main procedure. However, the temporary breakpoint
2152 will remain to halt execution.
2154 Specify the arguments to give to your program as arguments to the
2155 @samp{start} command. These arguments will be given verbatim to the
2156 underlying @samp{run} command. Note that the same arguments will be
2157 reused if no argument is provided during subsequent calls to
2158 @samp{start} or @samp{run}.
2160 It is sometimes necessary to debug the program during elaboration. In
2161 these cases, using the @code{start} command would stop the execution
2162 of your program too late, as the program would have already completed
2163 the elaboration phase. Under these circumstances, either insert
2164 breakpoints in your elaboration code before running your program or
2165 use the @code{starti} command.
2169 @cindex run to first instruction
2170 The @samp{starti} command does the equivalent of setting a temporary
2171 breakpoint at the first instruction of a program's execution and then
2172 invoking the @samp{run} command. For programs containing an
2173 elaboration phase, the @code{starti} command will stop execution at
2174 the start of the elaboration phase.
2176 @anchor{set exec-wrapper}
2177 @kindex set exec-wrapper
2178 @item set exec-wrapper @var{wrapper}
2179 @itemx show exec-wrapper
2180 @itemx unset exec-wrapper
2181 When @samp{exec-wrapper} is set, the specified wrapper is used to
2182 launch programs for debugging. @value{GDBN} starts your program
2183 with a shell command of the form @kbd{exec @var{wrapper}
2184 @var{program}}. Quoting is added to @var{program} and its
2185 arguments, but not to @var{wrapper}, so you should add quotes if
2186 appropriate for your shell. The wrapper runs until it executes
2187 your program, and then @value{GDBN} takes control.
2189 You can use any program that eventually calls @code{execve} with
2190 its arguments as a wrapper. Several standard Unix utilities do
2191 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2192 with @code{exec "$@@"} will also work.
2194 For example, you can use @code{env} to pass an environment variable to
2195 the debugged program, without setting the variable in your shell's
2199 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2203 This command is available when debugging locally on most targets, excluding
2204 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2206 @kindex set startup-with-shell
2207 @anchor{set startup-with-shell}
2208 @item set startup-with-shell
2209 @itemx set startup-with-shell on
2210 @itemx set startup-with-shell off
2211 @itemx show startup-with-shell
2212 On Unix systems, by default, if a shell is available on your target,
2213 @value{GDBN}) uses it to start your program. Arguments of the
2214 @code{run} command are passed to the shell, which does variable
2215 substitution, expands wildcard characters and performs redirection of
2216 I/O. In some circumstances, it may be useful to disable such use of a
2217 shell, for example, when debugging the shell itself or diagnosing
2218 startup failures such as:
2222 Starting program: ./a.out
2223 During startup program terminated with signal SIGSEGV, Segmentation fault.
2227 which indicates the shell or the wrapper specified with
2228 @samp{exec-wrapper} crashed, not your program. Most often, this is
2229 caused by something odd in your shell's non-interactive mode
2230 initialization file---such as @file{.cshrc} for C-shell,
2231 $@file{.zshenv} for the Z shell, or the file specified in the
2232 @samp{BASH_ENV} environment variable for BASH.
2234 @anchor{set auto-connect-native-target}
2235 @kindex set auto-connect-native-target
2236 @item set auto-connect-native-target
2237 @itemx set auto-connect-native-target on
2238 @itemx set auto-connect-native-target off
2239 @itemx show auto-connect-native-target
2241 By default, if not connected to any target yet (e.g., with
2242 @code{target remote}), the @code{run} command starts your program as a
2243 native process under @value{GDBN}, on your local machine. If you're
2244 sure you don't want to debug programs on your local machine, you can
2245 tell @value{GDBN} to not connect to the native target automatically
2246 with the @code{set auto-connect-native-target off} command.
2248 If @code{on}, which is the default, and if @value{GDBN} is not
2249 connected to a target already, the @code{run} command automaticaly
2250 connects to the native target, if one is available.
2252 If @code{off}, and if @value{GDBN} is not connected to a target
2253 already, the @code{run} command fails with an error:
2257 Don't know how to run. Try "help target".
2260 If @value{GDBN} is already connected to a target, @value{GDBN} always
2261 uses it with the @code{run} command.
2263 In any case, you can explicitly connect to the native target with the
2264 @code{target native} command. For example,
2267 (@value{GDBP}) set auto-connect-native-target off
2269 Don't know how to run. Try "help target".
2270 (@value{GDBP}) target native
2272 Starting program: ./a.out
2273 [Inferior 1 (process 10421) exited normally]
2276 In case you connected explicitly to the @code{native} target,
2277 @value{GDBN} remains connected even if all inferiors exit, ready for
2278 the next @code{run} command. Use the @code{disconnect} command to
2281 Examples of other commands that likewise respect the
2282 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2283 proc}, @code{info os}.
2285 @kindex set disable-randomization
2286 @item set disable-randomization
2287 @itemx set disable-randomization on
2288 This option (enabled by default in @value{GDBN}) will turn off the native
2289 randomization of the virtual address space of the started program. This option
2290 is useful for multiple debugging sessions to make the execution better
2291 reproducible and memory addresses reusable across debugging sessions.
2293 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2294 On @sc{gnu}/Linux you can get the same behavior using
2297 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2300 @item set disable-randomization off
2301 Leave the behavior of the started executable unchanged. Some bugs rear their
2302 ugly heads only when the program is loaded at certain addresses. If your bug
2303 disappears when you run the program under @value{GDBN}, that might be because
2304 @value{GDBN} by default disables the address randomization on platforms, such
2305 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2306 disable-randomization off} to try to reproduce such elusive bugs.
2308 On targets where it is available, virtual address space randomization
2309 protects the programs against certain kinds of security attacks. In these
2310 cases the attacker needs to know the exact location of a concrete executable
2311 code. Randomizing its location makes it impossible to inject jumps misusing
2312 a code at its expected addresses.
2314 Prelinking shared libraries provides a startup performance advantage but it
2315 makes addresses in these libraries predictable for privileged processes by
2316 having just unprivileged access at the target system. Reading the shared
2317 library binary gives enough information for assembling the malicious code
2318 misusing it. Still even a prelinked shared library can get loaded at a new
2319 random address just requiring the regular relocation process during the
2320 startup. Shared libraries not already prelinked are always loaded at
2321 a randomly chosen address.
2323 Position independent executables (PIE) contain position independent code
2324 similar to the shared libraries and therefore such executables get loaded at
2325 a randomly chosen address upon startup. PIE executables always load even
2326 already prelinked shared libraries at a random address. You can build such
2327 executable using @command{gcc -fPIE -pie}.
2329 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2330 (as long as the randomization is enabled).
2332 @item show disable-randomization
2333 Show the current setting of the explicit disable of the native randomization of
2334 the virtual address space of the started program.
2339 @section Your Program's Arguments
2341 @cindex arguments (to your program)
2342 The arguments to your program can be specified by the arguments of the
2344 They are passed to a shell, which expands wildcard characters and
2345 performs redirection of I/O, and thence to your program. Your
2346 @code{SHELL} environment variable (if it exists) specifies what shell
2347 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2348 the default shell (@file{/bin/sh} on Unix).
2350 On non-Unix systems, the program is usually invoked directly by
2351 @value{GDBN}, which emulates I/O redirection via the appropriate system
2352 calls, and the wildcard characters are expanded by the startup code of
2353 the program, not by the shell.
2355 @code{run} with no arguments uses the same arguments used by the previous
2356 @code{run}, or those set by the @code{set args} command.
2361 Specify the arguments to be used the next time your program is run. If
2362 @code{set args} has no arguments, @code{run} executes your program
2363 with no arguments. Once you have run your program with arguments,
2364 using @code{set args} before the next @code{run} is the only way to run
2365 it again without arguments.
2369 Show the arguments to give your program when it is started.
2373 @section Your Program's Environment
2375 @cindex environment (of your program)
2376 The @dfn{environment} consists of a set of environment variables and
2377 their values. Environment variables conventionally record such things as
2378 your user name, your home directory, your terminal type, and your search
2379 path for programs to run. Usually you set up environment variables with
2380 the shell and they are inherited by all the other programs you run. When
2381 debugging, it can be useful to try running your program with a modified
2382 environment without having to start @value{GDBN} over again.
2386 @item path @var{directory}
2387 Add @var{directory} to the front of the @code{PATH} environment variable
2388 (the search path for executables) that will be passed to your program.
2389 The value of @code{PATH} used by @value{GDBN} does not change.
2390 You may specify several directory names, separated by whitespace or by a
2391 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2392 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2393 is moved to the front, so it is searched sooner.
2395 You can use the string @samp{$cwd} to refer to whatever is the current
2396 working directory at the time @value{GDBN} searches the path. If you
2397 use @samp{.} instead, it refers to the directory where you executed the
2398 @code{path} command. @value{GDBN} replaces @samp{.} in the
2399 @var{directory} argument (with the current path) before adding
2400 @var{directory} to the search path.
2401 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2402 @c document that, since repeating it would be a no-op.
2406 Display the list of search paths for executables (the @code{PATH}
2407 environment variable).
2409 @kindex show environment
2410 @item show environment @r{[}@var{varname}@r{]}
2411 Print the value of environment variable @var{varname} to be given to
2412 your program when it starts. If you do not supply @var{varname},
2413 print the names and values of all environment variables to be given to
2414 your program. You can abbreviate @code{environment} as @code{env}.
2416 @kindex set environment
2417 @anchor{set environment}
2418 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2419 Set environment variable @var{varname} to @var{value}. The value
2420 changes for your program (and the shell @value{GDBN} uses to launch
2421 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2422 values of environment variables are just strings, and any
2423 interpretation is supplied by your program itself. The @var{value}
2424 parameter is optional; if it is eliminated, the variable is set to a
2426 @c "any string" here does not include leading, trailing
2427 @c blanks. Gnu asks: does anyone care?
2429 For example, this command:
2436 tells the debugged program, when subsequently run, that its user is named
2437 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2438 are not actually required.)
2440 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2441 which also inherits the environment set with @code{set environment}.
2442 If necessary, you can avoid that by using the @samp{env} program as a
2443 wrapper instead of using @code{set environment}. @xref{set
2444 exec-wrapper}, for an example doing just that.
2446 Environment variables that are set by the user are also transmitted to
2447 @command{gdbserver} to be used when starting the remote inferior.
2448 @pxref{QEnvironmentHexEncoded}.
2450 @kindex unset environment
2451 @anchor{unset environment}
2452 @item unset environment @var{varname}
2453 Remove variable @var{varname} from the environment to be passed to your
2454 program. This is different from @samp{set env @var{varname} =};
2455 @code{unset environment} removes the variable from the environment,
2456 rather than assigning it an empty value.
2458 Environment variables that are unset by the user are also unset on
2459 @command{gdbserver} when starting the remote inferior.
2460 @pxref{QEnvironmentUnset}.
2463 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2464 the shell indicated by your @code{SHELL} environment variable if it
2465 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2466 names a shell that runs an initialization file when started
2467 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2468 for the Z shell, or the file specified in the @samp{BASH_ENV}
2469 environment variable for BASH---any variables you set in that file
2470 affect your program. You may wish to move setting of environment
2471 variables to files that are only run when you sign on, such as
2472 @file{.login} or @file{.profile}.
2474 @node Working Directory
2475 @section Your Program's Working Directory
2477 @cindex working directory (of your program)
2478 Each time you start your program with @code{run}, the inferior will be
2479 initialized with the current working directory specified by the
2480 @kbd{set cwd} command. If no directory has been specified by this
2481 command, then the inferior will inherit @value{GDBN}'s current working
2482 directory as its working directory if native debugging, or it will
2483 inherit the remote server's current working directory if remote
2488 @cindex change inferior's working directory
2489 @anchor{set cwd command}
2490 @item set cwd @r{[}@var{directory}@r{]}
2491 Set the inferior's working directory to @var{directory}, which will be
2492 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2493 argument has been specified, the command clears the setting and resets
2494 it to an empty state. This setting has no effect on @value{GDBN}'s
2495 working directory, and it only takes effect the next time you start
2496 the inferior. The @file{~} in @var{directory} is a short for the
2497 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2498 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2499 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2502 You can also change @value{GDBN}'s current working directory by using
2503 the @code{cd} command.
2507 @cindex show inferior's working directory
2509 Show the inferior's working directory. If no directory has been
2510 specified by @kbd{set cwd}, then the default inferior's working
2511 directory is the same as @value{GDBN}'s working directory.
2514 @cindex change @value{GDBN}'s working directory
2516 @item cd @r{[}@var{directory}@r{]}
2517 Set the @value{GDBN} working directory to @var{directory}. If not
2518 given, @var{directory} uses @file{'~'}.
2520 The @value{GDBN} working directory serves as a default for the
2521 commands that specify files for @value{GDBN} to operate on.
2522 @xref{Files, ,Commands to Specify Files}.
2523 @xref{set cwd command}.
2527 Print the @value{GDBN} working directory.
2530 It is generally impossible to find the current working directory of
2531 the process being debugged (since a program can change its directory
2532 during its run). If you work on a system where @value{GDBN} supports
2533 the @code{info proc} command (@pxref{Process Information}), you can
2534 use the @code{info proc} command to find out the
2535 current working directory of the debuggee.
2538 @section Your Program's Input and Output
2543 By default, the program you run under @value{GDBN} does input and output to
2544 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2545 to its own terminal modes to interact with you, but it records the terminal
2546 modes your program was using and switches back to them when you continue
2547 running your program.
2550 @kindex info terminal
2552 Displays information recorded by @value{GDBN} about the terminal modes your
2556 You can redirect your program's input and/or output using shell
2557 redirection with the @code{run} command. For example,
2564 starts your program, diverting its output to the file @file{outfile}.
2567 @cindex controlling terminal
2568 Another way to specify where your program should do input and output is
2569 with the @code{tty} command. This command accepts a file name as
2570 argument, and causes this file to be the default for future @code{run}
2571 commands. It also resets the controlling terminal for the child
2572 process, for future @code{run} commands. For example,
2579 directs that processes started with subsequent @code{run} commands
2580 default to do input and output on the terminal @file{/dev/ttyb} and have
2581 that as their controlling terminal.
2583 An explicit redirection in @code{run} overrides the @code{tty} command's
2584 effect on the input/output device, but not its effect on the controlling
2587 When you use the @code{tty} command or redirect input in the @code{run}
2588 command, only the input @emph{for your program} is affected. The input
2589 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2590 for @code{set inferior-tty}.
2592 @cindex inferior tty
2593 @cindex set inferior controlling terminal
2594 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2595 display the name of the terminal that will be used for future runs of your
2599 @item set inferior-tty [ @var{tty} ]
2600 @kindex set inferior-tty
2601 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2602 restores the default behavior, which is to use the same terminal as
2605 @item show inferior-tty
2606 @kindex show inferior-tty
2607 Show the current tty for the program being debugged.
2611 @section Debugging an Already-running Process
2616 @item attach @var{process-id}
2617 This command attaches to a running process---one that was started
2618 outside @value{GDBN}. (@code{info files} shows your active
2619 targets.) The command takes as argument a process ID. The usual way to
2620 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2621 or with the @samp{jobs -l} shell command.
2623 @code{attach} does not repeat if you press @key{RET} a second time after
2624 executing the command.
2627 To use @code{attach}, your program must be running in an environment
2628 which supports processes; for example, @code{attach} does not work for
2629 programs on bare-board targets that lack an operating system. You must
2630 also have permission to send the process a signal.
2632 When you use @code{attach}, the debugger finds the program running in
2633 the process first by looking in the current working directory, then (if
2634 the program is not found) by using the source file search path
2635 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2636 the @code{file} command to load the program. @xref{Files, ,Commands to
2639 The first thing @value{GDBN} does after arranging to debug the specified
2640 process is to stop it. You can examine and modify an attached process
2641 with all the @value{GDBN} commands that are ordinarily available when
2642 you start processes with @code{run}. You can insert breakpoints; you
2643 can step and continue; you can modify storage. If you would rather the
2644 process continue running, you may use the @code{continue} command after
2645 attaching @value{GDBN} to the process.
2650 When you have finished debugging the attached process, you can use the
2651 @code{detach} command to release it from @value{GDBN} control. Detaching
2652 the process continues its execution. After the @code{detach} command,
2653 that process and @value{GDBN} become completely independent once more, and you
2654 are ready to @code{attach} another process or start one with @code{run}.
2655 @code{detach} does not repeat if you press @key{RET} again after
2656 executing the command.
2659 If you exit @value{GDBN} while you have an attached process, you detach
2660 that process. If you use the @code{run} command, you kill that process.
2661 By default, @value{GDBN} asks for confirmation if you try to do either of these
2662 things; you can control whether or not you need to confirm by using the
2663 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2667 @section Killing the Child Process
2672 Kill the child process in which your program is running under @value{GDBN}.
2675 This command is useful if you wish to debug a core dump instead of a
2676 running process. @value{GDBN} ignores any core dump file while your program
2679 On some operating systems, a program cannot be executed outside @value{GDBN}
2680 while you have breakpoints set on it inside @value{GDBN}. You can use the
2681 @code{kill} command in this situation to permit running your program
2682 outside the debugger.
2684 The @code{kill} command is also useful if you wish to recompile and
2685 relink your program, since on many systems it is impossible to modify an
2686 executable file while it is running in a process. In this case, when you
2687 next type @code{run}, @value{GDBN} notices that the file has changed, and
2688 reads the symbol table again (while trying to preserve your current
2689 breakpoint settings).
2691 @node Inferiors and Programs
2692 @section Debugging Multiple Inferiors and Programs
2694 @value{GDBN} lets you run and debug multiple programs in a single
2695 session. In addition, @value{GDBN} on some systems may let you run
2696 several programs simultaneously (otherwise you have to exit from one
2697 before starting another). In the most general case, you can have
2698 multiple threads of execution in each of multiple processes, launched
2699 from multiple executables.
2702 @value{GDBN} represents the state of each program execution with an
2703 object called an @dfn{inferior}. An inferior typically corresponds to
2704 a process, but is more general and applies also to targets that do not
2705 have processes. Inferiors may be created before a process runs, and
2706 may be retained after a process exits. Inferiors have unique
2707 identifiers that are different from process ids. Usually each
2708 inferior will also have its own distinct address space, although some
2709 embedded targets may have several inferiors running in different parts
2710 of a single address space. Each inferior may in turn have multiple
2711 threads running in it.
2713 To find out what inferiors exist at any moment, use @w{@code{info
2717 @kindex info inferiors [ @var{id}@dots{} ]
2718 @item info inferiors
2719 Print a list of all inferiors currently being managed by @value{GDBN}.
2720 By default all inferiors are printed, but the argument @var{id}@dots{}
2721 -- a space separated list of inferior numbers -- can be used to limit
2722 the display to just the requested inferiors.
2724 @value{GDBN} displays for each inferior (in this order):
2728 the inferior number assigned by @value{GDBN}
2731 the target system's inferior identifier
2734 the name of the executable the inferior is running.
2739 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2740 indicates the current inferior.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info inferiors
2748 Num Description Executable
2749 2 process 2307 hello
2750 * 1 process 3401 goodbye
2753 To switch focus between inferiors, use the @code{inferior} command:
2756 @kindex inferior @var{infno}
2757 @item inferior @var{infno}
2758 Make inferior number @var{infno} the current inferior. The argument
2759 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2760 in the first field of the @samp{info inferiors} display.
2763 @vindex $_inferior@r{, convenience variable}
2764 The debugger convenience variable @samp{$_inferior} contains the
2765 number of the current inferior. You may find this useful in writing
2766 breakpoint conditional expressions, command scripts, and so forth.
2767 @xref{Convenience Vars,, Convenience Variables}, for general
2768 information on convenience variables.
2770 You can get multiple executables into a debugging session via the
2771 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2772 systems @value{GDBN} can add inferiors to the debug session
2773 automatically by following calls to @code{fork} and @code{exec}. To
2774 remove inferiors from the debugging session use the
2775 @w{@code{remove-inferiors}} command.
2778 @kindex add-inferior
2779 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2780 Adds @var{n} inferiors to be run using @var{executable} as the
2781 executable; @var{n} defaults to 1. If no executable is specified,
2782 the inferiors begins empty, with no program. You can still assign or
2783 change the program assigned to the inferior at any time by using the
2784 @code{file} command with the executable name as its argument.
2786 @kindex clone-inferior
2787 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2788 Adds @var{n} inferiors ready to execute the same program as inferior
2789 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2790 number of the current inferior. This is a convenient command when you
2791 want to run another instance of the inferior you are debugging.
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2796 * 1 process 29964 helloworld
2797 (@value{GDBP}) clone-inferior
2800 (@value{GDBP}) info inferiors
2801 Num Description Executable
2803 * 1 process 29964 helloworld
2806 You can now simply switch focus to inferior 2 and run it.
2808 @kindex remove-inferiors
2809 @item remove-inferiors @var{infno}@dots{}
2810 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2811 possible to remove an inferior that is running with this command. For
2812 those, use the @code{kill} or @code{detach} command first.
2816 To quit debugging one of the running inferiors that is not the current
2817 inferior, you can either detach from it by using the @w{@code{detach
2818 inferior}} command (allowing it to run independently), or kill it
2819 using the @w{@code{kill inferiors}} command:
2822 @kindex detach inferiors @var{infno}@dots{}
2823 @item detach inferior @var{infno}@dots{}
2824 Detach from the inferior or inferiors identified by @value{GDBN}
2825 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2826 still stays on the list of inferiors shown by @code{info inferiors},
2827 but its Description will show @samp{<null>}.
2829 @kindex kill inferiors @var{infno}@dots{}
2830 @item kill inferiors @var{infno}@dots{}
2831 Kill the inferior or inferiors identified by @value{GDBN} inferior
2832 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2833 stays on the list of inferiors shown by @code{info inferiors}, but its
2834 Description will show @samp{<null>}.
2837 After the successful completion of a command such as @code{detach},
2838 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2839 a normal process exit, the inferior is still valid and listed with
2840 @code{info inferiors}, ready to be restarted.
2843 To be notified when inferiors are started or exit under @value{GDBN}'s
2844 control use @w{@code{set print inferior-events}}:
2847 @kindex set print inferior-events
2848 @cindex print messages on inferior start and exit
2849 @item set print inferior-events
2850 @itemx set print inferior-events on
2851 @itemx set print inferior-events off
2852 The @code{set print inferior-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new
2854 inferiors have started or that inferiors have exited or have been
2855 detached. By default, these messages will not be printed.
2857 @kindex show print inferior-events
2858 @item show print inferior-events
2859 Show whether messages will be printed when @value{GDBN} detects that
2860 inferiors have started, exited or have been detached.
2863 Many commands will work the same with multiple programs as with a
2864 single program: e.g., @code{print myglobal} will simply display the
2865 value of @code{myglobal} in the current inferior.
2868 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2869 get more info about the relationship of inferiors, programs, address
2870 spaces in a debug session. You can do that with the @w{@code{maint
2871 info program-spaces}} command.
2874 @kindex maint info program-spaces
2875 @item maint info program-spaces
2876 Print a list of all program spaces currently being managed by
2879 @value{GDBN} displays for each program space (in this order):
2883 the program space number assigned by @value{GDBN}
2886 the name of the executable loaded into the program space, with e.g.,
2887 the @code{file} command.
2892 An asterisk @samp{*} preceding the @value{GDBN} program space number
2893 indicates the current program space.
2895 In addition, below each program space line, @value{GDBN} prints extra
2896 information that isn't suitable to display in tabular form. For
2897 example, the list of inferiors bound to the program space.
2900 (@value{GDBP}) maint info program-spaces
2904 Bound inferiors: ID 1 (process 21561)
2907 Here we can see that no inferior is running the program @code{hello},
2908 while @code{process 21561} is running the program @code{goodbye}. On
2909 some targets, it is possible that multiple inferiors are bound to the
2910 same program space. The most common example is that of debugging both
2911 the parent and child processes of a @code{vfork} call. For example,
2914 (@value{GDBP}) maint info program-spaces
2917 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2920 Here, both inferior 2 and inferior 1 are running in the same program
2921 space as a result of inferior 1 having executed a @code{vfork} call.
2925 @section Debugging Programs with Multiple Threads
2927 @cindex threads of execution
2928 @cindex multiple threads
2929 @cindex switching threads
2930 In some operating systems, such as GNU/Linux and Solaris, a single program
2931 may have more than one @dfn{thread} of execution. The precise semantics
2932 of threads differ from one operating system to another, but in general
2933 the threads of a single program are akin to multiple processes---except
2934 that they share one address space (that is, they can all examine and
2935 modify the same variables). On the other hand, each thread has its own
2936 registers and execution stack, and perhaps private memory.
2938 @value{GDBN} provides these facilities for debugging multi-thread
2942 @item automatic notification of new threads
2943 @item @samp{thread @var{thread-id}}, a command to switch among threads
2944 @item @samp{info threads}, a command to inquire about existing threads
2945 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2946 a command to apply a command to a list of threads
2947 @item thread-specific breakpoints
2948 @item @samp{set print thread-events}, which controls printing of
2949 messages on thread start and exit.
2950 @item @samp{set libthread-db-search-path @var{path}}, which lets
2951 the user specify which @code{libthread_db} to use if the default choice
2952 isn't compatible with the program.
2955 @cindex focus of debugging
2956 @cindex current thread
2957 The @value{GDBN} thread debugging facility allows you to observe all
2958 threads while your program runs---but whenever @value{GDBN} takes
2959 control, one thread in particular is always the focus of debugging.
2960 This thread is called the @dfn{current thread}. Debugging commands show
2961 program information from the perspective of the current thread.
2963 @cindex @code{New} @var{systag} message
2964 @cindex thread identifier (system)
2965 @c FIXME-implementors!! It would be more helpful if the [New...] message
2966 @c included GDB's numeric thread handle, so you could just go to that
2967 @c thread without first checking `info threads'.
2968 Whenever @value{GDBN} detects a new thread in your program, it displays
2969 the target system's identification for the thread with a message in the
2970 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2971 whose form varies depending on the particular system. For example, on
2972 @sc{gnu}/Linux, you might see
2975 [New Thread 0x41e02940 (LWP 25582)]
2979 when @value{GDBN} notices a new thread. In contrast, on other systems,
2980 the @var{systag} is simply something like @samp{process 368}, with no
2983 @c FIXME!! (1) Does the [New...] message appear even for the very first
2984 @c thread of a program, or does it only appear for the
2985 @c second---i.e.@: when it becomes obvious we have a multithread
2987 @c (2) *Is* there necessarily a first thread always? Or do some
2988 @c multithread systems permit starting a program with multiple
2989 @c threads ab initio?
2991 @anchor{thread numbers}
2992 @cindex thread number, per inferior
2993 @cindex thread identifier (GDB)
2994 For debugging purposes, @value{GDBN} associates its own thread number
2995 ---always a single integer---with each thread of an inferior. This
2996 number is unique between all threads of an inferior, but not unique
2997 between threads of different inferiors.
2999 @cindex qualified thread ID
3000 You can refer to a given thread in an inferior using the qualified
3001 @var{inferior-num}.@var{thread-num} syntax, also known as
3002 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3003 number and @var{thread-num} being the thread number of the given
3004 inferior. For example, thread @code{2.3} refers to thread number 3 of
3005 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3006 then @value{GDBN} infers you're referring to a thread of the current
3009 Until you create a second inferior, @value{GDBN} does not show the
3010 @var{inferior-num} part of thread IDs, even though you can always use
3011 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3012 of inferior 1, the initial inferior.
3014 @anchor{thread ID lists}
3015 @cindex thread ID lists
3016 Some commands accept a space-separated @dfn{thread ID list} as
3017 argument. A list element can be:
3021 A thread ID as shown in the first field of the @samp{info threads}
3022 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3026 A range of thread numbers, again with or without an inferior
3027 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3028 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3031 All threads of an inferior, specified with a star wildcard, with or
3032 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3033 @samp{1.*}) or @code{*}. The former refers to all threads of the
3034 given inferior, and the latter form without an inferior qualifier
3035 refers to all threads of the current inferior.
3039 For example, if the current inferior is 1, and inferior 7 has one
3040 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3041 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3042 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3043 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3047 @anchor{global thread numbers}
3048 @cindex global thread number
3049 @cindex global thread identifier (GDB)
3050 In addition to a @emph{per-inferior} number, each thread is also
3051 assigned a unique @emph{global} number, also known as @dfn{global
3052 thread ID}, a single integer. Unlike the thread number component of
3053 the thread ID, no two threads have the same global ID, even when
3054 you're debugging multiple inferiors.
3056 From @value{GDBN}'s perspective, a process always has at least one
3057 thread. In other words, @value{GDBN} assigns a thread number to the
3058 program's ``main thread'' even if the program is not multi-threaded.
3060 @vindex $_thread@r{, convenience variable}
3061 @vindex $_gthread@r{, convenience variable}
3062 The debugger convenience variables @samp{$_thread} and
3063 @samp{$_gthread} contain, respectively, the per-inferior thread number
3064 and the global thread number of the current thread. You may find this
3065 useful in writing breakpoint conditional expressions, command scripts,
3066 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3067 general information on convenience variables.
3069 If @value{GDBN} detects the program is multi-threaded, it augments the
3070 usual message about stopping at a breakpoint with the ID and name of
3071 the thread that hit the breakpoint.
3074 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3077 Likewise when the program receives a signal:
3080 Thread 1 "main" received signal SIGINT, Interrupt.
3084 @kindex info threads
3085 @item info threads @r{[}@var{thread-id-list}@r{]}
3087 Display information about one or more threads. With no arguments
3088 displays information about all threads. You can specify the list of
3089 threads that you want to display using the thread ID list syntax
3090 (@pxref{thread ID lists}).
3092 @value{GDBN} displays for each thread (in this order):
3096 the per-inferior thread number assigned by @value{GDBN}
3099 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3100 option was specified
3103 the target system's thread identifier (@var{systag})
3106 the thread's name, if one is known. A thread can either be named by
3107 the user (see @code{thread name}, below), or, in some cases, by the
3111 the current stack frame summary for that thread
3115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3116 indicates the current thread.
3120 @c end table here to get a little more width for example
3123 (@value{GDBP}) info threads
3125 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3126 2 process 35 thread 23 0x34e5 in sigpause ()
3127 3 process 35 thread 27 0x34e5 in sigpause ()
3131 If you're debugging multiple inferiors, @value{GDBN} displays thread
3132 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3133 Otherwise, only @var{thread-num} is shown.
3135 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3136 indicating each thread's global thread ID:
3139 (@value{GDBP}) info threads
3140 Id GId Target Id Frame
3141 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3142 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3143 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3144 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3147 On Solaris, you can display more information about user threads with a
3148 Solaris-specific command:
3151 @item maint info sol-threads
3152 @kindex maint info sol-threads
3153 @cindex thread info (Solaris)
3154 Display info on Solaris user threads.
3158 @kindex thread @var{thread-id}
3159 @item thread @var{thread-id}
3160 Make thread ID @var{thread-id} the current thread. The command
3161 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3162 the first field of the @samp{info threads} display, with or without an
3163 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3165 @value{GDBN} responds by displaying the system identifier of the
3166 thread you selected, and its current stack frame summary:
3169 (@value{GDBP}) thread 2
3170 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3171 #0 some_function (ignore=0x0) at example.c:8
3172 8 printf ("hello\n");
3176 As with the @samp{[New @dots{}]} message, the form of the text after
3177 @samp{Switching to} depends on your system's conventions for identifying
3180 @kindex thread apply
3181 @cindex apply command to several threads
3182 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3183 The @code{thread apply} command allows you to apply the named
3184 @var{command} to one or more threads. Specify the threads that you
3185 want affected using the thread ID list syntax (@pxref{thread ID
3186 lists}), or specify @code{all} to apply to all threads. To apply a
3187 command to all threads in descending order, type @kbd{thread apply all
3188 @var{command}}. To apply a command to all threads in ascending order,
3189 type @kbd{thread apply all -ascending @var{command}}.
3191 The @var{flag} arguments control what output to produce and how to handle
3192 errors raised when applying @var{command} to a thread. @var{flag}
3193 must start with a @code{-} directly followed by one letter in
3194 @code{qcs}. If several flags are provided, they must be given
3195 individually, such as @code{-c -q}.
3197 By default, @value{GDBN} displays some thread information before the
3198 output produced by @var{command}, and an error raised during the
3199 execution of a @var{command} will abort @code{thread apply}. The
3200 following flags can be used to fine-tune this behavior:
3204 The flag @code{-c}, which stands for @samp{continue}, causes any
3205 errors in @var{command} to be displayed, and the execution of
3206 @code{thread apply} then continues.
3208 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3209 or empty output produced by a @var{command} to be silently ignored.
3210 That is, the execution continues, but the thread information and errors
3213 The flag @code{-q} (@samp{quiet}) disables printing the thread
3217 Flags @code{-c} and @code{-s} cannot be used together.
3220 @cindex apply command to all threads (ignoring errors and empty output)
3221 @item taas @var{command}
3222 Shortcut for @code{thread apply all -s @var{command}}.
3223 Applies @var{command} on all threads, ignoring errors and empty output.
3226 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3227 @item tfaas @var{command}
3228 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3229 Applies @var{command} on all frames of all threads, ignoring errors
3230 and empty output. Note that the flag @code{-s} is specified twice:
3231 The first @code{-s} ensures that @code{thread apply} only shows the thread
3232 information of the threads for which @code{frame apply} produces
3233 some output. The second @code{-s} is needed to ensure that @code{frame
3234 apply} shows the frame information of a frame only if the
3235 @var{command} successfully produced some output.
3237 It can for example be used to print a local variable or a function
3238 argument without knowing the thread or frame where this variable or argument
3241 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3246 @cindex name a thread
3247 @item thread name [@var{name}]
3248 This command assigns a name to the current thread. If no argument is
3249 given, any existing user-specified name is removed. The thread name
3250 appears in the @samp{info threads} display.
3252 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3253 determine the name of the thread as given by the OS. On these
3254 systems, a name specified with @samp{thread name} will override the
3255 system-give name, and removing the user-specified name will cause
3256 @value{GDBN} to once again display the system-specified name.
3259 @cindex search for a thread
3260 @item thread find [@var{regexp}]
3261 Search for and display thread ids whose name or @var{systag}
3262 matches the supplied regular expression.
3264 As well as being the complement to the @samp{thread name} command,
3265 this command also allows you to identify a thread by its target
3266 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3270 (@value{GDBN}) thread find 26688
3271 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3272 (@value{GDBN}) info thread 4
3274 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3277 @kindex set print thread-events
3278 @cindex print messages on thread start and exit
3279 @item set print thread-events
3280 @itemx set print thread-events on
3281 @itemx set print thread-events off
3282 The @code{set print thread-events} command allows you to enable or
3283 disable printing of messages when @value{GDBN} notices that new threads have
3284 started or that threads have exited. By default, these messages will
3285 be printed if detection of these events is supported by the target.
3286 Note that these messages cannot be disabled on all targets.
3288 @kindex show print thread-events
3289 @item show print thread-events
3290 Show whether messages will be printed when @value{GDBN} detects that threads
3291 have started and exited.
3294 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3295 more information about how @value{GDBN} behaves when you stop and start
3296 programs with multiple threads.
3298 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3299 watchpoints in programs with multiple threads.
3301 @anchor{set libthread-db-search-path}
3303 @kindex set libthread-db-search-path
3304 @cindex search path for @code{libthread_db}
3305 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3306 If this variable is set, @var{path} is a colon-separated list of
3307 directories @value{GDBN} will use to search for @code{libthread_db}.
3308 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3309 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3310 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3313 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3314 @code{libthread_db} library to obtain information about threads in the
3315 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3316 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3317 specific thread debugging library loading is enabled
3318 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3321 refers to the default system directories that are
3322 normally searched for loading shared libraries. The @samp{$sdir} entry
3323 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3324 (@pxref{libthread_db.so.1 file}).
3326 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3327 refers to the directory from which @code{libpthread}
3328 was loaded in the inferior process.
3330 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3331 @value{GDBN} attempts to initialize it with the current inferior process.
3332 If this initialization fails (which could happen because of a version
3333 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3334 will unload @code{libthread_db}, and continue with the next directory.
3335 If none of @code{libthread_db} libraries initialize successfully,
3336 @value{GDBN} will issue a warning and thread debugging will be disabled.
3338 Setting @code{libthread-db-search-path} is currently implemented
3339 only on some platforms.
3341 @kindex show libthread-db-search-path
3342 @item show libthread-db-search-path
3343 Display current libthread_db search path.
3345 @kindex set debug libthread-db
3346 @kindex show debug libthread-db
3347 @cindex debugging @code{libthread_db}
3348 @item set debug libthread-db
3349 @itemx show debug libthread-db
3350 Turns on or off display of @code{libthread_db}-related events.
3351 Use @code{1} to enable, @code{0} to disable.
3355 @section Debugging Forks
3357 @cindex fork, debugging programs which call
3358 @cindex multiple processes
3359 @cindex processes, multiple
3360 On most systems, @value{GDBN} has no special support for debugging
3361 programs which create additional processes using the @code{fork}
3362 function. When a program forks, @value{GDBN} will continue to debug the
3363 parent process and the child process will run unimpeded. If you have
3364 set a breakpoint in any code which the child then executes, the child
3365 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3366 will cause it to terminate.
3368 However, if you want to debug the child process there is a workaround
3369 which isn't too painful. Put a call to @code{sleep} in the code which
3370 the child process executes after the fork. It may be useful to sleep
3371 only if a certain environment variable is set, or a certain file exists,
3372 so that the delay need not occur when you don't want to run @value{GDBN}
3373 on the child. While the child is sleeping, use the @code{ps} program to
3374 get its process ID. Then tell @value{GDBN} (a new invocation of
3375 @value{GDBN} if you are also debugging the parent process) to attach to
3376 the child process (@pxref{Attach}). From that point on you can debug
3377 the child process just like any other process which you attached to.
3379 On some systems, @value{GDBN} provides support for debugging programs
3380 that create additional processes using the @code{fork} or @code{vfork}
3381 functions. On @sc{gnu}/Linux platforms, this feature is supported
3382 with kernel version 2.5.46 and later.
3384 The fork debugging commands are supported in native mode and when
3385 connected to @code{gdbserver} in either @code{target remote} mode or
3386 @code{target extended-remote} mode.
3388 By default, when a program forks, @value{GDBN} will continue to debug
3389 the parent process and the child process will run unimpeded.
3391 If you want to follow the child process instead of the parent process,
3392 use the command @w{@code{set follow-fork-mode}}.
3395 @kindex set follow-fork-mode
3396 @item set follow-fork-mode @var{mode}
3397 Set the debugger response to a program call of @code{fork} or
3398 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3399 process. The @var{mode} argument can be:
3403 The original process is debugged after a fork. The child process runs
3404 unimpeded. This is the default.
3407 The new process is debugged after a fork. The parent process runs
3412 @kindex show follow-fork-mode
3413 @item show follow-fork-mode
3414 Display the current debugger response to a @code{fork} or @code{vfork} call.
3417 @cindex debugging multiple processes
3418 On Linux, if you want to debug both the parent and child processes, use the
3419 command @w{@code{set detach-on-fork}}.
3422 @kindex set detach-on-fork
3423 @item set detach-on-fork @var{mode}
3424 Tells gdb whether to detach one of the processes after a fork, or
3425 retain debugger control over them both.
3429 The child process (or parent process, depending on the value of
3430 @code{follow-fork-mode}) will be detached and allowed to run
3431 independently. This is the default.
3434 Both processes will be held under the control of @value{GDBN}.
3435 One process (child or parent, depending on the value of
3436 @code{follow-fork-mode}) is debugged as usual, while the other
3441 @kindex show detach-on-fork
3442 @item show detach-on-fork
3443 Show whether detach-on-fork mode is on/off.
3446 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3447 will retain control of all forked processes (including nested forks).
3448 You can list the forked processes under the control of @value{GDBN} by
3449 using the @w{@code{info inferiors}} command, and switch from one fork
3450 to another by using the @code{inferior} command (@pxref{Inferiors and
3451 Programs, ,Debugging Multiple Inferiors and Programs}).
3453 To quit debugging one of the forked processes, you can either detach
3454 from it by using the @w{@code{detach inferiors}} command (allowing it
3455 to run independently), or kill it using the @w{@code{kill inferiors}}
3456 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3459 If you ask to debug a child process and a @code{vfork} is followed by an
3460 @code{exec}, @value{GDBN} executes the new target up to the first
3461 breakpoint in the new target. If you have a breakpoint set on
3462 @code{main} in your original program, the breakpoint will also be set on
3463 the child process's @code{main}.
3465 On some systems, when a child process is spawned by @code{vfork}, you
3466 cannot debug the child or parent until an @code{exec} call completes.
3468 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3469 call executes, the new target restarts. To restart the parent
3470 process, use the @code{file} command with the parent executable name
3471 as its argument. By default, after an @code{exec} call executes,
3472 @value{GDBN} discards the symbols of the previous executable image.
3473 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3477 @kindex set follow-exec-mode
3478 @item set follow-exec-mode @var{mode}
3480 Set debugger response to a program call of @code{exec}. An
3481 @code{exec} call replaces the program image of a process.
3483 @code{follow-exec-mode} can be:
3487 @value{GDBN} creates a new inferior and rebinds the process to this
3488 new inferior. The program the process was running before the
3489 @code{exec} call can be restarted afterwards by restarting the
3495 (@value{GDBP}) info inferiors
3497 Id Description Executable
3500 process 12020 is executing new program: prog2
3501 Program exited normally.
3502 (@value{GDBP}) info inferiors
3503 Id Description Executable
3509 @value{GDBN} keeps the process bound to the same inferior. The new
3510 executable image replaces the previous executable loaded in the
3511 inferior. Restarting the inferior after the @code{exec} call, with
3512 e.g., the @code{run} command, restarts the executable the process was
3513 running after the @code{exec} call. This is the default mode.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3522 process 12020 is executing new program: prog2
3523 Program exited normally.
3524 (@value{GDBP}) info inferiors
3525 Id Description Executable
3532 @code{follow-exec-mode} is supported in native mode and
3533 @code{target extended-remote} mode.
3535 You can use the @code{catch} command to make @value{GDBN} stop whenever
3536 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3537 Catchpoints, ,Setting Catchpoints}.
3539 @node Checkpoint/Restart
3540 @section Setting a @emph{Bookmark} to Return to Later
3545 @cindex snapshot of a process
3546 @cindex rewind program state
3548 On certain operating systems@footnote{Currently, only
3549 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3550 program's state, called a @dfn{checkpoint}, and come back to it
3553 Returning to a checkpoint effectively undoes everything that has
3554 happened in the program since the @code{checkpoint} was saved. This
3555 includes changes in memory, registers, and even (within some limits)
3556 system state. Effectively, it is like going back in time to the
3557 moment when the checkpoint was saved.
3559 Thus, if you're stepping thru a program and you think you're
3560 getting close to the point where things go wrong, you can save
3561 a checkpoint. Then, if you accidentally go too far and miss
3562 the critical statement, instead of having to restart your program
3563 from the beginning, you can just go back to the checkpoint and
3564 start again from there.
3566 This can be especially useful if it takes a lot of time or
3567 steps to reach the point where you think the bug occurs.
3569 To use the @code{checkpoint}/@code{restart} method of debugging:
3574 Save a snapshot of the debugged program's current execution state.
3575 The @code{checkpoint} command takes no arguments, but each checkpoint
3576 is assigned a small integer id, similar to a breakpoint id.
3578 @kindex info checkpoints
3579 @item info checkpoints
3580 List the checkpoints that have been saved in the current debugging
3581 session. For each checkpoint, the following information will be
3588 @item Source line, or label
3591 @kindex restart @var{checkpoint-id}
3592 @item restart @var{checkpoint-id}
3593 Restore the program state that was saved as checkpoint number
3594 @var{checkpoint-id}. All program variables, registers, stack frames
3595 etc.@: will be returned to the values that they had when the checkpoint
3596 was saved. In essence, gdb will ``wind back the clock'' to the point
3597 in time when the checkpoint was saved.
3599 Note that breakpoints, @value{GDBN} variables, command history etc.
3600 are not affected by restoring a checkpoint. In general, a checkpoint
3601 only restores things that reside in the program being debugged, not in
3604 @kindex delete checkpoint @var{checkpoint-id}
3605 @item delete checkpoint @var{checkpoint-id}
3606 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3610 Returning to a previously saved checkpoint will restore the user state
3611 of the program being debugged, plus a significant subset of the system
3612 (OS) state, including file pointers. It won't ``un-write'' data from
3613 a file, but it will rewind the file pointer to the previous location,
3614 so that the previously written data can be overwritten. For files
3615 opened in read mode, the pointer will also be restored so that the
3616 previously read data can be read again.
3618 Of course, characters that have been sent to a printer (or other
3619 external device) cannot be ``snatched back'', and characters received
3620 from eg.@: a serial device can be removed from internal program buffers,
3621 but they cannot be ``pushed back'' into the serial pipeline, ready to
3622 be received again. Similarly, the actual contents of files that have
3623 been changed cannot be restored (at this time).
3625 However, within those constraints, you actually can ``rewind'' your
3626 program to a previously saved point in time, and begin debugging it
3627 again --- and you can change the course of events so as to debug a
3628 different execution path this time.
3630 @cindex checkpoints and process id
3631 Finally, there is one bit of internal program state that will be
3632 different when you return to a checkpoint --- the program's process
3633 id. Each checkpoint will have a unique process id (or @var{pid}),
3634 and each will be different from the program's original @var{pid}.
3635 If your program has saved a local copy of its process id, this could
3636 potentially pose a problem.
3638 @subsection A Non-obvious Benefit of Using Checkpoints
3640 On some systems such as @sc{gnu}/Linux, address space randomization
3641 is performed on new processes for security reasons. This makes it
3642 difficult or impossible to set a breakpoint, or watchpoint, on an
3643 absolute address if you have to restart the program, since the
3644 absolute location of a symbol will change from one execution to the
3647 A checkpoint, however, is an @emph{identical} copy of a process.
3648 Therefore if you create a checkpoint at (eg.@:) the start of main,
3649 and simply return to that checkpoint instead of restarting the
3650 process, you can avoid the effects of address randomization and
3651 your symbols will all stay in the same place.
3654 @chapter Stopping and Continuing
3656 The principal purposes of using a debugger are so that you can stop your
3657 program before it terminates; or so that, if your program runs into
3658 trouble, you can investigate and find out why.
3660 Inside @value{GDBN}, your program may stop for any of several reasons,
3661 such as a signal, a breakpoint, or reaching a new line after a
3662 @value{GDBN} command such as @code{step}. You may then examine and
3663 change variables, set new breakpoints or remove old ones, and then
3664 continue execution. Usually, the messages shown by @value{GDBN} provide
3665 ample explanation of the status of your program---but you can also
3666 explicitly request this information at any time.
3669 @kindex info program
3671 Display information about the status of your program: whether it is
3672 running or not, what process it is, and why it stopped.
3676 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3677 * Continuing and Stepping:: Resuming execution
3678 * Skipping Over Functions and Files::
3679 Skipping over functions and files
3681 * Thread Stops:: Stopping and starting multi-thread programs
3685 @section Breakpoints, Watchpoints, and Catchpoints
3688 A @dfn{breakpoint} makes your program stop whenever a certain point in
3689 the program is reached. For each breakpoint, you can add conditions to
3690 control in finer detail whether your program stops. You can set
3691 breakpoints with the @code{break} command and its variants (@pxref{Set
3692 Breaks, ,Setting Breakpoints}), to specify the place where your program
3693 should stop by line number, function name or exact address in the
3696 On some systems, you can set breakpoints in shared libraries before
3697 the executable is run.
3700 @cindex data breakpoints
3701 @cindex memory tracing
3702 @cindex breakpoint on memory address
3703 @cindex breakpoint on variable modification
3704 A @dfn{watchpoint} is a special breakpoint that stops your program
3705 when the value of an expression changes. The expression may be a value
3706 of a variable, or it could involve values of one or more variables
3707 combined by operators, such as @samp{a + b}. This is sometimes called
3708 @dfn{data breakpoints}. You must use a different command to set
3709 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3710 from that, you can manage a watchpoint like any other breakpoint: you
3711 enable, disable, and delete both breakpoints and watchpoints using the
3714 You can arrange to have values from your program displayed automatically
3715 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3719 @cindex breakpoint on events
3720 A @dfn{catchpoint} is another special breakpoint that stops your program
3721 when a certain kind of event occurs, such as the throwing of a C@t{++}
3722 exception or the loading of a library. As with watchpoints, you use a
3723 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3724 Catchpoints}), but aside from that, you can manage a catchpoint like any
3725 other breakpoint. (To stop when your program receives a signal, use the
3726 @code{handle} command; see @ref{Signals, ,Signals}.)
3728 @cindex breakpoint numbers
3729 @cindex numbers for breakpoints
3730 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3731 catchpoint when you create it; these numbers are successive integers
3732 starting with one. In many of the commands for controlling various
3733 features of breakpoints you use the breakpoint number to say which
3734 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3735 @dfn{disabled}; if disabled, it has no effect on your program until you
3738 @cindex breakpoint ranges
3739 @cindex breakpoint lists
3740 @cindex ranges of breakpoints
3741 @cindex lists of breakpoints
3742 Some @value{GDBN} commands accept a space-separated list of breakpoints
3743 on which to operate. A list element can be either a single breakpoint number,
3744 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3745 When a breakpoint list is given to a command, all breakpoints in that list
3749 * Set Breaks:: Setting breakpoints
3750 * Set Watchpoints:: Setting watchpoints
3751 * Set Catchpoints:: Setting catchpoints
3752 * Delete Breaks:: Deleting breakpoints
3753 * Disabling:: Disabling breakpoints
3754 * Conditions:: Break conditions
3755 * Break Commands:: Breakpoint command lists
3756 * Dynamic Printf:: Dynamic printf
3757 * Save Breakpoints:: How to save breakpoints in a file
3758 * Static Probe Points:: Listing static probe points
3759 * Error in Breakpoints:: ``Cannot insert breakpoints''
3760 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3764 @subsection Setting Breakpoints
3766 @c FIXME LMB what does GDB do if no code on line of breakpt?
3767 @c consider in particular declaration with/without initialization.
3769 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3772 @kindex b @r{(@code{break})}
3773 @vindex $bpnum@r{, convenience variable}
3774 @cindex latest breakpoint
3775 Breakpoints are set with the @code{break} command (abbreviated
3776 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3777 number of the breakpoint you've set most recently; see @ref{Convenience
3778 Vars,, Convenience Variables}, for a discussion of what you can do with
3779 convenience variables.
3782 @item break @var{location}
3783 Set a breakpoint at the given @var{location}, which can specify a
3784 function name, a line number, or an address of an instruction.
3785 (@xref{Specify Location}, for a list of all the possible ways to
3786 specify a @var{location}.) The breakpoint will stop your program just
3787 before it executes any of the code in the specified @var{location}.
3789 When using source languages that permit overloading of symbols, such as
3790 C@t{++}, a function name may refer to more than one possible place to break.
3791 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3794 It is also possible to insert a breakpoint that will stop the program
3795 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3796 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3799 When called without any arguments, @code{break} sets a breakpoint at
3800 the next instruction to be executed in the selected stack frame
3801 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3802 innermost, this makes your program stop as soon as control
3803 returns to that frame. This is similar to the effect of a
3804 @code{finish} command in the frame inside the selected frame---except
3805 that @code{finish} does not leave an active breakpoint. If you use
3806 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3807 the next time it reaches the current location; this may be useful
3810 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3811 least one instruction has been executed. If it did not do this, you
3812 would be unable to proceed past a breakpoint without first disabling the
3813 breakpoint. This rule applies whether or not the breakpoint already
3814 existed when your program stopped.
3816 @item break @dots{} if @var{cond}
3817 Set a breakpoint with condition @var{cond}; evaluate the expression
3818 @var{cond} each time the breakpoint is reached, and stop only if the
3819 value is nonzero---that is, if @var{cond} evaluates as true.
3820 @samp{@dots{}} stands for one of the possible arguments described
3821 above (or no argument) specifying where to break. @xref{Conditions,
3822 ,Break Conditions}, for more information on breakpoint conditions.
3825 @item tbreak @var{args}
3826 Set a breakpoint enabled only for one stop. The @var{args} are the
3827 same as for the @code{break} command, and the breakpoint is set in the same
3828 way, but the breakpoint is automatically deleted after the first time your
3829 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3832 @cindex hardware breakpoints
3833 @item hbreak @var{args}
3834 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3835 @code{break} command and the breakpoint is set in the same way, but the
3836 breakpoint requires hardware support and some target hardware may not
3837 have this support. The main purpose of this is EPROM/ROM code
3838 debugging, so you can set a breakpoint at an instruction without
3839 changing the instruction. This can be used with the new trap-generation
3840 provided by SPARClite DSU and most x86-based targets. These targets
3841 will generate traps when a program accesses some data or instruction
3842 address that is assigned to the debug registers. However the hardware
3843 breakpoint registers can take a limited number of breakpoints. For
3844 example, on the DSU, only two data breakpoints can be set at a time, and
3845 @value{GDBN} will reject this command if more than two are used. Delete
3846 or disable unused hardware breakpoints before setting new ones
3847 (@pxref{Disabling, ,Disabling Breakpoints}).
3848 @xref{Conditions, ,Break Conditions}.
3849 For remote targets, you can restrict the number of hardware
3850 breakpoints @value{GDBN} will use, see @ref{set remote
3851 hardware-breakpoint-limit}.
3854 @item thbreak @var{args}
3855 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3856 are the same as for the @code{hbreak} command and the breakpoint is set in
3857 the same way. However, like the @code{tbreak} command,
3858 the breakpoint is automatically deleted after the
3859 first time your program stops there. Also, like the @code{hbreak}
3860 command, the breakpoint requires hardware support and some target hardware
3861 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3862 See also @ref{Conditions, ,Break Conditions}.
3865 @cindex regular expression
3866 @cindex breakpoints at functions matching a regexp
3867 @cindex set breakpoints in many functions
3868 @item rbreak @var{regex}
3869 Set breakpoints on all functions matching the regular expression
3870 @var{regex}. This command sets an unconditional breakpoint on all
3871 matches, printing a list of all breakpoints it set. Once these
3872 breakpoints are set, they are treated just like the breakpoints set with
3873 the @code{break} command. You can delete them, disable them, or make
3874 them conditional the same way as any other breakpoint.
3876 In programs using different languages, @value{GDBN} chooses the syntax
3877 to print the list of all breakpoints it sets according to the
3878 @samp{set language} value: using @samp{set language auto}
3879 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3880 language of the breakpoint's function, other values mean to use
3881 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3883 The syntax of the regular expression is the standard one used with tools
3884 like @file{grep}. Note that this is different from the syntax used by
3885 shells, so for instance @code{foo*} matches all functions that include
3886 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3887 @code{.*} leading and trailing the regular expression you supply, so to
3888 match only functions that begin with @code{foo}, use @code{^foo}.
3890 @cindex non-member C@t{++} functions, set breakpoint in
3891 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3892 breakpoints on overloaded functions that are not members of any special
3895 @cindex set breakpoints on all functions
3896 The @code{rbreak} command can be used to set breakpoints in
3897 @strong{all} the functions in a program, like this:
3900 (@value{GDBP}) rbreak .
3903 @item rbreak @var{file}:@var{regex}
3904 If @code{rbreak} is called with a filename qualification, it limits
3905 the search for functions matching the given regular expression to the
3906 specified @var{file}. This can be used, for example, to set breakpoints on
3907 every function in a given file:
3910 (@value{GDBP}) rbreak file.c:.
3913 The colon separating the filename qualifier from the regex may
3914 optionally be surrounded by spaces.
3916 @kindex info breakpoints
3917 @cindex @code{$_} and @code{info breakpoints}
3918 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3919 @itemx info break @r{[}@var{list}@dots{}@r{]}
3920 Print a table of all breakpoints, watchpoints, and catchpoints set and
3921 not deleted. Optional argument @var{n} means print information only
3922 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3923 For each breakpoint, following columns are printed:
3926 @item Breakpoint Numbers
3928 Breakpoint, watchpoint, or catchpoint.
3930 Whether the breakpoint is marked to be disabled or deleted when hit.
3931 @item Enabled or Disabled
3932 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3933 that are not enabled.
3935 Where the breakpoint is in your program, as a memory address. For a
3936 pending breakpoint whose address is not yet known, this field will
3937 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3938 library that has the symbol or line referred by breakpoint is loaded.
3939 See below for details. A breakpoint with several locations will
3940 have @samp{<MULTIPLE>} in this field---see below for details.
3942 Where the breakpoint is in the source for your program, as a file and
3943 line number. For a pending breakpoint, the original string passed to
3944 the breakpoint command will be listed as it cannot be resolved until
3945 the appropriate shared library is loaded in the future.
3949 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3950 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3951 @value{GDBN} on the host's side. If it is ``target'', then the condition
3952 is evaluated by the target. The @code{info break} command shows
3953 the condition on the line following the affected breakpoint, together with
3954 its condition evaluation mode in between parentheses.
3956 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3957 allowed to have a condition specified for it. The condition is not parsed for
3958 validity until a shared library is loaded that allows the pending
3959 breakpoint to resolve to a valid location.
3962 @code{info break} with a breakpoint
3963 number @var{n} as argument lists only that breakpoint. The
3964 convenience variable @code{$_} and the default examining-address for
3965 the @code{x} command are set to the address of the last breakpoint
3966 listed (@pxref{Memory, ,Examining Memory}).
3969 @code{info break} displays a count of the number of times the breakpoint
3970 has been hit. This is especially useful in conjunction with the
3971 @code{ignore} command. You can ignore a large number of breakpoint
3972 hits, look at the breakpoint info to see how many times the breakpoint
3973 was hit, and then run again, ignoring one less than that number. This
3974 will get you quickly to the last hit of that breakpoint.
3977 For a breakpoints with an enable count (xref) greater than 1,
3978 @code{info break} also displays that count.
3982 @value{GDBN} allows you to set any number of breakpoints at the same place in
3983 your program. There is nothing silly or meaningless about this. When
3984 the breakpoints are conditional, this is even useful
3985 (@pxref{Conditions, ,Break Conditions}).
3987 @cindex multiple locations, breakpoints
3988 @cindex breakpoints, multiple locations
3989 It is possible that a breakpoint corresponds to several locations
3990 in your program. Examples of this situation are:
3994 Multiple functions in the program may have the same name.
3997 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3998 instances of the function body, used in different cases.
4001 For a C@t{++} template function, a given line in the function can
4002 correspond to any number of instantiations.
4005 For an inlined function, a given source line can correspond to
4006 several places where that function is inlined.
4009 In all those cases, @value{GDBN} will insert a breakpoint at all
4010 the relevant locations.
4012 A breakpoint with multiple locations is displayed in the breakpoint
4013 table using several rows---one header row, followed by one row for
4014 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4015 address column. The rows for individual locations contain the actual
4016 addresses for locations, and show the functions to which those
4017 locations belong. The number column for a location is of the form
4018 @var{breakpoint-number}.@var{location-number}.
4023 Num Type Disp Enb Address What
4024 1 breakpoint keep y <MULTIPLE>
4026 breakpoint already hit 1 time
4027 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4028 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4031 You cannot delete the individual locations from a breakpoint. However,
4032 each location can be individually enabled or disabled by passing
4033 @var{breakpoint-number}.@var{location-number} as argument to the
4034 @code{enable} and @code{disable} commands. It's also possible to
4035 @code{enable} and @code{disable} a range of @var{location-number}
4036 locations using a @var{breakpoint-number} and two @var{location-number}s,
4037 in increasing order, separated by a hyphen, like
4038 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4039 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4040 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4041 all of the locations that belong to that breakpoint.
4043 @cindex pending breakpoints
4044 It's quite common to have a breakpoint inside a shared library.
4045 Shared libraries can be loaded and unloaded explicitly,
4046 and possibly repeatedly, as the program is executed. To support
4047 this use case, @value{GDBN} updates breakpoint locations whenever
4048 any shared library is loaded or unloaded. Typically, you would
4049 set a breakpoint in a shared library at the beginning of your
4050 debugging session, when the library is not loaded, and when the
4051 symbols from the library are not available. When you try to set
4052 breakpoint, @value{GDBN} will ask you if you want to set
4053 a so called @dfn{pending breakpoint}---breakpoint whose address
4054 is not yet resolved.
4056 After the program is run, whenever a new shared library is loaded,
4057 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4058 shared library contains the symbol or line referred to by some
4059 pending breakpoint, that breakpoint is resolved and becomes an
4060 ordinary breakpoint. When a library is unloaded, all breakpoints
4061 that refer to its symbols or source lines become pending again.
4063 This logic works for breakpoints with multiple locations, too. For
4064 example, if you have a breakpoint in a C@t{++} template function, and
4065 a newly loaded shared library has an instantiation of that template,
4066 a new location is added to the list of locations for the breakpoint.
4068 Except for having unresolved address, pending breakpoints do not
4069 differ from regular breakpoints. You can set conditions or commands,
4070 enable and disable them and perform other breakpoint operations.
4072 @value{GDBN} provides some additional commands for controlling what
4073 happens when the @samp{break} command cannot resolve breakpoint
4074 address specification to an address:
4076 @kindex set breakpoint pending
4077 @kindex show breakpoint pending
4079 @item set breakpoint pending auto
4080 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4081 location, it queries you whether a pending breakpoint should be created.
4083 @item set breakpoint pending on
4084 This indicates that an unrecognized breakpoint location should automatically
4085 result in a pending breakpoint being created.
4087 @item set breakpoint pending off
4088 This indicates that pending breakpoints are not to be created. Any
4089 unrecognized breakpoint location results in an error. This setting does
4090 not affect any pending breakpoints previously created.
4092 @item show breakpoint pending
4093 Show the current behavior setting for creating pending breakpoints.
4096 The settings above only affect the @code{break} command and its
4097 variants. Once breakpoint is set, it will be automatically updated
4098 as shared libraries are loaded and unloaded.
4100 @cindex automatic hardware breakpoints
4101 For some targets, @value{GDBN} can automatically decide if hardware or
4102 software breakpoints should be used, depending on whether the
4103 breakpoint address is read-only or read-write. This applies to
4104 breakpoints set with the @code{break} command as well as to internal
4105 breakpoints set by commands like @code{next} and @code{finish}. For
4106 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4109 You can control this automatic behaviour with the following commands:
4111 @kindex set breakpoint auto-hw
4112 @kindex show breakpoint auto-hw
4114 @item set breakpoint auto-hw on
4115 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4116 will try to use the target memory map to decide if software or hardware
4117 breakpoint must be used.
4119 @item set breakpoint auto-hw off
4120 This indicates @value{GDBN} should not automatically select breakpoint
4121 type. If the target provides a memory map, @value{GDBN} will warn when
4122 trying to set software breakpoint at a read-only address.
4125 @value{GDBN} normally implements breakpoints by replacing the program code
4126 at the breakpoint address with a special instruction, which, when
4127 executed, given control to the debugger. By default, the program
4128 code is so modified only when the program is resumed. As soon as
4129 the program stops, @value{GDBN} restores the original instructions. This
4130 behaviour guards against leaving breakpoints inserted in the
4131 target should gdb abrubptly disconnect. However, with slow remote
4132 targets, inserting and removing breakpoint can reduce the performance.
4133 This behavior can be controlled with the following commands::
4135 @kindex set breakpoint always-inserted
4136 @kindex show breakpoint always-inserted
4138 @item set breakpoint always-inserted off
4139 All breakpoints, including newly added by the user, are inserted in
4140 the target only when the target is resumed. All breakpoints are
4141 removed from the target when it stops. This is the default mode.
4143 @item set breakpoint always-inserted on
4144 Causes all breakpoints to be inserted in the target at all times. If
4145 the user adds a new breakpoint, or changes an existing breakpoint, the
4146 breakpoints in the target are updated immediately. A breakpoint is
4147 removed from the target only when breakpoint itself is deleted.
4150 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4151 when a breakpoint breaks. If the condition is true, then the process being
4152 debugged stops, otherwise the process is resumed.
4154 If the target supports evaluating conditions on its end, @value{GDBN} may
4155 download the breakpoint, together with its conditions, to it.
4157 This feature can be controlled via the following commands:
4159 @kindex set breakpoint condition-evaluation
4160 @kindex show breakpoint condition-evaluation
4162 @item set breakpoint condition-evaluation host
4163 This option commands @value{GDBN} to evaluate the breakpoint
4164 conditions on the host's side. Unconditional breakpoints are sent to
4165 the target which in turn receives the triggers and reports them back to GDB
4166 for condition evaluation. This is the standard evaluation mode.
4168 @item set breakpoint condition-evaluation target
4169 This option commands @value{GDBN} to download breakpoint conditions
4170 to the target at the moment of their insertion. The target
4171 is responsible for evaluating the conditional expression and reporting
4172 breakpoint stop events back to @value{GDBN} whenever the condition
4173 is true. Due to limitations of target-side evaluation, some conditions
4174 cannot be evaluated there, e.g., conditions that depend on local data
4175 that is only known to the host. Examples include
4176 conditional expressions involving convenience variables, complex types
4177 that cannot be handled by the agent expression parser and expressions
4178 that are too long to be sent over to the target, specially when the
4179 target is a remote system. In these cases, the conditions will be
4180 evaluated by @value{GDBN}.
4182 @item set breakpoint condition-evaluation auto
4183 This is the default mode. If the target supports evaluating breakpoint
4184 conditions on its end, @value{GDBN} will download breakpoint conditions to
4185 the target (limitations mentioned previously apply). If the target does
4186 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4187 to evaluating all these conditions on the host's side.
4191 @cindex negative breakpoint numbers
4192 @cindex internal @value{GDBN} breakpoints
4193 @value{GDBN} itself sometimes sets breakpoints in your program for
4194 special purposes, such as proper handling of @code{longjmp} (in C
4195 programs). These internal breakpoints are assigned negative numbers,
4196 starting with @code{-1}; @samp{info breakpoints} does not display them.
4197 You can see these breakpoints with the @value{GDBN} maintenance command
4198 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4201 @node Set Watchpoints
4202 @subsection Setting Watchpoints
4204 @cindex setting watchpoints
4205 You can use a watchpoint to stop execution whenever the value of an
4206 expression changes, without having to predict a particular place where
4207 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4208 The expression may be as simple as the value of a single variable, or
4209 as complex as many variables combined by operators. Examples include:
4213 A reference to the value of a single variable.
4216 An address cast to an appropriate data type. For example,
4217 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4218 address (assuming an @code{int} occupies 4 bytes).
4221 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4222 expression can use any operators valid in the program's native
4223 language (@pxref{Languages}).
4226 You can set a watchpoint on an expression even if the expression can
4227 not be evaluated yet. For instance, you can set a watchpoint on
4228 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4229 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4230 the expression produces a valid value. If the expression becomes
4231 valid in some other way than changing a variable (e.g.@: if the memory
4232 pointed to by @samp{*global_ptr} becomes readable as the result of a
4233 @code{malloc} call), @value{GDBN} may not stop until the next time
4234 the expression changes.
4236 @cindex software watchpoints
4237 @cindex hardware watchpoints
4238 Depending on your system, watchpoints may be implemented in software or
4239 hardware. @value{GDBN} does software watchpointing by single-stepping your
4240 program and testing the variable's value each time, which is hundreds of
4241 times slower than normal execution. (But this may still be worth it, to
4242 catch errors where you have no clue what part of your program is the
4245 On some systems, such as most PowerPC or x86-based targets,
4246 @value{GDBN} includes support for hardware watchpoints, which do not
4247 slow down the running of your program.
4251 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4252 Set a watchpoint for an expression. @value{GDBN} will break when the
4253 expression @var{expr} is written into by the program and its value
4254 changes. The simplest (and the most popular) use of this command is
4255 to watch the value of a single variable:
4258 (@value{GDBP}) watch foo
4261 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4262 argument, @value{GDBN} breaks only when the thread identified by
4263 @var{thread-id} changes the value of @var{expr}. If any other threads
4264 change the value of @var{expr}, @value{GDBN} will not break. Note
4265 that watchpoints restricted to a single thread in this way only work
4266 with Hardware Watchpoints.
4268 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4269 (see below). The @code{-location} argument tells @value{GDBN} to
4270 instead watch the memory referred to by @var{expr}. In this case,
4271 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4272 and watch the memory at that address. The type of the result is used
4273 to determine the size of the watched memory. If the expression's
4274 result does not have an address, then @value{GDBN} will print an
4277 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4278 of masked watchpoints, if the current architecture supports this
4279 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4280 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4281 to an address to watch. The mask specifies that some bits of an address
4282 (the bits which are reset in the mask) should be ignored when matching
4283 the address accessed by the inferior against the watchpoint address.
4284 Thus, a masked watchpoint watches many addresses simultaneously---those
4285 addresses whose unmasked bits are identical to the unmasked bits in the
4286 watchpoint address. The @code{mask} argument implies @code{-location}.
4290 (@value{GDBP}) watch foo mask 0xffff00ff
4291 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4295 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4296 Set a watchpoint that will break when the value of @var{expr} is read
4300 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4301 Set a watchpoint that will break when @var{expr} is either read from
4302 or written into by the program.
4304 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4305 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4306 This command prints a list of watchpoints, using the same format as
4307 @code{info break} (@pxref{Set Breaks}).
4310 If you watch for a change in a numerically entered address you need to
4311 dereference it, as the address itself is just a constant number which will
4312 never change. @value{GDBN} refuses to create a watchpoint that watches
4313 a never-changing value:
4316 (@value{GDBP}) watch 0x600850
4317 Cannot watch constant value 0x600850.
4318 (@value{GDBP}) watch *(int *) 0x600850
4319 Watchpoint 1: *(int *) 6293584
4322 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4323 watchpoints execute very quickly, and the debugger reports a change in
4324 value at the exact instruction where the change occurs. If @value{GDBN}
4325 cannot set a hardware watchpoint, it sets a software watchpoint, which
4326 executes more slowly and reports the change in value at the next
4327 @emph{statement}, not the instruction, after the change occurs.
4329 @cindex use only software watchpoints
4330 You can force @value{GDBN} to use only software watchpoints with the
4331 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4332 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4333 the underlying system supports them. (Note that hardware-assisted
4334 watchpoints that were set @emph{before} setting
4335 @code{can-use-hw-watchpoints} to zero will still use the hardware
4336 mechanism of watching expression values.)
4339 @item set can-use-hw-watchpoints
4340 @kindex set can-use-hw-watchpoints
4341 Set whether or not to use hardware watchpoints.
4343 @item show can-use-hw-watchpoints
4344 @kindex show can-use-hw-watchpoints
4345 Show the current mode of using hardware watchpoints.
4348 For remote targets, you can restrict the number of hardware
4349 watchpoints @value{GDBN} will use, see @ref{set remote
4350 hardware-breakpoint-limit}.
4352 When you issue the @code{watch} command, @value{GDBN} reports
4355 Hardware watchpoint @var{num}: @var{expr}
4359 if it was able to set a hardware watchpoint.
4361 Currently, the @code{awatch} and @code{rwatch} commands can only set
4362 hardware watchpoints, because accesses to data that don't change the
4363 value of the watched expression cannot be detected without examining
4364 every instruction as it is being executed, and @value{GDBN} does not do
4365 that currently. If @value{GDBN} finds that it is unable to set a
4366 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4367 will print a message like this:
4370 Expression cannot be implemented with read/access watchpoint.
4373 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4374 data type of the watched expression is wider than what a hardware
4375 watchpoint on the target machine can handle. For example, some systems
4376 can only watch regions that are up to 4 bytes wide; on such systems you
4377 cannot set hardware watchpoints for an expression that yields a
4378 double-precision floating-point number (which is typically 8 bytes
4379 wide). As a work-around, it might be possible to break the large region
4380 into a series of smaller ones and watch them with separate watchpoints.
4382 If you set too many hardware watchpoints, @value{GDBN} might be unable
4383 to insert all of them when you resume the execution of your program.
4384 Since the precise number of active watchpoints is unknown until such
4385 time as the program is about to be resumed, @value{GDBN} might not be
4386 able to warn you about this when you set the watchpoints, and the
4387 warning will be printed only when the program is resumed:
4390 Hardware watchpoint @var{num}: Could not insert watchpoint
4394 If this happens, delete or disable some of the watchpoints.
4396 Watching complex expressions that reference many variables can also
4397 exhaust the resources available for hardware-assisted watchpoints.
4398 That's because @value{GDBN} needs to watch every variable in the
4399 expression with separately allocated resources.
4401 If you call a function interactively using @code{print} or @code{call},
4402 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4403 kind of breakpoint or the call completes.
4405 @value{GDBN} automatically deletes watchpoints that watch local
4406 (automatic) variables, or expressions that involve such variables, when
4407 they go out of scope, that is, when the execution leaves the block in
4408 which these variables were defined. In particular, when the program
4409 being debugged terminates, @emph{all} local variables go out of scope,
4410 and so only watchpoints that watch global variables remain set. If you
4411 rerun the program, you will need to set all such watchpoints again. One
4412 way of doing that would be to set a code breakpoint at the entry to the
4413 @code{main} function and when it breaks, set all the watchpoints.
4415 @cindex watchpoints and threads
4416 @cindex threads and watchpoints
4417 In multi-threaded programs, watchpoints will detect changes to the
4418 watched expression from every thread.
4421 @emph{Warning:} In multi-threaded programs, software watchpoints
4422 have only limited usefulness. If @value{GDBN} creates a software
4423 watchpoint, it can only watch the value of an expression @emph{in a
4424 single thread}. If you are confident that the expression can only
4425 change due to the current thread's activity (and if you are also
4426 confident that no other thread can become current), then you can use
4427 software watchpoints as usual. However, @value{GDBN} may not notice
4428 when a non-current thread's activity changes the expression. (Hardware
4429 watchpoints, in contrast, watch an expression in all threads.)
4432 @xref{set remote hardware-watchpoint-limit}.
4434 @node Set Catchpoints
4435 @subsection Setting Catchpoints
4436 @cindex catchpoints, setting
4437 @cindex exception handlers
4438 @cindex event handling
4440 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4441 kinds of program events, such as C@t{++} exceptions or the loading of a
4442 shared library. Use the @code{catch} command to set a catchpoint.
4446 @item catch @var{event}
4447 Stop when @var{event} occurs. The @var{event} can be any of the following:
4450 @item throw @r{[}@var{regexp}@r{]}
4451 @itemx rethrow @r{[}@var{regexp}@r{]}
4452 @itemx catch @r{[}@var{regexp}@r{]}
4454 @kindex catch rethrow
4456 @cindex stop on C@t{++} exceptions
4457 The throwing, re-throwing, or catching of a C@t{++} exception.
4459 If @var{regexp} is given, then only exceptions whose type matches the
4460 regular expression will be caught.
4462 @vindex $_exception@r{, convenience variable}
4463 The convenience variable @code{$_exception} is available at an
4464 exception-related catchpoint, on some systems. This holds the
4465 exception being thrown.
4467 There are currently some limitations to C@t{++} exception handling in
4472 The support for these commands is system-dependent. Currently, only
4473 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4477 The regular expression feature and the @code{$_exception} convenience
4478 variable rely on the presence of some SDT probes in @code{libstdc++}.
4479 If these probes are not present, then these features cannot be used.
4480 These probes were first available in the GCC 4.8 release, but whether
4481 or not they are available in your GCC also depends on how it was
4485 The @code{$_exception} convenience variable is only valid at the
4486 instruction at which an exception-related catchpoint is set.
4489 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4490 location in the system library which implements runtime exception
4491 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4492 (@pxref{Selection}) to get to your code.
4495 If you call a function interactively, @value{GDBN} normally returns
4496 control to you when the function has finished executing. If the call
4497 raises an exception, however, the call may bypass the mechanism that
4498 returns control to you and cause your program either to abort or to
4499 simply continue running until it hits a breakpoint, catches a signal
4500 that @value{GDBN} is listening for, or exits. This is the case even if
4501 you set a catchpoint for the exception; catchpoints on exceptions are
4502 disabled within interactive calls. @xref{Calling}, for information on
4503 controlling this with @code{set unwind-on-terminating-exception}.
4506 You cannot raise an exception interactively.
4509 You cannot install an exception handler interactively.
4513 @kindex catch exception
4514 @cindex Ada exception catching
4515 @cindex catch Ada exceptions
4516 An Ada exception being raised. If an exception name is specified
4517 at the end of the command (eg @code{catch exception Program_Error}),
4518 the debugger will stop only when this specific exception is raised.
4519 Otherwise, the debugger stops execution when any Ada exception is raised.
4521 When inserting an exception catchpoint on a user-defined exception whose
4522 name is identical to one of the exceptions defined by the language, the
4523 fully qualified name must be used as the exception name. Otherwise,
4524 @value{GDBN} will assume that it should stop on the pre-defined exception
4525 rather than the user-defined one. For instance, assuming an exception
4526 called @code{Constraint_Error} is defined in package @code{Pck}, then
4527 the command to use to catch such exceptions is @kbd{catch exception
4528 Pck.Constraint_Error}.
4531 @kindex catch handlers
4532 @cindex Ada exception handlers catching
4533 @cindex catch Ada exceptions when handled
4534 An Ada exception being handled. If an exception name is
4535 specified at the end of the command
4536 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4537 only when this specific exception is handled.
4538 Otherwise, the debugger stops execution when any Ada exception is handled.
4540 When inserting a handlers catchpoint on a user-defined
4541 exception whose name is identical to one of the exceptions
4542 defined by the language, the fully qualified name must be used
4543 as the exception name. Otherwise, @value{GDBN} will assume that it
4544 should stop on the pre-defined exception rather than the
4545 user-defined one. For instance, assuming an exception called
4546 @code{Constraint_Error} is defined in package @code{Pck}, then the
4547 command to use to catch such exceptions handling is
4548 @kbd{catch handlers Pck.Constraint_Error}.
4550 @item exception unhandled
4551 @kindex catch exception unhandled
4552 An exception that was raised but is not handled by the program.
4555 @kindex catch assert
4556 A failed Ada assertion.
4560 @cindex break on fork/exec
4561 A call to @code{exec}.
4564 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4565 @kindex catch syscall
4566 @cindex break on a system call.
4567 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4568 syscall is a mechanism for application programs to request a service
4569 from the operating system (OS) or one of the OS system services.
4570 @value{GDBN} can catch some or all of the syscalls issued by the
4571 debuggee, and show the related information for each syscall. If no
4572 argument is specified, calls to and returns from all system calls
4575 @var{name} can be any system call name that is valid for the
4576 underlying OS. Just what syscalls are valid depends on the OS. On
4577 GNU and Unix systems, you can find the full list of valid syscall
4578 names on @file{/usr/include/asm/unistd.h}.
4580 @c For MS-Windows, the syscall names and the corresponding numbers
4581 @c can be found, e.g., on this URL:
4582 @c http://www.metasploit.com/users/opcode/syscalls.html
4583 @c but we don't support Windows syscalls yet.
4585 Normally, @value{GDBN} knows in advance which syscalls are valid for
4586 each OS, so you can use the @value{GDBN} command-line completion
4587 facilities (@pxref{Completion,, command completion}) to list the
4590 You may also specify the system call numerically. A syscall's
4591 number is the value passed to the OS's syscall dispatcher to
4592 identify the requested service. When you specify the syscall by its
4593 name, @value{GDBN} uses its database of syscalls to convert the name
4594 into the corresponding numeric code, but using the number directly
4595 may be useful if @value{GDBN}'s database does not have the complete
4596 list of syscalls on your system (e.g., because @value{GDBN} lags
4597 behind the OS upgrades).
4599 You may specify a group of related syscalls to be caught at once using
4600 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4601 instance, on some platforms @value{GDBN} allows you to catch all
4602 network related syscalls, by passing the argument @code{group:network}
4603 to @code{catch syscall}. Note that not all syscall groups are
4604 available in every system. You can use the command completion
4605 facilities (@pxref{Completion,, command completion}) to list the
4606 syscall groups available on your environment.
4608 The example below illustrates how this command works if you don't provide
4612 (@value{GDBP}) catch syscall
4613 Catchpoint 1 (syscall)
4615 Starting program: /tmp/catch-syscall
4617 Catchpoint 1 (call to syscall 'close'), \
4618 0xffffe424 in __kernel_vsyscall ()
4622 Catchpoint 1 (returned from syscall 'close'), \
4623 0xffffe424 in __kernel_vsyscall ()
4627 Here is an example of catching a system call by name:
4630 (@value{GDBP}) catch syscall chroot
4631 Catchpoint 1 (syscall 'chroot' [61])
4633 Starting program: /tmp/catch-syscall
4635 Catchpoint 1 (call to syscall 'chroot'), \
4636 0xffffe424 in __kernel_vsyscall ()
4640 Catchpoint 1 (returned from syscall 'chroot'), \
4641 0xffffe424 in __kernel_vsyscall ()
4645 An example of specifying a system call numerically. In the case
4646 below, the syscall number has a corresponding entry in the XML
4647 file, so @value{GDBN} finds its name and prints it:
4650 (@value{GDBP}) catch syscall 252
4651 Catchpoint 1 (syscall(s) 'exit_group')
4653 Starting program: /tmp/catch-syscall
4655 Catchpoint 1 (call to syscall 'exit_group'), \
4656 0xffffe424 in __kernel_vsyscall ()
4660 Program exited normally.
4664 Here is an example of catching a syscall group:
4667 (@value{GDBP}) catch syscall group:process
4668 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4669 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4670 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4672 Starting program: /tmp/catch-syscall
4674 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4675 from /lib64/ld-linux-x86-64.so.2
4681 However, there can be situations when there is no corresponding name
4682 in XML file for that syscall number. In this case, @value{GDBN} prints
4683 a warning message saying that it was not able to find the syscall name,
4684 but the catchpoint will be set anyway. See the example below:
4687 (@value{GDBP}) catch syscall 764
4688 warning: The number '764' does not represent a known syscall.
4689 Catchpoint 2 (syscall 764)
4693 If you configure @value{GDBN} using the @samp{--without-expat} option,
4694 it will not be able to display syscall names. Also, if your
4695 architecture does not have an XML file describing its system calls,
4696 you will not be able to see the syscall names. It is important to
4697 notice that these two features are used for accessing the syscall
4698 name database. In either case, you will see a warning like this:
4701 (@value{GDBP}) catch syscall
4702 warning: Could not open "syscalls/i386-linux.xml"
4703 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4704 GDB will not be able to display syscall names.
4705 Catchpoint 1 (syscall)
4709 Of course, the file name will change depending on your architecture and system.
4711 Still using the example above, you can also try to catch a syscall by its
4712 number. In this case, you would see something like:
4715 (@value{GDBP}) catch syscall 252
4716 Catchpoint 1 (syscall(s) 252)
4719 Again, in this case @value{GDBN} would not be able to display syscall's names.
4723 A call to @code{fork}.
4727 A call to @code{vfork}.
4729 @item load @r{[}regexp@r{]}
4730 @itemx unload @r{[}regexp@r{]}
4732 @kindex catch unload
4733 The loading or unloading of a shared library. If @var{regexp} is
4734 given, then the catchpoint will stop only if the regular expression
4735 matches one of the affected libraries.
4737 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4738 @kindex catch signal
4739 The delivery of a signal.
4741 With no arguments, this catchpoint will catch any signal that is not
4742 used internally by @value{GDBN}, specifically, all signals except
4743 @samp{SIGTRAP} and @samp{SIGINT}.
4745 With the argument @samp{all}, all signals, including those used by
4746 @value{GDBN}, will be caught. This argument cannot be used with other
4749 Otherwise, the arguments are a list of signal names as given to
4750 @code{handle} (@pxref{Signals}). Only signals specified in this list
4753 One reason that @code{catch signal} can be more useful than
4754 @code{handle} is that you can attach commands and conditions to the
4757 When a signal is caught by a catchpoint, the signal's @code{stop} and
4758 @code{print} settings, as specified by @code{handle}, are ignored.
4759 However, whether the signal is still delivered to the inferior depends
4760 on the @code{pass} setting; this can be changed in the catchpoint's
4765 @item tcatch @var{event}
4767 Set a catchpoint that is enabled only for one stop. The catchpoint is
4768 automatically deleted after the first time the event is caught.
4772 Use the @code{info break} command to list the current catchpoints.
4776 @subsection Deleting Breakpoints
4778 @cindex clearing breakpoints, watchpoints, catchpoints
4779 @cindex deleting breakpoints, watchpoints, catchpoints
4780 It is often necessary to eliminate a breakpoint, watchpoint, or
4781 catchpoint once it has done its job and you no longer want your program
4782 to stop there. This is called @dfn{deleting} the breakpoint. A
4783 breakpoint that has been deleted no longer exists; it is forgotten.
4785 With the @code{clear} command you can delete breakpoints according to
4786 where they are in your program. With the @code{delete} command you can
4787 delete individual breakpoints, watchpoints, or catchpoints by specifying
4788 their breakpoint numbers.
4790 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4791 automatically ignores breakpoints on the first instruction to be executed
4792 when you continue execution without changing the execution address.
4797 Delete any breakpoints at the next instruction to be executed in the
4798 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4799 the innermost frame is selected, this is a good way to delete a
4800 breakpoint where your program just stopped.
4802 @item clear @var{location}
4803 Delete any breakpoints set at the specified @var{location}.
4804 @xref{Specify Location}, for the various forms of @var{location}; the
4805 most useful ones are listed below:
4808 @item clear @var{function}
4809 @itemx clear @var{filename}:@var{function}
4810 Delete any breakpoints set at entry to the named @var{function}.
4812 @item clear @var{linenum}
4813 @itemx clear @var{filename}:@var{linenum}
4814 Delete any breakpoints set at or within the code of the specified
4815 @var{linenum} of the specified @var{filename}.
4818 @cindex delete breakpoints
4820 @kindex d @r{(@code{delete})}
4821 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4822 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4823 list specified as argument. If no argument is specified, delete all
4824 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4825 confirm off}). You can abbreviate this command as @code{d}.
4829 @subsection Disabling Breakpoints
4831 @cindex enable/disable a breakpoint
4832 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4833 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4834 it had been deleted, but remembers the information on the breakpoint so
4835 that you can @dfn{enable} it again later.
4837 You disable and enable breakpoints, watchpoints, and catchpoints with
4838 the @code{enable} and @code{disable} commands, optionally specifying
4839 one or more breakpoint numbers as arguments. Use @code{info break} to
4840 print a list of all breakpoints, watchpoints, and catchpoints if you
4841 do not know which numbers to use.
4843 Disabling and enabling a breakpoint that has multiple locations
4844 affects all of its locations.
4846 A breakpoint, watchpoint, or catchpoint can have any of several
4847 different states of enablement:
4851 Enabled. The breakpoint stops your program. A breakpoint set
4852 with the @code{break} command starts out in this state.
4854 Disabled. The breakpoint has no effect on your program.
4856 Enabled once. The breakpoint stops your program, but then becomes
4859 Enabled for a count. The breakpoint stops your program for the next
4860 N times, then becomes disabled.
4862 Enabled for deletion. The breakpoint stops your program, but
4863 immediately after it does so it is deleted permanently. A breakpoint
4864 set with the @code{tbreak} command starts out in this state.
4867 You can use the following commands to enable or disable breakpoints,
4868 watchpoints, and catchpoints:
4872 @kindex dis @r{(@code{disable})}
4873 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4874 Disable the specified breakpoints---or all breakpoints, if none are
4875 listed. A disabled breakpoint has no effect but is not forgotten. All
4876 options such as ignore-counts, conditions and commands are remembered in
4877 case the breakpoint is enabled again later. You may abbreviate
4878 @code{disable} as @code{dis}.
4881 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4882 Enable the specified breakpoints (or all defined breakpoints). They
4883 become effective once again in stopping your program.
4885 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4886 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4887 of these breakpoints immediately after stopping your program.
4889 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4890 Enable the specified breakpoints temporarily. @value{GDBN} records
4891 @var{count} with each of the specified breakpoints, and decrements a
4892 breakpoint's count when it is hit. When any count reaches 0,
4893 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4894 count (@pxref{Conditions, ,Break Conditions}), that will be
4895 decremented to 0 before @var{count} is affected.
4897 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4898 Enable the specified breakpoints to work once, then die. @value{GDBN}
4899 deletes any of these breakpoints as soon as your program stops there.
4900 Breakpoints set by the @code{tbreak} command start out in this state.
4903 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4904 @c confusing: tbreak is also initially enabled.
4905 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4906 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4907 subsequently, they become disabled or enabled only when you use one of
4908 the commands above. (The command @code{until} can set and delete a
4909 breakpoint of its own, but it does not change the state of your other
4910 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4914 @subsection Break Conditions
4915 @cindex conditional breakpoints
4916 @cindex breakpoint conditions
4918 @c FIXME what is scope of break condition expr? Context where wanted?
4919 @c in particular for a watchpoint?
4920 The simplest sort of breakpoint breaks every time your program reaches a
4921 specified place. You can also specify a @dfn{condition} for a
4922 breakpoint. A condition is just a Boolean expression in your
4923 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4924 a condition evaluates the expression each time your program reaches it,
4925 and your program stops only if the condition is @emph{true}.
4927 This is the converse of using assertions for program validation; in that
4928 situation, you want to stop when the assertion is violated---that is,
4929 when the condition is false. In C, if you want to test an assertion expressed
4930 by the condition @var{assert}, you should set the condition
4931 @samp{! @var{assert}} on the appropriate breakpoint.
4933 Conditions are also accepted for watchpoints; you may not need them,
4934 since a watchpoint is inspecting the value of an expression anyhow---but
4935 it might be simpler, say, to just set a watchpoint on a variable name,
4936 and specify a condition that tests whether the new value is an interesting
4939 Break conditions can have side effects, and may even call functions in
4940 your program. This can be useful, for example, to activate functions
4941 that log program progress, or to use your own print functions to
4942 format special data structures. The effects are completely predictable
4943 unless there is another enabled breakpoint at the same address. (In
4944 that case, @value{GDBN} might see the other breakpoint first and stop your
4945 program without checking the condition of this one.) Note that
4946 breakpoint commands are usually more convenient and flexible than break
4948 purpose of performing side effects when a breakpoint is reached
4949 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4951 Breakpoint conditions can also be evaluated on the target's side if
4952 the target supports it. Instead of evaluating the conditions locally,
4953 @value{GDBN} encodes the expression into an agent expression
4954 (@pxref{Agent Expressions}) suitable for execution on the target,
4955 independently of @value{GDBN}. Global variables become raw memory
4956 locations, locals become stack accesses, and so forth.
4958 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4959 when its condition evaluates to true. This mechanism may provide faster
4960 response times depending on the performance characteristics of the target
4961 since it does not need to keep @value{GDBN} informed about
4962 every breakpoint trigger, even those with false conditions.
4964 Break conditions can be specified when a breakpoint is set, by using
4965 @samp{if} in the arguments to the @code{break} command. @xref{Set
4966 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4967 with the @code{condition} command.
4969 You can also use the @code{if} keyword with the @code{watch} command.
4970 The @code{catch} command does not recognize the @code{if} keyword;
4971 @code{condition} is the only way to impose a further condition on a
4976 @item condition @var{bnum} @var{expression}
4977 Specify @var{expression} as the break condition for breakpoint,
4978 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4979 breakpoint @var{bnum} stops your program only if the value of
4980 @var{expression} is true (nonzero, in C). When you use
4981 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4982 syntactic correctness, and to determine whether symbols in it have
4983 referents in the context of your breakpoint. If @var{expression} uses
4984 symbols not referenced in the context of the breakpoint, @value{GDBN}
4985 prints an error message:
4988 No symbol "foo" in current context.
4993 not actually evaluate @var{expression} at the time the @code{condition}
4994 command (or a command that sets a breakpoint with a condition, like
4995 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4997 @item condition @var{bnum}
4998 Remove the condition from breakpoint number @var{bnum}. It becomes
4999 an ordinary unconditional breakpoint.
5002 @cindex ignore count (of breakpoint)
5003 A special case of a breakpoint condition is to stop only when the
5004 breakpoint has been reached a certain number of times. This is so
5005 useful that there is a special way to do it, using the @dfn{ignore
5006 count} of the breakpoint. Every breakpoint has an ignore count, which
5007 is an integer. Most of the time, the ignore count is zero, and
5008 therefore has no effect. But if your program reaches a breakpoint whose
5009 ignore count is positive, then instead of stopping, it just decrements
5010 the ignore count by one and continues. As a result, if the ignore count
5011 value is @var{n}, the breakpoint does not stop the next @var{n} times
5012 your program reaches it.
5016 @item ignore @var{bnum} @var{count}
5017 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5018 The next @var{count} times the breakpoint is reached, your program's
5019 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5022 To make the breakpoint stop the next time it is reached, specify
5025 When you use @code{continue} to resume execution of your program from a
5026 breakpoint, you can specify an ignore count directly as an argument to
5027 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5028 Stepping,,Continuing and Stepping}.
5030 If a breakpoint has a positive ignore count and a condition, the
5031 condition is not checked. Once the ignore count reaches zero,
5032 @value{GDBN} resumes checking the condition.
5034 You could achieve the effect of the ignore count with a condition such
5035 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5036 is decremented each time. @xref{Convenience Vars, ,Convenience
5040 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5043 @node Break Commands
5044 @subsection Breakpoint Command Lists
5046 @cindex breakpoint commands
5047 You can give any breakpoint (or watchpoint or catchpoint) a series of
5048 commands to execute when your program stops due to that breakpoint. For
5049 example, you might want to print the values of certain expressions, or
5050 enable other breakpoints.
5054 @kindex end@r{ (breakpoint commands)}
5055 @item commands @r{[}@var{list}@dots{}@r{]}
5056 @itemx @dots{} @var{command-list} @dots{}
5058 Specify a list of commands for the given breakpoints. The commands
5059 themselves appear on the following lines. Type a line containing just
5060 @code{end} to terminate the commands.
5062 To remove all commands from a breakpoint, type @code{commands} and
5063 follow it immediately with @code{end}; that is, give no commands.
5065 With no argument, @code{commands} refers to the last breakpoint,
5066 watchpoint, or catchpoint set (not to the breakpoint most recently
5067 encountered). If the most recent breakpoints were set with a single
5068 command, then the @code{commands} will apply to all the breakpoints
5069 set by that command. This applies to breakpoints set by
5070 @code{rbreak}, and also applies when a single @code{break} command
5071 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5075 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5076 disabled within a @var{command-list}.
5078 You can use breakpoint commands to start your program up again. Simply
5079 use the @code{continue} command, or @code{step}, or any other command
5080 that resumes execution.
5082 Any other commands in the command list, after a command that resumes
5083 execution, are ignored. This is because any time you resume execution
5084 (even with a simple @code{next} or @code{step}), you may encounter
5085 another breakpoint---which could have its own command list, leading to
5086 ambiguities about which list to execute.
5089 If the first command you specify in a command list is @code{silent}, the
5090 usual message about stopping at a breakpoint is not printed. This may
5091 be desirable for breakpoints that are to print a specific message and
5092 then continue. If none of the remaining commands print anything, you
5093 see no sign that the breakpoint was reached. @code{silent} is
5094 meaningful only at the beginning of a breakpoint command list.
5096 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5097 print precisely controlled output, and are often useful in silent
5098 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5100 For example, here is how you could use breakpoint commands to print the
5101 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5107 printf "x is %d\n",x
5112 One application for breakpoint commands is to compensate for one bug so
5113 you can test for another. Put a breakpoint just after the erroneous line
5114 of code, give it a condition to detect the case in which something
5115 erroneous has been done, and give it commands to assign correct values
5116 to any variables that need them. End with the @code{continue} command
5117 so that your program does not stop, and start with the @code{silent}
5118 command so that no output is produced. Here is an example:
5129 @node Dynamic Printf
5130 @subsection Dynamic Printf
5132 @cindex dynamic printf
5134 The dynamic printf command @code{dprintf} combines a breakpoint with
5135 formatted printing of your program's data to give you the effect of
5136 inserting @code{printf} calls into your program on-the-fly, without
5137 having to recompile it.
5139 In its most basic form, the output goes to the GDB console. However,
5140 you can set the variable @code{dprintf-style} for alternate handling.
5141 For instance, you can ask to format the output by calling your
5142 program's @code{printf} function. This has the advantage that the
5143 characters go to the program's output device, so they can recorded in
5144 redirects to files and so forth.
5146 If you are doing remote debugging with a stub or agent, you can also
5147 ask to have the printf handled by the remote agent. In addition to
5148 ensuring that the output goes to the remote program's device along
5149 with any other output the program might produce, you can also ask that
5150 the dprintf remain active even after disconnecting from the remote
5151 target. Using the stub/agent is also more efficient, as it can do
5152 everything without needing to communicate with @value{GDBN}.
5156 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5157 Whenever execution reaches @var{location}, print the values of one or
5158 more @var{expressions} under the control of the string @var{template}.
5159 To print several values, separate them with commas.
5161 @item set dprintf-style @var{style}
5162 Set the dprintf output to be handled in one of several different
5163 styles enumerated below. A change of style affects all existing
5164 dynamic printfs immediately. (If you need individual control over the
5165 print commands, simply define normal breakpoints with
5166 explicitly-supplied command lists.)
5170 @kindex dprintf-style gdb
5171 Handle the output using the @value{GDBN} @code{printf} command.
5174 @kindex dprintf-style call
5175 Handle the output by calling a function in your program (normally
5179 @kindex dprintf-style agent
5180 Have the remote debugging agent (such as @code{gdbserver}) handle
5181 the output itself. This style is only available for agents that
5182 support running commands on the target.
5185 @item set dprintf-function @var{function}
5186 Set the function to call if the dprintf style is @code{call}. By
5187 default its value is @code{printf}. You may set it to any expression.
5188 that @value{GDBN} can evaluate to a function, as per the @code{call}
5191 @item set dprintf-channel @var{channel}
5192 Set a ``channel'' for dprintf. If set to a non-empty value,
5193 @value{GDBN} will evaluate it as an expression and pass the result as
5194 a first argument to the @code{dprintf-function}, in the manner of
5195 @code{fprintf} and similar functions. Otherwise, the dprintf format
5196 string will be the first argument, in the manner of @code{printf}.
5198 As an example, if you wanted @code{dprintf} output to go to a logfile
5199 that is a standard I/O stream assigned to the variable @code{mylog},
5200 you could do the following:
5203 (gdb) set dprintf-style call
5204 (gdb) set dprintf-function fprintf
5205 (gdb) set dprintf-channel mylog
5206 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5207 Dprintf 1 at 0x123456: file main.c, line 25.
5209 1 dprintf keep y 0x00123456 in main at main.c:25
5210 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5215 Note that the @code{info break} displays the dynamic printf commands
5216 as normal breakpoint commands; you can thus easily see the effect of
5217 the variable settings.
5219 @item set disconnected-dprintf on
5220 @itemx set disconnected-dprintf off
5221 @kindex set disconnected-dprintf
5222 Choose whether @code{dprintf} commands should continue to run if
5223 @value{GDBN} has disconnected from the target. This only applies
5224 if the @code{dprintf-style} is @code{agent}.
5226 @item show disconnected-dprintf off
5227 @kindex show disconnected-dprintf
5228 Show the current choice for disconnected @code{dprintf}.
5232 @value{GDBN} does not check the validity of function and channel,
5233 relying on you to supply values that are meaningful for the contexts
5234 in which they are being used. For instance, the function and channel
5235 may be the values of local variables, but if that is the case, then
5236 all enabled dynamic prints must be at locations within the scope of
5237 those locals. If evaluation fails, @value{GDBN} will report an error.
5239 @node Save Breakpoints
5240 @subsection How to save breakpoints to a file
5242 To save breakpoint definitions to a file use the @w{@code{save
5243 breakpoints}} command.
5246 @kindex save breakpoints
5247 @cindex save breakpoints to a file for future sessions
5248 @item save breakpoints [@var{filename}]
5249 This command saves all current breakpoint definitions together with
5250 their commands and ignore counts, into a file @file{@var{filename}}
5251 suitable for use in a later debugging session. This includes all
5252 types of breakpoints (breakpoints, watchpoints, catchpoints,
5253 tracepoints). To read the saved breakpoint definitions, use the
5254 @code{source} command (@pxref{Command Files}). Note that watchpoints
5255 with expressions involving local variables may fail to be recreated
5256 because it may not be possible to access the context where the
5257 watchpoint is valid anymore. Because the saved breakpoint definitions
5258 are simply a sequence of @value{GDBN} commands that recreate the
5259 breakpoints, you can edit the file in your favorite editing program,
5260 and remove the breakpoint definitions you're not interested in, or
5261 that can no longer be recreated.
5264 @node Static Probe Points
5265 @subsection Static Probe Points
5267 @cindex static probe point, SystemTap
5268 @cindex static probe point, DTrace
5269 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5270 for Statically Defined Tracing, and the probes are designed to have a tiny
5271 runtime code and data footprint, and no dynamic relocations.
5273 Currently, the following types of probes are supported on
5274 ELF-compatible systems:
5278 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5279 @acronym{SDT} probes@footnote{See
5280 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5281 for more information on how to add @code{SystemTap} @acronym{SDT}
5282 probes in your applications.}. @code{SystemTap} probes are usable
5283 from assembly, C and C@t{++} languages@footnote{See
5284 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5285 for a good reference on how the @acronym{SDT} probes are implemented.}.
5287 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5288 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5292 @cindex semaphores on static probe points
5293 Some @code{SystemTap} probes have an associated semaphore variable;
5294 for instance, this happens automatically if you defined your probe
5295 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5296 @value{GDBN} will automatically enable it when you specify a
5297 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5298 breakpoint at a probe's location by some other method (e.g.,
5299 @code{break file:line}), then @value{GDBN} will not automatically set
5300 the semaphore. @code{DTrace} probes do not support semaphores.
5302 You can examine the available static static probes using @code{info
5303 probes}, with optional arguments:
5307 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5308 If given, @var{type} is either @code{stap} for listing
5309 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5310 probes. If omitted all probes are listed regardless of their types.
5312 If given, @var{provider} is a regular expression used to match against provider
5313 names when selecting which probes to list. If omitted, probes by all
5314 probes from all providers are listed.
5316 If given, @var{name} is a regular expression to match against probe names
5317 when selecting which probes to list. If omitted, probe names are not
5318 considered when deciding whether to display them.
5320 If given, @var{objfile} is a regular expression used to select which
5321 object files (executable or shared libraries) to examine. If not
5322 given, all object files are considered.
5324 @item info probes all
5325 List the available static probes, from all types.
5328 @cindex enabling and disabling probes
5329 Some probe points can be enabled and/or disabled. The effect of
5330 enabling or disabling a probe depends on the type of probe being
5331 handled. Some @code{DTrace} probes can be enabled or
5332 disabled, but @code{SystemTap} probes cannot be disabled.
5334 You can enable (or disable) one or more probes using the following
5335 commands, with optional arguments:
5338 @kindex enable probes
5339 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5340 If given, @var{provider} is a regular expression used to match against
5341 provider names when selecting which probes to enable. If omitted,
5342 all probes from all providers are enabled.
5344 If given, @var{name} is a regular expression to match against probe
5345 names when selecting which probes to enable. If omitted, probe names
5346 are not considered when deciding whether to enable them.
5348 If given, @var{objfile} is a regular expression used to select which
5349 object files (executable or shared libraries) to examine. If not
5350 given, all object files are considered.
5352 @kindex disable probes
5353 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5354 See the @code{enable probes} command above for a description of the
5355 optional arguments accepted by this command.
5358 @vindex $_probe_arg@r{, convenience variable}
5359 A probe may specify up to twelve arguments. These are available at the
5360 point at which the probe is defined---that is, when the current PC is
5361 at the probe's location. The arguments are available using the
5362 convenience variables (@pxref{Convenience Vars})
5363 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5364 probes each probe argument is an integer of the appropriate size;
5365 types are not preserved. In @code{DTrace} probes types are preserved
5366 provided that they are recognized as such by @value{GDBN}; otherwise
5367 the value of the probe argument will be a long integer. The
5368 convenience variable @code{$_probe_argc} holds the number of arguments
5369 at the current probe point.
5371 These variables are always available, but attempts to access them at
5372 any location other than a probe point will cause @value{GDBN} to give
5376 @c @ifclear BARETARGET
5377 @node Error in Breakpoints
5378 @subsection ``Cannot insert breakpoints''
5380 If you request too many active hardware-assisted breakpoints and
5381 watchpoints, you will see this error message:
5383 @c FIXME: the precise wording of this message may change; the relevant
5384 @c source change is not committed yet (Sep 3, 1999).
5386 Stopped; cannot insert breakpoints.
5387 You may have requested too many hardware breakpoints and watchpoints.
5391 This message is printed when you attempt to resume the program, since
5392 only then @value{GDBN} knows exactly how many hardware breakpoints and
5393 watchpoints it needs to insert.
5395 When this message is printed, you need to disable or remove some of the
5396 hardware-assisted breakpoints and watchpoints, and then continue.
5398 @node Breakpoint-related Warnings
5399 @subsection ``Breakpoint address adjusted...''
5400 @cindex breakpoint address adjusted
5402 Some processor architectures place constraints on the addresses at
5403 which breakpoints may be placed. For architectures thus constrained,
5404 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5405 with the constraints dictated by the architecture.
5407 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5408 a VLIW architecture in which a number of RISC-like instructions may be
5409 bundled together for parallel execution. The FR-V architecture
5410 constrains the location of a breakpoint instruction within such a
5411 bundle to the instruction with the lowest address. @value{GDBN}
5412 honors this constraint by adjusting a breakpoint's address to the
5413 first in the bundle.
5415 It is not uncommon for optimized code to have bundles which contain
5416 instructions from different source statements, thus it may happen that
5417 a breakpoint's address will be adjusted from one source statement to
5418 another. Since this adjustment may significantly alter @value{GDBN}'s
5419 breakpoint related behavior from what the user expects, a warning is
5420 printed when the breakpoint is first set and also when the breakpoint
5423 A warning like the one below is printed when setting a breakpoint
5424 that's been subject to address adjustment:
5427 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5430 Such warnings are printed both for user settable and @value{GDBN}'s
5431 internal breakpoints. If you see one of these warnings, you should
5432 verify that a breakpoint set at the adjusted address will have the
5433 desired affect. If not, the breakpoint in question may be removed and
5434 other breakpoints may be set which will have the desired behavior.
5435 E.g., it may be sufficient to place the breakpoint at a later
5436 instruction. A conditional breakpoint may also be useful in some
5437 cases to prevent the breakpoint from triggering too often.
5439 @value{GDBN} will also issue a warning when stopping at one of these
5440 adjusted breakpoints:
5443 warning: Breakpoint 1 address previously adjusted from 0x00010414
5447 When this warning is encountered, it may be too late to take remedial
5448 action except in cases where the breakpoint is hit earlier or more
5449 frequently than expected.
5451 @node Continuing and Stepping
5452 @section Continuing and Stepping
5456 @cindex resuming execution
5457 @dfn{Continuing} means resuming program execution until your program
5458 completes normally. In contrast, @dfn{stepping} means executing just
5459 one more ``step'' of your program, where ``step'' may mean either one
5460 line of source code, or one machine instruction (depending on what
5461 particular command you use). Either when continuing or when stepping,
5462 your program may stop even sooner, due to a breakpoint or a signal. (If
5463 it stops due to a signal, you may want to use @code{handle}, or use
5464 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5465 or you may step into the signal's handler (@pxref{stepping and signal
5470 @kindex c @r{(@code{continue})}
5471 @kindex fg @r{(resume foreground execution)}
5472 @item continue @r{[}@var{ignore-count}@r{]}
5473 @itemx c @r{[}@var{ignore-count}@r{]}
5474 @itemx fg @r{[}@var{ignore-count}@r{]}
5475 Resume program execution, at the address where your program last stopped;
5476 any breakpoints set at that address are bypassed. The optional argument
5477 @var{ignore-count} allows you to specify a further number of times to
5478 ignore a breakpoint at this location; its effect is like that of
5479 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5481 The argument @var{ignore-count} is meaningful only when your program
5482 stopped due to a breakpoint. At other times, the argument to
5483 @code{continue} is ignored.
5485 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5486 debugged program is deemed to be the foreground program) are provided
5487 purely for convenience, and have exactly the same behavior as
5491 To resume execution at a different place, you can use @code{return}
5492 (@pxref{Returning, ,Returning from a Function}) to go back to the
5493 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5494 Different Address}) to go to an arbitrary location in your program.
5496 A typical technique for using stepping is to set a breakpoint
5497 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5498 beginning of the function or the section of your program where a problem
5499 is believed to lie, run your program until it stops at that breakpoint,
5500 and then step through the suspect area, examining the variables that are
5501 interesting, until you see the problem happen.
5505 @kindex s @r{(@code{step})}
5507 Continue running your program until control reaches a different source
5508 line, then stop it and return control to @value{GDBN}. This command is
5509 abbreviated @code{s}.
5512 @c "without debugging information" is imprecise; actually "without line
5513 @c numbers in the debugging information". (gcc -g1 has debugging info but
5514 @c not line numbers). But it seems complex to try to make that
5515 @c distinction here.
5516 @emph{Warning:} If you use the @code{step} command while control is
5517 within a function that was compiled without debugging information,
5518 execution proceeds until control reaches a function that does have
5519 debugging information. Likewise, it will not step into a function which
5520 is compiled without debugging information. To step through functions
5521 without debugging information, use the @code{stepi} command, described
5525 The @code{step} command only stops at the first instruction of a source
5526 line. This prevents the multiple stops that could otherwise occur in
5527 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5528 to stop if a function that has debugging information is called within
5529 the line. In other words, @code{step} @emph{steps inside} any functions
5530 called within the line.
5532 Also, the @code{step} command only enters a function if there is line
5533 number information for the function. Otherwise it acts like the
5534 @code{next} command. This avoids problems when using @code{cc -gl}
5535 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5536 was any debugging information about the routine.
5538 @item step @var{count}
5539 Continue running as in @code{step}, but do so @var{count} times. If a
5540 breakpoint is reached, or a signal not related to stepping occurs before
5541 @var{count} steps, stepping stops right away.
5544 @kindex n @r{(@code{next})}
5545 @item next @r{[}@var{count}@r{]}
5546 Continue to the next source line in the current (innermost) stack frame.
5547 This is similar to @code{step}, but function calls that appear within
5548 the line of code are executed without stopping. Execution stops when
5549 control reaches a different line of code at the original stack level
5550 that was executing when you gave the @code{next} command. This command
5551 is abbreviated @code{n}.
5553 An argument @var{count} is a repeat count, as for @code{step}.
5556 @c FIX ME!! Do we delete this, or is there a way it fits in with
5557 @c the following paragraph? --- Vctoria
5559 @c @code{next} within a function that lacks debugging information acts like
5560 @c @code{step}, but any function calls appearing within the code of the
5561 @c function are executed without stopping.
5563 The @code{next} command only stops at the first instruction of a
5564 source line. This prevents multiple stops that could otherwise occur in
5565 @code{switch} statements, @code{for} loops, etc.
5567 @kindex set step-mode
5569 @cindex functions without line info, and stepping
5570 @cindex stepping into functions with no line info
5571 @itemx set step-mode on
5572 The @code{set step-mode on} command causes the @code{step} command to
5573 stop at the first instruction of a function which contains no debug line
5574 information rather than stepping over it.
5576 This is useful in cases where you may be interested in inspecting the
5577 machine instructions of a function which has no symbolic info and do not
5578 want @value{GDBN} to automatically skip over this function.
5580 @item set step-mode off
5581 Causes the @code{step} command to step over any functions which contains no
5582 debug information. This is the default.
5584 @item show step-mode
5585 Show whether @value{GDBN} will stop in or step over functions without
5586 source line debug information.
5589 @kindex fin @r{(@code{finish})}
5591 Continue running until just after function in the selected stack frame
5592 returns. Print the returned value (if any). This command can be
5593 abbreviated as @code{fin}.
5595 Contrast this with the @code{return} command (@pxref{Returning,
5596 ,Returning from a Function}).
5599 @kindex u @r{(@code{until})}
5600 @cindex run until specified location
5603 Continue running until a source line past the current line, in the
5604 current stack frame, is reached. This command is used to avoid single
5605 stepping through a loop more than once. It is like the @code{next}
5606 command, except that when @code{until} encounters a jump, it
5607 automatically continues execution until the program counter is greater
5608 than the address of the jump.
5610 This means that when you reach the end of a loop after single stepping
5611 though it, @code{until} makes your program continue execution until it
5612 exits the loop. In contrast, a @code{next} command at the end of a loop
5613 simply steps back to the beginning of the loop, which forces you to step
5614 through the next iteration.
5616 @code{until} always stops your program if it attempts to exit the current
5619 @code{until} may produce somewhat counterintuitive results if the order
5620 of machine code does not match the order of the source lines. For
5621 example, in the following excerpt from a debugging session, the @code{f}
5622 (@code{frame}) command shows that execution is stopped at line
5623 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5627 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5629 (@value{GDBP}) until
5630 195 for ( ; argc > 0; NEXTARG) @{
5633 This happened because, for execution efficiency, the compiler had
5634 generated code for the loop closure test at the end, rather than the
5635 start, of the loop---even though the test in a C @code{for}-loop is
5636 written before the body of the loop. The @code{until} command appeared
5637 to step back to the beginning of the loop when it advanced to this
5638 expression; however, it has not really gone to an earlier
5639 statement---not in terms of the actual machine code.
5641 @code{until} with no argument works by means of single
5642 instruction stepping, and hence is slower than @code{until} with an
5645 @item until @var{location}
5646 @itemx u @var{location}
5647 Continue running your program until either the specified @var{location} is
5648 reached, or the current stack frame returns. The location is any of
5649 the forms described in @ref{Specify Location}.
5650 This form of the command uses temporary breakpoints, and
5651 hence is quicker than @code{until} without an argument. The specified
5652 location is actually reached only if it is in the current frame. This
5653 implies that @code{until} can be used to skip over recursive function
5654 invocations. For instance in the code below, if the current location is
5655 line @code{96}, issuing @code{until 99} will execute the program up to
5656 line @code{99} in the same invocation of factorial, i.e., after the inner
5657 invocations have returned.
5660 94 int factorial (int value)
5662 96 if (value > 1) @{
5663 97 value *= factorial (value - 1);
5670 @kindex advance @var{location}
5671 @item advance @var{location}
5672 Continue running the program up to the given @var{location}. An argument is
5673 required, which should be of one of the forms described in
5674 @ref{Specify Location}.
5675 Execution will also stop upon exit from the current stack
5676 frame. This command is similar to @code{until}, but @code{advance} will
5677 not skip over recursive function calls, and the target location doesn't
5678 have to be in the same frame as the current one.
5682 @kindex si @r{(@code{stepi})}
5684 @itemx stepi @var{arg}
5686 Execute one machine instruction, then stop and return to the debugger.
5688 It is often useful to do @samp{display/i $pc} when stepping by machine
5689 instructions. This makes @value{GDBN} automatically display the next
5690 instruction to be executed, each time your program stops. @xref{Auto
5691 Display,, Automatic Display}.
5693 An argument is a repeat count, as in @code{step}.
5697 @kindex ni @r{(@code{nexti})}
5699 @itemx nexti @var{arg}
5701 Execute one machine instruction, but if it is a function call,
5702 proceed until the function returns.
5704 An argument is a repeat count, as in @code{next}.
5708 @anchor{range stepping}
5709 @cindex range stepping
5710 @cindex target-assisted range stepping
5711 By default, and if available, @value{GDBN} makes use of
5712 target-assisted @dfn{range stepping}. In other words, whenever you
5713 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5714 tells the target to step the corresponding range of instruction
5715 addresses instead of issuing multiple single-steps. This speeds up
5716 line stepping, particularly for remote targets. Ideally, there should
5717 be no reason you would want to turn range stepping off. However, it's
5718 possible that a bug in the debug info, a bug in the remote stub (for
5719 remote targets), or even a bug in @value{GDBN} could make line
5720 stepping behave incorrectly when target-assisted range stepping is
5721 enabled. You can use the following command to turn off range stepping
5725 @kindex set range-stepping
5726 @kindex show range-stepping
5727 @item set range-stepping
5728 @itemx show range-stepping
5729 Control whether range stepping is enabled.
5731 If @code{on}, and the target supports it, @value{GDBN} tells the
5732 target to step a range of addresses itself, instead of issuing
5733 multiple single-steps. If @code{off}, @value{GDBN} always issues
5734 single-steps, even if range stepping is supported by the target. The
5735 default is @code{on}.
5739 @node Skipping Over Functions and Files
5740 @section Skipping Over Functions and Files
5741 @cindex skipping over functions and files
5743 The program you are debugging may contain some functions which are
5744 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5745 skip a function, all functions in a file or a particular function in
5746 a particular file when stepping.
5748 For example, consider the following C function:
5759 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5760 are not interested in stepping through @code{boring}. If you run @code{step}
5761 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5762 step over both @code{foo} and @code{boring}!
5764 One solution is to @code{step} into @code{boring} and use the @code{finish}
5765 command to immediately exit it. But this can become tedious if @code{boring}
5766 is called from many places.
5768 A more flexible solution is to execute @kbd{skip boring}. This instructs
5769 @value{GDBN} never to step into @code{boring}. Now when you execute
5770 @code{step} at line 103, you'll step over @code{boring} and directly into
5773 Functions may be skipped by providing either a function name, linespec
5774 (@pxref{Specify Location}), regular expression that matches the function's
5775 name, file name or a @code{glob}-style pattern that matches the file name.
5777 On Posix systems the form of the regular expression is
5778 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5779 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5780 expression is whatever is provided by the @code{regcomp} function of
5781 the underlying system.
5782 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5783 description of @code{glob}-style patterns.
5787 @item skip @r{[}@var{options}@r{]}
5788 The basic form of the @code{skip} command takes zero or more options
5789 that specify what to skip.
5790 The @var{options} argument is any useful combination of the following:
5793 @item -file @var{file}
5794 @itemx -fi @var{file}
5795 Functions in @var{file} will be skipped over when stepping.
5797 @item -gfile @var{file-glob-pattern}
5798 @itemx -gfi @var{file-glob-pattern}
5799 @cindex skipping over files via glob-style patterns
5800 Functions in files matching @var{file-glob-pattern} will be skipped
5804 (gdb) skip -gfi utils/*.c
5807 @item -function @var{linespec}
5808 @itemx -fu @var{linespec}
5809 Functions named by @var{linespec} or the function containing the line
5810 named by @var{linespec} will be skipped over when stepping.
5811 @xref{Specify Location}.
5813 @item -rfunction @var{regexp}
5814 @itemx -rfu @var{regexp}
5815 @cindex skipping over functions via regular expressions
5816 Functions whose name matches @var{regexp} will be skipped over when stepping.
5818 This form is useful for complex function names.
5819 For example, there is generally no need to step into C@t{++} @code{std::string}
5820 constructors or destructors. Plus with C@t{++} templates it can be hard to
5821 write out the full name of the function, and often it doesn't matter what
5822 the template arguments are. Specifying the function to be skipped as a
5823 regular expression makes this easier.
5826 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5829 If you want to skip every templated C@t{++} constructor and destructor
5830 in the @code{std} namespace you can do:
5833 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5837 If no options are specified, the function you're currently debugging
5840 @kindex skip function
5841 @item skip function @r{[}@var{linespec}@r{]}
5842 After running this command, the function named by @var{linespec} or the
5843 function containing the line named by @var{linespec} will be skipped over when
5844 stepping. @xref{Specify Location}.
5846 If you do not specify @var{linespec}, the function you're currently debugging
5849 (If you have a function called @code{file} that you want to skip, use
5850 @kbd{skip function file}.)
5853 @item skip file @r{[}@var{filename}@r{]}
5854 After running this command, any function whose source lives in @var{filename}
5855 will be skipped over when stepping.
5858 (gdb) skip file boring.c
5859 File boring.c will be skipped when stepping.
5862 If you do not specify @var{filename}, functions whose source lives in the file
5863 you're currently debugging will be skipped.
5866 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5867 These are the commands for managing your list of skips:
5871 @item info skip @r{[}@var{range}@r{]}
5872 Print details about the specified skip(s). If @var{range} is not specified,
5873 print a table with details about all functions and files marked for skipping.
5874 @code{info skip} prints the following information about each skip:
5878 A number identifying this skip.
5879 @item Enabled or Disabled
5880 Enabled skips are marked with @samp{y}.
5881 Disabled skips are marked with @samp{n}.
5883 If the file name is a @samp{glob} pattern this is @samp{y}.
5884 Otherwise it is @samp{n}.
5886 The name or @samp{glob} pattern of the file to be skipped.
5887 If no file is specified this is @samp{<none>}.
5889 If the function name is a @samp{regular expression} this is @samp{y}.
5890 Otherwise it is @samp{n}.
5892 The name or regular expression of the function to skip.
5893 If no function is specified this is @samp{<none>}.
5897 @item skip delete @r{[}@var{range}@r{]}
5898 Delete the specified skip(s). If @var{range} is not specified, delete all
5902 @item skip enable @r{[}@var{range}@r{]}
5903 Enable the specified skip(s). If @var{range} is not specified, enable all
5906 @kindex skip disable
5907 @item skip disable @r{[}@var{range}@r{]}
5908 Disable the specified skip(s). If @var{range} is not specified, disable all
5911 @kindex set debug skip
5912 @item set debug skip @r{[}on|off@r{]}
5913 Set whether to print the debug output about skipping files and functions.
5915 @kindex show debug skip
5916 @item show debug skip
5917 Show whether the debug output about skipping files and functions is printed.
5925 A signal is an asynchronous event that can happen in a program. The
5926 operating system defines the possible kinds of signals, and gives each
5927 kind a name and a number. For example, in Unix @code{SIGINT} is the
5928 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5929 @code{SIGSEGV} is the signal a program gets from referencing a place in
5930 memory far away from all the areas in use; @code{SIGALRM} occurs when
5931 the alarm clock timer goes off (which happens only if your program has
5932 requested an alarm).
5934 @cindex fatal signals
5935 Some signals, including @code{SIGALRM}, are a normal part of the
5936 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5937 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5938 program has not specified in advance some other way to handle the signal.
5939 @code{SIGINT} does not indicate an error in your program, but it is normally
5940 fatal so it can carry out the purpose of the interrupt: to kill the program.
5942 @value{GDBN} has the ability to detect any occurrence of a signal in your
5943 program. You can tell @value{GDBN} in advance what to do for each kind of
5946 @cindex handling signals
5947 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5948 @code{SIGALRM} be silently passed to your program
5949 (so as not to interfere with their role in the program's functioning)
5950 but to stop your program immediately whenever an error signal happens.
5951 You can change these settings with the @code{handle} command.
5954 @kindex info signals
5958 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5959 handle each one. You can use this to see the signal numbers of all
5960 the defined types of signals.
5962 @item info signals @var{sig}
5963 Similar, but print information only about the specified signal number.
5965 @code{info handle} is an alias for @code{info signals}.
5967 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5968 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5969 for details about this command.
5972 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5973 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5974 can be the number of a signal or its name (with or without the
5975 @samp{SIG} at the beginning); a list of signal numbers of the form
5976 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5977 known signals. Optional arguments @var{keywords}, described below,
5978 say what change to make.
5982 The keywords allowed by the @code{handle} command can be abbreviated.
5983 Their full names are:
5987 @value{GDBN} should not stop your program when this signal happens. It may
5988 still print a message telling you that the signal has come in.
5991 @value{GDBN} should stop your program when this signal happens. This implies
5992 the @code{print} keyword as well.
5995 @value{GDBN} should print a message when this signal happens.
5998 @value{GDBN} should not mention the occurrence of the signal at all. This
5999 implies the @code{nostop} keyword as well.
6003 @value{GDBN} should allow your program to see this signal; your program
6004 can handle the signal, or else it may terminate if the signal is fatal
6005 and not handled. @code{pass} and @code{noignore} are synonyms.
6009 @value{GDBN} should not allow your program to see this signal.
6010 @code{nopass} and @code{ignore} are synonyms.
6014 When a signal stops your program, the signal is not visible to the
6016 continue. Your program sees the signal then, if @code{pass} is in
6017 effect for the signal in question @emph{at that time}. In other words,
6018 after @value{GDBN} reports a signal, you can use the @code{handle}
6019 command with @code{pass} or @code{nopass} to control whether your
6020 program sees that signal when you continue.
6022 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6023 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6024 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6027 You can also use the @code{signal} command to prevent your program from
6028 seeing a signal, or cause it to see a signal it normally would not see,
6029 or to give it any signal at any time. For example, if your program stopped
6030 due to some sort of memory reference error, you might store correct
6031 values into the erroneous variables and continue, hoping to see more
6032 execution; but your program would probably terminate immediately as
6033 a result of the fatal signal once it saw the signal. To prevent this,
6034 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6037 @cindex stepping and signal handlers
6038 @anchor{stepping and signal handlers}
6040 @value{GDBN} optimizes for stepping the mainline code. If a signal
6041 that has @code{handle nostop} and @code{handle pass} set arrives while
6042 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6043 in progress, @value{GDBN} lets the signal handler run and then resumes
6044 stepping the mainline code once the signal handler returns. In other
6045 words, @value{GDBN} steps over the signal handler. This prevents
6046 signals that you've specified as not interesting (with @code{handle
6047 nostop}) from changing the focus of debugging unexpectedly. Note that
6048 the signal handler itself may still hit a breakpoint, stop for another
6049 signal that has @code{handle stop} in effect, or for any other event
6050 that normally results in stopping the stepping command sooner. Also
6051 note that @value{GDBN} still informs you that the program received a
6052 signal if @code{handle print} is set.
6054 @anchor{stepping into signal handlers}
6056 If you set @code{handle pass} for a signal, and your program sets up a
6057 handler for it, then issuing a stepping command, such as @code{step}
6058 or @code{stepi}, when your program is stopped due to the signal will
6059 step @emph{into} the signal handler (if the target supports that).
6061 Likewise, if you use the @code{queue-signal} command to queue a signal
6062 to be delivered to the current thread when execution of the thread
6063 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6064 stepping command will step into the signal handler.
6066 Here's an example, using @code{stepi} to step to the first instruction
6067 of @code{SIGUSR1}'s handler:
6070 (@value{GDBP}) handle SIGUSR1
6071 Signal Stop Print Pass to program Description
6072 SIGUSR1 Yes Yes Yes User defined signal 1
6076 Program received signal SIGUSR1, User defined signal 1.
6077 main () sigusr1.c:28
6080 sigusr1_handler () at sigusr1.c:9
6084 The same, but using @code{queue-signal} instead of waiting for the
6085 program to receive the signal first:
6090 (@value{GDBP}) queue-signal SIGUSR1
6092 sigusr1_handler () at sigusr1.c:9
6097 @cindex extra signal information
6098 @anchor{extra signal information}
6100 On some targets, @value{GDBN} can inspect extra signal information
6101 associated with the intercepted signal, before it is actually
6102 delivered to the program being debugged. This information is exported
6103 by the convenience variable @code{$_siginfo}, and consists of data
6104 that is passed by the kernel to the signal handler at the time of the
6105 receipt of a signal. The data type of the information itself is
6106 target dependent. You can see the data type using the @code{ptype
6107 $_siginfo} command. On Unix systems, it typically corresponds to the
6108 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6111 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6112 referenced address that raised a segmentation fault.
6116 (@value{GDBP}) continue
6117 Program received signal SIGSEGV, Segmentation fault.
6118 0x0000000000400766 in main ()
6120 (@value{GDBP}) ptype $_siginfo
6127 struct @{...@} _kill;
6128 struct @{...@} _timer;
6130 struct @{...@} _sigchld;
6131 struct @{...@} _sigfault;
6132 struct @{...@} _sigpoll;
6135 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6139 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6140 $1 = (void *) 0x7ffff7ff7000
6144 Depending on target support, @code{$_siginfo} may also be writable.
6146 @cindex Intel MPX boundary violations
6147 @cindex boundary violations, Intel MPX
6148 On some targets, a @code{SIGSEGV} can be caused by a boundary
6149 violation, i.e., accessing an address outside of the allowed range.
6150 In those cases @value{GDBN} may displays additional information,
6151 depending on how @value{GDBN} has been told to handle the signal.
6152 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6153 kind: "Upper" or "Lower", the memory address accessed and the
6154 bounds, while with @code{handle nostop SIGSEGV} no additional
6155 information is displayed.
6157 The usual output of a segfault is:
6159 Program received signal SIGSEGV, Segmentation fault
6160 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6161 68 value = *(p + len);
6164 While a bound violation is presented as:
6166 Program received signal SIGSEGV, Segmentation fault
6167 Upper bound violation while accessing address 0x7fffffffc3b3
6168 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6169 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6170 68 value = *(p + len);
6174 @section Stopping and Starting Multi-thread Programs
6176 @cindex stopped threads
6177 @cindex threads, stopped
6179 @cindex continuing threads
6180 @cindex threads, continuing
6182 @value{GDBN} supports debugging programs with multiple threads
6183 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6184 are two modes of controlling execution of your program within the
6185 debugger. In the default mode, referred to as @dfn{all-stop mode},
6186 when any thread in your program stops (for example, at a breakpoint
6187 or while being stepped), all other threads in the program are also stopped by
6188 @value{GDBN}. On some targets, @value{GDBN} also supports
6189 @dfn{non-stop mode}, in which other threads can continue to run freely while
6190 you examine the stopped thread in the debugger.
6193 * All-Stop Mode:: All threads stop when GDB takes control
6194 * Non-Stop Mode:: Other threads continue to execute
6195 * Background Execution:: Running your program asynchronously
6196 * Thread-Specific Breakpoints:: Controlling breakpoints
6197 * Interrupted System Calls:: GDB may interfere with system calls
6198 * Observer Mode:: GDB does not alter program behavior
6202 @subsection All-Stop Mode
6204 @cindex all-stop mode
6206 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6207 @emph{all} threads of execution stop, not just the current thread. This
6208 allows you to examine the overall state of the program, including
6209 switching between threads, without worrying that things may change
6212 Conversely, whenever you restart the program, @emph{all} threads start
6213 executing. @emph{This is true even when single-stepping} with commands
6214 like @code{step} or @code{next}.
6216 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6217 Since thread scheduling is up to your debugging target's operating
6218 system (not controlled by @value{GDBN}), other threads may
6219 execute more than one statement while the current thread completes a
6220 single step. Moreover, in general other threads stop in the middle of a
6221 statement, rather than at a clean statement boundary, when the program
6224 You might even find your program stopped in another thread after
6225 continuing or even single-stepping. This happens whenever some other
6226 thread runs into a breakpoint, a signal, or an exception before the
6227 first thread completes whatever you requested.
6229 @cindex automatic thread selection
6230 @cindex switching threads automatically
6231 @cindex threads, automatic switching
6232 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6233 signal, it automatically selects the thread where that breakpoint or
6234 signal happened. @value{GDBN} alerts you to the context switch with a
6235 message such as @samp{[Switching to Thread @var{n}]} to identify the
6238 On some OSes, you can modify @value{GDBN}'s default behavior by
6239 locking the OS scheduler to allow only a single thread to run.
6242 @item set scheduler-locking @var{mode}
6243 @cindex scheduler locking mode
6244 @cindex lock scheduler
6245 Set the scheduler locking mode. It applies to normal execution,
6246 record mode, and replay mode. If it is @code{off}, then there is no
6247 locking and any thread may run at any time. If @code{on}, then only
6248 the current thread may run when the inferior is resumed. The
6249 @code{step} mode optimizes for single-stepping; it prevents other
6250 threads from preempting the current thread while you are stepping, so
6251 that the focus of debugging does not change unexpectedly. Other
6252 threads never get a chance to run when you step, and they are
6253 completely free to run when you use commands like @samp{continue},
6254 @samp{until}, or @samp{finish}. However, unless another thread hits a
6255 breakpoint during its timeslice, @value{GDBN} does not change the
6256 current thread away from the thread that you are debugging. The
6257 @code{replay} mode behaves like @code{off} in record mode and like
6258 @code{on} in replay mode.
6260 @item show scheduler-locking
6261 Display the current scheduler locking mode.
6264 @cindex resume threads of multiple processes simultaneously
6265 By default, when you issue one of the execution commands such as
6266 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6267 threads of the current inferior to run. For example, if @value{GDBN}
6268 is attached to two inferiors, each with two threads, the
6269 @code{continue} command resumes only the two threads of the current
6270 inferior. This is useful, for example, when you debug a program that
6271 forks and you want to hold the parent stopped (so that, for instance,
6272 it doesn't run to exit), while you debug the child. In other
6273 situations, you may not be interested in inspecting the current state
6274 of any of the processes @value{GDBN} is attached to, and you may want
6275 to resume them all until some breakpoint is hit. In the latter case,
6276 you can instruct @value{GDBN} to allow all threads of all the
6277 inferiors to run with the @w{@code{set schedule-multiple}} command.
6280 @kindex set schedule-multiple
6281 @item set schedule-multiple
6282 Set the mode for allowing threads of multiple processes to be resumed
6283 when an execution command is issued. When @code{on}, all threads of
6284 all processes are allowed to run. When @code{off}, only the threads
6285 of the current process are resumed. The default is @code{off}. The
6286 @code{scheduler-locking} mode takes precedence when set to @code{on},
6287 or while you are stepping and set to @code{step}.
6289 @item show schedule-multiple
6290 Display the current mode for resuming the execution of threads of
6295 @subsection Non-Stop Mode
6297 @cindex non-stop mode
6299 @c This section is really only a place-holder, and needs to be expanded
6300 @c with more details.
6302 For some multi-threaded targets, @value{GDBN} supports an optional
6303 mode of operation in which you can examine stopped program threads in
6304 the debugger while other threads continue to execute freely. This
6305 minimizes intrusion when debugging live systems, such as programs
6306 where some threads have real-time constraints or must continue to
6307 respond to external events. This is referred to as @dfn{non-stop} mode.
6309 In non-stop mode, when a thread stops to report a debugging event,
6310 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6311 threads as well, in contrast to the all-stop mode behavior. Additionally,
6312 execution commands such as @code{continue} and @code{step} apply by default
6313 only to the current thread in non-stop mode, rather than all threads as
6314 in all-stop mode. This allows you to control threads explicitly in
6315 ways that are not possible in all-stop mode --- for example, stepping
6316 one thread while allowing others to run freely, stepping
6317 one thread while holding all others stopped, or stepping several threads
6318 independently and simultaneously.
6320 To enter non-stop mode, use this sequence of commands before you run
6321 or attach to your program:
6324 # If using the CLI, pagination breaks non-stop.
6327 # Finally, turn it on!
6331 You can use these commands to manipulate the non-stop mode setting:
6334 @kindex set non-stop
6335 @item set non-stop on
6336 Enable selection of non-stop mode.
6337 @item set non-stop off
6338 Disable selection of non-stop mode.
6339 @kindex show non-stop
6341 Show the current non-stop enablement setting.
6344 Note these commands only reflect whether non-stop mode is enabled,
6345 not whether the currently-executing program is being run in non-stop mode.
6346 In particular, the @code{set non-stop} preference is only consulted when
6347 @value{GDBN} starts or connects to the target program, and it is generally
6348 not possible to switch modes once debugging has started. Furthermore,
6349 since not all targets support non-stop mode, even when you have enabled
6350 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6353 In non-stop mode, all execution commands apply only to the current thread
6354 by default. That is, @code{continue} only continues one thread.
6355 To continue all threads, issue @code{continue -a} or @code{c -a}.
6357 You can use @value{GDBN}'s background execution commands
6358 (@pxref{Background Execution}) to run some threads in the background
6359 while you continue to examine or step others from @value{GDBN}.
6360 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6361 always executed asynchronously in non-stop mode.
6363 Suspending execution is done with the @code{interrupt} command when
6364 running in the background, or @kbd{Ctrl-c} during foreground execution.
6365 In all-stop mode, this stops the whole process;
6366 but in non-stop mode the interrupt applies only to the current thread.
6367 To stop the whole program, use @code{interrupt -a}.
6369 Other execution commands do not currently support the @code{-a} option.
6371 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6372 that thread current, as it does in all-stop mode. This is because the
6373 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6374 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6375 changed to a different thread just as you entered a command to operate on the
6376 previously current thread.
6378 @node Background Execution
6379 @subsection Background Execution
6381 @cindex foreground execution
6382 @cindex background execution
6383 @cindex asynchronous execution
6384 @cindex execution, foreground, background and asynchronous
6386 @value{GDBN}'s execution commands have two variants: the normal
6387 foreground (synchronous) behavior, and a background
6388 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6389 the program to report that some thread has stopped before prompting for
6390 another command. In background execution, @value{GDBN} immediately gives
6391 a command prompt so that you can issue other commands while your program runs.
6393 If the target doesn't support async mode, @value{GDBN} issues an error
6394 message if you attempt to use the background execution commands.
6396 @cindex @code{&}, background execution of commands
6397 To specify background execution, add a @code{&} to the command. For example,
6398 the background form of the @code{continue} command is @code{continue&}, or
6399 just @code{c&}. The execution commands that accept background execution
6405 @xref{Starting, , Starting your Program}.
6409 @xref{Attach, , Debugging an Already-running Process}.
6413 @xref{Continuing and Stepping, step}.
6417 @xref{Continuing and Stepping, stepi}.
6421 @xref{Continuing and Stepping, next}.
6425 @xref{Continuing and Stepping, nexti}.
6429 @xref{Continuing and Stepping, continue}.
6433 @xref{Continuing and Stepping, finish}.
6437 @xref{Continuing and Stepping, until}.
6441 Background execution is especially useful in conjunction with non-stop
6442 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6443 However, you can also use these commands in the normal all-stop mode with
6444 the restriction that you cannot issue another execution command until the
6445 previous one finishes. Examples of commands that are valid in all-stop
6446 mode while the program is running include @code{help} and @code{info break}.
6448 You can interrupt your program while it is running in the background by
6449 using the @code{interrupt} command.
6456 Suspend execution of the running program. In all-stop mode,
6457 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6458 only the current thread. To stop the whole program in non-stop mode,
6459 use @code{interrupt -a}.
6462 @node Thread-Specific Breakpoints
6463 @subsection Thread-Specific Breakpoints
6465 When your program has multiple threads (@pxref{Threads,, Debugging
6466 Programs with Multiple Threads}), you can choose whether to set
6467 breakpoints on all threads, or on a particular thread.
6470 @cindex breakpoints and threads
6471 @cindex thread breakpoints
6472 @kindex break @dots{} thread @var{thread-id}
6473 @item break @var{location} thread @var{thread-id}
6474 @itemx break @var{location} thread @var{thread-id} if @dots{}
6475 @var{location} specifies source lines; there are several ways of
6476 writing them (@pxref{Specify Location}), but the effect is always to
6477 specify some source line.
6479 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6480 to specify that you only want @value{GDBN} to stop the program when a
6481 particular thread reaches this breakpoint. The @var{thread-id} specifier
6482 is one of the thread identifiers assigned by @value{GDBN}, shown
6483 in the first column of the @samp{info threads} display.
6485 If you do not specify @samp{thread @var{thread-id}} when you set a
6486 breakpoint, the breakpoint applies to @emph{all} threads of your
6489 You can use the @code{thread} qualifier on conditional breakpoints as
6490 well; in this case, place @samp{thread @var{thread-id}} before or
6491 after the breakpoint condition, like this:
6494 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6499 Thread-specific breakpoints are automatically deleted when
6500 @value{GDBN} detects the corresponding thread is no longer in the
6501 thread list. For example:
6505 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6508 There are several ways for a thread to disappear, such as a regular
6509 thread exit, but also when you detach from the process with the
6510 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6511 Process}), or if @value{GDBN} loses the remote connection
6512 (@pxref{Remote Debugging}), etc. Note that with some targets,
6513 @value{GDBN} is only able to detect a thread has exited when the user
6514 explictly asks for the thread list with the @code{info threads}
6517 @node Interrupted System Calls
6518 @subsection Interrupted System Calls
6520 @cindex thread breakpoints and system calls
6521 @cindex system calls and thread breakpoints
6522 @cindex premature return from system calls
6523 There is an unfortunate side effect when using @value{GDBN} to debug
6524 multi-threaded programs. If one thread stops for a
6525 breakpoint, or for some other reason, and another thread is blocked in a
6526 system call, then the system call may return prematurely. This is a
6527 consequence of the interaction between multiple threads and the signals
6528 that @value{GDBN} uses to implement breakpoints and other events that
6531 To handle this problem, your program should check the return value of
6532 each system call and react appropriately. This is good programming
6535 For example, do not write code like this:
6541 The call to @code{sleep} will return early if a different thread stops
6542 at a breakpoint or for some other reason.
6544 Instead, write this:
6549 unslept = sleep (unslept);
6552 A system call is allowed to return early, so the system is still
6553 conforming to its specification. But @value{GDBN} does cause your
6554 multi-threaded program to behave differently than it would without
6557 Also, @value{GDBN} uses internal breakpoints in the thread library to
6558 monitor certain events such as thread creation and thread destruction.
6559 When such an event happens, a system call in another thread may return
6560 prematurely, even though your program does not appear to stop.
6563 @subsection Observer Mode
6565 If you want to build on non-stop mode and observe program behavior
6566 without any chance of disruption by @value{GDBN}, you can set
6567 variables to disable all of the debugger's attempts to modify state,
6568 whether by writing memory, inserting breakpoints, etc. These operate
6569 at a low level, intercepting operations from all commands.
6571 When all of these are set to @code{off}, then @value{GDBN} is said to
6572 be @dfn{observer mode}. As a convenience, the variable
6573 @code{observer} can be set to disable these, plus enable non-stop
6576 Note that @value{GDBN} will not prevent you from making nonsensical
6577 combinations of these settings. For instance, if you have enabled
6578 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6579 then breakpoints that work by writing trap instructions into the code
6580 stream will still not be able to be placed.
6585 @item set observer on
6586 @itemx set observer off
6587 When set to @code{on}, this disables all the permission variables
6588 below (except for @code{insert-fast-tracepoints}), plus enables
6589 non-stop debugging. Setting this to @code{off} switches back to
6590 normal debugging, though remaining in non-stop mode.
6593 Show whether observer mode is on or off.
6595 @kindex may-write-registers
6596 @item set may-write-registers on
6597 @itemx set may-write-registers off
6598 This controls whether @value{GDBN} will attempt to alter the values of
6599 registers, such as with assignment expressions in @code{print}, or the
6600 @code{jump} command. It defaults to @code{on}.
6602 @item show may-write-registers
6603 Show the current permission to write registers.
6605 @kindex may-write-memory
6606 @item set may-write-memory on
6607 @itemx set may-write-memory off
6608 This controls whether @value{GDBN} will attempt to alter the contents
6609 of memory, such as with assignment expressions in @code{print}. It
6610 defaults to @code{on}.
6612 @item show may-write-memory
6613 Show the current permission to write memory.
6615 @kindex may-insert-breakpoints
6616 @item set may-insert-breakpoints on
6617 @itemx set may-insert-breakpoints off
6618 This controls whether @value{GDBN} will attempt to insert breakpoints.
6619 This affects all breakpoints, including internal breakpoints defined
6620 by @value{GDBN}. It defaults to @code{on}.
6622 @item show may-insert-breakpoints
6623 Show the current permission to insert breakpoints.
6625 @kindex may-insert-tracepoints
6626 @item set may-insert-tracepoints on
6627 @itemx set may-insert-tracepoints off
6628 This controls whether @value{GDBN} will attempt to insert (regular)
6629 tracepoints at the beginning of a tracing experiment. It affects only
6630 non-fast tracepoints, fast tracepoints being under the control of
6631 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6633 @item show may-insert-tracepoints
6634 Show the current permission to insert tracepoints.
6636 @kindex may-insert-fast-tracepoints
6637 @item set may-insert-fast-tracepoints on
6638 @itemx set may-insert-fast-tracepoints off
6639 This controls whether @value{GDBN} will attempt to insert fast
6640 tracepoints at the beginning of a tracing experiment. It affects only
6641 fast tracepoints, regular (non-fast) tracepoints being under the
6642 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6644 @item show may-insert-fast-tracepoints
6645 Show the current permission to insert fast tracepoints.
6647 @kindex may-interrupt
6648 @item set may-interrupt on
6649 @itemx set may-interrupt off
6650 This controls whether @value{GDBN} will attempt to interrupt or stop
6651 program execution. When this variable is @code{off}, the
6652 @code{interrupt} command will have no effect, nor will
6653 @kbd{Ctrl-c}. It defaults to @code{on}.
6655 @item show may-interrupt
6656 Show the current permission to interrupt or stop the program.
6660 @node Reverse Execution
6661 @chapter Running programs backward
6662 @cindex reverse execution
6663 @cindex running programs backward
6665 When you are debugging a program, it is not unusual to realize that
6666 you have gone too far, and some event of interest has already happened.
6667 If the target environment supports it, @value{GDBN} can allow you to
6668 ``rewind'' the program by running it backward.
6670 A target environment that supports reverse execution should be able
6671 to ``undo'' the changes in machine state that have taken place as the
6672 program was executing normally. Variables, registers etc.@: should
6673 revert to their previous values. Obviously this requires a great
6674 deal of sophistication on the part of the target environment; not
6675 all target environments can support reverse execution.
6677 When a program is executed in reverse, the instructions that
6678 have most recently been executed are ``un-executed'', in reverse
6679 order. The program counter runs backward, following the previous
6680 thread of execution in reverse. As each instruction is ``un-executed'',
6681 the values of memory and/or registers that were changed by that
6682 instruction are reverted to their previous states. After executing
6683 a piece of source code in reverse, all side effects of that code
6684 should be ``undone'', and all variables should be returned to their
6685 prior values@footnote{
6686 Note that some side effects are easier to undo than others. For instance,
6687 memory and registers are relatively easy, but device I/O is hard. Some
6688 targets may be able undo things like device I/O, and some may not.
6690 The contract between @value{GDBN} and the reverse executing target
6691 requires only that the target do something reasonable when
6692 @value{GDBN} tells it to execute backwards, and then report the
6693 results back to @value{GDBN}. Whatever the target reports back to
6694 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6695 assumes that the memory and registers that the target reports are in a
6696 consistant state, but @value{GDBN} accepts whatever it is given.
6699 If you are debugging in a target environment that supports
6700 reverse execution, @value{GDBN} provides the following commands.
6703 @kindex reverse-continue
6704 @kindex rc @r{(@code{reverse-continue})}
6705 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6706 @itemx rc @r{[}@var{ignore-count}@r{]}
6707 Beginning at the point where your program last stopped, start executing
6708 in reverse. Reverse execution will stop for breakpoints and synchronous
6709 exceptions (signals), just like normal execution. Behavior of
6710 asynchronous signals depends on the target environment.
6712 @kindex reverse-step
6713 @kindex rs @r{(@code{step})}
6714 @item reverse-step @r{[}@var{count}@r{]}
6715 Run the program backward until control reaches the start of a
6716 different source line; then stop it, and return control to @value{GDBN}.
6718 Like the @code{step} command, @code{reverse-step} will only stop
6719 at the beginning of a source line. It ``un-executes'' the previously
6720 executed source line. If the previous source line included calls to
6721 debuggable functions, @code{reverse-step} will step (backward) into
6722 the called function, stopping at the beginning of the @emph{last}
6723 statement in the called function (typically a return statement).
6725 Also, as with the @code{step} command, if non-debuggable functions are
6726 called, @code{reverse-step} will run thru them backward without stopping.
6728 @kindex reverse-stepi
6729 @kindex rsi @r{(@code{reverse-stepi})}
6730 @item reverse-stepi @r{[}@var{count}@r{]}
6731 Reverse-execute one machine instruction. Note that the instruction
6732 to be reverse-executed is @emph{not} the one pointed to by the program
6733 counter, but the instruction executed prior to that one. For instance,
6734 if the last instruction was a jump, @code{reverse-stepi} will take you
6735 back from the destination of the jump to the jump instruction itself.
6737 @kindex reverse-next
6738 @kindex rn @r{(@code{reverse-next})}
6739 @item reverse-next @r{[}@var{count}@r{]}
6740 Run backward to the beginning of the previous line executed in
6741 the current (innermost) stack frame. If the line contains function
6742 calls, they will be ``un-executed'' without stopping. Starting from
6743 the first line of a function, @code{reverse-next} will take you back
6744 to the caller of that function, @emph{before} the function was called,
6745 just as the normal @code{next} command would take you from the last
6746 line of a function back to its return to its caller
6747 @footnote{Unless the code is too heavily optimized.}.
6749 @kindex reverse-nexti
6750 @kindex rni @r{(@code{reverse-nexti})}
6751 @item reverse-nexti @r{[}@var{count}@r{]}
6752 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6753 in reverse, except that called functions are ``un-executed'' atomically.
6754 That is, if the previously executed instruction was a return from
6755 another function, @code{reverse-nexti} will continue to execute
6756 in reverse until the call to that function (from the current stack
6759 @kindex reverse-finish
6760 @item reverse-finish
6761 Just as the @code{finish} command takes you to the point where the
6762 current function returns, @code{reverse-finish} takes you to the point
6763 where it was called. Instead of ending up at the end of the current
6764 function invocation, you end up at the beginning.
6766 @kindex set exec-direction
6767 @item set exec-direction
6768 Set the direction of target execution.
6769 @item set exec-direction reverse
6770 @cindex execute forward or backward in time
6771 @value{GDBN} will perform all execution commands in reverse, until the
6772 exec-direction mode is changed to ``forward''. Affected commands include
6773 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6774 command cannot be used in reverse mode.
6775 @item set exec-direction forward
6776 @value{GDBN} will perform all execution commands in the normal fashion.
6777 This is the default.
6781 @node Process Record and Replay
6782 @chapter Recording Inferior's Execution and Replaying It
6783 @cindex process record and replay
6784 @cindex recording inferior's execution and replaying it
6786 On some platforms, @value{GDBN} provides a special @dfn{process record
6787 and replay} target that can record a log of the process execution, and
6788 replay it later with both forward and reverse execution commands.
6791 When this target is in use, if the execution log includes the record
6792 for the next instruction, @value{GDBN} will debug in @dfn{replay
6793 mode}. In the replay mode, the inferior does not really execute code
6794 instructions. Instead, all the events that normally happen during
6795 code execution are taken from the execution log. While code is not
6796 really executed in replay mode, the values of registers (including the
6797 program counter register) and the memory of the inferior are still
6798 changed as they normally would. Their contents are taken from the
6802 If the record for the next instruction is not in the execution log,
6803 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6804 inferior executes normally, and @value{GDBN} records the execution log
6807 The process record and replay target supports reverse execution
6808 (@pxref{Reverse Execution}), even if the platform on which the
6809 inferior runs does not. However, the reverse execution is limited in
6810 this case by the range of the instructions recorded in the execution
6811 log. In other words, reverse execution on platforms that don't
6812 support it directly can only be done in the replay mode.
6814 When debugging in the reverse direction, @value{GDBN} will work in
6815 replay mode as long as the execution log includes the record for the
6816 previous instruction; otherwise, it will work in record mode, if the
6817 platform supports reverse execution, or stop if not.
6819 For architecture environments that support process record and replay,
6820 @value{GDBN} provides the following commands:
6823 @kindex target record
6824 @kindex target record-full
6825 @kindex target record-btrace
6828 @kindex record btrace
6829 @kindex record btrace bts
6830 @kindex record btrace pt
6836 @kindex rec btrace bts
6837 @kindex rec btrace pt
6840 @item record @var{method}
6841 This command starts the process record and replay target. The
6842 recording method can be specified as parameter. Without a parameter
6843 the command uses the @code{full} recording method. The following
6844 recording methods are available:
6848 Full record/replay recording using @value{GDBN}'s software record and
6849 replay implementation. This method allows replaying and reverse
6852 @item btrace @var{format}
6853 Hardware-supported instruction recording. This method does not record
6854 data. Further, the data is collected in a ring buffer so old data will
6855 be overwritten when the buffer is full. It allows limited reverse
6856 execution. Variables and registers are not available during reverse
6857 execution. In remote debugging, recording continues on disconnect.
6858 Recorded data can be inspected after reconnecting. The recording may
6859 be stopped using @code{record stop}.
6861 The recording format can be specified as parameter. Without a parameter
6862 the command chooses the recording format. The following recording
6863 formats are available:
6867 @cindex branch trace store
6868 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6869 this format, the processor stores a from/to record for each executed
6870 branch in the btrace ring buffer.
6873 @cindex Intel Processor Trace
6874 Use the @dfn{Intel Processor Trace} recording format. In this
6875 format, the processor stores the execution trace in a compressed form
6876 that is afterwards decoded by @value{GDBN}.
6878 The trace can be recorded with very low overhead. The compressed
6879 trace format also allows small trace buffers to already contain a big
6880 number of instructions compared to @acronym{BTS}.
6882 Decoding the recorded execution trace, on the other hand, is more
6883 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6884 increased number of instructions to process. You should increase the
6885 buffer-size with care.
6888 Not all recording formats may be available on all processors.
6891 The process record and replay target can only debug a process that is
6892 already running. Therefore, you need first to start the process with
6893 the @kbd{run} or @kbd{start} commands, and then start the recording
6894 with the @kbd{record @var{method}} command.
6896 @cindex displaced stepping, and process record and replay
6897 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6898 will be automatically disabled when process record and replay target
6899 is started. That's because the process record and replay target
6900 doesn't support displaced stepping.
6902 @cindex non-stop mode, and process record and replay
6903 @cindex asynchronous execution, and process record and replay
6904 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6905 the asynchronous execution mode (@pxref{Background Execution}), not
6906 all recording methods are available. The @code{full} recording method
6907 does not support these two modes.
6912 Stop the process record and replay target. When process record and
6913 replay target stops, the entire execution log will be deleted and the
6914 inferior will either be terminated, or will remain in its final state.
6916 When you stop the process record and replay target in record mode (at
6917 the end of the execution log), the inferior will be stopped at the
6918 next instruction that would have been recorded. In other words, if
6919 you record for a while and then stop recording, the inferior process
6920 will be left in the same state as if the recording never happened.
6922 On the other hand, if the process record and replay target is stopped
6923 while in replay mode (that is, not at the end of the execution log,
6924 but at some earlier point), the inferior process will become ``live''
6925 at that earlier state, and it will then be possible to continue the
6926 usual ``live'' debugging of the process from that state.
6928 When the inferior process exits, or @value{GDBN} detaches from it,
6929 process record and replay target will automatically stop itself.
6933 Go to a specific location in the execution log. There are several
6934 ways to specify the location to go to:
6937 @item record goto begin
6938 @itemx record goto start
6939 Go to the beginning of the execution log.
6941 @item record goto end
6942 Go to the end of the execution log.
6944 @item record goto @var{n}
6945 Go to instruction number @var{n} in the execution log.
6949 @item record save @var{filename}
6950 Save the execution log to a file @file{@var{filename}}.
6951 Default filename is @file{gdb_record.@var{process_id}}, where
6952 @var{process_id} is the process ID of the inferior.
6954 This command may not be available for all recording methods.
6956 @kindex record restore
6957 @item record restore @var{filename}
6958 Restore the execution log from a file @file{@var{filename}}.
6959 File must have been created with @code{record save}.
6961 @kindex set record full
6962 @item set record full insn-number-max @var{limit}
6963 @itemx set record full insn-number-max unlimited
6964 Set the limit of instructions to be recorded for the @code{full}
6965 recording method. Default value is 200000.
6967 If @var{limit} is a positive number, then @value{GDBN} will start
6968 deleting instructions from the log once the number of the record
6969 instructions becomes greater than @var{limit}. For every new recorded
6970 instruction, @value{GDBN} will delete the earliest recorded
6971 instruction to keep the number of recorded instructions at the limit.
6972 (Since deleting recorded instructions loses information, @value{GDBN}
6973 lets you control what happens when the limit is reached, by means of
6974 the @code{stop-at-limit} option, described below.)
6976 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6977 delete recorded instructions from the execution log. The number of
6978 recorded instructions is limited only by the available memory.
6980 @kindex show record full
6981 @item show record full insn-number-max
6982 Show the limit of instructions to be recorded with the @code{full}
6985 @item set record full stop-at-limit
6986 Control the behavior of the @code{full} recording method when the
6987 number of recorded instructions reaches the limit. If ON (the
6988 default), @value{GDBN} will stop when the limit is reached for the
6989 first time and ask you whether you want to stop the inferior or
6990 continue running it and recording the execution log. If you decide
6991 to continue recording, each new recorded instruction will cause the
6992 oldest one to be deleted.
6994 If this option is OFF, @value{GDBN} will automatically delete the
6995 oldest record to make room for each new one, without asking.
6997 @item show record full stop-at-limit
6998 Show the current setting of @code{stop-at-limit}.
7000 @item set record full memory-query
7001 Control the behavior when @value{GDBN} is unable to record memory
7002 changes caused by an instruction for the @code{full} recording method.
7003 If ON, @value{GDBN} will query whether to stop the inferior in that
7006 If this option is OFF (the default), @value{GDBN} will automatically
7007 ignore the effect of such instructions on memory. Later, when
7008 @value{GDBN} replays this execution log, it will mark the log of this
7009 instruction as not accessible, and it will not affect the replay
7012 @item show record full memory-query
7013 Show the current setting of @code{memory-query}.
7015 @kindex set record btrace
7016 The @code{btrace} record target does not trace data. As a
7017 convenience, when replaying, @value{GDBN} reads read-only memory off
7018 the live program directly, assuming that the addresses of the
7019 read-only areas don't change. This for example makes it possible to
7020 disassemble code while replaying, but not to print variables.
7021 In some cases, being able to inspect variables might be useful.
7022 You can use the following command for that:
7024 @item set record btrace replay-memory-access
7025 Control the behavior of the @code{btrace} recording method when
7026 accessing memory during replay. If @code{read-only} (the default),
7027 @value{GDBN} will only allow accesses to read-only memory.
7028 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7029 and to read-write memory. Beware that the accessed memory corresponds
7030 to the live target and not necessarily to the current replay
7033 @item set record btrace cpu @var{identifier}
7034 Set the processor to be used for enabling workarounds for processor
7035 errata when decoding the trace.
7037 Processor errata are defects in processor operation, caused by its
7038 design or manufacture. They can cause a trace not to match the
7039 specification. This, in turn, may cause trace decode to fail.
7040 @value{GDBN} can detect erroneous trace packets and correct them, thus
7041 avoiding the decoding failures. These corrections are known as
7042 @dfn{errata workarounds}, and are enabled based on the processor on
7043 which the trace was recorded.
7045 By default, @value{GDBN} attempts to detect the processor
7046 automatically, and apply the necessary workarounds for it. However,
7047 you may need to specify the processor if @value{GDBN} does not yet
7048 support it. This command allows you to do that, and also allows to
7049 disable the workarounds.
7051 The argument @var{identifier} identifies the @sc{cpu} and is of the
7052 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7053 there are two special identifiers, @code{none} and @code{auto}
7056 The following vendor identifiers and corresponding processor
7057 identifiers are currently supported:
7059 @multitable @columnfractions .1 .9
7062 @tab @var{family}/@var{model}[/@var{stepping}]
7066 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7067 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7069 If @var{identifier} is @code{auto}, enable errata workarounds for the
7070 processor on which the trace was recorded. If @var{identifier} is
7071 @code{none}, errata workarounds are disabled.
7073 For example, when using an old @value{GDBN} on a new system, decode
7074 may fail because @value{GDBN} does not support the new processor. It
7075 often suffices to specify an older processor that @value{GDBN}
7080 Active record target: record-btrace
7081 Recording format: Intel Processor Trace.
7083 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7084 (gdb) set record btrace cpu intel:6/158
7086 Active record target: record-btrace
7087 Recording format: Intel Processor Trace.
7089 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7092 @kindex show record btrace
7093 @item show record btrace replay-memory-access
7094 Show the current setting of @code{replay-memory-access}.
7096 @item show record btrace cpu
7097 Show the processor to be used for enabling trace decode errata
7100 @kindex set record btrace bts
7101 @item set record btrace bts buffer-size @var{size}
7102 @itemx set record btrace bts buffer-size unlimited
7103 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7104 format. Default is 64KB.
7106 If @var{size} is a positive number, then @value{GDBN} will try to
7107 allocate a buffer of at least @var{size} bytes for each new thread
7108 that uses the btrace recording method and the @acronym{BTS} format.
7109 The actually obtained buffer size may differ from the requested
7110 @var{size}. Use the @code{info record} command to see the actual
7111 buffer size for each thread that uses the btrace recording method and
7112 the @acronym{BTS} format.
7114 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7115 allocate a buffer of 4MB.
7117 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7118 also need longer to process the branch trace data before it can be used.
7120 @item show record btrace bts buffer-size @var{size}
7121 Show the current setting of the requested ring buffer size for branch
7122 tracing in @acronym{BTS} format.
7124 @kindex set record btrace pt
7125 @item set record btrace pt buffer-size @var{size}
7126 @itemx set record btrace pt buffer-size unlimited
7127 Set the requested ring buffer size for branch tracing in Intel
7128 Processor Trace format. Default is 16KB.
7130 If @var{size} is a positive number, then @value{GDBN} will try to
7131 allocate a buffer of at least @var{size} bytes for each new thread
7132 that uses the btrace recording method and the Intel Processor Trace
7133 format. The actually obtained buffer size may differ from the
7134 requested @var{size}. Use the @code{info record} command to see the
7135 actual buffer size for each thread.
7137 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7138 allocate a buffer of 4MB.
7140 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7141 also need longer to process the branch trace data before it can be used.
7143 @item show record btrace pt buffer-size @var{size}
7144 Show the current setting of the requested ring buffer size for branch
7145 tracing in Intel Processor Trace format.
7149 Show various statistics about the recording depending on the recording
7154 For the @code{full} recording method, it shows the state of process
7155 record and its in-memory execution log buffer, including:
7159 Whether in record mode or replay mode.
7161 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7163 Highest recorded instruction number.
7165 Current instruction about to be replayed (if in replay mode).
7167 Number of instructions contained in the execution log.
7169 Maximum number of instructions that may be contained in the execution log.
7173 For the @code{btrace} recording method, it shows:
7179 Number of instructions that have been recorded.
7181 Number of blocks of sequential control-flow formed by the recorded
7184 Whether in record mode or replay mode.
7187 For the @code{bts} recording format, it also shows:
7190 Size of the perf ring buffer.
7193 For the @code{pt} recording format, it also shows:
7196 Size of the perf ring buffer.
7200 @kindex record delete
7203 When record target runs in replay mode (``in the past''), delete the
7204 subsequent execution log and begin to record a new execution log starting
7205 from the current address. This means you will abandon the previously
7206 recorded ``future'' and begin recording a new ``future''.
7208 @kindex record instruction-history
7209 @kindex rec instruction-history
7210 @item record instruction-history
7211 Disassembles instructions from the recorded execution log. By
7212 default, ten instructions are disassembled. This can be changed using
7213 the @code{set record instruction-history-size} command. Instructions
7214 are printed in execution order.
7216 It can also print mixed source+disassembly if you specify the the
7217 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7218 as well as in symbolic form by specifying the @code{/r} modifier.
7220 The current position marker is printed for the instruction at the
7221 current program counter value. This instruction can appear multiple
7222 times in the trace and the current position marker will be printed
7223 every time. To omit the current position marker, specify the
7226 To better align the printed instructions when the trace contains
7227 instructions from more than one function, the function name may be
7228 omitted by specifying the @code{/f} modifier.
7230 Speculatively executed instructions are prefixed with @samp{?}. This
7231 feature is not available for all recording formats.
7233 There are several ways to specify what part of the execution log to
7237 @item record instruction-history @var{insn}
7238 Disassembles ten instructions starting from instruction number
7241 @item record instruction-history @var{insn}, +/-@var{n}
7242 Disassembles @var{n} instructions around instruction number
7243 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7244 @var{n} instructions after instruction number @var{insn}. If
7245 @var{n} is preceded with @code{-}, disassembles @var{n}
7246 instructions before instruction number @var{insn}.
7248 @item record instruction-history
7249 Disassembles ten more instructions after the last disassembly.
7251 @item record instruction-history -
7252 Disassembles ten more instructions before the last disassembly.
7254 @item record instruction-history @var{begin}, @var{end}
7255 Disassembles instructions beginning with instruction number
7256 @var{begin} until instruction number @var{end}. The instruction
7257 number @var{end} is included.
7260 This command may not be available for all recording methods.
7263 @item set record instruction-history-size @var{size}
7264 @itemx set record instruction-history-size unlimited
7265 Define how many instructions to disassemble in the @code{record
7266 instruction-history} command. The default value is 10.
7267 A @var{size} of @code{unlimited} means unlimited instructions.
7270 @item show record instruction-history-size
7271 Show how many instructions to disassemble in the @code{record
7272 instruction-history} command.
7274 @kindex record function-call-history
7275 @kindex rec function-call-history
7276 @item record function-call-history
7277 Prints the execution history at function granularity. It prints one
7278 line for each sequence of instructions that belong to the same
7279 function giving the name of that function, the source lines
7280 for this instruction sequence (if the @code{/l} modifier is
7281 specified), and the instructions numbers that form the sequence (if
7282 the @code{/i} modifier is specified). The function names are indented
7283 to reflect the call stack depth if the @code{/c} modifier is
7284 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7288 (@value{GDBP}) @b{list 1, 10}
7299 (@value{GDBP}) @b{record function-call-history /ilc}
7300 1 bar inst 1,4 at foo.c:6,8
7301 2 foo inst 5,10 at foo.c:2,3
7302 3 bar inst 11,13 at foo.c:9,10
7305 By default, ten lines are printed. This can be changed using the
7306 @code{set record function-call-history-size} command. Functions are
7307 printed in execution order. There are several ways to specify what
7311 @item record function-call-history @var{func}
7312 Prints ten functions starting from function number @var{func}.
7314 @item record function-call-history @var{func}, +/-@var{n}
7315 Prints @var{n} functions around function number @var{func}. If
7316 @var{n} is preceded with @code{+}, prints @var{n} functions after
7317 function number @var{func}. If @var{n} is preceded with @code{-},
7318 prints @var{n} functions before function number @var{func}.
7320 @item record function-call-history
7321 Prints ten more functions after the last ten-line print.
7323 @item record function-call-history -
7324 Prints ten more functions before the last ten-line print.
7326 @item record function-call-history @var{begin}, @var{end}
7327 Prints functions beginning with function number @var{begin} until
7328 function number @var{end}. The function number @var{end} is included.
7331 This command may not be available for all recording methods.
7333 @item set record function-call-history-size @var{size}
7334 @itemx set record function-call-history-size unlimited
7335 Define how many lines to print in the
7336 @code{record function-call-history} command. The default value is 10.
7337 A size of @code{unlimited} means unlimited lines.
7339 @item show record function-call-history-size
7340 Show how many lines to print in the
7341 @code{record function-call-history} command.
7346 @chapter Examining the Stack
7348 When your program has stopped, the first thing you need to know is where it
7349 stopped and how it got there.
7352 Each time your program performs a function call, information about the call
7354 That information includes the location of the call in your program,
7355 the arguments of the call,
7356 and the local variables of the function being called.
7357 The information is saved in a block of data called a @dfn{stack frame}.
7358 The stack frames are allocated in a region of memory called the @dfn{call
7361 When your program stops, the @value{GDBN} commands for examining the
7362 stack allow you to see all of this information.
7364 @cindex selected frame
7365 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7366 @value{GDBN} commands refer implicitly to the selected frame. In
7367 particular, whenever you ask @value{GDBN} for the value of a variable in
7368 your program, the value is found in the selected frame. There are
7369 special @value{GDBN} commands to select whichever frame you are
7370 interested in. @xref{Selection, ,Selecting a Frame}.
7372 When your program stops, @value{GDBN} automatically selects the
7373 currently executing frame and describes it briefly, similar to the
7374 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7377 * Frames:: Stack frames
7378 * Backtrace:: Backtraces
7379 * Selection:: Selecting a frame
7380 * Frame Info:: Information on a frame
7381 * Frame Apply:: Applying a command to several frames
7382 * Frame Filter Management:: Managing frame filters
7387 @section Stack Frames
7389 @cindex frame, definition
7391 The call stack is divided up into contiguous pieces called @dfn{stack
7392 frames}, or @dfn{frames} for short; each frame is the data associated
7393 with one call to one function. The frame contains the arguments given
7394 to the function, the function's local variables, and the address at
7395 which the function is executing.
7397 @cindex initial frame
7398 @cindex outermost frame
7399 @cindex innermost frame
7400 When your program is started, the stack has only one frame, that of the
7401 function @code{main}. This is called the @dfn{initial} frame or the
7402 @dfn{outermost} frame. Each time a function is called, a new frame is
7403 made. Each time a function returns, the frame for that function invocation
7404 is eliminated. If a function is recursive, there can be many frames for
7405 the same function. The frame for the function in which execution is
7406 actually occurring is called the @dfn{innermost} frame. This is the most
7407 recently created of all the stack frames that still exist.
7409 @cindex frame pointer
7410 Inside your program, stack frames are identified by their addresses. A
7411 stack frame consists of many bytes, each of which has its own address; each
7412 kind of computer has a convention for choosing one byte whose
7413 address serves as the address of the frame. Usually this address is kept
7414 in a register called the @dfn{frame pointer register}
7415 (@pxref{Registers, $fp}) while execution is going on in that frame.
7418 @cindex frame number
7419 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7420 number that is zero for the innermost frame, one for the frame that
7421 called it, and so on upward. These level numbers give you a way of
7422 designating stack frames in @value{GDBN} commands. The terms
7423 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7424 describe this number.
7426 @c The -fomit-frame-pointer below perennially causes hbox overflow
7427 @c underflow problems.
7428 @cindex frameless execution
7429 Some compilers provide a way to compile functions so that they operate
7430 without stack frames. (For example, the @value{NGCC} option
7432 @samp{-fomit-frame-pointer}
7434 generates functions without a frame.)
7435 This is occasionally done with heavily used library functions to save
7436 the frame setup time. @value{GDBN} has limited facilities for dealing
7437 with these function invocations. If the innermost function invocation
7438 has no stack frame, @value{GDBN} nevertheless regards it as though
7439 it had a separate frame, which is numbered zero as usual, allowing
7440 correct tracing of the function call chain. However, @value{GDBN} has
7441 no provision for frameless functions elsewhere in the stack.
7447 @cindex call stack traces
7448 A backtrace is a summary of how your program got where it is. It shows one
7449 line per frame, for many frames, starting with the currently executing
7450 frame (frame zero), followed by its caller (frame one), and on up the
7453 @anchor{backtrace-command}
7455 @kindex bt @r{(@code{backtrace})}
7456 To print a backtrace of the entire stack, use the @code{backtrace}
7457 command, or its alias @code{bt}. This command will print one line per
7458 frame for frames in the stack. By default, all stack frames are
7459 printed. You can stop the backtrace at any time by typing the system
7460 interrupt character, normally @kbd{Ctrl-c}.
7463 @item backtrace [@var{args}@dots{}]
7464 @itemx bt [@var{args}@dots{}]
7465 Print the backtrace of the entire stack. The optional @var{args} can
7466 be one of the following:
7471 Print only the innermost @var{n} frames, where @var{n} is a positive
7476 Print only the outermost @var{n} frames, where @var{n} is a positive
7480 Print the values of the local variables also. This can be combined
7481 with a number to limit the number of frames shown.
7484 Do not run Python frame filters on this backtrace. @xref{Frame
7485 Filter API}, for more information. Additionally use @ref{disable
7486 frame-filter all} to turn off all frame filters. This is only
7487 relevant when @value{GDBN} has been configured with @code{Python}
7491 A Python frame filter might decide to ``elide'' some frames. Normally
7492 such elided frames are still printed, but they are indented relative
7493 to the filtered frames that cause them to be elided. The @code{hide}
7494 option causes elided frames to not be printed at all.
7500 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7501 are additional aliases for @code{backtrace}.
7503 @cindex multiple threads, backtrace
7504 In a multi-threaded program, @value{GDBN} by default shows the
7505 backtrace only for the current thread. To display the backtrace for
7506 several or all of the threads, use the command @code{thread apply}
7507 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7508 apply all backtrace}, @value{GDBN} will display the backtrace for all
7509 the threads; this is handy when you debug a core dump of a
7510 multi-threaded program.
7512 Each line in the backtrace shows the frame number and the function name.
7513 The program counter value is also shown---unless you use @code{set
7514 print address off}. The backtrace also shows the source file name and
7515 line number, as well as the arguments to the function. The program
7516 counter value is omitted if it is at the beginning of the code for that
7519 Here is an example of a backtrace. It was made with the command
7520 @samp{bt 3}, so it shows the innermost three frames.
7524 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7526 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7527 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7529 (More stack frames follow...)
7534 The display for frame zero does not begin with a program counter
7535 value, indicating that your program has stopped at the beginning of the
7536 code for line @code{993} of @code{builtin.c}.
7539 The value of parameter @code{data} in frame 1 has been replaced by
7540 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7541 only if it is a scalar (integer, pointer, enumeration, etc). See command
7542 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7543 on how to configure the way function parameter values are printed.
7545 @cindex optimized out, in backtrace
7546 @cindex function call arguments, optimized out
7547 If your program was compiled with optimizations, some compilers will
7548 optimize away arguments passed to functions if those arguments are
7549 never used after the call. Such optimizations generate code that
7550 passes arguments through registers, but doesn't store those arguments
7551 in the stack frame. @value{GDBN} has no way of displaying such
7552 arguments in stack frames other than the innermost one. Here's what
7553 such a backtrace might look like:
7557 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7559 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7560 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7562 (More stack frames follow...)
7567 The values of arguments that were not saved in their stack frames are
7568 shown as @samp{<optimized out>}.
7570 If you need to display the values of such optimized-out arguments,
7571 either deduce that from other variables whose values depend on the one
7572 you are interested in, or recompile without optimizations.
7574 @cindex backtrace beyond @code{main} function
7575 @cindex program entry point
7576 @cindex startup code, and backtrace
7577 Most programs have a standard user entry point---a place where system
7578 libraries and startup code transition into user code. For C this is
7579 @code{main}@footnote{
7580 Note that embedded programs (the so-called ``free-standing''
7581 environment) are not required to have a @code{main} function as the
7582 entry point. They could even have multiple entry points.}.
7583 When @value{GDBN} finds the entry function in a backtrace
7584 it will terminate the backtrace, to avoid tracing into highly
7585 system-specific (and generally uninteresting) code.
7587 If you need to examine the startup code, or limit the number of levels
7588 in a backtrace, you can change this behavior:
7591 @item set backtrace past-main
7592 @itemx set backtrace past-main on
7593 @kindex set backtrace
7594 Backtraces will continue past the user entry point.
7596 @item set backtrace past-main off
7597 Backtraces will stop when they encounter the user entry point. This is the
7600 @item show backtrace past-main
7601 @kindex show backtrace
7602 Display the current user entry point backtrace policy.
7604 @item set backtrace past-entry
7605 @itemx set backtrace past-entry on
7606 Backtraces will continue past the internal entry point of an application.
7607 This entry point is encoded by the linker when the application is built,
7608 and is likely before the user entry point @code{main} (or equivalent) is called.
7610 @item set backtrace past-entry off
7611 Backtraces will stop when they encounter the internal entry point of an
7612 application. This is the default.
7614 @item show backtrace past-entry
7615 Display the current internal entry point backtrace policy.
7617 @item set backtrace limit @var{n}
7618 @itemx set backtrace limit 0
7619 @itemx set backtrace limit unlimited
7620 @cindex backtrace limit
7621 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7622 or zero means unlimited levels.
7624 @item show backtrace limit
7625 Display the current limit on backtrace levels.
7628 You can control how file names are displayed.
7631 @item set filename-display
7632 @itemx set filename-display relative
7633 @cindex filename-display
7634 Display file names relative to the compilation directory. This is the default.
7636 @item set filename-display basename
7637 Display only basename of a filename.
7639 @item set filename-display absolute
7640 Display an absolute filename.
7642 @item show filename-display
7643 Show the current way to display filenames.
7647 @section Selecting a Frame
7649 Most commands for examining the stack and other data in your program work on
7650 whichever stack frame is selected at the moment. Here are the commands for
7651 selecting a stack frame; all of them finish by printing a brief description
7652 of the stack frame just selected.
7655 @kindex frame@r{, selecting}
7656 @kindex f @r{(@code{frame})}
7657 @item frame @r{[} @var{frame-selection-spec} @r{]}
7658 @item f @r{[} @var{frame-selection-spec} @r{]}
7659 The @command{frame} command allows different stack frames to be
7660 selected. The @var{frame-selection-spec} can be any of the following:
7665 @item level @var{num}
7666 Select frame level @var{num}. Recall that frame zero is the innermost
7667 (currently executing) frame, frame one is the frame that called the
7668 innermost one, and so on. The highest level frame is usually the one
7671 As this is the most common method of navigating the frame stack, the
7672 string @command{level} can be omitted. For example, the following two
7673 commands are equivalent:
7676 (@value{GDBP}) frame 3
7677 (@value{GDBP}) frame level 3
7680 @kindex frame address
7681 @item address @var{stack-address}
7682 Select the frame with stack address @var{stack-address}. The
7683 @var{stack-address} for a frame can be seen in the output of
7684 @command{info frame}, for example:
7688 Stack level 1, frame at 0x7fffffffda30:
7689 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7690 tail call frame, caller of frame at 0x7fffffffda30
7691 source language c++.
7692 Arglist at unknown address.
7693 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7696 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7697 indicated by the line:
7700 Stack level 1, frame at 0x7fffffffda30:
7703 @kindex frame function
7704 @item function @var{function-name}
7705 Select the stack frame for function @var{function-name}. If there are
7706 multiple stack frames for function @var{function-name} then the inner
7707 most stack frame is selected.
7710 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7711 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7712 viewed has stack address @var{stack-addr}, and optionally, a program
7713 counter address of @var{pc-addr}.
7715 This is useful mainly if the chaining of stack frames has been
7716 damaged by a bug, making it impossible for @value{GDBN} to assign
7717 numbers properly to all frames. In addition, this can be useful
7718 when your program has multiple stacks and switches between them.
7720 When viewing a frame outside the current backtrace using
7721 @command{frame view} then you can always return to the original
7722 stack using one of the previous stack frame selection instructions,
7723 for example @command{frame level 0}.
7729 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7730 numbers @var{n}, this advances toward the outermost frame, to higher
7731 frame numbers, to frames that have existed longer.
7734 @kindex do @r{(@code{down})}
7736 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7737 positive numbers @var{n}, this advances toward the innermost frame, to
7738 lower frame numbers, to frames that were created more recently.
7739 You may abbreviate @code{down} as @code{do}.
7742 All of these commands end by printing two lines of output describing the
7743 frame. The first line shows the frame number, the function name, the
7744 arguments, and the source file and line number of execution in that
7745 frame. The second line shows the text of that source line.
7753 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7755 10 read_input_file (argv[i]);
7759 After such a printout, the @code{list} command with no arguments
7760 prints ten lines centered on the point of execution in the frame.
7761 You can also edit the program at the point of execution with your favorite
7762 editing program by typing @code{edit}.
7763 @xref{List, ,Printing Source Lines},
7767 @kindex select-frame
7768 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7769 The @code{select-frame} command is a variant of @code{frame} that does
7770 not display the new frame after selecting it. This command is
7771 intended primarily for use in @value{GDBN} command scripts, where the
7772 output might be unnecessary and distracting. The
7773 @var{frame-selection-spec} is as for the @command{frame} command
7774 described in @ref{Selection, ,Selecting a Frame}.
7776 @kindex down-silently
7778 @item up-silently @var{n}
7779 @itemx down-silently @var{n}
7780 These two commands are variants of @code{up} and @code{down},
7781 respectively; they differ in that they do their work silently, without
7782 causing display of the new frame. They are intended primarily for use
7783 in @value{GDBN} command scripts, where the output might be unnecessary and
7788 @section Information About a Frame
7790 There are several other commands to print information about the selected
7796 When used without any argument, this command does not change which
7797 frame is selected, but prints a brief description of the currently
7798 selected stack frame. It can be abbreviated @code{f}. With an
7799 argument, this command is used to select a stack frame.
7800 @xref{Selection, ,Selecting a Frame}.
7803 @kindex info f @r{(@code{info frame})}
7806 This command prints a verbose description of the selected stack frame,
7811 the address of the frame
7813 the address of the next frame down (called by this frame)
7815 the address of the next frame up (caller of this frame)
7817 the language in which the source code corresponding to this frame is written
7819 the address of the frame's arguments
7821 the address of the frame's local variables
7823 the program counter saved in it (the address of execution in the caller frame)
7825 which registers were saved in the frame
7828 @noindent The verbose description is useful when
7829 something has gone wrong that has made the stack format fail to fit
7830 the usual conventions.
7832 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7833 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7834 Print a verbose description of the frame selected by
7835 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7836 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7837 a Frame}). The selected frame remains unchanged by this command.
7840 @item info args [-q]
7841 Print the arguments of the selected frame, each on a separate line.
7843 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7844 printing header information and messages explaining why no argument
7847 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7848 Like @kbd{info args}, but only print the arguments selected
7849 with the provided regexp(s).
7851 If @var{regexp} is provided, print only the arguments whose names
7852 match the regular expression @var{regexp}.
7854 If @var{type_regexp} is provided, print only the arguments whose
7855 types, as printed by the @code{whatis} command, match
7856 the regular expression @var{type_regexp}.
7857 If @var{type_regexp} contains space(s), it should be enclosed in
7858 quote characters. If needed, use backslash to escape the meaning
7859 of special characters or quotes.
7861 If both @var{regexp} and @var{type_regexp} are provided, an argument
7862 is printed only if its name matches @var{regexp} and its type matches
7865 @item info locals [-q]
7867 Print the local variables of the selected frame, each on a separate
7868 line. These are all variables (declared either static or automatic)
7869 accessible at the point of execution of the selected frame.
7871 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7872 printing header information and messages explaining why no local variables
7875 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7876 Like @kbd{info locals}, but only print the local variables selected
7877 with the provided regexp(s).
7879 If @var{regexp} is provided, print only the local variables whose names
7880 match the regular expression @var{regexp}.
7882 If @var{type_regexp} is provided, print only the local variables whose
7883 types, as printed by the @code{whatis} command, match
7884 the regular expression @var{type_regexp}.
7885 If @var{type_regexp} contains space(s), it should be enclosed in
7886 quote characters. If needed, use backslash to escape the meaning
7887 of special characters or quotes.
7889 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7890 is printed only if its name matches @var{regexp} and its type matches
7893 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7894 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7895 For example, your program might use Resource Acquisition Is
7896 Initialization types (RAII) such as @code{lock_something_t}: each
7897 local variable of type @code{lock_something_t} automatically places a
7898 lock that is destroyed when the variable goes out of scope. You can
7899 then list all acquired locks in your program by doing
7901 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7904 or the equivalent shorter form
7906 tfaas i lo -q -t lock_something_t
7912 @section Applying a Command to Several Frames.
7914 @cindex apply command to several frames
7916 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7917 The @code{frame apply} command allows you to apply the named
7918 @var{command} to one or more frames.
7922 Specify @code{all} to apply @var{command} to all frames.
7925 Use @var{count} to apply @var{command} to the innermost @var{count}
7926 frames, where @var{count} is a positive number.
7929 Use @var{-count} to apply @var{command} to the outermost @var{count}
7930 frames, where @var{count} is a positive number.
7933 Use @code{level} to apply @var{command} to the set of frames identified
7934 by the @var{level} list. @var{level} is a frame level or a range of frame
7935 levels as @var{level1}-@var{level2}. The frame level is the number shown
7936 in the first field of the @samp{backtrace} command output.
7937 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7938 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7944 Note that the frames on which @code{frame apply} applies a command are
7945 also influenced by the @code{set backtrace} settings such as @code{set
7946 backtrace past-main} and @code{set backtrace limit N}. See
7947 @xref{Backtrace,,Backtraces}.
7949 The @var{flag} arguments control what output to produce and how to handle
7950 errors raised when applying @var{command} to a frame. @var{flag}
7951 must start with a @code{-} directly followed by one letter in
7952 @code{qcs}. If several flags are provided, they must be given
7953 individually, such as @code{-c -q}.
7955 By default, @value{GDBN} displays some frame information before the
7956 output produced by @var{command}, and an error raised during the
7957 execution of a @var{command} will abort @code{frame apply}. The
7958 following flags can be used to fine-tune this behavior:
7962 The flag @code{-c}, which stands for @samp{continue}, causes any
7963 errors in @var{command} to be displayed, and the execution of
7964 @code{frame apply} then continues.
7966 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7967 or empty output produced by a @var{command} to be silently ignored.
7968 That is, the execution continues, but the frame information and errors
7971 The flag @code{-q} (@samp{quiet}) disables printing the frame
7975 The following example shows how the flags @code{-c} and @code{-s} are
7976 working when applying the command @code{p j} to all frames, where
7977 variable @code{j} can only be successfully printed in the outermost
7978 @code{#1 main} frame.
7982 (gdb) frame apply all p j
7983 #0 some_function (i=5) at fun.c:4
7984 No symbol "j" in current context.
7985 (gdb) frame apply all -c p j
7986 #0 some_function (i=5) at fun.c:4
7987 No symbol "j" in current context.
7988 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7990 (gdb) frame apply all -s p j
7991 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7997 By default, @samp{frame apply}, prints the frame location
7998 information before the command output:
8002 (gdb) frame apply all p $sp
8003 #0 some_function (i=5) at fun.c:4
8004 $4 = (void *) 0xffffd1e0
8005 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8006 $5 = (void *) 0xffffd1f0
8011 If flag @code{-q} is given, no frame information is printed:
8014 (gdb) frame apply all -q p $sp
8015 $12 = (void *) 0xffffd1e0
8016 $13 = (void *) 0xffffd1f0
8024 @cindex apply a command to all frames (ignoring errors and empty output)
8025 @item faas @var{command}
8026 Shortcut for @code{frame apply all -s @var{command}}.
8027 Applies @var{command} on all frames, ignoring errors and empty output.
8029 It can for example be used to print a local variable or a function
8030 argument without knowing the frame where this variable or argument
8033 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8036 Note that the command @code{tfaas @var{command}} applies @var{command}
8037 on all frames of all threads. See @xref{Threads,,Threads}.
8041 @node Frame Filter Management
8042 @section Management of Frame Filters.
8043 @cindex managing frame filters
8045 Frame filters are Python based utilities to manage and decorate the
8046 output of frames. @xref{Frame Filter API}, for further information.
8048 Managing frame filters is performed by several commands available
8049 within @value{GDBN}, detailed here.
8052 @kindex info frame-filter
8053 @item info frame-filter
8054 Print a list of installed frame filters from all dictionaries, showing
8055 their name, priority and enabled status.
8057 @kindex disable frame-filter
8058 @anchor{disable frame-filter all}
8059 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8060 Disable a frame filter in the dictionary matching
8061 @var{filter-dictionary} and @var{filter-name}. The
8062 @var{filter-dictionary} may be @code{all}, @code{global},
8063 @code{progspace}, or the name of the object file where the frame filter
8064 dictionary resides. When @code{all} is specified, all frame filters
8065 across all dictionaries are disabled. The @var{filter-name} is the name
8066 of the frame filter and is used when @code{all} is not the option for
8067 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8068 may be enabled again later.
8070 @kindex enable frame-filter
8071 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8072 Enable a frame filter in the dictionary matching
8073 @var{filter-dictionary} and @var{filter-name}. The
8074 @var{filter-dictionary} may be @code{all}, @code{global},
8075 @code{progspace} or the name of the object file where the frame filter
8076 dictionary resides. When @code{all} is specified, all frame filters across
8077 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8078 filter and is used when @code{all} is not the option for
8079 @var{filter-dictionary}.
8084 (gdb) info frame-filter
8086 global frame-filters:
8087 Priority Enabled Name
8088 1000 No PrimaryFunctionFilter
8091 progspace /build/test frame-filters:
8092 Priority Enabled Name
8093 100 Yes ProgspaceFilter
8095 objfile /build/test frame-filters:
8096 Priority Enabled Name
8097 999 Yes BuildProgra Filter
8099 (gdb) disable frame-filter /build/test BuildProgramFilter
8100 (gdb) info frame-filter
8102 global frame-filters:
8103 Priority Enabled Name
8104 1000 No PrimaryFunctionFilter
8107 progspace /build/test frame-filters:
8108 Priority Enabled Name
8109 100 Yes ProgspaceFilter
8111 objfile /build/test frame-filters:
8112 Priority Enabled Name
8113 999 No BuildProgramFilter
8115 (gdb) enable frame-filter global PrimaryFunctionFilter
8116 (gdb) info frame-filter
8118 global frame-filters:
8119 Priority Enabled Name
8120 1000 Yes PrimaryFunctionFilter
8123 progspace /build/test frame-filters:
8124 Priority Enabled Name
8125 100 Yes ProgspaceFilter
8127 objfile /build/test frame-filters:
8128 Priority Enabled Name
8129 999 No BuildProgramFilter
8132 @kindex set frame-filter priority
8133 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8134 Set the @var{priority} of a frame filter in the dictionary matching
8135 @var{filter-dictionary}, and the frame filter name matching
8136 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8137 @code{progspace} or the name of the object file where the frame filter
8138 dictionary resides. The @var{priority} is an integer.
8140 @kindex show frame-filter priority
8141 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8142 Show the @var{priority} of a frame filter in the dictionary matching
8143 @var{filter-dictionary}, and the frame filter name matching
8144 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8145 @code{progspace} or the name of the object file where the frame filter
8151 (gdb) info frame-filter
8153 global frame-filters:
8154 Priority Enabled Name
8155 1000 Yes PrimaryFunctionFilter
8158 progspace /build/test frame-filters:
8159 Priority Enabled Name
8160 100 Yes ProgspaceFilter
8162 objfile /build/test frame-filters:
8163 Priority Enabled Name
8164 999 No BuildProgramFilter
8166 (gdb) set frame-filter priority global Reverse 50
8167 (gdb) info frame-filter
8169 global frame-filters:
8170 Priority Enabled Name
8171 1000 Yes PrimaryFunctionFilter
8174 progspace /build/test frame-filters:
8175 Priority Enabled Name
8176 100 Yes ProgspaceFilter
8178 objfile /build/test frame-filters:
8179 Priority Enabled Name
8180 999 No BuildProgramFilter
8185 @chapter Examining Source Files
8187 @value{GDBN} can print parts of your program's source, since the debugging
8188 information recorded in the program tells @value{GDBN} what source files were
8189 used to build it. When your program stops, @value{GDBN} spontaneously prints
8190 the line where it stopped. Likewise, when you select a stack frame
8191 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8192 execution in that frame has stopped. You can print other portions of
8193 source files by explicit command.
8195 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8196 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8197 @value{GDBN} under @sc{gnu} Emacs}.
8200 * List:: Printing source lines
8201 * Specify Location:: How to specify code locations
8202 * Edit:: Editing source files
8203 * Search:: Searching source files
8204 * Source Path:: Specifying source directories
8205 * Machine Code:: Source and machine code
8209 @section Printing Source Lines
8212 @kindex l @r{(@code{list})}
8213 To print lines from a source file, use the @code{list} command
8214 (abbreviated @code{l}). By default, ten lines are printed.
8215 There are several ways to specify what part of the file you want to
8216 print; see @ref{Specify Location}, for the full list.
8218 Here are the forms of the @code{list} command most commonly used:
8221 @item list @var{linenum}
8222 Print lines centered around line number @var{linenum} in the
8223 current source file.
8225 @item list @var{function}
8226 Print lines centered around the beginning of function
8230 Print more lines. If the last lines printed were printed with a
8231 @code{list} command, this prints lines following the last lines
8232 printed; however, if the last line printed was a solitary line printed
8233 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8234 Stack}), this prints lines centered around that line.
8237 Print lines just before the lines last printed.
8240 @cindex @code{list}, how many lines to display
8241 By default, @value{GDBN} prints ten source lines with any of these forms of
8242 the @code{list} command. You can change this using @code{set listsize}:
8245 @kindex set listsize
8246 @item set listsize @var{count}
8247 @itemx set listsize unlimited
8248 Make the @code{list} command display @var{count} source lines (unless
8249 the @code{list} argument explicitly specifies some other number).
8250 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8252 @kindex show listsize
8254 Display the number of lines that @code{list} prints.
8257 Repeating a @code{list} command with @key{RET} discards the argument,
8258 so it is equivalent to typing just @code{list}. This is more useful
8259 than listing the same lines again. An exception is made for an
8260 argument of @samp{-}; that argument is preserved in repetition so that
8261 each repetition moves up in the source file.
8263 In general, the @code{list} command expects you to supply zero, one or two
8264 @dfn{locations}. Locations specify source lines; there are several ways
8265 of writing them (@pxref{Specify Location}), but the effect is always
8266 to specify some source line.
8268 Here is a complete description of the possible arguments for @code{list}:
8271 @item list @var{location}
8272 Print lines centered around the line specified by @var{location}.
8274 @item list @var{first},@var{last}
8275 Print lines from @var{first} to @var{last}. Both arguments are
8276 locations. When a @code{list} command has two locations, and the
8277 source file of the second location is omitted, this refers to
8278 the same source file as the first location.
8280 @item list ,@var{last}
8281 Print lines ending with @var{last}.
8283 @item list @var{first},
8284 Print lines starting with @var{first}.
8287 Print lines just after the lines last printed.
8290 Print lines just before the lines last printed.
8293 As described in the preceding table.
8296 @node Specify Location
8297 @section Specifying a Location
8298 @cindex specifying location
8300 @cindex source location
8303 * Linespec Locations:: Linespec locations
8304 * Explicit Locations:: Explicit locations
8305 * Address Locations:: Address locations
8308 Several @value{GDBN} commands accept arguments that specify a location
8309 of your program's code. Since @value{GDBN} is a source-level
8310 debugger, a location usually specifies some line in the source code.
8311 Locations may be specified using three different formats:
8312 linespec locations, explicit locations, or address locations.
8314 @node Linespec Locations
8315 @subsection Linespec Locations
8316 @cindex linespec locations
8318 A @dfn{linespec} is a colon-separated list of source location parameters such
8319 as file name, function name, etc. Here are all the different ways of
8320 specifying a linespec:
8324 Specifies the line number @var{linenum} of the current source file.
8327 @itemx +@var{offset}
8328 Specifies the line @var{offset} lines before or after the @dfn{current
8329 line}. For the @code{list} command, the current line is the last one
8330 printed; for the breakpoint commands, this is the line at which
8331 execution stopped in the currently selected @dfn{stack frame}
8332 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8333 used as the second of the two linespecs in a @code{list} command,
8334 this specifies the line @var{offset} lines up or down from the first
8337 @item @var{filename}:@var{linenum}
8338 Specifies the line @var{linenum} in the source file @var{filename}.
8339 If @var{filename} is a relative file name, then it will match any
8340 source file name with the same trailing components. For example, if
8341 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8342 name of @file{/build/trunk/gcc/expr.c}, but not
8343 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8345 @item @var{function}
8346 Specifies the line that begins the body of the function @var{function}.
8347 For example, in C, this is the line with the open brace.
8349 By default, in C@t{++} and Ada, @var{function} is interpreted as
8350 specifying all functions named @var{function} in all scopes. For
8351 C@t{++}, this means in all namespaces and classes. For Ada, this
8352 means in all packages.
8354 For example, assuming a program with C@t{++} symbols named
8355 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8356 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8358 Commands that accept a linespec let you override this with the
8359 @code{-qualified} option. For example, @w{@kbd{break -qualified
8360 func}} sets a breakpoint on a free-function named @code{func} ignoring
8361 any C@t{++} class methods and namespace functions called @code{func}.
8363 @xref{Explicit Locations}.
8365 @item @var{function}:@var{label}
8366 Specifies the line where @var{label} appears in @var{function}.
8368 @item @var{filename}:@var{function}
8369 Specifies the line that begins the body of the function @var{function}
8370 in the file @var{filename}. You only need the file name with a
8371 function name to avoid ambiguity when there are identically named
8372 functions in different source files.
8375 Specifies the line at which the label named @var{label} appears
8376 in the function corresponding to the currently selected stack frame.
8377 If there is no current selected stack frame (for instance, if the inferior
8378 is not running), then @value{GDBN} will not search for a label.
8380 @cindex breakpoint at static probe point
8381 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8382 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8383 applications to embed static probes. @xref{Static Probe Points}, for more
8384 information on finding and using static probes. This form of linespec
8385 specifies the location of such a static probe.
8387 If @var{objfile} is given, only probes coming from that shared library
8388 or executable matching @var{objfile} as a regular expression are considered.
8389 If @var{provider} is given, then only probes from that provider are considered.
8390 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8391 each one of those probes.
8394 @node Explicit Locations
8395 @subsection Explicit Locations
8396 @cindex explicit locations
8398 @dfn{Explicit locations} allow the user to directly specify the source
8399 location's parameters using option-value pairs.
8401 Explicit locations are useful when several functions, labels, or
8402 file names have the same name (base name for files) in the program's
8403 sources. In these cases, explicit locations point to the source
8404 line you meant more accurately and unambiguously. Also, using
8405 explicit locations might be faster in large programs.
8407 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8408 defined in the file named @file{foo} or the label @code{bar} in a function
8409 named @code{foo}. @value{GDBN} must search either the file system or
8410 the symbol table to know.
8412 The list of valid explicit location options is summarized in the
8416 @item -source @var{filename}
8417 The value specifies the source file name. To differentiate between
8418 files with the same base name, prepend as many directories as is necessary
8419 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8420 @value{GDBN} will use the first file it finds with the given base
8421 name. This option requires the use of either @code{-function} or @code{-line}.
8423 @item -function @var{function}
8424 The value specifies the name of a function. Operations
8425 on function locations unmodified by other options (such as @code{-label}
8426 or @code{-line}) refer to the line that begins the body of the function.
8427 In C, for example, this is the line with the open brace.
8429 By default, in C@t{++} and Ada, @var{function} is interpreted as
8430 specifying all functions named @var{function} in all scopes. For
8431 C@t{++}, this means in all namespaces and classes. For Ada, this
8432 means in all packages.
8434 For example, assuming a program with C@t{++} symbols named
8435 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8436 -function func}} and @w{@kbd{break -function B::func}} set a
8437 breakpoint on both symbols.
8439 You can use the @kbd{-qualified} flag to override this (see below).
8443 This flag makes @value{GDBN} interpret a function name specified with
8444 @kbd{-function} as a complete fully-qualified name.
8446 For example, assuming a C@t{++} program with symbols named
8447 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8448 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8450 (Note: the @kbd{-qualified} option can precede a linespec as well
8451 (@pxref{Linespec Locations}), so the particular example above could be
8452 simplified as @w{@kbd{break -qualified B::func}}.)
8454 @item -label @var{label}
8455 The value specifies the name of a label. When the function
8456 name is not specified, the label is searched in the function of the currently
8457 selected stack frame.
8459 @item -line @var{number}
8460 The value specifies a line offset for the location. The offset may either
8461 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8462 the command. When specified without any other options, the line offset is
8463 relative to the current line.
8466 Explicit location options may be abbreviated by omitting any non-unique
8467 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8469 @node Address Locations
8470 @subsection Address Locations
8471 @cindex address locations
8473 @dfn{Address locations} indicate a specific program address. They have
8474 the generalized form *@var{address}.
8476 For line-oriented commands, such as @code{list} and @code{edit}, this
8477 specifies a source line that contains @var{address}. For @code{break} and
8478 other breakpoint-oriented commands, this can be used to set breakpoints in
8479 parts of your program which do not have debugging information or
8482 Here @var{address} may be any expression valid in the current working
8483 language (@pxref{Languages, working language}) that specifies a code
8484 address. In addition, as a convenience, @value{GDBN} extends the
8485 semantics of expressions used in locations to cover several situations
8486 that frequently occur during debugging. Here are the various forms
8490 @item @var{expression}
8491 Any expression valid in the current working language.
8493 @item @var{funcaddr}
8494 An address of a function or procedure derived from its name. In C,
8495 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8496 simply the function's name @var{function} (and actually a special case
8497 of a valid expression). In Pascal and Modula-2, this is
8498 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8499 (although the Pascal form also works).
8501 This form specifies the address of the function's first instruction,
8502 before the stack frame and arguments have been set up.
8504 @item '@var{filename}':@var{funcaddr}
8505 Like @var{funcaddr} above, but also specifies the name of the source
8506 file explicitly. This is useful if the name of the function does not
8507 specify the function unambiguously, e.g., if there are several
8508 functions with identical names in different source files.
8512 @section Editing Source Files
8513 @cindex editing source files
8516 @kindex e @r{(@code{edit})}
8517 To edit the lines in a source file, use the @code{edit} command.
8518 The editing program of your choice
8519 is invoked with the current line set to
8520 the active line in the program.
8521 Alternatively, there are several ways to specify what part of the file you
8522 want to print if you want to see other parts of the program:
8525 @item edit @var{location}
8526 Edit the source file specified by @code{location}. Editing starts at
8527 that @var{location}, e.g., at the specified source line of the
8528 specified file. @xref{Specify Location}, for all the possible forms
8529 of the @var{location} argument; here are the forms of the @code{edit}
8530 command most commonly used:
8533 @item edit @var{number}
8534 Edit the current source file with @var{number} as the active line number.
8536 @item edit @var{function}
8537 Edit the file containing @var{function} at the beginning of its definition.
8542 @subsection Choosing your Editor
8543 You can customize @value{GDBN} to use any editor you want
8545 The only restriction is that your editor (say @code{ex}), recognizes the
8546 following command-line syntax:
8548 ex +@var{number} file
8550 The optional numeric value +@var{number} specifies the number of the line in
8551 the file where to start editing.}.
8552 By default, it is @file{@value{EDITOR}}, but you can change this
8553 by setting the environment variable @code{EDITOR} before using
8554 @value{GDBN}. For example, to configure @value{GDBN} to use the
8555 @code{vi} editor, you could use these commands with the @code{sh} shell:
8561 or in the @code{csh} shell,
8563 setenv EDITOR /usr/bin/vi
8568 @section Searching Source Files
8569 @cindex searching source files
8571 There are two commands for searching through the current source file for a
8576 @kindex forward-search
8577 @kindex fo @r{(@code{forward-search})}
8578 @item forward-search @var{regexp}
8579 @itemx search @var{regexp}
8580 The command @samp{forward-search @var{regexp}} checks each line,
8581 starting with the one following the last line listed, for a match for
8582 @var{regexp}. It lists the line that is found. You can use the
8583 synonym @samp{search @var{regexp}} or abbreviate the command name as
8586 @kindex reverse-search
8587 @item reverse-search @var{regexp}
8588 The command @samp{reverse-search @var{regexp}} checks each line, starting
8589 with the one before the last line listed and going backward, for a match
8590 for @var{regexp}. It lists the line that is found. You can abbreviate
8591 this command as @code{rev}.
8595 @section Specifying Source Directories
8598 @cindex directories for source files
8599 Executable programs sometimes do not record the directories of the source
8600 files from which they were compiled, just the names. Even when they do,
8601 the directories could be moved between the compilation and your debugging
8602 session. @value{GDBN} has a list of directories to search for source files;
8603 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8604 it tries all the directories in the list, in the order they are present
8605 in the list, until it finds a file with the desired name.
8607 For example, suppose an executable references the file
8608 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8609 @file{/mnt/cross}. The file is first looked up literally; if this
8610 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8611 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8612 message is printed. @value{GDBN} does not look up the parts of the
8613 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8614 Likewise, the subdirectories of the source path are not searched: if
8615 the source path is @file{/mnt/cross}, and the binary refers to
8616 @file{foo.c}, @value{GDBN} would not find it under
8617 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8619 Plain file names, relative file names with leading directories, file
8620 names containing dots, etc.@: are all treated as described above; for
8621 instance, if the source path is @file{/mnt/cross}, and the source file
8622 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8623 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8624 that---@file{/mnt/cross/foo.c}.
8626 Note that the executable search path is @emph{not} used to locate the
8629 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8630 any information it has cached about where source files are found and where
8631 each line is in the file.
8635 When you start @value{GDBN}, its source path includes only @samp{cdir}
8636 and @samp{cwd}, in that order.
8637 To add other directories, use the @code{directory} command.
8639 The search path is used to find both program source files and @value{GDBN}
8640 script files (read using the @samp{-command} option and @samp{source} command).
8642 In addition to the source path, @value{GDBN} provides a set of commands
8643 that manage a list of source path substitution rules. A @dfn{substitution
8644 rule} specifies how to rewrite source directories stored in the program's
8645 debug information in case the sources were moved to a different
8646 directory between compilation and debugging. A rule is made of
8647 two strings, the first specifying what needs to be rewritten in
8648 the path, and the second specifying how it should be rewritten.
8649 In @ref{set substitute-path}, we name these two parts @var{from} and
8650 @var{to} respectively. @value{GDBN} does a simple string replacement
8651 of @var{from} with @var{to} at the start of the directory part of the
8652 source file name, and uses that result instead of the original file
8653 name to look up the sources.
8655 Using the previous example, suppose the @file{foo-1.0} tree has been
8656 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8657 @value{GDBN} to replace @file{/usr/src} in all source path names with
8658 @file{/mnt/cross}. The first lookup will then be
8659 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8660 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8661 substitution rule, use the @code{set substitute-path} command
8662 (@pxref{set substitute-path}).
8664 To avoid unexpected substitution results, a rule is applied only if the
8665 @var{from} part of the directory name ends at a directory separator.
8666 For instance, a rule substituting @file{/usr/source} into
8667 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8668 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8669 is applied only at the beginning of the directory name, this rule will
8670 not be applied to @file{/root/usr/source/baz.c} either.
8672 In many cases, you can achieve the same result using the @code{directory}
8673 command. However, @code{set substitute-path} can be more efficient in
8674 the case where the sources are organized in a complex tree with multiple
8675 subdirectories. With the @code{directory} command, you need to add each
8676 subdirectory of your project. If you moved the entire tree while
8677 preserving its internal organization, then @code{set substitute-path}
8678 allows you to direct the debugger to all the sources with one single
8681 @code{set substitute-path} is also more than just a shortcut command.
8682 The source path is only used if the file at the original location no
8683 longer exists. On the other hand, @code{set substitute-path} modifies
8684 the debugger behavior to look at the rewritten location instead. So, if
8685 for any reason a source file that is not relevant to your executable is
8686 located at the original location, a substitution rule is the only
8687 method available to point @value{GDBN} at the new location.
8689 @cindex @samp{--with-relocated-sources}
8690 @cindex default source path substitution
8691 You can configure a default source path substitution rule by
8692 configuring @value{GDBN} with the
8693 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8694 should be the name of a directory under @value{GDBN}'s configured
8695 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8696 directory names in debug information under @var{dir} will be adjusted
8697 automatically if the installed @value{GDBN} is moved to a new
8698 location. This is useful if @value{GDBN}, libraries or executables
8699 with debug information and corresponding source code are being moved
8703 @item directory @var{dirname} @dots{}
8704 @item dir @var{dirname} @dots{}
8705 Add directory @var{dirname} to the front of the source path. Several
8706 directory names may be given to this command, separated by @samp{:}
8707 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8708 part of absolute file names) or
8709 whitespace. You may specify a directory that is already in the source
8710 path; this moves it forward, so @value{GDBN} searches it sooner.
8714 @vindex $cdir@r{, convenience variable}
8715 @vindex $cwd@r{, convenience variable}
8716 @cindex compilation directory
8717 @cindex current directory
8718 @cindex working directory
8719 @cindex directory, current
8720 @cindex directory, compilation
8721 You can use the string @samp{$cdir} to refer to the compilation
8722 directory (if one is recorded), and @samp{$cwd} to refer to the current
8723 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8724 tracks the current working directory as it changes during your @value{GDBN}
8725 session, while the latter is immediately expanded to the current
8726 directory at the time you add an entry to the source path.
8729 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8731 @c RET-repeat for @code{directory} is explicitly disabled, but since
8732 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8734 @item set directories @var{path-list}
8735 @kindex set directories
8736 Set the source path to @var{path-list}.
8737 @samp{$cdir:$cwd} are added if missing.
8739 @item show directories
8740 @kindex show directories
8741 Print the source path: show which directories it contains.
8743 @anchor{set substitute-path}
8744 @item set substitute-path @var{from} @var{to}
8745 @kindex set substitute-path
8746 Define a source path substitution rule, and add it at the end of the
8747 current list of existing substitution rules. If a rule with the same
8748 @var{from} was already defined, then the old rule is also deleted.
8750 For example, if the file @file{/foo/bar/baz.c} was moved to
8751 @file{/mnt/cross/baz.c}, then the command
8754 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8758 will tell @value{GDBN} to replace @samp{/foo/bar} with
8759 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8760 @file{baz.c} even though it was moved.
8762 In the case when more than one substitution rule have been defined,
8763 the rules are evaluated one by one in the order where they have been
8764 defined. The first one matching, if any, is selected to perform
8767 For instance, if we had entered the following commands:
8770 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8771 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8775 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8776 @file{/mnt/include/defs.h} by using the first rule. However, it would
8777 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8778 @file{/mnt/src/lib/foo.c}.
8781 @item unset substitute-path [path]
8782 @kindex unset substitute-path
8783 If a path is specified, search the current list of substitution rules
8784 for a rule that would rewrite that path. Delete that rule if found.
8785 A warning is emitted by the debugger if no rule could be found.
8787 If no path is specified, then all substitution rules are deleted.
8789 @item show substitute-path [path]
8790 @kindex show substitute-path
8791 If a path is specified, then print the source path substitution rule
8792 which would rewrite that path, if any.
8794 If no path is specified, then print all existing source path substitution
8799 If your source path is cluttered with directories that are no longer of
8800 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8801 versions of source. You can correct the situation as follows:
8805 Use @code{directory} with no argument to reset the source path to its default value.
8808 Use @code{directory} with suitable arguments to reinstall the
8809 directories you want in the source path. You can add all the
8810 directories in one command.
8814 @section Source and Machine Code
8815 @cindex source line and its code address
8817 You can use the command @code{info line} to map source lines to program
8818 addresses (and vice versa), and the command @code{disassemble} to display
8819 a range of addresses as machine instructions. You can use the command
8820 @code{set disassemble-next-line} to set whether to disassemble next
8821 source line when execution stops. When run under @sc{gnu} Emacs
8822 mode, the @code{info line} command causes the arrow to point to the
8823 line specified. Also, @code{info line} prints addresses in symbolic form as
8829 @itemx info line @var{location}
8830 Print the starting and ending addresses of the compiled code for
8831 source line @var{location}. You can specify source lines in any of
8832 the ways documented in @ref{Specify Location}. With no @var{location}
8833 information about the current source line is printed.
8836 For example, we can use @code{info line} to discover the location of
8837 the object code for the first line of function
8838 @code{m4_changequote}:
8841 (@value{GDBP}) info line m4_changequote
8842 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8843 ends at 0x6350 <m4_changequote+4>.
8847 @cindex code address and its source line
8848 We can also inquire (using @code{*@var{addr}} as the form for
8849 @var{location}) what source line covers a particular address:
8851 (@value{GDBP}) info line *0x63ff
8852 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8853 ends at 0x6404 <m4_changequote+184>.
8856 @cindex @code{$_} and @code{info line}
8857 @cindex @code{x} command, default address
8858 @kindex x@r{(examine), and} info line
8859 After @code{info line}, the default address for the @code{x} command
8860 is changed to the starting address of the line, so that @samp{x/i} is
8861 sufficient to begin examining the machine code (@pxref{Memory,
8862 ,Examining Memory}). Also, this address is saved as the value of the
8863 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8866 @cindex info line, repeated calls
8867 After @code{info line}, using @code{info line} again without
8868 specifying a location will display information about the next source
8873 @cindex assembly instructions
8874 @cindex instructions, assembly
8875 @cindex machine instructions
8876 @cindex listing machine instructions
8878 @itemx disassemble /m
8879 @itemx disassemble /s
8880 @itemx disassemble /r
8881 This specialized command dumps a range of memory as machine
8882 instructions. It can also print mixed source+disassembly by specifying
8883 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8884 as well as in symbolic form by specifying the @code{/r} modifier.
8885 The default memory range is the function surrounding the
8886 program counter of the selected frame. A single argument to this
8887 command is a program counter value; @value{GDBN} dumps the function
8888 surrounding this value. When two arguments are given, they should
8889 be separated by a comma, possibly surrounded by whitespace. The
8890 arguments specify a range of addresses to dump, in one of two forms:
8893 @item @var{start},@var{end}
8894 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8895 @item @var{start},+@var{length}
8896 the addresses from @var{start} (inclusive) to
8897 @code{@var{start}+@var{length}} (exclusive).
8901 When 2 arguments are specified, the name of the function is also
8902 printed (since there could be several functions in the given range).
8904 The argument(s) can be any expression yielding a numeric value, such as
8905 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8907 If the range of memory being disassembled contains current program counter,
8908 the instruction at that location is shown with a @code{=>} marker.
8911 The following example shows the disassembly of a range of addresses of
8912 HP PA-RISC 2.0 code:
8915 (@value{GDBP}) disas 0x32c4, 0x32e4
8916 Dump of assembler code from 0x32c4 to 0x32e4:
8917 0x32c4 <main+204>: addil 0,dp
8918 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8919 0x32cc <main+212>: ldil 0x3000,r31
8920 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8921 0x32d4 <main+220>: ldo 0(r31),rp
8922 0x32d8 <main+224>: addil -0x800,dp
8923 0x32dc <main+228>: ldo 0x588(r1),r26
8924 0x32e0 <main+232>: ldil 0x3000,r31
8925 End of assembler dump.
8928 Here is an example showing mixed source+assembly for Intel x86
8929 with @code{/m} or @code{/s}, when the program is stopped just after
8930 function prologue in a non-optimized function with no inline code.
8933 (@value{GDBP}) disas /m main
8934 Dump of assembler code for function main:
8936 0x08048330 <+0>: push %ebp
8937 0x08048331 <+1>: mov %esp,%ebp
8938 0x08048333 <+3>: sub $0x8,%esp
8939 0x08048336 <+6>: and $0xfffffff0,%esp
8940 0x08048339 <+9>: sub $0x10,%esp
8942 6 printf ("Hello.\n");
8943 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8944 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8948 0x08048348 <+24>: mov $0x0,%eax
8949 0x0804834d <+29>: leave
8950 0x0804834e <+30>: ret
8952 End of assembler dump.
8955 The @code{/m} option is deprecated as its output is not useful when
8956 there is either inlined code or re-ordered code.
8957 The @code{/s} option is the preferred choice.
8958 Here is an example for AMD x86-64 showing the difference between
8959 @code{/m} output and @code{/s} output.
8960 This example has one inline function defined in a header file,
8961 and the code is compiled with @samp{-O2} optimization.
8962 Note how the @code{/m} output is missing the disassembly of
8963 several instructions that are present in the @code{/s} output.
8993 (@value{GDBP}) disas /m main
8994 Dump of assembler code for function main:
8998 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8999 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9003 0x000000000040041d <+29>: xor %eax,%eax
9004 0x000000000040041f <+31>: retq
9005 0x0000000000400420 <+32>: add %eax,%eax
9006 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9008 End of assembler dump.
9009 (@value{GDBP}) disas /s main
9010 Dump of assembler code for function main:
9014 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9018 0x0000000000400406 <+6>: test %eax,%eax
9019 0x0000000000400408 <+8>: js 0x400420 <main+32>
9024 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9025 0x000000000040040d <+13>: test %eax,%eax
9026 0x000000000040040f <+15>: mov $0x1,%eax
9027 0x0000000000400414 <+20>: cmovne %edx,%eax
9031 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9035 0x000000000040041d <+29>: xor %eax,%eax
9036 0x000000000040041f <+31>: retq
9040 0x0000000000400420 <+32>: add %eax,%eax
9041 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9042 End of assembler dump.
9045 Here is another example showing raw instructions in hex for AMD x86-64,
9048 (gdb) disas /r 0x400281,+10
9049 Dump of assembler code from 0x400281 to 0x40028b:
9050 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9051 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9052 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9053 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9054 End of assembler dump.
9057 Addresses cannot be specified as a location (@pxref{Specify Location}).
9058 So, for example, if you want to disassemble function @code{bar}
9059 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9060 and not @samp{disassemble foo.c:bar}.
9062 Some architectures have more than one commonly-used set of instruction
9063 mnemonics or other syntax.
9065 For programs that were dynamically linked and use shared libraries,
9066 instructions that call functions or branch to locations in the shared
9067 libraries might show a seemingly bogus location---it's actually a
9068 location of the relocation table. On some architectures, @value{GDBN}
9069 might be able to resolve these to actual function names.
9072 @kindex set disassembler-options
9073 @cindex disassembler options
9074 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9075 This command controls the passing of target specific information to
9076 the disassembler. For a list of valid options, please refer to the
9077 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9078 manual and/or the output of @kbd{objdump --help}
9079 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9080 The default value is the empty string.
9082 If it is necessary to specify more than one disassembler option, then
9083 multiple options can be placed together into a comma separated list.
9084 Currently this command is only supported on targets ARM, MIPS, PowerPC
9087 @kindex show disassembler-options
9088 @item show disassembler-options
9089 Show the current setting of the disassembler options.
9093 @kindex set disassembly-flavor
9094 @cindex Intel disassembly flavor
9095 @cindex AT&T disassembly flavor
9096 @item set disassembly-flavor @var{instruction-set}
9097 Select the instruction set to use when disassembling the
9098 program via the @code{disassemble} or @code{x/i} commands.
9100 Currently this command is only defined for the Intel x86 family. You
9101 can set @var{instruction-set} to either @code{intel} or @code{att}.
9102 The default is @code{att}, the AT&T flavor used by default by Unix
9103 assemblers for x86-based targets.
9105 @kindex show disassembly-flavor
9106 @item show disassembly-flavor
9107 Show the current setting of the disassembly flavor.
9111 @kindex set disassemble-next-line
9112 @kindex show disassemble-next-line
9113 @item set disassemble-next-line
9114 @itemx show disassemble-next-line
9115 Control whether or not @value{GDBN} will disassemble the next source
9116 line or instruction when execution stops. If ON, @value{GDBN} will
9117 display disassembly of the next source line when execution of the
9118 program being debugged stops. This is @emph{in addition} to
9119 displaying the source line itself, which @value{GDBN} always does if
9120 possible. If the next source line cannot be displayed for some reason
9121 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9122 info in the debug info), @value{GDBN} will display disassembly of the
9123 next @emph{instruction} instead of showing the next source line. If
9124 AUTO, @value{GDBN} will display disassembly of next instruction only
9125 if the source line cannot be displayed. This setting causes
9126 @value{GDBN} to display some feedback when you step through a function
9127 with no line info or whose source file is unavailable. The default is
9128 OFF, which means never display the disassembly of the next line or
9134 @chapter Examining Data
9136 @cindex printing data
9137 @cindex examining data
9140 The usual way to examine data in your program is with the @code{print}
9141 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9142 evaluates and prints the value of an expression of the language your
9143 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9144 Different Languages}). It may also print the expression using a
9145 Python-based pretty-printer (@pxref{Pretty Printing}).
9148 @item print @var{expr}
9149 @itemx print /@var{f} @var{expr}
9150 @var{expr} is an expression (in the source language). By default the
9151 value of @var{expr} is printed in a format appropriate to its data type;
9152 you can choose a different format by specifying @samp{/@var{f}}, where
9153 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9157 @itemx print /@var{f}
9158 @cindex reprint the last value
9159 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9160 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9161 conveniently inspect the same value in an alternative format.
9164 A more low-level way of examining data is with the @code{x} command.
9165 It examines data in memory at a specified address and prints it in a
9166 specified format. @xref{Memory, ,Examining Memory}.
9168 If you are interested in information about types, or about how the
9169 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9170 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9173 @cindex exploring hierarchical data structures
9175 Another way of examining values of expressions and type information is
9176 through the Python extension command @code{explore} (available only if
9177 the @value{GDBN} build is configured with @code{--with-python}). It
9178 offers an interactive way to start at the highest level (or, the most
9179 abstract level) of the data type of an expression (or, the data type
9180 itself) and explore all the way down to leaf scalar values/fields
9181 embedded in the higher level data types.
9184 @item explore @var{arg}
9185 @var{arg} is either an expression (in the source language), or a type
9186 visible in the current context of the program being debugged.
9189 The working of the @code{explore} command can be illustrated with an
9190 example. If a data type @code{struct ComplexStruct} is defined in your
9200 struct ComplexStruct
9202 struct SimpleStruct *ss_p;
9208 followed by variable declarations as
9211 struct SimpleStruct ss = @{ 10, 1.11 @};
9212 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9216 then, the value of the variable @code{cs} can be explored using the
9217 @code{explore} command as follows.
9221 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9222 the following fields:
9224 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9225 arr = <Enter 1 to explore this field of type `int [10]'>
9227 Enter the field number of choice:
9231 Since the fields of @code{cs} are not scalar values, you are being
9232 prompted to chose the field you want to explore. Let's say you choose
9233 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9234 pointer, you will be asked if it is pointing to a single value. From
9235 the declaration of @code{cs} above, it is indeed pointing to a single
9236 value, hence you enter @code{y}. If you enter @code{n}, then you will
9237 be asked if it were pointing to an array of values, in which case this
9238 field will be explored as if it were an array.
9241 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9242 Continue exploring it as a pointer to a single value [y/n]: y
9243 The value of `*(cs.ss_p)' is a struct/class of type `struct
9244 SimpleStruct' with the following fields:
9246 i = 10 .. (Value of type `int')
9247 d = 1.1100000000000001 .. (Value of type `double')
9249 Press enter to return to parent value:
9253 If the field @code{arr} of @code{cs} was chosen for exploration by
9254 entering @code{1} earlier, then since it is as array, you will be
9255 prompted to enter the index of the element in the array that you want
9259 `cs.arr' is an array of `int'.
9260 Enter the index of the element you want to explore in `cs.arr': 5
9262 `(cs.arr)[5]' is a scalar value of type `int'.
9266 Press enter to return to parent value:
9269 In general, at any stage of exploration, you can go deeper towards the
9270 leaf values by responding to the prompts appropriately, or hit the
9271 return key to return to the enclosing data structure (the @i{higher}
9272 level data structure).
9274 Similar to exploring values, you can use the @code{explore} command to
9275 explore types. Instead of specifying a value (which is typically a
9276 variable name or an expression valid in the current context of the
9277 program being debugged), you specify a type name. If you consider the
9278 same example as above, your can explore the type
9279 @code{struct ComplexStruct} by passing the argument
9280 @code{struct ComplexStruct} to the @code{explore} command.
9283 (gdb) explore struct ComplexStruct
9287 By responding to the prompts appropriately in the subsequent interactive
9288 session, you can explore the type @code{struct ComplexStruct} in a
9289 manner similar to how the value @code{cs} was explored in the above
9292 The @code{explore} command also has two sub-commands,
9293 @code{explore value} and @code{explore type}. The former sub-command is
9294 a way to explicitly specify that value exploration of the argument is
9295 being invoked, while the latter is a way to explicitly specify that type
9296 exploration of the argument is being invoked.
9299 @item explore value @var{expr}
9300 @cindex explore value
9301 This sub-command of @code{explore} explores the value of the
9302 expression @var{expr} (if @var{expr} is an expression valid in the
9303 current context of the program being debugged). The behavior of this
9304 command is identical to that of the behavior of the @code{explore}
9305 command being passed the argument @var{expr}.
9307 @item explore type @var{arg}
9308 @cindex explore type
9309 This sub-command of @code{explore} explores the type of @var{arg} (if
9310 @var{arg} is a type visible in the current context of program being
9311 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9312 is an expression valid in the current context of the program being
9313 debugged). If @var{arg} is a type, then the behavior of this command is
9314 identical to that of the @code{explore} command being passed the
9315 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9316 this command will be identical to that of the @code{explore} command
9317 being passed the type of @var{arg} as the argument.
9321 * Expressions:: Expressions
9322 * Ambiguous Expressions:: Ambiguous Expressions
9323 * Variables:: Program variables
9324 * Arrays:: Artificial arrays
9325 * Output Formats:: Output formats
9326 * Memory:: Examining memory
9327 * Auto Display:: Automatic display
9328 * Print Settings:: Print settings
9329 * Pretty Printing:: Python pretty printing
9330 * Value History:: Value history
9331 * Convenience Vars:: Convenience variables
9332 * Convenience Funs:: Convenience functions
9333 * Registers:: Registers
9334 * Floating Point Hardware:: Floating point hardware
9335 * Vector Unit:: Vector Unit
9336 * OS Information:: Auxiliary data provided by operating system
9337 * Memory Region Attributes:: Memory region attributes
9338 * Dump/Restore Files:: Copy between memory and a file
9339 * Core File Generation:: Cause a program dump its core
9340 * Character Sets:: Debugging programs that use a different
9341 character set than GDB does
9342 * Caching Target Data:: Data caching for targets
9343 * Searching Memory:: Searching memory for a sequence of bytes
9344 * Value Sizes:: Managing memory allocated for values
9348 @section Expressions
9351 @code{print} and many other @value{GDBN} commands accept an expression and
9352 compute its value. Any kind of constant, variable or operator defined
9353 by the programming language you are using is valid in an expression in
9354 @value{GDBN}. This includes conditional expressions, function calls,
9355 casts, and string constants. It also includes preprocessor macros, if
9356 you compiled your program to include this information; see
9359 @cindex arrays in expressions
9360 @value{GDBN} supports array constants in expressions input by
9361 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9362 you can use the command @code{print @{1, 2, 3@}} to create an array
9363 of three integers. If you pass an array to a function or assign it
9364 to a program variable, @value{GDBN} copies the array to memory that
9365 is @code{malloc}ed in the target program.
9367 Because C is so widespread, most of the expressions shown in examples in
9368 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9369 Languages}, for information on how to use expressions in other
9372 In this section, we discuss operators that you can use in @value{GDBN}
9373 expressions regardless of your programming language.
9375 @cindex casts, in expressions
9376 Casts are supported in all languages, not just in C, because it is so
9377 useful to cast a number into a pointer in order to examine a structure
9378 at that address in memory.
9379 @c FIXME: casts supported---Mod2 true?
9381 @value{GDBN} supports these operators, in addition to those common
9382 to programming languages:
9386 @samp{@@} is a binary operator for treating parts of memory as arrays.
9387 @xref{Arrays, ,Artificial Arrays}, for more information.
9390 @samp{::} allows you to specify a variable in terms of the file or
9391 function where it is defined. @xref{Variables, ,Program Variables}.
9393 @cindex @{@var{type}@}
9394 @cindex type casting memory
9395 @cindex memory, viewing as typed object
9396 @cindex casts, to view memory
9397 @item @{@var{type}@} @var{addr}
9398 Refers to an object of type @var{type} stored at address @var{addr} in
9399 memory. The address @var{addr} may be any expression whose value is
9400 an integer or pointer (but parentheses are required around binary
9401 operators, just as in a cast). This construct is allowed regardless
9402 of what kind of data is normally supposed to reside at @var{addr}.
9405 @node Ambiguous Expressions
9406 @section Ambiguous Expressions
9407 @cindex ambiguous expressions
9409 Expressions can sometimes contain some ambiguous elements. For instance,
9410 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9411 a single function name to be defined several times, for application in
9412 different contexts. This is called @dfn{overloading}. Another example
9413 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9414 templates and is typically instantiated several times, resulting in
9415 the same function name being defined in different contexts.
9417 In some cases and depending on the language, it is possible to adjust
9418 the expression to remove the ambiguity. For instance in C@t{++}, you
9419 can specify the signature of the function you want to break on, as in
9420 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9421 qualified name of your function often makes the expression unambiguous
9424 When an ambiguity that needs to be resolved is detected, the debugger
9425 has the capability to display a menu of numbered choices for each
9426 possibility, and then waits for the selection with the prompt @samp{>}.
9427 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9428 aborts the current command. If the command in which the expression was
9429 used allows more than one choice to be selected, the next option in the
9430 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9433 For example, the following session excerpt shows an attempt to set a
9434 breakpoint at the overloaded symbol @code{String::after}.
9435 We choose three particular definitions of that function name:
9437 @c FIXME! This is likely to change to show arg type lists, at least
9440 (@value{GDBP}) b String::after
9443 [2] file:String.cc; line number:867
9444 [3] file:String.cc; line number:860
9445 [4] file:String.cc; line number:875
9446 [5] file:String.cc; line number:853
9447 [6] file:String.cc; line number:846
9448 [7] file:String.cc; line number:735
9450 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9451 Breakpoint 2 at 0xb344: file String.cc, line 875.
9452 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9453 Multiple breakpoints were set.
9454 Use the "delete" command to delete unwanted
9461 @kindex set multiple-symbols
9462 @item set multiple-symbols @var{mode}
9463 @cindex multiple-symbols menu
9465 This option allows you to adjust the debugger behavior when an expression
9468 By default, @var{mode} is set to @code{all}. If the command with which
9469 the expression is used allows more than one choice, then @value{GDBN}
9470 automatically selects all possible choices. For instance, inserting
9471 a breakpoint on a function using an ambiguous name results in a breakpoint
9472 inserted on each possible match. However, if a unique choice must be made,
9473 then @value{GDBN} uses the menu to help you disambiguate the expression.
9474 For instance, printing the address of an overloaded function will result
9475 in the use of the menu.
9477 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9478 when an ambiguity is detected.
9480 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9481 an error due to the ambiguity and the command is aborted.
9483 @kindex show multiple-symbols
9484 @item show multiple-symbols
9485 Show the current value of the @code{multiple-symbols} setting.
9489 @section Program Variables
9491 The most common kind of expression to use is the name of a variable
9494 Variables in expressions are understood in the selected stack frame
9495 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9499 global (or file-static)
9506 visible according to the scope rules of the
9507 programming language from the point of execution in that frame
9510 @noindent This means that in the function
9525 you can examine and use the variable @code{a} whenever your program is
9526 executing within the function @code{foo}, but you can only use or
9527 examine the variable @code{b} while your program is executing inside
9528 the block where @code{b} is declared.
9530 @cindex variable name conflict
9531 There is an exception: you can refer to a variable or function whose
9532 scope is a single source file even if the current execution point is not
9533 in this file. But it is possible to have more than one such variable or
9534 function with the same name (in different source files). If that
9535 happens, referring to that name has unpredictable effects. If you wish,
9536 you can specify a static variable in a particular function or file by
9537 using the colon-colon (@code{::}) notation:
9539 @cindex colon-colon, context for variables/functions
9541 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9542 @cindex @code{::}, context for variables/functions
9545 @var{file}::@var{variable}
9546 @var{function}::@var{variable}
9550 Here @var{file} or @var{function} is the name of the context for the
9551 static @var{variable}. In the case of file names, you can use quotes to
9552 make sure @value{GDBN} parses the file name as a single word---for example,
9553 to print a global value of @code{x} defined in @file{f2.c}:
9556 (@value{GDBP}) p 'f2.c'::x
9559 The @code{::} notation is normally used for referring to
9560 static variables, since you typically disambiguate uses of local variables
9561 in functions by selecting the appropriate frame and using the
9562 simple name of the variable. However, you may also use this notation
9563 to refer to local variables in frames enclosing the selected frame:
9572 process (a); /* Stop here */
9583 For example, if there is a breakpoint at the commented line,
9584 here is what you might see
9585 when the program stops after executing the call @code{bar(0)}:
9590 (@value{GDBP}) p bar::a
9593 #2 0x080483d0 in foo (a=5) at foobar.c:12
9596 (@value{GDBP}) p bar::a
9600 @cindex C@t{++} scope resolution
9601 These uses of @samp{::} are very rarely in conflict with the very
9602 similar use of the same notation in C@t{++}. When they are in
9603 conflict, the C@t{++} meaning takes precedence; however, this can be
9604 overridden by quoting the file or function name with single quotes.
9606 For example, suppose the program is stopped in a method of a class
9607 that has a field named @code{includefile}, and there is also an
9608 include file named @file{includefile} that defines a variable,
9612 (@value{GDBP}) p includefile
9614 (@value{GDBP}) p includefile::some_global
9615 A syntax error in expression, near `'.
9616 (@value{GDBP}) p 'includefile'::some_global
9620 @cindex wrong values
9621 @cindex variable values, wrong
9622 @cindex function entry/exit, wrong values of variables
9623 @cindex optimized code, wrong values of variables
9625 @emph{Warning:} Occasionally, a local variable may appear to have the
9626 wrong value at certain points in a function---just after entry to a new
9627 scope, and just before exit.
9629 You may see this problem when you are stepping by machine instructions.
9630 This is because, on most machines, it takes more than one instruction to
9631 set up a stack frame (including local variable definitions); if you are
9632 stepping by machine instructions, variables may appear to have the wrong
9633 values until the stack frame is completely built. On exit, it usually
9634 also takes more than one machine instruction to destroy a stack frame;
9635 after you begin stepping through that group of instructions, local
9636 variable definitions may be gone.
9638 This may also happen when the compiler does significant optimizations.
9639 To be sure of always seeing accurate values, turn off all optimization
9642 @cindex ``No symbol "foo" in current context''
9643 Another possible effect of compiler optimizations is to optimize
9644 unused variables out of existence, or assign variables to registers (as
9645 opposed to memory addresses). Depending on the support for such cases
9646 offered by the debug info format used by the compiler, @value{GDBN}
9647 might not be able to display values for such local variables. If that
9648 happens, @value{GDBN} will print a message like this:
9651 No symbol "foo" in current context.
9654 To solve such problems, either recompile without optimizations, or use a
9655 different debug info format, if the compiler supports several such
9656 formats. @xref{Compilation}, for more information on choosing compiler
9657 options. @xref{C, ,C and C@t{++}}, for more information about debug
9658 info formats that are best suited to C@t{++} programs.
9660 If you ask to print an object whose contents are unknown to
9661 @value{GDBN}, e.g., because its data type is not completely specified
9662 by the debug information, @value{GDBN} will say @samp{<incomplete
9663 type>}. @xref{Symbols, incomplete type}, for more about this.
9665 @cindex no debug info variables
9666 If you try to examine or use the value of a (global) variable for
9667 which @value{GDBN} has no type information, e.g., because the program
9668 includes no debug information, @value{GDBN} displays an error message.
9669 @xref{Symbols, unknown type}, for more about unknown types. If you
9670 cast the variable to its declared type, @value{GDBN} gets the
9671 variable's value using the cast-to type as the variable's type. For
9672 example, in a C program:
9675 (@value{GDBP}) p var
9676 'var' has unknown type; cast it to its declared type
9677 (@value{GDBP}) p (float) var
9681 If you append @kbd{@@entry} string to a function parameter name you get its
9682 value at the time the function got called. If the value is not available an
9683 error message is printed. Entry values are available only with some compilers.
9684 Entry values are normally also printed at the function parameter list according
9685 to @ref{set print entry-values}.
9688 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9694 (gdb) print i@@entry
9698 Strings are identified as arrays of @code{char} values without specified
9699 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9700 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9701 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9702 defines literal string type @code{"char"} as @code{char} without a sign.
9707 signed char var1[] = "A";
9710 You get during debugging
9715 $2 = @{65 'A', 0 '\0'@}
9719 @section Artificial Arrays
9721 @cindex artificial array
9723 @kindex @@@r{, referencing memory as an array}
9724 It is often useful to print out several successive objects of the
9725 same type in memory; a section of an array, or an array of
9726 dynamically determined size for which only a pointer exists in the
9729 You can do this by referring to a contiguous span of memory as an
9730 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9731 operand of @samp{@@} should be the first element of the desired array
9732 and be an individual object. The right operand should be the desired length
9733 of the array. The result is an array value whose elements are all of
9734 the type of the left argument. The first element is actually the left
9735 argument; the second element comes from bytes of memory immediately
9736 following those that hold the first element, and so on. Here is an
9737 example. If a program says
9740 int *array = (int *) malloc (len * sizeof (int));
9744 you can print the contents of @code{array} with
9750 The left operand of @samp{@@} must reside in memory. Array values made
9751 with @samp{@@} in this way behave just like other arrays in terms of
9752 subscripting, and are coerced to pointers when used in expressions.
9753 Artificial arrays most often appear in expressions via the value history
9754 (@pxref{Value History, ,Value History}), after printing one out.
9756 Another way to create an artificial array is to use a cast.
9757 This re-interprets a value as if it were an array.
9758 The value need not be in memory:
9760 (@value{GDBP}) p/x (short[2])0x12345678
9761 $1 = @{0x1234, 0x5678@}
9764 As a convenience, if you leave the array length out (as in
9765 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9766 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9768 (@value{GDBP}) p/x (short[])0x12345678
9769 $2 = @{0x1234, 0x5678@}
9772 Sometimes the artificial array mechanism is not quite enough; in
9773 moderately complex data structures, the elements of interest may not
9774 actually be adjacent---for example, if you are interested in the values
9775 of pointers in an array. One useful work-around in this situation is
9776 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9777 Variables}) as a counter in an expression that prints the first
9778 interesting value, and then repeat that expression via @key{RET}. For
9779 instance, suppose you have an array @code{dtab} of pointers to
9780 structures, and you are interested in the values of a field @code{fv}
9781 in each structure. Here is an example of what you might type:
9791 @node Output Formats
9792 @section Output Formats
9794 @cindex formatted output
9795 @cindex output formats
9796 By default, @value{GDBN} prints a value according to its data type. Sometimes
9797 this is not what you want. For example, you might want to print a number
9798 in hex, or a pointer in decimal. Or you might want to view data in memory
9799 at a certain address as a character string or as an instruction. To do
9800 these things, specify an @dfn{output format} when you print a value.
9802 The simplest use of output formats is to say how to print a value
9803 already computed. This is done by starting the arguments of the
9804 @code{print} command with a slash and a format letter. The format
9805 letters supported are:
9809 Regard the bits of the value as an integer, and print the integer in
9813 Print as integer in signed decimal.
9816 Print as integer in unsigned decimal.
9819 Print as integer in octal.
9822 Print as integer in binary. The letter @samp{t} stands for ``two''.
9823 @footnote{@samp{b} cannot be used because these format letters are also
9824 used with the @code{x} command, where @samp{b} stands for ``byte'';
9825 see @ref{Memory,,Examining Memory}.}
9828 @cindex unknown address, locating
9829 @cindex locate address
9830 Print as an address, both absolute in hexadecimal and as an offset from
9831 the nearest preceding symbol. You can use this format used to discover
9832 where (in what function) an unknown address is located:
9835 (@value{GDBP}) p/a 0x54320
9836 $3 = 0x54320 <_initialize_vx+396>
9840 The command @code{info symbol 0x54320} yields similar results.
9841 @xref{Symbols, info symbol}.
9844 Regard as an integer and print it as a character constant. This
9845 prints both the numerical value and its character representation. The
9846 character representation is replaced with the octal escape @samp{\nnn}
9847 for characters outside the 7-bit @sc{ascii} range.
9849 Without this format, @value{GDBN} displays @code{char},
9850 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9851 constants. Single-byte members of vectors are displayed as integer
9855 Regard the bits of the value as a floating point number and print
9856 using typical floating point syntax.
9859 @cindex printing strings
9860 @cindex printing byte arrays
9861 Regard as a string, if possible. With this format, pointers to single-byte
9862 data are displayed as null-terminated strings and arrays of single-byte data
9863 are displayed as fixed-length strings. Other values are displayed in their
9866 Without this format, @value{GDBN} displays pointers to and arrays of
9867 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9868 strings. Single-byte members of a vector are displayed as an integer
9872 Like @samp{x} formatting, the value is treated as an integer and
9873 printed as hexadecimal, but leading zeros are printed to pad the value
9874 to the size of the integer type.
9877 @cindex raw printing
9878 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9879 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9880 Printing}). This typically results in a higher-level display of the
9881 value's contents. The @samp{r} format bypasses any Python
9882 pretty-printer which might exist.
9885 For example, to print the program counter in hex (@pxref{Registers}), type
9892 Note that no space is required before the slash; this is because command
9893 names in @value{GDBN} cannot contain a slash.
9895 To reprint the last value in the value history with a different format,
9896 you can use the @code{print} command with just a format and no
9897 expression. For example, @samp{p/x} reprints the last value in hex.
9900 @section Examining Memory
9902 You can use the command @code{x} (for ``examine'') to examine memory in
9903 any of several formats, independently of your program's data types.
9905 @cindex examining memory
9907 @kindex x @r{(examine memory)}
9908 @item x/@var{nfu} @var{addr}
9911 Use the @code{x} command to examine memory.
9914 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9915 much memory to display and how to format it; @var{addr} is an
9916 expression giving the address where you want to start displaying memory.
9917 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9918 Several commands set convenient defaults for @var{addr}.
9921 @item @var{n}, the repeat count
9922 The repeat count is a decimal integer; the default is 1. It specifies
9923 how much memory (counting by units @var{u}) to display. If a negative
9924 number is specified, memory is examined backward from @var{addr}.
9925 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9928 @item @var{f}, the display format
9929 The display format is one of the formats used by @code{print}
9930 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9931 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9932 The default is @samp{x} (hexadecimal) initially. The default changes
9933 each time you use either @code{x} or @code{print}.
9935 @item @var{u}, the unit size
9936 The unit size is any of
9942 Halfwords (two bytes).
9944 Words (four bytes). This is the initial default.
9946 Giant words (eight bytes).
9949 Each time you specify a unit size with @code{x}, that size becomes the
9950 default unit the next time you use @code{x}. For the @samp{i} format,
9951 the unit size is ignored and is normally not written. For the @samp{s} format,
9952 the unit size defaults to @samp{b}, unless it is explicitly given.
9953 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9954 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9955 Note that the results depend on the programming language of the
9956 current compilation unit. If the language is C, the @samp{s}
9957 modifier will use the UTF-16 encoding while @samp{w} will use
9958 UTF-32. The encoding is set by the programming language and cannot
9961 @item @var{addr}, starting display address
9962 @var{addr} is the address where you want @value{GDBN} to begin displaying
9963 memory. The expression need not have a pointer value (though it may);
9964 it is always interpreted as an integer address of a byte of memory.
9965 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9966 @var{addr} is usually just after the last address examined---but several
9967 other commands also set the default address: @code{info breakpoints} (to
9968 the address of the last breakpoint listed), @code{info line} (to the
9969 starting address of a line), and @code{print} (if you use it to display
9970 a value from memory).
9973 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9974 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9975 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9976 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9977 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9979 You can also specify a negative repeat count to examine memory backward
9980 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9981 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9983 Since the letters indicating unit sizes are all distinct from the
9984 letters specifying output formats, you do not have to remember whether
9985 unit size or format comes first; either order works. The output
9986 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9987 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9989 Even though the unit size @var{u} is ignored for the formats @samp{s}
9990 and @samp{i}, you might still want to use a count @var{n}; for example,
9991 @samp{3i} specifies that you want to see three machine instructions,
9992 including any operands. For convenience, especially when used with
9993 the @code{display} command, the @samp{i} format also prints branch delay
9994 slot instructions, if any, beyond the count specified, which immediately
9995 follow the last instruction that is within the count. The command
9996 @code{disassemble} gives an alternative way of inspecting machine
9997 instructions; see @ref{Machine Code,,Source and Machine Code}.
9999 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10000 the command displays null-terminated strings or instructions before the given
10001 address as many as the absolute value of the given number. For the @samp{i}
10002 format, we use line number information in the debug info to accurately locate
10003 instruction boundaries while disassembling backward. If line info is not
10004 available, the command stops examining memory with an error message.
10006 All the defaults for the arguments to @code{x} are designed to make it
10007 easy to continue scanning memory with minimal specifications each time
10008 you use @code{x}. For example, after you have inspected three machine
10009 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10010 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10011 the repeat count @var{n} is used again; the other arguments default as
10012 for successive uses of @code{x}.
10014 When examining machine instructions, the instruction at current program
10015 counter is shown with a @code{=>} marker. For example:
10018 (@value{GDBP}) x/5i $pc-6
10019 0x804837f <main+11>: mov %esp,%ebp
10020 0x8048381 <main+13>: push %ecx
10021 0x8048382 <main+14>: sub $0x4,%esp
10022 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10023 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10026 @cindex @code{$_}, @code{$__}, and value history
10027 The addresses and contents printed by the @code{x} command are not saved
10028 in the value history because there is often too much of them and they
10029 would get in the way. Instead, @value{GDBN} makes these values available for
10030 subsequent use in expressions as values of the convenience variables
10031 @code{$_} and @code{$__}. After an @code{x} command, the last address
10032 examined is available for use in expressions in the convenience variable
10033 @code{$_}. The contents of that address, as examined, are available in
10034 the convenience variable @code{$__}.
10036 If the @code{x} command has a repeat count, the address and contents saved
10037 are from the last memory unit printed; this is not the same as the last
10038 address printed if several units were printed on the last line of output.
10040 @anchor{addressable memory unit}
10041 @cindex addressable memory unit
10042 Most targets have an addressable memory unit size of 8 bits. This means
10043 that to each memory address are associated 8 bits of data. Some
10044 targets, however, have other addressable memory unit sizes.
10045 Within @value{GDBN} and this document, the term
10046 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10047 when explicitly referring to a chunk of data of that size. The word
10048 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10049 the addressable memory unit size of the target. For most systems,
10050 addressable memory unit is a synonym of byte.
10052 @cindex remote memory comparison
10053 @cindex target memory comparison
10054 @cindex verify remote memory image
10055 @cindex verify target memory image
10056 When you are debugging a program running on a remote target machine
10057 (@pxref{Remote Debugging}), you may wish to verify the program's image
10058 in the remote machine's memory against the executable file you
10059 downloaded to the target. Or, on any target, you may want to check
10060 whether the program has corrupted its own read-only sections. The
10061 @code{compare-sections} command is provided for such situations.
10064 @kindex compare-sections
10065 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10066 Compare the data of a loadable section @var{section-name} in the
10067 executable file of the program being debugged with the same section in
10068 the target machine's memory, and report any mismatches. With no
10069 arguments, compares all loadable sections. With an argument of
10070 @code{-r}, compares all loadable read-only sections.
10072 Note: for remote targets, this command can be accelerated if the
10073 target supports computing the CRC checksum of a block of memory
10074 (@pxref{qCRC packet}).
10078 @section Automatic Display
10079 @cindex automatic display
10080 @cindex display of expressions
10082 If you find that you want to print the value of an expression frequently
10083 (to see how it changes), you might want to add it to the @dfn{automatic
10084 display list} so that @value{GDBN} prints its value each time your program stops.
10085 Each expression added to the list is given a number to identify it;
10086 to remove an expression from the list, you specify that number.
10087 The automatic display looks like this:
10091 3: bar[5] = (struct hack *) 0x3804
10095 This display shows item numbers, expressions and their current values. As with
10096 displays you request manually using @code{x} or @code{print}, you can
10097 specify the output format you prefer; in fact, @code{display} decides
10098 whether to use @code{print} or @code{x} depending your format
10099 specification---it uses @code{x} if you specify either the @samp{i}
10100 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10104 @item display @var{expr}
10105 Add the expression @var{expr} to the list of expressions to display
10106 each time your program stops. @xref{Expressions, ,Expressions}.
10108 @code{display} does not repeat if you press @key{RET} again after using it.
10110 @item display/@var{fmt} @var{expr}
10111 For @var{fmt} specifying only a display format and not a size or
10112 count, add the expression @var{expr} to the auto-display list but
10113 arrange to display it each time in the specified format @var{fmt}.
10114 @xref{Output Formats,,Output Formats}.
10116 @item display/@var{fmt} @var{addr}
10117 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10118 number of units, add the expression @var{addr} as a memory address to
10119 be examined each time your program stops. Examining means in effect
10120 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10123 For example, @samp{display/i $pc} can be helpful, to see the machine
10124 instruction about to be executed each time execution stops (@samp{$pc}
10125 is a common name for the program counter; @pxref{Registers, ,Registers}).
10128 @kindex delete display
10130 @item undisplay @var{dnums}@dots{}
10131 @itemx delete display @var{dnums}@dots{}
10132 Remove items from the list of expressions to display. Specify the
10133 numbers of the displays that you want affected with the command
10134 argument @var{dnums}. It can be a single display number, one of the
10135 numbers shown in the first field of the @samp{info display} display;
10136 or it could be a range of display numbers, as in @code{2-4}.
10138 @code{undisplay} does not repeat if you press @key{RET} after using it.
10139 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10141 @kindex disable display
10142 @item disable display @var{dnums}@dots{}
10143 Disable the display of item numbers @var{dnums}. A disabled display
10144 item is not printed automatically, but is not forgotten. It may be
10145 enabled again later. Specify the numbers of the displays that you
10146 want affected with the command argument @var{dnums}. It can be a
10147 single display number, one of the numbers shown in the first field of
10148 the @samp{info display} display; or it could be a range of display
10149 numbers, as in @code{2-4}.
10151 @kindex enable display
10152 @item enable display @var{dnums}@dots{}
10153 Enable display of item numbers @var{dnums}. It becomes effective once
10154 again in auto display of its expression, until you specify otherwise.
10155 Specify the numbers of the displays that you want affected with the
10156 command argument @var{dnums}. It can be a single display number, one
10157 of the numbers shown in the first field of the @samp{info display}
10158 display; or it could be a range of display numbers, as in @code{2-4}.
10161 Display the current values of the expressions on the list, just as is
10162 done when your program stops.
10164 @kindex info display
10166 Print the list of expressions previously set up to display
10167 automatically, each one with its item number, but without showing the
10168 values. This includes disabled expressions, which are marked as such.
10169 It also includes expressions which would not be displayed right now
10170 because they refer to automatic variables not currently available.
10173 @cindex display disabled out of scope
10174 If a display expression refers to local variables, then it does not make
10175 sense outside the lexical context for which it was set up. Such an
10176 expression is disabled when execution enters a context where one of its
10177 variables is not defined. For example, if you give the command
10178 @code{display last_char} while inside a function with an argument
10179 @code{last_char}, @value{GDBN} displays this argument while your program
10180 continues to stop inside that function. When it stops elsewhere---where
10181 there is no variable @code{last_char}---the display is disabled
10182 automatically. The next time your program stops where @code{last_char}
10183 is meaningful, you can enable the display expression once again.
10185 @node Print Settings
10186 @section Print Settings
10188 @cindex format options
10189 @cindex print settings
10190 @value{GDBN} provides the following ways to control how arrays, structures,
10191 and symbols are printed.
10194 These settings are useful for debugging programs in any language:
10198 @item set print address
10199 @itemx set print address on
10200 @cindex print/don't print memory addresses
10201 @value{GDBN} prints memory addresses showing the location of stack
10202 traces, structure values, pointer values, breakpoints, and so forth,
10203 even when it also displays the contents of those addresses. The default
10204 is @code{on}. For example, this is what a stack frame display looks like with
10205 @code{set print address on}:
10210 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10212 530 if (lquote != def_lquote)
10216 @item set print address off
10217 Do not print addresses when displaying their contents. For example,
10218 this is the same stack frame displayed with @code{set print address off}:
10222 (@value{GDBP}) set print addr off
10224 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10225 530 if (lquote != def_lquote)
10229 You can use @samp{set print address off} to eliminate all machine
10230 dependent displays from the @value{GDBN} interface. For example, with
10231 @code{print address off}, you should get the same text for backtraces on
10232 all machines---whether or not they involve pointer arguments.
10235 @item show print address
10236 Show whether or not addresses are to be printed.
10239 When @value{GDBN} prints a symbolic address, it normally prints the
10240 closest earlier symbol plus an offset. If that symbol does not uniquely
10241 identify the address (for example, it is a name whose scope is a single
10242 source file), you may need to clarify. One way to do this is with
10243 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10244 you can set @value{GDBN} to print the source file and line number when
10245 it prints a symbolic address:
10248 @item set print symbol-filename on
10249 @cindex source file and line of a symbol
10250 @cindex symbol, source file and line
10251 Tell @value{GDBN} to print the source file name and line number of a
10252 symbol in the symbolic form of an address.
10254 @item set print symbol-filename off
10255 Do not print source file name and line number of a symbol. This is the
10258 @item show print symbol-filename
10259 Show whether or not @value{GDBN} will print the source file name and
10260 line number of a symbol in the symbolic form of an address.
10263 Another situation where it is helpful to show symbol filenames and line
10264 numbers is when disassembling code; @value{GDBN} shows you the line
10265 number and source file that corresponds to each instruction.
10267 Also, you may wish to see the symbolic form only if the address being
10268 printed is reasonably close to the closest earlier symbol:
10271 @item set print max-symbolic-offset @var{max-offset}
10272 @itemx set print max-symbolic-offset unlimited
10273 @cindex maximum value for offset of closest symbol
10274 Tell @value{GDBN} to only display the symbolic form of an address if the
10275 offset between the closest earlier symbol and the address is less than
10276 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10277 to always print the symbolic form of an address if any symbol precedes
10278 it. Zero is equivalent to @code{unlimited}.
10280 @item show print max-symbolic-offset
10281 Ask how large the maximum offset is that @value{GDBN} prints in a
10285 @cindex wild pointer, interpreting
10286 @cindex pointer, finding referent
10287 If you have a pointer and you are not sure where it points, try
10288 @samp{set print symbol-filename on}. Then you can determine the name
10289 and source file location of the variable where it points, using
10290 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10291 For example, here @value{GDBN} shows that a variable @code{ptt} points
10292 at another variable @code{t}, defined in @file{hi2.c}:
10295 (@value{GDBP}) set print symbol-filename on
10296 (@value{GDBP}) p/a ptt
10297 $4 = 0xe008 <t in hi2.c>
10301 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10302 does not show the symbol name and filename of the referent, even with
10303 the appropriate @code{set print} options turned on.
10306 You can also enable @samp{/a}-like formatting all the time using
10307 @samp{set print symbol on}:
10310 @item set print symbol on
10311 Tell @value{GDBN} to print the symbol corresponding to an address, if
10314 @item set print symbol off
10315 Tell @value{GDBN} not to print the symbol corresponding to an
10316 address. In this mode, @value{GDBN} will still print the symbol
10317 corresponding to pointers to functions. This is the default.
10319 @item show print symbol
10320 Show whether @value{GDBN} will display the symbol corresponding to an
10324 Other settings control how different kinds of objects are printed:
10327 @item set print array
10328 @itemx set print array on
10329 @cindex pretty print arrays
10330 Pretty print arrays. This format is more convenient to read,
10331 but uses more space. The default is off.
10333 @item set print array off
10334 Return to compressed format for arrays.
10336 @item show print array
10337 Show whether compressed or pretty format is selected for displaying
10340 @cindex print array indexes
10341 @item set print array-indexes
10342 @itemx set print array-indexes on
10343 Print the index of each element when displaying arrays. May be more
10344 convenient to locate a given element in the array or quickly find the
10345 index of a given element in that printed array. The default is off.
10347 @item set print array-indexes off
10348 Stop printing element indexes when displaying arrays.
10350 @item show print array-indexes
10351 Show whether the index of each element is printed when displaying
10354 @item set print elements @var{number-of-elements}
10355 @itemx set print elements unlimited
10356 @cindex number of array elements to print
10357 @cindex limit on number of printed array elements
10358 Set a limit on how many elements of an array @value{GDBN} will print.
10359 If @value{GDBN} is printing a large array, it stops printing after it has
10360 printed the number of elements set by the @code{set print elements} command.
10361 This limit also applies to the display of strings.
10362 When @value{GDBN} starts, this limit is set to 200.
10363 Setting @var{number-of-elements} to @code{unlimited} or zero means
10364 that the number of elements to print is unlimited.
10366 @item show print elements
10367 Display the number of elements of a large array that @value{GDBN} will print.
10368 If the number is 0, then the printing is unlimited.
10370 @item set print frame-arguments @var{value}
10371 @kindex set print frame-arguments
10372 @cindex printing frame argument values
10373 @cindex print all frame argument values
10374 @cindex print frame argument values for scalars only
10375 @cindex do not print frame argument values
10376 This command allows to control how the values of arguments are printed
10377 when the debugger prints a frame (@pxref{Frames}). The possible
10382 The values of all arguments are printed.
10385 Print the value of an argument only if it is a scalar. The value of more
10386 complex arguments such as arrays, structures, unions, etc, is replaced
10387 by @code{@dots{}}. This is the default. Here is an example where
10388 only scalar arguments are shown:
10391 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10396 None of the argument values are printed. Instead, the value of each argument
10397 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10400 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10405 By default, only scalar arguments are printed. This command can be used
10406 to configure the debugger to print the value of all arguments, regardless
10407 of their type. However, it is often advantageous to not print the value
10408 of more complex parameters. For instance, it reduces the amount of
10409 information printed in each frame, making the backtrace more readable.
10410 Also, it improves performance when displaying Ada frames, because
10411 the computation of large arguments can sometimes be CPU-intensive,
10412 especially in large applications. Setting @code{print frame-arguments}
10413 to @code{scalars} (the default) or @code{none} avoids this computation,
10414 thus speeding up the display of each Ada frame.
10416 @item show print frame-arguments
10417 Show how the value of arguments should be displayed when printing a frame.
10419 @item set print raw frame-arguments on
10420 Print frame arguments in raw, non pretty-printed, form.
10422 @item set print raw frame-arguments off
10423 Print frame arguments in pretty-printed form, if there is a pretty-printer
10424 for the value (@pxref{Pretty Printing}),
10425 otherwise print the value in raw form.
10426 This is the default.
10428 @item show print raw frame-arguments
10429 Show whether to print frame arguments in raw form.
10431 @anchor{set print entry-values}
10432 @item set print entry-values @var{value}
10433 @kindex set print entry-values
10434 Set printing of frame argument values at function entry. In some cases
10435 @value{GDBN} can determine the value of function argument which was passed by
10436 the function caller, even if the value was modified inside the called function
10437 and therefore is different. With optimized code, the current value could be
10438 unavailable, but the entry value may still be known.
10440 The default value is @code{default} (see below for its description). Older
10441 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10442 this feature will behave in the @code{default} setting the same way as with the
10445 This functionality is currently supported only by DWARF 2 debugging format and
10446 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10447 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10450 The @var{value} parameter can be one of the following:
10454 Print only actual parameter values, never print values from function entry
10458 #0 different (val=6)
10459 #0 lost (val=<optimized out>)
10461 #0 invalid (val=<optimized out>)
10465 Print only parameter values from function entry point. The actual parameter
10466 values are never printed.
10468 #0 equal (val@@entry=5)
10469 #0 different (val@@entry=5)
10470 #0 lost (val@@entry=5)
10471 #0 born (val@@entry=<optimized out>)
10472 #0 invalid (val@@entry=<optimized out>)
10476 Print only parameter values from function entry point. If value from function
10477 entry point is not known while the actual value is known, print the actual
10478 value for such parameter.
10480 #0 equal (val@@entry=5)
10481 #0 different (val@@entry=5)
10482 #0 lost (val@@entry=5)
10484 #0 invalid (val@@entry=<optimized out>)
10488 Print actual parameter values. If actual parameter value is not known while
10489 value from function entry point is known, print the entry point value for such
10493 #0 different (val=6)
10494 #0 lost (val@@entry=5)
10496 #0 invalid (val=<optimized out>)
10500 Always print both the actual parameter value and its value from function entry
10501 point, even if values of one or both are not available due to compiler
10504 #0 equal (val=5, val@@entry=5)
10505 #0 different (val=6, val@@entry=5)
10506 #0 lost (val=<optimized out>, val@@entry=5)
10507 #0 born (val=10, val@@entry=<optimized out>)
10508 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10512 Print the actual parameter value if it is known and also its value from
10513 function entry point if it is known. If neither is known, print for the actual
10514 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10515 values are known and identical, print the shortened
10516 @code{param=param@@entry=VALUE} notation.
10518 #0 equal (val=val@@entry=5)
10519 #0 different (val=6, val@@entry=5)
10520 #0 lost (val@@entry=5)
10522 #0 invalid (val=<optimized out>)
10526 Always print the actual parameter value. Print also its value from function
10527 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10528 if both values are known and identical, print the shortened
10529 @code{param=param@@entry=VALUE} notation.
10531 #0 equal (val=val@@entry=5)
10532 #0 different (val=6, val@@entry=5)
10533 #0 lost (val=<optimized out>, val@@entry=5)
10535 #0 invalid (val=<optimized out>)
10539 For analysis messages on possible failures of frame argument values at function
10540 entry resolution see @ref{set debug entry-values}.
10542 @item show print entry-values
10543 Show the method being used for printing of frame argument values at function
10546 @item set print repeats @var{number-of-repeats}
10547 @itemx set print repeats unlimited
10548 @cindex repeated array elements
10549 Set the threshold for suppressing display of repeated array
10550 elements. When the number of consecutive identical elements of an
10551 array exceeds the threshold, @value{GDBN} prints the string
10552 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10553 identical repetitions, instead of displaying the identical elements
10554 themselves. Setting the threshold to @code{unlimited} or zero will
10555 cause all elements to be individually printed. The default threshold
10558 @item show print repeats
10559 Display the current threshold for printing repeated identical
10562 @item set print null-stop
10563 @cindex @sc{null} elements in arrays
10564 Cause @value{GDBN} to stop printing the characters of an array when the first
10565 @sc{null} is encountered. This is useful when large arrays actually
10566 contain only short strings.
10567 The default is off.
10569 @item show print null-stop
10570 Show whether @value{GDBN} stops printing an array on the first
10571 @sc{null} character.
10573 @item set print pretty on
10574 @cindex print structures in indented form
10575 @cindex indentation in structure display
10576 Cause @value{GDBN} to print structures in an indented format with one member
10577 per line, like this:
10592 @item set print pretty off
10593 Cause @value{GDBN} to print structures in a compact format, like this:
10597 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10598 meat = 0x54 "Pork"@}
10603 This is the default format.
10605 @item show print pretty
10606 Show which format @value{GDBN} is using to print structures.
10608 @item set print sevenbit-strings on
10609 @cindex eight-bit characters in strings
10610 @cindex octal escapes in strings
10611 Print using only seven-bit characters; if this option is set,
10612 @value{GDBN} displays any eight-bit characters (in strings or
10613 character values) using the notation @code{\}@var{nnn}. This setting is
10614 best if you are working in English (@sc{ascii}) and you use the
10615 high-order bit of characters as a marker or ``meta'' bit.
10617 @item set print sevenbit-strings off
10618 Print full eight-bit characters. This allows the use of more
10619 international character sets, and is the default.
10621 @item show print sevenbit-strings
10622 Show whether or not @value{GDBN} is printing only seven-bit characters.
10624 @item set print union on
10625 @cindex unions in structures, printing
10626 Tell @value{GDBN} to print unions which are contained in structures
10627 and other unions. This is the default setting.
10629 @item set print union off
10630 Tell @value{GDBN} not to print unions which are contained in
10631 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10634 @item show print union
10635 Ask @value{GDBN} whether or not it will print unions which are contained in
10636 structures and other unions.
10638 For example, given the declarations
10641 typedef enum @{Tree, Bug@} Species;
10642 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10643 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10654 struct thing foo = @{Tree, @{Acorn@}@};
10658 with @code{set print union on} in effect @samp{p foo} would print
10661 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10665 and with @code{set print union off} in effect it would print
10668 $1 = @{it = Tree, form = @{...@}@}
10672 @code{set print union} affects programs written in C-like languages
10678 These settings are of interest when debugging C@t{++} programs:
10681 @cindex demangling C@t{++} names
10682 @item set print demangle
10683 @itemx set print demangle on
10684 Print C@t{++} names in their source form rather than in the encoded
10685 (``mangled'') form passed to the assembler and linker for type-safe
10686 linkage. The default is on.
10688 @item show print demangle
10689 Show whether C@t{++} names are printed in mangled or demangled form.
10691 @item set print asm-demangle
10692 @itemx set print asm-demangle on
10693 Print C@t{++} names in their source form rather than their mangled form, even
10694 in assembler code printouts such as instruction disassemblies.
10695 The default is off.
10697 @item show print asm-demangle
10698 Show whether C@t{++} names in assembly listings are printed in mangled
10701 @cindex C@t{++} symbol decoding style
10702 @cindex symbol decoding style, C@t{++}
10703 @kindex set demangle-style
10704 @item set demangle-style @var{style}
10705 Choose among several encoding schemes used by different compilers to
10706 represent C@t{++} names. The choices for @var{style} are currently:
10710 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10711 This is the default.
10714 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10717 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10720 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10723 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10724 @strong{Warning:} this setting alone is not sufficient to allow
10725 debugging @code{cfront}-generated executables. @value{GDBN} would
10726 require further enhancement to permit that.
10729 If you omit @var{style}, you will see a list of possible formats.
10731 @item show demangle-style
10732 Display the encoding style currently in use for decoding C@t{++} symbols.
10734 @item set print object
10735 @itemx set print object on
10736 @cindex derived type of an object, printing
10737 @cindex display derived types
10738 When displaying a pointer to an object, identify the @emph{actual}
10739 (derived) type of the object rather than the @emph{declared} type, using
10740 the virtual function table. Note that the virtual function table is
10741 required---this feature can only work for objects that have run-time
10742 type identification; a single virtual method in the object's declared
10743 type is sufficient. Note that this setting is also taken into account when
10744 working with variable objects via MI (@pxref{GDB/MI}).
10746 @item set print object off
10747 Display only the declared type of objects, without reference to the
10748 virtual function table. This is the default setting.
10750 @item show print object
10751 Show whether actual, or declared, object types are displayed.
10753 @item set print static-members
10754 @itemx set print static-members on
10755 @cindex static members of C@t{++} objects
10756 Print static members when displaying a C@t{++} object. The default is on.
10758 @item set print static-members off
10759 Do not print static members when displaying a C@t{++} object.
10761 @item show print static-members
10762 Show whether C@t{++} static members are printed or not.
10764 @item set print pascal_static-members
10765 @itemx set print pascal_static-members on
10766 @cindex static members of Pascal objects
10767 @cindex Pascal objects, static members display
10768 Print static members when displaying a Pascal object. The default is on.
10770 @item set print pascal_static-members off
10771 Do not print static members when displaying a Pascal object.
10773 @item show print pascal_static-members
10774 Show whether Pascal static members are printed or not.
10776 @c These don't work with HP ANSI C++ yet.
10777 @item set print vtbl
10778 @itemx set print vtbl on
10779 @cindex pretty print C@t{++} virtual function tables
10780 @cindex virtual functions (C@t{++}) display
10781 @cindex VTBL display
10782 Pretty print C@t{++} virtual function tables. The default is off.
10783 (The @code{vtbl} commands do not work on programs compiled with the HP
10784 ANSI C@t{++} compiler (@code{aCC}).)
10786 @item set print vtbl off
10787 Do not pretty print C@t{++} virtual function tables.
10789 @item show print vtbl
10790 Show whether C@t{++} virtual function tables are pretty printed, or not.
10793 @node Pretty Printing
10794 @section Pretty Printing
10796 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10797 Python code. It greatly simplifies the display of complex objects. This
10798 mechanism works for both MI and the CLI.
10801 * Pretty-Printer Introduction:: Introduction to pretty-printers
10802 * Pretty-Printer Example:: An example pretty-printer
10803 * Pretty-Printer Commands:: Pretty-printer commands
10806 @node Pretty-Printer Introduction
10807 @subsection Pretty-Printer Introduction
10809 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10810 registered for the value. If there is then @value{GDBN} invokes the
10811 pretty-printer to print the value. Otherwise the value is printed normally.
10813 Pretty-printers are normally named. This makes them easy to manage.
10814 The @samp{info pretty-printer} command will list all the installed
10815 pretty-printers with their names.
10816 If a pretty-printer can handle multiple data types, then its
10817 @dfn{subprinters} are the printers for the individual data types.
10818 Each such subprinter has its own name.
10819 The format of the name is @var{printer-name};@var{subprinter-name}.
10821 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10822 Typically they are automatically loaded and registered when the corresponding
10823 debug information is loaded, thus making them available without having to
10824 do anything special.
10826 There are three places where a pretty-printer can be registered.
10830 Pretty-printers registered globally are available when debugging
10834 Pretty-printers registered with a program space are available only
10835 when debugging that program.
10836 @xref{Progspaces In Python}, for more details on program spaces in Python.
10839 Pretty-printers registered with an objfile are loaded and unloaded
10840 with the corresponding objfile (e.g., shared library).
10841 @xref{Objfiles In Python}, for more details on objfiles in Python.
10844 @xref{Selecting Pretty-Printers}, for further information on how
10845 pretty-printers are selected,
10847 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10850 @node Pretty-Printer Example
10851 @subsection Pretty-Printer Example
10853 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10856 (@value{GDBP}) print s
10858 static npos = 4294967295,
10860 <std::allocator<char>> = @{
10861 <__gnu_cxx::new_allocator<char>> = @{
10862 <No data fields>@}, <No data fields>
10864 members of std::basic_string<char, std::char_traits<char>,
10865 std::allocator<char> >::_Alloc_hider:
10866 _M_p = 0x804a014 "abcd"
10871 With a pretty-printer for @code{std::string} only the contents are printed:
10874 (@value{GDBP}) print s
10878 @node Pretty-Printer Commands
10879 @subsection Pretty-Printer Commands
10880 @cindex pretty-printer commands
10883 @kindex info pretty-printer
10884 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10885 Print the list of installed pretty-printers.
10886 This includes disabled pretty-printers, which are marked as such.
10888 @var{object-regexp} is a regular expression matching the objects
10889 whose pretty-printers to list.
10890 Objects can be @code{global}, the program space's file
10891 (@pxref{Progspaces In Python}),
10892 and the object files within that program space (@pxref{Objfiles In Python}).
10893 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10894 looks up a printer from these three objects.
10896 @var{name-regexp} is a regular expression matching the name of the printers
10899 @kindex disable pretty-printer
10900 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10901 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10902 A disabled pretty-printer is not forgotten, it may be enabled again later.
10904 @kindex enable pretty-printer
10905 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10906 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10911 Suppose we have three pretty-printers installed: one from library1.so
10912 named @code{foo} that prints objects of type @code{foo}, and
10913 another from library2.so named @code{bar} that prints two types of objects,
10914 @code{bar1} and @code{bar2}.
10917 (gdb) info pretty-printer
10924 (gdb) info pretty-printer library2
10929 (gdb) disable pretty-printer library1
10931 2 of 3 printers enabled
10932 (gdb) info pretty-printer
10939 (gdb) disable pretty-printer library2 bar;bar1
10941 1 of 3 printers enabled
10942 (gdb) info pretty-printer library2
10949 (gdb) disable pretty-printer library2 bar
10951 0 of 3 printers enabled
10952 (gdb) info pretty-printer library2
10961 Note that for @code{bar} the entire printer can be disabled,
10962 as can each individual subprinter.
10964 @node Value History
10965 @section Value History
10967 @cindex value history
10968 @cindex history of values printed by @value{GDBN}
10969 Values printed by the @code{print} command are saved in the @value{GDBN}
10970 @dfn{value history}. This allows you to refer to them in other expressions.
10971 Values are kept until the symbol table is re-read or discarded
10972 (for example with the @code{file} or @code{symbol-file} commands).
10973 When the symbol table changes, the value history is discarded,
10974 since the values may contain pointers back to the types defined in the
10979 @cindex history number
10980 The values printed are given @dfn{history numbers} by which you can
10981 refer to them. These are successive integers starting with one.
10982 @code{print} shows you the history number assigned to a value by
10983 printing @samp{$@var{num} = } before the value; here @var{num} is the
10986 To refer to any previous value, use @samp{$} followed by the value's
10987 history number. The way @code{print} labels its output is designed to
10988 remind you of this. Just @code{$} refers to the most recent value in
10989 the history, and @code{$$} refers to the value before that.
10990 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10991 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10992 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10994 For example, suppose you have just printed a pointer to a structure and
10995 want to see the contents of the structure. It suffices to type
11001 If you have a chain of structures where the component @code{next} points
11002 to the next one, you can print the contents of the next one with this:
11009 You can print successive links in the chain by repeating this
11010 command---which you can do by just typing @key{RET}.
11012 Note that the history records values, not expressions. If the value of
11013 @code{x} is 4 and you type these commands:
11021 then the value recorded in the value history by the @code{print} command
11022 remains 4 even though the value of @code{x} has changed.
11025 @kindex show values
11027 Print the last ten values in the value history, with their item numbers.
11028 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11029 values} does not change the history.
11031 @item show values @var{n}
11032 Print ten history values centered on history item number @var{n}.
11034 @item show values +
11035 Print ten history values just after the values last printed. If no more
11036 values are available, @code{show values +} produces no display.
11039 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11040 same effect as @samp{show values +}.
11042 @node Convenience Vars
11043 @section Convenience Variables
11045 @cindex convenience variables
11046 @cindex user-defined variables
11047 @value{GDBN} provides @dfn{convenience variables} that you can use within
11048 @value{GDBN} to hold on to a value and refer to it later. These variables
11049 exist entirely within @value{GDBN}; they are not part of your program, and
11050 setting a convenience variable has no direct effect on further execution
11051 of your program. That is why you can use them freely.
11053 Convenience variables are prefixed with @samp{$}. Any name preceded by
11054 @samp{$} can be used for a convenience variable, unless it is one of
11055 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11056 (Value history references, in contrast, are @emph{numbers} preceded
11057 by @samp{$}. @xref{Value History, ,Value History}.)
11059 You can save a value in a convenience variable with an assignment
11060 expression, just as you would set a variable in your program.
11064 set $foo = *object_ptr
11068 would save in @code{$foo} the value contained in the object pointed to by
11071 Using a convenience variable for the first time creates it, but its
11072 value is @code{void} until you assign a new value. You can alter the
11073 value with another assignment at any time.
11075 Convenience variables have no fixed types. You can assign a convenience
11076 variable any type of value, including structures and arrays, even if
11077 that variable already has a value of a different type. The convenience
11078 variable, when used as an expression, has the type of its current value.
11081 @kindex show convenience
11082 @cindex show all user variables and functions
11083 @item show convenience
11084 Print a list of convenience variables used so far, and their values,
11085 as well as a list of the convenience functions.
11086 Abbreviated @code{show conv}.
11088 @kindex init-if-undefined
11089 @cindex convenience variables, initializing
11090 @item init-if-undefined $@var{variable} = @var{expression}
11091 Set a convenience variable if it has not already been set. This is useful
11092 for user-defined commands that keep some state. It is similar, in concept,
11093 to using local static variables with initializers in C (except that
11094 convenience variables are global). It can also be used to allow users to
11095 override default values used in a command script.
11097 If the variable is already defined then the expression is not evaluated so
11098 any side-effects do not occur.
11101 One of the ways to use a convenience variable is as a counter to be
11102 incremented or a pointer to be advanced. For example, to print
11103 a field from successive elements of an array of structures:
11107 print bar[$i++]->contents
11111 Repeat that command by typing @key{RET}.
11113 Some convenience variables are created automatically by @value{GDBN} and given
11114 values likely to be useful.
11117 @vindex $_@r{, convenience variable}
11119 The variable @code{$_} is automatically set by the @code{x} command to
11120 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11121 commands which provide a default address for @code{x} to examine also
11122 set @code{$_} to that address; these commands include @code{info line}
11123 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11124 except when set by the @code{x} command, in which case it is a pointer
11125 to the type of @code{$__}.
11127 @vindex $__@r{, convenience variable}
11129 The variable @code{$__} is automatically set by the @code{x} command
11130 to the value found in the last address examined. Its type is chosen
11131 to match the format in which the data was printed.
11134 @vindex $_exitcode@r{, convenience variable}
11135 When the program being debugged terminates normally, @value{GDBN}
11136 automatically sets this variable to the exit code of the program, and
11137 resets @code{$_exitsignal} to @code{void}.
11140 @vindex $_exitsignal@r{, convenience variable}
11141 When the program being debugged dies due to an uncaught signal,
11142 @value{GDBN} automatically sets this variable to that signal's number,
11143 and resets @code{$_exitcode} to @code{void}.
11145 To distinguish between whether the program being debugged has exited
11146 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11147 @code{$_exitsignal} is not @code{void}), the convenience function
11148 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11149 Functions}). For example, considering the following source code:
11152 #include <signal.h>
11155 main (int argc, char *argv[])
11162 A valid way of telling whether the program being debugged has exited
11163 or signalled would be:
11166 (@value{GDBP}) define has_exited_or_signalled
11167 Type commands for definition of ``has_exited_or_signalled''.
11168 End with a line saying just ``end''.
11169 >if $_isvoid ($_exitsignal)
11170 >echo The program has exited\n
11172 >echo The program has signalled\n
11178 Program terminated with signal SIGALRM, Alarm clock.
11179 The program no longer exists.
11180 (@value{GDBP}) has_exited_or_signalled
11181 The program has signalled
11184 As can be seen, @value{GDBN} correctly informs that the program being
11185 debugged has signalled, since it calls @code{raise} and raises a
11186 @code{SIGALRM} signal. If the program being debugged had not called
11187 @code{raise}, then @value{GDBN} would report a normal exit:
11190 (@value{GDBP}) has_exited_or_signalled
11191 The program has exited
11195 The variable @code{$_exception} is set to the exception object being
11196 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11199 @itemx $_probe_arg0@dots{}$_probe_arg11
11200 Arguments to a static probe. @xref{Static Probe Points}.
11203 @vindex $_sdata@r{, inspect, convenience variable}
11204 The variable @code{$_sdata} contains extra collected static tracepoint
11205 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11206 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11207 if extra static tracepoint data has not been collected.
11210 @vindex $_siginfo@r{, convenience variable}
11211 The variable @code{$_siginfo} contains extra signal information
11212 (@pxref{extra signal information}). Note that @code{$_siginfo}
11213 could be empty, if the application has not yet received any signals.
11214 For example, it will be empty before you execute the @code{run} command.
11217 @vindex $_tlb@r{, convenience variable}
11218 The variable @code{$_tlb} is automatically set when debugging
11219 applications running on MS-Windows in native mode or connected to
11220 gdbserver that supports the @code{qGetTIBAddr} request.
11221 @xref{General Query Packets}.
11222 This variable contains the address of the thread information block.
11225 The number of the current inferior. @xref{Inferiors and
11226 Programs, ,Debugging Multiple Inferiors and Programs}.
11229 The thread number of the current thread. @xref{thread numbers}.
11232 The global number of the current thread. @xref{global thread numbers}.
11236 @node Convenience Funs
11237 @section Convenience Functions
11239 @cindex convenience functions
11240 @value{GDBN} also supplies some @dfn{convenience functions}. These
11241 have a syntax similar to convenience variables. A convenience
11242 function can be used in an expression just like an ordinary function;
11243 however, a convenience function is implemented internally to
11246 These functions do not require @value{GDBN} to be configured with
11247 @code{Python} support, which means that they are always available.
11251 @item $_isvoid (@var{expr})
11252 @findex $_isvoid@r{, convenience function}
11253 Return one if the expression @var{expr} is @code{void}. Otherwise it
11256 A @code{void} expression is an expression where the type of the result
11257 is @code{void}. For example, you can examine a convenience variable
11258 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11262 (@value{GDBP}) print $_exitcode
11264 (@value{GDBP}) print $_isvoid ($_exitcode)
11267 Starting program: ./a.out
11268 [Inferior 1 (process 29572) exited normally]
11269 (@value{GDBP}) print $_exitcode
11271 (@value{GDBP}) print $_isvoid ($_exitcode)
11275 In the example above, we used @code{$_isvoid} to check whether
11276 @code{$_exitcode} is @code{void} before and after the execution of the
11277 program being debugged. Before the execution there is no exit code to
11278 be examined, therefore @code{$_exitcode} is @code{void}. After the
11279 execution the program being debugged returned zero, therefore
11280 @code{$_exitcode} is zero, which means that it is not @code{void}
11283 The @code{void} expression can also be a call of a function from the
11284 program being debugged. For example, given the following function:
11293 The result of calling it inside @value{GDBN} is @code{void}:
11296 (@value{GDBP}) print foo ()
11298 (@value{GDBP}) print $_isvoid (foo ())
11300 (@value{GDBP}) set $v = foo ()
11301 (@value{GDBP}) print $v
11303 (@value{GDBP}) print $_isvoid ($v)
11309 These functions require @value{GDBN} to be configured with
11310 @code{Python} support.
11314 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11315 @findex $_memeq@r{, convenience function}
11316 Returns one if the @var{length} bytes at the addresses given by
11317 @var{buf1} and @var{buf2} are equal.
11318 Otherwise it returns zero.
11320 @item $_regex(@var{str}, @var{regex})
11321 @findex $_regex@r{, convenience function}
11322 Returns one if the string @var{str} matches the regular expression
11323 @var{regex}. Otherwise it returns zero.
11324 The syntax of the regular expression is that specified by @code{Python}'s
11325 regular expression support.
11327 @item $_streq(@var{str1}, @var{str2})
11328 @findex $_streq@r{, convenience function}
11329 Returns one if the strings @var{str1} and @var{str2} are equal.
11330 Otherwise it returns zero.
11332 @item $_strlen(@var{str})
11333 @findex $_strlen@r{, convenience function}
11334 Returns the length of string @var{str}.
11336 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11337 @findex $_caller_is@r{, convenience function}
11338 Returns one if the calling function's name is equal to @var{name}.
11339 Otherwise it returns zero.
11341 If the optional argument @var{number_of_frames} is provided,
11342 it is the number of frames up in the stack to look.
11350 at testsuite/gdb.python/py-caller-is.c:21
11351 #1 0x00000000004005a0 in middle_func ()
11352 at testsuite/gdb.python/py-caller-is.c:27
11353 #2 0x00000000004005ab in top_func ()
11354 at testsuite/gdb.python/py-caller-is.c:33
11355 #3 0x00000000004005b6 in main ()
11356 at testsuite/gdb.python/py-caller-is.c:39
11357 (gdb) print $_caller_is ("middle_func")
11359 (gdb) print $_caller_is ("top_func", 2)
11363 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11364 @findex $_caller_matches@r{, convenience function}
11365 Returns one if the calling function's name matches the regular expression
11366 @var{regexp}. Otherwise it returns zero.
11368 If the optional argument @var{number_of_frames} is provided,
11369 it is the number of frames up in the stack to look.
11372 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11373 @findex $_any_caller_is@r{, convenience function}
11374 Returns one if any calling function's name is equal to @var{name}.
11375 Otherwise it returns zero.
11377 If the optional argument @var{number_of_frames} is provided,
11378 it is the number of frames up in the stack to look.
11381 This function differs from @code{$_caller_is} in that this function
11382 checks all stack frames from the immediate caller to the frame specified
11383 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11384 frame specified by @var{number_of_frames}.
11386 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11387 @findex $_any_caller_matches@r{, convenience function}
11388 Returns one if any calling function's name matches the regular expression
11389 @var{regexp}. Otherwise it returns zero.
11391 If the optional argument @var{number_of_frames} is provided,
11392 it is the number of frames up in the stack to look.
11395 This function differs from @code{$_caller_matches} in that this function
11396 checks all stack frames from the immediate caller to the frame specified
11397 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11398 frame specified by @var{number_of_frames}.
11400 @item $_as_string(@var{value})
11401 @findex $_as_string@r{, convenience function}
11402 Return the string representation of @var{value}.
11404 This function is useful to obtain the textual label (enumerator) of an
11405 enumeration value. For example, assuming the variable @var{node} is of
11406 an enumerated type:
11409 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11410 Visiting node of type NODE_INTEGER
11415 @value{GDBN} provides the ability to list and get help on
11416 convenience functions.
11419 @item help function
11420 @kindex help function
11421 @cindex show all convenience functions
11422 Print a list of all convenience functions.
11429 You can refer to machine register contents, in expressions, as variables
11430 with names starting with @samp{$}. The names of registers are different
11431 for each machine; use @code{info registers} to see the names used on
11435 @kindex info registers
11436 @item info registers
11437 Print the names and values of all registers except floating-point
11438 and vector registers (in the selected stack frame).
11440 @kindex info all-registers
11441 @cindex floating point registers
11442 @item info all-registers
11443 Print the names and values of all registers, including floating-point
11444 and vector registers (in the selected stack frame).
11446 @item info registers @var{reggroup} @dots{}
11447 Print the name and value of the registers in each of the specified
11448 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11449 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11451 @item info registers @var{regname} @dots{}
11452 Print the @dfn{relativized} value of each specified register @var{regname}.
11453 As discussed in detail below, register values are normally relative to
11454 the selected stack frame. The @var{regname} may be any register name valid on
11455 the machine you are using, with or without the initial @samp{$}.
11458 @anchor{standard registers}
11459 @cindex stack pointer register
11460 @cindex program counter register
11461 @cindex process status register
11462 @cindex frame pointer register
11463 @cindex standard registers
11464 @value{GDBN} has four ``standard'' register names that are available (in
11465 expressions) on most machines---whenever they do not conflict with an
11466 architecture's canonical mnemonics for registers. The register names
11467 @code{$pc} and @code{$sp} are used for the program counter register and
11468 the stack pointer. @code{$fp} is used for a register that contains a
11469 pointer to the current stack frame, and @code{$ps} is used for a
11470 register that contains the processor status. For example,
11471 you could print the program counter in hex with
11478 or print the instruction to be executed next with
11485 or add four to the stack pointer@footnote{This is a way of removing
11486 one word from the stack, on machines where stacks grow downward in
11487 memory (most machines, nowadays). This assumes that the innermost
11488 stack frame is selected; setting @code{$sp} is not allowed when other
11489 stack frames are selected. To pop entire frames off the stack,
11490 regardless of machine architecture, use @code{return};
11491 see @ref{Returning, ,Returning from a Function}.} with
11497 Whenever possible, these four standard register names are available on
11498 your machine even though the machine has different canonical mnemonics,
11499 so long as there is no conflict. The @code{info registers} command
11500 shows the canonical names. For example, on the SPARC, @code{info
11501 registers} displays the processor status register as @code{$psr} but you
11502 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11503 is an alias for the @sc{eflags} register.
11505 @value{GDBN} always considers the contents of an ordinary register as an
11506 integer when the register is examined in this way. Some machines have
11507 special registers which can hold nothing but floating point; these
11508 registers are considered to have floating point values. There is no way
11509 to refer to the contents of an ordinary register as floating point value
11510 (although you can @emph{print} it as a floating point value with
11511 @samp{print/f $@var{regname}}).
11513 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11514 means that the data format in which the register contents are saved by
11515 the operating system is not the same one that your program normally
11516 sees. For example, the registers of the 68881 floating point
11517 coprocessor are always saved in ``extended'' (raw) format, but all C
11518 programs expect to work with ``double'' (virtual) format. In such
11519 cases, @value{GDBN} normally works with the virtual format only (the format
11520 that makes sense for your program), but the @code{info registers} command
11521 prints the data in both formats.
11523 @cindex SSE registers (x86)
11524 @cindex MMX registers (x86)
11525 Some machines have special registers whose contents can be interpreted
11526 in several different ways. For example, modern x86-based machines
11527 have SSE and MMX registers that can hold several values packed
11528 together in several different formats. @value{GDBN} refers to such
11529 registers in @code{struct} notation:
11532 (@value{GDBP}) print $xmm1
11534 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11535 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11536 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11537 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11538 v4_int32 = @{0, 20657912, 11, 13@},
11539 v2_int64 = @{88725056443645952, 55834574859@},
11540 uint128 = 0x0000000d0000000b013b36f800000000
11545 To set values of such registers, you need to tell @value{GDBN} which
11546 view of the register you wish to change, as if you were assigning
11547 value to a @code{struct} member:
11550 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11553 Normally, register values are relative to the selected stack frame
11554 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11555 value that the register would contain if all stack frames farther in
11556 were exited and their saved registers restored. In order to see the
11557 true contents of hardware registers, you must select the innermost
11558 frame (with @samp{frame 0}).
11560 @cindex caller-saved registers
11561 @cindex call-clobbered registers
11562 @cindex volatile registers
11563 @cindex <not saved> values
11564 Usually ABIs reserve some registers as not needed to be saved by the
11565 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11566 registers). It may therefore not be possible for @value{GDBN} to know
11567 the value a register had before the call (in other words, in the outer
11568 frame), if the register value has since been changed by the callee.
11569 @value{GDBN} tries to deduce where the inner frame saved
11570 (``callee-saved'') registers, from the debug info, unwind info, or the
11571 machine code generated by your compiler. If some register is not
11572 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11573 its own knowledge of the ABI, or because the debug/unwind info
11574 explicitly says the register's value is undefined), @value{GDBN}
11575 displays @w{@samp{<not saved>}} as the register's value. With targets
11576 that @value{GDBN} has no knowledge of the register saving convention,
11577 if a register was not saved by the callee, then its value and location
11578 in the outer frame are assumed to be the same of the inner frame.
11579 This is usually harmless, because if the register is call-clobbered,
11580 the caller either does not care what is in the register after the
11581 call, or has code to restore the value that it does care about. Note,
11582 however, that if you change such a register in the outer frame, you
11583 may also be affecting the inner frame. Also, the more ``outer'' the
11584 frame is you're looking at, the more likely a call-clobbered
11585 register's value is to be wrong, in the sense that it doesn't actually
11586 represent the value the register had just before the call.
11588 @node Floating Point Hardware
11589 @section Floating Point Hardware
11590 @cindex floating point
11592 Depending on the configuration, @value{GDBN} may be able to give
11593 you more information about the status of the floating point hardware.
11598 Display hardware-dependent information about the floating
11599 point unit. The exact contents and layout vary depending on the
11600 floating point chip. Currently, @samp{info float} is supported on
11601 the ARM and x86 machines.
11605 @section Vector Unit
11606 @cindex vector unit
11608 Depending on the configuration, @value{GDBN} may be able to give you
11609 more information about the status of the vector unit.
11612 @kindex info vector
11614 Display information about the vector unit. The exact contents and
11615 layout vary depending on the hardware.
11618 @node OS Information
11619 @section Operating System Auxiliary Information
11620 @cindex OS information
11622 @value{GDBN} provides interfaces to useful OS facilities that can help
11623 you debug your program.
11625 @cindex auxiliary vector
11626 @cindex vector, auxiliary
11627 Some operating systems supply an @dfn{auxiliary vector} to programs at
11628 startup. This is akin to the arguments and environment that you
11629 specify for a program, but contains a system-dependent variety of
11630 binary values that tell system libraries important details about the
11631 hardware, operating system, and process. Each value's purpose is
11632 identified by an integer tag; the meanings are well-known but system-specific.
11633 Depending on the configuration and operating system facilities,
11634 @value{GDBN} may be able to show you this information. For remote
11635 targets, this functionality may further depend on the remote stub's
11636 support of the @samp{qXfer:auxv:read} packet, see
11637 @ref{qXfer auxiliary vector read}.
11642 Display the auxiliary vector of the inferior, which can be either a
11643 live process or a core dump file. @value{GDBN} prints each tag value
11644 numerically, and also shows names and text descriptions for recognized
11645 tags. Some values in the vector are numbers, some bit masks, and some
11646 pointers to strings or other data. @value{GDBN} displays each value in the
11647 most appropriate form for a recognized tag, and in hexadecimal for
11648 an unrecognized tag.
11651 On some targets, @value{GDBN} can access operating system-specific
11652 information and show it to you. The types of information available
11653 will differ depending on the type of operating system running on the
11654 target. The mechanism used to fetch the data is described in
11655 @ref{Operating System Information}. For remote targets, this
11656 functionality depends on the remote stub's support of the
11657 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11661 @item info os @var{infotype}
11663 Display OS information of the requested type.
11665 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11667 @anchor{linux info os infotypes}
11669 @kindex info os cpus
11671 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11672 the available fields from /proc/cpuinfo. For each supported architecture
11673 different fields are available. Two common entries are processor which gives
11674 CPU number and bogomips; a system constant that is calculated during
11675 kernel initialization.
11677 @kindex info os files
11679 Display the list of open file descriptors on the target. For each
11680 file descriptor, @value{GDBN} prints the identifier of the process
11681 owning the descriptor, the command of the owning process, the value
11682 of the descriptor, and the target of the descriptor.
11684 @kindex info os modules
11686 Display the list of all loaded kernel modules on the target. For each
11687 module, @value{GDBN} prints the module name, the size of the module in
11688 bytes, the number of times the module is used, the dependencies of the
11689 module, the status of the module, and the address of the loaded module
11692 @kindex info os msg
11694 Display the list of all System V message queues on the target. For each
11695 message queue, @value{GDBN} prints the message queue key, the message
11696 queue identifier, the access permissions, the current number of bytes
11697 on the queue, the current number of messages on the queue, the processes
11698 that last sent and received a message on the queue, the user and group
11699 of the owner and creator of the message queue, the times at which a
11700 message was last sent and received on the queue, and the time at which
11701 the message queue was last changed.
11703 @kindex info os processes
11705 Display the list of processes on the target. For each process,
11706 @value{GDBN} prints the process identifier, the name of the user, the
11707 command corresponding to the process, and the list of processor cores
11708 that the process is currently running on. (To understand what these
11709 properties mean, for this and the following info types, please consult
11710 the general @sc{gnu}/Linux documentation.)
11712 @kindex info os procgroups
11714 Display the list of process groups on the target. For each process,
11715 @value{GDBN} prints the identifier of the process group that it belongs
11716 to, the command corresponding to the process group leader, the process
11717 identifier, and the command line of the process. The list is sorted
11718 first by the process group identifier, then by the process identifier,
11719 so that processes belonging to the same process group are grouped together
11720 and the process group leader is listed first.
11722 @kindex info os semaphores
11724 Display the list of all System V semaphore sets on the target. For each
11725 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11726 set identifier, the access permissions, the number of semaphores in the
11727 set, the user and group of the owner and creator of the semaphore set,
11728 and the times at which the semaphore set was operated upon and changed.
11730 @kindex info os shm
11732 Display the list of all System V shared-memory regions on the target.
11733 For each shared-memory region, @value{GDBN} prints the region key,
11734 the shared-memory identifier, the access permissions, the size of the
11735 region, the process that created the region, the process that last
11736 attached to or detached from the region, the current number of live
11737 attaches to the region, and the times at which the region was last
11738 attached to, detach from, and changed.
11740 @kindex info os sockets
11742 Display the list of Internet-domain sockets on the target. For each
11743 socket, @value{GDBN} prints the address and port of the local and
11744 remote endpoints, the current state of the connection, the creator of
11745 the socket, the IP address family of the socket, and the type of the
11748 @kindex info os threads
11750 Display the list of threads running on the target. For each thread,
11751 @value{GDBN} prints the identifier of the process that the thread
11752 belongs to, the command of the process, the thread identifier, and the
11753 processor core that it is currently running on. The main thread of a
11754 process is not listed.
11758 If @var{infotype} is omitted, then list the possible values for
11759 @var{infotype} and the kind of OS information available for each
11760 @var{infotype}. If the target does not return a list of possible
11761 types, this command will report an error.
11764 @node Memory Region Attributes
11765 @section Memory Region Attributes
11766 @cindex memory region attributes
11768 @dfn{Memory region attributes} allow you to describe special handling
11769 required by regions of your target's memory. @value{GDBN} uses
11770 attributes to determine whether to allow certain types of memory
11771 accesses; whether to use specific width accesses; and whether to cache
11772 target memory. By default the description of memory regions is
11773 fetched from the target (if the current target supports this), but the
11774 user can override the fetched regions.
11776 Defined memory regions can be individually enabled and disabled. When a
11777 memory region is disabled, @value{GDBN} uses the default attributes when
11778 accessing memory in that region. Similarly, if no memory regions have
11779 been defined, @value{GDBN} uses the default attributes when accessing
11782 When a memory region is defined, it is given a number to identify it;
11783 to enable, disable, or remove a memory region, you specify that number.
11787 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11788 Define a memory region bounded by @var{lower} and @var{upper} with
11789 attributes @var{attributes}@dots{}, and add it to the list of regions
11790 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11791 case: it is treated as the target's maximum memory address.
11792 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11795 Discard any user changes to the memory regions and use target-supplied
11796 regions, if available, or no regions if the target does not support.
11799 @item delete mem @var{nums}@dots{}
11800 Remove memory regions @var{nums}@dots{} from the list of regions
11801 monitored by @value{GDBN}.
11803 @kindex disable mem
11804 @item disable mem @var{nums}@dots{}
11805 Disable monitoring of memory regions @var{nums}@dots{}.
11806 A disabled memory region is not forgotten.
11807 It may be enabled again later.
11810 @item enable mem @var{nums}@dots{}
11811 Enable monitoring of memory regions @var{nums}@dots{}.
11815 Print a table of all defined memory regions, with the following columns
11819 @item Memory Region Number
11820 @item Enabled or Disabled.
11821 Enabled memory regions are marked with @samp{y}.
11822 Disabled memory regions are marked with @samp{n}.
11825 The address defining the inclusive lower bound of the memory region.
11828 The address defining the exclusive upper bound of the memory region.
11831 The list of attributes set for this memory region.
11836 @subsection Attributes
11838 @subsubsection Memory Access Mode
11839 The access mode attributes set whether @value{GDBN} may make read or
11840 write accesses to a memory region.
11842 While these attributes prevent @value{GDBN} from performing invalid
11843 memory accesses, they do nothing to prevent the target system, I/O DMA,
11844 etc.@: from accessing memory.
11848 Memory is read only.
11850 Memory is write only.
11852 Memory is read/write. This is the default.
11855 @subsubsection Memory Access Size
11856 The access size attribute tells @value{GDBN} to use specific sized
11857 accesses in the memory region. Often memory mapped device registers
11858 require specific sized accesses. If no access size attribute is
11859 specified, @value{GDBN} may use accesses of any size.
11863 Use 8 bit memory accesses.
11865 Use 16 bit memory accesses.
11867 Use 32 bit memory accesses.
11869 Use 64 bit memory accesses.
11872 @c @subsubsection Hardware/Software Breakpoints
11873 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11874 @c will use hardware or software breakpoints for the internal breakpoints
11875 @c used by the step, next, finish, until, etc. commands.
11879 @c Always use hardware breakpoints
11880 @c @item swbreak (default)
11883 @subsubsection Data Cache
11884 The data cache attributes set whether @value{GDBN} will cache target
11885 memory. While this generally improves performance by reducing debug
11886 protocol overhead, it can lead to incorrect results because @value{GDBN}
11887 does not know about volatile variables or memory mapped device
11892 Enable @value{GDBN} to cache target memory.
11894 Disable @value{GDBN} from caching target memory. This is the default.
11897 @subsection Memory Access Checking
11898 @value{GDBN} can be instructed to refuse accesses to memory that is
11899 not explicitly described. This can be useful if accessing such
11900 regions has undesired effects for a specific target, or to provide
11901 better error checking. The following commands control this behaviour.
11904 @kindex set mem inaccessible-by-default
11905 @item set mem inaccessible-by-default [on|off]
11906 If @code{on} is specified, make @value{GDBN} treat memory not
11907 explicitly described by the memory ranges as non-existent and refuse accesses
11908 to such memory. The checks are only performed if there's at least one
11909 memory range defined. If @code{off} is specified, make @value{GDBN}
11910 treat the memory not explicitly described by the memory ranges as RAM.
11911 The default value is @code{on}.
11912 @kindex show mem inaccessible-by-default
11913 @item show mem inaccessible-by-default
11914 Show the current handling of accesses to unknown memory.
11918 @c @subsubsection Memory Write Verification
11919 @c The memory write verification attributes set whether @value{GDBN}
11920 @c will re-reads data after each write to verify the write was successful.
11924 @c @item noverify (default)
11927 @node Dump/Restore Files
11928 @section Copy Between Memory and a File
11929 @cindex dump/restore files
11930 @cindex append data to a file
11931 @cindex dump data to a file
11932 @cindex restore data from a file
11934 You can use the commands @code{dump}, @code{append}, and
11935 @code{restore} to copy data between target memory and a file. The
11936 @code{dump} and @code{append} commands write data to a file, and the
11937 @code{restore} command reads data from a file back into the inferior's
11938 memory. Files may be in binary, Motorola S-record, Intel hex,
11939 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11940 append to binary files, and cannot read from Verilog Hex files.
11945 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11946 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11947 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11948 or the value of @var{expr}, to @var{filename} in the given format.
11950 The @var{format} parameter may be any one of:
11957 Motorola S-record format.
11959 Tektronix Hex format.
11961 Verilog Hex format.
11964 @value{GDBN} uses the same definitions of these formats as the
11965 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11966 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11970 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11971 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11972 Append the contents of memory from @var{start_addr} to @var{end_addr},
11973 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11974 (@value{GDBN} can only append data to files in raw binary form.)
11977 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11978 Restore the contents of file @var{filename} into memory. The
11979 @code{restore} command can automatically recognize any known @sc{bfd}
11980 file format, except for raw binary. To restore a raw binary file you
11981 must specify the optional keyword @code{binary} after the filename.
11983 If @var{bias} is non-zero, its value will be added to the addresses
11984 contained in the file. Binary files always start at address zero, so
11985 they will be restored at address @var{bias}. Other bfd files have
11986 a built-in location; they will be restored at offset @var{bias}
11987 from that location.
11989 If @var{start} and/or @var{end} are non-zero, then only data between
11990 file offset @var{start} and file offset @var{end} will be restored.
11991 These offsets are relative to the addresses in the file, before
11992 the @var{bias} argument is applied.
11996 @node Core File Generation
11997 @section How to Produce a Core File from Your Program
11998 @cindex dump core from inferior
12000 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12001 image of a running process and its process status (register values
12002 etc.). Its primary use is post-mortem debugging of a program that
12003 crashed while it ran outside a debugger. A program that crashes
12004 automatically produces a core file, unless this feature is disabled by
12005 the user. @xref{Files}, for information on invoking @value{GDBN} in
12006 the post-mortem debugging mode.
12008 Occasionally, you may wish to produce a core file of the program you
12009 are debugging in order to preserve a snapshot of its state.
12010 @value{GDBN} has a special command for that.
12014 @kindex generate-core-file
12015 @item generate-core-file [@var{file}]
12016 @itemx gcore [@var{file}]
12017 Produce a core dump of the inferior process. The optional argument
12018 @var{file} specifies the file name where to put the core dump. If not
12019 specified, the file name defaults to @file{core.@var{pid}}, where
12020 @var{pid} is the inferior process ID.
12022 Note that this command is implemented only for some systems (as of
12023 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12025 On @sc{gnu}/Linux, this command can take into account the value of the
12026 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12027 dump (@pxref{set use-coredump-filter}), and by default honors the
12028 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12029 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12031 @kindex set use-coredump-filter
12032 @anchor{set use-coredump-filter}
12033 @item set use-coredump-filter on
12034 @itemx set use-coredump-filter off
12035 Enable or disable the use of the file
12036 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12037 files. This file is used by the Linux kernel to decide what types of
12038 memory mappings will be dumped or ignored when generating a core dump
12039 file. @var{pid} is the process ID of a currently running process.
12041 To make use of this feature, you have to write in the
12042 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12043 which is a bit mask representing the memory mapping types. If a bit
12044 is set in the bit mask, then the memory mappings of the corresponding
12045 types will be dumped; otherwise, they will be ignored. This
12046 configuration is inherited by child processes. For more information
12047 about the bits that can be set in the
12048 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12049 manpage of @code{core(5)}.
12051 By default, this option is @code{on}. If this option is turned
12052 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12053 and instead uses the same default value as the Linux kernel in order
12054 to decide which pages will be dumped in the core dump file. This
12055 value is currently @code{0x33}, which means that bits @code{0}
12056 (anonymous private mappings), @code{1} (anonymous shared mappings),
12057 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12058 This will cause these memory mappings to be dumped automatically.
12060 @kindex set dump-excluded-mappings
12061 @anchor{set dump-excluded-mappings}
12062 @item set dump-excluded-mappings on
12063 @itemx set dump-excluded-mappings off
12064 If @code{on} is specified, @value{GDBN} will dump memory mappings
12065 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12066 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12068 The default value is @code{off}.
12071 @node Character Sets
12072 @section Character Sets
12073 @cindex character sets
12075 @cindex translating between character sets
12076 @cindex host character set
12077 @cindex target character set
12079 If the program you are debugging uses a different character set to
12080 represent characters and strings than the one @value{GDBN} uses itself,
12081 @value{GDBN} can automatically translate between the character sets for
12082 you. The character set @value{GDBN} uses we call the @dfn{host
12083 character set}; the one the inferior program uses we call the
12084 @dfn{target character set}.
12086 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12087 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12088 remote protocol (@pxref{Remote Debugging}) to debug a program
12089 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12090 then the host character set is Latin-1, and the target character set is
12091 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12092 target-charset EBCDIC-US}, then @value{GDBN} translates between
12093 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12094 character and string literals in expressions.
12096 @value{GDBN} has no way to automatically recognize which character set
12097 the inferior program uses; you must tell it, using the @code{set
12098 target-charset} command, described below.
12100 Here are the commands for controlling @value{GDBN}'s character set
12104 @item set target-charset @var{charset}
12105 @kindex set target-charset
12106 Set the current target character set to @var{charset}. To display the
12107 list of supported target character sets, type
12108 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12110 @item set host-charset @var{charset}
12111 @kindex set host-charset
12112 Set the current host character set to @var{charset}.
12114 By default, @value{GDBN} uses a host character set appropriate to the
12115 system it is running on; you can override that default using the
12116 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12117 automatically determine the appropriate host character set. In this
12118 case, @value{GDBN} uses @samp{UTF-8}.
12120 @value{GDBN} can only use certain character sets as its host character
12121 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12122 @value{GDBN} will list the host character sets it supports.
12124 @item set charset @var{charset}
12125 @kindex set charset
12126 Set the current host and target character sets to @var{charset}. As
12127 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12128 @value{GDBN} will list the names of the character sets that can be used
12129 for both host and target.
12132 @kindex show charset
12133 Show the names of the current host and target character sets.
12135 @item show host-charset
12136 @kindex show host-charset
12137 Show the name of the current host character set.
12139 @item show target-charset
12140 @kindex show target-charset
12141 Show the name of the current target character set.
12143 @item set target-wide-charset @var{charset}
12144 @kindex set target-wide-charset
12145 Set the current target's wide character set to @var{charset}. This is
12146 the character set used by the target's @code{wchar_t} type. To
12147 display the list of supported wide character sets, type
12148 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12150 @item show target-wide-charset
12151 @kindex show target-wide-charset
12152 Show the name of the current target's wide character set.
12155 Here is an example of @value{GDBN}'s character set support in action.
12156 Assume that the following source code has been placed in the file
12157 @file{charset-test.c}:
12163 = @{72, 101, 108, 108, 111, 44, 32, 119,
12164 111, 114, 108, 100, 33, 10, 0@};
12165 char ibm1047_hello[]
12166 = @{200, 133, 147, 147, 150, 107, 64, 166,
12167 150, 153, 147, 132, 90, 37, 0@};
12171 printf ("Hello, world!\n");
12175 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12176 containing the string @samp{Hello, world!} followed by a newline,
12177 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12179 We compile the program, and invoke the debugger on it:
12182 $ gcc -g charset-test.c -o charset-test
12183 $ gdb -nw charset-test
12184 GNU gdb 2001-12-19-cvs
12185 Copyright 2001 Free Software Foundation, Inc.
12190 We can use the @code{show charset} command to see what character sets
12191 @value{GDBN} is currently using to interpret and display characters and
12195 (@value{GDBP}) show charset
12196 The current host and target character set is `ISO-8859-1'.
12200 For the sake of printing this manual, let's use @sc{ascii} as our
12201 initial character set:
12203 (@value{GDBP}) set charset ASCII
12204 (@value{GDBP}) show charset
12205 The current host and target character set is `ASCII'.
12209 Let's assume that @sc{ascii} is indeed the correct character set for our
12210 host system --- in other words, let's assume that if @value{GDBN} prints
12211 characters using the @sc{ascii} character set, our terminal will display
12212 them properly. Since our current target character set is also
12213 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12216 (@value{GDBP}) print ascii_hello
12217 $1 = 0x401698 "Hello, world!\n"
12218 (@value{GDBP}) print ascii_hello[0]
12223 @value{GDBN} uses the target character set for character and string
12224 literals you use in expressions:
12227 (@value{GDBP}) print '+'
12232 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12235 @value{GDBN} relies on the user to tell it which character set the
12236 target program uses. If we print @code{ibm1047_hello} while our target
12237 character set is still @sc{ascii}, we get jibberish:
12240 (@value{GDBP}) print ibm1047_hello
12241 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12242 (@value{GDBP}) print ibm1047_hello[0]
12247 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12248 @value{GDBN} tells us the character sets it supports:
12251 (@value{GDBP}) set target-charset
12252 ASCII EBCDIC-US IBM1047 ISO-8859-1
12253 (@value{GDBP}) set target-charset
12256 We can select @sc{ibm1047} as our target character set, and examine the
12257 program's strings again. Now the @sc{ascii} string is wrong, but
12258 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12259 target character set, @sc{ibm1047}, to the host character set,
12260 @sc{ascii}, and they display correctly:
12263 (@value{GDBP}) set target-charset IBM1047
12264 (@value{GDBP}) show charset
12265 The current host character set is `ASCII'.
12266 The current target character set is `IBM1047'.
12267 (@value{GDBP}) print ascii_hello
12268 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12269 (@value{GDBP}) print ascii_hello[0]
12271 (@value{GDBP}) print ibm1047_hello
12272 $8 = 0x4016a8 "Hello, world!\n"
12273 (@value{GDBP}) print ibm1047_hello[0]
12278 As above, @value{GDBN} uses the target character set for character and
12279 string literals you use in expressions:
12282 (@value{GDBP}) print '+'
12287 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12290 @node Caching Target Data
12291 @section Caching Data of Targets
12292 @cindex caching data of targets
12294 @value{GDBN} caches data exchanged between the debugger and a target.
12295 Each cache is associated with the address space of the inferior.
12296 @xref{Inferiors and Programs}, about inferior and address space.
12297 Such caching generally improves performance in remote debugging
12298 (@pxref{Remote Debugging}), because it reduces the overhead of the
12299 remote protocol by bundling memory reads and writes into large chunks.
12300 Unfortunately, simply caching everything would lead to incorrect results,
12301 since @value{GDBN} does not necessarily know anything about volatile
12302 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12303 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12305 Therefore, by default, @value{GDBN} only caches data
12306 known to be on the stack@footnote{In non-stop mode, it is moderately
12307 rare for a running thread to modify the stack of a stopped thread
12308 in a way that would interfere with a backtrace, and caching of
12309 stack reads provides a significant speed up of remote backtraces.} or
12310 in the code segment.
12311 Other regions of memory can be explicitly marked as
12312 cacheable; @pxref{Memory Region Attributes}.
12315 @kindex set remotecache
12316 @item set remotecache on
12317 @itemx set remotecache off
12318 This option no longer does anything; it exists for compatibility
12321 @kindex show remotecache
12322 @item show remotecache
12323 Show the current state of the obsolete remotecache flag.
12325 @kindex set stack-cache
12326 @item set stack-cache on
12327 @itemx set stack-cache off
12328 Enable or disable caching of stack accesses. When @code{on}, use
12329 caching. By default, this option is @code{on}.
12331 @kindex show stack-cache
12332 @item show stack-cache
12333 Show the current state of data caching for memory accesses.
12335 @kindex set code-cache
12336 @item set code-cache on
12337 @itemx set code-cache off
12338 Enable or disable caching of code segment accesses. When @code{on},
12339 use caching. By default, this option is @code{on}. This improves
12340 performance of disassembly in remote debugging.
12342 @kindex show code-cache
12343 @item show code-cache
12344 Show the current state of target memory cache for code segment
12347 @kindex info dcache
12348 @item info dcache @r{[}line@r{]}
12349 Print the information about the performance of data cache of the
12350 current inferior's address space. The information displayed
12351 includes the dcache width and depth, and for each cache line, its
12352 number, address, and how many times it was referenced. This
12353 command is useful for debugging the data cache operation.
12355 If a line number is specified, the contents of that line will be
12358 @item set dcache size @var{size}
12359 @cindex dcache size
12360 @kindex set dcache size
12361 Set maximum number of entries in dcache (dcache depth above).
12363 @item set dcache line-size @var{line-size}
12364 @cindex dcache line-size
12365 @kindex set dcache line-size
12366 Set number of bytes each dcache entry caches (dcache width above).
12367 Must be a power of 2.
12369 @item show dcache size
12370 @kindex show dcache size
12371 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12373 @item show dcache line-size
12374 @kindex show dcache line-size
12375 Show default size of dcache lines.
12379 @node Searching Memory
12380 @section Search Memory
12381 @cindex searching memory
12383 Memory can be searched for a particular sequence of bytes with the
12384 @code{find} command.
12388 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12389 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12390 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12391 etc. The search begins at address @var{start_addr} and continues for either
12392 @var{len} bytes or through to @var{end_addr} inclusive.
12395 @var{s} and @var{n} are optional parameters.
12396 They may be specified in either order, apart or together.
12399 @item @var{s}, search query size
12400 The size of each search query value.
12406 halfwords (two bytes)
12410 giant words (eight bytes)
12413 All values are interpreted in the current language.
12414 This means, for example, that if the current source language is C/C@t{++}
12415 then searching for the string ``hello'' includes the trailing '\0'.
12416 The null terminator can be removed from searching by using casts,
12417 e.g.: @samp{@{char[5]@}"hello"}.
12419 If the value size is not specified, it is taken from the
12420 value's type in the current language.
12421 This is useful when one wants to specify the search
12422 pattern as a mixture of types.
12423 Note that this means, for example, that in the case of C-like languages
12424 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12425 which is typically four bytes.
12427 @item @var{n}, maximum number of finds
12428 The maximum number of matches to print. The default is to print all finds.
12431 You can use strings as search values. Quote them with double-quotes
12433 The string value is copied into the search pattern byte by byte,
12434 regardless of the endianness of the target and the size specification.
12436 The address of each match found is printed as well as a count of the
12437 number of matches found.
12439 The address of the last value found is stored in convenience variable
12441 A count of the number of matches is stored in @samp{$numfound}.
12443 For example, if stopped at the @code{printf} in this function:
12449 static char hello[] = "hello-hello";
12450 static struct @{ char c; short s; int i; @}
12451 __attribute__ ((packed)) mixed
12452 = @{ 'c', 0x1234, 0x87654321 @};
12453 printf ("%s\n", hello);
12458 you get during debugging:
12461 (gdb) find &hello[0], +sizeof(hello), "hello"
12462 0x804956d <hello.1620+6>
12464 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12465 0x8049567 <hello.1620>
12466 0x804956d <hello.1620+6>
12468 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12469 0x8049567 <hello.1620>
12470 0x804956d <hello.1620+6>
12472 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12473 0x8049567 <hello.1620>
12475 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12476 0x8049560 <mixed.1625>
12478 (gdb) print $numfound
12481 $2 = (void *) 0x8049560
12485 @section Value Sizes
12487 Whenever @value{GDBN} prints a value memory will be allocated within
12488 @value{GDBN} to hold the contents of the value. It is possible in
12489 some languages with dynamic typing systems, that an invalid program
12490 may indicate a value that is incorrectly large, this in turn may cause
12491 @value{GDBN} to try and allocate an overly large ammount of memory.
12494 @kindex set max-value-size
12495 @item set max-value-size @var{bytes}
12496 @itemx set max-value-size unlimited
12497 Set the maximum size of memory that @value{GDBN} will allocate for the
12498 contents of a value to @var{bytes}, trying to display a value that
12499 requires more memory than that will result in an error.
12501 Setting this variable does not effect values that have already been
12502 allocated within @value{GDBN}, only future allocations.
12504 There's a minimum size that @code{max-value-size} can be set to in
12505 order that @value{GDBN} can still operate correctly, this minimum is
12506 currently 16 bytes.
12508 The limit applies to the results of some subexpressions as well as to
12509 complete expressions. For example, an expression denoting a simple
12510 integer component, such as @code{x.y.z}, may fail if the size of
12511 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12512 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12513 @var{A} is an array variable with non-constant size, will generally
12514 succeed regardless of the bounds on @var{A}, as long as the component
12515 size is less than @var{bytes}.
12517 The default value of @code{max-value-size} is currently 64k.
12519 @kindex show max-value-size
12520 @item show max-value-size
12521 Show the maximum size of memory, in bytes, that @value{GDBN} will
12522 allocate for the contents of a value.
12525 @node Optimized Code
12526 @chapter Debugging Optimized Code
12527 @cindex optimized code, debugging
12528 @cindex debugging optimized code
12530 Almost all compilers support optimization. With optimization
12531 disabled, the compiler generates assembly code that corresponds
12532 directly to your source code, in a simplistic way. As the compiler
12533 applies more powerful optimizations, the generated assembly code
12534 diverges from your original source code. With help from debugging
12535 information generated by the compiler, @value{GDBN} can map from
12536 the running program back to constructs from your original source.
12538 @value{GDBN} is more accurate with optimization disabled. If you
12539 can recompile without optimization, it is easier to follow the
12540 progress of your program during debugging. But, there are many cases
12541 where you may need to debug an optimized version.
12543 When you debug a program compiled with @samp{-g -O}, remember that the
12544 optimizer has rearranged your code; the debugger shows you what is
12545 really there. Do not be too surprised when the execution path does not
12546 exactly match your source file! An extreme example: if you define a
12547 variable, but never use it, @value{GDBN} never sees that
12548 variable---because the compiler optimizes it out of existence.
12550 Some things do not work as well with @samp{-g -O} as with just
12551 @samp{-g}, particularly on machines with instruction scheduling. If in
12552 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12553 please report it to us as a bug (including a test case!).
12554 @xref{Variables}, for more information about debugging optimized code.
12557 * Inline Functions:: How @value{GDBN} presents inlining
12558 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12561 @node Inline Functions
12562 @section Inline Functions
12563 @cindex inline functions, debugging
12565 @dfn{Inlining} is an optimization that inserts a copy of the function
12566 body directly at each call site, instead of jumping to a shared
12567 routine. @value{GDBN} displays inlined functions just like
12568 non-inlined functions. They appear in backtraces. You can view their
12569 arguments and local variables, step into them with @code{step}, skip
12570 them with @code{next}, and escape from them with @code{finish}.
12571 You can check whether a function was inlined by using the
12572 @code{info frame} command.
12574 For @value{GDBN} to support inlined functions, the compiler must
12575 record information about inlining in the debug information ---
12576 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12577 other compilers do also. @value{GDBN} only supports inlined functions
12578 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12579 do not emit two required attributes (@samp{DW_AT_call_file} and
12580 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12581 function calls with earlier versions of @value{NGCC}. It instead
12582 displays the arguments and local variables of inlined functions as
12583 local variables in the caller.
12585 The body of an inlined function is directly included at its call site;
12586 unlike a non-inlined function, there are no instructions devoted to
12587 the call. @value{GDBN} still pretends that the call site and the
12588 start of the inlined function are different instructions. Stepping to
12589 the call site shows the call site, and then stepping again shows
12590 the first line of the inlined function, even though no additional
12591 instructions are executed.
12593 This makes source-level debugging much clearer; you can see both the
12594 context of the call and then the effect of the call. Only stepping by
12595 a single instruction using @code{stepi} or @code{nexti} does not do
12596 this; single instruction steps always show the inlined body.
12598 There are some ways that @value{GDBN} does not pretend that inlined
12599 function calls are the same as normal calls:
12603 Setting breakpoints at the call site of an inlined function may not
12604 work, because the call site does not contain any code. @value{GDBN}
12605 may incorrectly move the breakpoint to the next line of the enclosing
12606 function, after the call. This limitation will be removed in a future
12607 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12608 or inside the inlined function instead.
12611 @value{GDBN} cannot locate the return value of inlined calls after
12612 using the @code{finish} command. This is a limitation of compiler-generated
12613 debugging information; after @code{finish}, you can step to the next line
12614 and print a variable where your program stored the return value.
12618 @node Tail Call Frames
12619 @section Tail Call Frames
12620 @cindex tail call frames, debugging
12622 Function @code{B} can call function @code{C} in its very last statement. In
12623 unoptimized compilation the call of @code{C} is immediately followed by return
12624 instruction at the end of @code{B} code. Optimizing compiler may replace the
12625 call and return in function @code{B} into one jump to function @code{C}
12626 instead. Such use of a jump instruction is called @dfn{tail call}.
12628 During execution of function @code{C}, there will be no indication in the
12629 function call stack frames that it was tail-called from @code{B}. If function
12630 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12631 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12632 some cases @value{GDBN} can determine that @code{C} was tail-called from
12633 @code{B}, and it will then create fictitious call frame for that, with the
12634 return address set up as if @code{B} called @code{C} normally.
12636 This functionality is currently supported only by DWARF 2 debugging format and
12637 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12638 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12641 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12642 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12646 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12648 Stack level 1, frame at 0x7fffffffda30:
12649 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12650 tail call frame, caller of frame at 0x7fffffffda30
12651 source language c++.
12652 Arglist at unknown address.
12653 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12656 The detection of all the possible code path executions can find them ambiguous.
12657 There is no execution history stored (possible @ref{Reverse Execution} is never
12658 used for this purpose) and the last known caller could have reached the known
12659 callee by multiple different jump sequences. In such case @value{GDBN} still
12660 tries to show at least all the unambiguous top tail callers and all the
12661 unambiguous bottom tail calees, if any.
12664 @anchor{set debug entry-values}
12665 @item set debug entry-values
12666 @kindex set debug entry-values
12667 When set to on, enables printing of analysis messages for both frame argument
12668 values at function entry and tail calls. It will show all the possible valid
12669 tail calls code paths it has considered. It will also print the intersection
12670 of them with the final unambiguous (possibly partial or even empty) code path
12673 @item show debug entry-values
12674 @kindex show debug entry-values
12675 Show the current state of analysis messages printing for both frame argument
12676 values at function entry and tail calls.
12679 The analysis messages for tail calls can for example show why the virtual tail
12680 call frame for function @code{c} has not been recognized (due to the indirect
12681 reference by variable @code{x}):
12684 static void __attribute__((noinline, noclone)) c (void);
12685 void (*x) (void) = c;
12686 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12687 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12688 int main (void) @{ x (); return 0; @}
12690 Breakpoint 1, DW_OP_entry_value resolving cannot find
12691 DW_TAG_call_site 0x40039a in main
12693 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12696 #1 0x000000000040039a in main () at t.c:5
12699 Another possibility is an ambiguous virtual tail call frames resolution:
12703 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12704 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12705 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12706 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12707 static void __attribute__((noinline, noclone)) b (void)
12708 @{ if (i) c (); else e (); @}
12709 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12710 int main (void) @{ a (); return 0; @}
12712 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12713 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12714 tailcall: reduced: 0x4004d2(a) |
12717 #1 0x00000000004004d2 in a () at t.c:8
12718 #2 0x0000000000400395 in main () at t.c:9
12721 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12722 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12724 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12725 @ifset HAVE_MAKEINFO_CLICK
12726 @set ARROW @click{}
12727 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12728 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12730 @ifclear HAVE_MAKEINFO_CLICK
12732 @set CALLSEQ1B @value{CALLSEQ1A}
12733 @set CALLSEQ2B @value{CALLSEQ2A}
12736 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12737 The code can have possible execution paths @value{CALLSEQ1B} or
12738 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12740 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12741 has found. It then finds another possible calling sequcen - that one is
12742 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12743 printed as the @code{reduced:} calling sequence. That one could have many
12744 futher @code{compare:} and @code{reduced:} statements as long as there remain
12745 any non-ambiguous sequence entries.
12747 For the frame of function @code{b} in both cases there are different possible
12748 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12749 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12750 therefore this one is displayed to the user while the ambiguous frames are
12753 There can be also reasons why printing of frame argument values at function
12758 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12759 static void __attribute__((noinline, noclone)) a (int i);
12760 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12761 static void __attribute__((noinline, noclone)) a (int i)
12762 @{ if (i) b (i - 1); else c (0); @}
12763 int main (void) @{ a (5); return 0; @}
12766 #0 c (i=i@@entry=0) at t.c:2
12767 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12768 function "a" at 0x400420 can call itself via tail calls
12769 i=<optimized out>) at t.c:6
12770 #2 0x000000000040036e in main () at t.c:7
12773 @value{GDBN} cannot find out from the inferior state if and how many times did
12774 function @code{a} call itself (via function @code{b}) as these calls would be
12775 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12776 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12777 prints @code{<optimized out>} instead.
12780 @chapter C Preprocessor Macros
12782 Some languages, such as C and C@t{++}, provide a way to define and invoke
12783 ``preprocessor macros'' which expand into strings of tokens.
12784 @value{GDBN} can evaluate expressions containing macro invocations, show
12785 the result of macro expansion, and show a macro's definition, including
12786 where it was defined.
12788 You may need to compile your program specially to provide @value{GDBN}
12789 with information about preprocessor macros. Most compilers do not
12790 include macros in their debugging information, even when you compile
12791 with the @option{-g} flag. @xref{Compilation}.
12793 A program may define a macro at one point, remove that definition later,
12794 and then provide a different definition after that. Thus, at different
12795 points in the program, a macro may have different definitions, or have
12796 no definition at all. If there is a current stack frame, @value{GDBN}
12797 uses the macros in scope at that frame's source code line. Otherwise,
12798 @value{GDBN} uses the macros in scope at the current listing location;
12801 Whenever @value{GDBN} evaluates an expression, it always expands any
12802 macro invocations present in the expression. @value{GDBN} also provides
12803 the following commands for working with macros explicitly.
12807 @kindex macro expand
12808 @cindex macro expansion, showing the results of preprocessor
12809 @cindex preprocessor macro expansion, showing the results of
12810 @cindex expanding preprocessor macros
12811 @item macro expand @var{expression}
12812 @itemx macro exp @var{expression}
12813 Show the results of expanding all preprocessor macro invocations in
12814 @var{expression}. Since @value{GDBN} simply expands macros, but does
12815 not parse the result, @var{expression} need not be a valid expression;
12816 it can be any string of tokens.
12819 @item macro expand-once @var{expression}
12820 @itemx macro exp1 @var{expression}
12821 @cindex expand macro once
12822 @i{(This command is not yet implemented.)} Show the results of
12823 expanding those preprocessor macro invocations that appear explicitly in
12824 @var{expression}. Macro invocations appearing in that expansion are
12825 left unchanged. This command allows you to see the effect of a
12826 particular macro more clearly, without being confused by further
12827 expansions. Since @value{GDBN} simply expands macros, but does not
12828 parse the result, @var{expression} need not be a valid expression; it
12829 can be any string of tokens.
12832 @cindex macro definition, showing
12833 @cindex definition of a macro, showing
12834 @cindex macros, from debug info
12835 @item info macro [-a|-all] [--] @var{macro}
12836 Show the current definition or all definitions of the named @var{macro},
12837 and describe the source location or compiler command-line where that
12838 definition was established. The optional double dash is to signify the end of
12839 argument processing and the beginning of @var{macro} for non C-like macros where
12840 the macro may begin with a hyphen.
12842 @kindex info macros
12843 @item info macros @var{location}
12844 Show all macro definitions that are in effect at the location specified
12845 by @var{location}, and describe the source location or compiler
12846 command-line where those definitions were established.
12848 @kindex macro define
12849 @cindex user-defined macros
12850 @cindex defining macros interactively
12851 @cindex macros, user-defined
12852 @item macro define @var{macro} @var{replacement-list}
12853 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12854 Introduce a definition for a preprocessor macro named @var{macro},
12855 invocations of which are replaced by the tokens given in
12856 @var{replacement-list}. The first form of this command defines an
12857 ``object-like'' macro, which takes no arguments; the second form
12858 defines a ``function-like'' macro, which takes the arguments given in
12861 A definition introduced by this command is in scope in every
12862 expression evaluated in @value{GDBN}, until it is removed with the
12863 @code{macro undef} command, described below. The definition overrides
12864 all definitions for @var{macro} present in the program being debugged,
12865 as well as any previous user-supplied definition.
12867 @kindex macro undef
12868 @item macro undef @var{macro}
12869 Remove any user-supplied definition for the macro named @var{macro}.
12870 This command only affects definitions provided with the @code{macro
12871 define} command, described above; it cannot remove definitions present
12872 in the program being debugged.
12876 List all the macros defined using the @code{macro define} command.
12879 @cindex macros, example of debugging with
12880 Here is a transcript showing the above commands in action. First, we
12881 show our source files:
12886 #include "sample.h"
12889 #define ADD(x) (M + x)
12894 printf ("Hello, world!\n");
12896 printf ("We're so creative.\n");
12898 printf ("Goodbye, world!\n");
12905 Now, we compile the program using the @sc{gnu} C compiler,
12906 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12907 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12908 and @option{-gdwarf-4}; we recommend always choosing the most recent
12909 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12910 includes information about preprocessor macros in the debugging
12914 $ gcc -gdwarf-2 -g3 sample.c -o sample
12918 Now, we start @value{GDBN} on our sample program:
12922 GNU gdb 2002-05-06-cvs
12923 Copyright 2002 Free Software Foundation, Inc.
12924 GDB is free software, @dots{}
12928 We can expand macros and examine their definitions, even when the
12929 program is not running. @value{GDBN} uses the current listing position
12930 to decide which macro definitions are in scope:
12933 (@value{GDBP}) list main
12936 5 #define ADD(x) (M + x)
12941 10 printf ("Hello, world!\n");
12943 12 printf ("We're so creative.\n");
12944 (@value{GDBP}) info macro ADD
12945 Defined at /home/jimb/gdb/macros/play/sample.c:5
12946 #define ADD(x) (M + x)
12947 (@value{GDBP}) info macro Q
12948 Defined at /home/jimb/gdb/macros/play/sample.h:1
12949 included at /home/jimb/gdb/macros/play/sample.c:2
12951 (@value{GDBP}) macro expand ADD(1)
12952 expands to: (42 + 1)
12953 (@value{GDBP}) macro expand-once ADD(1)
12954 expands to: once (M + 1)
12958 In the example above, note that @code{macro expand-once} expands only
12959 the macro invocation explicit in the original text --- the invocation of
12960 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12961 which was introduced by @code{ADD}.
12963 Once the program is running, @value{GDBN} uses the macro definitions in
12964 force at the source line of the current stack frame:
12967 (@value{GDBP}) break main
12968 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12970 Starting program: /home/jimb/gdb/macros/play/sample
12972 Breakpoint 1, main () at sample.c:10
12973 10 printf ("Hello, world!\n");
12977 At line 10, the definition of the macro @code{N} at line 9 is in force:
12980 (@value{GDBP}) info macro N
12981 Defined at /home/jimb/gdb/macros/play/sample.c:9
12983 (@value{GDBP}) macro expand N Q M
12984 expands to: 28 < 42
12985 (@value{GDBP}) print N Q M
12990 As we step over directives that remove @code{N}'s definition, and then
12991 give it a new definition, @value{GDBN} finds the definition (or lack
12992 thereof) in force at each point:
12995 (@value{GDBP}) next
12997 12 printf ("We're so creative.\n");
12998 (@value{GDBP}) info macro N
12999 The symbol `N' has no definition as a C/C++ preprocessor macro
13000 at /home/jimb/gdb/macros/play/sample.c:12
13001 (@value{GDBP}) next
13003 14 printf ("Goodbye, world!\n");
13004 (@value{GDBP}) info macro N
13005 Defined at /home/jimb/gdb/macros/play/sample.c:13
13007 (@value{GDBP}) macro expand N Q M
13008 expands to: 1729 < 42
13009 (@value{GDBP}) print N Q M
13014 In addition to source files, macros can be defined on the compilation command
13015 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13016 such a way, @value{GDBN} displays the location of their definition as line zero
13017 of the source file submitted to the compiler.
13020 (@value{GDBP}) info macro __STDC__
13021 Defined at /home/jimb/gdb/macros/play/sample.c:0
13028 @chapter Tracepoints
13029 @c This chapter is based on the documentation written by Michael
13030 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13032 @cindex tracepoints
13033 In some applications, it is not feasible for the debugger to interrupt
13034 the program's execution long enough for the developer to learn
13035 anything helpful about its behavior. If the program's correctness
13036 depends on its real-time behavior, delays introduced by a debugger
13037 might cause the program to change its behavior drastically, or perhaps
13038 fail, even when the code itself is correct. It is useful to be able
13039 to observe the program's behavior without interrupting it.
13041 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13042 specify locations in the program, called @dfn{tracepoints}, and
13043 arbitrary expressions to evaluate when those tracepoints are reached.
13044 Later, using the @code{tfind} command, you can examine the values
13045 those expressions had when the program hit the tracepoints. The
13046 expressions may also denote objects in memory---structures or arrays,
13047 for example---whose values @value{GDBN} should record; while visiting
13048 a particular tracepoint, you may inspect those objects as if they were
13049 in memory at that moment. However, because @value{GDBN} records these
13050 values without interacting with you, it can do so quickly and
13051 unobtrusively, hopefully not disturbing the program's behavior.
13053 The tracepoint facility is currently available only for remote
13054 targets. @xref{Targets}. In addition, your remote target must know
13055 how to collect trace data. This functionality is implemented in the
13056 remote stub; however, none of the stubs distributed with @value{GDBN}
13057 support tracepoints as of this writing. The format of the remote
13058 packets used to implement tracepoints are described in @ref{Tracepoint
13061 It is also possible to get trace data from a file, in a manner reminiscent
13062 of corefiles; you specify the filename, and use @code{tfind} to search
13063 through the file. @xref{Trace Files}, for more details.
13065 This chapter describes the tracepoint commands and features.
13068 * Set Tracepoints::
13069 * Analyze Collected Data::
13070 * Tracepoint Variables::
13074 @node Set Tracepoints
13075 @section Commands to Set Tracepoints
13077 Before running such a @dfn{trace experiment}, an arbitrary number of
13078 tracepoints can be set. A tracepoint is actually a special type of
13079 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13080 standard breakpoint commands. For instance, as with breakpoints,
13081 tracepoint numbers are successive integers starting from one, and many
13082 of the commands associated with tracepoints take the tracepoint number
13083 as their argument, to identify which tracepoint to work on.
13085 For each tracepoint, you can specify, in advance, some arbitrary set
13086 of data that you want the target to collect in the trace buffer when
13087 it hits that tracepoint. The collected data can include registers,
13088 local variables, or global data. Later, you can use @value{GDBN}
13089 commands to examine the values these data had at the time the
13090 tracepoint was hit.
13092 Tracepoints do not support every breakpoint feature. Ignore counts on
13093 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13094 commands when they are hit. Tracepoints may not be thread-specific
13097 @cindex fast tracepoints
13098 Some targets may support @dfn{fast tracepoints}, which are inserted in
13099 a different way (such as with a jump instead of a trap), that is
13100 faster but possibly restricted in where they may be installed.
13102 @cindex static tracepoints
13103 @cindex markers, static tracepoints
13104 @cindex probing markers, static tracepoints
13105 Regular and fast tracepoints are dynamic tracing facilities, meaning
13106 that they can be used to insert tracepoints at (almost) any location
13107 in the target. Some targets may also support controlling @dfn{static
13108 tracepoints} from @value{GDBN}. With static tracing, a set of
13109 instrumentation points, also known as @dfn{markers}, are embedded in
13110 the target program, and can be activated or deactivated by name or
13111 address. These are usually placed at locations which facilitate
13112 investigating what the target is actually doing. @value{GDBN}'s
13113 support for static tracing includes being able to list instrumentation
13114 points, and attach them with @value{GDBN} defined high level
13115 tracepoints that expose the whole range of convenience of
13116 @value{GDBN}'s tracepoints support. Namely, support for collecting
13117 registers values and values of global or local (to the instrumentation
13118 point) variables; tracepoint conditions and trace state variables.
13119 The act of installing a @value{GDBN} static tracepoint on an
13120 instrumentation point, or marker, is referred to as @dfn{probing} a
13121 static tracepoint marker.
13123 @code{gdbserver} supports tracepoints on some target systems.
13124 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13126 This section describes commands to set tracepoints and associated
13127 conditions and actions.
13130 * Create and Delete Tracepoints::
13131 * Enable and Disable Tracepoints::
13132 * Tracepoint Passcounts::
13133 * Tracepoint Conditions::
13134 * Trace State Variables::
13135 * Tracepoint Actions::
13136 * Listing Tracepoints::
13137 * Listing Static Tracepoint Markers::
13138 * Starting and Stopping Trace Experiments::
13139 * Tracepoint Restrictions::
13142 @node Create and Delete Tracepoints
13143 @subsection Create and Delete Tracepoints
13146 @cindex set tracepoint
13148 @item trace @var{location}
13149 The @code{trace} command is very similar to the @code{break} command.
13150 Its argument @var{location} can be any valid location.
13151 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13152 which is a point in the target program where the debugger will briefly stop,
13153 collect some data, and then allow the program to continue. Setting a tracepoint
13154 or changing its actions takes effect immediately if the remote stub
13155 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13157 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13158 these changes don't take effect until the next @code{tstart}
13159 command, and once a trace experiment is running, further changes will
13160 not have any effect until the next trace experiment starts. In addition,
13161 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13162 address is not yet resolved. (This is similar to pending breakpoints.)
13163 Pending tracepoints are not downloaded to the target and not installed
13164 until they are resolved. The resolution of pending tracepoints requires
13165 @value{GDBN} support---when debugging with the remote target, and
13166 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13167 tracing}), pending tracepoints can not be resolved (and downloaded to
13168 the remote stub) while @value{GDBN} is disconnected.
13170 Here are some examples of using the @code{trace} command:
13173 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13175 (@value{GDBP}) @b{trace +2} // 2 lines forward
13177 (@value{GDBP}) @b{trace my_function} // first source line of function
13179 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13181 (@value{GDBP}) @b{trace *0x2117c4} // an address
13185 You can abbreviate @code{trace} as @code{tr}.
13187 @item trace @var{location} if @var{cond}
13188 Set a tracepoint with condition @var{cond}; evaluate the expression
13189 @var{cond} each time the tracepoint is reached, and collect data only
13190 if the value is nonzero---that is, if @var{cond} evaluates as true.
13191 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13192 information on tracepoint conditions.
13194 @item ftrace @var{location} [ if @var{cond} ]
13195 @cindex set fast tracepoint
13196 @cindex fast tracepoints, setting
13198 The @code{ftrace} command sets a fast tracepoint. For targets that
13199 support them, fast tracepoints will use a more efficient but possibly
13200 less general technique to trigger data collection, such as a jump
13201 instruction instead of a trap, or some sort of hardware support. It
13202 may not be possible to create a fast tracepoint at the desired
13203 location, in which case the command will exit with an explanatory
13206 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13209 On 32-bit x86-architecture systems, fast tracepoints normally need to
13210 be placed at an instruction that is 5 bytes or longer, but can be
13211 placed at 4-byte instructions if the low 64K of memory of the target
13212 program is available to install trampolines. Some Unix-type systems,
13213 such as @sc{gnu}/Linux, exclude low addresses from the program's
13214 address space; but for instance with the Linux kernel it is possible
13215 to let @value{GDBN} use this area by doing a @command{sysctl} command
13216 to set the @code{mmap_min_addr} kernel parameter, as in
13219 sudo sysctl -w vm.mmap_min_addr=32768
13223 which sets the low address to 32K, which leaves plenty of room for
13224 trampolines. The minimum address should be set to a page boundary.
13226 @item strace @var{location} [ if @var{cond} ]
13227 @cindex set static tracepoint
13228 @cindex static tracepoints, setting
13229 @cindex probe static tracepoint marker
13231 The @code{strace} command sets a static tracepoint. For targets that
13232 support it, setting a static tracepoint probes a static
13233 instrumentation point, or marker, found at @var{location}. It may not
13234 be possible to set a static tracepoint at the desired location, in
13235 which case the command will exit with an explanatory message.
13237 @value{GDBN} handles arguments to @code{strace} exactly as for
13238 @code{trace}, with the addition that the user can also specify
13239 @code{-m @var{marker}} as @var{location}. This probes the marker
13240 identified by the @var{marker} string identifier. This identifier
13241 depends on the static tracepoint backend library your program is
13242 using. You can find all the marker identifiers in the @samp{ID} field
13243 of the @code{info static-tracepoint-markers} command output.
13244 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13245 Markers}. For example, in the following small program using the UST
13251 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13256 the marker id is composed of joining the first two arguments to the
13257 @code{trace_mark} call with a slash, which translates to:
13260 (@value{GDBP}) info static-tracepoint-markers
13261 Cnt Enb ID Address What
13262 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13268 so you may probe the marker above with:
13271 (@value{GDBP}) strace -m ust/bar33
13274 Static tracepoints accept an extra collect action --- @code{collect
13275 $_sdata}. This collects arbitrary user data passed in the probe point
13276 call to the tracing library. In the UST example above, you'll see
13277 that the third argument to @code{trace_mark} is a printf-like format
13278 string. The user data is then the result of running that formating
13279 string against the following arguments. Note that @code{info
13280 static-tracepoint-markers} command output lists that format string in
13281 the @samp{Data:} field.
13283 You can inspect this data when analyzing the trace buffer, by printing
13284 the $_sdata variable like any other variable available to
13285 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13288 @cindex last tracepoint number
13289 @cindex recent tracepoint number
13290 @cindex tracepoint number
13291 The convenience variable @code{$tpnum} records the tracepoint number
13292 of the most recently set tracepoint.
13294 @kindex delete tracepoint
13295 @cindex tracepoint deletion
13296 @item delete tracepoint @r{[}@var{num}@r{]}
13297 Permanently delete one or more tracepoints. With no argument, the
13298 default is to delete all tracepoints. Note that the regular
13299 @code{delete} command can remove tracepoints also.
13304 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13306 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13310 You can abbreviate this command as @code{del tr}.
13313 @node Enable and Disable Tracepoints
13314 @subsection Enable and Disable Tracepoints
13316 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13319 @kindex disable tracepoint
13320 @item disable tracepoint @r{[}@var{num}@r{]}
13321 Disable tracepoint @var{num}, or all tracepoints if no argument
13322 @var{num} is given. A disabled tracepoint will have no effect during
13323 a trace experiment, but it is not forgotten. You can re-enable
13324 a disabled tracepoint using the @code{enable tracepoint} command.
13325 If the command is issued during a trace experiment and the debug target
13326 has support for disabling tracepoints during a trace experiment, then the
13327 change will be effective immediately. Otherwise, it will be applied to the
13328 next trace experiment.
13330 @kindex enable tracepoint
13331 @item enable tracepoint @r{[}@var{num}@r{]}
13332 Enable tracepoint @var{num}, or all tracepoints. If this command is
13333 issued during a trace experiment and the debug target supports enabling
13334 tracepoints during a trace experiment, then the enabled tracepoints will
13335 become effective immediately. Otherwise, they will become effective the
13336 next time a trace experiment is run.
13339 @node Tracepoint Passcounts
13340 @subsection Tracepoint Passcounts
13344 @cindex tracepoint pass count
13345 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13346 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13347 automatically stop a trace experiment. If a tracepoint's passcount is
13348 @var{n}, then the trace experiment will be automatically stopped on
13349 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13350 @var{num} is not specified, the @code{passcount} command sets the
13351 passcount of the most recently defined tracepoint. If no passcount is
13352 given, the trace experiment will run until stopped explicitly by the
13358 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13359 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13361 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13362 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13363 (@value{GDBP}) @b{trace foo}
13364 (@value{GDBP}) @b{pass 3}
13365 (@value{GDBP}) @b{trace bar}
13366 (@value{GDBP}) @b{pass 2}
13367 (@value{GDBP}) @b{trace baz}
13368 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13369 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13370 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13371 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13375 @node Tracepoint Conditions
13376 @subsection Tracepoint Conditions
13377 @cindex conditional tracepoints
13378 @cindex tracepoint conditions
13380 The simplest sort of tracepoint collects data every time your program
13381 reaches a specified place. You can also specify a @dfn{condition} for
13382 a tracepoint. A condition is just a Boolean expression in your
13383 programming language (@pxref{Expressions, ,Expressions}). A
13384 tracepoint with a condition evaluates the expression each time your
13385 program reaches it, and data collection happens only if the condition
13388 Tracepoint conditions can be specified when a tracepoint is set, by
13389 using @samp{if} in the arguments to the @code{trace} command.
13390 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13391 also be set or changed at any time with the @code{condition} command,
13392 just as with breakpoints.
13394 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13395 the conditional expression itself. Instead, @value{GDBN} encodes the
13396 expression into an agent expression (@pxref{Agent Expressions})
13397 suitable for execution on the target, independently of @value{GDBN}.
13398 Global variables become raw memory locations, locals become stack
13399 accesses, and so forth.
13401 For instance, suppose you have a function that is usually called
13402 frequently, but should not be called after an error has occurred. You
13403 could use the following tracepoint command to collect data about calls
13404 of that function that happen while the error code is propagating
13405 through the program; an unconditional tracepoint could end up
13406 collecting thousands of useless trace frames that you would have to
13410 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13413 @node Trace State Variables
13414 @subsection Trace State Variables
13415 @cindex trace state variables
13417 A @dfn{trace state variable} is a special type of variable that is
13418 created and managed by target-side code. The syntax is the same as
13419 that for GDB's convenience variables (a string prefixed with ``$''),
13420 but they are stored on the target. They must be created explicitly,
13421 using a @code{tvariable} command. They are always 64-bit signed
13424 Trace state variables are remembered by @value{GDBN}, and downloaded
13425 to the target along with tracepoint information when the trace
13426 experiment starts. There are no intrinsic limits on the number of
13427 trace state variables, beyond memory limitations of the target.
13429 @cindex convenience variables, and trace state variables
13430 Although trace state variables are managed by the target, you can use
13431 them in print commands and expressions as if they were convenience
13432 variables; @value{GDBN} will get the current value from the target
13433 while the trace experiment is running. Trace state variables share
13434 the same namespace as other ``$'' variables, which means that you
13435 cannot have trace state variables with names like @code{$23} or
13436 @code{$pc}, nor can you have a trace state variable and a convenience
13437 variable with the same name.
13441 @item tvariable $@var{name} [ = @var{expression} ]
13443 The @code{tvariable} command creates a new trace state variable named
13444 @code{$@var{name}}, and optionally gives it an initial value of
13445 @var{expression}. The @var{expression} is evaluated when this command is
13446 entered; the result will be converted to an integer if possible,
13447 otherwise @value{GDBN} will report an error. A subsequent
13448 @code{tvariable} command specifying the same name does not create a
13449 variable, but instead assigns the supplied initial value to the
13450 existing variable of that name, overwriting any previous initial
13451 value. The default initial value is 0.
13453 @item info tvariables
13454 @kindex info tvariables
13455 List all the trace state variables along with their initial values.
13456 Their current values may also be displayed, if the trace experiment is
13459 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13460 @kindex delete tvariable
13461 Delete the given trace state variables, or all of them if no arguments
13466 @node Tracepoint Actions
13467 @subsection Tracepoint Action Lists
13471 @cindex tracepoint actions
13472 @item actions @r{[}@var{num}@r{]}
13473 This command will prompt for a list of actions to be taken when the
13474 tracepoint is hit. If the tracepoint number @var{num} is not
13475 specified, this command sets the actions for the one that was most
13476 recently defined (so that you can define a tracepoint and then say
13477 @code{actions} without bothering about its number). You specify the
13478 actions themselves on the following lines, one action at a time, and
13479 terminate the actions list with a line containing just @code{end}. So
13480 far, the only defined actions are @code{collect}, @code{teval}, and
13481 @code{while-stepping}.
13483 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13484 Commands, ,Breakpoint Command Lists}), except that only the defined
13485 actions are allowed; any other @value{GDBN} command is rejected.
13487 @cindex remove actions from a tracepoint
13488 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13489 and follow it immediately with @samp{end}.
13492 (@value{GDBP}) @b{collect @var{data}} // collect some data
13494 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13496 (@value{GDBP}) @b{end} // signals the end of actions.
13499 In the following example, the action list begins with @code{collect}
13500 commands indicating the things to be collected when the tracepoint is
13501 hit. Then, in order to single-step and collect additional data
13502 following the tracepoint, a @code{while-stepping} command is used,
13503 followed by the list of things to be collected after each step in a
13504 sequence of single steps. The @code{while-stepping} command is
13505 terminated by its own separate @code{end} command. Lastly, the action
13506 list is terminated by an @code{end} command.
13509 (@value{GDBP}) @b{trace foo}
13510 (@value{GDBP}) @b{actions}
13511 Enter actions for tracepoint 1, one per line:
13514 > while-stepping 12
13515 > collect $pc, arr[i]
13520 @kindex collect @r{(tracepoints)}
13521 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13522 Collect values of the given expressions when the tracepoint is hit.
13523 This command accepts a comma-separated list of any valid expressions.
13524 In addition to global, static, or local variables, the following
13525 special arguments are supported:
13529 Collect all registers.
13532 Collect all function arguments.
13535 Collect all local variables.
13538 Collect the return address. This is helpful if you want to see more
13541 @emph{Note:} The return address location can not always be reliably
13542 determined up front, and the wrong address / registers may end up
13543 collected instead. On some architectures the reliability is higher
13544 for tracepoints at function entry, while on others it's the opposite.
13545 When this happens, backtracing will stop because the return address is
13546 found unavailable (unless another collect rule happened to match it).
13549 Collects the number of arguments from the static probe at which the
13550 tracepoint is located.
13551 @xref{Static Probe Points}.
13553 @item $_probe_arg@var{n}
13554 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13555 from the static probe at which the tracepoint is located.
13556 @xref{Static Probe Points}.
13559 @vindex $_sdata@r{, collect}
13560 Collect static tracepoint marker specific data. Only available for
13561 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13562 Lists}. On the UST static tracepoints library backend, an
13563 instrumentation point resembles a @code{printf} function call. The
13564 tracing library is able to collect user specified data formatted to a
13565 character string using the format provided by the programmer that
13566 instrumented the program. Other backends have similar mechanisms.
13567 Here's an example of a UST marker call:
13570 const char master_name[] = "$your_name";
13571 trace_mark(channel1, marker1, "hello %s", master_name)
13574 In this case, collecting @code{$_sdata} collects the string
13575 @samp{hello $yourname}. When analyzing the trace buffer, you can
13576 inspect @samp{$_sdata} like any other variable available to
13580 You can give several consecutive @code{collect} commands, each one
13581 with a single argument, or one @code{collect} command with several
13582 arguments separated by commas; the effect is the same.
13584 The optional @var{mods} changes the usual handling of the arguments.
13585 @code{s} requests that pointers to chars be handled as strings, in
13586 particular collecting the contents of the memory being pointed at, up
13587 to the first zero. The upper bound is by default the value of the
13588 @code{print elements} variable; if @code{s} is followed by a decimal
13589 number, that is the upper bound instead. So for instance
13590 @samp{collect/s25 mystr} collects as many as 25 characters at
13593 The command @code{info scope} (@pxref{Symbols, info scope}) is
13594 particularly useful for figuring out what data to collect.
13596 @kindex teval @r{(tracepoints)}
13597 @item teval @var{expr1}, @var{expr2}, @dots{}
13598 Evaluate the given expressions when the tracepoint is hit. This
13599 command accepts a comma-separated list of expressions. The results
13600 are discarded, so this is mainly useful for assigning values to trace
13601 state variables (@pxref{Trace State Variables}) without adding those
13602 values to the trace buffer, as would be the case if the @code{collect}
13605 @kindex while-stepping @r{(tracepoints)}
13606 @item while-stepping @var{n}
13607 Perform @var{n} single-step instruction traces after the tracepoint,
13608 collecting new data after each step. The @code{while-stepping}
13609 command is followed by the list of what to collect while stepping
13610 (followed by its own @code{end} command):
13613 > while-stepping 12
13614 > collect $regs, myglobal
13620 Note that @code{$pc} is not automatically collected by
13621 @code{while-stepping}; you need to explicitly collect that register if
13622 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13625 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13626 @kindex set default-collect
13627 @cindex default collection action
13628 This variable is a list of expressions to collect at each tracepoint
13629 hit. It is effectively an additional @code{collect} action prepended
13630 to every tracepoint action list. The expressions are parsed
13631 individually for each tracepoint, so for instance a variable named
13632 @code{xyz} may be interpreted as a global for one tracepoint, and a
13633 local for another, as appropriate to the tracepoint's location.
13635 @item show default-collect
13636 @kindex show default-collect
13637 Show the list of expressions that are collected by default at each
13642 @node Listing Tracepoints
13643 @subsection Listing Tracepoints
13646 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13647 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13648 @cindex information about tracepoints
13649 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13650 Display information about the tracepoint @var{num}. If you don't
13651 specify a tracepoint number, displays information about all the
13652 tracepoints defined so far. The format is similar to that used for
13653 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13654 command, simply restricting itself to tracepoints.
13656 A tracepoint's listing may include additional information specific to
13661 its passcount as given by the @code{passcount @var{n}} command
13664 the state about installed on target of each location
13668 (@value{GDBP}) @b{info trace}
13669 Num Type Disp Enb Address What
13670 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13672 collect globfoo, $regs
13677 2 tracepoint keep y <MULTIPLE>
13679 2.1 y 0x0804859c in func4 at change-loc.h:35
13680 installed on target
13681 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13682 installed on target
13683 2.3 y <PENDING> set_tracepoint
13684 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13685 not installed on target
13690 This command can be abbreviated @code{info tp}.
13693 @node Listing Static Tracepoint Markers
13694 @subsection Listing Static Tracepoint Markers
13697 @kindex info static-tracepoint-markers
13698 @cindex information about static tracepoint markers
13699 @item info static-tracepoint-markers
13700 Display information about all static tracepoint markers defined in the
13703 For each marker, the following columns are printed:
13707 An incrementing counter, output to help readability. This is not a
13710 The marker ID, as reported by the target.
13711 @item Enabled or Disabled
13712 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13713 that are not enabled.
13715 Where the marker is in your program, as a memory address.
13717 Where the marker is in the source for your program, as a file and line
13718 number. If the debug information included in the program does not
13719 allow @value{GDBN} to locate the source of the marker, this column
13720 will be left blank.
13724 In addition, the following information may be printed for each marker:
13728 User data passed to the tracing library by the marker call. In the
13729 UST backend, this is the format string passed as argument to the
13731 @item Static tracepoints probing the marker
13732 The list of static tracepoints attached to the marker.
13736 (@value{GDBP}) info static-tracepoint-markers
13737 Cnt ID Enb Address What
13738 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13739 Data: number1 %d number2 %d
13740 Probed by static tracepoints: #2
13741 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13747 @node Starting and Stopping Trace Experiments
13748 @subsection Starting and Stopping Trace Experiments
13751 @kindex tstart [ @var{notes} ]
13752 @cindex start a new trace experiment
13753 @cindex collected data discarded
13755 This command starts the trace experiment, and begins collecting data.
13756 It has the side effect of discarding all the data collected in the
13757 trace buffer during the previous trace experiment. If any arguments
13758 are supplied, they are taken as a note and stored with the trace
13759 experiment's state. The notes may be arbitrary text, and are
13760 especially useful with disconnected tracing in a multi-user context;
13761 the notes can explain what the trace is doing, supply user contact
13762 information, and so forth.
13764 @kindex tstop [ @var{notes} ]
13765 @cindex stop a running trace experiment
13767 This command stops the trace experiment. If any arguments are
13768 supplied, they are recorded with the experiment as a note. This is
13769 useful if you are stopping a trace started by someone else, for
13770 instance if the trace is interfering with the system's behavior and
13771 needs to be stopped quickly.
13773 @strong{Note}: a trace experiment and data collection may stop
13774 automatically if any tracepoint's passcount is reached
13775 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13778 @cindex status of trace data collection
13779 @cindex trace experiment, status of
13781 This command displays the status of the current trace data
13785 Here is an example of the commands we described so far:
13788 (@value{GDBP}) @b{trace gdb_c_test}
13789 (@value{GDBP}) @b{actions}
13790 Enter actions for tracepoint #1, one per line.
13791 > collect $regs,$locals,$args
13792 > while-stepping 11
13796 (@value{GDBP}) @b{tstart}
13797 [time passes @dots{}]
13798 (@value{GDBP}) @b{tstop}
13801 @anchor{disconnected tracing}
13802 @cindex disconnected tracing
13803 You can choose to continue running the trace experiment even if
13804 @value{GDBN} disconnects from the target, voluntarily or
13805 involuntarily. For commands such as @code{detach}, the debugger will
13806 ask what you want to do with the trace. But for unexpected
13807 terminations (@value{GDBN} crash, network outage), it would be
13808 unfortunate to lose hard-won trace data, so the variable
13809 @code{disconnected-tracing} lets you decide whether the trace should
13810 continue running without @value{GDBN}.
13813 @item set disconnected-tracing on
13814 @itemx set disconnected-tracing off
13815 @kindex set disconnected-tracing
13816 Choose whether a tracing run should continue to run if @value{GDBN}
13817 has disconnected from the target. Note that @code{detach} or
13818 @code{quit} will ask you directly what to do about a running trace no
13819 matter what this variable's setting, so the variable is mainly useful
13820 for handling unexpected situations, such as loss of the network.
13822 @item show disconnected-tracing
13823 @kindex show disconnected-tracing
13824 Show the current choice for disconnected tracing.
13828 When you reconnect to the target, the trace experiment may or may not
13829 still be running; it might have filled the trace buffer in the
13830 meantime, or stopped for one of the other reasons. If it is running,
13831 it will continue after reconnection.
13833 Upon reconnection, the target will upload information about the
13834 tracepoints in effect. @value{GDBN} will then compare that
13835 information to the set of tracepoints currently defined, and attempt
13836 to match them up, allowing for the possibility that the numbers may
13837 have changed due to creation and deletion in the meantime. If one of
13838 the target's tracepoints does not match any in @value{GDBN}, the
13839 debugger will create a new tracepoint, so that you have a number with
13840 which to specify that tracepoint. This matching-up process is
13841 necessarily heuristic, and it may result in useless tracepoints being
13842 created; you may simply delete them if they are of no use.
13844 @cindex circular trace buffer
13845 If your target agent supports a @dfn{circular trace buffer}, then you
13846 can run a trace experiment indefinitely without filling the trace
13847 buffer; when space runs out, the agent deletes already-collected trace
13848 frames, oldest first, until there is enough room to continue
13849 collecting. This is especially useful if your tracepoints are being
13850 hit too often, and your trace gets terminated prematurely because the
13851 buffer is full. To ask for a circular trace buffer, simply set
13852 @samp{circular-trace-buffer} to on. You can set this at any time,
13853 including during tracing; if the agent can do it, it will change
13854 buffer handling on the fly, otherwise it will not take effect until
13858 @item set circular-trace-buffer on
13859 @itemx set circular-trace-buffer off
13860 @kindex set circular-trace-buffer
13861 Choose whether a tracing run should use a linear or circular buffer
13862 for trace data. A linear buffer will not lose any trace data, but may
13863 fill up prematurely, while a circular buffer will discard old trace
13864 data, but it will have always room for the latest tracepoint hits.
13866 @item show circular-trace-buffer
13867 @kindex show circular-trace-buffer
13868 Show the current choice for the trace buffer. Note that this may not
13869 match the agent's current buffer handling, nor is it guaranteed to
13870 match the setting that might have been in effect during a past run,
13871 for instance if you are looking at frames from a trace file.
13876 @item set trace-buffer-size @var{n}
13877 @itemx set trace-buffer-size unlimited
13878 @kindex set trace-buffer-size
13879 Request that the target use a trace buffer of @var{n} bytes. Not all
13880 targets will honor the request; they may have a compiled-in size for
13881 the trace buffer, or some other limitation. Set to a value of
13882 @code{unlimited} or @code{-1} to let the target use whatever size it
13883 likes. This is also the default.
13885 @item show trace-buffer-size
13886 @kindex show trace-buffer-size
13887 Show the current requested size for the trace buffer. Note that this
13888 will only match the actual size if the target supports size-setting,
13889 and was able to handle the requested size. For instance, if the
13890 target can only change buffer size between runs, this variable will
13891 not reflect the change until the next run starts. Use @code{tstatus}
13892 to get a report of the actual buffer size.
13896 @item set trace-user @var{text}
13897 @kindex set trace-user
13899 @item show trace-user
13900 @kindex show trace-user
13902 @item set trace-notes @var{text}
13903 @kindex set trace-notes
13904 Set the trace run's notes.
13906 @item show trace-notes
13907 @kindex show trace-notes
13908 Show the trace run's notes.
13910 @item set trace-stop-notes @var{text}
13911 @kindex set trace-stop-notes
13912 Set the trace run's stop notes. The handling of the note is as for
13913 @code{tstop} arguments; the set command is convenient way to fix a
13914 stop note that is mistaken or incomplete.
13916 @item show trace-stop-notes
13917 @kindex show trace-stop-notes
13918 Show the trace run's stop notes.
13922 @node Tracepoint Restrictions
13923 @subsection Tracepoint Restrictions
13925 @cindex tracepoint restrictions
13926 There are a number of restrictions on the use of tracepoints. As
13927 described above, tracepoint data gathering occurs on the target
13928 without interaction from @value{GDBN}. Thus the full capabilities of
13929 the debugger are not available during data gathering, and then at data
13930 examination time, you will be limited by only having what was
13931 collected. The following items describe some common problems, but it
13932 is not exhaustive, and you may run into additional difficulties not
13938 Tracepoint expressions are intended to gather objects (lvalues). Thus
13939 the full flexibility of GDB's expression evaluator is not available.
13940 You cannot call functions, cast objects to aggregate types, access
13941 convenience variables or modify values (except by assignment to trace
13942 state variables). Some language features may implicitly call
13943 functions (for instance Objective-C fields with accessors), and therefore
13944 cannot be collected either.
13947 Collection of local variables, either individually or in bulk with
13948 @code{$locals} or @code{$args}, during @code{while-stepping} may
13949 behave erratically. The stepping action may enter a new scope (for
13950 instance by stepping into a function), or the location of the variable
13951 may change (for instance it is loaded into a register). The
13952 tracepoint data recorded uses the location information for the
13953 variables that is correct for the tracepoint location. When the
13954 tracepoint is created, it is not possible, in general, to determine
13955 where the steps of a @code{while-stepping} sequence will advance the
13956 program---particularly if a conditional branch is stepped.
13959 Collection of an incompletely-initialized or partially-destroyed object
13960 may result in something that @value{GDBN} cannot display, or displays
13961 in a misleading way.
13964 When @value{GDBN} displays a pointer to character it automatically
13965 dereferences the pointer to also display characters of the string
13966 being pointed to. However, collecting the pointer during tracing does
13967 not automatically collect the string. You need to explicitly
13968 dereference the pointer and provide size information if you want to
13969 collect not only the pointer, but the memory pointed to. For example,
13970 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13974 It is not possible to collect a complete stack backtrace at a
13975 tracepoint. Instead, you may collect the registers and a few hundred
13976 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13977 (adjust to use the name of the actual stack pointer register on your
13978 target architecture, and the amount of stack you wish to capture).
13979 Then the @code{backtrace} command will show a partial backtrace when
13980 using a trace frame. The number of stack frames that can be examined
13981 depends on the sizes of the frames in the collected stack. Note that
13982 if you ask for a block so large that it goes past the bottom of the
13983 stack, the target agent may report an error trying to read from an
13987 If you do not collect registers at a tracepoint, @value{GDBN} can
13988 infer that the value of @code{$pc} must be the same as the address of
13989 the tracepoint and use that when you are looking at a trace frame
13990 for that tracepoint. However, this cannot work if the tracepoint has
13991 multiple locations (for instance if it was set in a function that was
13992 inlined), or if it has a @code{while-stepping} loop. In those cases
13993 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13998 @node Analyze Collected Data
13999 @section Using the Collected Data
14001 After the tracepoint experiment ends, you use @value{GDBN} commands
14002 for examining the trace data. The basic idea is that each tracepoint
14003 collects a trace @dfn{snapshot} every time it is hit and another
14004 snapshot every time it single-steps. All these snapshots are
14005 consecutively numbered from zero and go into a buffer, and you can
14006 examine them later. The way you examine them is to @dfn{focus} on a
14007 specific trace snapshot. When the remote stub is focused on a trace
14008 snapshot, it will respond to all @value{GDBN} requests for memory and
14009 registers by reading from the buffer which belongs to that snapshot,
14010 rather than from @emph{real} memory or registers of the program being
14011 debugged. This means that @strong{all} @value{GDBN} commands
14012 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14013 behave as if we were currently debugging the program state as it was
14014 when the tracepoint occurred. Any requests for data that are not in
14015 the buffer will fail.
14018 * tfind:: How to select a trace snapshot
14019 * tdump:: How to display all data for a snapshot
14020 * save tracepoints:: How to save tracepoints for a future run
14024 @subsection @code{tfind @var{n}}
14027 @cindex select trace snapshot
14028 @cindex find trace snapshot
14029 The basic command for selecting a trace snapshot from the buffer is
14030 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14031 counting from zero. If no argument @var{n} is given, the next
14032 snapshot is selected.
14034 Here are the various forms of using the @code{tfind} command.
14038 Find the first snapshot in the buffer. This is a synonym for
14039 @code{tfind 0} (since 0 is the number of the first snapshot).
14042 Stop debugging trace snapshots, resume @emph{live} debugging.
14045 Same as @samp{tfind none}.
14048 No argument means find the next trace snapshot or find the first
14049 one if no trace snapshot is selected.
14052 Find the previous trace snapshot before the current one. This permits
14053 retracing earlier steps.
14055 @item tfind tracepoint @var{num}
14056 Find the next snapshot associated with tracepoint @var{num}. Search
14057 proceeds forward from the last examined trace snapshot. If no
14058 argument @var{num} is given, it means find the next snapshot collected
14059 for the same tracepoint as the current snapshot.
14061 @item tfind pc @var{addr}
14062 Find the next snapshot associated with the value @var{addr} of the
14063 program counter. Search proceeds forward from the last examined trace
14064 snapshot. If no argument @var{addr} is given, it means find the next
14065 snapshot with the same value of PC as the current snapshot.
14067 @item tfind outside @var{addr1}, @var{addr2}
14068 Find the next snapshot whose PC is outside the given range of
14069 addresses (exclusive).
14071 @item tfind range @var{addr1}, @var{addr2}
14072 Find the next snapshot whose PC is between @var{addr1} and
14073 @var{addr2} (inclusive).
14075 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14076 Find the next snapshot associated with the source line @var{n}. If
14077 the optional argument @var{file} is given, refer to line @var{n} in
14078 that source file. Search proceeds forward from the last examined
14079 trace snapshot. If no argument @var{n} is given, it means find the
14080 next line other than the one currently being examined; thus saying
14081 @code{tfind line} repeatedly can appear to have the same effect as
14082 stepping from line to line in a @emph{live} debugging session.
14085 The default arguments for the @code{tfind} commands are specifically
14086 designed to make it easy to scan through the trace buffer. For
14087 instance, @code{tfind} with no argument selects the next trace
14088 snapshot, and @code{tfind -} with no argument selects the previous
14089 trace snapshot. So, by giving one @code{tfind} command, and then
14090 simply hitting @key{RET} repeatedly you can examine all the trace
14091 snapshots in order. Or, by saying @code{tfind -} and then hitting
14092 @key{RET} repeatedly you can examine the snapshots in reverse order.
14093 The @code{tfind line} command with no argument selects the snapshot
14094 for the next source line executed. The @code{tfind pc} command with
14095 no argument selects the next snapshot with the same program counter
14096 (PC) as the current frame. The @code{tfind tracepoint} command with
14097 no argument selects the next trace snapshot collected by the same
14098 tracepoint as the current one.
14100 In addition to letting you scan through the trace buffer manually,
14101 these commands make it easy to construct @value{GDBN} scripts that
14102 scan through the trace buffer and print out whatever collected data
14103 you are interested in. Thus, if we want to examine the PC, FP, and SP
14104 registers from each trace frame in the buffer, we can say this:
14107 (@value{GDBP}) @b{tfind start}
14108 (@value{GDBP}) @b{while ($trace_frame != -1)}
14109 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14110 $trace_frame, $pc, $sp, $fp
14114 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14115 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14116 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14117 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14118 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14119 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14120 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14121 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14122 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14123 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14124 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14127 Or, if we want to examine the variable @code{X} at each source line in
14131 (@value{GDBP}) @b{tfind start}
14132 (@value{GDBP}) @b{while ($trace_frame != -1)}
14133 > printf "Frame %d, X == %d\n", $trace_frame, X
14143 @subsection @code{tdump}
14145 @cindex dump all data collected at tracepoint
14146 @cindex tracepoint data, display
14148 This command takes no arguments. It prints all the data collected at
14149 the current trace snapshot.
14152 (@value{GDBP}) @b{trace 444}
14153 (@value{GDBP}) @b{actions}
14154 Enter actions for tracepoint #2, one per line:
14155 > collect $regs, $locals, $args, gdb_long_test
14158 (@value{GDBP}) @b{tstart}
14160 (@value{GDBP}) @b{tfind line 444}
14161 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14163 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14165 (@value{GDBP}) @b{tdump}
14166 Data collected at tracepoint 2, trace frame 1:
14167 d0 0xc4aa0085 -995491707
14171 d4 0x71aea3d 119204413
14174 d7 0x380035 3670069
14175 a0 0x19e24a 1696330
14176 a1 0x3000668 50333288
14178 a3 0x322000 3284992
14179 a4 0x3000698 50333336
14180 a5 0x1ad3cc 1758156
14181 fp 0x30bf3c 0x30bf3c
14182 sp 0x30bf34 0x30bf34
14184 pc 0x20b2c8 0x20b2c8
14188 p = 0x20e5b4 "gdb-test"
14195 gdb_long_test = 17 '\021'
14200 @code{tdump} works by scanning the tracepoint's current collection
14201 actions and printing the value of each expression listed. So
14202 @code{tdump} can fail, if after a run, you change the tracepoint's
14203 actions to mention variables that were not collected during the run.
14205 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14206 uses the collected value of @code{$pc} to distinguish between trace
14207 frames that were collected at the tracepoint hit, and frames that were
14208 collected while stepping. This allows it to correctly choose whether
14209 to display the basic list of collections, or the collections from the
14210 body of the while-stepping loop. However, if @code{$pc} was not collected,
14211 then @code{tdump} will always attempt to dump using the basic collection
14212 list, and may fail if a while-stepping frame does not include all the
14213 same data that is collected at the tracepoint hit.
14214 @c This is getting pretty arcane, example would be good.
14216 @node save tracepoints
14217 @subsection @code{save tracepoints @var{filename}}
14218 @kindex save tracepoints
14219 @kindex save-tracepoints
14220 @cindex save tracepoints for future sessions
14222 This command saves all current tracepoint definitions together with
14223 their actions and passcounts, into a file @file{@var{filename}}
14224 suitable for use in a later debugging session. To read the saved
14225 tracepoint definitions, use the @code{source} command (@pxref{Command
14226 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14227 alias for @w{@code{save tracepoints}}
14229 @node Tracepoint Variables
14230 @section Convenience Variables for Tracepoints
14231 @cindex tracepoint variables
14232 @cindex convenience variables for tracepoints
14235 @vindex $trace_frame
14236 @item (int) $trace_frame
14237 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14238 snapshot is selected.
14240 @vindex $tracepoint
14241 @item (int) $tracepoint
14242 The tracepoint for the current trace snapshot.
14244 @vindex $trace_line
14245 @item (int) $trace_line
14246 The line number for the current trace snapshot.
14248 @vindex $trace_file
14249 @item (char []) $trace_file
14250 The source file for the current trace snapshot.
14252 @vindex $trace_func
14253 @item (char []) $trace_func
14254 The name of the function containing @code{$tracepoint}.
14257 Note: @code{$trace_file} is not suitable for use in @code{printf},
14258 use @code{output} instead.
14260 Here's a simple example of using these convenience variables for
14261 stepping through all the trace snapshots and printing some of their
14262 data. Note that these are not the same as trace state variables,
14263 which are managed by the target.
14266 (@value{GDBP}) @b{tfind start}
14268 (@value{GDBP}) @b{while $trace_frame != -1}
14269 > output $trace_file
14270 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14276 @section Using Trace Files
14277 @cindex trace files
14279 In some situations, the target running a trace experiment may no
14280 longer be available; perhaps it crashed, or the hardware was needed
14281 for a different activity. To handle these cases, you can arrange to
14282 dump the trace data into a file, and later use that file as a source
14283 of trace data, via the @code{target tfile} command.
14288 @item tsave [ -r ] @var{filename}
14289 @itemx tsave [-ctf] @var{dirname}
14290 Save the trace data to @var{filename}. By default, this command
14291 assumes that @var{filename} refers to the host filesystem, so if
14292 necessary @value{GDBN} will copy raw trace data up from the target and
14293 then save it. If the target supports it, you can also supply the
14294 optional argument @code{-r} (``remote'') to direct the target to save
14295 the data directly into @var{filename} in its own filesystem, which may be
14296 more efficient if the trace buffer is very large. (Note, however, that
14297 @code{target tfile} can only read from files accessible to the host.)
14298 By default, this command will save trace frame in tfile format.
14299 You can supply the optional argument @code{-ctf} to save data in CTF
14300 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14301 that can be shared by multiple debugging and tracing tools. Please go to
14302 @indicateurl{http://www.efficios.com/ctf} to get more information.
14304 @kindex target tfile
14308 @item target tfile @var{filename}
14309 @itemx target ctf @var{dirname}
14310 Use the file named @var{filename} or directory named @var{dirname} as
14311 a source of trace data. Commands that examine data work as they do with
14312 a live target, but it is not possible to run any new trace experiments.
14313 @code{tstatus} will report the state of the trace run at the moment
14314 the data was saved, as well as the current trace frame you are examining.
14315 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14319 (@value{GDBP}) target ctf ctf.ctf
14320 (@value{GDBP}) tfind
14321 Found trace frame 0, tracepoint 2
14322 39 ++a; /* set tracepoint 1 here */
14323 (@value{GDBP}) tdump
14324 Data collected at tracepoint 2, trace frame 0:
14328 c = @{"123", "456", "789", "123", "456", "789"@}
14329 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14337 @chapter Debugging Programs That Use Overlays
14340 If your program is too large to fit completely in your target system's
14341 memory, you can sometimes use @dfn{overlays} to work around this
14342 problem. @value{GDBN} provides some support for debugging programs that
14346 * How Overlays Work:: A general explanation of overlays.
14347 * Overlay Commands:: Managing overlays in @value{GDBN}.
14348 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14349 mapped by asking the inferior.
14350 * Overlay Sample Program:: A sample program using overlays.
14353 @node How Overlays Work
14354 @section How Overlays Work
14355 @cindex mapped overlays
14356 @cindex unmapped overlays
14357 @cindex load address, overlay's
14358 @cindex mapped address
14359 @cindex overlay area
14361 Suppose you have a computer whose instruction address space is only 64
14362 kilobytes long, but which has much more memory which can be accessed by
14363 other means: special instructions, segment registers, or memory
14364 management hardware, for example. Suppose further that you want to
14365 adapt a program which is larger than 64 kilobytes to run on this system.
14367 One solution is to identify modules of your program which are relatively
14368 independent, and need not call each other directly; call these modules
14369 @dfn{overlays}. Separate the overlays from the main program, and place
14370 their machine code in the larger memory. Place your main program in
14371 instruction memory, but leave at least enough space there to hold the
14372 largest overlay as well.
14374 Now, to call a function located in an overlay, you must first copy that
14375 overlay's machine code from the large memory into the space set aside
14376 for it in the instruction memory, and then jump to its entry point
14379 @c NB: In the below the mapped area's size is greater or equal to the
14380 @c size of all overlays. This is intentional to remind the developer
14381 @c that overlays don't necessarily need to be the same size.
14385 Data Instruction Larger
14386 Address Space Address Space Address Space
14387 +-----------+ +-----------+ +-----------+
14389 +-----------+ +-----------+ +-----------+<-- overlay 1
14390 | program | | main | .----| overlay 1 | load address
14391 | variables | | program | | +-----------+
14392 | and heap | | | | | |
14393 +-----------+ | | | +-----------+<-- overlay 2
14394 | | +-----------+ | | | load address
14395 +-----------+ | | | .-| overlay 2 |
14397 mapped --->+-----------+ | | +-----------+
14398 address | | | | | |
14399 | overlay | <-' | | |
14400 | area | <---' +-----------+<-- overlay 3
14401 | | <---. | | load address
14402 +-----------+ `--| overlay 3 |
14409 @anchor{A code overlay}A code overlay
14413 The diagram (@pxref{A code overlay}) shows a system with separate data
14414 and instruction address spaces. To map an overlay, the program copies
14415 its code from the larger address space to the instruction address space.
14416 Since the overlays shown here all use the same mapped address, only one
14417 may be mapped at a time. For a system with a single address space for
14418 data and instructions, the diagram would be similar, except that the
14419 program variables and heap would share an address space with the main
14420 program and the overlay area.
14422 An overlay loaded into instruction memory and ready for use is called a
14423 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14424 instruction memory. An overlay not present (or only partially present)
14425 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14426 is its address in the larger memory. The mapped address is also called
14427 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14428 called the @dfn{load memory address}, or @dfn{LMA}.
14430 Unfortunately, overlays are not a completely transparent way to adapt a
14431 program to limited instruction memory. They introduce a new set of
14432 global constraints you must keep in mind as you design your program:
14437 Before calling or returning to a function in an overlay, your program
14438 must make sure that overlay is actually mapped. Otherwise, the call or
14439 return will transfer control to the right address, but in the wrong
14440 overlay, and your program will probably crash.
14443 If the process of mapping an overlay is expensive on your system, you
14444 will need to choose your overlays carefully to minimize their effect on
14445 your program's performance.
14448 The executable file you load onto your system must contain each
14449 overlay's instructions, appearing at the overlay's load address, not its
14450 mapped address. However, each overlay's instructions must be relocated
14451 and its symbols defined as if the overlay were at its mapped address.
14452 You can use GNU linker scripts to specify different load and relocation
14453 addresses for pieces of your program; see @ref{Overlay Description,,,
14454 ld.info, Using ld: the GNU linker}.
14457 The procedure for loading executable files onto your system must be able
14458 to load their contents into the larger address space as well as the
14459 instruction and data spaces.
14463 The overlay system described above is rather simple, and could be
14464 improved in many ways:
14469 If your system has suitable bank switch registers or memory management
14470 hardware, you could use those facilities to make an overlay's load area
14471 contents simply appear at their mapped address in instruction space.
14472 This would probably be faster than copying the overlay to its mapped
14473 area in the usual way.
14476 If your overlays are small enough, you could set aside more than one
14477 overlay area, and have more than one overlay mapped at a time.
14480 You can use overlays to manage data, as well as instructions. In
14481 general, data overlays are even less transparent to your design than
14482 code overlays: whereas code overlays only require care when you call or
14483 return to functions, data overlays require care every time you access
14484 the data. Also, if you change the contents of a data overlay, you
14485 must copy its contents back out to its load address before you can copy a
14486 different data overlay into the same mapped area.
14491 @node Overlay Commands
14492 @section Overlay Commands
14494 To use @value{GDBN}'s overlay support, each overlay in your program must
14495 correspond to a separate section of the executable file. The section's
14496 virtual memory address and load memory address must be the overlay's
14497 mapped and load addresses. Identifying overlays with sections allows
14498 @value{GDBN} to determine the appropriate address of a function or
14499 variable, depending on whether the overlay is mapped or not.
14501 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14502 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14507 Disable @value{GDBN}'s overlay support. When overlay support is
14508 disabled, @value{GDBN} assumes that all functions and variables are
14509 always present at their mapped addresses. By default, @value{GDBN}'s
14510 overlay support is disabled.
14512 @item overlay manual
14513 @cindex manual overlay debugging
14514 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14515 relies on you to tell it which overlays are mapped, and which are not,
14516 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14517 commands described below.
14519 @item overlay map-overlay @var{overlay}
14520 @itemx overlay map @var{overlay}
14521 @cindex map an overlay
14522 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14523 be the name of the object file section containing the overlay. When an
14524 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14525 functions and variables at their mapped addresses. @value{GDBN} assumes
14526 that any other overlays whose mapped ranges overlap that of
14527 @var{overlay} are now unmapped.
14529 @item overlay unmap-overlay @var{overlay}
14530 @itemx overlay unmap @var{overlay}
14531 @cindex unmap an overlay
14532 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14533 must be the name of the object file section containing the overlay.
14534 When an overlay is unmapped, @value{GDBN} assumes it can find the
14535 overlay's functions and variables at their load addresses.
14538 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14539 consults a data structure the overlay manager maintains in the inferior
14540 to see which overlays are mapped. For details, see @ref{Automatic
14541 Overlay Debugging}.
14543 @item overlay load-target
14544 @itemx overlay load
14545 @cindex reloading the overlay table
14546 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14547 re-reads the table @value{GDBN} automatically each time the inferior
14548 stops, so this command should only be necessary if you have changed the
14549 overlay mapping yourself using @value{GDBN}. This command is only
14550 useful when using automatic overlay debugging.
14552 @item overlay list-overlays
14553 @itemx overlay list
14554 @cindex listing mapped overlays
14555 Display a list of the overlays currently mapped, along with their mapped
14556 addresses, load addresses, and sizes.
14560 Normally, when @value{GDBN} prints a code address, it includes the name
14561 of the function the address falls in:
14564 (@value{GDBP}) print main
14565 $3 = @{int ()@} 0x11a0 <main>
14568 When overlay debugging is enabled, @value{GDBN} recognizes code in
14569 unmapped overlays, and prints the names of unmapped functions with
14570 asterisks around them. For example, if @code{foo} is a function in an
14571 unmapped overlay, @value{GDBN} prints it this way:
14574 (@value{GDBP}) overlay list
14575 No sections are mapped.
14576 (@value{GDBP}) print foo
14577 $5 = @{int (int)@} 0x100000 <*foo*>
14580 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14584 (@value{GDBP}) overlay list
14585 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14586 mapped at 0x1016 - 0x104a
14587 (@value{GDBP}) print foo
14588 $6 = @{int (int)@} 0x1016 <foo>
14591 When overlay debugging is enabled, @value{GDBN} can find the correct
14592 address for functions and variables in an overlay, whether or not the
14593 overlay is mapped. This allows most @value{GDBN} commands, like
14594 @code{break} and @code{disassemble}, to work normally, even on unmapped
14595 code. However, @value{GDBN}'s breakpoint support has some limitations:
14599 @cindex breakpoints in overlays
14600 @cindex overlays, setting breakpoints in
14601 You can set breakpoints in functions in unmapped overlays, as long as
14602 @value{GDBN} can write to the overlay at its load address.
14604 @value{GDBN} can not set hardware or simulator-based breakpoints in
14605 unmapped overlays. However, if you set a breakpoint at the end of your
14606 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14607 you are using manual overlay management), @value{GDBN} will re-set its
14608 breakpoints properly.
14612 @node Automatic Overlay Debugging
14613 @section Automatic Overlay Debugging
14614 @cindex automatic overlay debugging
14616 @value{GDBN} can automatically track which overlays are mapped and which
14617 are not, given some simple co-operation from the overlay manager in the
14618 inferior. If you enable automatic overlay debugging with the
14619 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14620 looks in the inferior's memory for certain variables describing the
14621 current state of the overlays.
14623 Here are the variables your overlay manager must define to support
14624 @value{GDBN}'s automatic overlay debugging:
14628 @item @code{_ovly_table}:
14629 This variable must be an array of the following structures:
14634 /* The overlay's mapped address. */
14637 /* The size of the overlay, in bytes. */
14638 unsigned long size;
14640 /* The overlay's load address. */
14643 /* Non-zero if the overlay is currently mapped;
14645 unsigned long mapped;
14649 @item @code{_novlys}:
14650 This variable must be a four-byte signed integer, holding the total
14651 number of elements in @code{_ovly_table}.
14655 To decide whether a particular overlay is mapped or not, @value{GDBN}
14656 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14657 @code{lma} members equal the VMA and LMA of the overlay's section in the
14658 executable file. When @value{GDBN} finds a matching entry, it consults
14659 the entry's @code{mapped} member to determine whether the overlay is
14662 In addition, your overlay manager may define a function called
14663 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14664 will silently set a breakpoint there. If the overlay manager then
14665 calls this function whenever it has changed the overlay table, this
14666 will enable @value{GDBN} to accurately keep track of which overlays
14667 are in program memory, and update any breakpoints that may be set
14668 in overlays. This will allow breakpoints to work even if the
14669 overlays are kept in ROM or other non-writable memory while they
14670 are not being executed.
14672 @node Overlay Sample Program
14673 @section Overlay Sample Program
14674 @cindex overlay example program
14676 When linking a program which uses overlays, you must place the overlays
14677 at their load addresses, while relocating them to run at their mapped
14678 addresses. To do this, you must write a linker script (@pxref{Overlay
14679 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14680 since linker scripts are specific to a particular host system, target
14681 architecture, and target memory layout, this manual cannot provide
14682 portable sample code demonstrating @value{GDBN}'s overlay support.
14684 However, the @value{GDBN} source distribution does contain an overlaid
14685 program, with linker scripts for a few systems, as part of its test
14686 suite. The program consists of the following files from
14687 @file{gdb/testsuite/gdb.base}:
14691 The main program file.
14693 A simple overlay manager, used by @file{overlays.c}.
14698 Overlay modules, loaded and used by @file{overlays.c}.
14701 Linker scripts for linking the test program on the @code{d10v-elf}
14702 and @code{m32r-elf} targets.
14705 You can build the test program using the @code{d10v-elf} GCC
14706 cross-compiler like this:
14709 $ d10v-elf-gcc -g -c overlays.c
14710 $ d10v-elf-gcc -g -c ovlymgr.c
14711 $ d10v-elf-gcc -g -c foo.c
14712 $ d10v-elf-gcc -g -c bar.c
14713 $ d10v-elf-gcc -g -c baz.c
14714 $ d10v-elf-gcc -g -c grbx.c
14715 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14716 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14719 The build process is identical for any other architecture, except that
14720 you must substitute the appropriate compiler and linker script for the
14721 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14725 @chapter Using @value{GDBN} with Different Languages
14728 Although programming languages generally have common aspects, they are
14729 rarely expressed in the same manner. For instance, in ANSI C,
14730 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14731 Modula-2, it is accomplished by @code{p^}. Values can also be
14732 represented (and displayed) differently. Hex numbers in C appear as
14733 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14735 @cindex working language
14736 Language-specific information is built into @value{GDBN} for some languages,
14737 allowing you to express operations like the above in your program's
14738 native language, and allowing @value{GDBN} to output values in a manner
14739 consistent with the syntax of your program's native language. The
14740 language you use to build expressions is called the @dfn{working
14744 * Setting:: Switching between source languages
14745 * Show:: Displaying the language
14746 * Checks:: Type and range checks
14747 * Supported Languages:: Supported languages
14748 * Unsupported Languages:: Unsupported languages
14752 @section Switching Between Source Languages
14754 There are two ways to control the working language---either have @value{GDBN}
14755 set it automatically, or select it manually yourself. You can use the
14756 @code{set language} command for either purpose. On startup, @value{GDBN}
14757 defaults to setting the language automatically. The working language is
14758 used to determine how expressions you type are interpreted, how values
14761 In addition to the working language, every source file that
14762 @value{GDBN} knows about has its own working language. For some object
14763 file formats, the compiler might indicate which language a particular
14764 source file is in. However, most of the time @value{GDBN} infers the
14765 language from the name of the file. The language of a source file
14766 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14767 show each frame appropriately for its own language. There is no way to
14768 set the language of a source file from within @value{GDBN}, but you can
14769 set the language associated with a filename extension. @xref{Show, ,
14770 Displaying the Language}.
14772 This is most commonly a problem when you use a program, such
14773 as @code{cfront} or @code{f2c}, that generates C but is written in
14774 another language. In that case, make the
14775 program use @code{#line} directives in its C output; that way
14776 @value{GDBN} will know the correct language of the source code of the original
14777 program, and will display that source code, not the generated C code.
14780 * Filenames:: Filename extensions and languages.
14781 * Manually:: Setting the working language manually
14782 * Automatically:: Having @value{GDBN} infer the source language
14786 @subsection List of Filename Extensions and Languages
14788 If a source file name ends in one of the following extensions, then
14789 @value{GDBN} infers that its language is the one indicated.
14807 C@t{++} source file
14813 Objective-C source file
14817 Fortran source file
14820 Modula-2 source file
14824 Assembler source file. This actually behaves almost like C, but
14825 @value{GDBN} does not skip over function prologues when stepping.
14828 In addition, you may set the language associated with a filename
14829 extension. @xref{Show, , Displaying the Language}.
14832 @subsection Setting the Working Language
14834 If you allow @value{GDBN} to set the language automatically,
14835 expressions are interpreted the same way in your debugging session and
14838 @kindex set language
14839 If you wish, you may set the language manually. To do this, issue the
14840 command @samp{set language @var{lang}}, where @var{lang} is the name of
14841 a language, such as
14842 @code{c} or @code{modula-2}.
14843 For a list of the supported languages, type @samp{set language}.
14845 Setting the language manually prevents @value{GDBN} from updating the working
14846 language automatically. This can lead to confusion if you try
14847 to debug a program when the working language is not the same as the
14848 source language, when an expression is acceptable to both
14849 languages---but means different things. For instance, if the current
14850 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14858 might not have the effect you intended. In C, this means to add
14859 @code{b} and @code{c} and place the result in @code{a}. The result
14860 printed would be the value of @code{a}. In Modula-2, this means to compare
14861 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14863 @node Automatically
14864 @subsection Having @value{GDBN} Infer the Source Language
14866 To have @value{GDBN} set the working language automatically, use
14867 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14868 then infers the working language. That is, when your program stops in a
14869 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14870 working language to the language recorded for the function in that
14871 frame. If the language for a frame is unknown (that is, if the function
14872 or block corresponding to the frame was defined in a source file that
14873 does not have a recognized extension), the current working language is
14874 not changed, and @value{GDBN} issues a warning.
14876 This may not seem necessary for most programs, which are written
14877 entirely in one source language. However, program modules and libraries
14878 written in one source language can be used by a main program written in
14879 a different source language. Using @samp{set language auto} in this
14880 case frees you from having to set the working language manually.
14883 @section Displaying the Language
14885 The following commands help you find out which language is the
14886 working language, and also what language source files were written in.
14889 @item show language
14890 @anchor{show language}
14891 @kindex show language
14892 Display the current working language. This is the
14893 language you can use with commands such as @code{print} to
14894 build and compute expressions that may involve variables in your program.
14897 @kindex info frame@r{, show the source language}
14898 Display the source language for this frame. This language becomes the
14899 working language if you use an identifier from this frame.
14900 @xref{Frame Info, ,Information about a Frame}, to identify the other
14901 information listed here.
14904 @kindex info source@r{, show the source language}
14905 Display the source language of this source file.
14906 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14907 information listed here.
14910 In unusual circumstances, you may have source files with extensions
14911 not in the standard list. You can then set the extension associated
14912 with a language explicitly:
14915 @item set extension-language @var{ext} @var{language}
14916 @kindex set extension-language
14917 Tell @value{GDBN} that source files with extension @var{ext} are to be
14918 assumed as written in the source language @var{language}.
14920 @item info extensions
14921 @kindex info extensions
14922 List all the filename extensions and the associated languages.
14926 @section Type and Range Checking
14928 Some languages are designed to guard you against making seemingly common
14929 errors through a series of compile- and run-time checks. These include
14930 checking the type of arguments to functions and operators and making
14931 sure mathematical overflows are caught at run time. Checks such as
14932 these help to ensure a program's correctness once it has been compiled
14933 by eliminating type mismatches and providing active checks for range
14934 errors when your program is running.
14936 By default @value{GDBN} checks for these errors according to the
14937 rules of the current source language. Although @value{GDBN} does not check
14938 the statements in your program, it can check expressions entered directly
14939 into @value{GDBN} for evaluation via the @code{print} command, for example.
14942 * Type Checking:: An overview of type checking
14943 * Range Checking:: An overview of range checking
14946 @cindex type checking
14947 @cindex checks, type
14948 @node Type Checking
14949 @subsection An Overview of Type Checking
14951 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14952 arguments to operators and functions have to be of the correct type,
14953 otherwise an error occurs. These checks prevent type mismatch
14954 errors from ever causing any run-time problems. For example,
14957 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14959 (@value{GDBP}) print obj.my_method (0)
14962 (@value{GDBP}) print obj.my_method (0x1234)
14963 Cannot resolve method klass::my_method to any overloaded instance
14966 The second example fails because in C@t{++} the integer constant
14967 @samp{0x1234} is not type-compatible with the pointer parameter type.
14969 For the expressions you use in @value{GDBN} commands, you can tell
14970 @value{GDBN} to not enforce strict type checking or
14971 to treat any mismatches as errors and abandon the expression;
14972 When type checking is disabled, @value{GDBN} successfully evaluates
14973 expressions like the second example above.
14975 Even if type checking is off, there may be other reasons
14976 related to type that prevent @value{GDBN} from evaluating an expression.
14977 For instance, @value{GDBN} does not know how to add an @code{int} and
14978 a @code{struct foo}. These particular type errors have nothing to do
14979 with the language in use and usually arise from expressions which make
14980 little sense to evaluate anyway.
14982 @value{GDBN} provides some additional commands for controlling type checking:
14984 @kindex set check type
14985 @kindex show check type
14987 @item set check type on
14988 @itemx set check type off
14989 Set strict type checking on or off. If any type mismatches occur in
14990 evaluating an expression while type checking is on, @value{GDBN} prints a
14991 message and aborts evaluation of the expression.
14993 @item show check type
14994 Show the current setting of type checking and whether @value{GDBN}
14995 is enforcing strict type checking rules.
14998 @cindex range checking
14999 @cindex checks, range
15000 @node Range Checking
15001 @subsection An Overview of Range Checking
15003 In some languages (such as Modula-2), it is an error to exceed the
15004 bounds of a type; this is enforced with run-time checks. Such range
15005 checking is meant to ensure program correctness by making sure
15006 computations do not overflow, or indices on an array element access do
15007 not exceed the bounds of the array.
15009 For expressions you use in @value{GDBN} commands, you can tell
15010 @value{GDBN} to treat range errors in one of three ways: ignore them,
15011 always treat them as errors and abandon the expression, or issue
15012 warnings but evaluate the expression anyway.
15014 A range error can result from numerical overflow, from exceeding an
15015 array index bound, or when you type a constant that is not a member
15016 of any type. Some languages, however, do not treat overflows as an
15017 error. In many implementations of C, mathematical overflow causes the
15018 result to ``wrap around'' to lower values---for example, if @var{m} is
15019 the largest integer value, and @var{s} is the smallest, then
15022 @var{m} + 1 @result{} @var{s}
15025 This, too, is specific to individual languages, and in some cases
15026 specific to individual compilers or machines. @xref{Supported Languages, ,
15027 Supported Languages}, for further details on specific languages.
15029 @value{GDBN} provides some additional commands for controlling the range checker:
15031 @kindex set check range
15032 @kindex show check range
15034 @item set check range auto
15035 Set range checking on or off based on the current working language.
15036 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15039 @item set check range on
15040 @itemx set check range off
15041 Set range checking on or off, overriding the default setting for the
15042 current working language. A warning is issued if the setting does not
15043 match the language default. If a range error occurs and range checking is on,
15044 then a message is printed and evaluation of the expression is aborted.
15046 @item set check range warn
15047 Output messages when the @value{GDBN} range checker detects a range error,
15048 but attempt to evaluate the expression anyway. Evaluating the
15049 expression may still be impossible for other reasons, such as accessing
15050 memory that the process does not own (a typical example from many Unix
15054 Show the current setting of the range checker, and whether or not it is
15055 being set automatically by @value{GDBN}.
15058 @node Supported Languages
15059 @section Supported Languages
15061 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15062 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15063 @c This is false ...
15064 Some @value{GDBN} features may be used in expressions regardless of the
15065 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15066 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15067 ,Expressions}) can be used with the constructs of any supported
15070 The following sections detail to what degree each source language is
15071 supported by @value{GDBN}. These sections are not meant to be language
15072 tutorials or references, but serve only as a reference guide to what the
15073 @value{GDBN} expression parser accepts, and what input and output
15074 formats should look like for different languages. There are many good
15075 books written on each of these languages; please look to these for a
15076 language reference or tutorial.
15079 * C:: C and C@t{++}
15082 * Objective-C:: Objective-C
15083 * OpenCL C:: OpenCL C
15084 * Fortran:: Fortran
15087 * Modula-2:: Modula-2
15092 @subsection C and C@t{++}
15094 @cindex C and C@t{++}
15095 @cindex expressions in C or C@t{++}
15097 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15098 to both languages. Whenever this is the case, we discuss those languages
15102 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15103 @cindex @sc{gnu} C@t{++}
15104 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15105 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15106 effectively, you must compile your C@t{++} programs with a supported
15107 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15108 compiler (@code{aCC}).
15111 * C Operators:: C and C@t{++} operators
15112 * C Constants:: C and C@t{++} constants
15113 * C Plus Plus Expressions:: C@t{++} expressions
15114 * C Defaults:: Default settings for C and C@t{++}
15115 * C Checks:: C and C@t{++} type and range checks
15116 * Debugging C:: @value{GDBN} and C
15117 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15118 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15122 @subsubsection C and C@t{++} Operators
15124 @cindex C and C@t{++} operators
15126 Operators must be defined on values of specific types. For instance,
15127 @code{+} is defined on numbers, but not on structures. Operators are
15128 often defined on groups of types.
15130 For the purposes of C and C@t{++}, the following definitions hold:
15135 @emph{Integral types} include @code{int} with any of its storage-class
15136 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15139 @emph{Floating-point types} include @code{float}, @code{double}, and
15140 @code{long double} (if supported by the target platform).
15143 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15146 @emph{Scalar types} include all of the above.
15151 The following operators are supported. They are listed here
15152 in order of increasing precedence:
15156 The comma or sequencing operator. Expressions in a comma-separated list
15157 are evaluated from left to right, with the result of the entire
15158 expression being the last expression evaluated.
15161 Assignment. The value of an assignment expression is the value
15162 assigned. Defined on scalar types.
15165 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15166 and translated to @w{@code{@var{a} = @var{a op b}}}.
15167 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15168 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15169 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15172 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15173 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15174 should be of an integral type.
15177 Logical @sc{or}. Defined on integral types.
15180 Logical @sc{and}. Defined on integral types.
15183 Bitwise @sc{or}. Defined on integral types.
15186 Bitwise exclusive-@sc{or}. Defined on integral types.
15189 Bitwise @sc{and}. Defined on integral types.
15192 Equality and inequality. Defined on scalar types. The value of these
15193 expressions is 0 for false and non-zero for true.
15195 @item <@r{, }>@r{, }<=@r{, }>=
15196 Less than, greater than, less than or equal, greater than or equal.
15197 Defined on scalar types. The value of these expressions is 0 for false
15198 and non-zero for true.
15201 left shift, and right shift. Defined on integral types.
15204 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15207 Addition and subtraction. Defined on integral types, floating-point types and
15210 @item *@r{, }/@r{, }%
15211 Multiplication, division, and modulus. Multiplication and division are
15212 defined on integral and floating-point types. Modulus is defined on
15216 Increment and decrement. When appearing before a variable, the
15217 operation is performed before the variable is used in an expression;
15218 when appearing after it, the variable's value is used before the
15219 operation takes place.
15222 Pointer dereferencing. Defined on pointer types. Same precedence as
15226 Address operator. Defined on variables. Same precedence as @code{++}.
15228 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15229 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15230 to examine the address
15231 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15235 Negative. Defined on integral and floating-point types. Same
15236 precedence as @code{++}.
15239 Logical negation. Defined on integral types. Same precedence as
15243 Bitwise complement operator. Defined on integral types. Same precedence as
15248 Structure member, and pointer-to-structure member. For convenience,
15249 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15250 pointer based on the stored type information.
15251 Defined on @code{struct} and @code{union} data.
15254 Dereferences of pointers to members.
15257 Array indexing. @code{@var{a}[@var{i}]} is defined as
15258 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15261 Function parameter list. Same precedence as @code{->}.
15264 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15265 and @code{class} types.
15268 Doubled colons also represent the @value{GDBN} scope operator
15269 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15273 If an operator is redefined in the user code, @value{GDBN} usually
15274 attempts to invoke the redefined version instead of using the operator's
15275 predefined meaning.
15278 @subsubsection C and C@t{++} Constants
15280 @cindex C and C@t{++} constants
15282 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15287 Integer constants are a sequence of digits. Octal constants are
15288 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15289 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15290 @samp{l}, specifying that the constant should be treated as a
15294 Floating point constants are a sequence of digits, followed by a decimal
15295 point, followed by a sequence of digits, and optionally followed by an
15296 exponent. An exponent is of the form:
15297 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15298 sequence of digits. The @samp{+} is optional for positive exponents.
15299 A floating-point constant may also end with a letter @samp{f} or
15300 @samp{F}, specifying that the constant should be treated as being of
15301 the @code{float} (as opposed to the default @code{double}) type; or with
15302 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15306 Enumerated constants consist of enumerated identifiers, or their
15307 integral equivalents.
15310 Character constants are a single character surrounded by single quotes
15311 (@code{'}), or a number---the ordinal value of the corresponding character
15312 (usually its @sc{ascii} value). Within quotes, the single character may
15313 be represented by a letter or by @dfn{escape sequences}, which are of
15314 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15315 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15316 @samp{@var{x}} is a predefined special character---for example,
15317 @samp{\n} for newline.
15319 Wide character constants can be written by prefixing a character
15320 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15321 form of @samp{x}. The target wide character set is used when
15322 computing the value of this constant (@pxref{Character Sets}).
15325 String constants are a sequence of character constants surrounded by
15326 double quotes (@code{"}). Any valid character constant (as described
15327 above) may appear. Double quotes within the string must be preceded by
15328 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15331 Wide string constants can be written by prefixing a string constant
15332 with @samp{L}, as in C. The target wide character set is used when
15333 computing the value of this constant (@pxref{Character Sets}).
15336 Pointer constants are an integral value. You can also write pointers
15337 to constants using the C operator @samp{&}.
15340 Array constants are comma-separated lists surrounded by braces @samp{@{}
15341 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15342 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15343 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15346 @node C Plus Plus Expressions
15347 @subsubsection C@t{++} Expressions
15349 @cindex expressions in C@t{++}
15350 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15352 @cindex debugging C@t{++} programs
15353 @cindex C@t{++} compilers
15354 @cindex debug formats and C@t{++}
15355 @cindex @value{NGCC} and C@t{++}
15357 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15358 the proper compiler and the proper debug format. Currently,
15359 @value{GDBN} works best when debugging C@t{++} code that is compiled
15360 with the most recent version of @value{NGCC} possible. The DWARF
15361 debugging format is preferred; @value{NGCC} defaults to this on most
15362 popular platforms. Other compilers and/or debug formats are likely to
15363 work badly or not at all when using @value{GDBN} to debug C@t{++}
15364 code. @xref{Compilation}.
15369 @cindex member functions
15371 Member function calls are allowed; you can use expressions like
15374 count = aml->GetOriginal(x, y)
15377 @vindex this@r{, inside C@t{++} member functions}
15378 @cindex namespace in C@t{++}
15380 While a member function is active (in the selected stack frame), your
15381 expressions have the same namespace available as the member function;
15382 that is, @value{GDBN} allows implicit references to the class instance
15383 pointer @code{this} following the same rules as C@t{++}. @code{using}
15384 declarations in the current scope are also respected by @value{GDBN}.
15386 @cindex call overloaded functions
15387 @cindex overloaded functions, calling
15388 @cindex type conversions in C@t{++}
15390 You can call overloaded functions; @value{GDBN} resolves the function
15391 call to the right definition, with some restrictions. @value{GDBN} does not
15392 perform overload resolution involving user-defined type conversions,
15393 calls to constructors, or instantiations of templates that do not exist
15394 in the program. It also cannot handle ellipsis argument lists or
15397 It does perform integral conversions and promotions, floating-point
15398 promotions, arithmetic conversions, pointer conversions, conversions of
15399 class objects to base classes, and standard conversions such as those of
15400 functions or arrays to pointers; it requires an exact match on the
15401 number of function arguments.
15403 Overload resolution is always performed, unless you have specified
15404 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15405 ,@value{GDBN} Features for C@t{++}}.
15407 You must specify @code{set overload-resolution off} in order to use an
15408 explicit function signature to call an overloaded function, as in
15410 p 'foo(char,int)'('x', 13)
15413 The @value{GDBN} command-completion facility can simplify this;
15414 see @ref{Completion, ,Command Completion}.
15416 @cindex reference declarations
15418 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15419 references; you can use them in expressions just as you do in C@t{++}
15420 source---they are automatically dereferenced.
15422 In the parameter list shown when @value{GDBN} displays a frame, the values of
15423 reference variables are not displayed (unlike other variables); this
15424 avoids clutter, since references are often used for large structures.
15425 The @emph{address} of a reference variable is always shown, unless
15426 you have specified @samp{set print address off}.
15429 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15430 expressions can use it just as expressions in your program do. Since
15431 one scope may be defined in another, you can use @code{::} repeatedly if
15432 necessary, for example in an expression like
15433 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15434 resolving name scope by reference to source files, in both C and C@t{++}
15435 debugging (@pxref{Variables, ,Program Variables}).
15438 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15443 @subsubsection C and C@t{++} Defaults
15445 @cindex C and C@t{++} defaults
15447 If you allow @value{GDBN} to set range checking automatically, it
15448 defaults to @code{off} whenever the working language changes to
15449 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15450 selects the working language.
15452 If you allow @value{GDBN} to set the language automatically, it
15453 recognizes source files whose names end with @file{.c}, @file{.C}, or
15454 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15455 these files, it sets the working language to C or C@t{++}.
15456 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15457 for further details.
15460 @subsubsection C and C@t{++} Type and Range Checks
15462 @cindex C and C@t{++} checks
15464 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15465 checking is used. However, if you turn type checking off, @value{GDBN}
15466 will allow certain non-standard conversions, such as promoting integer
15467 constants to pointers.
15469 Range checking, if turned on, is done on mathematical operations. Array
15470 indices are not checked, since they are often used to index a pointer
15471 that is not itself an array.
15474 @subsubsection @value{GDBN} and C
15476 The @code{set print union} and @code{show print union} commands apply to
15477 the @code{union} type. When set to @samp{on}, any @code{union} that is
15478 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15479 appears as @samp{@{...@}}.
15481 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15482 with pointers and a memory allocation function. @xref{Expressions,
15485 @node Debugging C Plus Plus
15486 @subsubsection @value{GDBN} Features for C@t{++}
15488 @cindex commands for C@t{++}
15490 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15491 designed specifically for use with C@t{++}. Here is a summary:
15494 @cindex break in overloaded functions
15495 @item @r{breakpoint menus}
15496 When you want a breakpoint in a function whose name is overloaded,
15497 @value{GDBN} has the capability to display a menu of possible breakpoint
15498 locations to help you specify which function definition you want.
15499 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15501 @cindex overloading in C@t{++}
15502 @item rbreak @var{regex}
15503 Setting breakpoints using regular expressions is helpful for setting
15504 breakpoints on overloaded functions that are not members of any special
15506 @xref{Set Breaks, ,Setting Breakpoints}.
15508 @cindex C@t{++} exception handling
15510 @itemx catch rethrow
15512 Debug C@t{++} exception handling using these commands. @xref{Set
15513 Catchpoints, , Setting Catchpoints}.
15515 @cindex inheritance
15516 @item ptype @var{typename}
15517 Print inheritance relationships as well as other information for type
15519 @xref{Symbols, ,Examining the Symbol Table}.
15521 @item info vtbl @var{expression}.
15522 The @code{info vtbl} command can be used to display the virtual
15523 method tables of the object computed by @var{expression}. This shows
15524 one entry per virtual table; there may be multiple virtual tables when
15525 multiple inheritance is in use.
15527 @cindex C@t{++} demangling
15528 @item demangle @var{name}
15529 Demangle @var{name}.
15530 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15532 @cindex C@t{++} symbol display
15533 @item set print demangle
15534 @itemx show print demangle
15535 @itemx set print asm-demangle
15536 @itemx show print asm-demangle
15537 Control whether C@t{++} symbols display in their source form, both when
15538 displaying code as C@t{++} source and when displaying disassemblies.
15539 @xref{Print Settings, ,Print Settings}.
15541 @item set print object
15542 @itemx show print object
15543 Choose whether to print derived (actual) or declared types of objects.
15544 @xref{Print Settings, ,Print Settings}.
15546 @item set print vtbl
15547 @itemx show print vtbl
15548 Control the format for printing virtual function tables.
15549 @xref{Print Settings, ,Print Settings}.
15550 (The @code{vtbl} commands do not work on programs compiled with the HP
15551 ANSI C@t{++} compiler (@code{aCC}).)
15553 @kindex set overload-resolution
15554 @cindex overloaded functions, overload resolution
15555 @item set overload-resolution on
15556 Enable overload resolution for C@t{++} expression evaluation. The default
15557 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15558 and searches for a function whose signature matches the argument types,
15559 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15560 Expressions, ,C@t{++} Expressions}, for details).
15561 If it cannot find a match, it emits a message.
15563 @item set overload-resolution off
15564 Disable overload resolution for C@t{++} expression evaluation. For
15565 overloaded functions that are not class member functions, @value{GDBN}
15566 chooses the first function of the specified name that it finds in the
15567 symbol table, whether or not its arguments are of the correct type. For
15568 overloaded functions that are class member functions, @value{GDBN}
15569 searches for a function whose signature @emph{exactly} matches the
15572 @kindex show overload-resolution
15573 @item show overload-resolution
15574 Show the current setting of overload resolution.
15576 @item @r{Overloaded symbol names}
15577 You can specify a particular definition of an overloaded symbol, using
15578 the same notation that is used to declare such symbols in C@t{++}: type
15579 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15580 also use the @value{GDBN} command-line word completion facilities to list the
15581 available choices, or to finish the type list for you.
15582 @xref{Completion,, Command Completion}, for details on how to do this.
15584 @item @r{Breakpoints in functions with ABI tags}
15586 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15587 correspond to changes in the ABI of a type, function, or variable that
15588 would not otherwise be reflected in a mangled name. See
15589 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15592 The ABI tags are visible in C@t{++} demangled names. For example, a
15593 function that returns a std::string:
15596 std::string function(int);
15600 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15601 tag, and @value{GDBN} displays the symbol like this:
15604 function[abi:cxx11](int)
15607 You can set a breakpoint on such functions simply as if they had no
15611 (gdb) b function(int)
15612 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15613 (gdb) info breakpoints
15614 Num Type Disp Enb Address What
15615 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15619 On the rare occasion you need to disambiguate between different ABI
15620 tags, you can do so by simply including the ABI tag in the function
15624 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15628 @node Decimal Floating Point
15629 @subsubsection Decimal Floating Point format
15630 @cindex decimal floating point format
15632 @value{GDBN} can examine, set and perform computations with numbers in
15633 decimal floating point format, which in the C language correspond to the
15634 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15635 specified by the extension to support decimal floating-point arithmetic.
15637 There are two encodings in use, depending on the architecture: BID (Binary
15638 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15639 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15642 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15643 to manipulate decimal floating point numbers, it is not possible to convert
15644 (using a cast, for example) integers wider than 32-bit to decimal float.
15646 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15647 point computations, error checking in decimal float operations ignores
15648 underflow, overflow and divide by zero exceptions.
15650 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15651 to inspect @code{_Decimal128} values stored in floating point registers.
15652 See @ref{PowerPC,,PowerPC} for more details.
15658 @value{GDBN} can be used to debug programs written in D and compiled with
15659 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15660 specific feature --- dynamic arrays.
15665 @cindex Go (programming language)
15666 @value{GDBN} can be used to debug programs written in Go and compiled with
15667 @file{gccgo} or @file{6g} compilers.
15669 Here is a summary of the Go-specific features and restrictions:
15672 @cindex current Go package
15673 @item The current Go package
15674 The name of the current package does not need to be specified when
15675 specifying global variables and functions.
15677 For example, given the program:
15681 var myglob = "Shall we?"
15687 When stopped inside @code{main} either of these work:
15691 (gdb) p main.myglob
15694 @cindex builtin Go types
15695 @item Builtin Go types
15696 The @code{string} type is recognized by @value{GDBN} and is printed
15699 @cindex builtin Go functions
15700 @item Builtin Go functions
15701 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15702 function and handles it internally.
15704 @cindex restrictions on Go expressions
15705 @item Restrictions on Go expressions
15706 All Go operators are supported except @code{&^}.
15707 The Go @code{_} ``blank identifier'' is not supported.
15708 Automatic dereferencing of pointers is not supported.
15712 @subsection Objective-C
15714 @cindex Objective-C
15715 This section provides information about some commands and command
15716 options that are useful for debugging Objective-C code. See also
15717 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15718 few more commands specific to Objective-C support.
15721 * Method Names in Commands::
15722 * The Print Command with Objective-C::
15725 @node Method Names in Commands
15726 @subsubsection Method Names in Commands
15728 The following commands have been extended to accept Objective-C method
15729 names as line specifications:
15731 @kindex clear@r{, and Objective-C}
15732 @kindex break@r{, and Objective-C}
15733 @kindex info line@r{, and Objective-C}
15734 @kindex jump@r{, and Objective-C}
15735 @kindex list@r{, and Objective-C}
15739 @item @code{info line}
15744 A fully qualified Objective-C method name is specified as
15747 -[@var{Class} @var{methodName}]
15750 where the minus sign is used to indicate an instance method and a
15751 plus sign (not shown) is used to indicate a class method. The class
15752 name @var{Class} and method name @var{methodName} are enclosed in
15753 brackets, similar to the way messages are specified in Objective-C
15754 source code. For example, to set a breakpoint at the @code{create}
15755 instance method of class @code{Fruit} in the program currently being
15759 break -[Fruit create]
15762 To list ten program lines around the @code{initialize} class method,
15766 list +[NSText initialize]
15769 In the current version of @value{GDBN}, the plus or minus sign is
15770 required. In future versions of @value{GDBN}, the plus or minus
15771 sign will be optional, but you can use it to narrow the search. It
15772 is also possible to specify just a method name:
15778 You must specify the complete method name, including any colons. If
15779 your program's source files contain more than one @code{create} method,
15780 you'll be presented with a numbered list of classes that implement that
15781 method. Indicate your choice by number, or type @samp{0} to exit if
15784 As another example, to clear a breakpoint established at the
15785 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15788 clear -[NSWindow makeKeyAndOrderFront:]
15791 @node The Print Command with Objective-C
15792 @subsubsection The Print Command With Objective-C
15793 @cindex Objective-C, print objects
15794 @kindex print-object
15795 @kindex po @r{(@code{print-object})}
15797 The print command has also been extended to accept methods. For example:
15800 print -[@var{object} hash]
15803 @cindex print an Objective-C object description
15804 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15806 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15807 and print the result. Also, an additional command has been added,
15808 @code{print-object} or @code{po} for short, which is meant to print
15809 the description of an object. However, this command may only work
15810 with certain Objective-C libraries that have a particular hook
15811 function, @code{_NSPrintForDebugger}, defined.
15814 @subsection OpenCL C
15817 This section provides information about @value{GDBN}s OpenCL C support.
15820 * OpenCL C Datatypes::
15821 * OpenCL C Expressions::
15822 * OpenCL C Operators::
15825 @node OpenCL C Datatypes
15826 @subsubsection OpenCL C Datatypes
15828 @cindex OpenCL C Datatypes
15829 @value{GDBN} supports the builtin scalar and vector datatypes specified
15830 by OpenCL 1.1. In addition the half- and double-precision floating point
15831 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15832 extensions are also known to @value{GDBN}.
15834 @node OpenCL C Expressions
15835 @subsubsection OpenCL C Expressions
15837 @cindex OpenCL C Expressions
15838 @value{GDBN} supports accesses to vector components including the access as
15839 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15840 supported by @value{GDBN} can be used as well.
15842 @node OpenCL C Operators
15843 @subsubsection OpenCL C Operators
15845 @cindex OpenCL C Operators
15846 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15850 @subsection Fortran
15851 @cindex Fortran-specific support in @value{GDBN}
15853 @value{GDBN} can be used to debug programs written in Fortran, but it
15854 currently supports only the features of Fortran 77 language.
15856 @cindex trailing underscore, in Fortran symbols
15857 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15858 among them) append an underscore to the names of variables and
15859 functions. When you debug programs compiled by those compilers, you
15860 will need to refer to variables and functions with a trailing
15864 * Fortran Operators:: Fortran operators and expressions
15865 * Fortran Defaults:: Default settings for Fortran
15866 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15869 @node Fortran Operators
15870 @subsubsection Fortran Operators and Expressions
15872 @cindex Fortran operators and expressions
15874 Operators must be defined on values of specific types. For instance,
15875 @code{+} is defined on numbers, but not on characters or other non-
15876 arithmetic types. Operators are often defined on groups of types.
15880 The exponentiation operator. It raises the first operand to the power
15884 The range operator. Normally used in the form of array(low:high) to
15885 represent a section of array.
15888 The access component operator. Normally used to access elements in derived
15889 types. Also suitable for unions. As unions aren't part of regular Fortran,
15890 this can only happen when accessing a register that uses a gdbarch-defined
15894 @node Fortran Defaults
15895 @subsubsection Fortran Defaults
15897 @cindex Fortran Defaults
15899 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15900 default uses case-insensitive matches for Fortran symbols. You can
15901 change that with the @samp{set case-insensitive} command, see
15902 @ref{Symbols}, for the details.
15904 @node Special Fortran Commands
15905 @subsubsection Special Fortran Commands
15907 @cindex Special Fortran commands
15909 @value{GDBN} has some commands to support Fortran-specific features,
15910 such as displaying common blocks.
15913 @cindex @code{COMMON} blocks, Fortran
15914 @kindex info common
15915 @item info common @r{[}@var{common-name}@r{]}
15916 This command prints the values contained in the Fortran @code{COMMON}
15917 block whose name is @var{common-name}. With no argument, the names of
15918 all @code{COMMON} blocks visible at the current program location are
15925 @cindex Pascal support in @value{GDBN}, limitations
15926 Debugging Pascal programs which use sets, subranges, file variables, or
15927 nested functions does not currently work. @value{GDBN} does not support
15928 entering expressions, printing values, or similar features using Pascal
15931 The Pascal-specific command @code{set print pascal_static-members}
15932 controls whether static members of Pascal objects are displayed.
15933 @xref{Print Settings, pascal_static-members}.
15938 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15939 Programming Language}. Type- and value-printing, and expression
15940 parsing, are reasonably complete. However, there are a few
15941 peculiarities and holes to be aware of.
15945 Linespecs (@pxref{Specify Location}) are never relative to the current
15946 crate. Instead, they act as if there were a global namespace of
15947 crates, somewhat similar to the way @code{extern crate} behaves.
15949 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15950 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15951 to set a breakpoint in a function named @samp{f} in a crate named
15954 As a consequence of this approach, linespecs also cannot refer to
15955 items using @samp{self::} or @samp{super::}.
15958 Because @value{GDBN} implements Rust name-lookup semantics in
15959 expressions, it will sometimes prepend the current crate to a name.
15960 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15961 @samp{K}, then @code{print ::x::y} will try to find the symbol
15964 However, since it is useful to be able to refer to other crates when
15965 debugging, @value{GDBN} provides the @code{extern} extension to
15966 circumvent this. To use the extension, just put @code{extern} before
15967 a path expression to refer to the otherwise unavailable ``global''
15970 In the above example, if you wanted to refer to the symbol @samp{y} in
15971 the crate @samp{x}, you would use @code{print extern x::y}.
15974 The Rust expression evaluator does not support ``statement-like''
15975 expressions such as @code{if} or @code{match}, or lambda expressions.
15978 Tuple expressions are not implemented.
15981 The Rust expression evaluator does not currently implement the
15982 @code{Drop} trait. Objects that may be created by the evaluator will
15983 never be destroyed.
15986 @value{GDBN} does not implement type inference for generics. In order
15987 to call generic functions or otherwise refer to generic items, you
15988 will have to specify the type parameters manually.
15991 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15992 cases this does not cause any problems. However, in an expression
15993 context, completing a generic function name will give syntactically
15994 invalid results. This happens because Rust requires the @samp{::}
15995 operator between the function name and its generic arguments. For
15996 example, @value{GDBN} might provide a completion like
15997 @code{crate::f<u32>}, where the parser would require
15998 @code{crate::f::<u32>}.
16001 As of this writing, the Rust compiler (version 1.8) has a few holes in
16002 the debugging information it generates. These holes prevent certain
16003 features from being implemented by @value{GDBN}:
16007 Method calls cannot be made via traits.
16010 Operator overloading is not implemented.
16013 When debugging in a monomorphized function, you cannot use the generic
16017 The type @code{Self} is not available.
16020 @code{use} statements are not available, so some names may not be
16021 available in the crate.
16026 @subsection Modula-2
16028 @cindex Modula-2, @value{GDBN} support
16030 The extensions made to @value{GDBN} to support Modula-2 only support
16031 output from the @sc{gnu} Modula-2 compiler (which is currently being
16032 developed). Other Modula-2 compilers are not currently supported, and
16033 attempting to debug executables produced by them is most likely
16034 to give an error as @value{GDBN} reads in the executable's symbol
16037 @cindex expressions in Modula-2
16039 * M2 Operators:: Built-in operators
16040 * Built-In Func/Proc:: Built-in functions and procedures
16041 * M2 Constants:: Modula-2 constants
16042 * M2 Types:: Modula-2 types
16043 * M2 Defaults:: Default settings for Modula-2
16044 * Deviations:: Deviations from standard Modula-2
16045 * M2 Checks:: Modula-2 type and range checks
16046 * M2 Scope:: The scope operators @code{::} and @code{.}
16047 * GDB/M2:: @value{GDBN} and Modula-2
16051 @subsubsection Operators
16052 @cindex Modula-2 operators
16054 Operators must be defined on values of specific types. For instance,
16055 @code{+} is defined on numbers, but not on structures. Operators are
16056 often defined on groups of types. For the purposes of Modula-2, the
16057 following definitions hold:
16062 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16066 @emph{Character types} consist of @code{CHAR} and its subranges.
16069 @emph{Floating-point types} consist of @code{REAL}.
16072 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16076 @emph{Scalar types} consist of all of the above.
16079 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16082 @emph{Boolean types} consist of @code{BOOLEAN}.
16086 The following operators are supported, and appear in order of
16087 increasing precedence:
16091 Function argument or array index separator.
16094 Assignment. The value of @var{var} @code{:=} @var{value} is
16098 Less than, greater than on integral, floating-point, or enumerated
16102 Less than or equal to, greater than or equal to
16103 on integral, floating-point and enumerated types, or set inclusion on
16104 set types. Same precedence as @code{<}.
16106 @item =@r{, }<>@r{, }#
16107 Equality and two ways of expressing inequality, valid on scalar types.
16108 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16109 available for inequality, since @code{#} conflicts with the script
16113 Set membership. Defined on set types and the types of their members.
16114 Same precedence as @code{<}.
16117 Boolean disjunction. Defined on boolean types.
16120 Boolean conjunction. Defined on boolean types.
16123 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16126 Addition and subtraction on integral and floating-point types, or union
16127 and difference on set types.
16130 Multiplication on integral and floating-point types, or set intersection
16134 Division on floating-point types, or symmetric set difference on set
16135 types. Same precedence as @code{*}.
16138 Integer division and remainder. Defined on integral types. Same
16139 precedence as @code{*}.
16142 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16145 Pointer dereferencing. Defined on pointer types.
16148 Boolean negation. Defined on boolean types. Same precedence as
16152 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16153 precedence as @code{^}.
16156 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16159 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16163 @value{GDBN} and Modula-2 scope operators.
16167 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16168 treats the use of the operator @code{IN}, or the use of operators
16169 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16170 @code{<=}, and @code{>=} on sets as an error.
16174 @node Built-In Func/Proc
16175 @subsubsection Built-in Functions and Procedures
16176 @cindex Modula-2 built-ins
16178 Modula-2 also makes available several built-in procedures and functions.
16179 In describing these, the following metavariables are used:
16184 represents an @code{ARRAY} variable.
16187 represents a @code{CHAR} constant or variable.
16190 represents a variable or constant of integral type.
16193 represents an identifier that belongs to a set. Generally used in the
16194 same function with the metavariable @var{s}. The type of @var{s} should
16195 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16198 represents a variable or constant of integral or floating-point type.
16201 represents a variable or constant of floating-point type.
16207 represents a variable.
16210 represents a variable or constant of one of many types. See the
16211 explanation of the function for details.
16214 All Modula-2 built-in procedures also return a result, described below.
16218 Returns the absolute value of @var{n}.
16221 If @var{c} is a lower case letter, it returns its upper case
16222 equivalent, otherwise it returns its argument.
16225 Returns the character whose ordinal value is @var{i}.
16228 Decrements the value in the variable @var{v} by one. Returns the new value.
16230 @item DEC(@var{v},@var{i})
16231 Decrements the value in the variable @var{v} by @var{i}. Returns the
16234 @item EXCL(@var{m},@var{s})
16235 Removes the element @var{m} from the set @var{s}. Returns the new
16238 @item FLOAT(@var{i})
16239 Returns the floating point equivalent of the integer @var{i}.
16241 @item HIGH(@var{a})
16242 Returns the index of the last member of @var{a}.
16245 Increments the value in the variable @var{v} by one. Returns the new value.
16247 @item INC(@var{v},@var{i})
16248 Increments the value in the variable @var{v} by @var{i}. Returns the
16251 @item INCL(@var{m},@var{s})
16252 Adds the element @var{m} to the set @var{s} if it is not already
16253 there. Returns the new set.
16256 Returns the maximum value of the type @var{t}.
16259 Returns the minimum value of the type @var{t}.
16262 Returns boolean TRUE if @var{i} is an odd number.
16265 Returns the ordinal value of its argument. For example, the ordinal
16266 value of a character is its @sc{ascii} value (on machines supporting
16267 the @sc{ascii} character set). The argument @var{x} must be of an
16268 ordered type, which include integral, character and enumerated types.
16270 @item SIZE(@var{x})
16271 Returns the size of its argument. The argument @var{x} can be a
16272 variable or a type.
16274 @item TRUNC(@var{r})
16275 Returns the integral part of @var{r}.
16277 @item TSIZE(@var{x})
16278 Returns the size of its argument. The argument @var{x} can be a
16279 variable or a type.
16281 @item VAL(@var{t},@var{i})
16282 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16286 @emph{Warning:} Sets and their operations are not yet supported, so
16287 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16291 @cindex Modula-2 constants
16293 @subsubsection Constants
16295 @value{GDBN} allows you to express the constants of Modula-2 in the following
16301 Integer constants are simply a sequence of digits. When used in an
16302 expression, a constant is interpreted to be type-compatible with the
16303 rest of the expression. Hexadecimal integers are specified by a
16304 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16307 Floating point constants appear as a sequence of digits, followed by a
16308 decimal point and another sequence of digits. An optional exponent can
16309 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16310 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16311 digits of the floating point constant must be valid decimal (base 10)
16315 Character constants consist of a single character enclosed by a pair of
16316 like quotes, either single (@code{'}) or double (@code{"}). They may
16317 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16318 followed by a @samp{C}.
16321 String constants consist of a sequence of characters enclosed by a
16322 pair of like quotes, either single (@code{'}) or double (@code{"}).
16323 Escape sequences in the style of C are also allowed. @xref{C
16324 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16328 Enumerated constants consist of an enumerated identifier.
16331 Boolean constants consist of the identifiers @code{TRUE} and
16335 Pointer constants consist of integral values only.
16338 Set constants are not yet supported.
16342 @subsubsection Modula-2 Types
16343 @cindex Modula-2 types
16345 Currently @value{GDBN} can print the following data types in Modula-2
16346 syntax: array types, record types, set types, pointer types, procedure
16347 types, enumerated types, subrange types and base types. You can also
16348 print the contents of variables declared using these type.
16349 This section gives a number of simple source code examples together with
16350 sample @value{GDBN} sessions.
16352 The first example contains the following section of code:
16361 and you can request @value{GDBN} to interrogate the type and value of
16362 @code{r} and @code{s}.
16365 (@value{GDBP}) print s
16367 (@value{GDBP}) ptype s
16369 (@value{GDBP}) print r
16371 (@value{GDBP}) ptype r
16376 Likewise if your source code declares @code{s} as:
16380 s: SET ['A'..'Z'] ;
16384 then you may query the type of @code{s} by:
16387 (@value{GDBP}) ptype s
16388 type = SET ['A'..'Z']
16392 Note that at present you cannot interactively manipulate set
16393 expressions using the debugger.
16395 The following example shows how you might declare an array in Modula-2
16396 and how you can interact with @value{GDBN} to print its type and contents:
16400 s: ARRAY [-10..10] OF CHAR ;
16404 (@value{GDBP}) ptype s
16405 ARRAY [-10..10] OF CHAR
16408 Note that the array handling is not yet complete and although the type
16409 is printed correctly, expression handling still assumes that all
16410 arrays have a lower bound of zero and not @code{-10} as in the example
16413 Here are some more type related Modula-2 examples:
16417 colour = (blue, red, yellow, green) ;
16418 t = [blue..yellow] ;
16426 The @value{GDBN} interaction shows how you can query the data type
16427 and value of a variable.
16430 (@value{GDBP}) print s
16432 (@value{GDBP}) ptype t
16433 type = [blue..yellow]
16437 In this example a Modula-2 array is declared and its contents
16438 displayed. Observe that the contents are written in the same way as
16439 their @code{C} counterparts.
16443 s: ARRAY [1..5] OF CARDINAL ;
16449 (@value{GDBP}) print s
16450 $1 = @{1, 0, 0, 0, 0@}
16451 (@value{GDBP}) ptype s
16452 type = ARRAY [1..5] OF CARDINAL
16455 The Modula-2 language interface to @value{GDBN} also understands
16456 pointer types as shown in this example:
16460 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16467 and you can request that @value{GDBN} describes the type of @code{s}.
16470 (@value{GDBP}) ptype s
16471 type = POINTER TO ARRAY [1..5] OF CARDINAL
16474 @value{GDBN} handles compound types as we can see in this example.
16475 Here we combine array types, record types, pointer types and subrange
16486 myarray = ARRAY myrange OF CARDINAL ;
16487 myrange = [-2..2] ;
16489 s: POINTER TO ARRAY myrange OF foo ;
16493 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16497 (@value{GDBP}) ptype s
16498 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16501 f3 : ARRAY [-2..2] OF CARDINAL;
16506 @subsubsection Modula-2 Defaults
16507 @cindex Modula-2 defaults
16509 If type and range checking are set automatically by @value{GDBN}, they
16510 both default to @code{on} whenever the working language changes to
16511 Modula-2. This happens regardless of whether you or @value{GDBN}
16512 selected the working language.
16514 If you allow @value{GDBN} to set the language automatically, then entering
16515 code compiled from a file whose name ends with @file{.mod} sets the
16516 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16517 Infer the Source Language}, for further details.
16520 @subsubsection Deviations from Standard Modula-2
16521 @cindex Modula-2, deviations from
16523 A few changes have been made to make Modula-2 programs easier to debug.
16524 This is done primarily via loosening its type strictness:
16528 Unlike in standard Modula-2, pointer constants can be formed by
16529 integers. This allows you to modify pointer variables during
16530 debugging. (In standard Modula-2, the actual address contained in a
16531 pointer variable is hidden from you; it can only be modified
16532 through direct assignment to another pointer variable or expression that
16533 returned a pointer.)
16536 C escape sequences can be used in strings and characters to represent
16537 non-printable characters. @value{GDBN} prints out strings with these
16538 escape sequences embedded. Single non-printable characters are
16539 printed using the @samp{CHR(@var{nnn})} format.
16542 The assignment operator (@code{:=}) returns the value of its right-hand
16546 All built-in procedures both modify @emph{and} return their argument.
16550 @subsubsection Modula-2 Type and Range Checks
16551 @cindex Modula-2 checks
16554 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16557 @c FIXME remove warning when type/range checks added
16559 @value{GDBN} considers two Modula-2 variables type equivalent if:
16563 They are of types that have been declared equivalent via a @code{TYPE
16564 @var{t1} = @var{t2}} statement
16567 They have been declared on the same line. (Note: This is true of the
16568 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16571 As long as type checking is enabled, any attempt to combine variables
16572 whose types are not equivalent is an error.
16574 Range checking is done on all mathematical operations, assignment, array
16575 index bounds, and all built-in functions and procedures.
16578 @subsubsection The Scope Operators @code{::} and @code{.}
16580 @cindex @code{.}, Modula-2 scope operator
16581 @cindex colon, doubled as scope operator
16583 @vindex colon-colon@r{, in Modula-2}
16584 @c Info cannot handle :: but TeX can.
16587 @vindex ::@r{, in Modula-2}
16590 There are a few subtle differences between the Modula-2 scope operator
16591 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16596 @var{module} . @var{id}
16597 @var{scope} :: @var{id}
16601 where @var{scope} is the name of a module or a procedure,
16602 @var{module} the name of a module, and @var{id} is any declared
16603 identifier within your program, except another module.
16605 Using the @code{::} operator makes @value{GDBN} search the scope
16606 specified by @var{scope} for the identifier @var{id}. If it is not
16607 found in the specified scope, then @value{GDBN} searches all scopes
16608 enclosing the one specified by @var{scope}.
16610 Using the @code{.} operator makes @value{GDBN} search the current scope for
16611 the identifier specified by @var{id} that was imported from the
16612 definition module specified by @var{module}. With this operator, it is
16613 an error if the identifier @var{id} was not imported from definition
16614 module @var{module}, or if @var{id} is not an identifier in
16618 @subsubsection @value{GDBN} and Modula-2
16620 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16621 Five subcommands of @code{set print} and @code{show print} apply
16622 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16623 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16624 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16625 analogue in Modula-2.
16627 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16628 with any language, is not useful with Modula-2. Its
16629 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16630 created in Modula-2 as they can in C or C@t{++}. However, because an
16631 address can be specified by an integral constant, the construct
16632 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16634 @cindex @code{#} in Modula-2
16635 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16636 interpreted as the beginning of a comment. Use @code{<>} instead.
16642 The extensions made to @value{GDBN} for Ada only support
16643 output from the @sc{gnu} Ada (GNAT) compiler.
16644 Other Ada compilers are not currently supported, and
16645 attempting to debug executables produced by them is most likely
16649 @cindex expressions in Ada
16651 * Ada Mode Intro:: General remarks on the Ada syntax
16652 and semantics supported by Ada mode
16654 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16655 * Additions to Ada:: Extensions of the Ada expression syntax.
16656 * Overloading support for Ada:: Support for expressions involving overloaded
16658 * Stopping Before Main Program:: Debugging the program during elaboration.
16659 * Ada Exceptions:: Ada Exceptions
16660 * Ada Tasks:: Listing and setting breakpoints in tasks.
16661 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16662 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16664 * Ada Settings:: New settable GDB parameters for Ada.
16665 * Ada Glitches:: Known peculiarities of Ada mode.
16668 @node Ada Mode Intro
16669 @subsubsection Introduction
16670 @cindex Ada mode, general
16672 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16673 syntax, with some extensions.
16674 The philosophy behind the design of this subset is
16678 That @value{GDBN} should provide basic literals and access to operations for
16679 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16680 leaving more sophisticated computations to subprograms written into the
16681 program (which therefore may be called from @value{GDBN}).
16684 That type safety and strict adherence to Ada language restrictions
16685 are not particularly important to the @value{GDBN} user.
16688 That brevity is important to the @value{GDBN} user.
16691 Thus, for brevity, the debugger acts as if all names declared in
16692 user-written packages are directly visible, even if they are not visible
16693 according to Ada rules, thus making it unnecessary to fully qualify most
16694 names with their packages, regardless of context. Where this causes
16695 ambiguity, @value{GDBN} asks the user's intent.
16697 The debugger will start in Ada mode if it detects an Ada main program.
16698 As for other languages, it will enter Ada mode when stopped in a program that
16699 was translated from an Ada source file.
16701 While in Ada mode, you may use `@t{--}' for comments. This is useful
16702 mostly for documenting command files. The standard @value{GDBN} comment
16703 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16704 middle (to allow based literals).
16706 @node Omissions from Ada
16707 @subsubsection Omissions from Ada
16708 @cindex Ada, omissions from
16710 Here are the notable omissions from the subset:
16714 Only a subset of the attributes are supported:
16718 @t{'First}, @t{'Last}, and @t{'Length}
16719 on array objects (not on types and subtypes).
16722 @t{'Min} and @t{'Max}.
16725 @t{'Pos} and @t{'Val}.
16731 @t{'Range} on array objects (not subtypes), but only as the right
16732 operand of the membership (@code{in}) operator.
16735 @t{'Access}, @t{'Unchecked_Access}, and
16736 @t{'Unrestricted_Access} (a GNAT extension).
16744 @code{Characters.Latin_1} are not available and
16745 concatenation is not implemented. Thus, escape characters in strings are
16746 not currently available.
16749 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16750 equality of representations. They will generally work correctly
16751 for strings and arrays whose elements have integer or enumeration types.
16752 They may not work correctly for arrays whose element
16753 types have user-defined equality, for arrays of real values
16754 (in particular, IEEE-conformant floating point, because of negative
16755 zeroes and NaNs), and for arrays whose elements contain unused bits with
16756 indeterminate values.
16759 The other component-by-component array operations (@code{and}, @code{or},
16760 @code{xor}, @code{not}, and relational tests other than equality)
16761 are not implemented.
16764 @cindex array aggregates (Ada)
16765 @cindex record aggregates (Ada)
16766 @cindex aggregates (Ada)
16767 There is limited support for array and record aggregates. They are
16768 permitted only on the right sides of assignments, as in these examples:
16771 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16772 (@value{GDBP}) set An_Array := (1, others => 0)
16773 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16774 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16775 (@value{GDBP}) set A_Record := (1, "Peter", True);
16776 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16780 discriminant's value by assigning an aggregate has an
16781 undefined effect if that discriminant is used within the record.
16782 However, you can first modify discriminants by directly assigning to
16783 them (which normally would not be allowed in Ada), and then performing an
16784 aggregate assignment. For example, given a variable @code{A_Rec}
16785 declared to have a type such as:
16788 type Rec (Len : Small_Integer := 0) is record
16790 Vals : IntArray (1 .. Len);
16794 you can assign a value with a different size of @code{Vals} with two
16798 (@value{GDBP}) set A_Rec.Len := 4
16799 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16802 As this example also illustrates, @value{GDBN} is very loose about the usual
16803 rules concerning aggregates. You may leave out some of the
16804 components of an array or record aggregate (such as the @code{Len}
16805 component in the assignment to @code{A_Rec} above); they will retain their
16806 original values upon assignment. You may freely use dynamic values as
16807 indices in component associations. You may even use overlapping or
16808 redundant component associations, although which component values are
16809 assigned in such cases is not defined.
16812 Calls to dispatching subprograms are not implemented.
16815 The overloading algorithm is much more limited (i.e., less selective)
16816 than that of real Ada. It makes only limited use of the context in
16817 which a subexpression appears to resolve its meaning, and it is much
16818 looser in its rules for allowing type matches. As a result, some
16819 function calls will be ambiguous, and the user will be asked to choose
16820 the proper resolution.
16823 The @code{new} operator is not implemented.
16826 Entry calls are not implemented.
16829 Aside from printing, arithmetic operations on the native VAX floating-point
16830 formats are not supported.
16833 It is not possible to slice a packed array.
16836 The names @code{True} and @code{False}, when not part of a qualified name,
16837 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16839 Should your program
16840 redefine these names in a package or procedure (at best a dubious practice),
16841 you will have to use fully qualified names to access their new definitions.
16844 @node Additions to Ada
16845 @subsubsection Additions to Ada
16846 @cindex Ada, deviations from
16848 As it does for other languages, @value{GDBN} makes certain generic
16849 extensions to Ada (@pxref{Expressions}):
16853 If the expression @var{E} is a variable residing in memory (typically
16854 a local variable or array element) and @var{N} is a positive integer,
16855 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16856 @var{N}-1 adjacent variables following it in memory as an array. In
16857 Ada, this operator is generally not necessary, since its prime use is
16858 in displaying parts of an array, and slicing will usually do this in
16859 Ada. However, there are occasional uses when debugging programs in
16860 which certain debugging information has been optimized away.
16863 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16864 appears in function or file @var{B}.'' When @var{B} is a file name,
16865 you must typically surround it in single quotes.
16868 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16869 @var{type} that appears at address @var{addr}.''
16872 A name starting with @samp{$} is a convenience variable
16873 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16876 In addition, @value{GDBN} provides a few other shortcuts and outright
16877 additions specific to Ada:
16881 The assignment statement is allowed as an expression, returning
16882 its right-hand operand as its value. Thus, you may enter
16885 (@value{GDBP}) set x := y + 3
16886 (@value{GDBP}) print A(tmp := y + 1)
16890 The semicolon is allowed as an ``operator,'' returning as its value
16891 the value of its right-hand operand.
16892 This allows, for example,
16893 complex conditional breaks:
16896 (@value{GDBP}) break f
16897 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16901 Rather than use catenation and symbolic character names to introduce special
16902 characters into strings, one may instead use a special bracket notation,
16903 which is also used to print strings. A sequence of characters of the form
16904 @samp{["@var{XX}"]} within a string or character literal denotes the
16905 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16906 sequence of characters @samp{["""]} also denotes a single quotation mark
16907 in strings. For example,
16909 "One line.["0a"]Next line.["0a"]"
16912 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16916 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16917 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16921 (@value{GDBP}) print 'max(x, y)
16925 When printing arrays, @value{GDBN} uses positional notation when the
16926 array has a lower bound of 1, and uses a modified named notation otherwise.
16927 For example, a one-dimensional array of three integers with a lower bound
16928 of 3 might print as
16935 That is, in contrast to valid Ada, only the first component has a @code{=>}
16939 You may abbreviate attributes in expressions with any unique,
16940 multi-character subsequence of
16941 their names (an exact match gets preference).
16942 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16943 in place of @t{a'length}.
16946 @cindex quoting Ada internal identifiers
16947 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16948 to lower case. The GNAT compiler uses upper-case characters for
16949 some of its internal identifiers, which are normally of no interest to users.
16950 For the rare occasions when you actually have to look at them,
16951 enclose them in angle brackets to avoid the lower-case mapping.
16954 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16958 Printing an object of class-wide type or dereferencing an
16959 access-to-class-wide value will display all the components of the object's
16960 specific type (as indicated by its run-time tag). Likewise, component
16961 selection on such a value will operate on the specific type of the
16966 @node Overloading support for Ada
16967 @subsubsection Overloading support for Ada
16968 @cindex overloading, Ada
16970 The debugger supports limited overloading. Given a subprogram call in which
16971 the function symbol has multiple definitions, it will use the number of
16972 actual parameters and some information about their types to attempt to narrow
16973 the set of definitions. It also makes very limited use of context, preferring
16974 procedures to functions in the context of the @code{call} command, and
16975 functions to procedures elsewhere.
16977 If, after narrowing, the set of matching definitions still contains more than
16978 one definition, @value{GDBN} will display a menu to query which one it should
16982 (@value{GDBP}) print f(1)
16983 Multiple matches for f
16985 [1] foo.f (integer) return boolean at foo.adb:23
16986 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16990 In this case, just select one menu entry either to cancel expression evaluation
16991 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16992 instance (type the corresponding number and press @key{RET}).
16994 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16999 @kindex set ada print-signatures
17000 @item set ada print-signatures
17001 Control whether parameter types and return types are displayed in overloads
17002 selection menus. It is @code{on} by default.
17003 @xref{Overloading support for Ada}.
17005 @kindex show ada print-signatures
17006 @item show ada print-signatures
17007 Show the current setting for displaying parameter types and return types in
17008 overloads selection menu.
17009 @xref{Overloading support for Ada}.
17013 @node Stopping Before Main Program
17014 @subsubsection Stopping at the Very Beginning
17016 @cindex breakpointing Ada elaboration code
17017 It is sometimes necessary to debug the program during elaboration, and
17018 before reaching the main procedure.
17019 As defined in the Ada Reference
17020 Manual, the elaboration code is invoked from a procedure called
17021 @code{adainit}. To run your program up to the beginning of
17022 elaboration, simply use the following two commands:
17023 @code{tbreak adainit} and @code{run}.
17025 @node Ada Exceptions
17026 @subsubsection Ada Exceptions
17028 A command is provided to list all Ada exceptions:
17031 @kindex info exceptions
17032 @item info exceptions
17033 @itemx info exceptions @var{regexp}
17034 The @code{info exceptions} command allows you to list all Ada exceptions
17035 defined within the program being debugged, as well as their addresses.
17036 With a regular expression, @var{regexp}, as argument, only those exceptions
17037 whose names match @var{regexp} are listed.
17040 Below is a small example, showing how the command can be used, first
17041 without argument, and next with a regular expression passed as an
17045 (@value{GDBP}) info exceptions
17046 All defined Ada exceptions:
17047 constraint_error: 0x613da0
17048 program_error: 0x613d20
17049 storage_error: 0x613ce0
17050 tasking_error: 0x613ca0
17051 const.aint_global_e: 0x613b00
17052 (@value{GDBP}) info exceptions const.aint
17053 All Ada exceptions matching regular expression "const.aint":
17054 constraint_error: 0x613da0
17055 const.aint_global_e: 0x613b00
17058 It is also possible to ask @value{GDBN} to stop your program's execution
17059 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17062 @subsubsection Extensions for Ada Tasks
17063 @cindex Ada, tasking
17065 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17066 @value{GDBN} provides the following task-related commands:
17071 This command shows a list of current Ada tasks, as in the following example:
17078 (@value{GDBP}) info tasks
17079 ID TID P-ID Pri State Name
17080 1 8088000 0 15 Child Activation Wait main_task
17081 2 80a4000 1 15 Accept Statement b
17082 3 809a800 1 15 Child Activation Wait a
17083 * 4 80ae800 3 15 Runnable c
17088 In this listing, the asterisk before the last task indicates it to be the
17089 task currently being inspected.
17093 Represents @value{GDBN}'s internal task number.
17099 The parent's task ID (@value{GDBN}'s internal task number).
17102 The base priority of the task.
17105 Current state of the task.
17109 The task has been created but has not been activated. It cannot be
17113 The task is not blocked for any reason known to Ada. (It may be waiting
17114 for a mutex, though.) It is conceptually "executing" in normal mode.
17117 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17118 that were waiting on terminate alternatives have been awakened and have
17119 terminated themselves.
17121 @item Child Activation Wait
17122 The task is waiting for created tasks to complete activation.
17124 @item Accept Statement
17125 The task is waiting on an accept or selective wait statement.
17127 @item Waiting on entry call
17128 The task is waiting on an entry call.
17130 @item Async Select Wait
17131 The task is waiting to start the abortable part of an asynchronous
17135 The task is waiting on a select statement with only a delay
17138 @item Child Termination Wait
17139 The task is sleeping having completed a master within itself, and is
17140 waiting for the tasks dependent on that master to become terminated or
17141 waiting on a terminate Phase.
17143 @item Wait Child in Term Alt
17144 The task is sleeping waiting for tasks on terminate alternatives to
17145 finish terminating.
17147 @item Accepting RV with @var{taskno}
17148 The task is accepting a rendez-vous with the task @var{taskno}.
17152 Name of the task in the program.
17156 @kindex info task @var{taskno}
17157 @item info task @var{taskno}
17158 This command shows detailled informations on the specified task, as in
17159 the following example:
17164 (@value{GDBP}) info tasks
17165 ID TID P-ID Pri State Name
17166 1 8077880 0 15 Child Activation Wait main_task
17167 * 2 807c468 1 15 Runnable task_1
17168 (@value{GDBP}) info task 2
17169 Ada Task: 0x807c468
17173 Parent: 1 (main_task)
17179 @kindex task@r{ (Ada)}
17180 @cindex current Ada task ID
17181 This command prints the ID of the current task.
17187 (@value{GDBP}) info tasks
17188 ID TID P-ID Pri State Name
17189 1 8077870 0 15 Child Activation Wait main_task
17190 * 2 807c458 1 15 Runnable t
17191 (@value{GDBP}) task
17192 [Current task is 2]
17195 @item task @var{taskno}
17196 @cindex Ada task switching
17197 This command is like the @code{thread @var{thread-id}}
17198 command (@pxref{Threads}). It switches the context of debugging
17199 from the current task to the given task.
17205 (@value{GDBP}) info tasks
17206 ID TID P-ID Pri State Name
17207 1 8077870 0 15 Child Activation Wait main_task
17208 * 2 807c458 1 15 Runnable t
17209 (@value{GDBP}) task 1
17210 [Switching to task 1]
17211 #0 0x8067726 in pthread_cond_wait ()
17213 #0 0x8067726 in pthread_cond_wait ()
17214 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17215 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17216 #3 0x806153e in system.tasking.stages.activate_tasks ()
17217 #4 0x804aacc in un () at un.adb:5
17220 @item break @var{location} task @var{taskno}
17221 @itemx break @var{location} task @var{taskno} if @dots{}
17222 @cindex breakpoints and tasks, in Ada
17223 @cindex task breakpoints, in Ada
17224 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17225 These commands are like the @code{break @dots{} thread @dots{}}
17226 command (@pxref{Thread Stops}). The
17227 @var{location} argument specifies source lines, as described
17228 in @ref{Specify Location}.
17230 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17231 to specify that you only want @value{GDBN} to stop the program when a
17232 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17233 numeric task identifiers assigned by @value{GDBN}, shown in the first
17234 column of the @samp{info tasks} display.
17236 If you do not specify @samp{task @var{taskno}} when you set a
17237 breakpoint, the breakpoint applies to @emph{all} tasks of your
17240 You can use the @code{task} qualifier on conditional breakpoints as
17241 well; in this case, place @samp{task @var{taskno}} before the
17242 breakpoint condition (before the @code{if}).
17250 (@value{GDBP}) info tasks
17251 ID TID P-ID Pri State Name
17252 1 140022020 0 15 Child Activation Wait main_task
17253 2 140045060 1 15 Accept/Select Wait t2
17254 3 140044840 1 15 Runnable t1
17255 * 4 140056040 1 15 Runnable t3
17256 (@value{GDBP}) b 15 task 2
17257 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17258 (@value{GDBP}) cont
17263 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17265 (@value{GDBP}) info tasks
17266 ID TID P-ID Pri State Name
17267 1 140022020 0 15 Child Activation Wait main_task
17268 * 2 140045060 1 15 Runnable t2
17269 3 140044840 1 15 Runnable t1
17270 4 140056040 1 15 Delay Sleep t3
17274 @node Ada Tasks and Core Files
17275 @subsubsection Tasking Support when Debugging Core Files
17276 @cindex Ada tasking and core file debugging
17278 When inspecting a core file, as opposed to debugging a live program,
17279 tasking support may be limited or even unavailable, depending on
17280 the platform being used.
17281 For instance, on x86-linux, the list of tasks is available, but task
17282 switching is not supported.
17284 On certain platforms, the debugger needs to perform some
17285 memory writes in order to provide Ada tasking support. When inspecting
17286 a core file, this means that the core file must be opened with read-write
17287 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17288 Under these circumstances, you should make a backup copy of the core
17289 file before inspecting it with @value{GDBN}.
17291 @node Ravenscar Profile
17292 @subsubsection Tasking Support when using the Ravenscar Profile
17293 @cindex Ravenscar Profile
17295 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17296 specifically designed for systems with safety-critical real-time
17300 @kindex set ravenscar task-switching on
17301 @cindex task switching with program using Ravenscar Profile
17302 @item set ravenscar task-switching on
17303 Allows task switching when debugging a program that uses the Ravenscar
17304 Profile. This is the default.
17306 @kindex set ravenscar task-switching off
17307 @item set ravenscar task-switching off
17308 Turn off task switching when debugging a program that uses the Ravenscar
17309 Profile. This is mostly intended to disable the code that adds support
17310 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17311 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17312 To be effective, this command should be run before the program is started.
17314 @kindex show ravenscar task-switching
17315 @item show ravenscar task-switching
17316 Show whether it is possible to switch from task to task in a program
17317 using the Ravenscar Profile.
17322 @subsubsection Ada Settings
17323 @cindex Ada settings
17326 @kindex set varsize-limit
17327 @item set varsize-limit @var{size}
17328 Prevent @value{GDBN} from attempting to evaluate objects whose size
17329 is above the given limit (@var{size}) when those sizes are computed
17330 from run-time quantities. This is typically the case when the object
17331 has a variable size, such as an array whose bounds are not known at
17332 compile time for example. Setting @var{size} to @code{unlimited}
17333 removes the size limitation. By default, the limit is about 65KB.
17335 The purpose of having such a limit is to prevent @value{GDBN} from
17336 trying to grab enormous chunks of virtual memory when asked to evaluate
17337 a quantity whose bounds have been corrupted or have not yet been fully
17338 initialized. The limit applies to the results of some subexpressions
17339 as well as to complete expressions. For example, an expression denoting
17340 a simple integer component, such as @code{x.y.z}, may fail if the size of
17341 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17342 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17343 @code{A} is an array variable with non-constant size, will generally
17344 succeed regardless of the bounds on @code{A}, as long as the component
17345 size is less than @var{size}.
17347 @kindex show varsize-limit
17348 @item show varsize-limit
17349 Show the limit on types whose size is determined by run-time quantities.
17353 @subsubsection Known Peculiarities of Ada Mode
17354 @cindex Ada, problems
17356 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17357 we know of several problems with and limitations of Ada mode in
17359 some of which will be fixed with planned future releases of the debugger
17360 and the GNU Ada compiler.
17364 Static constants that the compiler chooses not to materialize as objects in
17365 storage are invisible to the debugger.
17368 Named parameter associations in function argument lists are ignored (the
17369 argument lists are treated as positional).
17372 Many useful library packages are currently invisible to the debugger.
17375 Fixed-point arithmetic, conversions, input, and output is carried out using
17376 floating-point arithmetic, and may give results that only approximate those on
17380 The GNAT compiler never generates the prefix @code{Standard} for any of
17381 the standard symbols defined by the Ada language. @value{GDBN} knows about
17382 this: it will strip the prefix from names when you use it, and will never
17383 look for a name you have so qualified among local symbols, nor match against
17384 symbols in other packages or subprograms. If you have
17385 defined entities anywhere in your program other than parameters and
17386 local variables whose simple names match names in @code{Standard},
17387 GNAT's lack of qualification here can cause confusion. When this happens,
17388 you can usually resolve the confusion
17389 by qualifying the problematic names with package
17390 @code{Standard} explicitly.
17393 Older versions of the compiler sometimes generate erroneous debugging
17394 information, resulting in the debugger incorrectly printing the value
17395 of affected entities. In some cases, the debugger is able to work
17396 around an issue automatically. In other cases, the debugger is able
17397 to work around the issue, but the work-around has to be specifically
17400 @kindex set ada trust-PAD-over-XVS
17401 @kindex show ada trust-PAD-over-XVS
17404 @item set ada trust-PAD-over-XVS on
17405 Configure GDB to strictly follow the GNAT encoding when computing the
17406 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17407 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17408 a complete description of the encoding used by the GNAT compiler).
17409 This is the default.
17411 @item set ada trust-PAD-over-XVS off
17412 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17413 sometimes prints the wrong value for certain entities, changing @code{ada
17414 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17415 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17416 @code{off}, but this incurs a slight performance penalty, so it is
17417 recommended to leave this setting to @code{on} unless necessary.
17421 @cindex GNAT descriptive types
17422 @cindex GNAT encoding
17423 Internally, the debugger also relies on the compiler following a number
17424 of conventions known as the @samp{GNAT Encoding}, all documented in
17425 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17426 how the debugging information should be generated for certain types.
17427 In particular, this convention makes use of @dfn{descriptive types},
17428 which are artificial types generated purely to help the debugger.
17430 These encodings were defined at a time when the debugging information
17431 format used was not powerful enough to describe some of the more complex
17432 types available in Ada. Since DWARF allows us to express nearly all
17433 Ada features, the long-term goal is to slowly replace these descriptive
17434 types by their pure DWARF equivalent. To facilitate that transition,
17435 a new maintenance option is available to force the debugger to ignore
17436 those descriptive types. It allows the user to quickly evaluate how
17437 well @value{GDBN} works without them.
17441 @kindex maint ada set ignore-descriptive-types
17442 @item maintenance ada set ignore-descriptive-types [on|off]
17443 Control whether the debugger should ignore descriptive types.
17444 The default is not to ignore descriptives types (@code{off}).
17446 @kindex maint ada show ignore-descriptive-types
17447 @item maintenance ada show ignore-descriptive-types
17448 Show if descriptive types are ignored by @value{GDBN}.
17452 @node Unsupported Languages
17453 @section Unsupported Languages
17455 @cindex unsupported languages
17456 @cindex minimal language
17457 In addition to the other fully-supported programming languages,
17458 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17459 It does not represent a real programming language, but provides a set
17460 of capabilities close to what the C or assembly languages provide.
17461 This should allow most simple operations to be performed while debugging
17462 an application that uses a language currently not supported by @value{GDBN}.
17464 If the language is set to @code{auto}, @value{GDBN} will automatically
17465 select this language if the current frame corresponds to an unsupported
17469 @chapter Examining the Symbol Table
17471 The commands described in this chapter allow you to inquire about the
17472 symbols (names of variables, functions and types) defined in your
17473 program. This information is inherent in the text of your program and
17474 does not change as your program executes. @value{GDBN} finds it in your
17475 program's symbol table, in the file indicated when you started @value{GDBN}
17476 (@pxref{File Options, ,Choosing Files}), or by one of the
17477 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17479 @cindex symbol names
17480 @cindex names of symbols
17481 @cindex quoting names
17482 @anchor{quoting names}
17483 Occasionally, you may need to refer to symbols that contain unusual
17484 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17485 most frequent case is in referring to static variables in other
17486 source files (@pxref{Variables,,Program Variables}). File names
17487 are recorded in object files as debugging symbols, but @value{GDBN} would
17488 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17489 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17490 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17497 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17500 @cindex case-insensitive symbol names
17501 @cindex case sensitivity in symbol names
17502 @kindex set case-sensitive
17503 @item set case-sensitive on
17504 @itemx set case-sensitive off
17505 @itemx set case-sensitive auto
17506 Normally, when @value{GDBN} looks up symbols, it matches their names
17507 with case sensitivity determined by the current source language.
17508 Occasionally, you may wish to control that. The command @code{set
17509 case-sensitive} lets you do that by specifying @code{on} for
17510 case-sensitive matches or @code{off} for case-insensitive ones. If
17511 you specify @code{auto}, case sensitivity is reset to the default
17512 suitable for the source language. The default is case-sensitive
17513 matches for all languages except for Fortran, for which the default is
17514 case-insensitive matches.
17516 @kindex show case-sensitive
17517 @item show case-sensitive
17518 This command shows the current setting of case sensitivity for symbols
17521 @kindex set print type methods
17522 @item set print type methods
17523 @itemx set print type methods on
17524 @itemx set print type methods off
17525 Normally, when @value{GDBN} prints a class, it displays any methods
17526 declared in that class. You can control this behavior either by
17527 passing the appropriate flag to @code{ptype}, or using @command{set
17528 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17529 display the methods; this is the default. Specifying @code{off} will
17530 cause @value{GDBN} to omit the methods.
17532 @kindex show print type methods
17533 @item show print type methods
17534 This command shows the current setting of method display when printing
17537 @kindex set print type nested-type-limit
17538 @item set print type nested-type-limit @var{limit}
17539 @itemx set print type nested-type-limit unlimited
17540 Set the limit of displayed nested types that the type printer will
17541 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17542 nested definitions. By default, the type printer will not show any nested
17543 types defined in classes.
17545 @kindex show print type nested-type-limit
17546 @item show print type nested-type-limit
17547 This command shows the current display limit of nested types when
17550 @kindex set print type typedefs
17551 @item set print type typedefs
17552 @itemx set print type typedefs on
17553 @itemx set print type typedefs off
17555 Normally, when @value{GDBN} prints a class, it displays any typedefs
17556 defined in that class. You can control this behavior either by
17557 passing the appropriate flag to @code{ptype}, or using @command{set
17558 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17559 display the typedef definitions; this is the default. Specifying
17560 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17561 Note that this controls whether the typedef definition itself is
17562 printed, not whether typedef names are substituted when printing other
17565 @kindex show print type typedefs
17566 @item show print type typedefs
17567 This command shows the current setting of typedef display when
17570 @kindex info address
17571 @cindex address of a symbol
17572 @item info address @var{symbol}
17573 Describe where the data for @var{symbol} is stored. For a register
17574 variable, this says which register it is kept in. For a non-register
17575 local variable, this prints the stack-frame offset at which the variable
17578 Note the contrast with @samp{print &@var{symbol}}, which does not work
17579 at all for a register variable, and for a stack local variable prints
17580 the exact address of the current instantiation of the variable.
17582 @kindex info symbol
17583 @cindex symbol from address
17584 @cindex closest symbol and offset for an address
17585 @item info symbol @var{addr}
17586 Print the name of a symbol which is stored at the address @var{addr}.
17587 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17588 nearest symbol and an offset from it:
17591 (@value{GDBP}) info symbol 0x54320
17592 _initialize_vx + 396 in section .text
17596 This is the opposite of the @code{info address} command. You can use
17597 it to find out the name of a variable or a function given its address.
17599 For dynamically linked executables, the name of executable or shared
17600 library containing the symbol is also printed:
17603 (@value{GDBP}) info symbol 0x400225
17604 _start + 5 in section .text of /tmp/a.out
17605 (@value{GDBP}) info symbol 0x2aaaac2811cf
17606 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17611 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17612 Demangle @var{name}.
17613 If @var{language} is provided it is the name of the language to demangle
17614 @var{name} in. Otherwise @var{name} is demangled in the current language.
17616 The @samp{--} option specifies the end of options,
17617 and is useful when @var{name} begins with a dash.
17619 The parameter @code{demangle-style} specifies how to interpret the kind
17620 of mangling used. @xref{Print Settings}.
17623 @item whatis[/@var{flags}] [@var{arg}]
17624 Print the data type of @var{arg}, which can be either an expression
17625 or a name of a data type. With no argument, print the data type of
17626 @code{$}, the last value in the value history.
17628 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17629 is not actually evaluated, and any side-effecting operations (such as
17630 assignments or function calls) inside it do not take place.
17632 If @var{arg} is a variable or an expression, @code{whatis} prints its
17633 literal type as it is used in the source code. If the type was
17634 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17635 the data type underlying the @code{typedef}. If the type of the
17636 variable or the expression is a compound data type, such as
17637 @code{struct} or @code{class}, @code{whatis} never prints their
17638 fields or methods. It just prints the @code{struct}/@code{class}
17639 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17640 such a compound data type, use @code{ptype}.
17642 If @var{arg} is a type name that was defined using @code{typedef},
17643 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17644 Unrolling means that @code{whatis} will show the underlying type used
17645 in the @code{typedef} declaration of @var{arg}. However, if that
17646 underlying type is also a @code{typedef}, @code{whatis} will not
17649 For C code, the type names may also have the form @samp{class
17650 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17651 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17653 @var{flags} can be used to modify how the type is displayed.
17654 Available flags are:
17658 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17659 parameters and typedefs defined in a class when printing the class'
17660 members. The @code{/r} flag disables this.
17663 Do not print methods defined in the class.
17666 Print methods defined in the class. This is the default, but the flag
17667 exists in case you change the default with @command{set print type methods}.
17670 Do not print typedefs defined in the class. Note that this controls
17671 whether the typedef definition itself is printed, not whether typedef
17672 names are substituted when printing other types.
17675 Print typedefs defined in the class. This is the default, but the flag
17676 exists in case you change the default with @command{set print type typedefs}.
17679 Print the offsets and sizes of fields in a struct, similar to what the
17680 @command{pahole} tool does. This option implies the @code{/tm} flags.
17682 For example, given the following declarations:
17718 Issuing a @kbd{ptype /o struct tuv} command would print:
17721 (@value{GDBP}) ptype /o struct tuv
17722 /* offset | size */ type = struct tuv @{
17723 /* 0 | 4 */ int a1;
17724 /* XXX 4-byte hole */
17725 /* 8 | 8 */ char *a2;
17726 /* 16 | 4 */ int a3;
17728 /* total size (bytes): 24 */
17732 Notice the format of the first column of comments. There, you can
17733 find two parts separated by the @samp{|} character: the @emph{offset},
17734 which indicates where the field is located inside the struct, in
17735 bytes, and the @emph{size} of the field. Another interesting line is
17736 the marker of a @emph{hole} in the struct, indicating that it may be
17737 possible to pack the struct and make it use less space by reorganizing
17740 It is also possible to print offsets inside an union:
17743 (@value{GDBP}) ptype /o union qwe
17744 /* offset | size */ type = union qwe @{
17745 /* 24 */ struct tuv @{
17746 /* 0 | 4 */ int a1;
17747 /* XXX 4-byte hole */
17748 /* 8 | 8 */ char *a2;
17749 /* 16 | 4 */ int a3;
17751 /* total size (bytes): 24 */
17753 /* 40 */ struct xyz @{
17754 /* 0 | 4 */ int f1;
17755 /* 4 | 1 */ char f2;
17756 /* XXX 3-byte hole */
17757 /* 8 | 8 */ void *f3;
17758 /* 16 | 24 */ struct tuv @{
17759 /* 16 | 4 */ int a1;
17760 /* XXX 4-byte hole */
17761 /* 24 | 8 */ char *a2;
17762 /* 32 | 4 */ int a3;
17764 /* total size (bytes): 24 */
17767 /* total size (bytes): 40 */
17770 /* total size (bytes): 40 */
17774 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17775 same space (because we are dealing with an union), the offset is not
17776 printed for them. However, you can still examine the offset of each
17777 of these structures' fields.
17779 Another useful scenario is printing the offsets of a struct containing
17783 (@value{GDBP}) ptype /o struct tyu
17784 /* offset | size */ type = struct tyu @{
17785 /* 0:31 | 4 */ int a1 : 1;
17786 /* 0:28 | 4 */ int a2 : 3;
17787 /* 0: 5 | 4 */ int a3 : 23;
17788 /* 3: 3 | 1 */ signed char a4 : 2;
17789 /* XXX 3-bit hole */
17790 /* XXX 4-byte hole */
17791 /* 8 | 8 */ int64_t a5;
17792 /* 16:27 | 4 */ int a6 : 5;
17793 /* 16:56 | 8 */ int64_t a7 : 3;
17795 /* total size (bytes): 24 */
17799 Note how the offset information is now extended to also include how
17800 many bits are left to be used in each bitfield.
17804 @item ptype[/@var{flags}] [@var{arg}]
17805 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17806 detailed description of the type, instead of just the name of the type.
17807 @xref{Expressions, ,Expressions}.
17809 Contrary to @code{whatis}, @code{ptype} always unrolls any
17810 @code{typedef}s in its argument declaration, whether the argument is
17811 a variable, expression, or a data type. This means that @code{ptype}
17812 of a variable or an expression will not print literally its type as
17813 present in the source code---use @code{whatis} for that. @code{typedef}s at
17814 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17815 fields, methods and inner @code{class typedef}s of @code{struct}s,
17816 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17818 For example, for this variable declaration:
17821 typedef double real_t;
17822 struct complex @{ real_t real; double imag; @};
17823 typedef struct complex complex_t;
17825 real_t *real_pointer_var;
17829 the two commands give this output:
17833 (@value{GDBP}) whatis var
17835 (@value{GDBP}) ptype var
17836 type = struct complex @{
17840 (@value{GDBP}) whatis complex_t
17841 type = struct complex
17842 (@value{GDBP}) whatis struct complex
17843 type = struct complex
17844 (@value{GDBP}) ptype struct complex
17845 type = struct complex @{
17849 (@value{GDBP}) whatis real_pointer_var
17851 (@value{GDBP}) ptype real_pointer_var
17857 As with @code{whatis}, using @code{ptype} without an argument refers to
17858 the type of @code{$}, the last value in the value history.
17860 @cindex incomplete type
17861 Sometimes, programs use opaque data types or incomplete specifications
17862 of complex data structure. If the debug information included in the
17863 program does not allow @value{GDBN} to display a full declaration of
17864 the data type, it will say @samp{<incomplete type>}. For example,
17865 given these declarations:
17869 struct foo *fooptr;
17873 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17876 (@value{GDBP}) ptype foo
17877 $1 = <incomplete type>
17881 ``Incomplete type'' is C terminology for data types that are not
17882 completely specified.
17884 @cindex unknown type
17885 Othertimes, information about a variable's type is completely absent
17886 from the debug information included in the program. This most often
17887 happens when the program or library where the variable is defined
17888 includes no debug information at all. @value{GDBN} knows the variable
17889 exists from inspecting the linker/loader symbol table (e.g., the ELF
17890 dynamic symbol table), but such symbols do not contain type
17891 information. Inspecting the type of a (global) variable for which
17892 @value{GDBN} has no type information shows:
17895 (@value{GDBP}) ptype var
17896 type = <data variable, no debug info>
17899 @xref{Variables, no debug info variables}, for how to print the values
17903 @item info types @var{regexp}
17905 Print a brief description of all types whose names match the regular
17906 expression @var{regexp} (or all types in your program, if you supply
17907 no argument). Each complete typename is matched as though it were a
17908 complete line; thus, @samp{i type value} gives information on all
17909 types in your program whose names include the string @code{value}, but
17910 @samp{i type ^value$} gives information only on types whose complete
17911 name is @code{value}.
17913 In programs using different languages, @value{GDBN} chooses the syntax
17914 to print the type description according to the
17915 @samp{set language} value: using @samp{set language auto}
17916 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17917 language of the type, other values mean to use
17918 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17920 This command differs from @code{ptype} in two ways: first, like
17921 @code{whatis}, it does not print a detailed description; second, it
17922 lists all source files and line numbers where a type is defined.
17924 @kindex info type-printers
17925 @item info type-printers
17926 Versions of @value{GDBN} that ship with Python scripting enabled may
17927 have ``type printers'' available. When using @command{ptype} or
17928 @command{whatis}, these printers are consulted when the name of a type
17929 is needed. @xref{Type Printing API}, for more information on writing
17932 @code{info type-printers} displays all the available type printers.
17934 @kindex enable type-printer
17935 @kindex disable type-printer
17936 @item enable type-printer @var{name}@dots{}
17937 @item disable type-printer @var{name}@dots{}
17938 These commands can be used to enable or disable type printers.
17941 @cindex local variables
17942 @item info scope @var{location}
17943 List all the variables local to a particular scope. This command
17944 accepts a @var{location} argument---a function name, a source line, or
17945 an address preceded by a @samp{*}, and prints all the variables local
17946 to the scope defined by that location. (@xref{Specify Location}, for
17947 details about supported forms of @var{location}.) For example:
17950 (@value{GDBP}) @b{info scope command_line_handler}
17951 Scope for command_line_handler:
17952 Symbol rl is an argument at stack/frame offset 8, length 4.
17953 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17954 Symbol linelength is in static storage at address 0x150a1c, length 4.
17955 Symbol p is a local variable in register $esi, length 4.
17956 Symbol p1 is a local variable in register $ebx, length 4.
17957 Symbol nline is a local variable in register $edx, length 4.
17958 Symbol repeat is a local variable at frame offset -8, length 4.
17962 This command is especially useful for determining what data to collect
17963 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17966 @kindex info source
17968 Show information about the current source file---that is, the source file for
17969 the function containing the current point of execution:
17972 the name of the source file, and the directory containing it,
17974 the directory it was compiled in,
17976 its length, in lines,
17978 which programming language it is written in,
17980 if the debug information provides it, the program that compiled the file
17981 (which may include, e.g., the compiler version and command line arguments),
17983 whether the executable includes debugging information for that file, and
17984 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17986 whether the debugging information includes information about
17987 preprocessor macros.
17991 @kindex info sources
17993 Print the names of all source files in your program for which there is
17994 debugging information, organized into two lists: files whose symbols
17995 have already been read, and files whose symbols will be read when needed.
17997 @kindex info functions
17998 @item info functions [-q]
17999 Print the names and data types of all defined functions.
18000 Similarly to @samp{info types}, this command groups its output by source
18001 files and annotates each function definition with its source line
18004 In programs using different languages, @value{GDBN} chooses the syntax
18005 to print the function name and type according to the
18006 @samp{set language} value: using @samp{set language auto}
18007 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18008 language of the function, other values mean to use
18009 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18011 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18012 printing header information and messages explaining why no functions
18015 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18016 Like @samp{info functions}, but only print the names and data types
18017 of the functions selected with the provided regexp(s).
18019 If @var{regexp} is provided, print only the functions whose names
18020 match the regular expression @var{regexp}.
18021 Thus, @samp{info fun step} finds all functions whose
18022 names include @code{step}; @samp{info fun ^step} finds those whose names
18023 start with @code{step}. If a function name contains characters that
18024 conflict with the regular expression language (e.g.@:
18025 @samp{operator*()}), they may be quoted with a backslash.
18027 If @var{type_regexp} is provided, print only the functions whose
18028 types, as printed by the @code{whatis} command, match
18029 the regular expression @var{type_regexp}.
18030 If @var{type_regexp} contains space(s), it should be enclosed in
18031 quote characters. If needed, use backslash to escape the meaning
18032 of special characters or quotes.
18033 Thus, @samp{info fun -t '^int ('} finds the functions that return
18034 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18035 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18036 finds the functions whose names start with @code{step} and that return
18039 If both @var{regexp} and @var{type_regexp} are provided, a function
18040 is printed only if its name matches @var{regexp} and its type matches
18044 @kindex info variables
18045 @item info variables [-q]
18046 Print the names and data types of all variables that are defined
18047 outside of functions (i.e.@: excluding local variables).
18048 The printed variables are grouped by source files and annotated with
18049 their respective source line numbers.
18051 In programs using different languages, @value{GDBN} chooses the syntax
18052 to print the variable name and type according to the
18053 @samp{set language} value: using @samp{set language auto}
18054 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18055 language of the variable, other values mean to use
18056 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18058 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18059 printing header information and messages explaining why no variables
18062 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18063 Like @kbd{info variables}, but only print the variables selected
18064 with the provided regexp(s).
18066 If @var{regexp} is provided, print only the variables whose names
18067 match the regular expression @var{regexp}.
18069 If @var{type_regexp} is provided, print only the variables whose
18070 types, as printed by the @code{whatis} command, match
18071 the regular expression @var{type_regexp}.
18072 If @var{type_regexp} contains space(s), it should be enclosed in
18073 quote characters. If needed, use backslash to escape the meaning
18074 of special characters or quotes.
18076 If both @var{regexp} and @var{type_regexp} are provided, an argument
18077 is printed only if its name matches @var{regexp} and its type matches
18080 @kindex info classes
18081 @cindex Objective-C, classes and selectors
18083 @itemx info classes @var{regexp}
18084 Display all Objective-C classes in your program, or
18085 (with the @var{regexp} argument) all those matching a particular regular
18088 @kindex info selectors
18089 @item info selectors
18090 @itemx info selectors @var{regexp}
18091 Display all Objective-C selectors in your program, or
18092 (with the @var{regexp} argument) all those matching a particular regular
18096 This was never implemented.
18097 @kindex info methods
18099 @itemx info methods @var{regexp}
18100 The @code{info methods} command permits the user to examine all defined
18101 methods within C@t{++} program, or (with the @var{regexp} argument) a
18102 specific set of methods found in the various C@t{++} classes. Many
18103 C@t{++} classes provide a large number of methods. Thus, the output
18104 from the @code{ptype} command can be overwhelming and hard to use. The
18105 @code{info-methods} command filters the methods, printing only those
18106 which match the regular-expression @var{regexp}.
18109 @cindex opaque data types
18110 @kindex set opaque-type-resolution
18111 @item set opaque-type-resolution on
18112 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18113 declared as a pointer to a @code{struct}, @code{class}, or
18114 @code{union}---for example, @code{struct MyType *}---that is used in one
18115 source file although the full declaration of @code{struct MyType} is in
18116 another source file. The default is on.
18118 A change in the setting of this subcommand will not take effect until
18119 the next time symbols for a file are loaded.
18121 @item set opaque-type-resolution off
18122 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18123 is printed as follows:
18125 @{<no data fields>@}
18128 @kindex show opaque-type-resolution
18129 @item show opaque-type-resolution
18130 Show whether opaque types are resolved or not.
18132 @kindex set print symbol-loading
18133 @cindex print messages when symbols are loaded
18134 @item set print symbol-loading
18135 @itemx set print symbol-loading full
18136 @itemx set print symbol-loading brief
18137 @itemx set print symbol-loading off
18138 The @code{set print symbol-loading} command allows you to control the
18139 printing of messages when @value{GDBN} loads symbol information.
18140 By default a message is printed for the executable and one for each
18141 shared library, and normally this is what you want. However, when
18142 debugging apps with large numbers of shared libraries these messages
18144 When set to @code{brief} a message is printed for each executable,
18145 and when @value{GDBN} loads a collection of shared libraries at once
18146 it will only print one message regardless of the number of shared
18147 libraries. When set to @code{off} no messages are printed.
18149 @kindex show print symbol-loading
18150 @item show print symbol-loading
18151 Show whether messages will be printed when a @value{GDBN} command
18152 entered from the keyboard causes symbol information to be loaded.
18154 @kindex maint print symbols
18155 @cindex symbol dump
18156 @kindex maint print psymbols
18157 @cindex partial symbol dump
18158 @kindex maint print msymbols
18159 @cindex minimal symbol dump
18160 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18161 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18162 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18163 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18164 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18165 Write a dump of debugging symbol data into the file @var{filename} or
18166 the terminal if @var{filename} is unspecified.
18167 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18169 If @code{-pc @var{address}} is specified, only dump symbols for the file
18170 with code at that address. Note that @var{address} may be a symbol like
18172 If @code{-source @var{source}} is specified, only dump symbols for that
18175 These commands are used to debug the @value{GDBN} symbol-reading code.
18176 These commands do not modify internal @value{GDBN} state, therefore
18177 @samp{maint print symbols} will only print symbols for already expanded symbol
18179 You can use the command @code{info sources} to find out which files these are.
18180 If you use @samp{maint print psymbols} instead, the dump shows information
18181 about symbols that @value{GDBN} only knows partially---that is, symbols
18182 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18183 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18186 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18187 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18189 @kindex maint info symtabs
18190 @kindex maint info psymtabs
18191 @cindex listing @value{GDBN}'s internal symbol tables
18192 @cindex symbol tables, listing @value{GDBN}'s internal
18193 @cindex full symbol tables, listing @value{GDBN}'s internal
18194 @cindex partial symbol tables, listing @value{GDBN}'s internal
18195 @item maint info symtabs @r{[} @var{regexp} @r{]}
18196 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18198 List the @code{struct symtab} or @code{struct partial_symtab}
18199 structures whose names match @var{regexp}. If @var{regexp} is not
18200 given, list them all. The output includes expressions which you can
18201 copy into a @value{GDBN} debugging this one to examine a particular
18202 structure in more detail. For example:
18205 (@value{GDBP}) maint info psymtabs dwarf2read
18206 @{ objfile /home/gnu/build/gdb/gdb
18207 ((struct objfile *) 0x82e69d0)
18208 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18209 ((struct partial_symtab *) 0x8474b10)
18212 text addresses 0x814d3c8 -- 0x8158074
18213 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18214 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18215 dependencies (none)
18218 (@value{GDBP}) maint info symtabs
18222 We see that there is one partial symbol table whose filename contains
18223 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18224 and we see that @value{GDBN} has not read in any symtabs yet at all.
18225 If we set a breakpoint on a function, that will cause @value{GDBN} to
18226 read the symtab for the compilation unit containing that function:
18229 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18230 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18232 (@value{GDBP}) maint info symtabs
18233 @{ objfile /home/gnu/build/gdb/gdb
18234 ((struct objfile *) 0x82e69d0)
18235 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18236 ((struct symtab *) 0x86c1f38)
18239 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18240 linetable ((struct linetable *) 0x8370fa0)
18241 debugformat DWARF 2
18247 @kindex maint info line-table
18248 @cindex listing @value{GDBN}'s internal line tables
18249 @cindex line tables, listing @value{GDBN}'s internal
18250 @item maint info line-table @r{[} @var{regexp} @r{]}
18252 List the @code{struct linetable} from all @code{struct symtab}
18253 instances whose name matches @var{regexp}. If @var{regexp} is not
18254 given, list the @code{struct linetable} from all @code{struct symtab}.
18256 @kindex maint set symbol-cache-size
18257 @cindex symbol cache size
18258 @item maint set symbol-cache-size @var{size}
18259 Set the size of the symbol cache to @var{size}.
18260 The default size is intended to be good enough for debugging
18261 most applications. This option exists to allow for experimenting
18262 with different sizes.
18264 @kindex maint show symbol-cache-size
18265 @item maint show symbol-cache-size
18266 Show the size of the symbol cache.
18268 @kindex maint print symbol-cache
18269 @cindex symbol cache, printing its contents
18270 @item maint print symbol-cache
18271 Print the contents of the symbol cache.
18272 This is useful when debugging symbol cache issues.
18274 @kindex maint print symbol-cache-statistics
18275 @cindex symbol cache, printing usage statistics
18276 @item maint print symbol-cache-statistics
18277 Print symbol cache usage statistics.
18278 This helps determine how well the cache is being utilized.
18280 @kindex maint flush-symbol-cache
18281 @cindex symbol cache, flushing
18282 @item maint flush-symbol-cache
18283 Flush the contents of the symbol cache, all entries are removed.
18284 This command is useful when debugging the symbol cache.
18285 It is also useful when collecting performance data.
18290 @chapter Altering Execution
18292 Once you think you have found an error in your program, you might want to
18293 find out for certain whether correcting the apparent error would lead to
18294 correct results in the rest of the run. You can find the answer by
18295 experiment, using the @value{GDBN} features for altering execution of the
18298 For example, you can store new values into variables or memory
18299 locations, give your program a signal, restart it at a different
18300 address, or even return prematurely from a function.
18303 * Assignment:: Assignment to variables
18304 * Jumping:: Continuing at a different address
18305 * Signaling:: Giving your program a signal
18306 * Returning:: Returning from a function
18307 * Calling:: Calling your program's functions
18308 * Patching:: Patching your program
18309 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18313 @section Assignment to Variables
18316 @cindex setting variables
18317 To alter the value of a variable, evaluate an assignment expression.
18318 @xref{Expressions, ,Expressions}. For example,
18325 stores the value 4 into the variable @code{x}, and then prints the
18326 value of the assignment expression (which is 4).
18327 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18328 information on operators in supported languages.
18330 @kindex set variable
18331 @cindex variables, setting
18332 If you are not interested in seeing the value of the assignment, use the
18333 @code{set} command instead of the @code{print} command. @code{set} is
18334 really the same as @code{print} except that the expression's value is
18335 not printed and is not put in the value history (@pxref{Value History,
18336 ,Value History}). The expression is evaluated only for its effects.
18338 If the beginning of the argument string of the @code{set} command
18339 appears identical to a @code{set} subcommand, use the @code{set
18340 variable} command instead of just @code{set}. This command is identical
18341 to @code{set} except for its lack of subcommands. For example, if your
18342 program has a variable @code{width}, you get an error if you try to set
18343 a new value with just @samp{set width=13}, because @value{GDBN} has the
18344 command @code{set width}:
18347 (@value{GDBP}) whatis width
18349 (@value{GDBP}) p width
18351 (@value{GDBP}) set width=47
18352 Invalid syntax in expression.
18356 The invalid expression, of course, is @samp{=47}. In
18357 order to actually set the program's variable @code{width}, use
18360 (@value{GDBP}) set var width=47
18363 Because the @code{set} command has many subcommands that can conflict
18364 with the names of program variables, it is a good idea to use the
18365 @code{set variable} command instead of just @code{set}. For example, if
18366 your program has a variable @code{g}, you run into problems if you try
18367 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18368 the command @code{set gnutarget}, abbreviated @code{set g}:
18372 (@value{GDBP}) whatis g
18376 (@value{GDBP}) set g=4
18380 The program being debugged has been started already.
18381 Start it from the beginning? (y or n) y
18382 Starting program: /home/smith/cc_progs/a.out
18383 "/home/smith/cc_progs/a.out": can't open to read symbols:
18384 Invalid bfd target.
18385 (@value{GDBP}) show g
18386 The current BFD target is "=4".
18391 The program variable @code{g} did not change, and you silently set the
18392 @code{gnutarget} to an invalid value. In order to set the variable
18396 (@value{GDBP}) set var g=4
18399 @value{GDBN} allows more implicit conversions in assignments than C; you can
18400 freely store an integer value into a pointer variable or vice versa,
18401 and you can convert any structure to any other structure that is the
18402 same length or shorter.
18403 @comment FIXME: how do structs align/pad in these conversions?
18404 @comment /doc@cygnus.com 18dec1990
18406 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18407 construct to generate a value of specified type at a specified address
18408 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18409 to memory location @code{0x83040} as an integer (which implies a certain size
18410 and representation in memory), and
18413 set @{int@}0x83040 = 4
18417 stores the value 4 into that memory location.
18420 @section Continuing at a Different Address
18422 Ordinarily, when you continue your program, you do so at the place where
18423 it stopped, with the @code{continue} command. You can instead continue at
18424 an address of your own choosing, with the following commands:
18428 @kindex j @r{(@code{jump})}
18429 @item jump @var{location}
18430 @itemx j @var{location}
18431 Resume execution at @var{location}. Execution stops again immediately
18432 if there is a breakpoint there. @xref{Specify Location}, for a description
18433 of the different forms of @var{location}. It is common
18434 practice to use the @code{tbreak} command in conjunction with
18435 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18437 The @code{jump} command does not change the current stack frame, or
18438 the stack pointer, or the contents of any memory location or any
18439 register other than the program counter. If @var{location} is in
18440 a different function from the one currently executing, the results may
18441 be bizarre if the two functions expect different patterns of arguments or
18442 of local variables. For this reason, the @code{jump} command requests
18443 confirmation if the specified line is not in the function currently
18444 executing. However, even bizarre results are predictable if you are
18445 well acquainted with the machine-language code of your program.
18448 On many systems, you can get much the same effect as the @code{jump}
18449 command by storing a new value into the register @code{$pc}. The
18450 difference is that this does not start your program running; it only
18451 changes the address of where it @emph{will} run when you continue. For
18459 makes the next @code{continue} command or stepping command execute at
18460 address @code{0x485}, rather than at the address where your program stopped.
18461 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18463 The most common occasion to use the @code{jump} command is to back
18464 up---perhaps with more breakpoints set---over a portion of a program
18465 that has already executed, in order to examine its execution in more
18470 @section Giving your Program a Signal
18471 @cindex deliver a signal to a program
18475 @item signal @var{signal}
18476 Resume execution where your program is stopped, but immediately give it the
18477 signal @var{signal}. The @var{signal} can be the name or the number of a
18478 signal. For example, on many systems @code{signal 2} and @code{signal
18479 SIGINT} are both ways of sending an interrupt signal.
18481 Alternatively, if @var{signal} is zero, continue execution without
18482 giving a signal. This is useful when your program stopped on account of
18483 a signal and would ordinarily see the signal when resumed with the
18484 @code{continue} command; @samp{signal 0} causes it to resume without a
18487 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18488 delivered to the currently selected thread, not the thread that last
18489 reported a stop. This includes the situation where a thread was
18490 stopped due to a signal. So if you want to continue execution
18491 suppressing the signal that stopped a thread, you should select that
18492 same thread before issuing the @samp{signal 0} command. If you issue
18493 the @samp{signal 0} command with another thread as the selected one,
18494 @value{GDBN} detects that and asks for confirmation.
18496 Invoking the @code{signal} command is not the same as invoking the
18497 @code{kill} utility from the shell. Sending a signal with @code{kill}
18498 causes @value{GDBN} to decide what to do with the signal depending on
18499 the signal handling tables (@pxref{Signals}). The @code{signal} command
18500 passes the signal directly to your program.
18502 @code{signal} does not repeat when you press @key{RET} a second time
18503 after executing the command.
18505 @kindex queue-signal
18506 @item queue-signal @var{signal}
18507 Queue @var{signal} to be delivered immediately to the current thread
18508 when execution of the thread resumes. The @var{signal} can be the name or
18509 the number of a signal. For example, on many systems @code{signal 2} and
18510 @code{signal SIGINT} are both ways of sending an interrupt signal.
18511 The handling of the signal must be set to pass the signal to the program,
18512 otherwise @value{GDBN} will report an error.
18513 You can control the handling of signals from @value{GDBN} with the
18514 @code{handle} command (@pxref{Signals}).
18516 Alternatively, if @var{signal} is zero, any currently queued signal
18517 for the current thread is discarded and when execution resumes no signal
18518 will be delivered. This is useful when your program stopped on account
18519 of a signal and would ordinarily see the signal when resumed with the
18520 @code{continue} command.
18522 This command differs from the @code{signal} command in that the signal
18523 is just queued, execution is not resumed. And @code{queue-signal} cannot
18524 be used to pass a signal whose handling state has been set to @code{nopass}
18529 @xref{stepping into signal handlers}, for information on how stepping
18530 commands behave when the thread has a signal queued.
18533 @section Returning from a Function
18536 @cindex returning from a function
18539 @itemx return @var{expression}
18540 You can cancel execution of a function call with the @code{return}
18541 command. If you give an
18542 @var{expression} argument, its value is used as the function's return
18546 When you use @code{return}, @value{GDBN} discards the selected stack frame
18547 (and all frames within it). You can think of this as making the
18548 discarded frame return prematurely. If you wish to specify a value to
18549 be returned, give that value as the argument to @code{return}.
18551 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18552 Frame}), and any other frames inside of it, leaving its caller as the
18553 innermost remaining frame. That frame becomes selected. The
18554 specified value is stored in the registers used for returning values
18557 The @code{return} command does not resume execution; it leaves the
18558 program stopped in the state that would exist if the function had just
18559 returned. In contrast, the @code{finish} command (@pxref{Continuing
18560 and Stepping, ,Continuing and Stepping}) resumes execution until the
18561 selected stack frame returns naturally.
18563 @value{GDBN} needs to know how the @var{expression} argument should be set for
18564 the inferior. The concrete registers assignment depends on the OS ABI and the
18565 type being returned by the selected stack frame. For example it is common for
18566 OS ABI to return floating point values in FPU registers while integer values in
18567 CPU registers. Still some ABIs return even floating point values in CPU
18568 registers. Larger integer widths (such as @code{long long int}) also have
18569 specific placement rules. @value{GDBN} already knows the OS ABI from its
18570 current target so it needs to find out also the type being returned to make the
18571 assignment into the right register(s).
18573 Normally, the selected stack frame has debug info. @value{GDBN} will always
18574 use the debug info instead of the implicit type of @var{expression} when the
18575 debug info is available. For example, if you type @kbd{return -1}, and the
18576 function in the current stack frame is declared to return a @code{long long
18577 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18578 into a @code{long long int}:
18581 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18583 (@value{GDBP}) return -1
18584 Make func return now? (y or n) y
18585 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18586 43 printf ("result=%lld\n", func ());
18590 However, if the selected stack frame does not have a debug info, e.g., if the
18591 function was compiled without debug info, @value{GDBN} has to find out the type
18592 to return from user. Specifying a different type by mistake may set the value
18593 in different inferior registers than the caller code expects. For example,
18594 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18595 of a @code{long long int} result for a debug info less function (on 32-bit
18596 architectures). Therefore the user is required to specify the return type by
18597 an appropriate cast explicitly:
18600 Breakpoint 2, 0x0040050b in func ()
18601 (@value{GDBP}) return -1
18602 Return value type not available for selected stack frame.
18603 Please use an explicit cast of the value to return.
18604 (@value{GDBP}) return (long long int) -1
18605 Make selected stack frame return now? (y or n) y
18606 #0 0x00400526 in main ()
18611 @section Calling Program Functions
18614 @cindex calling functions
18615 @cindex inferior functions, calling
18616 @item print @var{expr}
18617 Evaluate the expression @var{expr} and display the resulting value.
18618 The expression may include calls to functions in the program being
18622 @item call @var{expr}
18623 Evaluate the expression @var{expr} without displaying @code{void}
18626 You can use this variant of the @code{print} command if you want to
18627 execute a function from your program that does not return anything
18628 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18629 with @code{void} returned values that @value{GDBN} will otherwise
18630 print. If the result is not void, it is printed and saved in the
18634 It is possible for the function you call via the @code{print} or
18635 @code{call} command to generate a signal (e.g., if there's a bug in
18636 the function, or if you passed it incorrect arguments). What happens
18637 in that case is controlled by the @code{set unwindonsignal} command.
18639 Similarly, with a C@t{++} program it is possible for the function you
18640 call via the @code{print} or @code{call} command to generate an
18641 exception that is not handled due to the constraints of the dummy
18642 frame. In this case, any exception that is raised in the frame, but has
18643 an out-of-frame exception handler will not be found. GDB builds a
18644 dummy-frame for the inferior function call, and the unwinder cannot
18645 seek for exception handlers outside of this dummy-frame. What happens
18646 in that case is controlled by the
18647 @code{set unwind-on-terminating-exception} command.
18650 @item set unwindonsignal
18651 @kindex set unwindonsignal
18652 @cindex unwind stack in called functions
18653 @cindex call dummy stack unwinding
18654 Set unwinding of the stack if a signal is received while in a function
18655 that @value{GDBN} called in the program being debugged. If set to on,
18656 @value{GDBN} unwinds the stack it created for the call and restores
18657 the context to what it was before the call. If set to off (the
18658 default), @value{GDBN} stops in the frame where the signal was
18661 @item show unwindonsignal
18662 @kindex show unwindonsignal
18663 Show the current setting of stack unwinding in the functions called by
18666 @item set unwind-on-terminating-exception
18667 @kindex set unwind-on-terminating-exception
18668 @cindex unwind stack in called functions with unhandled exceptions
18669 @cindex call dummy stack unwinding on unhandled exception.
18670 Set unwinding of the stack if a C@t{++} exception is raised, but left
18671 unhandled while in a function that @value{GDBN} called in the program being
18672 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18673 it created for the call and restores the context to what it was before
18674 the call. If set to off, @value{GDBN} the exception is delivered to
18675 the default C@t{++} exception handler and the inferior terminated.
18677 @item show unwind-on-terminating-exception
18678 @kindex show unwind-on-terminating-exception
18679 Show the current setting of stack unwinding in the functions called by
18684 @subsection Calling functions with no debug info
18686 @cindex no debug info functions
18687 Sometimes, a function you wish to call is missing debug information.
18688 In such case, @value{GDBN} does not know the type of the function,
18689 including the types of the function's parameters. To avoid calling
18690 the inferior function incorrectly, which could result in the called
18691 function functioning erroneously and even crash, @value{GDBN} refuses
18692 to call the function unless you tell it the type of the function.
18694 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18695 to do that. The simplest is to cast the call to the function's
18696 declared return type. For example:
18699 (@value{GDBP}) p getenv ("PATH")
18700 'getenv' has unknown return type; cast the call to its declared return type
18701 (@value{GDBP}) p (char *) getenv ("PATH")
18702 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18705 Casting the return type of a no-debug function is equivalent to
18706 casting the function to a pointer to a prototyped function that has a
18707 prototype that matches the types of the passed-in arguments, and
18708 calling that. I.e., the call above is equivalent to:
18711 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18715 and given this prototyped C or C++ function with float parameters:
18718 float multiply (float v1, float v2) @{ return v1 * v2; @}
18722 these calls are equivalent:
18725 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18726 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18729 If the function you wish to call is declared as unprototyped (i.e.@:
18730 old K&R style), you must use the cast-to-function-pointer syntax, so
18731 that @value{GDBN} knows that it needs to apply default argument
18732 promotions (promote float arguments to double). @xref{ABI, float
18733 promotion}. For example, given this unprototyped C function with
18734 float parameters, and no debug info:
18738 multiply_noproto (v1, v2)
18746 you call it like this:
18749 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18753 @section Patching Programs
18755 @cindex patching binaries
18756 @cindex writing into executables
18757 @cindex writing into corefiles
18759 By default, @value{GDBN} opens the file containing your program's
18760 executable code (or the corefile) read-only. This prevents accidental
18761 alterations to machine code; but it also prevents you from intentionally
18762 patching your program's binary.
18764 If you'd like to be able to patch the binary, you can specify that
18765 explicitly with the @code{set write} command. For example, you might
18766 want to turn on internal debugging flags, or even to make emergency
18772 @itemx set write off
18773 If you specify @samp{set write on}, @value{GDBN} opens executable and
18774 core files for both reading and writing; if you specify @kbd{set write
18775 off} (the default), @value{GDBN} opens them read-only.
18777 If you have already loaded a file, you must load it again (using the
18778 @code{exec-file} or @code{core-file} command) after changing @code{set
18779 write}, for your new setting to take effect.
18783 Display whether executable files and core files are opened for writing
18784 as well as reading.
18787 @node Compiling and Injecting Code
18788 @section Compiling and injecting code in @value{GDBN}
18789 @cindex injecting code
18790 @cindex writing into executables
18791 @cindex compiling code
18793 @value{GDBN} supports on-demand compilation and code injection into
18794 programs running under @value{GDBN}. GCC 5.0 or higher built with
18795 @file{libcc1.so} must be installed for this functionality to be enabled.
18796 This functionality is implemented with the following commands.
18799 @kindex compile code
18800 @item compile code @var{source-code}
18801 @itemx compile code -raw @var{--} @var{source-code}
18802 Compile @var{source-code} with the compiler language found as the current
18803 language in @value{GDBN} (@pxref{Languages}). If compilation and
18804 injection is not supported with the current language specified in
18805 @value{GDBN}, or the compiler does not support this feature, an error
18806 message will be printed. If @var{source-code} compiles and links
18807 successfully, @value{GDBN} will load the object-code emitted,
18808 and execute it within the context of the currently selected inferior.
18809 It is important to note that the compiled code is executed immediately.
18810 After execution, the compiled code is removed from @value{GDBN} and any
18811 new types or variables you have defined will be deleted.
18813 The command allows you to specify @var{source-code} in two ways.
18814 The simplest method is to provide a single line of code to the command.
18818 compile code printf ("hello world\n");
18821 If you specify options on the command line as well as source code, they
18822 may conflict. The @samp{--} delimiter can be used to separate options
18823 from actual source code. E.g.:
18826 compile code -r -- printf ("hello world\n");
18829 Alternatively you can enter source code as multiple lines of text. To
18830 enter this mode, invoke the @samp{compile code} command without any text
18831 following the command. This will start the multiple-line editor and
18832 allow you to type as many lines of source code as required. When you
18833 have completed typing, enter @samp{end} on its own line to exit the
18838 >printf ("hello\n");
18839 >printf ("world\n");
18843 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18844 provided @var{source-code} in a callable scope. In this case, you must
18845 specify the entry point of the code by defining a function named
18846 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18847 inferior. Using @samp{-raw} option may be needed for example when
18848 @var{source-code} requires @samp{#include} lines which may conflict with
18849 inferior symbols otherwise.
18851 @kindex compile file
18852 @item compile file @var{filename}
18853 @itemx compile file -raw @var{filename}
18854 Like @code{compile code}, but take the source code from @var{filename}.
18857 compile file /home/user/example.c
18862 @item compile print @var{expr}
18863 @itemx compile print /@var{f} @var{expr}
18864 Compile and execute @var{expr} with the compiler language found as the
18865 current language in @value{GDBN} (@pxref{Languages}). By default the
18866 value of @var{expr} is printed in a format appropriate to its data type;
18867 you can choose a different format by specifying @samp{/@var{f}}, where
18868 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18871 @item compile print
18872 @itemx compile print /@var{f}
18873 @cindex reprint the last value
18874 Alternatively you can enter the expression (source code producing it) as
18875 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18876 command without any text following the command. This will start the
18877 multiple-line editor.
18881 The process of compiling and injecting the code can be inspected using:
18884 @anchor{set debug compile}
18885 @item set debug compile
18886 @cindex compile command debugging info
18887 Turns on or off display of @value{GDBN} process of compiling and
18888 injecting the code. The default is off.
18890 @item show debug compile
18891 Displays the current state of displaying @value{GDBN} process of
18892 compiling and injecting the code.
18894 @anchor{set debug compile-cplus-types}
18895 @item set debug compile-cplus-types
18896 @cindex compile C@t{++} type conversion
18897 Turns on or off the display of C@t{++} type conversion debugging information.
18898 The default is off.
18900 @item show debug compile-cplus-types
18901 Displays the current state of displaying debugging information for
18902 C@t{++} type conversion.
18905 @subsection Compilation options for the @code{compile} command
18907 @value{GDBN} needs to specify the right compilation options for the code
18908 to be injected, in part to make its ABI compatible with the inferior
18909 and in part to make the injected code compatible with @value{GDBN}'s
18913 The options used, in increasing precedence:
18916 @item target architecture and OS options (@code{gdbarch})
18917 These options depend on target processor type and target operating
18918 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18919 (@code{-m64}) compilation option.
18921 @item compilation options recorded in the target
18922 @value{NGCC} (since version 4.7) stores the options used for compilation
18923 into @code{DW_AT_producer} part of DWARF debugging information according
18924 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18925 explicitly specify @code{-g} during inferior compilation otherwise
18926 @value{NGCC} produces no DWARF. This feature is only relevant for
18927 platforms where @code{-g} produces DWARF by default, otherwise one may
18928 try to enforce DWARF by using @code{-gdwarf-4}.
18930 @item compilation options set by @code{set compile-args}
18934 You can override compilation options using the following command:
18937 @item set compile-args
18938 @cindex compile command options override
18939 Set compilation options used for compiling and injecting code with the
18940 @code{compile} commands. These options override any conflicting ones
18941 from the target architecture and/or options stored during inferior
18944 @item show compile-args
18945 Displays the current state of compilation options override.
18946 This does not show all the options actually used during compilation,
18947 use @ref{set debug compile} for that.
18950 @subsection Caveats when using the @code{compile} command
18952 There are a few caveats to keep in mind when using the @code{compile}
18953 command. As the caveats are different per language, the table below
18954 highlights specific issues on a per language basis.
18957 @item C code examples and caveats
18958 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18959 attempt to compile the source code with a @samp{C} compiler. The source
18960 code provided to the @code{compile} command will have much the same
18961 access to variables and types as it normally would if it were part of
18962 the program currently being debugged in @value{GDBN}.
18964 Below is a sample program that forms the basis of the examples that
18965 follow. This program has been compiled and loaded into @value{GDBN},
18966 much like any other normal debugging session.
18969 void function1 (void)
18972 printf ("function 1\n");
18975 void function2 (void)
18990 For the purposes of the examples in this section, the program above has
18991 been compiled, loaded into @value{GDBN}, stopped at the function
18992 @code{main}, and @value{GDBN} is awaiting input from the user.
18994 To access variables and types for any program in @value{GDBN}, the
18995 program must be compiled and packaged with debug information. The
18996 @code{compile} command is not an exception to this rule. Without debug
18997 information, you can still use the @code{compile} command, but you will
18998 be very limited in what variables and types you can access.
19000 So with that in mind, the example above has been compiled with debug
19001 information enabled. The @code{compile} command will have access to
19002 all variables and types (except those that may have been optimized
19003 out). Currently, as @value{GDBN} has stopped the program in the
19004 @code{main} function, the @code{compile} command would have access to
19005 the variable @code{k}. You could invoke the @code{compile} command
19006 and type some source code to set the value of @code{k}. You can also
19007 read it, or do anything with that variable you would normally do in
19008 @code{C}. Be aware that changes to inferior variables in the
19009 @code{compile} command are persistent. In the following example:
19012 compile code k = 3;
19016 the variable @code{k} is now 3. It will retain that value until
19017 something else in the example program changes it, or another
19018 @code{compile} command changes it.
19020 Normal scope and access rules apply to source code compiled and
19021 injected by the @code{compile} command. In the example, the variables
19022 @code{j} and @code{k} are not accessible yet, because the program is
19023 currently stopped in the @code{main} function, where these variables
19024 are not in scope. Therefore, the following command
19027 compile code j = 3;
19031 will result in a compilation error message.
19033 Once the program is continued, execution will bring these variables in
19034 scope, and they will become accessible; then the code you specify via
19035 the @code{compile} command will be able to access them.
19037 You can create variables and types with the @code{compile} command as
19038 part of your source code. Variables and types that are created as part
19039 of the @code{compile} command are not visible to the rest of the program for
19040 the duration of its run. This example is valid:
19043 compile code int ff = 5; printf ("ff is %d\n", ff);
19046 However, if you were to type the following into @value{GDBN} after that
19047 command has completed:
19050 compile code printf ("ff is %d\n'', ff);
19054 a compiler error would be raised as the variable @code{ff} no longer
19055 exists. Object code generated and injected by the @code{compile}
19056 command is removed when its execution ends. Caution is advised
19057 when assigning to program variables values of variables created by the
19058 code submitted to the @code{compile} command. This example is valid:
19061 compile code int ff = 5; k = ff;
19064 The value of the variable @code{ff} is assigned to @code{k}. The variable
19065 @code{k} does not require the existence of @code{ff} to maintain the value
19066 it has been assigned. However, pointers require particular care in
19067 assignment. If the source code compiled with the @code{compile} command
19068 changed the address of a pointer in the example program, perhaps to a
19069 variable created in the @code{compile} command, that pointer would point
19070 to an invalid location when the command exits. The following example
19071 would likely cause issues with your debugged program:
19074 compile code int ff = 5; p = &ff;
19077 In this example, @code{p} would point to @code{ff} when the
19078 @code{compile} command is executing the source code provided to it.
19079 However, as variables in the (example) program persist with their
19080 assigned values, the variable @code{p} would point to an invalid
19081 location when the command exists. A general rule should be followed
19082 in that you should either assign @code{NULL} to any assigned pointers,
19083 or restore a valid location to the pointer before the command exits.
19085 Similar caution must be exercised with any structs, unions, and typedefs
19086 defined in @code{compile} command. Types defined in the @code{compile}
19087 command will no longer be available in the next @code{compile} command.
19088 Therefore, if you cast a variable to a type defined in the
19089 @code{compile} command, care must be taken to ensure that any future
19090 need to resolve the type can be achieved.
19093 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19094 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19095 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19096 Compilation failed.
19097 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19101 Variables that have been optimized away by the compiler are not
19102 accessible to the code submitted to the @code{compile} command.
19103 Access to those variables will generate a compiler error which @value{GDBN}
19104 will print to the console.
19107 @subsection Compiler search for the @code{compile} command
19109 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19110 which may not be obvious for remote targets of different architecture
19111 than where @value{GDBN} is running. Environment variable @code{PATH} on
19112 @value{GDBN} host is searched for @value{NGCC} binary matching the
19113 target architecture and operating system. This search can be overriden
19114 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19115 taken from shell that executed @value{GDBN}, it is not the value set by
19116 @value{GDBN} command @code{set environment}). @xref{Environment}.
19119 Specifically @code{PATH} is searched for binaries matching regular expression
19120 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19121 debugged. @var{arch} is processor name --- multiarch is supported, so for
19122 example both @code{i386} and @code{x86_64} targets look for pattern
19123 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19124 for pattern @code{s390x?}. @var{os} is currently supported only for
19125 pattern @code{linux(-gnu)?}.
19127 On Posix hosts the compiler driver @value{GDBN} needs to find also
19128 shared library @file{libcc1.so} from the compiler. It is searched in
19129 default shared library search path (overridable with usual environment
19130 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19131 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19132 according to the installation of the found compiler --- as possibly
19133 specified by the @code{set compile-gcc} command.
19136 @item set compile-gcc
19137 @cindex compile command driver filename override
19138 Set compilation command used for compiling and injecting code with the
19139 @code{compile} commands. If this option is not set (it is set to
19140 an empty string), the search described above will occur --- that is the
19143 @item show compile-gcc
19144 Displays the current compile command @value{NGCC} driver filename.
19145 If set, it is the main command @command{gcc}, found usually for example
19146 under name @file{x86_64-linux-gnu-gcc}.
19150 @chapter @value{GDBN} Files
19152 @value{GDBN} needs to know the file name of the program to be debugged,
19153 both in order to read its symbol table and in order to start your
19154 program. To debug a core dump of a previous run, you must also tell
19155 @value{GDBN} the name of the core dump file.
19158 * Files:: Commands to specify files
19159 * File Caching:: Information about @value{GDBN}'s file caching
19160 * Separate Debug Files:: Debugging information in separate files
19161 * MiniDebugInfo:: Debugging information in a special section
19162 * Index Files:: Index files speed up GDB
19163 * Symbol Errors:: Errors reading symbol files
19164 * Data Files:: GDB data files
19168 @section Commands to Specify Files
19170 @cindex symbol table
19171 @cindex core dump file
19173 You may want to specify executable and core dump file names. The usual
19174 way to do this is at start-up time, using the arguments to
19175 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19176 Out of @value{GDBN}}).
19178 Occasionally it is necessary to change to a different file during a
19179 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19180 specify a file you want to use. Or you are debugging a remote target
19181 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19182 Program}). In these situations the @value{GDBN} commands to specify
19183 new files are useful.
19186 @cindex executable file
19188 @item file @var{filename}
19189 Use @var{filename} as the program to be debugged. It is read for its
19190 symbols and for the contents of pure memory. It is also the program
19191 executed when you use the @code{run} command. If you do not specify a
19192 directory and the file is not found in the @value{GDBN} working directory,
19193 @value{GDBN} uses the environment variable @code{PATH} as a list of
19194 directories to search, just as the shell does when looking for a program
19195 to run. You can change the value of this variable, for both @value{GDBN}
19196 and your program, using the @code{path} command.
19198 @cindex unlinked object files
19199 @cindex patching object files
19200 You can load unlinked object @file{.o} files into @value{GDBN} using
19201 the @code{file} command. You will not be able to ``run'' an object
19202 file, but you can disassemble functions and inspect variables. Also,
19203 if the underlying BFD functionality supports it, you could use
19204 @kbd{gdb -write} to patch object files using this technique. Note
19205 that @value{GDBN} can neither interpret nor modify relocations in this
19206 case, so branches and some initialized variables will appear to go to
19207 the wrong place. But this feature is still handy from time to time.
19210 @code{file} with no argument makes @value{GDBN} discard any information it
19211 has on both executable file and the symbol table.
19214 @item exec-file @r{[} @var{filename} @r{]}
19215 Specify that the program to be run (but not the symbol table) is found
19216 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19217 if necessary to locate your program. Omitting @var{filename} means to
19218 discard information on the executable file.
19220 @kindex symbol-file
19221 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19222 Read symbol table information from file @var{filename}. @code{PATH} is
19223 searched when necessary. Use the @code{file} command to get both symbol
19224 table and program to run from the same file.
19226 If an optional @var{offset} is specified, it is added to the start
19227 address of each section in the symbol file. This is useful if the
19228 program is relocated at runtime, such as the Linux kernel with kASLR
19231 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19232 program's symbol table.
19234 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19235 some breakpoints and auto-display expressions. This is because they may
19236 contain pointers to the internal data recording symbols and data types,
19237 which are part of the old symbol table data being discarded inside
19240 @code{symbol-file} does not repeat if you press @key{RET} again after
19243 When @value{GDBN} is configured for a particular environment, it
19244 understands debugging information in whatever format is the standard
19245 generated for that environment; you may use either a @sc{gnu} compiler, or
19246 other compilers that adhere to the local conventions.
19247 Best results are usually obtained from @sc{gnu} compilers; for example,
19248 using @code{@value{NGCC}} you can generate debugging information for
19251 For most kinds of object files, with the exception of old SVR3 systems
19252 using COFF, the @code{symbol-file} command does not normally read the
19253 symbol table in full right away. Instead, it scans the symbol table
19254 quickly to find which source files and which symbols are present. The
19255 details are read later, one source file at a time, as they are needed.
19257 The purpose of this two-stage reading strategy is to make @value{GDBN}
19258 start up faster. For the most part, it is invisible except for
19259 occasional pauses while the symbol table details for a particular source
19260 file are being read. (The @code{set verbose} command can turn these
19261 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19262 Warnings and Messages}.)
19264 We have not implemented the two-stage strategy for COFF yet. When the
19265 symbol table is stored in COFF format, @code{symbol-file} reads the
19266 symbol table data in full right away. Note that ``stabs-in-COFF''
19267 still does the two-stage strategy, since the debug info is actually
19271 @cindex reading symbols immediately
19272 @cindex symbols, reading immediately
19273 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19274 @itemx file @r{[} -readnow @r{]} @var{filename}
19275 You can override the @value{GDBN} two-stage strategy for reading symbol
19276 tables by using the @samp{-readnow} option with any of the commands that
19277 load symbol table information, if you want to be sure @value{GDBN} has the
19278 entire symbol table available.
19280 @cindex @code{-readnever}, option for symbol-file command
19281 @cindex never read symbols
19282 @cindex symbols, never read
19283 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19284 @itemx file @r{[} -readnever @r{]} @var{filename}
19285 You can instruct @value{GDBN} to never read the symbolic information
19286 contained in @var{filename} by using the @samp{-readnever} option.
19287 @xref{--readnever}.
19289 @c FIXME: for now no mention of directories, since this seems to be in
19290 @c flux. 13mar1992 status is that in theory GDB would look either in
19291 @c current dir or in same dir as myprog; but issues like competing
19292 @c GDB's, or clutter in system dirs, mean that in practice right now
19293 @c only current dir is used. FFish says maybe a special GDB hierarchy
19294 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19298 @item core-file @r{[}@var{filename}@r{]}
19300 Specify the whereabouts of a core dump file to be used as the ``contents
19301 of memory''. Traditionally, core files contain only some parts of the
19302 address space of the process that generated them; @value{GDBN} can access the
19303 executable file itself for other parts.
19305 @code{core-file} with no argument specifies that no core file is
19308 Note that the core file is ignored when your program is actually running
19309 under @value{GDBN}. So, if you have been running your program and you
19310 wish to debug a core file instead, you must kill the subprocess in which
19311 the program is running. To do this, use the @code{kill} command
19312 (@pxref{Kill Process, ,Killing the Child Process}).
19314 @kindex add-symbol-file
19315 @cindex dynamic linking
19316 @item add-symbol-file @var{filename} @r{[} -readnow @r{|} -readnever @r{]} @r{[} -o @var{offset} @r{]} @r{[} @var{textaddress} @r{]} @r{[} -s @var{section} @var{address} @dots{} @r{]}
19317 The @code{add-symbol-file} command reads additional symbol table
19318 information from the file @var{filename}. You would use this command
19319 when @var{filename} has been dynamically loaded (by some other means)
19320 into the program that is running. The @var{textaddress} parameter gives
19321 the memory address at which the file's text section has been loaded.
19322 You can additionally specify the base address of other sections using
19323 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19324 If a section is omitted, @value{GDBN} will use its default addresses
19325 as found in @var{filename}. Any @var{address} or @var{textaddress}
19326 can be given as an expression.
19328 If an optional @var{offset} is specified, it is added to the start
19329 address of each section, except those for which the address was
19330 specified explicitly.
19332 The symbol table of the file @var{filename} is added to the symbol table
19333 originally read with the @code{symbol-file} command. You can use the
19334 @code{add-symbol-file} command any number of times; the new symbol data
19335 thus read is kept in addition to the old.
19337 Changes can be reverted using the command @code{remove-symbol-file}.
19339 @cindex relocatable object files, reading symbols from
19340 @cindex object files, relocatable, reading symbols from
19341 @cindex reading symbols from relocatable object files
19342 @cindex symbols, reading from relocatable object files
19343 @cindex @file{.o} files, reading symbols from
19344 Although @var{filename} is typically a shared library file, an
19345 executable file, or some other object file which has been fully
19346 relocated for loading into a process, you can also load symbolic
19347 information from relocatable @file{.o} files, as long as:
19351 the file's symbolic information refers only to linker symbols defined in
19352 that file, not to symbols defined by other object files,
19354 every section the file's symbolic information refers to has actually
19355 been loaded into the inferior, as it appears in the file, and
19357 you can determine the address at which every section was loaded, and
19358 provide these to the @code{add-symbol-file} command.
19362 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19363 relocatable files into an already running program; such systems
19364 typically make the requirements above easy to meet. However, it's
19365 important to recognize that many native systems use complex link
19366 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19367 assembly, for example) that make the requirements difficult to meet. In
19368 general, one cannot assume that using @code{add-symbol-file} to read a
19369 relocatable object file's symbolic information will have the same effect
19370 as linking the relocatable object file into the program in the normal
19373 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19375 @kindex remove-symbol-file
19376 @item remove-symbol-file @var{filename}
19377 @item remove-symbol-file -a @var{address}
19378 Remove a symbol file added via the @code{add-symbol-file} command. The
19379 file to remove can be identified by its @var{filename} or by an @var{address}
19380 that lies within the boundaries of this symbol file in memory. Example:
19383 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19384 add symbol table from file "/home/user/gdb/mylib.so" at
19385 .text_addr = 0x7ffff7ff9480
19387 Reading symbols from /home/user/gdb/mylib.so...done.
19388 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19389 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19394 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19396 @kindex add-symbol-file-from-memory
19397 @cindex @code{syscall DSO}
19398 @cindex load symbols from memory
19399 @item add-symbol-file-from-memory @var{address}
19400 Load symbols from the given @var{address} in a dynamically loaded
19401 object file whose image is mapped directly into the inferior's memory.
19402 For example, the Linux kernel maps a @code{syscall DSO} into each
19403 process's address space; this DSO provides kernel-specific code for
19404 some system calls. The argument can be any expression whose
19405 evaluation yields the address of the file's shared object file header.
19406 For this command to work, you must have used @code{symbol-file} or
19407 @code{exec-file} commands in advance.
19410 @item section @var{section} @var{addr}
19411 The @code{section} command changes the base address of the named
19412 @var{section} of the exec file to @var{addr}. This can be used if the
19413 exec file does not contain section addresses, (such as in the
19414 @code{a.out} format), or when the addresses specified in the file
19415 itself are wrong. Each section must be changed separately. The
19416 @code{info files} command, described below, lists all the sections and
19420 @kindex info target
19423 @code{info files} and @code{info target} are synonymous; both print the
19424 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19425 including the names of the executable and core dump files currently in
19426 use by @value{GDBN}, and the files from which symbols were loaded. The
19427 command @code{help target} lists all possible targets rather than
19430 @kindex maint info sections
19431 @item maint info sections
19432 Another command that can give you extra information about program sections
19433 is @code{maint info sections}. In addition to the section information
19434 displayed by @code{info files}, this command displays the flags and file
19435 offset of each section in the executable and core dump files. In addition,
19436 @code{maint info sections} provides the following command options (which
19437 may be arbitrarily combined):
19441 Display sections for all loaded object files, including shared libraries.
19442 @item @var{sections}
19443 Display info only for named @var{sections}.
19444 @item @var{section-flags}
19445 Display info only for sections for which @var{section-flags} are true.
19446 The section flags that @value{GDBN} currently knows about are:
19449 Section will have space allocated in the process when loaded.
19450 Set for all sections except those containing debug information.
19452 Section will be loaded from the file into the child process memory.
19453 Set for pre-initialized code and data, clear for @code{.bss} sections.
19455 Section needs to be relocated before loading.
19457 Section cannot be modified by the child process.
19459 Section contains executable code only.
19461 Section contains data only (no executable code).
19463 Section will reside in ROM.
19465 Section contains data for constructor/destructor lists.
19467 Section is not empty.
19469 An instruction to the linker to not output the section.
19470 @item COFF_SHARED_LIBRARY
19471 A notification to the linker that the section contains
19472 COFF shared library information.
19474 Section contains common symbols.
19477 @kindex set trust-readonly-sections
19478 @cindex read-only sections
19479 @item set trust-readonly-sections on
19480 Tell @value{GDBN} that readonly sections in your object file
19481 really are read-only (i.e.@: that their contents will not change).
19482 In that case, @value{GDBN} can fetch values from these sections
19483 out of the object file, rather than from the target program.
19484 For some targets (notably embedded ones), this can be a significant
19485 enhancement to debugging performance.
19487 The default is off.
19489 @item set trust-readonly-sections off
19490 Tell @value{GDBN} not to trust readonly sections. This means that
19491 the contents of the section might change while the program is running,
19492 and must therefore be fetched from the target when needed.
19494 @item show trust-readonly-sections
19495 Show the current setting of trusting readonly sections.
19498 All file-specifying commands allow both absolute and relative file names
19499 as arguments. @value{GDBN} always converts the file name to an absolute file
19500 name and remembers it that way.
19502 @cindex shared libraries
19503 @anchor{Shared Libraries}
19504 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19505 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19506 DSBT (TIC6X) shared libraries.
19508 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19509 shared libraries. @xref{Expat}.
19511 @value{GDBN} automatically loads symbol definitions from shared libraries
19512 when you use the @code{run} command, or when you examine a core file.
19513 (Before you issue the @code{run} command, @value{GDBN} does not understand
19514 references to a function in a shared library, however---unless you are
19515 debugging a core file).
19517 @c FIXME: some @value{GDBN} release may permit some refs to undef
19518 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19519 @c FIXME...lib; check this from time to time when updating manual
19521 There are times, however, when you may wish to not automatically load
19522 symbol definitions from shared libraries, such as when they are
19523 particularly large or there are many of them.
19525 To control the automatic loading of shared library symbols, use the
19529 @kindex set auto-solib-add
19530 @item set auto-solib-add @var{mode}
19531 If @var{mode} is @code{on}, symbols from all shared object libraries
19532 will be loaded automatically when the inferior begins execution, you
19533 attach to an independently started inferior, or when the dynamic linker
19534 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19535 is @code{off}, symbols must be loaded manually, using the
19536 @code{sharedlibrary} command. The default value is @code{on}.
19538 @cindex memory used for symbol tables
19539 If your program uses lots of shared libraries with debug info that
19540 takes large amounts of memory, you can decrease the @value{GDBN}
19541 memory footprint by preventing it from automatically loading the
19542 symbols from shared libraries. To that end, type @kbd{set
19543 auto-solib-add off} before running the inferior, then load each
19544 library whose debug symbols you do need with @kbd{sharedlibrary
19545 @var{regexp}}, where @var{regexp} is a regular expression that matches
19546 the libraries whose symbols you want to be loaded.
19548 @kindex show auto-solib-add
19549 @item show auto-solib-add
19550 Display the current autoloading mode.
19553 @cindex load shared library
19554 To explicitly load shared library symbols, use the @code{sharedlibrary}
19558 @kindex info sharedlibrary
19560 @item info share @var{regex}
19561 @itemx info sharedlibrary @var{regex}
19562 Print the names of the shared libraries which are currently loaded
19563 that match @var{regex}. If @var{regex} is omitted then print
19564 all shared libraries that are loaded.
19567 @item info dll @var{regex}
19568 This is an alias of @code{info sharedlibrary}.
19570 @kindex sharedlibrary
19572 @item sharedlibrary @var{regex}
19573 @itemx share @var{regex}
19574 Load shared object library symbols for files matching a
19575 Unix regular expression.
19576 As with files loaded automatically, it only loads shared libraries
19577 required by your program for a core file or after typing @code{run}. If
19578 @var{regex} is omitted all shared libraries required by your program are
19581 @item nosharedlibrary
19582 @kindex nosharedlibrary
19583 @cindex unload symbols from shared libraries
19584 Unload all shared object library symbols. This discards all symbols
19585 that have been loaded from all shared libraries. Symbols from shared
19586 libraries that were loaded by explicit user requests are not
19590 Sometimes you may wish that @value{GDBN} stops and gives you control
19591 when any of shared library events happen. The best way to do this is
19592 to use @code{catch load} and @code{catch unload} (@pxref{Set
19595 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19596 command for this. This command exists for historical reasons. It is
19597 less useful than setting a catchpoint, because it does not allow for
19598 conditions or commands as a catchpoint does.
19601 @item set stop-on-solib-events
19602 @kindex set stop-on-solib-events
19603 This command controls whether @value{GDBN} should give you control
19604 when the dynamic linker notifies it about some shared library event.
19605 The most common event of interest is loading or unloading of a new
19608 @item show stop-on-solib-events
19609 @kindex show stop-on-solib-events
19610 Show whether @value{GDBN} stops and gives you control when shared
19611 library events happen.
19614 Shared libraries are also supported in many cross or remote debugging
19615 configurations. @value{GDBN} needs to have access to the target's libraries;
19616 this can be accomplished either by providing copies of the libraries
19617 on the host system, or by asking @value{GDBN} to automatically retrieve the
19618 libraries from the target. If copies of the target libraries are
19619 provided, they need to be the same as the target libraries, although the
19620 copies on the target can be stripped as long as the copies on the host are
19623 @cindex where to look for shared libraries
19624 For remote debugging, you need to tell @value{GDBN} where the target
19625 libraries are, so that it can load the correct copies---otherwise, it
19626 may try to load the host's libraries. @value{GDBN} has two variables
19627 to specify the search directories for target libraries.
19630 @cindex prefix for executable and shared library file names
19631 @cindex system root, alternate
19632 @kindex set solib-absolute-prefix
19633 @kindex set sysroot
19634 @item set sysroot @var{path}
19635 Use @var{path} as the system root for the program being debugged. Any
19636 absolute shared library paths will be prefixed with @var{path}; many
19637 runtime loaders store the absolute paths to the shared library in the
19638 target program's memory. When starting processes remotely, and when
19639 attaching to already-running processes (local or remote), their
19640 executable filenames will be prefixed with @var{path} if reported to
19641 @value{GDBN} as absolute by the operating system. If you use
19642 @code{set sysroot} to find executables and shared libraries, they need
19643 to be laid out in the same way that they are on the target, with
19644 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19647 If @var{path} starts with the sequence @file{target:} and the target
19648 system is remote then @value{GDBN} will retrieve the target binaries
19649 from the remote system. This is only supported when using a remote
19650 target that supports the @code{remote get} command (@pxref{File
19651 Transfer,,Sending files to a remote system}). The part of @var{path}
19652 following the initial @file{target:} (if present) is used as system
19653 root prefix on the remote file system. If @var{path} starts with the
19654 sequence @file{remote:} this is converted to the sequence
19655 @file{target:} by @code{set sysroot}@footnote{Historically the
19656 functionality to retrieve binaries from the remote system was
19657 provided by prefixing @var{path} with @file{remote:}}. If you want
19658 to specify a local system root using a directory that happens to be
19659 named @file{target:} or @file{remote:}, you need to use some
19660 equivalent variant of the name like @file{./target:}.
19662 For targets with an MS-DOS based filesystem, such as MS-Windows and
19663 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19664 absolute file name with @var{path}. But first, on Unix hosts,
19665 @value{GDBN} converts all backslash directory separators into forward
19666 slashes, because the backslash is not a directory separator on Unix:
19669 c:\foo\bar.dll @result{} c:/foo/bar.dll
19672 Then, @value{GDBN} attempts prefixing the target file name with
19673 @var{path}, and looks for the resulting file name in the host file
19677 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19680 If that does not find the binary, @value{GDBN} tries removing
19681 the @samp{:} character from the drive spec, both for convenience, and,
19682 for the case of the host file system not supporting file names with
19686 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19689 This makes it possible to have a system root that mirrors a target
19690 with more than one drive. E.g., you may want to setup your local
19691 copies of the target system shared libraries like so (note @samp{c} vs
19695 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19696 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19697 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19701 and point the system root at @file{/path/to/sysroot}, so that
19702 @value{GDBN} can find the correct copies of both
19703 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19705 If that still does not find the binary, @value{GDBN} tries
19706 removing the whole drive spec from the target file name:
19709 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19712 This last lookup makes it possible to not care about the drive name,
19713 if you don't want or need to.
19715 The @code{set solib-absolute-prefix} command is an alias for @code{set
19718 @cindex default system root
19719 @cindex @samp{--with-sysroot}
19720 You can set the default system root by using the configure-time
19721 @samp{--with-sysroot} option. If the system root is inside
19722 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19723 @samp{--exec-prefix}), then the default system root will be updated
19724 automatically if the installed @value{GDBN} is moved to a new
19727 @kindex show sysroot
19729 Display the current executable and shared library prefix.
19731 @kindex set solib-search-path
19732 @item set solib-search-path @var{path}
19733 If this variable is set, @var{path} is a colon-separated list of
19734 directories to search for shared libraries. @samp{solib-search-path}
19735 is used after @samp{sysroot} fails to locate the library, or if the
19736 path to the library is relative instead of absolute. If you want to
19737 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19738 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19739 finding your host's libraries. @samp{sysroot} is preferred; setting
19740 it to a nonexistent directory may interfere with automatic loading
19741 of shared library symbols.
19743 @kindex show solib-search-path
19744 @item show solib-search-path
19745 Display the current shared library search path.
19747 @cindex DOS file-name semantics of file names.
19748 @kindex set target-file-system-kind (unix|dos-based|auto)
19749 @kindex show target-file-system-kind
19750 @item set target-file-system-kind @var{kind}
19751 Set assumed file system kind for target reported file names.
19753 Shared library file names as reported by the target system may not
19754 make sense as is on the system @value{GDBN} is running on. For
19755 example, when remote debugging a target that has MS-DOS based file
19756 system semantics, from a Unix host, the target may be reporting to
19757 @value{GDBN} a list of loaded shared libraries with file names such as
19758 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19759 drive letters, so the @samp{c:\} prefix is not normally understood as
19760 indicating an absolute file name, and neither is the backslash
19761 normally considered a directory separator character. In that case,
19762 the native file system would interpret this whole absolute file name
19763 as a relative file name with no directory components. This would make
19764 it impossible to point @value{GDBN} at a copy of the remote target's
19765 shared libraries on the host using @code{set sysroot}, and impractical
19766 with @code{set solib-search-path}. Setting
19767 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19768 to interpret such file names similarly to how the target would, and to
19769 map them to file names valid on @value{GDBN}'s native file system
19770 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19771 to one of the supported file system kinds. In that case, @value{GDBN}
19772 tries to determine the appropriate file system variant based on the
19773 current target's operating system (@pxref{ABI, ,Configuring the
19774 Current ABI}). The supported file system settings are:
19778 Instruct @value{GDBN} to assume the target file system is of Unix
19779 kind. Only file names starting the forward slash (@samp{/}) character
19780 are considered absolute, and the directory separator character is also
19784 Instruct @value{GDBN} to assume the target file system is DOS based.
19785 File names starting with either a forward slash, or a drive letter
19786 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19787 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19788 considered directory separators.
19791 Instruct @value{GDBN} to use the file system kind associated with the
19792 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19793 This is the default.
19797 @cindex file name canonicalization
19798 @cindex base name differences
19799 When processing file names provided by the user, @value{GDBN}
19800 frequently needs to compare them to the file names recorded in the
19801 program's debug info. Normally, @value{GDBN} compares just the
19802 @dfn{base names} of the files as strings, which is reasonably fast
19803 even for very large programs. (The base name of a file is the last
19804 portion of its name, after stripping all the leading directories.)
19805 This shortcut in comparison is based upon the assumption that files
19806 cannot have more than one base name. This is usually true, but
19807 references to files that use symlinks or similar filesystem
19808 facilities violate that assumption. If your program records files
19809 using such facilities, or if you provide file names to @value{GDBN}
19810 using symlinks etc., you can set @code{basenames-may-differ} to
19811 @code{true} to instruct @value{GDBN} to completely canonicalize each
19812 pair of file names it needs to compare. This will make file-name
19813 comparisons accurate, but at a price of a significant slowdown.
19816 @item set basenames-may-differ
19817 @kindex set basenames-may-differ
19818 Set whether a source file may have multiple base names.
19820 @item show basenames-may-differ
19821 @kindex show basenames-may-differ
19822 Show whether a source file may have multiple base names.
19826 @section File Caching
19827 @cindex caching of opened files
19828 @cindex caching of bfd objects
19830 To speed up file loading, and reduce memory usage, @value{GDBN} will
19831 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19832 BFD, bfd, The Binary File Descriptor Library}. The following commands
19833 allow visibility and control of the caching behavior.
19836 @kindex maint info bfds
19837 @item maint info bfds
19838 This prints information about each @code{bfd} object that is known to
19841 @kindex maint set bfd-sharing
19842 @kindex maint show bfd-sharing
19843 @kindex bfd caching
19844 @item maint set bfd-sharing
19845 @item maint show bfd-sharing
19846 Control whether @code{bfd} objects can be shared. When sharing is
19847 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19848 than reopening the same file. Turning sharing off does not cause
19849 already shared @code{bfd} objects to be unshared, but all future files
19850 that are opened will create a new @code{bfd} object. Similarly,
19851 re-enabling sharing does not cause multiple existing @code{bfd}
19852 objects to be collapsed into a single shared @code{bfd} object.
19854 @kindex set debug bfd-cache @var{level}
19855 @kindex bfd caching
19856 @item set debug bfd-cache @var{level}
19857 Turns on debugging of the bfd cache, setting the level to @var{level}.
19859 @kindex show debug bfd-cache
19860 @kindex bfd caching
19861 @item show debug bfd-cache
19862 Show the current debugging level of the bfd cache.
19865 @node Separate Debug Files
19866 @section Debugging Information in Separate Files
19867 @cindex separate debugging information files
19868 @cindex debugging information in separate files
19869 @cindex @file{.debug} subdirectories
19870 @cindex debugging information directory, global
19871 @cindex global debugging information directories
19872 @cindex build ID, and separate debugging files
19873 @cindex @file{.build-id} directory
19875 @value{GDBN} allows you to put a program's debugging information in a
19876 file separate from the executable itself, in a way that allows
19877 @value{GDBN} to find and load the debugging information automatically.
19878 Since debugging information can be very large---sometimes larger
19879 than the executable code itself---some systems distribute debugging
19880 information for their executables in separate files, which users can
19881 install only when they need to debug a problem.
19883 @value{GDBN} supports two ways of specifying the separate debug info
19888 The executable contains a @dfn{debug link} that specifies the name of
19889 the separate debug info file. The separate debug file's name is
19890 usually @file{@var{executable}.debug}, where @var{executable} is the
19891 name of the corresponding executable file without leading directories
19892 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19893 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19894 checksum for the debug file, which @value{GDBN} uses to validate that
19895 the executable and the debug file came from the same build.
19898 The executable contains a @dfn{build ID}, a unique bit string that is
19899 also present in the corresponding debug info file. (This is supported
19900 only on some operating systems, when using the ELF or PE file formats
19901 for binary files and the @sc{gnu} Binutils.) For more details about
19902 this feature, see the description of the @option{--build-id}
19903 command-line option in @ref{Options, , Command Line Options, ld,
19904 The GNU Linker}. The debug info file's name is not specified
19905 explicitly by the build ID, but can be computed from the build ID, see
19909 Depending on the way the debug info file is specified, @value{GDBN}
19910 uses two different methods of looking for the debug file:
19914 For the ``debug link'' method, @value{GDBN} looks up the named file in
19915 the directory of the executable file, then in a subdirectory of that
19916 directory named @file{.debug}, and finally under each one of the global debug
19917 directories, in a subdirectory whose name is identical to the leading
19918 directories of the executable's absolute file name.
19921 For the ``build ID'' method, @value{GDBN} looks in the
19922 @file{.build-id} subdirectory of each one of the global debug directories for
19923 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19924 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19925 are the rest of the bit string. (Real build ID strings are 32 or more
19926 hex characters, not 10.)
19929 So, for example, suppose you ask @value{GDBN} to debug
19930 @file{/usr/bin/ls}, which has a debug link that specifies the
19931 file @file{ls.debug}, and a build ID whose value in hex is
19932 @code{abcdef1234}. If the list of the global debug directories includes
19933 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19934 debug information files, in the indicated order:
19938 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19940 @file{/usr/bin/ls.debug}
19942 @file{/usr/bin/.debug/ls.debug}
19944 @file{/usr/lib/debug/usr/bin/ls.debug}.
19947 @anchor{debug-file-directory}
19948 Global debugging info directories default to what is set by @value{GDBN}
19949 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19950 you can also set the global debugging info directories, and view the list
19951 @value{GDBN} is currently using.
19955 @kindex set debug-file-directory
19956 @item set debug-file-directory @var{directories}
19957 Set the directories which @value{GDBN} searches for separate debugging
19958 information files to @var{directory}. Multiple path components can be set
19959 concatenating them by a path separator.
19961 @kindex show debug-file-directory
19962 @item show debug-file-directory
19963 Show the directories @value{GDBN} searches for separate debugging
19968 @cindex @code{.gnu_debuglink} sections
19969 @cindex debug link sections
19970 A debug link is a special section of the executable file named
19971 @code{.gnu_debuglink}. The section must contain:
19975 A filename, with any leading directory components removed, followed by
19978 zero to three bytes of padding, as needed to reach the next four-byte
19979 boundary within the section, and
19981 a four-byte CRC checksum, stored in the same endianness used for the
19982 executable file itself. The checksum is computed on the debugging
19983 information file's full contents by the function given below, passing
19984 zero as the @var{crc} argument.
19987 Any executable file format can carry a debug link, as long as it can
19988 contain a section named @code{.gnu_debuglink} with the contents
19991 @cindex @code{.note.gnu.build-id} sections
19992 @cindex build ID sections
19993 The build ID is a special section in the executable file (and in other
19994 ELF binary files that @value{GDBN} may consider). This section is
19995 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19996 It contains unique identification for the built files---the ID remains
19997 the same across multiple builds of the same build tree. The default
19998 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19999 content for the build ID string. The same section with an identical
20000 value is present in the original built binary with symbols, in its
20001 stripped variant, and in the separate debugging information file.
20003 The debugging information file itself should be an ordinary
20004 executable, containing a full set of linker symbols, sections, and
20005 debugging information. The sections of the debugging information file
20006 should have the same names, addresses, and sizes as the original file,
20007 but they need not contain any data---much like a @code{.bss} section
20008 in an ordinary executable.
20010 The @sc{gnu} binary utilities (Binutils) package includes the
20011 @samp{objcopy} utility that can produce
20012 the separated executable / debugging information file pairs using the
20013 following commands:
20016 @kbd{objcopy --only-keep-debug foo foo.debug}
20021 These commands remove the debugging
20022 information from the executable file @file{foo} and place it in the file
20023 @file{foo.debug}. You can use the first, second or both methods to link the
20028 The debug link method needs the following additional command to also leave
20029 behind a debug link in @file{foo}:
20032 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20035 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20036 a version of the @code{strip} command such that the command @kbd{strip foo -f
20037 foo.debug} has the same functionality as the two @code{objcopy} commands and
20038 the @code{ln -s} command above, together.
20041 Build ID gets embedded into the main executable using @code{ld --build-id} or
20042 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20043 compatibility fixes for debug files separation are present in @sc{gnu} binary
20044 utilities (Binutils) package since version 2.18.
20049 @cindex CRC algorithm definition
20050 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20051 IEEE 802.3 using the polynomial:
20053 @c TexInfo requires naked braces for multi-digit exponents for Tex
20054 @c output, but this causes HTML output to barf. HTML has to be set using
20055 @c raw commands. So we end up having to specify this equation in 2
20060 <em>x</em><sup>32</sup> + <em>x</em><sup>26</sup> + <em>x</em><sup>23</sup> + <em>x</em><sup>22</sup> + <em>x</em><sup>16</sup> + <em>x</em><sup>12</sup> + <em>x</em><sup>11</sup>
20061 + <em>x</em><sup>10</sup> + <em>x</em><sup>8</sup> + <em>x</em><sup>7</sup> + <em>x</em><sup>5</sup> + <em>x</em><sup>4</sup> + <em>x</em><sup>2</sup> + <em>x</em> + 1
20067 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20068 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20072 The function is computed byte at a time, taking the least
20073 significant bit of each byte first. The initial pattern
20074 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20075 the final result is inverted to ensure trailing zeros also affect the
20078 @emph{Note:} This is the same CRC polynomial as used in handling the
20079 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20080 However in the case of the Remote Serial Protocol, the CRC is computed
20081 @emph{most} significant bit first, and the result is not inverted, so
20082 trailing zeros have no effect on the CRC value.
20084 To complete the description, we show below the code of the function
20085 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20086 initially supplied @code{crc} argument means that an initial call to
20087 this function passing in zero will start computing the CRC using
20090 @kindex gnu_debuglink_crc32
20093 gnu_debuglink_crc32 (unsigned long crc,
20094 unsigned char *buf, size_t len)
20096 static const unsigned long crc32_table[256] =
20098 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20099 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20100 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20101 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20102 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20103 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20104 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20105 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20106 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20107 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20108 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20109 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20110 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20111 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20112 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20113 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20114 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20115 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20116 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20117 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20118 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20119 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20120 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20121 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20122 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20123 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20124 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20125 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20126 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20127 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20128 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20129 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20130 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20131 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20132 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20133 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20134 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20135 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20136 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20137 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20138 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20139 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20140 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20141 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20142 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20143 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20144 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20145 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20146 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20147 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20148 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20151 unsigned char *end;
20153 crc = ~crc & 0xffffffff;
20154 for (end = buf + len; buf < end; ++buf)
20155 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20156 return ~crc & 0xffffffff;
20161 This computation does not apply to the ``build ID'' method.
20163 @node MiniDebugInfo
20164 @section Debugging information in a special section
20165 @cindex separate debug sections
20166 @cindex @samp{.gnu_debugdata} section
20168 Some systems ship pre-built executables and libraries that have a
20169 special @samp{.gnu_debugdata} section. This feature is called
20170 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20171 is used to supply extra symbols for backtraces.
20173 The intent of this section is to provide extra minimal debugging
20174 information for use in simple backtraces. It is not intended to be a
20175 replacement for full separate debugging information (@pxref{Separate
20176 Debug Files}). The example below shows the intended use; however,
20177 @value{GDBN} does not currently put restrictions on what sort of
20178 debugging information might be included in the section.
20180 @value{GDBN} has support for this extension. If the section exists,
20181 then it is used provided that no other source of debugging information
20182 can be found, and that @value{GDBN} was configured with LZMA support.
20184 This section can be easily created using @command{objcopy} and other
20185 standard utilities:
20188 # Extract the dynamic symbols from the main binary, there is no need
20189 # to also have these in the normal symbol table.
20190 nm -D @var{binary} --format=posix --defined-only \
20191 | awk '@{ print $1 @}' | sort > dynsyms
20193 # Extract all the text (i.e. function) symbols from the debuginfo.
20194 # (Note that we actually also accept "D" symbols, for the benefit
20195 # of platforms like PowerPC64 that use function descriptors.)
20196 nm @var{binary} --format=posix --defined-only \
20197 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20200 # Keep all the function symbols not already in the dynamic symbol
20202 comm -13 dynsyms funcsyms > keep_symbols
20204 # Separate full debug info into debug binary.
20205 objcopy --only-keep-debug @var{binary} debug
20207 # Copy the full debuginfo, keeping only a minimal set of symbols and
20208 # removing some unnecessary sections.
20209 objcopy -S --remove-section .gdb_index --remove-section .comment \
20210 --keep-symbols=keep_symbols debug mini_debuginfo
20212 # Drop the full debug info from the original binary.
20213 strip --strip-all -R .comment @var{binary}
20215 # Inject the compressed data into the .gnu_debugdata section of the
20218 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20222 @section Index Files Speed Up @value{GDBN}
20223 @cindex index files
20224 @cindex @samp{.gdb_index} section
20226 When @value{GDBN} finds a symbol file, it scans the symbols in the
20227 file in order to construct an internal symbol table. This lets most
20228 @value{GDBN} operations work quickly---at the cost of a delay early
20229 on. For large programs, this delay can be quite lengthy, so
20230 @value{GDBN} provides a way to build an index, which speeds up
20233 For convenience, @value{GDBN} comes with a program,
20234 @command{gdb-add-index}, which can be used to add the index to a
20235 symbol file. It takes the symbol file as its only argument:
20238 $ gdb-add-index symfile
20241 @xref{gdb-add-index}.
20243 It is also possible to do the work manually. Here is what
20244 @command{gdb-add-index} does behind the curtains.
20246 The index is stored as a section in the symbol file. @value{GDBN} can
20247 write the index to a file, then you can put it into the symbol file
20248 using @command{objcopy}.
20250 To create an index file, use the @code{save gdb-index} command:
20253 @item save gdb-index [-dwarf-5] @var{directory}
20254 @kindex save gdb-index
20255 Create index files for all symbol files currently known by
20256 @value{GDBN}. For each known @var{symbol-file}, this command by
20257 default creates it produces a single file
20258 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20259 the @option{-dwarf-5} option, it produces 2 files:
20260 @file{@var{symbol-file}.debug_names} and
20261 @file{@var{symbol-file}.debug_str}. The files are created in the
20262 given @var{directory}.
20265 Once you have created an index file you can merge it into your symbol
20266 file, here named @file{symfile}, using @command{objcopy}:
20269 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20270 --set-section-flags .gdb_index=readonly symfile symfile
20273 Or for @code{-dwarf-5}:
20276 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20277 $ cat symfile.debug_str >>symfile.debug_str.new
20278 $ objcopy --add-section .debug_names=symfile.gdb-index \
20279 --set-section-flags .debug_names=readonly \
20280 --update-section .debug_str=symfile.debug_str.new symfile symfile
20283 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20284 sections that have been deprecated. Usually they are deprecated because
20285 they are missing a new feature or have performance issues.
20286 To tell @value{GDBN} to use a deprecated index section anyway
20287 specify @code{set use-deprecated-index-sections on}.
20288 The default is @code{off}.
20289 This can speed up startup, but may result in some functionality being lost.
20290 @xref{Index Section Format}.
20292 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20293 must be done before gdb reads the file. The following will not work:
20296 $ gdb -ex "set use-deprecated-index-sections on" <program>
20299 Instead you must do, for example,
20302 $ gdb -iex "set use-deprecated-index-sections on" <program>
20305 There are currently some limitation on indices. They only work when
20306 for DWARF debugging information, not stabs. And, they do not
20307 currently work for programs using Ada.
20309 @subsection Automatic symbol index cache
20311 It is possible for @value{GDBN} to automatically save a copy of this index in a
20312 cache on disk and retrieve it from there when loading the same binary in the
20313 future. This feature can be turned on with @kbd{set index-cache on}. The
20314 following commands can be used to tweak the behavior of the index cache.
20318 @item set index-cache on
20319 @itemx set index-cache off
20320 Enable or disable the use of the symbol index cache.
20322 @item set index-cache directory @var{directory}
20323 @itemx show index-cache directory
20324 Set/show the directory where index files will be saved.
20326 The default value for this directory depends on the host platform. On
20327 most systems, the index is cached in the @file{gdb} subdirectory of
20328 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20329 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20330 of your home directory. However, on some systems, the default may
20331 differ according to local convention.
20333 There is no limit on the disk space used by index cache. It is perfectly safe
20334 to delete the content of that directory to free up disk space.
20336 @item show index-cache stats
20337 Print the number of cache hits and misses since the launch of @value{GDBN}.
20341 @node Symbol Errors
20342 @section Errors Reading Symbol Files
20344 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20345 such as symbol types it does not recognize, or known bugs in compiler
20346 output. By default, @value{GDBN} does not notify you of such problems, since
20347 they are relatively common and primarily of interest to people
20348 debugging compilers. If you are interested in seeing information
20349 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20350 only one message about each such type of problem, no matter how many
20351 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20352 to see how many times the problems occur, with the @code{set
20353 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20356 The messages currently printed, and their meanings, include:
20359 @item inner block not inside outer block in @var{symbol}
20361 The symbol information shows where symbol scopes begin and end
20362 (such as at the start of a function or a block of statements). This
20363 error indicates that an inner scope block is not fully contained
20364 in its outer scope blocks.
20366 @value{GDBN} circumvents the problem by treating the inner block as if it had
20367 the same scope as the outer block. In the error message, @var{symbol}
20368 may be shown as ``@code{(don't know)}'' if the outer block is not a
20371 @item block at @var{address} out of order
20373 The symbol information for symbol scope blocks should occur in
20374 order of increasing addresses. This error indicates that it does not
20377 @value{GDBN} does not circumvent this problem, and has trouble
20378 locating symbols in the source file whose symbols it is reading. (You
20379 can often determine what source file is affected by specifying
20380 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20383 @item bad block start address patched
20385 The symbol information for a symbol scope block has a start address
20386 smaller than the address of the preceding source line. This is known
20387 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20389 @value{GDBN} circumvents the problem by treating the symbol scope block as
20390 starting on the previous source line.
20392 @item bad string table offset in symbol @var{n}
20395 Symbol number @var{n} contains a pointer into the string table which is
20396 larger than the size of the string table.
20398 @value{GDBN} circumvents the problem by considering the symbol to have the
20399 name @code{foo}, which may cause other problems if many symbols end up
20402 @item unknown symbol type @code{0x@var{nn}}
20404 The symbol information contains new data types that @value{GDBN} does
20405 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20406 uncomprehended information, in hexadecimal.
20408 @value{GDBN} circumvents the error by ignoring this symbol information.
20409 This usually allows you to debug your program, though certain symbols
20410 are not accessible. If you encounter such a problem and feel like
20411 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20412 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20413 and examine @code{*bufp} to see the symbol.
20415 @item stub type has NULL name
20417 @value{GDBN} could not find the full definition for a struct or class.
20419 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20420 The symbol information for a C@t{++} member function is missing some
20421 information that recent versions of the compiler should have output for
20424 @item info mismatch between compiler and debugger
20426 @value{GDBN} could not parse a type specification output by the compiler.
20431 @section GDB Data Files
20433 @cindex prefix for data files
20434 @value{GDBN} will sometimes read an auxiliary data file. These files
20435 are kept in a directory known as the @dfn{data directory}.
20437 You can set the data directory's name, and view the name @value{GDBN}
20438 is currently using.
20441 @kindex set data-directory
20442 @item set data-directory @var{directory}
20443 Set the directory which @value{GDBN} searches for auxiliary data files
20444 to @var{directory}.
20446 @kindex show data-directory
20447 @item show data-directory
20448 Show the directory @value{GDBN} searches for auxiliary data files.
20451 @cindex default data directory
20452 @cindex @samp{--with-gdb-datadir}
20453 You can set the default data directory by using the configure-time
20454 @samp{--with-gdb-datadir} option. If the data directory is inside
20455 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20456 @samp{--exec-prefix}), then the default data directory will be updated
20457 automatically if the installed @value{GDBN} is moved to a new
20460 The data directory may also be specified with the
20461 @code{--data-directory} command line option.
20462 @xref{Mode Options}.
20465 @chapter Specifying a Debugging Target
20467 @cindex debugging target
20468 A @dfn{target} is the execution environment occupied by your program.
20470 Often, @value{GDBN} runs in the same host environment as your program;
20471 in that case, the debugging target is specified as a side effect when
20472 you use the @code{file} or @code{core} commands. When you need more
20473 flexibility---for example, running @value{GDBN} on a physically separate
20474 host, or controlling a standalone system over a serial port or a
20475 realtime system over a TCP/IP connection---you can use the @code{target}
20476 command to specify one of the target types configured for @value{GDBN}
20477 (@pxref{Target Commands, ,Commands for Managing Targets}).
20479 @cindex target architecture
20480 It is possible to build @value{GDBN} for several different @dfn{target
20481 architectures}. When @value{GDBN} is built like that, you can choose
20482 one of the available architectures with the @kbd{set architecture}
20486 @kindex set architecture
20487 @kindex show architecture
20488 @item set architecture @var{arch}
20489 This command sets the current target architecture to @var{arch}. The
20490 value of @var{arch} can be @code{"auto"}, in addition to one of the
20491 supported architectures.
20493 @item show architecture
20494 Show the current target architecture.
20496 @item set processor
20498 @kindex set processor
20499 @kindex show processor
20500 These are alias commands for, respectively, @code{set architecture}
20501 and @code{show architecture}.
20505 * Active Targets:: Active targets
20506 * Target Commands:: Commands for managing targets
20507 * Byte Order:: Choosing target byte order
20510 @node Active Targets
20511 @section Active Targets
20513 @cindex stacking targets
20514 @cindex active targets
20515 @cindex multiple targets
20517 There are multiple classes of targets such as: processes, executable files or
20518 recording sessions. Core files belong to the process class, making core file
20519 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20520 on multiple active targets, one in each class. This allows you to (for
20521 example) start a process and inspect its activity, while still having access to
20522 the executable file after the process finishes. Or if you start process
20523 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20524 presented a virtual layer of the recording target, while the process target
20525 remains stopped at the chronologically last point of the process execution.
20527 Use the @code{core-file} and @code{exec-file} commands to select a new core
20528 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20529 specify as a target a process that is already running, use the @code{attach}
20530 command (@pxref{Attach, ,Debugging an Already-running Process}).
20532 @node Target Commands
20533 @section Commands for Managing Targets
20536 @item target @var{type} @var{parameters}
20537 Connects the @value{GDBN} host environment to a target machine or
20538 process. A target is typically a protocol for talking to debugging
20539 facilities. You use the argument @var{type} to specify the type or
20540 protocol of the target machine.
20542 Further @var{parameters} are interpreted by the target protocol, but
20543 typically include things like device names or host names to connect
20544 with, process numbers, and baud rates.
20546 The @code{target} command does not repeat if you press @key{RET} again
20547 after executing the command.
20549 @kindex help target
20551 Displays the names of all targets available. To display targets
20552 currently selected, use either @code{info target} or @code{info files}
20553 (@pxref{Files, ,Commands to Specify Files}).
20555 @item help target @var{name}
20556 Describe a particular target, including any parameters necessary to
20559 @kindex set gnutarget
20560 @item set gnutarget @var{args}
20561 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20562 knows whether it is reading an @dfn{executable},
20563 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20564 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20565 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20568 @emph{Warning:} To specify a file format with @code{set gnutarget},
20569 you must know the actual BFD name.
20573 @xref{Files, , Commands to Specify Files}.
20575 @kindex show gnutarget
20576 @item show gnutarget
20577 Use the @code{show gnutarget} command to display what file format
20578 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20579 @value{GDBN} will determine the file format for each file automatically,
20580 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20583 @cindex common targets
20584 Here are some common targets (available, or not, depending on the GDB
20589 @item target exec @var{program}
20590 @cindex executable file target
20591 An executable file. @samp{target exec @var{program}} is the same as
20592 @samp{exec-file @var{program}}.
20594 @item target core @var{filename}
20595 @cindex core dump file target
20596 A core dump file. @samp{target core @var{filename}} is the same as
20597 @samp{core-file @var{filename}}.
20599 @item target remote @var{medium}
20600 @cindex remote target
20601 A remote system connected to @value{GDBN} via a serial line or network
20602 connection. This command tells @value{GDBN} to use its own remote
20603 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20605 For example, if you have a board connected to @file{/dev/ttya} on the
20606 machine running @value{GDBN}, you could say:
20609 target remote /dev/ttya
20612 @code{target remote} supports the @code{load} command. This is only
20613 useful if you have some other way of getting the stub to the target
20614 system, and you can put it somewhere in memory where it won't get
20615 clobbered by the download.
20617 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20618 @cindex built-in simulator target
20619 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20627 works; however, you cannot assume that a specific memory map, device
20628 drivers, or even basic I/O is available, although some simulators do
20629 provide these. For info about any processor-specific simulator details,
20630 see the appropriate section in @ref{Embedded Processors, ,Embedded
20633 @item target native
20634 @cindex native target
20635 Setup for local/native process debugging. Useful to make the
20636 @code{run} command spawn native processes (likewise @code{attach},
20637 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20638 (@pxref{set auto-connect-native-target}).
20642 Different targets are available on different configurations of @value{GDBN};
20643 your configuration may have more or fewer targets.
20645 Many remote targets require you to download the executable's code once
20646 you've successfully established a connection. You may wish to control
20647 various aspects of this process.
20652 @kindex set hash@r{, for remote monitors}
20653 @cindex hash mark while downloading
20654 This command controls whether a hash mark @samp{#} is displayed while
20655 downloading a file to the remote monitor. If on, a hash mark is
20656 displayed after each S-record is successfully downloaded to the
20660 @kindex show hash@r{, for remote monitors}
20661 Show the current status of displaying the hash mark.
20663 @item set debug monitor
20664 @kindex set debug monitor
20665 @cindex display remote monitor communications
20666 Enable or disable display of communications messages between
20667 @value{GDBN} and the remote monitor.
20669 @item show debug monitor
20670 @kindex show debug monitor
20671 Show the current status of displaying communications between
20672 @value{GDBN} and the remote monitor.
20677 @kindex load @var{filename} @var{offset}
20678 @item load @var{filename} @var{offset}
20680 Depending on what remote debugging facilities are configured into
20681 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20682 is meant to make @var{filename} (an executable) available for debugging
20683 on the remote system---by downloading, or dynamic linking, for example.
20684 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20685 the @code{add-symbol-file} command.
20687 If your @value{GDBN} does not have a @code{load} command, attempting to
20688 execute it gets the error message ``@code{You can't do that when your
20689 target is @dots{}}''
20691 The file is loaded at whatever address is specified in the executable.
20692 For some object file formats, you can specify the load address when you
20693 link the program; for other formats, like a.out, the object file format
20694 specifies a fixed address.
20695 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20697 It is also possible to tell @value{GDBN} to load the executable file at a
20698 specific offset described by the optional argument @var{offset}. When
20699 @var{offset} is provided, @var{filename} must also be provided.
20701 Depending on the remote side capabilities, @value{GDBN} may be able to
20702 load programs into flash memory.
20704 @code{load} does not repeat if you press @key{RET} again after using it.
20709 @kindex flash-erase
20711 @anchor{flash-erase}
20713 Erases all known flash memory regions on the target.
20718 @section Choosing Target Byte Order
20720 @cindex choosing target byte order
20721 @cindex target byte order
20723 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20724 offer the ability to run either big-endian or little-endian byte
20725 orders. Usually the executable or symbol will include a bit to
20726 designate the endian-ness, and you will not need to worry about
20727 which to use. However, you may still find it useful to adjust
20728 @value{GDBN}'s idea of processor endian-ness manually.
20732 @item set endian big
20733 Instruct @value{GDBN} to assume the target is big-endian.
20735 @item set endian little
20736 Instruct @value{GDBN} to assume the target is little-endian.
20738 @item set endian auto
20739 Instruct @value{GDBN} to use the byte order associated with the
20743 Display @value{GDBN}'s current idea of the target byte order.
20747 If the @code{set endian auto} mode is in effect and no executable has
20748 been selected, then the endianness used is the last one chosen either
20749 by one of the @code{set endian big} and @code{set endian little}
20750 commands or by inferring from the last executable used. If no
20751 endianness has been previously chosen, then the default for this mode
20752 is inferred from the target @value{GDBN} has been built for, and is
20753 @code{little} if the name of the target CPU has an @code{el} suffix
20754 and @code{big} otherwise.
20756 Note that these commands merely adjust interpretation of symbolic
20757 data on the host, and that they have absolutely no effect on the
20761 @node Remote Debugging
20762 @chapter Debugging Remote Programs
20763 @cindex remote debugging
20765 If you are trying to debug a program running on a machine that cannot run
20766 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20767 For example, you might use remote debugging on an operating system kernel,
20768 or on a small system which does not have a general purpose operating system
20769 powerful enough to run a full-featured debugger.
20771 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20772 to make this work with particular debugging targets. In addition,
20773 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20774 but not specific to any particular target system) which you can use if you
20775 write the remote stubs---the code that runs on the remote system to
20776 communicate with @value{GDBN}.
20778 Other remote targets may be available in your
20779 configuration of @value{GDBN}; use @code{help target} to list them.
20782 * Connecting:: Connecting to a remote target
20783 * File Transfer:: Sending files to a remote system
20784 * Server:: Using the gdbserver program
20785 * Remote Configuration:: Remote configuration
20786 * Remote Stub:: Implementing a remote stub
20790 @section Connecting to a Remote Target
20791 @cindex remote debugging, connecting
20792 @cindex @code{gdbserver}, connecting
20793 @cindex remote debugging, types of connections
20794 @cindex @code{gdbserver}, types of connections
20795 @cindex @code{gdbserver}, @code{target remote} mode
20796 @cindex @code{gdbserver}, @code{target extended-remote} mode
20798 This section describes how to connect to a remote target, including the
20799 types of connections and their differences, how to set up executable and
20800 symbol files on the host and target, and the commands used for
20801 connecting to and disconnecting from the remote target.
20803 @subsection Types of Remote Connections
20805 @value{GDBN} supports two types of remote connections, @code{target remote}
20806 mode and @code{target extended-remote} mode. Note that many remote targets
20807 support only @code{target remote} mode. There are several major
20808 differences between the two types of connections, enumerated here:
20812 @cindex remote debugging, detach and program exit
20813 @item Result of detach or program exit
20814 @strong{With target remote mode:} When the debugged program exits or you
20815 detach from it, @value{GDBN} disconnects from the target. When using
20816 @code{gdbserver}, @code{gdbserver} will exit.
20818 @strong{With target extended-remote mode:} When the debugged program exits or
20819 you detach from it, @value{GDBN} remains connected to the target, even
20820 though no program is running. You can rerun the program, attach to a
20821 running program, or use @code{monitor} commands specific to the target.
20823 When using @code{gdbserver} in this case, it does not exit unless it was
20824 invoked using the @option{--once} option. If the @option{--once} option
20825 was not used, you can ask @code{gdbserver} to exit using the
20826 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20828 @item Specifying the program to debug
20829 For both connection types you use the @code{file} command to specify the
20830 program on the host system. If you are using @code{gdbserver} there are
20831 some differences in how to specify the location of the program on the
20834 @strong{With target remote mode:} You must either specify the program to debug
20835 on the @code{gdbserver} command line or use the @option{--attach} option
20836 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20838 @cindex @option{--multi}, @code{gdbserver} option
20839 @strong{With target extended-remote mode:} You may specify the program to debug
20840 on the @code{gdbserver} command line, or you can load the program or attach
20841 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20843 @anchor{--multi Option in Types of Remote Connnections}
20844 You can start @code{gdbserver} without supplying an initial command to run
20845 or process ID to attach. To do this, use the @option{--multi} command line
20846 option. Then you can connect using @code{target extended-remote} and start
20847 the program you want to debug (see below for details on using the
20848 @code{run} command in this scenario). Note that the conditions under which
20849 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20850 (@code{target remote} or @code{target extended-remote}). The
20851 @option{--multi} option to @code{gdbserver} has no influence on that.
20853 @item The @code{run} command
20854 @strong{With target remote mode:} The @code{run} command is not
20855 supported. Once a connection has been established, you can use all
20856 the usual @value{GDBN} commands to examine and change data. The
20857 remote program is already running, so you can use commands like
20858 @kbd{step} and @kbd{continue}.
20860 @strong{With target extended-remote mode:} The @code{run} command is
20861 supported. The @code{run} command uses the value set by
20862 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20863 the program to run. Command line arguments are supported, except for
20864 wildcard expansion and I/O redirection (@pxref{Arguments}).
20866 If you specify the program to debug on the command line, then the
20867 @code{run} command is not required to start execution, and you can
20868 resume using commands like @kbd{step} and @kbd{continue} as with
20869 @code{target remote} mode.
20871 @anchor{Attaching in Types of Remote Connections}
20873 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20874 not supported. To attach to a running program using @code{gdbserver}, you
20875 must use the @option{--attach} option (@pxref{Running gdbserver}).
20877 @strong{With target extended-remote mode:} To attach to a running program,
20878 you may use the @code{attach} command after the connection has been
20879 established. If you are using @code{gdbserver}, you may also invoke
20880 @code{gdbserver} using the @option{--attach} option
20881 (@pxref{Running gdbserver}).
20885 @anchor{Host and target files}
20886 @subsection Host and Target Files
20887 @cindex remote debugging, symbol files
20888 @cindex symbol files, remote debugging
20890 @value{GDBN}, running on the host, needs access to symbol and debugging
20891 information for your program running on the target. This requires
20892 access to an unstripped copy of your program, and possibly any associated
20893 symbol files. Note that this section applies equally to both @code{target
20894 remote} mode and @code{target extended-remote} mode.
20896 Some remote targets (@pxref{qXfer executable filename read}, and
20897 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20898 the same connection used to communicate with @value{GDBN}. With such a
20899 target, if the remote program is unstripped, the only command you need is
20900 @code{target remote} (or @code{target extended-remote}).
20902 If the remote program is stripped, or the target does not support remote
20903 program file access, start up @value{GDBN} using the name of the local
20904 unstripped copy of your program as the first argument, or use the
20905 @code{file} command. Use @code{set sysroot} to specify the location (on
20906 the host) of target libraries (unless your @value{GDBN} was compiled with
20907 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20908 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20911 The symbol file and target libraries must exactly match the executable
20912 and libraries on the target, with one exception: the files on the host
20913 system should not be stripped, even if the files on the target system
20914 are. Mismatched or missing files will lead to confusing results
20915 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20916 files may also prevent @code{gdbserver} from debugging multi-threaded
20919 @subsection Remote Connection Commands
20920 @cindex remote connection commands
20921 @value{GDBN} can communicate with the target over a serial line, a
20922 local Unix domain socket, or
20923 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20924 each case, @value{GDBN} uses the same protocol for debugging your
20925 program; only the medium carrying the debugging packets varies. The
20926 @code{target remote} and @code{target extended-remote} commands
20927 establish a connection to the target. Both commands accept the same
20928 arguments, which indicate the medium to use:
20932 @item target remote @var{serial-device}
20933 @itemx target extended-remote @var{serial-device}
20934 @cindex serial line, @code{target remote}
20935 Use @var{serial-device} to communicate with the target. For example,
20936 to use a serial line connected to the device named @file{/dev/ttyb}:
20939 target remote /dev/ttyb
20942 If you're using a serial line, you may want to give @value{GDBN} the
20943 @samp{--baud} option, or use the @code{set serial baud} command
20944 (@pxref{Remote Configuration, set serial baud}) before the
20945 @code{target} command.
20947 @item target remote @var{local-socket}
20948 @itemx target extended-remote @var{local-socket}
20949 @cindex local socket, @code{target remote}
20950 @cindex Unix domain socket
20951 Use @var{local-socket} to communicate with the target. For example,
20952 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20955 target remote /tmp/gdb-socket0
20958 Note that this command has the same form as the command to connect
20959 to a serial line. @value{GDBN} will automatically determine which
20960 kind of file you have specified and will make the appropriate kind
20962 This feature is not available if the host system does not support
20963 Unix domain sockets.
20965 @item target remote @code{@var{host}:@var{port}}
20966 @itemx target remote @code{@var{[host]}:@var{port}}
20967 @itemx target remote @code{tcp:@var{host}:@var{port}}
20968 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20969 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20970 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20971 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20972 @itemx target extended-remote @code{@var{host}:@var{port}}
20973 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20974 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20975 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20976 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20977 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20978 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20979 @cindex @acronym{TCP} port, @code{target remote}
20980 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20981 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20982 address, or a numeric @acronym{IPv6} address (with or without the
20983 square brackets to separate the address from the port); @var{port}
20984 must be a decimal number. The @var{host} could be the target machine
20985 itself, if it is directly connected to the net, or it might be a
20986 terminal server which in turn has a serial line to the target.
20988 For example, to connect to port 2828 on a terminal server named
20992 target remote manyfarms:2828
20995 To connect to port 2828 on a terminal server whose address is
20996 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20997 square bracket syntax:
21000 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21004 or explicitly specify the @acronym{IPv6} protocol:
21007 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21010 This last example may be confusing to the reader, because there is no
21011 visible separation between the hostname and the port number.
21012 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21013 using square brackets for clarity. However, it is important to
21014 mention that for @value{GDBN} there is no ambiguity: the number after
21015 the last colon is considered to be the port number.
21017 If your remote target is actually running on the same machine as your
21018 debugger session (e.g.@: a simulator for your target running on the
21019 same host), you can omit the hostname. For example, to connect to
21020 port 1234 on your local machine:
21023 target remote :1234
21027 Note that the colon is still required here.
21029 @item target remote @code{udp:@var{host}:@var{port}}
21030 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21031 @itemx target remote @code{udp4:@var{host}:@var{port}}
21032 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21033 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21034 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21035 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21036 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21037 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21038 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21039 @cindex @acronym{UDP} port, @code{target remote}
21040 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21041 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21044 target remote udp:manyfarms:2828
21047 When using a @acronym{UDP} connection for remote debugging, you should
21048 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21049 can silently drop packets on busy or unreliable networks, which will
21050 cause havoc with your debugging session.
21052 @item target remote | @var{command}
21053 @itemx target extended-remote | @var{command}
21054 @cindex pipe, @code{target remote} to
21055 Run @var{command} in the background and communicate with it using a
21056 pipe. The @var{command} is a shell command, to be parsed and expanded
21057 by the system's command shell, @code{/bin/sh}; it should expect remote
21058 protocol packets on its standard input, and send replies on its
21059 standard output. You could use this to run a stand-alone simulator
21060 that speaks the remote debugging protocol, to make net connections
21061 using programs like @code{ssh}, or for other similar tricks.
21063 If @var{command} closes its standard output (perhaps by exiting),
21064 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21065 program has already exited, this will have no effect.)
21069 @cindex interrupting remote programs
21070 @cindex remote programs, interrupting
21071 Whenever @value{GDBN} is waiting for the remote program, if you type the
21072 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21073 program. This may or may not succeed, depending in part on the hardware
21074 and the serial drivers the remote system uses. If you type the
21075 interrupt character once again, @value{GDBN} displays this prompt:
21078 Interrupted while waiting for the program.
21079 Give up (and stop debugging it)? (y or n)
21082 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21083 the remote debugging session. (If you decide you want to try again later,
21084 you can use @kbd{target remote} again to connect once more.) If you type
21085 @kbd{n}, @value{GDBN} goes back to waiting.
21087 In @code{target extended-remote} mode, typing @kbd{n} will leave
21088 @value{GDBN} connected to the target.
21091 @kindex detach (remote)
21093 When you have finished debugging the remote program, you can use the
21094 @code{detach} command to release it from @value{GDBN} control.
21095 Detaching from the target normally resumes its execution, but the results
21096 will depend on your particular remote stub. After the @code{detach}
21097 command in @code{target remote} mode, @value{GDBN} is free to connect to
21098 another target. In @code{target extended-remote} mode, @value{GDBN} is
21099 still connected to the target.
21103 The @code{disconnect} command closes the connection to the target, and
21104 the target is generally not resumed. It will wait for @value{GDBN}
21105 (this instance or another one) to connect and continue debugging. After
21106 the @code{disconnect} command, @value{GDBN} is again free to connect to
21109 @cindex send command to remote monitor
21110 @cindex extend @value{GDBN} for remote targets
21111 @cindex add new commands for external monitor
21113 @item monitor @var{cmd}
21114 This command allows you to send arbitrary commands directly to the
21115 remote monitor. Since @value{GDBN} doesn't care about the commands it
21116 sends like this, this command is the way to extend @value{GDBN}---you
21117 can add new commands that only the external monitor will understand
21121 @node File Transfer
21122 @section Sending files to a remote system
21123 @cindex remote target, file transfer
21124 @cindex file transfer
21125 @cindex sending files to remote systems
21127 Some remote targets offer the ability to transfer files over the same
21128 connection used to communicate with @value{GDBN}. This is convenient
21129 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21130 running @code{gdbserver} over a network interface. For other targets,
21131 e.g.@: embedded devices with only a single serial port, this may be
21132 the only way to upload or download files.
21134 Not all remote targets support these commands.
21138 @item remote put @var{hostfile} @var{targetfile}
21139 Copy file @var{hostfile} from the host system (the machine running
21140 @value{GDBN}) to @var{targetfile} on the target system.
21143 @item remote get @var{targetfile} @var{hostfile}
21144 Copy file @var{targetfile} from the target system to @var{hostfile}
21145 on the host system.
21147 @kindex remote delete
21148 @item remote delete @var{targetfile}
21149 Delete @var{targetfile} from the target system.
21154 @section Using the @code{gdbserver} Program
21157 @cindex remote connection without stubs
21158 @code{gdbserver} is a control program for Unix-like systems, which
21159 allows you to connect your program with a remote @value{GDBN} via
21160 @code{target remote} or @code{target extended-remote}---but without
21161 linking in the usual debugging stub.
21163 @code{gdbserver} is not a complete replacement for the debugging stubs,
21164 because it requires essentially the same operating-system facilities
21165 that @value{GDBN} itself does. In fact, a system that can run
21166 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21167 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21168 because it is a much smaller program than @value{GDBN} itself. It is
21169 also easier to port than all of @value{GDBN}, so you may be able to get
21170 started more quickly on a new system by using @code{gdbserver}.
21171 Finally, if you develop code for real-time systems, you may find that
21172 the tradeoffs involved in real-time operation make it more convenient to
21173 do as much development work as possible on another system, for example
21174 by cross-compiling. You can use @code{gdbserver} to make a similar
21175 choice for debugging.
21177 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21178 or a TCP connection, using the standard @value{GDBN} remote serial
21182 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21183 Do not run @code{gdbserver} connected to any public network; a
21184 @value{GDBN} connection to @code{gdbserver} provides access to the
21185 target system with the same privileges as the user running
21189 @anchor{Running gdbserver}
21190 @subsection Running @code{gdbserver}
21191 @cindex arguments, to @code{gdbserver}
21192 @cindex @code{gdbserver}, command-line arguments
21194 Run @code{gdbserver} on the target system. You need a copy of the
21195 program you want to debug, including any libraries it requires.
21196 @code{gdbserver} does not need your program's symbol table, so you can
21197 strip the program if necessary to save space. @value{GDBN} on the host
21198 system does all the symbol handling.
21200 To use the server, you must tell it how to communicate with @value{GDBN};
21201 the name of your program; and the arguments for your program. The usual
21205 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21208 @var{comm} is either a device name (to use a serial line), or a TCP
21209 hostname and portnumber, or @code{-} or @code{stdio} to use
21210 stdin/stdout of @code{gdbserver}.
21211 For example, to debug Emacs with the argument
21212 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21216 target> gdbserver /dev/com1 emacs foo.txt
21219 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21222 To use a TCP connection instead of a serial line:
21225 target> gdbserver host:2345 emacs foo.txt
21228 The only difference from the previous example is the first argument,
21229 specifying that you are communicating with the host @value{GDBN} via
21230 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21231 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21232 (Currently, the @samp{host} part is ignored.) You can choose any number
21233 you want for the port number as long as it does not conflict with any
21234 TCP ports already in use on the target system (for example, @code{23} is
21235 reserved for @code{telnet}).@footnote{If you choose a port number that
21236 conflicts with another service, @code{gdbserver} prints an error message
21237 and exits.} You must use the same port number with the host @value{GDBN}
21238 @code{target remote} command.
21240 The @code{stdio} connection is useful when starting @code{gdbserver}
21244 (gdb) target remote | ssh -T hostname gdbserver - hello
21247 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21248 and we don't want escape-character handling. Ssh does this by default when
21249 a command is provided, the flag is provided to make it explicit.
21250 You could elide it if you want to.
21252 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21253 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21254 display through a pipe connected to gdbserver.
21255 Both @code{stdout} and @code{stderr} use the same pipe.
21257 @anchor{Attaching to a program}
21258 @subsubsection Attaching to a Running Program
21259 @cindex attach to a program, @code{gdbserver}
21260 @cindex @option{--attach}, @code{gdbserver} option
21262 On some targets, @code{gdbserver} can also attach to running programs.
21263 This is accomplished via the @code{--attach} argument. The syntax is:
21266 target> gdbserver --attach @var{comm} @var{pid}
21269 @var{pid} is the process ID of a currently running process. It isn't
21270 necessary to point @code{gdbserver} at a binary for the running process.
21272 In @code{target extended-remote} mode, you can also attach using the
21273 @value{GDBN} attach command
21274 (@pxref{Attaching in Types of Remote Connections}).
21277 You can debug processes by name instead of process ID if your target has the
21278 @code{pidof} utility:
21281 target> gdbserver --attach @var{comm} `pidof @var{program}`
21284 In case more than one copy of @var{program} is running, or @var{program}
21285 has multiple threads, most versions of @code{pidof} support the
21286 @code{-s} option to only return the first process ID.
21288 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21290 This section applies only when @code{gdbserver} is run to listen on a TCP
21293 @code{gdbserver} normally terminates after all of its debugged processes have
21294 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21295 extended-remote}, @code{gdbserver} stays running even with no processes left.
21296 @value{GDBN} normally terminates the spawned debugged process on its exit,
21297 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21298 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21299 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21300 stays running even in the @kbd{target remote} mode.
21302 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21303 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21304 completeness, at most one @value{GDBN} can be connected at a time.
21306 @cindex @option{--once}, @code{gdbserver} option
21307 By default, @code{gdbserver} keeps the listening TCP port open, so that
21308 subsequent connections are possible. However, if you start @code{gdbserver}
21309 with the @option{--once} option, it will stop listening for any further
21310 connection attempts after connecting to the first @value{GDBN} session. This
21311 means no further connections to @code{gdbserver} will be possible after the
21312 first one. It also means @code{gdbserver} will terminate after the first
21313 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21314 connections and even in the @kbd{target extended-remote} mode. The
21315 @option{--once} option allows reusing the same port number for connecting to
21316 multiple instances of @code{gdbserver} running on the same host, since each
21317 instance closes its port after the first connection.
21319 @anchor{Other Command-Line Arguments for gdbserver}
21320 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21322 You can use the @option{--multi} option to start @code{gdbserver} without
21323 specifying a program to debug or a process to attach to. Then you can
21324 attach in @code{target extended-remote} mode and run or attach to a
21325 program. For more information,
21326 @pxref{--multi Option in Types of Remote Connnections}.
21328 @cindex @option{--debug}, @code{gdbserver} option
21329 The @option{--debug} option tells @code{gdbserver} to display extra
21330 status information about the debugging process.
21331 @cindex @option{--remote-debug}, @code{gdbserver} option
21332 The @option{--remote-debug} option tells @code{gdbserver} to display
21333 remote protocol debug output. These options are intended for
21334 @code{gdbserver} development and for bug reports to the developers.
21336 @cindex @option{--debug-format}, @code{gdbserver} option
21337 The @option{--debug-format=option1[,option2,...]} option tells
21338 @code{gdbserver} to include additional information in each output.
21339 Possible options are:
21343 Turn off all extra information in debugging output.
21345 Turn on all extra information in debugging output.
21347 Include a timestamp in each line of debugging output.
21350 Options are processed in order. Thus, for example, if @option{none}
21351 appears last then no additional information is added to debugging output.
21353 @cindex @option{--wrapper}, @code{gdbserver} option
21354 The @option{--wrapper} option specifies a wrapper to launch programs
21355 for debugging. The option should be followed by the name of the
21356 wrapper, then any command-line arguments to pass to the wrapper, then
21357 @kbd{--} indicating the end of the wrapper arguments.
21359 @code{gdbserver} runs the specified wrapper program with a combined
21360 command line including the wrapper arguments, then the name of the
21361 program to debug, then any arguments to the program. The wrapper
21362 runs until it executes your program, and then @value{GDBN} gains control.
21364 You can use any program that eventually calls @code{execve} with
21365 its arguments as a wrapper. Several standard Unix utilities do
21366 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21367 with @code{exec "$@@"} will also work.
21369 For example, you can use @code{env} to pass an environment variable to
21370 the debugged program, without setting the variable in @code{gdbserver}'s
21374 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21377 @cindex @option{--selftest}
21378 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21381 $ gdbserver --selftest
21382 Ran 2 unit tests, 0 failed
21385 These tests are disabled in release.
21386 @subsection Connecting to @code{gdbserver}
21388 The basic procedure for connecting to the remote target is:
21392 Run @value{GDBN} on the host system.
21395 Make sure you have the necessary symbol files
21396 (@pxref{Host and target files}).
21397 Load symbols for your application using the @code{file} command before you
21398 connect. Use @code{set sysroot} to locate target libraries (unless your
21399 @value{GDBN} was compiled with the correct sysroot using
21400 @code{--with-sysroot}).
21403 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21404 For TCP connections, you must start up @code{gdbserver} prior to using
21405 the @code{target} command. Otherwise you may get an error whose
21406 text depends on the host system, but which usually looks something like
21407 @samp{Connection refused}. Don't use the @code{load}
21408 command in @value{GDBN} when using @code{target remote} mode, since the
21409 program is already on the target.
21413 @anchor{Monitor Commands for gdbserver}
21414 @subsection Monitor Commands for @code{gdbserver}
21415 @cindex monitor commands, for @code{gdbserver}
21417 During a @value{GDBN} session using @code{gdbserver}, you can use the
21418 @code{monitor} command to send special requests to @code{gdbserver}.
21419 Here are the available commands.
21423 List the available monitor commands.
21425 @item monitor set debug 0
21426 @itemx monitor set debug 1
21427 Disable or enable general debugging messages.
21429 @item monitor set remote-debug 0
21430 @itemx monitor set remote-debug 1
21431 Disable or enable specific debugging messages associated with the remote
21432 protocol (@pxref{Remote Protocol}).
21434 @item monitor set debug-format option1@r{[},option2,...@r{]}
21435 Specify additional text to add to debugging messages.
21436 Possible options are:
21440 Turn off all extra information in debugging output.
21442 Turn on all extra information in debugging output.
21444 Include a timestamp in each line of debugging output.
21447 Options are processed in order. Thus, for example, if @option{none}
21448 appears last then no additional information is added to debugging output.
21450 @item monitor set libthread-db-search-path [PATH]
21451 @cindex gdbserver, search path for @code{libthread_db}
21452 When this command is issued, @var{path} is a colon-separated list of
21453 directories to search for @code{libthread_db} (@pxref{Threads,,set
21454 libthread-db-search-path}). If you omit @var{path},
21455 @samp{libthread-db-search-path} will be reset to its default value.
21457 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21458 not supported in @code{gdbserver}.
21461 Tell gdbserver to exit immediately. This command should be followed by
21462 @code{disconnect} to close the debugging session. @code{gdbserver} will
21463 detach from any attached processes and kill any processes it created.
21464 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21465 of a multi-process mode debug session.
21469 @subsection Tracepoints support in @code{gdbserver}
21470 @cindex tracepoints support in @code{gdbserver}
21472 On some targets, @code{gdbserver} supports tracepoints, fast
21473 tracepoints and static tracepoints.
21475 For fast or static tracepoints to work, a special library called the
21476 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21477 This library is built and distributed as an integral part of
21478 @code{gdbserver}. In addition, support for static tracepoints
21479 requires building the in-process agent library with static tracepoints
21480 support. At present, the UST (LTTng Userspace Tracer,
21481 @url{http://lttng.org/ust}) tracing engine is supported. This support
21482 is automatically available if UST development headers are found in the
21483 standard include path when @code{gdbserver} is built, or if
21484 @code{gdbserver} was explicitly configured using @option{--with-ust}
21485 to point at such headers. You can explicitly disable the support
21486 using @option{--with-ust=no}.
21488 There are several ways to load the in-process agent in your program:
21491 @item Specifying it as dependency at link time
21493 You can link your program dynamically with the in-process agent
21494 library. On most systems, this is accomplished by adding
21495 @code{-linproctrace} to the link command.
21497 @item Using the system's preloading mechanisms
21499 You can force loading the in-process agent at startup time by using
21500 your system's support for preloading shared libraries. Many Unixes
21501 support the concept of preloading user defined libraries. In most
21502 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21503 in the environment. See also the description of @code{gdbserver}'s
21504 @option{--wrapper} command line option.
21506 @item Using @value{GDBN} to force loading the agent at run time
21508 On some systems, you can force the inferior to load a shared library,
21509 by calling a dynamic loader function in the inferior that takes care
21510 of dynamically looking up and loading a shared library. On most Unix
21511 systems, the function is @code{dlopen}. You'll use the @code{call}
21512 command for that. For example:
21515 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21518 Note that on most Unix systems, for the @code{dlopen} function to be
21519 available, the program needs to be linked with @code{-ldl}.
21522 On systems that have a userspace dynamic loader, like most Unix
21523 systems, when you connect to @code{gdbserver} using @code{target
21524 remote}, you'll find that the program is stopped at the dynamic
21525 loader's entry point, and no shared library has been loaded in the
21526 program's address space yet, including the in-process agent. In that
21527 case, before being able to use any of the fast or static tracepoints
21528 features, you need to let the loader run and load the shared
21529 libraries. The simplest way to do that is to run the program to the
21530 main procedure. E.g., if debugging a C or C@t{++} program, start
21531 @code{gdbserver} like so:
21534 $ gdbserver :9999 myprogram
21537 Start GDB and connect to @code{gdbserver} like so, and run to main:
21541 (@value{GDBP}) target remote myhost:9999
21542 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21543 (@value{GDBP}) b main
21544 (@value{GDBP}) continue
21547 The in-process tracing agent library should now be loaded into the
21548 process; you can confirm it with the @code{info sharedlibrary}
21549 command, which will list @file{libinproctrace.so} as loaded in the
21550 process. You are now ready to install fast tracepoints, list static
21551 tracepoint markers, probe static tracepoints markers, and start
21554 @node Remote Configuration
21555 @section Remote Configuration
21558 @kindex show remote
21559 This section documents the configuration options available when
21560 debugging remote programs. For the options related to the File I/O
21561 extensions of the remote protocol, see @ref{system,
21562 system-call-allowed}.
21565 @item set remoteaddresssize @var{bits}
21566 @cindex address size for remote targets
21567 @cindex bits in remote address
21568 Set the maximum size of address in a memory packet to the specified
21569 number of bits. @value{GDBN} will mask off the address bits above
21570 that number, when it passes addresses to the remote target. The
21571 default value is the number of bits in the target's address.
21573 @item show remoteaddresssize
21574 Show the current value of remote address size in bits.
21576 @item set serial baud @var{n}
21577 @cindex baud rate for remote targets
21578 Set the baud rate for the remote serial I/O to @var{n} baud. The
21579 value is used to set the speed of the serial port used for debugging
21582 @item show serial baud
21583 Show the current speed of the remote connection.
21585 @item set serial parity @var{parity}
21586 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21587 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21589 @item show serial parity
21590 Show the current parity of the serial port.
21592 @item set remotebreak
21593 @cindex interrupt remote programs
21594 @cindex BREAK signal instead of Ctrl-C
21595 @anchor{set remotebreak}
21596 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21597 when you type @kbd{Ctrl-c} to interrupt the program running
21598 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21599 character instead. The default is off, since most remote systems
21600 expect to see @samp{Ctrl-C} as the interrupt signal.
21602 @item show remotebreak
21603 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21604 interrupt the remote program.
21606 @item set remoteflow on
21607 @itemx set remoteflow off
21608 @kindex set remoteflow
21609 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21610 on the serial port used to communicate to the remote target.
21612 @item show remoteflow
21613 @kindex show remoteflow
21614 Show the current setting of hardware flow control.
21616 @item set remotelogbase @var{base}
21617 Set the base (a.k.a.@: radix) of logging serial protocol
21618 communications to @var{base}. Supported values of @var{base} are:
21619 @code{ascii}, @code{octal}, and @code{hex}. The default is
21622 @item show remotelogbase
21623 Show the current setting of the radix for logging remote serial
21626 @item set remotelogfile @var{file}
21627 @cindex record serial communications on file
21628 Record remote serial communications on the named @var{file}. The
21629 default is not to record at all.
21631 @item show remotelogfile.
21632 Show the current setting of the file name on which to record the
21633 serial communications.
21635 @item set remotetimeout @var{num}
21636 @cindex timeout for serial communications
21637 @cindex remote timeout
21638 Set the timeout limit to wait for the remote target to respond to
21639 @var{num} seconds. The default is 2 seconds.
21641 @item show remotetimeout
21642 Show the current number of seconds to wait for the remote target
21645 @cindex limit hardware breakpoints and watchpoints
21646 @cindex remote target, limit break- and watchpoints
21647 @anchor{set remote hardware-watchpoint-limit}
21648 @anchor{set remote hardware-breakpoint-limit}
21649 @item set remote hardware-watchpoint-limit @var{limit}
21650 @itemx set remote hardware-breakpoint-limit @var{limit}
21651 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21652 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21653 watchpoints or breakpoints, and @code{unlimited} for unlimited
21654 watchpoints or breakpoints.
21656 @item show remote hardware-watchpoint-limit
21657 @itemx show remote hardware-breakpoint-limit
21658 Show the current limit for the number of hardware watchpoints or
21659 breakpoints that @value{GDBN} can use.
21661 @cindex limit hardware watchpoints length
21662 @cindex remote target, limit watchpoints length
21663 @anchor{set remote hardware-watchpoint-length-limit}
21664 @item set remote hardware-watchpoint-length-limit @var{limit}
21665 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21666 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21667 hardware watchpoints and @code{unlimited} allows watchpoints of any
21670 @item show remote hardware-watchpoint-length-limit
21671 Show the current limit (in bytes) of the maximum length of
21672 a remote hardware watchpoint.
21674 @item set remote exec-file @var{filename}
21675 @itemx show remote exec-file
21676 @anchor{set remote exec-file}
21677 @cindex executable file, for remote target
21678 Select the file used for @code{run} with @code{target
21679 extended-remote}. This should be set to a filename valid on the
21680 target system. If it is not set, the target will use a default
21681 filename (e.g.@: the last program run).
21683 @item set remote interrupt-sequence
21684 @cindex interrupt remote programs
21685 @cindex select Ctrl-C, BREAK or BREAK-g
21686 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21687 @samp{BREAK-g} as the
21688 sequence to the remote target in order to interrupt the execution.
21689 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21690 is high level of serial line for some certain time.
21691 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21692 It is @code{BREAK} signal followed by character @code{g}.
21694 @item show interrupt-sequence
21695 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21696 is sent by @value{GDBN} to interrupt the remote program.
21697 @code{BREAK-g} is BREAK signal followed by @code{g} and
21698 also known as Magic SysRq g.
21700 @item set remote interrupt-on-connect
21701 @cindex send interrupt-sequence on start
21702 Specify whether interrupt-sequence is sent to remote target when
21703 @value{GDBN} connects to it. This is mostly needed when you debug
21704 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21705 which is known as Magic SysRq g in order to connect @value{GDBN}.
21707 @item show interrupt-on-connect
21708 Show whether interrupt-sequence is sent
21709 to remote target when @value{GDBN} connects to it.
21713 @item set tcp auto-retry on
21714 @cindex auto-retry, for remote TCP target
21715 Enable auto-retry for remote TCP connections. This is useful if the remote
21716 debugging agent is launched in parallel with @value{GDBN}; there is a race
21717 condition because the agent may not become ready to accept the connection
21718 before @value{GDBN} attempts to connect. When auto-retry is
21719 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21720 to establish the connection using the timeout specified by
21721 @code{set tcp connect-timeout}.
21723 @item set tcp auto-retry off
21724 Do not auto-retry failed TCP connections.
21726 @item show tcp auto-retry
21727 Show the current auto-retry setting.
21729 @item set tcp connect-timeout @var{seconds}
21730 @itemx set tcp connect-timeout unlimited
21731 @cindex connection timeout, for remote TCP target
21732 @cindex timeout, for remote target connection
21733 Set the timeout for establishing a TCP connection to the remote target to
21734 @var{seconds}. The timeout affects both polling to retry failed connections
21735 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21736 that are merely slow to complete, and represents an approximate cumulative
21737 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21738 @value{GDBN} will keep attempting to establish a connection forever,
21739 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21741 @item show tcp connect-timeout
21742 Show the current connection timeout setting.
21745 @cindex remote packets, enabling and disabling
21746 The @value{GDBN} remote protocol autodetects the packets supported by
21747 your debugging stub. If you need to override the autodetection, you
21748 can use these commands to enable or disable individual packets. Each
21749 packet can be set to @samp{on} (the remote target supports this
21750 packet), @samp{off} (the remote target does not support this packet),
21751 or @samp{auto} (detect remote target support for this packet). They
21752 all default to @samp{auto}. For more information about each packet,
21753 see @ref{Remote Protocol}.
21755 During normal use, you should not have to use any of these commands.
21756 If you do, that may be a bug in your remote debugging stub, or a bug
21757 in @value{GDBN}. You may want to report the problem to the
21758 @value{GDBN} developers.
21760 For each packet @var{name}, the command to enable or disable the
21761 packet is @code{set remote @var{name}-packet}. The available settings
21764 @multitable @columnfractions 0.28 0.32 0.25
21767 @tab Related Features
21769 @item @code{fetch-register}
21771 @tab @code{info registers}
21773 @item @code{set-register}
21777 @item @code{binary-download}
21779 @tab @code{load}, @code{set}
21781 @item @code{read-aux-vector}
21782 @tab @code{qXfer:auxv:read}
21783 @tab @code{info auxv}
21785 @item @code{symbol-lookup}
21786 @tab @code{qSymbol}
21787 @tab Detecting multiple threads
21789 @item @code{attach}
21790 @tab @code{vAttach}
21793 @item @code{verbose-resume}
21795 @tab Stepping or resuming multiple threads
21801 @item @code{software-breakpoint}
21805 @item @code{hardware-breakpoint}
21809 @item @code{write-watchpoint}
21813 @item @code{read-watchpoint}
21817 @item @code{access-watchpoint}
21821 @item @code{pid-to-exec-file}
21822 @tab @code{qXfer:exec-file:read}
21823 @tab @code{attach}, @code{run}
21825 @item @code{target-features}
21826 @tab @code{qXfer:features:read}
21827 @tab @code{set architecture}
21829 @item @code{library-info}
21830 @tab @code{qXfer:libraries:read}
21831 @tab @code{info sharedlibrary}
21833 @item @code{memory-map}
21834 @tab @code{qXfer:memory-map:read}
21835 @tab @code{info mem}
21837 @item @code{read-sdata-object}
21838 @tab @code{qXfer:sdata:read}
21839 @tab @code{print $_sdata}
21841 @item @code{read-spu-object}
21842 @tab @code{qXfer:spu:read}
21843 @tab @code{info spu}
21845 @item @code{write-spu-object}
21846 @tab @code{qXfer:spu:write}
21847 @tab @code{info spu}
21849 @item @code{read-siginfo-object}
21850 @tab @code{qXfer:siginfo:read}
21851 @tab @code{print $_siginfo}
21853 @item @code{write-siginfo-object}
21854 @tab @code{qXfer:siginfo:write}
21855 @tab @code{set $_siginfo}
21857 @item @code{threads}
21858 @tab @code{qXfer:threads:read}
21859 @tab @code{info threads}
21861 @item @code{get-thread-local-@*storage-address}
21862 @tab @code{qGetTLSAddr}
21863 @tab Displaying @code{__thread} variables
21865 @item @code{get-thread-information-block-address}
21866 @tab @code{qGetTIBAddr}
21867 @tab Display MS-Windows Thread Information Block.
21869 @item @code{search-memory}
21870 @tab @code{qSearch:memory}
21873 @item @code{supported-packets}
21874 @tab @code{qSupported}
21875 @tab Remote communications parameters
21877 @item @code{catch-syscalls}
21878 @tab @code{QCatchSyscalls}
21879 @tab @code{catch syscall}
21881 @item @code{pass-signals}
21882 @tab @code{QPassSignals}
21883 @tab @code{handle @var{signal}}
21885 @item @code{program-signals}
21886 @tab @code{QProgramSignals}
21887 @tab @code{handle @var{signal}}
21889 @item @code{hostio-close-packet}
21890 @tab @code{vFile:close}
21891 @tab @code{remote get}, @code{remote put}
21893 @item @code{hostio-open-packet}
21894 @tab @code{vFile:open}
21895 @tab @code{remote get}, @code{remote put}
21897 @item @code{hostio-pread-packet}
21898 @tab @code{vFile:pread}
21899 @tab @code{remote get}, @code{remote put}
21901 @item @code{hostio-pwrite-packet}
21902 @tab @code{vFile:pwrite}
21903 @tab @code{remote get}, @code{remote put}
21905 @item @code{hostio-unlink-packet}
21906 @tab @code{vFile:unlink}
21907 @tab @code{remote delete}
21909 @item @code{hostio-readlink-packet}
21910 @tab @code{vFile:readlink}
21913 @item @code{hostio-fstat-packet}
21914 @tab @code{vFile:fstat}
21917 @item @code{hostio-setfs-packet}
21918 @tab @code{vFile:setfs}
21921 @item @code{noack-packet}
21922 @tab @code{QStartNoAckMode}
21923 @tab Packet acknowledgment
21925 @item @code{osdata}
21926 @tab @code{qXfer:osdata:read}
21927 @tab @code{info os}
21929 @item @code{query-attached}
21930 @tab @code{qAttached}
21931 @tab Querying remote process attach state.
21933 @item @code{trace-buffer-size}
21934 @tab @code{QTBuffer:size}
21935 @tab @code{set trace-buffer-size}
21937 @item @code{trace-status}
21938 @tab @code{qTStatus}
21939 @tab @code{tstatus}
21941 @item @code{traceframe-info}
21942 @tab @code{qXfer:traceframe-info:read}
21943 @tab Traceframe info
21945 @item @code{install-in-trace}
21946 @tab @code{InstallInTrace}
21947 @tab Install tracepoint in tracing
21949 @item @code{disable-randomization}
21950 @tab @code{QDisableRandomization}
21951 @tab @code{set disable-randomization}
21953 @item @code{startup-with-shell}
21954 @tab @code{QStartupWithShell}
21955 @tab @code{set startup-with-shell}
21957 @item @code{environment-hex-encoded}
21958 @tab @code{QEnvironmentHexEncoded}
21959 @tab @code{set environment}
21961 @item @code{environment-unset}
21962 @tab @code{QEnvironmentUnset}
21963 @tab @code{unset environment}
21965 @item @code{environment-reset}
21966 @tab @code{QEnvironmentReset}
21967 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21969 @item @code{set-working-dir}
21970 @tab @code{QSetWorkingDir}
21971 @tab @code{set cwd}
21973 @item @code{conditional-breakpoints-packet}
21974 @tab @code{Z0 and Z1}
21975 @tab @code{Support for target-side breakpoint condition evaluation}
21977 @item @code{multiprocess-extensions}
21978 @tab @code{multiprocess extensions}
21979 @tab Debug multiple processes and remote process PID awareness
21981 @item @code{swbreak-feature}
21982 @tab @code{swbreak stop reason}
21985 @item @code{hwbreak-feature}
21986 @tab @code{hwbreak stop reason}
21989 @item @code{fork-event-feature}
21990 @tab @code{fork stop reason}
21993 @item @code{vfork-event-feature}
21994 @tab @code{vfork stop reason}
21997 @item @code{exec-event-feature}
21998 @tab @code{exec stop reason}
22001 @item @code{thread-events}
22002 @tab @code{QThreadEvents}
22003 @tab Tracking thread lifetime.
22005 @item @code{no-resumed-stop-reply}
22006 @tab @code{no resumed thread left stop reply}
22007 @tab Tracking thread lifetime.
22012 @section Implementing a Remote Stub
22014 @cindex debugging stub, example
22015 @cindex remote stub, example
22016 @cindex stub example, remote debugging
22017 The stub files provided with @value{GDBN} implement the target side of the
22018 communication protocol, and the @value{GDBN} side is implemented in the
22019 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22020 these subroutines to communicate, and ignore the details. (If you're
22021 implementing your own stub file, you can still ignore the details: start
22022 with one of the existing stub files. @file{sparc-stub.c} is the best
22023 organized, and therefore the easiest to read.)
22025 @cindex remote serial debugging, overview
22026 To debug a program running on another machine (the debugging
22027 @dfn{target} machine), you must first arrange for all the usual
22028 prerequisites for the program to run by itself. For example, for a C
22033 A startup routine to set up the C runtime environment; these usually
22034 have a name like @file{crt0}. The startup routine may be supplied by
22035 your hardware supplier, or you may have to write your own.
22038 A C subroutine library to support your program's
22039 subroutine calls, notably managing input and output.
22042 A way of getting your program to the other machine---for example, a
22043 download program. These are often supplied by the hardware
22044 manufacturer, but you may have to write your own from hardware
22048 The next step is to arrange for your program to use a serial port to
22049 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22050 machine). In general terms, the scheme looks like this:
22054 @value{GDBN} already understands how to use this protocol; when everything
22055 else is set up, you can simply use the @samp{target remote} command
22056 (@pxref{Targets,,Specifying a Debugging Target}).
22058 @item On the target,
22059 you must link with your program a few special-purpose subroutines that
22060 implement the @value{GDBN} remote serial protocol. The file containing these
22061 subroutines is called a @dfn{debugging stub}.
22063 On certain remote targets, you can use an auxiliary program
22064 @code{gdbserver} instead of linking a stub into your program.
22065 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22068 The debugging stub is specific to the architecture of the remote
22069 machine; for example, use @file{sparc-stub.c} to debug programs on
22072 @cindex remote serial stub list
22073 These working remote stubs are distributed with @value{GDBN}:
22078 @cindex @file{i386-stub.c}
22081 For Intel 386 and compatible architectures.
22084 @cindex @file{m68k-stub.c}
22085 @cindex Motorola 680x0
22087 For Motorola 680x0 architectures.
22090 @cindex @file{sh-stub.c}
22093 For Renesas SH architectures.
22096 @cindex @file{sparc-stub.c}
22098 For @sc{sparc} architectures.
22100 @item sparcl-stub.c
22101 @cindex @file{sparcl-stub.c}
22104 For Fujitsu @sc{sparclite} architectures.
22108 The @file{README} file in the @value{GDBN} distribution may list other
22109 recently added stubs.
22112 * Stub Contents:: What the stub can do for you
22113 * Bootstrapping:: What you must do for the stub
22114 * Debug Session:: Putting it all together
22117 @node Stub Contents
22118 @subsection What the Stub Can Do for You
22120 @cindex remote serial stub
22121 The debugging stub for your architecture supplies these three
22125 @item set_debug_traps
22126 @findex set_debug_traps
22127 @cindex remote serial stub, initialization
22128 This routine arranges for @code{handle_exception} to run when your
22129 program stops. You must call this subroutine explicitly in your
22130 program's startup code.
22132 @item handle_exception
22133 @findex handle_exception
22134 @cindex remote serial stub, main routine
22135 This is the central workhorse, but your program never calls it
22136 explicitly---the setup code arranges for @code{handle_exception} to
22137 run when a trap is triggered.
22139 @code{handle_exception} takes control when your program stops during
22140 execution (for example, on a breakpoint), and mediates communications
22141 with @value{GDBN} on the host machine. This is where the communications
22142 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22143 representative on the target machine. It begins by sending summary
22144 information on the state of your program, then continues to execute,
22145 retrieving and transmitting any information @value{GDBN} needs, until you
22146 execute a @value{GDBN} command that makes your program resume; at that point,
22147 @code{handle_exception} returns control to your own code on the target
22151 @cindex @code{breakpoint} subroutine, remote
22152 Use this auxiliary subroutine to make your program contain a
22153 breakpoint. Depending on the particular situation, this may be the only
22154 way for @value{GDBN} to get control. For instance, if your target
22155 machine has some sort of interrupt button, you won't need to call this;
22156 pressing the interrupt button transfers control to
22157 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22158 simply receiving characters on the serial port may also trigger a trap;
22159 again, in that situation, you don't need to call @code{breakpoint} from
22160 your own program---simply running @samp{target remote} from the host
22161 @value{GDBN} session gets control.
22163 Call @code{breakpoint} if none of these is true, or if you simply want
22164 to make certain your program stops at a predetermined point for the
22165 start of your debugging session.
22168 @node Bootstrapping
22169 @subsection What You Must Do for the Stub
22171 @cindex remote stub, support routines
22172 The debugging stubs that come with @value{GDBN} are set up for a particular
22173 chip architecture, but they have no information about the rest of your
22174 debugging target machine.
22176 First of all you need to tell the stub how to communicate with the
22180 @item int getDebugChar()
22181 @findex getDebugChar
22182 Write this subroutine to read a single character from the serial port.
22183 It may be identical to @code{getchar} for your target system; a
22184 different name is used to allow you to distinguish the two if you wish.
22186 @item void putDebugChar(int)
22187 @findex putDebugChar
22188 Write this subroutine to write a single character to the serial port.
22189 It may be identical to @code{putchar} for your target system; a
22190 different name is used to allow you to distinguish the two if you wish.
22193 @cindex control C, and remote debugging
22194 @cindex interrupting remote targets
22195 If you want @value{GDBN} to be able to stop your program while it is
22196 running, you need to use an interrupt-driven serial driver, and arrange
22197 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22198 character). That is the character which @value{GDBN} uses to tell the
22199 remote system to stop.
22201 Getting the debugging target to return the proper status to @value{GDBN}
22202 probably requires changes to the standard stub; one quick and dirty way
22203 is to just execute a breakpoint instruction (the ``dirty'' part is that
22204 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22206 Other routines you need to supply are:
22209 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22210 @findex exceptionHandler
22211 Write this function to install @var{exception_address} in the exception
22212 handling tables. You need to do this because the stub does not have any
22213 way of knowing what the exception handling tables on your target system
22214 are like (for example, the processor's table might be in @sc{rom},
22215 containing entries which point to a table in @sc{ram}).
22216 The @var{exception_number} specifies the exception which should be changed;
22217 its meaning is architecture-dependent (for example, different numbers
22218 might represent divide by zero, misaligned access, etc). When this
22219 exception occurs, control should be transferred directly to
22220 @var{exception_address}, and the processor state (stack, registers,
22221 and so on) should be just as it is when a processor exception occurs. So if
22222 you want to use a jump instruction to reach @var{exception_address}, it
22223 should be a simple jump, not a jump to subroutine.
22225 For the 386, @var{exception_address} should be installed as an interrupt
22226 gate so that interrupts are masked while the handler runs. The gate
22227 should be at privilege level 0 (the most privileged level). The
22228 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22229 help from @code{exceptionHandler}.
22231 @item void flush_i_cache()
22232 @findex flush_i_cache
22233 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22234 instruction cache, if any, on your target machine. If there is no
22235 instruction cache, this subroutine may be a no-op.
22237 On target machines that have instruction caches, @value{GDBN} requires this
22238 function to make certain that the state of your program is stable.
22242 You must also make sure this library routine is available:
22245 @item void *memset(void *, int, int)
22247 This is the standard library function @code{memset} that sets an area of
22248 memory to a known value. If you have one of the free versions of
22249 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22250 either obtain it from your hardware manufacturer, or write your own.
22253 If you do not use the GNU C compiler, you may need other standard
22254 library subroutines as well; this varies from one stub to another,
22255 but in general the stubs are likely to use any of the common library
22256 subroutines which @code{@value{NGCC}} generates as inline code.
22259 @node Debug Session
22260 @subsection Putting it All Together
22262 @cindex remote serial debugging summary
22263 In summary, when your program is ready to debug, you must follow these
22268 Make sure you have defined the supporting low-level routines
22269 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22271 @code{getDebugChar}, @code{putDebugChar},
22272 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22276 Insert these lines in your program's startup code, before the main
22277 procedure is called:
22284 On some machines, when a breakpoint trap is raised, the hardware
22285 automatically makes the PC point to the instruction after the
22286 breakpoint. If your machine doesn't do that, you may need to adjust
22287 @code{handle_exception} to arrange for it to return to the instruction
22288 after the breakpoint on this first invocation, so that your program
22289 doesn't keep hitting the initial breakpoint instead of making
22293 For the 680x0 stub only, you need to provide a variable called
22294 @code{exceptionHook}. Normally you just use:
22297 void (*exceptionHook)() = 0;
22301 but if before calling @code{set_debug_traps}, you set it to point to a
22302 function in your program, that function is called when
22303 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22304 error). The function indicated by @code{exceptionHook} is called with
22305 one parameter: an @code{int} which is the exception number.
22308 Compile and link together: your program, the @value{GDBN} debugging stub for
22309 your target architecture, and the supporting subroutines.
22312 Make sure you have a serial connection between your target machine and
22313 the @value{GDBN} host, and identify the serial port on the host.
22316 @c The "remote" target now provides a `load' command, so we should
22317 @c document that. FIXME.
22318 Download your program to your target machine (or get it there by
22319 whatever means the manufacturer provides), and start it.
22322 Start @value{GDBN} on the host, and connect to the target
22323 (@pxref{Connecting,,Connecting to a Remote Target}).
22327 @node Configurations
22328 @chapter Configuration-Specific Information
22330 While nearly all @value{GDBN} commands are available for all native and
22331 cross versions of the debugger, there are some exceptions. This chapter
22332 describes things that are only available in certain configurations.
22334 There are three major categories of configurations: native
22335 configurations, where the host and target are the same, embedded
22336 operating system configurations, which are usually the same for several
22337 different processor architectures, and bare embedded processors, which
22338 are quite different from each other.
22343 * Embedded Processors::
22350 This section describes details specific to particular native
22354 * BSD libkvm Interface:: Debugging BSD kernel memory images
22355 * Process Information:: Process information
22356 * DJGPP Native:: Features specific to the DJGPP port
22357 * Cygwin Native:: Features specific to the Cygwin port
22358 * Hurd Native:: Features specific to @sc{gnu} Hurd
22359 * Darwin:: Features specific to Darwin
22362 @node BSD libkvm Interface
22363 @subsection BSD libkvm Interface
22366 @cindex kernel memory image
22367 @cindex kernel crash dump
22369 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22370 interface that provides a uniform interface for accessing kernel virtual
22371 memory images, including live systems and crash dumps. @value{GDBN}
22372 uses this interface to allow you to debug live kernels and kernel crash
22373 dumps on many native BSD configurations. This is implemented as a
22374 special @code{kvm} debugging target. For debugging a live system, load
22375 the currently running kernel into @value{GDBN} and connect to the
22379 (@value{GDBP}) @b{target kvm}
22382 For debugging crash dumps, provide the file name of the crash dump as an
22386 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22389 Once connected to the @code{kvm} target, the following commands are
22395 Set current context from the @dfn{Process Control Block} (PCB) address.
22398 Set current context from proc address. This command isn't available on
22399 modern FreeBSD systems.
22402 @node Process Information
22403 @subsection Process Information
22405 @cindex examine process image
22406 @cindex process info via @file{/proc}
22408 Some operating systems provide interfaces to fetch additional
22409 information about running processes beyond memory and per-thread
22410 register state. If @value{GDBN} is configured for an operating system
22411 with a supported interface, the command @code{info proc} is available
22412 to report information about the process running your program, or about
22413 any process running on your system.
22415 One supported interface is a facility called @samp{/proc} that can be
22416 used to examine the image of a running process using file-system
22417 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22420 On FreeBSD systems, system control nodes are used to query process
22423 In addition, some systems may provide additional process information
22424 in core files. Note that a core file may include a subset of the
22425 information available from a live process. Process information is
22426 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22433 @itemx info proc @var{process-id}
22434 Summarize available information about a process. If a
22435 process ID is specified by @var{process-id}, display information about
22436 that process; otherwise display information about the program being
22437 debugged. The summary includes the debugged process ID, the command
22438 line used to invoke it, its current working directory, and its
22439 executable file's absolute file name.
22441 On some systems, @var{process-id} can be of the form
22442 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22443 within a process. If the optional @var{pid} part is missing, it means
22444 a thread from the process being debugged (the leading @samp{/} still
22445 needs to be present, or else @value{GDBN} will interpret the number as
22446 a process ID rather than a thread ID).
22448 @item info proc cmdline
22449 @cindex info proc cmdline
22450 Show the original command line of the process. This command is
22451 supported on @sc{gnu}/Linux and FreeBSD.
22453 @item info proc cwd
22454 @cindex info proc cwd
22455 Show the current working directory of the process. This command is
22456 supported on @sc{gnu}/Linux and FreeBSD.
22458 @item info proc exe
22459 @cindex info proc exe
22460 Show the name of executable of the process. This command is supported
22461 on @sc{gnu}/Linux and FreeBSD.
22463 @item info proc files
22464 @cindex info proc files
22465 Show the file descriptors open by the process. For each open file
22466 descriptor, @value{GDBN} shows its number, type (file, directory,
22467 character device, socket), file pointer offset, and the name of the
22468 resource open on the descriptor. The resource name can be a file name
22469 (for files, directories, and devices) or a protocol followed by socket
22470 address (for network connections). This command is supported on
22473 This example shows the open file descriptors for a process using a
22474 tty for standard input and output as well as two network sockets:
22477 (gdb) info proc files 22136
22481 FD Type Offset Flags Name
22482 text file - r-------- /usr/bin/ssh
22483 ctty chr - rw------- /dev/pts/20
22484 cwd dir - r-------- /usr/home/john
22485 root dir - r-------- /
22486 0 chr 0x32933a4 rw------- /dev/pts/20
22487 1 chr 0x32933a4 rw------- /dev/pts/20
22488 2 chr 0x32933a4 rw------- /dev/pts/20
22489 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22490 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22493 @item info proc mappings
22494 @cindex memory address space mappings
22495 Report the memory address space ranges accessible in a process. On
22496 Solaris and FreeBSD systems, each memory range includes information on
22497 whether the process has read, write, or execute access rights to each
22498 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22499 includes the object file which is mapped to that range.
22501 @item info proc stat
22502 @itemx info proc status
22503 @cindex process detailed status information
22504 Show additional process-related information, including the user ID and
22505 group ID; virtual memory usage; the signals that are pending, blocked,
22506 and ignored; its TTY; its consumption of system and user time; its
22507 stack size; its @samp{nice} value; etc. These commands are supported
22508 on @sc{gnu}/Linux and FreeBSD.
22510 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22511 information (type @kbd{man 5 proc} from your shell prompt).
22513 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22516 @item info proc all
22517 Show all the information about the process described under all of the
22518 above @code{info proc} subcommands.
22521 @comment These sub-options of 'info proc' were not included when
22522 @comment procfs.c was re-written. Keep their descriptions around
22523 @comment against the day when someone finds the time to put them back in.
22524 @kindex info proc times
22525 @item info proc times
22526 Starting time, user CPU time, and system CPU time for your program and
22529 @kindex info proc id
22531 Report on the process IDs related to your program: its own process ID,
22532 the ID of its parent, the process group ID, and the session ID.
22535 @item set procfs-trace
22536 @kindex set procfs-trace
22537 @cindex @code{procfs} API calls
22538 This command enables and disables tracing of @code{procfs} API calls.
22540 @item show procfs-trace
22541 @kindex show procfs-trace
22542 Show the current state of @code{procfs} API call tracing.
22544 @item set procfs-file @var{file}
22545 @kindex set procfs-file
22546 Tell @value{GDBN} to write @code{procfs} API trace to the named
22547 @var{file}. @value{GDBN} appends the trace info to the previous
22548 contents of the file. The default is to display the trace on the
22551 @item show procfs-file
22552 @kindex show procfs-file
22553 Show the file to which @code{procfs} API trace is written.
22555 @item proc-trace-entry
22556 @itemx proc-trace-exit
22557 @itemx proc-untrace-entry
22558 @itemx proc-untrace-exit
22559 @kindex proc-trace-entry
22560 @kindex proc-trace-exit
22561 @kindex proc-untrace-entry
22562 @kindex proc-untrace-exit
22563 These commands enable and disable tracing of entries into and exits
22564 from the @code{syscall} interface.
22567 @kindex info pidlist
22568 @cindex process list, QNX Neutrino
22569 For QNX Neutrino only, this command displays the list of all the
22570 processes and all the threads within each process.
22573 @kindex info meminfo
22574 @cindex mapinfo list, QNX Neutrino
22575 For QNX Neutrino only, this command displays the list of all mapinfos.
22579 @subsection Features for Debugging @sc{djgpp} Programs
22580 @cindex @sc{djgpp} debugging
22581 @cindex native @sc{djgpp} debugging
22582 @cindex MS-DOS-specific commands
22585 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22586 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22587 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22588 top of real-mode DOS systems and their emulations.
22590 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22591 defines a few commands specific to the @sc{djgpp} port. This
22592 subsection describes those commands.
22597 This is a prefix of @sc{djgpp}-specific commands which print
22598 information about the target system and important OS structures.
22601 @cindex MS-DOS system info
22602 @cindex free memory information (MS-DOS)
22603 @item info dos sysinfo
22604 This command displays assorted information about the underlying
22605 platform: the CPU type and features, the OS version and flavor, the
22606 DPMI version, and the available conventional and DPMI memory.
22611 @cindex segment descriptor tables
22612 @cindex descriptor tables display
22614 @itemx info dos ldt
22615 @itemx info dos idt
22616 These 3 commands display entries from, respectively, Global, Local,
22617 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22618 tables are data structures which store a descriptor for each segment
22619 that is currently in use. The segment's selector is an index into a
22620 descriptor table; the table entry for that index holds the
22621 descriptor's base address and limit, and its attributes and access
22624 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22625 segment (used for both data and the stack), and a DOS segment (which
22626 allows access to DOS/BIOS data structures and absolute addresses in
22627 conventional memory). However, the DPMI host will usually define
22628 additional segments in order to support the DPMI environment.
22630 @cindex garbled pointers
22631 These commands allow to display entries from the descriptor tables.
22632 Without an argument, all entries from the specified table are
22633 displayed. An argument, which should be an integer expression, means
22634 display a single entry whose index is given by the argument. For
22635 example, here's a convenient way to display information about the
22636 debugged program's data segment:
22639 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22640 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22644 This comes in handy when you want to see whether a pointer is outside
22645 the data segment's limit (i.e.@: @dfn{garbled}).
22647 @cindex page tables display (MS-DOS)
22649 @itemx info dos pte
22650 These two commands display entries from, respectively, the Page
22651 Directory and the Page Tables. Page Directories and Page Tables are
22652 data structures which control how virtual memory addresses are mapped
22653 into physical addresses. A Page Table includes an entry for every
22654 page of memory that is mapped into the program's address space; there
22655 may be several Page Tables, each one holding up to 4096 entries. A
22656 Page Directory has up to 4096 entries, one each for every Page Table
22657 that is currently in use.
22659 Without an argument, @kbd{info dos pde} displays the entire Page
22660 Directory, and @kbd{info dos pte} displays all the entries in all of
22661 the Page Tables. An argument, an integer expression, given to the
22662 @kbd{info dos pde} command means display only that entry from the Page
22663 Directory table. An argument given to the @kbd{info dos pte} command
22664 means display entries from a single Page Table, the one pointed to by
22665 the specified entry in the Page Directory.
22667 @cindex direct memory access (DMA) on MS-DOS
22668 These commands are useful when your program uses @dfn{DMA} (Direct
22669 Memory Access), which needs physical addresses to program the DMA
22672 These commands are supported only with some DPMI servers.
22674 @cindex physical address from linear address
22675 @item info dos address-pte @var{addr}
22676 This command displays the Page Table entry for a specified linear
22677 address. The argument @var{addr} is a linear address which should
22678 already have the appropriate segment's base address added to it,
22679 because this command accepts addresses which may belong to @emph{any}
22680 segment. For example, here's how to display the Page Table entry for
22681 the page where a variable @code{i} is stored:
22684 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22685 @exdent @code{Page Table entry for address 0x11a00d30:}
22686 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22690 This says that @code{i} is stored at offset @code{0xd30} from the page
22691 whose physical base address is @code{0x02698000}, and shows all the
22692 attributes of that page.
22694 Note that you must cast the addresses of variables to a @code{char *},
22695 since otherwise the value of @code{__djgpp_base_address}, the base
22696 address of all variables and functions in a @sc{djgpp} program, will
22697 be added using the rules of C pointer arithmetics: if @code{i} is
22698 declared an @code{int}, @value{GDBN} will add 4 times the value of
22699 @code{__djgpp_base_address} to the address of @code{i}.
22701 Here's another example, it displays the Page Table entry for the
22705 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22706 @exdent @code{Page Table entry for address 0x29110:}
22707 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22711 (The @code{+ 3} offset is because the transfer buffer's address is the
22712 3rd member of the @code{_go32_info_block} structure.) The output
22713 clearly shows that this DPMI server maps the addresses in conventional
22714 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22715 linear (@code{0x29110}) addresses are identical.
22717 This command is supported only with some DPMI servers.
22720 @cindex DOS serial data link, remote debugging
22721 In addition to native debugging, the DJGPP port supports remote
22722 debugging via a serial data link. The following commands are specific
22723 to remote serial debugging in the DJGPP port of @value{GDBN}.
22726 @kindex set com1base
22727 @kindex set com1irq
22728 @kindex set com2base
22729 @kindex set com2irq
22730 @kindex set com3base
22731 @kindex set com3irq
22732 @kindex set com4base
22733 @kindex set com4irq
22734 @item set com1base @var{addr}
22735 This command sets the base I/O port address of the @file{COM1} serial
22738 @item set com1irq @var{irq}
22739 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22740 for the @file{COM1} serial port.
22742 There are similar commands @samp{set com2base}, @samp{set com3irq},
22743 etc.@: for setting the port address and the @code{IRQ} lines for the
22746 @kindex show com1base
22747 @kindex show com1irq
22748 @kindex show com2base
22749 @kindex show com2irq
22750 @kindex show com3base
22751 @kindex show com3irq
22752 @kindex show com4base
22753 @kindex show com4irq
22754 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22755 display the current settings of the base address and the @code{IRQ}
22756 lines used by the COM ports.
22759 @kindex info serial
22760 @cindex DOS serial port status
22761 This command prints the status of the 4 DOS serial ports. For each
22762 port, it prints whether it's active or not, its I/O base address and
22763 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22764 counts of various errors encountered so far.
22768 @node Cygwin Native
22769 @subsection Features for Debugging MS Windows PE Executables
22770 @cindex MS Windows debugging
22771 @cindex native Cygwin debugging
22772 @cindex Cygwin-specific commands
22774 @value{GDBN} supports native debugging of MS Windows programs, including
22775 DLLs with and without symbolic debugging information.
22777 @cindex Ctrl-BREAK, MS-Windows
22778 @cindex interrupt debuggee on MS-Windows
22779 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22780 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22781 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22782 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22783 sequence, which can be used to interrupt the debuggee even if it
22786 There are various additional Cygwin-specific commands, described in
22787 this section. Working with DLLs that have no debugging symbols is
22788 described in @ref{Non-debug DLL Symbols}.
22793 This is a prefix of MS Windows-specific commands which print
22794 information about the target system and important OS structures.
22796 @item info w32 selector
22797 This command displays information returned by
22798 the Win32 API @code{GetThreadSelectorEntry} function.
22799 It takes an optional argument that is evaluated to
22800 a long value to give the information about this given selector.
22801 Without argument, this command displays information
22802 about the six segment registers.
22804 @item info w32 thread-information-block
22805 This command displays thread specific information stored in the
22806 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22807 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22809 @kindex signal-event
22810 @item signal-event @var{id}
22811 This command signals an event with user-provided @var{id}. Used to resume
22812 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22814 To use it, create or edit the following keys in
22815 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22816 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22817 (for x86_64 versions):
22821 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22822 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22823 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22825 The first @code{%ld} will be replaced by the process ID of the
22826 crashing process, the second @code{%ld} will be replaced by the ID of
22827 the event that blocks the crashing process, waiting for @value{GDBN}
22831 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22832 make the system run debugger specified by the Debugger key
22833 automatically, @code{0} will cause a dialog box with ``OK'' and
22834 ``Cancel'' buttons to appear, which allows the user to either
22835 terminate the crashing process (OK) or debug it (Cancel).
22838 @kindex set cygwin-exceptions
22839 @cindex debugging the Cygwin DLL
22840 @cindex Cygwin DLL, debugging
22841 @item set cygwin-exceptions @var{mode}
22842 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22843 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22844 @value{GDBN} will delay recognition of exceptions, and may ignore some
22845 exceptions which seem to be caused by internal Cygwin DLL
22846 ``bookkeeping''. This option is meant primarily for debugging the
22847 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22848 @value{GDBN} users with false @code{SIGSEGV} signals.
22850 @kindex show cygwin-exceptions
22851 @item show cygwin-exceptions
22852 Displays whether @value{GDBN} will break on exceptions that happen
22853 inside the Cygwin DLL itself.
22855 @kindex set new-console
22856 @item set new-console @var{mode}
22857 If @var{mode} is @code{on} the debuggee will
22858 be started in a new console on next start.
22859 If @var{mode} is @code{off}, the debuggee will
22860 be started in the same console as the debugger.
22862 @kindex show new-console
22863 @item show new-console
22864 Displays whether a new console is used
22865 when the debuggee is started.
22867 @kindex set new-group
22868 @item set new-group @var{mode}
22869 This boolean value controls whether the debuggee should
22870 start a new group or stay in the same group as the debugger.
22871 This affects the way the Windows OS handles
22874 @kindex show new-group
22875 @item show new-group
22876 Displays current value of new-group boolean.
22878 @kindex set debugevents
22879 @item set debugevents
22880 This boolean value adds debug output concerning kernel events related
22881 to the debuggee seen by the debugger. This includes events that
22882 signal thread and process creation and exit, DLL loading and
22883 unloading, console interrupts, and debugging messages produced by the
22884 Windows @code{OutputDebugString} API call.
22886 @kindex set debugexec
22887 @item set debugexec
22888 This boolean value adds debug output concerning execute events
22889 (such as resume thread) seen by the debugger.
22891 @kindex set debugexceptions
22892 @item set debugexceptions
22893 This boolean value adds debug output concerning exceptions in the
22894 debuggee seen by the debugger.
22896 @kindex set debugmemory
22897 @item set debugmemory
22898 This boolean value adds debug output concerning debuggee memory reads
22899 and writes by the debugger.
22903 This boolean values specifies whether the debuggee is called
22904 via a shell or directly (default value is on).
22908 Displays if the debuggee will be started with a shell.
22913 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22916 @node Non-debug DLL Symbols
22917 @subsubsection Support for DLLs without Debugging Symbols
22918 @cindex DLLs with no debugging symbols
22919 @cindex Minimal symbols and DLLs
22921 Very often on windows, some of the DLLs that your program relies on do
22922 not include symbolic debugging information (for example,
22923 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22924 symbols in a DLL, it relies on the minimal amount of symbolic
22925 information contained in the DLL's export table. This section
22926 describes working with such symbols, known internally to @value{GDBN} as
22927 ``minimal symbols''.
22929 Note that before the debugged program has started execution, no DLLs
22930 will have been loaded. The easiest way around this problem is simply to
22931 start the program --- either by setting a breakpoint or letting the
22932 program run once to completion.
22934 @subsubsection DLL Name Prefixes
22936 In keeping with the naming conventions used by the Microsoft debugging
22937 tools, DLL export symbols are made available with a prefix based on the
22938 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22939 also entered into the symbol table, so @code{CreateFileA} is often
22940 sufficient. In some cases there will be name clashes within a program
22941 (particularly if the executable itself includes full debugging symbols)
22942 necessitating the use of the fully qualified name when referring to the
22943 contents of the DLL. Use single-quotes around the name to avoid the
22944 exclamation mark (``!'') being interpreted as a language operator.
22946 Note that the internal name of the DLL may be all upper-case, even
22947 though the file name of the DLL is lower-case, or vice-versa. Since
22948 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22949 some confusion. If in doubt, try the @code{info functions} and
22950 @code{info variables} commands or even @code{maint print msymbols}
22951 (@pxref{Symbols}). Here's an example:
22954 (@value{GDBP}) info function CreateFileA
22955 All functions matching regular expression "CreateFileA":
22957 Non-debugging symbols:
22958 0x77e885f4 CreateFileA
22959 0x77e885f4 KERNEL32!CreateFileA
22963 (@value{GDBP}) info function !
22964 All functions matching regular expression "!":
22966 Non-debugging symbols:
22967 0x6100114c cygwin1!__assert
22968 0x61004034 cygwin1!_dll_crt0@@0
22969 0x61004240 cygwin1!dll_crt0(per_process *)
22973 @subsubsection Working with Minimal Symbols
22975 Symbols extracted from a DLL's export table do not contain very much
22976 type information. All that @value{GDBN} can do is guess whether a symbol
22977 refers to a function or variable depending on the linker section that
22978 contains the symbol. Also note that the actual contents of the memory
22979 contained in a DLL are not available unless the program is running. This
22980 means that you cannot examine the contents of a variable or disassemble
22981 a function within a DLL without a running program.
22983 Variables are generally treated as pointers and dereferenced
22984 automatically. For this reason, it is often necessary to prefix a
22985 variable name with the address-of operator (``&'') and provide explicit
22986 type information in the command. Here's an example of the type of
22990 (@value{GDBP}) print 'cygwin1!__argv'
22991 'cygwin1!__argv' has unknown type; cast it to its declared type
22995 (@value{GDBP}) x 'cygwin1!__argv'
22996 'cygwin1!__argv' has unknown type; cast it to its declared type
22999 And two possible solutions:
23002 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23003 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23007 (@value{GDBP}) x/2x &'cygwin1!__argv'
23008 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23009 (@value{GDBP}) x/x 0x10021608
23010 0x10021608: 0x0022fd98
23011 (@value{GDBP}) x/s 0x0022fd98
23012 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23015 Setting a break point within a DLL is possible even before the program
23016 starts execution. However, under these circumstances, @value{GDBN} can't
23017 examine the initial instructions of the function in order to skip the
23018 function's frame set-up code. You can work around this by using ``*&''
23019 to set the breakpoint at a raw memory address:
23022 (@value{GDBP}) break *&'python22!PyOS_Readline'
23023 Breakpoint 1 at 0x1e04eff0
23026 The author of these extensions is not entirely convinced that setting a
23027 break point within a shared DLL like @file{kernel32.dll} is completely
23031 @subsection Commands Specific to @sc{gnu} Hurd Systems
23032 @cindex @sc{gnu} Hurd debugging
23034 This subsection describes @value{GDBN} commands specific to the
23035 @sc{gnu} Hurd native debugging.
23040 @kindex set signals@r{, Hurd command}
23041 @kindex set sigs@r{, Hurd command}
23042 This command toggles the state of inferior signal interception by
23043 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23044 affected by this command. @code{sigs} is a shorthand alias for
23049 @kindex show signals@r{, Hurd command}
23050 @kindex show sigs@r{, Hurd command}
23051 Show the current state of intercepting inferior's signals.
23053 @item set signal-thread
23054 @itemx set sigthread
23055 @kindex set signal-thread
23056 @kindex set sigthread
23057 This command tells @value{GDBN} which thread is the @code{libc} signal
23058 thread. That thread is run when a signal is delivered to a running
23059 process. @code{set sigthread} is the shorthand alias of @code{set
23062 @item show signal-thread
23063 @itemx show sigthread
23064 @kindex show signal-thread
23065 @kindex show sigthread
23066 These two commands show which thread will run when the inferior is
23067 delivered a signal.
23070 @kindex set stopped@r{, Hurd command}
23071 This commands tells @value{GDBN} that the inferior process is stopped,
23072 as with the @code{SIGSTOP} signal. The stopped process can be
23073 continued by delivering a signal to it.
23076 @kindex show stopped@r{, Hurd command}
23077 This command shows whether @value{GDBN} thinks the debuggee is
23080 @item set exceptions
23081 @kindex set exceptions@r{, Hurd command}
23082 Use this command to turn off trapping of exceptions in the inferior.
23083 When exception trapping is off, neither breakpoints nor
23084 single-stepping will work. To restore the default, set exception
23087 @item show exceptions
23088 @kindex show exceptions@r{, Hurd command}
23089 Show the current state of trapping exceptions in the inferior.
23091 @item set task pause
23092 @kindex set task@r{, Hurd commands}
23093 @cindex task attributes (@sc{gnu} Hurd)
23094 @cindex pause current task (@sc{gnu} Hurd)
23095 This command toggles task suspension when @value{GDBN} has control.
23096 Setting it to on takes effect immediately, and the task is suspended
23097 whenever @value{GDBN} gets control. Setting it to off will take
23098 effect the next time the inferior is continued. If this option is set
23099 to off, you can use @code{set thread default pause on} or @code{set
23100 thread pause on} (see below) to pause individual threads.
23102 @item show task pause
23103 @kindex show task@r{, Hurd commands}
23104 Show the current state of task suspension.
23106 @item set task detach-suspend-count
23107 @cindex task suspend count
23108 @cindex detach from task, @sc{gnu} Hurd
23109 This command sets the suspend count the task will be left with when
23110 @value{GDBN} detaches from it.
23112 @item show task detach-suspend-count
23113 Show the suspend count the task will be left with when detaching.
23115 @item set task exception-port
23116 @itemx set task excp
23117 @cindex task exception port, @sc{gnu} Hurd
23118 This command sets the task exception port to which @value{GDBN} will
23119 forward exceptions. The argument should be the value of the @dfn{send
23120 rights} of the task. @code{set task excp} is a shorthand alias.
23122 @item set noninvasive
23123 @cindex noninvasive task options
23124 This command switches @value{GDBN} to a mode that is the least
23125 invasive as far as interfering with the inferior is concerned. This
23126 is the same as using @code{set task pause}, @code{set exceptions}, and
23127 @code{set signals} to values opposite to the defaults.
23129 @item info send-rights
23130 @itemx info receive-rights
23131 @itemx info port-rights
23132 @itemx info port-sets
23133 @itemx info dead-names
23136 @cindex send rights, @sc{gnu} Hurd
23137 @cindex receive rights, @sc{gnu} Hurd
23138 @cindex port rights, @sc{gnu} Hurd
23139 @cindex port sets, @sc{gnu} Hurd
23140 @cindex dead names, @sc{gnu} Hurd
23141 These commands display information about, respectively, send rights,
23142 receive rights, port rights, port sets, and dead names of a task.
23143 There are also shorthand aliases: @code{info ports} for @code{info
23144 port-rights} and @code{info psets} for @code{info port-sets}.
23146 @item set thread pause
23147 @kindex set thread@r{, Hurd command}
23148 @cindex thread properties, @sc{gnu} Hurd
23149 @cindex pause current thread (@sc{gnu} Hurd)
23150 This command toggles current thread suspension when @value{GDBN} has
23151 control. Setting it to on takes effect immediately, and the current
23152 thread is suspended whenever @value{GDBN} gets control. Setting it to
23153 off will take effect the next time the inferior is continued.
23154 Normally, this command has no effect, since when @value{GDBN} has
23155 control, the whole task is suspended. However, if you used @code{set
23156 task pause off} (see above), this command comes in handy to suspend
23157 only the current thread.
23159 @item show thread pause
23160 @kindex show thread@r{, Hurd command}
23161 This command shows the state of current thread suspension.
23163 @item set thread run
23164 This command sets whether the current thread is allowed to run.
23166 @item show thread run
23167 Show whether the current thread is allowed to run.
23169 @item set thread detach-suspend-count
23170 @cindex thread suspend count, @sc{gnu} Hurd
23171 @cindex detach from thread, @sc{gnu} Hurd
23172 This command sets the suspend count @value{GDBN} will leave on a
23173 thread when detaching. This number is relative to the suspend count
23174 found by @value{GDBN} when it notices the thread; use @code{set thread
23175 takeover-suspend-count} to force it to an absolute value.
23177 @item show thread detach-suspend-count
23178 Show the suspend count @value{GDBN} will leave on the thread when
23181 @item set thread exception-port
23182 @itemx set thread excp
23183 Set the thread exception port to which to forward exceptions. This
23184 overrides the port set by @code{set task exception-port} (see above).
23185 @code{set thread excp} is the shorthand alias.
23187 @item set thread takeover-suspend-count
23188 Normally, @value{GDBN}'s thread suspend counts are relative to the
23189 value @value{GDBN} finds when it notices each thread. This command
23190 changes the suspend counts to be absolute instead.
23192 @item set thread default
23193 @itemx show thread default
23194 @cindex thread default settings, @sc{gnu} Hurd
23195 Each of the above @code{set thread} commands has a @code{set thread
23196 default} counterpart (e.g., @code{set thread default pause}, @code{set
23197 thread default exception-port}, etc.). The @code{thread default}
23198 variety of commands sets the default thread properties for all
23199 threads; you can then change the properties of individual threads with
23200 the non-default commands.
23207 @value{GDBN} provides the following commands specific to the Darwin target:
23210 @item set debug darwin @var{num}
23211 @kindex set debug darwin
23212 When set to a non zero value, enables debugging messages specific to
23213 the Darwin support. Higher values produce more verbose output.
23215 @item show debug darwin
23216 @kindex show debug darwin
23217 Show the current state of Darwin messages.
23219 @item set debug mach-o @var{num}
23220 @kindex set debug mach-o
23221 When set to a non zero value, enables debugging messages while
23222 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23223 file format used on Darwin for object and executable files.) Higher
23224 values produce more verbose output. This is a command to diagnose
23225 problems internal to @value{GDBN} and should not be needed in normal
23228 @item show debug mach-o
23229 @kindex show debug mach-o
23230 Show the current state of Mach-O file messages.
23232 @item set mach-exceptions on
23233 @itemx set mach-exceptions off
23234 @kindex set mach-exceptions
23235 On Darwin, faults are first reported as a Mach exception and are then
23236 mapped to a Posix signal. Use this command to turn on trapping of
23237 Mach exceptions in the inferior. This might be sometimes useful to
23238 better understand the cause of a fault. The default is off.
23240 @item show mach-exceptions
23241 @kindex show mach-exceptions
23242 Show the current state of exceptions trapping.
23247 @section Embedded Operating Systems
23249 This section describes configurations involving the debugging of
23250 embedded operating systems that are available for several different
23253 @value{GDBN} includes the ability to debug programs running on
23254 various real-time operating systems.
23256 @node Embedded Processors
23257 @section Embedded Processors
23259 This section goes into details specific to particular embedded
23262 @cindex send command to simulator
23263 Whenever a specific embedded processor has a simulator, @value{GDBN}
23264 allows to send an arbitrary command to the simulator.
23267 @item sim @var{command}
23268 @kindex sim@r{, a command}
23269 Send an arbitrary @var{command} string to the simulator. Consult the
23270 documentation for the specific simulator in use for information about
23271 acceptable commands.
23276 * ARC:: Synopsys ARC
23278 * M68K:: Motorola M68K
23279 * MicroBlaze:: Xilinx MicroBlaze
23280 * MIPS Embedded:: MIPS Embedded
23281 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23282 * PowerPC Embedded:: PowerPC Embedded
23285 * Super-H:: Renesas Super-H
23289 @subsection Synopsys ARC
23290 @cindex Synopsys ARC
23291 @cindex ARC specific commands
23297 @value{GDBN} provides the following ARC-specific commands:
23300 @item set debug arc
23301 @kindex set debug arc
23302 Control the level of ARC specific debug messages. Use 0 for no messages (the
23303 default), 1 for debug messages, and 2 for even more debug messages.
23305 @item show debug arc
23306 @kindex show debug arc
23307 Show the level of ARC specific debugging in operation.
23309 @item maint print arc arc-instruction @var{address}
23310 @kindex maint print arc arc-instruction
23311 Print internal disassembler information about instruction at a given address.
23318 @value{GDBN} provides the following ARM-specific commands:
23321 @item set arm disassembler
23323 This commands selects from a list of disassembly styles. The
23324 @code{"std"} style is the standard style.
23326 @item show arm disassembler
23328 Show the current disassembly style.
23330 @item set arm apcs32
23331 @cindex ARM 32-bit mode
23332 This command toggles ARM operation mode between 32-bit and 26-bit.
23334 @item show arm apcs32
23335 Display the current usage of the ARM 32-bit mode.
23337 @item set arm fpu @var{fputype}
23338 This command sets the ARM floating-point unit (FPU) type. The
23339 argument @var{fputype} can be one of these:
23343 Determine the FPU type by querying the OS ABI.
23345 Software FPU, with mixed-endian doubles on little-endian ARM
23348 GCC-compiled FPA co-processor.
23350 Software FPU with pure-endian doubles.
23356 Show the current type of the FPU.
23359 This command forces @value{GDBN} to use the specified ABI.
23362 Show the currently used ABI.
23364 @item set arm fallback-mode (arm|thumb|auto)
23365 @value{GDBN} uses the symbol table, when available, to determine
23366 whether instructions are ARM or Thumb. This command controls
23367 @value{GDBN}'s default behavior when the symbol table is not
23368 available. The default is @samp{auto}, which causes @value{GDBN} to
23369 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23372 @item show arm fallback-mode
23373 Show the current fallback instruction mode.
23375 @item set arm force-mode (arm|thumb|auto)
23376 This command overrides use of the symbol table to determine whether
23377 instructions are ARM or Thumb. The default is @samp{auto}, which
23378 causes @value{GDBN} to use the symbol table and then the setting
23379 of @samp{set arm fallback-mode}.
23381 @item show arm force-mode
23382 Show the current forced instruction mode.
23384 @item set debug arm
23385 Toggle whether to display ARM-specific debugging messages from the ARM
23386 target support subsystem.
23388 @item show debug arm
23389 Show whether ARM-specific debugging messages are enabled.
23393 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23394 The @value{GDBN} ARM simulator accepts the following optional arguments.
23397 @item --swi-support=@var{type}
23398 Tell the simulator which SWI interfaces to support. The argument
23399 @var{type} may be a comma separated list of the following values.
23400 The default value is @code{all}.
23415 The Motorola m68k configuration includes ColdFire support.
23418 @subsection MicroBlaze
23419 @cindex Xilinx MicroBlaze
23420 @cindex XMD, Xilinx Microprocessor Debugger
23422 The MicroBlaze is a soft-core processor supported on various Xilinx
23423 FPGAs, such as Spartan or Virtex series. Boards with these processors
23424 usually have JTAG ports which connect to a host system running the Xilinx
23425 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23426 This host system is used to download the configuration bitstream to
23427 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23428 communicates with the target board using the JTAG interface and
23429 presents a @code{gdbserver} interface to the board. By default
23430 @code{xmd} uses port @code{1234}. (While it is possible to change
23431 this default port, it requires the use of undocumented @code{xmd}
23432 commands. Contact Xilinx support if you need to do this.)
23434 Use these GDB commands to connect to the MicroBlaze target processor.
23437 @item target remote :1234
23438 Use this command to connect to the target if you are running @value{GDBN}
23439 on the same system as @code{xmd}.
23441 @item target remote @var{xmd-host}:1234
23442 Use this command to connect to the target if it is connected to @code{xmd}
23443 running on a different system named @var{xmd-host}.
23446 Use this command to download a program to the MicroBlaze target.
23448 @item set debug microblaze @var{n}
23449 Enable MicroBlaze-specific debugging messages if non-zero.
23451 @item show debug microblaze @var{n}
23452 Show MicroBlaze-specific debugging level.
23455 @node MIPS Embedded
23456 @subsection @acronym{MIPS} Embedded
23459 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23462 @item set mipsfpu double
23463 @itemx set mipsfpu single
23464 @itemx set mipsfpu none
23465 @itemx set mipsfpu auto
23466 @itemx show mipsfpu
23467 @kindex set mipsfpu
23468 @kindex show mipsfpu
23469 @cindex @acronym{MIPS} remote floating point
23470 @cindex floating point, @acronym{MIPS} remote
23471 If your target board does not support the @acronym{MIPS} floating point
23472 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23473 need this, you may wish to put the command in your @value{GDBN} init
23474 file). This tells @value{GDBN} how to find the return value of
23475 functions which return floating point values. It also allows
23476 @value{GDBN} to avoid saving the floating point registers when calling
23477 functions on the board. If you are using a floating point coprocessor
23478 with only single precision floating point support, as on the @sc{r4650}
23479 processor, use the command @samp{set mipsfpu single}. The default
23480 double precision floating point coprocessor may be selected using
23481 @samp{set mipsfpu double}.
23483 In previous versions the only choices were double precision or no
23484 floating point, so @samp{set mipsfpu on} will select double precision
23485 and @samp{set mipsfpu off} will select no floating point.
23487 As usual, you can inquire about the @code{mipsfpu} variable with
23488 @samp{show mipsfpu}.
23491 @node OpenRISC 1000
23492 @subsection OpenRISC 1000
23493 @cindex OpenRISC 1000
23496 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23497 mainly provided as a soft-core which can run on Xilinx, Altera and other
23500 @value{GDBN} for OpenRISC supports the below commands when connecting to
23508 Runs the builtin CPU simulator which can run very basic
23509 programs but does not support most hardware functions like MMU.
23510 For more complex use cases the user is advised to run an external
23511 target, and connect using @samp{target remote}.
23513 Example: @code{target sim}
23515 @item set debug or1k
23516 Toggle whether to display OpenRISC-specific debugging messages from the
23517 OpenRISC target support subsystem.
23519 @item show debug or1k
23520 Show whether OpenRISC-specific debugging messages are enabled.
23523 @node PowerPC Embedded
23524 @subsection PowerPC Embedded
23526 @cindex DVC register
23527 @value{GDBN} supports using the DVC (Data Value Compare) register to
23528 implement in hardware simple hardware watchpoint conditions of the form:
23531 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23532 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23535 The DVC register will be automatically used when @value{GDBN} detects
23536 such pattern in a condition expression, and the created watchpoint uses one
23537 debug register (either the @code{exact-watchpoints} option is on and the
23538 variable is scalar, or the variable has a length of one byte). This feature
23539 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23542 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23543 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23544 in which case watchpoints using only one debug register are created when
23545 watching variables of scalar types.
23547 You can create an artificial array to watch an arbitrary memory
23548 region using one of the following commands (@pxref{Expressions}):
23551 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23552 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23555 PowerPC embedded processors support masked watchpoints. See the discussion
23556 about the @code{mask} argument in @ref{Set Watchpoints}.
23558 @cindex ranged breakpoint
23559 PowerPC embedded processors support hardware accelerated
23560 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23561 the inferior whenever it executes an instruction at any address within
23562 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23563 use the @code{break-range} command.
23565 @value{GDBN} provides the following PowerPC-specific commands:
23568 @kindex break-range
23569 @item break-range @var{start-location}, @var{end-location}
23570 Set a breakpoint for an address range given by
23571 @var{start-location} and @var{end-location}, which can specify a function name,
23572 a line number, an offset of lines from the current line or from the start
23573 location, or an address of an instruction (see @ref{Specify Location},
23574 for a list of all the possible ways to specify a @var{location}.)
23575 The breakpoint will stop execution of the inferior whenever it
23576 executes an instruction at any address within the specified range,
23577 (including @var{start-location} and @var{end-location}.)
23579 @kindex set powerpc
23580 @item set powerpc soft-float
23581 @itemx show powerpc soft-float
23582 Force @value{GDBN} to use (or not use) a software floating point calling
23583 convention. By default, @value{GDBN} selects the calling convention based
23584 on the selected architecture and the provided executable file.
23586 @item set powerpc vector-abi
23587 @itemx show powerpc vector-abi
23588 Force @value{GDBN} to use the specified calling convention for vector
23589 arguments and return values. The valid options are @samp{auto};
23590 @samp{generic}, to avoid vector registers even if they are present;
23591 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23592 registers. By default, @value{GDBN} selects the calling convention
23593 based on the selected architecture and the provided executable file.
23595 @item set powerpc exact-watchpoints
23596 @itemx show powerpc exact-watchpoints
23597 Allow @value{GDBN} to use only one debug register when watching a variable
23598 of scalar type, thus assuming that the variable is accessed through the
23599 address of its first byte.
23604 @subsection Atmel AVR
23607 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23608 following AVR-specific commands:
23611 @item info io_registers
23612 @kindex info io_registers@r{, AVR}
23613 @cindex I/O registers (Atmel AVR)
23614 This command displays information about the AVR I/O registers. For
23615 each register, @value{GDBN} prints its number and value.
23622 When configured for debugging CRIS, @value{GDBN} provides the
23623 following CRIS-specific commands:
23626 @item set cris-version @var{ver}
23627 @cindex CRIS version
23628 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23629 The CRIS version affects register names and sizes. This command is useful in
23630 case autodetection of the CRIS version fails.
23632 @item show cris-version
23633 Show the current CRIS version.
23635 @item set cris-dwarf2-cfi
23636 @cindex DWARF-2 CFI and CRIS
23637 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23638 Change to @samp{off} when using @code{gcc-cris} whose version is below
23641 @item show cris-dwarf2-cfi
23642 Show the current state of using DWARF-2 CFI.
23644 @item set cris-mode @var{mode}
23646 Set the current CRIS mode to @var{mode}. It should only be changed when
23647 debugging in guru mode, in which case it should be set to
23648 @samp{guru} (the default is @samp{normal}).
23650 @item show cris-mode
23651 Show the current CRIS mode.
23655 @subsection Renesas Super-H
23658 For the Renesas Super-H processor, @value{GDBN} provides these
23662 @item set sh calling-convention @var{convention}
23663 @kindex set sh calling-convention
23664 Set the calling-convention used when calling functions from @value{GDBN}.
23665 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23666 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23667 convention. If the DWARF-2 information of the called function specifies
23668 that the function follows the Renesas calling convention, the function
23669 is called using the Renesas calling convention. If the calling convention
23670 is set to @samp{renesas}, the Renesas calling convention is always used,
23671 regardless of the DWARF-2 information. This can be used to override the
23672 default of @samp{gcc} if debug information is missing, or the compiler
23673 does not emit the DWARF-2 calling convention entry for a function.
23675 @item show sh calling-convention
23676 @kindex show sh calling-convention
23677 Show the current calling convention setting.
23682 @node Architectures
23683 @section Architectures
23685 This section describes characteristics of architectures that affect
23686 all uses of @value{GDBN} with the architecture, both native and cross.
23693 * HPPA:: HP PA architecture
23694 * SPU:: Cell Broadband Engine SPU architecture
23702 @subsection AArch64
23703 @cindex AArch64 support
23705 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23706 following special commands:
23709 @item set debug aarch64
23710 @kindex set debug aarch64
23711 This command determines whether AArch64 architecture-specific debugging
23712 messages are to be displayed.
23714 @item show debug aarch64
23715 Show whether AArch64 debugging messages are displayed.
23719 @subsubsection AArch64 SVE.
23720 @cindex AArch64 SVE.
23722 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23723 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23724 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23725 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23726 @code{$vg} will be provided. This is the vector granule for the current thread
23727 and represents the number of 64-bit chunks in an SVE @code{z} register.
23729 If the vector length changes, then the @code{$vg} register will be updated,
23730 but the lengths of the @code{z} and @code{p} registers will not change. This
23731 is a known limitation of @value{GDBN} and does not affect the execution of the
23736 @subsection x86 Architecture-specific Issues
23739 @item set struct-convention @var{mode}
23740 @kindex set struct-convention
23741 @cindex struct return convention
23742 @cindex struct/union returned in registers
23743 Set the convention used by the inferior to return @code{struct}s and
23744 @code{union}s from functions to @var{mode}. Possible values of
23745 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23746 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23747 are returned on the stack, while @code{"reg"} means that a
23748 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23749 be returned in a register.
23751 @item show struct-convention
23752 @kindex show struct-convention
23753 Show the current setting of the convention to return @code{struct}s
23758 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23759 @cindex Intel Memory Protection Extensions (MPX).
23761 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23762 @footnote{The register named with capital letters represent the architecture
23763 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23764 which are the lower bound and upper bound. Bounds are effective addresses or
23765 memory locations. The upper bounds are architecturally represented in 1's
23766 complement form. A bound having lower bound = 0, and upper bound = 0
23767 (1's complement of all bits set) will allow access to the entire address space.
23769 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23770 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23771 display the upper bound performing the complement of one operation on the
23772 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23773 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23774 can also be noted that the upper bounds are inclusive.
23776 As an example, assume that the register BND0 holds bounds for a pointer having
23777 access allowed for the range between 0x32 and 0x71. The values present on
23778 bnd0raw and bnd registers are presented as follows:
23781 bnd0raw = @{0x32, 0xffffffff8e@}
23782 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23785 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23786 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23787 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23788 Python, the display includes the memory size, in bits, accessible to
23791 Bounds can also be stored in bounds tables, which are stored in
23792 application memory. These tables store bounds for pointers by specifying
23793 the bounds pointer's value along with its bounds. Evaluating and changing
23794 bounds located in bound tables is therefore interesting while investigating
23795 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23798 @item show mpx bound @var{pointer}
23799 @kindex show mpx bound
23800 Display bounds of the given @var{pointer}.
23802 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23803 @kindex set mpx bound
23804 Set the bounds of a pointer in the bound table.
23805 This command takes three parameters: @var{pointer} is the pointers
23806 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23807 for lower and upper bounds respectively.
23810 When you call an inferior function on an Intel MPX enabled program,
23811 GDB sets the inferior's bound registers to the init (disabled) state
23812 before calling the function. As a consequence, bounds checks for the
23813 pointer arguments passed to the function will always pass.
23815 This is necessary because when you call an inferior function, the
23816 program is usually in the middle of the execution of other function.
23817 Since at that point bound registers are in an arbitrary state, not
23818 clearing them would lead to random bound violations in the called
23821 You can still examine the influence of the bound registers on the
23822 execution of the called function by stopping the execution of the
23823 called function at its prologue, setting bound registers, and
23824 continuing the execution. For example:
23828 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23829 $ print upper (a, b, c, d, 1)
23830 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23832 @{lbound = 0x0, ubound = ffffffff@} : size -1
23835 At this last step the value of bnd0 can be changed for investigation of bound
23836 violations caused along the execution of the call. In order to know how to
23837 set the bound registers or bound table for the call consult the ABI.
23842 See the following section.
23845 @subsection @acronym{MIPS}
23847 @cindex stack on Alpha
23848 @cindex stack on @acronym{MIPS}
23849 @cindex Alpha stack
23850 @cindex @acronym{MIPS} stack
23851 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23852 sometimes requires @value{GDBN} to search backward in the object code to
23853 find the beginning of a function.
23855 @cindex response time, @acronym{MIPS} debugging
23856 To improve response time (especially for embedded applications, where
23857 @value{GDBN} may be restricted to a slow serial line for this search)
23858 you may want to limit the size of this search, using one of these
23862 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23863 @item set heuristic-fence-post @var{limit}
23864 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23865 search for the beginning of a function. A value of @var{0} (the
23866 default) means there is no limit. However, except for @var{0}, the
23867 larger the limit the more bytes @code{heuristic-fence-post} must search
23868 and therefore the longer it takes to run. You should only need to use
23869 this command when debugging a stripped executable.
23871 @item show heuristic-fence-post
23872 Display the current limit.
23876 These commands are available @emph{only} when @value{GDBN} is configured
23877 for debugging programs on Alpha or @acronym{MIPS} processors.
23879 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23883 @item set mips abi @var{arg}
23884 @kindex set mips abi
23885 @cindex set ABI for @acronym{MIPS}
23886 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23887 values of @var{arg} are:
23891 The default ABI associated with the current binary (this is the
23901 @item show mips abi
23902 @kindex show mips abi
23903 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23905 @item set mips compression @var{arg}
23906 @kindex set mips compression
23907 @cindex code compression, @acronym{MIPS}
23908 Tell @value{GDBN} which @acronym{MIPS} compressed
23909 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23910 inferior. @value{GDBN} uses this for code disassembly and other
23911 internal interpretation purposes. This setting is only referred to
23912 when no executable has been associated with the debugging session or
23913 the executable does not provide information about the encoding it uses.
23914 Otherwise this setting is automatically updated from information
23915 provided by the executable.
23917 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23918 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23919 executables containing @acronym{MIPS16} code frequently are not
23920 identified as such.
23922 This setting is ``sticky''; that is, it retains its value across
23923 debugging sessions until reset either explicitly with this command or
23924 implicitly from an executable.
23926 The compiler and/or assembler typically add symbol table annotations to
23927 identify functions compiled for the @acronym{MIPS16} or
23928 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23929 are present, @value{GDBN} uses them in preference to the global
23930 compressed @acronym{ISA} encoding setting.
23932 @item show mips compression
23933 @kindex show mips compression
23934 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23935 @value{GDBN} to debug the inferior.
23938 @itemx show mipsfpu
23939 @xref{MIPS Embedded, set mipsfpu}.
23941 @item set mips mask-address @var{arg}
23942 @kindex set mips mask-address
23943 @cindex @acronym{MIPS} addresses, masking
23944 This command determines whether the most-significant 32 bits of 64-bit
23945 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23946 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23947 setting, which lets @value{GDBN} determine the correct value.
23949 @item show mips mask-address
23950 @kindex show mips mask-address
23951 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23954 @item set remote-mips64-transfers-32bit-regs
23955 @kindex set remote-mips64-transfers-32bit-regs
23956 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23957 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23958 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23959 and 64 bits for other registers, set this option to @samp{on}.
23961 @item show remote-mips64-transfers-32bit-regs
23962 @kindex show remote-mips64-transfers-32bit-regs
23963 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23965 @item set debug mips
23966 @kindex set debug mips
23967 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23968 target code in @value{GDBN}.
23970 @item show debug mips
23971 @kindex show debug mips
23972 Show the current setting of @acronym{MIPS} debugging messages.
23978 @cindex HPPA support
23980 When @value{GDBN} is debugging the HP PA architecture, it provides the
23981 following special commands:
23984 @item set debug hppa
23985 @kindex set debug hppa
23986 This command determines whether HPPA architecture-specific debugging
23987 messages are to be displayed.
23989 @item show debug hppa
23990 Show whether HPPA debugging messages are displayed.
23992 @item maint print unwind @var{address}
23993 @kindex maint print unwind@r{, HPPA}
23994 This command displays the contents of the unwind table entry at the
23995 given @var{address}.
24001 @subsection Cell Broadband Engine SPU architecture
24002 @cindex Cell Broadband Engine
24005 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24006 it provides the following special commands:
24009 @item info spu event
24011 Display SPU event facility status. Shows current event mask
24012 and pending event status.
24014 @item info spu signal
24015 Display SPU signal notification facility status. Shows pending
24016 signal-control word and signal notification mode of both signal
24017 notification channels.
24019 @item info spu mailbox
24020 Display SPU mailbox facility status. Shows all pending entries,
24021 in order of processing, in each of the SPU Write Outbound,
24022 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24025 Display MFC DMA status. Shows all pending commands in the MFC
24026 DMA queue. For each entry, opcode, tag, class IDs, effective
24027 and local store addresses and transfer size are shown.
24029 @item info spu proxydma
24030 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24031 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24032 and local store addresses and transfer size are shown.
24036 When @value{GDBN} is debugging a combined PowerPC/SPU application
24037 on the Cell Broadband Engine, it provides in addition the following
24041 @item set spu stop-on-load @var{arg}
24043 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24044 will give control to the user when a new SPE thread enters its @code{main}
24045 function. The default is @code{off}.
24047 @item show spu stop-on-load
24049 Show whether to stop for new SPE threads.
24051 @item set spu auto-flush-cache @var{arg}
24052 Set whether to automatically flush the software-managed cache. When set to
24053 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24054 cache to be flushed whenever SPE execution stops. This provides a consistent
24055 view of PowerPC memory that is accessed via the cache. If an application
24056 does not use the software-managed cache, this option has no effect.
24058 @item show spu auto-flush-cache
24059 Show whether to automatically flush the software-managed cache.
24064 @subsection PowerPC
24065 @cindex PowerPC architecture
24067 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24068 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24069 numbers stored in the floating point registers. These values must be stored
24070 in two consecutive registers, always starting at an even register like
24071 @code{f0} or @code{f2}.
24073 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24074 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24075 @code{f2} and @code{f3} for @code{$dl1} and so on.
24077 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24078 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24081 @subsection Nios II
24082 @cindex Nios II architecture
24084 When @value{GDBN} is debugging the Nios II architecture,
24085 it provides the following special commands:
24089 @item set debug nios2
24090 @kindex set debug nios2
24091 This command turns on and off debugging messages for the Nios II
24092 target code in @value{GDBN}.
24094 @item show debug nios2
24095 @kindex show debug nios2
24096 Show the current setting of Nios II debugging messages.
24100 @subsection Sparc64
24101 @cindex Sparc64 support
24102 @cindex Application Data Integrity
24103 @subsubsection ADI Support
24105 The M7 processor supports an Application Data Integrity (ADI) feature that
24106 detects invalid data accesses. When software allocates memory and enables
24107 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24108 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24109 the 4-bit version in every cacheline of that data. Hardware saves the latter
24110 in spare bits in the cache and memory hierarchy. On each load and store,
24111 the processor compares the upper 4 VA (virtual address) bits to the
24112 cacheline's version. If there is a mismatch, the processor generates a
24113 version mismatch trap which can be either precise or disrupting. The trap
24114 is an error condition which the kernel delivers to the process as a SIGSEGV
24117 Note that only 64-bit applications can use ADI and need to be built with
24120 Values of the ADI version tags, which are in granularity of a
24121 cacheline (64 bytes), can be viewed or modified.
24125 @kindex adi examine
24126 @item adi (examine | x) [ / @var{n} ] @var{addr}
24128 The @code{adi examine} command displays the value of one ADI version tag per
24131 @var{n} is a decimal integer specifying the number in bytes; the default
24132 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24133 block size, to display.
24135 @var{addr} is the address in user address space where you want @value{GDBN}
24136 to begin displaying the ADI version tags.
24138 Below is an example of displaying ADI versions of variable "shmaddr".
24141 (@value{GDBP}) adi x/100 shmaddr
24142 0xfff800010002c000: 0 0
24146 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24148 The @code{adi assign} command is used to assign new ADI version tag
24151 @var{n} is a decimal integer specifying the number in bytes;
24152 the default is 1. It specifies how much ADI version information, at the
24153 ratio of 1:ADI block size, to modify.
24155 @var{addr} is the address in user address space where you want @value{GDBN}
24156 to begin modifying the ADI version tags.
24158 @var{tag} is the new ADI version tag.
24160 For example, do the following to modify then verify ADI versions of
24161 variable "shmaddr":
24164 (@value{GDBP}) adi a/100 shmaddr = 7
24165 (@value{GDBP}) adi x/100 shmaddr
24166 0xfff800010002c000: 7 7
24173 @cindex S12Z support
24175 When @value{GDBN} is debugging the S12Z architecture,
24176 it provides the following special command:
24179 @item maint info bdccsr
24180 @kindex maint info bdccsr@r{, S12Z}
24181 This command displays the current value of the microprocessor's
24186 @node Controlling GDB
24187 @chapter Controlling @value{GDBN}
24189 You can alter the way @value{GDBN} interacts with you by using the
24190 @code{set} command. For commands controlling how @value{GDBN} displays
24191 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24196 * Editing:: Command editing
24197 * Command History:: Command history
24198 * Screen Size:: Screen size
24199 * Numbers:: Numbers
24200 * ABI:: Configuring the current ABI
24201 * Auto-loading:: Automatically loading associated files
24202 * Messages/Warnings:: Optional warnings and messages
24203 * Debugging Output:: Optional messages about internal happenings
24204 * Other Misc Settings:: Other Miscellaneous Settings
24212 @value{GDBN} indicates its readiness to read a command by printing a string
24213 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24214 can change the prompt string with the @code{set prompt} command. For
24215 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24216 the prompt in one of the @value{GDBN} sessions so that you can always tell
24217 which one you are talking to.
24219 @emph{Note:} @code{set prompt} does not add a space for you after the
24220 prompt you set. This allows you to set a prompt which ends in a space
24221 or a prompt that does not.
24225 @item set prompt @var{newprompt}
24226 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24228 @kindex show prompt
24230 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24233 Versions of @value{GDBN} that ship with Python scripting enabled have
24234 prompt extensions. The commands for interacting with these extensions
24238 @kindex set extended-prompt
24239 @item set extended-prompt @var{prompt}
24240 Set an extended prompt that allows for substitutions.
24241 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24242 substitution. Any escape sequences specified as part of the prompt
24243 string are replaced with the corresponding strings each time the prompt
24249 set extended-prompt Current working directory: \w (gdb)
24252 Note that when an extended-prompt is set, it takes control of the
24253 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24255 @kindex show extended-prompt
24256 @item show extended-prompt
24257 Prints the extended prompt. Any escape sequences specified as part of
24258 the prompt string with @code{set extended-prompt}, are replaced with the
24259 corresponding strings each time the prompt is displayed.
24263 @section Command Editing
24265 @cindex command line editing
24267 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24268 @sc{gnu} library provides consistent behavior for programs which provide a
24269 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24270 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24271 substitution, and a storage and recall of command history across
24272 debugging sessions.
24274 You may control the behavior of command line editing in @value{GDBN} with the
24275 command @code{set}.
24278 @kindex set editing
24281 @itemx set editing on
24282 Enable command line editing (enabled by default).
24284 @item set editing off
24285 Disable command line editing.
24287 @kindex show editing
24289 Show whether command line editing is enabled.
24292 @ifset SYSTEM_READLINE
24293 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24295 @ifclear SYSTEM_READLINE
24296 @xref{Command Line Editing},
24298 for more details about the Readline
24299 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24300 encouraged to read that chapter.
24302 @node Command History
24303 @section Command History
24304 @cindex command history
24306 @value{GDBN} can keep track of the commands you type during your
24307 debugging sessions, so that you can be certain of precisely what
24308 happened. Use these commands to manage the @value{GDBN} command
24311 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24312 package, to provide the history facility.
24313 @ifset SYSTEM_READLINE
24314 @xref{Using History Interactively, , , history, GNU History Library},
24316 @ifclear SYSTEM_READLINE
24317 @xref{Using History Interactively},
24319 for the detailed description of the History library.
24321 To issue a command to @value{GDBN} without affecting certain aspects of
24322 the state which is seen by users, prefix it with @samp{server }
24323 (@pxref{Server Prefix}). This
24324 means that this command will not affect the command history, nor will it
24325 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24326 pressed on a line by itself.
24328 @cindex @code{server}, command prefix
24329 The server prefix does not affect the recording of values into the value
24330 history; to print a value without recording it into the value history,
24331 use the @code{output} command instead of the @code{print} command.
24333 Here is the description of @value{GDBN} commands related to command
24337 @cindex history substitution
24338 @cindex history file
24339 @kindex set history filename
24340 @cindex @env{GDBHISTFILE}, environment variable
24341 @item set history filename @var{fname}
24342 Set the name of the @value{GDBN} command history file to @var{fname}.
24343 This is the file where @value{GDBN} reads an initial command history
24344 list, and where it writes the command history from this session when it
24345 exits. You can access this list through history expansion or through
24346 the history command editing characters listed below. This file defaults
24347 to the value of the environment variable @code{GDBHISTFILE}, or to
24348 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24351 @cindex save command history
24352 @kindex set history save
24353 @item set history save
24354 @itemx set history save on
24355 Record command history in a file, whose name may be specified with the
24356 @code{set history filename} command. By default, this option is disabled.
24358 @item set history save off
24359 Stop recording command history in a file.
24361 @cindex history size
24362 @kindex set history size
24363 @cindex @env{GDBHISTSIZE}, environment variable
24364 @item set history size @var{size}
24365 @itemx set history size unlimited
24366 Set the number of commands which @value{GDBN} keeps in its history list.
24367 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24368 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24369 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24370 either a negative number or the empty string, then the number of commands
24371 @value{GDBN} keeps in the history list is unlimited.
24373 @cindex remove duplicate history
24374 @kindex set history remove-duplicates
24375 @item set history remove-duplicates @var{count}
24376 @itemx set history remove-duplicates unlimited
24377 Control the removal of duplicate history entries in the command history list.
24378 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24379 history entries and remove the first entry that is a duplicate of the current
24380 entry being added to the command history list. If @var{count} is
24381 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24382 removal of duplicate history entries is disabled.
24384 Only history entries added during the current session are considered for
24385 removal. This option is set to 0 by default.
24389 History expansion assigns special meaning to the character @kbd{!}.
24390 @ifset SYSTEM_READLINE
24391 @xref{Event Designators, , , history, GNU History Library},
24393 @ifclear SYSTEM_READLINE
24394 @xref{Event Designators},
24398 @cindex history expansion, turn on/off
24399 Since @kbd{!} is also the logical not operator in C, history expansion
24400 is off by default. If you decide to enable history expansion with the
24401 @code{set history expansion on} command, you may sometimes need to
24402 follow @kbd{!} (when it is used as logical not, in an expression) with
24403 a space or a tab to prevent it from being expanded. The readline
24404 history facilities do not attempt substitution on the strings
24405 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24407 The commands to control history expansion are:
24410 @item set history expansion on
24411 @itemx set history expansion
24412 @kindex set history expansion
24413 Enable history expansion. History expansion is off by default.
24415 @item set history expansion off
24416 Disable history expansion.
24419 @kindex show history
24421 @itemx show history filename
24422 @itemx show history save
24423 @itemx show history size
24424 @itemx show history expansion
24425 These commands display the state of the @value{GDBN} history parameters.
24426 @code{show history} by itself displays all four states.
24431 @kindex show commands
24432 @cindex show last commands
24433 @cindex display command history
24434 @item show commands
24435 Display the last ten commands in the command history.
24437 @item show commands @var{n}
24438 Print ten commands centered on command number @var{n}.
24440 @item show commands +
24441 Print ten commands just after the commands last printed.
24445 @section Screen Size
24446 @cindex size of screen
24447 @cindex screen size
24450 @cindex pauses in output
24452 Certain commands to @value{GDBN} may produce large amounts of
24453 information output to the screen. To help you read all of it,
24454 @value{GDBN} pauses and asks you for input at the end of each page of
24455 output. Type @key{RET} when you want to see one more page of output,
24456 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24457 without paging for the rest of the current command. Also, the screen
24458 width setting determines when to wrap lines of output. Depending on
24459 what is being printed, @value{GDBN} tries to break the line at a
24460 readable place, rather than simply letting it overflow onto the
24463 Normally @value{GDBN} knows the size of the screen from the terminal
24464 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24465 together with the value of the @code{TERM} environment variable and the
24466 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24467 you can override it with the @code{set height} and @code{set
24474 @kindex show height
24475 @item set height @var{lpp}
24476 @itemx set height unlimited
24478 @itemx set width @var{cpl}
24479 @itemx set width unlimited
24481 These @code{set} commands specify a screen height of @var{lpp} lines and
24482 a screen width of @var{cpl} characters. The associated @code{show}
24483 commands display the current settings.
24485 If you specify a height of either @code{unlimited} or zero lines,
24486 @value{GDBN} does not pause during output no matter how long the
24487 output is. This is useful if output is to a file or to an editor
24490 Likewise, you can specify @samp{set width unlimited} or @samp{set
24491 width 0} to prevent @value{GDBN} from wrapping its output.
24493 @item set pagination on
24494 @itemx set pagination off
24495 @kindex set pagination
24496 Turn the output pagination on or off; the default is on. Turning
24497 pagination off is the alternative to @code{set height unlimited}. Note that
24498 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24499 Options, -batch}) also automatically disables pagination.
24501 @item show pagination
24502 @kindex show pagination
24503 Show the current pagination mode.
24508 @cindex number representation
24509 @cindex entering numbers
24511 You can always enter numbers in octal, decimal, or hexadecimal in
24512 @value{GDBN} by the usual conventions: octal numbers begin with
24513 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24514 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24515 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24516 10; likewise, the default display for numbers---when no particular
24517 format is specified---is base 10. You can change the default base for
24518 both input and output with the commands described below.
24521 @kindex set input-radix
24522 @item set input-radix @var{base}
24523 Set the default base for numeric input. Supported choices
24524 for @var{base} are decimal 8, 10, or 16. The base must itself be
24525 specified either unambiguously or using the current input radix; for
24529 set input-radix 012
24530 set input-radix 10.
24531 set input-radix 0xa
24535 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24536 leaves the input radix unchanged, no matter what it was, since
24537 @samp{10}, being without any leading or trailing signs of its base, is
24538 interpreted in the current radix. Thus, if the current radix is 16,
24539 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24542 @kindex set output-radix
24543 @item set output-radix @var{base}
24544 Set the default base for numeric display. Supported choices
24545 for @var{base} are decimal 8, 10, or 16. The base must itself be
24546 specified either unambiguously or using the current input radix.
24548 @kindex show input-radix
24549 @item show input-radix
24550 Display the current default base for numeric input.
24552 @kindex show output-radix
24553 @item show output-radix
24554 Display the current default base for numeric display.
24556 @item set radix @r{[}@var{base}@r{]}
24560 These commands set and show the default base for both input and output
24561 of numbers. @code{set radix} sets the radix of input and output to
24562 the same base; without an argument, it resets the radix back to its
24563 default value of 10.
24568 @section Configuring the Current ABI
24570 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24571 application automatically. However, sometimes you need to override its
24572 conclusions. Use these commands to manage @value{GDBN}'s view of the
24578 @cindex Newlib OS ABI and its influence on the longjmp handling
24580 One @value{GDBN} configuration can debug binaries for multiple operating
24581 system targets, either via remote debugging or native emulation.
24582 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24583 but you can override its conclusion using the @code{set osabi} command.
24584 One example where this is useful is in debugging of binaries which use
24585 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24586 not have the same identifying marks that the standard C library for your
24589 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24590 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24591 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24592 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24596 Show the OS ABI currently in use.
24599 With no argument, show the list of registered available OS ABI's.
24601 @item set osabi @var{abi}
24602 Set the current OS ABI to @var{abi}.
24605 @cindex float promotion
24607 Generally, the way that an argument of type @code{float} is passed to a
24608 function depends on whether the function is prototyped. For a prototyped
24609 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24610 according to the architecture's convention for @code{float}. For unprototyped
24611 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24612 @code{double} and then passed.
24614 Unfortunately, some forms of debug information do not reliably indicate whether
24615 a function is prototyped. If @value{GDBN} calls a function that is not marked
24616 as prototyped, it consults @kbd{set coerce-float-to-double}.
24619 @kindex set coerce-float-to-double
24620 @item set coerce-float-to-double
24621 @itemx set coerce-float-to-double on
24622 Arguments of type @code{float} will be promoted to @code{double} when passed
24623 to an unprototyped function. This is the default setting.
24625 @item set coerce-float-to-double off
24626 Arguments of type @code{float} will be passed directly to unprototyped
24629 @kindex show coerce-float-to-double
24630 @item show coerce-float-to-double
24631 Show the current setting of promoting @code{float} to @code{double}.
24635 @kindex show cp-abi
24636 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24637 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24638 used to build your application. @value{GDBN} only fully supports
24639 programs with a single C@t{++} ABI; if your program contains code using
24640 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24641 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24642 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24643 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24644 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24645 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24650 Show the C@t{++} ABI currently in use.
24653 With no argument, show the list of supported C@t{++} ABI's.
24655 @item set cp-abi @var{abi}
24656 @itemx set cp-abi auto
24657 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24661 @section Automatically loading associated files
24662 @cindex auto-loading
24664 @value{GDBN} sometimes reads files with commands and settings automatically,
24665 without being explicitly told so by the user. We call this feature
24666 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24667 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24668 results or introduce security risks (e.g., if the file comes from untrusted
24672 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24673 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24675 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24676 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24679 There are various kinds of files @value{GDBN} can automatically load.
24680 In addition to these files, @value{GDBN} supports auto-loading code written
24681 in various extension languages. @xref{Auto-loading extensions}.
24683 Note that loading of these associated files (including the local @file{.gdbinit}
24684 file) requires accordingly configured @code{auto-load safe-path}
24685 (@pxref{Auto-loading safe path}).
24687 For these reasons, @value{GDBN} includes commands and options to let you
24688 control when to auto-load files and which files should be auto-loaded.
24691 @anchor{set auto-load off}
24692 @kindex set auto-load off
24693 @item set auto-load off
24694 Globally disable loading of all auto-loaded files.
24695 You may want to use this command with the @samp{-iex} option
24696 (@pxref{Option -init-eval-command}) such as:
24698 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24701 Be aware that system init file (@pxref{System-wide configuration})
24702 and init files from your home directory (@pxref{Home Directory Init File})
24703 still get read (as they come from generally trusted directories).
24704 To prevent @value{GDBN} from auto-loading even those init files, use the
24705 @option{-nx} option (@pxref{Mode Options}), in addition to
24706 @code{set auto-load no}.
24708 @anchor{show auto-load}
24709 @kindex show auto-load
24710 @item show auto-load
24711 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24715 (gdb) show auto-load
24716 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24717 libthread-db: Auto-loading of inferior specific libthread_db is on.
24718 local-gdbinit: Auto-loading of .gdbinit script from current directory
24720 python-scripts: Auto-loading of Python scripts is on.
24721 safe-path: List of directories from which it is safe to auto-load files
24722 is $debugdir:$datadir/auto-load.
24723 scripts-directory: List of directories from which to load auto-loaded scripts
24724 is $debugdir:$datadir/auto-load.
24727 @anchor{info auto-load}
24728 @kindex info auto-load
24729 @item info auto-load
24730 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24734 (gdb) info auto-load
24737 Yes /home/user/gdb/gdb-gdb.gdb
24738 libthread-db: No auto-loaded libthread-db.
24739 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24743 Yes /home/user/gdb/gdb-gdb.py
24747 These are @value{GDBN} control commands for the auto-loading:
24749 @multitable @columnfractions .5 .5
24750 @item @xref{set auto-load off}.
24751 @tab Disable auto-loading globally.
24752 @item @xref{show auto-load}.
24753 @tab Show setting of all kinds of files.
24754 @item @xref{info auto-load}.
24755 @tab Show state of all kinds of files.
24756 @item @xref{set auto-load gdb-scripts}.
24757 @tab Control for @value{GDBN} command scripts.
24758 @item @xref{show auto-load gdb-scripts}.
24759 @tab Show setting of @value{GDBN} command scripts.
24760 @item @xref{info auto-load gdb-scripts}.
24761 @tab Show state of @value{GDBN} command scripts.
24762 @item @xref{set auto-load python-scripts}.
24763 @tab Control for @value{GDBN} Python scripts.
24764 @item @xref{show auto-load python-scripts}.
24765 @tab Show setting of @value{GDBN} Python scripts.
24766 @item @xref{info auto-load python-scripts}.
24767 @tab Show state of @value{GDBN} Python scripts.
24768 @item @xref{set auto-load guile-scripts}.
24769 @tab Control for @value{GDBN} Guile scripts.
24770 @item @xref{show auto-load guile-scripts}.
24771 @tab Show setting of @value{GDBN} Guile scripts.
24772 @item @xref{info auto-load guile-scripts}.
24773 @tab Show state of @value{GDBN} Guile scripts.
24774 @item @xref{set auto-load scripts-directory}.
24775 @tab Control for @value{GDBN} auto-loaded scripts location.
24776 @item @xref{show auto-load scripts-directory}.
24777 @tab Show @value{GDBN} auto-loaded scripts location.
24778 @item @xref{add-auto-load-scripts-directory}.
24779 @tab Add directory for auto-loaded scripts location list.
24780 @item @xref{set auto-load local-gdbinit}.
24781 @tab Control for init file in the current directory.
24782 @item @xref{show auto-load local-gdbinit}.
24783 @tab Show setting of init file in the current directory.
24784 @item @xref{info auto-load local-gdbinit}.
24785 @tab Show state of init file in the current directory.
24786 @item @xref{set auto-load libthread-db}.
24787 @tab Control for thread debugging library.
24788 @item @xref{show auto-load libthread-db}.
24789 @tab Show setting of thread debugging library.
24790 @item @xref{info auto-load libthread-db}.
24791 @tab Show state of thread debugging library.
24792 @item @xref{set auto-load safe-path}.
24793 @tab Control directories trusted for automatic loading.
24794 @item @xref{show auto-load safe-path}.
24795 @tab Show directories trusted for automatic loading.
24796 @item @xref{add-auto-load-safe-path}.
24797 @tab Add directory trusted for automatic loading.
24800 @node Init File in the Current Directory
24801 @subsection Automatically loading init file in the current directory
24802 @cindex auto-loading init file in the current directory
24804 By default, @value{GDBN} reads and executes the canned sequences of commands
24805 from init file (if any) in the current working directory,
24806 see @ref{Init File in the Current Directory during Startup}.
24808 Note that loading of this local @file{.gdbinit} file also requires accordingly
24809 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24812 @anchor{set auto-load local-gdbinit}
24813 @kindex set auto-load local-gdbinit
24814 @item set auto-load local-gdbinit [on|off]
24815 Enable or disable the auto-loading of canned sequences of commands
24816 (@pxref{Sequences}) found in init file in the current directory.
24818 @anchor{show auto-load local-gdbinit}
24819 @kindex show auto-load local-gdbinit
24820 @item show auto-load local-gdbinit
24821 Show whether auto-loading of canned sequences of commands from init file in the
24822 current directory is enabled or disabled.
24824 @anchor{info auto-load local-gdbinit}
24825 @kindex info auto-load local-gdbinit
24826 @item info auto-load local-gdbinit
24827 Print whether canned sequences of commands from init file in the
24828 current directory have been auto-loaded.
24831 @node libthread_db.so.1 file
24832 @subsection Automatically loading thread debugging library
24833 @cindex auto-loading libthread_db.so.1
24835 This feature is currently present only on @sc{gnu}/Linux native hosts.
24837 @value{GDBN} reads in some cases thread debugging library from places specific
24838 to the inferior (@pxref{set libthread-db-search-path}).
24840 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24841 without checking this @samp{set auto-load libthread-db} switch as system
24842 libraries have to be trusted in general. In all other cases of
24843 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24844 auto-load libthread-db} is enabled before trying to open such thread debugging
24847 Note that loading of this debugging library also requires accordingly configured
24848 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24851 @anchor{set auto-load libthread-db}
24852 @kindex set auto-load libthread-db
24853 @item set auto-load libthread-db [on|off]
24854 Enable or disable the auto-loading of inferior specific thread debugging library.
24856 @anchor{show auto-load libthread-db}
24857 @kindex show auto-load libthread-db
24858 @item show auto-load libthread-db
24859 Show whether auto-loading of inferior specific thread debugging library is
24860 enabled or disabled.
24862 @anchor{info auto-load libthread-db}
24863 @kindex info auto-load libthread-db
24864 @item info auto-load libthread-db
24865 Print the list of all loaded inferior specific thread debugging libraries and
24866 for each such library print list of inferior @var{pid}s using it.
24869 @node Auto-loading safe path
24870 @subsection Security restriction for auto-loading
24871 @cindex auto-loading safe-path
24873 As the files of inferior can come from untrusted source (such as submitted by
24874 an application user) @value{GDBN} does not always load any files automatically.
24875 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24876 directories trusted for loading files not explicitly requested by user.
24877 Each directory can also be a shell wildcard pattern.
24879 If the path is not set properly you will see a warning and the file will not
24884 Reading symbols from /home/user/gdb/gdb...done.
24885 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24886 declined by your `auto-load safe-path' set
24887 to "$debugdir:$datadir/auto-load".
24888 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24889 declined by your `auto-load safe-path' set
24890 to "$debugdir:$datadir/auto-load".
24894 To instruct @value{GDBN} to go ahead and use the init files anyway,
24895 invoke @value{GDBN} like this:
24898 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24901 The list of trusted directories is controlled by the following commands:
24904 @anchor{set auto-load safe-path}
24905 @kindex set auto-load safe-path
24906 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24907 Set the list of directories (and their subdirectories) trusted for automatic
24908 loading and execution of scripts. You can also enter a specific trusted file.
24909 Each directory can also be a shell wildcard pattern; wildcards do not match
24910 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24911 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24912 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24913 its default value as specified during @value{GDBN} compilation.
24915 The list of directories uses path separator (@samp{:} on GNU and Unix
24916 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24917 to the @env{PATH} environment variable.
24919 @anchor{show auto-load safe-path}
24920 @kindex show auto-load safe-path
24921 @item show auto-load safe-path
24922 Show the list of directories trusted for automatic loading and execution of
24925 @anchor{add-auto-load-safe-path}
24926 @kindex add-auto-load-safe-path
24927 @item add-auto-load-safe-path
24928 Add an entry (or list of entries) to the list of directories trusted for
24929 automatic loading and execution of scripts. Multiple entries may be delimited
24930 by the host platform path separator in use.
24933 This variable defaults to what @code{--with-auto-load-dir} has been configured
24934 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24935 substitution applies the same as for @ref{set auto-load scripts-directory}.
24936 The default @code{set auto-load safe-path} value can be also overriden by
24937 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24939 Setting this variable to @file{/} disables this security protection,
24940 corresponding @value{GDBN} configuration option is
24941 @option{--without-auto-load-safe-path}.
24942 This variable is supposed to be set to the system directories writable by the
24943 system superuser only. Users can add their source directories in init files in
24944 their home directories (@pxref{Home Directory Init File}). See also deprecated
24945 init file in the current directory
24946 (@pxref{Init File in the Current Directory during Startup}).
24948 To force @value{GDBN} to load the files it declined to load in the previous
24949 example, you could use one of the following ways:
24952 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24953 Specify this trusted directory (or a file) as additional component of the list.
24954 You have to specify also any existing directories displayed by
24955 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24957 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24958 Specify this directory as in the previous case but just for a single
24959 @value{GDBN} session.
24961 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24962 Disable auto-loading safety for a single @value{GDBN} session.
24963 This assumes all the files you debug during this @value{GDBN} session will come
24964 from trusted sources.
24966 @item @kbd{./configure --without-auto-load-safe-path}
24967 During compilation of @value{GDBN} you may disable any auto-loading safety.
24968 This assumes all the files you will ever debug with this @value{GDBN} come from
24972 On the other hand you can also explicitly forbid automatic files loading which
24973 also suppresses any such warning messages:
24976 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24977 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24979 @item @file{~/.gdbinit}: @samp{set auto-load no}
24980 Disable auto-loading globally for the user
24981 (@pxref{Home Directory Init File}). While it is improbable, you could also
24982 use system init file instead (@pxref{System-wide configuration}).
24985 This setting applies to the file names as entered by user. If no entry matches
24986 @value{GDBN} tries as a last resort to also resolve all the file names into
24987 their canonical form (typically resolving symbolic links) and compare the
24988 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24989 own before starting the comparison so a canonical form of directories is
24990 recommended to be entered.
24992 @node Auto-loading verbose mode
24993 @subsection Displaying files tried for auto-load
24994 @cindex auto-loading verbose mode
24996 For better visibility of all the file locations where you can place scripts to
24997 be auto-loaded with inferior --- or to protect yourself against accidental
24998 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24999 all the files attempted to be loaded. Both existing and non-existing files may
25002 For example the list of directories from which it is safe to auto-load files
25003 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25004 may not be too obvious while setting it up.
25007 (gdb) set debug auto-load on
25008 (gdb) file ~/src/t/true
25009 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25010 for objfile "/tmp/true".
25011 auto-load: Updating directories of "/usr:/opt".
25012 auto-load: Using directory "/usr".
25013 auto-load: Using directory "/opt".
25014 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25015 by your `auto-load safe-path' set to "/usr:/opt".
25019 @anchor{set debug auto-load}
25020 @kindex set debug auto-load
25021 @item set debug auto-load [on|off]
25022 Set whether to print the filenames attempted to be auto-loaded.
25024 @anchor{show debug auto-load}
25025 @kindex show debug auto-load
25026 @item show debug auto-load
25027 Show whether printing of the filenames attempted to be auto-loaded is turned
25031 @node Messages/Warnings
25032 @section Optional Warnings and Messages
25034 @cindex verbose operation
25035 @cindex optional warnings
25036 By default, @value{GDBN} is silent about its inner workings. If you are
25037 running on a slow machine, you may want to use the @code{set verbose}
25038 command. This makes @value{GDBN} tell you when it does a lengthy
25039 internal operation, so you will not think it has crashed.
25041 Currently, the messages controlled by @code{set verbose} are those
25042 which announce that the symbol table for a source file is being read;
25043 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25046 @kindex set verbose
25047 @item set verbose on
25048 Enables @value{GDBN} output of certain informational messages.
25050 @item set verbose off
25051 Disables @value{GDBN} output of certain informational messages.
25053 @kindex show verbose
25055 Displays whether @code{set verbose} is on or off.
25058 By default, if @value{GDBN} encounters bugs in the symbol table of an
25059 object file, it is silent; but if you are debugging a compiler, you may
25060 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25065 @kindex set complaints
25066 @item set complaints @var{limit}
25067 Permits @value{GDBN} to output @var{limit} complaints about each type of
25068 unusual symbols before becoming silent about the problem. Set
25069 @var{limit} to zero to suppress all complaints; set it to a large number
25070 to prevent complaints from being suppressed.
25072 @kindex show complaints
25073 @item show complaints
25074 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25078 @anchor{confirmation requests}
25079 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25080 lot of stupid questions to confirm certain commands. For example, if
25081 you try to run a program which is already running:
25085 The program being debugged has been started already.
25086 Start it from the beginning? (y or n)
25089 If you are willing to unflinchingly face the consequences of your own
25090 commands, you can disable this ``feature'':
25094 @kindex set confirm
25096 @cindex confirmation
25097 @cindex stupid questions
25098 @item set confirm off
25099 Disables confirmation requests. Note that running @value{GDBN} with
25100 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25101 automatically disables confirmation requests.
25103 @item set confirm on
25104 Enables confirmation requests (the default).
25106 @kindex show confirm
25108 Displays state of confirmation requests.
25112 @cindex command tracing
25113 If you need to debug user-defined commands or sourced files you may find it
25114 useful to enable @dfn{command tracing}. In this mode each command will be
25115 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25116 quantity denoting the call depth of each command.
25119 @kindex set trace-commands
25120 @cindex command scripts, debugging
25121 @item set trace-commands on
25122 Enable command tracing.
25123 @item set trace-commands off
25124 Disable command tracing.
25125 @item show trace-commands
25126 Display the current state of command tracing.
25129 @node Debugging Output
25130 @section Optional Messages about Internal Happenings
25131 @cindex optional debugging messages
25133 @value{GDBN} has commands that enable optional debugging messages from
25134 various @value{GDBN} subsystems; normally these commands are of
25135 interest to @value{GDBN} maintainers, or when reporting a bug. This
25136 section documents those commands.
25139 @kindex set exec-done-display
25140 @item set exec-done-display
25141 Turns on or off the notification of asynchronous commands'
25142 completion. When on, @value{GDBN} will print a message when an
25143 asynchronous command finishes its execution. The default is off.
25144 @kindex show exec-done-display
25145 @item show exec-done-display
25146 Displays the current setting of asynchronous command completion
25149 @cindex ARM AArch64
25150 @item set debug aarch64
25151 Turns on or off display of debugging messages related to ARM AArch64.
25152 The default is off.
25154 @item show debug aarch64
25155 Displays the current state of displaying debugging messages related to
25157 @cindex gdbarch debugging info
25158 @cindex architecture debugging info
25159 @item set debug arch
25160 Turns on or off display of gdbarch debugging info. The default is off
25161 @item show debug arch
25162 Displays the current state of displaying gdbarch debugging info.
25163 @item set debug aix-solib
25164 @cindex AIX shared library debugging
25165 Control display of debugging messages from the AIX shared library
25166 support module. The default is off.
25167 @item show debug aix-thread
25168 Show the current state of displaying AIX shared library debugging messages.
25169 @item set debug aix-thread
25170 @cindex AIX threads
25171 Display debugging messages about inner workings of the AIX thread
25173 @item show debug aix-thread
25174 Show the current state of AIX thread debugging info display.
25175 @item set debug check-physname
25177 Check the results of the ``physname'' computation. When reading DWARF
25178 debugging information for C@t{++}, @value{GDBN} attempts to compute
25179 each entity's name. @value{GDBN} can do this computation in two
25180 different ways, depending on exactly what information is present.
25181 When enabled, this setting causes @value{GDBN} to compute the names
25182 both ways and display any discrepancies.
25183 @item show debug check-physname
25184 Show the current state of ``physname'' checking.
25185 @item set debug coff-pe-read
25186 @cindex COFF/PE exported symbols
25187 Control display of debugging messages related to reading of COFF/PE
25188 exported symbols. The default is off.
25189 @item show debug coff-pe-read
25190 Displays the current state of displaying debugging messages related to
25191 reading of COFF/PE exported symbols.
25192 @item set debug dwarf-die
25194 Dump DWARF DIEs after they are read in.
25195 The value is the number of nesting levels to print.
25196 A value of zero turns off the display.
25197 @item show debug dwarf-die
25198 Show the current state of DWARF DIE debugging.
25199 @item set debug dwarf-line
25200 @cindex DWARF Line Tables
25201 Turns on or off display of debugging messages related to reading
25202 DWARF line tables. The default is 0 (off).
25203 A value of 1 provides basic information.
25204 A value greater than 1 provides more verbose information.
25205 @item show debug dwarf-line
25206 Show the current state of DWARF line table debugging.
25207 @item set debug dwarf-read
25208 @cindex DWARF Reading
25209 Turns on or off display of debugging messages related to reading
25210 DWARF debug info. The default is 0 (off).
25211 A value of 1 provides basic information.
25212 A value greater than 1 provides more verbose information.
25213 @item show debug dwarf-read
25214 Show the current state of DWARF reader debugging.
25215 @item set debug displaced
25216 @cindex displaced stepping debugging info
25217 Turns on or off display of @value{GDBN} debugging info for the
25218 displaced stepping support. The default is off.
25219 @item show debug displaced
25220 Displays the current state of displaying @value{GDBN} debugging info
25221 related to displaced stepping.
25222 @item set debug event
25223 @cindex event debugging info
25224 Turns on or off display of @value{GDBN} event debugging info. The
25226 @item show debug event
25227 Displays the current state of displaying @value{GDBN} event debugging
25229 @item set debug expression
25230 @cindex expression debugging info
25231 Turns on or off display of debugging info about @value{GDBN}
25232 expression parsing. The default is off.
25233 @item show debug expression
25234 Displays the current state of displaying debugging info about
25235 @value{GDBN} expression parsing.
25236 @item set debug fbsd-lwp
25237 @cindex FreeBSD LWP debug messages
25238 Turns on or off debugging messages from the FreeBSD LWP debug support.
25239 @item show debug fbsd-lwp
25240 Show the current state of FreeBSD LWP debugging messages.
25241 @item set debug fbsd-nat
25242 @cindex FreeBSD native target debug messages
25243 Turns on or off debugging messages from the FreeBSD native target.
25244 @item show debug fbsd-nat
25245 Show the current state of FreeBSD native target debugging messages.
25246 @item set debug frame
25247 @cindex frame debugging info
25248 Turns on or off display of @value{GDBN} frame debugging info. The
25250 @item show debug frame
25251 Displays the current state of displaying @value{GDBN} frame debugging
25253 @item set debug gnu-nat
25254 @cindex @sc{gnu}/Hurd debug messages
25255 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25256 @item show debug gnu-nat
25257 Show the current state of @sc{gnu}/Hurd debugging messages.
25258 @item set debug infrun
25259 @cindex inferior debugging info
25260 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25261 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25262 for implementing operations such as single-stepping the inferior.
25263 @item show debug infrun
25264 Displays the current state of @value{GDBN} inferior debugging.
25265 @item set debug jit
25266 @cindex just-in-time compilation, debugging messages
25267 Turn on or off debugging messages from JIT debug support.
25268 @item show debug jit
25269 Displays the current state of @value{GDBN} JIT debugging.
25270 @item set debug lin-lwp
25271 @cindex @sc{gnu}/Linux LWP debug messages
25272 @cindex Linux lightweight processes
25273 Turn on or off debugging messages from the Linux LWP debug support.
25274 @item show debug lin-lwp
25275 Show the current state of Linux LWP debugging messages.
25276 @item set debug linux-namespaces
25277 @cindex @sc{gnu}/Linux namespaces debug messages
25278 Turn on or off debugging messages from the Linux namespaces debug support.
25279 @item show debug linux-namespaces
25280 Show the current state of Linux namespaces debugging messages.
25281 @item set debug mach-o
25282 @cindex Mach-O symbols processing
25283 Control display of debugging messages related to Mach-O symbols
25284 processing. The default is off.
25285 @item show debug mach-o
25286 Displays the current state of displaying debugging messages related to
25287 reading of COFF/PE exported symbols.
25288 @item set debug notification
25289 @cindex remote async notification debugging info
25290 Turn on or off debugging messages about remote async notification.
25291 The default is off.
25292 @item show debug notification
25293 Displays the current state of remote async notification debugging messages.
25294 @item set debug observer
25295 @cindex observer debugging info
25296 Turns on or off display of @value{GDBN} observer debugging. This
25297 includes info such as the notification of observable events.
25298 @item show debug observer
25299 Displays the current state of observer debugging.
25300 @item set debug overload
25301 @cindex C@t{++} overload debugging info
25302 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25303 info. This includes info such as ranking of functions, etc. The default
25305 @item show debug overload
25306 Displays the current state of displaying @value{GDBN} C@t{++} overload
25308 @cindex expression parser, debugging info
25309 @cindex debug expression parser
25310 @item set debug parser
25311 Turns on or off the display of expression parser debugging output.
25312 Internally, this sets the @code{yydebug} variable in the expression
25313 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25314 details. The default is off.
25315 @item show debug parser
25316 Show the current state of expression parser debugging.
25317 @cindex packets, reporting on stdout
25318 @cindex serial connections, debugging
25319 @cindex debug remote protocol
25320 @cindex remote protocol debugging
25321 @cindex display remote packets
25322 @item set debug remote
25323 Turns on or off display of reports on all packets sent back and forth across
25324 the serial line to the remote machine. The info is printed on the
25325 @value{GDBN} standard output stream. The default is off.
25326 @item show debug remote
25327 Displays the state of display of remote packets.
25329 @item set debug separate-debug-file
25330 Turns on or off display of debug output about separate debug file search.
25331 @item show debug separate-debug-file
25332 Displays the state of separate debug file search debug output.
25334 @item set debug serial
25335 Turns on or off display of @value{GDBN} serial debugging info. The
25337 @item show debug serial
25338 Displays the current state of displaying @value{GDBN} serial debugging
25340 @item set debug solib-frv
25341 @cindex FR-V shared-library debugging
25342 Turn on or off debugging messages for FR-V shared-library code.
25343 @item show debug solib-frv
25344 Display the current state of FR-V shared-library code debugging
25346 @item set debug symbol-lookup
25347 @cindex symbol lookup
25348 Turns on or off display of debugging messages related to symbol lookup.
25349 The default is 0 (off).
25350 A value of 1 provides basic information.
25351 A value greater than 1 provides more verbose information.
25352 @item show debug symbol-lookup
25353 Show the current state of symbol lookup debugging messages.
25354 @item set debug symfile
25355 @cindex symbol file functions
25356 Turns on or off display of debugging messages related to symbol file functions.
25357 The default is off. @xref{Files}.
25358 @item show debug symfile
25359 Show the current state of symbol file debugging messages.
25360 @item set debug symtab-create
25361 @cindex symbol table creation
25362 Turns on or off display of debugging messages related to symbol table creation.
25363 The default is 0 (off).
25364 A value of 1 provides basic information.
25365 A value greater than 1 provides more verbose information.
25366 @item show debug symtab-create
25367 Show the current state of symbol table creation debugging.
25368 @item set debug target
25369 @cindex target debugging info
25370 Turns on or off display of @value{GDBN} target debugging info. This info
25371 includes what is going on at the target level of GDB, as it happens. The
25372 default is 0. Set it to 1 to track events, and to 2 to also track the
25373 value of large memory transfers.
25374 @item show debug target
25375 Displays the current state of displaying @value{GDBN} target debugging
25377 @item set debug timestamp
25378 @cindex timestampping debugging info
25379 Turns on or off display of timestamps with @value{GDBN} debugging info.
25380 When enabled, seconds and microseconds are displayed before each debugging
25382 @item show debug timestamp
25383 Displays the current state of displaying timestamps with @value{GDBN}
25385 @item set debug varobj
25386 @cindex variable object debugging info
25387 Turns on or off display of @value{GDBN} variable object debugging
25388 info. The default is off.
25389 @item show debug varobj
25390 Displays the current state of displaying @value{GDBN} variable object
25392 @item set debug xml
25393 @cindex XML parser debugging
25394 Turn on or off debugging messages for built-in XML parsers.
25395 @item show debug xml
25396 Displays the current state of XML debugging messages.
25399 @node Other Misc Settings
25400 @section Other Miscellaneous Settings
25401 @cindex miscellaneous settings
25404 @kindex set interactive-mode
25405 @item set interactive-mode
25406 If @code{on}, forces @value{GDBN} to assume that GDB was started
25407 in a terminal. In practice, this means that @value{GDBN} should wait
25408 for the user to answer queries generated by commands entered at
25409 the command prompt. If @code{off}, forces @value{GDBN} to operate
25410 in the opposite mode, and it uses the default answers to all queries.
25411 If @code{auto} (the default), @value{GDBN} tries to determine whether
25412 its standard input is a terminal, and works in interactive-mode if it
25413 is, non-interactively otherwise.
25415 In the vast majority of cases, the debugger should be able to guess
25416 correctly which mode should be used. But this setting can be useful
25417 in certain specific cases, such as running a MinGW @value{GDBN}
25418 inside a cygwin window.
25420 @kindex show interactive-mode
25421 @item show interactive-mode
25422 Displays whether the debugger is operating in interactive mode or not.
25425 @node Extending GDB
25426 @chapter Extending @value{GDBN}
25427 @cindex extending GDB
25429 @value{GDBN} provides several mechanisms for extension.
25430 @value{GDBN} also provides the ability to automatically load
25431 extensions when it reads a file for debugging. This allows the
25432 user to automatically customize @value{GDBN} for the program
25436 * Sequences:: Canned Sequences of @value{GDBN} Commands
25437 * Python:: Extending @value{GDBN} using Python
25438 * Guile:: Extending @value{GDBN} using Guile
25439 * Auto-loading extensions:: Automatically loading extensions
25440 * Multiple Extension Languages:: Working with multiple extension languages
25441 * Aliases:: Creating new spellings of existing commands
25444 To facilitate the use of extension languages, @value{GDBN} is capable
25445 of evaluating the contents of a file. When doing so, @value{GDBN}
25446 can recognize which extension language is being used by looking at
25447 the filename extension. Files with an unrecognized filename extension
25448 are always treated as a @value{GDBN} Command Files.
25449 @xref{Command Files,, Command files}.
25451 You can control how @value{GDBN} evaluates these files with the following
25455 @kindex set script-extension
25456 @kindex show script-extension
25457 @item set script-extension off
25458 All scripts are always evaluated as @value{GDBN} Command Files.
25460 @item set script-extension soft
25461 The debugger determines the scripting language based on filename
25462 extension. If this scripting language is supported, @value{GDBN}
25463 evaluates the script using that language. Otherwise, it evaluates
25464 the file as a @value{GDBN} Command File.
25466 @item set script-extension strict
25467 The debugger determines the scripting language based on filename
25468 extension, and evaluates the script using that language. If the
25469 language is not supported, then the evaluation fails.
25471 @item show script-extension
25472 Display the current value of the @code{script-extension} option.
25477 @section Canned Sequences of Commands
25479 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25480 Command Lists}), @value{GDBN} provides two ways to store sequences of
25481 commands for execution as a unit: user-defined commands and command
25485 * Define:: How to define your own commands
25486 * Hooks:: Hooks for user-defined commands
25487 * Command Files:: How to write scripts of commands to be stored in a file
25488 * Output:: Commands for controlled output
25489 * Auto-loading sequences:: Controlling auto-loaded command files
25493 @subsection User-defined Commands
25495 @cindex user-defined command
25496 @cindex arguments, to user-defined commands
25497 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25498 which you assign a new name as a command. This is done with the
25499 @code{define} command. User commands may accept an unlimited number of arguments
25500 separated by whitespace. Arguments are accessed within the user command
25501 via @code{$arg0@dots{}$argN}. A trivial example:
25505 print $arg0 + $arg1 + $arg2
25510 To execute the command use:
25517 This defines the command @code{adder}, which prints the sum of
25518 its three arguments. Note the arguments are text substitutions, so they may
25519 reference variables, use complex expressions, or even perform inferior
25522 @cindex argument count in user-defined commands
25523 @cindex how many arguments (user-defined commands)
25524 In addition, @code{$argc} may be used to find out how many arguments have
25530 print $arg0 + $arg1
25533 print $arg0 + $arg1 + $arg2
25538 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25539 to process a variable number of arguments:
25546 eval "set $sum = $sum + $arg%d", $i
25556 @item define @var{commandname}
25557 Define a command named @var{commandname}. If there is already a command
25558 by that name, you are asked to confirm that you want to redefine it.
25559 The argument @var{commandname} may be a bare command name consisting of letters,
25560 numbers, dashes, and underscores. It may also start with any predefined
25561 prefix command. For example, @samp{define target my-target} creates
25562 a user-defined @samp{target my-target} command.
25564 The definition of the command is made up of other @value{GDBN} command lines,
25565 which are given following the @code{define} command. The end of these
25566 commands is marked by a line containing @code{end}.
25569 @kindex end@r{ (user-defined commands)}
25570 @item document @var{commandname}
25571 Document the user-defined command @var{commandname}, so that it can be
25572 accessed by @code{help}. The command @var{commandname} must already be
25573 defined. This command reads lines of documentation just as @code{define}
25574 reads the lines of the command definition, ending with @code{end}.
25575 After the @code{document} command is finished, @code{help} on command
25576 @var{commandname} displays the documentation you have written.
25578 You may use the @code{document} command again to change the
25579 documentation of a command. Redefining the command with @code{define}
25580 does not change the documentation.
25582 @kindex dont-repeat
25583 @cindex don't repeat command
25585 Used inside a user-defined command, this tells @value{GDBN} that this
25586 command should not be repeated when the user hits @key{RET}
25587 (@pxref{Command Syntax, repeat last command}).
25589 @kindex help user-defined
25590 @item help user-defined
25591 List all user-defined commands and all python commands defined in class
25592 COMAND_USER. The first line of the documentation or docstring is
25597 @itemx show user @var{commandname}
25598 Display the @value{GDBN} commands used to define @var{commandname} (but
25599 not its documentation). If no @var{commandname} is given, display the
25600 definitions for all user-defined commands.
25601 This does not work for user-defined python commands.
25603 @cindex infinite recursion in user-defined commands
25604 @kindex show max-user-call-depth
25605 @kindex set max-user-call-depth
25606 @item show max-user-call-depth
25607 @itemx set max-user-call-depth
25608 The value of @code{max-user-call-depth} controls how many recursion
25609 levels are allowed in user-defined commands before @value{GDBN} suspects an
25610 infinite recursion and aborts the command.
25611 This does not apply to user-defined python commands.
25614 In addition to the above commands, user-defined commands frequently
25615 use control flow commands, described in @ref{Command Files}.
25617 When user-defined commands are executed, the
25618 commands of the definition are not printed. An error in any command
25619 stops execution of the user-defined command.
25621 If used interactively, commands that would ask for confirmation proceed
25622 without asking when used inside a user-defined command. Many @value{GDBN}
25623 commands that normally print messages to say what they are doing omit the
25624 messages when used in a user-defined command.
25627 @subsection User-defined Command Hooks
25628 @cindex command hooks
25629 @cindex hooks, for commands
25630 @cindex hooks, pre-command
25633 You may define @dfn{hooks}, which are a special kind of user-defined
25634 command. Whenever you run the command @samp{foo}, if the user-defined
25635 command @samp{hook-foo} exists, it is executed (with no arguments)
25636 before that command.
25638 @cindex hooks, post-command
25640 A hook may also be defined which is run after the command you executed.
25641 Whenever you run the command @samp{foo}, if the user-defined command
25642 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25643 that command. Post-execution hooks may exist simultaneously with
25644 pre-execution hooks, for the same command.
25646 It is valid for a hook to call the command which it hooks. If this
25647 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25649 @c It would be nice if hookpost could be passed a parameter indicating
25650 @c if the command it hooks executed properly or not. FIXME!
25652 @kindex stop@r{, a pseudo-command}
25653 In addition, a pseudo-command, @samp{stop} exists. Defining
25654 (@samp{hook-stop}) makes the associated commands execute every time
25655 execution stops in your program: before breakpoint commands are run,
25656 displays are printed, or the stack frame is printed.
25658 For example, to ignore @code{SIGALRM} signals while
25659 single-stepping, but treat them normally during normal execution,
25664 handle SIGALRM nopass
25668 handle SIGALRM pass
25671 define hook-continue
25672 handle SIGALRM pass
25676 As a further example, to hook at the beginning and end of the @code{echo}
25677 command, and to add extra text to the beginning and end of the message,
25685 define hookpost-echo
25689 (@value{GDBP}) echo Hello World
25690 <<<---Hello World--->>>
25695 You can define a hook for any single-word command in @value{GDBN}, but
25696 not for command aliases; you should define a hook for the basic command
25697 name, e.g.@: @code{backtrace} rather than @code{bt}.
25698 @c FIXME! So how does Joe User discover whether a command is an alias
25700 You can hook a multi-word command by adding @code{hook-} or
25701 @code{hookpost-} to the last word of the command, e.g.@:
25702 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25704 If an error occurs during the execution of your hook, execution of
25705 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25706 (before the command that you actually typed had a chance to run).
25708 If you try to define a hook which does not match any known command, you
25709 get a warning from the @code{define} command.
25711 @node Command Files
25712 @subsection Command Files
25714 @cindex command files
25715 @cindex scripting commands
25716 A command file for @value{GDBN} is a text file made of lines that are
25717 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25718 also be included. An empty line in a command file does nothing; it
25719 does not mean to repeat the last command, as it would from the
25722 You can request the execution of a command file with the @code{source}
25723 command. Note that the @code{source} command is also used to evaluate
25724 scripts that are not Command Files. The exact behavior can be configured
25725 using the @code{script-extension} setting.
25726 @xref{Extending GDB,, Extending GDB}.
25730 @cindex execute commands from a file
25731 @item source [-s] [-v] @var{filename}
25732 Execute the command file @var{filename}.
25735 The lines in a command file are generally executed sequentially,
25736 unless the order of execution is changed by one of the
25737 @emph{flow-control commands} described below. The commands are not
25738 printed as they are executed. An error in any command terminates
25739 execution of the command file and control is returned to the console.
25741 @value{GDBN} first searches for @var{filename} in the current directory.
25742 If the file is not found there, and @var{filename} does not specify a
25743 directory, then @value{GDBN} also looks for the file on the source search path
25744 (specified with the @samp{directory} command);
25745 except that @file{$cdir} is not searched because the compilation directory
25746 is not relevant to scripts.
25748 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25749 on the search path even if @var{filename} specifies a directory.
25750 The search is done by appending @var{filename} to each element of the
25751 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25752 and the search path contains @file{/home/user} then @value{GDBN} will
25753 look for the script @file{/home/user/mylib/myscript}.
25754 The search is also done if @var{filename} is an absolute path.
25755 For example, if @var{filename} is @file{/tmp/myscript} and
25756 the search path contains @file{/home/user} then @value{GDBN} will
25757 look for the script @file{/home/user/tmp/myscript}.
25758 For DOS-like systems, if @var{filename} contains a drive specification,
25759 it is stripped before concatenation. For example, if @var{filename} is
25760 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25761 will look for the script @file{c:/tmp/myscript}.
25763 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25764 each command as it is executed. The option must be given before
25765 @var{filename}, and is interpreted as part of the filename anywhere else.
25767 Commands that would ask for confirmation if used interactively proceed
25768 without asking when used in a command file. Many @value{GDBN} commands that
25769 normally print messages to say what they are doing omit the messages
25770 when called from command files.
25772 @value{GDBN} also accepts command input from standard input. In this
25773 mode, normal output goes to standard output and error output goes to
25774 standard error. Errors in a command file supplied on standard input do
25775 not terminate execution of the command file---execution continues with
25779 gdb < cmds > log 2>&1
25782 (The syntax above will vary depending on the shell used.) This example
25783 will execute commands from the file @file{cmds}. All output and errors
25784 would be directed to @file{log}.
25786 Since commands stored on command files tend to be more general than
25787 commands typed interactively, they frequently need to deal with
25788 complicated situations, such as different or unexpected values of
25789 variables and symbols, changes in how the program being debugged is
25790 built, etc. @value{GDBN} provides a set of flow-control commands to
25791 deal with these complexities. Using these commands, you can write
25792 complex scripts that loop over data structures, execute commands
25793 conditionally, etc.
25800 This command allows to include in your script conditionally executed
25801 commands. The @code{if} command takes a single argument, which is an
25802 expression to evaluate. It is followed by a series of commands that
25803 are executed only if the expression is true (its value is nonzero).
25804 There can then optionally be an @code{else} line, followed by a series
25805 of commands that are only executed if the expression was false. The
25806 end of the list is marked by a line containing @code{end}.
25810 This command allows to write loops. Its syntax is similar to
25811 @code{if}: the command takes a single argument, which is an expression
25812 to evaluate, and must be followed by the commands to execute, one per
25813 line, terminated by an @code{end}. These commands are called the
25814 @dfn{body} of the loop. The commands in the body of @code{while} are
25815 executed repeatedly as long as the expression evaluates to true.
25819 This command exits the @code{while} loop in whose body it is included.
25820 Execution of the script continues after that @code{while}s @code{end}
25823 @kindex loop_continue
25824 @item loop_continue
25825 This command skips the execution of the rest of the body of commands
25826 in the @code{while} loop in whose body it is included. Execution
25827 branches to the beginning of the @code{while} loop, where it evaluates
25828 the controlling expression.
25830 @kindex end@r{ (if/else/while commands)}
25832 Terminate the block of commands that are the body of @code{if},
25833 @code{else}, or @code{while} flow-control commands.
25838 @subsection Commands for Controlled Output
25840 During the execution of a command file or a user-defined command, normal
25841 @value{GDBN} output is suppressed; the only output that appears is what is
25842 explicitly printed by the commands in the definition. This section
25843 describes three commands useful for generating exactly the output you
25848 @item echo @var{text}
25849 @c I do not consider backslash-space a standard C escape sequence
25850 @c because it is not in ANSI.
25851 Print @var{text}. Nonprinting characters can be included in
25852 @var{text} using C escape sequences, such as @samp{\n} to print a
25853 newline. @strong{No newline is printed unless you specify one.}
25854 In addition to the standard C escape sequences, a backslash followed
25855 by a space stands for a space. This is useful for displaying a
25856 string with spaces at the beginning or the end, since leading and
25857 trailing spaces are otherwise trimmed from all arguments.
25858 To print @samp{@w{ }and foo =@w{ }}, use the command
25859 @samp{echo \@w{ }and foo = \@w{ }}.
25861 A backslash at the end of @var{text} can be used, as in C, to continue
25862 the command onto subsequent lines. For example,
25865 echo This is some text\n\
25866 which is continued\n\
25867 onto several lines.\n
25870 produces the same output as
25873 echo This is some text\n
25874 echo which is continued\n
25875 echo onto several lines.\n
25879 @item output @var{expression}
25880 Print the value of @var{expression} and nothing but that value: no
25881 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25882 value history either. @xref{Expressions, ,Expressions}, for more information
25885 @item output/@var{fmt} @var{expression}
25886 Print the value of @var{expression} in format @var{fmt}. You can use
25887 the same formats as for @code{print}. @xref{Output Formats,,Output
25888 Formats}, for more information.
25891 @item printf @var{template}, @var{expressions}@dots{}
25892 Print the values of one or more @var{expressions} under the control of
25893 the string @var{template}. To print several values, make
25894 @var{expressions} be a comma-separated list of individual expressions,
25895 which may be either numbers or pointers. Their values are printed as
25896 specified by @var{template}, exactly as a C program would do by
25897 executing the code below:
25900 printf (@var{template}, @var{expressions}@dots{});
25903 As in @code{C} @code{printf}, ordinary characters in @var{template}
25904 are printed verbatim, while @dfn{conversion specification} introduced
25905 by the @samp{%} character cause subsequent @var{expressions} to be
25906 evaluated, their values converted and formatted according to type and
25907 style information encoded in the conversion specifications, and then
25910 For example, you can print two values in hex like this:
25913 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25916 @code{printf} supports all the standard @code{C} conversion
25917 specifications, including the flags and modifiers between the @samp{%}
25918 character and the conversion letter, with the following exceptions:
25922 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25925 The modifier @samp{*} is not supported for specifying precision or
25929 The @samp{'} flag (for separation of digits into groups according to
25930 @code{LC_NUMERIC'}) is not supported.
25933 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25937 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25940 The conversion letters @samp{a} and @samp{A} are not supported.
25944 Note that the @samp{ll} type modifier is supported only if the
25945 underlying @code{C} implementation used to build @value{GDBN} supports
25946 the @code{long long int} type, and the @samp{L} type modifier is
25947 supported only if @code{long double} type is available.
25949 As in @code{C}, @code{printf} supports simple backslash-escape
25950 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25951 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25952 single character. Octal and hexadecimal escape sequences are not
25955 Additionally, @code{printf} supports conversion specifications for DFP
25956 (@dfn{Decimal Floating Point}) types using the following length modifiers
25957 together with a floating point specifier.
25962 @samp{H} for printing @code{Decimal32} types.
25965 @samp{D} for printing @code{Decimal64} types.
25968 @samp{DD} for printing @code{Decimal128} types.
25971 If the underlying @code{C} implementation used to build @value{GDBN} has
25972 support for the three length modifiers for DFP types, other modifiers
25973 such as width and precision will also be available for @value{GDBN} to use.
25975 In case there is no such @code{C} support, no additional modifiers will be
25976 available and the value will be printed in the standard way.
25978 Here's an example of printing DFP types using the above conversion letters:
25980 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25985 @item eval @var{template}, @var{expressions}@dots{}
25986 Convert the values of one or more @var{expressions} under the control of
25987 the string @var{template} to a command line, and call it.
25991 @node Auto-loading sequences
25992 @subsection Controlling auto-loading native @value{GDBN} scripts
25993 @cindex native script auto-loading
25995 When a new object file is read (for example, due to the @code{file}
25996 command, or because the inferior has loaded a shared library),
25997 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25998 @xref{Auto-loading extensions}.
26000 Auto-loading can be enabled or disabled,
26001 and the list of auto-loaded scripts can be printed.
26004 @anchor{set auto-load gdb-scripts}
26005 @kindex set auto-load gdb-scripts
26006 @item set auto-load gdb-scripts [on|off]
26007 Enable or disable the auto-loading of canned sequences of commands scripts.
26009 @anchor{show auto-load gdb-scripts}
26010 @kindex show auto-load gdb-scripts
26011 @item show auto-load gdb-scripts
26012 Show whether auto-loading of canned sequences of commands scripts is enabled or
26015 @anchor{info auto-load gdb-scripts}
26016 @kindex info auto-load gdb-scripts
26017 @cindex print list of auto-loaded canned sequences of commands scripts
26018 @item info auto-load gdb-scripts [@var{regexp}]
26019 Print the list of all canned sequences of commands scripts that @value{GDBN}
26023 If @var{regexp} is supplied only canned sequences of commands scripts with
26024 matching names are printed.
26026 @c Python docs live in a separate file.
26027 @include python.texi
26029 @c Guile docs live in a separate file.
26030 @include guile.texi
26032 @node Auto-loading extensions
26033 @section Auto-loading extensions
26034 @cindex auto-loading extensions
26036 @value{GDBN} provides two mechanisms for automatically loading extensions
26037 when a new object file is read (for example, due to the @code{file}
26038 command, or because the inferior has loaded a shared library):
26039 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26040 section of modern file formats like ELF.
26043 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26044 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26045 * Which flavor to choose?::
26048 The auto-loading feature is useful for supplying application-specific
26049 debugging commands and features.
26051 Auto-loading can be enabled or disabled,
26052 and the list of auto-loaded scripts can be printed.
26053 See the @samp{auto-loading} section of each extension language
26054 for more information.
26055 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26056 For Python files see @ref{Python Auto-loading}.
26058 Note that loading of this script file also requires accordingly configured
26059 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26061 @node objfile-gdbdotext file
26062 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26063 @cindex @file{@var{objfile}-gdb.gdb}
26064 @cindex @file{@var{objfile}-gdb.py}
26065 @cindex @file{@var{objfile}-gdb.scm}
26067 When a new object file is read, @value{GDBN} looks for a file named
26068 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26069 where @var{objfile} is the object file's name and
26070 where @var{ext} is the file extension for the extension language:
26073 @item @file{@var{objfile}-gdb.gdb}
26074 GDB's own command language
26075 @item @file{@var{objfile}-gdb.py}
26077 @item @file{@var{objfile}-gdb.scm}
26081 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26082 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26083 components, and appending the @file{-gdb.@var{ext}} suffix.
26084 If this file exists and is readable, @value{GDBN} will evaluate it as a
26085 script in the specified extension language.
26087 If this file does not exist, then @value{GDBN} will look for
26088 @var{script-name} file in all of the directories as specified below.
26090 Note that loading of these files requires an accordingly configured
26091 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26093 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26094 scripts normally according to its @file{.exe} filename. But if no scripts are
26095 found @value{GDBN} also tries script filenames matching the object file without
26096 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26097 is attempted on any platform. This makes the script filenames compatible
26098 between Unix and MS-Windows hosts.
26101 @anchor{set auto-load scripts-directory}
26102 @kindex set auto-load scripts-directory
26103 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26104 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26105 may be delimited by the host platform path separator in use
26106 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26108 Each entry here needs to be covered also by the security setting
26109 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26111 @anchor{with-auto-load-dir}
26112 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26113 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26114 configuration option @option{--with-auto-load-dir}.
26116 Any reference to @file{$debugdir} will get replaced by
26117 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26118 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26119 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26120 @file{$datadir} must be placed as a directory component --- either alone or
26121 delimited by @file{/} or @file{\} directory separators, depending on the host
26124 The list of directories uses path separator (@samp{:} on GNU and Unix
26125 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26126 to the @env{PATH} environment variable.
26128 @anchor{show auto-load scripts-directory}
26129 @kindex show auto-load scripts-directory
26130 @item show auto-load scripts-directory
26131 Show @value{GDBN} auto-loaded scripts location.
26133 @anchor{add-auto-load-scripts-directory}
26134 @kindex add-auto-load-scripts-directory
26135 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26136 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26137 Multiple entries may be delimited by the host platform path separator in use.
26140 @value{GDBN} does not track which files it has already auto-loaded this way.
26141 @value{GDBN} will load the associated script every time the corresponding
26142 @var{objfile} is opened.
26143 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26144 is evaluated more than once.
26146 @node dotdebug_gdb_scripts section
26147 @subsection The @code{.debug_gdb_scripts} section
26148 @cindex @code{.debug_gdb_scripts} section
26150 For systems using file formats like ELF and COFF,
26151 when @value{GDBN} loads a new object file
26152 it will look for a special section named @code{.debug_gdb_scripts}.
26153 If this section exists, its contents is a list of null-terminated entries
26154 specifying scripts to load. Each entry begins with a non-null prefix byte that
26155 specifies the kind of entry, typically the extension language and whether the
26156 script is in a file or inlined in @code{.debug_gdb_scripts}.
26158 The following entries are supported:
26161 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26162 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26163 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26164 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26167 @subsubsection Script File Entries
26169 If the entry specifies a file, @value{GDBN} will look for the file first
26170 in the current directory and then along the source search path
26171 (@pxref{Source Path, ,Specifying Source Directories}),
26172 except that @file{$cdir} is not searched, since the compilation
26173 directory is not relevant to scripts.
26175 File entries can be placed in section @code{.debug_gdb_scripts} with,
26176 for example, this GCC macro for Python scripts.
26179 /* Note: The "MS" section flags are to remove duplicates. */
26180 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26182 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26183 .byte 1 /* Python */\n\
26184 .asciz \"" script_name "\"\n\
26190 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26191 Then one can reference the macro in a header or source file like this:
26194 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26197 The script name may include directories if desired.
26199 Note that loading of this script file also requires accordingly configured
26200 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26202 If the macro invocation is put in a header, any application or library
26203 using this header will get a reference to the specified script,
26204 and with the use of @code{"MS"} attributes on the section, the linker
26205 will remove duplicates.
26207 @subsubsection Script Text Entries
26209 Script text entries allow to put the executable script in the entry
26210 itself instead of loading it from a file.
26211 The first line of the entry, everything after the prefix byte and up to
26212 the first newline (@code{0xa}) character, is the script name, and must not
26213 contain any kind of space character, e.g., spaces or tabs.
26214 The rest of the entry, up to the trailing null byte, is the script to
26215 execute in the specified language. The name needs to be unique among
26216 all script names, as @value{GDBN} executes each script only once based
26219 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26223 #include "symcat.h"
26224 #include "gdb/section-scripts.h"
26226 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26227 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26228 ".ascii \"gdb.inlined-script\\n\"\n"
26229 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26230 ".ascii \" def __init__ (self):\\n\"\n"
26231 ".ascii \" super (test_cmd, self).__init__ ("
26232 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26233 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26234 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26235 ".ascii \"test_cmd ()\\n\"\n"
26241 Loading of inlined scripts requires a properly configured
26242 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26243 The path to specify in @code{auto-load safe-path} is the path of the file
26244 containing the @code{.debug_gdb_scripts} section.
26246 @node Which flavor to choose?
26247 @subsection Which flavor to choose?
26249 Given the multiple ways of auto-loading extensions, it might not always
26250 be clear which one to choose. This section provides some guidance.
26253 Benefits of the @file{-gdb.@var{ext}} way:
26257 Can be used with file formats that don't support multiple sections.
26260 Ease of finding scripts for public libraries.
26262 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26263 in the source search path.
26264 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26265 isn't a source directory in which to find the script.
26268 Doesn't require source code additions.
26272 Benefits of the @code{.debug_gdb_scripts} way:
26276 Works with static linking.
26278 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26279 trigger their loading. When an application is statically linked the only
26280 objfile available is the executable, and it is cumbersome to attach all the
26281 scripts from all the input libraries to the executable's
26282 @file{-gdb.@var{ext}} script.
26285 Works with classes that are entirely inlined.
26287 Some classes can be entirely inlined, and thus there may not be an associated
26288 shared library to attach a @file{-gdb.@var{ext}} script to.
26291 Scripts needn't be copied out of the source tree.
26293 In some circumstances, apps can be built out of large collections of internal
26294 libraries, and the build infrastructure necessary to install the
26295 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26296 cumbersome. It may be easier to specify the scripts in the
26297 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26298 top of the source tree to the source search path.
26301 @node Multiple Extension Languages
26302 @section Multiple Extension Languages
26304 The Guile and Python extension languages do not share any state,
26305 and generally do not interfere with each other.
26306 There are some things to be aware of, however.
26308 @subsection Python comes first
26310 Python was @value{GDBN}'s first extension language, and to avoid breaking
26311 existing behaviour Python comes first. This is generally solved by the
26312 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26313 extension languages, and when it makes a call to an extension language,
26314 (say to pretty-print a value), it tries each in turn until an extension
26315 language indicates it has performed the request (e.g., has returned the
26316 pretty-printed form of a value).
26317 This extends to errors while performing such requests: If an error happens
26318 while, for example, trying to pretty-print an object then the error is
26319 reported and any following extension languages are not tried.
26322 @section Creating new spellings of existing commands
26323 @cindex aliases for commands
26325 It is often useful to define alternate spellings of existing commands.
26326 For example, if a new @value{GDBN} command defined in Python has
26327 a long name to type, it is handy to have an abbreviated version of it
26328 that involves less typing.
26330 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26331 of the @samp{step} command even though it is otherwise an ambiguous
26332 abbreviation of other commands like @samp{set} and @samp{show}.
26334 Aliases are also used to provide shortened or more common versions
26335 of multi-word commands. For example, @value{GDBN} provides the
26336 @samp{tty} alias of the @samp{set inferior-tty} command.
26338 You can define a new alias with the @samp{alias} command.
26343 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26347 @var{ALIAS} specifies the name of the new alias.
26348 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26351 @var{COMMAND} specifies the name of an existing command
26352 that is being aliased.
26354 The @samp{-a} option specifies that the new alias is an abbreviation
26355 of the command. Abbreviations are not shown in command
26356 lists displayed by the @samp{help} command.
26358 The @samp{--} option specifies the end of options,
26359 and is useful when @var{ALIAS} begins with a dash.
26361 Here is a simple example showing how to make an abbreviation
26362 of a command so that there is less to type.
26363 Suppose you were tired of typing @samp{disas}, the current
26364 shortest unambiguous abbreviation of the @samp{disassemble} command
26365 and you wanted an even shorter version named @samp{di}.
26366 The following will accomplish this.
26369 (gdb) alias -a di = disas
26372 Note that aliases are different from user-defined commands.
26373 With a user-defined command, you also need to write documentation
26374 for it with the @samp{document} command.
26375 An alias automatically picks up the documentation of the existing command.
26377 Here is an example where we make @samp{elms} an abbreviation of
26378 @samp{elements} in the @samp{set print elements} command.
26379 This is to show that you can make an abbreviation of any part
26383 (gdb) alias -a set print elms = set print elements
26384 (gdb) alias -a show print elms = show print elements
26385 (gdb) set p elms 20
26387 Limit on string chars or array elements to print is 200.
26390 Note that if you are defining an alias of a @samp{set} command,
26391 and you want to have an alias for the corresponding @samp{show}
26392 command, then you need to define the latter separately.
26394 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26395 @var{ALIAS}, just as they are normally.
26398 (gdb) alias -a set pr elms = set p ele
26401 Finally, here is an example showing the creation of a one word
26402 alias for a more complex command.
26403 This creates alias @samp{spe} of the command @samp{set print elements}.
26406 (gdb) alias spe = set print elements
26411 @chapter Command Interpreters
26412 @cindex command interpreters
26414 @value{GDBN} supports multiple command interpreters, and some command
26415 infrastructure to allow users or user interface writers to switch
26416 between interpreters or run commands in other interpreters.
26418 @value{GDBN} currently supports two command interpreters, the console
26419 interpreter (sometimes called the command-line interpreter or @sc{cli})
26420 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26421 describes both of these interfaces in great detail.
26423 By default, @value{GDBN} will start with the console interpreter.
26424 However, the user may choose to start @value{GDBN} with another
26425 interpreter by specifying the @option{-i} or @option{--interpreter}
26426 startup options. Defined interpreters include:
26430 @cindex console interpreter
26431 The traditional console or command-line interpreter. This is the most often
26432 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26433 @value{GDBN} will use this interpreter.
26436 @cindex mi interpreter
26437 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26438 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26439 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26443 @cindex mi2 interpreter
26444 The current @sc{gdb/mi} interface.
26447 @cindex mi1 interpreter
26448 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26452 @cindex invoke another interpreter
26454 @kindex interpreter-exec
26455 You may execute commands in any interpreter from the current
26456 interpreter using the appropriate command. If you are running the
26457 console interpreter, simply use the @code{interpreter-exec} command:
26460 interpreter-exec mi "-data-list-register-names"
26463 @sc{gdb/mi} has a similar command, although it is only available in versions of
26464 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26466 Note that @code{interpreter-exec} only changes the interpreter for the
26467 duration of the specified command. It does not change the interpreter
26470 @cindex start a new independent interpreter
26472 Although you may only choose a single interpreter at startup, it is
26473 possible to run an independent interpreter on a specified input/output
26474 device (usually a tty).
26476 For example, consider a debugger GUI or IDE that wants to provide a
26477 @value{GDBN} console view. It may do so by embedding a terminal
26478 emulator widget in its GUI, starting @value{GDBN} in the traditional
26479 command-line mode with stdin/stdout/stderr redirected to that
26480 terminal, and then creating an MI interpreter running on a specified
26481 input/output device. The console interpreter created by @value{GDBN}
26482 at startup handles commands the user types in the terminal widget,
26483 while the GUI controls and synchronizes state with @value{GDBN} using
26484 the separate MI interpreter.
26486 To start a new secondary @dfn{user interface} running MI, use the
26487 @code{new-ui} command:
26490 @cindex new user interface
26492 new-ui @var{interpreter} @var{tty}
26495 The @var{interpreter} parameter specifies the interpreter to run.
26496 This accepts the same values as the @code{interpreter-exec} command.
26497 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26498 @var{tty} parameter specifies the name of the bidirectional file the
26499 interpreter uses for input/output, usually the name of a
26500 pseudoterminal slave on Unix systems. For example:
26503 (@value{GDBP}) new-ui mi /dev/pts/9
26507 runs an MI interpreter on @file{/dev/pts/9}.
26510 @chapter @value{GDBN} Text User Interface
26512 @cindex Text User Interface
26515 * TUI Overview:: TUI overview
26516 * TUI Keys:: TUI key bindings
26517 * TUI Single Key Mode:: TUI single key mode
26518 * TUI Commands:: TUI-specific commands
26519 * TUI Configuration:: TUI configuration variables
26522 The @value{GDBN} Text User Interface (TUI) is a terminal
26523 interface which uses the @code{curses} library to show the source
26524 file, the assembly output, the program registers and @value{GDBN}
26525 commands in separate text windows. The TUI mode is supported only
26526 on platforms where a suitable version of the @code{curses} library
26529 The TUI mode is enabled by default when you invoke @value{GDBN} as
26530 @samp{@value{GDBP} -tui}.
26531 You can also switch in and out of TUI mode while @value{GDBN} runs by
26532 using various TUI commands and key bindings, such as @command{tui
26533 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26534 @ref{TUI Keys, ,TUI Key Bindings}.
26537 @section TUI Overview
26539 In TUI mode, @value{GDBN} can display several text windows:
26543 This window is the @value{GDBN} command window with the @value{GDBN}
26544 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26545 managed using readline.
26548 The source window shows the source file of the program. The current
26549 line and active breakpoints are displayed in this window.
26552 The assembly window shows the disassembly output of the program.
26555 This window shows the processor registers. Registers are highlighted
26556 when their values change.
26559 The source and assembly windows show the current program position
26560 by highlighting the current line and marking it with a @samp{>} marker.
26561 Breakpoints are indicated with two markers. The first marker
26562 indicates the breakpoint type:
26566 Breakpoint which was hit at least once.
26569 Breakpoint which was never hit.
26572 Hardware breakpoint which was hit at least once.
26575 Hardware breakpoint which was never hit.
26578 The second marker indicates whether the breakpoint is enabled or not:
26582 Breakpoint is enabled.
26585 Breakpoint is disabled.
26588 The source, assembly and register windows are updated when the current
26589 thread changes, when the frame changes, or when the program counter
26592 These windows are not all visible at the same time. The command
26593 window is always visible. The others can be arranged in several
26604 source and assembly,
26607 source and registers, or
26610 assembly and registers.
26613 A status line above the command window shows the following information:
26617 Indicates the current @value{GDBN} target.
26618 (@pxref{Targets, ,Specifying a Debugging Target}).
26621 Gives the current process or thread number.
26622 When no process is being debugged, this field is set to @code{No process}.
26625 Gives the current function name for the selected frame.
26626 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26627 When there is no symbol corresponding to the current program counter,
26628 the string @code{??} is displayed.
26631 Indicates the current line number for the selected frame.
26632 When the current line number is not known, the string @code{??} is displayed.
26635 Indicates the current program counter address.
26639 @section TUI Key Bindings
26640 @cindex TUI key bindings
26642 The TUI installs several key bindings in the readline keymaps
26643 @ifset SYSTEM_READLINE
26644 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26646 @ifclear SYSTEM_READLINE
26647 (@pxref{Command Line Editing}).
26649 The following key bindings are installed for both TUI mode and the
26650 @value{GDBN} standard mode.
26659 Enter or leave the TUI mode. When leaving the TUI mode,
26660 the curses window management stops and @value{GDBN} operates using
26661 its standard mode, writing on the terminal directly. When reentering
26662 the TUI mode, control is given back to the curses windows.
26663 The screen is then refreshed.
26667 Use a TUI layout with only one window. The layout will
26668 either be @samp{source} or @samp{assembly}. When the TUI mode
26669 is not active, it will switch to the TUI mode.
26671 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26675 Use a TUI layout with at least two windows. When the current
26676 layout already has two windows, the next layout with two windows is used.
26677 When a new layout is chosen, one window will always be common to the
26678 previous layout and the new one.
26680 Think of it as the Emacs @kbd{C-x 2} binding.
26684 Change the active window. The TUI associates several key bindings
26685 (like scrolling and arrow keys) with the active window. This command
26686 gives the focus to the next TUI window.
26688 Think of it as the Emacs @kbd{C-x o} binding.
26692 Switch in and out of the TUI SingleKey mode that binds single
26693 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26696 The following key bindings only work in the TUI mode:
26701 Scroll the active window one page up.
26705 Scroll the active window one page down.
26709 Scroll the active window one line up.
26713 Scroll the active window one line down.
26717 Scroll the active window one column left.
26721 Scroll the active window one column right.
26725 Refresh the screen.
26728 Because the arrow keys scroll the active window in the TUI mode, they
26729 are not available for their normal use by readline unless the command
26730 window has the focus. When another window is active, you must use
26731 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26732 and @kbd{C-f} to control the command window.
26734 @node TUI Single Key Mode
26735 @section TUI Single Key Mode
26736 @cindex TUI single key mode
26738 The TUI also provides a @dfn{SingleKey} mode, which binds several
26739 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26740 switch into this mode, where the following key bindings are used:
26743 @kindex c @r{(SingleKey TUI key)}
26747 @kindex d @r{(SingleKey TUI key)}
26751 @kindex f @r{(SingleKey TUI key)}
26755 @kindex n @r{(SingleKey TUI key)}
26759 @kindex o @r{(SingleKey TUI key)}
26761 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26763 @kindex q @r{(SingleKey TUI key)}
26765 exit the SingleKey mode.
26767 @kindex r @r{(SingleKey TUI key)}
26771 @kindex s @r{(SingleKey TUI key)}
26775 @kindex i @r{(SingleKey TUI key)}
26777 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26779 @kindex u @r{(SingleKey TUI key)}
26783 @kindex v @r{(SingleKey TUI key)}
26787 @kindex w @r{(SingleKey TUI key)}
26792 Other keys temporarily switch to the @value{GDBN} command prompt.
26793 The key that was pressed is inserted in the editing buffer so that
26794 it is possible to type most @value{GDBN} commands without interaction
26795 with the TUI SingleKey mode. Once the command is entered the TUI
26796 SingleKey mode is restored. The only way to permanently leave
26797 this mode is by typing @kbd{q} or @kbd{C-x s}.
26801 @section TUI-specific Commands
26802 @cindex TUI commands
26804 The TUI has specific commands to control the text windows.
26805 These commands are always available, even when @value{GDBN} is not in
26806 the TUI mode. When @value{GDBN} is in the standard mode, most
26807 of these commands will automatically switch to the TUI mode.
26809 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26810 terminal, or @value{GDBN} has been started with the machine interface
26811 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26812 these commands will fail with an error, because it would not be
26813 possible or desirable to enable curses window management.
26818 Activate TUI mode. The last active TUI window layout will be used if
26819 TUI mode has prevsiouly been used in the current debugging session,
26820 otherwise a default layout is used.
26823 @kindex tui disable
26824 Disable TUI mode, returning to the console interpreter.
26828 List and give the size of all displayed windows.
26830 @item layout @var{name}
26832 Changes which TUI windows are displayed. In each layout the command
26833 window is always displayed, the @var{name} parameter controls which
26834 additional windows are displayed, and can be any of the following:
26838 Display the next layout.
26841 Display the previous layout.
26844 Display the source and command windows.
26847 Display the assembly and command windows.
26850 Display the source, assembly, and command windows.
26853 When in @code{src} layout display the register, source, and command
26854 windows. When in @code{asm} or @code{split} layout display the
26855 register, assembler, and command windows.
26858 @item focus @var{name}
26860 Changes which TUI window is currently active for scrolling. The
26861 @var{name} parameter can be any of the following:
26865 Make the next window active for scrolling.
26868 Make the previous window active for scrolling.
26871 Make the source window active for scrolling.
26874 Make the assembly window active for scrolling.
26877 Make the register window active for scrolling.
26880 Make the command window active for scrolling.
26885 Refresh the screen. This is similar to typing @kbd{C-L}.
26887 @item tui reg @var{group}
26889 Changes the register group displayed in the tui register window to
26890 @var{group}. If the register window is not currently displayed this
26891 command will cause the register window to be displayed. The list of
26892 register groups, as well as their order is target specific. The
26893 following groups are available on most targets:
26896 Repeatedly selecting this group will cause the display to cycle
26897 through all of the available register groups.
26900 Repeatedly selecting this group will cause the display to cycle
26901 through all of the available register groups in the reverse order to
26905 Display the general registers.
26907 Display the floating point registers.
26909 Display the system registers.
26911 Display the vector registers.
26913 Display all registers.
26918 Update the source window and the current execution point.
26920 @item winheight @var{name} +@var{count}
26921 @itemx winheight @var{name} -@var{count}
26923 Change the height of the window @var{name} by @var{count}
26924 lines. Positive counts increase the height, while negative counts
26925 decrease it. The @var{name} parameter can be one of @code{src} (the
26926 source window), @code{cmd} (the command window), @code{asm} (the
26927 disassembly window), or @code{regs} (the register display window).
26930 @node TUI Configuration
26931 @section TUI Configuration Variables
26932 @cindex TUI configuration variables
26934 Several configuration variables control the appearance of TUI windows.
26937 @item set tui border-kind @var{kind}
26938 @kindex set tui border-kind
26939 Select the border appearance for the source, assembly and register windows.
26940 The possible values are the following:
26943 Use a space character to draw the border.
26946 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26949 Use the Alternate Character Set to draw the border. The border is
26950 drawn using character line graphics if the terminal supports them.
26953 @item set tui border-mode @var{mode}
26954 @kindex set tui border-mode
26955 @itemx set tui active-border-mode @var{mode}
26956 @kindex set tui active-border-mode
26957 Select the display attributes for the borders of the inactive windows
26958 or the active window. The @var{mode} can be one of the following:
26961 Use normal attributes to display the border.
26967 Use reverse video mode.
26970 Use half bright mode.
26972 @item half-standout
26973 Use half bright and standout mode.
26976 Use extra bright or bold mode.
26978 @item bold-standout
26979 Use extra bright or bold and standout mode.
26982 @item set tui tab-width @var{nchars}
26983 @kindex set tui tab-width
26985 Set the width of tab stops to be @var{nchars} characters. This
26986 setting affects the display of TAB characters in the source and
26991 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26994 @cindex @sc{gnu} Emacs
26995 A special interface allows you to use @sc{gnu} Emacs to view (and
26996 edit) the source files for the program you are debugging with
26999 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27000 executable file you want to debug as an argument. This command starts
27001 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27002 created Emacs buffer.
27003 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27005 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27010 All ``terminal'' input and output goes through an Emacs buffer, called
27013 This applies both to @value{GDBN} commands and their output, and to the input
27014 and output done by the program you are debugging.
27016 This is useful because it means that you can copy the text of previous
27017 commands and input them again; you can even use parts of the output
27020 All the facilities of Emacs' Shell mode are available for interacting
27021 with your program. In particular, you can send signals the usual
27022 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27026 @value{GDBN} displays source code through Emacs.
27028 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27029 source file for that frame and puts an arrow (@samp{=>}) at the
27030 left margin of the current line. Emacs uses a separate buffer for
27031 source display, and splits the screen to show both your @value{GDBN} session
27034 Explicit @value{GDBN} @code{list} or search commands still produce output as
27035 usual, but you probably have no reason to use them from Emacs.
27038 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27039 a graphical mode, enabled by default, which provides further buffers
27040 that can control the execution and describe the state of your program.
27041 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27043 If you specify an absolute file name when prompted for the @kbd{M-x
27044 gdb} argument, then Emacs sets your current working directory to where
27045 your program resides. If you only specify the file name, then Emacs
27046 sets your current working directory to the directory associated
27047 with the previous buffer. In this case, @value{GDBN} may find your
27048 program by searching your environment's @code{PATH} variable, but on
27049 some operating systems it might not find the source. So, although the
27050 @value{GDBN} input and output session proceeds normally, the auxiliary
27051 buffer does not display the current source and line of execution.
27053 The initial working directory of @value{GDBN} is printed on the top
27054 line of the GUD buffer and this serves as a default for the commands
27055 that specify files for @value{GDBN} to operate on. @xref{Files,
27056 ,Commands to Specify Files}.
27058 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27059 need to call @value{GDBN} by a different name (for example, if you
27060 keep several configurations around, with different names) you can
27061 customize the Emacs variable @code{gud-gdb-command-name} to run the
27064 In the GUD buffer, you can use these special Emacs commands in
27065 addition to the standard Shell mode commands:
27069 Describe the features of Emacs' GUD Mode.
27072 Execute to another source line, like the @value{GDBN} @code{step} command; also
27073 update the display window to show the current file and location.
27076 Execute to next source line in this function, skipping all function
27077 calls, like the @value{GDBN} @code{next} command. Then update the display window
27078 to show the current file and location.
27081 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27082 display window accordingly.
27085 Execute until exit from the selected stack frame, like the @value{GDBN}
27086 @code{finish} command.
27089 Continue execution of your program, like the @value{GDBN} @code{continue}
27093 Go up the number of frames indicated by the numeric argument
27094 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27095 like the @value{GDBN} @code{up} command.
27098 Go down the number of frames indicated by the numeric argument, like the
27099 @value{GDBN} @code{down} command.
27102 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27103 tells @value{GDBN} to set a breakpoint on the source line point is on.
27105 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27106 separate frame which shows a backtrace when the GUD buffer is current.
27107 Move point to any frame in the stack and type @key{RET} to make it
27108 become the current frame and display the associated source in the
27109 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27110 selected frame become the current one. In graphical mode, the
27111 speedbar displays watch expressions.
27113 If you accidentally delete the source-display buffer, an easy way to get
27114 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27115 request a frame display; when you run under Emacs, this recreates
27116 the source buffer if necessary to show you the context of the current
27119 The source files displayed in Emacs are in ordinary Emacs buffers
27120 which are visiting the source files in the usual way. You can edit
27121 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27122 communicates with Emacs in terms of line numbers. If you add or
27123 delete lines from the text, the line numbers that @value{GDBN} knows cease
27124 to correspond properly with the code.
27126 A more detailed description of Emacs' interaction with @value{GDBN} is
27127 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27131 @chapter The @sc{gdb/mi} Interface
27133 @unnumberedsec Function and Purpose
27135 @cindex @sc{gdb/mi}, its purpose
27136 @sc{gdb/mi} is a line based machine oriented text interface to
27137 @value{GDBN} and is activated by specifying using the
27138 @option{--interpreter} command line option (@pxref{Mode Options}). It
27139 is specifically intended to support the development of systems which
27140 use the debugger as just one small component of a larger system.
27142 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27143 in the form of a reference manual.
27145 Note that @sc{gdb/mi} is still under construction, so some of the
27146 features described below are incomplete and subject to change
27147 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27149 @unnumberedsec Notation and Terminology
27151 @cindex notational conventions, for @sc{gdb/mi}
27152 This chapter uses the following notation:
27156 @code{|} separates two alternatives.
27159 @code{[ @var{something} ]} indicates that @var{something} is optional:
27160 it may or may not be given.
27163 @code{( @var{group} )*} means that @var{group} inside the parentheses
27164 may repeat zero or more times.
27167 @code{( @var{group} )+} means that @var{group} inside the parentheses
27168 may repeat one or more times.
27171 @code{"@var{string}"} means a literal @var{string}.
27175 @heading Dependencies
27179 * GDB/MI General Design::
27180 * GDB/MI Command Syntax::
27181 * GDB/MI Compatibility with CLI::
27182 * GDB/MI Development and Front Ends::
27183 * GDB/MI Output Records::
27184 * GDB/MI Simple Examples::
27185 * GDB/MI Command Description Format::
27186 * GDB/MI Breakpoint Commands::
27187 * GDB/MI Catchpoint Commands::
27188 * GDB/MI Program Context::
27189 * GDB/MI Thread Commands::
27190 * GDB/MI Ada Tasking Commands::
27191 * GDB/MI Program Execution::
27192 * GDB/MI Stack Manipulation::
27193 * GDB/MI Variable Objects::
27194 * GDB/MI Data Manipulation::
27195 * GDB/MI Tracepoint Commands::
27196 * GDB/MI Symbol Query::
27197 * GDB/MI File Commands::
27199 * GDB/MI Kod Commands::
27200 * GDB/MI Memory Overlay Commands::
27201 * GDB/MI Signal Handling Commands::
27203 * GDB/MI Target Manipulation::
27204 * GDB/MI File Transfer Commands::
27205 * GDB/MI Ada Exceptions Commands::
27206 * GDB/MI Support Commands::
27207 * GDB/MI Miscellaneous Commands::
27210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27211 @node GDB/MI General Design
27212 @section @sc{gdb/mi} General Design
27213 @cindex GDB/MI General Design
27215 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27216 parts---commands sent to @value{GDBN}, responses to those commands
27217 and notifications. Each command results in exactly one response,
27218 indicating either successful completion of the command, or an error.
27219 For the commands that do not resume the target, the response contains the
27220 requested information. For the commands that resume the target, the
27221 response only indicates whether the target was successfully resumed.
27222 Notifications is the mechanism for reporting changes in the state of the
27223 target, or in @value{GDBN} state, that cannot conveniently be associated with
27224 a command and reported as part of that command response.
27226 The important examples of notifications are:
27230 Exec notifications. These are used to report changes in
27231 target state---when a target is resumed, or stopped. It would not
27232 be feasible to include this information in response of resuming
27233 commands, because one resume commands can result in multiple events in
27234 different threads. Also, quite some time may pass before any event
27235 happens in the target, while a frontend needs to know whether the resuming
27236 command itself was successfully executed.
27239 Console output, and status notifications. Console output
27240 notifications are used to report output of CLI commands, as well as
27241 diagnostics for other commands. Status notifications are used to
27242 report the progress of a long-running operation. Naturally, including
27243 this information in command response would mean no output is produced
27244 until the command is finished, which is undesirable.
27247 General notifications. Commands may have various side effects on
27248 the @value{GDBN} or target state beyond their official purpose. For example,
27249 a command may change the selected thread. Although such changes can
27250 be included in command response, using notification allows for more
27251 orthogonal frontend design.
27255 There's no guarantee that whenever an MI command reports an error,
27256 @value{GDBN} or the target are in any specific state, and especially,
27257 the state is not reverted to the state before the MI command was
27258 processed. Therefore, whenever an MI command results in an error,
27259 we recommend that the frontend refreshes all the information shown in
27260 the user interface.
27264 * Context management::
27265 * Asynchronous and non-stop modes::
27269 @node Context management
27270 @subsection Context management
27272 @subsubsection Threads and Frames
27274 In most cases when @value{GDBN} accesses the target, this access is
27275 done in context of a specific thread and frame (@pxref{Frames}).
27276 Often, even when accessing global data, the target requires that a thread
27277 be specified. The CLI interface maintains the selected thread and frame,
27278 and supplies them to target on each command. This is convenient,
27279 because a command line user would not want to specify that information
27280 explicitly on each command, and because user interacts with
27281 @value{GDBN} via a single terminal, so no confusion is possible as
27282 to what thread and frame are the current ones.
27284 In the case of MI, the concept of selected thread and frame is less
27285 useful. First, a frontend can easily remember this information
27286 itself. Second, a graphical frontend can have more than one window,
27287 each one used for debugging a different thread, and the frontend might
27288 want to access additional threads for internal purposes. This
27289 increases the risk that by relying on implicitly selected thread, the
27290 frontend may be operating on a wrong one. Therefore, each MI command
27291 should explicitly specify which thread and frame to operate on. To
27292 make it possible, each MI command accepts the @samp{--thread} and
27293 @samp{--frame} options, the value to each is @value{GDBN} global
27294 identifier for thread and frame to operate on.
27296 Usually, each top-level window in a frontend allows the user to select
27297 a thread and a frame, and remembers the user selection for further
27298 operations. However, in some cases @value{GDBN} may suggest that the
27299 current thread or frame be changed. For example, when stopping on a
27300 breakpoint it is reasonable to switch to the thread where breakpoint is
27301 hit. For another example, if the user issues the CLI @samp{thread} or
27302 @samp{frame} commands via the frontend, it is desirable to change the
27303 frontend's selection to the one specified by user. @value{GDBN}
27304 communicates the suggestion to change current thread and frame using the
27305 @samp{=thread-selected} notification.
27307 Note that historically, MI shares the selected thread with CLI, so
27308 frontends used the @code{-thread-select} to execute commands in the
27309 right context. However, getting this to work right is cumbersome. The
27310 simplest way is for frontend to emit @code{-thread-select} command
27311 before every command. This doubles the number of commands that need
27312 to be sent. The alternative approach is to suppress @code{-thread-select}
27313 if the selected thread in @value{GDBN} is supposed to be identical to the
27314 thread the frontend wants to operate on. However, getting this
27315 optimization right can be tricky. In particular, if the frontend
27316 sends several commands to @value{GDBN}, and one of the commands changes the
27317 selected thread, then the behaviour of subsequent commands will
27318 change. So, a frontend should either wait for response from such
27319 problematic commands, or explicitly add @code{-thread-select} for
27320 all subsequent commands. No frontend is known to do this exactly
27321 right, so it is suggested to just always pass the @samp{--thread} and
27322 @samp{--frame} options.
27324 @subsubsection Language
27326 The execution of several commands depends on which language is selected.
27327 By default, the current language (@pxref{show language}) is used.
27328 But for commands known to be language-sensitive, it is recommended
27329 to use the @samp{--language} option. This option takes one argument,
27330 which is the name of the language to use while executing the command.
27334 -data-evaluate-expression --language c "sizeof (void*)"
27339 The valid language names are the same names accepted by the
27340 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27341 @samp{local} or @samp{unknown}.
27343 @node Asynchronous and non-stop modes
27344 @subsection Asynchronous command execution and non-stop mode
27346 On some targets, @value{GDBN} is capable of processing MI commands
27347 even while the target is running. This is called @dfn{asynchronous
27348 command execution} (@pxref{Background Execution}). The frontend may
27349 specify a preferrence for asynchronous execution using the
27350 @code{-gdb-set mi-async 1} command, which should be emitted before
27351 either running the executable or attaching to the target. After the
27352 frontend has started the executable or attached to the target, it can
27353 find if asynchronous execution is enabled using the
27354 @code{-list-target-features} command.
27357 @item -gdb-set mi-async on
27358 @item -gdb-set mi-async off
27359 Set whether MI is in asynchronous mode.
27361 When @code{off}, which is the default, MI execution commands (e.g.,
27362 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27363 for the program to stop before processing further commands.
27365 When @code{on}, MI execution commands are background execution
27366 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27367 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27368 MI commands even while the target is running.
27370 @item -gdb-show mi-async
27371 Show whether MI asynchronous mode is enabled.
27374 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27375 @code{target-async} instead of @code{mi-async}, and it had the effect
27376 of both putting MI in asynchronous mode and making CLI background
27377 commands possible. CLI background commands are now always possible
27378 ``out of the box'' if the target supports them. The old spelling is
27379 kept as a deprecated alias for backwards compatibility.
27381 Even if @value{GDBN} can accept a command while target is running,
27382 many commands that access the target do not work when the target is
27383 running. Therefore, asynchronous command execution is most useful
27384 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27385 it is possible to examine the state of one thread, while other threads
27388 When a given thread is running, MI commands that try to access the
27389 target in the context of that thread may not work, or may work only on
27390 some targets. In particular, commands that try to operate on thread's
27391 stack will not work, on any target. Commands that read memory, or
27392 modify breakpoints, may work or not work, depending on the target. Note
27393 that even commands that operate on global state, such as @code{print},
27394 @code{set}, and breakpoint commands, still access the target in the
27395 context of a specific thread, so frontend should try to find a
27396 stopped thread and perform the operation on that thread (using the
27397 @samp{--thread} option).
27399 Which commands will work in the context of a running thread is
27400 highly target dependent. However, the two commands
27401 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27402 to find the state of a thread, will always work.
27404 @node Thread groups
27405 @subsection Thread groups
27406 @value{GDBN} may be used to debug several processes at the same time.
27407 On some platfroms, @value{GDBN} may support debugging of several
27408 hardware systems, each one having several cores with several different
27409 processes running on each core. This section describes the MI
27410 mechanism to support such debugging scenarios.
27412 The key observation is that regardless of the structure of the
27413 target, MI can have a global list of threads, because most commands that
27414 accept the @samp{--thread} option do not need to know what process that
27415 thread belongs to. Therefore, it is not necessary to introduce
27416 neither additional @samp{--process} option, nor an notion of the
27417 current process in the MI interface. The only strictly new feature
27418 that is required is the ability to find how the threads are grouped
27421 To allow the user to discover such grouping, and to support arbitrary
27422 hierarchy of machines/cores/processes, MI introduces the concept of a
27423 @dfn{thread group}. Thread group is a collection of threads and other
27424 thread groups. A thread group always has a string identifier, a type,
27425 and may have additional attributes specific to the type. A new
27426 command, @code{-list-thread-groups}, returns the list of top-level
27427 thread groups, which correspond to processes that @value{GDBN} is
27428 debugging at the moment. By passing an identifier of a thread group
27429 to the @code{-list-thread-groups} command, it is possible to obtain
27430 the members of specific thread group.
27432 To allow the user to easily discover processes, and other objects, he
27433 wishes to debug, a concept of @dfn{available thread group} is
27434 introduced. Available thread group is an thread group that
27435 @value{GDBN} is not debugging, but that can be attached to, using the
27436 @code{-target-attach} command. The list of available top-level thread
27437 groups can be obtained using @samp{-list-thread-groups --available}.
27438 In general, the content of a thread group may be only retrieved only
27439 after attaching to that thread group.
27441 Thread groups are related to inferiors (@pxref{Inferiors and
27442 Programs}). Each inferior corresponds to a thread group of a special
27443 type @samp{process}, and some additional operations are permitted on
27444 such thread groups.
27446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27447 @node GDB/MI Command Syntax
27448 @section @sc{gdb/mi} Command Syntax
27451 * GDB/MI Input Syntax::
27452 * GDB/MI Output Syntax::
27455 @node GDB/MI Input Syntax
27456 @subsection @sc{gdb/mi} Input Syntax
27458 @cindex input syntax for @sc{gdb/mi}
27459 @cindex @sc{gdb/mi}, input syntax
27461 @item @var{command} @expansion{}
27462 @code{@var{cli-command} | @var{mi-command}}
27464 @item @var{cli-command} @expansion{}
27465 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27466 @var{cli-command} is any existing @value{GDBN} CLI command.
27468 @item @var{mi-command} @expansion{}
27469 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27470 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27472 @item @var{token} @expansion{}
27473 "any sequence of digits"
27475 @item @var{option} @expansion{}
27476 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27478 @item @var{parameter} @expansion{}
27479 @code{@var{non-blank-sequence} | @var{c-string}}
27481 @item @var{operation} @expansion{}
27482 @emph{any of the operations described in this chapter}
27484 @item @var{non-blank-sequence} @expansion{}
27485 @emph{anything, provided it doesn't contain special characters such as
27486 "-", @var{nl}, """ and of course " "}
27488 @item @var{c-string} @expansion{}
27489 @code{""" @var{seven-bit-iso-c-string-content} """}
27491 @item @var{nl} @expansion{}
27500 The CLI commands are still handled by the @sc{mi} interpreter; their
27501 output is described below.
27504 The @code{@var{token}}, when present, is passed back when the command
27508 Some @sc{mi} commands accept optional arguments as part of the parameter
27509 list. Each option is identified by a leading @samp{-} (dash) and may be
27510 followed by an optional argument parameter. Options occur first in the
27511 parameter list and can be delimited from normal parameters using
27512 @samp{--} (this is useful when some parameters begin with a dash).
27519 We want easy access to the existing CLI syntax (for debugging).
27522 We want it to be easy to spot a @sc{mi} operation.
27525 @node GDB/MI Output Syntax
27526 @subsection @sc{gdb/mi} Output Syntax
27528 @cindex output syntax of @sc{gdb/mi}
27529 @cindex @sc{gdb/mi}, output syntax
27530 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27531 followed, optionally, by a single result record. This result record
27532 is for the most recent command. The sequence of output records is
27533 terminated by @samp{(gdb)}.
27535 If an input command was prefixed with a @code{@var{token}} then the
27536 corresponding output for that command will also be prefixed by that same
27540 @item @var{output} @expansion{}
27541 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27543 @item @var{result-record} @expansion{}
27544 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27546 @item @var{out-of-band-record} @expansion{}
27547 @code{@var{async-record} | @var{stream-record}}
27549 @item @var{async-record} @expansion{}
27550 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27552 @item @var{exec-async-output} @expansion{}
27553 @code{[ @var{token} ] "*" @var{async-output nl}}
27555 @item @var{status-async-output} @expansion{}
27556 @code{[ @var{token} ] "+" @var{async-output nl}}
27558 @item @var{notify-async-output} @expansion{}
27559 @code{[ @var{token} ] "=" @var{async-output nl}}
27561 @item @var{async-output} @expansion{}
27562 @code{@var{async-class} ( "," @var{result} )*}
27564 @item @var{result-class} @expansion{}
27565 @code{"done" | "running" | "connected" | "error" | "exit"}
27567 @item @var{async-class} @expansion{}
27568 @code{"stopped" | @var{others}} (where @var{others} will be added
27569 depending on the needs---this is still in development).
27571 @item @var{result} @expansion{}
27572 @code{ @var{variable} "=" @var{value}}
27574 @item @var{variable} @expansion{}
27575 @code{ @var{string} }
27577 @item @var{value} @expansion{}
27578 @code{ @var{const} | @var{tuple} | @var{list} }
27580 @item @var{const} @expansion{}
27581 @code{@var{c-string}}
27583 @item @var{tuple} @expansion{}
27584 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27586 @item @var{list} @expansion{}
27587 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27588 @var{result} ( "," @var{result} )* "]" }
27590 @item @var{stream-record} @expansion{}
27591 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27593 @item @var{console-stream-output} @expansion{}
27594 @code{"~" @var{c-string nl}}
27596 @item @var{target-stream-output} @expansion{}
27597 @code{"@@" @var{c-string nl}}
27599 @item @var{log-stream-output} @expansion{}
27600 @code{"&" @var{c-string nl}}
27602 @item @var{nl} @expansion{}
27605 @item @var{token} @expansion{}
27606 @emph{any sequence of digits}.
27614 All output sequences end in a single line containing a period.
27617 The @code{@var{token}} is from the corresponding request. Note that
27618 for all async output, while the token is allowed by the grammar and
27619 may be output by future versions of @value{GDBN} for select async
27620 output messages, it is generally omitted. Frontends should treat
27621 all async output as reporting general changes in the state of the
27622 target and there should be no need to associate async output to any
27626 @cindex status output in @sc{gdb/mi}
27627 @var{status-async-output} contains on-going status information about the
27628 progress of a slow operation. It can be discarded. All status output is
27629 prefixed by @samp{+}.
27632 @cindex async output in @sc{gdb/mi}
27633 @var{exec-async-output} contains asynchronous state change on the target
27634 (stopped, started, disappeared). All async output is prefixed by
27638 @cindex notify output in @sc{gdb/mi}
27639 @var{notify-async-output} contains supplementary information that the
27640 client should handle (e.g., a new breakpoint information). All notify
27641 output is prefixed by @samp{=}.
27644 @cindex console output in @sc{gdb/mi}
27645 @var{console-stream-output} is output that should be displayed as is in the
27646 console. It is the textual response to a CLI command. All the console
27647 output is prefixed by @samp{~}.
27650 @cindex target output in @sc{gdb/mi}
27651 @var{target-stream-output} is the output produced by the target program.
27652 All the target output is prefixed by @samp{@@}.
27655 @cindex log output in @sc{gdb/mi}
27656 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27657 instance messages that should be displayed as part of an error log. All
27658 the log output is prefixed by @samp{&}.
27661 @cindex list output in @sc{gdb/mi}
27662 New @sc{gdb/mi} commands should only output @var{lists} containing
27668 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27669 details about the various output records.
27671 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27672 @node GDB/MI Compatibility with CLI
27673 @section @sc{gdb/mi} Compatibility with CLI
27675 @cindex compatibility, @sc{gdb/mi} and CLI
27676 @cindex @sc{gdb/mi}, compatibility with CLI
27678 For the developers convenience CLI commands can be entered directly,
27679 but there may be some unexpected behaviour. For example, commands
27680 that query the user will behave as if the user replied yes, breakpoint
27681 command lists are not executed and some CLI commands, such as
27682 @code{if}, @code{when} and @code{define}, prompt for further input with
27683 @samp{>}, which is not valid MI output.
27685 This feature may be removed at some stage in the future and it is
27686 recommended that front ends use the @code{-interpreter-exec} command
27687 (@pxref{-interpreter-exec}).
27689 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27690 @node GDB/MI Development and Front Ends
27691 @section @sc{gdb/mi} Development and Front Ends
27692 @cindex @sc{gdb/mi} development
27694 The application which takes the MI output and presents the state of the
27695 program being debugged to the user is called a @dfn{front end}.
27697 Although @sc{gdb/mi} is still incomplete, it is currently being used
27698 by a variety of front ends to @value{GDBN}. This makes it difficult
27699 to introduce new functionality without breaking existing usage. This
27700 section tries to minimize the problems by describing how the protocol
27703 Some changes in MI need not break a carefully designed front end, and
27704 for these the MI version will remain unchanged. The following is a
27705 list of changes that may occur within one level, so front ends should
27706 parse MI output in a way that can handle them:
27710 New MI commands may be added.
27713 New fields may be added to the output of any MI command.
27716 The range of values for fields with specified values, e.g.,
27717 @code{in_scope} (@pxref{-var-update}) may be extended.
27719 @c The format of field's content e.g type prefix, may change so parse it
27720 @c at your own risk. Yes, in general?
27722 @c The order of fields may change? Shouldn't really matter but it might
27723 @c resolve inconsistencies.
27726 If the changes are likely to break front ends, the MI version level
27727 will be increased by one. This will allow the front end to parse the
27728 output according to the MI version. Apart from mi0, new versions of
27729 @value{GDBN} will not support old versions of MI and it will be the
27730 responsibility of the front end to work with the new one.
27732 @c Starting with mi3, add a new command -mi-version that prints the MI
27735 The best way to avoid unexpected changes in MI that might break your front
27736 end is to make your project known to @value{GDBN} developers and
27737 follow development on @email{gdb@@sourceware.org} and
27738 @email{gdb-patches@@sourceware.org}.
27739 @cindex mailing lists
27741 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27742 @node GDB/MI Output Records
27743 @section @sc{gdb/mi} Output Records
27746 * GDB/MI Result Records::
27747 * GDB/MI Stream Records::
27748 * GDB/MI Async Records::
27749 * GDB/MI Breakpoint Information::
27750 * GDB/MI Frame Information::
27751 * GDB/MI Thread Information::
27752 * GDB/MI Ada Exception Information::
27755 @node GDB/MI Result Records
27756 @subsection @sc{gdb/mi} Result Records
27758 @cindex result records in @sc{gdb/mi}
27759 @cindex @sc{gdb/mi}, result records
27760 In addition to a number of out-of-band notifications, the response to a
27761 @sc{gdb/mi} command includes one of the following result indications:
27765 @item "^done" [ "," @var{results} ]
27766 The synchronous operation was successful, @code{@var{results}} are the return
27771 This result record is equivalent to @samp{^done}. Historically, it
27772 was output instead of @samp{^done} if the command has resumed the
27773 target. This behaviour is maintained for backward compatibility, but
27774 all frontends should treat @samp{^done} and @samp{^running}
27775 identically and rely on the @samp{*running} output record to determine
27776 which threads are resumed.
27780 @value{GDBN} has connected to a remote target.
27782 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27784 The operation failed. The @code{msg=@var{c-string}} variable contains
27785 the corresponding error message.
27787 If present, the @code{code=@var{c-string}} variable provides an error
27788 code on which consumers can rely on to detect the corresponding
27789 error condition. At present, only one error code is defined:
27792 @item "undefined-command"
27793 Indicates that the command causing the error does not exist.
27798 @value{GDBN} has terminated.
27802 @node GDB/MI Stream Records
27803 @subsection @sc{gdb/mi} Stream Records
27805 @cindex @sc{gdb/mi}, stream records
27806 @cindex stream records in @sc{gdb/mi}
27807 @value{GDBN} internally maintains a number of output streams: the console, the
27808 target, and the log. The output intended for each of these streams is
27809 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27811 Each stream record begins with a unique @dfn{prefix character} which
27812 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27813 Syntax}). In addition to the prefix, each stream record contains a
27814 @code{@var{string-output}}. This is either raw text (with an implicit new
27815 line) or a quoted C string (which does not contain an implicit newline).
27818 @item "~" @var{string-output}
27819 The console output stream contains text that should be displayed in the
27820 CLI console window. It contains the textual responses to CLI commands.
27822 @item "@@" @var{string-output}
27823 The target output stream contains any textual output from the running
27824 target. This is only present when GDB's event loop is truly
27825 asynchronous, which is currently only the case for remote targets.
27827 @item "&" @var{string-output}
27828 The log stream contains debugging messages being produced by @value{GDBN}'s
27832 @node GDB/MI Async Records
27833 @subsection @sc{gdb/mi} Async Records
27835 @cindex async records in @sc{gdb/mi}
27836 @cindex @sc{gdb/mi}, async records
27837 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27838 additional changes that have occurred. Those changes can either be a
27839 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27840 target activity (e.g., target stopped).
27842 The following is the list of possible async records:
27846 @item *running,thread-id="@var{thread}"
27847 The target is now running. The @var{thread} field can be the global
27848 thread ID of the the thread that is now running, and it can be
27849 @samp{all} if all threads are running. The frontend should assume
27850 that no interaction with a running thread is possible after this
27851 notification is produced. The frontend should not assume that this
27852 notification is output only once for any command. @value{GDBN} may
27853 emit this notification several times, either for different threads,
27854 because it cannot resume all threads together, or even for a single
27855 thread, if the thread must be stepped though some code before letting
27858 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27859 The target has stopped. The @var{reason} field can have one of the
27863 @item breakpoint-hit
27864 A breakpoint was reached.
27865 @item watchpoint-trigger
27866 A watchpoint was triggered.
27867 @item read-watchpoint-trigger
27868 A read watchpoint was triggered.
27869 @item access-watchpoint-trigger
27870 An access watchpoint was triggered.
27871 @item function-finished
27872 An -exec-finish or similar CLI command was accomplished.
27873 @item location-reached
27874 An -exec-until or similar CLI command was accomplished.
27875 @item watchpoint-scope
27876 A watchpoint has gone out of scope.
27877 @item end-stepping-range
27878 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27879 similar CLI command was accomplished.
27880 @item exited-signalled
27881 The inferior exited because of a signal.
27883 The inferior exited.
27884 @item exited-normally
27885 The inferior exited normally.
27886 @item signal-received
27887 A signal was received by the inferior.
27889 The inferior has stopped due to a library being loaded or unloaded.
27890 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27891 set or when a @code{catch load} or @code{catch unload} catchpoint is
27892 in use (@pxref{Set Catchpoints}).
27894 The inferior has forked. This is reported when @code{catch fork}
27895 (@pxref{Set Catchpoints}) has been used.
27897 The inferior has vforked. This is reported in when @code{catch vfork}
27898 (@pxref{Set Catchpoints}) has been used.
27899 @item syscall-entry
27900 The inferior entered a system call. This is reported when @code{catch
27901 syscall} (@pxref{Set Catchpoints}) has been used.
27902 @item syscall-return
27903 The inferior returned from a system call. This is reported when
27904 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27906 The inferior called @code{exec}. This is reported when @code{catch exec}
27907 (@pxref{Set Catchpoints}) has been used.
27910 The @var{id} field identifies the global thread ID of the thread
27911 that directly caused the stop -- for example by hitting a breakpoint.
27912 Depending on whether all-stop
27913 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27914 stop all threads, or only the thread that directly triggered the stop.
27915 If all threads are stopped, the @var{stopped} field will have the
27916 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27917 field will be a list of thread identifiers. Presently, this list will
27918 always include a single thread, but frontend should be prepared to see
27919 several threads in the list. The @var{core} field reports the
27920 processor core on which the stop event has happened. This field may be absent
27921 if such information is not available.
27923 @item =thread-group-added,id="@var{id}"
27924 @itemx =thread-group-removed,id="@var{id}"
27925 A thread group was either added or removed. The @var{id} field
27926 contains the @value{GDBN} identifier of the thread group. When a thread
27927 group is added, it generally might not be associated with a running
27928 process. When a thread group is removed, its id becomes invalid and
27929 cannot be used in any way.
27931 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27932 A thread group became associated with a running program,
27933 either because the program was just started or the thread group
27934 was attached to a program. The @var{id} field contains the
27935 @value{GDBN} identifier of the thread group. The @var{pid} field
27936 contains process identifier, specific to the operating system.
27938 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27939 A thread group is no longer associated with a running program,
27940 either because the program has exited, or because it was detached
27941 from. The @var{id} field contains the @value{GDBN} identifier of the
27942 thread group. The @var{code} field is the exit code of the inferior; it exists
27943 only when the inferior exited with some code.
27945 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27946 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27947 A thread either was created, or has exited. The @var{id} field
27948 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27949 field identifies the thread group this thread belongs to.
27951 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27952 Informs that the selected thread or frame were changed. This notification
27953 is not emitted as result of the @code{-thread-select} or
27954 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27955 that is not documented to change the selected thread and frame actually
27956 changes them. In particular, invoking, directly or indirectly
27957 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27958 will generate this notification. Changing the thread or frame from another
27959 user interface (see @ref{Interpreters}) will also generate this notification.
27961 The @var{frame} field is only present if the newly selected thread is
27962 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27964 We suggest that in response to this notification, front ends
27965 highlight the selected thread and cause subsequent commands to apply to
27968 @item =library-loaded,...
27969 Reports that a new library file was loaded by the program. This
27970 notification has 5 fields---@var{id}, @var{target-name},
27971 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27972 opaque identifier of the library. For remote debugging case,
27973 @var{target-name} and @var{host-name} fields give the name of the
27974 library file on the target, and on the host respectively. For native
27975 debugging, both those fields have the same value. The
27976 @var{symbols-loaded} field is emitted only for backward compatibility
27977 and should not be relied on to convey any useful information. The
27978 @var{thread-group} field, if present, specifies the id of the thread
27979 group in whose context the library was loaded. If the field is
27980 absent, it means the library was loaded in the context of all present
27981 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27984 @item =library-unloaded,...
27985 Reports that a library was unloaded by the program. This notification
27986 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27987 the same meaning as for the @code{=library-loaded} notification.
27988 The @var{thread-group} field, if present, specifies the id of the
27989 thread group in whose context the library was unloaded. If the field is
27990 absent, it means the library was unloaded in the context of all present
27993 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27994 @itemx =traceframe-changed,end
27995 Reports that the trace frame was changed and its new number is
27996 @var{tfnum}. The number of the tracepoint associated with this trace
27997 frame is @var{tpnum}.
27999 @item =tsv-created,name=@var{name},initial=@var{initial}
28000 Reports that the new trace state variable @var{name} is created with
28001 initial value @var{initial}.
28003 @item =tsv-deleted,name=@var{name}
28004 @itemx =tsv-deleted
28005 Reports that the trace state variable @var{name} is deleted or all
28006 trace state variables are deleted.
28008 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28009 Reports that the trace state variable @var{name} is modified with
28010 the initial value @var{initial}. The current value @var{current} of
28011 trace state variable is optional and is reported if the current
28012 value of trace state variable is known.
28014 @item =breakpoint-created,bkpt=@{...@}
28015 @itemx =breakpoint-modified,bkpt=@{...@}
28016 @itemx =breakpoint-deleted,id=@var{number}
28017 Reports that a breakpoint was created, modified, or deleted,
28018 respectively. Only user-visible breakpoints are reported to the MI
28021 The @var{bkpt} argument is of the same form as returned by the various
28022 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28023 @var{number} is the ordinal number of the breakpoint.
28025 Note that if a breakpoint is emitted in the result record of a
28026 command, then it will not also be emitted in an async record.
28028 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28029 @itemx =record-stopped,thread-group="@var{id}"
28030 Execution log recording was either started or stopped on an
28031 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28032 group corresponding to the affected inferior.
28034 The @var{method} field indicates the method used to record execution. If the
28035 method in use supports multiple recording formats, @var{format} will be present
28036 and contain the currently used format. @xref{Process Record and Replay},
28037 for existing method and format values.
28039 @item =cmd-param-changed,param=@var{param},value=@var{value}
28040 Reports that a parameter of the command @code{set @var{param}} is
28041 changed to @var{value}. In the multi-word @code{set} command,
28042 the @var{param} is the whole parameter list to @code{set} command.
28043 For example, In command @code{set check type on}, @var{param}
28044 is @code{check type} and @var{value} is @code{on}.
28046 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28047 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28048 written in an inferior. The @var{id} is the identifier of the
28049 thread group corresponding to the affected inferior. The optional
28050 @code{type="code"} part is reported if the memory written to holds
28054 @node GDB/MI Breakpoint Information
28055 @subsection @sc{gdb/mi} Breakpoint Information
28057 When @value{GDBN} reports information about a breakpoint, a
28058 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28063 The breakpoint number. For a breakpoint that represents one location
28064 of a multi-location breakpoint, this will be a dotted pair, like
28068 The type of the breakpoint. For ordinary breakpoints this will be
28069 @samp{breakpoint}, but many values are possible.
28072 If the type of the breakpoint is @samp{catchpoint}, then this
28073 indicates the exact type of catchpoint.
28076 This is the breakpoint disposition---either @samp{del}, meaning that
28077 the breakpoint will be deleted at the next stop, or @samp{keep},
28078 meaning that the breakpoint will not be deleted.
28081 This indicates whether the breakpoint is enabled, in which case the
28082 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28083 Note that this is not the same as the field @code{enable}.
28086 The address of the breakpoint. This may be a hexidecimal number,
28087 giving the address; or the string @samp{<PENDING>}, for a pending
28088 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28089 multiple locations. This field will not be present if no address can
28090 be determined. For example, a watchpoint does not have an address.
28093 If known, the function in which the breakpoint appears.
28094 If not known, this field is not present.
28097 The name of the source file which contains this function, if known.
28098 If not known, this field is not present.
28101 The full file name of the source file which contains this function, if
28102 known. If not known, this field is not present.
28105 The line number at which this breakpoint appears, if known.
28106 If not known, this field is not present.
28109 If the source file is not known, this field may be provided. If
28110 provided, this holds the address of the breakpoint, possibly followed
28114 If this breakpoint is pending, this field is present and holds the
28115 text used to set the breakpoint, as entered by the user.
28118 Where this breakpoint's condition is evaluated, either @samp{host} or
28122 If this is a thread-specific breakpoint, then this identifies the
28123 thread in which the breakpoint can trigger.
28126 If this breakpoint is restricted to a particular Ada task, then this
28127 field will hold the task identifier.
28130 If the breakpoint is conditional, this is the condition expression.
28133 The ignore count of the breakpoint.
28136 The enable count of the breakpoint.
28138 @item traceframe-usage
28141 @item static-tracepoint-marker-string-id
28142 For a static tracepoint, the name of the static tracepoint marker.
28145 For a masked watchpoint, this is the mask.
28148 A tracepoint's pass count.
28150 @item original-location
28151 The location of the breakpoint as originally specified by the user.
28152 This field is optional.
28155 The number of times the breakpoint has been hit.
28158 This field is only given for tracepoints. This is either @samp{y},
28159 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28163 Some extra data, the exact contents of which are type-dependent.
28167 For example, here is what the output of @code{-break-insert}
28168 (@pxref{GDB/MI Breakpoint Commands}) might be:
28171 -> -break-insert main
28172 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28173 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28174 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28179 @node GDB/MI Frame Information
28180 @subsection @sc{gdb/mi} Frame Information
28182 Response from many MI commands includes an information about stack
28183 frame. This information is a tuple that may have the following
28188 The level of the stack frame. The innermost frame has the level of
28189 zero. This field is always present.
28192 The name of the function corresponding to the frame. This field may
28193 be absent if @value{GDBN} is unable to determine the function name.
28196 The code address for the frame. This field is always present.
28199 The name of the source files that correspond to the frame's code
28200 address. This field may be absent.
28203 The source line corresponding to the frames' code address. This field
28207 The name of the binary file (either executable or shared library) the
28208 corresponds to the frame's code address. This field may be absent.
28212 @node GDB/MI Thread Information
28213 @subsection @sc{gdb/mi} Thread Information
28215 Whenever @value{GDBN} has to report an information about a thread, it
28216 uses a tuple with the following fields. The fields are always present unless
28221 The global numeric id assigned to the thread by @value{GDBN}.
28224 The target-specific string identifying the thread.
28227 Additional information about the thread provided by the target.
28228 It is supposed to be human-readable and not interpreted by the
28229 frontend. This field is optional.
28232 The name of the thread. If the user specified a name using the
28233 @code{thread name} command, then this name is given. Otherwise, if
28234 @value{GDBN} can extract the thread name from the target, then that
28235 name is given. If @value{GDBN} cannot find the thread name, then this
28239 The execution state of the thread, either @samp{stopped} or @samp{running},
28240 depending on whether the thread is presently running.
28243 The stack frame currently executing in the thread. This field is only present
28244 if the thread is stopped. Its format is documented in
28245 @ref{GDB/MI Frame Information}.
28248 The value of this field is an integer number of the processor core the
28249 thread was last seen on. This field is optional.
28252 @node GDB/MI Ada Exception Information
28253 @subsection @sc{gdb/mi} Ada Exception Information
28255 Whenever a @code{*stopped} record is emitted because the program
28256 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28257 @value{GDBN} provides the name of the exception that was raised via
28258 the @code{exception-name} field. Also, for exceptions that were raised
28259 with an exception message, @value{GDBN} provides that message via
28260 the @code{exception-message} field.
28262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28263 @node GDB/MI Simple Examples
28264 @section Simple Examples of @sc{gdb/mi} Interaction
28265 @cindex @sc{gdb/mi}, simple examples
28267 This subsection presents several simple examples of interaction using
28268 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28269 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28270 the output received from @sc{gdb/mi}.
28272 Note the line breaks shown in the examples are here only for
28273 readability, they don't appear in the real output.
28275 @subheading Setting a Breakpoint
28277 Setting a breakpoint generates synchronous output which contains detailed
28278 information of the breakpoint.
28281 -> -break-insert main
28282 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28283 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28284 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28289 @subheading Program Execution
28291 Program execution generates asynchronous records and MI gives the
28292 reason that execution stopped.
28298 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28299 frame=@{addr="0x08048564",func="main",
28300 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28301 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28302 arch="i386:x86_64"@}
28307 <- *stopped,reason="exited-normally"
28311 @subheading Quitting @value{GDBN}
28313 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28321 Please note that @samp{^exit} is printed immediately, but it might
28322 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28323 performs necessary cleanups, including killing programs being debugged
28324 or disconnecting from debug hardware, so the frontend should wait till
28325 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28326 fails to exit in reasonable time.
28328 @subheading A Bad Command
28330 Here's what happens if you pass a non-existent command:
28334 <- ^error,msg="Undefined MI command: rubbish"
28339 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28340 @node GDB/MI Command Description Format
28341 @section @sc{gdb/mi} Command Description Format
28343 The remaining sections describe blocks of commands. Each block of
28344 commands is laid out in a fashion similar to this section.
28346 @subheading Motivation
28348 The motivation for this collection of commands.
28350 @subheading Introduction
28352 A brief introduction to this collection of commands as a whole.
28354 @subheading Commands
28356 For each command in the block, the following is described:
28358 @subsubheading Synopsis
28361 -command @var{args}@dots{}
28364 @subsubheading Result
28366 @subsubheading @value{GDBN} Command
28368 The corresponding @value{GDBN} CLI command(s), if any.
28370 @subsubheading Example
28372 Example(s) formatted for readability. Some of the described commands have
28373 not been implemented yet and these are labeled N.A.@: (not available).
28376 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28377 @node GDB/MI Breakpoint Commands
28378 @section @sc{gdb/mi} Breakpoint Commands
28380 @cindex breakpoint commands for @sc{gdb/mi}
28381 @cindex @sc{gdb/mi}, breakpoint commands
28382 This section documents @sc{gdb/mi} commands for manipulating
28385 @subheading The @code{-break-after} Command
28386 @findex -break-after
28388 @subsubheading Synopsis
28391 -break-after @var{number} @var{count}
28394 The breakpoint number @var{number} is not in effect until it has been
28395 hit @var{count} times. To see how this is reflected in the output of
28396 the @samp{-break-list} command, see the description of the
28397 @samp{-break-list} command below.
28399 @subsubheading @value{GDBN} Command
28401 The corresponding @value{GDBN} command is @samp{ignore}.
28403 @subsubheading Example
28408 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28409 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28410 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28418 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28419 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28420 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28421 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28422 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28423 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28424 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28425 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28426 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28427 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28432 @subheading The @code{-break-catch} Command
28433 @findex -break-catch
28436 @subheading The @code{-break-commands} Command
28437 @findex -break-commands
28439 @subsubheading Synopsis
28442 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28445 Specifies the CLI commands that should be executed when breakpoint
28446 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28447 are the commands. If no command is specified, any previously-set
28448 commands are cleared. @xref{Break Commands}. Typical use of this
28449 functionality is tracing a program, that is, printing of values of
28450 some variables whenever breakpoint is hit and then continuing.
28452 @subsubheading @value{GDBN} Command
28454 The corresponding @value{GDBN} command is @samp{commands}.
28456 @subsubheading Example
28461 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28462 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28463 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28466 -break-commands 1 "print v" "continue"
28471 @subheading The @code{-break-condition} Command
28472 @findex -break-condition
28474 @subsubheading Synopsis
28477 -break-condition @var{number} @var{expr}
28480 Breakpoint @var{number} will stop the program only if the condition in
28481 @var{expr} is true. The condition becomes part of the
28482 @samp{-break-list} output (see the description of the @samp{-break-list}
28485 @subsubheading @value{GDBN} Command
28487 The corresponding @value{GDBN} command is @samp{condition}.
28489 @subsubheading Example
28493 -break-condition 1 1
28497 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28504 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28505 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28506 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28510 @subheading The @code{-break-delete} Command
28511 @findex -break-delete
28513 @subsubheading Synopsis
28516 -break-delete ( @var{breakpoint} )+
28519 Delete the breakpoint(s) whose number(s) are specified in the argument
28520 list. This is obviously reflected in the breakpoint list.
28522 @subsubheading @value{GDBN} Command
28524 The corresponding @value{GDBN} command is @samp{delete}.
28526 @subsubheading Example
28534 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28535 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28536 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28537 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28538 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28539 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28540 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28545 @subheading The @code{-break-disable} Command
28546 @findex -break-disable
28548 @subsubheading Synopsis
28551 -break-disable ( @var{breakpoint} )+
28554 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28555 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28557 @subsubheading @value{GDBN} Command
28559 The corresponding @value{GDBN} command is @samp{disable}.
28561 @subsubheading Example
28569 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28570 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28571 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28572 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28573 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28574 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28575 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28576 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28577 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28578 line="5",thread-groups=["i1"],times="0"@}]@}
28582 @subheading The @code{-break-enable} Command
28583 @findex -break-enable
28585 @subsubheading Synopsis
28588 -break-enable ( @var{breakpoint} )+
28591 Enable (previously disabled) @var{breakpoint}(s).
28593 @subsubheading @value{GDBN} Command
28595 The corresponding @value{GDBN} command is @samp{enable}.
28597 @subsubheading Example
28605 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28606 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28607 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28608 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28609 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28610 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28611 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28612 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28613 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28614 line="5",thread-groups=["i1"],times="0"@}]@}
28618 @subheading The @code{-break-info} Command
28619 @findex -break-info
28621 @subsubheading Synopsis
28624 -break-info @var{breakpoint}
28628 Get information about a single breakpoint.
28630 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28631 Information}, for details on the format of each breakpoint in the
28634 @subsubheading @value{GDBN} Command
28636 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28638 @subsubheading Example
28641 @subheading The @code{-break-insert} Command
28642 @findex -break-insert
28643 @anchor{-break-insert}
28645 @subsubheading Synopsis
28648 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28649 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28650 [ -p @var{thread-id} ] [ @var{location} ]
28654 If specified, @var{location}, can be one of:
28657 @item linespec location
28658 A linespec location. @xref{Linespec Locations}.
28660 @item explicit location
28661 An explicit location. @sc{gdb/mi} explicit locations are
28662 analogous to the CLI's explicit locations using the option names
28663 listed below. @xref{Explicit Locations}.
28666 @item --source @var{filename}
28667 The source file name of the location. This option requires the use
28668 of either @samp{--function} or @samp{--line}.
28670 @item --function @var{function}
28671 The name of a function or method.
28673 @item --label @var{label}
28674 The name of a label.
28676 @item --line @var{lineoffset}
28677 An absolute or relative line offset from the start of the location.
28680 @item address location
28681 An address location, *@var{address}. @xref{Address Locations}.
28685 The possible optional parameters of this command are:
28689 Insert a temporary breakpoint.
28691 Insert a hardware breakpoint.
28693 If @var{location} cannot be parsed (for example if it
28694 refers to unknown files or functions), create a pending
28695 breakpoint. Without this flag, @value{GDBN} will report
28696 an error, and won't create a breakpoint, if @var{location}
28699 Create a disabled breakpoint.
28701 Create a tracepoint. @xref{Tracepoints}. When this parameter
28702 is used together with @samp{-h}, a fast tracepoint is created.
28703 @item -c @var{condition}
28704 Make the breakpoint conditional on @var{condition}.
28705 @item -i @var{ignore-count}
28706 Initialize the @var{ignore-count}.
28707 @item -p @var{thread-id}
28708 Restrict the breakpoint to the thread with the specified global
28712 @subsubheading Result
28714 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28715 resulting breakpoint.
28717 Note: this format is open to change.
28718 @c An out-of-band breakpoint instead of part of the result?
28720 @subsubheading @value{GDBN} Command
28722 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28723 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28725 @subsubheading Example
28730 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28731 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28734 -break-insert -t foo
28735 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28736 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28740 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28747 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28748 addr="0x0001072c", func="main",file="recursive2.c",
28749 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28751 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28752 addr="0x00010774",func="foo",file="recursive2.c",
28753 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28756 @c -break-insert -r foo.*
28757 @c ~int foo(int, int);
28758 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28759 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28764 @subheading The @code{-dprintf-insert} Command
28765 @findex -dprintf-insert
28767 @subsubheading Synopsis
28770 -dprintf-insert [ -t ] [ -f ] [ -d ]
28771 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28772 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28777 If supplied, @var{location} may be specified the same way as for
28778 the @code{-break-insert} command. @xref{-break-insert}.
28780 The possible optional parameters of this command are:
28784 Insert a temporary breakpoint.
28786 If @var{location} cannot be parsed (for example, if it
28787 refers to unknown files or functions), create a pending
28788 breakpoint. Without this flag, @value{GDBN} will report
28789 an error, and won't create a breakpoint, if @var{location}
28792 Create a disabled breakpoint.
28793 @item -c @var{condition}
28794 Make the breakpoint conditional on @var{condition}.
28795 @item -i @var{ignore-count}
28796 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28797 to @var{ignore-count}.
28798 @item -p @var{thread-id}
28799 Restrict the breakpoint to the thread with the specified global
28803 @subsubheading Result
28805 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28806 resulting breakpoint.
28808 @c An out-of-band breakpoint instead of part of the result?
28810 @subsubheading @value{GDBN} Command
28812 The corresponding @value{GDBN} command is @samp{dprintf}.
28814 @subsubheading Example
28818 4-dprintf-insert foo "At foo entry\n"
28819 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28820 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28821 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28822 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28823 original-location="foo"@}
28825 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28826 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28827 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28828 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28829 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28830 original-location="mi-dprintf.c:26"@}
28834 @subheading The @code{-break-list} Command
28835 @findex -break-list
28837 @subsubheading Synopsis
28843 Displays the list of inserted breakpoints, showing the following fields:
28847 number of the breakpoint
28849 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28851 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28854 is the breakpoint enabled or no: @samp{y} or @samp{n}
28856 memory location at which the breakpoint is set
28858 logical location of the breakpoint, expressed by function name, file
28860 @item Thread-groups
28861 list of thread groups to which this breakpoint applies
28863 number of times the breakpoint has been hit
28866 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28867 @code{body} field is an empty list.
28869 @subsubheading @value{GDBN} Command
28871 The corresponding @value{GDBN} command is @samp{info break}.
28873 @subsubheading Example
28878 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28879 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28880 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28881 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28882 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28883 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28884 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28885 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28886 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28888 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28889 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28890 line="13",thread-groups=["i1"],times="0"@}]@}
28894 Here's an example of the result when there are no breakpoints:
28899 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28900 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28901 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28902 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28903 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28904 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28905 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28910 @subheading The @code{-break-passcount} Command
28911 @findex -break-passcount
28913 @subsubheading Synopsis
28916 -break-passcount @var{tracepoint-number} @var{passcount}
28919 Set the passcount for tracepoint @var{tracepoint-number} to
28920 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28921 is not a tracepoint, error is emitted. This corresponds to CLI
28922 command @samp{passcount}.
28924 @subheading The @code{-break-watch} Command
28925 @findex -break-watch
28927 @subsubheading Synopsis
28930 -break-watch [ -a | -r ]
28933 Create a watchpoint. With the @samp{-a} option it will create an
28934 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28935 read from or on a write to the memory location. With the @samp{-r}
28936 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28937 trigger only when the memory location is accessed for reading. Without
28938 either of the options, the watchpoint created is a regular watchpoint,
28939 i.e., it will trigger when the memory location is accessed for writing.
28940 @xref{Set Watchpoints, , Setting Watchpoints}.
28942 Note that @samp{-break-list} will report a single list of watchpoints and
28943 breakpoints inserted.
28945 @subsubheading @value{GDBN} Command
28947 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28950 @subsubheading Example
28952 Setting a watchpoint on a variable in the @code{main} function:
28957 ^done,wpt=@{number="2",exp="x"@}
28962 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28963 value=@{old="-268439212",new="55"@},
28964 frame=@{func="main",args=[],file="recursive2.c",
28965 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
28969 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28970 the program execution twice: first for the variable changing value, then
28971 for the watchpoint going out of scope.
28976 ^done,wpt=@{number="5",exp="C"@}
28981 *stopped,reason="watchpoint-trigger",
28982 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28983 frame=@{func="callee4",args=[],
28984 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28985 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
28986 arch="i386:x86_64"@}
28991 *stopped,reason="watchpoint-scope",wpnum="5",
28992 frame=@{func="callee3",args=[@{name="strarg",
28993 value="0x11940 \"A string argument.\""@}],
28994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28995 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
28996 arch="i386:x86_64"@}
29000 Listing breakpoints and watchpoints, at different points in the program
29001 execution. Note that once the watchpoint goes out of scope, it is
29007 ^done,wpt=@{number="2",exp="C"@}
29010 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29011 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29012 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29013 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29014 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29015 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29016 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29017 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29018 addr="0x00010734",func="callee4",
29019 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29020 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29022 bkpt=@{number="2",type="watchpoint",disp="keep",
29023 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29028 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29029 value=@{old="-276895068",new="3"@},
29030 frame=@{func="callee4",args=[],
29031 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29032 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29033 arch="i386:x86_64"@}
29036 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29037 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29038 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29039 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29040 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29041 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29042 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29043 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29044 addr="0x00010734",func="callee4",
29045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29046 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29048 bkpt=@{number="2",type="watchpoint",disp="keep",
29049 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29053 ^done,reason="watchpoint-scope",wpnum="2",
29054 frame=@{func="callee3",args=[@{name="strarg",
29055 value="0x11940 \"A string argument.\""@}],
29056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29057 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29058 arch="i386:x86_64"@}
29061 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29062 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29063 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29064 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29065 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29066 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29067 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29068 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29069 addr="0x00010734",func="callee4",
29070 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29071 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29072 thread-groups=["i1"],times="1"@}]@}
29077 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29078 @node GDB/MI Catchpoint Commands
29079 @section @sc{gdb/mi} Catchpoint Commands
29081 This section documents @sc{gdb/mi} commands for manipulating
29085 * Shared Library GDB/MI Catchpoint Commands::
29086 * Ada Exception GDB/MI Catchpoint Commands::
29089 @node Shared Library GDB/MI Catchpoint Commands
29090 @subsection Shared Library @sc{gdb/mi} Catchpoints
29092 @subheading The @code{-catch-load} Command
29093 @findex -catch-load
29095 @subsubheading Synopsis
29098 -catch-load [ -t ] [ -d ] @var{regexp}
29101 Add a catchpoint for library load events. If the @samp{-t} option is used,
29102 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29103 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29104 in a disabled state. The @samp{regexp} argument is a regular
29105 expression used to match the name of the loaded library.
29108 @subsubheading @value{GDBN} Command
29110 The corresponding @value{GDBN} command is @samp{catch load}.
29112 @subsubheading Example
29115 -catch-load -t foo.so
29116 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29117 what="load of library matching foo.so",catch-type="load",times="0"@}
29122 @subheading The @code{-catch-unload} Command
29123 @findex -catch-unload
29125 @subsubheading Synopsis
29128 -catch-unload [ -t ] [ -d ] @var{regexp}
29131 Add a catchpoint for library unload events. If the @samp{-t} option is
29132 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29133 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29134 created in a disabled state. The @samp{regexp} argument is a regular
29135 expression used to match the name of the unloaded library.
29137 @subsubheading @value{GDBN} Command
29139 The corresponding @value{GDBN} command is @samp{catch unload}.
29141 @subsubheading Example
29144 -catch-unload -d bar.so
29145 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29146 what="load of library matching bar.so",catch-type="unload",times="0"@}
29150 @node Ada Exception GDB/MI Catchpoint Commands
29151 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29153 The following @sc{gdb/mi} commands can be used to create catchpoints
29154 that stop the execution when Ada exceptions are being raised.
29156 @subheading The @code{-catch-assert} Command
29157 @findex -catch-assert
29159 @subsubheading Synopsis
29162 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29165 Add a catchpoint for failed Ada assertions.
29167 The possible optional parameters for this command are:
29170 @item -c @var{condition}
29171 Make the catchpoint conditional on @var{condition}.
29173 Create a disabled catchpoint.
29175 Create a temporary catchpoint.
29178 @subsubheading @value{GDBN} Command
29180 The corresponding @value{GDBN} command is @samp{catch assert}.
29182 @subsubheading Example
29186 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29187 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29188 thread-groups=["i1"],times="0",
29189 original-location="__gnat_debug_raise_assert_failure"@}
29193 @subheading The @code{-catch-exception} Command
29194 @findex -catch-exception
29196 @subsubheading Synopsis
29199 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29203 Add a catchpoint stopping when Ada exceptions are raised.
29204 By default, the command stops the program when any Ada exception
29205 gets raised. But it is also possible, by using some of the
29206 optional parameters described below, to create more selective
29209 The possible optional parameters for this command are:
29212 @item -c @var{condition}
29213 Make the catchpoint conditional on @var{condition}.
29215 Create a disabled catchpoint.
29216 @item -e @var{exception-name}
29217 Only stop when @var{exception-name} is raised. This option cannot
29218 be used combined with @samp{-u}.
29220 Create a temporary catchpoint.
29222 Stop only when an unhandled exception gets raised. This option
29223 cannot be used combined with @samp{-e}.
29226 @subsubheading @value{GDBN} Command
29228 The corresponding @value{GDBN} commands are @samp{catch exception}
29229 and @samp{catch exception unhandled}.
29231 @subsubheading Example
29234 -catch-exception -e Program_Error
29235 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29236 enabled="y",addr="0x0000000000404874",
29237 what="`Program_Error' Ada exception", thread-groups=["i1"],
29238 times="0",original-location="__gnat_debug_raise_exception"@}
29242 @subheading The @code{-catch-handlers} Command
29243 @findex -catch-handlers
29245 @subsubheading Synopsis
29248 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29252 Add a catchpoint stopping when Ada exceptions are handled.
29253 By default, the command stops the program when any Ada exception
29254 gets handled. But it is also possible, by using some of the
29255 optional parameters described below, to create more selective
29258 The possible optional parameters for this command are:
29261 @item -c @var{condition}
29262 Make the catchpoint conditional on @var{condition}.
29264 Create a disabled catchpoint.
29265 @item -e @var{exception-name}
29266 Only stop when @var{exception-name} is handled.
29268 Create a temporary catchpoint.
29271 @subsubheading @value{GDBN} Command
29273 The corresponding @value{GDBN} command is @samp{catch handlers}.
29275 @subsubheading Example
29278 -catch-handlers -e Constraint_Error
29279 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29280 enabled="y",addr="0x0000000000402f68",
29281 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29282 times="0",original-location="__gnat_begin_handler"@}
29286 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29287 @node GDB/MI Program Context
29288 @section @sc{gdb/mi} Program Context
29290 @subheading The @code{-exec-arguments} Command
29291 @findex -exec-arguments
29294 @subsubheading Synopsis
29297 -exec-arguments @var{args}
29300 Set the inferior program arguments, to be used in the next
29303 @subsubheading @value{GDBN} Command
29305 The corresponding @value{GDBN} command is @samp{set args}.
29307 @subsubheading Example
29311 -exec-arguments -v word
29318 @subheading The @code{-exec-show-arguments} Command
29319 @findex -exec-show-arguments
29321 @subsubheading Synopsis
29324 -exec-show-arguments
29327 Print the arguments of the program.
29329 @subsubheading @value{GDBN} Command
29331 The corresponding @value{GDBN} command is @samp{show args}.
29333 @subsubheading Example
29338 @subheading The @code{-environment-cd} Command
29339 @findex -environment-cd
29341 @subsubheading Synopsis
29344 -environment-cd @var{pathdir}
29347 Set @value{GDBN}'s working directory.
29349 @subsubheading @value{GDBN} Command
29351 The corresponding @value{GDBN} command is @samp{cd}.
29353 @subsubheading Example
29357 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29363 @subheading The @code{-environment-directory} Command
29364 @findex -environment-directory
29366 @subsubheading Synopsis
29369 -environment-directory [ -r ] [ @var{pathdir} ]+
29372 Add directories @var{pathdir} to beginning of search path for source files.
29373 If the @samp{-r} option is used, the search path is reset to the default
29374 search path. If directories @var{pathdir} are supplied in addition to the
29375 @samp{-r} option, the search path is first reset and then addition
29377 Multiple directories may be specified, separated by blanks. Specifying
29378 multiple directories in a single command
29379 results in the directories added to the beginning of the
29380 search path in the same order they were presented in the command.
29381 If blanks are needed as
29382 part of a directory name, double-quotes should be used around
29383 the name. In the command output, the path will show up separated
29384 by the system directory-separator character. The directory-separator
29385 character must not be used
29386 in any directory name.
29387 If no directories are specified, the current search path is displayed.
29389 @subsubheading @value{GDBN} Command
29391 The corresponding @value{GDBN} command is @samp{dir}.
29393 @subsubheading Example
29397 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29398 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29400 -environment-directory ""
29401 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29403 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29404 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29406 -environment-directory -r
29407 ^done,source-path="$cdir:$cwd"
29412 @subheading The @code{-environment-path} Command
29413 @findex -environment-path
29415 @subsubheading Synopsis
29418 -environment-path [ -r ] [ @var{pathdir} ]+
29421 Add directories @var{pathdir} to beginning of search path for object files.
29422 If the @samp{-r} option is used, the search path is reset to the original
29423 search path that existed at gdb start-up. If directories @var{pathdir} are
29424 supplied in addition to the
29425 @samp{-r} option, the search path is first reset and then addition
29427 Multiple directories may be specified, separated by blanks. Specifying
29428 multiple directories in a single command
29429 results in the directories added to the beginning of the
29430 search path in the same order they were presented in the command.
29431 If blanks are needed as
29432 part of a directory name, double-quotes should be used around
29433 the name. In the command output, the path will show up separated
29434 by the system directory-separator character. The directory-separator
29435 character must not be used
29436 in any directory name.
29437 If no directories are specified, the current path is displayed.
29440 @subsubheading @value{GDBN} Command
29442 The corresponding @value{GDBN} command is @samp{path}.
29444 @subsubheading Example
29449 ^done,path="/usr/bin"
29451 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29452 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29454 -environment-path -r /usr/local/bin
29455 ^done,path="/usr/local/bin:/usr/bin"
29460 @subheading The @code{-environment-pwd} Command
29461 @findex -environment-pwd
29463 @subsubheading Synopsis
29469 Show the current working directory.
29471 @subsubheading @value{GDBN} Command
29473 The corresponding @value{GDBN} command is @samp{pwd}.
29475 @subsubheading Example
29480 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29484 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29485 @node GDB/MI Thread Commands
29486 @section @sc{gdb/mi} Thread Commands
29489 @subheading The @code{-thread-info} Command
29490 @findex -thread-info
29492 @subsubheading Synopsis
29495 -thread-info [ @var{thread-id} ]
29498 Reports information about either a specific thread, if the
29499 @var{thread-id} parameter is present, or about all threads.
29500 @var{thread-id} is the thread's global thread ID. When printing
29501 information about all threads, also reports the global ID of the
29504 @subsubheading @value{GDBN} Command
29506 The @samp{info thread} command prints the same information
29509 @subsubheading Result
29511 The result contains the following attributes:
29515 A list of threads. The format of the elements of the list is described in
29516 @ref{GDB/MI Thread Information}.
29518 @item current-thread-id
29519 The global id of the currently selected thread. This field is omitted if there
29520 is no selected thread (for example, when the selected inferior is not running,
29521 and therefore has no threads) or if a @var{thread-id} argument was passed to
29526 @subsubheading Example
29531 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29532 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29533 args=[]@},state="running"@},
29534 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29535 frame=@{level="0",addr="0x0804891f",func="foo",
29536 args=[@{name="i",value="10"@}],
29537 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29538 state="running"@}],
29539 current-thread-id="1"
29543 @subheading The @code{-thread-list-ids} Command
29544 @findex -thread-list-ids
29546 @subsubheading Synopsis
29552 Produces a list of the currently known global @value{GDBN} thread ids.
29553 At the end of the list it also prints the total number of such
29556 This command is retained for historical reasons, the
29557 @code{-thread-info} command should be used instead.
29559 @subsubheading @value{GDBN} Command
29561 Part of @samp{info threads} supplies the same information.
29563 @subsubheading Example
29568 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29569 current-thread-id="1",number-of-threads="3"
29574 @subheading The @code{-thread-select} Command
29575 @findex -thread-select
29577 @subsubheading Synopsis
29580 -thread-select @var{thread-id}
29583 Make thread with global thread number @var{thread-id} the current
29584 thread. It prints the number of the new current thread, and the
29585 topmost frame for that thread.
29587 This command is deprecated in favor of explicitly using the
29588 @samp{--thread} option to each command.
29590 @subsubheading @value{GDBN} Command
29592 The corresponding @value{GDBN} command is @samp{thread}.
29594 @subsubheading Example
29601 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29602 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29606 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29607 number-of-threads="3"
29610 ^done,new-thread-id="3",
29611 frame=@{level="0",func="vprintf",
29612 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29613 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29617 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29618 @node GDB/MI Ada Tasking Commands
29619 @section @sc{gdb/mi} Ada Tasking Commands
29621 @subheading The @code{-ada-task-info} Command
29622 @findex -ada-task-info
29624 @subsubheading Synopsis
29627 -ada-task-info [ @var{task-id} ]
29630 Reports information about either a specific Ada task, if the
29631 @var{task-id} parameter is present, or about all Ada tasks.
29633 @subsubheading @value{GDBN} Command
29635 The @samp{info tasks} command prints the same information
29636 about all Ada tasks (@pxref{Ada Tasks}).
29638 @subsubheading Result
29640 The result is a table of Ada tasks. The following columns are
29641 defined for each Ada task:
29645 This field exists only for the current thread. It has the value @samp{*}.
29648 The identifier that @value{GDBN} uses to refer to the Ada task.
29651 The identifier that the target uses to refer to the Ada task.
29654 The global thread identifier of the thread corresponding to the Ada
29657 This field should always exist, as Ada tasks are always implemented
29658 on top of a thread. But if @value{GDBN} cannot find this corresponding
29659 thread for any reason, the field is omitted.
29662 This field exists only when the task was created by another task.
29663 In this case, it provides the ID of the parent task.
29666 The base priority of the task.
29669 The current state of the task. For a detailed description of the
29670 possible states, see @ref{Ada Tasks}.
29673 The name of the task.
29677 @subsubheading Example
29681 ^done,tasks=@{nr_rows="3",nr_cols="8",
29682 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29683 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29684 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29685 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29686 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29687 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29688 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29689 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29690 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29691 state="Child Termination Wait",name="main_task"@}]@}
29695 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29696 @node GDB/MI Program Execution
29697 @section @sc{gdb/mi} Program Execution
29699 These are the asynchronous commands which generate the out-of-band
29700 record @samp{*stopped}. Currently @value{GDBN} only really executes
29701 asynchronously with remote targets and this interaction is mimicked in
29704 @subheading The @code{-exec-continue} Command
29705 @findex -exec-continue
29707 @subsubheading Synopsis
29710 -exec-continue [--reverse] [--all|--thread-group N]
29713 Resumes the execution of the inferior program, which will continue
29714 to execute until it reaches a debugger stop event. If the
29715 @samp{--reverse} option is specified, execution resumes in reverse until
29716 it reaches a stop event. Stop events may include
29719 breakpoints or watchpoints
29721 signals or exceptions
29723 the end of the process (or its beginning under @samp{--reverse})
29725 the end or beginning of a replay log if one is being used.
29727 In all-stop mode (@pxref{All-Stop
29728 Mode}), may resume only one thread, or all threads, depending on the
29729 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29730 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29731 ignored in all-stop mode. If the @samp{--thread-group} options is
29732 specified, then all threads in that thread group are resumed.
29734 @subsubheading @value{GDBN} Command
29736 The corresponding @value{GDBN} corresponding is @samp{continue}.
29738 @subsubheading Example
29745 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29746 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29747 line="13",arch="i386:x86_64"@}
29752 @subheading The @code{-exec-finish} Command
29753 @findex -exec-finish
29755 @subsubheading Synopsis
29758 -exec-finish [--reverse]
29761 Resumes the execution of the inferior program until the current
29762 function is exited. Displays the results returned by the function.
29763 If the @samp{--reverse} option is specified, resumes the reverse
29764 execution of the inferior program until the point where current
29765 function was called.
29767 @subsubheading @value{GDBN} Command
29769 The corresponding @value{GDBN} command is @samp{finish}.
29771 @subsubheading Example
29773 Function returning @code{void}.
29780 *stopped,reason="function-finished",frame=@{func="main",args=[],
29781 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
29785 Function returning other than @code{void}. The name of the internal
29786 @value{GDBN} variable storing the result is printed, together with the
29793 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29794 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29795 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
29796 arch="i386:x86_64"@},
29797 gdb-result-var="$1",return-value="0"
29802 @subheading The @code{-exec-interrupt} Command
29803 @findex -exec-interrupt
29805 @subsubheading Synopsis
29808 -exec-interrupt [--all|--thread-group N]
29811 Interrupts the background execution of the target. Note how the token
29812 associated with the stop message is the one for the execution command
29813 that has been interrupted. The token for the interrupt itself only
29814 appears in the @samp{^done} output. If the user is trying to
29815 interrupt a non-running program, an error message will be printed.
29817 Note that when asynchronous execution is enabled, this command is
29818 asynchronous just like other execution commands. That is, first the
29819 @samp{^done} response will be printed, and the target stop will be
29820 reported after that using the @samp{*stopped} notification.
29822 In non-stop mode, only the context thread is interrupted by default.
29823 All threads (in all inferiors) will be interrupted if the
29824 @samp{--all} option is specified. If the @samp{--thread-group}
29825 option is specified, all threads in that group will be interrupted.
29827 @subsubheading @value{GDBN} Command
29829 The corresponding @value{GDBN} command is @samp{interrupt}.
29831 @subsubheading Example
29842 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29843 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29844 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
29849 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29853 @subheading The @code{-exec-jump} Command
29856 @subsubheading Synopsis
29859 -exec-jump @var{location}
29862 Resumes execution of the inferior program at the location specified by
29863 parameter. @xref{Specify Location}, for a description of the
29864 different forms of @var{location}.
29866 @subsubheading @value{GDBN} Command
29868 The corresponding @value{GDBN} command is @samp{jump}.
29870 @subsubheading Example
29873 -exec-jump foo.c:10
29874 *running,thread-id="all"
29879 @subheading The @code{-exec-next} Command
29882 @subsubheading Synopsis
29885 -exec-next [--reverse]
29888 Resumes execution of the inferior program, stopping when the beginning
29889 of the next source line is reached.
29891 If the @samp{--reverse} option is specified, resumes reverse execution
29892 of the inferior program, stopping at the beginning of the previous
29893 source line. If you issue this command on the first line of a
29894 function, it will take you back to the caller of that function, to the
29895 source line where the function was called.
29898 @subsubheading @value{GDBN} Command
29900 The corresponding @value{GDBN} command is @samp{next}.
29902 @subsubheading Example
29908 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29913 @subheading The @code{-exec-next-instruction} Command
29914 @findex -exec-next-instruction
29916 @subsubheading Synopsis
29919 -exec-next-instruction [--reverse]
29922 Executes one machine instruction. If the instruction is a function
29923 call, continues until the function returns. If the program stops at an
29924 instruction in the middle of a source line, the address will be
29927 If the @samp{--reverse} option is specified, resumes reverse execution
29928 of the inferior program, stopping at the previous instruction. If the
29929 previously executed instruction was a return from another function,
29930 it will continue to execute in reverse until the call to that function
29931 (from the current stack frame) is reached.
29933 @subsubheading @value{GDBN} Command
29935 The corresponding @value{GDBN} command is @samp{nexti}.
29937 @subsubheading Example
29941 -exec-next-instruction
29945 *stopped,reason="end-stepping-range",
29946 addr="0x000100d4",line="5",file="hello.c"
29951 @subheading The @code{-exec-return} Command
29952 @findex -exec-return
29954 @subsubheading Synopsis
29960 Makes current function return immediately. Doesn't execute the inferior.
29961 Displays the new current frame.
29963 @subsubheading @value{GDBN} Command
29965 The corresponding @value{GDBN} command is @samp{return}.
29967 @subsubheading Example
29971 200-break-insert callee4
29972 200^done,bkpt=@{number="1",addr="0x00010734",
29973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29978 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29979 frame=@{func="callee4",args=[],
29980 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29981 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29982 arch="i386:x86_64"@}
29988 111^done,frame=@{level="0",func="callee3",
29989 args=[@{name="strarg",
29990 value="0x11940 \"A string argument.\""@}],
29991 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29992 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29993 arch="i386:x86_64"@}
29998 @subheading The @code{-exec-run} Command
30001 @subsubheading Synopsis
30004 -exec-run [ --all | --thread-group N ] [ --start ]
30007 Starts execution of the inferior from the beginning. The inferior
30008 executes until either a breakpoint is encountered or the program
30009 exits. In the latter case the output will include an exit code, if
30010 the program has exited exceptionally.
30012 When neither the @samp{--all} nor the @samp{--thread-group} option
30013 is specified, the current inferior is started. If the
30014 @samp{--thread-group} option is specified, it should refer to a thread
30015 group of type @samp{process}, and that thread group will be started.
30016 If the @samp{--all} option is specified, then all inferiors will be started.
30018 Using the @samp{--start} option instructs the debugger to stop
30019 the execution at the start of the inferior's main subprogram,
30020 following the same behavior as the @code{start} command
30021 (@pxref{Starting}).
30023 @subsubheading @value{GDBN} Command
30025 The corresponding @value{GDBN} command is @samp{run}.
30027 @subsubheading Examples
30032 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30037 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30038 frame=@{func="main",args=[],file="recursive2.c",
30039 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30044 Program exited normally:
30052 *stopped,reason="exited-normally"
30057 Program exited exceptionally:
30065 *stopped,reason="exited",exit-code="01"
30069 Another way the program can terminate is if it receives a signal such as
30070 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30074 *stopped,reason="exited-signalled",signal-name="SIGINT",
30075 signal-meaning="Interrupt"
30079 @c @subheading -exec-signal
30082 @subheading The @code{-exec-step} Command
30085 @subsubheading Synopsis
30088 -exec-step [--reverse]
30091 Resumes execution of the inferior program, stopping when the beginning
30092 of the next source line is reached, if the next source line is not a
30093 function call. If it is, stop at the first instruction of the called
30094 function. If the @samp{--reverse} option is specified, resumes reverse
30095 execution of the inferior program, stopping at the beginning of the
30096 previously executed source line.
30098 @subsubheading @value{GDBN} Command
30100 The corresponding @value{GDBN} command is @samp{step}.
30102 @subsubheading Example
30104 Stepping into a function:
30110 *stopped,reason="end-stepping-range",
30111 frame=@{func="foo",args=[@{name="a",value="10"@},
30112 @{name="b",value="0"@}],file="recursive2.c",
30113 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30123 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30128 @subheading The @code{-exec-step-instruction} Command
30129 @findex -exec-step-instruction
30131 @subsubheading Synopsis
30134 -exec-step-instruction [--reverse]
30137 Resumes the inferior which executes one machine instruction. If the
30138 @samp{--reverse} option is specified, resumes reverse execution of the
30139 inferior program, stopping at the previously executed instruction.
30140 The output, once @value{GDBN} has stopped, will vary depending on
30141 whether we have stopped in the middle of a source line or not. In the
30142 former case, the address at which the program stopped will be printed
30145 @subsubheading @value{GDBN} Command
30147 The corresponding @value{GDBN} command is @samp{stepi}.
30149 @subsubheading Example
30153 -exec-step-instruction
30157 *stopped,reason="end-stepping-range",
30158 frame=@{func="foo",args=[],file="try.c",
30159 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30161 -exec-step-instruction
30165 *stopped,reason="end-stepping-range",
30166 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30167 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30172 @subheading The @code{-exec-until} Command
30173 @findex -exec-until
30175 @subsubheading Synopsis
30178 -exec-until [ @var{location} ]
30181 Executes the inferior until the @var{location} specified in the
30182 argument is reached. If there is no argument, the inferior executes
30183 until a source line greater than the current one is reached. The
30184 reason for stopping in this case will be @samp{location-reached}.
30186 @subsubheading @value{GDBN} Command
30188 The corresponding @value{GDBN} command is @samp{until}.
30190 @subsubheading Example
30194 -exec-until recursive2.c:6
30198 *stopped,reason="location-reached",frame=@{func="main",args=[],
30199 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30200 arch="i386:x86_64"@}
30205 @subheading -file-clear
30206 Is this going away????
30209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30210 @node GDB/MI Stack Manipulation
30211 @section @sc{gdb/mi} Stack Manipulation Commands
30213 @subheading The @code{-enable-frame-filters} Command
30214 @findex -enable-frame-filters
30217 -enable-frame-filters
30220 @value{GDBN} allows Python-based frame filters to affect the output of
30221 the MI commands relating to stack traces. As there is no way to
30222 implement this in a fully backward-compatible way, a front end must
30223 request that this functionality be enabled.
30225 Once enabled, this feature cannot be disabled.
30227 Note that if Python support has not been compiled into @value{GDBN},
30228 this command will still succeed (and do nothing).
30230 @subheading The @code{-stack-info-frame} Command
30231 @findex -stack-info-frame
30233 @subsubheading Synopsis
30239 Get info on the selected frame.
30241 @subsubheading @value{GDBN} Command
30243 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30244 (without arguments).
30246 @subsubheading Example
30251 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30252 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30253 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30254 arch="i386:x86_64"@}
30258 @subheading The @code{-stack-info-depth} Command
30259 @findex -stack-info-depth
30261 @subsubheading Synopsis
30264 -stack-info-depth [ @var{max-depth} ]
30267 Return the depth of the stack. If the integer argument @var{max-depth}
30268 is specified, do not count beyond @var{max-depth} frames.
30270 @subsubheading @value{GDBN} Command
30272 There's no equivalent @value{GDBN} command.
30274 @subsubheading Example
30276 For a stack with frame levels 0 through 11:
30283 -stack-info-depth 4
30286 -stack-info-depth 12
30289 -stack-info-depth 11
30292 -stack-info-depth 13
30297 @anchor{-stack-list-arguments}
30298 @subheading The @code{-stack-list-arguments} Command
30299 @findex -stack-list-arguments
30301 @subsubheading Synopsis
30304 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30305 [ @var{low-frame} @var{high-frame} ]
30308 Display a list of the arguments for the frames between @var{low-frame}
30309 and @var{high-frame} (inclusive). If @var{low-frame} and
30310 @var{high-frame} are not provided, list the arguments for the whole
30311 call stack. If the two arguments are equal, show the single frame
30312 at the corresponding level. It is an error if @var{low-frame} is
30313 larger than the actual number of frames. On the other hand,
30314 @var{high-frame} may be larger than the actual number of frames, in
30315 which case only existing frames will be returned.
30317 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30318 the variables; if it is 1 or @code{--all-values}, print also their
30319 values; and if it is 2 or @code{--simple-values}, print the name,
30320 type and value for simple data types, and the name and type for arrays,
30321 structures and unions. If the option @code{--no-frame-filters} is
30322 supplied, then Python frame filters will not be executed.
30324 If the @code{--skip-unavailable} option is specified, arguments that
30325 are not available are not listed. Partially available arguments
30326 are still displayed, however.
30328 Use of this command to obtain arguments in a single frame is
30329 deprecated in favor of the @samp{-stack-list-variables} command.
30331 @subsubheading @value{GDBN} Command
30333 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30334 @samp{gdb_get_args} command which partially overlaps with the
30335 functionality of @samp{-stack-list-arguments}.
30337 @subsubheading Example
30344 frame=@{level="0",addr="0x00010734",func="callee4",
30345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30346 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30347 arch="i386:x86_64"@},
30348 frame=@{level="1",addr="0x0001076c",func="callee3",
30349 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30350 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30351 arch="i386:x86_64"@},
30352 frame=@{level="2",addr="0x0001078c",func="callee2",
30353 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30354 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30355 arch="i386:x86_64"@},
30356 frame=@{level="3",addr="0x000107b4",func="callee1",
30357 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30358 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30359 arch="i386:x86_64"@},
30360 frame=@{level="4",addr="0x000107e0",func="main",
30361 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30362 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30363 arch="i386:x86_64"@}]
30365 -stack-list-arguments 0
30368 frame=@{level="0",args=[]@},
30369 frame=@{level="1",args=[name="strarg"]@},
30370 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30371 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30372 frame=@{level="4",args=[]@}]
30374 -stack-list-arguments 1
30377 frame=@{level="0",args=[]@},
30379 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30380 frame=@{level="2",args=[
30381 @{name="intarg",value="2"@},
30382 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30383 @{frame=@{level="3",args=[
30384 @{name="intarg",value="2"@},
30385 @{name="strarg",value="0x11940 \"A string argument.\""@},
30386 @{name="fltarg",value="3.5"@}]@},
30387 frame=@{level="4",args=[]@}]
30389 -stack-list-arguments 0 2 2
30390 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30392 -stack-list-arguments 1 2 2
30393 ^done,stack-args=[frame=@{level="2",
30394 args=[@{name="intarg",value="2"@},
30395 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30399 @c @subheading -stack-list-exception-handlers
30402 @anchor{-stack-list-frames}
30403 @subheading The @code{-stack-list-frames} Command
30404 @findex -stack-list-frames
30406 @subsubheading Synopsis
30409 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30412 List the frames currently on the stack. For each frame it displays the
30417 The frame number, 0 being the topmost frame, i.e., the innermost function.
30419 The @code{$pc} value for that frame.
30423 File name of the source file where the function lives.
30424 @item @var{fullname}
30425 The full file name of the source file where the function lives.
30427 Line number corresponding to the @code{$pc}.
30429 The shared library where this function is defined. This is only given
30430 if the frame's function is not known.
30432 Frame's architecture.
30435 If invoked without arguments, this command prints a backtrace for the
30436 whole stack. If given two integer arguments, it shows the frames whose
30437 levels are between the two arguments (inclusive). If the two arguments
30438 are equal, it shows the single frame at the corresponding level. It is
30439 an error if @var{low-frame} is larger than the actual number of
30440 frames. On the other hand, @var{high-frame} may be larger than the
30441 actual number of frames, in which case only existing frames will be
30442 returned. If the option @code{--no-frame-filters} is supplied, then
30443 Python frame filters will not be executed.
30445 @subsubheading @value{GDBN} Command
30447 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30449 @subsubheading Example
30451 Full stack backtrace:
30457 [frame=@{level="0",addr="0x0001076c",func="foo",
30458 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30459 arch="i386:x86_64"@},
30460 frame=@{level="1",addr="0x000107a4",func="foo",
30461 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30462 arch="i386:x86_64"@},
30463 frame=@{level="2",addr="0x000107a4",func="foo",
30464 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30465 arch="i386:x86_64"@},
30466 frame=@{level="3",addr="0x000107a4",func="foo",
30467 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30468 arch="i386:x86_64"@},
30469 frame=@{level="4",addr="0x000107a4",func="foo",
30470 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30471 arch="i386:x86_64"@},
30472 frame=@{level="5",addr="0x000107a4",func="foo",
30473 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30474 arch="i386:x86_64"@},
30475 frame=@{level="6",addr="0x000107a4",func="foo",
30476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30477 arch="i386:x86_64"@},
30478 frame=@{level="7",addr="0x000107a4",func="foo",
30479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30480 arch="i386:x86_64"@},
30481 frame=@{level="8",addr="0x000107a4",func="foo",
30482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30483 arch="i386:x86_64"@},
30484 frame=@{level="9",addr="0x000107a4",func="foo",
30485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30486 arch="i386:x86_64"@},
30487 frame=@{level="10",addr="0x000107a4",func="foo",
30488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30489 arch="i386:x86_64"@},
30490 frame=@{level="11",addr="0x00010738",func="main",
30491 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30492 arch="i386:x86_64"@}]
30496 Show frames between @var{low_frame} and @var{high_frame}:
30500 -stack-list-frames 3 5
30502 [frame=@{level="3",addr="0x000107a4",func="foo",
30503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30504 arch="i386:x86_64"@},
30505 frame=@{level="4",addr="0x000107a4",func="foo",
30506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30507 arch="i386:x86_64"@},
30508 frame=@{level="5",addr="0x000107a4",func="foo",
30509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30510 arch="i386:x86_64"@}]
30514 Show a single frame:
30518 -stack-list-frames 3 3
30520 [frame=@{level="3",addr="0x000107a4",func="foo",
30521 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30522 arch="i386:x86_64"@}]
30527 @subheading The @code{-stack-list-locals} Command
30528 @findex -stack-list-locals
30529 @anchor{-stack-list-locals}
30531 @subsubheading Synopsis
30534 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30537 Display the local variable names for the selected frame. If
30538 @var{print-values} is 0 or @code{--no-values}, print only the names of
30539 the variables; if it is 1 or @code{--all-values}, print also their
30540 values; and if it is 2 or @code{--simple-values}, print the name,
30541 type and value for simple data types, and the name and type for arrays,
30542 structures and unions. In this last case, a frontend can immediately
30543 display the value of simple data types and create variable objects for
30544 other data types when the user wishes to explore their values in
30545 more detail. If the option @code{--no-frame-filters} is supplied, then
30546 Python frame filters will not be executed.
30548 If the @code{--skip-unavailable} option is specified, local variables
30549 that are not available are not listed. Partially available local
30550 variables are still displayed, however.
30552 This command is deprecated in favor of the
30553 @samp{-stack-list-variables} command.
30555 @subsubheading @value{GDBN} Command
30557 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30559 @subsubheading Example
30563 -stack-list-locals 0
30564 ^done,locals=[name="A",name="B",name="C"]
30566 -stack-list-locals --all-values
30567 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30568 @{name="C",value="@{1, 2, 3@}"@}]
30569 -stack-list-locals --simple-values
30570 ^done,locals=[@{name="A",type="int",value="1"@},
30571 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30575 @anchor{-stack-list-variables}
30576 @subheading The @code{-stack-list-variables} Command
30577 @findex -stack-list-variables
30579 @subsubheading Synopsis
30582 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30585 Display the names of local variables and function arguments for the selected frame. If
30586 @var{print-values} is 0 or @code{--no-values}, print only the names of
30587 the variables; if it is 1 or @code{--all-values}, print also their
30588 values; and if it is 2 or @code{--simple-values}, print the name,
30589 type and value for simple data types, and the name and type for arrays,
30590 structures and unions. If the option @code{--no-frame-filters} is
30591 supplied, then Python frame filters will not be executed.
30593 If the @code{--skip-unavailable} option is specified, local variables
30594 and arguments that are not available are not listed. Partially
30595 available arguments and local variables are still displayed, however.
30597 @subsubheading Example
30601 -stack-list-variables --thread 1 --frame 0 --all-values
30602 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30607 @subheading The @code{-stack-select-frame} Command
30608 @findex -stack-select-frame
30610 @subsubheading Synopsis
30613 -stack-select-frame @var{framenum}
30616 Change the selected frame. Select a different frame @var{framenum} on
30619 This command in deprecated in favor of passing the @samp{--frame}
30620 option to every command.
30622 @subsubheading @value{GDBN} Command
30624 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30625 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30627 @subsubheading Example
30631 -stack-select-frame 2
30636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30637 @node GDB/MI Variable Objects
30638 @section @sc{gdb/mi} Variable Objects
30642 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30644 For the implementation of a variable debugger window (locals, watched
30645 expressions, etc.), we are proposing the adaptation of the existing code
30646 used by @code{Insight}.
30648 The two main reasons for that are:
30652 It has been proven in practice (it is already on its second generation).
30655 It will shorten development time (needless to say how important it is
30659 The original interface was designed to be used by Tcl code, so it was
30660 slightly changed so it could be used through @sc{gdb/mi}. This section
30661 describes the @sc{gdb/mi} operations that will be available and gives some
30662 hints about their use.
30664 @emph{Note}: In addition to the set of operations described here, we
30665 expect the @sc{gui} implementation of a variable window to require, at
30666 least, the following operations:
30669 @item @code{-gdb-show} @code{output-radix}
30670 @item @code{-stack-list-arguments}
30671 @item @code{-stack-list-locals}
30672 @item @code{-stack-select-frame}
30677 @subheading Introduction to Variable Objects
30679 @cindex variable objects in @sc{gdb/mi}
30681 Variable objects are "object-oriented" MI interface for examining and
30682 changing values of expressions. Unlike some other MI interfaces that
30683 work with expressions, variable objects are specifically designed for
30684 simple and efficient presentation in the frontend. A variable object
30685 is identified by string name. When a variable object is created, the
30686 frontend specifies the expression for that variable object. The
30687 expression can be a simple variable, or it can be an arbitrary complex
30688 expression, and can even involve CPU registers. After creating a
30689 variable object, the frontend can invoke other variable object
30690 operations---for example to obtain or change the value of a variable
30691 object, or to change display format.
30693 Variable objects have hierarchical tree structure. Any variable object
30694 that corresponds to a composite type, such as structure in C, has
30695 a number of child variable objects, for example corresponding to each
30696 element of a structure. A child variable object can itself have
30697 children, recursively. Recursion ends when we reach
30698 leaf variable objects, which always have built-in types. Child variable
30699 objects are created only by explicit request, so if a frontend
30700 is not interested in the children of a particular variable object, no
30701 child will be created.
30703 For a leaf variable object it is possible to obtain its value as a
30704 string, or set the value from a string. String value can be also
30705 obtained for a non-leaf variable object, but it's generally a string
30706 that only indicates the type of the object, and does not list its
30707 contents. Assignment to a non-leaf variable object is not allowed.
30709 A frontend does not need to read the values of all variable objects each time
30710 the program stops. Instead, MI provides an update command that lists all
30711 variable objects whose values has changed since the last update
30712 operation. This considerably reduces the amount of data that must
30713 be transferred to the frontend. As noted above, children variable
30714 objects are created on demand, and only leaf variable objects have a
30715 real value. As result, gdb will read target memory only for leaf
30716 variables that frontend has created.
30718 The automatic update is not always desirable. For example, a frontend
30719 might want to keep a value of some expression for future reference,
30720 and never update it. For another example, fetching memory is
30721 relatively slow for embedded targets, so a frontend might want
30722 to disable automatic update for the variables that are either not
30723 visible on the screen, or ``closed''. This is possible using so
30724 called ``frozen variable objects''. Such variable objects are never
30725 implicitly updated.
30727 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30728 fixed variable object, the expression is parsed when the variable
30729 object is created, including associating identifiers to specific
30730 variables. The meaning of expression never changes. For a floating
30731 variable object the values of variables whose names appear in the
30732 expressions are re-evaluated every time in the context of the current
30733 frame. Consider this example:
30738 struct work_state state;
30745 If a fixed variable object for the @code{state} variable is created in
30746 this function, and we enter the recursive call, the variable
30747 object will report the value of @code{state} in the top-level
30748 @code{do_work} invocation. On the other hand, a floating variable
30749 object will report the value of @code{state} in the current frame.
30751 If an expression specified when creating a fixed variable object
30752 refers to a local variable, the variable object becomes bound to the
30753 thread and frame in which the variable object is created. When such
30754 variable object is updated, @value{GDBN} makes sure that the
30755 thread/frame combination the variable object is bound to still exists,
30756 and re-evaluates the variable object in context of that thread/frame.
30758 The following is the complete set of @sc{gdb/mi} operations defined to
30759 access this functionality:
30761 @multitable @columnfractions .4 .6
30762 @item @strong{Operation}
30763 @tab @strong{Description}
30765 @item @code{-enable-pretty-printing}
30766 @tab enable Python-based pretty-printing
30767 @item @code{-var-create}
30768 @tab create a variable object
30769 @item @code{-var-delete}
30770 @tab delete the variable object and/or its children
30771 @item @code{-var-set-format}
30772 @tab set the display format of this variable
30773 @item @code{-var-show-format}
30774 @tab show the display format of this variable
30775 @item @code{-var-info-num-children}
30776 @tab tells how many children this object has
30777 @item @code{-var-list-children}
30778 @tab return a list of the object's children
30779 @item @code{-var-info-type}
30780 @tab show the type of this variable object
30781 @item @code{-var-info-expression}
30782 @tab print parent-relative expression that this variable object represents
30783 @item @code{-var-info-path-expression}
30784 @tab print full expression that this variable object represents
30785 @item @code{-var-show-attributes}
30786 @tab is this variable editable? does it exist here?
30787 @item @code{-var-evaluate-expression}
30788 @tab get the value of this variable
30789 @item @code{-var-assign}
30790 @tab set the value of this variable
30791 @item @code{-var-update}
30792 @tab update the variable and its children
30793 @item @code{-var-set-frozen}
30794 @tab set frozeness attribute
30795 @item @code{-var-set-update-range}
30796 @tab set range of children to display on update
30799 In the next subsection we describe each operation in detail and suggest
30800 how it can be used.
30802 @subheading Description And Use of Operations on Variable Objects
30804 @subheading The @code{-enable-pretty-printing} Command
30805 @findex -enable-pretty-printing
30808 -enable-pretty-printing
30811 @value{GDBN} allows Python-based visualizers to affect the output of the
30812 MI variable object commands. However, because there was no way to
30813 implement this in a fully backward-compatible way, a front end must
30814 request that this functionality be enabled.
30816 Once enabled, this feature cannot be disabled.
30818 Note that if Python support has not been compiled into @value{GDBN},
30819 this command will still succeed (and do nothing).
30821 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30822 may work differently in future versions of @value{GDBN}.
30824 @subheading The @code{-var-create} Command
30825 @findex -var-create
30827 @subsubheading Synopsis
30830 -var-create @{@var{name} | "-"@}
30831 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30834 This operation creates a variable object, which allows the monitoring of
30835 a variable, the result of an expression, a memory cell or a CPU
30838 The @var{name} parameter is the string by which the object can be
30839 referenced. It must be unique. If @samp{-} is specified, the varobj
30840 system will generate a string ``varNNNNNN'' automatically. It will be
30841 unique provided that one does not specify @var{name} of that format.
30842 The command fails if a duplicate name is found.
30844 The frame under which the expression should be evaluated can be
30845 specified by @var{frame-addr}. A @samp{*} indicates that the current
30846 frame should be used. A @samp{@@} indicates that a floating variable
30847 object must be created.
30849 @var{expression} is any expression valid on the current language set (must not
30850 begin with a @samp{*}), or one of the following:
30854 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30857 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30860 @samp{$@var{regname}} --- a CPU register name
30863 @cindex dynamic varobj
30864 A varobj's contents may be provided by a Python-based pretty-printer. In this
30865 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30866 have slightly different semantics in some cases. If the
30867 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30868 will never create a dynamic varobj. This ensures backward
30869 compatibility for existing clients.
30871 @subsubheading Result
30873 This operation returns attributes of the newly-created varobj. These
30878 The name of the varobj.
30881 The number of children of the varobj. This number is not necessarily
30882 reliable for a dynamic varobj. Instead, you must examine the
30883 @samp{has_more} attribute.
30886 The varobj's scalar value. For a varobj whose type is some sort of
30887 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30888 will not be interesting.
30891 The varobj's type. This is a string representation of the type, as
30892 would be printed by the @value{GDBN} CLI. If @samp{print object}
30893 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30894 @emph{actual} (derived) type of the object is shown rather than the
30895 @emph{declared} one.
30898 If a variable object is bound to a specific thread, then this is the
30899 thread's global identifier.
30902 For a dynamic varobj, this indicates whether there appear to be any
30903 children available. For a non-dynamic varobj, this will be 0.
30906 This attribute will be present and have the value @samp{1} if the
30907 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30908 then this attribute will not be present.
30911 A dynamic varobj can supply a display hint to the front end. The
30912 value comes directly from the Python pretty-printer object's
30913 @code{display_hint} method. @xref{Pretty Printing API}.
30916 Typical output will look like this:
30919 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30920 has_more="@var{has_more}"
30924 @subheading The @code{-var-delete} Command
30925 @findex -var-delete
30927 @subsubheading Synopsis
30930 -var-delete [ -c ] @var{name}
30933 Deletes a previously created variable object and all of its children.
30934 With the @samp{-c} option, just deletes the children.
30936 Returns an error if the object @var{name} is not found.
30939 @subheading The @code{-var-set-format} Command
30940 @findex -var-set-format
30942 @subsubheading Synopsis
30945 -var-set-format @var{name} @var{format-spec}
30948 Sets the output format for the value of the object @var{name} to be
30951 @anchor{-var-set-format}
30952 The syntax for the @var{format-spec} is as follows:
30955 @var{format-spec} @expansion{}
30956 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30959 The natural format is the default format choosen automatically
30960 based on the variable type (like decimal for an @code{int}, hex
30961 for pointers, etc.).
30963 The zero-hexadecimal format has a representation similar to hexadecimal
30964 but with padding zeroes to the left of the value. For example, a 32-bit
30965 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30966 zero-hexadecimal format.
30968 For a variable with children, the format is set only on the
30969 variable itself, and the children are not affected.
30971 @subheading The @code{-var-show-format} Command
30972 @findex -var-show-format
30974 @subsubheading Synopsis
30977 -var-show-format @var{name}
30980 Returns the format used to display the value of the object @var{name}.
30983 @var{format} @expansion{}
30988 @subheading The @code{-var-info-num-children} Command
30989 @findex -var-info-num-children
30991 @subsubheading Synopsis
30994 -var-info-num-children @var{name}
30997 Returns the number of children of a variable object @var{name}:
31003 Note that this number is not completely reliable for a dynamic varobj.
31004 It will return the current number of children, but more children may
31008 @subheading The @code{-var-list-children} Command
31009 @findex -var-list-children
31011 @subsubheading Synopsis
31014 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31016 @anchor{-var-list-children}
31018 Return a list of the children of the specified variable object and
31019 create variable objects for them, if they do not already exist. With
31020 a single argument or if @var{print-values} has a value of 0 or
31021 @code{--no-values}, print only the names of the variables; if
31022 @var{print-values} is 1 or @code{--all-values}, also print their
31023 values; and if it is 2 or @code{--simple-values} print the name and
31024 value for simple data types and just the name for arrays, structures
31027 @var{from} and @var{to}, if specified, indicate the range of children
31028 to report. If @var{from} or @var{to} is less than zero, the range is
31029 reset and all children will be reported. Otherwise, children starting
31030 at @var{from} (zero-based) and up to and excluding @var{to} will be
31033 If a child range is requested, it will only affect the current call to
31034 @code{-var-list-children}, but not future calls to @code{-var-update}.
31035 For this, you must instead use @code{-var-set-update-range}. The
31036 intent of this approach is to enable a front end to implement any
31037 update approach it likes; for example, scrolling a view may cause the
31038 front end to request more children with @code{-var-list-children}, and
31039 then the front end could call @code{-var-set-update-range} with a
31040 different range to ensure that future updates are restricted to just
31043 For each child the following results are returned:
31048 Name of the variable object created for this child.
31051 The expression to be shown to the user by the front end to designate this child.
31052 For example this may be the name of a structure member.
31054 For a dynamic varobj, this value cannot be used to form an
31055 expression. There is no way to do this at all with a dynamic varobj.
31057 For C/C@t{++} structures there are several pseudo children returned to
31058 designate access qualifiers. For these pseudo children @var{exp} is
31059 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31060 type and value are not present.
31062 A dynamic varobj will not report the access qualifying
31063 pseudo-children, regardless of the language. This information is not
31064 available at all with a dynamic varobj.
31067 Number of children this child has. For a dynamic varobj, this will be
31071 The type of the child. If @samp{print object}
31072 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31073 @emph{actual} (derived) type of the object is shown rather than the
31074 @emph{declared} one.
31077 If values were requested, this is the value.
31080 If this variable object is associated with a thread, this is the
31081 thread's global thread id. Otherwise this result is not present.
31084 If the variable object is frozen, this variable will be present with a value of 1.
31087 A dynamic varobj can supply a display hint to the front end. The
31088 value comes directly from the Python pretty-printer object's
31089 @code{display_hint} method. @xref{Pretty Printing API}.
31092 This attribute will be present and have the value @samp{1} if the
31093 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31094 then this attribute will not be present.
31098 The result may have its own attributes:
31102 A dynamic varobj can supply a display hint to the front end. The
31103 value comes directly from the Python pretty-printer object's
31104 @code{display_hint} method. @xref{Pretty Printing API}.
31107 This is an integer attribute which is nonzero if there are children
31108 remaining after the end of the selected range.
31111 @subsubheading Example
31115 -var-list-children n
31116 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31117 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31119 -var-list-children --all-values n
31120 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31121 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31125 @subheading The @code{-var-info-type} Command
31126 @findex -var-info-type
31128 @subsubheading Synopsis
31131 -var-info-type @var{name}
31134 Returns the type of the specified variable @var{name}. The type is
31135 returned as a string in the same format as it is output by the
31139 type=@var{typename}
31143 @subheading The @code{-var-info-expression} Command
31144 @findex -var-info-expression
31146 @subsubheading Synopsis
31149 -var-info-expression @var{name}
31152 Returns a string that is suitable for presenting this
31153 variable object in user interface. The string is generally
31154 not valid expression in the current language, and cannot be evaluated.
31156 For example, if @code{a} is an array, and variable object
31157 @code{A} was created for @code{a}, then we'll get this output:
31160 (gdb) -var-info-expression A.1
31161 ^done,lang="C",exp="1"
31165 Here, the value of @code{lang} is the language name, which can be
31166 found in @ref{Supported Languages}.
31168 Note that the output of the @code{-var-list-children} command also
31169 includes those expressions, so the @code{-var-info-expression} command
31172 @subheading The @code{-var-info-path-expression} Command
31173 @findex -var-info-path-expression
31175 @subsubheading Synopsis
31178 -var-info-path-expression @var{name}
31181 Returns an expression that can be evaluated in the current
31182 context and will yield the same value that a variable object has.
31183 Compare this with the @code{-var-info-expression} command, which
31184 result can be used only for UI presentation. Typical use of
31185 the @code{-var-info-path-expression} command is creating a
31186 watchpoint from a variable object.
31188 This command is currently not valid for children of a dynamic varobj,
31189 and will give an error when invoked on one.
31191 For example, suppose @code{C} is a C@t{++} class, derived from class
31192 @code{Base}, and that the @code{Base} class has a member called
31193 @code{m_size}. Assume a variable @code{c} is has the type of
31194 @code{C} and a variable object @code{C} was created for variable
31195 @code{c}. Then, we'll get this output:
31197 (gdb) -var-info-path-expression C.Base.public.m_size
31198 ^done,path_expr=((Base)c).m_size)
31201 @subheading The @code{-var-show-attributes} Command
31202 @findex -var-show-attributes
31204 @subsubheading Synopsis
31207 -var-show-attributes @var{name}
31210 List attributes of the specified variable object @var{name}:
31213 status=@var{attr} [ ( ,@var{attr} )* ]
31217 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31219 @subheading The @code{-var-evaluate-expression} Command
31220 @findex -var-evaluate-expression
31222 @subsubheading Synopsis
31225 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31228 Evaluates the expression that is represented by the specified variable
31229 object and returns its value as a string. The format of the string
31230 can be specified with the @samp{-f} option. The possible values of
31231 this option are the same as for @code{-var-set-format}
31232 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31233 the current display format will be used. The current display format
31234 can be changed using the @code{-var-set-format} command.
31240 Note that one must invoke @code{-var-list-children} for a variable
31241 before the value of a child variable can be evaluated.
31243 @subheading The @code{-var-assign} Command
31244 @findex -var-assign
31246 @subsubheading Synopsis
31249 -var-assign @var{name} @var{expression}
31252 Assigns the value of @var{expression} to the variable object specified
31253 by @var{name}. The object must be @samp{editable}. If the variable's
31254 value is altered by the assign, the variable will show up in any
31255 subsequent @code{-var-update} list.
31257 @subsubheading Example
31265 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31269 @subheading The @code{-var-update} Command
31270 @findex -var-update
31272 @subsubheading Synopsis
31275 -var-update [@var{print-values}] @{@var{name} | "*"@}
31278 Reevaluate the expressions corresponding to the variable object
31279 @var{name} and all its direct and indirect children, and return the
31280 list of variable objects whose values have changed; @var{name} must
31281 be a root variable object. Here, ``changed'' means that the result of
31282 @code{-var-evaluate-expression} before and after the
31283 @code{-var-update} is different. If @samp{*} is used as the variable
31284 object names, all existing variable objects are updated, except
31285 for frozen ones (@pxref{-var-set-frozen}). The option
31286 @var{print-values} determines whether both names and values, or just
31287 names are printed. The possible values of this option are the same
31288 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31289 recommended to use the @samp{--all-values} option, to reduce the
31290 number of MI commands needed on each program stop.
31292 With the @samp{*} parameter, if a variable object is bound to a
31293 currently running thread, it will not be updated, without any
31296 If @code{-var-set-update-range} was previously used on a varobj, then
31297 only the selected range of children will be reported.
31299 @code{-var-update} reports all the changed varobjs in a tuple named
31302 Each item in the change list is itself a tuple holding:
31306 The name of the varobj.
31309 If values were requested for this update, then this field will be
31310 present and will hold the value of the varobj.
31313 @anchor{-var-update}
31314 This field is a string which may take one of three values:
31318 The variable object's current value is valid.
31321 The variable object does not currently hold a valid value but it may
31322 hold one in the future if its associated expression comes back into
31326 The variable object no longer holds a valid value.
31327 This can occur when the executable file being debugged has changed,
31328 either through recompilation or by using the @value{GDBN} @code{file}
31329 command. The front end should normally choose to delete these variable
31333 In the future new values may be added to this list so the front should
31334 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31337 This is only present if the varobj is still valid. If the type
31338 changed, then this will be the string @samp{true}; otherwise it will
31341 When a varobj's type changes, its children are also likely to have
31342 become incorrect. Therefore, the varobj's children are automatically
31343 deleted when this attribute is @samp{true}. Also, the varobj's update
31344 range, when set using the @code{-var-set-update-range} command, is
31348 If the varobj's type changed, then this field will be present and will
31351 @item new_num_children
31352 For a dynamic varobj, if the number of children changed, or if the
31353 type changed, this will be the new number of children.
31355 The @samp{numchild} field in other varobj responses is generally not
31356 valid for a dynamic varobj -- it will show the number of children that
31357 @value{GDBN} knows about, but because dynamic varobjs lazily
31358 instantiate their children, this will not reflect the number of
31359 children which may be available.
31361 The @samp{new_num_children} attribute only reports changes to the
31362 number of children known by @value{GDBN}. This is the only way to
31363 detect whether an update has removed children (which necessarily can
31364 only happen at the end of the update range).
31367 The display hint, if any.
31370 This is an integer value, which will be 1 if there are more children
31371 available outside the varobj's update range.
31374 This attribute will be present and have the value @samp{1} if the
31375 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31376 then this attribute will not be present.
31379 If new children were added to a dynamic varobj within the selected
31380 update range (as set by @code{-var-set-update-range}), then they will
31381 be listed in this attribute.
31384 @subsubheading Example
31391 -var-update --all-values var1
31392 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31393 type_changed="false"@}]
31397 @subheading The @code{-var-set-frozen} Command
31398 @findex -var-set-frozen
31399 @anchor{-var-set-frozen}
31401 @subsubheading Synopsis
31404 -var-set-frozen @var{name} @var{flag}
31407 Set the frozenness flag on the variable object @var{name}. The
31408 @var{flag} parameter should be either @samp{1} to make the variable
31409 frozen or @samp{0} to make it unfrozen. If a variable object is
31410 frozen, then neither itself, nor any of its children, are
31411 implicitly updated by @code{-var-update} of
31412 a parent variable or by @code{-var-update *}. Only
31413 @code{-var-update} of the variable itself will update its value and
31414 values of its children. After a variable object is unfrozen, it is
31415 implicitly updated by all subsequent @code{-var-update} operations.
31416 Unfreezing a variable does not update it, only subsequent
31417 @code{-var-update} does.
31419 @subsubheading Example
31423 -var-set-frozen V 1
31428 @subheading The @code{-var-set-update-range} command
31429 @findex -var-set-update-range
31430 @anchor{-var-set-update-range}
31432 @subsubheading Synopsis
31435 -var-set-update-range @var{name} @var{from} @var{to}
31438 Set the range of children to be returned by future invocations of
31439 @code{-var-update}.
31441 @var{from} and @var{to} indicate the range of children to report. If
31442 @var{from} or @var{to} is less than zero, the range is reset and all
31443 children will be reported. Otherwise, children starting at @var{from}
31444 (zero-based) and up to and excluding @var{to} will be reported.
31446 @subsubheading Example
31450 -var-set-update-range V 1 2
31454 @subheading The @code{-var-set-visualizer} command
31455 @findex -var-set-visualizer
31456 @anchor{-var-set-visualizer}
31458 @subsubheading Synopsis
31461 -var-set-visualizer @var{name} @var{visualizer}
31464 Set a visualizer for the variable object @var{name}.
31466 @var{visualizer} is the visualizer to use. The special value
31467 @samp{None} means to disable any visualizer in use.
31469 If not @samp{None}, @var{visualizer} must be a Python expression.
31470 This expression must evaluate to a callable object which accepts a
31471 single argument. @value{GDBN} will call this object with the value of
31472 the varobj @var{name} as an argument (this is done so that the same
31473 Python pretty-printing code can be used for both the CLI and MI).
31474 When called, this object must return an object which conforms to the
31475 pretty-printing interface (@pxref{Pretty Printing API}).
31477 The pre-defined function @code{gdb.default_visualizer} may be used to
31478 select a visualizer by following the built-in process
31479 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31480 a varobj is created, and so ordinarily is not needed.
31482 This feature is only available if Python support is enabled. The MI
31483 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31484 can be used to check this.
31486 @subsubheading Example
31488 Resetting the visualizer:
31492 -var-set-visualizer V None
31496 Reselecting the default (type-based) visualizer:
31500 -var-set-visualizer V gdb.default_visualizer
31504 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31505 can be used to instantiate this class for a varobj:
31509 -var-set-visualizer V "lambda val: SomeClass()"
31513 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31514 @node GDB/MI Data Manipulation
31515 @section @sc{gdb/mi} Data Manipulation
31517 @cindex data manipulation, in @sc{gdb/mi}
31518 @cindex @sc{gdb/mi}, data manipulation
31519 This section describes the @sc{gdb/mi} commands that manipulate data:
31520 examine memory and registers, evaluate expressions, etc.
31522 For details about what an addressable memory unit is,
31523 @pxref{addressable memory unit}.
31525 @c REMOVED FROM THE INTERFACE.
31526 @c @subheading -data-assign
31527 @c Change the value of a program variable. Plenty of side effects.
31528 @c @subsubheading GDB Command
31530 @c @subsubheading Example
31533 @subheading The @code{-data-disassemble} Command
31534 @findex -data-disassemble
31536 @subsubheading Synopsis
31540 [ -s @var{start-addr} -e @var{end-addr} ]
31541 | [ -a @var{addr} ]
31542 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31550 @item @var{start-addr}
31551 is the beginning address (or @code{$pc})
31552 @item @var{end-addr}
31555 is an address anywhere within (or the name of) the function to
31556 disassemble. If an address is specified, the whole function
31557 surrounding that address will be disassembled. If a name is
31558 specified, the whole function with that name will be disassembled.
31559 @item @var{filename}
31560 is the name of the file to disassemble
31561 @item @var{linenum}
31562 is the line number to disassemble around
31564 is the number of disassembly lines to be produced. If it is -1,
31565 the whole function will be disassembled, in case no @var{end-addr} is
31566 specified. If @var{end-addr} is specified as a non-zero value, and
31567 @var{lines} is lower than the number of disassembly lines between
31568 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31569 displayed; if @var{lines} is higher than the number of lines between
31570 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31575 @item 0 disassembly only
31576 @item 1 mixed source and disassembly (deprecated)
31577 @item 2 disassembly with raw opcodes
31578 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31579 @item 4 mixed source and disassembly
31580 @item 5 mixed source and disassembly with raw opcodes
31583 Modes 1 and 3 are deprecated. The output is ``source centric''
31584 which hasn't proved useful in practice.
31585 @xref{Machine Code}, for a discussion of the difference between
31586 @code{/m} and @code{/s} output of the @code{disassemble} command.
31589 @subsubheading Result
31591 The result of the @code{-data-disassemble} command will be a list named
31592 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31593 used with the @code{-data-disassemble} command.
31595 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31600 The address at which this instruction was disassembled.
31603 The name of the function this instruction is within.
31606 The decimal offset in bytes from the start of @samp{func-name}.
31609 The text disassembly for this @samp{address}.
31612 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31613 bytes for the @samp{inst} field.
31617 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31618 @samp{src_and_asm_line}, each of which has the following fields:
31622 The line number within @samp{file}.
31625 The file name from the compilation unit. This might be an absolute
31626 file name or a relative file name depending on the compile command
31630 Absolute file name of @samp{file}. It is converted to a canonical form
31631 using the source file search path
31632 (@pxref{Source Path, ,Specifying Source Directories})
31633 and after resolving all the symbolic links.
31635 If the source file is not found this field will contain the path as
31636 present in the debug information.
31638 @item line_asm_insn
31639 This is a list of tuples containing the disassembly for @samp{line} in
31640 @samp{file}. The fields of each tuple are the same as for
31641 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31642 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31647 Note that whatever included in the @samp{inst} field, is not
31648 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31651 @subsubheading @value{GDBN} Command
31653 The corresponding @value{GDBN} command is @samp{disassemble}.
31655 @subsubheading Example
31657 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31661 -data-disassemble -s $pc -e "$pc + 20" -- 0
31664 @{address="0x000107c0",func-name="main",offset="4",
31665 inst="mov 2, %o0"@},
31666 @{address="0x000107c4",func-name="main",offset="8",
31667 inst="sethi %hi(0x11800), %o2"@},
31668 @{address="0x000107c8",func-name="main",offset="12",
31669 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31670 @{address="0x000107cc",func-name="main",offset="16",
31671 inst="sethi %hi(0x11800), %o2"@},
31672 @{address="0x000107d0",func-name="main",offset="20",
31673 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31677 Disassemble the whole @code{main} function. Line 32 is part of
31681 -data-disassemble -f basics.c -l 32 -- 0
31683 @{address="0x000107bc",func-name="main",offset="0",
31684 inst="save %sp, -112, %sp"@},
31685 @{address="0x000107c0",func-name="main",offset="4",
31686 inst="mov 2, %o0"@},
31687 @{address="0x000107c4",func-name="main",offset="8",
31688 inst="sethi %hi(0x11800), %o2"@},
31690 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31691 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31695 Disassemble 3 instructions from the start of @code{main}:
31699 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31701 @{address="0x000107bc",func-name="main",offset="0",
31702 inst="save %sp, -112, %sp"@},
31703 @{address="0x000107c0",func-name="main",offset="4",
31704 inst="mov 2, %o0"@},
31705 @{address="0x000107c4",func-name="main",offset="8",
31706 inst="sethi %hi(0x11800), %o2"@}]
31710 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31714 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31716 src_and_asm_line=@{line="31",
31717 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31718 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31719 line_asm_insn=[@{address="0x000107bc",
31720 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31721 src_and_asm_line=@{line="32",
31722 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31723 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31724 line_asm_insn=[@{address="0x000107c0",
31725 func-name="main",offset="4",inst="mov 2, %o0"@},
31726 @{address="0x000107c4",func-name="main",offset="8",
31727 inst="sethi %hi(0x11800), %o2"@}]@}]
31732 @subheading The @code{-data-evaluate-expression} Command
31733 @findex -data-evaluate-expression
31735 @subsubheading Synopsis
31738 -data-evaluate-expression @var{expr}
31741 Evaluate @var{expr} as an expression. The expression could contain an
31742 inferior function call. The function call will execute synchronously.
31743 If the expression contains spaces, it must be enclosed in double quotes.
31745 @subsubheading @value{GDBN} Command
31747 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31748 @samp{call}. In @code{gdbtk} only, there's a corresponding
31749 @samp{gdb_eval} command.
31751 @subsubheading Example
31753 In the following example, the numbers that precede the commands are the
31754 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31755 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31759 211-data-evaluate-expression A
31762 311-data-evaluate-expression &A
31763 311^done,value="0xefffeb7c"
31765 411-data-evaluate-expression A+3
31768 511-data-evaluate-expression "A + 3"
31774 @subheading The @code{-data-list-changed-registers} Command
31775 @findex -data-list-changed-registers
31777 @subsubheading Synopsis
31780 -data-list-changed-registers
31783 Display a list of the registers that have changed.
31785 @subsubheading @value{GDBN} Command
31787 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31788 has the corresponding command @samp{gdb_changed_register_list}.
31790 @subsubheading Example
31792 On a PPC MBX board:
31800 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31801 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31802 line="5",arch="powerpc"@}
31804 -data-list-changed-registers
31805 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31806 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31807 "24","25","26","27","28","30","31","64","65","66","67","69"]
31812 @subheading The @code{-data-list-register-names} Command
31813 @findex -data-list-register-names
31815 @subsubheading Synopsis
31818 -data-list-register-names [ ( @var{regno} )+ ]
31821 Show a list of register names for the current target. If no arguments
31822 are given, it shows a list of the names of all the registers. If
31823 integer numbers are given as arguments, it will print a list of the
31824 names of the registers corresponding to the arguments. To ensure
31825 consistency between a register name and its number, the output list may
31826 include empty register names.
31828 @subsubheading @value{GDBN} Command
31830 @value{GDBN} does not have a command which corresponds to
31831 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31832 corresponding command @samp{gdb_regnames}.
31834 @subsubheading Example
31836 For the PPC MBX board:
31839 -data-list-register-names
31840 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31841 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31842 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31843 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31844 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31845 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31846 "", "pc","ps","cr","lr","ctr","xer"]
31848 -data-list-register-names 1 2 3
31849 ^done,register-names=["r1","r2","r3"]
31853 @subheading The @code{-data-list-register-values} Command
31854 @findex -data-list-register-values
31856 @subsubheading Synopsis
31859 -data-list-register-values
31860 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31863 Display the registers' contents. The format according to which the
31864 registers' contents are to be returned is given by @var{fmt}, followed
31865 by an optional list of numbers specifying the registers to display. A
31866 missing list of numbers indicates that the contents of all the
31867 registers must be returned. The @code{--skip-unavailable} option
31868 indicates that only the available registers are to be returned.
31870 Allowed formats for @var{fmt} are:
31887 @subsubheading @value{GDBN} Command
31889 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31890 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31892 @subsubheading Example
31894 For a PPC MBX board (note: line breaks are for readability only, they
31895 don't appear in the actual output):
31899 -data-list-register-values r 64 65
31900 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31901 @{number="65",value="0x00029002"@}]
31903 -data-list-register-values x
31904 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31905 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31906 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31907 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31908 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31909 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31910 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31911 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31912 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31913 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31914 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31915 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31916 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31917 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31918 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31919 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31920 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31921 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31922 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31923 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31924 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31925 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31926 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31927 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31928 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31929 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31930 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31931 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31932 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31933 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31934 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31935 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31936 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31937 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31938 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31939 @{number="69",value="0x20002b03"@}]
31944 @subheading The @code{-data-read-memory} Command
31945 @findex -data-read-memory
31947 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31949 @subsubheading Synopsis
31952 -data-read-memory [ -o @var{byte-offset} ]
31953 @var{address} @var{word-format} @var{word-size}
31954 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31961 @item @var{address}
31962 An expression specifying the address of the first memory word to be
31963 read. Complex expressions containing embedded white space should be
31964 quoted using the C convention.
31966 @item @var{word-format}
31967 The format to be used to print the memory words. The notation is the
31968 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31971 @item @var{word-size}
31972 The size of each memory word in bytes.
31974 @item @var{nr-rows}
31975 The number of rows in the output table.
31977 @item @var{nr-cols}
31978 The number of columns in the output table.
31981 If present, indicates that each row should include an @sc{ascii} dump. The
31982 value of @var{aschar} is used as a padding character when a byte is not a
31983 member of the printable @sc{ascii} character set (printable @sc{ascii}
31984 characters are those whose code is between 32 and 126, inclusively).
31986 @item @var{byte-offset}
31987 An offset to add to the @var{address} before fetching memory.
31990 This command displays memory contents as a table of @var{nr-rows} by
31991 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31992 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31993 (returned as @samp{total-bytes}). Should less than the requested number
31994 of bytes be returned by the target, the missing words are identified
31995 using @samp{N/A}. The number of bytes read from the target is returned
31996 in @samp{nr-bytes} and the starting address used to read memory in
31999 The address of the next/previous row or page is available in
32000 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32003 @subsubheading @value{GDBN} Command
32005 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32006 @samp{gdb_get_mem} memory read command.
32008 @subsubheading Example
32010 Read six bytes of memory starting at @code{bytes+6} but then offset by
32011 @code{-6} bytes. Format as three rows of two columns. One byte per
32012 word. Display each word in hex.
32016 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32017 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32018 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32019 prev-page="0x0000138a",memory=[
32020 @{addr="0x00001390",data=["0x00","0x01"]@},
32021 @{addr="0x00001392",data=["0x02","0x03"]@},
32022 @{addr="0x00001394",data=["0x04","0x05"]@}]
32026 Read two bytes of memory starting at address @code{shorts + 64} and
32027 display as a single word formatted in decimal.
32031 5-data-read-memory shorts+64 d 2 1 1
32032 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32033 next-row="0x00001512",prev-row="0x0000150e",
32034 next-page="0x00001512",prev-page="0x0000150e",memory=[
32035 @{addr="0x00001510",data=["128"]@}]
32039 Read thirty two bytes of memory starting at @code{bytes+16} and format
32040 as eight rows of four columns. Include a string encoding with @samp{x}
32041 used as the non-printable character.
32045 4-data-read-memory bytes+16 x 1 8 4 x
32046 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32047 next-row="0x000013c0",prev-row="0x0000139c",
32048 next-page="0x000013c0",prev-page="0x00001380",memory=[
32049 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32050 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32051 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32052 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32053 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32054 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32055 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32056 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32060 @subheading The @code{-data-read-memory-bytes} Command
32061 @findex -data-read-memory-bytes
32063 @subsubheading Synopsis
32066 -data-read-memory-bytes [ -o @var{offset} ]
32067 @var{address} @var{count}
32074 @item @var{address}
32075 An expression specifying the address of the first addressable memory unit
32076 to be read. Complex expressions containing embedded white space should be
32077 quoted using the C convention.
32080 The number of addressable memory units to read. This should be an integer
32084 The offset relative to @var{address} at which to start reading. This
32085 should be an integer literal. This option is provided so that a frontend
32086 is not required to first evaluate address and then perform address
32087 arithmetics itself.
32091 This command attempts to read all accessible memory regions in the
32092 specified range. First, all regions marked as unreadable in the memory
32093 map (if one is defined) will be skipped. @xref{Memory Region
32094 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32095 regions. For each one, if reading full region results in an errors,
32096 @value{GDBN} will try to read a subset of the region.
32098 In general, every single memory unit in the region may be readable or not,
32099 and the only way to read every readable unit is to try a read at
32100 every address, which is not practical. Therefore, @value{GDBN} will
32101 attempt to read all accessible memory units at either beginning or the end
32102 of the region, using a binary division scheme. This heuristic works
32103 well for reading accross a memory map boundary. Note that if a region
32104 has a readable range that is neither at the beginning or the end,
32105 @value{GDBN} will not read it.
32107 The result record (@pxref{GDB/MI Result Records}) that is output of
32108 the command includes a field named @samp{memory} whose content is a
32109 list of tuples. Each tuple represent a successfully read memory block
32110 and has the following fields:
32114 The start address of the memory block, as hexadecimal literal.
32117 The end address of the memory block, as hexadecimal literal.
32120 The offset of the memory block, as hexadecimal literal, relative to
32121 the start address passed to @code{-data-read-memory-bytes}.
32124 The contents of the memory block, in hex.
32130 @subsubheading @value{GDBN} Command
32132 The corresponding @value{GDBN} command is @samp{x}.
32134 @subsubheading Example
32138 -data-read-memory-bytes &a 10
32139 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32141 contents="01000000020000000300"@}]
32146 @subheading The @code{-data-write-memory-bytes} Command
32147 @findex -data-write-memory-bytes
32149 @subsubheading Synopsis
32152 -data-write-memory-bytes @var{address} @var{contents}
32153 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32160 @item @var{address}
32161 An expression specifying the address of the first addressable memory unit
32162 to be written. Complex expressions containing embedded white space should
32163 be quoted using the C convention.
32165 @item @var{contents}
32166 The hex-encoded data to write. It is an error if @var{contents} does
32167 not represent an integral number of addressable memory units.
32170 Optional argument indicating the number of addressable memory units to be
32171 written. If @var{count} is greater than @var{contents}' length,
32172 @value{GDBN} will repeatedly write @var{contents} until it fills
32173 @var{count} memory units.
32177 @subsubheading @value{GDBN} Command
32179 There's no corresponding @value{GDBN} command.
32181 @subsubheading Example
32185 -data-write-memory-bytes &a "aabbccdd"
32192 -data-write-memory-bytes &a "aabbccdd" 16e
32197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32198 @node GDB/MI Tracepoint Commands
32199 @section @sc{gdb/mi} Tracepoint Commands
32201 The commands defined in this section implement MI support for
32202 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32204 @subheading The @code{-trace-find} Command
32205 @findex -trace-find
32207 @subsubheading Synopsis
32210 -trace-find @var{mode} [@var{parameters}@dots{}]
32213 Find a trace frame using criteria defined by @var{mode} and
32214 @var{parameters}. The following table lists permissible
32215 modes and their parameters. For details of operation, see @ref{tfind}.
32220 No parameters are required. Stops examining trace frames.
32223 An integer is required as parameter. Selects tracepoint frame with
32226 @item tracepoint-number
32227 An integer is required as parameter. Finds next
32228 trace frame that corresponds to tracepoint with the specified number.
32231 An address is required as parameter. Finds
32232 next trace frame that corresponds to any tracepoint at the specified
32235 @item pc-inside-range
32236 Two addresses are required as parameters. Finds next trace
32237 frame that corresponds to a tracepoint at an address inside the
32238 specified range. Both bounds are considered to be inside the range.
32240 @item pc-outside-range
32241 Two addresses are required as parameters. Finds
32242 next trace frame that corresponds to a tracepoint at an address outside
32243 the specified range. Both bounds are considered to be inside the range.
32246 Line specification is required as parameter. @xref{Specify Location}.
32247 Finds next trace frame that corresponds to a tracepoint at
32248 the specified location.
32252 If @samp{none} was passed as @var{mode}, the response does not
32253 have fields. Otherwise, the response may have the following fields:
32257 This field has either @samp{0} or @samp{1} as the value, depending
32258 on whether a matching tracepoint was found.
32261 The index of the found traceframe. This field is present iff
32262 the @samp{found} field has value of @samp{1}.
32265 The index of the found tracepoint. This field is present iff
32266 the @samp{found} field has value of @samp{1}.
32269 The information about the frame corresponding to the found trace
32270 frame. This field is present only if a trace frame was found.
32271 @xref{GDB/MI Frame Information}, for description of this field.
32275 @subsubheading @value{GDBN} Command
32277 The corresponding @value{GDBN} command is @samp{tfind}.
32279 @subheading -trace-define-variable
32280 @findex -trace-define-variable
32282 @subsubheading Synopsis
32285 -trace-define-variable @var{name} [ @var{value} ]
32288 Create trace variable @var{name} if it does not exist. If
32289 @var{value} is specified, sets the initial value of the specified
32290 trace variable to that value. Note that the @var{name} should start
32291 with the @samp{$} character.
32293 @subsubheading @value{GDBN} Command
32295 The corresponding @value{GDBN} command is @samp{tvariable}.
32297 @subheading The @code{-trace-frame-collected} Command
32298 @findex -trace-frame-collected
32300 @subsubheading Synopsis
32303 -trace-frame-collected
32304 [--var-print-values @var{var_pval}]
32305 [--comp-print-values @var{comp_pval}]
32306 [--registers-format @var{regformat}]
32307 [--memory-contents]
32310 This command returns the set of collected objects, register names,
32311 trace state variable names, memory ranges and computed expressions
32312 that have been collected at a particular trace frame. The optional
32313 parameters to the command affect the output format in different ways.
32314 See the output description table below for more details.
32316 The reported names can be used in the normal manner to create
32317 varobjs and inspect the objects themselves. The items returned by
32318 this command are categorized so that it is clear which is a variable,
32319 which is a register, which is a trace state variable, which is a
32320 memory range and which is a computed expression.
32322 For instance, if the actions were
32324 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32325 collect *(int*)0xaf02bef0@@40
32329 the object collected in its entirety would be @code{myVar}. The
32330 object @code{myArray} would be partially collected, because only the
32331 element at index @code{myIndex} would be collected. The remaining
32332 objects would be computed expressions.
32334 An example output would be:
32338 -trace-frame-collected
32340 explicit-variables=[@{name="myVar",value="1"@}],
32341 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32342 @{name="myObj.field",value="0"@},
32343 @{name="myPtr->field",value="1"@},
32344 @{name="myCount + 2",value="3"@},
32345 @{name="$tvar1 + 1",value="43970027"@}],
32346 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32347 @{number="1",value="0x0"@},
32348 @{number="2",value="0x4"@},
32350 @{number="125",value="0x0"@}],
32351 tvars=[@{name="$tvar1",current="43970026"@}],
32352 memory=[@{address="0x0000000000602264",length="4"@},
32353 @{address="0x0000000000615bc0",length="4"@}]
32360 @item explicit-variables
32361 The set of objects that have been collected in their entirety (as
32362 opposed to collecting just a few elements of an array or a few struct
32363 members). For each object, its name and value are printed.
32364 The @code{--var-print-values} option affects how or whether the value
32365 field is output. If @var{var_pval} is 0, then print only the names;
32366 if it is 1, print also their values; and if it is 2, print the name,
32367 type and value for simple data types, and the name and type for
32368 arrays, structures and unions.
32370 @item computed-expressions
32371 The set of computed expressions that have been collected at the
32372 current trace frame. The @code{--comp-print-values} option affects
32373 this set like the @code{--var-print-values} option affects the
32374 @code{explicit-variables} set. See above.
32377 The registers that have been collected at the current trace frame.
32378 For each register collected, the name and current value are returned.
32379 The value is formatted according to the @code{--registers-format}
32380 option. See the @command{-data-list-register-values} command for a
32381 list of the allowed formats. The default is @samp{x}.
32384 The trace state variables that have been collected at the current
32385 trace frame. For each trace state variable collected, the name and
32386 current value are returned.
32389 The set of memory ranges that have been collected at the current trace
32390 frame. Its content is a list of tuples. Each tuple represents a
32391 collected memory range and has the following fields:
32395 The start address of the memory range, as hexadecimal literal.
32398 The length of the memory range, as decimal literal.
32401 The contents of the memory block, in hex. This field is only present
32402 if the @code{--memory-contents} option is specified.
32408 @subsubheading @value{GDBN} Command
32410 There is no corresponding @value{GDBN} command.
32412 @subsubheading Example
32414 @subheading -trace-list-variables
32415 @findex -trace-list-variables
32417 @subsubheading Synopsis
32420 -trace-list-variables
32423 Return a table of all defined trace variables. Each element of the
32424 table has the following fields:
32428 The name of the trace variable. This field is always present.
32431 The initial value. This is a 64-bit signed integer. This
32432 field is always present.
32435 The value the trace variable has at the moment. This is a 64-bit
32436 signed integer. This field is absent iff current value is
32437 not defined, for example if the trace was never run, or is
32442 @subsubheading @value{GDBN} Command
32444 The corresponding @value{GDBN} command is @samp{tvariables}.
32446 @subsubheading Example
32450 -trace-list-variables
32451 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32452 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32453 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32454 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32455 body=[variable=@{name="$trace_timestamp",initial="0"@}
32456 variable=@{name="$foo",initial="10",current="15"@}]@}
32460 @subheading -trace-save
32461 @findex -trace-save
32463 @subsubheading Synopsis
32466 -trace-save [ -r ] [ -ctf ] @var{filename}
32469 Saves the collected trace data to @var{filename}. Without the
32470 @samp{-r} option, the data is downloaded from the target and saved
32471 in a local file. With the @samp{-r} option the target is asked
32472 to perform the save.
32474 By default, this command will save the trace in the tfile format. You can
32475 supply the optional @samp{-ctf} argument to save it the CTF format. See
32476 @ref{Trace Files} for more information about CTF.
32478 @subsubheading @value{GDBN} Command
32480 The corresponding @value{GDBN} command is @samp{tsave}.
32483 @subheading -trace-start
32484 @findex -trace-start
32486 @subsubheading Synopsis
32492 Starts a tracing experiment. The result of this command does not
32495 @subsubheading @value{GDBN} Command
32497 The corresponding @value{GDBN} command is @samp{tstart}.
32499 @subheading -trace-status
32500 @findex -trace-status
32502 @subsubheading Synopsis
32508 Obtains the status of a tracing experiment. The result may include
32509 the following fields:
32514 May have a value of either @samp{0}, when no tracing operations are
32515 supported, @samp{1}, when all tracing operations are supported, or
32516 @samp{file} when examining trace file. In the latter case, examining
32517 of trace frame is possible but new tracing experiement cannot be
32518 started. This field is always present.
32521 May have a value of either @samp{0} or @samp{1} depending on whether
32522 tracing experiement is in progress on target. This field is present
32523 if @samp{supported} field is not @samp{0}.
32526 Report the reason why the tracing was stopped last time. This field
32527 may be absent iff tracing was never stopped on target yet. The
32528 value of @samp{request} means the tracing was stopped as result of
32529 the @code{-trace-stop} command. The value of @samp{overflow} means
32530 the tracing buffer is full. The value of @samp{disconnection} means
32531 tracing was automatically stopped when @value{GDBN} has disconnected.
32532 The value of @samp{passcount} means tracing was stopped when a
32533 tracepoint was passed a maximal number of times for that tracepoint.
32534 This field is present if @samp{supported} field is not @samp{0}.
32536 @item stopping-tracepoint
32537 The number of tracepoint whose passcount as exceeded. This field is
32538 present iff the @samp{stop-reason} field has the value of
32542 @itemx frames-created
32543 The @samp{frames} field is a count of the total number of trace frames
32544 in the trace buffer, while @samp{frames-created} is the total created
32545 during the run, including ones that were discarded, such as when a
32546 circular trace buffer filled up. Both fields are optional.
32550 These fields tell the current size of the tracing buffer and the
32551 remaining space. These fields are optional.
32554 The value of the circular trace buffer flag. @code{1} means that the
32555 trace buffer is circular and old trace frames will be discarded if
32556 necessary to make room, @code{0} means that the trace buffer is linear
32560 The value of the disconnected tracing flag. @code{1} means that
32561 tracing will continue after @value{GDBN} disconnects, @code{0} means
32562 that the trace run will stop.
32565 The filename of the trace file being examined. This field is
32566 optional, and only present when examining a trace file.
32570 @subsubheading @value{GDBN} Command
32572 The corresponding @value{GDBN} command is @samp{tstatus}.
32574 @subheading -trace-stop
32575 @findex -trace-stop
32577 @subsubheading Synopsis
32583 Stops a tracing experiment. The result of this command has the same
32584 fields as @code{-trace-status}, except that the @samp{supported} and
32585 @samp{running} fields are not output.
32587 @subsubheading @value{GDBN} Command
32589 The corresponding @value{GDBN} command is @samp{tstop}.
32592 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32593 @node GDB/MI Symbol Query
32594 @section @sc{gdb/mi} Symbol Query Commands
32598 @subheading The @code{-symbol-info-address} Command
32599 @findex -symbol-info-address
32601 @subsubheading Synopsis
32604 -symbol-info-address @var{symbol}
32607 Describe where @var{symbol} is stored.
32609 @subsubheading @value{GDBN} Command
32611 The corresponding @value{GDBN} command is @samp{info address}.
32613 @subsubheading Example
32617 @subheading The @code{-symbol-info-file} Command
32618 @findex -symbol-info-file
32620 @subsubheading Synopsis
32626 Show the file for the symbol.
32628 @subsubheading @value{GDBN} Command
32630 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32631 @samp{gdb_find_file}.
32633 @subsubheading Example
32637 @subheading The @code{-symbol-info-function} Command
32638 @findex -symbol-info-function
32640 @subsubheading Synopsis
32643 -symbol-info-function
32646 Show which function the symbol lives in.
32648 @subsubheading @value{GDBN} Command
32650 @samp{gdb_get_function} in @code{gdbtk}.
32652 @subsubheading Example
32656 @subheading The @code{-symbol-info-line} Command
32657 @findex -symbol-info-line
32659 @subsubheading Synopsis
32665 Show the core addresses of the code for a source line.
32667 @subsubheading @value{GDBN} Command
32669 The corresponding @value{GDBN} command is @samp{info line}.
32670 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32672 @subsubheading Example
32676 @subheading The @code{-symbol-info-symbol} Command
32677 @findex -symbol-info-symbol
32679 @subsubheading Synopsis
32682 -symbol-info-symbol @var{addr}
32685 Describe what symbol is at location @var{addr}.
32687 @subsubheading @value{GDBN} Command
32689 The corresponding @value{GDBN} command is @samp{info symbol}.
32691 @subsubheading Example
32695 @subheading The @code{-symbol-list-functions} Command
32696 @findex -symbol-list-functions
32698 @subsubheading Synopsis
32701 -symbol-list-functions
32704 List the functions in the executable.
32706 @subsubheading @value{GDBN} Command
32708 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32709 @samp{gdb_search} in @code{gdbtk}.
32711 @subsubheading Example
32716 @subheading The @code{-symbol-list-lines} Command
32717 @findex -symbol-list-lines
32719 @subsubheading Synopsis
32722 -symbol-list-lines @var{filename}
32725 Print the list of lines that contain code and their associated program
32726 addresses for the given source filename. The entries are sorted in
32727 ascending PC order.
32729 @subsubheading @value{GDBN} Command
32731 There is no corresponding @value{GDBN} command.
32733 @subsubheading Example
32736 -symbol-list-lines basics.c
32737 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32743 @subheading The @code{-symbol-list-types} Command
32744 @findex -symbol-list-types
32746 @subsubheading Synopsis
32752 List all the type names.
32754 @subsubheading @value{GDBN} Command
32756 The corresponding commands are @samp{info types} in @value{GDBN},
32757 @samp{gdb_search} in @code{gdbtk}.
32759 @subsubheading Example
32763 @subheading The @code{-symbol-list-variables} Command
32764 @findex -symbol-list-variables
32766 @subsubheading Synopsis
32769 -symbol-list-variables
32772 List all the global and static variable names.
32774 @subsubheading @value{GDBN} Command
32776 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32778 @subsubheading Example
32782 @subheading The @code{-symbol-locate} Command
32783 @findex -symbol-locate
32785 @subsubheading Synopsis
32791 @subsubheading @value{GDBN} Command
32793 @samp{gdb_loc} in @code{gdbtk}.
32795 @subsubheading Example
32799 @subheading The @code{-symbol-type} Command
32800 @findex -symbol-type
32802 @subsubheading Synopsis
32805 -symbol-type @var{variable}
32808 Show type of @var{variable}.
32810 @subsubheading @value{GDBN} Command
32812 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32813 @samp{gdb_obj_variable}.
32815 @subsubheading Example
32820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32821 @node GDB/MI File Commands
32822 @section @sc{gdb/mi} File Commands
32824 This section describes the GDB/MI commands to specify executable file names
32825 and to read in and obtain symbol table information.
32827 @subheading The @code{-file-exec-and-symbols} Command
32828 @findex -file-exec-and-symbols
32830 @subsubheading Synopsis
32833 -file-exec-and-symbols @var{file}
32836 Specify the executable file to be debugged. This file is the one from
32837 which the symbol table is also read. If no file is specified, the
32838 command clears the executable and symbol information. If breakpoints
32839 are set when using this command with no arguments, @value{GDBN} will produce
32840 error messages. Otherwise, no output is produced, except a completion
32843 @subsubheading @value{GDBN} Command
32845 The corresponding @value{GDBN} command is @samp{file}.
32847 @subsubheading Example
32851 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32857 @subheading The @code{-file-exec-file} Command
32858 @findex -file-exec-file
32860 @subsubheading Synopsis
32863 -file-exec-file @var{file}
32866 Specify the executable file to be debugged. Unlike
32867 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32868 from this file. If used without argument, @value{GDBN} clears the information
32869 about the executable file. No output is produced, except a completion
32872 @subsubheading @value{GDBN} Command
32874 The corresponding @value{GDBN} command is @samp{exec-file}.
32876 @subsubheading Example
32880 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32887 @subheading The @code{-file-list-exec-sections} Command
32888 @findex -file-list-exec-sections
32890 @subsubheading Synopsis
32893 -file-list-exec-sections
32896 List the sections of the current executable file.
32898 @subsubheading @value{GDBN} Command
32900 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32901 information as this command. @code{gdbtk} has a corresponding command
32902 @samp{gdb_load_info}.
32904 @subsubheading Example
32909 @subheading The @code{-file-list-exec-source-file} Command
32910 @findex -file-list-exec-source-file
32912 @subsubheading Synopsis
32915 -file-list-exec-source-file
32918 List the line number, the current source file, and the absolute path
32919 to the current source file for the current executable. The macro
32920 information field has a value of @samp{1} or @samp{0} depending on
32921 whether or not the file includes preprocessor macro information.
32923 @subsubheading @value{GDBN} Command
32925 The @value{GDBN} equivalent is @samp{info source}
32927 @subsubheading Example
32931 123-file-list-exec-source-file
32932 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32937 @subheading The @code{-file-list-exec-source-files} Command
32938 @findex -file-list-exec-source-files
32940 @subsubheading Synopsis
32943 -file-list-exec-source-files
32946 List the source files for the current executable.
32948 It will always output both the filename and fullname (absolute file
32949 name) of a source file.
32951 @subsubheading @value{GDBN} Command
32953 The @value{GDBN} equivalent is @samp{info sources}.
32954 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32956 @subsubheading Example
32959 -file-list-exec-source-files
32961 @{file=foo.c,fullname=/home/foo.c@},
32962 @{file=/home/bar.c,fullname=/home/bar.c@},
32963 @{file=gdb_could_not_find_fullpath.c@}]
32967 @subheading The @code{-file-list-shared-libraries} Command
32968 @findex -file-list-shared-libraries
32970 @subsubheading Synopsis
32973 -file-list-shared-libraries [ @var{regexp} ]
32976 List the shared libraries in the program.
32977 With a regular expression @var{regexp}, only those libraries whose
32978 names match @var{regexp} are listed.
32980 @subsubheading @value{GDBN} Command
32982 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32983 have a similar meaning to the @code{=library-loaded} notification.
32984 The @code{ranges} field specifies the multiple segments belonging to this
32985 library. Each range has the following fields:
32989 The address defining the inclusive lower bound of the segment.
32991 The address defining the exclusive upper bound of the segment.
32994 @subsubheading Example
32997 -file-list-exec-source-files
32998 ^done,shared-libraries=[
32999 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
33000 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
33006 @subheading The @code{-file-list-symbol-files} Command
33007 @findex -file-list-symbol-files
33009 @subsubheading Synopsis
33012 -file-list-symbol-files
33017 @subsubheading @value{GDBN} Command
33019 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33021 @subsubheading Example
33026 @subheading The @code{-file-symbol-file} Command
33027 @findex -file-symbol-file
33029 @subsubheading Synopsis
33032 -file-symbol-file @var{file}
33035 Read symbol table info from the specified @var{file} argument. When
33036 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33037 produced, except for a completion notification.
33039 @subsubheading @value{GDBN} Command
33041 The corresponding @value{GDBN} command is @samp{symbol-file}.
33043 @subsubheading Example
33047 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33053 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33054 @node GDB/MI Memory Overlay Commands
33055 @section @sc{gdb/mi} Memory Overlay Commands
33057 The memory overlay commands are not implemented.
33059 @c @subheading -overlay-auto
33061 @c @subheading -overlay-list-mapping-state
33063 @c @subheading -overlay-list-overlays
33065 @c @subheading -overlay-map
33067 @c @subheading -overlay-off
33069 @c @subheading -overlay-on
33071 @c @subheading -overlay-unmap
33073 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33074 @node GDB/MI Signal Handling Commands
33075 @section @sc{gdb/mi} Signal Handling Commands
33077 Signal handling commands are not implemented.
33079 @c @subheading -signal-handle
33081 @c @subheading -signal-list-handle-actions
33083 @c @subheading -signal-list-signal-types
33087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33088 @node GDB/MI Target Manipulation
33089 @section @sc{gdb/mi} Target Manipulation Commands
33092 @subheading The @code{-target-attach} Command
33093 @findex -target-attach
33095 @subsubheading Synopsis
33098 -target-attach @var{pid} | @var{gid} | @var{file}
33101 Attach to a process @var{pid} or a file @var{file} outside of
33102 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33103 group, the id previously returned by
33104 @samp{-list-thread-groups --available} must be used.
33106 @subsubheading @value{GDBN} Command
33108 The corresponding @value{GDBN} command is @samp{attach}.
33110 @subsubheading Example
33114 =thread-created,id="1"
33115 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33121 @subheading The @code{-target-compare-sections} Command
33122 @findex -target-compare-sections
33124 @subsubheading Synopsis
33127 -target-compare-sections [ @var{section} ]
33130 Compare data of section @var{section} on target to the exec file.
33131 Without the argument, all sections are compared.
33133 @subsubheading @value{GDBN} Command
33135 The @value{GDBN} equivalent is @samp{compare-sections}.
33137 @subsubheading Example
33142 @subheading The @code{-target-detach} Command
33143 @findex -target-detach
33145 @subsubheading Synopsis
33148 -target-detach [ @var{pid} | @var{gid} ]
33151 Detach from the remote target which normally resumes its execution.
33152 If either @var{pid} or @var{gid} is specified, detaches from either
33153 the specified process, or specified thread group. There's no output.
33155 @subsubheading @value{GDBN} Command
33157 The corresponding @value{GDBN} command is @samp{detach}.
33159 @subsubheading Example
33169 @subheading The @code{-target-disconnect} Command
33170 @findex -target-disconnect
33172 @subsubheading Synopsis
33178 Disconnect from the remote target. There's no output and the target is
33179 generally not resumed.
33181 @subsubheading @value{GDBN} Command
33183 The corresponding @value{GDBN} command is @samp{disconnect}.
33185 @subsubheading Example
33195 @subheading The @code{-target-download} Command
33196 @findex -target-download
33198 @subsubheading Synopsis
33204 Loads the executable onto the remote target.
33205 It prints out an update message every half second, which includes the fields:
33209 The name of the section.
33211 The size of what has been sent so far for that section.
33213 The size of the section.
33215 The total size of what was sent so far (the current and the previous sections).
33217 The size of the overall executable to download.
33221 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33222 @sc{gdb/mi} Output Syntax}).
33224 In addition, it prints the name and size of the sections, as they are
33225 downloaded. These messages include the following fields:
33229 The name of the section.
33231 The size of the section.
33233 The size of the overall executable to download.
33237 At the end, a summary is printed.
33239 @subsubheading @value{GDBN} Command
33241 The corresponding @value{GDBN} command is @samp{load}.
33243 @subsubheading Example
33245 Note: each status message appears on a single line. Here the messages
33246 have been broken down so that they can fit onto a page.
33251 +download,@{section=".text",section-size="6668",total-size="9880"@}
33252 +download,@{section=".text",section-sent="512",section-size="6668",
33253 total-sent="512",total-size="9880"@}
33254 +download,@{section=".text",section-sent="1024",section-size="6668",
33255 total-sent="1024",total-size="9880"@}
33256 +download,@{section=".text",section-sent="1536",section-size="6668",
33257 total-sent="1536",total-size="9880"@}
33258 +download,@{section=".text",section-sent="2048",section-size="6668",
33259 total-sent="2048",total-size="9880"@}
33260 +download,@{section=".text",section-sent="2560",section-size="6668",
33261 total-sent="2560",total-size="9880"@}
33262 +download,@{section=".text",section-sent="3072",section-size="6668",
33263 total-sent="3072",total-size="9880"@}
33264 +download,@{section=".text",section-sent="3584",section-size="6668",
33265 total-sent="3584",total-size="9880"@}
33266 +download,@{section=".text",section-sent="4096",section-size="6668",
33267 total-sent="4096",total-size="9880"@}
33268 +download,@{section=".text",section-sent="4608",section-size="6668",
33269 total-sent="4608",total-size="9880"@}
33270 +download,@{section=".text",section-sent="5120",section-size="6668",
33271 total-sent="5120",total-size="9880"@}
33272 +download,@{section=".text",section-sent="5632",section-size="6668",
33273 total-sent="5632",total-size="9880"@}
33274 +download,@{section=".text",section-sent="6144",section-size="6668",
33275 total-sent="6144",total-size="9880"@}
33276 +download,@{section=".text",section-sent="6656",section-size="6668",
33277 total-sent="6656",total-size="9880"@}
33278 +download,@{section=".init",section-size="28",total-size="9880"@}
33279 +download,@{section=".fini",section-size="28",total-size="9880"@}
33280 +download,@{section=".data",section-size="3156",total-size="9880"@}
33281 +download,@{section=".data",section-sent="512",section-size="3156",
33282 total-sent="7236",total-size="9880"@}
33283 +download,@{section=".data",section-sent="1024",section-size="3156",
33284 total-sent="7748",total-size="9880"@}
33285 +download,@{section=".data",section-sent="1536",section-size="3156",
33286 total-sent="8260",total-size="9880"@}
33287 +download,@{section=".data",section-sent="2048",section-size="3156",
33288 total-sent="8772",total-size="9880"@}
33289 +download,@{section=".data",section-sent="2560",section-size="3156",
33290 total-sent="9284",total-size="9880"@}
33291 +download,@{section=".data",section-sent="3072",section-size="3156",
33292 total-sent="9796",total-size="9880"@}
33293 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33300 @subheading The @code{-target-exec-status} Command
33301 @findex -target-exec-status
33303 @subsubheading Synopsis
33306 -target-exec-status
33309 Provide information on the state of the target (whether it is running or
33310 not, for instance).
33312 @subsubheading @value{GDBN} Command
33314 There's no equivalent @value{GDBN} command.
33316 @subsubheading Example
33320 @subheading The @code{-target-list-available-targets} Command
33321 @findex -target-list-available-targets
33323 @subsubheading Synopsis
33326 -target-list-available-targets
33329 List the possible targets to connect to.
33331 @subsubheading @value{GDBN} Command
33333 The corresponding @value{GDBN} command is @samp{help target}.
33335 @subsubheading Example
33339 @subheading The @code{-target-list-current-targets} Command
33340 @findex -target-list-current-targets
33342 @subsubheading Synopsis
33345 -target-list-current-targets
33348 Describe the current target.
33350 @subsubheading @value{GDBN} Command
33352 The corresponding information is printed by @samp{info file} (among
33355 @subsubheading Example
33359 @subheading The @code{-target-list-parameters} Command
33360 @findex -target-list-parameters
33362 @subsubheading Synopsis
33365 -target-list-parameters
33371 @subsubheading @value{GDBN} Command
33375 @subsubheading Example
33378 @subheading The @code{-target-flash-erase} Command
33379 @findex -target-flash-erase
33381 @subsubheading Synopsis
33384 -target-flash-erase
33387 Erases all known flash memory regions on the target.
33389 The corresponding @value{GDBN} command is @samp{flash-erase}.
33391 The output is a list of flash regions that have been erased, with starting
33392 addresses and memory region sizes.
33396 -target-flash-erase
33397 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33401 @subheading The @code{-target-select} Command
33402 @findex -target-select
33404 @subsubheading Synopsis
33407 -target-select @var{type} @var{parameters @dots{}}
33410 Connect @value{GDBN} to the remote target. This command takes two args:
33414 The type of target, for instance @samp{remote}, etc.
33415 @item @var{parameters}
33416 Device names, host names and the like. @xref{Target Commands, ,
33417 Commands for Managing Targets}, for more details.
33420 The output is a connection notification, followed by the address at
33421 which the target program is, in the following form:
33424 ^connected,addr="@var{address}",func="@var{function name}",
33425 args=[@var{arg list}]
33428 @subsubheading @value{GDBN} Command
33430 The corresponding @value{GDBN} command is @samp{target}.
33432 @subsubheading Example
33436 -target-select remote /dev/ttya
33437 ^connected,addr="0xfe00a300",func="??",args=[]
33441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33442 @node GDB/MI File Transfer Commands
33443 @section @sc{gdb/mi} File Transfer Commands
33446 @subheading The @code{-target-file-put} Command
33447 @findex -target-file-put
33449 @subsubheading Synopsis
33452 -target-file-put @var{hostfile} @var{targetfile}
33455 Copy file @var{hostfile} from the host system (the machine running
33456 @value{GDBN}) to @var{targetfile} on the target system.
33458 @subsubheading @value{GDBN} Command
33460 The corresponding @value{GDBN} command is @samp{remote put}.
33462 @subsubheading Example
33466 -target-file-put localfile remotefile
33472 @subheading The @code{-target-file-get} Command
33473 @findex -target-file-get
33475 @subsubheading Synopsis
33478 -target-file-get @var{targetfile} @var{hostfile}
33481 Copy file @var{targetfile} from the target system to @var{hostfile}
33482 on the host system.
33484 @subsubheading @value{GDBN} Command
33486 The corresponding @value{GDBN} command is @samp{remote get}.
33488 @subsubheading Example
33492 -target-file-get remotefile localfile
33498 @subheading The @code{-target-file-delete} Command
33499 @findex -target-file-delete
33501 @subsubheading Synopsis
33504 -target-file-delete @var{targetfile}
33507 Delete @var{targetfile} from the target system.
33509 @subsubheading @value{GDBN} Command
33511 The corresponding @value{GDBN} command is @samp{remote delete}.
33513 @subsubheading Example
33517 -target-file-delete remotefile
33523 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33524 @node GDB/MI Ada Exceptions Commands
33525 @section Ada Exceptions @sc{gdb/mi} Commands
33527 @subheading The @code{-info-ada-exceptions} Command
33528 @findex -info-ada-exceptions
33530 @subsubheading Synopsis
33533 -info-ada-exceptions [ @var{regexp}]
33536 List all Ada exceptions defined within the program being debugged.
33537 With a regular expression @var{regexp}, only those exceptions whose
33538 names match @var{regexp} are listed.
33540 @subsubheading @value{GDBN} Command
33542 The corresponding @value{GDBN} command is @samp{info exceptions}.
33544 @subsubheading Result
33546 The result is a table of Ada exceptions. The following columns are
33547 defined for each exception:
33551 The name of the exception.
33554 The address of the exception.
33558 @subsubheading Example
33561 -info-ada-exceptions aint
33562 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33563 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33564 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33565 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33566 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33569 @subheading Catching Ada Exceptions
33571 The commands describing how to ask @value{GDBN} to stop when a program
33572 raises an exception are described at @ref{Ada Exception GDB/MI
33573 Catchpoint Commands}.
33576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33577 @node GDB/MI Support Commands
33578 @section @sc{gdb/mi} Support Commands
33580 Since new commands and features get regularly added to @sc{gdb/mi},
33581 some commands are available to help front-ends query the debugger
33582 about support for these capabilities. Similarly, it is also possible
33583 to query @value{GDBN} about target support of certain features.
33585 @subheading The @code{-info-gdb-mi-command} Command
33586 @cindex @code{-info-gdb-mi-command}
33587 @findex -info-gdb-mi-command
33589 @subsubheading Synopsis
33592 -info-gdb-mi-command @var{cmd_name}
33595 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33597 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33598 is technically not part of the command name (@pxref{GDB/MI Input
33599 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33600 for ease of use, this command also accepts the form with the leading
33603 @subsubheading @value{GDBN} Command
33605 There is no corresponding @value{GDBN} command.
33607 @subsubheading Result
33609 The result is a tuple. There is currently only one field:
33613 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33614 @code{"false"} otherwise.
33618 @subsubheading Example
33620 Here is an example where the @sc{gdb/mi} command does not exist:
33623 -info-gdb-mi-command unsupported-command
33624 ^done,command=@{exists="false"@}
33628 And here is an example where the @sc{gdb/mi} command is known
33632 -info-gdb-mi-command symbol-list-lines
33633 ^done,command=@{exists="true"@}
33636 @subheading The @code{-list-features} Command
33637 @findex -list-features
33638 @cindex supported @sc{gdb/mi} features, list
33640 Returns a list of particular features of the MI protocol that
33641 this version of gdb implements. A feature can be a command,
33642 or a new field in an output of some command, or even an
33643 important bugfix. While a frontend can sometimes detect presence
33644 of a feature at runtime, it is easier to perform detection at debugger
33647 The command returns a list of strings, with each string naming an
33648 available feature. Each returned string is just a name, it does not
33649 have any internal structure. The list of possible feature names
33655 (gdb) -list-features
33656 ^done,result=["feature1","feature2"]
33659 The current list of features is:
33662 @item frozen-varobjs
33663 Indicates support for the @code{-var-set-frozen} command, as well
33664 as possible presense of the @code{frozen} field in the output
33665 of @code{-varobj-create}.
33666 @item pending-breakpoints
33667 Indicates support for the @option{-f} option to the @code{-break-insert}
33670 Indicates Python scripting support, Python-based
33671 pretty-printing commands, and possible presence of the
33672 @samp{display_hint} field in the output of @code{-var-list-children}
33674 Indicates support for the @code{-thread-info} command.
33675 @item data-read-memory-bytes
33676 Indicates support for the @code{-data-read-memory-bytes} and the
33677 @code{-data-write-memory-bytes} commands.
33678 @item breakpoint-notifications
33679 Indicates that changes to breakpoints and breakpoints created via the
33680 CLI will be announced via async records.
33681 @item ada-task-info
33682 Indicates support for the @code{-ada-task-info} command.
33683 @item language-option
33684 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33685 option (@pxref{Context management}).
33686 @item info-gdb-mi-command
33687 Indicates support for the @code{-info-gdb-mi-command} command.
33688 @item undefined-command-error-code
33689 Indicates support for the "undefined-command" error code in error result
33690 records, produced when trying to execute an undefined @sc{gdb/mi} command
33691 (@pxref{GDB/MI Result Records}).
33692 @item exec-run-start-option
33693 Indicates that the @code{-exec-run} command supports the @option{--start}
33694 option (@pxref{GDB/MI Program Execution}).
33695 @item data-disassemble-a-option
33696 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33697 option (@pxref{GDB/MI Data Manipulation}).
33700 @subheading The @code{-list-target-features} Command
33701 @findex -list-target-features
33703 Returns a list of particular features that are supported by the
33704 target. Those features affect the permitted MI commands, but
33705 unlike the features reported by the @code{-list-features} command, the
33706 features depend on which target GDB is using at the moment. Whenever
33707 a target can change, due to commands such as @code{-target-select},
33708 @code{-target-attach} or @code{-exec-run}, the list of target features
33709 may change, and the frontend should obtain it again.
33713 (gdb) -list-target-features
33714 ^done,result=["async"]
33717 The current list of features is:
33721 Indicates that the target is capable of asynchronous command
33722 execution, which means that @value{GDBN} will accept further commands
33723 while the target is running.
33726 Indicates that the target is capable of reverse execution.
33727 @xref{Reverse Execution}, for more information.
33731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33732 @node GDB/MI Miscellaneous Commands
33733 @section Miscellaneous @sc{gdb/mi} Commands
33735 @c @subheading -gdb-complete
33737 @subheading The @code{-gdb-exit} Command
33740 @subsubheading Synopsis
33746 Exit @value{GDBN} immediately.
33748 @subsubheading @value{GDBN} Command
33750 Approximately corresponds to @samp{quit}.
33752 @subsubheading Example
33762 @subheading The @code{-exec-abort} Command
33763 @findex -exec-abort
33765 @subsubheading Synopsis
33771 Kill the inferior running program.
33773 @subsubheading @value{GDBN} Command
33775 The corresponding @value{GDBN} command is @samp{kill}.
33777 @subsubheading Example
33782 @subheading The @code{-gdb-set} Command
33785 @subsubheading Synopsis
33791 Set an internal @value{GDBN} variable.
33792 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33794 @subsubheading @value{GDBN} Command
33796 The corresponding @value{GDBN} command is @samp{set}.
33798 @subsubheading Example
33808 @subheading The @code{-gdb-show} Command
33811 @subsubheading Synopsis
33817 Show the current value of a @value{GDBN} variable.
33819 @subsubheading @value{GDBN} Command
33821 The corresponding @value{GDBN} command is @samp{show}.
33823 @subsubheading Example
33832 @c @subheading -gdb-source
33835 @subheading The @code{-gdb-version} Command
33836 @findex -gdb-version
33838 @subsubheading Synopsis
33844 Show version information for @value{GDBN}. Used mostly in testing.
33846 @subsubheading @value{GDBN} Command
33848 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33849 default shows this information when you start an interactive session.
33851 @subsubheading Example
33853 @c This example modifies the actual output from GDB to avoid overfull
33859 ~Copyright 2000 Free Software Foundation, Inc.
33860 ~GDB is free software, covered by the GNU General Public License, and
33861 ~you are welcome to change it and/or distribute copies of it under
33862 ~ certain conditions.
33863 ~Type "show copying" to see the conditions.
33864 ~There is absolutely no warranty for GDB. Type "show warranty" for
33866 ~This GDB was configured as
33867 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33872 @subheading The @code{-list-thread-groups} Command
33873 @findex -list-thread-groups
33875 @subheading Synopsis
33878 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33881 Lists thread groups (@pxref{Thread groups}). When a single thread
33882 group is passed as the argument, lists the children of that group.
33883 When several thread group are passed, lists information about those
33884 thread groups. Without any parameters, lists information about all
33885 top-level thread groups.
33887 Normally, thread groups that are being debugged are reported.
33888 With the @samp{--available} option, @value{GDBN} reports thread groups
33889 available on the target.
33891 The output of this command may have either a @samp{threads} result or
33892 a @samp{groups} result. The @samp{thread} result has a list of tuples
33893 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33894 Information}). The @samp{groups} result has a list of tuples as value,
33895 each tuple describing a thread group. If top-level groups are
33896 requested (that is, no parameter is passed), or when several groups
33897 are passed, the output always has a @samp{groups} result. The format
33898 of the @samp{group} result is described below.
33900 To reduce the number of roundtrips it's possible to list thread groups
33901 together with their children, by passing the @samp{--recurse} option
33902 and the recursion depth. Presently, only recursion depth of 1 is
33903 permitted. If this option is present, then every reported thread group
33904 will also include its children, either as @samp{group} or
33905 @samp{threads} field.
33907 In general, any combination of option and parameters is permitted, with
33908 the following caveats:
33912 When a single thread group is passed, the output will typically
33913 be the @samp{threads} result. Because threads may not contain
33914 anything, the @samp{recurse} option will be ignored.
33917 When the @samp{--available} option is passed, limited information may
33918 be available. In particular, the list of threads of a process might
33919 be inaccessible. Further, specifying specific thread groups might
33920 not give any performance advantage over listing all thread groups.
33921 The frontend should assume that @samp{-list-thread-groups --available}
33922 is always an expensive operation and cache the results.
33926 The @samp{groups} result is a list of tuples, where each tuple may
33927 have the following fields:
33931 Identifier of the thread group. This field is always present.
33932 The identifier is an opaque string; frontends should not try to
33933 convert it to an integer, even though it might look like one.
33936 The type of the thread group. At present, only @samp{process} is a
33940 The target-specific process identifier. This field is only present
33941 for thread groups of type @samp{process} and only if the process exists.
33944 The exit code of this group's last exited thread, formatted in octal.
33945 This field is only present for thread groups of type @samp{process} and
33946 only if the process is not running.
33949 The number of children this thread group has. This field may be
33950 absent for an available thread group.
33953 This field has a list of tuples as value, each tuple describing a
33954 thread. It may be present if the @samp{--recurse} option is
33955 specified, and it's actually possible to obtain the threads.
33958 This field is a list of integers, each identifying a core that one
33959 thread of the group is running on. This field may be absent if
33960 such information is not available.
33963 The name of the executable file that corresponds to this thread group.
33964 The field is only present for thread groups of type @samp{process},
33965 and only if there is a corresponding executable file.
33969 @subheading Example
33973 -list-thread-groups
33974 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33975 -list-thread-groups 17
33976 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33977 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33978 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33979 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33980 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
33981 -list-thread-groups --available
33982 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33983 -list-thread-groups --available --recurse 1
33984 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33985 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33986 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33987 -list-thread-groups --available --recurse 1 17 18
33988 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33989 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33990 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33993 @subheading The @code{-info-os} Command
33996 @subsubheading Synopsis
33999 -info-os [ @var{type} ]
34002 If no argument is supplied, the command returns a table of available
34003 operating-system-specific information types. If one of these types is
34004 supplied as an argument @var{type}, then the command returns a table
34005 of data of that type.
34007 The types of information available depend on the target operating
34010 @subsubheading @value{GDBN} Command
34012 The corresponding @value{GDBN} command is @samp{info os}.
34014 @subsubheading Example
34016 When run on a @sc{gnu}/Linux system, the output will look something
34022 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34023 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34024 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34025 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34026 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34028 item=@{col0="files",col1="Listing of all file descriptors",
34029 col2="File descriptors"@},
34030 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34031 col2="Kernel modules"@},
34032 item=@{col0="msg",col1="Listing of all message queues",
34033 col2="Message queues"@},
34034 item=@{col0="processes",col1="Listing of all processes",
34035 col2="Processes"@},
34036 item=@{col0="procgroups",col1="Listing of all process groups",
34037 col2="Process groups"@},
34038 item=@{col0="semaphores",col1="Listing of all semaphores",
34039 col2="Semaphores"@},
34040 item=@{col0="shm",col1="Listing of all shared-memory regions",
34041 col2="Shared-memory regions"@},
34042 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34044 item=@{col0="threads",col1="Listing of all threads",
34048 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34049 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34050 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34051 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34052 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34053 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34054 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34055 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34057 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34058 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34062 (Note that the MI output here includes a @code{"Title"} column that
34063 does not appear in command-line @code{info os}; this column is useful
34064 for MI clients that want to enumerate the types of data, such as in a
34065 popup menu, but is needless clutter on the command line, and
34066 @code{info os} omits it.)
34068 @subheading The @code{-add-inferior} Command
34069 @findex -add-inferior
34071 @subheading Synopsis
34077 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34078 inferior is not associated with any executable. Such association may
34079 be established with the @samp{-file-exec-and-symbols} command
34080 (@pxref{GDB/MI File Commands}). The command response has a single
34081 field, @samp{inferior}, whose value is the identifier of the
34082 thread group corresponding to the new inferior.
34084 @subheading Example
34089 ^done,inferior="i3"
34092 @subheading The @code{-interpreter-exec} Command
34093 @findex -interpreter-exec
34095 @subheading Synopsis
34098 -interpreter-exec @var{interpreter} @var{command}
34100 @anchor{-interpreter-exec}
34102 Execute the specified @var{command} in the given @var{interpreter}.
34104 @subheading @value{GDBN} Command
34106 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34108 @subheading Example
34112 -interpreter-exec console "break main"
34113 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34114 &"During symbol reading, bad structure-type format.\n"
34115 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34120 @subheading The @code{-inferior-tty-set} Command
34121 @findex -inferior-tty-set
34123 @subheading Synopsis
34126 -inferior-tty-set /dev/pts/1
34129 Set terminal for future runs of the program being debugged.
34131 @subheading @value{GDBN} Command
34133 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34135 @subheading Example
34139 -inferior-tty-set /dev/pts/1
34144 @subheading The @code{-inferior-tty-show} Command
34145 @findex -inferior-tty-show
34147 @subheading Synopsis
34153 Show terminal for future runs of program being debugged.
34155 @subheading @value{GDBN} Command
34157 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34159 @subheading Example
34163 -inferior-tty-set /dev/pts/1
34167 ^done,inferior_tty_terminal="/dev/pts/1"
34171 @subheading The @code{-enable-timings} Command
34172 @findex -enable-timings
34174 @subheading Synopsis
34177 -enable-timings [yes | no]
34180 Toggle the printing of the wallclock, user and system times for an MI
34181 command as a field in its output. This command is to help frontend
34182 developers optimize the performance of their code. No argument is
34183 equivalent to @samp{yes}.
34185 @subheading @value{GDBN} Command
34189 @subheading Example
34197 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34198 addr="0x080484ed",func="main",file="myprog.c",
34199 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34201 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34209 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34210 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34211 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34212 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34217 @chapter @value{GDBN} Annotations
34219 This chapter describes annotations in @value{GDBN}. Annotations were
34220 designed to interface @value{GDBN} to graphical user interfaces or other
34221 similar programs which want to interact with @value{GDBN} at a
34222 relatively high level.
34224 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34228 This is Edition @value{EDITION}, @value{DATE}.
34232 * Annotations Overview:: What annotations are; the general syntax.
34233 * Server Prefix:: Issuing a command without affecting user state.
34234 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34235 * Errors:: Annotations for error messages.
34236 * Invalidation:: Some annotations describe things now invalid.
34237 * Annotations for Running::
34238 Whether the program is running, how it stopped, etc.
34239 * Source Annotations:: Annotations describing source code.
34242 @node Annotations Overview
34243 @section What is an Annotation?
34244 @cindex annotations
34246 Annotations start with a newline character, two @samp{control-z}
34247 characters, and the name of the annotation. If there is no additional
34248 information associated with this annotation, the name of the annotation
34249 is followed immediately by a newline. If there is additional
34250 information, the name of the annotation is followed by a space, the
34251 additional information, and a newline. The additional information
34252 cannot contain newline characters.
34254 Any output not beginning with a newline and two @samp{control-z}
34255 characters denotes literal output from @value{GDBN}. Currently there is
34256 no need for @value{GDBN} to output a newline followed by two
34257 @samp{control-z} characters, but if there was such a need, the
34258 annotations could be extended with an @samp{escape} annotation which
34259 means those three characters as output.
34261 The annotation @var{level}, which is specified using the
34262 @option{--annotate} command line option (@pxref{Mode Options}), controls
34263 how much information @value{GDBN} prints together with its prompt,
34264 values of expressions, source lines, and other types of output. Level 0
34265 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34266 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34267 for programs that control @value{GDBN}, and level 2 annotations have
34268 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34269 Interface, annotate, GDB's Obsolete Annotations}).
34272 @kindex set annotate
34273 @item set annotate @var{level}
34274 The @value{GDBN} command @code{set annotate} sets the level of
34275 annotations to the specified @var{level}.
34277 @item show annotate
34278 @kindex show annotate
34279 Show the current annotation level.
34282 This chapter describes level 3 annotations.
34284 A simple example of starting up @value{GDBN} with annotations is:
34287 $ @kbd{gdb --annotate=3}
34289 Copyright 2003 Free Software Foundation, Inc.
34290 GDB is free software, covered by the GNU General Public License,
34291 and you are welcome to change it and/or distribute copies of it
34292 under certain conditions.
34293 Type "show copying" to see the conditions.
34294 There is absolutely no warranty for GDB. Type "show warranty"
34296 This GDB was configured as "i386-pc-linux-gnu"
34307 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34308 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34309 denotes a @samp{control-z} character) are annotations; the rest is
34310 output from @value{GDBN}.
34312 @node Server Prefix
34313 @section The Server Prefix
34314 @cindex server prefix
34316 If you prefix a command with @samp{server } then it will not affect
34317 the command history, nor will it affect @value{GDBN}'s notion of which
34318 command to repeat if @key{RET} is pressed on a line by itself. This
34319 means that commands can be run behind a user's back by a front-end in
34320 a transparent manner.
34322 The @code{server } prefix does not affect the recording of values into
34323 the value history; to print a value without recording it into the
34324 value history, use the @code{output} command instead of the
34325 @code{print} command.
34327 Using this prefix also disables confirmation requests
34328 (@pxref{confirmation requests}).
34331 @section Annotation for @value{GDBN} Input
34333 @cindex annotations for prompts
34334 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34335 to know when to send output, when the output from a given command is
34338 Different kinds of input each have a different @dfn{input type}. Each
34339 input type has three annotations: a @code{pre-} annotation, which
34340 denotes the beginning of any prompt which is being output, a plain
34341 annotation, which denotes the end of the prompt, and then a @code{post-}
34342 annotation which denotes the end of any echo which may (or may not) be
34343 associated with the input. For example, the @code{prompt} input type
34344 features the following annotations:
34352 The input types are
34355 @findex pre-prompt annotation
34356 @findex prompt annotation
34357 @findex post-prompt annotation
34359 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34361 @findex pre-commands annotation
34362 @findex commands annotation
34363 @findex post-commands annotation
34365 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34366 command. The annotations are repeated for each command which is input.
34368 @findex pre-overload-choice annotation
34369 @findex overload-choice annotation
34370 @findex post-overload-choice annotation
34371 @item overload-choice
34372 When @value{GDBN} wants the user to select between various overloaded functions.
34374 @findex pre-query annotation
34375 @findex query annotation
34376 @findex post-query annotation
34378 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34380 @findex pre-prompt-for-continue annotation
34381 @findex prompt-for-continue annotation
34382 @findex post-prompt-for-continue annotation
34383 @item prompt-for-continue
34384 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34385 expect this to work well; instead use @code{set height 0} to disable
34386 prompting. This is because the counting of lines is buggy in the
34387 presence of annotations.
34392 @cindex annotations for errors, warnings and interrupts
34394 @findex quit annotation
34399 This annotation occurs right before @value{GDBN} responds to an interrupt.
34401 @findex error annotation
34406 This annotation occurs right before @value{GDBN} responds to an error.
34408 Quit and error annotations indicate that any annotations which @value{GDBN} was
34409 in the middle of may end abruptly. For example, if a
34410 @code{value-history-begin} annotation is followed by a @code{error}, one
34411 cannot expect to receive the matching @code{value-history-end}. One
34412 cannot expect not to receive it either, however; an error annotation
34413 does not necessarily mean that @value{GDBN} is immediately returning all the way
34416 @findex error-begin annotation
34417 A quit or error annotation may be preceded by
34423 Any output between that and the quit or error annotation is the error
34426 Warning messages are not yet annotated.
34427 @c If we want to change that, need to fix warning(), type_error(),
34428 @c range_error(), and possibly other places.
34431 @section Invalidation Notices
34433 @cindex annotations for invalidation messages
34434 The following annotations say that certain pieces of state may have
34438 @findex frames-invalid annotation
34439 @item ^Z^Zframes-invalid
34441 The frames (for example, output from the @code{backtrace} command) may
34444 @findex breakpoints-invalid annotation
34445 @item ^Z^Zbreakpoints-invalid
34447 The breakpoints may have changed. For example, the user just added or
34448 deleted a breakpoint.
34451 @node Annotations for Running
34452 @section Running the Program
34453 @cindex annotations for running programs
34455 @findex starting annotation
34456 @findex stopping annotation
34457 When the program starts executing due to a @value{GDBN} command such as
34458 @code{step} or @code{continue},
34464 is output. When the program stops,
34470 is output. Before the @code{stopped} annotation, a variety of
34471 annotations describe how the program stopped.
34474 @findex exited annotation
34475 @item ^Z^Zexited @var{exit-status}
34476 The program exited, and @var{exit-status} is the exit status (zero for
34477 successful exit, otherwise nonzero).
34479 @findex signalled annotation
34480 @findex signal-name annotation
34481 @findex signal-name-end annotation
34482 @findex signal-string annotation
34483 @findex signal-string-end annotation
34484 @item ^Z^Zsignalled
34485 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34486 annotation continues:
34492 ^Z^Zsignal-name-end
34496 ^Z^Zsignal-string-end
34501 where @var{name} is the name of the signal, such as @code{SIGILL} or
34502 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34503 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34504 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34505 user's benefit and have no particular format.
34507 @findex signal annotation
34509 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34510 just saying that the program received the signal, not that it was
34511 terminated with it.
34513 @findex breakpoint annotation
34514 @item ^Z^Zbreakpoint @var{number}
34515 The program hit breakpoint number @var{number}.
34517 @findex watchpoint annotation
34518 @item ^Z^Zwatchpoint @var{number}
34519 The program hit watchpoint number @var{number}.
34522 @node Source Annotations
34523 @section Displaying Source
34524 @cindex annotations for source display
34526 @findex source annotation
34527 The following annotation is used instead of displaying source code:
34530 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34533 where @var{filename} is an absolute file name indicating which source
34534 file, @var{line} is the line number within that file (where 1 is the
34535 first line in the file), @var{character} is the character position
34536 within the file (where 0 is the first character in the file) (for most
34537 debug formats this will necessarily point to the beginning of a line),
34538 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34539 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34540 @var{addr} is the address in the target program associated with the
34541 source which is being displayed. The @var{addr} is in the form @samp{0x}
34542 followed by one or more lowercase hex digits (note that this does not
34543 depend on the language).
34545 @node JIT Interface
34546 @chapter JIT Compilation Interface
34547 @cindex just-in-time compilation
34548 @cindex JIT compilation interface
34550 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34551 interface. A JIT compiler is a program or library that generates native
34552 executable code at runtime and executes it, usually in order to achieve good
34553 performance while maintaining platform independence.
34555 Programs that use JIT compilation are normally difficult to debug because
34556 portions of their code are generated at runtime, instead of being loaded from
34557 object files, which is where @value{GDBN} normally finds the program's symbols
34558 and debug information. In order to debug programs that use JIT compilation,
34559 @value{GDBN} has an interface that allows the program to register in-memory
34560 symbol files with @value{GDBN} at runtime.
34562 If you are using @value{GDBN} to debug a program that uses this interface, then
34563 it should work transparently so long as you have not stripped the binary. If
34564 you are developing a JIT compiler, then the interface is documented in the rest
34565 of this chapter. At this time, the only known client of this interface is the
34568 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34569 JIT compiler communicates with @value{GDBN} by writing data into a global
34570 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34571 attaches, it reads a linked list of symbol files from the global variable to
34572 find existing code, and puts a breakpoint in the function so that it can find
34573 out about additional code.
34576 * Declarations:: Relevant C struct declarations
34577 * Registering Code:: Steps to register code
34578 * Unregistering Code:: Steps to unregister code
34579 * Custom Debug Info:: Emit debug information in a custom format
34583 @section JIT Declarations
34585 These are the relevant struct declarations that a C program should include to
34586 implement the interface:
34596 struct jit_code_entry
34598 struct jit_code_entry *next_entry;
34599 struct jit_code_entry *prev_entry;
34600 const char *symfile_addr;
34601 uint64_t symfile_size;
34604 struct jit_descriptor
34607 /* This type should be jit_actions_t, but we use uint32_t
34608 to be explicit about the bitwidth. */
34609 uint32_t action_flag;
34610 struct jit_code_entry *relevant_entry;
34611 struct jit_code_entry *first_entry;
34614 /* GDB puts a breakpoint in this function. */
34615 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34617 /* Make sure to specify the version statically, because the
34618 debugger may check the version before we can set it. */
34619 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34622 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34623 modifications to this global data properly, which can easily be done by putting
34624 a global mutex around modifications to these structures.
34626 @node Registering Code
34627 @section Registering Code
34629 To register code with @value{GDBN}, the JIT should follow this protocol:
34633 Generate an object file in memory with symbols and other desired debug
34634 information. The file must include the virtual addresses of the sections.
34637 Create a code entry for the file, which gives the start and size of the symbol
34641 Add it to the linked list in the JIT descriptor.
34644 Point the relevant_entry field of the descriptor at the entry.
34647 Set @code{action_flag} to @code{JIT_REGISTER} and call
34648 @code{__jit_debug_register_code}.
34651 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34652 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34653 new code. However, the linked list must still be maintained in order to allow
34654 @value{GDBN} to attach to a running process and still find the symbol files.
34656 @node Unregistering Code
34657 @section Unregistering Code
34659 If code is freed, then the JIT should use the following protocol:
34663 Remove the code entry corresponding to the code from the linked list.
34666 Point the @code{relevant_entry} field of the descriptor at the code entry.
34669 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34670 @code{__jit_debug_register_code}.
34673 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34674 and the JIT will leak the memory used for the associated symbol files.
34676 @node Custom Debug Info
34677 @section Custom Debug Info
34678 @cindex custom JIT debug info
34679 @cindex JIT debug info reader
34681 Generating debug information in platform-native file formats (like ELF
34682 or COFF) may be an overkill for JIT compilers; especially if all the
34683 debug info is used for is displaying a meaningful backtrace. The
34684 issue can be resolved by having the JIT writers decide on a debug info
34685 format and also provide a reader that parses the debug info generated
34686 by the JIT compiler. This section gives a brief overview on writing
34687 such a parser. More specific details can be found in the source file
34688 @file{gdb/jit-reader.in}, which is also installed as a header at
34689 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34691 The reader is implemented as a shared object (so this functionality is
34692 not available on platforms which don't allow loading shared objects at
34693 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34694 @code{jit-reader-unload} are provided, to be used to load and unload
34695 the readers from a preconfigured directory. Once loaded, the shared
34696 object is used the parse the debug information emitted by the JIT
34700 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34701 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34704 @node Using JIT Debug Info Readers
34705 @subsection Using JIT Debug Info Readers
34706 @kindex jit-reader-load
34707 @kindex jit-reader-unload
34709 Readers can be loaded and unloaded using the @code{jit-reader-load}
34710 and @code{jit-reader-unload} commands.
34713 @item jit-reader-load @var{reader}
34714 Load the JIT reader named @var{reader}, which is a shared
34715 object specified as either an absolute or a relative file name. In
34716 the latter case, @value{GDBN} will try to load the reader from a
34717 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34718 system (here @var{libdir} is the system library directory, often
34719 @file{/usr/local/lib}).
34721 Only one reader can be active at a time; trying to load a second
34722 reader when one is already loaded will result in @value{GDBN}
34723 reporting an error. A new JIT reader can be loaded by first unloading
34724 the current one using @code{jit-reader-unload} and then invoking
34725 @code{jit-reader-load}.
34727 @item jit-reader-unload
34728 Unload the currently loaded JIT reader.
34732 @node Writing JIT Debug Info Readers
34733 @subsection Writing JIT Debug Info Readers
34734 @cindex writing JIT debug info readers
34736 As mentioned, a reader is essentially a shared object conforming to a
34737 certain ABI. This ABI is described in @file{jit-reader.h}.
34739 @file{jit-reader.h} defines the structures, macros and functions
34740 required to write a reader. It is installed (along with
34741 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34742 the system include directory.
34744 Readers need to be released under a GPL compatible license. A reader
34745 can be declared as released under such a license by placing the macro
34746 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34748 The entry point for readers is the symbol @code{gdb_init_reader},
34749 which is expected to be a function with the prototype
34751 @findex gdb_init_reader
34753 extern struct gdb_reader_funcs *gdb_init_reader (void);
34756 @cindex @code{struct gdb_reader_funcs}
34758 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34759 functions. These functions are executed to read the debug info
34760 generated by the JIT compiler (@code{read}), to unwind stack frames
34761 (@code{unwind}) and to create canonical frame IDs
34762 (@code{get_Frame_id}). It also has a callback that is called when the
34763 reader is being unloaded (@code{destroy}). The struct looks like this
34766 struct gdb_reader_funcs
34768 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34769 int reader_version;
34771 /* For use by the reader. */
34774 gdb_read_debug_info *read;
34775 gdb_unwind_frame *unwind;
34776 gdb_get_frame_id *get_frame_id;
34777 gdb_destroy_reader *destroy;
34781 @cindex @code{struct gdb_symbol_callbacks}
34782 @cindex @code{struct gdb_unwind_callbacks}
34784 The callbacks are provided with another set of callbacks by
34785 @value{GDBN} to do their job. For @code{read}, these callbacks are
34786 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34787 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34788 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34789 files and new symbol tables inside those object files. @code{struct
34790 gdb_unwind_callbacks} has callbacks to read registers off the current
34791 frame and to write out the values of the registers in the previous
34792 frame. Both have a callback (@code{target_read}) to read bytes off the
34793 target's address space.
34795 @node In-Process Agent
34796 @chapter In-Process Agent
34797 @cindex debugging agent
34798 The traditional debugging model is conceptually low-speed, but works fine,
34799 because most bugs can be reproduced in debugging-mode execution. However,
34800 as multi-core or many-core processors are becoming mainstream, and
34801 multi-threaded programs become more and more popular, there should be more
34802 and more bugs that only manifest themselves at normal-mode execution, for
34803 example, thread races, because debugger's interference with the program's
34804 timing may conceal the bugs. On the other hand, in some applications,
34805 it is not feasible for the debugger to interrupt the program's execution
34806 long enough for the developer to learn anything helpful about its behavior.
34807 If the program's correctness depends on its real-time behavior, delays
34808 introduced by a debugger might cause the program to fail, even when the
34809 code itself is correct. It is useful to be able to observe the program's
34810 behavior without interrupting it.
34812 Therefore, traditional debugging model is too intrusive to reproduce
34813 some bugs. In order to reduce the interference with the program, we can
34814 reduce the number of operations performed by debugger. The
34815 @dfn{In-Process Agent}, a shared library, is running within the same
34816 process with inferior, and is able to perform some debugging operations
34817 itself. As a result, debugger is only involved when necessary, and
34818 performance of debugging can be improved accordingly. Note that
34819 interference with program can be reduced but can't be removed completely,
34820 because the in-process agent will still stop or slow down the program.
34822 The in-process agent can interpret and execute Agent Expressions
34823 (@pxref{Agent Expressions}) during performing debugging operations. The
34824 agent expressions can be used for different purposes, such as collecting
34825 data in tracepoints, and condition evaluation in breakpoints.
34827 @anchor{Control Agent}
34828 You can control whether the in-process agent is used as an aid for
34829 debugging with the following commands:
34832 @kindex set agent on
34834 Causes the in-process agent to perform some operations on behalf of the
34835 debugger. Just which operations requested by the user will be done
34836 by the in-process agent depends on the its capabilities. For example,
34837 if you request to evaluate breakpoint conditions in the in-process agent,
34838 and the in-process agent has such capability as well, then breakpoint
34839 conditions will be evaluated in the in-process agent.
34841 @kindex set agent off
34842 @item set agent off
34843 Disables execution of debugging operations by the in-process agent. All
34844 of the operations will be performed by @value{GDBN}.
34848 Display the current setting of execution of debugging operations by
34849 the in-process agent.
34853 * In-Process Agent Protocol::
34856 @node In-Process Agent Protocol
34857 @section In-Process Agent Protocol
34858 @cindex in-process agent protocol
34860 The in-process agent is able to communicate with both @value{GDBN} and
34861 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34862 used for communications between @value{GDBN} or GDBserver and the IPA.
34863 In general, @value{GDBN} or GDBserver sends commands
34864 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34865 in-process agent replies back with the return result of the command, or
34866 some other information. The data sent to in-process agent is composed
34867 of primitive data types, such as 4-byte or 8-byte type, and composite
34868 types, which are called objects (@pxref{IPA Protocol Objects}).
34871 * IPA Protocol Objects::
34872 * IPA Protocol Commands::
34875 @node IPA Protocol Objects
34876 @subsection IPA Protocol Objects
34877 @cindex ipa protocol objects
34879 The commands sent to and results received from agent may contain some
34880 complex data types called @dfn{objects}.
34882 The in-process agent is running on the same machine with @value{GDBN}
34883 or GDBserver, so it doesn't have to handle as much differences between
34884 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34885 However, there are still some differences of two ends in two processes:
34889 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34890 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34892 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34893 GDBserver is compiled with one, and in-process agent is compiled with
34897 Here are the IPA Protocol Objects:
34901 agent expression object. It represents an agent expression
34902 (@pxref{Agent Expressions}).
34903 @anchor{agent expression object}
34905 tracepoint action object. It represents a tracepoint action
34906 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34907 memory, static trace data and to evaluate expression.
34908 @anchor{tracepoint action object}
34910 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34911 @anchor{tracepoint object}
34915 The following table describes important attributes of each IPA protocol
34918 @multitable @columnfractions .30 .20 .50
34919 @headitem Name @tab Size @tab Description
34920 @item @emph{agent expression object} @tab @tab
34921 @item length @tab 4 @tab length of bytes code
34922 @item byte code @tab @var{length} @tab contents of byte code
34923 @item @emph{tracepoint action for collecting memory} @tab @tab
34924 @item 'M' @tab 1 @tab type of tracepoint action
34925 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34926 address of the lowest byte to collect, otherwise @var{addr} is the offset
34927 of @var{basereg} for memory collecting.
34928 @item len @tab 8 @tab length of memory for collecting
34929 @item basereg @tab 4 @tab the register number containing the starting
34930 memory address for collecting.
34931 @item @emph{tracepoint action for collecting registers} @tab @tab
34932 @item 'R' @tab 1 @tab type of tracepoint action
34933 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34934 @item 'L' @tab 1 @tab type of tracepoint action
34935 @item @emph{tracepoint action for expression evaluation} @tab @tab
34936 @item 'X' @tab 1 @tab type of tracepoint action
34937 @item agent expression @tab length of @tab @ref{agent expression object}
34938 @item @emph{tracepoint object} @tab @tab
34939 @item number @tab 4 @tab number of tracepoint
34940 @item address @tab 8 @tab address of tracepoint inserted on
34941 @item type @tab 4 @tab type of tracepoint
34942 @item enabled @tab 1 @tab enable or disable of tracepoint
34943 @item step_count @tab 8 @tab step
34944 @item pass_count @tab 8 @tab pass
34945 @item numactions @tab 4 @tab number of tracepoint actions
34946 @item hit count @tab 8 @tab hit count
34947 @item trace frame usage @tab 8 @tab trace frame usage
34948 @item compiled_cond @tab 8 @tab compiled condition
34949 @item orig_size @tab 8 @tab orig size
34950 @item condition @tab 4 if condition is NULL otherwise length of
34951 @ref{agent expression object}
34952 @tab zero if condition is NULL, otherwise is
34953 @ref{agent expression object}
34954 @item actions @tab variable
34955 @tab numactions number of @ref{tracepoint action object}
34958 @node IPA Protocol Commands
34959 @subsection IPA Protocol Commands
34960 @cindex ipa protocol commands
34962 The spaces in each command are delimiters to ease reading this commands
34963 specification. They don't exist in real commands.
34967 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34968 Installs a new fast tracepoint described by @var{tracepoint_object}
34969 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34970 head of @dfn{jumppad}, which is used to jump to data collection routine
34975 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34976 @var{target_address} is address of tracepoint in the inferior.
34977 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34978 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34979 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34980 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34987 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34988 is about to kill inferiors.
34996 @item probe_marker_at:@var{address}
34997 Asks in-process agent to probe the marker at @var{address}.
35004 @item unprobe_marker_at:@var{address}
35005 Asks in-process agent to unprobe the marker at @var{address}.
35009 @chapter Reporting Bugs in @value{GDBN}
35010 @cindex bugs in @value{GDBN}
35011 @cindex reporting bugs in @value{GDBN}
35013 Your bug reports play an essential role in making @value{GDBN} reliable.
35015 Reporting a bug may help you by bringing a solution to your problem, or it
35016 may not. But in any case the principal function of a bug report is to help
35017 the entire community by making the next version of @value{GDBN} work better. Bug
35018 reports are your contribution to the maintenance of @value{GDBN}.
35020 In order for a bug report to serve its purpose, you must include the
35021 information that enables us to fix the bug.
35024 * Bug Criteria:: Have you found a bug?
35025 * Bug Reporting:: How to report bugs
35029 @section Have You Found a Bug?
35030 @cindex bug criteria
35032 If you are not sure whether you have found a bug, here are some guidelines:
35035 @cindex fatal signal
35036 @cindex debugger crash
35037 @cindex crash of debugger
35039 If the debugger gets a fatal signal, for any input whatever, that is a
35040 @value{GDBN} bug. Reliable debuggers never crash.
35042 @cindex error on valid input
35044 If @value{GDBN} produces an error message for valid input, that is a
35045 bug. (Note that if you're cross debugging, the problem may also be
35046 somewhere in the connection to the target.)
35048 @cindex invalid input
35050 If @value{GDBN} does not produce an error message for invalid input,
35051 that is a bug. However, you should note that your idea of
35052 ``invalid input'' might be our idea of ``an extension'' or ``support
35053 for traditional practice''.
35056 If you are an experienced user of debugging tools, your suggestions
35057 for improvement of @value{GDBN} are welcome in any case.
35060 @node Bug Reporting
35061 @section How to Report Bugs
35062 @cindex bug reports
35063 @cindex @value{GDBN} bugs, reporting
35065 A number of companies and individuals offer support for @sc{gnu} products.
35066 If you obtained @value{GDBN} from a support organization, we recommend you
35067 contact that organization first.
35069 You can find contact information for many support companies and
35070 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35072 @c should add a web page ref...
35075 @ifset BUGURL_DEFAULT
35076 In any event, we also recommend that you submit bug reports for
35077 @value{GDBN}. The preferred method is to submit them directly using
35078 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35079 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35082 @strong{Do not send bug reports to @samp{info-gdb}, or to
35083 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35084 not want to receive bug reports. Those that do have arranged to receive
35087 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35088 serves as a repeater. The mailing list and the newsgroup carry exactly
35089 the same messages. Often people think of posting bug reports to the
35090 newsgroup instead of mailing them. This appears to work, but it has one
35091 problem which can be crucial: a newsgroup posting often lacks a mail
35092 path back to the sender. Thus, if we need to ask for more information,
35093 we may be unable to reach you. For this reason, it is better to send
35094 bug reports to the mailing list.
35096 @ifclear BUGURL_DEFAULT
35097 In any event, we also recommend that you submit bug reports for
35098 @value{GDBN} to @value{BUGURL}.
35102 The fundamental principle of reporting bugs usefully is this:
35103 @strong{report all the facts}. If you are not sure whether to state a
35104 fact or leave it out, state it!
35106 Often people omit facts because they think they know what causes the
35107 problem and assume that some details do not matter. Thus, you might
35108 assume that the name of the variable you use in an example does not matter.
35109 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35110 stray memory reference which happens to fetch from the location where that
35111 name is stored in memory; perhaps, if the name were different, the contents
35112 of that location would fool the debugger into doing the right thing despite
35113 the bug. Play it safe and give a specific, complete example. That is the
35114 easiest thing for you to do, and the most helpful.
35116 Keep in mind that the purpose of a bug report is to enable us to fix the
35117 bug. It may be that the bug has been reported previously, but neither
35118 you nor we can know that unless your bug report is complete and
35121 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35122 bell?'' Those bug reports are useless, and we urge everyone to
35123 @emph{refuse to respond to them} except to chide the sender to report
35126 To enable us to fix the bug, you should include all these things:
35130 The version of @value{GDBN}. @value{GDBN} announces it if you start
35131 with no arguments; you can also print it at any time using @code{show
35134 Without this, we will not know whether there is any point in looking for
35135 the bug in the current version of @value{GDBN}.
35138 The type of machine you are using, and the operating system name and
35142 The details of the @value{GDBN} build-time configuration.
35143 @value{GDBN} shows these details if you invoke it with the
35144 @option{--configuration} command-line option, or if you type
35145 @code{show configuration} at @value{GDBN}'s prompt.
35148 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35149 ``@value{GCC}--2.8.1''.
35152 What compiler (and its version) was used to compile the program you are
35153 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35154 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35155 to get this information; for other compilers, see the documentation for
35159 The command arguments you gave the compiler to compile your example and
35160 observe the bug. For example, did you use @samp{-O}? To guarantee
35161 you will not omit something important, list them all. A copy of the
35162 Makefile (or the output from make) is sufficient.
35164 If we were to try to guess the arguments, we would probably guess wrong
35165 and then we might not encounter the bug.
35168 A complete input script, and all necessary source files, that will
35172 A description of what behavior you observe that you believe is
35173 incorrect. For example, ``It gets a fatal signal.''
35175 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35176 will certainly notice it. But if the bug is incorrect output, we might
35177 not notice unless it is glaringly wrong. You might as well not give us
35178 a chance to make a mistake.
35180 Even if the problem you experience is a fatal signal, you should still
35181 say so explicitly. Suppose something strange is going on, such as, your
35182 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35183 the C library on your system. (This has happened!) Your copy might
35184 crash and ours would not. If you told us to expect a crash, then when
35185 ours fails to crash, we would know that the bug was not happening for
35186 us. If you had not told us to expect a crash, then we would not be able
35187 to draw any conclusion from our observations.
35190 @cindex recording a session script
35191 To collect all this information, you can use a session recording program
35192 such as @command{script}, which is available on many Unix systems.
35193 Just run your @value{GDBN} session inside @command{script} and then
35194 include the @file{typescript} file with your bug report.
35196 Another way to record a @value{GDBN} session is to run @value{GDBN}
35197 inside Emacs and then save the entire buffer to a file.
35200 If you wish to suggest changes to the @value{GDBN} source, send us context
35201 diffs. If you even discuss something in the @value{GDBN} source, refer to
35202 it by context, not by line number.
35204 The line numbers in our development sources will not match those in your
35205 sources. Your line numbers would convey no useful information to us.
35209 Here are some things that are not necessary:
35213 A description of the envelope of the bug.
35215 Often people who encounter a bug spend a lot of time investigating
35216 which changes to the input file will make the bug go away and which
35217 changes will not affect it.
35219 This is often time consuming and not very useful, because the way we
35220 will find the bug is by running a single example under the debugger
35221 with breakpoints, not by pure deduction from a series of examples.
35222 We recommend that you save your time for something else.
35224 Of course, if you can find a simpler example to report @emph{instead}
35225 of the original one, that is a convenience for us. Errors in the
35226 output will be easier to spot, running under the debugger will take
35227 less time, and so on.
35229 However, simplification is not vital; if you do not want to do this,
35230 report the bug anyway and send us the entire test case you used.
35233 A patch for the bug.
35235 A patch for the bug does help us if it is a good one. But do not omit
35236 the necessary information, such as the test case, on the assumption that
35237 a patch is all we need. We might see problems with your patch and decide
35238 to fix the problem another way, or we might not understand it at all.
35240 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35241 construct an example that will make the program follow a certain path
35242 through the code. If you do not send us the example, we will not be able
35243 to construct one, so we will not be able to verify that the bug is fixed.
35245 And if we cannot understand what bug you are trying to fix, or why your
35246 patch should be an improvement, we will not install it. A test case will
35247 help us to understand.
35250 A guess about what the bug is or what it depends on.
35252 Such guesses are usually wrong. Even we cannot guess right about such
35253 things without first using the debugger to find the facts.
35256 @c The readline documentation is distributed with the readline code
35257 @c and consists of the two following files:
35260 @c Use -I with makeinfo to point to the appropriate directory,
35261 @c environment var TEXINPUTS with TeX.
35262 @ifclear SYSTEM_READLINE
35263 @include rluser.texi
35264 @include hsuser.texi
35268 @appendix In Memoriam
35270 The @value{GDBN} project mourns the loss of the following long-time
35275 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35276 to Free Software in general. Outside of @value{GDBN}, he was known in
35277 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35279 @item Michael Snyder
35280 Michael was one of the Global Maintainers of the @value{GDBN} project,
35281 with contributions recorded as early as 1996, until 2011. In addition
35282 to his day to day participation, he was a large driving force behind
35283 adding Reverse Debugging to @value{GDBN}.
35286 Beyond their technical contributions to the project, they were also
35287 enjoyable members of the Free Software Community. We will miss them.
35289 @node Formatting Documentation
35290 @appendix Formatting Documentation
35292 @cindex @value{GDBN} reference card
35293 @cindex reference card
35294 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35295 for printing with PostScript or Ghostscript, in the @file{gdb}
35296 subdirectory of the main source directory@footnote{In
35297 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35298 release.}. If you can use PostScript or Ghostscript with your printer,
35299 you can print the reference card immediately with @file{refcard.ps}.
35301 The release also includes the source for the reference card. You
35302 can format it, using @TeX{}, by typing:
35308 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35309 mode on US ``letter'' size paper;
35310 that is, on a sheet 11 inches wide by 8.5 inches
35311 high. You will need to specify this form of printing as an option to
35312 your @sc{dvi} output program.
35314 @cindex documentation
35316 All the documentation for @value{GDBN} comes as part of the machine-readable
35317 distribution. The documentation is written in Texinfo format, which is
35318 a documentation system that uses a single source file to produce both
35319 on-line information and a printed manual. You can use one of the Info
35320 formatting commands to create the on-line version of the documentation
35321 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35323 @value{GDBN} includes an already formatted copy of the on-line Info
35324 version of this manual in the @file{gdb} subdirectory. The main Info
35325 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35326 subordinate files matching @samp{gdb.info*} in the same directory. If
35327 necessary, you can print out these files, or read them with any editor;
35328 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35329 Emacs or the standalone @code{info} program, available as part of the
35330 @sc{gnu} Texinfo distribution.
35332 If you want to format these Info files yourself, you need one of the
35333 Info formatting programs, such as @code{texinfo-format-buffer} or
35336 If you have @code{makeinfo} installed, and are in the top level
35337 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35338 version @value{GDBVN}), you can make the Info file by typing:
35345 If you want to typeset and print copies of this manual, you need @TeX{},
35346 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35347 Texinfo definitions file.
35349 @TeX{} is a typesetting program; it does not print files directly, but
35350 produces output files called @sc{dvi} files. To print a typeset
35351 document, you need a program to print @sc{dvi} files. If your system
35352 has @TeX{} installed, chances are it has such a program. The precise
35353 command to use depends on your system; @kbd{lpr -d} is common; another
35354 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35355 require a file name without any extension or a @samp{.dvi} extension.
35357 @TeX{} also requires a macro definitions file called
35358 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35359 written in Texinfo format. On its own, @TeX{} cannot either read or
35360 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35361 and is located in the @file{gdb-@var{version-number}/texinfo}
35364 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35365 typeset and print this manual. First switch to the @file{gdb}
35366 subdirectory of the main source directory (for example, to
35367 @file{gdb-@value{GDBVN}/gdb}) and type:
35373 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35375 @node Installing GDB
35376 @appendix Installing @value{GDBN}
35377 @cindex installation
35380 * Requirements:: Requirements for building @value{GDBN}
35381 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35382 * Separate Objdir:: Compiling @value{GDBN} in another directory
35383 * Config Names:: Specifying names for hosts and targets
35384 * Configure Options:: Summary of options for configure
35385 * System-wide configuration:: Having a system-wide init file
35389 @section Requirements for Building @value{GDBN}
35390 @cindex building @value{GDBN}, requirements for
35392 Building @value{GDBN} requires various tools and packages to be available.
35393 Other packages will be used only if they are found.
35395 @heading Tools/Packages Necessary for Building @value{GDBN}
35397 @item C@t{++}11 compiler
35398 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35399 recent C@t{++}11 compiler, e.g.@: GCC.
35402 @value{GDBN}'s build system relies on features only found in the GNU
35403 make program. Other variants of @code{make} will not work.
35406 @heading Tools/Packages Optional for Building @value{GDBN}
35410 @value{GDBN} can use the Expat XML parsing library. This library may be
35411 included with your operating system distribution; if it is not, you
35412 can get the latest version from @url{http://expat.sourceforge.net}.
35413 The @file{configure} script will search for this library in several
35414 standard locations; if it is installed in an unusual path, you can
35415 use the @option{--with-libexpat-prefix} option to specify its location.
35421 Remote protocol memory maps (@pxref{Memory Map Format})
35423 Target descriptions (@pxref{Target Descriptions})
35425 Remote shared library lists (@xref{Library List Format},
35426 or alternatively @pxref{Library List Format for SVR4 Targets})
35428 MS-Windows shared libraries (@pxref{Shared Libraries})
35430 Traceframe info (@pxref{Traceframe Info Format})
35432 Branch trace (@pxref{Branch Trace Format},
35433 @pxref{Branch Trace Configuration Format})
35437 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35438 default, @value{GDBN} will be compiled if the Guile libraries are
35439 installed and are found by @file{configure}. You can use the
35440 @code{--with-guile} option to request Guile, and pass either the Guile
35441 version number or the file name of the relevant @code{pkg-config}
35442 program to choose a particular version of Guile.
35445 @value{GDBN}'s features related to character sets (@pxref{Character
35446 Sets}) require a functioning @code{iconv} implementation. If you are
35447 on a GNU system, then this is provided by the GNU C Library. Some
35448 other systems also provide a working @code{iconv}.
35450 If @value{GDBN} is using the @code{iconv} program which is installed
35451 in a non-standard place, you will need to tell @value{GDBN} where to
35452 find it. This is done with @option{--with-iconv-bin} which specifies
35453 the directory that contains the @code{iconv} program. This program is
35454 run in order to make a list of the available character sets.
35456 On systems without @code{iconv}, you can install GNU Libiconv. If
35457 Libiconv is installed in a standard place, @value{GDBN} will
35458 automatically use it if it is needed. If you have previously
35459 installed Libiconv in a non-standard place, you can use the
35460 @option{--with-libiconv-prefix} option to @file{configure}.
35462 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35463 arrange to build Libiconv if a directory named @file{libiconv} appears
35464 in the top-most source directory. If Libiconv is built this way, and
35465 if the operating system does not provide a suitable @code{iconv}
35466 implementation, then the just-built library will automatically be used
35467 by @value{GDBN}. One easy way to set this up is to download GNU
35468 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35469 source tree, and then rename the directory holding the Libiconv source
35470 code to @samp{libiconv}.
35473 @value{GDBN} can support debugging sections that are compressed with
35474 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35475 included with your operating system, you can find it in the xz package
35476 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35477 the usual place, then the @file{configure} script will use it
35478 automatically. If it is installed in an unusual path, you can use the
35479 @option{--with-lzma-prefix} option to specify its location.
35483 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35484 library. This library may be included with your operating system
35485 distribution; if it is not, you can get the latest version from
35486 @url{http://www.mpfr.org}. The @file{configure} script will search
35487 for this library in several standard locations; if it is installed
35488 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35489 option to specify its location.
35491 GNU MPFR is used to emulate target floating-point arithmetic during
35492 expression evaluation when the target uses different floating-point
35493 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35494 will fall back to using host floating-point arithmetic.
35497 @value{GDBN} can be scripted using Python language. @xref{Python}.
35498 By default, @value{GDBN} will be compiled if the Python libraries are
35499 installed and are found by @file{configure}. You can use the
35500 @code{--with-python} option to request Python, and pass either the
35501 file name of the relevant @code{python} executable, or the name of the
35502 directory in which Python is installed, to choose a particular
35503 installation of Python.
35506 @cindex compressed debug sections
35507 @value{GDBN} will use the @samp{zlib} library, if available, to read
35508 compressed debug sections. Some linkers, such as GNU gold, are capable
35509 of producing binaries with compressed debug sections. If @value{GDBN}
35510 is compiled with @samp{zlib}, it will be able to read the debug
35511 information in such binaries.
35513 The @samp{zlib} library is likely included with your operating system
35514 distribution; if it is not, you can get the latest version from
35515 @url{http://zlib.net}.
35518 @node Running Configure
35519 @section Invoking the @value{GDBN} @file{configure} Script
35520 @cindex configuring @value{GDBN}
35521 @value{GDBN} comes with a @file{configure} script that automates the process
35522 of preparing @value{GDBN} for installation; you can then use @code{make} to
35523 build the @code{gdb} program.
35525 @c irrelevant in info file; it's as current as the code it lives with.
35526 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35527 look at the @file{README} file in the sources; we may have improved the
35528 installation procedures since publishing this manual.}
35531 The @value{GDBN} distribution includes all the source code you need for
35532 @value{GDBN} in a single directory, whose name is usually composed by
35533 appending the version number to @samp{gdb}.
35535 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35536 @file{gdb-@value{GDBVN}} directory. That directory contains:
35539 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35540 script for configuring @value{GDBN} and all its supporting libraries
35542 @item gdb-@value{GDBVN}/gdb
35543 the source specific to @value{GDBN} itself
35545 @item gdb-@value{GDBVN}/bfd
35546 source for the Binary File Descriptor library
35548 @item gdb-@value{GDBVN}/include
35549 @sc{gnu} include files
35551 @item gdb-@value{GDBVN}/libiberty
35552 source for the @samp{-liberty} free software library
35554 @item gdb-@value{GDBVN}/opcodes
35555 source for the library of opcode tables and disassemblers
35557 @item gdb-@value{GDBVN}/readline
35558 source for the @sc{gnu} command-line interface
35561 There may be other subdirectories as well.
35563 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35564 from the @file{gdb-@var{version-number}} source directory, which in
35565 this example is the @file{gdb-@value{GDBVN}} directory.
35567 First switch to the @file{gdb-@var{version-number}} source directory
35568 if you are not already in it; then run @file{configure}. Pass the
35569 identifier for the platform on which @value{GDBN} will run as an
35575 cd gdb-@value{GDBVN}
35580 Running @samp{configure} and then running @code{make} builds the
35581 included supporting libraries, then @code{gdb} itself. The configured
35582 source files, and the binaries, are left in the corresponding source
35586 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35587 system does not recognize this automatically when you run a different
35588 shell, you may need to run @code{sh} on it explicitly:
35594 You should run the @file{configure} script from the top directory in the
35595 source tree, the @file{gdb-@var{version-number}} directory. If you run
35596 @file{configure} from one of the subdirectories, you will configure only
35597 that subdirectory. That is usually not what you want. In particular,
35598 if you run the first @file{configure} from the @file{gdb} subdirectory
35599 of the @file{gdb-@var{version-number}} directory, you will omit the
35600 configuration of @file{bfd}, @file{readline}, and other sibling
35601 directories of the @file{gdb} subdirectory. This leads to build errors
35602 about missing include files such as @file{bfd/bfd.h}.
35604 You can install @code{@value{GDBN}} anywhere. The best way to do this
35605 is to pass the @code{--prefix} option to @code{configure}, and then
35606 install it with @code{make install}.
35608 @node Separate Objdir
35609 @section Compiling @value{GDBN} in Another Directory
35611 If you want to run @value{GDBN} versions for several host or target machines,
35612 you need a different @code{gdb} compiled for each combination of
35613 host and target. @file{configure} is designed to make this easy by
35614 allowing you to generate each configuration in a separate subdirectory,
35615 rather than in the source directory. If your @code{make} program
35616 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35617 @code{make} in each of these directories builds the @code{gdb}
35618 program specified there.
35620 To build @code{gdb} in a separate directory, run @file{configure}
35621 with the @samp{--srcdir} option to specify where to find the source.
35622 (You also need to specify a path to find @file{configure}
35623 itself from your working directory. If the path to @file{configure}
35624 would be the same as the argument to @samp{--srcdir}, you can leave out
35625 the @samp{--srcdir} option; it is assumed.)
35627 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35628 separate directory for a Sun 4 like this:
35632 cd gdb-@value{GDBVN}
35635 ../gdb-@value{GDBVN}/configure
35640 When @file{configure} builds a configuration using a remote source
35641 directory, it creates a tree for the binaries with the same structure
35642 (and using the same names) as the tree under the source directory. In
35643 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35644 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35645 @file{gdb-sun4/gdb}.
35647 Make sure that your path to the @file{configure} script has just one
35648 instance of @file{gdb} in it. If your path to @file{configure} looks
35649 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35650 one subdirectory of @value{GDBN}, not the whole package. This leads to
35651 build errors about missing include files such as @file{bfd/bfd.h}.
35653 One popular reason to build several @value{GDBN} configurations in separate
35654 directories is to configure @value{GDBN} for cross-compiling (where
35655 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35656 programs that run on another machine---the @dfn{target}).
35657 You specify a cross-debugging target by
35658 giving the @samp{--target=@var{target}} option to @file{configure}.
35660 When you run @code{make} to build a program or library, you must run
35661 it in a configured directory---whatever directory you were in when you
35662 called @file{configure} (or one of its subdirectories).
35664 The @code{Makefile} that @file{configure} generates in each source
35665 directory also runs recursively. If you type @code{make} in a source
35666 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35667 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35668 will build all the required libraries, and then build GDB.
35670 When you have multiple hosts or targets configured in separate
35671 directories, you can run @code{make} on them in parallel (for example,
35672 if they are NFS-mounted on each of the hosts); they will not interfere
35676 @section Specifying Names for Hosts and Targets
35678 The specifications used for hosts and targets in the @file{configure}
35679 script are based on a three-part naming scheme, but some short predefined
35680 aliases are also supported. The full naming scheme encodes three pieces
35681 of information in the following pattern:
35684 @var{architecture}-@var{vendor}-@var{os}
35687 For example, you can use the alias @code{sun4} as a @var{host} argument,
35688 or as the value for @var{target} in a @code{--target=@var{target}}
35689 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35691 The @file{configure} script accompanying @value{GDBN} does not provide
35692 any query facility to list all supported host and target names or
35693 aliases. @file{configure} calls the Bourne shell script
35694 @code{config.sub} to map abbreviations to full names; you can read the
35695 script, if you wish, or you can use it to test your guesses on
35696 abbreviations---for example:
35699 % sh config.sub i386-linux
35701 % sh config.sub alpha-linux
35702 alpha-unknown-linux-gnu
35703 % sh config.sub hp9k700
35705 % sh config.sub sun4
35706 sparc-sun-sunos4.1.1
35707 % sh config.sub sun3
35708 m68k-sun-sunos4.1.1
35709 % sh config.sub i986v
35710 Invalid configuration `i986v': machine `i986v' not recognized
35714 @code{config.sub} is also distributed in the @value{GDBN} source
35715 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35717 @node Configure Options
35718 @section @file{configure} Options
35720 Here is a summary of the @file{configure} options and arguments that
35721 are most often useful for building @value{GDBN}. @file{configure}
35722 also has several other options not listed here. @inforef{Running
35723 configure scripts,,autoconf.info}, for a full
35724 explanation of @file{configure}.
35727 configure @r{[}--help@r{]}
35728 @r{[}--prefix=@var{dir}@r{]}
35729 @r{[}--exec-prefix=@var{dir}@r{]}
35730 @r{[}--srcdir=@var{dirname}@r{]}
35731 @r{[}--target=@var{target}@r{]}
35735 You may introduce options with a single @samp{-} rather than
35736 @samp{--} if you prefer; but you may abbreviate option names if you use
35741 Display a quick summary of how to invoke @file{configure}.
35743 @item --prefix=@var{dir}
35744 Configure the source to install programs and files under directory
35747 @item --exec-prefix=@var{dir}
35748 Configure the source to install programs under directory
35751 @c avoid splitting the warning from the explanation:
35753 @item --srcdir=@var{dirname}
35754 Use this option to make configurations in directories separate from the
35755 @value{GDBN} source directories. Among other things, you can use this to
35756 build (or maintain) several configurations simultaneously, in separate
35757 directories. @file{configure} writes configuration-specific files in
35758 the current directory, but arranges for them to use the source in the
35759 directory @var{dirname}. @file{configure} creates directories under
35760 the working directory in parallel to the source directories below
35763 @item --target=@var{target}
35764 Configure @value{GDBN} for cross-debugging programs running on the specified
35765 @var{target}. Without this option, @value{GDBN} is configured to debug
35766 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35768 There is no convenient way to generate a list of all available
35769 targets. Also see the @code{--enable-targets} option, below.
35772 There are many other options that are specific to @value{GDBN}. This
35773 lists just the most common ones; there are some very specialized
35774 options not described here.
35777 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
35778 @itemx --enable-targets=all
35779 Configure @value{GDBN} for cross-debugging programs running on the
35780 specified list of targets. The special value @samp{all} configures
35781 @value{GDBN} for debugging programs running on any target it supports.
35783 @item --with-gdb-datadir=@var{path}
35784 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
35785 here for certain supporting files or scripts. This defaults to the
35786 @file{gdb} subdirectory of @samp{datadi} (which can be set using
35789 @item --with-relocated-sources=@var{dir}
35790 Sets up the default source path substitution rule so that directory
35791 names recorded in debug information will be automatically adjusted for
35792 any directory under @var{dir}. @var{dir} should be a subdirectory of
35793 @value{GDBN}'s configured prefix, the one mentioned in the
35794 @code{--prefix} or @code{--exec-prefix} options to configure. This
35795 option is useful if GDB is supposed to be moved to a different place
35798 @item --enable-64-bit-bfd
35799 Enable 64-bit support in BFD on 32-bit hosts.
35801 @item --disable-gdbmi
35802 Build @value{GDBN} without the GDB/MI machine interface
35806 Build @value{GDBN} with the text-mode full-screen user interface
35807 (TUI). Requires a curses library (ncurses and cursesX are also
35810 @item --with-curses
35811 Use the curses library instead of the termcap library, for text-mode
35812 terminal operations.
35814 @item --with-libunwind-ia64
35815 Use the libunwind library for unwinding function call stack on ia64
35816 target platforms. See http://www.nongnu.org/libunwind/index.html for
35819 @item --with-system-readline
35820 Use the readline library installed on the host, rather than the
35821 library supplied as part of @value{GDBN}.
35823 @item --with-system-zlib
35824 Use the zlib library installed on the host, rather than the library
35825 supplied as part of @value{GDBN}.
35828 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
35829 default if libexpat is installed and found at configure time.) This
35830 library is used to read XML files supplied with @value{GDBN}. If it
35831 is unavailable, some features, such as remote protocol memory maps,
35832 target descriptions, and shared library lists, that are based on XML
35833 files, will not be available in @value{GDBN}. If your host does not
35834 have libexpat installed, you can get the latest version from
35835 `http://expat.sourceforge.net'.
35837 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
35839 Build @value{GDBN} with GNU libiconv, a character set encoding
35840 conversion library. This is not done by default, as on GNU systems
35841 the @code{iconv} that is built in to the C library is sufficient. If
35842 your host does not have a working @code{iconv}, you can get the latest
35843 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
35845 @value{GDBN}'s build system also supports building GNU libiconv as
35846 part of the overall build. @xref{Requirements}.
35849 Build @value{GDBN} with LZMA, a compression library. (Done by default
35850 if liblzma is installed and found at configure time.) LZMA is used by
35851 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
35852 platforms using the ELF object file format. If your host does not
35853 have liblzma installed, you can get the latest version from
35854 `https://tukaani.org/xz/'.
35857 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
35858 floating-point computation with correct rounding. (Done by default if
35859 GNU MPFR is installed and found at configure time.) This library is
35860 used to emulate target floating-point arithmetic during expression
35861 evaluation when the target uses different floating-point formats than
35862 the host. If GNU MPFR is not available, @value{GDBN} will fall back
35863 to using host floating-point arithmetic. If your host does not have
35864 GNU MPFR installed, you can get the latest version from
35865 `http://www.mpfr.org'.
35867 @item --with-python@r{[}=@var{python}@r{]}
35868 Build @value{GDBN} with Python scripting support. (Done by default if
35869 libpython is present and found at configure time.) Python makes
35870 @value{GDBN} scripting much more powerful than the restricted CLI
35871 scripting language. If your host does not have Python installed, you
35872 can find it on `http://www.python.org/download/'. The oldest version
35873 of Python supported by GDB is 2.4. The optional argument @var{python}
35874 is used to find the Python headers and libraries. It can be either
35875 the name of a Python executable, or the name of the directory in which
35876 Python is installed.
35878 @item --with-guile[=GUILE]'
35879 Build @value{GDBN} with GNU Guile scripting support. (Done by default
35880 if libguile is present and found at configure time.) If your host
35881 does not have Guile installed, you can find it at
35882 `https://www.gnu.org/software/guile/'. The optional argument GUILE
35883 can be a version number, which will cause @code{configure} to try to
35884 use that version of Guile; or the file name of a @code{pkg-config}
35885 executable, which will be queried to find the information needed to
35886 compile and link against Guile.
35888 @item --without-included-regex
35889 Don't use the regex library included with @value{GDBN} (as part of the
35890 libiberty library). This is the default on hosts with version 2 of
35893 @item --with-sysroot=@var{dir}
35894 Use @var{dir} as the default system root directory for libraries whose
35895 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
35896 @var{dir} can be modified at run time by using the @command{set
35897 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
35898 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
35899 default system root will be automatically adjusted if and when
35900 @value{GDBN} is moved to a different location.
35902 @item --with-system-gdbinit=@var{file}
35903 Configure @value{GDBN} to automatically load a system-wide init file.
35904 @var{file} should be an absolute file name. If @var{file} is in a
35905 directory under the configured prefix, and @value{GDBN} is moved to
35906 another location after being built, the location of the system-wide
35907 init file will be adjusted accordingly.
35909 @item --enable-build-warnings
35910 When building the @value{GDBN} sources, ask the compiler to warn about
35911 any code which looks even vaguely suspicious. It passes many
35912 different warning flags, depending on the exact version of the
35913 compiler you are using.
35915 @item --enable-werror
35916 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
35917 to the compiler, which will fail the compilation if the compiler
35918 outputs any warning messages.
35920 @item --enable-ubsan
35921 Enable the GCC undefined behavior sanitizer. This is disabled by
35922 default, but passing @code{--enable-ubsan=yes} or
35923 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
35924 undefined behavior sanitizer checks for C@t{++} undefined behavior.
35925 It has a performance cost, so if you are looking at @value{GDBN}'s
35926 performance, you should disable it. The undefined behavior sanitizer
35927 was first introduced in GCC 4.9.
35930 @node System-wide configuration
35931 @section System-wide configuration and settings
35932 @cindex system-wide init file
35934 @value{GDBN} can be configured to have a system-wide init file;
35935 this file will be read and executed at startup (@pxref{Startup, , What
35936 @value{GDBN} does during startup}).
35938 Here is the corresponding configure option:
35941 @item --with-system-gdbinit=@var{file}
35942 Specify that the default location of the system-wide init file is
35946 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35947 it may be subject to relocation. Two possible cases:
35951 If the default location of this init file contains @file{$prefix},
35952 it will be subject to relocation. Suppose that the configure options
35953 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35954 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35955 init file is looked for as @file{$install/etc/gdbinit} instead of
35956 @file{$prefix/etc/gdbinit}.
35959 By contrast, if the default location does not contain the prefix,
35960 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35961 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35962 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35963 wherever @value{GDBN} is installed.
35966 If the configured location of the system-wide init file (as given by the
35967 @option{--with-system-gdbinit} option at configure time) is in the
35968 data-directory (as specified by @option{--with-gdb-datadir} at configure
35969 time) or in one of its subdirectories, then @value{GDBN} will look for the
35970 system-wide init file in the directory specified by the
35971 @option{--data-directory} command-line option.
35972 Note that the system-wide init file is only read once, during @value{GDBN}
35973 initialization. If the data-directory is changed after @value{GDBN} has
35974 started with the @code{set data-directory} command, the file will not be
35978 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35981 @node System-wide Configuration Scripts
35982 @subsection Installed System-wide Configuration Scripts
35983 @cindex system-wide configuration scripts
35985 The @file{system-gdbinit} directory, located inside the data-directory
35986 (as specified by @option{--with-gdb-datadir} at configure time) contains
35987 a number of scripts which can be used as system-wide init files. To
35988 automatically source those scripts at startup, @value{GDBN} should be
35989 configured with @option{--with-system-gdbinit}. Otherwise, any user
35990 should be able to source them by hand as needed.
35992 The following scripts are currently available:
35995 @item @file{elinos.py}
35997 @cindex ELinOS system-wide configuration script
35998 This script is useful when debugging a program on an ELinOS target.
35999 It takes advantage of the environment variables defined in a standard
36000 ELinOS environment in order to determine the location of the system
36001 shared libraries, and then sets the @samp{solib-absolute-prefix}
36002 and @samp{solib-search-path} variables appropriately.
36004 @item @file{wrs-linux.py}
36005 @pindex wrs-linux.py
36006 @cindex Wind River Linux system-wide configuration script
36007 This script is useful when debugging a program on a target running
36008 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36009 the host-side sysroot used by the target system.
36013 @node Maintenance Commands
36014 @appendix Maintenance Commands
36015 @cindex maintenance commands
36016 @cindex internal commands
36018 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36019 includes a number of commands intended for @value{GDBN} developers,
36020 that are not documented elsewhere in this manual. These commands are
36021 provided here for reference. (For commands that turn on debugging
36022 messages, see @ref{Debugging Output}.)
36025 @kindex maint agent
36026 @kindex maint agent-eval
36027 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36028 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36029 Translate the given @var{expression} into remote agent bytecodes.
36030 This command is useful for debugging the Agent Expression mechanism
36031 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36032 expression useful for data collection, such as by tracepoints, while
36033 @samp{maint agent-eval} produces an expression that evaluates directly
36034 to a result. For instance, a collection expression for @code{globa +
36035 globb} will include bytecodes to record four bytes of memory at each
36036 of the addresses of @code{globa} and @code{globb}, while discarding
36037 the result of the addition, while an evaluation expression will do the
36038 addition and return the sum.
36039 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36040 If not, generate remote agent bytecode for current frame PC address.
36042 @kindex maint agent-printf
36043 @item maint agent-printf @var{format},@var{expr},...
36044 Translate the given format string and list of argument expressions
36045 into remote agent bytecodes and display them as a disassembled list.
36046 This command is useful for debugging the agent version of dynamic
36047 printf (@pxref{Dynamic Printf}).
36049 @kindex maint info breakpoints
36050 @item @anchor{maint info breakpoints}maint info breakpoints
36051 Using the same format as @samp{info breakpoints}, display both the
36052 breakpoints you've set explicitly, and those @value{GDBN} is using for
36053 internal purposes. Internal breakpoints are shown with negative
36054 breakpoint numbers. The type column identifies what kind of breakpoint
36059 Normal, explicitly set breakpoint.
36062 Normal, explicitly set watchpoint.
36065 Internal breakpoint, used to handle correctly stepping through
36066 @code{longjmp} calls.
36068 @item longjmp resume
36069 Internal breakpoint at the target of a @code{longjmp}.
36072 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36075 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36078 Shared library events.
36082 @kindex maint info btrace
36083 @item maint info btrace
36084 Pint information about raw branch tracing data.
36086 @kindex maint btrace packet-history
36087 @item maint btrace packet-history
36088 Print the raw branch trace packets that are used to compute the
36089 execution history for the @samp{record btrace} command. Both the
36090 information and the format in which it is printed depend on the btrace
36095 For the BTS recording format, print a list of blocks of sequential
36096 code. For each block, the following information is printed:
36100 Newer blocks have higher numbers. The oldest block has number zero.
36101 @item Lowest @samp{PC}
36102 @item Highest @samp{PC}
36106 For the Intel Processor Trace recording format, print a list of
36107 Intel Processor Trace packets. For each packet, the following
36108 information is printed:
36111 @item Packet number
36112 Newer packets have higher numbers. The oldest packet has number zero.
36114 The packet's offset in the trace stream.
36115 @item Packet opcode and payload
36119 @kindex maint btrace clear-packet-history
36120 @item maint btrace clear-packet-history
36121 Discards the cached packet history printed by the @samp{maint btrace
36122 packet-history} command. The history will be computed again when
36125 @kindex maint btrace clear
36126 @item maint btrace clear
36127 Discard the branch trace data. The data will be fetched anew and the
36128 branch trace will be recomputed when needed.
36130 This implicitly truncates the branch trace to a single branch trace
36131 buffer. When updating branch trace incrementally, the branch trace
36132 available to @value{GDBN} may be bigger than a single branch trace
36135 @kindex maint set btrace pt skip-pad
36136 @item maint set btrace pt skip-pad
36137 @kindex maint show btrace pt skip-pad
36138 @item maint show btrace pt skip-pad
36139 Control whether @value{GDBN} will skip PAD packets when computing the
36142 @kindex set displaced-stepping
36143 @kindex show displaced-stepping
36144 @cindex displaced stepping support
36145 @cindex out-of-line single-stepping
36146 @item set displaced-stepping
36147 @itemx show displaced-stepping
36148 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36149 if the target supports it. Displaced stepping is a way to single-step
36150 over breakpoints without removing them from the inferior, by executing
36151 an out-of-line copy of the instruction that was originally at the
36152 breakpoint location. It is also known as out-of-line single-stepping.
36155 @item set displaced-stepping on
36156 If the target architecture supports it, @value{GDBN} will use
36157 displaced stepping to step over breakpoints.
36159 @item set displaced-stepping off
36160 @value{GDBN} will not use displaced stepping to step over breakpoints,
36161 even if such is supported by the target architecture.
36163 @cindex non-stop mode, and @samp{set displaced-stepping}
36164 @item set displaced-stepping auto
36165 This is the default mode. @value{GDBN} will use displaced stepping
36166 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36167 architecture supports displaced stepping.
36170 @kindex maint check-psymtabs
36171 @item maint check-psymtabs
36172 Check the consistency of currently expanded psymtabs versus symtabs.
36173 Use this to check, for example, whether a symbol is in one but not the other.
36175 @kindex maint check-symtabs
36176 @item maint check-symtabs
36177 Check the consistency of currently expanded symtabs.
36179 @kindex maint expand-symtabs
36180 @item maint expand-symtabs [@var{regexp}]
36181 Expand symbol tables.
36182 If @var{regexp} is specified, only expand symbol tables for file
36183 names matching @var{regexp}.
36185 @kindex maint set catch-demangler-crashes
36186 @kindex maint show catch-demangler-crashes
36187 @cindex demangler crashes
36188 @item maint set catch-demangler-crashes [on|off]
36189 @itemx maint show catch-demangler-crashes
36190 Control whether @value{GDBN} should attempt to catch crashes in the
36191 symbol name demangler. The default is to attempt to catch crashes.
36192 If enabled, the first time a crash is caught, a core file is created,
36193 the offending symbol is displayed and the user is presented with the
36194 option to terminate the current session.
36196 @kindex maint cplus first_component
36197 @item maint cplus first_component @var{name}
36198 Print the first C@t{++} class/namespace component of @var{name}.
36200 @kindex maint cplus namespace
36201 @item maint cplus namespace
36202 Print the list of possible C@t{++} namespaces.
36204 @kindex maint deprecate
36205 @kindex maint undeprecate
36206 @cindex deprecated commands
36207 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36208 @itemx maint undeprecate @var{command}
36209 Deprecate or undeprecate the named @var{command}. Deprecated commands
36210 cause @value{GDBN} to issue a warning when you use them. The optional
36211 argument @var{replacement} says which newer command should be used in
36212 favor of the deprecated one; if it is given, @value{GDBN} will mention
36213 the replacement as part of the warning.
36215 @kindex maint dump-me
36216 @item maint dump-me
36217 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36218 Cause a fatal signal in the debugger and force it to dump its core.
36219 This is supported only on systems which support aborting a program
36220 with the @code{SIGQUIT} signal.
36222 @kindex maint internal-error
36223 @kindex maint internal-warning
36224 @kindex maint demangler-warning
36225 @cindex demangler crashes
36226 @item maint internal-error @r{[}@var{message-text}@r{]}
36227 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36228 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36230 Cause @value{GDBN} to call the internal function @code{internal_error},
36231 @code{internal_warning} or @code{demangler_warning} and hence behave
36232 as though an internal problem has been detected. In addition to
36233 reporting the internal problem, these functions give the user the
36234 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36235 and @code{internal_warning}) create a core file of the current
36236 @value{GDBN} session.
36238 These commands take an optional parameter @var{message-text} that is
36239 used as the text of the error or warning message.
36241 Here's an example of using @code{internal-error}:
36244 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36245 @dots{}/maint.c:121: internal-error: testing, 1, 2
36246 A problem internal to GDB has been detected. Further
36247 debugging may prove unreliable.
36248 Quit this debugging session? (y or n) @kbd{n}
36249 Create a core file? (y or n) @kbd{n}
36253 @cindex @value{GDBN} internal error
36254 @cindex internal errors, control of @value{GDBN} behavior
36255 @cindex demangler crashes
36257 @kindex maint set internal-error
36258 @kindex maint show internal-error
36259 @kindex maint set internal-warning
36260 @kindex maint show internal-warning
36261 @kindex maint set demangler-warning
36262 @kindex maint show demangler-warning
36263 @item maint set internal-error @var{action} [ask|yes|no]
36264 @itemx maint show internal-error @var{action}
36265 @itemx maint set internal-warning @var{action} [ask|yes|no]
36266 @itemx maint show internal-warning @var{action}
36267 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36268 @itemx maint show demangler-warning @var{action}
36269 When @value{GDBN} reports an internal problem (error or warning) it
36270 gives the user the opportunity to both quit @value{GDBN} and create a
36271 core file of the current @value{GDBN} session. These commands let you
36272 override the default behaviour for each particular @var{action},
36273 described in the table below.
36277 You can specify that @value{GDBN} should always (yes) or never (no)
36278 quit. The default is to ask the user what to do.
36281 You can specify that @value{GDBN} should always (yes) or never (no)
36282 create a core file. The default is to ask the user what to do. Note
36283 that there is no @code{corefile} option for @code{demangler-warning}:
36284 demangler warnings always create a core file and this cannot be
36288 @kindex maint packet
36289 @item maint packet @var{text}
36290 If @value{GDBN} is talking to an inferior via the serial protocol,
36291 then this command sends the string @var{text} to the inferior, and
36292 displays the response packet. @value{GDBN} supplies the initial
36293 @samp{$} character, the terminating @samp{#} character, and the
36296 @kindex maint print architecture
36297 @item maint print architecture @r{[}@var{file}@r{]}
36298 Print the entire architecture configuration. The optional argument
36299 @var{file} names the file where the output goes.
36301 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36302 @item maint print c-tdesc
36303 Print the target description (@pxref{Target Descriptions}) as
36304 a C source file. By default, the target description is for the current
36305 target, but if the optional argument @var{file} is provided, that file
36306 is used to produce the description. The @var{file} should be an XML
36307 document, of the form described in @ref{Target Description Format}.
36308 The created source file is built into @value{GDBN} when @value{GDBN} is
36309 built again. This command is used by developers after they add or
36310 modify XML target descriptions.
36312 @kindex maint check xml-descriptions
36313 @item maint check xml-descriptions @var{dir}
36314 Check that the target descriptions dynamically created by @value{GDBN}
36315 equal the descriptions created from XML files found in @var{dir}.
36317 @anchor{maint check libthread-db}
36318 @kindex maint check libthread-db
36319 @item maint check libthread-db
36320 Run integrity checks on the current inferior's thread debugging
36321 library. This exercises all @code{libthread_db} functionality used by
36322 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36323 @code{proc_service} functions provided by @value{GDBN} that
36324 @code{libthread_db} uses. Note that parts of the test may be skipped
36325 on some platforms when debugging core files.
36327 @kindex maint print dummy-frames
36328 @item maint print dummy-frames
36329 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36332 (@value{GDBP}) @kbd{b add}
36334 (@value{GDBP}) @kbd{print add(2,3)}
36335 Breakpoint 2, add (a=2, b=3) at @dots{}
36337 The program being debugged stopped while in a function called from GDB.
36339 (@value{GDBP}) @kbd{maint print dummy-frames}
36340 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36344 Takes an optional file parameter.
36346 @kindex maint print registers
36347 @kindex maint print raw-registers
36348 @kindex maint print cooked-registers
36349 @kindex maint print register-groups
36350 @kindex maint print remote-registers
36351 @item maint print registers @r{[}@var{file}@r{]}
36352 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36353 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36354 @itemx maint print register-groups @r{[}@var{file}@r{]}
36355 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36356 Print @value{GDBN}'s internal register data structures.
36358 The command @code{maint print raw-registers} includes the contents of
36359 the raw register cache; the command @code{maint print
36360 cooked-registers} includes the (cooked) value of all registers,
36361 including registers which aren't available on the target nor visible
36362 to user; the command @code{maint print register-groups} includes the
36363 groups that each register is a member of; and the command @code{maint
36364 print remote-registers} includes the remote target's register numbers
36365 and offsets in the `G' packets.
36367 These commands take an optional parameter, a file name to which to
36368 write the information.
36370 @kindex maint print reggroups
36371 @item maint print reggroups @r{[}@var{file}@r{]}
36372 Print @value{GDBN}'s internal register group data structures. The
36373 optional argument @var{file} tells to what file to write the
36376 The register groups info looks like this:
36379 (@value{GDBP}) @kbd{maint print reggroups}
36392 This command forces @value{GDBN} to flush its internal register cache.
36394 @kindex maint print objfiles
36395 @cindex info for known object files
36396 @item maint print objfiles @r{[}@var{regexp}@r{]}
36397 Print a dump of all known object files.
36398 If @var{regexp} is specified, only print object files whose names
36399 match @var{regexp}. For each object file, this command prints its name,
36400 address in memory, and all of its psymtabs and symtabs.
36402 @kindex maint print user-registers
36403 @cindex user registers
36404 @item maint print user-registers
36405 List all currently available @dfn{user registers}. User registers
36406 typically provide alternate names for actual hardware registers. They
36407 include the four ``standard'' registers @code{$fp}, @code{$pc},
36408 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36409 registers can be used in expressions in the same way as the canonical
36410 register names, but only the latter are listed by the @code{info
36411 registers} and @code{maint print registers} commands.
36413 @kindex maint print section-scripts
36414 @cindex info for known .debug_gdb_scripts-loaded scripts
36415 @item maint print section-scripts [@var{regexp}]
36416 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36417 If @var{regexp} is specified, only print scripts loaded by object files
36418 matching @var{regexp}.
36419 For each script, this command prints its name as specified in the objfile,
36420 and the full path if known.
36421 @xref{dotdebug_gdb_scripts section}.
36423 @kindex maint print statistics
36424 @cindex bcache statistics
36425 @item maint print statistics
36426 This command prints, for each object file in the program, various data
36427 about that object file followed by the byte cache (@dfn{bcache})
36428 statistics for the object file. The objfile data includes the number
36429 of minimal, partial, full, and stabs symbols, the number of types
36430 defined by the objfile, the number of as yet unexpanded psym tables,
36431 the number of line tables and string tables, and the amount of memory
36432 used by the various tables. The bcache statistics include the counts,
36433 sizes, and counts of duplicates of all and unique objects, max,
36434 average, and median entry size, total memory used and its overhead and
36435 savings, and various measures of the hash table size and chain
36438 @kindex maint print target-stack
36439 @cindex target stack description
36440 @item maint print target-stack
36441 A @dfn{target} is an interface between the debugger and a particular
36442 kind of file or process. Targets can be stacked in @dfn{strata},
36443 so that more than one target can potentially respond to a request.
36444 In particular, memory accesses will walk down the stack of targets
36445 until they find a target that is interested in handling that particular
36448 This command prints a short description of each layer that was pushed on
36449 the @dfn{target stack}, starting from the top layer down to the bottom one.
36451 @kindex maint print type
36452 @cindex type chain of a data type
36453 @item maint print type @var{expr}
36454 Print the type chain for a type specified by @var{expr}. The argument
36455 can be either a type name or a symbol. If it is a symbol, the type of
36456 that symbol is described. The type chain produced by this command is
36457 a recursive definition of the data type as stored in @value{GDBN}'s
36458 data structures, including its flags and contained types.
36460 @kindex maint selftest
36462 @item maint selftest @r{[}@var{filter}@r{]}
36463 Run any self tests that were compiled in to @value{GDBN}. This will
36464 print a message showing how many tests were run, and how many failed.
36465 If a @var{filter} is passed, only the tests with @var{filter} in their
36468 @kindex "maint info selftests"
36470 @item maint info selftests
36471 List the selftests compiled in to @value{GDBN}.
36473 @kindex maint set dwarf always-disassemble
36474 @kindex maint show dwarf always-disassemble
36475 @item maint set dwarf always-disassemble
36476 @item maint show dwarf always-disassemble
36477 Control the behavior of @code{info address} when using DWARF debugging
36480 The default is @code{off}, which means that @value{GDBN} should try to
36481 describe a variable's location in an easily readable format. When
36482 @code{on}, @value{GDBN} will instead display the DWARF location
36483 expression in an assembly-like format. Note that some locations are
36484 too complex for @value{GDBN} to describe simply; in this case you will
36485 always see the disassembly form.
36487 Here is an example of the resulting disassembly:
36490 (gdb) info addr argc
36491 Symbol "argc" is a complex DWARF expression:
36495 For more information on these expressions, see
36496 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36498 @kindex maint set dwarf max-cache-age
36499 @kindex maint show dwarf max-cache-age
36500 @item maint set dwarf max-cache-age
36501 @itemx maint show dwarf max-cache-age
36502 Control the DWARF compilation unit cache.
36504 @cindex DWARF compilation units cache
36505 In object files with inter-compilation-unit references, such as those
36506 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36507 reader needs to frequently refer to previously read compilation units.
36508 This setting controls how long a compilation unit will remain in the
36509 cache if it is not referenced. A higher limit means that cached
36510 compilation units will be stored in memory longer, and more total
36511 memory will be used. Setting it to zero disables caching, which will
36512 slow down @value{GDBN} startup, but reduce memory consumption.
36514 @kindex maint set dwarf unwinders
36515 @kindex maint show dwarf unwinders
36516 @item maint set dwarf unwinders
36517 @itemx maint show dwarf unwinders
36518 Control use of the DWARF frame unwinders.
36520 @cindex DWARF frame unwinders
36521 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36522 frame unwinders to build the backtrace. Many of these targets will
36523 also have a second mechanism for building the backtrace for use in
36524 cases where DWARF information is not available, this second mechanism
36525 is often an analysis of a function's prologue.
36527 In order to extend testing coverage of the second level stack
36528 unwinding mechanisms it is helpful to be able to disable the DWARF
36529 stack unwinders, this can be done with this switch.
36531 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36532 advisable, there are cases that are better handled through DWARF than
36533 prologue analysis, and the debug experience is likely to be better
36534 with the DWARF frame unwinders enabled.
36536 If DWARF frame unwinders are not supported for a particular target
36537 architecture, then enabling this flag does not cause them to be used.
36538 @kindex maint set profile
36539 @kindex maint show profile
36540 @cindex profiling GDB
36541 @item maint set profile
36542 @itemx maint show profile
36543 Control profiling of @value{GDBN}.
36545 Profiling will be disabled until you use the @samp{maint set profile}
36546 command to enable it. When you enable profiling, the system will begin
36547 collecting timing and execution count data; when you disable profiling or
36548 exit @value{GDBN}, the results will be written to a log file. Remember that
36549 if you use profiling, @value{GDBN} will overwrite the profiling log file
36550 (often called @file{gmon.out}). If you have a record of important profiling
36551 data in a @file{gmon.out} file, be sure to move it to a safe location.
36553 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36554 compiled with the @samp{-pg} compiler option.
36556 @kindex maint set show-debug-regs
36557 @kindex maint show show-debug-regs
36558 @cindex hardware debug registers
36559 @item maint set show-debug-regs
36560 @itemx maint show show-debug-regs
36561 Control whether to show variables that mirror the hardware debug
36562 registers. Use @code{on} to enable, @code{off} to disable. If
36563 enabled, the debug registers values are shown when @value{GDBN} inserts or
36564 removes a hardware breakpoint or watchpoint, and when the inferior
36565 triggers a hardware-assisted breakpoint or watchpoint.
36567 @kindex maint set show-all-tib
36568 @kindex maint show show-all-tib
36569 @item maint set show-all-tib
36570 @itemx maint show show-all-tib
36571 Control whether to show all non zero areas within a 1k block starting
36572 at thread local base, when using the @samp{info w32 thread-information-block}
36575 @kindex maint set target-async
36576 @kindex maint show target-async
36577 @item maint set target-async
36578 @itemx maint show target-async
36579 This controls whether @value{GDBN} targets operate in synchronous or
36580 asynchronous mode (@pxref{Background Execution}). Normally the
36581 default is asynchronous, if it is available; but this can be changed
36582 to more easily debug problems occurring only in synchronous mode.
36584 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36585 @kindex maint show target-non-stop
36586 @item maint set target-non-stop
36587 @itemx maint show target-non-stop
36589 This controls whether @value{GDBN} targets always operate in non-stop
36590 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36591 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36592 if supported by the target.
36595 @item maint set target-non-stop auto
36596 This is the default mode. @value{GDBN} controls the target in
36597 non-stop mode if the target supports it.
36599 @item maint set target-non-stop on
36600 @value{GDBN} controls the target in non-stop mode even if the target
36601 does not indicate support.
36603 @item maint set target-non-stop off
36604 @value{GDBN} does not control the target in non-stop mode even if the
36605 target supports it.
36608 @kindex maint set per-command
36609 @kindex maint show per-command
36610 @item maint set per-command
36611 @itemx maint show per-command
36612 @cindex resources used by commands
36614 @value{GDBN} can display the resources used by each command.
36615 This is useful in debugging performance problems.
36618 @item maint set per-command space [on|off]
36619 @itemx maint show per-command space
36620 Enable or disable the printing of the memory used by GDB for each command.
36621 If enabled, @value{GDBN} will display how much memory each command
36622 took, following the command's own output.
36623 This can also be requested by invoking @value{GDBN} with the
36624 @option{--statistics} command-line switch (@pxref{Mode Options}).
36626 @item maint set per-command time [on|off]
36627 @itemx maint show per-command time
36628 Enable or disable the printing of the execution time of @value{GDBN}
36630 If enabled, @value{GDBN} will display how much time it
36631 took to execute each command, following the command's own output.
36632 Both CPU time and wallclock time are printed.
36633 Printing both is useful when trying to determine whether the cost is
36634 CPU or, e.g., disk/network latency.
36635 Note that the CPU time printed is for @value{GDBN} only, it does not include
36636 the execution time of the inferior because there's no mechanism currently
36637 to compute how much time was spent by @value{GDBN} and how much time was
36638 spent by the program been debugged.
36639 This can also be requested by invoking @value{GDBN} with the
36640 @option{--statistics} command-line switch (@pxref{Mode Options}).
36642 @item maint set per-command symtab [on|off]
36643 @itemx maint show per-command symtab
36644 Enable or disable the printing of basic symbol table statistics
36646 If enabled, @value{GDBN} will display the following information:
36650 number of symbol tables
36652 number of primary symbol tables
36654 number of blocks in the blockvector
36658 @kindex maint set check-libthread-db
36659 @kindex maint show check-libthread-db
36660 @item maint set check-libthread-db [on|off]
36661 @itemx maint show check-libthread-db
36662 Control whether @value{GDBN} should run integrity checks on inferior
36663 specific thread debugging libraries as they are loaded. The default
36664 is not to perform such checks. If any check fails @value{GDBN} will
36665 unload the library and continue searching for a suitable candidate as
36666 described in @ref{set libthread-db-search-path}. For more information
36667 about the tests, see @ref{maint check libthread-db}.
36669 @kindex maint space
36670 @cindex memory used by commands
36671 @item maint space @var{value}
36672 An alias for @code{maint set per-command space}.
36673 A non-zero value enables it, zero disables it.
36676 @cindex time of command execution
36677 @item maint time @var{value}
36678 An alias for @code{maint set per-command time}.
36679 A non-zero value enables it, zero disables it.
36681 @kindex maint translate-address
36682 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36683 Find the symbol stored at the location specified by the address
36684 @var{addr} and an optional section name @var{section}. If found,
36685 @value{GDBN} prints the name of the closest symbol and an offset from
36686 the symbol's location to the specified address. This is similar to
36687 the @code{info address} command (@pxref{Symbols}), except that this
36688 command also allows to find symbols in other sections.
36690 If section was not specified, the section in which the symbol was found
36691 is also printed. For dynamically linked executables, the name of
36692 executable or shared library containing the symbol is printed as well.
36696 The following command is useful for non-interactive invocations of
36697 @value{GDBN}, such as in the test suite.
36700 @item set watchdog @var{nsec}
36701 @kindex set watchdog
36702 @cindex watchdog timer
36703 @cindex timeout for commands
36704 Set the maximum number of seconds @value{GDBN} will wait for the
36705 target operation to finish. If this time expires, @value{GDBN}
36706 reports and error and the command is aborted.
36708 @item show watchdog
36709 Show the current setting of the target wait timeout.
36712 @node Remote Protocol
36713 @appendix @value{GDBN} Remote Serial Protocol
36718 * Stop Reply Packets::
36719 * General Query Packets::
36720 * Architecture-Specific Protocol Details::
36721 * Tracepoint Packets::
36722 * Host I/O Packets::
36724 * Notification Packets::
36725 * Remote Non-Stop::
36726 * Packet Acknowledgment::
36728 * File-I/O Remote Protocol Extension::
36729 * Library List Format::
36730 * Library List Format for SVR4 Targets::
36731 * Memory Map Format::
36732 * Thread List Format::
36733 * Traceframe Info Format::
36734 * Branch Trace Format::
36735 * Branch Trace Configuration Format::
36741 There may be occasions when you need to know something about the
36742 protocol---for example, if there is only one serial port to your target
36743 machine, you might want your program to do something special if it
36744 recognizes a packet meant for @value{GDBN}.
36746 In the examples below, @samp{->} and @samp{<-} are used to indicate
36747 transmitted and received data, respectively.
36749 @cindex protocol, @value{GDBN} remote serial
36750 @cindex serial protocol, @value{GDBN} remote
36751 @cindex remote serial protocol
36752 All @value{GDBN} commands and responses (other than acknowledgments
36753 and notifications, see @ref{Notification Packets}) are sent as a
36754 @var{packet}. A @var{packet} is introduced with the character
36755 @samp{$}, the actual @var{packet-data}, and the terminating character
36756 @samp{#} followed by a two-digit @var{checksum}:
36759 @code{$}@var{packet-data}@code{#}@var{checksum}
36763 @cindex checksum, for @value{GDBN} remote
36765 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36766 characters between the leading @samp{$} and the trailing @samp{#} (an
36767 eight bit unsigned checksum).
36769 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36770 specification also included an optional two-digit @var{sequence-id}:
36773 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36776 @cindex sequence-id, for @value{GDBN} remote
36778 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36779 has never output @var{sequence-id}s. Stubs that handle packets added
36780 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36782 When either the host or the target machine receives a packet, the first
36783 response expected is an acknowledgment: either @samp{+} (to indicate
36784 the package was received correctly) or @samp{-} (to request
36788 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36793 The @samp{+}/@samp{-} acknowledgments can be disabled
36794 once a connection is established.
36795 @xref{Packet Acknowledgment}, for details.
36797 The host (@value{GDBN}) sends @var{command}s, and the target (the
36798 debugging stub incorporated in your program) sends a @var{response}. In
36799 the case of step and continue @var{command}s, the response is only sent
36800 when the operation has completed, and the target has again stopped all
36801 threads in all attached processes. This is the default all-stop mode
36802 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36803 execution mode; see @ref{Remote Non-Stop}, for details.
36805 @var{packet-data} consists of a sequence of characters with the
36806 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
36809 @cindex remote protocol, field separator
36810 Fields within the packet should be separated using @samp{,} @samp{;} or
36811 @samp{:}. Except where otherwise noted all numbers are represented in
36812 @sc{hex} with leading zeros suppressed.
36814 Implementors should note that prior to @value{GDBN} 5.0, the character
36815 @samp{:} could not appear as the third character in a packet (as it
36816 would potentially conflict with the @var{sequence-id}).
36818 @cindex remote protocol, binary data
36819 @anchor{Binary Data}
36820 Binary data in most packets is encoded either as two hexadecimal
36821 digits per byte of binary data. This allowed the traditional remote
36822 protocol to work over connections which were only seven-bit clean.
36823 Some packets designed more recently assume an eight-bit clean
36824 connection, and use a more efficient encoding to send and receive
36827 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36828 as an escape character. Any escaped byte is transmitted as the escape
36829 character followed by the original character XORed with @code{0x20}.
36830 For example, the byte @code{0x7d} would be transmitted as the two
36831 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36832 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36833 @samp{@}}) must always be escaped. Responses sent by the stub
36834 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36835 is not interpreted as the start of a run-length encoded sequence
36838 Response @var{data} can be run-length encoded to save space.
36839 Run-length encoding replaces runs of identical characters with one
36840 instance of the repeated character, followed by a @samp{*} and a
36841 repeat count. The repeat count is itself sent encoded, to avoid
36842 binary characters in @var{data}: a value of @var{n} is sent as
36843 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36844 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36845 code 32) for a repeat count of 3. (This is because run-length
36846 encoding starts to win for counts 3 or more.) Thus, for example,
36847 @samp{0* } is a run-length encoding of ``0000'': the space character
36848 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36851 The printable characters @samp{#} and @samp{$} or with a numeric value
36852 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36853 seven repeats (@samp{$}) can be expanded using a repeat count of only
36854 five (@samp{"}). For example, @samp{00000000} can be encoded as
36857 The error response returned for some packets includes a two character
36858 error number. That number is not well defined.
36860 @cindex empty response, for unsupported packets
36861 For any @var{command} not supported by the stub, an empty response
36862 (@samp{$#00}) should be returned. That way it is possible to extend the
36863 protocol. A newer @value{GDBN} can tell if a packet is supported based
36866 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36867 commands for register access, and the @samp{m} and @samp{M} commands
36868 for memory access. Stubs that only control single-threaded targets
36869 can implement run control with the @samp{c} (continue), and @samp{s}
36870 (step) commands. Stubs that support multi-threading targets should
36871 support the @samp{vCont} command. All other commands are optional.
36876 The following table provides a complete list of all currently defined
36877 @var{command}s and their corresponding response @var{data}.
36878 @xref{File-I/O Remote Protocol Extension}, for details about the File
36879 I/O extension of the remote protocol.
36881 Each packet's description has a template showing the packet's overall
36882 syntax, followed by an explanation of the packet's meaning. We
36883 include spaces in some of the templates for clarity; these are not
36884 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36885 separate its components. For example, a template like @samp{foo
36886 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36887 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36888 @var{baz}. @value{GDBN} does not transmit a space character between the
36889 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36892 @cindex @var{thread-id}, in remote protocol
36893 @anchor{thread-id syntax}
36894 Several packets and replies include a @var{thread-id} field to identify
36895 a thread. Normally these are positive numbers with a target-specific
36896 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36897 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36900 In addition, the remote protocol supports a multiprocess feature in
36901 which the @var{thread-id} syntax is extended to optionally include both
36902 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36903 The @var{pid} (process) and @var{tid} (thread) components each have the
36904 format described above: a positive number with target-specific
36905 interpretation formatted as a big-endian hex string, literal @samp{-1}
36906 to indicate all processes or threads (respectively), or @samp{0} to
36907 indicate an arbitrary process or thread. Specifying just a process, as
36908 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36909 error to specify all processes but a specific thread, such as
36910 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36911 for those packets and replies explicitly documented to include a process
36912 ID, rather than a @var{thread-id}.
36914 The multiprocess @var{thread-id} syntax extensions are only used if both
36915 @value{GDBN} and the stub report support for the @samp{multiprocess}
36916 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36919 Note that all packet forms beginning with an upper- or lower-case
36920 letter, other than those described here, are reserved for future use.
36922 Here are the packet descriptions.
36927 @cindex @samp{!} packet
36928 @anchor{extended mode}
36929 Enable extended mode. In extended mode, the remote server is made
36930 persistent. The @samp{R} packet is used to restart the program being
36936 The remote target both supports and has enabled extended mode.
36940 @cindex @samp{?} packet
36942 Indicate the reason the target halted. The reply is the same as for
36943 step and continue. This packet has a special interpretation when the
36944 target is in non-stop mode; see @ref{Remote Non-Stop}.
36947 @xref{Stop Reply Packets}, for the reply specifications.
36949 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36950 @cindex @samp{A} packet
36951 Initialized @code{argv[]} array passed into program. @var{arglen}
36952 specifies the number of bytes in the hex encoded byte stream
36953 @var{arg}. See @code{gdbserver} for more details.
36958 The arguments were set.
36964 @cindex @samp{b} packet
36965 (Don't use this packet; its behavior is not well-defined.)
36966 Change the serial line speed to @var{baud}.
36968 JTC: @emph{When does the transport layer state change? When it's
36969 received, or after the ACK is transmitted. In either case, there are
36970 problems if the command or the acknowledgment packet is dropped.}
36972 Stan: @emph{If people really wanted to add something like this, and get
36973 it working for the first time, they ought to modify ser-unix.c to send
36974 some kind of out-of-band message to a specially-setup stub and have the
36975 switch happen "in between" packets, so that from remote protocol's point
36976 of view, nothing actually happened.}
36978 @item B @var{addr},@var{mode}
36979 @cindex @samp{B} packet
36980 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36981 breakpoint at @var{addr}.
36983 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36984 (@pxref{insert breakpoint or watchpoint packet}).
36986 @cindex @samp{bc} packet
36989 Backward continue. Execute the target system in reverse. No parameter.
36990 @xref{Reverse Execution}, for more information.
36993 @xref{Stop Reply Packets}, for the reply specifications.
36995 @cindex @samp{bs} packet
36998 Backward single step. Execute one instruction in reverse. No parameter.
36999 @xref{Reverse Execution}, for more information.
37002 @xref{Stop Reply Packets}, for the reply specifications.
37004 @item c @r{[}@var{addr}@r{]}
37005 @cindex @samp{c} packet
37006 Continue at @var{addr}, which is the address to resume. If @var{addr}
37007 is omitted, resume at current address.
37009 This packet is deprecated for multi-threading support. @xref{vCont
37013 @xref{Stop Reply Packets}, for the reply specifications.
37015 @item C @var{sig}@r{[};@var{addr}@r{]}
37016 @cindex @samp{C} packet
37017 Continue with signal @var{sig} (hex signal number). If
37018 @samp{;@var{addr}} is omitted, resume at same address.
37020 This packet is deprecated for multi-threading support. @xref{vCont
37024 @xref{Stop Reply Packets}, for the reply specifications.
37027 @cindex @samp{d} packet
37030 Don't use this packet; instead, define a general set packet
37031 (@pxref{General Query Packets}).
37035 @cindex @samp{D} packet
37036 The first form of the packet is used to detach @value{GDBN} from the
37037 remote system. It is sent to the remote target
37038 before @value{GDBN} disconnects via the @code{detach} command.
37040 The second form, including a process ID, is used when multiprocess
37041 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37042 detach only a specific process. The @var{pid} is specified as a
37043 big-endian hex string.
37053 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37054 @cindex @samp{F} packet
37055 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37056 This is part of the File-I/O protocol extension. @xref{File-I/O
37057 Remote Protocol Extension}, for the specification.
37060 @anchor{read registers packet}
37061 @cindex @samp{g} packet
37062 Read general registers.
37066 @item @var{XX@dots{}}
37067 Each byte of register data is described by two hex digits. The bytes
37068 with the register are transmitted in target byte order. The size of
37069 each register and their position within the @samp{g} packet are
37070 determined by the @value{GDBN} internal gdbarch functions
37071 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37073 When reading registers from a trace frame (@pxref{Analyze Collected
37074 Data,,Using the Collected Data}), the stub may also return a string of
37075 literal @samp{x}'s in place of the register data digits, to indicate
37076 that the corresponding register has not been collected, thus its value
37077 is unavailable. For example, for an architecture with 4 registers of
37078 4 bytes each, the following reply indicates to @value{GDBN} that
37079 registers 0 and 2 have not been collected, while registers 1 and 3
37080 have been collected, and both have zero value:
37084 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37091 @item G @var{XX@dots{}}
37092 @cindex @samp{G} packet
37093 Write general registers. @xref{read registers packet}, for a
37094 description of the @var{XX@dots{}} data.
37104 @item H @var{op} @var{thread-id}
37105 @cindex @samp{H} packet
37106 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37107 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37108 should be @samp{c} for step and continue operations (note that this
37109 is deprecated, supporting the @samp{vCont} command is a better
37110 option), and @samp{g} for other operations. The thread designator
37111 @var{thread-id} has the format and interpretation described in
37112 @ref{thread-id syntax}.
37123 @c 'H': How restrictive (or permissive) is the thread model. If a
37124 @c thread is selected and stopped, are other threads allowed
37125 @c to continue to execute? As I mentioned above, I think the
37126 @c semantics of each command when a thread is selected must be
37127 @c described. For example:
37129 @c 'g': If the stub supports threads and a specific thread is
37130 @c selected, returns the register block from that thread;
37131 @c otherwise returns current registers.
37133 @c 'G' If the stub supports threads and a specific thread is
37134 @c selected, sets the registers of the register block of
37135 @c that thread; otherwise sets current registers.
37137 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37138 @anchor{cycle step packet}
37139 @cindex @samp{i} packet
37140 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37141 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37142 step starting at that address.
37145 @cindex @samp{I} packet
37146 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37150 @cindex @samp{k} packet
37153 The exact effect of this packet is not specified.
37155 For a bare-metal target, it may power cycle or reset the target
37156 system. For that reason, the @samp{k} packet has no reply.
37158 For a single-process target, it may kill that process if possible.
37160 A multiple-process target may choose to kill just one process, or all
37161 that are under @value{GDBN}'s control. For more precise control, use
37162 the vKill packet (@pxref{vKill packet}).
37164 If the target system immediately closes the connection in response to
37165 @samp{k}, @value{GDBN} does not consider the lack of packet
37166 acknowledgment to be an error, and assumes the kill was successful.
37168 If connected using @kbd{target extended-remote}, and the target does
37169 not close the connection in response to a kill request, @value{GDBN}
37170 probes the target state as if a new connection was opened
37171 (@pxref{? packet}).
37173 @item m @var{addr},@var{length}
37174 @cindex @samp{m} packet
37175 Read @var{length} addressable memory units starting at address @var{addr}
37176 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37177 any particular boundary.
37179 The stub need not use any particular size or alignment when gathering
37180 data from memory for the response; even if @var{addr} is word-aligned
37181 and @var{length} is a multiple of the word size, the stub is free to
37182 use byte accesses, or not. For this reason, this packet may not be
37183 suitable for accessing memory-mapped I/O devices.
37184 @cindex alignment of remote memory accesses
37185 @cindex size of remote memory accesses
37186 @cindex memory, alignment and size of remote accesses
37190 @item @var{XX@dots{}}
37191 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37192 The reply may contain fewer addressable memory units than requested if the
37193 server was able to read only part of the region of memory.
37198 @item M @var{addr},@var{length}:@var{XX@dots{}}
37199 @cindex @samp{M} packet
37200 Write @var{length} addressable memory units starting at address @var{addr}
37201 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37202 byte is transmitted as a two-digit hexadecimal number.
37209 for an error (this includes the case where only part of the data was
37214 @cindex @samp{p} packet
37215 Read the value of register @var{n}; @var{n} is in hex.
37216 @xref{read registers packet}, for a description of how the returned
37217 register value is encoded.
37221 @item @var{XX@dots{}}
37222 the register's value
37226 Indicating an unrecognized @var{query}.
37229 @item P @var{n@dots{}}=@var{r@dots{}}
37230 @anchor{write register packet}
37231 @cindex @samp{P} packet
37232 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37233 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37234 digits for each byte in the register (target byte order).
37244 @item q @var{name} @var{params}@dots{}
37245 @itemx Q @var{name} @var{params}@dots{}
37246 @cindex @samp{q} packet
37247 @cindex @samp{Q} packet
37248 General query (@samp{q}) and set (@samp{Q}). These packets are
37249 described fully in @ref{General Query Packets}.
37252 @cindex @samp{r} packet
37253 Reset the entire system.
37255 Don't use this packet; use the @samp{R} packet instead.
37258 @cindex @samp{R} packet
37259 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37260 This packet is only available in extended mode (@pxref{extended mode}).
37262 The @samp{R} packet has no reply.
37264 @item s @r{[}@var{addr}@r{]}
37265 @cindex @samp{s} packet
37266 Single step, resuming at @var{addr}. If
37267 @var{addr} is omitted, resume at same address.
37269 This packet is deprecated for multi-threading support. @xref{vCont
37273 @xref{Stop Reply Packets}, for the reply specifications.
37275 @item S @var{sig}@r{[};@var{addr}@r{]}
37276 @anchor{step with signal packet}
37277 @cindex @samp{S} packet
37278 Step with signal. This is analogous to the @samp{C} packet, but
37279 requests a single-step, rather than a normal resumption of execution.
37281 This packet is deprecated for multi-threading support. @xref{vCont
37285 @xref{Stop Reply Packets}, for the reply specifications.
37287 @item t @var{addr}:@var{PP},@var{MM}
37288 @cindex @samp{t} packet
37289 Search backwards starting at address @var{addr} for a match with pattern
37290 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37291 There must be at least 3 digits in @var{addr}.
37293 @item T @var{thread-id}
37294 @cindex @samp{T} packet
37295 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37300 thread is still alive
37306 Packets starting with @samp{v} are identified by a multi-letter name,
37307 up to the first @samp{;} or @samp{?} (or the end of the packet).
37309 @item vAttach;@var{pid}
37310 @cindex @samp{vAttach} packet
37311 Attach to a new process with the specified process ID @var{pid}.
37312 The process ID is a
37313 hexadecimal integer identifying the process. In all-stop mode, all
37314 threads in the attached process are stopped; in non-stop mode, it may be
37315 attached without being stopped if that is supported by the target.
37317 @c In non-stop mode, on a successful vAttach, the stub should set the
37318 @c current thread to a thread of the newly-attached process. After
37319 @c attaching, GDB queries for the attached process's thread ID with qC.
37320 @c Also note that, from a user perspective, whether or not the
37321 @c target is stopped on attach in non-stop mode depends on whether you
37322 @c use the foreground or background version of the attach command, not
37323 @c on what vAttach does; GDB does the right thing with respect to either
37324 @c stopping or restarting threads.
37326 This packet is only available in extended mode (@pxref{extended mode}).
37332 @item @r{Any stop packet}
37333 for success in all-stop mode (@pxref{Stop Reply Packets})
37335 for success in non-stop mode (@pxref{Remote Non-Stop})
37338 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37339 @cindex @samp{vCont} packet
37340 @anchor{vCont packet}
37341 Resume the inferior, specifying different actions for each thread.
37343 For each inferior thread, the leftmost action with a matching
37344 @var{thread-id} is applied. Threads that don't match any action
37345 remain in their current state. Thread IDs are specified using the
37346 syntax described in @ref{thread-id syntax}. If multiprocess
37347 extensions (@pxref{multiprocess extensions}) are supported, actions
37348 can be specified to match all threads in a process by using the
37349 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37350 @var{thread-id} matches all threads. Specifying no actions is an
37353 Currently supported actions are:
37359 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37363 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37366 @item r @var{start},@var{end}
37367 Step once, and then keep stepping as long as the thread stops at
37368 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37369 The remote stub reports a stop reply when either the thread goes out
37370 of the range or is stopped due to an unrelated reason, such as hitting
37371 a breakpoint. @xref{range stepping}.
37373 If the range is empty (@var{start} == @var{end}), then the action
37374 becomes equivalent to the @samp{s} action. In other words,
37375 single-step once, and report the stop (even if the stepped instruction
37376 jumps to @var{start}).
37378 (A stop reply may be sent at any point even if the PC is still within
37379 the stepping range; for example, it is valid to implement this packet
37380 in a degenerate way as a single instruction step operation.)
37384 The optional argument @var{addr} normally associated with the
37385 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37386 not supported in @samp{vCont}.
37388 The @samp{t} action is only relevant in non-stop mode
37389 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37390 A stop reply should be generated for any affected thread not already stopped.
37391 When a thread is stopped by means of a @samp{t} action,
37392 the corresponding stop reply should indicate that the thread has stopped with
37393 signal @samp{0}, regardless of whether the target uses some other signal
37394 as an implementation detail.
37396 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37397 @samp{r} actions for threads that are already running. Conversely,
37398 the server must ignore @samp{t} actions for threads that are already
37401 @emph{Note:} In non-stop mode, a thread is considered running until
37402 @value{GDBN} acknowleges an asynchronous stop notification for it with
37403 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37405 The stub must support @samp{vCont} if it reports support for
37406 multiprocess extensions (@pxref{multiprocess extensions}).
37409 @xref{Stop Reply Packets}, for the reply specifications.
37412 @cindex @samp{vCont?} packet
37413 Request a list of actions supported by the @samp{vCont} packet.
37417 @item vCont@r{[};@var{action}@dots{}@r{]}
37418 The @samp{vCont} packet is supported. Each @var{action} is a supported
37419 command in the @samp{vCont} packet.
37421 The @samp{vCont} packet is not supported.
37424 @anchor{vCtrlC packet}
37426 @cindex @samp{vCtrlC} packet
37427 Interrupt remote target as if a control-C was pressed on the remote
37428 terminal. This is the equivalent to reacting to the @code{^C}
37429 (@samp{\003}, the control-C character) character in all-stop mode
37430 while the target is running, except this works in non-stop mode.
37431 @xref{interrupting remote targets}, for more info on the all-stop
37442 @item vFile:@var{operation}:@var{parameter}@dots{}
37443 @cindex @samp{vFile} packet
37444 Perform a file operation on the target system. For details,
37445 see @ref{Host I/O Packets}.
37447 @item vFlashErase:@var{addr},@var{length}
37448 @cindex @samp{vFlashErase} packet
37449 Direct the stub to erase @var{length} bytes of flash starting at
37450 @var{addr}. The region may enclose any number of flash blocks, but
37451 its start and end must fall on block boundaries, as indicated by the
37452 flash block size appearing in the memory map (@pxref{Memory Map
37453 Format}). @value{GDBN} groups flash memory programming operations
37454 together, and sends a @samp{vFlashDone} request after each group; the
37455 stub is allowed to delay erase operation until the @samp{vFlashDone}
37456 packet is received.
37466 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37467 @cindex @samp{vFlashWrite} packet
37468 Direct the stub to write data to flash address @var{addr}. The data
37469 is passed in binary form using the same encoding as for the @samp{X}
37470 packet (@pxref{Binary Data}). The memory ranges specified by
37471 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37472 not overlap, and must appear in order of increasing addresses
37473 (although @samp{vFlashErase} packets for higher addresses may already
37474 have been received; the ordering is guaranteed only between
37475 @samp{vFlashWrite} packets). If a packet writes to an address that was
37476 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37477 target-specific method, the results are unpredictable.
37485 for vFlashWrite addressing non-flash memory
37491 @cindex @samp{vFlashDone} packet
37492 Indicate to the stub that flash programming operation is finished.
37493 The stub is permitted to delay or batch the effects of a group of
37494 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37495 @samp{vFlashDone} packet is received. The contents of the affected
37496 regions of flash memory are unpredictable until the @samp{vFlashDone}
37497 request is completed.
37499 @item vKill;@var{pid}
37500 @cindex @samp{vKill} packet
37501 @anchor{vKill packet}
37502 Kill the process with the specified process ID @var{pid}, which is a
37503 hexadecimal integer identifying the process. This packet is used in
37504 preference to @samp{k} when multiprocess protocol extensions are
37505 supported; see @ref{multiprocess extensions}.
37515 @item vMustReplyEmpty
37516 @cindex @samp{vMustReplyEmpty} packet
37517 The correct reply to an unknown @samp{v} packet is to return the empty
37518 string, however, some older versions of @command{gdbserver} would
37519 incorrectly return @samp{OK} for unknown @samp{v} packets.
37521 The @samp{vMustReplyEmpty} is used as a feature test to check how
37522 @command{gdbserver} handles unknown packets, it is important that this
37523 packet be handled in the same way as other unknown @samp{v} packets.
37524 If this packet is handled differently to other unknown @samp{v}
37525 packets then it is possile that @value{GDBN} may run into problems in
37526 other areas, specifically around use of @samp{vFile:setfs:}.
37528 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37529 @cindex @samp{vRun} packet
37530 Run the program @var{filename}, passing it each @var{argument} on its
37531 command line. The file and arguments are hex-encoded strings. If
37532 @var{filename} is an empty string, the stub may use a default program
37533 (e.g.@: the last program run). The program is created in the stopped
37536 @c FIXME: What about non-stop mode?
37538 This packet is only available in extended mode (@pxref{extended mode}).
37544 @item @r{Any stop packet}
37545 for success (@pxref{Stop Reply Packets})
37549 @cindex @samp{vStopped} packet
37550 @xref{Notification Packets}.
37552 @item X @var{addr},@var{length}:@var{XX@dots{}}
37554 @cindex @samp{X} packet
37555 Write data to memory, where the data is transmitted in binary.
37556 Memory is specified by its address @var{addr} and number of addressable memory
37557 units @var{length} (@pxref{addressable memory unit});
37558 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37568 @item z @var{type},@var{addr},@var{kind}
37569 @itemx Z @var{type},@var{addr},@var{kind}
37570 @anchor{insert breakpoint or watchpoint packet}
37571 @cindex @samp{z} packet
37572 @cindex @samp{Z} packets
37573 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37574 watchpoint starting at address @var{address} of kind @var{kind}.
37576 Each breakpoint and watchpoint packet @var{type} is documented
37579 @emph{Implementation notes: A remote target shall return an empty string
37580 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37581 remote target shall support either both or neither of a given
37582 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37583 avoid potential problems with duplicate packets, the operations should
37584 be implemented in an idempotent way.}
37586 @item z0,@var{addr},@var{kind}
37587 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37588 @cindex @samp{z0} packet
37589 @cindex @samp{Z0} packet
37590 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37591 @var{addr} of type @var{kind}.
37593 A software breakpoint is implemented by replacing the instruction at
37594 @var{addr} with a software breakpoint or trap instruction. The
37595 @var{kind} is target-specific and typically indicates the size of the
37596 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37597 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37598 architectures have additional meanings for @var{kind}
37599 (@pxref{Architecture-Specific Protocol Details}); if no
37600 architecture-specific value is being used, it should be @samp{0}.
37601 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37602 conditional expressions in bytecode form that should be evaluated on
37603 the target's side. These are the conditions that should be taken into
37604 consideration when deciding if the breakpoint trigger should be
37605 reported back to @value{GDBN}.
37607 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37608 for how to best report a software breakpoint event to @value{GDBN}.
37610 The @var{cond_list} parameter is comprised of a series of expressions,
37611 concatenated without separators. Each expression has the following form:
37615 @item X @var{len},@var{expr}
37616 @var{len} is the length of the bytecode expression and @var{expr} is the
37617 actual conditional expression in bytecode form.
37621 The optional @var{cmd_list} parameter introduces commands that may be
37622 run on the target, rather than being reported back to @value{GDBN}.
37623 The parameter starts with a numeric flag @var{persist}; if the flag is
37624 nonzero, then the breakpoint may remain active and the commands
37625 continue to be run even when @value{GDBN} disconnects from the target.
37626 Following this flag is a series of expressions concatenated with no
37627 separators. Each expression has the following form:
37631 @item X @var{len},@var{expr}
37632 @var{len} is the length of the bytecode expression and @var{expr} is the
37633 actual commands expression in bytecode form.
37637 @emph{Implementation note: It is possible for a target to copy or move
37638 code that contains software breakpoints (e.g., when implementing
37639 overlays). The behavior of this packet, in the presence of such a
37640 target, is not defined.}
37652 @item z1,@var{addr},@var{kind}
37653 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37654 @cindex @samp{z1} packet
37655 @cindex @samp{Z1} packet
37656 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37657 address @var{addr}.
37659 A hardware breakpoint is implemented using a mechanism that is not
37660 dependent on being able to modify the target's memory. The
37661 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37662 same meaning as in @samp{Z0} packets.
37664 @emph{Implementation note: A hardware breakpoint is not affected by code
37677 @item z2,@var{addr},@var{kind}
37678 @itemx Z2,@var{addr},@var{kind}
37679 @cindex @samp{z2} packet
37680 @cindex @samp{Z2} packet
37681 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37682 The number of bytes to watch is specified by @var{kind}.
37694 @item z3,@var{addr},@var{kind}
37695 @itemx Z3,@var{addr},@var{kind}
37696 @cindex @samp{z3} packet
37697 @cindex @samp{Z3} packet
37698 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37699 The number of bytes to watch is specified by @var{kind}.
37711 @item z4,@var{addr},@var{kind}
37712 @itemx Z4,@var{addr},@var{kind}
37713 @cindex @samp{z4} packet
37714 @cindex @samp{Z4} packet
37715 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37716 The number of bytes to watch is specified by @var{kind}.
37730 @node Stop Reply Packets
37731 @section Stop Reply Packets
37732 @cindex stop reply packets
37734 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37735 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37736 receive any of the below as a reply. Except for @samp{?}
37737 and @samp{vStopped}, that reply is only returned
37738 when the target halts. In the below the exact meaning of @dfn{signal
37739 number} is defined by the header @file{include/gdb/signals.h} in the
37740 @value{GDBN} source code.
37742 In non-stop mode, the server will simply reply @samp{OK} to commands
37743 such as @samp{vCont}; any stop will be the subject of a future
37744 notification. @xref{Remote Non-Stop}.
37746 As in the description of request packets, we include spaces in the
37747 reply templates for clarity; these are not part of the reply packet's
37748 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37754 The program received signal number @var{AA} (a two-digit hexadecimal
37755 number). This is equivalent to a @samp{T} response with no
37756 @var{n}:@var{r} pairs.
37758 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37759 @cindex @samp{T} packet reply
37760 The program received signal number @var{AA} (a two-digit hexadecimal
37761 number). This is equivalent to an @samp{S} response, except that the
37762 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37763 and other information directly in the stop reply packet, reducing
37764 round-trip latency. Single-step and breakpoint traps are reported
37765 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37769 If @var{n} is a hexadecimal number, it is a register number, and the
37770 corresponding @var{r} gives that register's value. The data @var{r} is a
37771 series of bytes in target byte order, with each byte given by a
37772 two-digit hex number.
37775 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37776 the stopped thread, as specified in @ref{thread-id syntax}.
37779 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37780 the core on which the stop event was detected.
37783 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37784 specific event that stopped the target. The currently defined stop
37785 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37786 signal. At most one stop reason should be present.
37789 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37790 and go on to the next; this allows us to extend the protocol in the
37794 The currently defined stop reasons are:
37800 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37803 @item syscall_entry
37804 @itemx syscall_return
37805 The packet indicates a syscall entry or return, and @var{r} is the
37806 syscall number, in hex.
37808 @cindex shared library events, remote reply
37810 The packet indicates that the loaded libraries have changed.
37811 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
37812 list of loaded libraries. The @var{r} part is ignored.
37814 @cindex replay log events, remote reply
37816 The packet indicates that the target cannot continue replaying
37817 logged execution events, because it has reached the end (or the
37818 beginning when executing backward) of the log. The value of @var{r}
37819 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
37820 for more information.
37823 @anchor{swbreak stop reason}
37824 The packet indicates a software breakpoint instruction was executed,
37825 irrespective of whether it was @value{GDBN} that planted the
37826 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37827 part must be left empty.
37829 On some architectures, such as x86, at the architecture level, when a
37830 breakpoint instruction executes the program counter points at the
37831 breakpoint address plus an offset. On such targets, the stub is
37832 responsible for adjusting the PC to point back at the breakpoint
37835 This packet should not be sent by default; older @value{GDBN} versions
37836 did not support it. @value{GDBN} requests it, by supplying an
37837 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37838 remote stub must also supply the appropriate @samp{qSupported} feature
37839 indicating support.
37841 This packet is required for correct non-stop mode operation.
37844 The packet indicates the target stopped for a hardware breakpoint.
37845 The @var{r} part must be left empty.
37847 The same remarks about @samp{qSupported} and non-stop mode above
37850 @cindex fork events, remote reply
37852 The packet indicates that @code{fork} was called, and @var{r}
37853 is the thread ID of the new child process. Refer to
37854 @ref{thread-id syntax} for the format of the @var{thread-id}
37855 field. This packet is only applicable to targets that support
37858 This packet should not be sent by default; older @value{GDBN} versions
37859 did not support it. @value{GDBN} requests it, by supplying an
37860 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37861 remote stub must also supply the appropriate @samp{qSupported} feature
37862 indicating support.
37864 @cindex vfork events, remote reply
37866 The packet indicates that @code{vfork} was called, and @var{r}
37867 is the thread ID of the new child process. Refer to
37868 @ref{thread-id syntax} for the format of the @var{thread-id}
37869 field. This packet is only applicable to targets that support
37872 This packet should not be sent by default; older @value{GDBN} versions
37873 did not support it. @value{GDBN} requests it, by supplying an
37874 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37875 remote stub must also supply the appropriate @samp{qSupported} feature
37876 indicating support.
37878 @cindex vforkdone events, remote reply
37880 The packet indicates that a child process created by a vfork
37881 has either called @code{exec} or terminated, so that the
37882 address spaces of the parent and child process are no longer
37883 shared. The @var{r} part is ignored. This packet is only
37884 applicable to targets that support vforkdone events.
37886 This packet should not be sent by default; older @value{GDBN} versions
37887 did not support it. @value{GDBN} requests it, by supplying an
37888 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37889 remote stub must also supply the appropriate @samp{qSupported} feature
37890 indicating support.
37892 @cindex exec events, remote reply
37894 The packet indicates that @code{execve} was called, and @var{r}
37895 is the absolute pathname of the file that was executed, in hex.
37896 This packet is only applicable to targets that support exec events.
37898 This packet should not be sent by default; older @value{GDBN} versions
37899 did not support it. @value{GDBN} requests it, by supplying an
37900 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37901 remote stub must also supply the appropriate @samp{qSupported} feature
37902 indicating support.
37904 @cindex thread create event, remote reply
37905 @anchor{thread create event}
37907 The packet indicates that the thread was just created. The new thread
37908 is stopped until @value{GDBN} sets it running with a resumption packet
37909 (@pxref{vCont packet}). This packet should not be sent by default;
37910 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37911 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37912 @var{r} part is ignored.
37917 @itemx W @var{AA} ; process:@var{pid}
37918 The process exited, and @var{AA} is the exit status. This is only
37919 applicable to certain targets.
37921 The second form of the response, including the process ID of the
37922 exited process, can be used only when @value{GDBN} has reported
37923 support for multiprocess protocol extensions; see @ref{multiprocess
37924 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37928 @itemx X @var{AA} ; process:@var{pid}
37929 The process terminated with signal @var{AA}.
37931 The second form of the response, including the process ID of the
37932 terminated process, can be used only when @value{GDBN} has reported
37933 support for multiprocess protocol extensions; see @ref{multiprocess
37934 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37937 @anchor{thread exit event}
37938 @cindex thread exit event, remote reply
37939 @item w @var{AA} ; @var{tid}
37941 The thread exited, and @var{AA} is the exit status. This response
37942 should not be sent by default; @value{GDBN} requests it with the
37943 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37944 @var{AA} is formatted as a big-endian hex string.
37947 There are no resumed threads left in the target. In other words, even
37948 though the process is alive, the last resumed thread has exited. For
37949 example, say the target process has two threads: thread 1 and thread
37950 2. The client leaves thread 1 stopped, and resumes thread 2, which
37951 subsequently exits. At this point, even though the process is still
37952 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37953 executing either. The @samp{N} stop reply thus informs the client
37954 that it can stop waiting for stop replies. This packet should not be
37955 sent by default; older @value{GDBN} versions did not support it.
37956 @value{GDBN} requests it, by supplying an appropriate
37957 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37958 also supply the appropriate @samp{qSupported} feature indicating
37961 @item O @var{XX}@dots{}
37962 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37963 written as the program's console output. This can happen at any time
37964 while the program is running and the debugger should continue to wait
37965 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37967 @item F @var{call-id},@var{parameter}@dots{}
37968 @var{call-id} is the identifier which says which host system call should
37969 be called. This is just the name of the function. Translation into the
37970 correct system call is only applicable as it's defined in @value{GDBN}.
37971 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37974 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37975 this very system call.
37977 The target replies with this packet when it expects @value{GDBN} to
37978 call a host system call on behalf of the target. @value{GDBN} replies
37979 with an appropriate @samp{F} packet and keeps up waiting for the next
37980 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37981 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37982 Protocol Extension}, for more details.
37986 @node General Query Packets
37987 @section General Query Packets
37988 @cindex remote query requests
37990 Packets starting with @samp{q} are @dfn{general query packets};
37991 packets starting with @samp{Q} are @dfn{general set packets}. General
37992 query and set packets are a semi-unified form for retrieving and
37993 sending information to and from the stub.
37995 The initial letter of a query or set packet is followed by a name
37996 indicating what sort of thing the packet applies to. For example,
37997 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37998 definitions with the stub. These packet names follow some
38003 The name must not contain commas, colons or semicolons.
38005 Most @value{GDBN} query and set packets have a leading upper case
38008 The names of custom vendor packets should use a company prefix, in
38009 lower case, followed by a period. For example, packets designed at
38010 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38011 foos) or @samp{Qacme.bar} (for setting bars).
38014 The name of a query or set packet should be separated from any
38015 parameters by a @samp{:}; the parameters themselves should be
38016 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38017 full packet name, and check for a separator or the end of the packet,
38018 in case two packet names share a common prefix. New packets should not begin
38019 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38020 packets predate these conventions, and have arguments without any terminator
38021 for the packet name; we suspect they are in widespread use in places that
38022 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38023 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38026 Like the descriptions of the other packets, each description here
38027 has a template showing the packet's overall syntax, followed by an
38028 explanation of the packet's meaning. We include spaces in some of the
38029 templates for clarity; these are not part of the packet's syntax. No
38030 @value{GDBN} packet uses spaces to separate its components.
38032 Here are the currently defined query and set packets:
38038 Turn on or off the agent as a helper to perform some debugging operations
38039 delegated from @value{GDBN} (@pxref{Control Agent}).
38041 @item QAllow:@var{op}:@var{val}@dots{}
38042 @cindex @samp{QAllow} packet
38043 Specify which operations @value{GDBN} expects to request of the
38044 target, as a semicolon-separated list of operation name and value
38045 pairs. Possible values for @var{op} include @samp{WriteReg},
38046 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38047 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38048 indicating that @value{GDBN} will not request the operation, or 1,
38049 indicating that it may. (The target can then use this to set up its
38050 own internals optimally, for instance if the debugger never expects to
38051 insert breakpoints, it may not need to install its own trap handler.)
38054 @cindex current thread, remote request
38055 @cindex @samp{qC} packet
38056 Return the current thread ID.
38060 @item QC @var{thread-id}
38061 Where @var{thread-id} is a thread ID as documented in
38062 @ref{thread-id syntax}.
38063 @item @r{(anything else)}
38064 Any other reply implies the old thread ID.
38067 @item qCRC:@var{addr},@var{length}
38068 @cindex CRC of memory block, remote request
38069 @cindex @samp{qCRC} packet
38070 @anchor{qCRC packet}
38071 Compute the CRC checksum of a block of memory using CRC-32 defined in
38072 IEEE 802.3. The CRC is computed byte at a time, taking the most
38073 significant bit of each byte first. The initial pattern code
38074 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38076 @emph{Note:} This is the same CRC used in validating separate debug
38077 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38078 Files}). However the algorithm is slightly different. When validating
38079 separate debug files, the CRC is computed taking the @emph{least}
38080 significant bit of each byte first, and the final result is inverted to
38081 detect trailing zeros.
38086 An error (such as memory fault)
38087 @item C @var{crc32}
38088 The specified memory region's checksum is @var{crc32}.
38091 @item QDisableRandomization:@var{value}
38092 @cindex disable address space randomization, remote request
38093 @cindex @samp{QDisableRandomization} packet
38094 Some target operating systems will randomize the virtual address space
38095 of the inferior process as a security feature, but provide a feature
38096 to disable such randomization, e.g.@: to allow for a more deterministic
38097 debugging experience. On such systems, this packet with a @var{value}
38098 of 1 directs the target to disable address space randomization for
38099 processes subsequently started via @samp{vRun} packets, while a packet
38100 with a @var{value} of 0 tells the target to enable address space
38103 This packet is only available in extended mode (@pxref{extended mode}).
38108 The request succeeded.
38111 An error occurred. The error number @var{nn} is given as hex digits.
38114 An empty reply indicates that @samp{QDisableRandomization} is not supported
38118 This packet is not probed by default; the remote stub must request it,
38119 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38120 This should only be done on targets that actually support disabling
38121 address space randomization.
38123 @item QStartupWithShell:@var{value}
38124 @cindex startup with shell, remote request
38125 @cindex @samp{QStartupWithShell} packet
38126 On UNIX-like targets, it is possible to start the inferior using a
38127 shell program. This is the default behavior on both @value{GDBN} and
38128 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38129 used to inform @command{gdbserver} whether it should start the
38130 inferior using a shell or not.
38132 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38133 to start the inferior. If @var{value} is @samp{1},
38134 @command{gdbserver} will use a shell to start the inferior. All other
38135 values are considered an error.
38137 This packet is only available in extended mode (@pxref{extended
38143 The request succeeded.
38146 An error occurred. The error number @var{nn} is given as hex digits.
38149 This packet is not probed by default; the remote stub must request it,
38150 by supplying an appropriate @samp{qSupported} response
38151 (@pxref{qSupported}). This should only be done on targets that
38152 actually support starting the inferior using a shell.
38154 Use of this packet is controlled by the @code{set startup-with-shell}
38155 command; @pxref{set startup-with-shell}.
38157 @item QEnvironmentHexEncoded:@var{hex-value}
38158 @anchor{QEnvironmentHexEncoded}
38159 @cindex set environment variable, remote request
38160 @cindex @samp{QEnvironmentHexEncoded} packet
38161 On UNIX-like targets, it is possible to set environment variables that
38162 will be passed to the inferior during the startup process. This
38163 packet is used to inform @command{gdbserver} of an environment
38164 variable that has been defined by the user on @value{GDBN} (@pxref{set
38167 The packet is composed by @var{hex-value}, an hex encoded
38168 representation of the @var{name=value} format representing an
38169 environment variable. The name of the environment variable is
38170 represented by @var{name}, and the value to be assigned to the
38171 environment variable is represented by @var{value}. If the variable
38172 has no value (i.e., the value is @code{null}), then @var{value} will
38175 This packet is only available in extended mode (@pxref{extended
38181 The request succeeded.
38184 This packet is not probed by default; the remote stub must request it,
38185 by supplying an appropriate @samp{qSupported} response
38186 (@pxref{qSupported}). This should only be done on targets that
38187 actually support passing environment variables to the starting
38190 This packet is related to the @code{set environment} command;
38191 @pxref{set environment}.
38193 @item QEnvironmentUnset:@var{hex-value}
38194 @anchor{QEnvironmentUnset}
38195 @cindex unset environment variable, remote request
38196 @cindex @samp{QEnvironmentUnset} packet
38197 On UNIX-like targets, it is possible to unset environment variables
38198 before starting the inferior in the remote target. This packet is
38199 used to inform @command{gdbserver} of an environment variable that has
38200 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38202 The packet is composed by @var{hex-value}, an hex encoded
38203 representation of the name of the environment variable to be unset.
38205 This packet is only available in extended mode (@pxref{extended
38211 The request succeeded.
38214 This packet is not probed by default; the remote stub must request it,
38215 by supplying an appropriate @samp{qSupported} response
38216 (@pxref{qSupported}). This should only be done on targets that
38217 actually support passing environment variables to the starting
38220 This packet is related to the @code{unset environment} command;
38221 @pxref{unset environment}.
38223 @item QEnvironmentReset
38224 @anchor{QEnvironmentReset}
38225 @cindex reset environment, remote request
38226 @cindex @samp{QEnvironmentReset} packet
38227 On UNIX-like targets, this packet is used to reset the state of
38228 environment variables in the remote target before starting the
38229 inferior. In this context, reset means unsetting all environment
38230 variables that were previously set by the user (i.e., were not
38231 initially present in the environment). It is sent to
38232 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38233 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38234 (@pxref{QEnvironmentUnset}) packets.
38236 This packet is only available in extended mode (@pxref{extended
38242 The request succeeded.
38245 This packet is not probed by default; the remote stub must request it,
38246 by supplying an appropriate @samp{qSupported} response
38247 (@pxref{qSupported}). This should only be done on targets that
38248 actually support passing environment variables to the starting
38251 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38252 @anchor{QSetWorkingDir packet}
38253 @cindex set working directory, remote request
38254 @cindex @samp{QSetWorkingDir} packet
38255 This packet is used to inform the remote server of the intended
38256 current working directory for programs that are going to be executed.
38258 The packet is composed by @var{directory}, an hex encoded
38259 representation of the directory that the remote inferior will use as
38260 its current working directory. If @var{directory} is an empty string,
38261 the remote server should reset the inferior's current working
38262 directory to its original, empty value.
38264 This packet is only available in extended mode (@pxref{extended
38270 The request succeeded.
38274 @itemx qsThreadInfo
38275 @cindex list active threads, remote request
38276 @cindex @samp{qfThreadInfo} packet
38277 @cindex @samp{qsThreadInfo} packet
38278 Obtain a list of all active thread IDs from the target (OS). Since there
38279 may be too many active threads to fit into one reply packet, this query
38280 works iteratively: it may require more than one query/reply sequence to
38281 obtain the entire list of threads. The first query of the sequence will
38282 be the @samp{qfThreadInfo} query; subsequent queries in the
38283 sequence will be the @samp{qsThreadInfo} query.
38285 NOTE: This packet replaces the @samp{qL} query (see below).
38289 @item m @var{thread-id}
38291 @item m @var{thread-id},@var{thread-id}@dots{}
38292 a comma-separated list of thread IDs
38294 (lower case letter @samp{L}) denotes end of list.
38297 In response to each query, the target will reply with a list of one or
38298 more thread IDs, separated by commas.
38299 @value{GDBN} will respond to each reply with a request for more thread
38300 ids (using the @samp{qs} form of the query), until the target responds
38301 with @samp{l} (lower-case ell, for @dfn{last}).
38302 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38305 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38306 initial connection with the remote target, and the very first thread ID
38307 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38308 message. Therefore, the stub should ensure that the first thread ID in
38309 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38311 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38312 @cindex get thread-local storage address, remote request
38313 @cindex @samp{qGetTLSAddr} packet
38314 Fetch the address associated with thread local storage specified
38315 by @var{thread-id}, @var{offset}, and @var{lm}.
38317 @var{thread-id} is the thread ID associated with the
38318 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38320 @var{offset} is the (big endian, hex encoded) offset associated with the
38321 thread local variable. (This offset is obtained from the debug
38322 information associated with the variable.)
38324 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38325 load module associated with the thread local storage. For example,
38326 a @sc{gnu}/Linux system will pass the link map address of the shared
38327 object associated with the thread local storage under consideration.
38328 Other operating environments may choose to represent the load module
38329 differently, so the precise meaning of this parameter will vary.
38333 @item @var{XX}@dots{}
38334 Hex encoded (big endian) bytes representing the address of the thread
38335 local storage requested.
38338 An error occurred. The error number @var{nn} is given as hex digits.
38341 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38344 @item qGetTIBAddr:@var{thread-id}
38345 @cindex get thread information block address
38346 @cindex @samp{qGetTIBAddr} packet
38347 Fetch address of the Windows OS specific Thread Information Block.
38349 @var{thread-id} is the thread ID associated with the thread.
38353 @item @var{XX}@dots{}
38354 Hex encoded (big endian) bytes representing the linear address of the
38355 thread information block.
38358 An error occured. This means that either the thread was not found, or the
38359 address could not be retrieved.
38362 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38365 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38366 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38367 digit) is one to indicate the first query and zero to indicate a
38368 subsequent query; @var{threadcount} (two hex digits) is the maximum
38369 number of threads the response packet can contain; and @var{nextthread}
38370 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38371 returned in the response as @var{argthread}.
38373 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38377 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38378 Where: @var{count} (two hex digits) is the number of threads being
38379 returned; @var{done} (one hex digit) is zero to indicate more threads
38380 and one indicates no further threads; @var{argthreadid} (eight hex
38381 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38382 is a sequence of thread IDs, @var{threadid} (eight hex
38383 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38387 @cindex section offsets, remote request
38388 @cindex @samp{qOffsets} packet
38389 Get section offsets that the target used when relocating the downloaded
38394 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38395 Relocate the @code{Text} section by @var{xxx} from its original address.
38396 Relocate the @code{Data} section by @var{yyy} from its original address.
38397 If the object file format provides segment information (e.g.@: @sc{elf}
38398 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38399 segments by the supplied offsets.
38401 @emph{Note: while a @code{Bss} offset may be included in the response,
38402 @value{GDBN} ignores this and instead applies the @code{Data} offset
38403 to the @code{Bss} section.}
38405 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38406 Relocate the first segment of the object file, which conventionally
38407 contains program code, to a starting address of @var{xxx}. If
38408 @samp{DataSeg} is specified, relocate the second segment, which
38409 conventionally contains modifiable data, to a starting address of
38410 @var{yyy}. @value{GDBN} will report an error if the object file
38411 does not contain segment information, or does not contain at least
38412 as many segments as mentioned in the reply. Extra segments are
38413 kept at fixed offsets relative to the last relocated segment.
38416 @item qP @var{mode} @var{thread-id}
38417 @cindex thread information, remote request
38418 @cindex @samp{qP} packet
38419 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38420 encoded 32 bit mode; @var{thread-id} is a thread ID
38421 (@pxref{thread-id syntax}).
38423 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38426 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38430 @cindex non-stop mode, remote request
38431 @cindex @samp{QNonStop} packet
38433 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38434 @xref{Remote Non-Stop}, for more information.
38439 The request succeeded.
38442 An error occurred. The error number @var{nn} is given as hex digits.
38445 An empty reply indicates that @samp{QNonStop} is not supported by
38449 This packet is not probed by default; the remote stub must request it,
38450 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38451 Use of this packet is controlled by the @code{set non-stop} command;
38452 @pxref{Non-Stop Mode}.
38454 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38455 @itemx QCatchSyscalls:0
38456 @cindex catch syscalls from inferior, remote request
38457 @cindex @samp{QCatchSyscalls} packet
38458 @anchor{QCatchSyscalls}
38459 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38460 catching syscalls from the inferior process.
38462 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38463 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38464 is listed, every system call should be reported.
38466 Note that if a syscall not in the list is reported, @value{GDBN} will
38467 still filter the event according to its own list from all corresponding
38468 @code{catch syscall} commands. However, it is more efficient to only
38469 report the requested syscalls.
38471 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38472 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38474 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38475 kept for the new process too. On targets where exec may affect syscall
38476 numbers, for example with exec between 32 and 64-bit processes, the
38477 client should send a new packet with the new syscall list.
38482 The request succeeded.
38485 An error occurred. @var{nn} are hex digits.
38488 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38492 Use of this packet is controlled by the @code{set remote catch-syscalls}
38493 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38494 This packet is not probed by default; the remote stub must request it,
38495 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38497 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38498 @cindex pass signals to inferior, remote request
38499 @cindex @samp{QPassSignals} packet
38500 @anchor{QPassSignals}
38501 Each listed @var{signal} should be passed directly to the inferior process.
38502 Signals are numbered identically to continue packets and stop replies
38503 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38504 strictly greater than the previous item. These signals do not need to stop
38505 the inferior, or be reported to @value{GDBN}. All other signals should be
38506 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38507 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38508 new list. This packet improves performance when using @samp{handle
38509 @var{signal} nostop noprint pass}.
38514 The request succeeded.
38517 An error occurred. The error number @var{nn} is given as hex digits.
38520 An empty reply indicates that @samp{QPassSignals} is not supported by
38524 Use of this packet is controlled by the @code{set remote pass-signals}
38525 command (@pxref{Remote Configuration, set remote pass-signals}).
38526 This packet is not probed by default; the remote stub must request it,
38527 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38529 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38530 @cindex signals the inferior may see, remote request
38531 @cindex @samp{QProgramSignals} packet
38532 @anchor{QProgramSignals}
38533 Each listed @var{signal} may be delivered to the inferior process.
38534 Others should be silently discarded.
38536 In some cases, the remote stub may need to decide whether to deliver a
38537 signal to the program or not without @value{GDBN} involvement. One
38538 example of that is while detaching --- the program's threads may have
38539 stopped for signals that haven't yet had a chance of being reported to
38540 @value{GDBN}, and so the remote stub can use the signal list specified
38541 by this packet to know whether to deliver or ignore those pending
38544 This does not influence whether to deliver a signal as requested by a
38545 resumption packet (@pxref{vCont packet}).
38547 Signals are numbered identically to continue packets and stop replies
38548 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38549 strictly greater than the previous item. Multiple
38550 @samp{QProgramSignals} packets do not combine; any earlier
38551 @samp{QProgramSignals} list is completely replaced by the new list.
38556 The request succeeded.
38559 An error occurred. The error number @var{nn} is given as hex digits.
38562 An empty reply indicates that @samp{QProgramSignals} is not supported
38566 Use of this packet is controlled by the @code{set remote program-signals}
38567 command (@pxref{Remote Configuration, set remote program-signals}).
38568 This packet is not probed by default; the remote stub must request it,
38569 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38571 @anchor{QThreadEvents}
38572 @item QThreadEvents:1
38573 @itemx QThreadEvents:0
38574 @cindex thread create/exit events, remote request
38575 @cindex @samp{QThreadEvents} packet
38577 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38578 reporting of thread create and exit events. @xref{thread create
38579 event}, for the reply specifications. For example, this is used in
38580 non-stop mode when @value{GDBN} stops a set of threads and
38581 synchronously waits for the their corresponding stop replies. Without
38582 exit events, if one of the threads exits, @value{GDBN} would hang
38583 forever not knowing that it should no longer expect a stop for that
38584 same thread. @value{GDBN} does not enable this feature unless the
38585 stub reports that it supports it by including @samp{QThreadEvents+} in
38586 its @samp{qSupported} reply.
38591 The request succeeded.
38594 An error occurred. The error number @var{nn} is given as hex digits.
38597 An empty reply indicates that @samp{QThreadEvents} is not supported by
38601 Use of this packet is controlled by the @code{set remote thread-events}
38602 command (@pxref{Remote Configuration, set remote thread-events}).
38604 @item qRcmd,@var{command}
38605 @cindex execute remote command, remote request
38606 @cindex @samp{qRcmd} packet
38607 @var{command} (hex encoded) is passed to the local interpreter for
38608 execution. Invalid commands should be reported using the output
38609 string. Before the final result packet, the target may also respond
38610 with a number of intermediate @samp{O@var{output}} console output
38611 packets. @emph{Implementors should note that providing access to a
38612 stubs's interpreter may have security implications}.
38617 A command response with no output.
38619 A command response with the hex encoded output string @var{OUTPUT}.
38621 Indicate a badly formed request.
38623 An empty reply indicates that @samp{qRcmd} is not recognized.
38626 (Note that the @code{qRcmd} packet's name is separated from the
38627 command by a @samp{,}, not a @samp{:}, contrary to the naming
38628 conventions above. Please don't use this packet as a model for new
38631 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38632 @cindex searching memory, in remote debugging
38634 @cindex @samp{qSearch:memory} packet
38636 @cindex @samp{qSearch memory} packet
38637 @anchor{qSearch memory}
38638 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38639 Both @var{address} and @var{length} are encoded in hex;
38640 @var{search-pattern} is a sequence of bytes, also hex encoded.
38645 The pattern was not found.
38647 The pattern was found at @var{address}.
38649 A badly formed request or an error was encountered while searching memory.
38651 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38654 @item QStartNoAckMode
38655 @cindex @samp{QStartNoAckMode} packet
38656 @anchor{QStartNoAckMode}
38657 Request that the remote stub disable the normal @samp{+}/@samp{-}
38658 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38663 The stub has switched to no-acknowledgment mode.
38664 @value{GDBN} acknowledges this reponse,
38665 but neither the stub nor @value{GDBN} shall send or expect further
38666 @samp{+}/@samp{-} acknowledgments in the current connection.
38668 An empty reply indicates that the stub does not support no-acknowledgment mode.
38671 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38672 @cindex supported packets, remote query
38673 @cindex features of the remote protocol
38674 @cindex @samp{qSupported} packet
38675 @anchor{qSupported}
38676 Tell the remote stub about features supported by @value{GDBN}, and
38677 query the stub for features it supports. This packet allows
38678 @value{GDBN} and the remote stub to take advantage of each others'
38679 features. @samp{qSupported} also consolidates multiple feature probes
38680 at startup, to improve @value{GDBN} performance---a single larger
38681 packet performs better than multiple smaller probe packets on
38682 high-latency links. Some features may enable behavior which must not
38683 be on by default, e.g.@: because it would confuse older clients or
38684 stubs. Other features may describe packets which could be
38685 automatically probed for, but are not. These features must be
38686 reported before @value{GDBN} will use them. This ``default
38687 unsupported'' behavior is not appropriate for all packets, but it
38688 helps to keep the initial connection time under control with new
38689 versions of @value{GDBN} which support increasing numbers of packets.
38693 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38694 The stub supports or does not support each returned @var{stubfeature},
38695 depending on the form of each @var{stubfeature} (see below for the
38698 An empty reply indicates that @samp{qSupported} is not recognized,
38699 or that no features needed to be reported to @value{GDBN}.
38702 The allowed forms for each feature (either a @var{gdbfeature} in the
38703 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38707 @item @var{name}=@var{value}
38708 The remote protocol feature @var{name} is supported, and associated
38709 with the specified @var{value}. The format of @var{value} depends
38710 on the feature, but it must not include a semicolon.
38712 The remote protocol feature @var{name} is supported, and does not
38713 need an associated value.
38715 The remote protocol feature @var{name} is not supported.
38717 The remote protocol feature @var{name} may be supported, and
38718 @value{GDBN} should auto-detect support in some other way when it is
38719 needed. This form will not be used for @var{gdbfeature} notifications,
38720 but may be used for @var{stubfeature} responses.
38723 Whenever the stub receives a @samp{qSupported} request, the
38724 supplied set of @value{GDBN} features should override any previous
38725 request. This allows @value{GDBN} to put the stub in a known
38726 state, even if the stub had previously been communicating with
38727 a different version of @value{GDBN}.
38729 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38734 This feature indicates whether @value{GDBN} supports multiprocess
38735 extensions to the remote protocol. @value{GDBN} does not use such
38736 extensions unless the stub also reports that it supports them by
38737 including @samp{multiprocess+} in its @samp{qSupported} reply.
38738 @xref{multiprocess extensions}, for details.
38741 This feature indicates that @value{GDBN} supports the XML target
38742 description. If the stub sees @samp{xmlRegisters=} with target
38743 specific strings separated by a comma, it will report register
38747 This feature indicates whether @value{GDBN} supports the
38748 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38749 instruction reply packet}).
38752 This feature indicates whether @value{GDBN} supports the swbreak stop
38753 reason in stop replies. @xref{swbreak stop reason}, for details.
38756 This feature indicates whether @value{GDBN} supports the hwbreak stop
38757 reason in stop replies. @xref{swbreak stop reason}, for details.
38760 This feature indicates whether @value{GDBN} supports fork event
38761 extensions to the remote protocol. @value{GDBN} does not use such
38762 extensions unless the stub also reports that it supports them by
38763 including @samp{fork-events+} in its @samp{qSupported} reply.
38766 This feature indicates whether @value{GDBN} supports vfork event
38767 extensions to the remote protocol. @value{GDBN} does not use such
38768 extensions unless the stub also reports that it supports them by
38769 including @samp{vfork-events+} in its @samp{qSupported} reply.
38772 This feature indicates whether @value{GDBN} supports exec event
38773 extensions to the remote protocol. @value{GDBN} does not use such
38774 extensions unless the stub also reports that it supports them by
38775 including @samp{exec-events+} in its @samp{qSupported} reply.
38777 @item vContSupported
38778 This feature indicates whether @value{GDBN} wants to know the
38779 supported actions in the reply to @samp{vCont?} packet.
38782 Stubs should ignore any unknown values for
38783 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38784 packet supports receiving packets of unlimited length (earlier
38785 versions of @value{GDBN} may reject overly long responses). Additional values
38786 for @var{gdbfeature} may be defined in the future to let the stub take
38787 advantage of new features in @value{GDBN}, e.g.@: incompatible
38788 improvements in the remote protocol---the @samp{multiprocess} feature is
38789 an example of such a feature. The stub's reply should be independent
38790 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38791 describes all the features it supports, and then the stub replies with
38792 all the features it supports.
38794 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38795 responses, as long as each response uses one of the standard forms.
38797 Some features are flags. A stub which supports a flag feature
38798 should respond with a @samp{+} form response. Other features
38799 require values, and the stub should respond with an @samp{=}
38802 Each feature has a default value, which @value{GDBN} will use if
38803 @samp{qSupported} is not available or if the feature is not mentioned
38804 in the @samp{qSupported} response. The default values are fixed; a
38805 stub is free to omit any feature responses that match the defaults.
38807 Not all features can be probed, but for those which can, the probing
38808 mechanism is useful: in some cases, a stub's internal
38809 architecture may not allow the protocol layer to know some information
38810 about the underlying target in advance. This is especially common in
38811 stubs which may be configured for multiple targets.
38813 These are the currently defined stub features and their properties:
38815 @multitable @columnfractions 0.35 0.2 0.12 0.2
38816 @c NOTE: The first row should be @headitem, but we do not yet require
38817 @c a new enough version of Texinfo (4.7) to use @headitem.
38819 @tab Value Required
38823 @item @samp{PacketSize}
38828 @item @samp{qXfer:auxv:read}
38833 @item @samp{qXfer:btrace:read}
38838 @item @samp{qXfer:btrace-conf:read}
38843 @item @samp{qXfer:exec-file:read}
38848 @item @samp{qXfer:features:read}
38853 @item @samp{qXfer:libraries:read}
38858 @item @samp{qXfer:libraries-svr4:read}
38863 @item @samp{augmented-libraries-svr4-read}
38868 @item @samp{qXfer:memory-map:read}
38873 @item @samp{qXfer:sdata:read}
38878 @item @samp{qXfer:spu:read}
38883 @item @samp{qXfer:spu:write}
38888 @item @samp{qXfer:siginfo:read}
38893 @item @samp{qXfer:siginfo:write}
38898 @item @samp{qXfer:threads:read}
38903 @item @samp{qXfer:traceframe-info:read}
38908 @item @samp{qXfer:uib:read}
38913 @item @samp{qXfer:fdpic:read}
38918 @item @samp{Qbtrace:off}
38923 @item @samp{Qbtrace:bts}
38928 @item @samp{Qbtrace:pt}
38933 @item @samp{Qbtrace-conf:bts:size}
38938 @item @samp{Qbtrace-conf:pt:size}
38943 @item @samp{QNonStop}
38948 @item @samp{QCatchSyscalls}
38953 @item @samp{QPassSignals}
38958 @item @samp{QStartNoAckMode}
38963 @item @samp{multiprocess}
38968 @item @samp{ConditionalBreakpoints}
38973 @item @samp{ConditionalTracepoints}
38978 @item @samp{ReverseContinue}
38983 @item @samp{ReverseStep}
38988 @item @samp{TracepointSource}
38993 @item @samp{QAgent}
38998 @item @samp{QAllow}
39003 @item @samp{QDisableRandomization}
39008 @item @samp{EnableDisableTracepoints}
39013 @item @samp{QTBuffer:size}
39018 @item @samp{tracenz}
39023 @item @samp{BreakpointCommands}
39028 @item @samp{swbreak}
39033 @item @samp{hwbreak}
39038 @item @samp{fork-events}
39043 @item @samp{vfork-events}
39048 @item @samp{exec-events}
39053 @item @samp{QThreadEvents}
39058 @item @samp{no-resumed}
39065 These are the currently defined stub features, in more detail:
39068 @cindex packet size, remote protocol
39069 @item PacketSize=@var{bytes}
39070 The remote stub can accept packets up to at least @var{bytes} in
39071 length. @value{GDBN} will send packets up to this size for bulk
39072 transfers, and will never send larger packets. This is a limit on the
39073 data characters in the packet, including the frame and checksum.
39074 There is no trailing NUL byte in a remote protocol packet; if the stub
39075 stores packets in a NUL-terminated format, it should allow an extra
39076 byte in its buffer for the NUL. If this stub feature is not supported,
39077 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39079 @item qXfer:auxv:read
39080 The remote stub understands the @samp{qXfer:auxv:read} packet
39081 (@pxref{qXfer auxiliary vector read}).
39083 @item qXfer:btrace:read
39084 The remote stub understands the @samp{qXfer:btrace:read}
39085 packet (@pxref{qXfer btrace read}).
39087 @item qXfer:btrace-conf:read
39088 The remote stub understands the @samp{qXfer:btrace-conf:read}
39089 packet (@pxref{qXfer btrace-conf read}).
39091 @item qXfer:exec-file:read
39092 The remote stub understands the @samp{qXfer:exec-file:read} packet
39093 (@pxref{qXfer executable filename read}).
39095 @item qXfer:features:read
39096 The remote stub understands the @samp{qXfer:features:read} packet
39097 (@pxref{qXfer target description read}).
39099 @item qXfer:libraries:read
39100 The remote stub understands the @samp{qXfer:libraries:read} packet
39101 (@pxref{qXfer library list read}).
39103 @item qXfer:libraries-svr4:read
39104 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39105 (@pxref{qXfer svr4 library list read}).
39107 @item augmented-libraries-svr4-read
39108 The remote stub understands the augmented form of the
39109 @samp{qXfer:libraries-svr4:read} packet
39110 (@pxref{qXfer svr4 library list read}).
39112 @item qXfer:memory-map:read
39113 The remote stub understands the @samp{qXfer:memory-map:read} packet
39114 (@pxref{qXfer memory map read}).
39116 @item qXfer:sdata:read
39117 The remote stub understands the @samp{qXfer:sdata:read} packet
39118 (@pxref{qXfer sdata read}).
39120 @item qXfer:spu:read
39121 The remote stub understands the @samp{qXfer:spu:read} packet
39122 (@pxref{qXfer spu read}).
39124 @item qXfer:spu:write
39125 The remote stub understands the @samp{qXfer:spu:write} packet
39126 (@pxref{qXfer spu write}).
39128 @item qXfer:siginfo:read
39129 The remote stub understands the @samp{qXfer:siginfo:read} packet
39130 (@pxref{qXfer siginfo read}).
39132 @item qXfer:siginfo:write
39133 The remote stub understands the @samp{qXfer:siginfo:write} packet
39134 (@pxref{qXfer siginfo write}).
39136 @item qXfer:threads:read
39137 The remote stub understands the @samp{qXfer:threads:read} packet
39138 (@pxref{qXfer threads read}).
39140 @item qXfer:traceframe-info:read
39141 The remote stub understands the @samp{qXfer:traceframe-info:read}
39142 packet (@pxref{qXfer traceframe info read}).
39144 @item qXfer:uib:read
39145 The remote stub understands the @samp{qXfer:uib:read}
39146 packet (@pxref{qXfer unwind info block}).
39148 @item qXfer:fdpic:read
39149 The remote stub understands the @samp{qXfer:fdpic:read}
39150 packet (@pxref{qXfer fdpic loadmap read}).
39153 The remote stub understands the @samp{QNonStop} packet
39154 (@pxref{QNonStop}).
39156 @item QCatchSyscalls
39157 The remote stub understands the @samp{QCatchSyscalls} packet
39158 (@pxref{QCatchSyscalls}).
39161 The remote stub understands the @samp{QPassSignals} packet
39162 (@pxref{QPassSignals}).
39164 @item QStartNoAckMode
39165 The remote stub understands the @samp{QStartNoAckMode} packet and
39166 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39169 @anchor{multiprocess extensions}
39170 @cindex multiprocess extensions, in remote protocol
39171 The remote stub understands the multiprocess extensions to the remote
39172 protocol syntax. The multiprocess extensions affect the syntax of
39173 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39174 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39175 replies. Note that reporting this feature indicates support for the
39176 syntactic extensions only, not that the stub necessarily supports
39177 debugging of more than one process at a time. The stub must not use
39178 multiprocess extensions in packet replies unless @value{GDBN} has also
39179 indicated it supports them in its @samp{qSupported} request.
39181 @item qXfer:osdata:read
39182 The remote stub understands the @samp{qXfer:osdata:read} packet
39183 ((@pxref{qXfer osdata read}).
39185 @item ConditionalBreakpoints
39186 The target accepts and implements evaluation of conditional expressions
39187 defined for breakpoints. The target will only report breakpoint triggers
39188 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39190 @item ConditionalTracepoints
39191 The remote stub accepts and implements conditional expressions defined
39192 for tracepoints (@pxref{Tracepoint Conditions}).
39194 @item ReverseContinue
39195 The remote stub accepts and implements the reverse continue packet
39199 The remote stub accepts and implements the reverse step packet
39202 @item TracepointSource
39203 The remote stub understands the @samp{QTDPsrc} packet that supplies
39204 the source form of tracepoint definitions.
39207 The remote stub understands the @samp{QAgent} packet.
39210 The remote stub understands the @samp{QAllow} packet.
39212 @item QDisableRandomization
39213 The remote stub understands the @samp{QDisableRandomization} packet.
39215 @item StaticTracepoint
39216 @cindex static tracepoints, in remote protocol
39217 The remote stub supports static tracepoints.
39219 @item InstallInTrace
39220 @anchor{install tracepoint in tracing}
39221 The remote stub supports installing tracepoint in tracing.
39223 @item EnableDisableTracepoints
39224 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39225 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39226 to be enabled and disabled while a trace experiment is running.
39228 @item QTBuffer:size
39229 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39230 packet that allows to change the size of the trace buffer.
39233 @cindex string tracing, in remote protocol
39234 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39235 See @ref{Bytecode Descriptions} for details about the bytecode.
39237 @item BreakpointCommands
39238 @cindex breakpoint commands, in remote protocol
39239 The remote stub supports running a breakpoint's command list itself,
39240 rather than reporting the hit to @value{GDBN}.
39243 The remote stub understands the @samp{Qbtrace:off} packet.
39246 The remote stub understands the @samp{Qbtrace:bts} packet.
39249 The remote stub understands the @samp{Qbtrace:pt} packet.
39251 @item Qbtrace-conf:bts:size
39252 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39254 @item Qbtrace-conf:pt:size
39255 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39258 The remote stub reports the @samp{swbreak} stop reason for memory
39262 The remote stub reports the @samp{hwbreak} stop reason for hardware
39266 The remote stub reports the @samp{fork} stop reason for fork events.
39269 The remote stub reports the @samp{vfork} stop reason for vfork events
39270 and vforkdone events.
39273 The remote stub reports the @samp{exec} stop reason for exec events.
39275 @item vContSupported
39276 The remote stub reports the supported actions in the reply to
39277 @samp{vCont?} packet.
39279 @item QThreadEvents
39280 The remote stub understands the @samp{QThreadEvents} packet.
39283 The remote stub reports the @samp{N} stop reply.
39288 @cindex symbol lookup, remote request
39289 @cindex @samp{qSymbol} packet
39290 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39291 requests. Accept requests from the target for the values of symbols.
39296 The target does not need to look up any (more) symbols.
39297 @item qSymbol:@var{sym_name}
39298 The target requests the value of symbol @var{sym_name} (hex encoded).
39299 @value{GDBN} may provide the value by using the
39300 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39304 @item qSymbol:@var{sym_value}:@var{sym_name}
39305 Set the value of @var{sym_name} to @var{sym_value}.
39307 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39308 target has previously requested.
39310 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39311 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39317 The target does not need to look up any (more) symbols.
39318 @item qSymbol:@var{sym_name}
39319 The target requests the value of a new symbol @var{sym_name} (hex
39320 encoded). @value{GDBN} will continue to supply the values of symbols
39321 (if available), until the target ceases to request them.
39326 @itemx QTDisconnected
39333 @itemx qTMinFTPILen
39335 @xref{Tracepoint Packets}.
39337 @item qThreadExtraInfo,@var{thread-id}
39338 @cindex thread attributes info, remote request
39339 @cindex @samp{qThreadExtraInfo} packet
39340 Obtain from the target OS a printable string description of thread
39341 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39342 for the forms of @var{thread-id}. This
39343 string may contain anything that the target OS thinks is interesting
39344 for @value{GDBN} to tell the user about the thread. The string is
39345 displayed in @value{GDBN}'s @code{info threads} display. Some
39346 examples of possible thread extra info strings are @samp{Runnable}, or
39347 @samp{Blocked on Mutex}.
39351 @item @var{XX}@dots{}
39352 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39353 comprising the printable string containing the extra information about
39354 the thread's attributes.
39357 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39358 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39359 conventions above. Please don't use this packet as a model for new
39378 @xref{Tracepoint Packets}.
39380 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39381 @cindex read special object, remote request
39382 @cindex @samp{qXfer} packet
39383 @anchor{qXfer read}
39384 Read uninterpreted bytes from the target's special data area
39385 identified by the keyword @var{object}. Request @var{length} bytes
39386 starting at @var{offset} bytes into the data. The content and
39387 encoding of @var{annex} is specific to @var{object}; it can supply
39388 additional details about what data to access.
39393 Data @var{data} (@pxref{Binary Data}) has been read from the
39394 target. There may be more data at a higher address (although
39395 it is permitted to return @samp{m} even for the last valid
39396 block of data, as long as at least one byte of data was read).
39397 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39401 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39402 There is no more data to be read. It is possible for @var{data} to
39403 have fewer bytes than the @var{length} in the request.
39406 The @var{offset} in the request is at the end of the data.
39407 There is no more data to be read.
39410 The request was malformed, or @var{annex} was invalid.
39413 The offset was invalid, or there was an error encountered reading the data.
39414 The @var{nn} part is a hex-encoded @code{errno} value.
39417 An empty reply indicates the @var{object} string was not recognized by
39418 the stub, or that the object does not support reading.
39421 Here are the specific requests of this form defined so far. All the
39422 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39423 formats, listed above.
39426 @item qXfer:auxv:read::@var{offset},@var{length}
39427 @anchor{qXfer auxiliary vector read}
39428 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39429 auxiliary vector}. Note @var{annex} must be empty.
39431 This packet is not probed by default; the remote stub must request it,
39432 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39434 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39435 @anchor{qXfer btrace read}
39437 Return a description of the current branch trace.
39438 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39439 packet may have one of the following values:
39443 Returns all available branch trace.
39446 Returns all available branch trace if the branch trace changed since
39447 the last read request.
39450 Returns the new branch trace since the last read request. Adds a new
39451 block to the end of the trace that begins at zero and ends at the source
39452 location of the first branch in the trace buffer. This extra block is
39453 used to stitch traces together.
39455 If the trace buffer overflowed, returns an error indicating the overflow.
39458 This packet is not probed by default; the remote stub must request it
39459 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39461 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39462 @anchor{qXfer btrace-conf read}
39464 Return a description of the current branch trace configuration.
39465 @xref{Branch Trace Configuration Format}.
39467 This packet is not probed by default; the remote stub must request it
39468 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39470 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39471 @anchor{qXfer executable filename read}
39472 Return the full absolute name of the file that was executed to create
39473 a process running on the remote system. The annex specifies the
39474 numeric process ID of the process to query, encoded as a hexadecimal
39475 number. If the annex part is empty the remote stub should return the
39476 filename corresponding to the currently executing process.
39478 This packet is not probed by default; the remote stub must request it,
39479 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39481 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39482 @anchor{qXfer target description read}
39483 Access the @dfn{target description}. @xref{Target Descriptions}. The
39484 annex specifies which XML document to access. The main description is
39485 always loaded from the @samp{target.xml} annex.
39487 This packet is not probed by default; the remote stub must request it,
39488 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39490 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39491 @anchor{qXfer library list read}
39492 Access the target's list of loaded libraries. @xref{Library List Format}.
39493 The annex part of the generic @samp{qXfer} packet must be empty
39494 (@pxref{qXfer read}).
39496 Targets which maintain a list of libraries in the program's memory do
39497 not need to implement this packet; it is designed for platforms where
39498 the operating system manages the list of loaded libraries.
39500 This packet is not probed by default; the remote stub must request it,
39501 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39503 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39504 @anchor{qXfer svr4 library list read}
39505 Access the target's list of loaded libraries when the target is an SVR4
39506 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39507 of the generic @samp{qXfer} packet must be empty unless the remote
39508 stub indicated it supports the augmented form of this packet
39509 by supplying an appropriate @samp{qSupported} response
39510 (@pxref{qXfer read}, @ref{qSupported}).
39512 This packet is optional for better performance on SVR4 targets.
39513 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39515 This packet is not probed by default; the remote stub must request it,
39516 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39518 If the remote stub indicates it supports the augmented form of this
39519 packet then the annex part of the generic @samp{qXfer} packet may
39520 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39521 arguments. The currently supported arguments are:
39524 @item start=@var{address}
39525 A hexadecimal number specifying the address of the @samp{struct
39526 link_map} to start reading the library list from. If unset or zero
39527 then the first @samp{struct link_map} in the library list will be
39528 chosen as the starting point.
39530 @item prev=@var{address}
39531 A hexadecimal number specifying the address of the @samp{struct
39532 link_map} immediately preceding the @samp{struct link_map}
39533 specified by the @samp{start} argument. If unset or zero then
39534 the remote stub will expect that no @samp{struct link_map}
39535 exists prior to the starting point.
39539 Arguments that are not understood by the remote stub will be silently
39542 @item qXfer:memory-map:read::@var{offset},@var{length}
39543 @anchor{qXfer memory map read}
39544 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39545 annex part of the generic @samp{qXfer} packet must be empty
39546 (@pxref{qXfer read}).
39548 This packet is not probed by default; the remote stub must request it,
39549 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39551 @item qXfer:sdata:read::@var{offset},@var{length}
39552 @anchor{qXfer sdata read}
39554 Read contents of the extra collected static tracepoint marker
39555 information. The annex part of the generic @samp{qXfer} packet must
39556 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39559 This packet is not probed by default; the remote stub must request it,
39560 by supplying an appropriate @samp{qSupported} response
39561 (@pxref{qSupported}).
39563 @item qXfer:siginfo:read::@var{offset},@var{length}
39564 @anchor{qXfer siginfo read}
39565 Read contents of the extra signal information on the target
39566 system. The annex part of the generic @samp{qXfer} packet must be
39567 empty (@pxref{qXfer read}).
39569 This packet is not probed by default; the remote stub must request it,
39570 by supplying an appropriate @samp{qSupported} response
39571 (@pxref{qSupported}).
39573 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39574 @anchor{qXfer spu read}
39575 Read contents of an @code{spufs} file on the target system. The
39576 annex specifies which file to read; it must be of the form
39577 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39578 in the target process, and @var{name} identifes the @code{spufs} file
39579 in that context to be accessed.
39581 This packet is not probed by default; the remote stub must request it,
39582 by supplying an appropriate @samp{qSupported} response
39583 (@pxref{qSupported}).
39585 @item qXfer:threads:read::@var{offset},@var{length}
39586 @anchor{qXfer threads read}
39587 Access the list of threads on target. @xref{Thread List Format}. The
39588 annex part of the generic @samp{qXfer} packet must be empty
39589 (@pxref{qXfer read}).
39591 This packet is not probed by default; the remote stub must request it,
39592 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39594 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39595 @anchor{qXfer traceframe info read}
39597 Return a description of the current traceframe's contents.
39598 @xref{Traceframe Info Format}. The annex part of the generic
39599 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39601 This packet is not probed by default; the remote stub must request it,
39602 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39604 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39605 @anchor{qXfer unwind info block}
39607 Return the unwind information block for @var{pc}. This packet is used
39608 on OpenVMS/ia64 to ask the kernel unwind information.
39610 This packet is not probed by default.
39612 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39613 @anchor{qXfer fdpic loadmap read}
39614 Read contents of @code{loadmap}s on the target system. The
39615 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39616 executable @code{loadmap} or interpreter @code{loadmap} to read.
39618 This packet is not probed by default; the remote stub must request it,
39619 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39621 @item qXfer:osdata:read::@var{offset},@var{length}
39622 @anchor{qXfer osdata read}
39623 Access the target's @dfn{operating system information}.
39624 @xref{Operating System Information}.
39628 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39629 @cindex write data into object, remote request
39630 @anchor{qXfer write}
39631 Write uninterpreted bytes into the target's special data area
39632 identified by the keyword @var{object}, starting at @var{offset} bytes
39633 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39634 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39635 is specific to @var{object}; it can supply additional details about what data
39641 @var{nn} (hex encoded) is the number of bytes written.
39642 This may be fewer bytes than supplied in the request.
39645 The request was malformed, or @var{annex} was invalid.
39648 The offset was invalid, or there was an error encountered writing the data.
39649 The @var{nn} part is a hex-encoded @code{errno} value.
39652 An empty reply indicates the @var{object} string was not
39653 recognized by the stub, or that the object does not support writing.
39656 Here are the specific requests of this form defined so far. All the
39657 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39658 formats, listed above.
39661 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39662 @anchor{qXfer siginfo write}
39663 Write @var{data} to the extra signal information on the target system.
39664 The annex part of the generic @samp{qXfer} packet must be
39665 empty (@pxref{qXfer write}).
39667 This packet is not probed by default; the remote stub must request it,
39668 by supplying an appropriate @samp{qSupported} response
39669 (@pxref{qSupported}).
39671 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39672 @anchor{qXfer spu write}
39673 Write @var{data} to an @code{spufs} file on the target system. The
39674 annex specifies which file to write; it must be of the form
39675 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39676 in the target process, and @var{name} identifes the @code{spufs} file
39677 in that context to be accessed.
39679 This packet is not probed by default; the remote stub must request it,
39680 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39683 @item qXfer:@var{object}:@var{operation}:@dots{}
39684 Requests of this form may be added in the future. When a stub does
39685 not recognize the @var{object} keyword, or its support for
39686 @var{object} does not recognize the @var{operation} keyword, the stub
39687 must respond with an empty packet.
39689 @item qAttached:@var{pid}
39690 @cindex query attached, remote request
39691 @cindex @samp{qAttached} packet
39692 Return an indication of whether the remote server attached to an
39693 existing process or created a new process. When the multiprocess
39694 protocol extensions are supported (@pxref{multiprocess extensions}),
39695 @var{pid} is an integer in hexadecimal format identifying the target
39696 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39697 the query packet will be simplified as @samp{qAttached}.
39699 This query is used, for example, to know whether the remote process
39700 should be detached or killed when a @value{GDBN} session is ended with
39701 the @code{quit} command.
39706 The remote server attached to an existing process.
39708 The remote server created a new process.
39710 A badly formed request or an error was encountered.
39714 Enable branch tracing for the current thread using Branch Trace Store.
39719 Branch tracing has been enabled.
39721 A badly formed request or an error was encountered.
39725 Enable branch tracing for the current thread using Intel Processor Trace.
39730 Branch tracing has been enabled.
39732 A badly formed request or an error was encountered.
39736 Disable branch tracing for the current thread.
39741 Branch tracing has been disabled.
39743 A badly formed request or an error was encountered.
39746 @item Qbtrace-conf:bts:size=@var{value}
39747 Set the requested ring buffer size for new threads that use the
39748 btrace recording method in bts format.
39753 The ring buffer size has been set.
39755 A badly formed request or an error was encountered.
39758 @item Qbtrace-conf:pt:size=@var{value}
39759 Set the requested ring buffer size for new threads that use the
39760 btrace recording method in pt format.
39765 The ring buffer size has been set.
39767 A badly formed request or an error was encountered.
39772 @node Architecture-Specific Protocol Details
39773 @section Architecture-Specific Protocol Details
39775 This section describes how the remote protocol is applied to specific
39776 target architectures. Also see @ref{Standard Target Features}, for
39777 details of XML target descriptions for each architecture.
39780 * ARM-Specific Protocol Details::
39781 * MIPS-Specific Protocol Details::
39784 @node ARM-Specific Protocol Details
39785 @subsection @acronym{ARM}-specific Protocol Details
39788 * ARM Breakpoint Kinds::
39791 @node ARM Breakpoint Kinds
39792 @subsubsection @acronym{ARM} Breakpoint Kinds
39793 @cindex breakpoint kinds, @acronym{ARM}
39795 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39800 16-bit Thumb mode breakpoint.
39803 32-bit Thumb mode (Thumb-2) breakpoint.
39806 32-bit @acronym{ARM} mode breakpoint.
39810 @node MIPS-Specific Protocol Details
39811 @subsection @acronym{MIPS}-specific Protocol Details
39814 * MIPS Register packet Format::
39815 * MIPS Breakpoint Kinds::
39818 @node MIPS Register packet Format
39819 @subsubsection @acronym{MIPS} Register Packet Format
39820 @cindex register packet format, @acronym{MIPS}
39822 The following @code{g}/@code{G} packets have previously been defined.
39823 In the below, some thirty-two bit registers are transferred as
39824 sixty-four bits. Those registers should be zero/sign extended (which?)
39825 to fill the space allocated. Register bytes are transferred in target
39826 byte order. The two nibbles within a register byte are transferred
39827 most-significant -- least-significant.
39832 All registers are transferred as thirty-two bit quantities in the order:
39833 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39834 registers; fsr; fir; fp.
39837 All registers are transferred as sixty-four bit quantities (including
39838 thirty-two bit registers such as @code{sr}). The ordering is the same
39843 @node MIPS Breakpoint Kinds
39844 @subsubsection @acronym{MIPS} Breakpoint Kinds
39845 @cindex breakpoint kinds, @acronym{MIPS}
39847 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39852 16-bit @acronym{MIPS16} mode breakpoint.
39855 16-bit @acronym{microMIPS} mode breakpoint.
39858 32-bit standard @acronym{MIPS} mode breakpoint.
39861 32-bit @acronym{microMIPS} mode breakpoint.
39865 @node Tracepoint Packets
39866 @section Tracepoint Packets
39867 @cindex tracepoint packets
39868 @cindex packets, tracepoint
39870 Here we describe the packets @value{GDBN} uses to implement
39871 tracepoints (@pxref{Tracepoints}).
39875 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39876 @cindex @samp{QTDP} packet
39877 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39878 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39879 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39880 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39881 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39882 the number of bytes that the target should copy elsewhere to make room
39883 for the tracepoint. If an @samp{X} is present, it introduces a
39884 tracepoint condition, which consists of a hexadecimal length, followed
39885 by a comma and hex-encoded bytes, in a manner similar to action
39886 encodings as described below. If the trailing @samp{-} is present,
39887 further @samp{QTDP} packets will follow to specify this tracepoint's
39893 The packet was understood and carried out.
39895 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39897 The packet was not recognized.
39900 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39901 Define actions to be taken when a tracepoint is hit. The @var{n} and
39902 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39903 this tracepoint. This packet may only be sent immediately after
39904 another @samp{QTDP} packet that ended with a @samp{-}. If the
39905 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39906 specifying more actions for this tracepoint.
39908 In the series of action packets for a given tracepoint, at most one
39909 can have an @samp{S} before its first @var{action}. If such a packet
39910 is sent, it and the following packets define ``while-stepping''
39911 actions. Any prior packets define ordinary actions --- that is, those
39912 taken when the tracepoint is first hit. If no action packet has an
39913 @samp{S}, then all the packets in the series specify ordinary
39914 tracepoint actions.
39916 The @samp{@var{action}@dots{}} portion of the packet is a series of
39917 actions, concatenated without separators. Each action has one of the
39923 Collect the registers whose bits are set in @var{mask},
39924 a hexadecimal number whose @var{i}'th bit is set if register number
39925 @var{i} should be collected. (The least significant bit is numbered
39926 zero.) Note that @var{mask} may be any number of digits long; it may
39927 not fit in a 32-bit word.
39929 @item M @var{basereg},@var{offset},@var{len}
39930 Collect @var{len} bytes of memory starting at the address in register
39931 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39932 @samp{-1}, then the range has a fixed address: @var{offset} is the
39933 address of the lowest byte to collect. The @var{basereg},
39934 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39935 values (the @samp{-1} value for @var{basereg} is a special case).
39937 @item X @var{len},@var{expr}
39938 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39939 it directs. The agent expression @var{expr} is as described in
39940 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39941 two-digit hex number in the packet; @var{len} is the number of bytes
39942 in the expression (and thus one-half the number of hex digits in the
39947 Any number of actions may be packed together in a single @samp{QTDP}
39948 packet, as long as the packet does not exceed the maximum packet
39949 length (400 bytes, for many stubs). There may be only one @samp{R}
39950 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39951 actions. Any registers referred to by @samp{M} and @samp{X} actions
39952 must be collected by a preceding @samp{R} action. (The
39953 ``while-stepping'' actions are treated as if they were attached to a
39954 separate tracepoint, as far as these restrictions are concerned.)
39959 The packet was understood and carried out.
39961 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39963 The packet was not recognized.
39966 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39967 @cindex @samp{QTDPsrc} packet
39968 Specify a source string of tracepoint @var{n} at address @var{addr}.
39969 This is useful to get accurate reproduction of the tracepoints
39970 originally downloaded at the beginning of the trace run. The @var{type}
39971 is the name of the tracepoint part, such as @samp{cond} for the
39972 tracepoint's conditional expression (see below for a list of types), while
39973 @var{bytes} is the string, encoded in hexadecimal.
39975 @var{start} is the offset of the @var{bytes} within the overall source
39976 string, while @var{slen} is the total length of the source string.
39977 This is intended for handling source strings that are longer than will
39978 fit in a single packet.
39979 @c Add detailed example when this info is moved into a dedicated
39980 @c tracepoint descriptions section.
39982 The available string types are @samp{at} for the location,
39983 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39984 @value{GDBN} sends a separate packet for each command in the action
39985 list, in the same order in which the commands are stored in the list.
39987 The target does not need to do anything with source strings except
39988 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39991 Although this packet is optional, and @value{GDBN} will only send it
39992 if the target replies with @samp{TracepointSource} @xref{General
39993 Query Packets}, it makes both disconnected tracing and trace files
39994 much easier to use. Otherwise the user must be careful that the
39995 tracepoints in effect while looking at trace frames are identical to
39996 the ones in effect during the trace run; even a small discrepancy
39997 could cause @samp{tdump} not to work, or a particular trace frame not
40000 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40001 @cindex define trace state variable, remote request
40002 @cindex @samp{QTDV} packet
40003 Create a new trace state variable, number @var{n}, with an initial
40004 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40005 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40006 the option of not using this packet for initial values of zero; the
40007 target should simply create the trace state variables as they are
40008 mentioned in expressions. The value @var{builtin} should be 1 (one)
40009 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40010 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40011 @samp{qTsV} packet had it set. The contents of @var{name} is the
40012 hex-encoded name (without the leading @samp{$}) of the trace state
40015 @item QTFrame:@var{n}
40016 @cindex @samp{QTFrame} packet
40017 Select the @var{n}'th tracepoint frame from the buffer, and use the
40018 register and memory contents recorded there to answer subsequent
40019 request packets from @value{GDBN}.
40021 A successful reply from the stub indicates that the stub has found the
40022 requested frame. The response is a series of parts, concatenated
40023 without separators, describing the frame we selected. Each part has
40024 one of the following forms:
40028 The selected frame is number @var{n} in the trace frame buffer;
40029 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40030 was no frame matching the criteria in the request packet.
40033 The selected trace frame records a hit of tracepoint number @var{t};
40034 @var{t} is a hexadecimal number.
40038 @item QTFrame:pc:@var{addr}
40039 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40040 currently selected frame whose PC is @var{addr};
40041 @var{addr} is a hexadecimal number.
40043 @item QTFrame:tdp:@var{t}
40044 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40045 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40046 is a hexadecimal number.
40048 @item QTFrame:range:@var{start}:@var{end}
40049 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40050 currently selected frame whose PC is between @var{start} (inclusive)
40051 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40054 @item QTFrame:outside:@var{start}:@var{end}
40055 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40056 frame @emph{outside} the given range of addresses (exclusive).
40059 @cindex @samp{qTMinFTPILen} packet
40060 This packet requests the minimum length of instruction at which a fast
40061 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40062 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40063 it depends on the target system being able to create trampolines in
40064 the first 64K of memory, which might or might not be possible for that
40065 system. So the reply to this packet will be 4 if it is able to
40072 The minimum instruction length is currently unknown.
40074 The minimum instruction length is @var{length}, where @var{length}
40075 is a hexadecimal number greater or equal to 1. A reply
40076 of 1 means that a fast tracepoint may be placed on any instruction
40077 regardless of size.
40079 An error has occurred.
40081 An empty reply indicates that the request is not supported by the stub.
40085 @cindex @samp{QTStart} packet
40086 Begin the tracepoint experiment. Begin collecting data from
40087 tracepoint hits in the trace frame buffer. This packet supports the
40088 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40089 instruction reply packet}).
40092 @cindex @samp{QTStop} packet
40093 End the tracepoint experiment. Stop collecting trace frames.
40095 @item QTEnable:@var{n}:@var{addr}
40097 @cindex @samp{QTEnable} packet
40098 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40099 experiment. If the tracepoint was previously disabled, then collection
40100 of data from it will resume.
40102 @item QTDisable:@var{n}:@var{addr}
40104 @cindex @samp{QTDisable} packet
40105 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40106 experiment. No more data will be collected from the tracepoint unless
40107 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40110 @cindex @samp{QTinit} packet
40111 Clear the table of tracepoints, and empty the trace frame buffer.
40113 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40114 @cindex @samp{QTro} packet
40115 Establish the given ranges of memory as ``transparent''. The stub
40116 will answer requests for these ranges from memory's current contents,
40117 if they were not collected as part of the tracepoint hit.
40119 @value{GDBN} uses this to mark read-only regions of memory, like those
40120 containing program code. Since these areas never change, they should
40121 still have the same contents they did when the tracepoint was hit, so
40122 there's no reason for the stub to refuse to provide their contents.
40124 @item QTDisconnected:@var{value}
40125 @cindex @samp{QTDisconnected} packet
40126 Set the choice to what to do with the tracing run when @value{GDBN}
40127 disconnects from the target. A @var{value} of 1 directs the target to
40128 continue the tracing run, while 0 tells the target to stop tracing if
40129 @value{GDBN} is no longer in the picture.
40132 @cindex @samp{qTStatus} packet
40133 Ask the stub if there is a trace experiment running right now.
40135 The reply has the form:
40139 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40140 @var{running} is a single digit @code{1} if the trace is presently
40141 running, or @code{0} if not. It is followed by semicolon-separated
40142 optional fields that an agent may use to report additional status.
40146 If the trace is not running, the agent may report any of several
40147 explanations as one of the optional fields:
40152 No trace has been run yet.
40154 @item tstop[:@var{text}]:0
40155 The trace was stopped by a user-originated stop command. The optional
40156 @var{text} field is a user-supplied string supplied as part of the
40157 stop command (for instance, an explanation of why the trace was
40158 stopped manually). It is hex-encoded.
40161 The trace stopped because the trace buffer filled up.
40163 @item tdisconnected:0
40164 The trace stopped because @value{GDBN} disconnected from the target.
40166 @item tpasscount:@var{tpnum}
40167 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40169 @item terror:@var{text}:@var{tpnum}
40170 The trace stopped because tracepoint @var{tpnum} had an error. The
40171 string @var{text} is available to describe the nature of the error
40172 (for instance, a divide by zero in the condition expression); it
40176 The trace stopped for some other reason.
40180 Additional optional fields supply statistical and other information.
40181 Although not required, they are extremely useful for users monitoring
40182 the progress of a trace run. If a trace has stopped, and these
40183 numbers are reported, they must reflect the state of the just-stopped
40188 @item tframes:@var{n}
40189 The number of trace frames in the buffer.
40191 @item tcreated:@var{n}
40192 The total number of trace frames created during the run. This may
40193 be larger than the trace frame count, if the buffer is circular.
40195 @item tsize:@var{n}
40196 The total size of the trace buffer, in bytes.
40198 @item tfree:@var{n}
40199 The number of bytes still unused in the buffer.
40201 @item circular:@var{n}
40202 The value of the circular trace buffer flag. @code{1} means that the
40203 trace buffer is circular and old trace frames will be discarded if
40204 necessary to make room, @code{0} means that the trace buffer is linear
40207 @item disconn:@var{n}
40208 The value of the disconnected tracing flag. @code{1} means that
40209 tracing will continue after @value{GDBN} disconnects, @code{0} means
40210 that the trace run will stop.
40214 @item qTP:@var{tp}:@var{addr}
40215 @cindex tracepoint status, remote request
40216 @cindex @samp{qTP} packet
40217 Ask the stub for the current state of tracepoint number @var{tp} at
40218 address @var{addr}.
40222 @item V@var{hits}:@var{usage}
40223 The tracepoint has been hit @var{hits} times so far during the trace
40224 run, and accounts for @var{usage} in the trace buffer. Note that
40225 @code{while-stepping} steps are not counted as separate hits, but the
40226 steps' space consumption is added into the usage number.
40230 @item qTV:@var{var}
40231 @cindex trace state variable value, remote request
40232 @cindex @samp{qTV} packet
40233 Ask the stub for the value of the trace state variable number @var{var}.
40238 The value of the variable is @var{value}. This will be the current
40239 value of the variable if the user is examining a running target, or a
40240 saved value if the variable was collected in the trace frame that the
40241 user is looking at. Note that multiple requests may result in
40242 different reply values, such as when requesting values while the
40243 program is running.
40246 The value of the variable is unknown. This would occur, for example,
40247 if the user is examining a trace frame in which the requested variable
40252 @cindex @samp{qTfP} packet
40254 @cindex @samp{qTsP} packet
40255 These packets request data about tracepoints that are being used by
40256 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40257 of data, and multiple @code{qTsP} to get additional pieces. Replies
40258 to these packets generally take the form of the @code{QTDP} packets
40259 that define tracepoints. (FIXME add detailed syntax)
40262 @cindex @samp{qTfV} packet
40264 @cindex @samp{qTsV} packet
40265 These packets request data about trace state variables that are on the
40266 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40267 and multiple @code{qTsV} to get additional variables. Replies to
40268 these packets follow the syntax of the @code{QTDV} packets that define
40269 trace state variables.
40275 @cindex @samp{qTfSTM} packet
40276 @cindex @samp{qTsSTM} packet
40277 These packets request data about static tracepoint markers that exist
40278 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40279 first piece of data, and multiple @code{qTsSTM} to get additional
40280 pieces. Replies to these packets take the following form:
40284 @item m @var{address}:@var{id}:@var{extra}
40286 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40287 a comma-separated list of markers
40289 (lower case letter @samp{L}) denotes end of list.
40291 An error occurred. The error number @var{nn} is given as hex digits.
40293 An empty reply indicates that the request is not supported by the
40297 The @var{address} is encoded in hex;
40298 @var{id} and @var{extra} are strings encoded in hex.
40300 In response to each query, the target will reply with a list of one or
40301 more markers, separated by commas. @value{GDBN} will respond to each
40302 reply with a request for more markers (using the @samp{qs} form of the
40303 query), until the target responds with @samp{l} (lower-case ell, for
40306 @item qTSTMat:@var{address}
40308 @cindex @samp{qTSTMat} packet
40309 This packets requests data about static tracepoint markers in the
40310 target program at @var{address}. Replies to this packet follow the
40311 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40312 tracepoint markers.
40314 @item QTSave:@var{filename}
40315 @cindex @samp{QTSave} packet
40316 This packet directs the target to save trace data to the file name
40317 @var{filename} in the target's filesystem. The @var{filename} is encoded
40318 as a hex string; the interpretation of the file name (relative vs
40319 absolute, wild cards, etc) is up to the target.
40321 @item qTBuffer:@var{offset},@var{len}
40322 @cindex @samp{qTBuffer} packet
40323 Return up to @var{len} bytes of the current contents of trace buffer,
40324 starting at @var{offset}. The trace buffer is treated as if it were
40325 a contiguous collection of traceframes, as per the trace file format.
40326 The reply consists as many hex-encoded bytes as the target can deliver
40327 in a packet; it is not an error to return fewer than were asked for.
40328 A reply consisting of just @code{l} indicates that no bytes are
40331 @item QTBuffer:circular:@var{value}
40332 This packet directs the target to use a circular trace buffer if
40333 @var{value} is 1, or a linear buffer if the value is 0.
40335 @item QTBuffer:size:@var{size}
40336 @anchor{QTBuffer-size}
40337 @cindex @samp{QTBuffer size} packet
40338 This packet directs the target to make the trace buffer be of size
40339 @var{size} if possible. A value of @code{-1} tells the target to
40340 use whatever size it prefers.
40342 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40343 @cindex @samp{QTNotes} packet
40344 This packet adds optional textual notes to the trace run. Allowable
40345 types include @code{user}, @code{notes}, and @code{tstop}, the
40346 @var{text} fields are arbitrary strings, hex-encoded.
40350 @subsection Relocate instruction reply packet
40351 When installing fast tracepoints in memory, the target may need to
40352 relocate the instruction currently at the tracepoint address to a
40353 different address in memory. For most instructions, a simple copy is
40354 enough, but, for example, call instructions that implicitly push the
40355 return address on the stack, and relative branches or other
40356 PC-relative instructions require offset adjustment, so that the effect
40357 of executing the instruction at a different address is the same as if
40358 it had executed in the original location.
40360 In response to several of the tracepoint packets, the target may also
40361 respond with a number of intermediate @samp{qRelocInsn} request
40362 packets before the final result packet, to have @value{GDBN} handle
40363 this relocation operation. If a packet supports this mechanism, its
40364 documentation will explicitly say so. See for example the above
40365 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40366 format of the request is:
40369 @item qRelocInsn:@var{from};@var{to}
40371 This requests @value{GDBN} to copy instruction at address @var{from}
40372 to address @var{to}, possibly adjusted so that executing the
40373 instruction at @var{to} has the same effect as executing it at
40374 @var{from}. @value{GDBN} writes the adjusted instruction to target
40375 memory starting at @var{to}.
40380 @item qRelocInsn:@var{adjusted_size}
40381 Informs the stub the relocation is complete. The @var{adjusted_size} is
40382 the length in bytes of resulting relocated instruction sequence.
40384 A badly formed request was detected, or an error was encountered while
40385 relocating the instruction.
40388 @node Host I/O Packets
40389 @section Host I/O Packets
40390 @cindex Host I/O, remote protocol
40391 @cindex file transfer, remote protocol
40393 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40394 operations on the far side of a remote link. For example, Host I/O is
40395 used to upload and download files to a remote target with its own
40396 filesystem. Host I/O uses the same constant values and data structure
40397 layout as the target-initiated File-I/O protocol. However, the
40398 Host I/O packets are structured differently. The target-initiated
40399 protocol relies on target memory to store parameters and buffers.
40400 Host I/O requests are initiated by @value{GDBN}, and the
40401 target's memory is not involved. @xref{File-I/O Remote Protocol
40402 Extension}, for more details on the target-initiated protocol.
40404 The Host I/O request packets all encode a single operation along with
40405 its arguments. They have this format:
40409 @item vFile:@var{operation}: @var{parameter}@dots{}
40410 @var{operation} is the name of the particular request; the target
40411 should compare the entire packet name up to the second colon when checking
40412 for a supported operation. The format of @var{parameter} depends on
40413 the operation. Numbers are always passed in hexadecimal. Negative
40414 numbers have an explicit minus sign (i.e.@: two's complement is not
40415 used). Strings (e.g.@: filenames) are encoded as a series of
40416 hexadecimal bytes. The last argument to a system call may be a
40417 buffer of escaped binary data (@pxref{Binary Data}).
40421 The valid responses to Host I/O packets are:
40425 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40426 @var{result} is the integer value returned by this operation, usually
40427 non-negative for success and -1 for errors. If an error has occured,
40428 @var{errno} will be included in the result specifying a
40429 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40430 operations which return data, @var{attachment} supplies the data as a
40431 binary buffer. Binary buffers in response packets are escaped in the
40432 normal way (@pxref{Binary Data}). See the individual packet
40433 documentation for the interpretation of @var{result} and
40437 An empty response indicates that this operation is not recognized.
40441 These are the supported Host I/O operations:
40444 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40445 Open a file at @var{filename} and return a file descriptor for it, or
40446 return -1 if an error occurs. The @var{filename} is a string,
40447 @var{flags} is an integer indicating a mask of open flags
40448 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40449 of mode bits to use if the file is created (@pxref{mode_t Values}).
40450 @xref{open}, for details of the open flags and mode values.
40452 @item vFile:close: @var{fd}
40453 Close the open file corresponding to @var{fd} and return 0, or
40454 -1 if an error occurs.
40456 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40457 Read data from the open file corresponding to @var{fd}. Up to
40458 @var{count} bytes will be read from the file, starting at @var{offset}
40459 relative to the start of the file. The target may read fewer bytes;
40460 common reasons include packet size limits and an end-of-file
40461 condition. The number of bytes read is returned. Zero should only be
40462 returned for a successful read at the end of the file, or if
40463 @var{count} was zero.
40465 The data read should be returned as a binary attachment on success.
40466 If zero bytes were read, the response should include an empty binary
40467 attachment (i.e.@: a trailing semicolon). The return value is the
40468 number of target bytes read; the binary attachment may be longer if
40469 some characters were escaped.
40471 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40472 Write @var{data} (a binary buffer) to the open file corresponding
40473 to @var{fd}. Start the write at @var{offset} from the start of the
40474 file. Unlike many @code{write} system calls, there is no
40475 separate @var{count} argument; the length of @var{data} in the
40476 packet is used. @samp{vFile:write} returns the number of bytes written,
40477 which may be shorter than the length of @var{data}, or -1 if an
40480 @item vFile:fstat: @var{fd}
40481 Get information about the open file corresponding to @var{fd}.
40482 On success the information is returned as a binary attachment
40483 and the return value is the size of this attachment in bytes.
40484 If an error occurs the return value is -1. The format of the
40485 returned binary attachment is as described in @ref{struct stat}.
40487 @item vFile:unlink: @var{filename}
40488 Delete the file at @var{filename} on the target. Return 0,
40489 or -1 if an error occurs. The @var{filename} is a string.
40491 @item vFile:readlink: @var{filename}
40492 Read value of symbolic link @var{filename} on the target. Return
40493 the number of bytes read, or -1 if an error occurs.
40495 The data read should be returned as a binary attachment on success.
40496 If zero bytes were read, the response should include an empty binary
40497 attachment (i.e.@: a trailing semicolon). The return value is the
40498 number of target bytes read; the binary attachment may be longer if
40499 some characters were escaped.
40501 @item vFile:setfs: @var{pid}
40502 Select the filesystem on which @code{vFile} operations with
40503 @var{filename} arguments will operate. This is required for
40504 @value{GDBN} to be able to access files on remote targets where
40505 the remote stub does not share a common filesystem with the
40508 If @var{pid} is nonzero, select the filesystem as seen by process
40509 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40510 the remote stub. Return 0 on success, or -1 if an error occurs.
40511 If @code{vFile:setfs:} indicates success, the selected filesystem
40512 remains selected until the next successful @code{vFile:setfs:}
40518 @section Interrupts
40519 @cindex interrupts (remote protocol)
40520 @anchor{interrupting remote targets}
40522 In all-stop mode, when a program on the remote target is running,
40523 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40524 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40525 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40527 The precise meaning of @code{BREAK} is defined by the transport
40528 mechanism and may, in fact, be undefined. @value{GDBN} does not
40529 currently define a @code{BREAK} mechanism for any of the network
40530 interfaces except for TCP, in which case @value{GDBN} sends the
40531 @code{telnet} BREAK sequence.
40533 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40534 transport mechanisms. It is represented by sending the single byte
40535 @code{0x03} without any of the usual packet overhead described in
40536 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40537 transmitted as part of a packet, it is considered to be packet data
40538 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40539 (@pxref{X packet}), used for binary downloads, may include an unescaped
40540 @code{0x03} as part of its packet.
40542 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40543 When Linux kernel receives this sequence from serial port,
40544 it stops execution and connects to gdb.
40546 In non-stop mode, because packet resumptions are asynchronous
40547 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40548 command to the remote stub, even when the target is running. For that
40549 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40550 packet}) with the usual packet framing instead of the single byte
40553 Stubs are not required to recognize these interrupt mechanisms and the
40554 precise meaning associated with receipt of the interrupt is
40555 implementation defined. If the target supports debugging of multiple
40556 threads and/or processes, it should attempt to interrupt all
40557 currently-executing threads and processes.
40558 If the stub is successful at interrupting the
40559 running program, it should send one of the stop
40560 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40561 of successfully stopping the program in all-stop mode, and a stop reply
40562 for each stopped thread in non-stop mode.
40563 Interrupts received while the
40564 program is stopped are queued and the program will be interrupted when
40565 it is resumed next time.
40567 @node Notification Packets
40568 @section Notification Packets
40569 @cindex notification packets
40570 @cindex packets, notification
40572 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40573 packets that require no acknowledgment. Both the GDB and the stub
40574 may send notifications (although the only notifications defined at
40575 present are sent by the stub). Notifications carry information
40576 without incurring the round-trip latency of an acknowledgment, and so
40577 are useful for low-impact communications where occasional packet loss
40580 A notification packet has the form @samp{% @var{data} #
40581 @var{checksum}}, where @var{data} is the content of the notification,
40582 and @var{checksum} is a checksum of @var{data}, computed and formatted
40583 as for ordinary @value{GDBN} packets. A notification's @var{data}
40584 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40585 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40586 to acknowledge the notification's receipt or to report its corruption.
40588 Every notification's @var{data} begins with a name, which contains no
40589 colon characters, followed by a colon character.
40591 Recipients should silently ignore corrupted notifications and
40592 notifications they do not understand. Recipients should restart
40593 timeout periods on receipt of a well-formed notification, whether or
40594 not they understand it.
40596 Senders should only send the notifications described here when this
40597 protocol description specifies that they are permitted. In the
40598 future, we may extend the protocol to permit existing notifications in
40599 new contexts; this rule helps older senders avoid confusing newer
40602 (Older versions of @value{GDBN} ignore bytes received until they see
40603 the @samp{$} byte that begins an ordinary packet, so new stubs may
40604 transmit notifications without fear of confusing older clients. There
40605 are no notifications defined for @value{GDBN} to send at the moment, but we
40606 assume that most older stubs would ignore them, as well.)
40608 Each notification is comprised of three parts:
40610 @item @var{name}:@var{event}
40611 The notification packet is sent by the side that initiates the
40612 exchange (currently, only the stub does that), with @var{event}
40613 carrying the specific information about the notification, and
40614 @var{name} specifying the name of the notification.
40616 The acknowledge sent by the other side, usually @value{GDBN}, to
40617 acknowledge the exchange and request the event.
40620 The purpose of an asynchronous notification mechanism is to report to
40621 @value{GDBN} that something interesting happened in the remote stub.
40623 The remote stub may send notification @var{name}:@var{event}
40624 at any time, but @value{GDBN} acknowledges the notification when
40625 appropriate. The notification event is pending before @value{GDBN}
40626 acknowledges. Only one notification at a time may be pending; if
40627 additional events occur before @value{GDBN} has acknowledged the
40628 previous notification, they must be queued by the stub for later
40629 synchronous transmission in response to @var{ack} packets from
40630 @value{GDBN}. Because the notification mechanism is unreliable,
40631 the stub is permitted to resend a notification if it believes
40632 @value{GDBN} may not have received it.
40634 Specifically, notifications may appear when @value{GDBN} is not
40635 otherwise reading input from the stub, or when @value{GDBN} is
40636 expecting to read a normal synchronous response or a
40637 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40638 Notification packets are distinct from any other communication from
40639 the stub so there is no ambiguity.
40641 After receiving a notification, @value{GDBN} shall acknowledge it by
40642 sending a @var{ack} packet as a regular, synchronous request to the
40643 stub. Such acknowledgment is not required to happen immediately, as
40644 @value{GDBN} is permitted to send other, unrelated packets to the
40645 stub first, which the stub should process normally.
40647 Upon receiving a @var{ack} packet, if the stub has other queued
40648 events to report to @value{GDBN}, it shall respond by sending a
40649 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40650 packet to solicit further responses; again, it is permitted to send
40651 other, unrelated packets as well which the stub should process
40654 If the stub receives a @var{ack} packet and there are no additional
40655 @var{event} to report, the stub shall return an @samp{OK} response.
40656 At this point, @value{GDBN} has finished processing a notification
40657 and the stub has completed sending any queued events. @value{GDBN}
40658 won't accept any new notifications until the final @samp{OK} is
40659 received . If further notification events occur, the stub shall send
40660 a new notification, @value{GDBN} shall accept the notification, and
40661 the process shall be repeated.
40663 The process of asynchronous notification can be illustrated by the
40666 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40669 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40671 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40676 The following notifications are defined:
40677 @multitable @columnfractions 0.12 0.12 0.38 0.38
40686 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40687 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40688 for information on how these notifications are acknowledged by
40690 @tab Report an asynchronous stop event in non-stop mode.
40694 @node Remote Non-Stop
40695 @section Remote Protocol Support for Non-Stop Mode
40697 @value{GDBN}'s remote protocol supports non-stop debugging of
40698 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40699 supports non-stop mode, it should report that to @value{GDBN} by including
40700 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40702 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40703 establishing a new connection with the stub. Entering non-stop mode
40704 does not alter the state of any currently-running threads, but targets
40705 must stop all threads in any already-attached processes when entering
40706 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40707 probe the target state after a mode change.
40709 In non-stop mode, when an attached process encounters an event that
40710 would otherwise be reported with a stop reply, it uses the
40711 asynchronous notification mechanism (@pxref{Notification Packets}) to
40712 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40713 in all processes are stopped when a stop reply is sent, in non-stop
40714 mode only the thread reporting the stop event is stopped. That is,
40715 when reporting a @samp{S} or @samp{T} response to indicate completion
40716 of a step operation, hitting a breakpoint, or a fault, only the
40717 affected thread is stopped; any other still-running threads continue
40718 to run. When reporting a @samp{W} or @samp{X} response, all running
40719 threads belonging to other attached processes continue to run.
40721 In non-stop mode, the target shall respond to the @samp{?} packet as
40722 follows. First, any incomplete stop reply notification/@samp{vStopped}
40723 sequence in progress is abandoned. The target must begin a new
40724 sequence reporting stop events for all stopped threads, whether or not
40725 it has previously reported those events to @value{GDBN}. The first
40726 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40727 subsequent stop replies are sent as responses to @samp{vStopped} packets
40728 using the mechanism described above. The target must not send
40729 asynchronous stop reply notifications until the sequence is complete.
40730 If all threads are running when the target receives the @samp{?} packet,
40731 or if the target is not attached to any process, it shall respond
40734 If the stub supports non-stop mode, it should also support the
40735 @samp{swbreak} stop reason if software breakpoints are supported, and
40736 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40737 (@pxref{swbreak stop reason}). This is because given the asynchronous
40738 nature of non-stop mode, between the time a thread hits a breakpoint
40739 and the time the event is finally processed by @value{GDBN}, the
40740 breakpoint may have already been removed from the target. Due to
40741 this, @value{GDBN} needs to be able to tell whether a trap stop was
40742 caused by a delayed breakpoint event, which should be ignored, as
40743 opposed to a random trap signal, which should be reported to the user.
40744 Note the @samp{swbreak} feature implies that the target is responsible
40745 for adjusting the PC when a software breakpoint triggers, if
40746 necessary, such as on the x86 architecture.
40748 @node Packet Acknowledgment
40749 @section Packet Acknowledgment
40751 @cindex acknowledgment, for @value{GDBN} remote
40752 @cindex packet acknowledgment, for @value{GDBN} remote
40753 By default, when either the host or the target machine receives a packet,
40754 the first response expected is an acknowledgment: either @samp{+} (to indicate
40755 the package was received correctly) or @samp{-} (to request retransmission).
40756 This mechanism allows the @value{GDBN} remote protocol to operate over
40757 unreliable transport mechanisms, such as a serial line.
40759 In cases where the transport mechanism is itself reliable (such as a pipe or
40760 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40761 It may be desirable to disable them in that case to reduce communication
40762 overhead, or for other reasons. This can be accomplished by means of the
40763 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40765 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40766 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40767 and response format still includes the normal checksum, as described in
40768 @ref{Overview}, but the checksum may be ignored by the receiver.
40770 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40771 no-acknowledgment mode, it should report that to @value{GDBN}
40772 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40773 @pxref{qSupported}.
40774 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40775 disabled via the @code{set remote noack-packet off} command
40776 (@pxref{Remote Configuration}),
40777 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40778 Only then may the stub actually turn off packet acknowledgments.
40779 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40780 response, which can be safely ignored by the stub.
40782 Note that @code{set remote noack-packet} command only affects negotiation
40783 between @value{GDBN} and the stub when subsequent connections are made;
40784 it does not affect the protocol acknowledgment state for any current
40786 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40787 new connection is established,
40788 there is also no protocol request to re-enable the acknowledgments
40789 for the current connection, once disabled.
40794 Example sequence of a target being re-started. Notice how the restart
40795 does not get any direct output:
40800 @emph{target restarts}
40803 <- @code{T001:1234123412341234}
40807 Example sequence of a target being stepped by a single instruction:
40810 -> @code{G1445@dots{}}
40815 <- @code{T001:1234123412341234}
40819 <- @code{1455@dots{}}
40823 @node File-I/O Remote Protocol Extension
40824 @section File-I/O Remote Protocol Extension
40825 @cindex File-I/O remote protocol extension
40828 * File-I/O Overview::
40829 * Protocol Basics::
40830 * The F Request Packet::
40831 * The F Reply Packet::
40832 * The Ctrl-C Message::
40834 * List of Supported Calls::
40835 * Protocol-specific Representation of Datatypes::
40837 * File-I/O Examples::
40840 @node File-I/O Overview
40841 @subsection File-I/O Overview
40842 @cindex file-i/o overview
40844 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40845 target to use the host's file system and console I/O to perform various
40846 system calls. System calls on the target system are translated into a
40847 remote protocol packet to the host system, which then performs the needed
40848 actions and returns a response packet to the target system.
40849 This simulates file system operations even on targets that lack file systems.
40851 The protocol is defined to be independent of both the host and target systems.
40852 It uses its own internal representation of datatypes and values. Both
40853 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40854 translating the system-dependent value representations into the internal
40855 protocol representations when data is transmitted.
40857 The communication is synchronous. A system call is possible only when
40858 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40859 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40860 the target is stopped to allow deterministic access to the target's
40861 memory. Therefore File-I/O is not interruptible by target signals. On
40862 the other hand, it is possible to interrupt File-I/O by a user interrupt
40863 (@samp{Ctrl-C}) within @value{GDBN}.
40865 The target's request to perform a host system call does not finish
40866 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40867 after finishing the system call, the target returns to continuing the
40868 previous activity (continue, step). No additional continue or step
40869 request from @value{GDBN} is required.
40872 (@value{GDBP}) continue
40873 <- target requests 'system call X'
40874 target is stopped, @value{GDBN} executes system call
40875 -> @value{GDBN} returns result
40876 ... target continues, @value{GDBN} returns to wait for the target
40877 <- target hits breakpoint and sends a Txx packet
40880 The protocol only supports I/O on the console and to regular files on
40881 the host file system. Character or block special devices, pipes,
40882 named pipes, sockets or any other communication method on the host
40883 system are not supported by this protocol.
40885 File I/O is not supported in non-stop mode.
40887 @node Protocol Basics
40888 @subsection Protocol Basics
40889 @cindex protocol basics, file-i/o
40891 The File-I/O protocol uses the @code{F} packet as the request as well
40892 as reply packet. Since a File-I/O system call can only occur when
40893 @value{GDBN} is waiting for a response from the continuing or stepping target,
40894 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40895 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40896 This @code{F} packet contains all information needed to allow @value{GDBN}
40897 to call the appropriate host system call:
40901 A unique identifier for the requested system call.
40904 All parameters to the system call. Pointers are given as addresses
40905 in the target memory address space. Pointers to strings are given as
40906 pointer/length pair. Numerical values are given as they are.
40907 Numerical control flags are given in a protocol-specific representation.
40911 At this point, @value{GDBN} has to perform the following actions.
40915 If the parameters include pointer values to data needed as input to a
40916 system call, @value{GDBN} requests this data from the target with a
40917 standard @code{m} packet request. This additional communication has to be
40918 expected by the target implementation and is handled as any other @code{m}
40922 @value{GDBN} translates all value from protocol representation to host
40923 representation as needed. Datatypes are coerced into the host types.
40926 @value{GDBN} calls the system call.
40929 It then coerces datatypes back to protocol representation.
40932 If the system call is expected to return data in buffer space specified
40933 by pointer parameters to the call, the data is transmitted to the
40934 target using a @code{M} or @code{X} packet. This packet has to be expected
40935 by the target implementation and is handled as any other @code{M} or @code{X}
40940 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40941 necessary information for the target to continue. This at least contains
40948 @code{errno}, if has been changed by the system call.
40955 After having done the needed type and value coercion, the target continues
40956 the latest continue or step action.
40958 @node The F Request Packet
40959 @subsection The @code{F} Request Packet
40960 @cindex file-i/o request packet
40961 @cindex @code{F} request packet
40963 The @code{F} request packet has the following format:
40966 @item F@var{call-id},@var{parameter@dots{}}
40968 @var{call-id} is the identifier to indicate the host system call to be called.
40969 This is just the name of the function.
40971 @var{parameter@dots{}} are the parameters to the system call.
40972 Parameters are hexadecimal integer values, either the actual values in case
40973 of scalar datatypes, pointers to target buffer space in case of compound
40974 datatypes and unspecified memory areas, or pointer/length pairs in case
40975 of string parameters. These are appended to the @var{call-id} as a
40976 comma-delimited list. All values are transmitted in ASCII
40977 string representation, pointer/length pairs separated by a slash.
40983 @node The F Reply Packet
40984 @subsection The @code{F} Reply Packet
40985 @cindex file-i/o reply packet
40986 @cindex @code{F} reply packet
40988 The @code{F} reply packet has the following format:
40992 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40994 @var{retcode} is the return code of the system call as hexadecimal value.
40996 @var{errno} is the @code{errno} set by the call, in protocol-specific
40998 This parameter can be omitted if the call was successful.
41000 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41001 case, @var{errno} must be sent as well, even if the call was successful.
41002 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41009 or, if the call was interrupted before the host call has been performed:
41016 assuming 4 is the protocol-specific representation of @code{EINTR}.
41021 @node The Ctrl-C Message
41022 @subsection The @samp{Ctrl-C} Message
41023 @cindex ctrl-c message, in file-i/o protocol
41025 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41026 reply packet (@pxref{The F Reply Packet}),
41027 the target should behave as if it had
41028 gotten a break message. The meaning for the target is ``system call
41029 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41030 (as with a break message) and return to @value{GDBN} with a @code{T02}
41033 It's important for the target to know in which
41034 state the system call was interrupted. There are two possible cases:
41038 The system call hasn't been performed on the host yet.
41041 The system call on the host has been finished.
41045 These two states can be distinguished by the target by the value of the
41046 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41047 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41048 on POSIX systems. In any other case, the target may presume that the
41049 system call has been finished --- successfully or not --- and should behave
41050 as if the break message arrived right after the system call.
41052 @value{GDBN} must behave reliably. If the system call has not been called
41053 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41054 @code{errno} in the packet. If the system call on the host has been finished
41055 before the user requests a break, the full action must be finished by
41056 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41057 The @code{F} packet may only be sent when either nothing has happened
41058 or the full action has been completed.
41061 @subsection Console I/O
41062 @cindex console i/o as part of file-i/o
41064 By default and if not explicitly closed by the target system, the file
41065 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41066 on the @value{GDBN} console is handled as any other file output operation
41067 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41068 by @value{GDBN} so that after the target read request from file descriptor
41069 0 all following typing is buffered until either one of the following
41074 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41076 system call is treated as finished.
41079 The user presses @key{RET}. This is treated as end of input with a trailing
41083 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41084 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41088 If the user has typed more characters than fit in the buffer given to
41089 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41090 either another @code{read(0, @dots{})} is requested by the target, or debugging
41091 is stopped at the user's request.
41094 @node List of Supported Calls
41095 @subsection List of Supported Calls
41096 @cindex list of supported file-i/o calls
41113 @unnumberedsubsubsec open
41114 @cindex open, file-i/o system call
41119 int open(const char *pathname, int flags);
41120 int open(const char *pathname, int flags, mode_t mode);
41124 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41127 @var{flags} is the bitwise @code{OR} of the following values:
41131 If the file does not exist it will be created. The host
41132 rules apply as far as file ownership and time stamps
41136 When used with @code{O_CREAT}, if the file already exists it is
41137 an error and open() fails.
41140 If the file already exists and the open mode allows
41141 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41142 truncated to zero length.
41145 The file is opened in append mode.
41148 The file is opened for reading only.
41151 The file is opened for writing only.
41154 The file is opened for reading and writing.
41158 Other bits are silently ignored.
41162 @var{mode} is the bitwise @code{OR} of the following values:
41166 User has read permission.
41169 User has write permission.
41172 Group has read permission.
41175 Group has write permission.
41178 Others have read permission.
41181 Others have write permission.
41185 Other bits are silently ignored.
41188 @item Return value:
41189 @code{open} returns the new file descriptor or -1 if an error
41196 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41199 @var{pathname} refers to a directory.
41202 The requested access is not allowed.
41205 @var{pathname} was too long.
41208 A directory component in @var{pathname} does not exist.
41211 @var{pathname} refers to a device, pipe, named pipe or socket.
41214 @var{pathname} refers to a file on a read-only filesystem and
41215 write access was requested.
41218 @var{pathname} is an invalid pointer value.
41221 No space on device to create the file.
41224 The process already has the maximum number of files open.
41227 The limit on the total number of files open on the system
41231 The call was interrupted by the user.
41237 @unnumberedsubsubsec close
41238 @cindex close, file-i/o system call
41247 @samp{Fclose,@var{fd}}
41249 @item Return value:
41250 @code{close} returns zero on success, or -1 if an error occurred.
41256 @var{fd} isn't a valid open file descriptor.
41259 The call was interrupted by the user.
41265 @unnumberedsubsubsec read
41266 @cindex read, file-i/o system call
41271 int read(int fd, void *buf, unsigned int count);
41275 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41277 @item Return value:
41278 On success, the number of bytes read is returned.
41279 Zero indicates end of file. If count is zero, read
41280 returns zero as well. On error, -1 is returned.
41286 @var{fd} is not a valid file descriptor or is not open for
41290 @var{bufptr} is an invalid pointer value.
41293 The call was interrupted by the user.
41299 @unnumberedsubsubsec write
41300 @cindex write, file-i/o system call
41305 int write(int fd, const void *buf, unsigned int count);
41309 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41311 @item Return value:
41312 On success, the number of bytes written are returned.
41313 Zero indicates nothing was written. On error, -1
41320 @var{fd} is not a valid file descriptor or is not open for
41324 @var{bufptr} is an invalid pointer value.
41327 An attempt was made to write a file that exceeds the
41328 host-specific maximum file size allowed.
41331 No space on device to write the data.
41334 The call was interrupted by the user.
41340 @unnumberedsubsubsec lseek
41341 @cindex lseek, file-i/o system call
41346 long lseek (int fd, long offset, int flag);
41350 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41352 @var{flag} is one of:
41356 The offset is set to @var{offset} bytes.
41359 The offset is set to its current location plus @var{offset}
41363 The offset is set to the size of the file plus @var{offset}
41367 @item Return value:
41368 On success, the resulting unsigned offset in bytes from
41369 the beginning of the file is returned. Otherwise, a
41370 value of -1 is returned.
41376 @var{fd} is not a valid open file descriptor.
41379 @var{fd} is associated with the @value{GDBN} console.
41382 @var{flag} is not a proper value.
41385 The call was interrupted by the user.
41391 @unnumberedsubsubsec rename
41392 @cindex rename, file-i/o system call
41397 int rename(const char *oldpath, const char *newpath);
41401 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41403 @item Return value:
41404 On success, zero is returned. On error, -1 is returned.
41410 @var{newpath} is an existing directory, but @var{oldpath} is not a
41414 @var{newpath} is a non-empty directory.
41417 @var{oldpath} or @var{newpath} is a directory that is in use by some
41421 An attempt was made to make a directory a subdirectory
41425 A component used as a directory in @var{oldpath} or new
41426 path is not a directory. Or @var{oldpath} is a directory
41427 and @var{newpath} exists but is not a directory.
41430 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41433 No access to the file or the path of the file.
41437 @var{oldpath} or @var{newpath} was too long.
41440 A directory component in @var{oldpath} or @var{newpath} does not exist.
41443 The file is on a read-only filesystem.
41446 The device containing the file has no room for the new
41450 The call was interrupted by the user.
41456 @unnumberedsubsubsec unlink
41457 @cindex unlink, file-i/o system call
41462 int unlink(const char *pathname);
41466 @samp{Funlink,@var{pathnameptr}/@var{len}}
41468 @item Return value:
41469 On success, zero is returned. On error, -1 is returned.
41475 No access to the file or the path of the file.
41478 The system does not allow unlinking of directories.
41481 The file @var{pathname} cannot be unlinked because it's
41482 being used by another process.
41485 @var{pathnameptr} is an invalid pointer value.
41488 @var{pathname} was too long.
41491 A directory component in @var{pathname} does not exist.
41494 A component of the path is not a directory.
41497 The file is on a read-only filesystem.
41500 The call was interrupted by the user.
41506 @unnumberedsubsubsec stat/fstat
41507 @cindex fstat, file-i/o system call
41508 @cindex stat, file-i/o system call
41513 int stat(const char *pathname, struct stat *buf);
41514 int fstat(int fd, struct stat *buf);
41518 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41519 @samp{Ffstat,@var{fd},@var{bufptr}}
41521 @item Return value:
41522 On success, zero is returned. On error, -1 is returned.
41528 @var{fd} is not a valid open file.
41531 A directory component in @var{pathname} does not exist or the
41532 path is an empty string.
41535 A component of the path is not a directory.
41538 @var{pathnameptr} is an invalid pointer value.
41541 No access to the file or the path of the file.
41544 @var{pathname} was too long.
41547 The call was interrupted by the user.
41553 @unnumberedsubsubsec gettimeofday
41554 @cindex gettimeofday, file-i/o system call
41559 int gettimeofday(struct timeval *tv, void *tz);
41563 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41565 @item Return value:
41566 On success, 0 is returned, -1 otherwise.
41572 @var{tz} is a non-NULL pointer.
41575 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41581 @unnumberedsubsubsec isatty
41582 @cindex isatty, file-i/o system call
41587 int isatty(int fd);
41591 @samp{Fisatty,@var{fd}}
41593 @item Return value:
41594 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41600 The call was interrupted by the user.
41605 Note that the @code{isatty} call is treated as a special case: it returns
41606 1 to the target if the file descriptor is attached
41607 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41608 would require implementing @code{ioctl} and would be more complex than
41613 @unnumberedsubsubsec system
41614 @cindex system, file-i/o system call
41619 int system(const char *command);
41623 @samp{Fsystem,@var{commandptr}/@var{len}}
41625 @item Return value:
41626 If @var{len} is zero, the return value indicates whether a shell is
41627 available. A zero return value indicates a shell is not available.
41628 For non-zero @var{len}, the value returned is -1 on error and the
41629 return status of the command otherwise. Only the exit status of the
41630 command is returned, which is extracted from the host's @code{system}
41631 return value by calling @code{WEXITSTATUS(retval)}. In case
41632 @file{/bin/sh} could not be executed, 127 is returned.
41638 The call was interrupted by the user.
41643 @value{GDBN} takes over the full task of calling the necessary host calls
41644 to perform the @code{system} call. The return value of @code{system} on
41645 the host is simplified before it's returned
41646 to the target. Any termination signal information from the child process
41647 is discarded, and the return value consists
41648 entirely of the exit status of the called command.
41650 Due to security concerns, the @code{system} call is by default refused
41651 by @value{GDBN}. The user has to allow this call explicitly with the
41652 @code{set remote system-call-allowed 1} command.
41655 @item set remote system-call-allowed
41656 @kindex set remote system-call-allowed
41657 Control whether to allow the @code{system} calls in the File I/O
41658 protocol for the remote target. The default is zero (disabled).
41660 @item show remote system-call-allowed
41661 @kindex show remote system-call-allowed
41662 Show whether the @code{system} calls are allowed in the File I/O
41666 @node Protocol-specific Representation of Datatypes
41667 @subsection Protocol-specific Representation of Datatypes
41668 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41671 * Integral Datatypes::
41673 * Memory Transfer::
41678 @node Integral Datatypes
41679 @unnumberedsubsubsec Integral Datatypes
41680 @cindex integral datatypes, in file-i/o protocol
41682 The integral datatypes used in the system calls are @code{int},
41683 @code{unsigned int}, @code{long}, @code{unsigned long},
41684 @code{mode_t}, and @code{time_t}.
41686 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41687 implemented as 32 bit values in this protocol.
41689 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41691 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41692 in @file{limits.h}) to allow range checking on host and target.
41694 @code{time_t} datatypes are defined as seconds since the Epoch.
41696 All integral datatypes transferred as part of a memory read or write of a
41697 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41700 @node Pointer Values
41701 @unnumberedsubsubsec Pointer Values
41702 @cindex pointer values, in file-i/o protocol
41704 Pointers to target data are transmitted as they are. An exception
41705 is made for pointers to buffers for which the length isn't
41706 transmitted as part of the function call, namely strings. Strings
41707 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41714 which is a pointer to data of length 18 bytes at position 0x1aaf.
41715 The length is defined as the full string length in bytes, including
41716 the trailing null byte. For example, the string @code{"hello world"}
41717 at address 0x123456 is transmitted as
41723 @node Memory Transfer
41724 @unnumberedsubsubsec Memory Transfer
41725 @cindex memory transfer, in file-i/o protocol
41727 Structured data which is transferred using a memory read or write (for
41728 example, a @code{struct stat}) is expected to be in a protocol-specific format
41729 with all scalar multibyte datatypes being big endian. Translation to
41730 this representation needs to be done both by the target before the @code{F}
41731 packet is sent, and by @value{GDBN} before
41732 it transfers memory to the target. Transferred pointers to structured
41733 data should point to the already-coerced data at any time.
41737 @unnumberedsubsubsec struct stat
41738 @cindex struct stat, in file-i/o protocol
41740 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41741 is defined as follows:
41745 unsigned int st_dev; /* device */
41746 unsigned int st_ino; /* inode */
41747 mode_t st_mode; /* protection */
41748 unsigned int st_nlink; /* number of hard links */
41749 unsigned int st_uid; /* user ID of owner */
41750 unsigned int st_gid; /* group ID of owner */
41751 unsigned int st_rdev; /* device type (if inode device) */
41752 unsigned long st_size; /* total size, in bytes */
41753 unsigned long st_blksize; /* blocksize for filesystem I/O */
41754 unsigned long st_blocks; /* number of blocks allocated */
41755 time_t st_atime; /* time of last access */
41756 time_t st_mtime; /* time of last modification */
41757 time_t st_ctime; /* time of last change */
41761 The integral datatypes conform to the definitions given in the
41762 appropriate section (see @ref{Integral Datatypes}, for details) so this
41763 structure is of size 64 bytes.
41765 The values of several fields have a restricted meaning and/or
41771 A value of 0 represents a file, 1 the console.
41774 No valid meaning for the target. Transmitted unchanged.
41777 Valid mode bits are described in @ref{Constants}. Any other
41778 bits have currently no meaning for the target.
41783 No valid meaning for the target. Transmitted unchanged.
41788 These values have a host and file system dependent
41789 accuracy. Especially on Windows hosts, the file system may not
41790 support exact timing values.
41793 The target gets a @code{struct stat} of the above representation and is
41794 responsible for coercing it to the target representation before
41797 Note that due to size differences between the host, target, and protocol
41798 representations of @code{struct stat} members, these members could eventually
41799 get truncated on the target.
41801 @node struct timeval
41802 @unnumberedsubsubsec struct timeval
41803 @cindex struct timeval, in file-i/o protocol
41805 The buffer of type @code{struct timeval} used by the File-I/O protocol
41806 is defined as follows:
41810 time_t tv_sec; /* second */
41811 long tv_usec; /* microsecond */
41815 The integral datatypes conform to the definitions given in the
41816 appropriate section (see @ref{Integral Datatypes}, for details) so this
41817 structure is of size 8 bytes.
41820 @subsection Constants
41821 @cindex constants, in file-i/o protocol
41823 The following values are used for the constants inside of the
41824 protocol. @value{GDBN} and target are responsible for translating these
41825 values before and after the call as needed.
41836 @unnumberedsubsubsec Open Flags
41837 @cindex open flags, in file-i/o protocol
41839 All values are given in hexadecimal representation.
41851 @node mode_t Values
41852 @unnumberedsubsubsec mode_t Values
41853 @cindex mode_t values, in file-i/o protocol
41855 All values are given in octal representation.
41872 @unnumberedsubsubsec Errno Values
41873 @cindex errno values, in file-i/o protocol
41875 All values are given in decimal representation.
41900 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41901 any error value not in the list of supported error numbers.
41904 @unnumberedsubsubsec Lseek Flags
41905 @cindex lseek flags, in file-i/o protocol
41914 @unnumberedsubsubsec Limits
41915 @cindex limits, in file-i/o protocol
41917 All values are given in decimal representation.
41920 INT_MIN -2147483648
41922 UINT_MAX 4294967295
41923 LONG_MIN -9223372036854775808
41924 LONG_MAX 9223372036854775807
41925 ULONG_MAX 18446744073709551615
41928 @node File-I/O Examples
41929 @subsection File-I/O Examples
41930 @cindex file-i/o examples
41932 Example sequence of a write call, file descriptor 3, buffer is at target
41933 address 0x1234, 6 bytes should be written:
41936 <- @code{Fwrite,3,1234,6}
41937 @emph{request memory read from target}
41940 @emph{return "6 bytes written"}
41944 Example sequence of a read call, file descriptor 3, buffer is at target
41945 address 0x1234, 6 bytes should be read:
41948 <- @code{Fread,3,1234,6}
41949 @emph{request memory write to target}
41950 -> @code{X1234,6:XXXXXX}
41951 @emph{return "6 bytes read"}
41955 Example sequence of a read call, call fails on the host due to invalid
41956 file descriptor (@code{EBADF}):
41959 <- @code{Fread,3,1234,6}
41963 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41967 <- @code{Fread,3,1234,6}
41972 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41976 <- @code{Fread,3,1234,6}
41977 -> @code{X1234,6:XXXXXX}
41981 @node Library List Format
41982 @section Library List Format
41983 @cindex library list format, remote protocol
41985 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41986 same process as your application to manage libraries. In this case,
41987 @value{GDBN} can use the loader's symbol table and normal memory
41988 operations to maintain a list of shared libraries. On other
41989 platforms, the operating system manages loaded libraries.
41990 @value{GDBN} can not retrieve the list of currently loaded libraries
41991 through memory operations, so it uses the @samp{qXfer:libraries:read}
41992 packet (@pxref{qXfer library list read}) instead. The remote stub
41993 queries the target's operating system and reports which libraries
41996 The @samp{qXfer:libraries:read} packet returns an XML document which
41997 lists loaded libraries and their offsets. Each library has an
41998 associated name and one or more segment or section base addresses,
41999 which report where the library was loaded in memory.
42001 For the common case of libraries that are fully linked binaries, the
42002 library should have a list of segments. If the target supports
42003 dynamic linking of a relocatable object file, its library XML element
42004 should instead include a list of allocated sections. The segment or
42005 section bases are start addresses, not relocation offsets; they do not
42006 depend on the library's link-time base addresses.
42008 @value{GDBN} must be linked with the Expat library to support XML
42009 library lists. @xref{Expat}.
42011 A simple memory map, with one loaded library relocated by a single
42012 offset, looks like this:
42016 <library name="/lib/libc.so.6">
42017 <segment address="0x10000000"/>
42022 Another simple memory map, with one loaded library with three
42023 allocated sections (.text, .data, .bss), looks like this:
42027 <library name="sharedlib.o">
42028 <section address="0x10000000"/>
42029 <section address="0x20000000"/>
42030 <section address="0x30000000"/>
42035 The format of a library list is described by this DTD:
42038 <!-- library-list: Root element with versioning -->
42039 <!ELEMENT library-list (library)*>
42040 <!ATTLIST library-list version CDATA #FIXED "1.0">
42041 <!ELEMENT library (segment*, section*)>
42042 <!ATTLIST library name CDATA #REQUIRED>
42043 <!ELEMENT segment EMPTY>
42044 <!ATTLIST segment address CDATA #REQUIRED>
42045 <!ELEMENT section EMPTY>
42046 <!ATTLIST section address CDATA #REQUIRED>
42049 In addition, segments and section descriptors cannot be mixed within a
42050 single library element, and you must supply at least one segment or
42051 section for each library.
42053 @node Library List Format for SVR4 Targets
42054 @section Library List Format for SVR4 Targets
42055 @cindex library list format, remote protocol
42057 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42058 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42059 shared libraries. Still a special library list provided by this packet is
42060 more efficient for the @value{GDBN} remote protocol.
42062 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42063 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42064 target, the following parameters are reported:
42068 @code{name}, the absolute file name from the @code{l_name} field of
42069 @code{struct link_map}.
42071 @code{lm} with address of @code{struct link_map} used for TLS
42072 (Thread Local Storage) access.
42074 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42075 @code{struct link_map}. For prelinked libraries this is not an absolute
42076 memory address. It is a displacement of absolute memory address against
42077 address the file was prelinked to during the library load.
42079 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42082 Additionally the single @code{main-lm} attribute specifies address of
42083 @code{struct link_map} used for the main executable. This parameter is used
42084 for TLS access and its presence is optional.
42086 @value{GDBN} must be linked with the Expat library to support XML
42087 SVR4 library lists. @xref{Expat}.
42089 A simple memory map, with two loaded libraries (which do not use prelink),
42093 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42094 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42096 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42098 </library-list-svr>
42101 The format of an SVR4 library list is described by this DTD:
42104 <!-- library-list-svr4: Root element with versioning -->
42105 <!ELEMENT library-list-svr4 (library)*>
42106 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42107 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42108 <!ELEMENT library EMPTY>
42109 <!ATTLIST library name CDATA #REQUIRED>
42110 <!ATTLIST library lm CDATA #REQUIRED>
42111 <!ATTLIST library l_addr CDATA #REQUIRED>
42112 <!ATTLIST library l_ld CDATA #REQUIRED>
42115 @node Memory Map Format
42116 @section Memory Map Format
42117 @cindex memory map format
42119 To be able to write into flash memory, @value{GDBN} needs to obtain a
42120 memory map from the target. This section describes the format of the
42123 The memory map is obtained using the @samp{qXfer:memory-map:read}
42124 (@pxref{qXfer memory map read}) packet and is an XML document that
42125 lists memory regions.
42127 @value{GDBN} must be linked with the Expat library to support XML
42128 memory maps. @xref{Expat}.
42130 The top-level structure of the document is shown below:
42133 <?xml version="1.0"?>
42134 <!DOCTYPE memory-map
42135 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42136 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42142 Each region can be either:
42147 A region of RAM starting at @var{addr} and extending for @var{length}
42151 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42156 A region of read-only memory:
42159 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42164 A region of flash memory, with erasure blocks @var{blocksize}
42168 <memory type="flash" start="@var{addr}" length="@var{length}">
42169 <property name="blocksize">@var{blocksize}</property>
42175 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42176 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42177 packets to write to addresses in such ranges.
42179 The formal DTD for memory map format is given below:
42182 <!-- ................................................... -->
42183 <!-- Memory Map XML DTD ................................ -->
42184 <!-- File: memory-map.dtd .............................. -->
42185 <!-- .................................... .............. -->
42186 <!-- memory-map.dtd -->
42187 <!-- memory-map: Root element with versioning -->
42188 <!ELEMENT memory-map (memory)*>
42189 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42190 <!ELEMENT memory (property)*>
42191 <!-- memory: Specifies a memory region,
42192 and its type, or device. -->
42193 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42194 start CDATA #REQUIRED
42195 length CDATA #REQUIRED>
42196 <!-- property: Generic attribute tag -->
42197 <!ELEMENT property (#PCDATA | property)*>
42198 <!ATTLIST property name (blocksize) #REQUIRED>
42201 @node Thread List Format
42202 @section Thread List Format
42203 @cindex thread list format
42205 To efficiently update the list of threads and their attributes,
42206 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42207 (@pxref{qXfer threads read}) and obtains the XML document with
42208 the following structure:
42211 <?xml version="1.0"?>
42213 <thread id="id" core="0" name="name">
42214 ... description ...
42219 Each @samp{thread} element must have the @samp{id} attribute that
42220 identifies the thread (@pxref{thread-id syntax}). The
42221 @samp{core} attribute, if present, specifies which processor core
42222 the thread was last executing on. The @samp{name} attribute, if
42223 present, specifies the human-readable name of the thread. The content
42224 of the of @samp{thread} element is interpreted as human-readable
42225 auxiliary information. The @samp{handle} attribute, if present,
42226 is a hex encoded representation of the thread handle.
42229 @node Traceframe Info Format
42230 @section Traceframe Info Format
42231 @cindex traceframe info format
42233 To be able to know which objects in the inferior can be examined when
42234 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42235 memory ranges, registers and trace state variables that have been
42236 collected in a traceframe.
42238 This list is obtained using the @samp{qXfer:traceframe-info:read}
42239 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42241 @value{GDBN} must be linked with the Expat library to support XML
42242 traceframe info discovery. @xref{Expat}.
42244 The top-level structure of the document is shown below:
42247 <?xml version="1.0"?>
42248 <!DOCTYPE traceframe-info
42249 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42250 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42256 Each traceframe block can be either:
42261 A region of collected memory starting at @var{addr} and extending for
42262 @var{length} bytes from there:
42265 <memory start="@var{addr}" length="@var{length}"/>
42269 A block indicating trace state variable numbered @var{number} has been
42273 <tvar id="@var{number}"/>
42278 The formal DTD for the traceframe info format is given below:
42281 <!ELEMENT traceframe-info (memory | tvar)* >
42282 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42284 <!ELEMENT memory EMPTY>
42285 <!ATTLIST memory start CDATA #REQUIRED
42286 length CDATA #REQUIRED>
42288 <!ATTLIST tvar id CDATA #REQUIRED>
42291 @node Branch Trace Format
42292 @section Branch Trace Format
42293 @cindex branch trace format
42295 In order to display the branch trace of an inferior thread,
42296 @value{GDBN} needs to obtain the list of branches. This list is
42297 represented as list of sequential code blocks that are connected via
42298 branches. The code in each block has been executed sequentially.
42300 This list is obtained using the @samp{qXfer:btrace:read}
42301 (@pxref{qXfer btrace read}) packet and is an XML document.
42303 @value{GDBN} must be linked with the Expat library to support XML
42304 traceframe info discovery. @xref{Expat}.
42306 The top-level structure of the document is shown below:
42309 <?xml version="1.0"?>
42311 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42312 "http://sourceware.org/gdb/gdb-btrace.dtd">
42321 A block of sequentially executed instructions starting at @var{begin}
42322 and ending at @var{end}:
42325 <block begin="@var{begin}" end="@var{end}"/>
42330 The formal DTD for the branch trace format is given below:
42333 <!ELEMENT btrace (block* | pt) >
42334 <!ATTLIST btrace version CDATA #FIXED "1.0">
42336 <!ELEMENT block EMPTY>
42337 <!ATTLIST block begin CDATA #REQUIRED
42338 end CDATA #REQUIRED>
42340 <!ELEMENT pt (pt-config?, raw?)>
42342 <!ELEMENT pt-config (cpu?)>
42344 <!ELEMENT cpu EMPTY>
42345 <!ATTLIST cpu vendor CDATA #REQUIRED
42346 family CDATA #REQUIRED
42347 model CDATA #REQUIRED
42348 stepping CDATA #REQUIRED>
42350 <!ELEMENT raw (#PCDATA)>
42353 @node Branch Trace Configuration Format
42354 @section Branch Trace Configuration Format
42355 @cindex branch trace configuration format
42357 For each inferior thread, @value{GDBN} can obtain the branch trace
42358 configuration using the @samp{qXfer:btrace-conf:read}
42359 (@pxref{qXfer btrace-conf read}) packet.
42361 The configuration describes the branch trace format and configuration
42362 settings for that format. The following information is described:
42366 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42369 The size of the @acronym{BTS} ring buffer in bytes.
42372 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42376 The size of the @acronym{Intel PT} ring buffer in bytes.
42380 @value{GDBN} must be linked with the Expat library to support XML
42381 branch trace configuration discovery. @xref{Expat}.
42383 The formal DTD for the branch trace configuration format is given below:
42386 <!ELEMENT btrace-conf (bts?, pt?)>
42387 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42389 <!ELEMENT bts EMPTY>
42390 <!ATTLIST bts size CDATA #IMPLIED>
42392 <!ELEMENT pt EMPTY>
42393 <!ATTLIST pt size CDATA #IMPLIED>
42396 @include agentexpr.texi
42398 @node Target Descriptions
42399 @appendix Target Descriptions
42400 @cindex target descriptions
42402 One of the challenges of using @value{GDBN} to debug embedded systems
42403 is that there are so many minor variants of each processor
42404 architecture in use. It is common practice for vendors to start with
42405 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42406 and then make changes to adapt it to a particular market niche. Some
42407 architectures have hundreds of variants, available from dozens of
42408 vendors. This leads to a number of problems:
42412 With so many different customized processors, it is difficult for
42413 the @value{GDBN} maintainers to keep up with the changes.
42415 Since individual variants may have short lifetimes or limited
42416 audiences, it may not be worthwhile to carry information about every
42417 variant in the @value{GDBN} source tree.
42419 When @value{GDBN} does support the architecture of the embedded system
42420 at hand, the task of finding the correct architecture name to give the
42421 @command{set architecture} command can be error-prone.
42424 To address these problems, the @value{GDBN} remote protocol allows a
42425 target system to not only identify itself to @value{GDBN}, but to
42426 actually describe its own features. This lets @value{GDBN} support
42427 processor variants it has never seen before --- to the extent that the
42428 descriptions are accurate, and that @value{GDBN} understands them.
42430 @value{GDBN} must be linked with the Expat library to support XML
42431 target descriptions. @xref{Expat}.
42434 * Retrieving Descriptions:: How descriptions are fetched from a target.
42435 * Target Description Format:: The contents of a target description.
42436 * Predefined Target Types:: Standard types available for target
42438 * Enum Target Types:: How to define enum target types.
42439 * Standard Target Features:: Features @value{GDBN} knows about.
42442 @node Retrieving Descriptions
42443 @section Retrieving Descriptions
42445 Target descriptions can be read from the target automatically, or
42446 specified by the user manually. The default behavior is to read the
42447 description from the target. @value{GDBN} retrieves it via the remote
42448 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42449 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42450 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42451 XML document, of the form described in @ref{Target Description
42454 Alternatively, you can specify a file to read for the target description.
42455 If a file is set, the target will not be queried. The commands to
42456 specify a file are:
42459 @cindex set tdesc filename
42460 @item set tdesc filename @var{path}
42461 Read the target description from @var{path}.
42463 @cindex unset tdesc filename
42464 @item unset tdesc filename
42465 Do not read the XML target description from a file. @value{GDBN}
42466 will use the description supplied by the current target.
42468 @cindex show tdesc filename
42469 @item show tdesc filename
42470 Show the filename to read for a target description, if any.
42474 @node Target Description Format
42475 @section Target Description Format
42476 @cindex target descriptions, XML format
42478 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42479 document which complies with the Document Type Definition provided in
42480 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42481 means you can use generally available tools like @command{xmllint} to
42482 check that your feature descriptions are well-formed and valid.
42483 However, to help people unfamiliar with XML write descriptions for
42484 their targets, we also describe the grammar here.
42486 Target descriptions can identify the architecture of the remote target
42487 and (for some architectures) provide information about custom register
42488 sets. They can also identify the OS ABI of the remote target.
42489 @value{GDBN} can use this information to autoconfigure for your
42490 target, or to warn you if you connect to an unsupported target.
42492 Here is a simple target description:
42495 <target version="1.0">
42496 <architecture>i386:x86-64</architecture>
42501 This minimal description only says that the target uses
42502 the x86-64 architecture.
42504 A target description has the following overall form, with [ ] marking
42505 optional elements and @dots{} marking repeatable elements. The elements
42506 are explained further below.
42509 <?xml version="1.0"?>
42510 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42511 <target version="1.0">
42512 @r{[}@var{architecture}@r{]}
42513 @r{[}@var{osabi}@r{]}
42514 @r{[}@var{compatible}@r{]}
42515 @r{[}@var{feature}@dots{}@r{]}
42520 The description is generally insensitive to whitespace and line
42521 breaks, under the usual common-sense rules. The XML version
42522 declaration and document type declaration can generally be omitted
42523 (@value{GDBN} does not require them), but specifying them may be
42524 useful for XML validation tools. The @samp{version} attribute for
42525 @samp{<target>} may also be omitted, but we recommend
42526 including it; if future versions of @value{GDBN} use an incompatible
42527 revision of @file{gdb-target.dtd}, they will detect and report
42528 the version mismatch.
42530 @subsection Inclusion
42531 @cindex target descriptions, inclusion
42534 @cindex <xi:include>
42537 It can sometimes be valuable to split a target description up into
42538 several different annexes, either for organizational purposes, or to
42539 share files between different possible target descriptions. You can
42540 divide a description into multiple files by replacing any element of
42541 the target description with an inclusion directive of the form:
42544 <xi:include href="@var{document}"/>
42548 When @value{GDBN} encounters an element of this form, it will retrieve
42549 the named XML @var{document}, and replace the inclusion directive with
42550 the contents of that document. If the current description was read
42551 using @samp{qXfer}, then so will be the included document;
42552 @var{document} will be interpreted as the name of an annex. If the
42553 current description was read from a file, @value{GDBN} will look for
42554 @var{document} as a file in the same directory where it found the
42555 original description.
42557 @subsection Architecture
42558 @cindex <architecture>
42560 An @samp{<architecture>} element has this form:
42563 <architecture>@var{arch}</architecture>
42566 @var{arch} is one of the architectures from the set accepted by
42567 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42570 @cindex @code{<osabi>}
42572 This optional field was introduced in @value{GDBN} version 7.0.
42573 Previous versions of @value{GDBN} ignore it.
42575 An @samp{<osabi>} element has this form:
42578 <osabi>@var{abi-name}</osabi>
42581 @var{abi-name} is an OS ABI name from the same selection accepted by
42582 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42584 @subsection Compatible Architecture
42585 @cindex @code{<compatible>}
42587 This optional field was introduced in @value{GDBN} version 7.0.
42588 Previous versions of @value{GDBN} ignore it.
42590 A @samp{<compatible>} element has this form:
42593 <compatible>@var{arch}</compatible>
42596 @var{arch} is one of the architectures from the set accepted by
42597 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42599 A @samp{<compatible>} element is used to specify that the target
42600 is able to run binaries in some other than the main target architecture
42601 given by the @samp{<architecture>} element. For example, on the
42602 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42603 or @code{powerpc:common64}, but the system is able to run binaries
42604 in the @code{spu} architecture as well. The way to describe this
42605 capability with @samp{<compatible>} is as follows:
42608 <architecture>powerpc:common</architecture>
42609 <compatible>spu</compatible>
42612 @subsection Features
42615 Each @samp{<feature>} describes some logical portion of the target
42616 system. Features are currently used to describe available CPU
42617 registers and the types of their contents. A @samp{<feature>} element
42621 <feature name="@var{name}">
42622 @r{[}@var{type}@dots{}@r{]}
42628 Each feature's name should be unique within the description. The name
42629 of a feature does not matter unless @value{GDBN} has some special
42630 knowledge of the contents of that feature; if it does, the feature
42631 should have its standard name. @xref{Standard Target Features}.
42635 Any register's value is a collection of bits which @value{GDBN} must
42636 interpret. The default interpretation is a two's complement integer,
42637 but other types can be requested by name in the register description.
42638 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42639 Target Types}), and the description can define additional composite
42642 Each type element must have an @samp{id} attribute, which gives
42643 a unique (within the containing @samp{<feature>}) name to the type.
42644 Types must be defined before they are used.
42647 Some targets offer vector registers, which can be treated as arrays
42648 of scalar elements. These types are written as @samp{<vector>} elements,
42649 specifying the array element type, @var{type}, and the number of elements,
42653 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42657 If a register's value is usefully viewed in multiple ways, define it
42658 with a union type containing the useful representations. The
42659 @samp{<union>} element contains one or more @samp{<field>} elements,
42660 each of which has a @var{name} and a @var{type}:
42663 <union id="@var{id}">
42664 <field name="@var{name}" type="@var{type}"/>
42671 If a register's value is composed from several separate values, define
42672 it with either a structure type or a flags type.
42673 A flags type may only contain bitfields.
42674 A structure type may either contain only bitfields or contain no bitfields.
42675 If the value contains only bitfields, its total size in bytes must be
42678 Non-bitfield values have a @var{name} and @var{type}.
42681 <struct id="@var{id}">
42682 <field name="@var{name}" type="@var{type}"/>
42687 Both @var{name} and @var{type} values are required.
42688 No implicit padding is added.
42690 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42693 <struct id="@var{id}" size="@var{size}">
42694 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42700 <flags id="@var{id}" size="@var{size}">
42701 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42706 The @var{name} value is required.
42707 Bitfield values may be named with the empty string, @samp{""},
42708 in which case the field is ``filler'' and its value is not printed.
42709 Not all bits need to be specified, so ``filler'' fields are optional.
42711 The @var{start} and @var{end} values are required, and @var{type}
42713 The field's @var{start} must be less than or equal to its @var{end},
42714 and zero represents the least significant bit.
42716 The default value of @var{type} is @code{bool} for single bit fields,
42717 and an unsigned integer otherwise.
42719 Which to choose? Structures or flags?
42721 Registers defined with @samp{flags} have these advantages over
42722 defining them with @samp{struct}:
42726 Arithmetic may be performed on them as if they were integers.
42728 They are printed in a more readable fashion.
42731 Registers defined with @samp{struct} have one advantage over
42732 defining them with @samp{flags}:
42736 One can fetch individual fields like in @samp{C}.
42739 (gdb) print $my_struct_reg.field3
42745 @subsection Registers
42748 Each register is represented as an element with this form:
42751 <reg name="@var{name}"
42752 bitsize="@var{size}"
42753 @r{[}regnum="@var{num}"@r{]}
42754 @r{[}save-restore="@var{save-restore}"@r{]}
42755 @r{[}type="@var{type}"@r{]}
42756 @r{[}group="@var{group}"@r{]}/>
42760 The components are as follows:
42765 The register's name; it must be unique within the target description.
42768 The register's size, in bits.
42771 The register's number. If omitted, a register's number is one greater
42772 than that of the previous register (either in the current feature or in
42773 a preceding feature); the first register in the target description
42774 defaults to zero. This register number is used to read or write
42775 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42776 packets, and registers appear in the @code{g} and @code{G} packets
42777 in order of increasing register number.
42780 Whether the register should be preserved across inferior function
42781 calls; this must be either @code{yes} or @code{no}. The default is
42782 @code{yes}, which is appropriate for most registers except for
42783 some system control registers; this is not related to the target's
42787 The type of the register. It may be a predefined type, a type
42788 defined in the current feature, or one of the special types @code{int}
42789 and @code{float}. @code{int} is an integer type of the correct size
42790 for @var{bitsize}, and @code{float} is a floating point type (in the
42791 architecture's normal floating point format) of the correct size for
42792 @var{bitsize}. The default is @code{int}.
42795 The register group to which this register belongs. It can be one of the
42796 standard register groups @code{general}, @code{float}, @code{vector} or an
42797 arbitrary string. Group names should be limited to alphanumeric characters.
42798 If a group name is made up of multiple words the words may be separated by
42799 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42800 @var{group} is specified, @value{GDBN} will not display the register in
42801 @code{info registers}.
42805 @node Predefined Target Types
42806 @section Predefined Target Types
42807 @cindex target descriptions, predefined types
42809 Type definitions in the self-description can build up composite types
42810 from basic building blocks, but can not define fundamental types. Instead,
42811 standard identifiers are provided by @value{GDBN} for the fundamental
42812 types. The currently supported types are:
42817 Boolean type, occupying a single bit.
42825 Signed integer types holding the specified number of bits.
42833 Unsigned integer types holding the specified number of bits.
42837 Pointers to unspecified code and data. The program counter and
42838 any dedicated return address register may be marked as code
42839 pointers; printing a code pointer converts it into a symbolic
42840 address. The stack pointer and any dedicated address registers
42841 may be marked as data pointers.
42844 Single precision IEEE floating point.
42847 Double precision IEEE floating point.
42850 The 12-byte extended precision format used by ARM FPA registers.
42853 The 10-byte extended precision format used by x87 registers.
42856 32bit @sc{eflags} register used by x86.
42859 32bit @sc{mxcsr} register used by x86.
42863 @node Enum Target Types
42864 @section Enum Target Types
42865 @cindex target descriptions, enum types
42867 Enum target types are useful in @samp{struct} and @samp{flags}
42868 register descriptions. @xref{Target Description Format}.
42870 Enum types have a name, size and a list of name/value pairs.
42873 <enum id="@var{id}" size="@var{size}">
42874 <evalue name="@var{name}" value="@var{value}"/>
42879 Enums must be defined before they are used.
42882 <enum id="levels_type" size="4">
42883 <evalue name="low" value="0"/>
42884 <evalue name="high" value="1"/>
42886 <flags id="flags_type" size="4">
42887 <field name="X" start="0"/>
42888 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42890 <reg name="flags" bitsize="32" type="flags_type"/>
42893 Given that description, a value of 3 for the @samp{flags} register
42894 would be printed as:
42897 (gdb) info register flags
42898 flags 0x3 [ X LEVEL=high ]
42901 @node Standard Target Features
42902 @section Standard Target Features
42903 @cindex target descriptions, standard features
42905 A target description must contain either no registers or all the
42906 target's registers. If the description contains no registers, then
42907 @value{GDBN} will assume a default register layout, selected based on
42908 the architecture. If the description contains any registers, the
42909 default layout will not be used; the standard registers must be
42910 described in the target description, in such a way that @value{GDBN}
42911 can recognize them.
42913 This is accomplished by giving specific names to feature elements
42914 which contain standard registers. @value{GDBN} will look for features
42915 with those names and verify that they contain the expected registers;
42916 if any known feature is missing required registers, or if any required
42917 feature is missing, @value{GDBN} will reject the target
42918 description. You can add additional registers to any of the
42919 standard features --- @value{GDBN} will display them just as if
42920 they were added to an unrecognized feature.
42922 This section lists the known features and their expected contents.
42923 Sample XML documents for these features are included in the
42924 @value{GDBN} source tree, in the directory @file{gdb/features}.
42926 Names recognized by @value{GDBN} should include the name of the
42927 company or organization which selected the name, and the overall
42928 architecture to which the feature applies; so e.g.@: the feature
42929 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42931 The names of registers are not case sensitive for the purpose
42932 of recognizing standard features, but @value{GDBN} will only display
42933 registers using the capitalization used in the description.
42936 * AArch64 Features::
42940 * MicroBlaze Features::
42944 * Nios II Features::
42945 * OpenRISC 1000 Features::
42946 * PowerPC Features::
42947 * RISC-V Features::
42948 * S/390 and System z Features::
42954 @node AArch64 Features
42955 @subsection AArch64 Features
42956 @cindex target descriptions, AArch64 features
42958 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42959 targets. It should contain registers @samp{x0} through @samp{x30},
42960 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42962 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42963 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42966 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42967 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42968 through @samp{p15}, @samp{ffr} and @samp{vg}.
42971 @subsection ARC Features
42972 @cindex target descriptions, ARC Features
42974 ARC processors are highly configurable, so even core registers and their number
42975 are not completely predetermined. In addition flags and PC registers which are
42976 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42977 that one of the core registers features is present.
42978 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42980 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42981 targets with a normal register file. It should contain registers @samp{r0}
42982 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42983 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42984 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42985 @samp{ilink} and extension core registers are not available to read/write, when
42986 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42988 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42989 ARC HS targets with a reduced register file. It should contain registers
42990 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42991 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42992 This feature may contain register @samp{ilink} and any of extension core
42993 registers @samp{r32} through @samp{r59/acch}.
42995 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42996 targets with a normal register file. It should contain registers @samp{r0}
42997 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42998 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42999 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43000 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43001 registers are not available when debugging GNU/Linux applications. The only
43002 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43003 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43004 ARC v2, but @samp{ilink2} is optional on ARCompact.
43006 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43007 targets. It should contain registers @samp{pc} and @samp{status32}.
43010 @subsection ARM Features
43011 @cindex target descriptions, ARM features
43013 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43015 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43016 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43018 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43019 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43020 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43023 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43024 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43026 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43027 it should contain at least registers @samp{wR0} through @samp{wR15} and
43028 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43029 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43031 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43032 should contain at least registers @samp{d0} through @samp{d15}. If
43033 they are present, @samp{d16} through @samp{d31} should also be included.
43034 @value{GDBN} will synthesize the single-precision registers from
43035 halves of the double-precision registers.
43037 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43038 need to contain registers; it instructs @value{GDBN} to display the
43039 VFP double-precision registers as vectors and to synthesize the
43040 quad-precision registers from pairs of double-precision registers.
43041 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43042 be present and include 32 double-precision registers.
43044 @node i386 Features
43045 @subsection i386 Features
43046 @cindex target descriptions, i386 features
43048 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43049 targets. It should describe the following registers:
43053 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43055 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43057 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43058 @samp{fs}, @samp{gs}
43060 @samp{st0} through @samp{st7}
43062 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43063 @samp{foseg}, @samp{fooff} and @samp{fop}
43066 The register sets may be different, depending on the target.
43068 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43069 describe registers:
43073 @samp{xmm0} through @samp{xmm7} for i386
43075 @samp{xmm0} through @samp{xmm15} for amd64
43080 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43081 @samp{org.gnu.gdb.i386.sse} feature. It should
43082 describe the upper 128 bits of @sc{ymm} registers:
43086 @samp{ymm0h} through @samp{ymm7h} for i386
43088 @samp{ymm0h} through @samp{ymm15h} for amd64
43091 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43092 Memory Protection Extension (MPX). It should describe the following registers:
43096 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43098 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43101 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43102 describe a single register, @samp{orig_eax}.
43104 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43105 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43107 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43108 @samp{org.gnu.gdb.i386.avx} feature. It should
43109 describe additional @sc{xmm} registers:
43113 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43116 It should describe the upper 128 bits of additional @sc{ymm} registers:
43120 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43124 describe the upper 256 bits of @sc{zmm} registers:
43128 @samp{zmm0h} through @samp{zmm7h} for i386.
43130 @samp{zmm0h} through @samp{zmm15h} for amd64.
43134 describe the additional @sc{zmm} registers:
43138 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43141 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43142 describe a single register, @samp{pkru}. It is a 32-bit register
43143 valid for i386 and amd64.
43145 @node MicroBlaze Features
43146 @subsection MicroBlaze Features
43147 @cindex target descriptions, MicroBlaze features
43149 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43150 targets. It should contain registers @samp{r0} through @samp{r31},
43151 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43152 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43153 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43155 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43156 If present, it should contain registers @samp{rshr} and @samp{rslr}
43158 @node MIPS Features
43159 @subsection @acronym{MIPS} Features
43160 @cindex target descriptions, @acronym{MIPS} features
43162 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43163 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43164 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43167 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43168 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43169 registers. They may be 32-bit or 64-bit depending on the target.
43171 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43172 it may be optional in a future version of @value{GDBN}. It should
43173 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43174 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43176 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43177 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43178 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43179 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43181 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43182 contain a single register, @samp{restart}, which is used by the
43183 Linux kernel to control restartable syscalls.
43185 @node M68K Features
43186 @subsection M68K Features
43187 @cindex target descriptions, M68K features
43190 @item @samp{org.gnu.gdb.m68k.core}
43191 @itemx @samp{org.gnu.gdb.coldfire.core}
43192 @itemx @samp{org.gnu.gdb.fido.core}
43193 One of those features must be always present.
43194 The feature that is present determines which flavor of m68k is
43195 used. The feature that is present should contain registers
43196 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43197 @samp{sp}, @samp{ps} and @samp{pc}.
43199 @item @samp{org.gnu.gdb.coldfire.fp}
43200 This feature is optional. If present, it should contain registers
43201 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43205 @node NDS32 Features
43206 @subsection NDS32 Features
43207 @cindex target descriptions, NDS32 features
43209 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43210 targets. It should contain at least registers @samp{r0} through
43211 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43214 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43215 it should contain 64-bit double-precision floating-point registers
43216 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43217 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43219 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43220 registers are overlapped with the thirty-two 32-bit single-precision
43221 floating-point registers. The 32-bit single-precision registers, if
43222 not being listed explicitly, will be synthesized from halves of the
43223 overlapping 64-bit double-precision registers. Listing 32-bit
43224 single-precision registers explicitly is deprecated, and the
43225 support to it could be totally removed some day.
43227 @node Nios II Features
43228 @subsection Nios II Features
43229 @cindex target descriptions, Nios II features
43231 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43232 targets. It should contain the 32 core registers (@samp{zero},
43233 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43234 @samp{pc}, and the 16 control registers (@samp{status} through
43237 @node OpenRISC 1000 Features
43238 @subsection Openrisc 1000 Features
43239 @cindex target descriptions, OpenRISC 1000 features
43241 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43242 targets. It should contain the 32 general purpose registers (@samp{r0}
43243 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43245 @node PowerPC Features
43246 @subsection PowerPC Features
43247 @cindex target descriptions, PowerPC features
43249 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43250 targets. It should contain registers @samp{r0} through @samp{r31},
43251 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43252 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43254 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43255 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43257 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43258 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43261 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43262 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43263 combine these registers with the floating point registers (@samp{f0}
43264 through @samp{f31}) and the altivec registers (@samp{vr0} through
43265 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43266 @samp{vs63}, the set of vector-scalar registers for POWER7.
43267 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43268 @samp{org.gnu.gdb.power.altivec}.
43270 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43271 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43272 @samp{spefscr}. SPE targets should provide 32-bit registers in
43273 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43274 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43275 these to present registers @samp{ev0} through @samp{ev31} to the
43278 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43279 contain the 64-bit register @samp{ppr}.
43281 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43282 contain the 64-bit register @samp{dscr}.
43284 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43285 contain the 64-bit register @samp{tar}.
43287 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43288 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43291 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43292 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43293 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43294 server PMU registers provided by @sc{gnu}/Linux.
43296 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43297 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43300 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43301 contain the checkpointed general-purpose registers @samp{cr0} through
43302 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43303 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43304 depending on the target. It should also contain the checkpointed
43305 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43308 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43309 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43310 through @samp{cf31}, as well as the checkpointed 64-bit register
43313 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43314 should contain the checkpointed altivec registers @samp{cvr0} through
43315 @samp{cvr31}, all 128-bit wide. It should also contain the
43316 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43319 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43320 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43321 will combine these registers with the checkpointed floating point
43322 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43323 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43324 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43325 @samp{cvs63}. Therefore, this feature requires both
43326 @samp{org.gnu.gdb.power.htm.altivec} and
43327 @samp{org.gnu.gdb.power.htm.fpu}.
43329 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43330 contain the 64-bit checkpointed register @samp{cppr}.
43332 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43333 contain the 64-bit checkpointed register @samp{cdscr}.
43335 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43336 contain the 64-bit checkpointed register @samp{ctar}.
43339 @node RISC-V Features
43340 @subsection RISC-V Features
43341 @cindex target descriptions, RISC-V Features
43343 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43344 targets. It should contain the registers @samp{x0} through
43345 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43346 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43349 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43350 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43351 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43352 architectural register names, or the ABI names can be used.
43354 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43355 it should contain registers that are not backed by real registers on
43356 the target, but are instead virtual, where the register value is
43357 derived from other target state. In many ways these are like
43358 @value{GDBN}s pseudo-registers, except implemented by the target.
43359 Currently the only register expected in this set is the one byte
43360 @samp{priv} register that contains the target's privilege level in the
43361 least significant two bits.
43363 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43364 should contain all of the target's standard CSRs. Standard CSRs are
43365 those defined in the RISC-V specification documents. There is some
43366 overlap between this feature and the fpu feature; the @samp{fflags},
43367 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43368 expectation is that these registers will be in the fpu feature if the
43369 target has floating point hardware, but can be moved into the csr
43370 feature if the target has the floating point control registers, but no
43371 other floating point hardware.
43373 @node S/390 and System z Features
43374 @subsection S/390 and System z Features
43375 @cindex target descriptions, S/390 features
43376 @cindex target descriptions, System z features
43378 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43379 System z targets. It should contain the PSW and the 16 general
43380 registers. In particular, System z targets should provide the 64-bit
43381 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43382 S/390 targets should provide the 32-bit versions of these registers.
43383 A System z target that runs in 31-bit addressing mode should provide
43384 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43385 register's upper halves @samp{r0h} through @samp{r15h}, and their
43386 lower halves @samp{r0l} through @samp{r15l}.
43388 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43389 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43392 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43393 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43395 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43396 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43397 targets and 32-bit otherwise. In addition, the feature may contain
43398 the @samp{last_break} register, whose width depends on the addressing
43399 mode, as well as the @samp{system_call} register, which is always
43402 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43403 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43404 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43406 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43407 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43408 combined by @value{GDBN} with the floating point registers @samp{f0}
43409 through @samp{f15} to present the 128-bit wide vector registers
43410 @samp{v0} through @samp{v15}. In addition, this feature should
43411 contain the 128-bit wide vector registers @samp{v16} through
43414 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43415 the 64-bit wide guarded-storage-control registers @samp{gsd},
43416 @samp{gssm}, and @samp{gsepla}.
43418 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43419 the 64-bit wide guarded-storage broadcast control registers
43420 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43422 @node Sparc Features
43423 @subsection Sparc Features
43424 @cindex target descriptions, sparc32 features
43425 @cindex target descriptions, sparc64 features
43426 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43427 targets. It should describe the following registers:
43431 @samp{g0} through @samp{g7}
43433 @samp{o0} through @samp{o7}
43435 @samp{l0} through @samp{l7}
43437 @samp{i0} through @samp{i7}
43440 They may be 32-bit or 64-bit depending on the target.
43442 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43443 targets. It should describe the following registers:
43447 @samp{f0} through @samp{f31}
43449 @samp{f32} through @samp{f62} for sparc64
43452 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43453 targets. It should describe the following registers:
43457 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43458 @samp{fsr}, and @samp{csr} for sparc32
43460 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43464 @node TIC6x Features
43465 @subsection TMS320C6x Features
43466 @cindex target descriptions, TIC6x features
43467 @cindex target descriptions, TMS320C6x features
43468 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43469 targets. It should contain registers @samp{A0} through @samp{A15},
43470 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43472 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43473 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43474 through @samp{B31}.
43476 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43477 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43479 @node Operating System Information
43480 @appendix Operating System Information
43481 @cindex operating system information
43487 Users of @value{GDBN} often wish to obtain information about the state of
43488 the operating system running on the target---for example the list of
43489 processes, or the list of open files. This section describes the
43490 mechanism that makes it possible. This mechanism is similar to the
43491 target features mechanism (@pxref{Target Descriptions}), but focuses
43492 on a different aspect of target.
43494 Operating system information is retrived from the target via the
43495 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43496 read}). The object name in the request should be @samp{osdata}, and
43497 the @var{annex} identifies the data to be fetched.
43500 @appendixsection Process list
43501 @cindex operating system information, process list
43503 When requesting the process list, the @var{annex} field in the
43504 @samp{qXfer} request should be @samp{processes}. The returned data is
43505 an XML document. The formal syntax of this document is defined in
43506 @file{gdb/features/osdata.dtd}.
43508 An example document is:
43511 <?xml version="1.0"?>
43512 <!DOCTYPE target SYSTEM "osdata.dtd">
43513 <osdata type="processes">
43515 <column name="pid">1</column>
43516 <column name="user">root</column>
43517 <column name="command">/sbin/init</column>
43518 <column name="cores">1,2,3</column>
43523 Each item should include a column whose name is @samp{pid}. The value
43524 of that column should identify the process on the target. The
43525 @samp{user} and @samp{command} columns are optional, and will be
43526 displayed by @value{GDBN}. The @samp{cores} column, if present,
43527 should contain a comma-separated list of cores that this process
43528 is running on. Target may provide additional columns,
43529 which @value{GDBN} currently ignores.
43531 @node Trace File Format
43532 @appendix Trace File Format
43533 @cindex trace file format
43535 The trace file comes in three parts: a header, a textual description
43536 section, and a trace frame section with binary data.
43538 The header has the form @code{\x7fTRACE0\n}. The first byte is
43539 @code{0x7f} so as to indicate that the file contains binary data,
43540 while the @code{0} is a version number that may have different values
43543 The description section consists of multiple lines of @sc{ascii} text
43544 separated by newline characters (@code{0xa}). The lines may include a
43545 variety of optional descriptive or context-setting information, such
43546 as tracepoint definitions or register set size. @value{GDBN} will
43547 ignore any line that it does not recognize. An empty line marks the end
43552 Specifies the size of a register block in bytes. This is equal to the
43553 size of a @code{g} packet payload in the remote protocol. @var{size}
43554 is an ascii decimal number. There should be only one such line in
43555 a single trace file.
43557 @item status @var{status}
43558 Trace status. @var{status} has the same format as a @code{qTStatus}
43559 remote packet reply. There should be only one such line in a single trace
43562 @item tp @var{payload}
43563 Tracepoint definition. The @var{payload} has the same format as
43564 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43565 may take multiple lines of definition, corresponding to the multiple
43568 @item tsv @var{payload}
43569 Trace state variable definition. The @var{payload} has the same format as
43570 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43571 may take multiple lines of definition, corresponding to the multiple
43574 @item tdesc @var{payload}
43575 Target description in XML format. The @var{payload} is a single line of
43576 the XML file. All such lines should be concatenated together to get
43577 the original XML file. This file is in the same format as @code{qXfer}
43578 @code{features} payload, and corresponds to the main @code{target.xml}
43579 file. Includes are not allowed.
43583 The trace frame section consists of a number of consecutive frames.
43584 Each frame begins with a two-byte tracepoint number, followed by a
43585 four-byte size giving the amount of data in the frame. The data in
43586 the frame consists of a number of blocks, each introduced by a
43587 character indicating its type (at least register, memory, and trace
43588 state variable). The data in this section is raw binary, not a
43589 hexadecimal or other encoding; its endianness matches the target's
43592 @c FIXME bi-arch may require endianness/arch info in description section
43595 @item R @var{bytes}
43596 Register block. The number and ordering of bytes matches that of a
43597 @code{g} packet in the remote protocol. Note that these are the
43598 actual bytes, in target order, not a hexadecimal encoding.
43600 @item M @var{address} @var{length} @var{bytes}...
43601 Memory block. This is a contiguous block of memory, at the 8-byte
43602 address @var{address}, with a 2-byte length @var{length}, followed by
43603 @var{length} bytes.
43605 @item V @var{number} @var{value}
43606 Trace state variable block. This records the 8-byte signed value
43607 @var{value} of trace state variable numbered @var{number}.
43611 Future enhancements of the trace file format may include additional types
43614 @node Index Section Format
43615 @appendix @code{.gdb_index} section format
43616 @cindex .gdb_index section format
43617 @cindex index section format
43619 This section documents the index section that is created by @code{save
43620 gdb-index} (@pxref{Index Files}). The index section is
43621 DWARF-specific; some knowledge of DWARF is assumed in this
43624 The mapped index file format is designed to be directly
43625 @code{mmap}able on any architecture. In most cases, a datum is
43626 represented using a little-endian 32-bit integer value, called an
43627 @code{offset_type}. Big endian machines must byte-swap the values
43628 before using them. Exceptions to this rule are noted. The data is
43629 laid out such that alignment is always respected.
43631 A mapped index consists of several areas, laid out in order.
43635 The file header. This is a sequence of values, of @code{offset_type}
43636 unless otherwise noted:
43640 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43641 Version 4 uses a different hashing function from versions 5 and 6.
43642 Version 6 includes symbols for inlined functions, whereas versions 4
43643 and 5 do not. Version 7 adds attributes to the CU indices in the
43644 symbol table. Version 8 specifies that symbols from DWARF type units
43645 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43646 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43648 @value{GDBN} will only read version 4, 5, or 6 indices
43649 by specifying @code{set use-deprecated-index-sections on}.
43650 GDB has a workaround for potentially broken version 7 indices so it is
43651 currently not flagged as deprecated.
43654 The offset, from the start of the file, of the CU list.
43657 The offset, from the start of the file, of the types CU list. Note
43658 that this area can be empty, in which case this offset will be equal
43659 to the next offset.
43662 The offset, from the start of the file, of the address area.
43665 The offset, from the start of the file, of the symbol table.
43668 The offset, from the start of the file, of the constant pool.
43672 The CU list. This is a sequence of pairs of 64-bit little-endian
43673 values, sorted by the CU offset. The first element in each pair is
43674 the offset of a CU in the @code{.debug_info} section. The second
43675 element in each pair is the length of that CU. References to a CU
43676 elsewhere in the map are done using a CU index, which is just the
43677 0-based index into this table. Note that if there are type CUs, then
43678 conceptually CUs and type CUs form a single list for the purposes of
43682 The types CU list. This is a sequence of triplets of 64-bit
43683 little-endian values. In a triplet, the first value is the CU offset,
43684 the second value is the type offset in the CU, and the third value is
43685 the type signature. The types CU list is not sorted.
43688 The address area. The address area consists of a sequence of address
43689 entries. Each address entry has three elements:
43693 The low address. This is a 64-bit little-endian value.
43696 The high address. This is a 64-bit little-endian value. Like
43697 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43700 The CU index. This is an @code{offset_type} value.
43704 The symbol table. This is an open-addressed hash table. The size of
43705 the hash table is always a power of 2.
43707 Each slot in the hash table consists of a pair of @code{offset_type}
43708 values. The first value is the offset of the symbol's name in the
43709 constant pool. The second value is the offset of the CU vector in the
43712 If both values are 0, then this slot in the hash table is empty. This
43713 is ok because while 0 is a valid constant pool index, it cannot be a
43714 valid index for both a string and a CU vector.
43716 The hash value for a table entry is computed by applying an
43717 iterative hash function to the symbol's name. Starting with an
43718 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43719 the string is incorporated into the hash using the formula depending on the
43724 The formula is @code{r = r * 67 + c - 113}.
43726 @item Versions 5 to 7
43727 The formula is @code{r = r * 67 + tolower (c) - 113}.
43730 The terminating @samp{\0} is not incorporated into the hash.
43732 The step size used in the hash table is computed via
43733 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43734 value, and @samp{size} is the size of the hash table. The step size
43735 is used to find the next candidate slot when handling a hash
43738 The names of C@t{++} symbols in the hash table are canonicalized. We
43739 don't currently have a simple description of the canonicalization
43740 algorithm; if you intend to create new index sections, you must read
43744 The constant pool. This is simply a bunch of bytes. It is organized
43745 so that alignment is correct: CU vectors are stored first, followed by
43748 A CU vector in the constant pool is a sequence of @code{offset_type}
43749 values. The first value is the number of CU indices in the vector.
43750 Each subsequent value is the index and symbol attributes of a CU in
43751 the CU list. This element in the hash table is used to indicate which
43752 CUs define the symbol and how the symbol is used.
43753 See below for the format of each CU index+attributes entry.
43755 A string in the constant pool is zero-terminated.
43758 Attributes were added to CU index values in @code{.gdb_index} version 7.
43759 If a symbol has multiple uses within a CU then there is one
43760 CU index+attributes value for each use.
43762 The format of each CU index+attributes entry is as follows
43768 This is the index of the CU in the CU list.
43770 These bits are reserved for future purposes and must be zero.
43772 The kind of the symbol in the CU.
43776 This value is reserved and should not be used.
43777 By reserving zero the full @code{offset_type} value is backwards compatible
43778 with previous versions of the index.
43780 The symbol is a type.
43782 The symbol is a variable or an enum value.
43784 The symbol is a function.
43786 Any other kind of symbol.
43788 These values are reserved.
43792 This bit is zero if the value is global and one if it is static.
43794 The determination of whether a symbol is global or static is complicated.
43795 The authorative reference is the file @file{dwarf2read.c} in
43796 @value{GDBN} sources.
43800 This pseudo-code describes the computation of a symbol's kind and
43801 global/static attributes in the index.
43804 is_external = get_attribute (die, DW_AT_external);
43805 language = get_attribute (cu_die, DW_AT_language);
43808 case DW_TAG_typedef:
43809 case DW_TAG_base_type:
43810 case DW_TAG_subrange_type:
43814 case DW_TAG_enumerator:
43816 is_static = language != CPLUS;
43818 case DW_TAG_subprogram:
43820 is_static = ! (is_external || language == ADA);
43822 case DW_TAG_constant:
43824 is_static = ! is_external;
43826 case DW_TAG_variable:
43828 is_static = ! is_external;
43830 case DW_TAG_namespace:
43834 case DW_TAG_class_type:
43835 case DW_TAG_interface_type:
43836 case DW_TAG_structure_type:
43837 case DW_TAG_union_type:
43838 case DW_TAG_enumeration_type:
43840 is_static = language != CPLUS;
43848 @appendix Manual pages
43852 * gdb man:: The GNU Debugger man page
43853 * gdbserver man:: Remote Server for the GNU Debugger man page
43854 * gcore man:: Generate a core file of a running program
43855 * gdbinit man:: gdbinit scripts
43856 * gdb-add-index man:: Add index files to speed up GDB
43862 @c man title gdb The GNU Debugger
43864 @c man begin SYNOPSIS gdb
43865 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43866 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43867 [@option{-b}@w{ }@var{bps}]
43868 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43869 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43870 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43871 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43872 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43875 @c man begin DESCRIPTION gdb
43876 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43877 going on ``inside'' another program while it executes -- or what another
43878 program was doing at the moment it crashed.
43880 @value{GDBN} can do four main kinds of things (plus other things in support of
43881 these) to help you catch bugs in the act:
43885 Start your program, specifying anything that might affect its behavior.
43888 Make your program stop on specified conditions.
43891 Examine what has happened, when your program has stopped.
43894 Change things in your program, so you can experiment with correcting the
43895 effects of one bug and go on to learn about another.
43898 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43901 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43902 commands from the terminal until you tell it to exit with the @value{GDBN}
43903 command @code{quit}. You can get online help from @value{GDBN} itself
43904 by using the command @code{help}.
43906 You can run @code{gdb} with no arguments or options; but the most
43907 usual way to start @value{GDBN} is with one argument or two, specifying an
43908 executable program as the argument:
43914 You can also start with both an executable program and a core file specified:
43920 You can, instead, specify a process ID as a second argument, if you want
43921 to debug a running process:
43929 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43930 named @file{1234}; @value{GDBN} does check for a core file first).
43931 With option @option{-p} you can omit the @var{program} filename.
43933 Here are some of the most frequently needed @value{GDBN} commands:
43935 @c pod2man highlights the right hand side of the @item lines.
43937 @item break [@var{file}:]@var{function}
43938 Set a breakpoint at @var{function} (in @var{file}).
43940 @item run [@var{arglist}]
43941 Start your program (with @var{arglist}, if specified).
43944 Backtrace: display the program stack.
43946 @item print @var{expr}
43947 Display the value of an expression.
43950 Continue running your program (after stopping, e.g. at a breakpoint).
43953 Execute next program line (after stopping); step @emph{over} any
43954 function calls in the line.
43956 @item edit [@var{file}:]@var{function}
43957 look at the program line where it is presently stopped.
43959 @item list [@var{file}:]@var{function}
43960 type the text of the program in the vicinity of where it is presently stopped.
43963 Execute next program line (after stopping); step @emph{into} any
43964 function calls in the line.
43966 @item help [@var{name}]
43967 Show information about @value{GDBN} command @var{name}, or general information
43968 about using @value{GDBN}.
43971 Exit from @value{GDBN}.
43975 For full details on @value{GDBN},
43976 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43977 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43978 as the @code{gdb} entry in the @code{info} program.
43982 @c man begin OPTIONS gdb
43983 Any arguments other than options specify an executable
43984 file and core file (or process ID); that is, the first argument
43985 encountered with no
43986 associated option flag is equivalent to a @option{-se} option, and the second,
43987 if any, is equivalent to a @option{-c} option if it's the name of a file.
43989 both long and short forms; both are shown here. The long forms are also
43990 recognized if you truncate them, so long as enough of the option is
43991 present to be unambiguous. (If you prefer, you can flag option
43992 arguments with @option{+} rather than @option{-}, though we illustrate the
43993 more usual convention.)
43995 All the options and command line arguments you give are processed
43996 in sequential order. The order makes a difference when the @option{-x}
44002 List all options, with brief explanations.
44004 @item -symbols=@var{file}
44005 @itemx -s @var{file}
44006 Read symbol table from file @var{file}.
44009 Enable writing into executable and core files.
44011 @item -exec=@var{file}
44012 @itemx -e @var{file}
44013 Use file @var{file} as the executable file to execute when
44014 appropriate, and for examining pure data in conjunction with a core
44017 @item -se=@var{file}
44018 Read symbol table from file @var{file} and use it as the executable
44021 @item -core=@var{file}
44022 @itemx -c @var{file}
44023 Use file @var{file} as a core dump to examine.
44025 @item -command=@var{file}
44026 @itemx -x @var{file}
44027 Execute @value{GDBN} commands from file @var{file}.
44029 @item -ex @var{command}
44030 Execute given @value{GDBN} @var{command}.
44032 @item -directory=@var{directory}
44033 @itemx -d @var{directory}
44034 Add @var{directory} to the path to search for source files.
44037 Do not execute commands from @file{~/.gdbinit}.
44041 Do not execute commands from any @file{.gdbinit} initialization files.
44045 ``Quiet''. Do not print the introductory and copyright messages. These
44046 messages are also suppressed in batch mode.
44049 Run in batch mode. Exit with status @code{0} after processing all the command
44050 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44051 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44052 commands in the command files.
44054 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44055 download and run a program on another computer; in order to make this
44056 more useful, the message
44059 Program exited normally.
44063 (which is ordinarily issued whenever a program running under @value{GDBN} control
44064 terminates) is not issued when running in batch mode.
44066 @item -cd=@var{directory}
44067 Run @value{GDBN} using @var{directory} as its working directory,
44068 instead of the current directory.
44072 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44073 @value{GDBN} to output the full file name and line number in a standard,
44074 recognizable fashion each time a stack frame is displayed (which
44075 includes each time the program stops). This recognizable format looks
44076 like two @samp{\032} characters, followed by the file name, line number
44077 and character position separated by colons, and a newline. The
44078 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44079 characters as a signal to display the source code for the frame.
44082 Set the line speed (baud rate or bits per second) of any serial
44083 interface used by @value{GDBN} for remote debugging.
44085 @item -tty=@var{device}
44086 Run using @var{device} for your program's standard input and output.
44090 @c man begin SEEALSO gdb
44092 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44093 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44094 documentation are properly installed at your site, the command
44101 should give you access to the complete manual.
44103 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44104 Richard M. Stallman and Roland H. Pesch, July 1991.
44108 @node gdbserver man
44109 @heading gdbserver man
44111 @c man title gdbserver Remote Server for the GNU Debugger
44113 @c man begin SYNOPSIS gdbserver
44114 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44116 gdbserver --attach @var{comm} @var{pid}
44118 gdbserver --multi @var{comm}
44122 @c man begin DESCRIPTION gdbserver
44123 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44124 than the one which is running the program being debugged.
44127 @subheading Usage (server (target) side)
44130 Usage (server (target) side):
44133 First, you need to have a copy of the program you want to debug put onto
44134 the target system. The program can be stripped to save space if needed, as
44135 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44136 the @value{GDBN} running on the host system.
44138 To use the server, you log on to the target system, and run the @command{gdbserver}
44139 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44140 your program, and (c) its arguments. The general syntax is:
44143 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44146 For example, using a serial port, you might say:
44150 @c @file would wrap it as F</dev/com1>.
44151 target> gdbserver /dev/com1 emacs foo.txt
44154 target> gdbserver @file{/dev/com1} emacs foo.txt
44158 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44159 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44160 waits patiently for the host @value{GDBN} to communicate with it.
44162 To use a TCP connection, you could say:
44165 target> gdbserver host:2345 emacs foo.txt
44168 This says pretty much the same thing as the last example, except that we are
44169 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44170 that we are expecting to see a TCP connection from @code{host} to local TCP port
44171 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44172 want for the port number as long as it does not conflict with any existing TCP
44173 ports on the target system. This same port number must be used in the host
44174 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44175 you chose a port number that conflicts with another service, @command{gdbserver} will
44176 print an error message and exit.
44178 @command{gdbserver} can also attach to running programs.
44179 This is accomplished via the @option{--attach} argument. The syntax is:
44182 target> gdbserver --attach @var{comm} @var{pid}
44185 @var{pid} is the process ID of a currently running process. It isn't
44186 necessary to point @command{gdbserver} at a binary for the running process.
44188 To start @code{gdbserver} without supplying an initial command to run
44189 or process ID to attach, use the @option{--multi} command line option.
44190 In such case you should connect using @kbd{target extended-remote} to start
44191 the program you want to debug.
44194 target> gdbserver --multi @var{comm}
44198 @subheading Usage (host side)
44204 You need an unstripped copy of the target program on your host system, since
44205 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44206 would, with the target program as the first argument. (You may need to use the
44207 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44208 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44209 new command you need to know about is @code{target remote}
44210 (or @code{target extended-remote}). Its argument is either
44211 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44212 descriptor. For example:
44216 @c @file would wrap it as F</dev/ttyb>.
44217 (gdb) target remote /dev/ttyb
44220 (gdb) target remote @file{/dev/ttyb}
44225 communicates with the server via serial line @file{/dev/ttyb}, and:
44228 (gdb) target remote the-target:2345
44232 communicates via a TCP connection to port 2345 on host `the-target', where
44233 you previously started up @command{gdbserver} with the same port number. Note that for
44234 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44235 command, otherwise you may get an error that looks something like
44236 `Connection refused'.
44238 @command{gdbserver} can also debug multiple inferiors at once,
44241 the @value{GDBN} manual in node @code{Inferiors and Programs}
44242 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44245 @ref{Inferiors and Programs}.
44247 In such case use the @code{extended-remote} @value{GDBN} command variant:
44250 (gdb) target extended-remote the-target:2345
44253 The @command{gdbserver} option @option{--multi} may or may not be used in such
44257 @c man begin OPTIONS gdbserver
44258 There are three different modes for invoking @command{gdbserver}:
44263 Debug a specific program specified by its program name:
44266 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44269 The @var{comm} parameter specifies how should the server communicate
44270 with @value{GDBN}; it is either a device name (to use a serial line),
44271 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44272 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44273 debug in @var{prog}. Any remaining arguments will be passed to the
44274 program verbatim. When the program exits, @value{GDBN} will close the
44275 connection, and @code{gdbserver} will exit.
44278 Debug a specific program by specifying the process ID of a running
44282 gdbserver --attach @var{comm} @var{pid}
44285 The @var{comm} parameter is as described above. Supply the process ID
44286 of a running program in @var{pid}; @value{GDBN} will do everything
44287 else. Like with the previous mode, when the process @var{pid} exits,
44288 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44291 Multi-process mode -- debug more than one program/process:
44294 gdbserver --multi @var{comm}
44297 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44298 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44299 close the connection when a process being debugged exits, so you can
44300 debug several processes in the same session.
44303 In each of the modes you may specify these options:
44308 List all options, with brief explanations.
44311 This option causes @command{gdbserver} to print its version number and exit.
44314 @command{gdbserver} will attach to a running program. The syntax is:
44317 target> gdbserver --attach @var{comm} @var{pid}
44320 @var{pid} is the process ID of a currently running process. It isn't
44321 necessary to point @command{gdbserver} at a binary for the running process.
44324 To start @code{gdbserver} without supplying an initial command to run
44325 or process ID to attach, use this command line option.
44326 Then you can connect using @kbd{target extended-remote} and start
44327 the program you want to debug. The syntax is:
44330 target> gdbserver --multi @var{comm}
44334 Instruct @code{gdbserver} to display extra status information about the debugging
44336 This option is intended for @code{gdbserver} development and for bug reports to
44339 @item --remote-debug
44340 Instruct @code{gdbserver} to display remote protocol debug output.
44341 This option is intended for @code{gdbserver} development and for bug reports to
44344 @item --debug-format=option1@r{[},option2,...@r{]}
44345 Instruct @code{gdbserver} to include extra information in each line
44346 of debugging output.
44347 @xref{Other Command-Line Arguments for gdbserver}.
44350 Specify a wrapper to launch programs
44351 for debugging. The option should be followed by the name of the
44352 wrapper, then any command-line arguments to pass to the wrapper, then
44353 @kbd{--} indicating the end of the wrapper arguments.
44356 By default, @command{gdbserver} keeps the listening TCP port open, so that
44357 additional connections are possible. However, if you start @code{gdbserver}
44358 with the @option{--once} option, it will stop listening for any further
44359 connection attempts after connecting to the first @value{GDBN} session.
44361 @c --disable-packet is not documented for users.
44363 @c --disable-randomization and --no-disable-randomization are superseded by
44364 @c QDisableRandomization.
44369 @c man begin SEEALSO gdbserver
44371 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44372 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44373 documentation are properly installed at your site, the command
44379 should give you access to the complete manual.
44381 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44382 Richard M. Stallman and Roland H. Pesch, July 1991.
44389 @c man title gcore Generate a core file of a running program
44392 @c man begin SYNOPSIS gcore
44393 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44397 @c man begin DESCRIPTION gcore
44398 Generate core dumps of one or more running programs with process IDs
44399 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44400 is equivalent to one produced by the kernel when the process crashes
44401 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44402 limit). However, unlike after a crash, after @command{gcore} finishes
44403 its job the program remains running without any change.
44406 @c man begin OPTIONS gcore
44409 Dump all memory mappings. The actual effect of this option depends on
44410 the Operating System. On @sc{gnu}/Linux, it will disable
44411 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44412 enable @code{dump-excluded-mappings} (@pxref{set
44413 dump-excluded-mappings}).
44415 @item -o @var{prefix}
44416 The optional argument @var{prefix} specifies the prefix to be used
44417 when composing the file names of the core dumps. The file name is
44418 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44419 process ID of the running program being analyzed by @command{gcore}.
44420 If not specified, @var{prefix} defaults to @var{gcore}.
44424 @c man begin SEEALSO gcore
44426 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44427 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44428 documentation are properly installed at your site, the command
44435 should give you access to the complete manual.
44437 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44438 Richard M. Stallman and Roland H. Pesch, July 1991.
44445 @c man title gdbinit GDB initialization scripts
44448 @c man begin SYNOPSIS gdbinit
44449 @ifset SYSTEM_GDBINIT
44450 @value{SYSTEM_GDBINIT}
44459 @c man begin DESCRIPTION gdbinit
44460 These files contain @value{GDBN} commands to automatically execute during
44461 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44464 the @value{GDBN} manual in node @code{Sequences}
44465 -- shell command @code{info -f gdb -n Sequences}.
44471 Please read more in
44473 the @value{GDBN} manual in node @code{Startup}
44474 -- shell command @code{info -f gdb -n Startup}.
44481 @ifset SYSTEM_GDBINIT
44482 @item @value{SYSTEM_GDBINIT}
44484 @ifclear SYSTEM_GDBINIT
44485 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44487 System-wide initialization file. It is executed unless user specified
44488 @value{GDBN} option @code{-nx} or @code{-n}.
44491 the @value{GDBN} manual in node @code{System-wide configuration}
44492 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44495 @ref{System-wide configuration}.
44499 User initialization file. It is executed unless user specified
44500 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44503 Initialization file for current directory. It may need to be enabled with
44504 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44507 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44508 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44511 @ref{Init File in the Current Directory}.
44516 @c man begin SEEALSO gdbinit
44518 gdb(1), @code{info -f gdb -n Startup}
44520 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44521 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44522 documentation are properly installed at your site, the command
44528 should give you access to the complete manual.
44530 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44531 Richard M. Stallman and Roland H. Pesch, July 1991.
44535 @node gdb-add-index man
44536 @heading gdb-add-index
44537 @pindex gdb-add-index
44538 @anchor{gdb-add-index}
44540 @c man title gdb-add-index Add index files to speed up GDB
44542 @c man begin SYNOPSIS gdb-add-index
44543 gdb-add-index @var{filename}
44546 @c man begin DESCRIPTION gdb-add-index
44547 When @value{GDBN} finds a symbol file, it scans the symbols in the
44548 file in order to construct an internal symbol table. This lets most
44549 @value{GDBN} operations work quickly--at the cost of a delay early on.
44550 For large programs, this delay can be quite lengthy, so @value{GDBN}
44551 provides a way to build an index, which speeds up startup.
44553 To determine whether a file contains such an index, use the command
44554 @kbd{readelf -S filename}: the index is stored in a section named
44555 @code{.gdb_index}. The index file can only be produced on systems
44556 which use ELF binaries and DWARF debug information (i.e., sections
44557 named @code{.debug_*}).
44559 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44560 in the @env{PATH} environment variable. If you want to use different
44561 versions of these programs, you can specify them through the
44562 @env{GDB} and @env{OBJDUMP} environment variables.
44566 the @value{GDBN} manual in node @code{Index Files}
44567 -- shell command @kbd{info -f gdb -n "Index Files"}.
44574 @c man begin SEEALSO gdb-add-index
44576 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44577 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44578 documentation are properly installed at your site, the command
44584 should give you access to the complete manual.
44586 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44587 Richard M. Stallman and Roland H. Pesch, July 1991.
44593 @node GNU Free Documentation License
44594 @appendix GNU Free Documentation License
44597 @node Concept Index
44598 @unnumbered Concept Index
44602 @node Command and Variable Index
44603 @unnumbered Command, Variable, and Function Index
44608 % I think something like @@colophon should be in texinfo. In the
44610 \long\def\colophon{\hbox to0pt{}\vfill
44611 \centerline{The body of this manual is set in}
44612 \centerline{\fontname\tenrm,}
44613 \centerline{with headings in {\bf\fontname\tenbf}}
44614 \centerline{and examples in {\tt\fontname\tentt}.}
44615 \centerline{{\it\fontname\tenit\/},}
44616 \centerline{{\bf\fontname\tenbf}, and}
44617 \centerline{{\sl\fontname\tensl\/}}
44618 \centerline{are used for emphasis.}\vfill}
44620 % Blame: doc@@cygnus.com, 1991.