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 The syntax of the regular expression is the standard one used with tools
3877 like @file{grep}. Note that this is different from the syntax used by
3878 shells, so for instance @code{foo*} matches all functions that include
3879 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3880 @code{.*} leading and trailing the regular expression you supply, so to
3881 match only functions that begin with @code{foo}, use @code{^foo}.
3883 @cindex non-member C@t{++} functions, set breakpoint in
3884 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3885 breakpoints on overloaded functions that are not members of any special
3888 @cindex set breakpoints on all functions
3889 The @code{rbreak} command can be used to set breakpoints in
3890 @strong{all} the functions in a program, like this:
3893 (@value{GDBP}) rbreak .
3896 @item rbreak @var{file}:@var{regex}
3897 If @code{rbreak} is called with a filename qualification, it limits
3898 the search for functions matching the given regular expression to the
3899 specified @var{file}. This can be used, for example, to set breakpoints on
3900 every function in a given file:
3903 (@value{GDBP}) rbreak file.c:.
3906 The colon separating the filename qualifier from the regex may
3907 optionally be surrounded by spaces.
3909 @kindex info breakpoints
3910 @cindex @code{$_} and @code{info breakpoints}
3911 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3912 @itemx info break @r{[}@var{list}@dots{}@r{]}
3913 Print a table of all breakpoints, watchpoints, and catchpoints set and
3914 not deleted. Optional argument @var{n} means print information only
3915 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3916 For each breakpoint, following columns are printed:
3919 @item Breakpoint Numbers
3921 Breakpoint, watchpoint, or catchpoint.
3923 Whether the breakpoint is marked to be disabled or deleted when hit.
3924 @item Enabled or Disabled
3925 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3926 that are not enabled.
3928 Where the breakpoint is in your program, as a memory address. For a
3929 pending breakpoint whose address is not yet known, this field will
3930 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3931 library that has the symbol or line referred by breakpoint is loaded.
3932 See below for details. A breakpoint with several locations will
3933 have @samp{<MULTIPLE>} in this field---see below for details.
3935 Where the breakpoint is in the source for your program, as a file and
3936 line number. For a pending breakpoint, the original string passed to
3937 the breakpoint command will be listed as it cannot be resolved until
3938 the appropriate shared library is loaded in the future.
3942 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3943 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3944 @value{GDBN} on the host's side. If it is ``target'', then the condition
3945 is evaluated by the target. The @code{info break} command shows
3946 the condition on the line following the affected breakpoint, together with
3947 its condition evaluation mode in between parentheses.
3949 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3950 allowed to have a condition specified for it. The condition is not parsed for
3951 validity until a shared library is loaded that allows the pending
3952 breakpoint to resolve to a valid location.
3955 @code{info break} with a breakpoint
3956 number @var{n} as argument lists only that breakpoint. The
3957 convenience variable @code{$_} and the default examining-address for
3958 the @code{x} command are set to the address of the last breakpoint
3959 listed (@pxref{Memory, ,Examining Memory}).
3962 @code{info break} displays a count of the number of times the breakpoint
3963 has been hit. This is especially useful in conjunction with the
3964 @code{ignore} command. You can ignore a large number of breakpoint
3965 hits, look at the breakpoint info to see how many times the breakpoint
3966 was hit, and then run again, ignoring one less than that number. This
3967 will get you quickly to the last hit of that breakpoint.
3970 For a breakpoints with an enable count (xref) greater than 1,
3971 @code{info break} also displays that count.
3975 @value{GDBN} allows you to set any number of breakpoints at the same place in
3976 your program. There is nothing silly or meaningless about this. When
3977 the breakpoints are conditional, this is even useful
3978 (@pxref{Conditions, ,Break Conditions}).
3980 @cindex multiple locations, breakpoints
3981 @cindex breakpoints, multiple locations
3982 It is possible that a breakpoint corresponds to several locations
3983 in your program. Examples of this situation are:
3987 Multiple functions in the program may have the same name.
3990 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3991 instances of the function body, used in different cases.
3994 For a C@t{++} template function, a given line in the function can
3995 correspond to any number of instantiations.
3998 For an inlined function, a given source line can correspond to
3999 several places where that function is inlined.
4002 In all those cases, @value{GDBN} will insert a breakpoint at all
4003 the relevant locations.
4005 A breakpoint with multiple locations is displayed in the breakpoint
4006 table using several rows---one header row, followed by one row for
4007 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4008 address column. The rows for individual locations contain the actual
4009 addresses for locations, and show the functions to which those
4010 locations belong. The number column for a location is of the form
4011 @var{breakpoint-number}.@var{location-number}.
4016 Num Type Disp Enb Address What
4017 1 breakpoint keep y <MULTIPLE>
4019 breakpoint already hit 1 time
4020 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4021 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4024 You cannot delete the individual locations from a breakpoint. However,
4025 each location can be individually enabled or disabled by passing
4026 @var{breakpoint-number}.@var{location-number} as argument to the
4027 @code{enable} and @code{disable} commands. It's also possible to
4028 @code{enable} and @code{disable} a range of @var{location-number}
4029 locations using a @var{breakpoint-number} and two @var{location-number}s,
4030 in increasing order, separated by a hyphen, like
4031 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4032 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4033 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4034 all of the locations that belong to that breakpoint.
4036 @cindex pending breakpoints
4037 It's quite common to have a breakpoint inside a shared library.
4038 Shared libraries can be loaded and unloaded explicitly,
4039 and possibly repeatedly, as the program is executed. To support
4040 this use case, @value{GDBN} updates breakpoint locations whenever
4041 any shared library is loaded or unloaded. Typically, you would
4042 set a breakpoint in a shared library at the beginning of your
4043 debugging session, when the library is not loaded, and when the
4044 symbols from the library are not available. When you try to set
4045 breakpoint, @value{GDBN} will ask you if you want to set
4046 a so called @dfn{pending breakpoint}---breakpoint whose address
4047 is not yet resolved.
4049 After the program is run, whenever a new shared library is loaded,
4050 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4051 shared library contains the symbol or line referred to by some
4052 pending breakpoint, that breakpoint is resolved and becomes an
4053 ordinary breakpoint. When a library is unloaded, all breakpoints
4054 that refer to its symbols or source lines become pending again.
4056 This logic works for breakpoints with multiple locations, too. For
4057 example, if you have a breakpoint in a C@t{++} template function, and
4058 a newly loaded shared library has an instantiation of that template,
4059 a new location is added to the list of locations for the breakpoint.
4061 Except for having unresolved address, pending breakpoints do not
4062 differ from regular breakpoints. You can set conditions or commands,
4063 enable and disable them and perform other breakpoint operations.
4065 @value{GDBN} provides some additional commands for controlling what
4066 happens when the @samp{break} command cannot resolve breakpoint
4067 address specification to an address:
4069 @kindex set breakpoint pending
4070 @kindex show breakpoint pending
4072 @item set breakpoint pending auto
4073 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4074 location, it queries you whether a pending breakpoint should be created.
4076 @item set breakpoint pending on
4077 This indicates that an unrecognized breakpoint location should automatically
4078 result in a pending breakpoint being created.
4080 @item set breakpoint pending off
4081 This indicates that pending breakpoints are not to be created. Any
4082 unrecognized breakpoint location results in an error. This setting does
4083 not affect any pending breakpoints previously created.
4085 @item show breakpoint pending
4086 Show the current behavior setting for creating pending breakpoints.
4089 The settings above only affect the @code{break} command and its
4090 variants. Once breakpoint is set, it will be automatically updated
4091 as shared libraries are loaded and unloaded.
4093 @cindex automatic hardware breakpoints
4094 For some targets, @value{GDBN} can automatically decide if hardware or
4095 software breakpoints should be used, depending on whether the
4096 breakpoint address is read-only or read-write. This applies to
4097 breakpoints set with the @code{break} command as well as to internal
4098 breakpoints set by commands like @code{next} and @code{finish}. For
4099 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4102 You can control this automatic behaviour with the following commands:
4104 @kindex set breakpoint auto-hw
4105 @kindex show breakpoint auto-hw
4107 @item set breakpoint auto-hw on
4108 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4109 will try to use the target memory map to decide if software or hardware
4110 breakpoint must be used.
4112 @item set breakpoint auto-hw off
4113 This indicates @value{GDBN} should not automatically select breakpoint
4114 type. If the target provides a memory map, @value{GDBN} will warn when
4115 trying to set software breakpoint at a read-only address.
4118 @value{GDBN} normally implements breakpoints by replacing the program code
4119 at the breakpoint address with a special instruction, which, when
4120 executed, given control to the debugger. By default, the program
4121 code is so modified only when the program is resumed. As soon as
4122 the program stops, @value{GDBN} restores the original instructions. This
4123 behaviour guards against leaving breakpoints inserted in the
4124 target should gdb abrubptly disconnect. However, with slow remote
4125 targets, inserting and removing breakpoint can reduce the performance.
4126 This behavior can be controlled with the following commands::
4128 @kindex set breakpoint always-inserted
4129 @kindex show breakpoint always-inserted
4131 @item set breakpoint always-inserted off
4132 All breakpoints, including newly added by the user, are inserted in
4133 the target only when the target is resumed. All breakpoints are
4134 removed from the target when it stops. This is the default mode.
4136 @item set breakpoint always-inserted on
4137 Causes all breakpoints to be inserted in the target at all times. If
4138 the user adds a new breakpoint, or changes an existing breakpoint, the
4139 breakpoints in the target are updated immediately. A breakpoint is
4140 removed from the target only when breakpoint itself is deleted.
4143 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4144 when a breakpoint breaks. If the condition is true, then the process being
4145 debugged stops, otherwise the process is resumed.
4147 If the target supports evaluating conditions on its end, @value{GDBN} may
4148 download the breakpoint, together with its conditions, to it.
4150 This feature can be controlled via the following commands:
4152 @kindex set breakpoint condition-evaluation
4153 @kindex show breakpoint condition-evaluation
4155 @item set breakpoint condition-evaluation host
4156 This option commands @value{GDBN} to evaluate the breakpoint
4157 conditions on the host's side. Unconditional breakpoints are sent to
4158 the target which in turn receives the triggers and reports them back to GDB
4159 for condition evaluation. This is the standard evaluation mode.
4161 @item set breakpoint condition-evaluation target
4162 This option commands @value{GDBN} to download breakpoint conditions
4163 to the target at the moment of their insertion. The target
4164 is responsible for evaluating the conditional expression and reporting
4165 breakpoint stop events back to @value{GDBN} whenever the condition
4166 is true. Due to limitations of target-side evaluation, some conditions
4167 cannot be evaluated there, e.g., conditions that depend on local data
4168 that is only known to the host. Examples include
4169 conditional expressions involving convenience variables, complex types
4170 that cannot be handled by the agent expression parser and expressions
4171 that are too long to be sent over to the target, specially when the
4172 target is a remote system. In these cases, the conditions will be
4173 evaluated by @value{GDBN}.
4175 @item set breakpoint condition-evaluation auto
4176 This is the default mode. If the target supports evaluating breakpoint
4177 conditions on its end, @value{GDBN} will download breakpoint conditions to
4178 the target (limitations mentioned previously apply). If the target does
4179 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4180 to evaluating all these conditions on the host's side.
4184 @cindex negative breakpoint numbers
4185 @cindex internal @value{GDBN} breakpoints
4186 @value{GDBN} itself sometimes sets breakpoints in your program for
4187 special purposes, such as proper handling of @code{longjmp} (in C
4188 programs). These internal breakpoints are assigned negative numbers,
4189 starting with @code{-1}; @samp{info breakpoints} does not display them.
4190 You can see these breakpoints with the @value{GDBN} maintenance command
4191 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4194 @node Set Watchpoints
4195 @subsection Setting Watchpoints
4197 @cindex setting watchpoints
4198 You can use a watchpoint to stop execution whenever the value of an
4199 expression changes, without having to predict a particular place where
4200 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4201 The expression may be as simple as the value of a single variable, or
4202 as complex as many variables combined by operators. Examples include:
4206 A reference to the value of a single variable.
4209 An address cast to an appropriate data type. For example,
4210 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4211 address (assuming an @code{int} occupies 4 bytes).
4214 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4215 expression can use any operators valid in the program's native
4216 language (@pxref{Languages}).
4219 You can set a watchpoint on an expression even if the expression can
4220 not be evaluated yet. For instance, you can set a watchpoint on
4221 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4222 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4223 the expression produces a valid value. If the expression becomes
4224 valid in some other way than changing a variable (e.g.@: if the memory
4225 pointed to by @samp{*global_ptr} becomes readable as the result of a
4226 @code{malloc} call), @value{GDBN} may not stop until the next time
4227 the expression changes.
4229 @cindex software watchpoints
4230 @cindex hardware watchpoints
4231 Depending on your system, watchpoints may be implemented in software or
4232 hardware. @value{GDBN} does software watchpointing by single-stepping your
4233 program and testing the variable's value each time, which is hundreds of
4234 times slower than normal execution. (But this may still be worth it, to
4235 catch errors where you have no clue what part of your program is the
4238 On some systems, such as most PowerPC or x86-based targets,
4239 @value{GDBN} includes support for hardware watchpoints, which do not
4240 slow down the running of your program.
4244 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4245 Set a watchpoint for an expression. @value{GDBN} will break when the
4246 expression @var{expr} is written into by the program and its value
4247 changes. The simplest (and the most popular) use of this command is
4248 to watch the value of a single variable:
4251 (@value{GDBP}) watch foo
4254 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4255 argument, @value{GDBN} breaks only when the thread identified by
4256 @var{thread-id} changes the value of @var{expr}. If any other threads
4257 change the value of @var{expr}, @value{GDBN} will not break. Note
4258 that watchpoints restricted to a single thread in this way only work
4259 with Hardware Watchpoints.
4261 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4262 (see below). The @code{-location} argument tells @value{GDBN} to
4263 instead watch the memory referred to by @var{expr}. In this case,
4264 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4265 and watch the memory at that address. The type of the result is used
4266 to determine the size of the watched memory. If the expression's
4267 result does not have an address, then @value{GDBN} will print an
4270 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4271 of masked watchpoints, if the current architecture supports this
4272 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4273 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4274 to an address to watch. The mask specifies that some bits of an address
4275 (the bits which are reset in the mask) should be ignored when matching
4276 the address accessed by the inferior against the watchpoint address.
4277 Thus, a masked watchpoint watches many addresses simultaneously---those
4278 addresses whose unmasked bits are identical to the unmasked bits in the
4279 watchpoint address. The @code{mask} argument implies @code{-location}.
4283 (@value{GDBP}) watch foo mask 0xffff00ff
4284 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4288 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4289 Set a watchpoint that will break when the value of @var{expr} is read
4293 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4294 Set a watchpoint that will break when @var{expr} is either read from
4295 or written into by the program.
4297 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4298 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4299 This command prints a list of watchpoints, using the same format as
4300 @code{info break} (@pxref{Set Breaks}).
4303 If you watch for a change in a numerically entered address you need to
4304 dereference it, as the address itself is just a constant number which will
4305 never change. @value{GDBN} refuses to create a watchpoint that watches
4306 a never-changing value:
4309 (@value{GDBP}) watch 0x600850
4310 Cannot watch constant value 0x600850.
4311 (@value{GDBP}) watch *(int *) 0x600850
4312 Watchpoint 1: *(int *) 6293584
4315 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4316 watchpoints execute very quickly, and the debugger reports a change in
4317 value at the exact instruction where the change occurs. If @value{GDBN}
4318 cannot set a hardware watchpoint, it sets a software watchpoint, which
4319 executes more slowly and reports the change in value at the next
4320 @emph{statement}, not the instruction, after the change occurs.
4322 @cindex use only software watchpoints
4323 You can force @value{GDBN} to use only software watchpoints with the
4324 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4325 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4326 the underlying system supports them. (Note that hardware-assisted
4327 watchpoints that were set @emph{before} setting
4328 @code{can-use-hw-watchpoints} to zero will still use the hardware
4329 mechanism of watching expression values.)
4332 @item set can-use-hw-watchpoints
4333 @kindex set can-use-hw-watchpoints
4334 Set whether or not to use hardware watchpoints.
4336 @item show can-use-hw-watchpoints
4337 @kindex show can-use-hw-watchpoints
4338 Show the current mode of using hardware watchpoints.
4341 For remote targets, you can restrict the number of hardware
4342 watchpoints @value{GDBN} will use, see @ref{set remote
4343 hardware-breakpoint-limit}.
4345 When you issue the @code{watch} command, @value{GDBN} reports
4348 Hardware watchpoint @var{num}: @var{expr}
4352 if it was able to set a hardware watchpoint.
4354 Currently, the @code{awatch} and @code{rwatch} commands can only set
4355 hardware watchpoints, because accesses to data that don't change the
4356 value of the watched expression cannot be detected without examining
4357 every instruction as it is being executed, and @value{GDBN} does not do
4358 that currently. If @value{GDBN} finds that it is unable to set a
4359 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4360 will print a message like this:
4363 Expression cannot be implemented with read/access watchpoint.
4366 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4367 data type of the watched expression is wider than what a hardware
4368 watchpoint on the target machine can handle. For example, some systems
4369 can only watch regions that are up to 4 bytes wide; on such systems you
4370 cannot set hardware watchpoints for an expression that yields a
4371 double-precision floating-point number (which is typically 8 bytes
4372 wide). As a work-around, it might be possible to break the large region
4373 into a series of smaller ones and watch them with separate watchpoints.
4375 If you set too many hardware watchpoints, @value{GDBN} might be unable
4376 to insert all of them when you resume the execution of your program.
4377 Since the precise number of active watchpoints is unknown until such
4378 time as the program is about to be resumed, @value{GDBN} might not be
4379 able to warn you about this when you set the watchpoints, and the
4380 warning will be printed only when the program is resumed:
4383 Hardware watchpoint @var{num}: Could not insert watchpoint
4387 If this happens, delete or disable some of the watchpoints.
4389 Watching complex expressions that reference many variables can also
4390 exhaust the resources available for hardware-assisted watchpoints.
4391 That's because @value{GDBN} needs to watch every variable in the
4392 expression with separately allocated resources.
4394 If you call a function interactively using @code{print} or @code{call},
4395 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4396 kind of breakpoint or the call completes.
4398 @value{GDBN} automatically deletes watchpoints that watch local
4399 (automatic) variables, or expressions that involve such variables, when
4400 they go out of scope, that is, when the execution leaves the block in
4401 which these variables were defined. In particular, when the program
4402 being debugged terminates, @emph{all} local variables go out of scope,
4403 and so only watchpoints that watch global variables remain set. If you
4404 rerun the program, you will need to set all such watchpoints again. One
4405 way of doing that would be to set a code breakpoint at the entry to the
4406 @code{main} function and when it breaks, set all the watchpoints.
4408 @cindex watchpoints and threads
4409 @cindex threads and watchpoints
4410 In multi-threaded programs, watchpoints will detect changes to the
4411 watched expression from every thread.
4414 @emph{Warning:} In multi-threaded programs, software watchpoints
4415 have only limited usefulness. If @value{GDBN} creates a software
4416 watchpoint, it can only watch the value of an expression @emph{in a
4417 single thread}. If you are confident that the expression can only
4418 change due to the current thread's activity (and if you are also
4419 confident that no other thread can become current), then you can use
4420 software watchpoints as usual. However, @value{GDBN} may not notice
4421 when a non-current thread's activity changes the expression. (Hardware
4422 watchpoints, in contrast, watch an expression in all threads.)
4425 @xref{set remote hardware-watchpoint-limit}.
4427 @node Set Catchpoints
4428 @subsection Setting Catchpoints
4429 @cindex catchpoints, setting
4430 @cindex exception handlers
4431 @cindex event handling
4433 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4434 kinds of program events, such as C@t{++} exceptions or the loading of a
4435 shared library. Use the @code{catch} command to set a catchpoint.
4439 @item catch @var{event}
4440 Stop when @var{event} occurs. The @var{event} can be any of the following:
4443 @item throw @r{[}@var{regexp}@r{]}
4444 @itemx rethrow @r{[}@var{regexp}@r{]}
4445 @itemx catch @r{[}@var{regexp}@r{]}
4447 @kindex catch rethrow
4449 @cindex stop on C@t{++} exceptions
4450 The throwing, re-throwing, or catching of a C@t{++} exception.
4452 If @var{regexp} is given, then only exceptions whose type matches the
4453 regular expression will be caught.
4455 @vindex $_exception@r{, convenience variable}
4456 The convenience variable @code{$_exception} is available at an
4457 exception-related catchpoint, on some systems. This holds the
4458 exception being thrown.
4460 There are currently some limitations to C@t{++} exception handling in
4465 The support for these commands is system-dependent. Currently, only
4466 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4470 The regular expression feature and the @code{$_exception} convenience
4471 variable rely on the presence of some SDT probes in @code{libstdc++}.
4472 If these probes are not present, then these features cannot be used.
4473 These probes were first available in the GCC 4.8 release, but whether
4474 or not they are available in your GCC also depends on how it was
4478 The @code{$_exception} convenience variable is only valid at the
4479 instruction at which an exception-related catchpoint is set.
4482 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4483 location in the system library which implements runtime exception
4484 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4485 (@pxref{Selection}) to get to your code.
4488 If you call a function interactively, @value{GDBN} normally returns
4489 control to you when the function has finished executing. If the call
4490 raises an exception, however, the call may bypass the mechanism that
4491 returns control to you and cause your program either to abort or to
4492 simply continue running until it hits a breakpoint, catches a signal
4493 that @value{GDBN} is listening for, or exits. This is the case even if
4494 you set a catchpoint for the exception; catchpoints on exceptions are
4495 disabled within interactive calls. @xref{Calling}, for information on
4496 controlling this with @code{set unwind-on-terminating-exception}.
4499 You cannot raise an exception interactively.
4502 You cannot install an exception handler interactively.
4506 @kindex catch exception
4507 @cindex Ada exception catching
4508 @cindex catch Ada exceptions
4509 An Ada exception being raised. If an exception name is specified
4510 at the end of the command (eg @code{catch exception Program_Error}),
4511 the debugger will stop only when this specific exception is raised.
4512 Otherwise, the debugger stops execution when any Ada exception is raised.
4514 When inserting an exception catchpoint on a user-defined exception whose
4515 name is identical to one of the exceptions defined by the language, the
4516 fully qualified name must be used as the exception name. Otherwise,
4517 @value{GDBN} will assume that it should stop on the pre-defined exception
4518 rather than the user-defined one. For instance, assuming an exception
4519 called @code{Constraint_Error} is defined in package @code{Pck}, then
4520 the command to use to catch such exceptions is @kbd{catch exception
4521 Pck.Constraint_Error}.
4524 @kindex catch handlers
4525 @cindex Ada exception handlers catching
4526 @cindex catch Ada exceptions when handled
4527 An Ada exception being handled. If an exception name is
4528 specified at the end of the command
4529 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4530 only when this specific exception is handled.
4531 Otherwise, the debugger stops execution when any Ada exception is handled.
4533 When inserting a handlers catchpoint on a user-defined
4534 exception whose name is identical to one of the exceptions
4535 defined by the language, the fully qualified name must be used
4536 as the exception name. Otherwise, @value{GDBN} will assume that it
4537 should stop on the pre-defined exception rather than the
4538 user-defined one. For instance, assuming an exception called
4539 @code{Constraint_Error} is defined in package @code{Pck}, then the
4540 command to use to catch such exceptions handling is
4541 @kbd{catch handlers Pck.Constraint_Error}.
4543 @item exception unhandled
4544 @kindex catch exception unhandled
4545 An exception that was raised but is not handled by the program.
4548 @kindex catch assert
4549 A failed Ada assertion.
4553 @cindex break on fork/exec
4554 A call to @code{exec}.
4557 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4558 @kindex catch syscall
4559 @cindex break on a system call.
4560 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4561 syscall is a mechanism for application programs to request a service
4562 from the operating system (OS) or one of the OS system services.
4563 @value{GDBN} can catch some or all of the syscalls issued by the
4564 debuggee, and show the related information for each syscall. If no
4565 argument is specified, calls to and returns from all system calls
4568 @var{name} can be any system call name that is valid for the
4569 underlying OS. Just what syscalls are valid depends on the OS. On
4570 GNU and Unix systems, you can find the full list of valid syscall
4571 names on @file{/usr/include/asm/unistd.h}.
4573 @c For MS-Windows, the syscall names and the corresponding numbers
4574 @c can be found, e.g., on this URL:
4575 @c http://www.metasploit.com/users/opcode/syscalls.html
4576 @c but we don't support Windows syscalls yet.
4578 Normally, @value{GDBN} knows in advance which syscalls are valid for
4579 each OS, so you can use the @value{GDBN} command-line completion
4580 facilities (@pxref{Completion,, command completion}) to list the
4583 You may also specify the system call numerically. A syscall's
4584 number is the value passed to the OS's syscall dispatcher to
4585 identify the requested service. When you specify the syscall by its
4586 name, @value{GDBN} uses its database of syscalls to convert the name
4587 into the corresponding numeric code, but using the number directly
4588 may be useful if @value{GDBN}'s database does not have the complete
4589 list of syscalls on your system (e.g., because @value{GDBN} lags
4590 behind the OS upgrades).
4592 You may specify a group of related syscalls to be caught at once using
4593 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4594 instance, on some platforms @value{GDBN} allows you to catch all
4595 network related syscalls, by passing the argument @code{group:network}
4596 to @code{catch syscall}. Note that not all syscall groups are
4597 available in every system. You can use the command completion
4598 facilities (@pxref{Completion,, command completion}) to list the
4599 syscall groups available on your environment.
4601 The example below illustrates how this command works if you don't provide
4605 (@value{GDBP}) catch syscall
4606 Catchpoint 1 (syscall)
4608 Starting program: /tmp/catch-syscall
4610 Catchpoint 1 (call to syscall 'close'), \
4611 0xffffe424 in __kernel_vsyscall ()
4615 Catchpoint 1 (returned from syscall 'close'), \
4616 0xffffe424 in __kernel_vsyscall ()
4620 Here is an example of catching a system call by name:
4623 (@value{GDBP}) catch syscall chroot
4624 Catchpoint 1 (syscall 'chroot' [61])
4626 Starting program: /tmp/catch-syscall
4628 Catchpoint 1 (call to syscall 'chroot'), \
4629 0xffffe424 in __kernel_vsyscall ()
4633 Catchpoint 1 (returned from syscall 'chroot'), \
4634 0xffffe424 in __kernel_vsyscall ()
4638 An example of specifying a system call numerically. In the case
4639 below, the syscall number has a corresponding entry in the XML
4640 file, so @value{GDBN} finds its name and prints it:
4643 (@value{GDBP}) catch syscall 252
4644 Catchpoint 1 (syscall(s) 'exit_group')
4646 Starting program: /tmp/catch-syscall
4648 Catchpoint 1 (call to syscall 'exit_group'), \
4649 0xffffe424 in __kernel_vsyscall ()
4653 Program exited normally.
4657 Here is an example of catching a syscall group:
4660 (@value{GDBP}) catch syscall group:process
4661 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4662 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4663 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4665 Starting program: /tmp/catch-syscall
4667 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4668 from /lib64/ld-linux-x86-64.so.2
4674 However, there can be situations when there is no corresponding name
4675 in XML file for that syscall number. In this case, @value{GDBN} prints
4676 a warning message saying that it was not able to find the syscall name,
4677 but the catchpoint will be set anyway. See the example below:
4680 (@value{GDBP}) catch syscall 764
4681 warning: The number '764' does not represent a known syscall.
4682 Catchpoint 2 (syscall 764)
4686 If you configure @value{GDBN} using the @samp{--without-expat} option,
4687 it will not be able to display syscall names. Also, if your
4688 architecture does not have an XML file describing its system calls,
4689 you will not be able to see the syscall names. It is important to
4690 notice that these two features are used for accessing the syscall
4691 name database. In either case, you will see a warning like this:
4694 (@value{GDBP}) catch syscall
4695 warning: Could not open "syscalls/i386-linux.xml"
4696 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4697 GDB will not be able to display syscall names.
4698 Catchpoint 1 (syscall)
4702 Of course, the file name will change depending on your architecture and system.
4704 Still using the example above, you can also try to catch a syscall by its
4705 number. In this case, you would see something like:
4708 (@value{GDBP}) catch syscall 252
4709 Catchpoint 1 (syscall(s) 252)
4712 Again, in this case @value{GDBN} would not be able to display syscall's names.
4716 A call to @code{fork}.
4720 A call to @code{vfork}.
4722 @item load @r{[}regexp@r{]}
4723 @itemx unload @r{[}regexp@r{]}
4725 @kindex catch unload
4726 The loading or unloading of a shared library. If @var{regexp} is
4727 given, then the catchpoint will stop only if the regular expression
4728 matches one of the affected libraries.
4730 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4731 @kindex catch signal
4732 The delivery of a signal.
4734 With no arguments, this catchpoint will catch any signal that is not
4735 used internally by @value{GDBN}, specifically, all signals except
4736 @samp{SIGTRAP} and @samp{SIGINT}.
4738 With the argument @samp{all}, all signals, including those used by
4739 @value{GDBN}, will be caught. This argument cannot be used with other
4742 Otherwise, the arguments are a list of signal names as given to
4743 @code{handle} (@pxref{Signals}). Only signals specified in this list
4746 One reason that @code{catch signal} can be more useful than
4747 @code{handle} is that you can attach commands and conditions to the
4750 When a signal is caught by a catchpoint, the signal's @code{stop} and
4751 @code{print} settings, as specified by @code{handle}, are ignored.
4752 However, whether the signal is still delivered to the inferior depends
4753 on the @code{pass} setting; this can be changed in the catchpoint's
4758 @item tcatch @var{event}
4760 Set a catchpoint that is enabled only for one stop. The catchpoint is
4761 automatically deleted after the first time the event is caught.
4765 Use the @code{info break} command to list the current catchpoints.
4769 @subsection Deleting Breakpoints
4771 @cindex clearing breakpoints, watchpoints, catchpoints
4772 @cindex deleting breakpoints, watchpoints, catchpoints
4773 It is often necessary to eliminate a breakpoint, watchpoint, or
4774 catchpoint once it has done its job and you no longer want your program
4775 to stop there. This is called @dfn{deleting} the breakpoint. A
4776 breakpoint that has been deleted no longer exists; it is forgotten.
4778 With the @code{clear} command you can delete breakpoints according to
4779 where they are in your program. With the @code{delete} command you can
4780 delete individual breakpoints, watchpoints, or catchpoints by specifying
4781 their breakpoint numbers.
4783 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4784 automatically ignores breakpoints on the first instruction to be executed
4785 when you continue execution without changing the execution address.
4790 Delete any breakpoints at the next instruction to be executed in the
4791 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4792 the innermost frame is selected, this is a good way to delete a
4793 breakpoint where your program just stopped.
4795 @item clear @var{location}
4796 Delete any breakpoints set at the specified @var{location}.
4797 @xref{Specify Location}, for the various forms of @var{location}; the
4798 most useful ones are listed below:
4801 @item clear @var{function}
4802 @itemx clear @var{filename}:@var{function}
4803 Delete any breakpoints set at entry to the named @var{function}.
4805 @item clear @var{linenum}
4806 @itemx clear @var{filename}:@var{linenum}
4807 Delete any breakpoints set at or within the code of the specified
4808 @var{linenum} of the specified @var{filename}.
4811 @cindex delete breakpoints
4813 @kindex d @r{(@code{delete})}
4814 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4815 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4816 list specified as argument. If no argument is specified, delete all
4817 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4818 confirm off}). You can abbreviate this command as @code{d}.
4822 @subsection Disabling Breakpoints
4824 @cindex enable/disable a breakpoint
4825 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4826 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4827 it had been deleted, but remembers the information on the breakpoint so
4828 that you can @dfn{enable} it again later.
4830 You disable and enable breakpoints, watchpoints, and catchpoints with
4831 the @code{enable} and @code{disable} commands, optionally specifying
4832 one or more breakpoint numbers as arguments. Use @code{info break} to
4833 print a list of all breakpoints, watchpoints, and catchpoints if you
4834 do not know which numbers to use.
4836 Disabling and enabling a breakpoint that has multiple locations
4837 affects all of its locations.
4839 A breakpoint, watchpoint, or catchpoint can have any of several
4840 different states of enablement:
4844 Enabled. The breakpoint stops your program. A breakpoint set
4845 with the @code{break} command starts out in this state.
4847 Disabled. The breakpoint has no effect on your program.
4849 Enabled once. The breakpoint stops your program, but then becomes
4852 Enabled for a count. The breakpoint stops your program for the next
4853 N times, then becomes disabled.
4855 Enabled for deletion. The breakpoint stops your program, but
4856 immediately after it does so it is deleted permanently. A breakpoint
4857 set with the @code{tbreak} command starts out in this state.
4860 You can use the following commands to enable or disable breakpoints,
4861 watchpoints, and catchpoints:
4865 @kindex dis @r{(@code{disable})}
4866 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4867 Disable the specified breakpoints---or all breakpoints, if none are
4868 listed. A disabled breakpoint has no effect but is not forgotten. All
4869 options such as ignore-counts, conditions and commands are remembered in
4870 case the breakpoint is enabled again later. You may abbreviate
4871 @code{disable} as @code{dis}.
4874 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Enable the specified breakpoints (or all defined breakpoints). They
4876 become effective once again in stopping your program.
4878 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4879 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4880 of these breakpoints immediately after stopping your program.
4882 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4883 Enable the specified breakpoints temporarily. @value{GDBN} records
4884 @var{count} with each of the specified breakpoints, and decrements a
4885 breakpoint's count when it is hit. When any count reaches 0,
4886 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4887 count (@pxref{Conditions, ,Break Conditions}), that will be
4888 decremented to 0 before @var{count} is affected.
4890 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4891 Enable the specified breakpoints to work once, then die. @value{GDBN}
4892 deletes any of these breakpoints as soon as your program stops there.
4893 Breakpoints set by the @code{tbreak} command start out in this state.
4896 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4897 @c confusing: tbreak is also initially enabled.
4898 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4899 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4900 subsequently, they become disabled or enabled only when you use one of
4901 the commands above. (The command @code{until} can set and delete a
4902 breakpoint of its own, but it does not change the state of your other
4903 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4907 @subsection Break Conditions
4908 @cindex conditional breakpoints
4909 @cindex breakpoint conditions
4911 @c FIXME what is scope of break condition expr? Context where wanted?
4912 @c in particular for a watchpoint?
4913 The simplest sort of breakpoint breaks every time your program reaches a
4914 specified place. You can also specify a @dfn{condition} for a
4915 breakpoint. A condition is just a Boolean expression in your
4916 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4917 a condition evaluates the expression each time your program reaches it,
4918 and your program stops only if the condition is @emph{true}.
4920 This is the converse of using assertions for program validation; in that
4921 situation, you want to stop when the assertion is violated---that is,
4922 when the condition is false. In C, if you want to test an assertion expressed
4923 by the condition @var{assert}, you should set the condition
4924 @samp{! @var{assert}} on the appropriate breakpoint.
4926 Conditions are also accepted for watchpoints; you may not need them,
4927 since a watchpoint is inspecting the value of an expression anyhow---but
4928 it might be simpler, say, to just set a watchpoint on a variable name,
4929 and specify a condition that tests whether the new value is an interesting
4932 Break conditions can have side effects, and may even call functions in
4933 your program. This can be useful, for example, to activate functions
4934 that log program progress, or to use your own print functions to
4935 format special data structures. The effects are completely predictable
4936 unless there is another enabled breakpoint at the same address. (In
4937 that case, @value{GDBN} might see the other breakpoint first and stop your
4938 program without checking the condition of this one.) Note that
4939 breakpoint commands are usually more convenient and flexible than break
4941 purpose of performing side effects when a breakpoint is reached
4942 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4944 Breakpoint conditions can also be evaluated on the target's side if
4945 the target supports it. Instead of evaluating the conditions locally,
4946 @value{GDBN} encodes the expression into an agent expression
4947 (@pxref{Agent Expressions}) suitable for execution on the target,
4948 independently of @value{GDBN}. Global variables become raw memory
4949 locations, locals become stack accesses, and so forth.
4951 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4952 when its condition evaluates to true. This mechanism may provide faster
4953 response times depending on the performance characteristics of the target
4954 since it does not need to keep @value{GDBN} informed about
4955 every breakpoint trigger, even those with false conditions.
4957 Break conditions can be specified when a breakpoint is set, by using
4958 @samp{if} in the arguments to the @code{break} command. @xref{Set
4959 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4960 with the @code{condition} command.
4962 You can also use the @code{if} keyword with the @code{watch} command.
4963 The @code{catch} command does not recognize the @code{if} keyword;
4964 @code{condition} is the only way to impose a further condition on a
4969 @item condition @var{bnum} @var{expression}
4970 Specify @var{expression} as the break condition for breakpoint,
4971 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4972 breakpoint @var{bnum} stops your program only if the value of
4973 @var{expression} is true (nonzero, in C). When you use
4974 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4975 syntactic correctness, and to determine whether symbols in it have
4976 referents in the context of your breakpoint. If @var{expression} uses
4977 symbols not referenced in the context of the breakpoint, @value{GDBN}
4978 prints an error message:
4981 No symbol "foo" in current context.
4986 not actually evaluate @var{expression} at the time the @code{condition}
4987 command (or a command that sets a breakpoint with a condition, like
4988 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4990 @item condition @var{bnum}
4991 Remove the condition from breakpoint number @var{bnum}. It becomes
4992 an ordinary unconditional breakpoint.
4995 @cindex ignore count (of breakpoint)
4996 A special case of a breakpoint condition is to stop only when the
4997 breakpoint has been reached a certain number of times. This is so
4998 useful that there is a special way to do it, using the @dfn{ignore
4999 count} of the breakpoint. Every breakpoint has an ignore count, which
5000 is an integer. Most of the time, the ignore count is zero, and
5001 therefore has no effect. But if your program reaches a breakpoint whose
5002 ignore count is positive, then instead of stopping, it just decrements
5003 the ignore count by one and continues. As a result, if the ignore count
5004 value is @var{n}, the breakpoint does not stop the next @var{n} times
5005 your program reaches it.
5009 @item ignore @var{bnum} @var{count}
5010 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5011 The next @var{count} times the breakpoint is reached, your program's
5012 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5015 To make the breakpoint stop the next time it is reached, specify
5018 When you use @code{continue} to resume execution of your program from a
5019 breakpoint, you can specify an ignore count directly as an argument to
5020 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5021 Stepping,,Continuing and Stepping}.
5023 If a breakpoint has a positive ignore count and a condition, the
5024 condition is not checked. Once the ignore count reaches zero,
5025 @value{GDBN} resumes checking the condition.
5027 You could achieve the effect of the ignore count with a condition such
5028 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5029 is decremented each time. @xref{Convenience Vars, ,Convenience
5033 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5036 @node Break Commands
5037 @subsection Breakpoint Command Lists
5039 @cindex breakpoint commands
5040 You can give any breakpoint (or watchpoint or catchpoint) a series of
5041 commands to execute when your program stops due to that breakpoint. For
5042 example, you might want to print the values of certain expressions, or
5043 enable other breakpoints.
5047 @kindex end@r{ (breakpoint commands)}
5048 @item commands @r{[}@var{list}@dots{}@r{]}
5049 @itemx @dots{} @var{command-list} @dots{}
5051 Specify a list of commands for the given breakpoints. The commands
5052 themselves appear on the following lines. Type a line containing just
5053 @code{end} to terminate the commands.
5055 To remove all commands from a breakpoint, type @code{commands} and
5056 follow it immediately with @code{end}; that is, give no commands.
5058 With no argument, @code{commands} refers to the last breakpoint,
5059 watchpoint, or catchpoint set (not to the breakpoint most recently
5060 encountered). If the most recent breakpoints were set with a single
5061 command, then the @code{commands} will apply to all the breakpoints
5062 set by that command. This applies to breakpoints set by
5063 @code{rbreak}, and also applies when a single @code{break} command
5064 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5068 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5069 disabled within a @var{command-list}.
5071 You can use breakpoint commands to start your program up again. Simply
5072 use the @code{continue} command, or @code{step}, or any other command
5073 that resumes execution.
5075 Any other commands in the command list, after a command that resumes
5076 execution, are ignored. This is because any time you resume execution
5077 (even with a simple @code{next} or @code{step}), you may encounter
5078 another breakpoint---which could have its own command list, leading to
5079 ambiguities about which list to execute.
5082 If the first command you specify in a command list is @code{silent}, the
5083 usual message about stopping at a breakpoint is not printed. This may
5084 be desirable for breakpoints that are to print a specific message and
5085 then continue. If none of the remaining commands print anything, you
5086 see no sign that the breakpoint was reached. @code{silent} is
5087 meaningful only at the beginning of a breakpoint command list.
5089 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5090 print precisely controlled output, and are often useful in silent
5091 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5093 For example, here is how you could use breakpoint commands to print the
5094 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5100 printf "x is %d\n",x
5105 One application for breakpoint commands is to compensate for one bug so
5106 you can test for another. Put a breakpoint just after the erroneous line
5107 of code, give it a condition to detect the case in which something
5108 erroneous has been done, and give it commands to assign correct values
5109 to any variables that need them. End with the @code{continue} command
5110 so that your program does not stop, and start with the @code{silent}
5111 command so that no output is produced. Here is an example:
5122 @node Dynamic Printf
5123 @subsection Dynamic Printf
5125 @cindex dynamic printf
5127 The dynamic printf command @code{dprintf} combines a breakpoint with
5128 formatted printing of your program's data to give you the effect of
5129 inserting @code{printf} calls into your program on-the-fly, without
5130 having to recompile it.
5132 In its most basic form, the output goes to the GDB console. However,
5133 you can set the variable @code{dprintf-style} for alternate handling.
5134 For instance, you can ask to format the output by calling your
5135 program's @code{printf} function. This has the advantage that the
5136 characters go to the program's output device, so they can recorded in
5137 redirects to files and so forth.
5139 If you are doing remote debugging with a stub or agent, you can also
5140 ask to have the printf handled by the remote agent. In addition to
5141 ensuring that the output goes to the remote program's device along
5142 with any other output the program might produce, you can also ask that
5143 the dprintf remain active even after disconnecting from the remote
5144 target. Using the stub/agent is also more efficient, as it can do
5145 everything without needing to communicate with @value{GDBN}.
5149 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5150 Whenever execution reaches @var{location}, print the values of one or
5151 more @var{expressions} under the control of the string @var{template}.
5152 To print several values, separate them with commas.
5154 @item set dprintf-style @var{style}
5155 Set the dprintf output to be handled in one of several different
5156 styles enumerated below. A change of style affects all existing
5157 dynamic printfs immediately. (If you need individual control over the
5158 print commands, simply define normal breakpoints with
5159 explicitly-supplied command lists.)
5163 @kindex dprintf-style gdb
5164 Handle the output using the @value{GDBN} @code{printf} command.
5167 @kindex dprintf-style call
5168 Handle the output by calling a function in your program (normally
5172 @kindex dprintf-style agent
5173 Have the remote debugging agent (such as @code{gdbserver}) handle
5174 the output itself. This style is only available for agents that
5175 support running commands on the target.
5178 @item set dprintf-function @var{function}
5179 Set the function to call if the dprintf style is @code{call}. By
5180 default its value is @code{printf}. You may set it to any expression.
5181 that @value{GDBN} can evaluate to a function, as per the @code{call}
5184 @item set dprintf-channel @var{channel}
5185 Set a ``channel'' for dprintf. If set to a non-empty value,
5186 @value{GDBN} will evaluate it as an expression and pass the result as
5187 a first argument to the @code{dprintf-function}, in the manner of
5188 @code{fprintf} and similar functions. Otherwise, the dprintf format
5189 string will be the first argument, in the manner of @code{printf}.
5191 As an example, if you wanted @code{dprintf} output to go to a logfile
5192 that is a standard I/O stream assigned to the variable @code{mylog},
5193 you could do the following:
5196 (gdb) set dprintf-style call
5197 (gdb) set dprintf-function fprintf
5198 (gdb) set dprintf-channel mylog
5199 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5200 Dprintf 1 at 0x123456: file main.c, line 25.
5202 1 dprintf keep y 0x00123456 in main at main.c:25
5203 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5208 Note that the @code{info break} displays the dynamic printf commands
5209 as normal breakpoint commands; you can thus easily see the effect of
5210 the variable settings.
5212 @item set disconnected-dprintf on
5213 @itemx set disconnected-dprintf off
5214 @kindex set disconnected-dprintf
5215 Choose whether @code{dprintf} commands should continue to run if
5216 @value{GDBN} has disconnected from the target. This only applies
5217 if the @code{dprintf-style} is @code{agent}.
5219 @item show disconnected-dprintf off
5220 @kindex show disconnected-dprintf
5221 Show the current choice for disconnected @code{dprintf}.
5225 @value{GDBN} does not check the validity of function and channel,
5226 relying on you to supply values that are meaningful for the contexts
5227 in which they are being used. For instance, the function and channel
5228 may be the values of local variables, but if that is the case, then
5229 all enabled dynamic prints must be at locations within the scope of
5230 those locals. If evaluation fails, @value{GDBN} will report an error.
5232 @node Save Breakpoints
5233 @subsection How to save breakpoints to a file
5235 To save breakpoint definitions to a file use the @w{@code{save
5236 breakpoints}} command.
5239 @kindex save breakpoints
5240 @cindex save breakpoints to a file for future sessions
5241 @item save breakpoints [@var{filename}]
5242 This command saves all current breakpoint definitions together with
5243 their commands and ignore counts, into a file @file{@var{filename}}
5244 suitable for use in a later debugging session. This includes all
5245 types of breakpoints (breakpoints, watchpoints, catchpoints,
5246 tracepoints). To read the saved breakpoint definitions, use the
5247 @code{source} command (@pxref{Command Files}). Note that watchpoints
5248 with expressions involving local variables may fail to be recreated
5249 because it may not be possible to access the context where the
5250 watchpoint is valid anymore. Because the saved breakpoint definitions
5251 are simply a sequence of @value{GDBN} commands that recreate the
5252 breakpoints, you can edit the file in your favorite editing program,
5253 and remove the breakpoint definitions you're not interested in, or
5254 that can no longer be recreated.
5257 @node Static Probe Points
5258 @subsection Static Probe Points
5260 @cindex static probe point, SystemTap
5261 @cindex static probe point, DTrace
5262 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5263 for Statically Defined Tracing, and the probes are designed to have a tiny
5264 runtime code and data footprint, and no dynamic relocations.
5266 Currently, the following types of probes are supported on
5267 ELF-compatible systems:
5271 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5272 @acronym{SDT} probes@footnote{See
5273 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5274 for more information on how to add @code{SystemTap} @acronym{SDT}
5275 probes in your applications.}. @code{SystemTap} probes are usable
5276 from assembly, C and C@t{++} languages@footnote{See
5277 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5278 for a good reference on how the @acronym{SDT} probes are implemented.}.
5280 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5281 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5285 @cindex semaphores on static probe points
5286 Some @code{SystemTap} probes have an associated semaphore variable;
5287 for instance, this happens automatically if you defined your probe
5288 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5289 @value{GDBN} will automatically enable it when you specify a
5290 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5291 breakpoint at a probe's location by some other method (e.g.,
5292 @code{break file:line}), then @value{GDBN} will not automatically set
5293 the semaphore. @code{DTrace} probes do not support semaphores.
5295 You can examine the available static static probes using @code{info
5296 probes}, with optional arguments:
5300 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5301 If given, @var{type} is either @code{stap} for listing
5302 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5303 probes. If omitted all probes are listed regardless of their types.
5305 If given, @var{provider} is a regular expression used to match against provider
5306 names when selecting which probes to list. If omitted, probes by all
5307 probes from all providers are listed.
5309 If given, @var{name} is a regular expression to match against probe names
5310 when selecting which probes to list. If omitted, probe names are not
5311 considered when deciding whether to display them.
5313 If given, @var{objfile} is a regular expression used to select which
5314 object files (executable or shared libraries) to examine. If not
5315 given, all object files are considered.
5317 @item info probes all
5318 List the available static probes, from all types.
5321 @cindex enabling and disabling probes
5322 Some probe points can be enabled and/or disabled. The effect of
5323 enabling or disabling a probe depends on the type of probe being
5324 handled. Some @code{DTrace} probes can be enabled or
5325 disabled, but @code{SystemTap} probes cannot be disabled.
5327 You can enable (or disable) one or more probes using the following
5328 commands, with optional arguments:
5331 @kindex enable probes
5332 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5333 If given, @var{provider} is a regular expression used to match against
5334 provider names when selecting which probes to enable. If omitted,
5335 all probes from all providers are enabled.
5337 If given, @var{name} is a regular expression to match against probe
5338 names when selecting which probes to enable. If omitted, probe names
5339 are not considered when deciding whether to enable them.
5341 If given, @var{objfile} is a regular expression used to select which
5342 object files (executable or shared libraries) to examine. If not
5343 given, all object files are considered.
5345 @kindex disable probes
5346 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5347 See the @code{enable probes} command above for a description of the
5348 optional arguments accepted by this command.
5351 @vindex $_probe_arg@r{, convenience variable}
5352 A probe may specify up to twelve arguments. These are available at the
5353 point at which the probe is defined---that is, when the current PC is
5354 at the probe's location. The arguments are available using the
5355 convenience variables (@pxref{Convenience Vars})
5356 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5357 probes each probe argument is an integer of the appropriate size;
5358 types are not preserved. In @code{DTrace} probes types are preserved
5359 provided that they are recognized as such by @value{GDBN}; otherwise
5360 the value of the probe argument will be a long integer. The
5361 convenience variable @code{$_probe_argc} holds the number of arguments
5362 at the current probe point.
5364 These variables are always available, but attempts to access them at
5365 any location other than a probe point will cause @value{GDBN} to give
5369 @c @ifclear BARETARGET
5370 @node Error in Breakpoints
5371 @subsection ``Cannot insert breakpoints''
5373 If you request too many active hardware-assisted breakpoints and
5374 watchpoints, you will see this error message:
5376 @c FIXME: the precise wording of this message may change; the relevant
5377 @c source change is not committed yet (Sep 3, 1999).
5379 Stopped; cannot insert breakpoints.
5380 You may have requested too many hardware breakpoints and watchpoints.
5384 This message is printed when you attempt to resume the program, since
5385 only then @value{GDBN} knows exactly how many hardware breakpoints and
5386 watchpoints it needs to insert.
5388 When this message is printed, you need to disable or remove some of the
5389 hardware-assisted breakpoints and watchpoints, and then continue.
5391 @node Breakpoint-related Warnings
5392 @subsection ``Breakpoint address adjusted...''
5393 @cindex breakpoint address adjusted
5395 Some processor architectures place constraints on the addresses at
5396 which breakpoints may be placed. For architectures thus constrained,
5397 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5398 with the constraints dictated by the architecture.
5400 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5401 a VLIW architecture in which a number of RISC-like instructions may be
5402 bundled together for parallel execution. The FR-V architecture
5403 constrains the location of a breakpoint instruction within such a
5404 bundle to the instruction with the lowest address. @value{GDBN}
5405 honors this constraint by adjusting a breakpoint's address to the
5406 first in the bundle.
5408 It is not uncommon for optimized code to have bundles which contain
5409 instructions from different source statements, thus it may happen that
5410 a breakpoint's address will be adjusted from one source statement to
5411 another. Since this adjustment may significantly alter @value{GDBN}'s
5412 breakpoint related behavior from what the user expects, a warning is
5413 printed when the breakpoint is first set and also when the breakpoint
5416 A warning like the one below is printed when setting a breakpoint
5417 that's been subject to address adjustment:
5420 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5423 Such warnings are printed both for user settable and @value{GDBN}'s
5424 internal breakpoints. If you see one of these warnings, you should
5425 verify that a breakpoint set at the adjusted address will have the
5426 desired affect. If not, the breakpoint in question may be removed and
5427 other breakpoints may be set which will have the desired behavior.
5428 E.g., it may be sufficient to place the breakpoint at a later
5429 instruction. A conditional breakpoint may also be useful in some
5430 cases to prevent the breakpoint from triggering too often.
5432 @value{GDBN} will also issue a warning when stopping at one of these
5433 adjusted breakpoints:
5436 warning: Breakpoint 1 address previously adjusted from 0x00010414
5440 When this warning is encountered, it may be too late to take remedial
5441 action except in cases where the breakpoint is hit earlier or more
5442 frequently than expected.
5444 @node Continuing and Stepping
5445 @section Continuing and Stepping
5449 @cindex resuming execution
5450 @dfn{Continuing} means resuming program execution until your program
5451 completes normally. In contrast, @dfn{stepping} means executing just
5452 one more ``step'' of your program, where ``step'' may mean either one
5453 line of source code, or one machine instruction (depending on what
5454 particular command you use). Either when continuing or when stepping,
5455 your program may stop even sooner, due to a breakpoint or a signal. (If
5456 it stops due to a signal, you may want to use @code{handle}, or use
5457 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5458 or you may step into the signal's handler (@pxref{stepping and signal
5463 @kindex c @r{(@code{continue})}
5464 @kindex fg @r{(resume foreground execution)}
5465 @item continue @r{[}@var{ignore-count}@r{]}
5466 @itemx c @r{[}@var{ignore-count}@r{]}
5467 @itemx fg @r{[}@var{ignore-count}@r{]}
5468 Resume program execution, at the address where your program last stopped;
5469 any breakpoints set at that address are bypassed. The optional argument
5470 @var{ignore-count} allows you to specify a further number of times to
5471 ignore a breakpoint at this location; its effect is like that of
5472 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5474 The argument @var{ignore-count} is meaningful only when your program
5475 stopped due to a breakpoint. At other times, the argument to
5476 @code{continue} is ignored.
5478 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5479 debugged program is deemed to be the foreground program) are provided
5480 purely for convenience, and have exactly the same behavior as
5484 To resume execution at a different place, you can use @code{return}
5485 (@pxref{Returning, ,Returning from a Function}) to go back to the
5486 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5487 Different Address}) to go to an arbitrary location in your program.
5489 A typical technique for using stepping is to set a breakpoint
5490 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5491 beginning of the function or the section of your program where a problem
5492 is believed to lie, run your program until it stops at that breakpoint,
5493 and then step through the suspect area, examining the variables that are
5494 interesting, until you see the problem happen.
5498 @kindex s @r{(@code{step})}
5500 Continue running your program until control reaches a different source
5501 line, then stop it and return control to @value{GDBN}. This command is
5502 abbreviated @code{s}.
5505 @c "without debugging information" is imprecise; actually "without line
5506 @c numbers in the debugging information". (gcc -g1 has debugging info but
5507 @c not line numbers). But it seems complex to try to make that
5508 @c distinction here.
5509 @emph{Warning:} If you use the @code{step} command while control is
5510 within a function that was compiled without debugging information,
5511 execution proceeds until control reaches a function that does have
5512 debugging information. Likewise, it will not step into a function which
5513 is compiled without debugging information. To step through functions
5514 without debugging information, use the @code{stepi} command, described
5518 The @code{step} command only stops at the first instruction of a source
5519 line. This prevents the multiple stops that could otherwise occur in
5520 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5521 to stop if a function that has debugging information is called within
5522 the line. In other words, @code{step} @emph{steps inside} any functions
5523 called within the line.
5525 Also, the @code{step} command only enters a function if there is line
5526 number information for the function. Otherwise it acts like the
5527 @code{next} command. This avoids problems when using @code{cc -gl}
5528 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5529 was any debugging information about the routine.
5531 @item step @var{count}
5532 Continue running as in @code{step}, but do so @var{count} times. If a
5533 breakpoint is reached, or a signal not related to stepping occurs before
5534 @var{count} steps, stepping stops right away.
5537 @kindex n @r{(@code{next})}
5538 @item next @r{[}@var{count}@r{]}
5539 Continue to the next source line in the current (innermost) stack frame.
5540 This is similar to @code{step}, but function calls that appear within
5541 the line of code are executed without stopping. Execution stops when
5542 control reaches a different line of code at the original stack level
5543 that was executing when you gave the @code{next} command. This command
5544 is abbreviated @code{n}.
5546 An argument @var{count} is a repeat count, as for @code{step}.
5549 @c FIX ME!! Do we delete this, or is there a way it fits in with
5550 @c the following paragraph? --- Vctoria
5552 @c @code{next} within a function that lacks debugging information acts like
5553 @c @code{step}, but any function calls appearing within the code of the
5554 @c function are executed without stopping.
5556 The @code{next} command only stops at the first instruction of a
5557 source line. This prevents multiple stops that could otherwise occur in
5558 @code{switch} statements, @code{for} loops, etc.
5560 @kindex set step-mode
5562 @cindex functions without line info, and stepping
5563 @cindex stepping into functions with no line info
5564 @itemx set step-mode on
5565 The @code{set step-mode on} command causes the @code{step} command to
5566 stop at the first instruction of a function which contains no debug line
5567 information rather than stepping over it.
5569 This is useful in cases where you may be interested in inspecting the
5570 machine instructions of a function which has no symbolic info and do not
5571 want @value{GDBN} to automatically skip over this function.
5573 @item set step-mode off
5574 Causes the @code{step} command to step over any functions which contains no
5575 debug information. This is the default.
5577 @item show step-mode
5578 Show whether @value{GDBN} will stop in or step over functions without
5579 source line debug information.
5582 @kindex fin @r{(@code{finish})}
5584 Continue running until just after function in the selected stack frame
5585 returns. Print the returned value (if any). This command can be
5586 abbreviated as @code{fin}.
5588 Contrast this with the @code{return} command (@pxref{Returning,
5589 ,Returning from a Function}).
5592 @kindex u @r{(@code{until})}
5593 @cindex run until specified location
5596 Continue running until a source line past the current line, in the
5597 current stack frame, is reached. This command is used to avoid single
5598 stepping through a loop more than once. It is like the @code{next}
5599 command, except that when @code{until} encounters a jump, it
5600 automatically continues execution until the program counter is greater
5601 than the address of the jump.
5603 This means that when you reach the end of a loop after single stepping
5604 though it, @code{until} makes your program continue execution until it
5605 exits the loop. In contrast, a @code{next} command at the end of a loop
5606 simply steps back to the beginning of the loop, which forces you to step
5607 through the next iteration.
5609 @code{until} always stops your program if it attempts to exit the current
5612 @code{until} may produce somewhat counterintuitive results if the order
5613 of machine code does not match the order of the source lines. For
5614 example, in the following excerpt from a debugging session, the @code{f}
5615 (@code{frame}) command shows that execution is stopped at line
5616 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5620 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5622 (@value{GDBP}) until
5623 195 for ( ; argc > 0; NEXTARG) @{
5626 This happened because, for execution efficiency, the compiler had
5627 generated code for the loop closure test at the end, rather than the
5628 start, of the loop---even though the test in a C @code{for}-loop is
5629 written before the body of the loop. The @code{until} command appeared
5630 to step back to the beginning of the loop when it advanced to this
5631 expression; however, it has not really gone to an earlier
5632 statement---not in terms of the actual machine code.
5634 @code{until} with no argument works by means of single
5635 instruction stepping, and hence is slower than @code{until} with an
5638 @item until @var{location}
5639 @itemx u @var{location}
5640 Continue running your program until either the specified @var{location} is
5641 reached, or the current stack frame returns. The location is any of
5642 the forms described in @ref{Specify Location}.
5643 This form of the command uses temporary breakpoints, and
5644 hence is quicker than @code{until} without an argument. The specified
5645 location is actually reached only if it is in the current frame. This
5646 implies that @code{until} can be used to skip over recursive function
5647 invocations. For instance in the code below, if the current location is
5648 line @code{96}, issuing @code{until 99} will execute the program up to
5649 line @code{99} in the same invocation of factorial, i.e., after the inner
5650 invocations have returned.
5653 94 int factorial (int value)
5655 96 if (value > 1) @{
5656 97 value *= factorial (value - 1);
5663 @kindex advance @var{location}
5664 @item advance @var{location}
5665 Continue running the program up to the given @var{location}. An argument is
5666 required, which should be of one of the forms described in
5667 @ref{Specify Location}.
5668 Execution will also stop upon exit from the current stack
5669 frame. This command is similar to @code{until}, but @code{advance} will
5670 not skip over recursive function calls, and the target location doesn't
5671 have to be in the same frame as the current one.
5675 @kindex si @r{(@code{stepi})}
5677 @itemx stepi @var{arg}
5679 Execute one machine instruction, then stop and return to the debugger.
5681 It is often useful to do @samp{display/i $pc} when stepping by machine
5682 instructions. This makes @value{GDBN} automatically display the next
5683 instruction to be executed, each time your program stops. @xref{Auto
5684 Display,, Automatic Display}.
5686 An argument is a repeat count, as in @code{step}.
5690 @kindex ni @r{(@code{nexti})}
5692 @itemx nexti @var{arg}
5694 Execute one machine instruction, but if it is a function call,
5695 proceed until the function returns.
5697 An argument is a repeat count, as in @code{next}.
5701 @anchor{range stepping}
5702 @cindex range stepping
5703 @cindex target-assisted range stepping
5704 By default, and if available, @value{GDBN} makes use of
5705 target-assisted @dfn{range stepping}. In other words, whenever you
5706 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5707 tells the target to step the corresponding range of instruction
5708 addresses instead of issuing multiple single-steps. This speeds up
5709 line stepping, particularly for remote targets. Ideally, there should
5710 be no reason you would want to turn range stepping off. However, it's
5711 possible that a bug in the debug info, a bug in the remote stub (for
5712 remote targets), or even a bug in @value{GDBN} could make line
5713 stepping behave incorrectly when target-assisted range stepping is
5714 enabled. You can use the following command to turn off range stepping
5718 @kindex set range-stepping
5719 @kindex show range-stepping
5720 @item set range-stepping
5721 @itemx show range-stepping
5722 Control whether range stepping is enabled.
5724 If @code{on}, and the target supports it, @value{GDBN} tells the
5725 target to step a range of addresses itself, instead of issuing
5726 multiple single-steps. If @code{off}, @value{GDBN} always issues
5727 single-steps, even if range stepping is supported by the target. The
5728 default is @code{on}.
5732 @node Skipping Over Functions and Files
5733 @section Skipping Over Functions and Files
5734 @cindex skipping over functions and files
5736 The program you are debugging may contain some functions which are
5737 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5738 skip a function, all functions in a file or a particular function in
5739 a particular file when stepping.
5741 For example, consider the following C function:
5752 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5753 are not interested in stepping through @code{boring}. If you run @code{step}
5754 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5755 step over both @code{foo} and @code{boring}!
5757 One solution is to @code{step} into @code{boring} and use the @code{finish}
5758 command to immediately exit it. But this can become tedious if @code{boring}
5759 is called from many places.
5761 A more flexible solution is to execute @kbd{skip boring}. This instructs
5762 @value{GDBN} never to step into @code{boring}. Now when you execute
5763 @code{step} at line 103, you'll step over @code{boring} and directly into
5766 Functions may be skipped by providing either a function name, linespec
5767 (@pxref{Specify Location}), regular expression that matches the function's
5768 name, file name or a @code{glob}-style pattern that matches the file name.
5770 On Posix systems the form of the regular expression is
5771 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5772 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5773 expression is whatever is provided by the @code{regcomp} function of
5774 the underlying system.
5775 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5776 description of @code{glob}-style patterns.
5780 @item skip @r{[}@var{options}@r{]}
5781 The basic form of the @code{skip} command takes zero or more options
5782 that specify what to skip.
5783 The @var{options} argument is any useful combination of the following:
5786 @item -file @var{file}
5787 @itemx -fi @var{file}
5788 Functions in @var{file} will be skipped over when stepping.
5790 @item -gfile @var{file-glob-pattern}
5791 @itemx -gfi @var{file-glob-pattern}
5792 @cindex skipping over files via glob-style patterns
5793 Functions in files matching @var{file-glob-pattern} will be skipped
5797 (gdb) skip -gfi utils/*.c
5800 @item -function @var{linespec}
5801 @itemx -fu @var{linespec}
5802 Functions named by @var{linespec} or the function containing the line
5803 named by @var{linespec} will be skipped over when stepping.
5804 @xref{Specify Location}.
5806 @item -rfunction @var{regexp}
5807 @itemx -rfu @var{regexp}
5808 @cindex skipping over functions via regular expressions
5809 Functions whose name matches @var{regexp} will be skipped over when stepping.
5811 This form is useful for complex function names.
5812 For example, there is generally no need to step into C@t{++} @code{std::string}
5813 constructors or destructors. Plus with C@t{++} templates it can be hard to
5814 write out the full name of the function, and often it doesn't matter what
5815 the template arguments are. Specifying the function to be skipped as a
5816 regular expression makes this easier.
5819 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5822 If you want to skip every templated C@t{++} constructor and destructor
5823 in the @code{std} namespace you can do:
5826 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5830 If no options are specified, the function you're currently debugging
5833 @kindex skip function
5834 @item skip function @r{[}@var{linespec}@r{]}
5835 After running this command, the function named by @var{linespec} or the
5836 function containing the line named by @var{linespec} will be skipped over when
5837 stepping. @xref{Specify Location}.
5839 If you do not specify @var{linespec}, the function you're currently debugging
5842 (If you have a function called @code{file} that you want to skip, use
5843 @kbd{skip function file}.)
5846 @item skip file @r{[}@var{filename}@r{]}
5847 After running this command, any function whose source lives in @var{filename}
5848 will be skipped over when stepping.
5851 (gdb) skip file boring.c
5852 File boring.c will be skipped when stepping.
5855 If you do not specify @var{filename}, functions whose source lives in the file
5856 you're currently debugging will be skipped.
5859 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5860 These are the commands for managing your list of skips:
5864 @item info skip @r{[}@var{range}@r{]}
5865 Print details about the specified skip(s). If @var{range} is not specified,
5866 print a table with details about all functions and files marked for skipping.
5867 @code{info skip} prints the following information about each skip:
5871 A number identifying this skip.
5872 @item Enabled or Disabled
5873 Enabled skips are marked with @samp{y}.
5874 Disabled skips are marked with @samp{n}.
5876 If the file name is a @samp{glob} pattern this is @samp{y}.
5877 Otherwise it is @samp{n}.
5879 The name or @samp{glob} pattern of the file to be skipped.
5880 If no file is specified this is @samp{<none>}.
5882 If the function name is a @samp{regular expression} this is @samp{y}.
5883 Otherwise it is @samp{n}.
5885 The name or regular expression of the function to skip.
5886 If no function is specified this is @samp{<none>}.
5890 @item skip delete @r{[}@var{range}@r{]}
5891 Delete the specified skip(s). If @var{range} is not specified, delete all
5895 @item skip enable @r{[}@var{range}@r{]}
5896 Enable the specified skip(s). If @var{range} is not specified, enable all
5899 @kindex skip disable
5900 @item skip disable @r{[}@var{range}@r{]}
5901 Disable the specified skip(s). If @var{range} is not specified, disable all
5904 @kindex set debug skip
5905 @item set debug skip @r{[}on|off@r{]}
5906 Set whether to print the debug output about skipping files and functions.
5908 @kindex show debug skip
5909 @item show debug skip
5910 Show whether the debug output about skipping files and functions is printed.
5918 A signal is an asynchronous event that can happen in a program. The
5919 operating system defines the possible kinds of signals, and gives each
5920 kind a name and a number. For example, in Unix @code{SIGINT} is the
5921 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5922 @code{SIGSEGV} is the signal a program gets from referencing a place in
5923 memory far away from all the areas in use; @code{SIGALRM} occurs when
5924 the alarm clock timer goes off (which happens only if your program has
5925 requested an alarm).
5927 @cindex fatal signals
5928 Some signals, including @code{SIGALRM}, are a normal part of the
5929 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5930 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5931 program has not specified in advance some other way to handle the signal.
5932 @code{SIGINT} does not indicate an error in your program, but it is normally
5933 fatal so it can carry out the purpose of the interrupt: to kill the program.
5935 @value{GDBN} has the ability to detect any occurrence of a signal in your
5936 program. You can tell @value{GDBN} in advance what to do for each kind of
5939 @cindex handling signals
5940 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5941 @code{SIGALRM} be silently passed to your program
5942 (so as not to interfere with their role in the program's functioning)
5943 but to stop your program immediately whenever an error signal happens.
5944 You can change these settings with the @code{handle} command.
5947 @kindex info signals
5951 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5952 handle each one. You can use this to see the signal numbers of all
5953 the defined types of signals.
5955 @item info signals @var{sig}
5956 Similar, but print information only about the specified signal number.
5958 @code{info handle} is an alias for @code{info signals}.
5960 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5961 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5962 for details about this command.
5965 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5966 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5967 can be the number of a signal or its name (with or without the
5968 @samp{SIG} at the beginning); a list of signal numbers of the form
5969 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5970 known signals. Optional arguments @var{keywords}, described below,
5971 say what change to make.
5975 The keywords allowed by the @code{handle} command can be abbreviated.
5976 Their full names are:
5980 @value{GDBN} should not stop your program when this signal happens. It may
5981 still print a message telling you that the signal has come in.
5984 @value{GDBN} should stop your program when this signal happens. This implies
5985 the @code{print} keyword as well.
5988 @value{GDBN} should print a message when this signal happens.
5991 @value{GDBN} should not mention the occurrence of the signal at all. This
5992 implies the @code{nostop} keyword as well.
5996 @value{GDBN} should allow your program to see this signal; your program
5997 can handle the signal, or else it may terminate if the signal is fatal
5998 and not handled. @code{pass} and @code{noignore} are synonyms.
6002 @value{GDBN} should not allow your program to see this signal.
6003 @code{nopass} and @code{ignore} are synonyms.
6007 When a signal stops your program, the signal is not visible to the
6009 continue. Your program sees the signal then, if @code{pass} is in
6010 effect for the signal in question @emph{at that time}. In other words,
6011 after @value{GDBN} reports a signal, you can use the @code{handle}
6012 command with @code{pass} or @code{nopass} to control whether your
6013 program sees that signal when you continue.
6015 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6016 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6017 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6020 You can also use the @code{signal} command to prevent your program from
6021 seeing a signal, or cause it to see a signal it normally would not see,
6022 or to give it any signal at any time. For example, if your program stopped
6023 due to some sort of memory reference error, you might store correct
6024 values into the erroneous variables and continue, hoping to see more
6025 execution; but your program would probably terminate immediately as
6026 a result of the fatal signal once it saw the signal. To prevent this,
6027 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6030 @cindex stepping and signal handlers
6031 @anchor{stepping and signal handlers}
6033 @value{GDBN} optimizes for stepping the mainline code. If a signal
6034 that has @code{handle nostop} and @code{handle pass} set arrives while
6035 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6036 in progress, @value{GDBN} lets the signal handler run and then resumes
6037 stepping the mainline code once the signal handler returns. In other
6038 words, @value{GDBN} steps over the signal handler. This prevents
6039 signals that you've specified as not interesting (with @code{handle
6040 nostop}) from changing the focus of debugging unexpectedly. Note that
6041 the signal handler itself may still hit a breakpoint, stop for another
6042 signal that has @code{handle stop} in effect, or for any other event
6043 that normally results in stopping the stepping command sooner. Also
6044 note that @value{GDBN} still informs you that the program received a
6045 signal if @code{handle print} is set.
6047 @anchor{stepping into signal handlers}
6049 If you set @code{handle pass} for a signal, and your program sets up a
6050 handler for it, then issuing a stepping command, such as @code{step}
6051 or @code{stepi}, when your program is stopped due to the signal will
6052 step @emph{into} the signal handler (if the target supports that).
6054 Likewise, if you use the @code{queue-signal} command to queue a signal
6055 to be delivered to the current thread when execution of the thread
6056 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6057 stepping command will step into the signal handler.
6059 Here's an example, using @code{stepi} to step to the first instruction
6060 of @code{SIGUSR1}'s handler:
6063 (@value{GDBP}) handle SIGUSR1
6064 Signal Stop Print Pass to program Description
6065 SIGUSR1 Yes Yes Yes User defined signal 1
6069 Program received signal SIGUSR1, User defined signal 1.
6070 main () sigusr1.c:28
6073 sigusr1_handler () at sigusr1.c:9
6077 The same, but using @code{queue-signal} instead of waiting for the
6078 program to receive the signal first:
6083 (@value{GDBP}) queue-signal SIGUSR1
6085 sigusr1_handler () at sigusr1.c:9
6090 @cindex extra signal information
6091 @anchor{extra signal information}
6093 On some targets, @value{GDBN} can inspect extra signal information
6094 associated with the intercepted signal, before it is actually
6095 delivered to the program being debugged. This information is exported
6096 by the convenience variable @code{$_siginfo}, and consists of data
6097 that is passed by the kernel to the signal handler at the time of the
6098 receipt of a signal. The data type of the information itself is
6099 target dependent. You can see the data type using the @code{ptype
6100 $_siginfo} command. On Unix systems, it typically corresponds to the
6101 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6104 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6105 referenced address that raised a segmentation fault.
6109 (@value{GDBP}) continue
6110 Program received signal SIGSEGV, Segmentation fault.
6111 0x0000000000400766 in main ()
6113 (@value{GDBP}) ptype $_siginfo
6120 struct @{...@} _kill;
6121 struct @{...@} _timer;
6123 struct @{...@} _sigchld;
6124 struct @{...@} _sigfault;
6125 struct @{...@} _sigpoll;
6128 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6132 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6133 $1 = (void *) 0x7ffff7ff7000
6137 Depending on target support, @code{$_siginfo} may also be writable.
6139 @cindex Intel MPX boundary violations
6140 @cindex boundary violations, Intel MPX
6141 On some targets, a @code{SIGSEGV} can be caused by a boundary
6142 violation, i.e., accessing an address outside of the allowed range.
6143 In those cases @value{GDBN} may displays additional information,
6144 depending on how @value{GDBN} has been told to handle the signal.
6145 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6146 kind: "Upper" or "Lower", the memory address accessed and the
6147 bounds, while with @code{handle nostop SIGSEGV} no additional
6148 information is displayed.
6150 The usual output of a segfault is:
6152 Program received signal SIGSEGV, Segmentation fault
6153 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6154 68 value = *(p + len);
6157 While a bound violation is presented as:
6159 Program received signal SIGSEGV, Segmentation fault
6160 Upper bound violation while accessing address 0x7fffffffc3b3
6161 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6162 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6163 68 value = *(p + len);
6167 @section Stopping and Starting Multi-thread Programs
6169 @cindex stopped threads
6170 @cindex threads, stopped
6172 @cindex continuing threads
6173 @cindex threads, continuing
6175 @value{GDBN} supports debugging programs with multiple threads
6176 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6177 are two modes of controlling execution of your program within the
6178 debugger. In the default mode, referred to as @dfn{all-stop mode},
6179 when any thread in your program stops (for example, at a breakpoint
6180 or while being stepped), all other threads in the program are also stopped by
6181 @value{GDBN}. On some targets, @value{GDBN} also supports
6182 @dfn{non-stop mode}, in which other threads can continue to run freely while
6183 you examine the stopped thread in the debugger.
6186 * All-Stop Mode:: All threads stop when GDB takes control
6187 * Non-Stop Mode:: Other threads continue to execute
6188 * Background Execution:: Running your program asynchronously
6189 * Thread-Specific Breakpoints:: Controlling breakpoints
6190 * Interrupted System Calls:: GDB may interfere with system calls
6191 * Observer Mode:: GDB does not alter program behavior
6195 @subsection All-Stop Mode
6197 @cindex all-stop mode
6199 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6200 @emph{all} threads of execution stop, not just the current thread. This
6201 allows you to examine the overall state of the program, including
6202 switching between threads, without worrying that things may change
6205 Conversely, whenever you restart the program, @emph{all} threads start
6206 executing. @emph{This is true even when single-stepping} with commands
6207 like @code{step} or @code{next}.
6209 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6210 Since thread scheduling is up to your debugging target's operating
6211 system (not controlled by @value{GDBN}), other threads may
6212 execute more than one statement while the current thread completes a
6213 single step. Moreover, in general other threads stop in the middle of a
6214 statement, rather than at a clean statement boundary, when the program
6217 You might even find your program stopped in another thread after
6218 continuing or even single-stepping. This happens whenever some other
6219 thread runs into a breakpoint, a signal, or an exception before the
6220 first thread completes whatever you requested.
6222 @cindex automatic thread selection
6223 @cindex switching threads automatically
6224 @cindex threads, automatic switching
6225 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6226 signal, it automatically selects the thread where that breakpoint or
6227 signal happened. @value{GDBN} alerts you to the context switch with a
6228 message such as @samp{[Switching to Thread @var{n}]} to identify the
6231 On some OSes, you can modify @value{GDBN}'s default behavior by
6232 locking the OS scheduler to allow only a single thread to run.
6235 @item set scheduler-locking @var{mode}
6236 @cindex scheduler locking mode
6237 @cindex lock scheduler
6238 Set the scheduler locking mode. It applies to normal execution,
6239 record mode, and replay mode. If it is @code{off}, then there is no
6240 locking and any thread may run at any time. If @code{on}, then only
6241 the current thread may run when the inferior is resumed. The
6242 @code{step} mode optimizes for single-stepping; it prevents other
6243 threads from preempting the current thread while you are stepping, so
6244 that the focus of debugging does not change unexpectedly. Other
6245 threads never get a chance to run when you step, and they are
6246 completely free to run when you use commands like @samp{continue},
6247 @samp{until}, or @samp{finish}. However, unless another thread hits a
6248 breakpoint during its timeslice, @value{GDBN} does not change the
6249 current thread away from the thread that you are debugging. The
6250 @code{replay} mode behaves like @code{off} in record mode and like
6251 @code{on} in replay mode.
6253 @item show scheduler-locking
6254 Display the current scheduler locking mode.
6257 @cindex resume threads of multiple processes simultaneously
6258 By default, when you issue one of the execution commands such as
6259 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6260 threads of the current inferior to run. For example, if @value{GDBN}
6261 is attached to two inferiors, each with two threads, the
6262 @code{continue} command resumes only the two threads of the current
6263 inferior. This is useful, for example, when you debug a program that
6264 forks and you want to hold the parent stopped (so that, for instance,
6265 it doesn't run to exit), while you debug the child. In other
6266 situations, you may not be interested in inspecting the current state
6267 of any of the processes @value{GDBN} is attached to, and you may want
6268 to resume them all until some breakpoint is hit. In the latter case,
6269 you can instruct @value{GDBN} to allow all threads of all the
6270 inferiors to run with the @w{@code{set schedule-multiple}} command.
6273 @kindex set schedule-multiple
6274 @item set schedule-multiple
6275 Set the mode for allowing threads of multiple processes to be resumed
6276 when an execution command is issued. When @code{on}, all threads of
6277 all processes are allowed to run. When @code{off}, only the threads
6278 of the current process are resumed. The default is @code{off}. The
6279 @code{scheduler-locking} mode takes precedence when set to @code{on},
6280 or while you are stepping and set to @code{step}.
6282 @item show schedule-multiple
6283 Display the current mode for resuming the execution of threads of
6288 @subsection Non-Stop Mode
6290 @cindex non-stop mode
6292 @c This section is really only a place-holder, and needs to be expanded
6293 @c with more details.
6295 For some multi-threaded targets, @value{GDBN} supports an optional
6296 mode of operation in which you can examine stopped program threads in
6297 the debugger while other threads continue to execute freely. This
6298 minimizes intrusion when debugging live systems, such as programs
6299 where some threads have real-time constraints or must continue to
6300 respond to external events. This is referred to as @dfn{non-stop} mode.
6302 In non-stop mode, when a thread stops to report a debugging event,
6303 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6304 threads as well, in contrast to the all-stop mode behavior. Additionally,
6305 execution commands such as @code{continue} and @code{step} apply by default
6306 only to the current thread in non-stop mode, rather than all threads as
6307 in all-stop mode. This allows you to control threads explicitly in
6308 ways that are not possible in all-stop mode --- for example, stepping
6309 one thread while allowing others to run freely, stepping
6310 one thread while holding all others stopped, or stepping several threads
6311 independently and simultaneously.
6313 To enter non-stop mode, use this sequence of commands before you run
6314 or attach to your program:
6317 # If using the CLI, pagination breaks non-stop.
6320 # Finally, turn it on!
6324 You can use these commands to manipulate the non-stop mode setting:
6327 @kindex set non-stop
6328 @item set non-stop on
6329 Enable selection of non-stop mode.
6330 @item set non-stop off
6331 Disable selection of non-stop mode.
6332 @kindex show non-stop
6334 Show the current non-stop enablement setting.
6337 Note these commands only reflect whether non-stop mode is enabled,
6338 not whether the currently-executing program is being run in non-stop mode.
6339 In particular, the @code{set non-stop} preference is only consulted when
6340 @value{GDBN} starts or connects to the target program, and it is generally
6341 not possible to switch modes once debugging has started. Furthermore,
6342 since not all targets support non-stop mode, even when you have enabled
6343 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6346 In non-stop mode, all execution commands apply only to the current thread
6347 by default. That is, @code{continue} only continues one thread.
6348 To continue all threads, issue @code{continue -a} or @code{c -a}.
6350 You can use @value{GDBN}'s background execution commands
6351 (@pxref{Background Execution}) to run some threads in the background
6352 while you continue to examine or step others from @value{GDBN}.
6353 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6354 always executed asynchronously in non-stop mode.
6356 Suspending execution is done with the @code{interrupt} command when
6357 running in the background, or @kbd{Ctrl-c} during foreground execution.
6358 In all-stop mode, this stops the whole process;
6359 but in non-stop mode the interrupt applies only to the current thread.
6360 To stop the whole program, use @code{interrupt -a}.
6362 Other execution commands do not currently support the @code{-a} option.
6364 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6365 that thread current, as it does in all-stop mode. This is because the
6366 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6367 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6368 changed to a different thread just as you entered a command to operate on the
6369 previously current thread.
6371 @node Background Execution
6372 @subsection Background Execution
6374 @cindex foreground execution
6375 @cindex background execution
6376 @cindex asynchronous execution
6377 @cindex execution, foreground, background and asynchronous
6379 @value{GDBN}'s execution commands have two variants: the normal
6380 foreground (synchronous) behavior, and a background
6381 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6382 the program to report that some thread has stopped before prompting for
6383 another command. In background execution, @value{GDBN} immediately gives
6384 a command prompt so that you can issue other commands while your program runs.
6386 If the target doesn't support async mode, @value{GDBN} issues an error
6387 message if you attempt to use the background execution commands.
6389 @cindex @code{&}, background execution of commands
6390 To specify background execution, add a @code{&} to the command. For example,
6391 the background form of the @code{continue} command is @code{continue&}, or
6392 just @code{c&}. The execution commands that accept background execution
6398 @xref{Starting, , Starting your Program}.
6402 @xref{Attach, , Debugging an Already-running Process}.
6406 @xref{Continuing and Stepping, step}.
6410 @xref{Continuing and Stepping, stepi}.
6414 @xref{Continuing and Stepping, next}.
6418 @xref{Continuing and Stepping, nexti}.
6422 @xref{Continuing and Stepping, continue}.
6426 @xref{Continuing and Stepping, finish}.
6430 @xref{Continuing and Stepping, until}.
6434 Background execution is especially useful in conjunction with non-stop
6435 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6436 However, you can also use these commands in the normal all-stop mode with
6437 the restriction that you cannot issue another execution command until the
6438 previous one finishes. Examples of commands that are valid in all-stop
6439 mode while the program is running include @code{help} and @code{info break}.
6441 You can interrupt your program while it is running in the background by
6442 using the @code{interrupt} command.
6449 Suspend execution of the running program. In all-stop mode,
6450 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6451 only the current thread. To stop the whole program in non-stop mode,
6452 use @code{interrupt -a}.
6455 @node Thread-Specific Breakpoints
6456 @subsection Thread-Specific Breakpoints
6458 When your program has multiple threads (@pxref{Threads,, Debugging
6459 Programs with Multiple Threads}), you can choose whether to set
6460 breakpoints on all threads, or on a particular thread.
6463 @cindex breakpoints and threads
6464 @cindex thread breakpoints
6465 @kindex break @dots{} thread @var{thread-id}
6466 @item break @var{location} thread @var{thread-id}
6467 @itemx break @var{location} thread @var{thread-id} if @dots{}
6468 @var{location} specifies source lines; there are several ways of
6469 writing them (@pxref{Specify Location}), but the effect is always to
6470 specify some source line.
6472 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6473 to specify that you only want @value{GDBN} to stop the program when a
6474 particular thread reaches this breakpoint. The @var{thread-id} specifier
6475 is one of the thread identifiers assigned by @value{GDBN}, shown
6476 in the first column of the @samp{info threads} display.
6478 If you do not specify @samp{thread @var{thread-id}} when you set a
6479 breakpoint, the breakpoint applies to @emph{all} threads of your
6482 You can use the @code{thread} qualifier on conditional breakpoints as
6483 well; in this case, place @samp{thread @var{thread-id}} before or
6484 after the breakpoint condition, like this:
6487 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6492 Thread-specific breakpoints are automatically deleted when
6493 @value{GDBN} detects the corresponding thread is no longer in the
6494 thread list. For example:
6498 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6501 There are several ways for a thread to disappear, such as a regular
6502 thread exit, but also when you detach from the process with the
6503 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6504 Process}), or if @value{GDBN} loses the remote connection
6505 (@pxref{Remote Debugging}), etc. Note that with some targets,
6506 @value{GDBN} is only able to detect a thread has exited when the user
6507 explictly asks for the thread list with the @code{info threads}
6510 @node Interrupted System Calls
6511 @subsection Interrupted System Calls
6513 @cindex thread breakpoints and system calls
6514 @cindex system calls and thread breakpoints
6515 @cindex premature return from system calls
6516 There is an unfortunate side effect when using @value{GDBN} to debug
6517 multi-threaded programs. If one thread stops for a
6518 breakpoint, or for some other reason, and another thread is blocked in a
6519 system call, then the system call may return prematurely. This is a
6520 consequence of the interaction between multiple threads and the signals
6521 that @value{GDBN} uses to implement breakpoints and other events that
6524 To handle this problem, your program should check the return value of
6525 each system call and react appropriately. This is good programming
6528 For example, do not write code like this:
6534 The call to @code{sleep} will return early if a different thread stops
6535 at a breakpoint or for some other reason.
6537 Instead, write this:
6542 unslept = sleep (unslept);
6545 A system call is allowed to return early, so the system is still
6546 conforming to its specification. But @value{GDBN} does cause your
6547 multi-threaded program to behave differently than it would without
6550 Also, @value{GDBN} uses internal breakpoints in the thread library to
6551 monitor certain events such as thread creation and thread destruction.
6552 When such an event happens, a system call in another thread may return
6553 prematurely, even though your program does not appear to stop.
6556 @subsection Observer Mode
6558 If you want to build on non-stop mode and observe program behavior
6559 without any chance of disruption by @value{GDBN}, you can set
6560 variables to disable all of the debugger's attempts to modify state,
6561 whether by writing memory, inserting breakpoints, etc. These operate
6562 at a low level, intercepting operations from all commands.
6564 When all of these are set to @code{off}, then @value{GDBN} is said to
6565 be @dfn{observer mode}. As a convenience, the variable
6566 @code{observer} can be set to disable these, plus enable non-stop
6569 Note that @value{GDBN} will not prevent you from making nonsensical
6570 combinations of these settings. For instance, if you have enabled
6571 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6572 then breakpoints that work by writing trap instructions into the code
6573 stream will still not be able to be placed.
6578 @item set observer on
6579 @itemx set observer off
6580 When set to @code{on}, this disables all the permission variables
6581 below (except for @code{insert-fast-tracepoints}), plus enables
6582 non-stop debugging. Setting this to @code{off} switches back to
6583 normal debugging, though remaining in non-stop mode.
6586 Show whether observer mode is on or off.
6588 @kindex may-write-registers
6589 @item set may-write-registers on
6590 @itemx set may-write-registers off
6591 This controls whether @value{GDBN} will attempt to alter the values of
6592 registers, such as with assignment expressions in @code{print}, or the
6593 @code{jump} command. It defaults to @code{on}.
6595 @item show may-write-registers
6596 Show the current permission to write registers.
6598 @kindex may-write-memory
6599 @item set may-write-memory on
6600 @itemx set may-write-memory off
6601 This controls whether @value{GDBN} will attempt to alter the contents
6602 of memory, such as with assignment expressions in @code{print}. It
6603 defaults to @code{on}.
6605 @item show may-write-memory
6606 Show the current permission to write memory.
6608 @kindex may-insert-breakpoints
6609 @item set may-insert-breakpoints on
6610 @itemx set may-insert-breakpoints off
6611 This controls whether @value{GDBN} will attempt to insert breakpoints.
6612 This affects all breakpoints, including internal breakpoints defined
6613 by @value{GDBN}. It defaults to @code{on}.
6615 @item show may-insert-breakpoints
6616 Show the current permission to insert breakpoints.
6618 @kindex may-insert-tracepoints
6619 @item set may-insert-tracepoints on
6620 @itemx set may-insert-tracepoints off
6621 This controls whether @value{GDBN} will attempt to insert (regular)
6622 tracepoints at the beginning of a tracing experiment. It affects only
6623 non-fast tracepoints, fast tracepoints being under the control of
6624 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6626 @item show may-insert-tracepoints
6627 Show the current permission to insert tracepoints.
6629 @kindex may-insert-fast-tracepoints
6630 @item set may-insert-fast-tracepoints on
6631 @itemx set may-insert-fast-tracepoints off
6632 This controls whether @value{GDBN} will attempt to insert fast
6633 tracepoints at the beginning of a tracing experiment. It affects only
6634 fast tracepoints, regular (non-fast) tracepoints being under the
6635 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6637 @item show may-insert-fast-tracepoints
6638 Show the current permission to insert fast tracepoints.
6640 @kindex may-interrupt
6641 @item set may-interrupt on
6642 @itemx set may-interrupt off
6643 This controls whether @value{GDBN} will attempt to interrupt or stop
6644 program execution. When this variable is @code{off}, the
6645 @code{interrupt} command will have no effect, nor will
6646 @kbd{Ctrl-c}. It defaults to @code{on}.
6648 @item show may-interrupt
6649 Show the current permission to interrupt or stop the program.
6653 @node Reverse Execution
6654 @chapter Running programs backward
6655 @cindex reverse execution
6656 @cindex running programs backward
6658 When you are debugging a program, it is not unusual to realize that
6659 you have gone too far, and some event of interest has already happened.
6660 If the target environment supports it, @value{GDBN} can allow you to
6661 ``rewind'' the program by running it backward.
6663 A target environment that supports reverse execution should be able
6664 to ``undo'' the changes in machine state that have taken place as the
6665 program was executing normally. Variables, registers etc.@: should
6666 revert to their previous values. Obviously this requires a great
6667 deal of sophistication on the part of the target environment; not
6668 all target environments can support reverse execution.
6670 When a program is executed in reverse, the instructions that
6671 have most recently been executed are ``un-executed'', in reverse
6672 order. The program counter runs backward, following the previous
6673 thread of execution in reverse. As each instruction is ``un-executed'',
6674 the values of memory and/or registers that were changed by that
6675 instruction are reverted to their previous states. After executing
6676 a piece of source code in reverse, all side effects of that code
6677 should be ``undone'', and all variables should be returned to their
6678 prior values@footnote{
6679 Note that some side effects are easier to undo than others. For instance,
6680 memory and registers are relatively easy, but device I/O is hard. Some
6681 targets may be able undo things like device I/O, and some may not.
6683 The contract between @value{GDBN} and the reverse executing target
6684 requires only that the target do something reasonable when
6685 @value{GDBN} tells it to execute backwards, and then report the
6686 results back to @value{GDBN}. Whatever the target reports back to
6687 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6688 assumes that the memory and registers that the target reports are in a
6689 consistant state, but @value{GDBN} accepts whatever it is given.
6692 If you are debugging in a target environment that supports
6693 reverse execution, @value{GDBN} provides the following commands.
6696 @kindex reverse-continue
6697 @kindex rc @r{(@code{reverse-continue})}
6698 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6699 @itemx rc @r{[}@var{ignore-count}@r{]}
6700 Beginning at the point where your program last stopped, start executing
6701 in reverse. Reverse execution will stop for breakpoints and synchronous
6702 exceptions (signals), just like normal execution. Behavior of
6703 asynchronous signals depends on the target environment.
6705 @kindex reverse-step
6706 @kindex rs @r{(@code{step})}
6707 @item reverse-step @r{[}@var{count}@r{]}
6708 Run the program backward until control reaches the start of a
6709 different source line; then stop it, and return control to @value{GDBN}.
6711 Like the @code{step} command, @code{reverse-step} will only stop
6712 at the beginning of a source line. It ``un-executes'' the previously
6713 executed source line. If the previous source line included calls to
6714 debuggable functions, @code{reverse-step} will step (backward) into
6715 the called function, stopping at the beginning of the @emph{last}
6716 statement in the called function (typically a return statement).
6718 Also, as with the @code{step} command, if non-debuggable functions are
6719 called, @code{reverse-step} will run thru them backward without stopping.
6721 @kindex reverse-stepi
6722 @kindex rsi @r{(@code{reverse-stepi})}
6723 @item reverse-stepi @r{[}@var{count}@r{]}
6724 Reverse-execute one machine instruction. Note that the instruction
6725 to be reverse-executed is @emph{not} the one pointed to by the program
6726 counter, but the instruction executed prior to that one. For instance,
6727 if the last instruction was a jump, @code{reverse-stepi} will take you
6728 back from the destination of the jump to the jump instruction itself.
6730 @kindex reverse-next
6731 @kindex rn @r{(@code{reverse-next})}
6732 @item reverse-next @r{[}@var{count}@r{]}
6733 Run backward to the beginning of the previous line executed in
6734 the current (innermost) stack frame. If the line contains function
6735 calls, they will be ``un-executed'' without stopping. Starting from
6736 the first line of a function, @code{reverse-next} will take you back
6737 to the caller of that function, @emph{before} the function was called,
6738 just as the normal @code{next} command would take you from the last
6739 line of a function back to its return to its caller
6740 @footnote{Unless the code is too heavily optimized.}.
6742 @kindex reverse-nexti
6743 @kindex rni @r{(@code{reverse-nexti})}
6744 @item reverse-nexti @r{[}@var{count}@r{]}
6745 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6746 in reverse, except that called functions are ``un-executed'' atomically.
6747 That is, if the previously executed instruction was a return from
6748 another function, @code{reverse-nexti} will continue to execute
6749 in reverse until the call to that function (from the current stack
6752 @kindex reverse-finish
6753 @item reverse-finish
6754 Just as the @code{finish} command takes you to the point where the
6755 current function returns, @code{reverse-finish} takes you to the point
6756 where it was called. Instead of ending up at the end of the current
6757 function invocation, you end up at the beginning.
6759 @kindex set exec-direction
6760 @item set exec-direction
6761 Set the direction of target execution.
6762 @item set exec-direction reverse
6763 @cindex execute forward or backward in time
6764 @value{GDBN} will perform all execution commands in reverse, until the
6765 exec-direction mode is changed to ``forward''. Affected commands include
6766 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6767 command cannot be used in reverse mode.
6768 @item set exec-direction forward
6769 @value{GDBN} will perform all execution commands in the normal fashion.
6770 This is the default.
6774 @node Process Record and Replay
6775 @chapter Recording Inferior's Execution and Replaying It
6776 @cindex process record and replay
6777 @cindex recording inferior's execution and replaying it
6779 On some platforms, @value{GDBN} provides a special @dfn{process record
6780 and replay} target that can record a log of the process execution, and
6781 replay it later with both forward and reverse execution commands.
6784 When this target is in use, if the execution log includes the record
6785 for the next instruction, @value{GDBN} will debug in @dfn{replay
6786 mode}. In the replay mode, the inferior does not really execute code
6787 instructions. Instead, all the events that normally happen during
6788 code execution are taken from the execution log. While code is not
6789 really executed in replay mode, the values of registers (including the
6790 program counter register) and the memory of the inferior are still
6791 changed as they normally would. Their contents are taken from the
6795 If the record for the next instruction is not in the execution log,
6796 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6797 inferior executes normally, and @value{GDBN} records the execution log
6800 The process record and replay target supports reverse execution
6801 (@pxref{Reverse Execution}), even if the platform on which the
6802 inferior runs does not. However, the reverse execution is limited in
6803 this case by the range of the instructions recorded in the execution
6804 log. In other words, reverse execution on platforms that don't
6805 support it directly can only be done in the replay mode.
6807 When debugging in the reverse direction, @value{GDBN} will work in
6808 replay mode as long as the execution log includes the record for the
6809 previous instruction; otherwise, it will work in record mode, if the
6810 platform supports reverse execution, or stop if not.
6812 For architecture environments that support process record and replay,
6813 @value{GDBN} provides the following commands:
6816 @kindex target record
6817 @kindex target record-full
6818 @kindex target record-btrace
6821 @kindex record btrace
6822 @kindex record btrace bts
6823 @kindex record btrace pt
6829 @kindex rec btrace bts
6830 @kindex rec btrace pt
6833 @item record @var{method}
6834 This command starts the process record and replay target. The
6835 recording method can be specified as parameter. Without a parameter
6836 the command uses the @code{full} recording method. The following
6837 recording methods are available:
6841 Full record/replay recording using @value{GDBN}'s software record and
6842 replay implementation. This method allows replaying and reverse
6845 @item btrace @var{format}
6846 Hardware-supported instruction recording. This method does not record
6847 data. Further, the data is collected in a ring buffer so old data will
6848 be overwritten when the buffer is full. It allows limited reverse
6849 execution. Variables and registers are not available during reverse
6850 execution. In remote debugging, recording continues on disconnect.
6851 Recorded data can be inspected after reconnecting. The recording may
6852 be stopped using @code{record stop}.
6854 The recording format can be specified as parameter. Without a parameter
6855 the command chooses the recording format. The following recording
6856 formats are available:
6860 @cindex branch trace store
6861 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6862 this format, the processor stores a from/to record for each executed
6863 branch in the btrace ring buffer.
6866 @cindex Intel Processor Trace
6867 Use the @dfn{Intel Processor Trace} recording format. In this
6868 format, the processor stores the execution trace in a compressed form
6869 that is afterwards decoded by @value{GDBN}.
6871 The trace can be recorded with very low overhead. The compressed
6872 trace format also allows small trace buffers to already contain a big
6873 number of instructions compared to @acronym{BTS}.
6875 Decoding the recorded execution trace, on the other hand, is more
6876 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6877 increased number of instructions to process. You should increase the
6878 buffer-size with care.
6881 Not all recording formats may be available on all processors.
6884 The process record and replay target can only debug a process that is
6885 already running. Therefore, you need first to start the process with
6886 the @kbd{run} or @kbd{start} commands, and then start the recording
6887 with the @kbd{record @var{method}} command.
6889 @cindex displaced stepping, and process record and replay
6890 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6891 will be automatically disabled when process record and replay target
6892 is started. That's because the process record and replay target
6893 doesn't support displaced stepping.
6895 @cindex non-stop mode, and process record and replay
6896 @cindex asynchronous execution, and process record and replay
6897 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6898 the asynchronous execution mode (@pxref{Background Execution}), not
6899 all recording methods are available. The @code{full} recording method
6900 does not support these two modes.
6905 Stop the process record and replay target. When process record and
6906 replay target stops, the entire execution log will be deleted and the
6907 inferior will either be terminated, or will remain in its final state.
6909 When you stop the process record and replay target in record mode (at
6910 the end of the execution log), the inferior will be stopped at the
6911 next instruction that would have been recorded. In other words, if
6912 you record for a while and then stop recording, the inferior process
6913 will be left in the same state as if the recording never happened.
6915 On the other hand, if the process record and replay target is stopped
6916 while in replay mode (that is, not at the end of the execution log,
6917 but at some earlier point), the inferior process will become ``live''
6918 at that earlier state, and it will then be possible to continue the
6919 usual ``live'' debugging of the process from that state.
6921 When the inferior process exits, or @value{GDBN} detaches from it,
6922 process record and replay target will automatically stop itself.
6926 Go to a specific location in the execution log. There are several
6927 ways to specify the location to go to:
6930 @item record goto begin
6931 @itemx record goto start
6932 Go to the beginning of the execution log.
6934 @item record goto end
6935 Go to the end of the execution log.
6937 @item record goto @var{n}
6938 Go to instruction number @var{n} in the execution log.
6942 @item record save @var{filename}
6943 Save the execution log to a file @file{@var{filename}}.
6944 Default filename is @file{gdb_record.@var{process_id}}, where
6945 @var{process_id} is the process ID of the inferior.
6947 This command may not be available for all recording methods.
6949 @kindex record restore
6950 @item record restore @var{filename}
6951 Restore the execution log from a file @file{@var{filename}}.
6952 File must have been created with @code{record save}.
6954 @kindex set record full
6955 @item set record full insn-number-max @var{limit}
6956 @itemx set record full insn-number-max unlimited
6957 Set the limit of instructions to be recorded for the @code{full}
6958 recording method. Default value is 200000.
6960 If @var{limit} is a positive number, then @value{GDBN} will start
6961 deleting instructions from the log once the number of the record
6962 instructions becomes greater than @var{limit}. For every new recorded
6963 instruction, @value{GDBN} will delete the earliest recorded
6964 instruction to keep the number of recorded instructions at the limit.
6965 (Since deleting recorded instructions loses information, @value{GDBN}
6966 lets you control what happens when the limit is reached, by means of
6967 the @code{stop-at-limit} option, described below.)
6969 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6970 delete recorded instructions from the execution log. The number of
6971 recorded instructions is limited only by the available memory.
6973 @kindex show record full
6974 @item show record full insn-number-max
6975 Show the limit of instructions to be recorded with the @code{full}
6978 @item set record full stop-at-limit
6979 Control the behavior of the @code{full} recording method when the
6980 number of recorded instructions reaches the limit. If ON (the
6981 default), @value{GDBN} will stop when the limit is reached for the
6982 first time and ask you whether you want to stop the inferior or
6983 continue running it and recording the execution log. If you decide
6984 to continue recording, each new recorded instruction will cause the
6985 oldest one to be deleted.
6987 If this option is OFF, @value{GDBN} will automatically delete the
6988 oldest record to make room for each new one, without asking.
6990 @item show record full stop-at-limit
6991 Show the current setting of @code{stop-at-limit}.
6993 @item set record full memory-query
6994 Control the behavior when @value{GDBN} is unable to record memory
6995 changes caused by an instruction for the @code{full} recording method.
6996 If ON, @value{GDBN} will query whether to stop the inferior in that
6999 If this option is OFF (the default), @value{GDBN} will automatically
7000 ignore the effect of such instructions on memory. Later, when
7001 @value{GDBN} replays this execution log, it will mark the log of this
7002 instruction as not accessible, and it will not affect the replay
7005 @item show record full memory-query
7006 Show the current setting of @code{memory-query}.
7008 @kindex set record btrace
7009 The @code{btrace} record target does not trace data. As a
7010 convenience, when replaying, @value{GDBN} reads read-only memory off
7011 the live program directly, assuming that the addresses of the
7012 read-only areas don't change. This for example makes it possible to
7013 disassemble code while replaying, but not to print variables.
7014 In some cases, being able to inspect variables might be useful.
7015 You can use the following command for that:
7017 @item set record btrace replay-memory-access
7018 Control the behavior of the @code{btrace} recording method when
7019 accessing memory during replay. If @code{read-only} (the default),
7020 @value{GDBN} will only allow accesses to read-only memory.
7021 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7022 and to read-write memory. Beware that the accessed memory corresponds
7023 to the live target and not necessarily to the current replay
7026 @item set record btrace cpu @var{identifier}
7027 Set the processor to be used for enabling workarounds for processor
7028 errata when decoding the trace.
7030 Processor errata are defects in processor operation, caused by its
7031 design or manufacture. They can cause a trace not to match the
7032 specification. This, in turn, may cause trace decode to fail.
7033 @value{GDBN} can detect erroneous trace packets and correct them, thus
7034 avoiding the decoding failures. These corrections are known as
7035 @dfn{errata workarounds}, and are enabled based on the processor on
7036 which the trace was recorded.
7038 By default, @value{GDBN} attempts to detect the processor
7039 automatically, and apply the necessary workarounds for it. However,
7040 you may need to specify the processor if @value{GDBN} does not yet
7041 support it. This command allows you to do that, and also allows to
7042 disable the workarounds.
7044 The argument @var{identifier} identifies the @sc{cpu} and is of the
7045 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7046 there are two special identifiers, @code{none} and @code{auto}
7049 The following vendor identifiers and corresponding processor
7050 identifiers are currently supported:
7052 @multitable @columnfractions .1 .9
7055 @tab @var{family}/@var{model}[/@var{stepping}]
7059 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7060 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7062 If @var{identifier} is @code{auto}, enable errata workarounds for the
7063 processor on which the trace was recorded. If @var{identifier} is
7064 @code{none}, errata workarounds are disabled.
7066 For example, when using an old @value{GDBN} on a new system, decode
7067 may fail because @value{GDBN} does not support the new processor. It
7068 often suffices to specify an older processor that @value{GDBN}
7073 Active record target: record-btrace
7074 Recording format: Intel Processor Trace.
7076 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7077 (gdb) set record btrace cpu intel:6/158
7079 Active record target: record-btrace
7080 Recording format: Intel Processor Trace.
7082 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7085 @kindex show record btrace
7086 @item show record btrace replay-memory-access
7087 Show the current setting of @code{replay-memory-access}.
7089 @item show record btrace cpu
7090 Show the processor to be used for enabling trace decode errata
7093 @kindex set record btrace bts
7094 @item set record btrace bts buffer-size @var{size}
7095 @itemx set record btrace bts buffer-size unlimited
7096 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7097 format. Default is 64KB.
7099 If @var{size} is a positive number, then @value{GDBN} will try to
7100 allocate a buffer of at least @var{size} bytes for each new thread
7101 that uses the btrace recording method and the @acronym{BTS} format.
7102 The actually obtained buffer size may differ from the requested
7103 @var{size}. Use the @code{info record} command to see the actual
7104 buffer size for each thread that uses the btrace recording method and
7105 the @acronym{BTS} format.
7107 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7108 allocate a buffer of 4MB.
7110 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7111 also need longer to process the branch trace data before it can be used.
7113 @item show record btrace bts buffer-size @var{size}
7114 Show the current setting of the requested ring buffer size for branch
7115 tracing in @acronym{BTS} format.
7117 @kindex set record btrace pt
7118 @item set record btrace pt buffer-size @var{size}
7119 @itemx set record btrace pt buffer-size unlimited
7120 Set the requested ring buffer size for branch tracing in Intel
7121 Processor Trace format. Default is 16KB.
7123 If @var{size} is a positive number, then @value{GDBN} will try to
7124 allocate a buffer of at least @var{size} bytes for each new thread
7125 that uses the btrace recording method and the Intel Processor Trace
7126 format. The actually obtained buffer size may differ from the
7127 requested @var{size}. Use the @code{info record} command to see the
7128 actual buffer size for each thread.
7130 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7131 allocate a buffer of 4MB.
7133 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7134 also need longer to process the branch trace data before it can be used.
7136 @item show record btrace pt buffer-size @var{size}
7137 Show the current setting of the requested ring buffer size for branch
7138 tracing in Intel Processor Trace format.
7142 Show various statistics about the recording depending on the recording
7147 For the @code{full} recording method, it shows the state of process
7148 record and its in-memory execution log buffer, including:
7152 Whether in record mode or replay mode.
7154 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7156 Highest recorded instruction number.
7158 Current instruction about to be replayed (if in replay mode).
7160 Number of instructions contained in the execution log.
7162 Maximum number of instructions that may be contained in the execution log.
7166 For the @code{btrace} recording method, it shows:
7172 Number of instructions that have been recorded.
7174 Number of blocks of sequential control-flow formed by the recorded
7177 Whether in record mode or replay mode.
7180 For the @code{bts} recording format, it also shows:
7183 Size of the perf ring buffer.
7186 For the @code{pt} recording format, it also shows:
7189 Size of the perf ring buffer.
7193 @kindex record delete
7196 When record target runs in replay mode (``in the past''), delete the
7197 subsequent execution log and begin to record a new execution log starting
7198 from the current address. This means you will abandon the previously
7199 recorded ``future'' and begin recording a new ``future''.
7201 @kindex record instruction-history
7202 @kindex rec instruction-history
7203 @item record instruction-history
7204 Disassembles instructions from the recorded execution log. By
7205 default, ten instructions are disassembled. This can be changed using
7206 the @code{set record instruction-history-size} command. Instructions
7207 are printed in execution order.
7209 It can also print mixed source+disassembly if you specify the the
7210 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7211 as well as in symbolic form by specifying the @code{/r} modifier.
7213 The current position marker is printed for the instruction at the
7214 current program counter value. This instruction can appear multiple
7215 times in the trace and the current position marker will be printed
7216 every time. To omit the current position marker, specify the
7219 To better align the printed instructions when the trace contains
7220 instructions from more than one function, the function name may be
7221 omitted by specifying the @code{/f} modifier.
7223 Speculatively executed instructions are prefixed with @samp{?}. This
7224 feature is not available for all recording formats.
7226 There are several ways to specify what part of the execution log to
7230 @item record instruction-history @var{insn}
7231 Disassembles ten instructions starting from instruction number
7234 @item record instruction-history @var{insn}, +/-@var{n}
7235 Disassembles @var{n} instructions around instruction number
7236 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7237 @var{n} instructions after instruction number @var{insn}. If
7238 @var{n} is preceded with @code{-}, disassembles @var{n}
7239 instructions before instruction number @var{insn}.
7241 @item record instruction-history
7242 Disassembles ten more instructions after the last disassembly.
7244 @item record instruction-history -
7245 Disassembles ten more instructions before the last disassembly.
7247 @item record instruction-history @var{begin}, @var{end}
7248 Disassembles instructions beginning with instruction number
7249 @var{begin} until instruction number @var{end}. The instruction
7250 number @var{end} is included.
7253 This command may not be available for all recording methods.
7256 @item set record instruction-history-size @var{size}
7257 @itemx set record instruction-history-size unlimited
7258 Define how many instructions to disassemble in the @code{record
7259 instruction-history} command. The default value is 10.
7260 A @var{size} of @code{unlimited} means unlimited instructions.
7263 @item show record instruction-history-size
7264 Show how many instructions to disassemble in the @code{record
7265 instruction-history} command.
7267 @kindex record function-call-history
7268 @kindex rec function-call-history
7269 @item record function-call-history
7270 Prints the execution history at function granularity. It prints one
7271 line for each sequence of instructions that belong to the same
7272 function giving the name of that function, the source lines
7273 for this instruction sequence (if the @code{/l} modifier is
7274 specified), and the instructions numbers that form the sequence (if
7275 the @code{/i} modifier is specified). The function names are indented
7276 to reflect the call stack depth if the @code{/c} modifier is
7277 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7281 (@value{GDBP}) @b{list 1, 10}
7292 (@value{GDBP}) @b{record function-call-history /ilc}
7293 1 bar inst 1,4 at foo.c:6,8
7294 2 foo inst 5,10 at foo.c:2,3
7295 3 bar inst 11,13 at foo.c:9,10
7298 By default, ten lines are printed. This can be changed using the
7299 @code{set record function-call-history-size} command. Functions are
7300 printed in execution order. There are several ways to specify what
7304 @item record function-call-history @var{func}
7305 Prints ten functions starting from function number @var{func}.
7307 @item record function-call-history @var{func}, +/-@var{n}
7308 Prints @var{n} functions around function number @var{func}. If
7309 @var{n} is preceded with @code{+}, prints @var{n} functions after
7310 function number @var{func}. If @var{n} is preceded with @code{-},
7311 prints @var{n} functions before function number @var{func}.
7313 @item record function-call-history
7314 Prints ten more functions after the last ten-line print.
7316 @item record function-call-history -
7317 Prints ten more functions before the last ten-line print.
7319 @item record function-call-history @var{begin}, @var{end}
7320 Prints functions beginning with function number @var{begin} until
7321 function number @var{end}. The function number @var{end} is included.
7324 This command may not be available for all recording methods.
7326 @item set record function-call-history-size @var{size}
7327 @itemx set record function-call-history-size unlimited
7328 Define how many lines to print in the
7329 @code{record function-call-history} command. The default value is 10.
7330 A size of @code{unlimited} means unlimited lines.
7332 @item show record function-call-history-size
7333 Show how many lines to print in the
7334 @code{record function-call-history} command.
7339 @chapter Examining the Stack
7341 When your program has stopped, the first thing you need to know is where it
7342 stopped and how it got there.
7345 Each time your program performs a function call, information about the call
7347 That information includes the location of the call in your program,
7348 the arguments of the call,
7349 and the local variables of the function being called.
7350 The information is saved in a block of data called a @dfn{stack frame}.
7351 The stack frames are allocated in a region of memory called the @dfn{call
7354 When your program stops, the @value{GDBN} commands for examining the
7355 stack allow you to see all of this information.
7357 @cindex selected frame
7358 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7359 @value{GDBN} commands refer implicitly to the selected frame. In
7360 particular, whenever you ask @value{GDBN} for the value of a variable in
7361 your program, the value is found in the selected frame. There are
7362 special @value{GDBN} commands to select whichever frame you are
7363 interested in. @xref{Selection, ,Selecting a Frame}.
7365 When your program stops, @value{GDBN} automatically selects the
7366 currently executing frame and describes it briefly, similar to the
7367 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7370 * Frames:: Stack frames
7371 * Backtrace:: Backtraces
7372 * Selection:: Selecting a frame
7373 * Frame Info:: Information on a frame
7374 * Frame Apply:: Applying a command to several frames
7375 * Frame Filter Management:: Managing frame filters
7380 @section Stack Frames
7382 @cindex frame, definition
7384 The call stack is divided up into contiguous pieces called @dfn{stack
7385 frames}, or @dfn{frames} for short; each frame is the data associated
7386 with one call to one function. The frame contains the arguments given
7387 to the function, the function's local variables, and the address at
7388 which the function is executing.
7390 @cindex initial frame
7391 @cindex outermost frame
7392 @cindex innermost frame
7393 When your program is started, the stack has only one frame, that of the
7394 function @code{main}. This is called the @dfn{initial} frame or the
7395 @dfn{outermost} frame. Each time a function is called, a new frame is
7396 made. Each time a function returns, the frame for that function invocation
7397 is eliminated. If a function is recursive, there can be many frames for
7398 the same function. The frame for the function in which execution is
7399 actually occurring is called the @dfn{innermost} frame. This is the most
7400 recently created of all the stack frames that still exist.
7402 @cindex frame pointer
7403 Inside your program, stack frames are identified by their addresses. A
7404 stack frame consists of many bytes, each of which has its own address; each
7405 kind of computer has a convention for choosing one byte whose
7406 address serves as the address of the frame. Usually this address is kept
7407 in a register called the @dfn{frame pointer register}
7408 (@pxref{Registers, $fp}) while execution is going on in that frame.
7411 @cindex frame number
7412 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7413 number that is zero for the innermost frame, one for the frame that
7414 called it, and so on upward. These level numbers give you a way of
7415 designating stack frames in @value{GDBN} commands. The terms
7416 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7417 describe this number.
7419 @c The -fomit-frame-pointer below perennially causes hbox overflow
7420 @c underflow problems.
7421 @cindex frameless execution
7422 Some compilers provide a way to compile functions so that they operate
7423 without stack frames. (For example, the @value{NGCC} option
7425 @samp{-fomit-frame-pointer}
7427 generates functions without a frame.)
7428 This is occasionally done with heavily used library functions to save
7429 the frame setup time. @value{GDBN} has limited facilities for dealing
7430 with these function invocations. If the innermost function invocation
7431 has no stack frame, @value{GDBN} nevertheless regards it as though
7432 it had a separate frame, which is numbered zero as usual, allowing
7433 correct tracing of the function call chain. However, @value{GDBN} has
7434 no provision for frameless functions elsewhere in the stack.
7440 @cindex call stack traces
7441 A backtrace is a summary of how your program got where it is. It shows one
7442 line per frame, for many frames, starting with the currently executing
7443 frame (frame zero), followed by its caller (frame one), and on up the
7446 @anchor{backtrace-command}
7448 @kindex bt @r{(@code{backtrace})}
7449 To print a backtrace of the entire stack, use the @code{backtrace}
7450 command, or its alias @code{bt}. This command will print one line per
7451 frame for frames in the stack. By default, all stack frames are
7452 printed. You can stop the backtrace at any time by typing the system
7453 interrupt character, normally @kbd{Ctrl-c}.
7456 @item backtrace [@var{args}@dots{}]
7457 @itemx bt [@var{args}@dots{}]
7458 Print the backtrace of the entire stack. The optional @var{args} can
7459 be one of the following:
7464 Print only the innermost @var{n} frames, where @var{n} is a positive
7469 Print only the outermost @var{n} frames, where @var{n} is a positive
7473 Print the values of the local variables also. This can be combined
7474 with a number to limit the number of frames shown.
7477 Do not run Python frame filters on this backtrace. @xref{Frame
7478 Filter API}, for more information. Additionally use @ref{disable
7479 frame-filter all} to turn off all frame filters. This is only
7480 relevant when @value{GDBN} has been configured with @code{Python}
7484 A Python frame filter might decide to ``elide'' some frames. Normally
7485 such elided frames are still printed, but they are indented relative
7486 to the filtered frames that cause them to be elided. The @code{hide}
7487 option causes elided frames to not be printed at all.
7493 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7494 are additional aliases for @code{backtrace}.
7496 @cindex multiple threads, backtrace
7497 In a multi-threaded program, @value{GDBN} by default shows the
7498 backtrace only for the current thread. To display the backtrace for
7499 several or all of the threads, use the command @code{thread apply}
7500 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7501 apply all backtrace}, @value{GDBN} will display the backtrace for all
7502 the threads; this is handy when you debug a core dump of a
7503 multi-threaded program.
7505 Each line in the backtrace shows the frame number and the function name.
7506 The program counter value is also shown---unless you use @code{set
7507 print address off}. The backtrace also shows the source file name and
7508 line number, as well as the arguments to the function. The program
7509 counter value is omitted if it is at the beginning of the code for that
7512 Here is an example of a backtrace. It was made with the command
7513 @samp{bt 3}, so it shows the innermost three frames.
7517 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7519 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7520 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7522 (More stack frames follow...)
7527 The display for frame zero does not begin with a program counter
7528 value, indicating that your program has stopped at the beginning of the
7529 code for line @code{993} of @code{builtin.c}.
7532 The value of parameter @code{data} in frame 1 has been replaced by
7533 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7534 only if it is a scalar (integer, pointer, enumeration, etc). See command
7535 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7536 on how to configure the way function parameter values are printed.
7538 @cindex optimized out, in backtrace
7539 @cindex function call arguments, optimized out
7540 If your program was compiled with optimizations, some compilers will
7541 optimize away arguments passed to functions if those arguments are
7542 never used after the call. Such optimizations generate code that
7543 passes arguments through registers, but doesn't store those arguments
7544 in the stack frame. @value{GDBN} has no way of displaying such
7545 arguments in stack frames other than the innermost one. Here's what
7546 such a backtrace might look like:
7550 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7552 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7553 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7555 (More stack frames follow...)
7560 The values of arguments that were not saved in their stack frames are
7561 shown as @samp{<optimized out>}.
7563 If you need to display the values of such optimized-out arguments,
7564 either deduce that from other variables whose values depend on the one
7565 you are interested in, or recompile without optimizations.
7567 @cindex backtrace beyond @code{main} function
7568 @cindex program entry point
7569 @cindex startup code, and backtrace
7570 Most programs have a standard user entry point---a place where system
7571 libraries and startup code transition into user code. For C this is
7572 @code{main}@footnote{
7573 Note that embedded programs (the so-called ``free-standing''
7574 environment) are not required to have a @code{main} function as the
7575 entry point. They could even have multiple entry points.}.
7576 When @value{GDBN} finds the entry function in a backtrace
7577 it will terminate the backtrace, to avoid tracing into highly
7578 system-specific (and generally uninteresting) code.
7580 If you need to examine the startup code, or limit the number of levels
7581 in a backtrace, you can change this behavior:
7584 @item set backtrace past-main
7585 @itemx set backtrace past-main on
7586 @kindex set backtrace
7587 Backtraces will continue past the user entry point.
7589 @item set backtrace past-main off
7590 Backtraces will stop when they encounter the user entry point. This is the
7593 @item show backtrace past-main
7594 @kindex show backtrace
7595 Display the current user entry point backtrace policy.
7597 @item set backtrace past-entry
7598 @itemx set backtrace past-entry on
7599 Backtraces will continue past the internal entry point of an application.
7600 This entry point is encoded by the linker when the application is built,
7601 and is likely before the user entry point @code{main} (or equivalent) is called.
7603 @item set backtrace past-entry off
7604 Backtraces will stop when they encounter the internal entry point of an
7605 application. This is the default.
7607 @item show backtrace past-entry
7608 Display the current internal entry point backtrace policy.
7610 @item set backtrace limit @var{n}
7611 @itemx set backtrace limit 0
7612 @itemx set backtrace limit unlimited
7613 @cindex backtrace limit
7614 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7615 or zero means unlimited levels.
7617 @item show backtrace limit
7618 Display the current limit on backtrace levels.
7621 You can control how file names are displayed.
7624 @item set filename-display
7625 @itemx set filename-display relative
7626 @cindex filename-display
7627 Display file names relative to the compilation directory. This is the default.
7629 @item set filename-display basename
7630 Display only basename of a filename.
7632 @item set filename-display absolute
7633 Display an absolute filename.
7635 @item show filename-display
7636 Show the current way to display filenames.
7640 @section Selecting a Frame
7642 Most commands for examining the stack and other data in your program work on
7643 whichever stack frame is selected at the moment. Here are the commands for
7644 selecting a stack frame; all of them finish by printing a brief description
7645 of the stack frame just selected.
7648 @kindex frame@r{, selecting}
7649 @kindex f @r{(@code{frame})}
7650 @item frame @r{[} @var{frame-selection-spec} @r{]}
7651 @item f @r{[} @var{frame-selection-spec} @r{]}
7652 The @command{frame} command allows different stack frames to be
7653 selected. The @var{frame-selection-spec} can be any of the following:
7658 @item level @var{num}
7659 Select frame level @var{num}. Recall that frame zero is the innermost
7660 (currently executing) frame, frame one is the frame that called the
7661 innermost one, and so on. The highest level frame is usually the one
7664 As this is the most common method of navigating the frame stack, the
7665 string @command{level} can be omitted. For example, the following two
7666 commands are equivalent:
7669 (@value{GDBP}) frame 3
7670 (@value{GDBP}) frame level 3
7673 @kindex frame address
7674 @item address @var{stack-address}
7675 Select the frame with stack address @var{stack-address}. The
7676 @var{stack-address} for a frame can be seen in the output of
7677 @command{info frame}, for example:
7681 Stack level 1, frame at 0x7fffffffda30:
7682 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7683 tail call frame, caller of frame at 0x7fffffffda30
7684 source language c++.
7685 Arglist at unknown address.
7686 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7689 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7690 indicated by the line:
7693 Stack level 1, frame at 0x7fffffffda30:
7696 @kindex frame function
7697 @item function @var{function-name}
7698 Select the stack frame for function @var{function-name}. If there are
7699 multiple stack frames for function @var{function-name} then the inner
7700 most stack frame is selected.
7703 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7704 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7705 viewed has stack address @var{stack-addr}, and optionally, a program
7706 counter address of @var{pc-addr}.
7708 This is useful mainly if the chaining of stack frames has been
7709 damaged by a bug, making it impossible for @value{GDBN} to assign
7710 numbers properly to all frames. In addition, this can be useful
7711 when your program has multiple stacks and switches between them.
7713 When viewing a frame outside the current backtrace using
7714 @command{frame view} then you can always return to the original
7715 stack using one of the previous stack frame selection instructions,
7716 for example @command{frame level 0}.
7722 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7723 numbers @var{n}, this advances toward the outermost frame, to higher
7724 frame numbers, to frames that have existed longer.
7727 @kindex do @r{(@code{down})}
7729 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7730 positive numbers @var{n}, this advances toward the innermost frame, to
7731 lower frame numbers, to frames that were created more recently.
7732 You may abbreviate @code{down} as @code{do}.
7735 All of these commands end by printing two lines of output describing the
7736 frame. The first line shows the frame number, the function name, the
7737 arguments, and the source file and line number of execution in that
7738 frame. The second line shows the text of that source line.
7746 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7748 10 read_input_file (argv[i]);
7752 After such a printout, the @code{list} command with no arguments
7753 prints ten lines centered on the point of execution in the frame.
7754 You can also edit the program at the point of execution with your favorite
7755 editing program by typing @code{edit}.
7756 @xref{List, ,Printing Source Lines},
7760 @kindex select-frame
7761 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7762 The @code{select-frame} command is a variant of @code{frame} that does
7763 not display the new frame after selecting it. This command is
7764 intended primarily for use in @value{GDBN} command scripts, where the
7765 output might be unnecessary and distracting. The
7766 @var{frame-selection-spec} is as for the @command{frame} command
7767 described in @ref{Selection, ,Selecting a Frame}.
7769 @kindex down-silently
7771 @item up-silently @var{n}
7772 @itemx down-silently @var{n}
7773 These two commands are variants of @code{up} and @code{down},
7774 respectively; they differ in that they do their work silently, without
7775 causing display of the new frame. They are intended primarily for use
7776 in @value{GDBN} command scripts, where the output might be unnecessary and
7781 @section Information About a Frame
7783 There are several other commands to print information about the selected
7789 When used without any argument, this command does not change which
7790 frame is selected, but prints a brief description of the currently
7791 selected stack frame. It can be abbreviated @code{f}. With an
7792 argument, this command is used to select a stack frame.
7793 @xref{Selection, ,Selecting a Frame}.
7796 @kindex info f @r{(@code{info frame})}
7799 This command prints a verbose description of the selected stack frame,
7804 the address of the frame
7806 the address of the next frame down (called by this frame)
7808 the address of the next frame up (caller of this frame)
7810 the language in which the source code corresponding to this frame is written
7812 the address of the frame's arguments
7814 the address of the frame's local variables
7816 the program counter saved in it (the address of execution in the caller frame)
7818 which registers were saved in the frame
7821 @noindent The verbose description is useful when
7822 something has gone wrong that has made the stack format fail to fit
7823 the usual conventions.
7825 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7826 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7827 Print a verbose description of the frame selected by
7828 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7829 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7830 a Frame}). The selected frame remains unchanged by this command.
7833 @item info args [-q]
7834 Print the arguments of the selected frame, each on a separate line.
7836 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7837 printing header information and messages explaining why no argument
7840 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7841 Like @kbd{info args}, but only print the arguments selected
7842 with the provided regexp(s).
7844 If @var{regexp} is provided, print only the arguments whose names
7845 match the regular expression @var{regexp}.
7847 If @var{type_regexp} is provided, print only the arguments whose
7848 types, as printed by the @code{whatis} command, match
7849 the regular expression @var{type_regexp}.
7850 If @var{type_regexp} contains space(s), it should be enclosed in
7851 quote characters. If needed, use backslash to escape the meaning
7852 of special characters or quotes.
7854 If both @var{regexp} and @var{type_regexp} are provided, an argument
7855 is printed only if its name matches @var{regexp} and its type matches
7858 @item info locals [-q]
7860 Print the local variables of the selected frame, each on a separate
7861 line. These are all variables (declared either static or automatic)
7862 accessible at the point of execution of the selected frame.
7864 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7865 printing header information and messages explaining why no local variables
7868 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7869 Like @kbd{info locals}, but only print the local variables selected
7870 with the provided regexp(s).
7872 If @var{regexp} is provided, print only the local variables whose names
7873 match the regular expression @var{regexp}.
7875 If @var{type_regexp} is provided, print only the local variables whose
7876 types, as printed by the @code{whatis} command, match
7877 the regular expression @var{type_regexp}.
7878 If @var{type_regexp} contains space(s), it should be enclosed in
7879 quote characters. If needed, use backslash to escape the meaning
7880 of special characters or quotes.
7882 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7883 is printed only if its name matches @var{regexp} and its type matches
7886 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7887 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7888 For example, your program might use Resource Acquisition Is
7889 Initialization types (RAII) such as @code{lock_something_t}: each
7890 local variable of type @code{lock_something_t} automatically places a
7891 lock that is destroyed when the variable goes out of scope. You can
7892 then list all acquired locks in your program by doing
7894 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7897 or the equivalent shorter form
7899 tfaas i lo -q -t lock_something_t
7905 @section Applying a Command to Several Frames.
7907 @cindex apply command to several frames
7909 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7910 The @code{frame apply} command allows you to apply the named
7911 @var{command} to one or more frames.
7915 Specify @code{all} to apply @var{command} to all frames.
7918 Use @var{count} to apply @var{command} to the innermost @var{count}
7919 frames, where @var{count} is a positive number.
7922 Use @var{-count} to apply @var{command} to the outermost @var{count}
7923 frames, where @var{count} is a positive number.
7926 Use @code{level} to apply @var{command} to the set of frames identified
7927 by the @var{level} list. @var{level} is a frame level or a range of frame
7928 levels as @var{level1}-@var{level2}. The frame level is the number shown
7929 in the first field of the @samp{backtrace} command output.
7930 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7931 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7937 Note that the frames on which @code{frame apply} applies a command are
7938 also influenced by the @code{set backtrace} settings such as @code{set
7939 backtrace past-main} and @code{set backtrace limit N}. See
7940 @xref{Backtrace,,Backtraces}.
7942 The @var{flag} arguments control what output to produce and how to handle
7943 errors raised when applying @var{command} to a frame. @var{flag}
7944 must start with a @code{-} directly followed by one letter in
7945 @code{qcs}. If several flags are provided, they must be given
7946 individually, such as @code{-c -q}.
7948 By default, @value{GDBN} displays some frame information before the
7949 output produced by @var{command}, and an error raised during the
7950 execution of a @var{command} will abort @code{frame apply}. The
7951 following flags can be used to fine-tune this behavior:
7955 The flag @code{-c}, which stands for @samp{continue}, causes any
7956 errors in @var{command} to be displayed, and the execution of
7957 @code{frame apply} then continues.
7959 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7960 or empty output produced by a @var{command} to be silently ignored.
7961 That is, the execution continues, but the frame information and errors
7964 The flag @code{-q} (@samp{quiet}) disables printing the frame
7968 The following example shows how the flags @code{-c} and @code{-s} are
7969 working when applying the command @code{p j} to all frames, where
7970 variable @code{j} can only be successfully printed in the outermost
7971 @code{#1 main} frame.
7975 (gdb) frame apply all p j
7976 #0 some_function (i=5) at fun.c:4
7977 No symbol "j" in current context.
7978 (gdb) frame apply all -c p j
7979 #0 some_function (i=5) at fun.c:4
7980 No symbol "j" in current context.
7981 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7983 (gdb) frame apply all -s p j
7984 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7990 By default, @samp{frame apply}, prints the frame location
7991 information before the command output:
7995 (gdb) frame apply all p $sp
7996 #0 some_function (i=5) at fun.c:4
7997 $4 = (void *) 0xffffd1e0
7998 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7999 $5 = (void *) 0xffffd1f0
8004 If flag @code{-q} is given, no frame information is printed:
8007 (gdb) frame apply all -q p $sp
8008 $12 = (void *) 0xffffd1e0
8009 $13 = (void *) 0xffffd1f0
8017 @cindex apply a command to all frames (ignoring errors and empty output)
8018 @item faas @var{command}
8019 Shortcut for @code{frame apply all -s @var{command}}.
8020 Applies @var{command} on all frames, ignoring errors and empty output.
8022 It can for example be used to print a local variable or a function
8023 argument without knowing the frame where this variable or argument
8026 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8029 Note that the command @code{tfaas @var{command}} applies @var{command}
8030 on all frames of all threads. See @xref{Threads,,Threads}.
8034 @node Frame Filter Management
8035 @section Management of Frame Filters.
8036 @cindex managing frame filters
8038 Frame filters are Python based utilities to manage and decorate the
8039 output of frames. @xref{Frame Filter API}, for further information.
8041 Managing frame filters is performed by several commands available
8042 within @value{GDBN}, detailed here.
8045 @kindex info frame-filter
8046 @item info frame-filter
8047 Print a list of installed frame filters from all dictionaries, showing
8048 their name, priority and enabled status.
8050 @kindex disable frame-filter
8051 @anchor{disable frame-filter all}
8052 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8053 Disable a frame filter in the dictionary matching
8054 @var{filter-dictionary} and @var{filter-name}. The
8055 @var{filter-dictionary} may be @code{all}, @code{global},
8056 @code{progspace}, or the name of the object file where the frame filter
8057 dictionary resides. When @code{all} is specified, all frame filters
8058 across all dictionaries are disabled. The @var{filter-name} is the name
8059 of the frame filter and is used when @code{all} is not the option for
8060 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8061 may be enabled again later.
8063 @kindex enable frame-filter
8064 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8065 Enable a frame filter in the dictionary matching
8066 @var{filter-dictionary} and @var{filter-name}. The
8067 @var{filter-dictionary} may be @code{all}, @code{global},
8068 @code{progspace} or the name of the object file where the frame filter
8069 dictionary resides. When @code{all} is specified, all frame filters across
8070 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8071 filter and is used when @code{all} is not the option for
8072 @var{filter-dictionary}.
8077 (gdb) info frame-filter
8079 global frame-filters:
8080 Priority Enabled Name
8081 1000 No PrimaryFunctionFilter
8084 progspace /build/test frame-filters:
8085 Priority Enabled Name
8086 100 Yes ProgspaceFilter
8088 objfile /build/test frame-filters:
8089 Priority Enabled Name
8090 999 Yes BuildProgra Filter
8092 (gdb) disable frame-filter /build/test BuildProgramFilter
8093 (gdb) info frame-filter
8095 global frame-filters:
8096 Priority Enabled Name
8097 1000 No PrimaryFunctionFilter
8100 progspace /build/test frame-filters:
8101 Priority Enabled Name
8102 100 Yes ProgspaceFilter
8104 objfile /build/test frame-filters:
8105 Priority Enabled Name
8106 999 No BuildProgramFilter
8108 (gdb) enable frame-filter global PrimaryFunctionFilter
8109 (gdb) info frame-filter
8111 global frame-filters:
8112 Priority Enabled Name
8113 1000 Yes PrimaryFunctionFilter
8116 progspace /build/test frame-filters:
8117 Priority Enabled Name
8118 100 Yes ProgspaceFilter
8120 objfile /build/test frame-filters:
8121 Priority Enabled Name
8122 999 No BuildProgramFilter
8125 @kindex set frame-filter priority
8126 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8127 Set the @var{priority} of a frame filter in the dictionary matching
8128 @var{filter-dictionary}, and the frame filter name matching
8129 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8130 @code{progspace} or the name of the object file where the frame filter
8131 dictionary resides. The @var{priority} is an integer.
8133 @kindex show frame-filter priority
8134 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8135 Show the @var{priority} of a frame filter in the dictionary matching
8136 @var{filter-dictionary}, and the frame filter name matching
8137 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8138 @code{progspace} or the name of the object file where the frame filter
8144 (gdb) info frame-filter
8146 global frame-filters:
8147 Priority Enabled Name
8148 1000 Yes PrimaryFunctionFilter
8151 progspace /build/test frame-filters:
8152 Priority Enabled Name
8153 100 Yes ProgspaceFilter
8155 objfile /build/test frame-filters:
8156 Priority Enabled Name
8157 999 No BuildProgramFilter
8159 (gdb) set frame-filter priority global Reverse 50
8160 (gdb) info frame-filter
8162 global frame-filters:
8163 Priority Enabled Name
8164 1000 Yes PrimaryFunctionFilter
8167 progspace /build/test frame-filters:
8168 Priority Enabled Name
8169 100 Yes ProgspaceFilter
8171 objfile /build/test frame-filters:
8172 Priority Enabled Name
8173 999 No BuildProgramFilter
8178 @chapter Examining Source Files
8180 @value{GDBN} can print parts of your program's source, since the debugging
8181 information recorded in the program tells @value{GDBN} what source files were
8182 used to build it. When your program stops, @value{GDBN} spontaneously prints
8183 the line where it stopped. Likewise, when you select a stack frame
8184 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8185 execution in that frame has stopped. You can print other portions of
8186 source files by explicit command.
8188 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8189 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8190 @value{GDBN} under @sc{gnu} Emacs}.
8193 * List:: Printing source lines
8194 * Specify Location:: How to specify code locations
8195 * Edit:: Editing source files
8196 * Search:: Searching source files
8197 * Source Path:: Specifying source directories
8198 * Machine Code:: Source and machine code
8202 @section Printing Source Lines
8205 @kindex l @r{(@code{list})}
8206 To print lines from a source file, use the @code{list} command
8207 (abbreviated @code{l}). By default, ten lines are printed.
8208 There are several ways to specify what part of the file you want to
8209 print; see @ref{Specify Location}, for the full list.
8211 Here are the forms of the @code{list} command most commonly used:
8214 @item list @var{linenum}
8215 Print lines centered around line number @var{linenum} in the
8216 current source file.
8218 @item list @var{function}
8219 Print lines centered around the beginning of function
8223 Print more lines. If the last lines printed were printed with a
8224 @code{list} command, this prints lines following the last lines
8225 printed; however, if the last line printed was a solitary line printed
8226 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8227 Stack}), this prints lines centered around that line.
8230 Print lines just before the lines last printed.
8233 @cindex @code{list}, how many lines to display
8234 By default, @value{GDBN} prints ten source lines with any of these forms of
8235 the @code{list} command. You can change this using @code{set listsize}:
8238 @kindex set listsize
8239 @item set listsize @var{count}
8240 @itemx set listsize unlimited
8241 Make the @code{list} command display @var{count} source lines (unless
8242 the @code{list} argument explicitly specifies some other number).
8243 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8245 @kindex show listsize
8247 Display the number of lines that @code{list} prints.
8250 Repeating a @code{list} command with @key{RET} discards the argument,
8251 so it is equivalent to typing just @code{list}. This is more useful
8252 than listing the same lines again. An exception is made for an
8253 argument of @samp{-}; that argument is preserved in repetition so that
8254 each repetition moves up in the source file.
8256 In general, the @code{list} command expects you to supply zero, one or two
8257 @dfn{locations}. Locations specify source lines; there are several ways
8258 of writing them (@pxref{Specify Location}), but the effect is always
8259 to specify some source line.
8261 Here is a complete description of the possible arguments for @code{list}:
8264 @item list @var{location}
8265 Print lines centered around the line specified by @var{location}.
8267 @item list @var{first},@var{last}
8268 Print lines from @var{first} to @var{last}. Both arguments are
8269 locations. When a @code{list} command has two locations, and the
8270 source file of the second location is omitted, this refers to
8271 the same source file as the first location.
8273 @item list ,@var{last}
8274 Print lines ending with @var{last}.
8276 @item list @var{first},
8277 Print lines starting with @var{first}.
8280 Print lines just after the lines last printed.
8283 Print lines just before the lines last printed.
8286 As described in the preceding table.
8289 @node Specify Location
8290 @section Specifying a Location
8291 @cindex specifying location
8293 @cindex source location
8296 * Linespec Locations:: Linespec locations
8297 * Explicit Locations:: Explicit locations
8298 * Address Locations:: Address locations
8301 Several @value{GDBN} commands accept arguments that specify a location
8302 of your program's code. Since @value{GDBN} is a source-level
8303 debugger, a location usually specifies some line in the source code.
8304 Locations may be specified using three different formats:
8305 linespec locations, explicit locations, or address locations.
8307 @node Linespec Locations
8308 @subsection Linespec Locations
8309 @cindex linespec locations
8311 A @dfn{linespec} is a colon-separated list of source location parameters such
8312 as file name, function name, etc. Here are all the different ways of
8313 specifying a linespec:
8317 Specifies the line number @var{linenum} of the current source file.
8320 @itemx +@var{offset}
8321 Specifies the line @var{offset} lines before or after the @dfn{current
8322 line}. For the @code{list} command, the current line is the last one
8323 printed; for the breakpoint commands, this is the line at which
8324 execution stopped in the currently selected @dfn{stack frame}
8325 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8326 used as the second of the two linespecs in a @code{list} command,
8327 this specifies the line @var{offset} lines up or down from the first
8330 @item @var{filename}:@var{linenum}
8331 Specifies the line @var{linenum} in the source file @var{filename}.
8332 If @var{filename} is a relative file name, then it will match any
8333 source file name with the same trailing components. For example, if
8334 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8335 name of @file{/build/trunk/gcc/expr.c}, but not
8336 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8338 @item @var{function}
8339 Specifies the line that begins the body of the function @var{function}.
8340 For example, in C, this is the line with the open brace.
8342 By default, in C@t{++} and Ada, @var{function} is interpreted as
8343 specifying all functions named @var{function} in all scopes. For
8344 C@t{++}, this means in all namespaces and classes. For Ada, this
8345 means in all packages.
8347 For example, assuming a program with C@t{++} symbols named
8348 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8349 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8351 Commands that accept a linespec let you override this with the
8352 @code{-qualified} option. For example, @w{@kbd{break -qualified
8353 func}} sets a breakpoint on a free-function named @code{func} ignoring
8354 any C@t{++} class methods and namespace functions called @code{func}.
8356 @xref{Explicit Locations}.
8358 @item @var{function}:@var{label}
8359 Specifies the line where @var{label} appears in @var{function}.
8361 @item @var{filename}:@var{function}
8362 Specifies the line that begins the body of the function @var{function}
8363 in the file @var{filename}. You only need the file name with a
8364 function name to avoid ambiguity when there are identically named
8365 functions in different source files.
8368 Specifies the line at which the label named @var{label} appears
8369 in the function corresponding to the currently selected stack frame.
8370 If there is no current selected stack frame (for instance, if the inferior
8371 is not running), then @value{GDBN} will not search for a label.
8373 @cindex breakpoint at static probe point
8374 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8375 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8376 applications to embed static probes. @xref{Static Probe Points}, for more
8377 information on finding and using static probes. This form of linespec
8378 specifies the location of such a static probe.
8380 If @var{objfile} is given, only probes coming from that shared library
8381 or executable matching @var{objfile} as a regular expression are considered.
8382 If @var{provider} is given, then only probes from that provider are considered.
8383 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8384 each one of those probes.
8387 @node Explicit Locations
8388 @subsection Explicit Locations
8389 @cindex explicit locations
8391 @dfn{Explicit locations} allow the user to directly specify the source
8392 location's parameters using option-value pairs.
8394 Explicit locations are useful when several functions, labels, or
8395 file names have the same name (base name for files) in the program's
8396 sources. In these cases, explicit locations point to the source
8397 line you meant more accurately and unambiguously. Also, using
8398 explicit locations might be faster in large programs.
8400 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8401 defined in the file named @file{foo} or the label @code{bar} in a function
8402 named @code{foo}. @value{GDBN} must search either the file system or
8403 the symbol table to know.
8405 The list of valid explicit location options is summarized in the
8409 @item -source @var{filename}
8410 The value specifies the source file name. To differentiate between
8411 files with the same base name, prepend as many directories as is necessary
8412 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8413 @value{GDBN} will use the first file it finds with the given base
8414 name. This option requires the use of either @code{-function} or @code{-line}.
8416 @item -function @var{function}
8417 The value specifies the name of a function. Operations
8418 on function locations unmodified by other options (such as @code{-label}
8419 or @code{-line}) refer to the line that begins the body of the function.
8420 In C, for example, this is the line with the open brace.
8422 By default, in C@t{++} and Ada, @var{function} is interpreted as
8423 specifying all functions named @var{function} in all scopes. For
8424 C@t{++}, this means in all namespaces and classes. For Ada, this
8425 means in all packages.
8427 For example, assuming a program with C@t{++} symbols named
8428 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8429 -function func}} and @w{@kbd{break -function B::func}} set a
8430 breakpoint on both symbols.
8432 You can use the @kbd{-qualified} flag to override this (see below).
8436 This flag makes @value{GDBN} interpret a function name specified with
8437 @kbd{-function} as a complete fully-qualified name.
8439 For example, assuming a C@t{++} program with symbols named
8440 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8441 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8443 (Note: the @kbd{-qualified} option can precede a linespec as well
8444 (@pxref{Linespec Locations}), so the particular example above could be
8445 simplified as @w{@kbd{break -qualified B::func}}.)
8447 @item -label @var{label}
8448 The value specifies the name of a label. When the function
8449 name is not specified, the label is searched in the function of the currently
8450 selected stack frame.
8452 @item -line @var{number}
8453 The value specifies a line offset for the location. The offset may either
8454 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8455 the command. When specified without any other options, the line offset is
8456 relative to the current line.
8459 Explicit location options may be abbreviated by omitting any non-unique
8460 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8462 @node Address Locations
8463 @subsection Address Locations
8464 @cindex address locations
8466 @dfn{Address locations} indicate a specific program address. They have
8467 the generalized form *@var{address}.
8469 For line-oriented commands, such as @code{list} and @code{edit}, this
8470 specifies a source line that contains @var{address}. For @code{break} and
8471 other breakpoint-oriented commands, this can be used to set breakpoints in
8472 parts of your program which do not have debugging information or
8475 Here @var{address} may be any expression valid in the current working
8476 language (@pxref{Languages, working language}) that specifies a code
8477 address. In addition, as a convenience, @value{GDBN} extends the
8478 semantics of expressions used in locations to cover several situations
8479 that frequently occur during debugging. Here are the various forms
8483 @item @var{expression}
8484 Any expression valid in the current working language.
8486 @item @var{funcaddr}
8487 An address of a function or procedure derived from its name. In C,
8488 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8489 simply the function's name @var{function} (and actually a special case
8490 of a valid expression). In Pascal and Modula-2, this is
8491 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8492 (although the Pascal form also works).
8494 This form specifies the address of the function's first instruction,
8495 before the stack frame and arguments have been set up.
8497 @item '@var{filename}':@var{funcaddr}
8498 Like @var{funcaddr} above, but also specifies the name of the source
8499 file explicitly. This is useful if the name of the function does not
8500 specify the function unambiguously, e.g., if there are several
8501 functions with identical names in different source files.
8505 @section Editing Source Files
8506 @cindex editing source files
8509 @kindex e @r{(@code{edit})}
8510 To edit the lines in a source file, use the @code{edit} command.
8511 The editing program of your choice
8512 is invoked with the current line set to
8513 the active line in the program.
8514 Alternatively, there are several ways to specify what part of the file you
8515 want to print if you want to see other parts of the program:
8518 @item edit @var{location}
8519 Edit the source file specified by @code{location}. Editing starts at
8520 that @var{location}, e.g., at the specified source line of the
8521 specified file. @xref{Specify Location}, for all the possible forms
8522 of the @var{location} argument; here are the forms of the @code{edit}
8523 command most commonly used:
8526 @item edit @var{number}
8527 Edit the current source file with @var{number} as the active line number.
8529 @item edit @var{function}
8530 Edit the file containing @var{function} at the beginning of its definition.
8535 @subsection Choosing your Editor
8536 You can customize @value{GDBN} to use any editor you want
8538 The only restriction is that your editor (say @code{ex}), recognizes the
8539 following command-line syntax:
8541 ex +@var{number} file
8543 The optional numeric value +@var{number} specifies the number of the line in
8544 the file where to start editing.}.
8545 By default, it is @file{@value{EDITOR}}, but you can change this
8546 by setting the environment variable @code{EDITOR} before using
8547 @value{GDBN}. For example, to configure @value{GDBN} to use the
8548 @code{vi} editor, you could use these commands with the @code{sh} shell:
8554 or in the @code{csh} shell,
8556 setenv EDITOR /usr/bin/vi
8561 @section Searching Source Files
8562 @cindex searching source files
8564 There are two commands for searching through the current source file for a
8569 @kindex forward-search
8570 @kindex fo @r{(@code{forward-search})}
8571 @item forward-search @var{regexp}
8572 @itemx search @var{regexp}
8573 The command @samp{forward-search @var{regexp}} checks each line,
8574 starting with the one following the last line listed, for a match for
8575 @var{regexp}. It lists the line that is found. You can use the
8576 synonym @samp{search @var{regexp}} or abbreviate the command name as
8579 @kindex reverse-search
8580 @item reverse-search @var{regexp}
8581 The command @samp{reverse-search @var{regexp}} checks each line, starting
8582 with the one before the last line listed and going backward, for a match
8583 for @var{regexp}. It lists the line that is found. You can abbreviate
8584 this command as @code{rev}.
8588 @section Specifying Source Directories
8591 @cindex directories for source files
8592 Executable programs sometimes do not record the directories of the source
8593 files from which they were compiled, just the names. Even when they do,
8594 the directories could be moved between the compilation and your debugging
8595 session. @value{GDBN} has a list of directories to search for source files;
8596 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8597 it tries all the directories in the list, in the order they are present
8598 in the list, until it finds a file with the desired name.
8600 For example, suppose an executable references the file
8601 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8602 @file{/mnt/cross}. The file is first looked up literally; if this
8603 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8604 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8605 message is printed. @value{GDBN} does not look up the parts of the
8606 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8607 Likewise, the subdirectories of the source path are not searched: if
8608 the source path is @file{/mnt/cross}, and the binary refers to
8609 @file{foo.c}, @value{GDBN} would not find it under
8610 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8612 Plain file names, relative file names with leading directories, file
8613 names containing dots, etc.@: are all treated as described above; for
8614 instance, if the source path is @file{/mnt/cross}, and the source file
8615 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8616 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8617 that---@file{/mnt/cross/foo.c}.
8619 Note that the executable search path is @emph{not} used to locate the
8622 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8623 any information it has cached about where source files are found and where
8624 each line is in the file.
8628 When you start @value{GDBN}, its source path includes only @samp{cdir}
8629 and @samp{cwd}, in that order.
8630 To add other directories, use the @code{directory} command.
8632 The search path is used to find both program source files and @value{GDBN}
8633 script files (read using the @samp{-command} option and @samp{source} command).
8635 In addition to the source path, @value{GDBN} provides a set of commands
8636 that manage a list of source path substitution rules. A @dfn{substitution
8637 rule} specifies how to rewrite source directories stored in the program's
8638 debug information in case the sources were moved to a different
8639 directory between compilation and debugging. A rule is made of
8640 two strings, the first specifying what needs to be rewritten in
8641 the path, and the second specifying how it should be rewritten.
8642 In @ref{set substitute-path}, we name these two parts @var{from} and
8643 @var{to} respectively. @value{GDBN} does a simple string replacement
8644 of @var{from} with @var{to} at the start of the directory part of the
8645 source file name, and uses that result instead of the original file
8646 name to look up the sources.
8648 Using the previous example, suppose the @file{foo-1.0} tree has been
8649 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8650 @value{GDBN} to replace @file{/usr/src} in all source path names with
8651 @file{/mnt/cross}. The first lookup will then be
8652 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8653 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8654 substitution rule, use the @code{set substitute-path} command
8655 (@pxref{set substitute-path}).
8657 To avoid unexpected substitution results, a rule is applied only if the
8658 @var{from} part of the directory name ends at a directory separator.
8659 For instance, a rule substituting @file{/usr/source} into
8660 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8661 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8662 is applied only at the beginning of the directory name, this rule will
8663 not be applied to @file{/root/usr/source/baz.c} either.
8665 In many cases, you can achieve the same result using the @code{directory}
8666 command. However, @code{set substitute-path} can be more efficient in
8667 the case where the sources are organized in a complex tree with multiple
8668 subdirectories. With the @code{directory} command, you need to add each
8669 subdirectory of your project. If you moved the entire tree while
8670 preserving its internal organization, then @code{set substitute-path}
8671 allows you to direct the debugger to all the sources with one single
8674 @code{set substitute-path} is also more than just a shortcut command.
8675 The source path is only used if the file at the original location no
8676 longer exists. On the other hand, @code{set substitute-path} modifies
8677 the debugger behavior to look at the rewritten location instead. So, if
8678 for any reason a source file that is not relevant to your executable is
8679 located at the original location, a substitution rule is the only
8680 method available to point @value{GDBN} at the new location.
8682 @cindex @samp{--with-relocated-sources}
8683 @cindex default source path substitution
8684 You can configure a default source path substitution rule by
8685 configuring @value{GDBN} with the
8686 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8687 should be the name of a directory under @value{GDBN}'s configured
8688 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8689 directory names in debug information under @var{dir} will be adjusted
8690 automatically if the installed @value{GDBN} is moved to a new
8691 location. This is useful if @value{GDBN}, libraries or executables
8692 with debug information and corresponding source code are being moved
8696 @item directory @var{dirname} @dots{}
8697 @item dir @var{dirname} @dots{}
8698 Add directory @var{dirname} to the front of the source path. Several
8699 directory names may be given to this command, separated by @samp{:}
8700 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8701 part of absolute file names) or
8702 whitespace. You may specify a directory that is already in the source
8703 path; this moves it forward, so @value{GDBN} searches it sooner.
8707 @vindex $cdir@r{, convenience variable}
8708 @vindex $cwd@r{, convenience variable}
8709 @cindex compilation directory
8710 @cindex current directory
8711 @cindex working directory
8712 @cindex directory, current
8713 @cindex directory, compilation
8714 You can use the string @samp{$cdir} to refer to the compilation
8715 directory (if one is recorded), and @samp{$cwd} to refer to the current
8716 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8717 tracks the current working directory as it changes during your @value{GDBN}
8718 session, while the latter is immediately expanded to the current
8719 directory at the time you add an entry to the source path.
8722 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8724 @c RET-repeat for @code{directory} is explicitly disabled, but since
8725 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8727 @item set directories @var{path-list}
8728 @kindex set directories
8729 Set the source path to @var{path-list}.
8730 @samp{$cdir:$cwd} are added if missing.
8732 @item show directories
8733 @kindex show directories
8734 Print the source path: show which directories it contains.
8736 @anchor{set substitute-path}
8737 @item set substitute-path @var{from} @var{to}
8738 @kindex set substitute-path
8739 Define a source path substitution rule, and add it at the end of the
8740 current list of existing substitution rules. If a rule with the same
8741 @var{from} was already defined, then the old rule is also deleted.
8743 For example, if the file @file{/foo/bar/baz.c} was moved to
8744 @file{/mnt/cross/baz.c}, then the command
8747 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8751 will tell @value{GDBN} to replace @samp{/foo/bar} with
8752 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8753 @file{baz.c} even though it was moved.
8755 In the case when more than one substitution rule have been defined,
8756 the rules are evaluated one by one in the order where they have been
8757 defined. The first one matching, if any, is selected to perform
8760 For instance, if we had entered the following commands:
8763 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8764 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8768 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8769 @file{/mnt/include/defs.h} by using the first rule. However, it would
8770 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8771 @file{/mnt/src/lib/foo.c}.
8774 @item unset substitute-path [path]
8775 @kindex unset substitute-path
8776 If a path is specified, search the current list of substitution rules
8777 for a rule that would rewrite that path. Delete that rule if found.
8778 A warning is emitted by the debugger if no rule could be found.
8780 If no path is specified, then all substitution rules are deleted.
8782 @item show substitute-path [path]
8783 @kindex show substitute-path
8784 If a path is specified, then print the source path substitution rule
8785 which would rewrite that path, if any.
8787 If no path is specified, then print all existing source path substitution
8792 If your source path is cluttered with directories that are no longer of
8793 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8794 versions of source. You can correct the situation as follows:
8798 Use @code{directory} with no argument to reset the source path to its default value.
8801 Use @code{directory} with suitable arguments to reinstall the
8802 directories you want in the source path. You can add all the
8803 directories in one command.
8807 @section Source and Machine Code
8808 @cindex source line and its code address
8810 You can use the command @code{info line} to map source lines to program
8811 addresses (and vice versa), and the command @code{disassemble} to display
8812 a range of addresses as machine instructions. You can use the command
8813 @code{set disassemble-next-line} to set whether to disassemble next
8814 source line when execution stops. When run under @sc{gnu} Emacs
8815 mode, the @code{info line} command causes the arrow to point to the
8816 line specified. Also, @code{info line} prints addresses in symbolic form as
8822 @itemx info line @var{location}
8823 Print the starting and ending addresses of the compiled code for
8824 source line @var{location}. You can specify source lines in any of
8825 the ways documented in @ref{Specify Location}. With no @var{location}
8826 information about the current source line is printed.
8829 For example, we can use @code{info line} to discover the location of
8830 the object code for the first line of function
8831 @code{m4_changequote}:
8834 (@value{GDBP}) info line m4_changequote
8835 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8836 ends at 0x6350 <m4_changequote+4>.
8840 @cindex code address and its source line
8841 We can also inquire (using @code{*@var{addr}} as the form for
8842 @var{location}) what source line covers a particular address:
8844 (@value{GDBP}) info line *0x63ff
8845 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8846 ends at 0x6404 <m4_changequote+184>.
8849 @cindex @code{$_} and @code{info line}
8850 @cindex @code{x} command, default address
8851 @kindex x@r{(examine), and} info line
8852 After @code{info line}, the default address for the @code{x} command
8853 is changed to the starting address of the line, so that @samp{x/i} is
8854 sufficient to begin examining the machine code (@pxref{Memory,
8855 ,Examining Memory}). Also, this address is saved as the value of the
8856 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8859 @cindex info line, repeated calls
8860 After @code{info line}, using @code{info line} again without
8861 specifying a location will display information about the next source
8866 @cindex assembly instructions
8867 @cindex instructions, assembly
8868 @cindex machine instructions
8869 @cindex listing machine instructions
8871 @itemx disassemble /m
8872 @itemx disassemble /s
8873 @itemx disassemble /r
8874 This specialized command dumps a range of memory as machine
8875 instructions. It can also print mixed source+disassembly by specifying
8876 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8877 as well as in symbolic form by specifying the @code{/r} modifier.
8878 The default memory range is the function surrounding the
8879 program counter of the selected frame. A single argument to this
8880 command is a program counter value; @value{GDBN} dumps the function
8881 surrounding this value. When two arguments are given, they should
8882 be separated by a comma, possibly surrounded by whitespace. The
8883 arguments specify a range of addresses to dump, in one of two forms:
8886 @item @var{start},@var{end}
8887 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8888 @item @var{start},+@var{length}
8889 the addresses from @var{start} (inclusive) to
8890 @code{@var{start}+@var{length}} (exclusive).
8894 When 2 arguments are specified, the name of the function is also
8895 printed (since there could be several functions in the given range).
8897 The argument(s) can be any expression yielding a numeric value, such as
8898 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8900 If the range of memory being disassembled contains current program counter,
8901 the instruction at that location is shown with a @code{=>} marker.
8904 The following example shows the disassembly of a range of addresses of
8905 HP PA-RISC 2.0 code:
8908 (@value{GDBP}) disas 0x32c4, 0x32e4
8909 Dump of assembler code from 0x32c4 to 0x32e4:
8910 0x32c4 <main+204>: addil 0,dp
8911 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8912 0x32cc <main+212>: ldil 0x3000,r31
8913 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8914 0x32d4 <main+220>: ldo 0(r31),rp
8915 0x32d8 <main+224>: addil -0x800,dp
8916 0x32dc <main+228>: ldo 0x588(r1),r26
8917 0x32e0 <main+232>: ldil 0x3000,r31
8918 End of assembler dump.
8921 Here is an example showing mixed source+assembly for Intel x86
8922 with @code{/m} or @code{/s}, when the program is stopped just after
8923 function prologue in a non-optimized function with no inline code.
8926 (@value{GDBP}) disas /m main
8927 Dump of assembler code for function main:
8929 0x08048330 <+0>: push %ebp
8930 0x08048331 <+1>: mov %esp,%ebp
8931 0x08048333 <+3>: sub $0x8,%esp
8932 0x08048336 <+6>: and $0xfffffff0,%esp
8933 0x08048339 <+9>: sub $0x10,%esp
8935 6 printf ("Hello.\n");
8936 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8937 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8941 0x08048348 <+24>: mov $0x0,%eax
8942 0x0804834d <+29>: leave
8943 0x0804834e <+30>: ret
8945 End of assembler dump.
8948 The @code{/m} option is deprecated as its output is not useful when
8949 there is either inlined code or re-ordered code.
8950 The @code{/s} option is the preferred choice.
8951 Here is an example for AMD x86-64 showing the difference between
8952 @code{/m} output and @code{/s} output.
8953 This example has one inline function defined in a header file,
8954 and the code is compiled with @samp{-O2} optimization.
8955 Note how the @code{/m} output is missing the disassembly of
8956 several instructions that are present in the @code{/s} output.
8986 (@value{GDBP}) disas /m main
8987 Dump of assembler code for function main:
8991 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8992 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8996 0x000000000040041d <+29>: xor %eax,%eax
8997 0x000000000040041f <+31>: retq
8998 0x0000000000400420 <+32>: add %eax,%eax
8999 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9001 End of assembler dump.
9002 (@value{GDBP}) disas /s main
9003 Dump of assembler code for function main:
9007 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9011 0x0000000000400406 <+6>: test %eax,%eax
9012 0x0000000000400408 <+8>: js 0x400420 <main+32>
9017 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9018 0x000000000040040d <+13>: test %eax,%eax
9019 0x000000000040040f <+15>: mov $0x1,%eax
9020 0x0000000000400414 <+20>: cmovne %edx,%eax
9024 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9028 0x000000000040041d <+29>: xor %eax,%eax
9029 0x000000000040041f <+31>: retq
9033 0x0000000000400420 <+32>: add %eax,%eax
9034 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9035 End of assembler dump.
9038 Here is another example showing raw instructions in hex for AMD x86-64,
9041 (gdb) disas /r 0x400281,+10
9042 Dump of assembler code from 0x400281 to 0x40028b:
9043 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9044 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9045 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9046 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9047 End of assembler dump.
9050 Addresses cannot be specified as a location (@pxref{Specify Location}).
9051 So, for example, if you want to disassemble function @code{bar}
9052 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9053 and not @samp{disassemble foo.c:bar}.
9055 Some architectures have more than one commonly-used set of instruction
9056 mnemonics or other syntax.
9058 For programs that were dynamically linked and use shared libraries,
9059 instructions that call functions or branch to locations in the shared
9060 libraries might show a seemingly bogus location---it's actually a
9061 location of the relocation table. On some architectures, @value{GDBN}
9062 might be able to resolve these to actual function names.
9065 @kindex set disassembler-options
9066 @cindex disassembler options
9067 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9068 This command controls the passing of target specific information to
9069 the disassembler. For a list of valid options, please refer to the
9070 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9071 manual and/or the output of @kbd{objdump --help}
9072 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9073 The default value is the empty string.
9075 If it is necessary to specify more than one disassembler option, then
9076 multiple options can be placed together into a comma separated list.
9077 Currently this command is only supported on targets ARM, MIPS, PowerPC
9080 @kindex show disassembler-options
9081 @item show disassembler-options
9082 Show the current setting of the disassembler options.
9086 @kindex set disassembly-flavor
9087 @cindex Intel disassembly flavor
9088 @cindex AT&T disassembly flavor
9089 @item set disassembly-flavor @var{instruction-set}
9090 Select the instruction set to use when disassembling the
9091 program via the @code{disassemble} or @code{x/i} commands.
9093 Currently this command is only defined for the Intel x86 family. You
9094 can set @var{instruction-set} to either @code{intel} or @code{att}.
9095 The default is @code{att}, the AT&T flavor used by default by Unix
9096 assemblers for x86-based targets.
9098 @kindex show disassembly-flavor
9099 @item show disassembly-flavor
9100 Show the current setting of the disassembly flavor.
9104 @kindex set disassemble-next-line
9105 @kindex show disassemble-next-line
9106 @item set disassemble-next-line
9107 @itemx show disassemble-next-line
9108 Control whether or not @value{GDBN} will disassemble the next source
9109 line or instruction when execution stops. If ON, @value{GDBN} will
9110 display disassembly of the next source line when execution of the
9111 program being debugged stops. This is @emph{in addition} to
9112 displaying the source line itself, which @value{GDBN} always does if
9113 possible. If the next source line cannot be displayed for some reason
9114 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9115 info in the debug info), @value{GDBN} will display disassembly of the
9116 next @emph{instruction} instead of showing the next source line. If
9117 AUTO, @value{GDBN} will display disassembly of next instruction only
9118 if the source line cannot be displayed. This setting causes
9119 @value{GDBN} to display some feedback when you step through a function
9120 with no line info or whose source file is unavailable. The default is
9121 OFF, which means never display the disassembly of the next line or
9127 @chapter Examining Data
9129 @cindex printing data
9130 @cindex examining data
9133 The usual way to examine data in your program is with the @code{print}
9134 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9135 evaluates and prints the value of an expression of the language your
9136 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9137 Different Languages}). It may also print the expression using a
9138 Python-based pretty-printer (@pxref{Pretty Printing}).
9141 @item print @var{expr}
9142 @itemx print /@var{f} @var{expr}
9143 @var{expr} is an expression (in the source language). By default the
9144 value of @var{expr} is printed in a format appropriate to its data type;
9145 you can choose a different format by specifying @samp{/@var{f}}, where
9146 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9150 @itemx print /@var{f}
9151 @cindex reprint the last value
9152 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9153 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9154 conveniently inspect the same value in an alternative format.
9157 A more low-level way of examining data is with the @code{x} command.
9158 It examines data in memory at a specified address and prints it in a
9159 specified format. @xref{Memory, ,Examining Memory}.
9161 If you are interested in information about types, or about how the
9162 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9163 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9166 @cindex exploring hierarchical data structures
9168 Another way of examining values of expressions and type information is
9169 through the Python extension command @code{explore} (available only if
9170 the @value{GDBN} build is configured with @code{--with-python}). It
9171 offers an interactive way to start at the highest level (or, the most
9172 abstract level) of the data type of an expression (or, the data type
9173 itself) and explore all the way down to leaf scalar values/fields
9174 embedded in the higher level data types.
9177 @item explore @var{arg}
9178 @var{arg} is either an expression (in the source language), or a type
9179 visible in the current context of the program being debugged.
9182 The working of the @code{explore} command can be illustrated with an
9183 example. If a data type @code{struct ComplexStruct} is defined in your
9193 struct ComplexStruct
9195 struct SimpleStruct *ss_p;
9201 followed by variable declarations as
9204 struct SimpleStruct ss = @{ 10, 1.11 @};
9205 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9209 then, the value of the variable @code{cs} can be explored using the
9210 @code{explore} command as follows.
9214 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9215 the following fields:
9217 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9218 arr = <Enter 1 to explore this field of type `int [10]'>
9220 Enter the field number of choice:
9224 Since the fields of @code{cs} are not scalar values, you are being
9225 prompted to chose the field you want to explore. Let's say you choose
9226 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9227 pointer, you will be asked if it is pointing to a single value. From
9228 the declaration of @code{cs} above, it is indeed pointing to a single
9229 value, hence you enter @code{y}. If you enter @code{n}, then you will
9230 be asked if it were pointing to an array of values, in which case this
9231 field will be explored as if it were an array.
9234 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9235 Continue exploring it as a pointer to a single value [y/n]: y
9236 The value of `*(cs.ss_p)' is a struct/class of type `struct
9237 SimpleStruct' with the following fields:
9239 i = 10 .. (Value of type `int')
9240 d = 1.1100000000000001 .. (Value of type `double')
9242 Press enter to return to parent value:
9246 If the field @code{arr} of @code{cs} was chosen for exploration by
9247 entering @code{1} earlier, then since it is as array, you will be
9248 prompted to enter the index of the element in the array that you want
9252 `cs.arr' is an array of `int'.
9253 Enter the index of the element you want to explore in `cs.arr': 5
9255 `(cs.arr)[5]' is a scalar value of type `int'.
9259 Press enter to return to parent value:
9262 In general, at any stage of exploration, you can go deeper towards the
9263 leaf values by responding to the prompts appropriately, or hit the
9264 return key to return to the enclosing data structure (the @i{higher}
9265 level data structure).
9267 Similar to exploring values, you can use the @code{explore} command to
9268 explore types. Instead of specifying a value (which is typically a
9269 variable name or an expression valid in the current context of the
9270 program being debugged), you specify a type name. If you consider the
9271 same example as above, your can explore the type
9272 @code{struct ComplexStruct} by passing the argument
9273 @code{struct ComplexStruct} to the @code{explore} command.
9276 (gdb) explore struct ComplexStruct
9280 By responding to the prompts appropriately in the subsequent interactive
9281 session, you can explore the type @code{struct ComplexStruct} in a
9282 manner similar to how the value @code{cs} was explored in the above
9285 The @code{explore} command also has two sub-commands,
9286 @code{explore value} and @code{explore type}. The former sub-command is
9287 a way to explicitly specify that value exploration of the argument is
9288 being invoked, while the latter is a way to explicitly specify that type
9289 exploration of the argument is being invoked.
9292 @item explore value @var{expr}
9293 @cindex explore value
9294 This sub-command of @code{explore} explores the value of the
9295 expression @var{expr} (if @var{expr} is an expression valid in the
9296 current context of the program being debugged). The behavior of this
9297 command is identical to that of the behavior of the @code{explore}
9298 command being passed the argument @var{expr}.
9300 @item explore type @var{arg}
9301 @cindex explore type
9302 This sub-command of @code{explore} explores the type of @var{arg} (if
9303 @var{arg} is a type visible in the current context of program being
9304 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9305 is an expression valid in the current context of the program being
9306 debugged). If @var{arg} is a type, then the behavior of this command is
9307 identical to that of the @code{explore} command being passed the
9308 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9309 this command will be identical to that of the @code{explore} command
9310 being passed the type of @var{arg} as the argument.
9314 * Expressions:: Expressions
9315 * Ambiguous Expressions:: Ambiguous Expressions
9316 * Variables:: Program variables
9317 * Arrays:: Artificial arrays
9318 * Output Formats:: Output formats
9319 * Memory:: Examining memory
9320 * Auto Display:: Automatic display
9321 * Print Settings:: Print settings
9322 * Pretty Printing:: Python pretty printing
9323 * Value History:: Value history
9324 * Convenience Vars:: Convenience variables
9325 * Convenience Funs:: Convenience functions
9326 * Registers:: Registers
9327 * Floating Point Hardware:: Floating point hardware
9328 * Vector Unit:: Vector Unit
9329 * OS Information:: Auxiliary data provided by operating system
9330 * Memory Region Attributes:: Memory region attributes
9331 * Dump/Restore Files:: Copy between memory and a file
9332 * Core File Generation:: Cause a program dump its core
9333 * Character Sets:: Debugging programs that use a different
9334 character set than GDB does
9335 * Caching Target Data:: Data caching for targets
9336 * Searching Memory:: Searching memory for a sequence of bytes
9337 * Value Sizes:: Managing memory allocated for values
9341 @section Expressions
9344 @code{print} and many other @value{GDBN} commands accept an expression and
9345 compute its value. Any kind of constant, variable or operator defined
9346 by the programming language you are using is valid in an expression in
9347 @value{GDBN}. This includes conditional expressions, function calls,
9348 casts, and string constants. It also includes preprocessor macros, if
9349 you compiled your program to include this information; see
9352 @cindex arrays in expressions
9353 @value{GDBN} supports array constants in expressions input by
9354 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9355 you can use the command @code{print @{1, 2, 3@}} to create an array
9356 of three integers. If you pass an array to a function or assign it
9357 to a program variable, @value{GDBN} copies the array to memory that
9358 is @code{malloc}ed in the target program.
9360 Because C is so widespread, most of the expressions shown in examples in
9361 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9362 Languages}, for information on how to use expressions in other
9365 In this section, we discuss operators that you can use in @value{GDBN}
9366 expressions regardless of your programming language.
9368 @cindex casts, in expressions
9369 Casts are supported in all languages, not just in C, because it is so
9370 useful to cast a number into a pointer in order to examine a structure
9371 at that address in memory.
9372 @c FIXME: casts supported---Mod2 true?
9374 @value{GDBN} supports these operators, in addition to those common
9375 to programming languages:
9379 @samp{@@} is a binary operator for treating parts of memory as arrays.
9380 @xref{Arrays, ,Artificial Arrays}, for more information.
9383 @samp{::} allows you to specify a variable in terms of the file or
9384 function where it is defined. @xref{Variables, ,Program Variables}.
9386 @cindex @{@var{type}@}
9387 @cindex type casting memory
9388 @cindex memory, viewing as typed object
9389 @cindex casts, to view memory
9390 @item @{@var{type}@} @var{addr}
9391 Refers to an object of type @var{type} stored at address @var{addr} in
9392 memory. The address @var{addr} may be any expression whose value is
9393 an integer or pointer (but parentheses are required around binary
9394 operators, just as in a cast). This construct is allowed regardless
9395 of what kind of data is normally supposed to reside at @var{addr}.
9398 @node Ambiguous Expressions
9399 @section Ambiguous Expressions
9400 @cindex ambiguous expressions
9402 Expressions can sometimes contain some ambiguous elements. For instance,
9403 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9404 a single function name to be defined several times, for application in
9405 different contexts. This is called @dfn{overloading}. Another example
9406 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9407 templates and is typically instantiated several times, resulting in
9408 the same function name being defined in different contexts.
9410 In some cases and depending on the language, it is possible to adjust
9411 the expression to remove the ambiguity. For instance in C@t{++}, you
9412 can specify the signature of the function you want to break on, as in
9413 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9414 qualified name of your function often makes the expression unambiguous
9417 When an ambiguity that needs to be resolved is detected, the debugger
9418 has the capability to display a menu of numbered choices for each
9419 possibility, and then waits for the selection with the prompt @samp{>}.
9420 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9421 aborts the current command. If the command in which the expression was
9422 used allows more than one choice to be selected, the next option in the
9423 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9426 For example, the following session excerpt shows an attempt to set a
9427 breakpoint at the overloaded symbol @code{String::after}.
9428 We choose three particular definitions of that function name:
9430 @c FIXME! This is likely to change to show arg type lists, at least
9433 (@value{GDBP}) b String::after
9436 [2] file:String.cc; line number:867
9437 [3] file:String.cc; line number:860
9438 [4] file:String.cc; line number:875
9439 [5] file:String.cc; line number:853
9440 [6] file:String.cc; line number:846
9441 [7] file:String.cc; line number:735
9443 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9444 Breakpoint 2 at 0xb344: file String.cc, line 875.
9445 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9446 Multiple breakpoints were set.
9447 Use the "delete" command to delete unwanted
9454 @kindex set multiple-symbols
9455 @item set multiple-symbols @var{mode}
9456 @cindex multiple-symbols menu
9458 This option allows you to adjust the debugger behavior when an expression
9461 By default, @var{mode} is set to @code{all}. If the command with which
9462 the expression is used allows more than one choice, then @value{GDBN}
9463 automatically selects all possible choices. For instance, inserting
9464 a breakpoint on a function using an ambiguous name results in a breakpoint
9465 inserted on each possible match. However, if a unique choice must be made,
9466 then @value{GDBN} uses the menu to help you disambiguate the expression.
9467 For instance, printing the address of an overloaded function will result
9468 in the use of the menu.
9470 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9471 when an ambiguity is detected.
9473 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9474 an error due to the ambiguity and the command is aborted.
9476 @kindex show multiple-symbols
9477 @item show multiple-symbols
9478 Show the current value of the @code{multiple-symbols} setting.
9482 @section Program Variables
9484 The most common kind of expression to use is the name of a variable
9487 Variables in expressions are understood in the selected stack frame
9488 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9492 global (or file-static)
9499 visible according to the scope rules of the
9500 programming language from the point of execution in that frame
9503 @noindent This means that in the function
9518 you can examine and use the variable @code{a} whenever your program is
9519 executing within the function @code{foo}, but you can only use or
9520 examine the variable @code{b} while your program is executing inside
9521 the block where @code{b} is declared.
9523 @cindex variable name conflict
9524 There is an exception: you can refer to a variable or function whose
9525 scope is a single source file even if the current execution point is not
9526 in this file. But it is possible to have more than one such variable or
9527 function with the same name (in different source files). If that
9528 happens, referring to that name has unpredictable effects. If you wish,
9529 you can specify a static variable in a particular function or file by
9530 using the colon-colon (@code{::}) notation:
9532 @cindex colon-colon, context for variables/functions
9534 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9535 @cindex @code{::}, context for variables/functions
9538 @var{file}::@var{variable}
9539 @var{function}::@var{variable}
9543 Here @var{file} or @var{function} is the name of the context for the
9544 static @var{variable}. In the case of file names, you can use quotes to
9545 make sure @value{GDBN} parses the file name as a single word---for example,
9546 to print a global value of @code{x} defined in @file{f2.c}:
9549 (@value{GDBP}) p 'f2.c'::x
9552 The @code{::} notation is normally used for referring to
9553 static variables, since you typically disambiguate uses of local variables
9554 in functions by selecting the appropriate frame and using the
9555 simple name of the variable. However, you may also use this notation
9556 to refer to local variables in frames enclosing the selected frame:
9565 process (a); /* Stop here */
9576 For example, if there is a breakpoint at the commented line,
9577 here is what you might see
9578 when the program stops after executing the call @code{bar(0)}:
9583 (@value{GDBP}) p bar::a
9586 #2 0x080483d0 in foo (a=5) at foobar.c:12
9589 (@value{GDBP}) p bar::a
9593 @cindex C@t{++} scope resolution
9594 These uses of @samp{::} are very rarely in conflict with the very
9595 similar use of the same notation in C@t{++}. When they are in
9596 conflict, the C@t{++} meaning takes precedence; however, this can be
9597 overridden by quoting the file or function name with single quotes.
9599 For example, suppose the program is stopped in a method of a class
9600 that has a field named @code{includefile}, and there is also an
9601 include file named @file{includefile} that defines a variable,
9605 (@value{GDBP}) p includefile
9607 (@value{GDBP}) p includefile::some_global
9608 A syntax error in expression, near `'.
9609 (@value{GDBP}) p 'includefile'::some_global
9613 @cindex wrong values
9614 @cindex variable values, wrong
9615 @cindex function entry/exit, wrong values of variables
9616 @cindex optimized code, wrong values of variables
9618 @emph{Warning:} Occasionally, a local variable may appear to have the
9619 wrong value at certain points in a function---just after entry to a new
9620 scope, and just before exit.
9622 You may see this problem when you are stepping by machine instructions.
9623 This is because, on most machines, it takes more than one instruction to
9624 set up a stack frame (including local variable definitions); if you are
9625 stepping by machine instructions, variables may appear to have the wrong
9626 values until the stack frame is completely built. On exit, it usually
9627 also takes more than one machine instruction to destroy a stack frame;
9628 after you begin stepping through that group of instructions, local
9629 variable definitions may be gone.
9631 This may also happen when the compiler does significant optimizations.
9632 To be sure of always seeing accurate values, turn off all optimization
9635 @cindex ``No symbol "foo" in current context''
9636 Another possible effect of compiler optimizations is to optimize
9637 unused variables out of existence, or assign variables to registers (as
9638 opposed to memory addresses). Depending on the support for such cases
9639 offered by the debug info format used by the compiler, @value{GDBN}
9640 might not be able to display values for such local variables. If that
9641 happens, @value{GDBN} will print a message like this:
9644 No symbol "foo" in current context.
9647 To solve such problems, either recompile without optimizations, or use a
9648 different debug info format, if the compiler supports several such
9649 formats. @xref{Compilation}, for more information on choosing compiler
9650 options. @xref{C, ,C and C@t{++}}, for more information about debug
9651 info formats that are best suited to C@t{++} programs.
9653 If you ask to print an object whose contents are unknown to
9654 @value{GDBN}, e.g., because its data type is not completely specified
9655 by the debug information, @value{GDBN} will say @samp{<incomplete
9656 type>}. @xref{Symbols, incomplete type}, for more about this.
9658 @cindex no debug info variables
9659 If you try to examine or use the value of a (global) variable for
9660 which @value{GDBN} has no type information, e.g., because the program
9661 includes no debug information, @value{GDBN} displays an error message.
9662 @xref{Symbols, unknown type}, for more about unknown types. If you
9663 cast the variable to its declared type, @value{GDBN} gets the
9664 variable's value using the cast-to type as the variable's type. For
9665 example, in a C program:
9668 (@value{GDBP}) p var
9669 'var' has unknown type; cast it to its declared type
9670 (@value{GDBP}) p (float) var
9674 If you append @kbd{@@entry} string to a function parameter name you get its
9675 value at the time the function got called. If the value is not available an
9676 error message is printed. Entry values are available only with some compilers.
9677 Entry values are normally also printed at the function parameter list according
9678 to @ref{set print entry-values}.
9681 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9687 (gdb) print i@@entry
9691 Strings are identified as arrays of @code{char} values without specified
9692 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9693 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9694 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9695 defines literal string type @code{"char"} as @code{char} without a sign.
9700 signed char var1[] = "A";
9703 You get during debugging
9708 $2 = @{65 'A', 0 '\0'@}
9712 @section Artificial Arrays
9714 @cindex artificial array
9716 @kindex @@@r{, referencing memory as an array}
9717 It is often useful to print out several successive objects of the
9718 same type in memory; a section of an array, or an array of
9719 dynamically determined size for which only a pointer exists in the
9722 You can do this by referring to a contiguous span of memory as an
9723 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9724 operand of @samp{@@} should be the first element of the desired array
9725 and be an individual object. The right operand should be the desired length
9726 of the array. The result is an array value whose elements are all of
9727 the type of the left argument. The first element is actually the left
9728 argument; the second element comes from bytes of memory immediately
9729 following those that hold the first element, and so on. Here is an
9730 example. If a program says
9733 int *array = (int *) malloc (len * sizeof (int));
9737 you can print the contents of @code{array} with
9743 The left operand of @samp{@@} must reside in memory. Array values made
9744 with @samp{@@} in this way behave just like other arrays in terms of
9745 subscripting, and are coerced to pointers when used in expressions.
9746 Artificial arrays most often appear in expressions via the value history
9747 (@pxref{Value History, ,Value History}), after printing one out.
9749 Another way to create an artificial array is to use a cast.
9750 This re-interprets a value as if it were an array.
9751 The value need not be in memory:
9753 (@value{GDBP}) p/x (short[2])0x12345678
9754 $1 = @{0x1234, 0x5678@}
9757 As a convenience, if you leave the array length out (as in
9758 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9759 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9761 (@value{GDBP}) p/x (short[])0x12345678
9762 $2 = @{0x1234, 0x5678@}
9765 Sometimes the artificial array mechanism is not quite enough; in
9766 moderately complex data structures, the elements of interest may not
9767 actually be adjacent---for example, if you are interested in the values
9768 of pointers in an array. One useful work-around in this situation is
9769 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9770 Variables}) as a counter in an expression that prints the first
9771 interesting value, and then repeat that expression via @key{RET}. For
9772 instance, suppose you have an array @code{dtab} of pointers to
9773 structures, and you are interested in the values of a field @code{fv}
9774 in each structure. Here is an example of what you might type:
9784 @node Output Formats
9785 @section Output Formats
9787 @cindex formatted output
9788 @cindex output formats
9789 By default, @value{GDBN} prints a value according to its data type. Sometimes
9790 this is not what you want. For example, you might want to print a number
9791 in hex, or a pointer in decimal. Or you might want to view data in memory
9792 at a certain address as a character string or as an instruction. To do
9793 these things, specify an @dfn{output format} when you print a value.
9795 The simplest use of output formats is to say how to print a value
9796 already computed. This is done by starting the arguments of the
9797 @code{print} command with a slash and a format letter. The format
9798 letters supported are:
9802 Regard the bits of the value as an integer, and print the integer in
9806 Print as integer in signed decimal.
9809 Print as integer in unsigned decimal.
9812 Print as integer in octal.
9815 Print as integer in binary. The letter @samp{t} stands for ``two''.
9816 @footnote{@samp{b} cannot be used because these format letters are also
9817 used with the @code{x} command, where @samp{b} stands for ``byte'';
9818 see @ref{Memory,,Examining Memory}.}
9821 @cindex unknown address, locating
9822 @cindex locate address
9823 Print as an address, both absolute in hexadecimal and as an offset from
9824 the nearest preceding symbol. You can use this format used to discover
9825 where (in what function) an unknown address is located:
9828 (@value{GDBP}) p/a 0x54320
9829 $3 = 0x54320 <_initialize_vx+396>
9833 The command @code{info symbol 0x54320} yields similar results.
9834 @xref{Symbols, info symbol}.
9837 Regard as an integer and print it as a character constant. This
9838 prints both the numerical value and its character representation. The
9839 character representation is replaced with the octal escape @samp{\nnn}
9840 for characters outside the 7-bit @sc{ascii} range.
9842 Without this format, @value{GDBN} displays @code{char},
9843 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9844 constants. Single-byte members of vectors are displayed as integer
9848 Regard the bits of the value as a floating point number and print
9849 using typical floating point syntax.
9852 @cindex printing strings
9853 @cindex printing byte arrays
9854 Regard as a string, if possible. With this format, pointers to single-byte
9855 data are displayed as null-terminated strings and arrays of single-byte data
9856 are displayed as fixed-length strings. Other values are displayed in their
9859 Without this format, @value{GDBN} displays pointers to and arrays of
9860 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9861 strings. Single-byte members of a vector are displayed as an integer
9865 Like @samp{x} formatting, the value is treated as an integer and
9866 printed as hexadecimal, but leading zeros are printed to pad the value
9867 to the size of the integer type.
9870 @cindex raw printing
9871 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9872 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9873 Printing}). This typically results in a higher-level display of the
9874 value's contents. The @samp{r} format bypasses any Python
9875 pretty-printer which might exist.
9878 For example, to print the program counter in hex (@pxref{Registers}), type
9885 Note that no space is required before the slash; this is because command
9886 names in @value{GDBN} cannot contain a slash.
9888 To reprint the last value in the value history with a different format,
9889 you can use the @code{print} command with just a format and no
9890 expression. For example, @samp{p/x} reprints the last value in hex.
9893 @section Examining Memory
9895 You can use the command @code{x} (for ``examine'') to examine memory in
9896 any of several formats, independently of your program's data types.
9898 @cindex examining memory
9900 @kindex x @r{(examine memory)}
9901 @item x/@var{nfu} @var{addr}
9904 Use the @code{x} command to examine memory.
9907 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9908 much memory to display and how to format it; @var{addr} is an
9909 expression giving the address where you want to start displaying memory.
9910 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9911 Several commands set convenient defaults for @var{addr}.
9914 @item @var{n}, the repeat count
9915 The repeat count is a decimal integer; the default is 1. It specifies
9916 how much memory (counting by units @var{u}) to display. If a negative
9917 number is specified, memory is examined backward from @var{addr}.
9918 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9921 @item @var{f}, the display format
9922 The display format is one of the formats used by @code{print}
9923 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9924 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9925 The default is @samp{x} (hexadecimal) initially. The default changes
9926 each time you use either @code{x} or @code{print}.
9928 @item @var{u}, the unit size
9929 The unit size is any of
9935 Halfwords (two bytes).
9937 Words (four bytes). This is the initial default.
9939 Giant words (eight bytes).
9942 Each time you specify a unit size with @code{x}, that size becomes the
9943 default unit the next time you use @code{x}. For the @samp{i} format,
9944 the unit size is ignored and is normally not written. For the @samp{s} format,
9945 the unit size defaults to @samp{b}, unless it is explicitly given.
9946 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9947 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9948 Note that the results depend on the programming language of the
9949 current compilation unit. If the language is C, the @samp{s}
9950 modifier will use the UTF-16 encoding while @samp{w} will use
9951 UTF-32. The encoding is set by the programming language and cannot
9954 @item @var{addr}, starting display address
9955 @var{addr} is the address where you want @value{GDBN} to begin displaying
9956 memory. The expression need not have a pointer value (though it may);
9957 it is always interpreted as an integer address of a byte of memory.
9958 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9959 @var{addr} is usually just after the last address examined---but several
9960 other commands also set the default address: @code{info breakpoints} (to
9961 the address of the last breakpoint listed), @code{info line} (to the
9962 starting address of a line), and @code{print} (if you use it to display
9963 a value from memory).
9966 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9967 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9968 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9969 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9970 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9972 You can also specify a negative repeat count to examine memory backward
9973 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9974 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9976 Since the letters indicating unit sizes are all distinct from the
9977 letters specifying output formats, you do not have to remember whether
9978 unit size or format comes first; either order works. The output
9979 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9980 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9982 Even though the unit size @var{u} is ignored for the formats @samp{s}
9983 and @samp{i}, you might still want to use a count @var{n}; for example,
9984 @samp{3i} specifies that you want to see three machine instructions,
9985 including any operands. For convenience, especially when used with
9986 the @code{display} command, the @samp{i} format also prints branch delay
9987 slot instructions, if any, beyond the count specified, which immediately
9988 follow the last instruction that is within the count. The command
9989 @code{disassemble} gives an alternative way of inspecting machine
9990 instructions; see @ref{Machine Code,,Source and Machine Code}.
9992 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9993 the command displays null-terminated strings or instructions before the given
9994 address as many as the absolute value of the given number. For the @samp{i}
9995 format, we use line number information in the debug info to accurately locate
9996 instruction boundaries while disassembling backward. If line info is not
9997 available, the command stops examining memory with an error message.
9999 All the defaults for the arguments to @code{x} are designed to make it
10000 easy to continue scanning memory with minimal specifications each time
10001 you use @code{x}. For example, after you have inspected three machine
10002 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10003 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10004 the repeat count @var{n} is used again; the other arguments default as
10005 for successive uses of @code{x}.
10007 When examining machine instructions, the instruction at current program
10008 counter is shown with a @code{=>} marker. For example:
10011 (@value{GDBP}) x/5i $pc-6
10012 0x804837f <main+11>: mov %esp,%ebp
10013 0x8048381 <main+13>: push %ecx
10014 0x8048382 <main+14>: sub $0x4,%esp
10015 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10016 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10019 @cindex @code{$_}, @code{$__}, and value history
10020 The addresses and contents printed by the @code{x} command are not saved
10021 in the value history because there is often too much of them and they
10022 would get in the way. Instead, @value{GDBN} makes these values available for
10023 subsequent use in expressions as values of the convenience variables
10024 @code{$_} and @code{$__}. After an @code{x} command, the last address
10025 examined is available for use in expressions in the convenience variable
10026 @code{$_}. The contents of that address, as examined, are available in
10027 the convenience variable @code{$__}.
10029 If the @code{x} command has a repeat count, the address and contents saved
10030 are from the last memory unit printed; this is not the same as the last
10031 address printed if several units were printed on the last line of output.
10033 @anchor{addressable memory unit}
10034 @cindex addressable memory unit
10035 Most targets have an addressable memory unit size of 8 bits. This means
10036 that to each memory address are associated 8 bits of data. Some
10037 targets, however, have other addressable memory unit sizes.
10038 Within @value{GDBN} and this document, the term
10039 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10040 when explicitly referring to a chunk of data of that size. The word
10041 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10042 the addressable memory unit size of the target. For most systems,
10043 addressable memory unit is a synonym of byte.
10045 @cindex remote memory comparison
10046 @cindex target memory comparison
10047 @cindex verify remote memory image
10048 @cindex verify target memory image
10049 When you are debugging a program running on a remote target machine
10050 (@pxref{Remote Debugging}), you may wish to verify the program's image
10051 in the remote machine's memory against the executable file you
10052 downloaded to the target. Or, on any target, you may want to check
10053 whether the program has corrupted its own read-only sections. The
10054 @code{compare-sections} command is provided for such situations.
10057 @kindex compare-sections
10058 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10059 Compare the data of a loadable section @var{section-name} in the
10060 executable file of the program being debugged with the same section in
10061 the target machine's memory, and report any mismatches. With no
10062 arguments, compares all loadable sections. With an argument of
10063 @code{-r}, compares all loadable read-only sections.
10065 Note: for remote targets, this command can be accelerated if the
10066 target supports computing the CRC checksum of a block of memory
10067 (@pxref{qCRC packet}).
10071 @section Automatic Display
10072 @cindex automatic display
10073 @cindex display of expressions
10075 If you find that you want to print the value of an expression frequently
10076 (to see how it changes), you might want to add it to the @dfn{automatic
10077 display list} so that @value{GDBN} prints its value each time your program stops.
10078 Each expression added to the list is given a number to identify it;
10079 to remove an expression from the list, you specify that number.
10080 The automatic display looks like this:
10084 3: bar[5] = (struct hack *) 0x3804
10088 This display shows item numbers, expressions and their current values. As with
10089 displays you request manually using @code{x} or @code{print}, you can
10090 specify the output format you prefer; in fact, @code{display} decides
10091 whether to use @code{print} or @code{x} depending your format
10092 specification---it uses @code{x} if you specify either the @samp{i}
10093 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10097 @item display @var{expr}
10098 Add the expression @var{expr} to the list of expressions to display
10099 each time your program stops. @xref{Expressions, ,Expressions}.
10101 @code{display} does not repeat if you press @key{RET} again after using it.
10103 @item display/@var{fmt} @var{expr}
10104 For @var{fmt} specifying only a display format and not a size or
10105 count, add the expression @var{expr} to the auto-display list but
10106 arrange to display it each time in the specified format @var{fmt}.
10107 @xref{Output Formats,,Output Formats}.
10109 @item display/@var{fmt} @var{addr}
10110 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10111 number of units, add the expression @var{addr} as a memory address to
10112 be examined each time your program stops. Examining means in effect
10113 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10116 For example, @samp{display/i $pc} can be helpful, to see the machine
10117 instruction about to be executed each time execution stops (@samp{$pc}
10118 is a common name for the program counter; @pxref{Registers, ,Registers}).
10121 @kindex delete display
10123 @item undisplay @var{dnums}@dots{}
10124 @itemx delete display @var{dnums}@dots{}
10125 Remove items from the list of expressions to display. Specify the
10126 numbers of the displays that you want affected with the command
10127 argument @var{dnums}. It can be a single display number, one of the
10128 numbers shown in the first field of the @samp{info display} display;
10129 or it could be a range of display numbers, as in @code{2-4}.
10131 @code{undisplay} does not repeat if you press @key{RET} after using it.
10132 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10134 @kindex disable display
10135 @item disable display @var{dnums}@dots{}
10136 Disable the display of item numbers @var{dnums}. A disabled display
10137 item is not printed automatically, but is not forgotten. It may be
10138 enabled again later. Specify the numbers of the displays that you
10139 want affected with the command argument @var{dnums}. It can be a
10140 single display number, one of the numbers shown in the first field of
10141 the @samp{info display} display; or it could be a range of display
10142 numbers, as in @code{2-4}.
10144 @kindex enable display
10145 @item enable display @var{dnums}@dots{}
10146 Enable display of item numbers @var{dnums}. It becomes effective once
10147 again in auto display of its expression, until you specify otherwise.
10148 Specify the numbers of the displays that you want affected with the
10149 command argument @var{dnums}. It can be a single display number, one
10150 of the numbers shown in the first field of the @samp{info display}
10151 display; or it could be a range of display numbers, as in @code{2-4}.
10154 Display the current values of the expressions on the list, just as is
10155 done when your program stops.
10157 @kindex info display
10159 Print the list of expressions previously set up to display
10160 automatically, each one with its item number, but without showing the
10161 values. This includes disabled expressions, which are marked as such.
10162 It also includes expressions which would not be displayed right now
10163 because they refer to automatic variables not currently available.
10166 @cindex display disabled out of scope
10167 If a display expression refers to local variables, then it does not make
10168 sense outside the lexical context for which it was set up. Such an
10169 expression is disabled when execution enters a context where one of its
10170 variables is not defined. For example, if you give the command
10171 @code{display last_char} while inside a function with an argument
10172 @code{last_char}, @value{GDBN} displays this argument while your program
10173 continues to stop inside that function. When it stops elsewhere---where
10174 there is no variable @code{last_char}---the display is disabled
10175 automatically. The next time your program stops where @code{last_char}
10176 is meaningful, you can enable the display expression once again.
10178 @node Print Settings
10179 @section Print Settings
10181 @cindex format options
10182 @cindex print settings
10183 @value{GDBN} provides the following ways to control how arrays, structures,
10184 and symbols are printed.
10187 These settings are useful for debugging programs in any language:
10191 @item set print address
10192 @itemx set print address on
10193 @cindex print/don't print memory addresses
10194 @value{GDBN} prints memory addresses showing the location of stack
10195 traces, structure values, pointer values, breakpoints, and so forth,
10196 even when it also displays the contents of those addresses. The default
10197 is @code{on}. For example, this is what a stack frame display looks like with
10198 @code{set print address on}:
10203 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10205 530 if (lquote != def_lquote)
10209 @item set print address off
10210 Do not print addresses when displaying their contents. For example,
10211 this is the same stack frame displayed with @code{set print address off}:
10215 (@value{GDBP}) set print addr off
10217 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10218 530 if (lquote != def_lquote)
10222 You can use @samp{set print address off} to eliminate all machine
10223 dependent displays from the @value{GDBN} interface. For example, with
10224 @code{print address off}, you should get the same text for backtraces on
10225 all machines---whether or not they involve pointer arguments.
10228 @item show print address
10229 Show whether or not addresses are to be printed.
10232 When @value{GDBN} prints a symbolic address, it normally prints the
10233 closest earlier symbol plus an offset. If that symbol does not uniquely
10234 identify the address (for example, it is a name whose scope is a single
10235 source file), you may need to clarify. One way to do this is with
10236 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10237 you can set @value{GDBN} to print the source file and line number when
10238 it prints a symbolic address:
10241 @item set print symbol-filename on
10242 @cindex source file and line of a symbol
10243 @cindex symbol, source file and line
10244 Tell @value{GDBN} to print the source file name and line number of a
10245 symbol in the symbolic form of an address.
10247 @item set print symbol-filename off
10248 Do not print source file name and line number of a symbol. This is the
10251 @item show print symbol-filename
10252 Show whether or not @value{GDBN} will print the source file name and
10253 line number of a symbol in the symbolic form of an address.
10256 Another situation where it is helpful to show symbol filenames and line
10257 numbers is when disassembling code; @value{GDBN} shows you the line
10258 number and source file that corresponds to each instruction.
10260 Also, you may wish to see the symbolic form only if the address being
10261 printed is reasonably close to the closest earlier symbol:
10264 @item set print max-symbolic-offset @var{max-offset}
10265 @itemx set print max-symbolic-offset unlimited
10266 @cindex maximum value for offset of closest symbol
10267 Tell @value{GDBN} to only display the symbolic form of an address if the
10268 offset between the closest earlier symbol and the address is less than
10269 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10270 to always print the symbolic form of an address if any symbol precedes
10271 it. Zero is equivalent to @code{unlimited}.
10273 @item show print max-symbolic-offset
10274 Ask how large the maximum offset is that @value{GDBN} prints in a
10278 @cindex wild pointer, interpreting
10279 @cindex pointer, finding referent
10280 If you have a pointer and you are not sure where it points, try
10281 @samp{set print symbol-filename on}. Then you can determine the name
10282 and source file location of the variable where it points, using
10283 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10284 For example, here @value{GDBN} shows that a variable @code{ptt} points
10285 at another variable @code{t}, defined in @file{hi2.c}:
10288 (@value{GDBP}) set print symbol-filename on
10289 (@value{GDBP}) p/a ptt
10290 $4 = 0xe008 <t in hi2.c>
10294 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10295 does not show the symbol name and filename of the referent, even with
10296 the appropriate @code{set print} options turned on.
10299 You can also enable @samp{/a}-like formatting all the time using
10300 @samp{set print symbol on}:
10303 @item set print symbol on
10304 Tell @value{GDBN} to print the symbol corresponding to an address, if
10307 @item set print symbol off
10308 Tell @value{GDBN} not to print the symbol corresponding to an
10309 address. In this mode, @value{GDBN} will still print the symbol
10310 corresponding to pointers to functions. This is the default.
10312 @item show print symbol
10313 Show whether @value{GDBN} will display the symbol corresponding to an
10317 Other settings control how different kinds of objects are printed:
10320 @item set print array
10321 @itemx set print array on
10322 @cindex pretty print arrays
10323 Pretty print arrays. This format is more convenient to read,
10324 but uses more space. The default is off.
10326 @item set print array off
10327 Return to compressed format for arrays.
10329 @item show print array
10330 Show whether compressed or pretty format is selected for displaying
10333 @cindex print array indexes
10334 @item set print array-indexes
10335 @itemx set print array-indexes on
10336 Print the index of each element when displaying arrays. May be more
10337 convenient to locate a given element in the array or quickly find the
10338 index of a given element in that printed array. The default is off.
10340 @item set print array-indexes off
10341 Stop printing element indexes when displaying arrays.
10343 @item show print array-indexes
10344 Show whether the index of each element is printed when displaying
10347 @item set print elements @var{number-of-elements}
10348 @itemx set print elements unlimited
10349 @cindex number of array elements to print
10350 @cindex limit on number of printed array elements
10351 Set a limit on how many elements of an array @value{GDBN} will print.
10352 If @value{GDBN} is printing a large array, it stops printing after it has
10353 printed the number of elements set by the @code{set print elements} command.
10354 This limit also applies to the display of strings.
10355 When @value{GDBN} starts, this limit is set to 200.
10356 Setting @var{number-of-elements} to @code{unlimited} or zero means
10357 that the number of elements to print is unlimited.
10359 @item show print elements
10360 Display the number of elements of a large array that @value{GDBN} will print.
10361 If the number is 0, then the printing is unlimited.
10363 @item set print frame-arguments @var{value}
10364 @kindex set print frame-arguments
10365 @cindex printing frame argument values
10366 @cindex print all frame argument values
10367 @cindex print frame argument values for scalars only
10368 @cindex do not print frame argument values
10369 This command allows to control how the values of arguments are printed
10370 when the debugger prints a frame (@pxref{Frames}). The possible
10375 The values of all arguments are printed.
10378 Print the value of an argument only if it is a scalar. The value of more
10379 complex arguments such as arrays, structures, unions, etc, is replaced
10380 by @code{@dots{}}. This is the default. Here is an example where
10381 only scalar arguments are shown:
10384 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10389 None of the argument values are printed. Instead, the value of each argument
10390 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10393 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10398 By default, only scalar arguments are printed. This command can be used
10399 to configure the debugger to print the value of all arguments, regardless
10400 of their type. However, it is often advantageous to not print the value
10401 of more complex parameters. For instance, it reduces the amount of
10402 information printed in each frame, making the backtrace more readable.
10403 Also, it improves performance when displaying Ada frames, because
10404 the computation of large arguments can sometimes be CPU-intensive,
10405 especially in large applications. Setting @code{print frame-arguments}
10406 to @code{scalars} (the default) or @code{none} avoids this computation,
10407 thus speeding up the display of each Ada frame.
10409 @item show print frame-arguments
10410 Show how the value of arguments should be displayed when printing a frame.
10412 @item set print raw frame-arguments on
10413 Print frame arguments in raw, non pretty-printed, form.
10415 @item set print raw frame-arguments off
10416 Print frame arguments in pretty-printed form, if there is a pretty-printer
10417 for the value (@pxref{Pretty Printing}),
10418 otherwise print the value in raw form.
10419 This is the default.
10421 @item show print raw frame-arguments
10422 Show whether to print frame arguments in raw form.
10424 @anchor{set print entry-values}
10425 @item set print entry-values @var{value}
10426 @kindex set print entry-values
10427 Set printing of frame argument values at function entry. In some cases
10428 @value{GDBN} can determine the value of function argument which was passed by
10429 the function caller, even if the value was modified inside the called function
10430 and therefore is different. With optimized code, the current value could be
10431 unavailable, but the entry value may still be known.
10433 The default value is @code{default} (see below for its description). Older
10434 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10435 this feature will behave in the @code{default} setting the same way as with the
10438 This functionality is currently supported only by DWARF 2 debugging format and
10439 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10440 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10443 The @var{value} parameter can be one of the following:
10447 Print only actual parameter values, never print values from function entry
10451 #0 different (val=6)
10452 #0 lost (val=<optimized out>)
10454 #0 invalid (val=<optimized out>)
10458 Print only parameter values from function entry point. The actual parameter
10459 values are never printed.
10461 #0 equal (val@@entry=5)
10462 #0 different (val@@entry=5)
10463 #0 lost (val@@entry=5)
10464 #0 born (val@@entry=<optimized out>)
10465 #0 invalid (val@@entry=<optimized out>)
10469 Print only parameter values from function entry point. If value from function
10470 entry point is not known while the actual value is known, print the actual
10471 value for such parameter.
10473 #0 equal (val@@entry=5)
10474 #0 different (val@@entry=5)
10475 #0 lost (val@@entry=5)
10477 #0 invalid (val@@entry=<optimized out>)
10481 Print actual parameter values. If actual parameter value is not known while
10482 value from function entry point is known, print the entry point value for such
10486 #0 different (val=6)
10487 #0 lost (val@@entry=5)
10489 #0 invalid (val=<optimized out>)
10493 Always print both the actual parameter value and its value from function entry
10494 point, even if values of one or both are not available due to compiler
10497 #0 equal (val=5, val@@entry=5)
10498 #0 different (val=6, val@@entry=5)
10499 #0 lost (val=<optimized out>, val@@entry=5)
10500 #0 born (val=10, val@@entry=<optimized out>)
10501 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10505 Print the actual parameter value if it is known and also its value from
10506 function entry point if it is known. If neither is known, print for the actual
10507 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10508 values are known and identical, print the shortened
10509 @code{param=param@@entry=VALUE} notation.
10511 #0 equal (val=val@@entry=5)
10512 #0 different (val=6, val@@entry=5)
10513 #0 lost (val@@entry=5)
10515 #0 invalid (val=<optimized out>)
10519 Always print the actual parameter value. Print also its value from function
10520 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10521 if both values are known and identical, print the shortened
10522 @code{param=param@@entry=VALUE} notation.
10524 #0 equal (val=val@@entry=5)
10525 #0 different (val=6, val@@entry=5)
10526 #0 lost (val=<optimized out>, val@@entry=5)
10528 #0 invalid (val=<optimized out>)
10532 For analysis messages on possible failures of frame argument values at function
10533 entry resolution see @ref{set debug entry-values}.
10535 @item show print entry-values
10536 Show the method being used for printing of frame argument values at function
10539 @item set print repeats @var{number-of-repeats}
10540 @itemx set print repeats unlimited
10541 @cindex repeated array elements
10542 Set the threshold for suppressing display of repeated array
10543 elements. When the number of consecutive identical elements of an
10544 array exceeds the threshold, @value{GDBN} prints the string
10545 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10546 identical repetitions, instead of displaying the identical elements
10547 themselves. Setting the threshold to @code{unlimited} or zero will
10548 cause all elements to be individually printed. The default threshold
10551 @item show print repeats
10552 Display the current threshold for printing repeated identical
10555 @item set print null-stop
10556 @cindex @sc{null} elements in arrays
10557 Cause @value{GDBN} to stop printing the characters of an array when the first
10558 @sc{null} is encountered. This is useful when large arrays actually
10559 contain only short strings.
10560 The default is off.
10562 @item show print null-stop
10563 Show whether @value{GDBN} stops printing an array on the first
10564 @sc{null} character.
10566 @item set print pretty on
10567 @cindex print structures in indented form
10568 @cindex indentation in structure display
10569 Cause @value{GDBN} to print structures in an indented format with one member
10570 per line, like this:
10585 @item set print pretty off
10586 Cause @value{GDBN} to print structures in a compact format, like this:
10590 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10591 meat = 0x54 "Pork"@}
10596 This is the default format.
10598 @item show print pretty
10599 Show which format @value{GDBN} is using to print structures.
10601 @item set print sevenbit-strings on
10602 @cindex eight-bit characters in strings
10603 @cindex octal escapes in strings
10604 Print using only seven-bit characters; if this option is set,
10605 @value{GDBN} displays any eight-bit characters (in strings or
10606 character values) using the notation @code{\}@var{nnn}. This setting is
10607 best if you are working in English (@sc{ascii}) and you use the
10608 high-order bit of characters as a marker or ``meta'' bit.
10610 @item set print sevenbit-strings off
10611 Print full eight-bit characters. This allows the use of more
10612 international character sets, and is the default.
10614 @item show print sevenbit-strings
10615 Show whether or not @value{GDBN} is printing only seven-bit characters.
10617 @item set print union on
10618 @cindex unions in structures, printing
10619 Tell @value{GDBN} to print unions which are contained in structures
10620 and other unions. This is the default setting.
10622 @item set print union off
10623 Tell @value{GDBN} not to print unions which are contained in
10624 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10627 @item show print union
10628 Ask @value{GDBN} whether or not it will print unions which are contained in
10629 structures and other unions.
10631 For example, given the declarations
10634 typedef enum @{Tree, Bug@} Species;
10635 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10636 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10647 struct thing foo = @{Tree, @{Acorn@}@};
10651 with @code{set print union on} in effect @samp{p foo} would print
10654 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10658 and with @code{set print union off} in effect it would print
10661 $1 = @{it = Tree, form = @{...@}@}
10665 @code{set print union} affects programs written in C-like languages
10671 These settings are of interest when debugging C@t{++} programs:
10674 @cindex demangling C@t{++} names
10675 @item set print demangle
10676 @itemx set print demangle on
10677 Print C@t{++} names in their source form rather than in the encoded
10678 (``mangled'') form passed to the assembler and linker for type-safe
10679 linkage. The default is on.
10681 @item show print demangle
10682 Show whether C@t{++} names are printed in mangled or demangled form.
10684 @item set print asm-demangle
10685 @itemx set print asm-demangle on
10686 Print C@t{++} names in their source form rather than their mangled form, even
10687 in assembler code printouts such as instruction disassemblies.
10688 The default is off.
10690 @item show print asm-demangle
10691 Show whether C@t{++} names in assembly listings are printed in mangled
10694 @cindex C@t{++} symbol decoding style
10695 @cindex symbol decoding style, C@t{++}
10696 @kindex set demangle-style
10697 @item set demangle-style @var{style}
10698 Choose among several encoding schemes used by different compilers to
10699 represent C@t{++} names. The choices for @var{style} are currently:
10703 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10704 This is the default.
10707 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10710 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10713 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10716 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10717 @strong{Warning:} this setting alone is not sufficient to allow
10718 debugging @code{cfront}-generated executables. @value{GDBN} would
10719 require further enhancement to permit that.
10722 If you omit @var{style}, you will see a list of possible formats.
10724 @item show demangle-style
10725 Display the encoding style currently in use for decoding C@t{++} symbols.
10727 @item set print object
10728 @itemx set print object on
10729 @cindex derived type of an object, printing
10730 @cindex display derived types
10731 When displaying a pointer to an object, identify the @emph{actual}
10732 (derived) type of the object rather than the @emph{declared} type, using
10733 the virtual function table. Note that the virtual function table is
10734 required---this feature can only work for objects that have run-time
10735 type identification; a single virtual method in the object's declared
10736 type is sufficient. Note that this setting is also taken into account when
10737 working with variable objects via MI (@pxref{GDB/MI}).
10739 @item set print object off
10740 Display only the declared type of objects, without reference to the
10741 virtual function table. This is the default setting.
10743 @item show print object
10744 Show whether actual, or declared, object types are displayed.
10746 @item set print static-members
10747 @itemx set print static-members on
10748 @cindex static members of C@t{++} objects
10749 Print static members when displaying a C@t{++} object. The default is on.
10751 @item set print static-members off
10752 Do not print static members when displaying a C@t{++} object.
10754 @item show print static-members
10755 Show whether C@t{++} static members are printed or not.
10757 @item set print pascal_static-members
10758 @itemx set print pascal_static-members on
10759 @cindex static members of Pascal objects
10760 @cindex Pascal objects, static members display
10761 Print static members when displaying a Pascal object. The default is on.
10763 @item set print pascal_static-members off
10764 Do not print static members when displaying a Pascal object.
10766 @item show print pascal_static-members
10767 Show whether Pascal static members are printed or not.
10769 @c These don't work with HP ANSI C++ yet.
10770 @item set print vtbl
10771 @itemx set print vtbl on
10772 @cindex pretty print C@t{++} virtual function tables
10773 @cindex virtual functions (C@t{++}) display
10774 @cindex VTBL display
10775 Pretty print C@t{++} virtual function tables. The default is off.
10776 (The @code{vtbl} commands do not work on programs compiled with the HP
10777 ANSI C@t{++} compiler (@code{aCC}).)
10779 @item set print vtbl off
10780 Do not pretty print C@t{++} virtual function tables.
10782 @item show print vtbl
10783 Show whether C@t{++} virtual function tables are pretty printed, or not.
10786 @node Pretty Printing
10787 @section Pretty Printing
10789 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10790 Python code. It greatly simplifies the display of complex objects. This
10791 mechanism works for both MI and the CLI.
10794 * Pretty-Printer Introduction:: Introduction to pretty-printers
10795 * Pretty-Printer Example:: An example pretty-printer
10796 * Pretty-Printer Commands:: Pretty-printer commands
10799 @node Pretty-Printer Introduction
10800 @subsection Pretty-Printer Introduction
10802 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10803 registered for the value. If there is then @value{GDBN} invokes the
10804 pretty-printer to print the value. Otherwise the value is printed normally.
10806 Pretty-printers are normally named. This makes them easy to manage.
10807 The @samp{info pretty-printer} command will list all the installed
10808 pretty-printers with their names.
10809 If a pretty-printer can handle multiple data types, then its
10810 @dfn{subprinters} are the printers for the individual data types.
10811 Each such subprinter has its own name.
10812 The format of the name is @var{printer-name};@var{subprinter-name}.
10814 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10815 Typically they are automatically loaded and registered when the corresponding
10816 debug information is loaded, thus making them available without having to
10817 do anything special.
10819 There are three places where a pretty-printer can be registered.
10823 Pretty-printers registered globally are available when debugging
10827 Pretty-printers registered with a program space are available only
10828 when debugging that program.
10829 @xref{Progspaces In Python}, for more details on program spaces in Python.
10832 Pretty-printers registered with an objfile are loaded and unloaded
10833 with the corresponding objfile (e.g., shared library).
10834 @xref{Objfiles In Python}, for more details on objfiles in Python.
10837 @xref{Selecting Pretty-Printers}, for further information on how
10838 pretty-printers are selected,
10840 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10843 @node Pretty-Printer Example
10844 @subsection Pretty-Printer Example
10846 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10849 (@value{GDBP}) print s
10851 static npos = 4294967295,
10853 <std::allocator<char>> = @{
10854 <__gnu_cxx::new_allocator<char>> = @{
10855 <No data fields>@}, <No data fields>
10857 members of std::basic_string<char, std::char_traits<char>,
10858 std::allocator<char> >::_Alloc_hider:
10859 _M_p = 0x804a014 "abcd"
10864 With a pretty-printer for @code{std::string} only the contents are printed:
10867 (@value{GDBP}) print s
10871 @node Pretty-Printer Commands
10872 @subsection Pretty-Printer Commands
10873 @cindex pretty-printer commands
10876 @kindex info pretty-printer
10877 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10878 Print the list of installed pretty-printers.
10879 This includes disabled pretty-printers, which are marked as such.
10881 @var{object-regexp} is a regular expression matching the objects
10882 whose pretty-printers to list.
10883 Objects can be @code{global}, the program space's file
10884 (@pxref{Progspaces In Python}),
10885 and the object files within that program space (@pxref{Objfiles In Python}).
10886 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10887 looks up a printer from these three objects.
10889 @var{name-regexp} is a regular expression matching the name of the printers
10892 @kindex disable pretty-printer
10893 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10894 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10895 A disabled pretty-printer is not forgotten, it may be enabled again later.
10897 @kindex enable pretty-printer
10898 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10899 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10904 Suppose we have three pretty-printers installed: one from library1.so
10905 named @code{foo} that prints objects of type @code{foo}, and
10906 another from library2.so named @code{bar} that prints two types of objects,
10907 @code{bar1} and @code{bar2}.
10910 (gdb) info pretty-printer
10917 (gdb) info pretty-printer library2
10922 (gdb) disable pretty-printer library1
10924 2 of 3 printers enabled
10925 (gdb) info pretty-printer
10932 (gdb) disable pretty-printer library2 bar;bar1
10934 1 of 3 printers enabled
10935 (gdb) info pretty-printer library2
10942 (gdb) disable pretty-printer library2 bar
10944 0 of 3 printers enabled
10945 (gdb) info pretty-printer library2
10954 Note that for @code{bar} the entire printer can be disabled,
10955 as can each individual subprinter.
10957 @node Value History
10958 @section Value History
10960 @cindex value history
10961 @cindex history of values printed by @value{GDBN}
10962 Values printed by the @code{print} command are saved in the @value{GDBN}
10963 @dfn{value history}. This allows you to refer to them in other expressions.
10964 Values are kept until the symbol table is re-read or discarded
10965 (for example with the @code{file} or @code{symbol-file} commands).
10966 When the symbol table changes, the value history is discarded,
10967 since the values may contain pointers back to the types defined in the
10972 @cindex history number
10973 The values printed are given @dfn{history numbers} by which you can
10974 refer to them. These are successive integers starting with one.
10975 @code{print} shows you the history number assigned to a value by
10976 printing @samp{$@var{num} = } before the value; here @var{num} is the
10979 To refer to any previous value, use @samp{$} followed by the value's
10980 history number. The way @code{print} labels its output is designed to
10981 remind you of this. Just @code{$} refers to the most recent value in
10982 the history, and @code{$$} refers to the value before that.
10983 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10984 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10985 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10987 For example, suppose you have just printed a pointer to a structure and
10988 want to see the contents of the structure. It suffices to type
10994 If you have a chain of structures where the component @code{next} points
10995 to the next one, you can print the contents of the next one with this:
11002 You can print successive links in the chain by repeating this
11003 command---which you can do by just typing @key{RET}.
11005 Note that the history records values, not expressions. If the value of
11006 @code{x} is 4 and you type these commands:
11014 then the value recorded in the value history by the @code{print} command
11015 remains 4 even though the value of @code{x} has changed.
11018 @kindex show values
11020 Print the last ten values in the value history, with their item numbers.
11021 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11022 values} does not change the history.
11024 @item show values @var{n}
11025 Print ten history values centered on history item number @var{n}.
11027 @item show values +
11028 Print ten history values just after the values last printed. If no more
11029 values are available, @code{show values +} produces no display.
11032 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11033 same effect as @samp{show values +}.
11035 @node Convenience Vars
11036 @section Convenience Variables
11038 @cindex convenience variables
11039 @cindex user-defined variables
11040 @value{GDBN} provides @dfn{convenience variables} that you can use within
11041 @value{GDBN} to hold on to a value and refer to it later. These variables
11042 exist entirely within @value{GDBN}; they are not part of your program, and
11043 setting a convenience variable has no direct effect on further execution
11044 of your program. That is why you can use them freely.
11046 Convenience variables are prefixed with @samp{$}. Any name preceded by
11047 @samp{$} can be used for a convenience variable, unless it is one of
11048 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11049 (Value history references, in contrast, are @emph{numbers} preceded
11050 by @samp{$}. @xref{Value History, ,Value History}.)
11052 You can save a value in a convenience variable with an assignment
11053 expression, just as you would set a variable in your program.
11057 set $foo = *object_ptr
11061 would save in @code{$foo} the value contained in the object pointed to by
11064 Using a convenience variable for the first time creates it, but its
11065 value is @code{void} until you assign a new value. You can alter the
11066 value with another assignment at any time.
11068 Convenience variables have no fixed types. You can assign a convenience
11069 variable any type of value, including structures and arrays, even if
11070 that variable already has a value of a different type. The convenience
11071 variable, when used as an expression, has the type of its current value.
11074 @kindex show convenience
11075 @cindex show all user variables and functions
11076 @item show convenience
11077 Print a list of convenience variables used so far, and their values,
11078 as well as a list of the convenience functions.
11079 Abbreviated @code{show conv}.
11081 @kindex init-if-undefined
11082 @cindex convenience variables, initializing
11083 @item init-if-undefined $@var{variable} = @var{expression}
11084 Set a convenience variable if it has not already been set. This is useful
11085 for user-defined commands that keep some state. It is similar, in concept,
11086 to using local static variables with initializers in C (except that
11087 convenience variables are global). It can also be used to allow users to
11088 override default values used in a command script.
11090 If the variable is already defined then the expression is not evaluated so
11091 any side-effects do not occur.
11094 One of the ways to use a convenience variable is as a counter to be
11095 incremented or a pointer to be advanced. For example, to print
11096 a field from successive elements of an array of structures:
11100 print bar[$i++]->contents
11104 Repeat that command by typing @key{RET}.
11106 Some convenience variables are created automatically by @value{GDBN} and given
11107 values likely to be useful.
11110 @vindex $_@r{, convenience variable}
11112 The variable @code{$_} is automatically set by the @code{x} command to
11113 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11114 commands which provide a default address for @code{x} to examine also
11115 set @code{$_} to that address; these commands include @code{info line}
11116 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11117 except when set by the @code{x} command, in which case it is a pointer
11118 to the type of @code{$__}.
11120 @vindex $__@r{, convenience variable}
11122 The variable @code{$__} is automatically set by the @code{x} command
11123 to the value found in the last address examined. Its type is chosen
11124 to match the format in which the data was printed.
11127 @vindex $_exitcode@r{, convenience variable}
11128 When the program being debugged terminates normally, @value{GDBN}
11129 automatically sets this variable to the exit code of the program, and
11130 resets @code{$_exitsignal} to @code{void}.
11133 @vindex $_exitsignal@r{, convenience variable}
11134 When the program being debugged dies due to an uncaught signal,
11135 @value{GDBN} automatically sets this variable to that signal's number,
11136 and resets @code{$_exitcode} to @code{void}.
11138 To distinguish between whether the program being debugged has exited
11139 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11140 @code{$_exitsignal} is not @code{void}), the convenience function
11141 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11142 Functions}). For example, considering the following source code:
11145 #include <signal.h>
11148 main (int argc, char *argv[])
11155 A valid way of telling whether the program being debugged has exited
11156 or signalled would be:
11159 (@value{GDBP}) define has_exited_or_signalled
11160 Type commands for definition of ``has_exited_or_signalled''.
11161 End with a line saying just ``end''.
11162 >if $_isvoid ($_exitsignal)
11163 >echo The program has exited\n
11165 >echo The program has signalled\n
11171 Program terminated with signal SIGALRM, Alarm clock.
11172 The program no longer exists.
11173 (@value{GDBP}) has_exited_or_signalled
11174 The program has signalled
11177 As can be seen, @value{GDBN} correctly informs that the program being
11178 debugged has signalled, since it calls @code{raise} and raises a
11179 @code{SIGALRM} signal. If the program being debugged had not called
11180 @code{raise}, then @value{GDBN} would report a normal exit:
11183 (@value{GDBP}) has_exited_or_signalled
11184 The program has exited
11188 The variable @code{$_exception} is set to the exception object being
11189 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11192 @itemx $_probe_arg0@dots{}$_probe_arg11
11193 Arguments to a static probe. @xref{Static Probe Points}.
11196 @vindex $_sdata@r{, inspect, convenience variable}
11197 The variable @code{$_sdata} contains extra collected static tracepoint
11198 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11199 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11200 if extra static tracepoint data has not been collected.
11203 @vindex $_siginfo@r{, convenience variable}
11204 The variable @code{$_siginfo} contains extra signal information
11205 (@pxref{extra signal information}). Note that @code{$_siginfo}
11206 could be empty, if the application has not yet received any signals.
11207 For example, it will be empty before you execute the @code{run} command.
11210 @vindex $_tlb@r{, convenience variable}
11211 The variable @code{$_tlb} is automatically set when debugging
11212 applications running on MS-Windows in native mode or connected to
11213 gdbserver that supports the @code{qGetTIBAddr} request.
11214 @xref{General Query Packets}.
11215 This variable contains the address of the thread information block.
11218 The number of the current inferior. @xref{Inferiors and
11219 Programs, ,Debugging Multiple Inferiors and Programs}.
11222 The thread number of the current thread. @xref{thread numbers}.
11225 The global number of the current thread. @xref{global thread numbers}.
11229 @node Convenience Funs
11230 @section Convenience Functions
11232 @cindex convenience functions
11233 @value{GDBN} also supplies some @dfn{convenience functions}. These
11234 have a syntax similar to convenience variables. A convenience
11235 function can be used in an expression just like an ordinary function;
11236 however, a convenience function is implemented internally to
11239 These functions do not require @value{GDBN} to be configured with
11240 @code{Python} support, which means that they are always available.
11244 @item $_isvoid (@var{expr})
11245 @findex $_isvoid@r{, convenience function}
11246 Return one if the expression @var{expr} is @code{void}. Otherwise it
11249 A @code{void} expression is an expression where the type of the result
11250 is @code{void}. For example, you can examine a convenience variable
11251 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11255 (@value{GDBP}) print $_exitcode
11257 (@value{GDBP}) print $_isvoid ($_exitcode)
11260 Starting program: ./a.out
11261 [Inferior 1 (process 29572) exited normally]
11262 (@value{GDBP}) print $_exitcode
11264 (@value{GDBP}) print $_isvoid ($_exitcode)
11268 In the example above, we used @code{$_isvoid} to check whether
11269 @code{$_exitcode} is @code{void} before and after the execution of the
11270 program being debugged. Before the execution there is no exit code to
11271 be examined, therefore @code{$_exitcode} is @code{void}. After the
11272 execution the program being debugged returned zero, therefore
11273 @code{$_exitcode} is zero, which means that it is not @code{void}
11276 The @code{void} expression can also be a call of a function from the
11277 program being debugged. For example, given the following function:
11286 The result of calling it inside @value{GDBN} is @code{void}:
11289 (@value{GDBP}) print foo ()
11291 (@value{GDBP}) print $_isvoid (foo ())
11293 (@value{GDBP}) set $v = foo ()
11294 (@value{GDBP}) print $v
11296 (@value{GDBP}) print $_isvoid ($v)
11302 These functions require @value{GDBN} to be configured with
11303 @code{Python} support.
11307 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11308 @findex $_memeq@r{, convenience function}
11309 Returns one if the @var{length} bytes at the addresses given by
11310 @var{buf1} and @var{buf2} are equal.
11311 Otherwise it returns zero.
11313 @item $_regex(@var{str}, @var{regex})
11314 @findex $_regex@r{, convenience function}
11315 Returns one if the string @var{str} matches the regular expression
11316 @var{regex}. Otherwise it returns zero.
11317 The syntax of the regular expression is that specified by @code{Python}'s
11318 regular expression support.
11320 @item $_streq(@var{str1}, @var{str2})
11321 @findex $_streq@r{, convenience function}
11322 Returns one if the strings @var{str1} and @var{str2} are equal.
11323 Otherwise it returns zero.
11325 @item $_strlen(@var{str})
11326 @findex $_strlen@r{, convenience function}
11327 Returns the length of string @var{str}.
11329 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11330 @findex $_caller_is@r{, convenience function}
11331 Returns one if the calling function's name is equal to @var{name}.
11332 Otherwise it returns zero.
11334 If the optional argument @var{number_of_frames} is provided,
11335 it is the number of frames up in the stack to look.
11343 at testsuite/gdb.python/py-caller-is.c:21
11344 #1 0x00000000004005a0 in middle_func ()
11345 at testsuite/gdb.python/py-caller-is.c:27
11346 #2 0x00000000004005ab in top_func ()
11347 at testsuite/gdb.python/py-caller-is.c:33
11348 #3 0x00000000004005b6 in main ()
11349 at testsuite/gdb.python/py-caller-is.c:39
11350 (gdb) print $_caller_is ("middle_func")
11352 (gdb) print $_caller_is ("top_func", 2)
11356 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11357 @findex $_caller_matches@r{, convenience function}
11358 Returns one if the calling function's name matches the regular expression
11359 @var{regexp}. Otherwise it returns zero.
11361 If the optional argument @var{number_of_frames} is provided,
11362 it is the number of frames up in the stack to look.
11365 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11366 @findex $_any_caller_is@r{, convenience function}
11367 Returns one if any calling function's name is equal to @var{name}.
11368 Otherwise it returns zero.
11370 If the optional argument @var{number_of_frames} is provided,
11371 it is the number of frames up in the stack to look.
11374 This function differs from @code{$_caller_is} in that this function
11375 checks all stack frames from the immediate caller to the frame specified
11376 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11377 frame specified by @var{number_of_frames}.
11379 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11380 @findex $_any_caller_matches@r{, convenience function}
11381 Returns one if any calling function's name matches the regular expression
11382 @var{regexp}. Otherwise it returns zero.
11384 If the optional argument @var{number_of_frames} is provided,
11385 it is the number of frames up in the stack to look.
11388 This function differs from @code{$_caller_matches} in that this function
11389 checks all stack frames from the immediate caller to the frame specified
11390 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11391 frame specified by @var{number_of_frames}.
11393 @item $_as_string(@var{value})
11394 @findex $_as_string@r{, convenience function}
11395 Return the string representation of @var{value}.
11397 This function is useful to obtain the textual label (enumerator) of an
11398 enumeration value. For example, assuming the variable @var{node} is of
11399 an enumerated type:
11402 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11403 Visiting node of type NODE_INTEGER
11408 @value{GDBN} provides the ability to list and get help on
11409 convenience functions.
11412 @item help function
11413 @kindex help function
11414 @cindex show all convenience functions
11415 Print a list of all convenience functions.
11422 You can refer to machine register contents, in expressions, as variables
11423 with names starting with @samp{$}. The names of registers are different
11424 for each machine; use @code{info registers} to see the names used on
11428 @kindex info registers
11429 @item info registers
11430 Print the names and values of all registers except floating-point
11431 and vector registers (in the selected stack frame).
11433 @kindex info all-registers
11434 @cindex floating point registers
11435 @item info all-registers
11436 Print the names and values of all registers, including floating-point
11437 and vector registers (in the selected stack frame).
11439 @item info registers @var{reggroup} @dots{}
11440 Print the name and value of the registers in each of the specified
11441 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11442 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11444 @item info registers @var{regname} @dots{}
11445 Print the @dfn{relativized} value of each specified register @var{regname}.
11446 As discussed in detail below, register values are normally relative to
11447 the selected stack frame. The @var{regname} may be any register name valid on
11448 the machine you are using, with or without the initial @samp{$}.
11451 @anchor{standard registers}
11452 @cindex stack pointer register
11453 @cindex program counter register
11454 @cindex process status register
11455 @cindex frame pointer register
11456 @cindex standard registers
11457 @value{GDBN} has four ``standard'' register names that are available (in
11458 expressions) on most machines---whenever they do not conflict with an
11459 architecture's canonical mnemonics for registers. The register names
11460 @code{$pc} and @code{$sp} are used for the program counter register and
11461 the stack pointer. @code{$fp} is used for a register that contains a
11462 pointer to the current stack frame, and @code{$ps} is used for a
11463 register that contains the processor status. For example,
11464 you could print the program counter in hex with
11471 or print the instruction to be executed next with
11478 or add four to the stack pointer@footnote{This is a way of removing
11479 one word from the stack, on machines where stacks grow downward in
11480 memory (most machines, nowadays). This assumes that the innermost
11481 stack frame is selected; setting @code{$sp} is not allowed when other
11482 stack frames are selected. To pop entire frames off the stack,
11483 regardless of machine architecture, use @code{return};
11484 see @ref{Returning, ,Returning from a Function}.} with
11490 Whenever possible, these four standard register names are available on
11491 your machine even though the machine has different canonical mnemonics,
11492 so long as there is no conflict. The @code{info registers} command
11493 shows the canonical names. For example, on the SPARC, @code{info
11494 registers} displays the processor status register as @code{$psr} but you
11495 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11496 is an alias for the @sc{eflags} register.
11498 @value{GDBN} always considers the contents of an ordinary register as an
11499 integer when the register is examined in this way. Some machines have
11500 special registers which can hold nothing but floating point; these
11501 registers are considered to have floating point values. There is no way
11502 to refer to the contents of an ordinary register as floating point value
11503 (although you can @emph{print} it as a floating point value with
11504 @samp{print/f $@var{regname}}).
11506 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11507 means that the data format in which the register contents are saved by
11508 the operating system is not the same one that your program normally
11509 sees. For example, the registers of the 68881 floating point
11510 coprocessor are always saved in ``extended'' (raw) format, but all C
11511 programs expect to work with ``double'' (virtual) format. In such
11512 cases, @value{GDBN} normally works with the virtual format only (the format
11513 that makes sense for your program), but the @code{info registers} command
11514 prints the data in both formats.
11516 @cindex SSE registers (x86)
11517 @cindex MMX registers (x86)
11518 Some machines have special registers whose contents can be interpreted
11519 in several different ways. For example, modern x86-based machines
11520 have SSE and MMX registers that can hold several values packed
11521 together in several different formats. @value{GDBN} refers to such
11522 registers in @code{struct} notation:
11525 (@value{GDBP}) print $xmm1
11527 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11528 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11529 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11530 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11531 v4_int32 = @{0, 20657912, 11, 13@},
11532 v2_int64 = @{88725056443645952, 55834574859@},
11533 uint128 = 0x0000000d0000000b013b36f800000000
11538 To set values of such registers, you need to tell @value{GDBN} which
11539 view of the register you wish to change, as if you were assigning
11540 value to a @code{struct} member:
11543 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11546 Normally, register values are relative to the selected stack frame
11547 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11548 value that the register would contain if all stack frames farther in
11549 were exited and their saved registers restored. In order to see the
11550 true contents of hardware registers, you must select the innermost
11551 frame (with @samp{frame 0}).
11553 @cindex caller-saved registers
11554 @cindex call-clobbered registers
11555 @cindex volatile registers
11556 @cindex <not saved> values
11557 Usually ABIs reserve some registers as not needed to be saved by the
11558 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11559 registers). It may therefore not be possible for @value{GDBN} to know
11560 the value a register had before the call (in other words, in the outer
11561 frame), if the register value has since been changed by the callee.
11562 @value{GDBN} tries to deduce where the inner frame saved
11563 (``callee-saved'') registers, from the debug info, unwind info, or the
11564 machine code generated by your compiler. If some register is not
11565 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11566 its own knowledge of the ABI, or because the debug/unwind info
11567 explicitly says the register's value is undefined), @value{GDBN}
11568 displays @w{@samp{<not saved>}} as the register's value. With targets
11569 that @value{GDBN} has no knowledge of the register saving convention,
11570 if a register was not saved by the callee, then its value and location
11571 in the outer frame are assumed to be the same of the inner frame.
11572 This is usually harmless, because if the register is call-clobbered,
11573 the caller either does not care what is in the register after the
11574 call, or has code to restore the value that it does care about. Note,
11575 however, that if you change such a register in the outer frame, you
11576 may also be affecting the inner frame. Also, the more ``outer'' the
11577 frame is you're looking at, the more likely a call-clobbered
11578 register's value is to be wrong, in the sense that it doesn't actually
11579 represent the value the register had just before the call.
11581 @node Floating Point Hardware
11582 @section Floating Point Hardware
11583 @cindex floating point
11585 Depending on the configuration, @value{GDBN} may be able to give
11586 you more information about the status of the floating point hardware.
11591 Display hardware-dependent information about the floating
11592 point unit. The exact contents and layout vary depending on the
11593 floating point chip. Currently, @samp{info float} is supported on
11594 the ARM and x86 machines.
11598 @section Vector Unit
11599 @cindex vector unit
11601 Depending on the configuration, @value{GDBN} may be able to give you
11602 more information about the status of the vector unit.
11605 @kindex info vector
11607 Display information about the vector unit. The exact contents and
11608 layout vary depending on the hardware.
11611 @node OS Information
11612 @section Operating System Auxiliary Information
11613 @cindex OS information
11615 @value{GDBN} provides interfaces to useful OS facilities that can help
11616 you debug your program.
11618 @cindex auxiliary vector
11619 @cindex vector, auxiliary
11620 Some operating systems supply an @dfn{auxiliary vector} to programs at
11621 startup. This is akin to the arguments and environment that you
11622 specify for a program, but contains a system-dependent variety of
11623 binary values that tell system libraries important details about the
11624 hardware, operating system, and process. Each value's purpose is
11625 identified by an integer tag; the meanings are well-known but system-specific.
11626 Depending on the configuration and operating system facilities,
11627 @value{GDBN} may be able to show you this information. For remote
11628 targets, this functionality may further depend on the remote stub's
11629 support of the @samp{qXfer:auxv:read} packet, see
11630 @ref{qXfer auxiliary vector read}.
11635 Display the auxiliary vector of the inferior, which can be either a
11636 live process or a core dump file. @value{GDBN} prints each tag value
11637 numerically, and also shows names and text descriptions for recognized
11638 tags. Some values in the vector are numbers, some bit masks, and some
11639 pointers to strings or other data. @value{GDBN} displays each value in the
11640 most appropriate form for a recognized tag, and in hexadecimal for
11641 an unrecognized tag.
11644 On some targets, @value{GDBN} can access operating system-specific
11645 information and show it to you. The types of information available
11646 will differ depending on the type of operating system running on the
11647 target. The mechanism used to fetch the data is described in
11648 @ref{Operating System Information}. For remote targets, this
11649 functionality depends on the remote stub's support of the
11650 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11654 @item info os @var{infotype}
11656 Display OS information of the requested type.
11658 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11660 @anchor{linux info os infotypes}
11662 @kindex info os cpus
11664 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11665 the available fields from /proc/cpuinfo. For each supported architecture
11666 different fields are available. Two common entries are processor which gives
11667 CPU number and bogomips; a system constant that is calculated during
11668 kernel initialization.
11670 @kindex info os files
11672 Display the list of open file descriptors on the target. For each
11673 file descriptor, @value{GDBN} prints the identifier of the process
11674 owning the descriptor, the command of the owning process, the value
11675 of the descriptor, and the target of the descriptor.
11677 @kindex info os modules
11679 Display the list of all loaded kernel modules on the target. For each
11680 module, @value{GDBN} prints the module name, the size of the module in
11681 bytes, the number of times the module is used, the dependencies of the
11682 module, the status of the module, and the address of the loaded module
11685 @kindex info os msg
11687 Display the list of all System V message queues on the target. For each
11688 message queue, @value{GDBN} prints the message queue key, the message
11689 queue identifier, the access permissions, the current number of bytes
11690 on the queue, the current number of messages on the queue, the processes
11691 that last sent and received a message on the queue, the user and group
11692 of the owner and creator of the message queue, the times at which a
11693 message was last sent and received on the queue, and the time at which
11694 the message queue was last changed.
11696 @kindex info os processes
11698 Display the list of processes on the target. For each process,
11699 @value{GDBN} prints the process identifier, the name of the user, the
11700 command corresponding to the process, and the list of processor cores
11701 that the process is currently running on. (To understand what these
11702 properties mean, for this and the following info types, please consult
11703 the general @sc{gnu}/Linux documentation.)
11705 @kindex info os procgroups
11707 Display the list of process groups on the target. For each process,
11708 @value{GDBN} prints the identifier of the process group that it belongs
11709 to, the command corresponding to the process group leader, the process
11710 identifier, and the command line of the process. The list is sorted
11711 first by the process group identifier, then by the process identifier,
11712 so that processes belonging to the same process group are grouped together
11713 and the process group leader is listed first.
11715 @kindex info os semaphores
11717 Display the list of all System V semaphore sets on the target. For each
11718 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11719 set identifier, the access permissions, the number of semaphores in the
11720 set, the user and group of the owner and creator of the semaphore set,
11721 and the times at which the semaphore set was operated upon and changed.
11723 @kindex info os shm
11725 Display the list of all System V shared-memory regions on the target.
11726 For each shared-memory region, @value{GDBN} prints the region key,
11727 the shared-memory identifier, the access permissions, the size of the
11728 region, the process that created the region, the process that last
11729 attached to or detached from the region, the current number of live
11730 attaches to the region, and the times at which the region was last
11731 attached to, detach from, and changed.
11733 @kindex info os sockets
11735 Display the list of Internet-domain sockets on the target. For each
11736 socket, @value{GDBN} prints the address and port of the local and
11737 remote endpoints, the current state of the connection, the creator of
11738 the socket, the IP address family of the socket, and the type of the
11741 @kindex info os threads
11743 Display the list of threads running on the target. For each thread,
11744 @value{GDBN} prints the identifier of the process that the thread
11745 belongs to, the command of the process, the thread identifier, and the
11746 processor core that it is currently running on. The main thread of a
11747 process is not listed.
11751 If @var{infotype} is omitted, then list the possible values for
11752 @var{infotype} and the kind of OS information available for each
11753 @var{infotype}. If the target does not return a list of possible
11754 types, this command will report an error.
11757 @node Memory Region Attributes
11758 @section Memory Region Attributes
11759 @cindex memory region attributes
11761 @dfn{Memory region attributes} allow you to describe special handling
11762 required by regions of your target's memory. @value{GDBN} uses
11763 attributes to determine whether to allow certain types of memory
11764 accesses; whether to use specific width accesses; and whether to cache
11765 target memory. By default the description of memory regions is
11766 fetched from the target (if the current target supports this), but the
11767 user can override the fetched regions.
11769 Defined memory regions can be individually enabled and disabled. When a
11770 memory region is disabled, @value{GDBN} uses the default attributes when
11771 accessing memory in that region. Similarly, if no memory regions have
11772 been defined, @value{GDBN} uses the default attributes when accessing
11775 When a memory region is defined, it is given a number to identify it;
11776 to enable, disable, or remove a memory region, you specify that number.
11780 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11781 Define a memory region bounded by @var{lower} and @var{upper} with
11782 attributes @var{attributes}@dots{}, and add it to the list of regions
11783 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11784 case: it is treated as the target's maximum memory address.
11785 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11788 Discard any user changes to the memory regions and use target-supplied
11789 regions, if available, or no regions if the target does not support.
11792 @item delete mem @var{nums}@dots{}
11793 Remove memory regions @var{nums}@dots{} from the list of regions
11794 monitored by @value{GDBN}.
11796 @kindex disable mem
11797 @item disable mem @var{nums}@dots{}
11798 Disable monitoring of memory regions @var{nums}@dots{}.
11799 A disabled memory region is not forgotten.
11800 It may be enabled again later.
11803 @item enable mem @var{nums}@dots{}
11804 Enable monitoring of memory regions @var{nums}@dots{}.
11808 Print a table of all defined memory regions, with the following columns
11812 @item Memory Region Number
11813 @item Enabled or Disabled.
11814 Enabled memory regions are marked with @samp{y}.
11815 Disabled memory regions are marked with @samp{n}.
11818 The address defining the inclusive lower bound of the memory region.
11821 The address defining the exclusive upper bound of the memory region.
11824 The list of attributes set for this memory region.
11829 @subsection Attributes
11831 @subsubsection Memory Access Mode
11832 The access mode attributes set whether @value{GDBN} may make read or
11833 write accesses to a memory region.
11835 While these attributes prevent @value{GDBN} from performing invalid
11836 memory accesses, they do nothing to prevent the target system, I/O DMA,
11837 etc.@: from accessing memory.
11841 Memory is read only.
11843 Memory is write only.
11845 Memory is read/write. This is the default.
11848 @subsubsection Memory Access Size
11849 The access size attribute tells @value{GDBN} to use specific sized
11850 accesses in the memory region. Often memory mapped device registers
11851 require specific sized accesses. If no access size attribute is
11852 specified, @value{GDBN} may use accesses of any size.
11856 Use 8 bit memory accesses.
11858 Use 16 bit memory accesses.
11860 Use 32 bit memory accesses.
11862 Use 64 bit memory accesses.
11865 @c @subsubsection Hardware/Software Breakpoints
11866 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11867 @c will use hardware or software breakpoints for the internal breakpoints
11868 @c used by the step, next, finish, until, etc. commands.
11872 @c Always use hardware breakpoints
11873 @c @item swbreak (default)
11876 @subsubsection Data Cache
11877 The data cache attributes set whether @value{GDBN} will cache target
11878 memory. While this generally improves performance by reducing debug
11879 protocol overhead, it can lead to incorrect results because @value{GDBN}
11880 does not know about volatile variables or memory mapped device
11885 Enable @value{GDBN} to cache target memory.
11887 Disable @value{GDBN} from caching target memory. This is the default.
11890 @subsection Memory Access Checking
11891 @value{GDBN} can be instructed to refuse accesses to memory that is
11892 not explicitly described. This can be useful if accessing such
11893 regions has undesired effects for a specific target, or to provide
11894 better error checking. The following commands control this behaviour.
11897 @kindex set mem inaccessible-by-default
11898 @item set mem inaccessible-by-default [on|off]
11899 If @code{on} is specified, make @value{GDBN} treat memory not
11900 explicitly described by the memory ranges as non-existent and refuse accesses
11901 to such memory. The checks are only performed if there's at least one
11902 memory range defined. If @code{off} is specified, make @value{GDBN}
11903 treat the memory not explicitly described by the memory ranges as RAM.
11904 The default value is @code{on}.
11905 @kindex show mem inaccessible-by-default
11906 @item show mem inaccessible-by-default
11907 Show the current handling of accesses to unknown memory.
11911 @c @subsubsection Memory Write Verification
11912 @c The memory write verification attributes set whether @value{GDBN}
11913 @c will re-reads data after each write to verify the write was successful.
11917 @c @item noverify (default)
11920 @node Dump/Restore Files
11921 @section Copy Between Memory and a File
11922 @cindex dump/restore files
11923 @cindex append data to a file
11924 @cindex dump data to a file
11925 @cindex restore data from a file
11927 You can use the commands @code{dump}, @code{append}, and
11928 @code{restore} to copy data between target memory and a file. The
11929 @code{dump} and @code{append} commands write data to a file, and the
11930 @code{restore} command reads data from a file back into the inferior's
11931 memory. Files may be in binary, Motorola S-record, Intel hex,
11932 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11933 append to binary files, and cannot read from Verilog Hex files.
11938 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11939 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11940 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11941 or the value of @var{expr}, to @var{filename} in the given format.
11943 The @var{format} parameter may be any one of:
11950 Motorola S-record format.
11952 Tektronix Hex format.
11954 Verilog Hex format.
11957 @value{GDBN} uses the same definitions of these formats as the
11958 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11959 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11963 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11964 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11965 Append the contents of memory from @var{start_addr} to @var{end_addr},
11966 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11967 (@value{GDBN} can only append data to files in raw binary form.)
11970 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11971 Restore the contents of file @var{filename} into memory. The
11972 @code{restore} command can automatically recognize any known @sc{bfd}
11973 file format, except for raw binary. To restore a raw binary file you
11974 must specify the optional keyword @code{binary} after the filename.
11976 If @var{bias} is non-zero, its value will be added to the addresses
11977 contained in the file. Binary files always start at address zero, so
11978 they will be restored at address @var{bias}. Other bfd files have
11979 a built-in location; they will be restored at offset @var{bias}
11980 from that location.
11982 If @var{start} and/or @var{end} are non-zero, then only data between
11983 file offset @var{start} and file offset @var{end} will be restored.
11984 These offsets are relative to the addresses in the file, before
11985 the @var{bias} argument is applied.
11989 @node Core File Generation
11990 @section How to Produce a Core File from Your Program
11991 @cindex dump core from inferior
11993 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11994 image of a running process and its process status (register values
11995 etc.). Its primary use is post-mortem debugging of a program that
11996 crashed while it ran outside a debugger. A program that crashes
11997 automatically produces a core file, unless this feature is disabled by
11998 the user. @xref{Files}, for information on invoking @value{GDBN} in
11999 the post-mortem debugging mode.
12001 Occasionally, you may wish to produce a core file of the program you
12002 are debugging in order to preserve a snapshot of its state.
12003 @value{GDBN} has a special command for that.
12007 @kindex generate-core-file
12008 @item generate-core-file [@var{file}]
12009 @itemx gcore [@var{file}]
12010 Produce a core dump of the inferior process. The optional argument
12011 @var{file} specifies the file name where to put the core dump. If not
12012 specified, the file name defaults to @file{core.@var{pid}}, where
12013 @var{pid} is the inferior process ID.
12015 Note that this command is implemented only for some systems (as of
12016 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12018 On @sc{gnu}/Linux, this command can take into account the value of the
12019 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12020 dump (@pxref{set use-coredump-filter}), and by default honors the
12021 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12022 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12024 @kindex set use-coredump-filter
12025 @anchor{set use-coredump-filter}
12026 @item set use-coredump-filter on
12027 @itemx set use-coredump-filter off
12028 Enable or disable the use of the file
12029 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12030 files. This file is used by the Linux kernel to decide what types of
12031 memory mappings will be dumped or ignored when generating a core dump
12032 file. @var{pid} is the process ID of a currently running process.
12034 To make use of this feature, you have to write in the
12035 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12036 which is a bit mask representing the memory mapping types. If a bit
12037 is set in the bit mask, then the memory mappings of the corresponding
12038 types will be dumped; otherwise, they will be ignored. This
12039 configuration is inherited by child processes. For more information
12040 about the bits that can be set in the
12041 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12042 manpage of @code{core(5)}.
12044 By default, this option is @code{on}. If this option is turned
12045 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12046 and instead uses the same default value as the Linux kernel in order
12047 to decide which pages will be dumped in the core dump file. This
12048 value is currently @code{0x33}, which means that bits @code{0}
12049 (anonymous private mappings), @code{1} (anonymous shared mappings),
12050 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12051 This will cause these memory mappings to be dumped automatically.
12053 @kindex set dump-excluded-mappings
12054 @anchor{set dump-excluded-mappings}
12055 @item set dump-excluded-mappings on
12056 @itemx set dump-excluded-mappings off
12057 If @code{on} is specified, @value{GDBN} will dump memory mappings
12058 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12059 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12061 The default value is @code{off}.
12064 @node Character Sets
12065 @section Character Sets
12066 @cindex character sets
12068 @cindex translating between character sets
12069 @cindex host character set
12070 @cindex target character set
12072 If the program you are debugging uses a different character set to
12073 represent characters and strings than the one @value{GDBN} uses itself,
12074 @value{GDBN} can automatically translate between the character sets for
12075 you. The character set @value{GDBN} uses we call the @dfn{host
12076 character set}; the one the inferior program uses we call the
12077 @dfn{target character set}.
12079 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12080 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12081 remote protocol (@pxref{Remote Debugging}) to debug a program
12082 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12083 then the host character set is Latin-1, and the target character set is
12084 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12085 target-charset EBCDIC-US}, then @value{GDBN} translates between
12086 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12087 character and string literals in expressions.
12089 @value{GDBN} has no way to automatically recognize which character set
12090 the inferior program uses; you must tell it, using the @code{set
12091 target-charset} command, described below.
12093 Here are the commands for controlling @value{GDBN}'s character set
12097 @item set target-charset @var{charset}
12098 @kindex set target-charset
12099 Set the current target character set to @var{charset}. To display the
12100 list of supported target character sets, type
12101 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12103 @item set host-charset @var{charset}
12104 @kindex set host-charset
12105 Set the current host character set to @var{charset}.
12107 By default, @value{GDBN} uses a host character set appropriate to the
12108 system it is running on; you can override that default using the
12109 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12110 automatically determine the appropriate host character set. In this
12111 case, @value{GDBN} uses @samp{UTF-8}.
12113 @value{GDBN} can only use certain character sets as its host character
12114 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12115 @value{GDBN} will list the host character sets it supports.
12117 @item set charset @var{charset}
12118 @kindex set charset
12119 Set the current host and target character sets to @var{charset}. As
12120 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12121 @value{GDBN} will list the names of the character sets that can be used
12122 for both host and target.
12125 @kindex show charset
12126 Show the names of the current host and target character sets.
12128 @item show host-charset
12129 @kindex show host-charset
12130 Show the name of the current host character set.
12132 @item show target-charset
12133 @kindex show target-charset
12134 Show the name of the current target character set.
12136 @item set target-wide-charset @var{charset}
12137 @kindex set target-wide-charset
12138 Set the current target's wide character set to @var{charset}. This is
12139 the character set used by the target's @code{wchar_t} type. To
12140 display the list of supported wide character sets, type
12141 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12143 @item show target-wide-charset
12144 @kindex show target-wide-charset
12145 Show the name of the current target's wide character set.
12148 Here is an example of @value{GDBN}'s character set support in action.
12149 Assume that the following source code has been placed in the file
12150 @file{charset-test.c}:
12156 = @{72, 101, 108, 108, 111, 44, 32, 119,
12157 111, 114, 108, 100, 33, 10, 0@};
12158 char ibm1047_hello[]
12159 = @{200, 133, 147, 147, 150, 107, 64, 166,
12160 150, 153, 147, 132, 90, 37, 0@};
12164 printf ("Hello, world!\n");
12168 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12169 containing the string @samp{Hello, world!} followed by a newline,
12170 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12172 We compile the program, and invoke the debugger on it:
12175 $ gcc -g charset-test.c -o charset-test
12176 $ gdb -nw charset-test
12177 GNU gdb 2001-12-19-cvs
12178 Copyright 2001 Free Software Foundation, Inc.
12183 We can use the @code{show charset} command to see what character sets
12184 @value{GDBN} is currently using to interpret and display characters and
12188 (@value{GDBP}) show charset
12189 The current host and target character set is `ISO-8859-1'.
12193 For the sake of printing this manual, let's use @sc{ascii} as our
12194 initial character set:
12196 (@value{GDBP}) set charset ASCII
12197 (@value{GDBP}) show charset
12198 The current host and target character set is `ASCII'.
12202 Let's assume that @sc{ascii} is indeed the correct character set for our
12203 host system --- in other words, let's assume that if @value{GDBN} prints
12204 characters using the @sc{ascii} character set, our terminal will display
12205 them properly. Since our current target character set is also
12206 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12209 (@value{GDBP}) print ascii_hello
12210 $1 = 0x401698 "Hello, world!\n"
12211 (@value{GDBP}) print ascii_hello[0]
12216 @value{GDBN} uses the target character set for character and string
12217 literals you use in expressions:
12220 (@value{GDBP}) print '+'
12225 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12228 @value{GDBN} relies on the user to tell it which character set the
12229 target program uses. If we print @code{ibm1047_hello} while our target
12230 character set is still @sc{ascii}, we get jibberish:
12233 (@value{GDBP}) print ibm1047_hello
12234 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12235 (@value{GDBP}) print ibm1047_hello[0]
12240 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12241 @value{GDBN} tells us the character sets it supports:
12244 (@value{GDBP}) set target-charset
12245 ASCII EBCDIC-US IBM1047 ISO-8859-1
12246 (@value{GDBP}) set target-charset
12249 We can select @sc{ibm1047} as our target character set, and examine the
12250 program's strings again. Now the @sc{ascii} string is wrong, but
12251 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12252 target character set, @sc{ibm1047}, to the host character set,
12253 @sc{ascii}, and they display correctly:
12256 (@value{GDBP}) set target-charset IBM1047
12257 (@value{GDBP}) show charset
12258 The current host character set is `ASCII'.
12259 The current target character set is `IBM1047'.
12260 (@value{GDBP}) print ascii_hello
12261 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12262 (@value{GDBP}) print ascii_hello[0]
12264 (@value{GDBP}) print ibm1047_hello
12265 $8 = 0x4016a8 "Hello, world!\n"
12266 (@value{GDBP}) print ibm1047_hello[0]
12271 As above, @value{GDBN} uses the target character set for character and
12272 string literals you use in expressions:
12275 (@value{GDBP}) print '+'
12280 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12283 @node Caching Target Data
12284 @section Caching Data of Targets
12285 @cindex caching data of targets
12287 @value{GDBN} caches data exchanged between the debugger and a target.
12288 Each cache is associated with the address space of the inferior.
12289 @xref{Inferiors and Programs}, about inferior and address space.
12290 Such caching generally improves performance in remote debugging
12291 (@pxref{Remote Debugging}), because it reduces the overhead of the
12292 remote protocol by bundling memory reads and writes into large chunks.
12293 Unfortunately, simply caching everything would lead to incorrect results,
12294 since @value{GDBN} does not necessarily know anything about volatile
12295 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12296 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12298 Therefore, by default, @value{GDBN} only caches data
12299 known to be on the stack@footnote{In non-stop mode, it is moderately
12300 rare for a running thread to modify the stack of a stopped thread
12301 in a way that would interfere with a backtrace, and caching of
12302 stack reads provides a significant speed up of remote backtraces.} or
12303 in the code segment.
12304 Other regions of memory can be explicitly marked as
12305 cacheable; @pxref{Memory Region Attributes}.
12308 @kindex set remotecache
12309 @item set remotecache on
12310 @itemx set remotecache off
12311 This option no longer does anything; it exists for compatibility
12314 @kindex show remotecache
12315 @item show remotecache
12316 Show the current state of the obsolete remotecache flag.
12318 @kindex set stack-cache
12319 @item set stack-cache on
12320 @itemx set stack-cache off
12321 Enable or disable caching of stack accesses. When @code{on}, use
12322 caching. By default, this option is @code{on}.
12324 @kindex show stack-cache
12325 @item show stack-cache
12326 Show the current state of data caching for memory accesses.
12328 @kindex set code-cache
12329 @item set code-cache on
12330 @itemx set code-cache off
12331 Enable or disable caching of code segment accesses. When @code{on},
12332 use caching. By default, this option is @code{on}. This improves
12333 performance of disassembly in remote debugging.
12335 @kindex show code-cache
12336 @item show code-cache
12337 Show the current state of target memory cache for code segment
12340 @kindex info dcache
12341 @item info dcache @r{[}line@r{]}
12342 Print the information about the performance of data cache of the
12343 current inferior's address space. The information displayed
12344 includes the dcache width and depth, and for each cache line, its
12345 number, address, and how many times it was referenced. This
12346 command is useful for debugging the data cache operation.
12348 If a line number is specified, the contents of that line will be
12351 @item set dcache size @var{size}
12352 @cindex dcache size
12353 @kindex set dcache size
12354 Set maximum number of entries in dcache (dcache depth above).
12356 @item set dcache line-size @var{line-size}
12357 @cindex dcache line-size
12358 @kindex set dcache line-size
12359 Set number of bytes each dcache entry caches (dcache width above).
12360 Must be a power of 2.
12362 @item show dcache size
12363 @kindex show dcache size
12364 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12366 @item show dcache line-size
12367 @kindex show dcache line-size
12368 Show default size of dcache lines.
12372 @node Searching Memory
12373 @section Search Memory
12374 @cindex searching memory
12376 Memory can be searched for a particular sequence of bytes with the
12377 @code{find} command.
12381 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12382 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12383 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12384 etc. The search begins at address @var{start_addr} and continues for either
12385 @var{len} bytes or through to @var{end_addr} inclusive.
12388 @var{s} and @var{n} are optional parameters.
12389 They may be specified in either order, apart or together.
12392 @item @var{s}, search query size
12393 The size of each search query value.
12399 halfwords (two bytes)
12403 giant words (eight bytes)
12406 All values are interpreted in the current language.
12407 This means, for example, that if the current source language is C/C@t{++}
12408 then searching for the string ``hello'' includes the trailing '\0'.
12409 The null terminator can be removed from searching by using casts,
12410 e.g.: @samp{@{char[5]@}"hello"}.
12412 If the value size is not specified, it is taken from the
12413 value's type in the current language.
12414 This is useful when one wants to specify the search
12415 pattern as a mixture of types.
12416 Note that this means, for example, that in the case of C-like languages
12417 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12418 which is typically four bytes.
12420 @item @var{n}, maximum number of finds
12421 The maximum number of matches to print. The default is to print all finds.
12424 You can use strings as search values. Quote them with double-quotes
12426 The string value is copied into the search pattern byte by byte,
12427 regardless of the endianness of the target and the size specification.
12429 The address of each match found is printed as well as a count of the
12430 number of matches found.
12432 The address of the last value found is stored in convenience variable
12434 A count of the number of matches is stored in @samp{$numfound}.
12436 For example, if stopped at the @code{printf} in this function:
12442 static char hello[] = "hello-hello";
12443 static struct @{ char c; short s; int i; @}
12444 __attribute__ ((packed)) mixed
12445 = @{ 'c', 0x1234, 0x87654321 @};
12446 printf ("%s\n", hello);
12451 you get during debugging:
12454 (gdb) find &hello[0], +sizeof(hello), "hello"
12455 0x804956d <hello.1620+6>
12457 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12458 0x8049567 <hello.1620>
12459 0x804956d <hello.1620+6>
12461 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12462 0x8049567 <hello.1620>
12463 0x804956d <hello.1620+6>
12465 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12466 0x8049567 <hello.1620>
12468 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12469 0x8049560 <mixed.1625>
12471 (gdb) print $numfound
12474 $2 = (void *) 0x8049560
12478 @section Value Sizes
12480 Whenever @value{GDBN} prints a value memory will be allocated within
12481 @value{GDBN} to hold the contents of the value. It is possible in
12482 some languages with dynamic typing systems, that an invalid program
12483 may indicate a value that is incorrectly large, this in turn may cause
12484 @value{GDBN} to try and allocate an overly large ammount of memory.
12487 @kindex set max-value-size
12488 @item set max-value-size @var{bytes}
12489 @itemx set max-value-size unlimited
12490 Set the maximum size of memory that @value{GDBN} will allocate for the
12491 contents of a value to @var{bytes}, trying to display a value that
12492 requires more memory than that will result in an error.
12494 Setting this variable does not effect values that have already been
12495 allocated within @value{GDBN}, only future allocations.
12497 There's a minimum size that @code{max-value-size} can be set to in
12498 order that @value{GDBN} can still operate correctly, this minimum is
12499 currently 16 bytes.
12501 The limit applies to the results of some subexpressions as well as to
12502 complete expressions. For example, an expression denoting a simple
12503 integer component, such as @code{x.y.z}, may fail if the size of
12504 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12505 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12506 @var{A} is an array variable with non-constant size, will generally
12507 succeed regardless of the bounds on @var{A}, as long as the component
12508 size is less than @var{bytes}.
12510 The default value of @code{max-value-size} is currently 64k.
12512 @kindex show max-value-size
12513 @item show max-value-size
12514 Show the maximum size of memory, in bytes, that @value{GDBN} will
12515 allocate for the contents of a value.
12518 @node Optimized Code
12519 @chapter Debugging Optimized Code
12520 @cindex optimized code, debugging
12521 @cindex debugging optimized code
12523 Almost all compilers support optimization. With optimization
12524 disabled, the compiler generates assembly code that corresponds
12525 directly to your source code, in a simplistic way. As the compiler
12526 applies more powerful optimizations, the generated assembly code
12527 diverges from your original source code. With help from debugging
12528 information generated by the compiler, @value{GDBN} can map from
12529 the running program back to constructs from your original source.
12531 @value{GDBN} is more accurate with optimization disabled. If you
12532 can recompile without optimization, it is easier to follow the
12533 progress of your program during debugging. But, there are many cases
12534 where you may need to debug an optimized version.
12536 When you debug a program compiled with @samp{-g -O}, remember that the
12537 optimizer has rearranged your code; the debugger shows you what is
12538 really there. Do not be too surprised when the execution path does not
12539 exactly match your source file! An extreme example: if you define a
12540 variable, but never use it, @value{GDBN} never sees that
12541 variable---because the compiler optimizes it out of existence.
12543 Some things do not work as well with @samp{-g -O} as with just
12544 @samp{-g}, particularly on machines with instruction scheduling. If in
12545 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12546 please report it to us as a bug (including a test case!).
12547 @xref{Variables}, for more information about debugging optimized code.
12550 * Inline Functions:: How @value{GDBN} presents inlining
12551 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12554 @node Inline Functions
12555 @section Inline Functions
12556 @cindex inline functions, debugging
12558 @dfn{Inlining} is an optimization that inserts a copy of the function
12559 body directly at each call site, instead of jumping to a shared
12560 routine. @value{GDBN} displays inlined functions just like
12561 non-inlined functions. They appear in backtraces. You can view their
12562 arguments and local variables, step into them with @code{step}, skip
12563 them with @code{next}, and escape from them with @code{finish}.
12564 You can check whether a function was inlined by using the
12565 @code{info frame} command.
12567 For @value{GDBN} to support inlined functions, the compiler must
12568 record information about inlining in the debug information ---
12569 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12570 other compilers do also. @value{GDBN} only supports inlined functions
12571 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12572 do not emit two required attributes (@samp{DW_AT_call_file} and
12573 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12574 function calls with earlier versions of @value{NGCC}. It instead
12575 displays the arguments and local variables of inlined functions as
12576 local variables in the caller.
12578 The body of an inlined function is directly included at its call site;
12579 unlike a non-inlined function, there are no instructions devoted to
12580 the call. @value{GDBN} still pretends that the call site and the
12581 start of the inlined function are different instructions. Stepping to
12582 the call site shows the call site, and then stepping again shows
12583 the first line of the inlined function, even though no additional
12584 instructions are executed.
12586 This makes source-level debugging much clearer; you can see both the
12587 context of the call and then the effect of the call. Only stepping by
12588 a single instruction using @code{stepi} or @code{nexti} does not do
12589 this; single instruction steps always show the inlined body.
12591 There are some ways that @value{GDBN} does not pretend that inlined
12592 function calls are the same as normal calls:
12596 Setting breakpoints at the call site of an inlined function may not
12597 work, because the call site does not contain any code. @value{GDBN}
12598 may incorrectly move the breakpoint to the next line of the enclosing
12599 function, after the call. This limitation will be removed in a future
12600 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12601 or inside the inlined function instead.
12604 @value{GDBN} cannot locate the return value of inlined calls after
12605 using the @code{finish} command. This is a limitation of compiler-generated
12606 debugging information; after @code{finish}, you can step to the next line
12607 and print a variable where your program stored the return value.
12611 @node Tail Call Frames
12612 @section Tail Call Frames
12613 @cindex tail call frames, debugging
12615 Function @code{B} can call function @code{C} in its very last statement. In
12616 unoptimized compilation the call of @code{C} is immediately followed by return
12617 instruction at the end of @code{B} code. Optimizing compiler may replace the
12618 call and return in function @code{B} into one jump to function @code{C}
12619 instead. Such use of a jump instruction is called @dfn{tail call}.
12621 During execution of function @code{C}, there will be no indication in the
12622 function call stack frames that it was tail-called from @code{B}. If function
12623 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12624 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12625 some cases @value{GDBN} can determine that @code{C} was tail-called from
12626 @code{B}, and it will then create fictitious call frame for that, with the
12627 return address set up as if @code{B} called @code{C} normally.
12629 This functionality is currently supported only by DWARF 2 debugging format and
12630 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12631 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12634 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12635 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12639 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12641 Stack level 1, frame at 0x7fffffffda30:
12642 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12643 tail call frame, caller of frame at 0x7fffffffda30
12644 source language c++.
12645 Arglist at unknown address.
12646 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12649 The detection of all the possible code path executions can find them ambiguous.
12650 There is no execution history stored (possible @ref{Reverse Execution} is never
12651 used for this purpose) and the last known caller could have reached the known
12652 callee by multiple different jump sequences. In such case @value{GDBN} still
12653 tries to show at least all the unambiguous top tail callers and all the
12654 unambiguous bottom tail calees, if any.
12657 @anchor{set debug entry-values}
12658 @item set debug entry-values
12659 @kindex set debug entry-values
12660 When set to on, enables printing of analysis messages for both frame argument
12661 values at function entry and tail calls. It will show all the possible valid
12662 tail calls code paths it has considered. It will also print the intersection
12663 of them with the final unambiguous (possibly partial or even empty) code path
12666 @item show debug entry-values
12667 @kindex show debug entry-values
12668 Show the current state of analysis messages printing for both frame argument
12669 values at function entry and tail calls.
12672 The analysis messages for tail calls can for example show why the virtual tail
12673 call frame for function @code{c} has not been recognized (due to the indirect
12674 reference by variable @code{x}):
12677 static void __attribute__((noinline, noclone)) c (void);
12678 void (*x) (void) = c;
12679 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12680 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12681 int main (void) @{ x (); return 0; @}
12683 Breakpoint 1, DW_OP_entry_value resolving cannot find
12684 DW_TAG_call_site 0x40039a in main
12686 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12689 #1 0x000000000040039a in main () at t.c:5
12692 Another possibility is an ambiguous virtual tail call frames resolution:
12696 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12697 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12698 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12699 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12700 static void __attribute__((noinline, noclone)) b (void)
12701 @{ if (i) c (); else e (); @}
12702 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12703 int main (void) @{ a (); return 0; @}
12705 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12706 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12707 tailcall: reduced: 0x4004d2(a) |
12710 #1 0x00000000004004d2 in a () at t.c:8
12711 #2 0x0000000000400395 in main () at t.c:9
12714 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12715 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12717 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12718 @ifset HAVE_MAKEINFO_CLICK
12719 @set ARROW @click{}
12720 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12721 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12723 @ifclear HAVE_MAKEINFO_CLICK
12725 @set CALLSEQ1B @value{CALLSEQ1A}
12726 @set CALLSEQ2B @value{CALLSEQ2A}
12729 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12730 The code can have possible execution paths @value{CALLSEQ1B} or
12731 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12733 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12734 has found. It then finds another possible calling sequcen - that one is
12735 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12736 printed as the @code{reduced:} calling sequence. That one could have many
12737 futher @code{compare:} and @code{reduced:} statements as long as there remain
12738 any non-ambiguous sequence entries.
12740 For the frame of function @code{b} in both cases there are different possible
12741 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12742 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12743 therefore this one is displayed to the user while the ambiguous frames are
12746 There can be also reasons why printing of frame argument values at function
12751 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12752 static void __attribute__((noinline, noclone)) a (int i);
12753 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12754 static void __attribute__((noinline, noclone)) a (int i)
12755 @{ if (i) b (i - 1); else c (0); @}
12756 int main (void) @{ a (5); return 0; @}
12759 #0 c (i=i@@entry=0) at t.c:2
12760 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12761 function "a" at 0x400420 can call itself via tail calls
12762 i=<optimized out>) at t.c:6
12763 #2 0x000000000040036e in main () at t.c:7
12766 @value{GDBN} cannot find out from the inferior state if and how many times did
12767 function @code{a} call itself (via function @code{b}) as these calls would be
12768 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12769 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12770 prints @code{<optimized out>} instead.
12773 @chapter C Preprocessor Macros
12775 Some languages, such as C and C@t{++}, provide a way to define and invoke
12776 ``preprocessor macros'' which expand into strings of tokens.
12777 @value{GDBN} can evaluate expressions containing macro invocations, show
12778 the result of macro expansion, and show a macro's definition, including
12779 where it was defined.
12781 You may need to compile your program specially to provide @value{GDBN}
12782 with information about preprocessor macros. Most compilers do not
12783 include macros in their debugging information, even when you compile
12784 with the @option{-g} flag. @xref{Compilation}.
12786 A program may define a macro at one point, remove that definition later,
12787 and then provide a different definition after that. Thus, at different
12788 points in the program, a macro may have different definitions, or have
12789 no definition at all. If there is a current stack frame, @value{GDBN}
12790 uses the macros in scope at that frame's source code line. Otherwise,
12791 @value{GDBN} uses the macros in scope at the current listing location;
12794 Whenever @value{GDBN} evaluates an expression, it always expands any
12795 macro invocations present in the expression. @value{GDBN} also provides
12796 the following commands for working with macros explicitly.
12800 @kindex macro expand
12801 @cindex macro expansion, showing the results of preprocessor
12802 @cindex preprocessor macro expansion, showing the results of
12803 @cindex expanding preprocessor macros
12804 @item macro expand @var{expression}
12805 @itemx macro exp @var{expression}
12806 Show the results of expanding all preprocessor macro invocations in
12807 @var{expression}. Since @value{GDBN} simply expands macros, but does
12808 not parse the result, @var{expression} need not be a valid expression;
12809 it can be any string of tokens.
12812 @item macro expand-once @var{expression}
12813 @itemx macro exp1 @var{expression}
12814 @cindex expand macro once
12815 @i{(This command is not yet implemented.)} Show the results of
12816 expanding those preprocessor macro invocations that appear explicitly in
12817 @var{expression}. Macro invocations appearing in that expansion are
12818 left unchanged. This command allows you to see the effect of a
12819 particular macro more clearly, without being confused by further
12820 expansions. Since @value{GDBN} simply expands macros, but does not
12821 parse the result, @var{expression} need not be a valid expression; it
12822 can be any string of tokens.
12825 @cindex macro definition, showing
12826 @cindex definition of a macro, showing
12827 @cindex macros, from debug info
12828 @item info macro [-a|-all] [--] @var{macro}
12829 Show the current definition or all definitions of the named @var{macro},
12830 and describe the source location or compiler command-line where that
12831 definition was established. The optional double dash is to signify the end of
12832 argument processing and the beginning of @var{macro} for non C-like macros where
12833 the macro may begin with a hyphen.
12835 @kindex info macros
12836 @item info macros @var{location}
12837 Show all macro definitions that are in effect at the location specified
12838 by @var{location}, and describe the source location or compiler
12839 command-line where those definitions were established.
12841 @kindex macro define
12842 @cindex user-defined macros
12843 @cindex defining macros interactively
12844 @cindex macros, user-defined
12845 @item macro define @var{macro} @var{replacement-list}
12846 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12847 Introduce a definition for a preprocessor macro named @var{macro},
12848 invocations of which are replaced by the tokens given in
12849 @var{replacement-list}. The first form of this command defines an
12850 ``object-like'' macro, which takes no arguments; the second form
12851 defines a ``function-like'' macro, which takes the arguments given in
12854 A definition introduced by this command is in scope in every
12855 expression evaluated in @value{GDBN}, until it is removed with the
12856 @code{macro undef} command, described below. The definition overrides
12857 all definitions for @var{macro} present in the program being debugged,
12858 as well as any previous user-supplied definition.
12860 @kindex macro undef
12861 @item macro undef @var{macro}
12862 Remove any user-supplied definition for the macro named @var{macro}.
12863 This command only affects definitions provided with the @code{macro
12864 define} command, described above; it cannot remove definitions present
12865 in the program being debugged.
12869 List all the macros defined using the @code{macro define} command.
12872 @cindex macros, example of debugging with
12873 Here is a transcript showing the above commands in action. First, we
12874 show our source files:
12879 #include "sample.h"
12882 #define ADD(x) (M + x)
12887 printf ("Hello, world!\n");
12889 printf ("We're so creative.\n");
12891 printf ("Goodbye, world!\n");
12898 Now, we compile the program using the @sc{gnu} C compiler,
12899 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12900 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12901 and @option{-gdwarf-4}; we recommend always choosing the most recent
12902 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12903 includes information about preprocessor macros in the debugging
12907 $ gcc -gdwarf-2 -g3 sample.c -o sample
12911 Now, we start @value{GDBN} on our sample program:
12915 GNU gdb 2002-05-06-cvs
12916 Copyright 2002 Free Software Foundation, Inc.
12917 GDB is free software, @dots{}
12921 We can expand macros and examine their definitions, even when the
12922 program is not running. @value{GDBN} uses the current listing position
12923 to decide which macro definitions are in scope:
12926 (@value{GDBP}) list main
12929 5 #define ADD(x) (M + x)
12934 10 printf ("Hello, world!\n");
12936 12 printf ("We're so creative.\n");
12937 (@value{GDBP}) info macro ADD
12938 Defined at /home/jimb/gdb/macros/play/sample.c:5
12939 #define ADD(x) (M + x)
12940 (@value{GDBP}) info macro Q
12941 Defined at /home/jimb/gdb/macros/play/sample.h:1
12942 included at /home/jimb/gdb/macros/play/sample.c:2
12944 (@value{GDBP}) macro expand ADD(1)
12945 expands to: (42 + 1)
12946 (@value{GDBP}) macro expand-once ADD(1)
12947 expands to: once (M + 1)
12951 In the example above, note that @code{macro expand-once} expands only
12952 the macro invocation explicit in the original text --- the invocation of
12953 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12954 which was introduced by @code{ADD}.
12956 Once the program is running, @value{GDBN} uses the macro definitions in
12957 force at the source line of the current stack frame:
12960 (@value{GDBP}) break main
12961 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12963 Starting program: /home/jimb/gdb/macros/play/sample
12965 Breakpoint 1, main () at sample.c:10
12966 10 printf ("Hello, world!\n");
12970 At line 10, the definition of the macro @code{N} at line 9 is in force:
12973 (@value{GDBP}) info macro N
12974 Defined at /home/jimb/gdb/macros/play/sample.c:9
12976 (@value{GDBP}) macro expand N Q M
12977 expands to: 28 < 42
12978 (@value{GDBP}) print N Q M
12983 As we step over directives that remove @code{N}'s definition, and then
12984 give it a new definition, @value{GDBN} finds the definition (or lack
12985 thereof) in force at each point:
12988 (@value{GDBP}) next
12990 12 printf ("We're so creative.\n");
12991 (@value{GDBP}) info macro N
12992 The symbol `N' has no definition as a C/C++ preprocessor macro
12993 at /home/jimb/gdb/macros/play/sample.c:12
12994 (@value{GDBP}) next
12996 14 printf ("Goodbye, world!\n");
12997 (@value{GDBP}) info macro N
12998 Defined at /home/jimb/gdb/macros/play/sample.c:13
13000 (@value{GDBP}) macro expand N Q M
13001 expands to: 1729 < 42
13002 (@value{GDBP}) print N Q M
13007 In addition to source files, macros can be defined on the compilation command
13008 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13009 such a way, @value{GDBN} displays the location of their definition as line zero
13010 of the source file submitted to the compiler.
13013 (@value{GDBP}) info macro __STDC__
13014 Defined at /home/jimb/gdb/macros/play/sample.c:0
13021 @chapter Tracepoints
13022 @c This chapter is based on the documentation written by Michael
13023 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13025 @cindex tracepoints
13026 In some applications, it is not feasible for the debugger to interrupt
13027 the program's execution long enough for the developer to learn
13028 anything helpful about its behavior. If the program's correctness
13029 depends on its real-time behavior, delays introduced by a debugger
13030 might cause the program to change its behavior drastically, or perhaps
13031 fail, even when the code itself is correct. It is useful to be able
13032 to observe the program's behavior without interrupting it.
13034 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13035 specify locations in the program, called @dfn{tracepoints}, and
13036 arbitrary expressions to evaluate when those tracepoints are reached.
13037 Later, using the @code{tfind} command, you can examine the values
13038 those expressions had when the program hit the tracepoints. The
13039 expressions may also denote objects in memory---structures or arrays,
13040 for example---whose values @value{GDBN} should record; while visiting
13041 a particular tracepoint, you may inspect those objects as if they were
13042 in memory at that moment. However, because @value{GDBN} records these
13043 values without interacting with you, it can do so quickly and
13044 unobtrusively, hopefully not disturbing the program's behavior.
13046 The tracepoint facility is currently available only for remote
13047 targets. @xref{Targets}. In addition, your remote target must know
13048 how to collect trace data. This functionality is implemented in the
13049 remote stub; however, none of the stubs distributed with @value{GDBN}
13050 support tracepoints as of this writing. The format of the remote
13051 packets used to implement tracepoints are described in @ref{Tracepoint
13054 It is also possible to get trace data from a file, in a manner reminiscent
13055 of corefiles; you specify the filename, and use @code{tfind} to search
13056 through the file. @xref{Trace Files}, for more details.
13058 This chapter describes the tracepoint commands and features.
13061 * Set Tracepoints::
13062 * Analyze Collected Data::
13063 * Tracepoint Variables::
13067 @node Set Tracepoints
13068 @section Commands to Set Tracepoints
13070 Before running such a @dfn{trace experiment}, an arbitrary number of
13071 tracepoints can be set. A tracepoint is actually a special type of
13072 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13073 standard breakpoint commands. For instance, as with breakpoints,
13074 tracepoint numbers are successive integers starting from one, and many
13075 of the commands associated with tracepoints take the tracepoint number
13076 as their argument, to identify which tracepoint to work on.
13078 For each tracepoint, you can specify, in advance, some arbitrary set
13079 of data that you want the target to collect in the trace buffer when
13080 it hits that tracepoint. The collected data can include registers,
13081 local variables, or global data. Later, you can use @value{GDBN}
13082 commands to examine the values these data had at the time the
13083 tracepoint was hit.
13085 Tracepoints do not support every breakpoint feature. Ignore counts on
13086 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13087 commands when they are hit. Tracepoints may not be thread-specific
13090 @cindex fast tracepoints
13091 Some targets may support @dfn{fast tracepoints}, which are inserted in
13092 a different way (such as with a jump instead of a trap), that is
13093 faster but possibly restricted in where they may be installed.
13095 @cindex static tracepoints
13096 @cindex markers, static tracepoints
13097 @cindex probing markers, static tracepoints
13098 Regular and fast tracepoints are dynamic tracing facilities, meaning
13099 that they can be used to insert tracepoints at (almost) any location
13100 in the target. Some targets may also support controlling @dfn{static
13101 tracepoints} from @value{GDBN}. With static tracing, a set of
13102 instrumentation points, also known as @dfn{markers}, are embedded in
13103 the target program, and can be activated or deactivated by name or
13104 address. These are usually placed at locations which facilitate
13105 investigating what the target is actually doing. @value{GDBN}'s
13106 support for static tracing includes being able to list instrumentation
13107 points, and attach them with @value{GDBN} defined high level
13108 tracepoints that expose the whole range of convenience of
13109 @value{GDBN}'s tracepoints support. Namely, support for collecting
13110 registers values and values of global or local (to the instrumentation
13111 point) variables; tracepoint conditions and trace state variables.
13112 The act of installing a @value{GDBN} static tracepoint on an
13113 instrumentation point, or marker, is referred to as @dfn{probing} a
13114 static tracepoint marker.
13116 @code{gdbserver} supports tracepoints on some target systems.
13117 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13119 This section describes commands to set tracepoints and associated
13120 conditions and actions.
13123 * Create and Delete Tracepoints::
13124 * Enable and Disable Tracepoints::
13125 * Tracepoint Passcounts::
13126 * Tracepoint Conditions::
13127 * Trace State Variables::
13128 * Tracepoint Actions::
13129 * Listing Tracepoints::
13130 * Listing Static Tracepoint Markers::
13131 * Starting and Stopping Trace Experiments::
13132 * Tracepoint Restrictions::
13135 @node Create and Delete Tracepoints
13136 @subsection Create and Delete Tracepoints
13139 @cindex set tracepoint
13141 @item trace @var{location}
13142 The @code{trace} command is very similar to the @code{break} command.
13143 Its argument @var{location} can be any valid location.
13144 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13145 which is a point in the target program where the debugger will briefly stop,
13146 collect some data, and then allow the program to continue. Setting a tracepoint
13147 or changing its actions takes effect immediately if the remote stub
13148 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13150 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13151 these changes don't take effect until the next @code{tstart}
13152 command, and once a trace experiment is running, further changes will
13153 not have any effect until the next trace experiment starts. In addition,
13154 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13155 address is not yet resolved. (This is similar to pending breakpoints.)
13156 Pending tracepoints are not downloaded to the target and not installed
13157 until they are resolved. The resolution of pending tracepoints requires
13158 @value{GDBN} support---when debugging with the remote target, and
13159 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13160 tracing}), pending tracepoints can not be resolved (and downloaded to
13161 the remote stub) while @value{GDBN} is disconnected.
13163 Here are some examples of using the @code{trace} command:
13166 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13168 (@value{GDBP}) @b{trace +2} // 2 lines forward
13170 (@value{GDBP}) @b{trace my_function} // first source line of function
13172 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13174 (@value{GDBP}) @b{trace *0x2117c4} // an address
13178 You can abbreviate @code{trace} as @code{tr}.
13180 @item trace @var{location} if @var{cond}
13181 Set a tracepoint with condition @var{cond}; evaluate the expression
13182 @var{cond} each time the tracepoint is reached, and collect data only
13183 if the value is nonzero---that is, if @var{cond} evaluates as true.
13184 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13185 information on tracepoint conditions.
13187 @item ftrace @var{location} [ if @var{cond} ]
13188 @cindex set fast tracepoint
13189 @cindex fast tracepoints, setting
13191 The @code{ftrace} command sets a fast tracepoint. For targets that
13192 support them, fast tracepoints will use a more efficient but possibly
13193 less general technique to trigger data collection, such as a jump
13194 instruction instead of a trap, or some sort of hardware support. It
13195 may not be possible to create a fast tracepoint at the desired
13196 location, in which case the command will exit with an explanatory
13199 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13202 On 32-bit x86-architecture systems, fast tracepoints normally need to
13203 be placed at an instruction that is 5 bytes or longer, but can be
13204 placed at 4-byte instructions if the low 64K of memory of the target
13205 program is available to install trampolines. Some Unix-type systems,
13206 such as @sc{gnu}/Linux, exclude low addresses from the program's
13207 address space; but for instance with the Linux kernel it is possible
13208 to let @value{GDBN} use this area by doing a @command{sysctl} command
13209 to set the @code{mmap_min_addr} kernel parameter, as in
13212 sudo sysctl -w vm.mmap_min_addr=32768
13216 which sets the low address to 32K, which leaves plenty of room for
13217 trampolines. The minimum address should be set to a page boundary.
13219 @item strace @var{location} [ if @var{cond} ]
13220 @cindex set static tracepoint
13221 @cindex static tracepoints, setting
13222 @cindex probe static tracepoint marker
13224 The @code{strace} command sets a static tracepoint. For targets that
13225 support it, setting a static tracepoint probes a static
13226 instrumentation point, or marker, found at @var{location}. It may not
13227 be possible to set a static tracepoint at the desired location, in
13228 which case the command will exit with an explanatory message.
13230 @value{GDBN} handles arguments to @code{strace} exactly as for
13231 @code{trace}, with the addition that the user can also specify
13232 @code{-m @var{marker}} as @var{location}. This probes the marker
13233 identified by the @var{marker} string identifier. This identifier
13234 depends on the static tracepoint backend library your program is
13235 using. You can find all the marker identifiers in the @samp{ID} field
13236 of the @code{info static-tracepoint-markers} command output.
13237 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13238 Markers}. For example, in the following small program using the UST
13244 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13249 the marker id is composed of joining the first two arguments to the
13250 @code{trace_mark} call with a slash, which translates to:
13253 (@value{GDBP}) info static-tracepoint-markers
13254 Cnt Enb ID Address What
13255 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13261 so you may probe the marker above with:
13264 (@value{GDBP}) strace -m ust/bar33
13267 Static tracepoints accept an extra collect action --- @code{collect
13268 $_sdata}. This collects arbitrary user data passed in the probe point
13269 call to the tracing library. In the UST example above, you'll see
13270 that the third argument to @code{trace_mark} is a printf-like format
13271 string. The user data is then the result of running that formating
13272 string against the following arguments. Note that @code{info
13273 static-tracepoint-markers} command output lists that format string in
13274 the @samp{Data:} field.
13276 You can inspect this data when analyzing the trace buffer, by printing
13277 the $_sdata variable like any other variable available to
13278 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13281 @cindex last tracepoint number
13282 @cindex recent tracepoint number
13283 @cindex tracepoint number
13284 The convenience variable @code{$tpnum} records the tracepoint number
13285 of the most recently set tracepoint.
13287 @kindex delete tracepoint
13288 @cindex tracepoint deletion
13289 @item delete tracepoint @r{[}@var{num}@r{]}
13290 Permanently delete one or more tracepoints. With no argument, the
13291 default is to delete all tracepoints. Note that the regular
13292 @code{delete} command can remove tracepoints also.
13297 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13299 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13303 You can abbreviate this command as @code{del tr}.
13306 @node Enable and Disable Tracepoints
13307 @subsection Enable and Disable Tracepoints
13309 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13312 @kindex disable tracepoint
13313 @item disable tracepoint @r{[}@var{num}@r{]}
13314 Disable tracepoint @var{num}, or all tracepoints if no argument
13315 @var{num} is given. A disabled tracepoint will have no effect during
13316 a trace experiment, but it is not forgotten. You can re-enable
13317 a disabled tracepoint using the @code{enable tracepoint} command.
13318 If the command is issued during a trace experiment and the debug target
13319 has support for disabling tracepoints during a trace experiment, then the
13320 change will be effective immediately. Otherwise, it will be applied to the
13321 next trace experiment.
13323 @kindex enable tracepoint
13324 @item enable tracepoint @r{[}@var{num}@r{]}
13325 Enable tracepoint @var{num}, or all tracepoints. If this command is
13326 issued during a trace experiment and the debug target supports enabling
13327 tracepoints during a trace experiment, then the enabled tracepoints will
13328 become effective immediately. Otherwise, they will become effective the
13329 next time a trace experiment is run.
13332 @node Tracepoint Passcounts
13333 @subsection Tracepoint Passcounts
13337 @cindex tracepoint pass count
13338 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13339 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13340 automatically stop a trace experiment. If a tracepoint's passcount is
13341 @var{n}, then the trace experiment will be automatically stopped on
13342 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13343 @var{num} is not specified, the @code{passcount} command sets the
13344 passcount of the most recently defined tracepoint. If no passcount is
13345 given, the trace experiment will run until stopped explicitly by the
13351 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13352 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13354 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13355 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13356 (@value{GDBP}) @b{trace foo}
13357 (@value{GDBP}) @b{pass 3}
13358 (@value{GDBP}) @b{trace bar}
13359 (@value{GDBP}) @b{pass 2}
13360 (@value{GDBP}) @b{trace baz}
13361 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13362 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13363 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13364 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13368 @node Tracepoint Conditions
13369 @subsection Tracepoint Conditions
13370 @cindex conditional tracepoints
13371 @cindex tracepoint conditions
13373 The simplest sort of tracepoint collects data every time your program
13374 reaches a specified place. You can also specify a @dfn{condition} for
13375 a tracepoint. A condition is just a Boolean expression in your
13376 programming language (@pxref{Expressions, ,Expressions}). A
13377 tracepoint with a condition evaluates the expression each time your
13378 program reaches it, and data collection happens only if the condition
13381 Tracepoint conditions can be specified when a tracepoint is set, by
13382 using @samp{if} in the arguments to the @code{trace} command.
13383 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13384 also be set or changed at any time with the @code{condition} command,
13385 just as with breakpoints.
13387 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13388 the conditional expression itself. Instead, @value{GDBN} encodes the
13389 expression into an agent expression (@pxref{Agent Expressions})
13390 suitable for execution on the target, independently of @value{GDBN}.
13391 Global variables become raw memory locations, locals become stack
13392 accesses, and so forth.
13394 For instance, suppose you have a function that is usually called
13395 frequently, but should not be called after an error has occurred. You
13396 could use the following tracepoint command to collect data about calls
13397 of that function that happen while the error code is propagating
13398 through the program; an unconditional tracepoint could end up
13399 collecting thousands of useless trace frames that you would have to
13403 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13406 @node Trace State Variables
13407 @subsection Trace State Variables
13408 @cindex trace state variables
13410 A @dfn{trace state variable} is a special type of variable that is
13411 created and managed by target-side code. The syntax is the same as
13412 that for GDB's convenience variables (a string prefixed with ``$''),
13413 but they are stored on the target. They must be created explicitly,
13414 using a @code{tvariable} command. They are always 64-bit signed
13417 Trace state variables are remembered by @value{GDBN}, and downloaded
13418 to the target along with tracepoint information when the trace
13419 experiment starts. There are no intrinsic limits on the number of
13420 trace state variables, beyond memory limitations of the target.
13422 @cindex convenience variables, and trace state variables
13423 Although trace state variables are managed by the target, you can use
13424 them in print commands and expressions as if they were convenience
13425 variables; @value{GDBN} will get the current value from the target
13426 while the trace experiment is running. Trace state variables share
13427 the same namespace as other ``$'' variables, which means that you
13428 cannot have trace state variables with names like @code{$23} or
13429 @code{$pc}, nor can you have a trace state variable and a convenience
13430 variable with the same name.
13434 @item tvariable $@var{name} [ = @var{expression} ]
13436 The @code{tvariable} command creates a new trace state variable named
13437 @code{$@var{name}}, and optionally gives it an initial value of
13438 @var{expression}. The @var{expression} is evaluated when this command is
13439 entered; the result will be converted to an integer if possible,
13440 otherwise @value{GDBN} will report an error. A subsequent
13441 @code{tvariable} command specifying the same name does not create a
13442 variable, but instead assigns the supplied initial value to the
13443 existing variable of that name, overwriting any previous initial
13444 value. The default initial value is 0.
13446 @item info tvariables
13447 @kindex info tvariables
13448 List all the trace state variables along with their initial values.
13449 Their current values may also be displayed, if the trace experiment is
13452 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13453 @kindex delete tvariable
13454 Delete the given trace state variables, or all of them if no arguments
13459 @node Tracepoint Actions
13460 @subsection Tracepoint Action Lists
13464 @cindex tracepoint actions
13465 @item actions @r{[}@var{num}@r{]}
13466 This command will prompt for a list of actions to be taken when the
13467 tracepoint is hit. If the tracepoint number @var{num} is not
13468 specified, this command sets the actions for the one that was most
13469 recently defined (so that you can define a tracepoint and then say
13470 @code{actions} without bothering about its number). You specify the
13471 actions themselves on the following lines, one action at a time, and
13472 terminate the actions list with a line containing just @code{end}. So
13473 far, the only defined actions are @code{collect}, @code{teval}, and
13474 @code{while-stepping}.
13476 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13477 Commands, ,Breakpoint Command Lists}), except that only the defined
13478 actions are allowed; any other @value{GDBN} command is rejected.
13480 @cindex remove actions from a tracepoint
13481 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13482 and follow it immediately with @samp{end}.
13485 (@value{GDBP}) @b{collect @var{data}} // collect some data
13487 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13489 (@value{GDBP}) @b{end} // signals the end of actions.
13492 In the following example, the action list begins with @code{collect}
13493 commands indicating the things to be collected when the tracepoint is
13494 hit. Then, in order to single-step and collect additional data
13495 following the tracepoint, a @code{while-stepping} command is used,
13496 followed by the list of things to be collected after each step in a
13497 sequence of single steps. The @code{while-stepping} command is
13498 terminated by its own separate @code{end} command. Lastly, the action
13499 list is terminated by an @code{end} command.
13502 (@value{GDBP}) @b{trace foo}
13503 (@value{GDBP}) @b{actions}
13504 Enter actions for tracepoint 1, one per line:
13507 > while-stepping 12
13508 > collect $pc, arr[i]
13513 @kindex collect @r{(tracepoints)}
13514 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13515 Collect values of the given expressions when the tracepoint is hit.
13516 This command accepts a comma-separated list of any valid expressions.
13517 In addition to global, static, or local variables, the following
13518 special arguments are supported:
13522 Collect all registers.
13525 Collect all function arguments.
13528 Collect all local variables.
13531 Collect the return address. This is helpful if you want to see more
13534 @emph{Note:} The return address location can not always be reliably
13535 determined up front, and the wrong address / registers may end up
13536 collected instead. On some architectures the reliability is higher
13537 for tracepoints at function entry, while on others it's the opposite.
13538 When this happens, backtracing will stop because the return address is
13539 found unavailable (unless another collect rule happened to match it).
13542 Collects the number of arguments from the static probe at which the
13543 tracepoint is located.
13544 @xref{Static Probe Points}.
13546 @item $_probe_arg@var{n}
13547 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13548 from the static probe at which the tracepoint is located.
13549 @xref{Static Probe Points}.
13552 @vindex $_sdata@r{, collect}
13553 Collect static tracepoint marker specific data. Only available for
13554 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13555 Lists}. On the UST static tracepoints library backend, an
13556 instrumentation point resembles a @code{printf} function call. The
13557 tracing library is able to collect user specified data formatted to a
13558 character string using the format provided by the programmer that
13559 instrumented the program. Other backends have similar mechanisms.
13560 Here's an example of a UST marker call:
13563 const char master_name[] = "$your_name";
13564 trace_mark(channel1, marker1, "hello %s", master_name)
13567 In this case, collecting @code{$_sdata} collects the string
13568 @samp{hello $yourname}. When analyzing the trace buffer, you can
13569 inspect @samp{$_sdata} like any other variable available to
13573 You can give several consecutive @code{collect} commands, each one
13574 with a single argument, or one @code{collect} command with several
13575 arguments separated by commas; the effect is the same.
13577 The optional @var{mods} changes the usual handling of the arguments.
13578 @code{s} requests that pointers to chars be handled as strings, in
13579 particular collecting the contents of the memory being pointed at, up
13580 to the first zero. The upper bound is by default the value of the
13581 @code{print elements} variable; if @code{s} is followed by a decimal
13582 number, that is the upper bound instead. So for instance
13583 @samp{collect/s25 mystr} collects as many as 25 characters at
13586 The command @code{info scope} (@pxref{Symbols, info scope}) is
13587 particularly useful for figuring out what data to collect.
13589 @kindex teval @r{(tracepoints)}
13590 @item teval @var{expr1}, @var{expr2}, @dots{}
13591 Evaluate the given expressions when the tracepoint is hit. This
13592 command accepts a comma-separated list of expressions. The results
13593 are discarded, so this is mainly useful for assigning values to trace
13594 state variables (@pxref{Trace State Variables}) without adding those
13595 values to the trace buffer, as would be the case if the @code{collect}
13598 @kindex while-stepping @r{(tracepoints)}
13599 @item while-stepping @var{n}
13600 Perform @var{n} single-step instruction traces after the tracepoint,
13601 collecting new data after each step. The @code{while-stepping}
13602 command is followed by the list of what to collect while stepping
13603 (followed by its own @code{end} command):
13606 > while-stepping 12
13607 > collect $regs, myglobal
13613 Note that @code{$pc} is not automatically collected by
13614 @code{while-stepping}; you need to explicitly collect that register if
13615 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13618 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13619 @kindex set default-collect
13620 @cindex default collection action
13621 This variable is a list of expressions to collect at each tracepoint
13622 hit. It is effectively an additional @code{collect} action prepended
13623 to every tracepoint action list. The expressions are parsed
13624 individually for each tracepoint, so for instance a variable named
13625 @code{xyz} may be interpreted as a global for one tracepoint, and a
13626 local for another, as appropriate to the tracepoint's location.
13628 @item show default-collect
13629 @kindex show default-collect
13630 Show the list of expressions that are collected by default at each
13635 @node Listing Tracepoints
13636 @subsection Listing Tracepoints
13639 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13640 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13641 @cindex information about tracepoints
13642 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13643 Display information about the tracepoint @var{num}. If you don't
13644 specify a tracepoint number, displays information about all the
13645 tracepoints defined so far. The format is similar to that used for
13646 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13647 command, simply restricting itself to tracepoints.
13649 A tracepoint's listing may include additional information specific to
13654 its passcount as given by the @code{passcount @var{n}} command
13657 the state about installed on target of each location
13661 (@value{GDBP}) @b{info trace}
13662 Num Type Disp Enb Address What
13663 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13665 collect globfoo, $regs
13670 2 tracepoint keep y <MULTIPLE>
13672 2.1 y 0x0804859c in func4 at change-loc.h:35
13673 installed on target
13674 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13675 installed on target
13676 2.3 y <PENDING> set_tracepoint
13677 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13678 not installed on target
13683 This command can be abbreviated @code{info tp}.
13686 @node Listing Static Tracepoint Markers
13687 @subsection Listing Static Tracepoint Markers
13690 @kindex info static-tracepoint-markers
13691 @cindex information about static tracepoint markers
13692 @item info static-tracepoint-markers
13693 Display information about all static tracepoint markers defined in the
13696 For each marker, the following columns are printed:
13700 An incrementing counter, output to help readability. This is not a
13703 The marker ID, as reported by the target.
13704 @item Enabled or Disabled
13705 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13706 that are not enabled.
13708 Where the marker is in your program, as a memory address.
13710 Where the marker is in the source for your program, as a file and line
13711 number. If the debug information included in the program does not
13712 allow @value{GDBN} to locate the source of the marker, this column
13713 will be left blank.
13717 In addition, the following information may be printed for each marker:
13721 User data passed to the tracing library by the marker call. In the
13722 UST backend, this is the format string passed as argument to the
13724 @item Static tracepoints probing the marker
13725 The list of static tracepoints attached to the marker.
13729 (@value{GDBP}) info static-tracepoint-markers
13730 Cnt ID Enb Address What
13731 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13732 Data: number1 %d number2 %d
13733 Probed by static tracepoints: #2
13734 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13740 @node Starting and Stopping Trace Experiments
13741 @subsection Starting and Stopping Trace Experiments
13744 @kindex tstart [ @var{notes} ]
13745 @cindex start a new trace experiment
13746 @cindex collected data discarded
13748 This command starts the trace experiment, and begins collecting data.
13749 It has the side effect of discarding all the data collected in the
13750 trace buffer during the previous trace experiment. If any arguments
13751 are supplied, they are taken as a note and stored with the trace
13752 experiment's state. The notes may be arbitrary text, and are
13753 especially useful with disconnected tracing in a multi-user context;
13754 the notes can explain what the trace is doing, supply user contact
13755 information, and so forth.
13757 @kindex tstop [ @var{notes} ]
13758 @cindex stop a running trace experiment
13760 This command stops the trace experiment. If any arguments are
13761 supplied, they are recorded with the experiment as a note. This is
13762 useful if you are stopping a trace started by someone else, for
13763 instance if the trace is interfering with the system's behavior and
13764 needs to be stopped quickly.
13766 @strong{Note}: a trace experiment and data collection may stop
13767 automatically if any tracepoint's passcount is reached
13768 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13771 @cindex status of trace data collection
13772 @cindex trace experiment, status of
13774 This command displays the status of the current trace data
13778 Here is an example of the commands we described so far:
13781 (@value{GDBP}) @b{trace gdb_c_test}
13782 (@value{GDBP}) @b{actions}
13783 Enter actions for tracepoint #1, one per line.
13784 > collect $regs,$locals,$args
13785 > while-stepping 11
13789 (@value{GDBP}) @b{tstart}
13790 [time passes @dots{}]
13791 (@value{GDBP}) @b{tstop}
13794 @anchor{disconnected tracing}
13795 @cindex disconnected tracing
13796 You can choose to continue running the trace experiment even if
13797 @value{GDBN} disconnects from the target, voluntarily or
13798 involuntarily. For commands such as @code{detach}, the debugger will
13799 ask what you want to do with the trace. But for unexpected
13800 terminations (@value{GDBN} crash, network outage), it would be
13801 unfortunate to lose hard-won trace data, so the variable
13802 @code{disconnected-tracing} lets you decide whether the trace should
13803 continue running without @value{GDBN}.
13806 @item set disconnected-tracing on
13807 @itemx set disconnected-tracing off
13808 @kindex set disconnected-tracing
13809 Choose whether a tracing run should continue to run if @value{GDBN}
13810 has disconnected from the target. Note that @code{detach} or
13811 @code{quit} will ask you directly what to do about a running trace no
13812 matter what this variable's setting, so the variable is mainly useful
13813 for handling unexpected situations, such as loss of the network.
13815 @item show disconnected-tracing
13816 @kindex show disconnected-tracing
13817 Show the current choice for disconnected tracing.
13821 When you reconnect to the target, the trace experiment may or may not
13822 still be running; it might have filled the trace buffer in the
13823 meantime, or stopped for one of the other reasons. If it is running,
13824 it will continue after reconnection.
13826 Upon reconnection, the target will upload information about the
13827 tracepoints in effect. @value{GDBN} will then compare that
13828 information to the set of tracepoints currently defined, and attempt
13829 to match them up, allowing for the possibility that the numbers may
13830 have changed due to creation and deletion in the meantime. If one of
13831 the target's tracepoints does not match any in @value{GDBN}, the
13832 debugger will create a new tracepoint, so that you have a number with
13833 which to specify that tracepoint. This matching-up process is
13834 necessarily heuristic, and it may result in useless tracepoints being
13835 created; you may simply delete them if they are of no use.
13837 @cindex circular trace buffer
13838 If your target agent supports a @dfn{circular trace buffer}, then you
13839 can run a trace experiment indefinitely without filling the trace
13840 buffer; when space runs out, the agent deletes already-collected trace
13841 frames, oldest first, until there is enough room to continue
13842 collecting. This is especially useful if your tracepoints are being
13843 hit too often, and your trace gets terminated prematurely because the
13844 buffer is full. To ask for a circular trace buffer, simply set
13845 @samp{circular-trace-buffer} to on. You can set this at any time,
13846 including during tracing; if the agent can do it, it will change
13847 buffer handling on the fly, otherwise it will not take effect until
13851 @item set circular-trace-buffer on
13852 @itemx set circular-trace-buffer off
13853 @kindex set circular-trace-buffer
13854 Choose whether a tracing run should use a linear or circular buffer
13855 for trace data. A linear buffer will not lose any trace data, but may
13856 fill up prematurely, while a circular buffer will discard old trace
13857 data, but it will have always room for the latest tracepoint hits.
13859 @item show circular-trace-buffer
13860 @kindex show circular-trace-buffer
13861 Show the current choice for the trace buffer. Note that this may not
13862 match the agent's current buffer handling, nor is it guaranteed to
13863 match the setting that might have been in effect during a past run,
13864 for instance if you are looking at frames from a trace file.
13869 @item set trace-buffer-size @var{n}
13870 @itemx set trace-buffer-size unlimited
13871 @kindex set trace-buffer-size
13872 Request that the target use a trace buffer of @var{n} bytes. Not all
13873 targets will honor the request; they may have a compiled-in size for
13874 the trace buffer, or some other limitation. Set to a value of
13875 @code{unlimited} or @code{-1} to let the target use whatever size it
13876 likes. This is also the default.
13878 @item show trace-buffer-size
13879 @kindex show trace-buffer-size
13880 Show the current requested size for the trace buffer. Note that this
13881 will only match the actual size if the target supports size-setting,
13882 and was able to handle the requested size. For instance, if the
13883 target can only change buffer size between runs, this variable will
13884 not reflect the change until the next run starts. Use @code{tstatus}
13885 to get a report of the actual buffer size.
13889 @item set trace-user @var{text}
13890 @kindex set trace-user
13892 @item show trace-user
13893 @kindex show trace-user
13895 @item set trace-notes @var{text}
13896 @kindex set trace-notes
13897 Set the trace run's notes.
13899 @item show trace-notes
13900 @kindex show trace-notes
13901 Show the trace run's notes.
13903 @item set trace-stop-notes @var{text}
13904 @kindex set trace-stop-notes
13905 Set the trace run's stop notes. The handling of the note is as for
13906 @code{tstop} arguments; the set command is convenient way to fix a
13907 stop note that is mistaken or incomplete.
13909 @item show trace-stop-notes
13910 @kindex show trace-stop-notes
13911 Show the trace run's stop notes.
13915 @node Tracepoint Restrictions
13916 @subsection Tracepoint Restrictions
13918 @cindex tracepoint restrictions
13919 There are a number of restrictions on the use of tracepoints. As
13920 described above, tracepoint data gathering occurs on the target
13921 without interaction from @value{GDBN}. Thus the full capabilities of
13922 the debugger are not available during data gathering, and then at data
13923 examination time, you will be limited by only having what was
13924 collected. The following items describe some common problems, but it
13925 is not exhaustive, and you may run into additional difficulties not
13931 Tracepoint expressions are intended to gather objects (lvalues). Thus
13932 the full flexibility of GDB's expression evaluator is not available.
13933 You cannot call functions, cast objects to aggregate types, access
13934 convenience variables or modify values (except by assignment to trace
13935 state variables). Some language features may implicitly call
13936 functions (for instance Objective-C fields with accessors), and therefore
13937 cannot be collected either.
13940 Collection of local variables, either individually or in bulk with
13941 @code{$locals} or @code{$args}, during @code{while-stepping} may
13942 behave erratically. The stepping action may enter a new scope (for
13943 instance by stepping into a function), or the location of the variable
13944 may change (for instance it is loaded into a register). The
13945 tracepoint data recorded uses the location information for the
13946 variables that is correct for the tracepoint location. When the
13947 tracepoint is created, it is not possible, in general, to determine
13948 where the steps of a @code{while-stepping} sequence will advance the
13949 program---particularly if a conditional branch is stepped.
13952 Collection of an incompletely-initialized or partially-destroyed object
13953 may result in something that @value{GDBN} cannot display, or displays
13954 in a misleading way.
13957 When @value{GDBN} displays a pointer to character it automatically
13958 dereferences the pointer to also display characters of the string
13959 being pointed to. However, collecting the pointer during tracing does
13960 not automatically collect the string. You need to explicitly
13961 dereference the pointer and provide size information if you want to
13962 collect not only the pointer, but the memory pointed to. For example,
13963 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13967 It is not possible to collect a complete stack backtrace at a
13968 tracepoint. Instead, you may collect the registers and a few hundred
13969 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13970 (adjust to use the name of the actual stack pointer register on your
13971 target architecture, and the amount of stack you wish to capture).
13972 Then the @code{backtrace} command will show a partial backtrace when
13973 using a trace frame. The number of stack frames that can be examined
13974 depends on the sizes of the frames in the collected stack. Note that
13975 if you ask for a block so large that it goes past the bottom of the
13976 stack, the target agent may report an error trying to read from an
13980 If you do not collect registers at a tracepoint, @value{GDBN} can
13981 infer that the value of @code{$pc} must be the same as the address of
13982 the tracepoint and use that when you are looking at a trace frame
13983 for that tracepoint. However, this cannot work if the tracepoint has
13984 multiple locations (for instance if it was set in a function that was
13985 inlined), or if it has a @code{while-stepping} loop. In those cases
13986 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13991 @node Analyze Collected Data
13992 @section Using the Collected Data
13994 After the tracepoint experiment ends, you use @value{GDBN} commands
13995 for examining the trace data. The basic idea is that each tracepoint
13996 collects a trace @dfn{snapshot} every time it is hit and another
13997 snapshot every time it single-steps. All these snapshots are
13998 consecutively numbered from zero and go into a buffer, and you can
13999 examine them later. The way you examine them is to @dfn{focus} on a
14000 specific trace snapshot. When the remote stub is focused on a trace
14001 snapshot, it will respond to all @value{GDBN} requests for memory and
14002 registers by reading from the buffer which belongs to that snapshot,
14003 rather than from @emph{real} memory or registers of the program being
14004 debugged. This means that @strong{all} @value{GDBN} commands
14005 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14006 behave as if we were currently debugging the program state as it was
14007 when the tracepoint occurred. Any requests for data that are not in
14008 the buffer will fail.
14011 * tfind:: How to select a trace snapshot
14012 * tdump:: How to display all data for a snapshot
14013 * save tracepoints:: How to save tracepoints for a future run
14017 @subsection @code{tfind @var{n}}
14020 @cindex select trace snapshot
14021 @cindex find trace snapshot
14022 The basic command for selecting a trace snapshot from the buffer is
14023 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14024 counting from zero. If no argument @var{n} is given, the next
14025 snapshot is selected.
14027 Here are the various forms of using the @code{tfind} command.
14031 Find the first snapshot in the buffer. This is a synonym for
14032 @code{tfind 0} (since 0 is the number of the first snapshot).
14035 Stop debugging trace snapshots, resume @emph{live} debugging.
14038 Same as @samp{tfind none}.
14041 No argument means find the next trace snapshot or find the first
14042 one if no trace snapshot is selected.
14045 Find the previous trace snapshot before the current one. This permits
14046 retracing earlier steps.
14048 @item tfind tracepoint @var{num}
14049 Find the next snapshot associated with tracepoint @var{num}. Search
14050 proceeds forward from the last examined trace snapshot. If no
14051 argument @var{num} is given, it means find the next snapshot collected
14052 for the same tracepoint as the current snapshot.
14054 @item tfind pc @var{addr}
14055 Find the next snapshot associated with the value @var{addr} of the
14056 program counter. Search proceeds forward from the last examined trace
14057 snapshot. If no argument @var{addr} is given, it means find the next
14058 snapshot with the same value of PC as the current snapshot.
14060 @item tfind outside @var{addr1}, @var{addr2}
14061 Find the next snapshot whose PC is outside the given range of
14062 addresses (exclusive).
14064 @item tfind range @var{addr1}, @var{addr2}
14065 Find the next snapshot whose PC is between @var{addr1} and
14066 @var{addr2} (inclusive).
14068 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14069 Find the next snapshot associated with the source line @var{n}. If
14070 the optional argument @var{file} is given, refer to line @var{n} in
14071 that source file. Search proceeds forward from the last examined
14072 trace snapshot. If no argument @var{n} is given, it means find the
14073 next line other than the one currently being examined; thus saying
14074 @code{tfind line} repeatedly can appear to have the same effect as
14075 stepping from line to line in a @emph{live} debugging session.
14078 The default arguments for the @code{tfind} commands are specifically
14079 designed to make it easy to scan through the trace buffer. For
14080 instance, @code{tfind} with no argument selects the next trace
14081 snapshot, and @code{tfind -} with no argument selects the previous
14082 trace snapshot. So, by giving one @code{tfind} command, and then
14083 simply hitting @key{RET} repeatedly you can examine all the trace
14084 snapshots in order. Or, by saying @code{tfind -} and then hitting
14085 @key{RET} repeatedly you can examine the snapshots in reverse order.
14086 The @code{tfind line} command with no argument selects the snapshot
14087 for the next source line executed. The @code{tfind pc} command with
14088 no argument selects the next snapshot with the same program counter
14089 (PC) as the current frame. The @code{tfind tracepoint} command with
14090 no argument selects the next trace snapshot collected by the same
14091 tracepoint as the current one.
14093 In addition to letting you scan through the trace buffer manually,
14094 these commands make it easy to construct @value{GDBN} scripts that
14095 scan through the trace buffer and print out whatever collected data
14096 you are interested in. Thus, if we want to examine the PC, FP, and SP
14097 registers from each trace frame in the buffer, we can say this:
14100 (@value{GDBP}) @b{tfind start}
14101 (@value{GDBP}) @b{while ($trace_frame != -1)}
14102 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14103 $trace_frame, $pc, $sp, $fp
14107 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14108 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14109 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14110 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14111 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14112 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14113 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14114 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14115 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14116 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14117 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14120 Or, if we want to examine the variable @code{X} at each source line in
14124 (@value{GDBP}) @b{tfind start}
14125 (@value{GDBP}) @b{while ($trace_frame != -1)}
14126 > printf "Frame %d, X == %d\n", $trace_frame, X
14136 @subsection @code{tdump}
14138 @cindex dump all data collected at tracepoint
14139 @cindex tracepoint data, display
14141 This command takes no arguments. It prints all the data collected at
14142 the current trace snapshot.
14145 (@value{GDBP}) @b{trace 444}
14146 (@value{GDBP}) @b{actions}
14147 Enter actions for tracepoint #2, one per line:
14148 > collect $regs, $locals, $args, gdb_long_test
14151 (@value{GDBP}) @b{tstart}
14153 (@value{GDBP}) @b{tfind line 444}
14154 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14156 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14158 (@value{GDBP}) @b{tdump}
14159 Data collected at tracepoint 2, trace frame 1:
14160 d0 0xc4aa0085 -995491707
14164 d4 0x71aea3d 119204413
14167 d7 0x380035 3670069
14168 a0 0x19e24a 1696330
14169 a1 0x3000668 50333288
14171 a3 0x322000 3284992
14172 a4 0x3000698 50333336
14173 a5 0x1ad3cc 1758156
14174 fp 0x30bf3c 0x30bf3c
14175 sp 0x30bf34 0x30bf34
14177 pc 0x20b2c8 0x20b2c8
14181 p = 0x20e5b4 "gdb-test"
14188 gdb_long_test = 17 '\021'
14193 @code{tdump} works by scanning the tracepoint's current collection
14194 actions and printing the value of each expression listed. So
14195 @code{tdump} can fail, if after a run, you change the tracepoint's
14196 actions to mention variables that were not collected during the run.
14198 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14199 uses the collected value of @code{$pc} to distinguish between trace
14200 frames that were collected at the tracepoint hit, and frames that were
14201 collected while stepping. This allows it to correctly choose whether
14202 to display the basic list of collections, or the collections from the
14203 body of the while-stepping loop. However, if @code{$pc} was not collected,
14204 then @code{tdump} will always attempt to dump using the basic collection
14205 list, and may fail if a while-stepping frame does not include all the
14206 same data that is collected at the tracepoint hit.
14207 @c This is getting pretty arcane, example would be good.
14209 @node save tracepoints
14210 @subsection @code{save tracepoints @var{filename}}
14211 @kindex save tracepoints
14212 @kindex save-tracepoints
14213 @cindex save tracepoints for future sessions
14215 This command saves all current tracepoint definitions together with
14216 their actions and passcounts, into a file @file{@var{filename}}
14217 suitable for use in a later debugging session. To read the saved
14218 tracepoint definitions, use the @code{source} command (@pxref{Command
14219 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14220 alias for @w{@code{save tracepoints}}
14222 @node Tracepoint Variables
14223 @section Convenience Variables for Tracepoints
14224 @cindex tracepoint variables
14225 @cindex convenience variables for tracepoints
14228 @vindex $trace_frame
14229 @item (int) $trace_frame
14230 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14231 snapshot is selected.
14233 @vindex $tracepoint
14234 @item (int) $tracepoint
14235 The tracepoint for the current trace snapshot.
14237 @vindex $trace_line
14238 @item (int) $trace_line
14239 The line number for the current trace snapshot.
14241 @vindex $trace_file
14242 @item (char []) $trace_file
14243 The source file for the current trace snapshot.
14245 @vindex $trace_func
14246 @item (char []) $trace_func
14247 The name of the function containing @code{$tracepoint}.
14250 Note: @code{$trace_file} is not suitable for use in @code{printf},
14251 use @code{output} instead.
14253 Here's a simple example of using these convenience variables for
14254 stepping through all the trace snapshots and printing some of their
14255 data. Note that these are not the same as trace state variables,
14256 which are managed by the target.
14259 (@value{GDBP}) @b{tfind start}
14261 (@value{GDBP}) @b{while $trace_frame != -1}
14262 > output $trace_file
14263 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14269 @section Using Trace Files
14270 @cindex trace files
14272 In some situations, the target running a trace experiment may no
14273 longer be available; perhaps it crashed, or the hardware was needed
14274 for a different activity. To handle these cases, you can arrange to
14275 dump the trace data into a file, and later use that file as a source
14276 of trace data, via the @code{target tfile} command.
14281 @item tsave [ -r ] @var{filename}
14282 @itemx tsave [-ctf] @var{dirname}
14283 Save the trace data to @var{filename}. By default, this command
14284 assumes that @var{filename} refers to the host filesystem, so if
14285 necessary @value{GDBN} will copy raw trace data up from the target and
14286 then save it. If the target supports it, you can also supply the
14287 optional argument @code{-r} (``remote'') to direct the target to save
14288 the data directly into @var{filename} in its own filesystem, which may be
14289 more efficient if the trace buffer is very large. (Note, however, that
14290 @code{target tfile} can only read from files accessible to the host.)
14291 By default, this command will save trace frame in tfile format.
14292 You can supply the optional argument @code{-ctf} to save data in CTF
14293 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14294 that can be shared by multiple debugging and tracing tools. Please go to
14295 @indicateurl{http://www.efficios.com/ctf} to get more information.
14297 @kindex target tfile
14301 @item target tfile @var{filename}
14302 @itemx target ctf @var{dirname}
14303 Use the file named @var{filename} or directory named @var{dirname} as
14304 a source of trace data. Commands that examine data work as they do with
14305 a live target, but it is not possible to run any new trace experiments.
14306 @code{tstatus} will report the state of the trace run at the moment
14307 the data was saved, as well as the current trace frame you are examining.
14308 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14312 (@value{GDBP}) target ctf ctf.ctf
14313 (@value{GDBP}) tfind
14314 Found trace frame 0, tracepoint 2
14315 39 ++a; /* set tracepoint 1 here */
14316 (@value{GDBP}) tdump
14317 Data collected at tracepoint 2, trace frame 0:
14321 c = @{"123", "456", "789", "123", "456", "789"@}
14322 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14330 @chapter Debugging Programs That Use Overlays
14333 If your program is too large to fit completely in your target system's
14334 memory, you can sometimes use @dfn{overlays} to work around this
14335 problem. @value{GDBN} provides some support for debugging programs that
14339 * How Overlays Work:: A general explanation of overlays.
14340 * Overlay Commands:: Managing overlays in @value{GDBN}.
14341 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14342 mapped by asking the inferior.
14343 * Overlay Sample Program:: A sample program using overlays.
14346 @node How Overlays Work
14347 @section How Overlays Work
14348 @cindex mapped overlays
14349 @cindex unmapped overlays
14350 @cindex load address, overlay's
14351 @cindex mapped address
14352 @cindex overlay area
14354 Suppose you have a computer whose instruction address space is only 64
14355 kilobytes long, but which has much more memory which can be accessed by
14356 other means: special instructions, segment registers, or memory
14357 management hardware, for example. Suppose further that you want to
14358 adapt a program which is larger than 64 kilobytes to run on this system.
14360 One solution is to identify modules of your program which are relatively
14361 independent, and need not call each other directly; call these modules
14362 @dfn{overlays}. Separate the overlays from the main program, and place
14363 their machine code in the larger memory. Place your main program in
14364 instruction memory, but leave at least enough space there to hold the
14365 largest overlay as well.
14367 Now, to call a function located in an overlay, you must first copy that
14368 overlay's machine code from the large memory into the space set aside
14369 for it in the instruction memory, and then jump to its entry point
14372 @c NB: In the below the mapped area's size is greater or equal to the
14373 @c size of all overlays. This is intentional to remind the developer
14374 @c that overlays don't necessarily need to be the same size.
14378 Data Instruction Larger
14379 Address Space Address Space Address Space
14380 +-----------+ +-----------+ +-----------+
14382 +-----------+ +-----------+ +-----------+<-- overlay 1
14383 | program | | main | .----| overlay 1 | load address
14384 | variables | | program | | +-----------+
14385 | and heap | | | | | |
14386 +-----------+ | | | +-----------+<-- overlay 2
14387 | | +-----------+ | | | load address
14388 +-----------+ | | | .-| overlay 2 |
14390 mapped --->+-----------+ | | +-----------+
14391 address | | | | | |
14392 | overlay | <-' | | |
14393 | area | <---' +-----------+<-- overlay 3
14394 | | <---. | | load address
14395 +-----------+ `--| overlay 3 |
14402 @anchor{A code overlay}A code overlay
14406 The diagram (@pxref{A code overlay}) shows a system with separate data
14407 and instruction address spaces. To map an overlay, the program copies
14408 its code from the larger address space to the instruction address space.
14409 Since the overlays shown here all use the same mapped address, only one
14410 may be mapped at a time. For a system with a single address space for
14411 data and instructions, the diagram would be similar, except that the
14412 program variables and heap would share an address space with the main
14413 program and the overlay area.
14415 An overlay loaded into instruction memory and ready for use is called a
14416 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14417 instruction memory. An overlay not present (or only partially present)
14418 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14419 is its address in the larger memory. The mapped address is also called
14420 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14421 called the @dfn{load memory address}, or @dfn{LMA}.
14423 Unfortunately, overlays are not a completely transparent way to adapt a
14424 program to limited instruction memory. They introduce a new set of
14425 global constraints you must keep in mind as you design your program:
14430 Before calling or returning to a function in an overlay, your program
14431 must make sure that overlay is actually mapped. Otherwise, the call or
14432 return will transfer control to the right address, but in the wrong
14433 overlay, and your program will probably crash.
14436 If the process of mapping an overlay is expensive on your system, you
14437 will need to choose your overlays carefully to minimize their effect on
14438 your program's performance.
14441 The executable file you load onto your system must contain each
14442 overlay's instructions, appearing at the overlay's load address, not its
14443 mapped address. However, each overlay's instructions must be relocated
14444 and its symbols defined as if the overlay were at its mapped address.
14445 You can use GNU linker scripts to specify different load and relocation
14446 addresses for pieces of your program; see @ref{Overlay Description,,,
14447 ld.info, Using ld: the GNU linker}.
14450 The procedure for loading executable files onto your system must be able
14451 to load their contents into the larger address space as well as the
14452 instruction and data spaces.
14456 The overlay system described above is rather simple, and could be
14457 improved in many ways:
14462 If your system has suitable bank switch registers or memory management
14463 hardware, you could use those facilities to make an overlay's load area
14464 contents simply appear at their mapped address in instruction space.
14465 This would probably be faster than copying the overlay to its mapped
14466 area in the usual way.
14469 If your overlays are small enough, you could set aside more than one
14470 overlay area, and have more than one overlay mapped at a time.
14473 You can use overlays to manage data, as well as instructions. In
14474 general, data overlays are even less transparent to your design than
14475 code overlays: whereas code overlays only require care when you call or
14476 return to functions, data overlays require care every time you access
14477 the data. Also, if you change the contents of a data overlay, you
14478 must copy its contents back out to its load address before you can copy a
14479 different data overlay into the same mapped area.
14484 @node Overlay Commands
14485 @section Overlay Commands
14487 To use @value{GDBN}'s overlay support, each overlay in your program must
14488 correspond to a separate section of the executable file. The section's
14489 virtual memory address and load memory address must be the overlay's
14490 mapped and load addresses. Identifying overlays with sections allows
14491 @value{GDBN} to determine the appropriate address of a function or
14492 variable, depending on whether the overlay is mapped or not.
14494 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14495 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14500 Disable @value{GDBN}'s overlay support. When overlay support is
14501 disabled, @value{GDBN} assumes that all functions and variables are
14502 always present at their mapped addresses. By default, @value{GDBN}'s
14503 overlay support is disabled.
14505 @item overlay manual
14506 @cindex manual overlay debugging
14507 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14508 relies on you to tell it which overlays are mapped, and which are not,
14509 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14510 commands described below.
14512 @item overlay map-overlay @var{overlay}
14513 @itemx overlay map @var{overlay}
14514 @cindex map an overlay
14515 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14516 be the name of the object file section containing the overlay. When an
14517 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14518 functions and variables at their mapped addresses. @value{GDBN} assumes
14519 that any other overlays whose mapped ranges overlap that of
14520 @var{overlay} are now unmapped.
14522 @item overlay unmap-overlay @var{overlay}
14523 @itemx overlay unmap @var{overlay}
14524 @cindex unmap an overlay
14525 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14526 must be the name of the object file section containing the overlay.
14527 When an overlay is unmapped, @value{GDBN} assumes it can find the
14528 overlay's functions and variables at their load addresses.
14531 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14532 consults a data structure the overlay manager maintains in the inferior
14533 to see which overlays are mapped. For details, see @ref{Automatic
14534 Overlay Debugging}.
14536 @item overlay load-target
14537 @itemx overlay load
14538 @cindex reloading the overlay table
14539 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14540 re-reads the table @value{GDBN} automatically each time the inferior
14541 stops, so this command should only be necessary if you have changed the
14542 overlay mapping yourself using @value{GDBN}. This command is only
14543 useful when using automatic overlay debugging.
14545 @item overlay list-overlays
14546 @itemx overlay list
14547 @cindex listing mapped overlays
14548 Display a list of the overlays currently mapped, along with their mapped
14549 addresses, load addresses, and sizes.
14553 Normally, when @value{GDBN} prints a code address, it includes the name
14554 of the function the address falls in:
14557 (@value{GDBP}) print main
14558 $3 = @{int ()@} 0x11a0 <main>
14561 When overlay debugging is enabled, @value{GDBN} recognizes code in
14562 unmapped overlays, and prints the names of unmapped functions with
14563 asterisks around them. For example, if @code{foo} is a function in an
14564 unmapped overlay, @value{GDBN} prints it this way:
14567 (@value{GDBP}) overlay list
14568 No sections are mapped.
14569 (@value{GDBP}) print foo
14570 $5 = @{int (int)@} 0x100000 <*foo*>
14573 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14577 (@value{GDBP}) overlay list
14578 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14579 mapped at 0x1016 - 0x104a
14580 (@value{GDBP}) print foo
14581 $6 = @{int (int)@} 0x1016 <foo>
14584 When overlay debugging is enabled, @value{GDBN} can find the correct
14585 address for functions and variables in an overlay, whether or not the
14586 overlay is mapped. This allows most @value{GDBN} commands, like
14587 @code{break} and @code{disassemble}, to work normally, even on unmapped
14588 code. However, @value{GDBN}'s breakpoint support has some limitations:
14592 @cindex breakpoints in overlays
14593 @cindex overlays, setting breakpoints in
14594 You can set breakpoints in functions in unmapped overlays, as long as
14595 @value{GDBN} can write to the overlay at its load address.
14597 @value{GDBN} can not set hardware or simulator-based breakpoints in
14598 unmapped overlays. However, if you set a breakpoint at the end of your
14599 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14600 you are using manual overlay management), @value{GDBN} will re-set its
14601 breakpoints properly.
14605 @node Automatic Overlay Debugging
14606 @section Automatic Overlay Debugging
14607 @cindex automatic overlay debugging
14609 @value{GDBN} can automatically track which overlays are mapped and which
14610 are not, given some simple co-operation from the overlay manager in the
14611 inferior. If you enable automatic overlay debugging with the
14612 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14613 looks in the inferior's memory for certain variables describing the
14614 current state of the overlays.
14616 Here are the variables your overlay manager must define to support
14617 @value{GDBN}'s automatic overlay debugging:
14621 @item @code{_ovly_table}:
14622 This variable must be an array of the following structures:
14627 /* The overlay's mapped address. */
14630 /* The size of the overlay, in bytes. */
14631 unsigned long size;
14633 /* The overlay's load address. */
14636 /* Non-zero if the overlay is currently mapped;
14638 unsigned long mapped;
14642 @item @code{_novlys}:
14643 This variable must be a four-byte signed integer, holding the total
14644 number of elements in @code{_ovly_table}.
14648 To decide whether a particular overlay is mapped or not, @value{GDBN}
14649 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14650 @code{lma} members equal the VMA and LMA of the overlay's section in the
14651 executable file. When @value{GDBN} finds a matching entry, it consults
14652 the entry's @code{mapped} member to determine whether the overlay is
14655 In addition, your overlay manager may define a function called
14656 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14657 will silently set a breakpoint there. If the overlay manager then
14658 calls this function whenever it has changed the overlay table, this
14659 will enable @value{GDBN} to accurately keep track of which overlays
14660 are in program memory, and update any breakpoints that may be set
14661 in overlays. This will allow breakpoints to work even if the
14662 overlays are kept in ROM or other non-writable memory while they
14663 are not being executed.
14665 @node Overlay Sample Program
14666 @section Overlay Sample Program
14667 @cindex overlay example program
14669 When linking a program which uses overlays, you must place the overlays
14670 at their load addresses, while relocating them to run at their mapped
14671 addresses. To do this, you must write a linker script (@pxref{Overlay
14672 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14673 since linker scripts are specific to a particular host system, target
14674 architecture, and target memory layout, this manual cannot provide
14675 portable sample code demonstrating @value{GDBN}'s overlay support.
14677 However, the @value{GDBN} source distribution does contain an overlaid
14678 program, with linker scripts for a few systems, as part of its test
14679 suite. The program consists of the following files from
14680 @file{gdb/testsuite/gdb.base}:
14684 The main program file.
14686 A simple overlay manager, used by @file{overlays.c}.
14691 Overlay modules, loaded and used by @file{overlays.c}.
14694 Linker scripts for linking the test program on the @code{d10v-elf}
14695 and @code{m32r-elf} targets.
14698 You can build the test program using the @code{d10v-elf} GCC
14699 cross-compiler like this:
14702 $ d10v-elf-gcc -g -c overlays.c
14703 $ d10v-elf-gcc -g -c ovlymgr.c
14704 $ d10v-elf-gcc -g -c foo.c
14705 $ d10v-elf-gcc -g -c bar.c
14706 $ d10v-elf-gcc -g -c baz.c
14707 $ d10v-elf-gcc -g -c grbx.c
14708 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14709 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14712 The build process is identical for any other architecture, except that
14713 you must substitute the appropriate compiler and linker script for the
14714 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14718 @chapter Using @value{GDBN} with Different Languages
14721 Although programming languages generally have common aspects, they are
14722 rarely expressed in the same manner. For instance, in ANSI C,
14723 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14724 Modula-2, it is accomplished by @code{p^}. Values can also be
14725 represented (and displayed) differently. Hex numbers in C appear as
14726 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14728 @cindex working language
14729 Language-specific information is built into @value{GDBN} for some languages,
14730 allowing you to express operations like the above in your program's
14731 native language, and allowing @value{GDBN} to output values in a manner
14732 consistent with the syntax of your program's native language. The
14733 language you use to build expressions is called the @dfn{working
14737 * Setting:: Switching between source languages
14738 * Show:: Displaying the language
14739 * Checks:: Type and range checks
14740 * Supported Languages:: Supported languages
14741 * Unsupported Languages:: Unsupported languages
14745 @section Switching Between Source Languages
14747 There are two ways to control the working language---either have @value{GDBN}
14748 set it automatically, or select it manually yourself. You can use the
14749 @code{set language} command for either purpose. On startup, @value{GDBN}
14750 defaults to setting the language automatically. The working language is
14751 used to determine how expressions you type are interpreted, how values
14754 In addition to the working language, every source file that
14755 @value{GDBN} knows about has its own working language. For some object
14756 file formats, the compiler might indicate which language a particular
14757 source file is in. However, most of the time @value{GDBN} infers the
14758 language from the name of the file. The language of a source file
14759 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14760 show each frame appropriately for its own language. There is no way to
14761 set the language of a source file from within @value{GDBN}, but you can
14762 set the language associated with a filename extension. @xref{Show, ,
14763 Displaying the Language}.
14765 This is most commonly a problem when you use a program, such
14766 as @code{cfront} or @code{f2c}, that generates C but is written in
14767 another language. In that case, make the
14768 program use @code{#line} directives in its C output; that way
14769 @value{GDBN} will know the correct language of the source code of the original
14770 program, and will display that source code, not the generated C code.
14773 * Filenames:: Filename extensions and languages.
14774 * Manually:: Setting the working language manually
14775 * Automatically:: Having @value{GDBN} infer the source language
14779 @subsection List of Filename Extensions and Languages
14781 If a source file name ends in one of the following extensions, then
14782 @value{GDBN} infers that its language is the one indicated.
14800 C@t{++} source file
14806 Objective-C source file
14810 Fortran source file
14813 Modula-2 source file
14817 Assembler source file. This actually behaves almost like C, but
14818 @value{GDBN} does not skip over function prologues when stepping.
14821 In addition, you may set the language associated with a filename
14822 extension. @xref{Show, , Displaying the Language}.
14825 @subsection Setting the Working Language
14827 If you allow @value{GDBN} to set the language automatically,
14828 expressions are interpreted the same way in your debugging session and
14831 @kindex set language
14832 If you wish, you may set the language manually. To do this, issue the
14833 command @samp{set language @var{lang}}, where @var{lang} is the name of
14834 a language, such as
14835 @code{c} or @code{modula-2}.
14836 For a list of the supported languages, type @samp{set language}.
14838 Setting the language manually prevents @value{GDBN} from updating the working
14839 language automatically. This can lead to confusion if you try
14840 to debug a program when the working language is not the same as the
14841 source language, when an expression is acceptable to both
14842 languages---but means different things. For instance, if the current
14843 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14851 might not have the effect you intended. In C, this means to add
14852 @code{b} and @code{c} and place the result in @code{a}. The result
14853 printed would be the value of @code{a}. In Modula-2, this means to compare
14854 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14856 @node Automatically
14857 @subsection Having @value{GDBN} Infer the Source Language
14859 To have @value{GDBN} set the working language automatically, use
14860 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14861 then infers the working language. That is, when your program stops in a
14862 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14863 working language to the language recorded for the function in that
14864 frame. If the language for a frame is unknown (that is, if the function
14865 or block corresponding to the frame was defined in a source file that
14866 does not have a recognized extension), the current working language is
14867 not changed, and @value{GDBN} issues a warning.
14869 This may not seem necessary for most programs, which are written
14870 entirely in one source language. However, program modules and libraries
14871 written in one source language can be used by a main program written in
14872 a different source language. Using @samp{set language auto} in this
14873 case frees you from having to set the working language manually.
14876 @section Displaying the Language
14878 The following commands help you find out which language is the
14879 working language, and also what language source files were written in.
14882 @item show language
14883 @anchor{show language}
14884 @kindex show language
14885 Display the current working language. This is the
14886 language you can use with commands such as @code{print} to
14887 build and compute expressions that may involve variables in your program.
14890 @kindex info frame@r{, show the source language}
14891 Display the source language for this frame. This language becomes the
14892 working language if you use an identifier from this frame.
14893 @xref{Frame Info, ,Information about a Frame}, to identify the other
14894 information listed here.
14897 @kindex info source@r{, show the source language}
14898 Display the source language of this source file.
14899 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14900 information listed here.
14903 In unusual circumstances, you may have source files with extensions
14904 not in the standard list. You can then set the extension associated
14905 with a language explicitly:
14908 @item set extension-language @var{ext} @var{language}
14909 @kindex set extension-language
14910 Tell @value{GDBN} that source files with extension @var{ext} are to be
14911 assumed as written in the source language @var{language}.
14913 @item info extensions
14914 @kindex info extensions
14915 List all the filename extensions and the associated languages.
14919 @section Type and Range Checking
14921 Some languages are designed to guard you against making seemingly common
14922 errors through a series of compile- and run-time checks. These include
14923 checking the type of arguments to functions and operators and making
14924 sure mathematical overflows are caught at run time. Checks such as
14925 these help to ensure a program's correctness once it has been compiled
14926 by eliminating type mismatches and providing active checks for range
14927 errors when your program is running.
14929 By default @value{GDBN} checks for these errors according to the
14930 rules of the current source language. Although @value{GDBN} does not check
14931 the statements in your program, it can check expressions entered directly
14932 into @value{GDBN} for evaluation via the @code{print} command, for example.
14935 * Type Checking:: An overview of type checking
14936 * Range Checking:: An overview of range checking
14939 @cindex type checking
14940 @cindex checks, type
14941 @node Type Checking
14942 @subsection An Overview of Type Checking
14944 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14945 arguments to operators and functions have to be of the correct type,
14946 otherwise an error occurs. These checks prevent type mismatch
14947 errors from ever causing any run-time problems. For example,
14950 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14952 (@value{GDBP}) print obj.my_method (0)
14955 (@value{GDBP}) print obj.my_method (0x1234)
14956 Cannot resolve method klass::my_method to any overloaded instance
14959 The second example fails because in C@t{++} the integer constant
14960 @samp{0x1234} is not type-compatible with the pointer parameter type.
14962 For the expressions you use in @value{GDBN} commands, you can tell
14963 @value{GDBN} to not enforce strict type checking or
14964 to treat any mismatches as errors and abandon the expression;
14965 When type checking is disabled, @value{GDBN} successfully evaluates
14966 expressions like the second example above.
14968 Even if type checking is off, there may be other reasons
14969 related to type that prevent @value{GDBN} from evaluating an expression.
14970 For instance, @value{GDBN} does not know how to add an @code{int} and
14971 a @code{struct foo}. These particular type errors have nothing to do
14972 with the language in use and usually arise from expressions which make
14973 little sense to evaluate anyway.
14975 @value{GDBN} provides some additional commands for controlling type checking:
14977 @kindex set check type
14978 @kindex show check type
14980 @item set check type on
14981 @itemx set check type off
14982 Set strict type checking on or off. If any type mismatches occur in
14983 evaluating an expression while type checking is on, @value{GDBN} prints a
14984 message and aborts evaluation of the expression.
14986 @item show check type
14987 Show the current setting of type checking and whether @value{GDBN}
14988 is enforcing strict type checking rules.
14991 @cindex range checking
14992 @cindex checks, range
14993 @node Range Checking
14994 @subsection An Overview of Range Checking
14996 In some languages (such as Modula-2), it is an error to exceed the
14997 bounds of a type; this is enforced with run-time checks. Such range
14998 checking is meant to ensure program correctness by making sure
14999 computations do not overflow, or indices on an array element access do
15000 not exceed the bounds of the array.
15002 For expressions you use in @value{GDBN} commands, you can tell
15003 @value{GDBN} to treat range errors in one of three ways: ignore them,
15004 always treat them as errors and abandon the expression, or issue
15005 warnings but evaluate the expression anyway.
15007 A range error can result from numerical overflow, from exceeding an
15008 array index bound, or when you type a constant that is not a member
15009 of any type. Some languages, however, do not treat overflows as an
15010 error. In many implementations of C, mathematical overflow causes the
15011 result to ``wrap around'' to lower values---for example, if @var{m} is
15012 the largest integer value, and @var{s} is the smallest, then
15015 @var{m} + 1 @result{} @var{s}
15018 This, too, is specific to individual languages, and in some cases
15019 specific to individual compilers or machines. @xref{Supported Languages, ,
15020 Supported Languages}, for further details on specific languages.
15022 @value{GDBN} provides some additional commands for controlling the range checker:
15024 @kindex set check range
15025 @kindex show check range
15027 @item set check range auto
15028 Set range checking on or off based on the current working language.
15029 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15032 @item set check range on
15033 @itemx set check range off
15034 Set range checking on or off, overriding the default setting for the
15035 current working language. A warning is issued if the setting does not
15036 match the language default. If a range error occurs and range checking is on,
15037 then a message is printed and evaluation of the expression is aborted.
15039 @item set check range warn
15040 Output messages when the @value{GDBN} range checker detects a range error,
15041 but attempt to evaluate the expression anyway. Evaluating the
15042 expression may still be impossible for other reasons, such as accessing
15043 memory that the process does not own (a typical example from many Unix
15047 Show the current setting of the range checker, and whether or not it is
15048 being set automatically by @value{GDBN}.
15051 @node Supported Languages
15052 @section Supported Languages
15054 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15055 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15056 @c This is false ...
15057 Some @value{GDBN} features may be used in expressions regardless of the
15058 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15059 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15060 ,Expressions}) can be used with the constructs of any supported
15063 The following sections detail to what degree each source language is
15064 supported by @value{GDBN}. These sections are not meant to be language
15065 tutorials or references, but serve only as a reference guide to what the
15066 @value{GDBN} expression parser accepts, and what input and output
15067 formats should look like for different languages. There are many good
15068 books written on each of these languages; please look to these for a
15069 language reference or tutorial.
15072 * C:: C and C@t{++}
15075 * Objective-C:: Objective-C
15076 * OpenCL C:: OpenCL C
15077 * Fortran:: Fortran
15080 * Modula-2:: Modula-2
15085 @subsection C and C@t{++}
15087 @cindex C and C@t{++}
15088 @cindex expressions in C or C@t{++}
15090 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15091 to both languages. Whenever this is the case, we discuss those languages
15095 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15096 @cindex @sc{gnu} C@t{++}
15097 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15098 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15099 effectively, you must compile your C@t{++} programs with a supported
15100 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15101 compiler (@code{aCC}).
15104 * C Operators:: C and C@t{++} operators
15105 * C Constants:: C and C@t{++} constants
15106 * C Plus Plus Expressions:: C@t{++} expressions
15107 * C Defaults:: Default settings for C and C@t{++}
15108 * C Checks:: C and C@t{++} type and range checks
15109 * Debugging C:: @value{GDBN} and C
15110 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15111 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15115 @subsubsection C and C@t{++} Operators
15117 @cindex C and C@t{++} operators
15119 Operators must be defined on values of specific types. For instance,
15120 @code{+} is defined on numbers, but not on structures. Operators are
15121 often defined on groups of types.
15123 For the purposes of C and C@t{++}, the following definitions hold:
15128 @emph{Integral types} include @code{int} with any of its storage-class
15129 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15132 @emph{Floating-point types} include @code{float}, @code{double}, and
15133 @code{long double} (if supported by the target platform).
15136 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15139 @emph{Scalar types} include all of the above.
15144 The following operators are supported. They are listed here
15145 in order of increasing precedence:
15149 The comma or sequencing operator. Expressions in a comma-separated list
15150 are evaluated from left to right, with the result of the entire
15151 expression being the last expression evaluated.
15154 Assignment. The value of an assignment expression is the value
15155 assigned. Defined on scalar types.
15158 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15159 and translated to @w{@code{@var{a} = @var{a op b}}}.
15160 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15161 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15162 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15165 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15166 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15167 should be of an integral type.
15170 Logical @sc{or}. Defined on integral types.
15173 Logical @sc{and}. Defined on integral types.
15176 Bitwise @sc{or}. Defined on integral types.
15179 Bitwise exclusive-@sc{or}. Defined on integral types.
15182 Bitwise @sc{and}. Defined on integral types.
15185 Equality and inequality. Defined on scalar types. The value of these
15186 expressions is 0 for false and non-zero for true.
15188 @item <@r{, }>@r{, }<=@r{, }>=
15189 Less than, greater than, less than or equal, greater than or equal.
15190 Defined on scalar types. The value of these expressions is 0 for false
15191 and non-zero for true.
15194 left shift, and right shift. Defined on integral types.
15197 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15200 Addition and subtraction. Defined on integral types, floating-point types and
15203 @item *@r{, }/@r{, }%
15204 Multiplication, division, and modulus. Multiplication and division are
15205 defined on integral and floating-point types. Modulus is defined on
15209 Increment and decrement. When appearing before a variable, the
15210 operation is performed before the variable is used in an expression;
15211 when appearing after it, the variable's value is used before the
15212 operation takes place.
15215 Pointer dereferencing. Defined on pointer types. Same precedence as
15219 Address operator. Defined on variables. Same precedence as @code{++}.
15221 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15222 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15223 to examine the address
15224 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15228 Negative. Defined on integral and floating-point types. Same
15229 precedence as @code{++}.
15232 Logical negation. Defined on integral types. Same precedence as
15236 Bitwise complement operator. Defined on integral types. Same precedence as
15241 Structure member, and pointer-to-structure member. For convenience,
15242 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15243 pointer based on the stored type information.
15244 Defined on @code{struct} and @code{union} data.
15247 Dereferences of pointers to members.
15250 Array indexing. @code{@var{a}[@var{i}]} is defined as
15251 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15254 Function parameter list. Same precedence as @code{->}.
15257 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15258 and @code{class} types.
15261 Doubled colons also represent the @value{GDBN} scope operator
15262 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15266 If an operator is redefined in the user code, @value{GDBN} usually
15267 attempts to invoke the redefined version instead of using the operator's
15268 predefined meaning.
15271 @subsubsection C and C@t{++} Constants
15273 @cindex C and C@t{++} constants
15275 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15280 Integer constants are a sequence of digits. Octal constants are
15281 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15282 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15283 @samp{l}, specifying that the constant should be treated as a
15287 Floating point constants are a sequence of digits, followed by a decimal
15288 point, followed by a sequence of digits, and optionally followed by an
15289 exponent. An exponent is of the form:
15290 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15291 sequence of digits. The @samp{+} is optional for positive exponents.
15292 A floating-point constant may also end with a letter @samp{f} or
15293 @samp{F}, specifying that the constant should be treated as being of
15294 the @code{float} (as opposed to the default @code{double}) type; or with
15295 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15299 Enumerated constants consist of enumerated identifiers, or their
15300 integral equivalents.
15303 Character constants are a single character surrounded by single quotes
15304 (@code{'}), or a number---the ordinal value of the corresponding character
15305 (usually its @sc{ascii} value). Within quotes, the single character may
15306 be represented by a letter or by @dfn{escape sequences}, which are of
15307 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15308 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15309 @samp{@var{x}} is a predefined special character---for example,
15310 @samp{\n} for newline.
15312 Wide character constants can be written by prefixing a character
15313 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15314 form of @samp{x}. The target wide character set is used when
15315 computing the value of this constant (@pxref{Character Sets}).
15318 String constants are a sequence of character constants surrounded by
15319 double quotes (@code{"}). Any valid character constant (as described
15320 above) may appear. Double quotes within the string must be preceded by
15321 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15324 Wide string constants can be written by prefixing a string constant
15325 with @samp{L}, as in C. The target wide character set is used when
15326 computing the value of this constant (@pxref{Character Sets}).
15329 Pointer constants are an integral value. You can also write pointers
15330 to constants using the C operator @samp{&}.
15333 Array constants are comma-separated lists surrounded by braces @samp{@{}
15334 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15335 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15336 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15339 @node C Plus Plus Expressions
15340 @subsubsection C@t{++} Expressions
15342 @cindex expressions in C@t{++}
15343 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15345 @cindex debugging C@t{++} programs
15346 @cindex C@t{++} compilers
15347 @cindex debug formats and C@t{++}
15348 @cindex @value{NGCC} and C@t{++}
15350 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15351 the proper compiler and the proper debug format. Currently,
15352 @value{GDBN} works best when debugging C@t{++} code that is compiled
15353 with the most recent version of @value{NGCC} possible. The DWARF
15354 debugging format is preferred; @value{NGCC} defaults to this on most
15355 popular platforms. Other compilers and/or debug formats are likely to
15356 work badly or not at all when using @value{GDBN} to debug C@t{++}
15357 code. @xref{Compilation}.
15362 @cindex member functions
15364 Member function calls are allowed; you can use expressions like
15367 count = aml->GetOriginal(x, y)
15370 @vindex this@r{, inside C@t{++} member functions}
15371 @cindex namespace in C@t{++}
15373 While a member function is active (in the selected stack frame), your
15374 expressions have the same namespace available as the member function;
15375 that is, @value{GDBN} allows implicit references to the class instance
15376 pointer @code{this} following the same rules as C@t{++}. @code{using}
15377 declarations in the current scope are also respected by @value{GDBN}.
15379 @cindex call overloaded functions
15380 @cindex overloaded functions, calling
15381 @cindex type conversions in C@t{++}
15383 You can call overloaded functions; @value{GDBN} resolves the function
15384 call to the right definition, with some restrictions. @value{GDBN} does not
15385 perform overload resolution involving user-defined type conversions,
15386 calls to constructors, or instantiations of templates that do not exist
15387 in the program. It also cannot handle ellipsis argument lists or
15390 It does perform integral conversions and promotions, floating-point
15391 promotions, arithmetic conversions, pointer conversions, conversions of
15392 class objects to base classes, and standard conversions such as those of
15393 functions or arrays to pointers; it requires an exact match on the
15394 number of function arguments.
15396 Overload resolution is always performed, unless you have specified
15397 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15398 ,@value{GDBN} Features for C@t{++}}.
15400 You must specify @code{set overload-resolution off} in order to use an
15401 explicit function signature to call an overloaded function, as in
15403 p 'foo(char,int)'('x', 13)
15406 The @value{GDBN} command-completion facility can simplify this;
15407 see @ref{Completion, ,Command Completion}.
15409 @cindex reference declarations
15411 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15412 references; you can use them in expressions just as you do in C@t{++}
15413 source---they are automatically dereferenced.
15415 In the parameter list shown when @value{GDBN} displays a frame, the values of
15416 reference variables are not displayed (unlike other variables); this
15417 avoids clutter, since references are often used for large structures.
15418 The @emph{address} of a reference variable is always shown, unless
15419 you have specified @samp{set print address off}.
15422 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15423 expressions can use it just as expressions in your program do. Since
15424 one scope may be defined in another, you can use @code{::} repeatedly if
15425 necessary, for example in an expression like
15426 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15427 resolving name scope by reference to source files, in both C and C@t{++}
15428 debugging (@pxref{Variables, ,Program Variables}).
15431 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15436 @subsubsection C and C@t{++} Defaults
15438 @cindex C and C@t{++} defaults
15440 If you allow @value{GDBN} to set range checking automatically, it
15441 defaults to @code{off} whenever the working language changes to
15442 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15443 selects the working language.
15445 If you allow @value{GDBN} to set the language automatically, it
15446 recognizes source files whose names end with @file{.c}, @file{.C}, or
15447 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15448 these files, it sets the working language to C or C@t{++}.
15449 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15450 for further details.
15453 @subsubsection C and C@t{++} Type and Range Checks
15455 @cindex C and C@t{++} checks
15457 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15458 checking is used. However, if you turn type checking off, @value{GDBN}
15459 will allow certain non-standard conversions, such as promoting integer
15460 constants to pointers.
15462 Range checking, if turned on, is done on mathematical operations. Array
15463 indices are not checked, since they are often used to index a pointer
15464 that is not itself an array.
15467 @subsubsection @value{GDBN} and C
15469 The @code{set print union} and @code{show print union} commands apply to
15470 the @code{union} type. When set to @samp{on}, any @code{union} that is
15471 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15472 appears as @samp{@{...@}}.
15474 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15475 with pointers and a memory allocation function. @xref{Expressions,
15478 @node Debugging C Plus Plus
15479 @subsubsection @value{GDBN} Features for C@t{++}
15481 @cindex commands for C@t{++}
15483 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15484 designed specifically for use with C@t{++}. Here is a summary:
15487 @cindex break in overloaded functions
15488 @item @r{breakpoint menus}
15489 When you want a breakpoint in a function whose name is overloaded,
15490 @value{GDBN} has the capability to display a menu of possible breakpoint
15491 locations to help you specify which function definition you want.
15492 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15494 @cindex overloading in C@t{++}
15495 @item rbreak @var{regex}
15496 Setting breakpoints using regular expressions is helpful for setting
15497 breakpoints on overloaded functions that are not members of any special
15499 @xref{Set Breaks, ,Setting Breakpoints}.
15501 @cindex C@t{++} exception handling
15503 @itemx catch rethrow
15505 Debug C@t{++} exception handling using these commands. @xref{Set
15506 Catchpoints, , Setting Catchpoints}.
15508 @cindex inheritance
15509 @item ptype @var{typename}
15510 Print inheritance relationships as well as other information for type
15512 @xref{Symbols, ,Examining the Symbol Table}.
15514 @item info vtbl @var{expression}.
15515 The @code{info vtbl} command can be used to display the virtual
15516 method tables of the object computed by @var{expression}. This shows
15517 one entry per virtual table; there may be multiple virtual tables when
15518 multiple inheritance is in use.
15520 @cindex C@t{++} demangling
15521 @item demangle @var{name}
15522 Demangle @var{name}.
15523 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15525 @cindex C@t{++} symbol display
15526 @item set print demangle
15527 @itemx show print demangle
15528 @itemx set print asm-demangle
15529 @itemx show print asm-demangle
15530 Control whether C@t{++} symbols display in their source form, both when
15531 displaying code as C@t{++} source and when displaying disassemblies.
15532 @xref{Print Settings, ,Print Settings}.
15534 @item set print object
15535 @itemx show print object
15536 Choose whether to print derived (actual) or declared types of objects.
15537 @xref{Print Settings, ,Print Settings}.
15539 @item set print vtbl
15540 @itemx show print vtbl
15541 Control the format for printing virtual function tables.
15542 @xref{Print Settings, ,Print Settings}.
15543 (The @code{vtbl} commands do not work on programs compiled with the HP
15544 ANSI C@t{++} compiler (@code{aCC}).)
15546 @kindex set overload-resolution
15547 @cindex overloaded functions, overload resolution
15548 @item set overload-resolution on
15549 Enable overload resolution for C@t{++} expression evaluation. The default
15550 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15551 and searches for a function whose signature matches the argument types,
15552 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15553 Expressions, ,C@t{++} Expressions}, for details).
15554 If it cannot find a match, it emits a message.
15556 @item set overload-resolution off
15557 Disable overload resolution for C@t{++} expression evaluation. For
15558 overloaded functions that are not class member functions, @value{GDBN}
15559 chooses the first function of the specified name that it finds in the
15560 symbol table, whether or not its arguments are of the correct type. For
15561 overloaded functions that are class member functions, @value{GDBN}
15562 searches for a function whose signature @emph{exactly} matches the
15565 @kindex show overload-resolution
15566 @item show overload-resolution
15567 Show the current setting of overload resolution.
15569 @item @r{Overloaded symbol names}
15570 You can specify a particular definition of an overloaded symbol, using
15571 the same notation that is used to declare such symbols in C@t{++}: type
15572 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15573 also use the @value{GDBN} command-line word completion facilities to list the
15574 available choices, or to finish the type list for you.
15575 @xref{Completion,, Command Completion}, for details on how to do this.
15577 @item @r{Breakpoints in functions with ABI tags}
15579 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15580 correspond to changes in the ABI of a type, function, or variable that
15581 would not otherwise be reflected in a mangled name. See
15582 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15585 The ABI tags are visible in C@t{++} demangled names. For example, a
15586 function that returns a std::string:
15589 std::string function(int);
15593 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15594 tag, and @value{GDBN} displays the symbol like this:
15597 function[abi:cxx11](int)
15600 You can set a breakpoint on such functions simply as if they had no
15604 (gdb) b function(int)
15605 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15606 (gdb) info breakpoints
15607 Num Type Disp Enb Address What
15608 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15612 On the rare occasion you need to disambiguate between different ABI
15613 tags, you can do so by simply including the ABI tag in the function
15617 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15621 @node Decimal Floating Point
15622 @subsubsection Decimal Floating Point format
15623 @cindex decimal floating point format
15625 @value{GDBN} can examine, set and perform computations with numbers in
15626 decimal floating point format, which in the C language correspond to the
15627 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15628 specified by the extension to support decimal floating-point arithmetic.
15630 There are two encodings in use, depending on the architecture: BID (Binary
15631 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15632 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15635 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15636 to manipulate decimal floating point numbers, it is not possible to convert
15637 (using a cast, for example) integers wider than 32-bit to decimal float.
15639 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15640 point computations, error checking in decimal float operations ignores
15641 underflow, overflow and divide by zero exceptions.
15643 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15644 to inspect @code{_Decimal128} values stored in floating point registers.
15645 See @ref{PowerPC,,PowerPC} for more details.
15651 @value{GDBN} can be used to debug programs written in D and compiled with
15652 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15653 specific feature --- dynamic arrays.
15658 @cindex Go (programming language)
15659 @value{GDBN} can be used to debug programs written in Go and compiled with
15660 @file{gccgo} or @file{6g} compilers.
15662 Here is a summary of the Go-specific features and restrictions:
15665 @cindex current Go package
15666 @item The current Go package
15667 The name of the current package does not need to be specified when
15668 specifying global variables and functions.
15670 For example, given the program:
15674 var myglob = "Shall we?"
15680 When stopped inside @code{main} either of these work:
15684 (gdb) p main.myglob
15687 @cindex builtin Go types
15688 @item Builtin Go types
15689 The @code{string} type is recognized by @value{GDBN} and is printed
15692 @cindex builtin Go functions
15693 @item Builtin Go functions
15694 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15695 function and handles it internally.
15697 @cindex restrictions on Go expressions
15698 @item Restrictions on Go expressions
15699 All Go operators are supported except @code{&^}.
15700 The Go @code{_} ``blank identifier'' is not supported.
15701 Automatic dereferencing of pointers is not supported.
15705 @subsection Objective-C
15707 @cindex Objective-C
15708 This section provides information about some commands and command
15709 options that are useful for debugging Objective-C code. See also
15710 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15711 few more commands specific to Objective-C support.
15714 * Method Names in Commands::
15715 * The Print Command with Objective-C::
15718 @node Method Names in Commands
15719 @subsubsection Method Names in Commands
15721 The following commands have been extended to accept Objective-C method
15722 names as line specifications:
15724 @kindex clear@r{, and Objective-C}
15725 @kindex break@r{, and Objective-C}
15726 @kindex info line@r{, and Objective-C}
15727 @kindex jump@r{, and Objective-C}
15728 @kindex list@r{, and Objective-C}
15732 @item @code{info line}
15737 A fully qualified Objective-C method name is specified as
15740 -[@var{Class} @var{methodName}]
15743 where the minus sign is used to indicate an instance method and a
15744 plus sign (not shown) is used to indicate a class method. The class
15745 name @var{Class} and method name @var{methodName} are enclosed in
15746 brackets, similar to the way messages are specified in Objective-C
15747 source code. For example, to set a breakpoint at the @code{create}
15748 instance method of class @code{Fruit} in the program currently being
15752 break -[Fruit create]
15755 To list ten program lines around the @code{initialize} class method,
15759 list +[NSText initialize]
15762 In the current version of @value{GDBN}, the plus or minus sign is
15763 required. In future versions of @value{GDBN}, the plus or minus
15764 sign will be optional, but you can use it to narrow the search. It
15765 is also possible to specify just a method name:
15771 You must specify the complete method name, including any colons. If
15772 your program's source files contain more than one @code{create} method,
15773 you'll be presented with a numbered list of classes that implement that
15774 method. Indicate your choice by number, or type @samp{0} to exit if
15777 As another example, to clear a breakpoint established at the
15778 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15781 clear -[NSWindow makeKeyAndOrderFront:]
15784 @node The Print Command with Objective-C
15785 @subsubsection The Print Command With Objective-C
15786 @cindex Objective-C, print objects
15787 @kindex print-object
15788 @kindex po @r{(@code{print-object})}
15790 The print command has also been extended to accept methods. For example:
15793 print -[@var{object} hash]
15796 @cindex print an Objective-C object description
15797 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15799 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15800 and print the result. Also, an additional command has been added,
15801 @code{print-object} or @code{po} for short, which is meant to print
15802 the description of an object. However, this command may only work
15803 with certain Objective-C libraries that have a particular hook
15804 function, @code{_NSPrintForDebugger}, defined.
15807 @subsection OpenCL C
15810 This section provides information about @value{GDBN}s OpenCL C support.
15813 * OpenCL C Datatypes::
15814 * OpenCL C Expressions::
15815 * OpenCL C Operators::
15818 @node OpenCL C Datatypes
15819 @subsubsection OpenCL C Datatypes
15821 @cindex OpenCL C Datatypes
15822 @value{GDBN} supports the builtin scalar and vector datatypes specified
15823 by OpenCL 1.1. In addition the half- and double-precision floating point
15824 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15825 extensions are also known to @value{GDBN}.
15827 @node OpenCL C Expressions
15828 @subsubsection OpenCL C Expressions
15830 @cindex OpenCL C Expressions
15831 @value{GDBN} supports accesses to vector components including the access as
15832 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15833 supported by @value{GDBN} can be used as well.
15835 @node OpenCL C Operators
15836 @subsubsection OpenCL C Operators
15838 @cindex OpenCL C Operators
15839 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15843 @subsection Fortran
15844 @cindex Fortran-specific support in @value{GDBN}
15846 @value{GDBN} can be used to debug programs written in Fortran, but it
15847 currently supports only the features of Fortran 77 language.
15849 @cindex trailing underscore, in Fortran symbols
15850 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15851 among them) append an underscore to the names of variables and
15852 functions. When you debug programs compiled by those compilers, you
15853 will need to refer to variables and functions with a trailing
15857 * Fortran Operators:: Fortran operators and expressions
15858 * Fortran Defaults:: Default settings for Fortran
15859 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15862 @node Fortran Operators
15863 @subsubsection Fortran Operators and Expressions
15865 @cindex Fortran operators and expressions
15867 Operators must be defined on values of specific types. For instance,
15868 @code{+} is defined on numbers, but not on characters or other non-
15869 arithmetic types. Operators are often defined on groups of types.
15873 The exponentiation operator. It raises the first operand to the power
15877 The range operator. Normally used in the form of array(low:high) to
15878 represent a section of array.
15881 The access component operator. Normally used to access elements in derived
15882 types. Also suitable for unions. As unions aren't part of regular Fortran,
15883 this can only happen when accessing a register that uses a gdbarch-defined
15887 @node Fortran Defaults
15888 @subsubsection Fortran Defaults
15890 @cindex Fortran Defaults
15892 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15893 default uses case-insensitive matches for Fortran symbols. You can
15894 change that with the @samp{set case-insensitive} command, see
15895 @ref{Symbols}, for the details.
15897 @node Special Fortran Commands
15898 @subsubsection Special Fortran Commands
15900 @cindex Special Fortran commands
15902 @value{GDBN} has some commands to support Fortran-specific features,
15903 such as displaying common blocks.
15906 @cindex @code{COMMON} blocks, Fortran
15907 @kindex info common
15908 @item info common @r{[}@var{common-name}@r{]}
15909 This command prints the values contained in the Fortran @code{COMMON}
15910 block whose name is @var{common-name}. With no argument, the names of
15911 all @code{COMMON} blocks visible at the current program location are
15918 @cindex Pascal support in @value{GDBN}, limitations
15919 Debugging Pascal programs which use sets, subranges, file variables, or
15920 nested functions does not currently work. @value{GDBN} does not support
15921 entering expressions, printing values, or similar features using Pascal
15924 The Pascal-specific command @code{set print pascal_static-members}
15925 controls whether static members of Pascal objects are displayed.
15926 @xref{Print Settings, pascal_static-members}.
15931 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15932 Programming Language}. Type- and value-printing, and expression
15933 parsing, are reasonably complete. However, there are a few
15934 peculiarities and holes to be aware of.
15938 Linespecs (@pxref{Specify Location}) are never relative to the current
15939 crate. Instead, they act as if there were a global namespace of
15940 crates, somewhat similar to the way @code{extern crate} behaves.
15942 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15943 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15944 to set a breakpoint in a function named @samp{f} in a crate named
15947 As a consequence of this approach, linespecs also cannot refer to
15948 items using @samp{self::} or @samp{super::}.
15951 Because @value{GDBN} implements Rust name-lookup semantics in
15952 expressions, it will sometimes prepend the current crate to a name.
15953 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15954 @samp{K}, then @code{print ::x::y} will try to find the symbol
15957 However, since it is useful to be able to refer to other crates when
15958 debugging, @value{GDBN} provides the @code{extern} extension to
15959 circumvent this. To use the extension, just put @code{extern} before
15960 a path expression to refer to the otherwise unavailable ``global''
15963 In the above example, if you wanted to refer to the symbol @samp{y} in
15964 the crate @samp{x}, you would use @code{print extern x::y}.
15967 The Rust expression evaluator does not support ``statement-like''
15968 expressions such as @code{if} or @code{match}, or lambda expressions.
15971 Tuple expressions are not implemented.
15974 The Rust expression evaluator does not currently implement the
15975 @code{Drop} trait. Objects that may be created by the evaluator will
15976 never be destroyed.
15979 @value{GDBN} does not implement type inference for generics. In order
15980 to call generic functions or otherwise refer to generic items, you
15981 will have to specify the type parameters manually.
15984 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15985 cases this does not cause any problems. However, in an expression
15986 context, completing a generic function name will give syntactically
15987 invalid results. This happens because Rust requires the @samp{::}
15988 operator between the function name and its generic arguments. For
15989 example, @value{GDBN} might provide a completion like
15990 @code{crate::f<u32>}, where the parser would require
15991 @code{crate::f::<u32>}.
15994 As of this writing, the Rust compiler (version 1.8) has a few holes in
15995 the debugging information it generates. These holes prevent certain
15996 features from being implemented by @value{GDBN}:
16000 Method calls cannot be made via traits.
16003 Operator overloading is not implemented.
16006 When debugging in a monomorphized function, you cannot use the generic
16010 The type @code{Self} is not available.
16013 @code{use} statements are not available, so some names may not be
16014 available in the crate.
16019 @subsection Modula-2
16021 @cindex Modula-2, @value{GDBN} support
16023 The extensions made to @value{GDBN} to support Modula-2 only support
16024 output from the @sc{gnu} Modula-2 compiler (which is currently being
16025 developed). Other Modula-2 compilers are not currently supported, and
16026 attempting to debug executables produced by them is most likely
16027 to give an error as @value{GDBN} reads in the executable's symbol
16030 @cindex expressions in Modula-2
16032 * M2 Operators:: Built-in operators
16033 * Built-In Func/Proc:: Built-in functions and procedures
16034 * M2 Constants:: Modula-2 constants
16035 * M2 Types:: Modula-2 types
16036 * M2 Defaults:: Default settings for Modula-2
16037 * Deviations:: Deviations from standard Modula-2
16038 * M2 Checks:: Modula-2 type and range checks
16039 * M2 Scope:: The scope operators @code{::} and @code{.}
16040 * GDB/M2:: @value{GDBN} and Modula-2
16044 @subsubsection Operators
16045 @cindex Modula-2 operators
16047 Operators must be defined on values of specific types. For instance,
16048 @code{+} is defined on numbers, but not on structures. Operators are
16049 often defined on groups of types. For the purposes of Modula-2, the
16050 following definitions hold:
16055 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16059 @emph{Character types} consist of @code{CHAR} and its subranges.
16062 @emph{Floating-point types} consist of @code{REAL}.
16065 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16069 @emph{Scalar types} consist of all of the above.
16072 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16075 @emph{Boolean types} consist of @code{BOOLEAN}.
16079 The following operators are supported, and appear in order of
16080 increasing precedence:
16084 Function argument or array index separator.
16087 Assignment. The value of @var{var} @code{:=} @var{value} is
16091 Less than, greater than on integral, floating-point, or enumerated
16095 Less than or equal to, greater than or equal to
16096 on integral, floating-point and enumerated types, or set inclusion on
16097 set types. Same precedence as @code{<}.
16099 @item =@r{, }<>@r{, }#
16100 Equality and two ways of expressing inequality, valid on scalar types.
16101 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16102 available for inequality, since @code{#} conflicts with the script
16106 Set membership. Defined on set types and the types of their members.
16107 Same precedence as @code{<}.
16110 Boolean disjunction. Defined on boolean types.
16113 Boolean conjunction. Defined on boolean types.
16116 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16119 Addition and subtraction on integral and floating-point types, or union
16120 and difference on set types.
16123 Multiplication on integral and floating-point types, or set intersection
16127 Division on floating-point types, or symmetric set difference on set
16128 types. Same precedence as @code{*}.
16131 Integer division and remainder. Defined on integral types. Same
16132 precedence as @code{*}.
16135 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16138 Pointer dereferencing. Defined on pointer types.
16141 Boolean negation. Defined on boolean types. Same precedence as
16145 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16146 precedence as @code{^}.
16149 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16152 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16156 @value{GDBN} and Modula-2 scope operators.
16160 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16161 treats the use of the operator @code{IN}, or the use of operators
16162 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16163 @code{<=}, and @code{>=} on sets as an error.
16167 @node Built-In Func/Proc
16168 @subsubsection Built-in Functions and Procedures
16169 @cindex Modula-2 built-ins
16171 Modula-2 also makes available several built-in procedures and functions.
16172 In describing these, the following metavariables are used:
16177 represents an @code{ARRAY} variable.
16180 represents a @code{CHAR} constant or variable.
16183 represents a variable or constant of integral type.
16186 represents an identifier that belongs to a set. Generally used in the
16187 same function with the metavariable @var{s}. The type of @var{s} should
16188 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16191 represents a variable or constant of integral or floating-point type.
16194 represents a variable or constant of floating-point type.
16200 represents a variable.
16203 represents a variable or constant of one of many types. See the
16204 explanation of the function for details.
16207 All Modula-2 built-in procedures also return a result, described below.
16211 Returns the absolute value of @var{n}.
16214 If @var{c} is a lower case letter, it returns its upper case
16215 equivalent, otherwise it returns its argument.
16218 Returns the character whose ordinal value is @var{i}.
16221 Decrements the value in the variable @var{v} by one. Returns the new value.
16223 @item DEC(@var{v},@var{i})
16224 Decrements the value in the variable @var{v} by @var{i}. Returns the
16227 @item EXCL(@var{m},@var{s})
16228 Removes the element @var{m} from the set @var{s}. Returns the new
16231 @item FLOAT(@var{i})
16232 Returns the floating point equivalent of the integer @var{i}.
16234 @item HIGH(@var{a})
16235 Returns the index of the last member of @var{a}.
16238 Increments the value in the variable @var{v} by one. Returns the new value.
16240 @item INC(@var{v},@var{i})
16241 Increments the value in the variable @var{v} by @var{i}. Returns the
16244 @item INCL(@var{m},@var{s})
16245 Adds the element @var{m} to the set @var{s} if it is not already
16246 there. Returns the new set.
16249 Returns the maximum value of the type @var{t}.
16252 Returns the minimum value of the type @var{t}.
16255 Returns boolean TRUE if @var{i} is an odd number.
16258 Returns the ordinal value of its argument. For example, the ordinal
16259 value of a character is its @sc{ascii} value (on machines supporting
16260 the @sc{ascii} character set). The argument @var{x} must be of an
16261 ordered type, which include integral, character and enumerated types.
16263 @item SIZE(@var{x})
16264 Returns the size of its argument. The argument @var{x} can be a
16265 variable or a type.
16267 @item TRUNC(@var{r})
16268 Returns the integral part of @var{r}.
16270 @item TSIZE(@var{x})
16271 Returns the size of its argument. The argument @var{x} can be a
16272 variable or a type.
16274 @item VAL(@var{t},@var{i})
16275 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16279 @emph{Warning:} Sets and their operations are not yet supported, so
16280 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16284 @cindex Modula-2 constants
16286 @subsubsection Constants
16288 @value{GDBN} allows you to express the constants of Modula-2 in the following
16294 Integer constants are simply a sequence of digits. When used in an
16295 expression, a constant is interpreted to be type-compatible with the
16296 rest of the expression. Hexadecimal integers are specified by a
16297 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16300 Floating point constants appear as a sequence of digits, followed by a
16301 decimal point and another sequence of digits. An optional exponent can
16302 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16303 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16304 digits of the floating point constant must be valid decimal (base 10)
16308 Character constants consist of a single character enclosed by a pair of
16309 like quotes, either single (@code{'}) or double (@code{"}). They may
16310 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16311 followed by a @samp{C}.
16314 String constants consist of a sequence of characters enclosed by a
16315 pair of like quotes, either single (@code{'}) or double (@code{"}).
16316 Escape sequences in the style of C are also allowed. @xref{C
16317 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16321 Enumerated constants consist of an enumerated identifier.
16324 Boolean constants consist of the identifiers @code{TRUE} and
16328 Pointer constants consist of integral values only.
16331 Set constants are not yet supported.
16335 @subsubsection Modula-2 Types
16336 @cindex Modula-2 types
16338 Currently @value{GDBN} can print the following data types in Modula-2
16339 syntax: array types, record types, set types, pointer types, procedure
16340 types, enumerated types, subrange types and base types. You can also
16341 print the contents of variables declared using these type.
16342 This section gives a number of simple source code examples together with
16343 sample @value{GDBN} sessions.
16345 The first example contains the following section of code:
16354 and you can request @value{GDBN} to interrogate the type and value of
16355 @code{r} and @code{s}.
16358 (@value{GDBP}) print s
16360 (@value{GDBP}) ptype s
16362 (@value{GDBP}) print r
16364 (@value{GDBP}) ptype r
16369 Likewise if your source code declares @code{s} as:
16373 s: SET ['A'..'Z'] ;
16377 then you may query the type of @code{s} by:
16380 (@value{GDBP}) ptype s
16381 type = SET ['A'..'Z']
16385 Note that at present you cannot interactively manipulate set
16386 expressions using the debugger.
16388 The following example shows how you might declare an array in Modula-2
16389 and how you can interact with @value{GDBN} to print its type and contents:
16393 s: ARRAY [-10..10] OF CHAR ;
16397 (@value{GDBP}) ptype s
16398 ARRAY [-10..10] OF CHAR
16401 Note that the array handling is not yet complete and although the type
16402 is printed correctly, expression handling still assumes that all
16403 arrays have a lower bound of zero and not @code{-10} as in the example
16406 Here are some more type related Modula-2 examples:
16410 colour = (blue, red, yellow, green) ;
16411 t = [blue..yellow] ;
16419 The @value{GDBN} interaction shows how you can query the data type
16420 and value of a variable.
16423 (@value{GDBP}) print s
16425 (@value{GDBP}) ptype t
16426 type = [blue..yellow]
16430 In this example a Modula-2 array is declared and its contents
16431 displayed. Observe that the contents are written in the same way as
16432 their @code{C} counterparts.
16436 s: ARRAY [1..5] OF CARDINAL ;
16442 (@value{GDBP}) print s
16443 $1 = @{1, 0, 0, 0, 0@}
16444 (@value{GDBP}) ptype s
16445 type = ARRAY [1..5] OF CARDINAL
16448 The Modula-2 language interface to @value{GDBN} also understands
16449 pointer types as shown in this example:
16453 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16460 and you can request that @value{GDBN} describes the type of @code{s}.
16463 (@value{GDBP}) ptype s
16464 type = POINTER TO ARRAY [1..5] OF CARDINAL
16467 @value{GDBN} handles compound types as we can see in this example.
16468 Here we combine array types, record types, pointer types and subrange
16479 myarray = ARRAY myrange OF CARDINAL ;
16480 myrange = [-2..2] ;
16482 s: POINTER TO ARRAY myrange OF foo ;
16486 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16490 (@value{GDBP}) ptype s
16491 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16494 f3 : ARRAY [-2..2] OF CARDINAL;
16499 @subsubsection Modula-2 Defaults
16500 @cindex Modula-2 defaults
16502 If type and range checking are set automatically by @value{GDBN}, they
16503 both default to @code{on} whenever the working language changes to
16504 Modula-2. This happens regardless of whether you or @value{GDBN}
16505 selected the working language.
16507 If you allow @value{GDBN} to set the language automatically, then entering
16508 code compiled from a file whose name ends with @file{.mod} sets the
16509 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16510 Infer the Source Language}, for further details.
16513 @subsubsection Deviations from Standard Modula-2
16514 @cindex Modula-2, deviations from
16516 A few changes have been made to make Modula-2 programs easier to debug.
16517 This is done primarily via loosening its type strictness:
16521 Unlike in standard Modula-2, pointer constants can be formed by
16522 integers. This allows you to modify pointer variables during
16523 debugging. (In standard Modula-2, the actual address contained in a
16524 pointer variable is hidden from you; it can only be modified
16525 through direct assignment to another pointer variable or expression that
16526 returned a pointer.)
16529 C escape sequences can be used in strings and characters to represent
16530 non-printable characters. @value{GDBN} prints out strings with these
16531 escape sequences embedded. Single non-printable characters are
16532 printed using the @samp{CHR(@var{nnn})} format.
16535 The assignment operator (@code{:=}) returns the value of its right-hand
16539 All built-in procedures both modify @emph{and} return their argument.
16543 @subsubsection Modula-2 Type and Range Checks
16544 @cindex Modula-2 checks
16547 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16550 @c FIXME remove warning when type/range checks added
16552 @value{GDBN} considers two Modula-2 variables type equivalent if:
16556 They are of types that have been declared equivalent via a @code{TYPE
16557 @var{t1} = @var{t2}} statement
16560 They have been declared on the same line. (Note: This is true of the
16561 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16564 As long as type checking is enabled, any attempt to combine variables
16565 whose types are not equivalent is an error.
16567 Range checking is done on all mathematical operations, assignment, array
16568 index bounds, and all built-in functions and procedures.
16571 @subsubsection The Scope Operators @code{::} and @code{.}
16573 @cindex @code{.}, Modula-2 scope operator
16574 @cindex colon, doubled as scope operator
16576 @vindex colon-colon@r{, in Modula-2}
16577 @c Info cannot handle :: but TeX can.
16580 @vindex ::@r{, in Modula-2}
16583 There are a few subtle differences between the Modula-2 scope operator
16584 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16589 @var{module} . @var{id}
16590 @var{scope} :: @var{id}
16594 where @var{scope} is the name of a module or a procedure,
16595 @var{module} the name of a module, and @var{id} is any declared
16596 identifier within your program, except another module.
16598 Using the @code{::} operator makes @value{GDBN} search the scope
16599 specified by @var{scope} for the identifier @var{id}. If it is not
16600 found in the specified scope, then @value{GDBN} searches all scopes
16601 enclosing the one specified by @var{scope}.
16603 Using the @code{.} operator makes @value{GDBN} search the current scope for
16604 the identifier specified by @var{id} that was imported from the
16605 definition module specified by @var{module}. With this operator, it is
16606 an error if the identifier @var{id} was not imported from definition
16607 module @var{module}, or if @var{id} is not an identifier in
16611 @subsubsection @value{GDBN} and Modula-2
16613 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16614 Five subcommands of @code{set print} and @code{show print} apply
16615 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16616 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16617 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16618 analogue in Modula-2.
16620 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16621 with any language, is not useful with Modula-2. Its
16622 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16623 created in Modula-2 as they can in C or C@t{++}. However, because an
16624 address can be specified by an integral constant, the construct
16625 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16627 @cindex @code{#} in Modula-2
16628 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16629 interpreted as the beginning of a comment. Use @code{<>} instead.
16635 The extensions made to @value{GDBN} for Ada only support
16636 output from the @sc{gnu} Ada (GNAT) compiler.
16637 Other Ada compilers are not currently supported, and
16638 attempting to debug executables produced by them is most likely
16642 @cindex expressions in Ada
16644 * Ada Mode Intro:: General remarks on the Ada syntax
16645 and semantics supported by Ada mode
16647 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16648 * Additions to Ada:: Extensions of the Ada expression syntax.
16649 * Overloading support for Ada:: Support for expressions involving overloaded
16651 * Stopping Before Main Program:: Debugging the program during elaboration.
16652 * Ada Exceptions:: Ada Exceptions
16653 * Ada Tasks:: Listing and setting breakpoints in tasks.
16654 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16655 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16657 * Ada Settings:: New settable GDB parameters for Ada.
16658 * Ada Glitches:: Known peculiarities of Ada mode.
16661 @node Ada Mode Intro
16662 @subsubsection Introduction
16663 @cindex Ada mode, general
16665 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16666 syntax, with some extensions.
16667 The philosophy behind the design of this subset is
16671 That @value{GDBN} should provide basic literals and access to operations for
16672 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16673 leaving more sophisticated computations to subprograms written into the
16674 program (which therefore may be called from @value{GDBN}).
16677 That type safety and strict adherence to Ada language restrictions
16678 are not particularly important to the @value{GDBN} user.
16681 That brevity is important to the @value{GDBN} user.
16684 Thus, for brevity, the debugger acts as if all names declared in
16685 user-written packages are directly visible, even if they are not visible
16686 according to Ada rules, thus making it unnecessary to fully qualify most
16687 names with their packages, regardless of context. Where this causes
16688 ambiguity, @value{GDBN} asks the user's intent.
16690 The debugger will start in Ada mode if it detects an Ada main program.
16691 As for other languages, it will enter Ada mode when stopped in a program that
16692 was translated from an Ada source file.
16694 While in Ada mode, you may use `@t{--}' for comments. This is useful
16695 mostly for documenting command files. The standard @value{GDBN} comment
16696 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16697 middle (to allow based literals).
16699 @node Omissions from Ada
16700 @subsubsection Omissions from Ada
16701 @cindex Ada, omissions from
16703 Here are the notable omissions from the subset:
16707 Only a subset of the attributes are supported:
16711 @t{'First}, @t{'Last}, and @t{'Length}
16712 on array objects (not on types and subtypes).
16715 @t{'Min} and @t{'Max}.
16718 @t{'Pos} and @t{'Val}.
16724 @t{'Range} on array objects (not subtypes), but only as the right
16725 operand of the membership (@code{in}) operator.
16728 @t{'Access}, @t{'Unchecked_Access}, and
16729 @t{'Unrestricted_Access} (a GNAT extension).
16737 @code{Characters.Latin_1} are not available and
16738 concatenation is not implemented. Thus, escape characters in strings are
16739 not currently available.
16742 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16743 equality of representations. They will generally work correctly
16744 for strings and arrays whose elements have integer or enumeration types.
16745 They may not work correctly for arrays whose element
16746 types have user-defined equality, for arrays of real values
16747 (in particular, IEEE-conformant floating point, because of negative
16748 zeroes and NaNs), and for arrays whose elements contain unused bits with
16749 indeterminate values.
16752 The other component-by-component array operations (@code{and}, @code{or},
16753 @code{xor}, @code{not}, and relational tests other than equality)
16754 are not implemented.
16757 @cindex array aggregates (Ada)
16758 @cindex record aggregates (Ada)
16759 @cindex aggregates (Ada)
16760 There is limited support for array and record aggregates. They are
16761 permitted only on the right sides of assignments, as in these examples:
16764 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16765 (@value{GDBP}) set An_Array := (1, others => 0)
16766 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16767 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16768 (@value{GDBP}) set A_Record := (1, "Peter", True);
16769 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16773 discriminant's value by assigning an aggregate has an
16774 undefined effect if that discriminant is used within the record.
16775 However, you can first modify discriminants by directly assigning to
16776 them (which normally would not be allowed in Ada), and then performing an
16777 aggregate assignment. For example, given a variable @code{A_Rec}
16778 declared to have a type such as:
16781 type Rec (Len : Small_Integer := 0) is record
16783 Vals : IntArray (1 .. Len);
16787 you can assign a value with a different size of @code{Vals} with two
16791 (@value{GDBP}) set A_Rec.Len := 4
16792 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16795 As this example also illustrates, @value{GDBN} is very loose about the usual
16796 rules concerning aggregates. You may leave out some of the
16797 components of an array or record aggregate (such as the @code{Len}
16798 component in the assignment to @code{A_Rec} above); they will retain their
16799 original values upon assignment. You may freely use dynamic values as
16800 indices in component associations. You may even use overlapping or
16801 redundant component associations, although which component values are
16802 assigned in such cases is not defined.
16805 Calls to dispatching subprograms are not implemented.
16808 The overloading algorithm is much more limited (i.e., less selective)
16809 than that of real Ada. It makes only limited use of the context in
16810 which a subexpression appears to resolve its meaning, and it is much
16811 looser in its rules for allowing type matches. As a result, some
16812 function calls will be ambiguous, and the user will be asked to choose
16813 the proper resolution.
16816 The @code{new} operator is not implemented.
16819 Entry calls are not implemented.
16822 Aside from printing, arithmetic operations on the native VAX floating-point
16823 formats are not supported.
16826 It is not possible to slice a packed array.
16829 The names @code{True} and @code{False}, when not part of a qualified name,
16830 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16832 Should your program
16833 redefine these names in a package or procedure (at best a dubious practice),
16834 you will have to use fully qualified names to access their new definitions.
16837 @node Additions to Ada
16838 @subsubsection Additions to Ada
16839 @cindex Ada, deviations from
16841 As it does for other languages, @value{GDBN} makes certain generic
16842 extensions to Ada (@pxref{Expressions}):
16846 If the expression @var{E} is a variable residing in memory (typically
16847 a local variable or array element) and @var{N} is a positive integer,
16848 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16849 @var{N}-1 adjacent variables following it in memory as an array. In
16850 Ada, this operator is generally not necessary, since its prime use is
16851 in displaying parts of an array, and slicing will usually do this in
16852 Ada. However, there are occasional uses when debugging programs in
16853 which certain debugging information has been optimized away.
16856 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16857 appears in function or file @var{B}.'' When @var{B} is a file name,
16858 you must typically surround it in single quotes.
16861 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16862 @var{type} that appears at address @var{addr}.''
16865 A name starting with @samp{$} is a convenience variable
16866 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16869 In addition, @value{GDBN} provides a few other shortcuts and outright
16870 additions specific to Ada:
16874 The assignment statement is allowed as an expression, returning
16875 its right-hand operand as its value. Thus, you may enter
16878 (@value{GDBP}) set x := y + 3
16879 (@value{GDBP}) print A(tmp := y + 1)
16883 The semicolon is allowed as an ``operator,'' returning as its value
16884 the value of its right-hand operand.
16885 This allows, for example,
16886 complex conditional breaks:
16889 (@value{GDBP}) break f
16890 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16894 Rather than use catenation and symbolic character names to introduce special
16895 characters into strings, one may instead use a special bracket notation,
16896 which is also used to print strings. A sequence of characters of the form
16897 @samp{["@var{XX}"]} within a string or character literal denotes the
16898 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16899 sequence of characters @samp{["""]} also denotes a single quotation mark
16900 in strings. For example,
16902 "One line.["0a"]Next line.["0a"]"
16905 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16909 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16910 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16914 (@value{GDBP}) print 'max(x, y)
16918 When printing arrays, @value{GDBN} uses positional notation when the
16919 array has a lower bound of 1, and uses a modified named notation otherwise.
16920 For example, a one-dimensional array of three integers with a lower bound
16921 of 3 might print as
16928 That is, in contrast to valid Ada, only the first component has a @code{=>}
16932 You may abbreviate attributes in expressions with any unique,
16933 multi-character subsequence of
16934 their names (an exact match gets preference).
16935 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16936 in place of @t{a'length}.
16939 @cindex quoting Ada internal identifiers
16940 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16941 to lower case. The GNAT compiler uses upper-case characters for
16942 some of its internal identifiers, which are normally of no interest to users.
16943 For the rare occasions when you actually have to look at them,
16944 enclose them in angle brackets to avoid the lower-case mapping.
16947 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16951 Printing an object of class-wide type or dereferencing an
16952 access-to-class-wide value will display all the components of the object's
16953 specific type (as indicated by its run-time tag). Likewise, component
16954 selection on such a value will operate on the specific type of the
16959 @node Overloading support for Ada
16960 @subsubsection Overloading support for Ada
16961 @cindex overloading, Ada
16963 The debugger supports limited overloading. Given a subprogram call in which
16964 the function symbol has multiple definitions, it will use the number of
16965 actual parameters and some information about their types to attempt to narrow
16966 the set of definitions. It also makes very limited use of context, preferring
16967 procedures to functions in the context of the @code{call} command, and
16968 functions to procedures elsewhere.
16970 If, after narrowing, the set of matching definitions still contains more than
16971 one definition, @value{GDBN} will display a menu to query which one it should
16975 (@value{GDBP}) print f(1)
16976 Multiple matches for f
16978 [1] foo.f (integer) return boolean at foo.adb:23
16979 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16983 In this case, just select one menu entry either to cancel expression evaluation
16984 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16985 instance (type the corresponding number and press @key{RET}).
16987 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16992 @kindex set ada print-signatures
16993 @item set ada print-signatures
16994 Control whether parameter types and return types are displayed in overloads
16995 selection menus. It is @code{on} by default.
16996 @xref{Overloading support for Ada}.
16998 @kindex show ada print-signatures
16999 @item show ada print-signatures
17000 Show the current setting for displaying parameter types and return types in
17001 overloads selection menu.
17002 @xref{Overloading support for Ada}.
17006 @node Stopping Before Main Program
17007 @subsubsection Stopping at the Very Beginning
17009 @cindex breakpointing Ada elaboration code
17010 It is sometimes necessary to debug the program during elaboration, and
17011 before reaching the main procedure.
17012 As defined in the Ada Reference
17013 Manual, the elaboration code is invoked from a procedure called
17014 @code{adainit}. To run your program up to the beginning of
17015 elaboration, simply use the following two commands:
17016 @code{tbreak adainit} and @code{run}.
17018 @node Ada Exceptions
17019 @subsubsection Ada Exceptions
17021 A command is provided to list all Ada exceptions:
17024 @kindex info exceptions
17025 @item info exceptions
17026 @itemx info exceptions @var{regexp}
17027 The @code{info exceptions} command allows you to list all Ada exceptions
17028 defined within the program being debugged, as well as their addresses.
17029 With a regular expression, @var{regexp}, as argument, only those exceptions
17030 whose names match @var{regexp} are listed.
17033 Below is a small example, showing how the command can be used, first
17034 without argument, and next with a regular expression passed as an
17038 (@value{GDBP}) info exceptions
17039 All defined Ada exceptions:
17040 constraint_error: 0x613da0
17041 program_error: 0x613d20
17042 storage_error: 0x613ce0
17043 tasking_error: 0x613ca0
17044 const.aint_global_e: 0x613b00
17045 (@value{GDBP}) info exceptions const.aint
17046 All Ada exceptions matching regular expression "const.aint":
17047 constraint_error: 0x613da0
17048 const.aint_global_e: 0x613b00
17051 It is also possible to ask @value{GDBN} to stop your program's execution
17052 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17055 @subsubsection Extensions for Ada Tasks
17056 @cindex Ada, tasking
17058 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17059 @value{GDBN} provides the following task-related commands:
17064 This command shows a list of current Ada tasks, as in the following example:
17071 (@value{GDBP}) info tasks
17072 ID TID P-ID Pri State Name
17073 1 8088000 0 15 Child Activation Wait main_task
17074 2 80a4000 1 15 Accept Statement b
17075 3 809a800 1 15 Child Activation Wait a
17076 * 4 80ae800 3 15 Runnable c
17081 In this listing, the asterisk before the last task indicates it to be the
17082 task currently being inspected.
17086 Represents @value{GDBN}'s internal task number.
17092 The parent's task ID (@value{GDBN}'s internal task number).
17095 The base priority of the task.
17098 Current state of the task.
17102 The task has been created but has not been activated. It cannot be
17106 The task is not blocked for any reason known to Ada. (It may be waiting
17107 for a mutex, though.) It is conceptually "executing" in normal mode.
17110 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17111 that were waiting on terminate alternatives have been awakened and have
17112 terminated themselves.
17114 @item Child Activation Wait
17115 The task is waiting for created tasks to complete activation.
17117 @item Accept Statement
17118 The task is waiting on an accept or selective wait statement.
17120 @item Waiting on entry call
17121 The task is waiting on an entry call.
17123 @item Async Select Wait
17124 The task is waiting to start the abortable part of an asynchronous
17128 The task is waiting on a select statement with only a delay
17131 @item Child Termination Wait
17132 The task is sleeping having completed a master within itself, and is
17133 waiting for the tasks dependent on that master to become terminated or
17134 waiting on a terminate Phase.
17136 @item Wait Child in Term Alt
17137 The task is sleeping waiting for tasks on terminate alternatives to
17138 finish terminating.
17140 @item Accepting RV with @var{taskno}
17141 The task is accepting a rendez-vous with the task @var{taskno}.
17145 Name of the task in the program.
17149 @kindex info task @var{taskno}
17150 @item info task @var{taskno}
17151 This command shows detailled informations on the specified task, as in
17152 the following example:
17157 (@value{GDBP}) info tasks
17158 ID TID P-ID Pri State Name
17159 1 8077880 0 15 Child Activation Wait main_task
17160 * 2 807c468 1 15 Runnable task_1
17161 (@value{GDBP}) info task 2
17162 Ada Task: 0x807c468
17165 Parent: 1 (main_task)
17171 @kindex task@r{ (Ada)}
17172 @cindex current Ada task ID
17173 This command prints the ID of the current task.
17179 (@value{GDBP}) info tasks
17180 ID TID P-ID Pri State Name
17181 1 8077870 0 15 Child Activation Wait main_task
17182 * 2 807c458 1 15 Runnable t
17183 (@value{GDBP}) task
17184 [Current task is 2]
17187 @item task @var{taskno}
17188 @cindex Ada task switching
17189 This command is like the @code{thread @var{thread-id}}
17190 command (@pxref{Threads}). It switches the context of debugging
17191 from the current task to the given task.
17197 (@value{GDBP}) info tasks
17198 ID TID P-ID Pri State Name
17199 1 8077870 0 15 Child Activation Wait main_task
17200 * 2 807c458 1 15 Runnable t
17201 (@value{GDBP}) task 1
17202 [Switching to task 1]
17203 #0 0x8067726 in pthread_cond_wait ()
17205 #0 0x8067726 in pthread_cond_wait ()
17206 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17207 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17208 #3 0x806153e in system.tasking.stages.activate_tasks ()
17209 #4 0x804aacc in un () at un.adb:5
17212 @item break @var{location} task @var{taskno}
17213 @itemx break @var{location} task @var{taskno} if @dots{}
17214 @cindex breakpoints and tasks, in Ada
17215 @cindex task breakpoints, in Ada
17216 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17217 These commands are like the @code{break @dots{} thread @dots{}}
17218 command (@pxref{Thread Stops}). The
17219 @var{location} argument specifies source lines, as described
17220 in @ref{Specify Location}.
17222 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17223 to specify that you only want @value{GDBN} to stop the program when a
17224 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17225 numeric task identifiers assigned by @value{GDBN}, shown in the first
17226 column of the @samp{info tasks} display.
17228 If you do not specify @samp{task @var{taskno}} when you set a
17229 breakpoint, the breakpoint applies to @emph{all} tasks of your
17232 You can use the @code{task} qualifier on conditional breakpoints as
17233 well; in this case, place @samp{task @var{taskno}} before the
17234 breakpoint condition (before the @code{if}).
17242 (@value{GDBP}) info tasks
17243 ID TID P-ID Pri State Name
17244 1 140022020 0 15 Child Activation Wait main_task
17245 2 140045060 1 15 Accept/Select Wait t2
17246 3 140044840 1 15 Runnable t1
17247 * 4 140056040 1 15 Runnable t3
17248 (@value{GDBP}) b 15 task 2
17249 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17250 (@value{GDBP}) cont
17255 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17257 (@value{GDBP}) info tasks
17258 ID TID P-ID Pri State Name
17259 1 140022020 0 15 Child Activation Wait main_task
17260 * 2 140045060 1 15 Runnable t2
17261 3 140044840 1 15 Runnable t1
17262 4 140056040 1 15 Delay Sleep t3
17266 @node Ada Tasks and Core Files
17267 @subsubsection Tasking Support when Debugging Core Files
17268 @cindex Ada tasking and core file debugging
17270 When inspecting a core file, as opposed to debugging a live program,
17271 tasking support may be limited or even unavailable, depending on
17272 the platform being used.
17273 For instance, on x86-linux, the list of tasks is available, but task
17274 switching is not supported.
17276 On certain platforms, the debugger needs to perform some
17277 memory writes in order to provide Ada tasking support. When inspecting
17278 a core file, this means that the core file must be opened with read-write
17279 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17280 Under these circumstances, you should make a backup copy of the core
17281 file before inspecting it with @value{GDBN}.
17283 @node Ravenscar Profile
17284 @subsubsection Tasking Support when using the Ravenscar Profile
17285 @cindex Ravenscar Profile
17287 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17288 specifically designed for systems with safety-critical real-time
17292 @kindex set ravenscar task-switching on
17293 @cindex task switching with program using Ravenscar Profile
17294 @item set ravenscar task-switching on
17295 Allows task switching when debugging a program that uses the Ravenscar
17296 Profile. This is the default.
17298 @kindex set ravenscar task-switching off
17299 @item set ravenscar task-switching off
17300 Turn off task switching when debugging a program that uses the Ravenscar
17301 Profile. This is mostly intended to disable the code that adds support
17302 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17303 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17304 To be effective, this command should be run before the program is started.
17306 @kindex show ravenscar task-switching
17307 @item show ravenscar task-switching
17308 Show whether it is possible to switch from task to task in a program
17309 using the Ravenscar Profile.
17314 @subsubsection Ada Settings
17315 @cindex Ada settings
17318 @kindex set varsize-limit
17319 @item set varsize-limit @var{size}
17320 Prevent @value{GDBN} from attempting to evaluate objects whose size
17321 is above the given limit (@var{size}) when those sizes are computed
17322 from run-time quantities. This is typically the case when the object
17323 has a variable size, such as an array whose bounds are not known at
17324 compile time for example. Setting @var{size} to @code{unlimited}
17325 removes the size limitation. By default, the limit is about 65KB.
17327 The purpose of having such a limit is to prevent @value{GDBN} from
17328 trying to grab enormous chunks of virtual memory when asked to evaluate
17329 a quantity whose bounds have been corrupted or have not yet been fully
17330 initialized. The limit applies to the results of some subexpressions
17331 as well as to complete expressions. For example, an expression denoting
17332 a simple integer component, such as @code{x.y.z}, may fail if the size of
17333 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17334 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17335 @code{A} is an array variable with non-constant size, will generally
17336 succeed regardless of the bounds on @code{A}, as long as the component
17337 size is less than @var{size}.
17339 @kindex show varsize-limit
17340 @item show varsize-limit
17341 Show the limit on types whose size is determined by run-time quantities.
17345 @subsubsection Known Peculiarities of Ada Mode
17346 @cindex Ada, problems
17348 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17349 we know of several problems with and limitations of Ada mode in
17351 some of which will be fixed with planned future releases of the debugger
17352 and the GNU Ada compiler.
17356 Static constants that the compiler chooses not to materialize as objects in
17357 storage are invisible to the debugger.
17360 Named parameter associations in function argument lists are ignored (the
17361 argument lists are treated as positional).
17364 Many useful library packages are currently invisible to the debugger.
17367 Fixed-point arithmetic, conversions, input, and output is carried out using
17368 floating-point arithmetic, and may give results that only approximate those on
17372 The GNAT compiler never generates the prefix @code{Standard} for any of
17373 the standard symbols defined by the Ada language. @value{GDBN} knows about
17374 this: it will strip the prefix from names when you use it, and will never
17375 look for a name you have so qualified among local symbols, nor match against
17376 symbols in other packages or subprograms. If you have
17377 defined entities anywhere in your program other than parameters and
17378 local variables whose simple names match names in @code{Standard},
17379 GNAT's lack of qualification here can cause confusion. When this happens,
17380 you can usually resolve the confusion
17381 by qualifying the problematic names with package
17382 @code{Standard} explicitly.
17385 Older versions of the compiler sometimes generate erroneous debugging
17386 information, resulting in the debugger incorrectly printing the value
17387 of affected entities. In some cases, the debugger is able to work
17388 around an issue automatically. In other cases, the debugger is able
17389 to work around the issue, but the work-around has to be specifically
17392 @kindex set ada trust-PAD-over-XVS
17393 @kindex show ada trust-PAD-over-XVS
17396 @item set ada trust-PAD-over-XVS on
17397 Configure GDB to strictly follow the GNAT encoding when computing the
17398 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17399 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17400 a complete description of the encoding used by the GNAT compiler).
17401 This is the default.
17403 @item set ada trust-PAD-over-XVS off
17404 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17405 sometimes prints the wrong value for certain entities, changing @code{ada
17406 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17407 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17408 @code{off}, but this incurs a slight performance penalty, so it is
17409 recommended to leave this setting to @code{on} unless necessary.
17413 @cindex GNAT descriptive types
17414 @cindex GNAT encoding
17415 Internally, the debugger also relies on the compiler following a number
17416 of conventions known as the @samp{GNAT Encoding}, all documented in
17417 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17418 how the debugging information should be generated for certain types.
17419 In particular, this convention makes use of @dfn{descriptive types},
17420 which are artificial types generated purely to help the debugger.
17422 These encodings were defined at a time when the debugging information
17423 format used was not powerful enough to describe some of the more complex
17424 types available in Ada. Since DWARF allows us to express nearly all
17425 Ada features, the long-term goal is to slowly replace these descriptive
17426 types by their pure DWARF equivalent. To facilitate that transition,
17427 a new maintenance option is available to force the debugger to ignore
17428 those descriptive types. It allows the user to quickly evaluate how
17429 well @value{GDBN} works without them.
17433 @kindex maint ada set ignore-descriptive-types
17434 @item maintenance ada set ignore-descriptive-types [on|off]
17435 Control whether the debugger should ignore descriptive types.
17436 The default is not to ignore descriptives types (@code{off}).
17438 @kindex maint ada show ignore-descriptive-types
17439 @item maintenance ada show ignore-descriptive-types
17440 Show if descriptive types are ignored by @value{GDBN}.
17444 @node Unsupported Languages
17445 @section Unsupported Languages
17447 @cindex unsupported languages
17448 @cindex minimal language
17449 In addition to the other fully-supported programming languages,
17450 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17451 It does not represent a real programming language, but provides a set
17452 of capabilities close to what the C or assembly languages provide.
17453 This should allow most simple operations to be performed while debugging
17454 an application that uses a language currently not supported by @value{GDBN}.
17456 If the language is set to @code{auto}, @value{GDBN} will automatically
17457 select this language if the current frame corresponds to an unsupported
17461 @chapter Examining the Symbol Table
17463 The commands described in this chapter allow you to inquire about the
17464 symbols (names of variables, functions and types) defined in your
17465 program. This information is inherent in the text of your program and
17466 does not change as your program executes. @value{GDBN} finds it in your
17467 program's symbol table, in the file indicated when you started @value{GDBN}
17468 (@pxref{File Options, ,Choosing Files}), or by one of the
17469 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17471 @cindex symbol names
17472 @cindex names of symbols
17473 @cindex quoting names
17474 @anchor{quoting names}
17475 Occasionally, you may need to refer to symbols that contain unusual
17476 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17477 most frequent case is in referring to static variables in other
17478 source files (@pxref{Variables,,Program Variables}). File names
17479 are recorded in object files as debugging symbols, but @value{GDBN} would
17480 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17481 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17482 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17489 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17492 @cindex case-insensitive symbol names
17493 @cindex case sensitivity in symbol names
17494 @kindex set case-sensitive
17495 @item set case-sensitive on
17496 @itemx set case-sensitive off
17497 @itemx set case-sensitive auto
17498 Normally, when @value{GDBN} looks up symbols, it matches their names
17499 with case sensitivity determined by the current source language.
17500 Occasionally, you may wish to control that. The command @code{set
17501 case-sensitive} lets you do that by specifying @code{on} for
17502 case-sensitive matches or @code{off} for case-insensitive ones. If
17503 you specify @code{auto}, case sensitivity is reset to the default
17504 suitable for the source language. The default is case-sensitive
17505 matches for all languages except for Fortran, for which the default is
17506 case-insensitive matches.
17508 @kindex show case-sensitive
17509 @item show case-sensitive
17510 This command shows the current setting of case sensitivity for symbols
17513 @kindex set print type methods
17514 @item set print type methods
17515 @itemx set print type methods on
17516 @itemx set print type methods off
17517 Normally, when @value{GDBN} prints a class, it displays any methods
17518 declared in that class. You can control this behavior either by
17519 passing the appropriate flag to @code{ptype}, or using @command{set
17520 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17521 display the methods; this is the default. Specifying @code{off} will
17522 cause @value{GDBN} to omit the methods.
17524 @kindex show print type methods
17525 @item show print type methods
17526 This command shows the current setting of method display when printing
17529 @kindex set print type nested-type-limit
17530 @item set print type nested-type-limit @var{limit}
17531 @itemx set print type nested-type-limit unlimited
17532 Set the limit of displayed nested types that the type printer will
17533 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17534 nested definitions. By default, the type printer will not show any nested
17535 types defined in classes.
17537 @kindex show print type nested-type-limit
17538 @item show print type nested-type-limit
17539 This command shows the current display limit of nested types when
17542 @kindex set print type typedefs
17543 @item set print type typedefs
17544 @itemx set print type typedefs on
17545 @itemx set print type typedefs off
17547 Normally, when @value{GDBN} prints a class, it displays any typedefs
17548 defined in that class. You can control this behavior either by
17549 passing the appropriate flag to @code{ptype}, or using @command{set
17550 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17551 display the typedef definitions; this is the default. Specifying
17552 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17553 Note that this controls whether the typedef definition itself is
17554 printed, not whether typedef names are substituted when printing other
17557 @kindex show print type typedefs
17558 @item show print type typedefs
17559 This command shows the current setting of typedef display when
17562 @kindex info address
17563 @cindex address of a symbol
17564 @item info address @var{symbol}
17565 Describe where the data for @var{symbol} is stored. For a register
17566 variable, this says which register it is kept in. For a non-register
17567 local variable, this prints the stack-frame offset at which the variable
17570 Note the contrast with @samp{print &@var{symbol}}, which does not work
17571 at all for a register variable, and for a stack local variable prints
17572 the exact address of the current instantiation of the variable.
17574 @kindex info symbol
17575 @cindex symbol from address
17576 @cindex closest symbol and offset for an address
17577 @item info symbol @var{addr}
17578 Print the name of a symbol which is stored at the address @var{addr}.
17579 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17580 nearest symbol and an offset from it:
17583 (@value{GDBP}) info symbol 0x54320
17584 _initialize_vx + 396 in section .text
17588 This is the opposite of the @code{info address} command. You can use
17589 it to find out the name of a variable or a function given its address.
17591 For dynamically linked executables, the name of executable or shared
17592 library containing the symbol is also printed:
17595 (@value{GDBP}) info symbol 0x400225
17596 _start + 5 in section .text of /tmp/a.out
17597 (@value{GDBP}) info symbol 0x2aaaac2811cf
17598 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17603 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17604 Demangle @var{name}.
17605 If @var{language} is provided it is the name of the language to demangle
17606 @var{name} in. Otherwise @var{name} is demangled in the current language.
17608 The @samp{--} option specifies the end of options,
17609 and is useful when @var{name} begins with a dash.
17611 The parameter @code{demangle-style} specifies how to interpret the kind
17612 of mangling used. @xref{Print Settings}.
17615 @item whatis[/@var{flags}] [@var{arg}]
17616 Print the data type of @var{arg}, which can be either an expression
17617 or a name of a data type. With no argument, print the data type of
17618 @code{$}, the last value in the value history.
17620 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17621 is not actually evaluated, and any side-effecting operations (such as
17622 assignments or function calls) inside it do not take place.
17624 If @var{arg} is a variable or an expression, @code{whatis} prints its
17625 literal type as it is used in the source code. If the type was
17626 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17627 the data type underlying the @code{typedef}. If the type of the
17628 variable or the expression is a compound data type, such as
17629 @code{struct} or @code{class}, @code{whatis} never prints their
17630 fields or methods. It just prints the @code{struct}/@code{class}
17631 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17632 such a compound data type, use @code{ptype}.
17634 If @var{arg} is a type name that was defined using @code{typedef},
17635 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17636 Unrolling means that @code{whatis} will show the underlying type used
17637 in the @code{typedef} declaration of @var{arg}. However, if that
17638 underlying type is also a @code{typedef}, @code{whatis} will not
17641 For C code, the type names may also have the form @samp{class
17642 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17643 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17645 @var{flags} can be used to modify how the type is displayed.
17646 Available flags are:
17650 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17651 parameters and typedefs defined in a class when printing the class'
17652 members. The @code{/r} flag disables this.
17655 Do not print methods defined in the class.
17658 Print methods defined in the class. This is the default, but the flag
17659 exists in case you change the default with @command{set print type methods}.
17662 Do not print typedefs defined in the class. Note that this controls
17663 whether the typedef definition itself is printed, not whether typedef
17664 names are substituted when printing other types.
17667 Print typedefs defined in the class. This is the default, but the flag
17668 exists in case you change the default with @command{set print type typedefs}.
17671 Print the offsets and sizes of fields in a struct, similar to what the
17672 @command{pahole} tool does. This option implies the @code{/tm} flags.
17674 For example, given the following declarations:
17710 Issuing a @kbd{ptype /o struct tuv} command would print:
17713 (@value{GDBP}) ptype /o struct tuv
17714 /* offset | size */ type = struct tuv @{
17715 /* 0 | 4 */ int a1;
17716 /* XXX 4-byte hole */
17717 /* 8 | 8 */ char *a2;
17718 /* 16 | 4 */ int a3;
17720 /* total size (bytes): 24 */
17724 Notice the format of the first column of comments. There, you can
17725 find two parts separated by the @samp{|} character: the @emph{offset},
17726 which indicates where the field is located inside the struct, in
17727 bytes, and the @emph{size} of the field. Another interesting line is
17728 the marker of a @emph{hole} in the struct, indicating that it may be
17729 possible to pack the struct and make it use less space by reorganizing
17732 It is also possible to print offsets inside an union:
17735 (@value{GDBP}) ptype /o union qwe
17736 /* offset | size */ type = union qwe @{
17737 /* 24 */ struct tuv @{
17738 /* 0 | 4 */ int a1;
17739 /* XXX 4-byte hole */
17740 /* 8 | 8 */ char *a2;
17741 /* 16 | 4 */ int a3;
17743 /* total size (bytes): 24 */
17745 /* 40 */ struct xyz @{
17746 /* 0 | 4 */ int f1;
17747 /* 4 | 1 */ char f2;
17748 /* XXX 3-byte hole */
17749 /* 8 | 8 */ void *f3;
17750 /* 16 | 24 */ struct tuv @{
17751 /* 16 | 4 */ int a1;
17752 /* XXX 4-byte hole */
17753 /* 24 | 8 */ char *a2;
17754 /* 32 | 4 */ int a3;
17756 /* total size (bytes): 24 */
17759 /* total size (bytes): 40 */
17762 /* total size (bytes): 40 */
17766 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17767 same space (because we are dealing with an union), the offset is not
17768 printed for them. However, you can still examine the offset of each
17769 of these structures' fields.
17771 Another useful scenario is printing the offsets of a struct containing
17775 (@value{GDBP}) ptype /o struct tyu
17776 /* offset | size */ type = struct tyu @{
17777 /* 0:31 | 4 */ int a1 : 1;
17778 /* 0:28 | 4 */ int a2 : 3;
17779 /* 0: 5 | 4 */ int a3 : 23;
17780 /* 3: 3 | 1 */ signed char a4 : 2;
17781 /* XXX 3-bit hole */
17782 /* XXX 4-byte hole */
17783 /* 8 | 8 */ int64_t a5;
17784 /* 16:27 | 4 */ int a6 : 5;
17785 /* 16:56 | 8 */ int64_t a7 : 3;
17787 /* total size (bytes): 24 */
17791 Note how the offset information is now extended to also include how
17792 many bits are left to be used in each bitfield.
17796 @item ptype[/@var{flags}] [@var{arg}]
17797 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17798 detailed description of the type, instead of just the name of the type.
17799 @xref{Expressions, ,Expressions}.
17801 Contrary to @code{whatis}, @code{ptype} always unrolls any
17802 @code{typedef}s in its argument declaration, whether the argument is
17803 a variable, expression, or a data type. This means that @code{ptype}
17804 of a variable or an expression will not print literally its type as
17805 present in the source code---use @code{whatis} for that. @code{typedef}s at
17806 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17807 fields, methods and inner @code{class typedef}s of @code{struct}s,
17808 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17810 For example, for this variable declaration:
17813 typedef double real_t;
17814 struct complex @{ real_t real; double imag; @};
17815 typedef struct complex complex_t;
17817 real_t *real_pointer_var;
17821 the two commands give this output:
17825 (@value{GDBP}) whatis var
17827 (@value{GDBP}) ptype var
17828 type = struct complex @{
17832 (@value{GDBP}) whatis complex_t
17833 type = struct complex
17834 (@value{GDBP}) whatis struct complex
17835 type = struct complex
17836 (@value{GDBP}) ptype struct complex
17837 type = struct complex @{
17841 (@value{GDBP}) whatis real_pointer_var
17843 (@value{GDBP}) ptype real_pointer_var
17849 As with @code{whatis}, using @code{ptype} without an argument refers to
17850 the type of @code{$}, the last value in the value history.
17852 @cindex incomplete type
17853 Sometimes, programs use opaque data types or incomplete specifications
17854 of complex data structure. If the debug information included in the
17855 program does not allow @value{GDBN} to display a full declaration of
17856 the data type, it will say @samp{<incomplete type>}. For example,
17857 given these declarations:
17861 struct foo *fooptr;
17865 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17868 (@value{GDBP}) ptype foo
17869 $1 = <incomplete type>
17873 ``Incomplete type'' is C terminology for data types that are not
17874 completely specified.
17876 @cindex unknown type
17877 Othertimes, information about a variable's type is completely absent
17878 from the debug information included in the program. This most often
17879 happens when the program or library where the variable is defined
17880 includes no debug information at all. @value{GDBN} knows the variable
17881 exists from inspecting the linker/loader symbol table (e.g., the ELF
17882 dynamic symbol table), but such symbols do not contain type
17883 information. Inspecting the type of a (global) variable for which
17884 @value{GDBN} has no type information shows:
17887 (@value{GDBP}) ptype var
17888 type = <data variable, no debug info>
17891 @xref{Variables, no debug info variables}, for how to print the values
17895 @item info types @var{regexp}
17897 Print a brief description of all types whose names match the regular
17898 expression @var{regexp} (or all types in your program, if you supply
17899 no argument). Each complete typename is matched as though it were a
17900 complete line; thus, @samp{i type value} gives information on all
17901 types in your program whose names include the string @code{value}, but
17902 @samp{i type ^value$} gives information only on types whose complete
17903 name is @code{value}.
17905 This command differs from @code{ptype} in two ways: first, like
17906 @code{whatis}, it does not print a detailed description; second, it
17907 lists all source files and line numbers where a type is defined.
17909 @kindex info type-printers
17910 @item info type-printers
17911 Versions of @value{GDBN} that ship with Python scripting enabled may
17912 have ``type printers'' available. When using @command{ptype} or
17913 @command{whatis}, these printers are consulted when the name of a type
17914 is needed. @xref{Type Printing API}, for more information on writing
17917 @code{info type-printers} displays all the available type printers.
17919 @kindex enable type-printer
17920 @kindex disable type-printer
17921 @item enable type-printer @var{name}@dots{}
17922 @item disable type-printer @var{name}@dots{}
17923 These commands can be used to enable or disable type printers.
17926 @cindex local variables
17927 @item info scope @var{location}
17928 List all the variables local to a particular scope. This command
17929 accepts a @var{location} argument---a function name, a source line, or
17930 an address preceded by a @samp{*}, and prints all the variables local
17931 to the scope defined by that location. (@xref{Specify Location}, for
17932 details about supported forms of @var{location}.) For example:
17935 (@value{GDBP}) @b{info scope command_line_handler}
17936 Scope for command_line_handler:
17937 Symbol rl is an argument at stack/frame offset 8, length 4.
17938 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17939 Symbol linelength is in static storage at address 0x150a1c, length 4.
17940 Symbol p is a local variable in register $esi, length 4.
17941 Symbol p1 is a local variable in register $ebx, length 4.
17942 Symbol nline is a local variable in register $edx, length 4.
17943 Symbol repeat is a local variable at frame offset -8, length 4.
17947 This command is especially useful for determining what data to collect
17948 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17951 @kindex info source
17953 Show information about the current source file---that is, the source file for
17954 the function containing the current point of execution:
17957 the name of the source file, and the directory containing it,
17959 the directory it was compiled in,
17961 its length, in lines,
17963 which programming language it is written in,
17965 if the debug information provides it, the program that compiled the file
17966 (which may include, e.g., the compiler version and command line arguments),
17968 whether the executable includes debugging information for that file, and
17969 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17971 whether the debugging information includes information about
17972 preprocessor macros.
17976 @kindex info sources
17978 Print the names of all source files in your program for which there is
17979 debugging information, organized into two lists: files whose symbols
17980 have already been read, and files whose symbols will be read when needed.
17982 @kindex info functions
17983 @item info functions [-q]
17984 Print the names and data types of all defined functions.
17985 Similarly to @samp{info types}, this command groups its output by source
17986 files and annotates each function definition with its source line
17989 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
17990 printing header information and messages explaining why no functions
17993 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
17994 Like @samp{info functions}, but only print the names and data types
17995 of the functions selected with the provided regexp(s).
17997 If @var{regexp} is provided, print only the functions whose names
17998 match the regular expression @var{regexp}.
17999 Thus, @samp{info fun step} finds all functions whose
18000 names include @code{step}; @samp{info fun ^step} finds those whose names
18001 start with @code{step}. If a function name contains characters that
18002 conflict with the regular expression language (e.g.@:
18003 @samp{operator*()}), they may be quoted with a backslash.
18005 If @var{type_regexp} is provided, print only the functions whose
18006 types, as printed by the @code{whatis} command, match
18007 the regular expression @var{type_regexp}.
18008 If @var{type_regexp} contains space(s), it should be enclosed in
18009 quote characters. If needed, use backslash to escape the meaning
18010 of special characters or quotes.
18011 Thus, @samp{info fun -t '^int ('} finds the functions that return
18012 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18013 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18014 finds the functions whose names start with @code{step} and that return
18017 If both @var{regexp} and @var{type_regexp} are provided, a function
18018 is printed only if its name matches @var{regexp} and its type matches
18022 @kindex info variables
18023 @item info variables [-q]
18024 Print the names and data types of all variables that are defined
18025 outside of functions (i.e.@: excluding local variables).
18026 The printed variables are grouped by source files and annotated with
18027 their respective source line numbers.
18029 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18030 printing header information and messages explaining why no variables
18033 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18034 Like @kbd{info variables}, but only print the variables selected
18035 with the provided regexp(s).
18037 If @var{regexp} is provided, print only the variables whose names
18038 match the regular expression @var{regexp}.
18040 If @var{type_regexp} is provided, print only the variables whose
18041 types, as printed by the @code{whatis} command, match
18042 the regular expression @var{type_regexp}.
18043 If @var{type_regexp} contains space(s), it should be enclosed in
18044 quote characters. If needed, use backslash to escape the meaning
18045 of special characters or quotes.
18047 If both @var{regexp} and @var{type_regexp} are provided, an argument
18048 is printed only if its name matches @var{regexp} and its type matches
18051 @kindex info classes
18052 @cindex Objective-C, classes and selectors
18054 @itemx info classes @var{regexp}
18055 Display all Objective-C classes in your program, or
18056 (with the @var{regexp} argument) all those matching a particular regular
18059 @kindex info selectors
18060 @item info selectors
18061 @itemx info selectors @var{regexp}
18062 Display all Objective-C selectors in your program, or
18063 (with the @var{regexp} argument) all those matching a particular regular
18067 This was never implemented.
18068 @kindex info methods
18070 @itemx info methods @var{regexp}
18071 The @code{info methods} command permits the user to examine all defined
18072 methods within C@t{++} program, or (with the @var{regexp} argument) a
18073 specific set of methods found in the various C@t{++} classes. Many
18074 C@t{++} classes provide a large number of methods. Thus, the output
18075 from the @code{ptype} command can be overwhelming and hard to use. The
18076 @code{info-methods} command filters the methods, printing only those
18077 which match the regular-expression @var{regexp}.
18080 @cindex opaque data types
18081 @kindex set opaque-type-resolution
18082 @item set opaque-type-resolution on
18083 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18084 declared as a pointer to a @code{struct}, @code{class}, or
18085 @code{union}---for example, @code{struct MyType *}---that is used in one
18086 source file although the full declaration of @code{struct MyType} is in
18087 another source file. The default is on.
18089 A change in the setting of this subcommand will not take effect until
18090 the next time symbols for a file are loaded.
18092 @item set opaque-type-resolution off
18093 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18094 is printed as follows:
18096 @{<no data fields>@}
18099 @kindex show opaque-type-resolution
18100 @item show opaque-type-resolution
18101 Show whether opaque types are resolved or not.
18103 @kindex set print symbol-loading
18104 @cindex print messages when symbols are loaded
18105 @item set print symbol-loading
18106 @itemx set print symbol-loading full
18107 @itemx set print symbol-loading brief
18108 @itemx set print symbol-loading off
18109 The @code{set print symbol-loading} command allows you to control the
18110 printing of messages when @value{GDBN} loads symbol information.
18111 By default a message is printed for the executable and one for each
18112 shared library, and normally this is what you want. However, when
18113 debugging apps with large numbers of shared libraries these messages
18115 When set to @code{brief} a message is printed for each executable,
18116 and when @value{GDBN} loads a collection of shared libraries at once
18117 it will only print one message regardless of the number of shared
18118 libraries. When set to @code{off} no messages are printed.
18120 @kindex show print symbol-loading
18121 @item show print symbol-loading
18122 Show whether messages will be printed when a @value{GDBN} command
18123 entered from the keyboard causes symbol information to be loaded.
18125 @kindex maint print symbols
18126 @cindex symbol dump
18127 @kindex maint print psymbols
18128 @cindex partial symbol dump
18129 @kindex maint print msymbols
18130 @cindex minimal symbol dump
18131 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18132 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18133 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18134 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18135 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18136 Write a dump of debugging symbol data into the file @var{filename} or
18137 the terminal if @var{filename} is unspecified.
18138 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18140 If @code{-pc @var{address}} is specified, only dump symbols for the file
18141 with code at that address. Note that @var{address} may be a symbol like
18143 If @code{-source @var{source}} is specified, only dump symbols for that
18146 These commands are used to debug the @value{GDBN} symbol-reading code.
18147 These commands do not modify internal @value{GDBN} state, therefore
18148 @samp{maint print symbols} will only print symbols for already expanded symbol
18150 You can use the command @code{info sources} to find out which files these are.
18151 If you use @samp{maint print psymbols} instead, the dump shows information
18152 about symbols that @value{GDBN} only knows partially---that is, symbols
18153 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18154 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18157 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18158 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18160 @kindex maint info symtabs
18161 @kindex maint info psymtabs
18162 @cindex listing @value{GDBN}'s internal symbol tables
18163 @cindex symbol tables, listing @value{GDBN}'s internal
18164 @cindex full symbol tables, listing @value{GDBN}'s internal
18165 @cindex partial symbol tables, listing @value{GDBN}'s internal
18166 @item maint info symtabs @r{[} @var{regexp} @r{]}
18167 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18169 List the @code{struct symtab} or @code{struct partial_symtab}
18170 structures whose names match @var{regexp}. If @var{regexp} is not
18171 given, list them all. The output includes expressions which you can
18172 copy into a @value{GDBN} debugging this one to examine a particular
18173 structure in more detail. For example:
18176 (@value{GDBP}) maint info psymtabs dwarf2read
18177 @{ objfile /home/gnu/build/gdb/gdb
18178 ((struct objfile *) 0x82e69d0)
18179 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18180 ((struct partial_symtab *) 0x8474b10)
18183 text addresses 0x814d3c8 -- 0x8158074
18184 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18185 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18186 dependencies (none)
18189 (@value{GDBP}) maint info symtabs
18193 We see that there is one partial symbol table whose filename contains
18194 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18195 and we see that @value{GDBN} has not read in any symtabs yet at all.
18196 If we set a breakpoint on a function, that will cause @value{GDBN} to
18197 read the symtab for the compilation unit containing that function:
18200 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18201 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18203 (@value{GDBP}) maint info symtabs
18204 @{ objfile /home/gnu/build/gdb/gdb
18205 ((struct objfile *) 0x82e69d0)
18206 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18207 ((struct symtab *) 0x86c1f38)
18210 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18211 linetable ((struct linetable *) 0x8370fa0)
18212 debugformat DWARF 2
18218 @kindex maint info line-table
18219 @cindex listing @value{GDBN}'s internal line tables
18220 @cindex line tables, listing @value{GDBN}'s internal
18221 @item maint info line-table @r{[} @var{regexp} @r{]}
18223 List the @code{struct linetable} from all @code{struct symtab}
18224 instances whose name matches @var{regexp}. If @var{regexp} is not
18225 given, list the @code{struct linetable} from all @code{struct symtab}.
18227 @kindex maint set symbol-cache-size
18228 @cindex symbol cache size
18229 @item maint set symbol-cache-size @var{size}
18230 Set the size of the symbol cache to @var{size}.
18231 The default size is intended to be good enough for debugging
18232 most applications. This option exists to allow for experimenting
18233 with different sizes.
18235 @kindex maint show symbol-cache-size
18236 @item maint show symbol-cache-size
18237 Show the size of the symbol cache.
18239 @kindex maint print symbol-cache
18240 @cindex symbol cache, printing its contents
18241 @item maint print symbol-cache
18242 Print the contents of the symbol cache.
18243 This is useful when debugging symbol cache issues.
18245 @kindex maint print symbol-cache-statistics
18246 @cindex symbol cache, printing usage statistics
18247 @item maint print symbol-cache-statistics
18248 Print symbol cache usage statistics.
18249 This helps determine how well the cache is being utilized.
18251 @kindex maint flush-symbol-cache
18252 @cindex symbol cache, flushing
18253 @item maint flush-symbol-cache
18254 Flush the contents of the symbol cache, all entries are removed.
18255 This command is useful when debugging the symbol cache.
18256 It is also useful when collecting performance data.
18261 @chapter Altering Execution
18263 Once you think you have found an error in your program, you might want to
18264 find out for certain whether correcting the apparent error would lead to
18265 correct results in the rest of the run. You can find the answer by
18266 experiment, using the @value{GDBN} features for altering execution of the
18269 For example, you can store new values into variables or memory
18270 locations, give your program a signal, restart it at a different
18271 address, or even return prematurely from a function.
18274 * Assignment:: Assignment to variables
18275 * Jumping:: Continuing at a different address
18276 * Signaling:: Giving your program a signal
18277 * Returning:: Returning from a function
18278 * Calling:: Calling your program's functions
18279 * Patching:: Patching your program
18280 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18284 @section Assignment to Variables
18287 @cindex setting variables
18288 To alter the value of a variable, evaluate an assignment expression.
18289 @xref{Expressions, ,Expressions}. For example,
18296 stores the value 4 into the variable @code{x}, and then prints the
18297 value of the assignment expression (which is 4).
18298 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18299 information on operators in supported languages.
18301 @kindex set variable
18302 @cindex variables, setting
18303 If you are not interested in seeing the value of the assignment, use the
18304 @code{set} command instead of the @code{print} command. @code{set} is
18305 really the same as @code{print} except that the expression's value is
18306 not printed and is not put in the value history (@pxref{Value History,
18307 ,Value History}). The expression is evaluated only for its effects.
18309 If the beginning of the argument string of the @code{set} command
18310 appears identical to a @code{set} subcommand, use the @code{set
18311 variable} command instead of just @code{set}. This command is identical
18312 to @code{set} except for its lack of subcommands. For example, if your
18313 program has a variable @code{width}, you get an error if you try to set
18314 a new value with just @samp{set width=13}, because @value{GDBN} has the
18315 command @code{set width}:
18318 (@value{GDBP}) whatis width
18320 (@value{GDBP}) p width
18322 (@value{GDBP}) set width=47
18323 Invalid syntax in expression.
18327 The invalid expression, of course, is @samp{=47}. In
18328 order to actually set the program's variable @code{width}, use
18331 (@value{GDBP}) set var width=47
18334 Because the @code{set} command has many subcommands that can conflict
18335 with the names of program variables, it is a good idea to use the
18336 @code{set variable} command instead of just @code{set}. For example, if
18337 your program has a variable @code{g}, you run into problems if you try
18338 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18339 the command @code{set gnutarget}, abbreviated @code{set g}:
18343 (@value{GDBP}) whatis g
18347 (@value{GDBP}) set g=4
18351 The program being debugged has been started already.
18352 Start it from the beginning? (y or n) y
18353 Starting program: /home/smith/cc_progs/a.out
18354 "/home/smith/cc_progs/a.out": can't open to read symbols:
18355 Invalid bfd target.
18356 (@value{GDBP}) show g
18357 The current BFD target is "=4".
18362 The program variable @code{g} did not change, and you silently set the
18363 @code{gnutarget} to an invalid value. In order to set the variable
18367 (@value{GDBP}) set var g=4
18370 @value{GDBN} allows more implicit conversions in assignments than C; you can
18371 freely store an integer value into a pointer variable or vice versa,
18372 and you can convert any structure to any other structure that is the
18373 same length or shorter.
18374 @comment FIXME: how do structs align/pad in these conversions?
18375 @comment /doc@cygnus.com 18dec1990
18377 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18378 construct to generate a value of specified type at a specified address
18379 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18380 to memory location @code{0x83040} as an integer (which implies a certain size
18381 and representation in memory), and
18384 set @{int@}0x83040 = 4
18388 stores the value 4 into that memory location.
18391 @section Continuing at a Different Address
18393 Ordinarily, when you continue your program, you do so at the place where
18394 it stopped, with the @code{continue} command. You can instead continue at
18395 an address of your own choosing, with the following commands:
18399 @kindex j @r{(@code{jump})}
18400 @item jump @var{location}
18401 @itemx j @var{location}
18402 Resume execution at @var{location}. Execution stops again immediately
18403 if there is a breakpoint there. @xref{Specify Location}, for a description
18404 of the different forms of @var{location}. It is common
18405 practice to use the @code{tbreak} command in conjunction with
18406 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18408 The @code{jump} command does not change the current stack frame, or
18409 the stack pointer, or the contents of any memory location or any
18410 register other than the program counter. If @var{location} is in
18411 a different function from the one currently executing, the results may
18412 be bizarre if the two functions expect different patterns of arguments or
18413 of local variables. For this reason, the @code{jump} command requests
18414 confirmation if the specified line is not in the function currently
18415 executing. However, even bizarre results are predictable if you are
18416 well acquainted with the machine-language code of your program.
18419 On many systems, you can get much the same effect as the @code{jump}
18420 command by storing a new value into the register @code{$pc}. The
18421 difference is that this does not start your program running; it only
18422 changes the address of where it @emph{will} run when you continue. For
18430 makes the next @code{continue} command or stepping command execute at
18431 address @code{0x485}, rather than at the address where your program stopped.
18432 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18434 The most common occasion to use the @code{jump} command is to back
18435 up---perhaps with more breakpoints set---over a portion of a program
18436 that has already executed, in order to examine its execution in more
18441 @section Giving your Program a Signal
18442 @cindex deliver a signal to a program
18446 @item signal @var{signal}
18447 Resume execution where your program is stopped, but immediately give it the
18448 signal @var{signal}. The @var{signal} can be the name or the number of a
18449 signal. For example, on many systems @code{signal 2} and @code{signal
18450 SIGINT} are both ways of sending an interrupt signal.
18452 Alternatively, if @var{signal} is zero, continue execution without
18453 giving a signal. This is useful when your program stopped on account of
18454 a signal and would ordinarily see the signal when resumed with the
18455 @code{continue} command; @samp{signal 0} causes it to resume without a
18458 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18459 delivered to the currently selected thread, not the thread that last
18460 reported a stop. This includes the situation where a thread was
18461 stopped due to a signal. So if you want to continue execution
18462 suppressing the signal that stopped a thread, you should select that
18463 same thread before issuing the @samp{signal 0} command. If you issue
18464 the @samp{signal 0} command with another thread as the selected one,
18465 @value{GDBN} detects that and asks for confirmation.
18467 Invoking the @code{signal} command is not the same as invoking the
18468 @code{kill} utility from the shell. Sending a signal with @code{kill}
18469 causes @value{GDBN} to decide what to do with the signal depending on
18470 the signal handling tables (@pxref{Signals}). The @code{signal} command
18471 passes the signal directly to your program.
18473 @code{signal} does not repeat when you press @key{RET} a second time
18474 after executing the command.
18476 @kindex queue-signal
18477 @item queue-signal @var{signal}
18478 Queue @var{signal} to be delivered immediately to the current thread
18479 when execution of the thread resumes. The @var{signal} can be the name or
18480 the number of a signal. For example, on many systems @code{signal 2} and
18481 @code{signal SIGINT} are both ways of sending an interrupt signal.
18482 The handling of the signal must be set to pass the signal to the program,
18483 otherwise @value{GDBN} will report an error.
18484 You can control the handling of signals from @value{GDBN} with the
18485 @code{handle} command (@pxref{Signals}).
18487 Alternatively, if @var{signal} is zero, any currently queued signal
18488 for the current thread is discarded and when execution resumes no signal
18489 will be delivered. This is useful when your program stopped on account
18490 of a signal and would ordinarily see the signal when resumed with the
18491 @code{continue} command.
18493 This command differs from the @code{signal} command in that the signal
18494 is just queued, execution is not resumed. And @code{queue-signal} cannot
18495 be used to pass a signal whose handling state has been set to @code{nopass}
18500 @xref{stepping into signal handlers}, for information on how stepping
18501 commands behave when the thread has a signal queued.
18504 @section Returning from a Function
18507 @cindex returning from a function
18510 @itemx return @var{expression}
18511 You can cancel execution of a function call with the @code{return}
18512 command. If you give an
18513 @var{expression} argument, its value is used as the function's return
18517 When you use @code{return}, @value{GDBN} discards the selected stack frame
18518 (and all frames within it). You can think of this as making the
18519 discarded frame return prematurely. If you wish to specify a value to
18520 be returned, give that value as the argument to @code{return}.
18522 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18523 Frame}), and any other frames inside of it, leaving its caller as the
18524 innermost remaining frame. That frame becomes selected. The
18525 specified value is stored in the registers used for returning values
18528 The @code{return} command does not resume execution; it leaves the
18529 program stopped in the state that would exist if the function had just
18530 returned. In contrast, the @code{finish} command (@pxref{Continuing
18531 and Stepping, ,Continuing and Stepping}) resumes execution until the
18532 selected stack frame returns naturally.
18534 @value{GDBN} needs to know how the @var{expression} argument should be set for
18535 the inferior. The concrete registers assignment depends on the OS ABI and the
18536 type being returned by the selected stack frame. For example it is common for
18537 OS ABI to return floating point values in FPU registers while integer values in
18538 CPU registers. Still some ABIs return even floating point values in CPU
18539 registers. Larger integer widths (such as @code{long long int}) also have
18540 specific placement rules. @value{GDBN} already knows the OS ABI from its
18541 current target so it needs to find out also the type being returned to make the
18542 assignment into the right register(s).
18544 Normally, the selected stack frame has debug info. @value{GDBN} will always
18545 use the debug info instead of the implicit type of @var{expression} when the
18546 debug info is available. For example, if you type @kbd{return -1}, and the
18547 function in the current stack frame is declared to return a @code{long long
18548 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18549 into a @code{long long int}:
18552 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18554 (@value{GDBP}) return -1
18555 Make func return now? (y or n) y
18556 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18557 43 printf ("result=%lld\n", func ());
18561 However, if the selected stack frame does not have a debug info, e.g., if the
18562 function was compiled without debug info, @value{GDBN} has to find out the type
18563 to return from user. Specifying a different type by mistake may set the value
18564 in different inferior registers than the caller code expects. For example,
18565 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18566 of a @code{long long int} result for a debug info less function (on 32-bit
18567 architectures). Therefore the user is required to specify the return type by
18568 an appropriate cast explicitly:
18571 Breakpoint 2, 0x0040050b in func ()
18572 (@value{GDBP}) return -1
18573 Return value type not available for selected stack frame.
18574 Please use an explicit cast of the value to return.
18575 (@value{GDBP}) return (long long int) -1
18576 Make selected stack frame return now? (y or n) y
18577 #0 0x00400526 in main ()
18582 @section Calling Program Functions
18585 @cindex calling functions
18586 @cindex inferior functions, calling
18587 @item print @var{expr}
18588 Evaluate the expression @var{expr} and display the resulting value.
18589 The expression may include calls to functions in the program being
18593 @item call @var{expr}
18594 Evaluate the expression @var{expr} without displaying @code{void}
18597 You can use this variant of the @code{print} command if you want to
18598 execute a function from your program that does not return anything
18599 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18600 with @code{void} returned values that @value{GDBN} will otherwise
18601 print. If the result is not void, it is printed and saved in the
18605 It is possible for the function you call via the @code{print} or
18606 @code{call} command to generate a signal (e.g., if there's a bug in
18607 the function, or if you passed it incorrect arguments). What happens
18608 in that case is controlled by the @code{set unwindonsignal} command.
18610 Similarly, with a C@t{++} program it is possible for the function you
18611 call via the @code{print} or @code{call} command to generate an
18612 exception that is not handled due to the constraints of the dummy
18613 frame. In this case, any exception that is raised in the frame, but has
18614 an out-of-frame exception handler will not be found. GDB builds a
18615 dummy-frame for the inferior function call, and the unwinder cannot
18616 seek for exception handlers outside of this dummy-frame. What happens
18617 in that case is controlled by the
18618 @code{set unwind-on-terminating-exception} command.
18621 @item set unwindonsignal
18622 @kindex set unwindonsignal
18623 @cindex unwind stack in called functions
18624 @cindex call dummy stack unwinding
18625 Set unwinding of the stack if a signal is received while in a function
18626 that @value{GDBN} called in the program being debugged. If set to on,
18627 @value{GDBN} unwinds the stack it created for the call and restores
18628 the context to what it was before the call. If set to off (the
18629 default), @value{GDBN} stops in the frame where the signal was
18632 @item show unwindonsignal
18633 @kindex show unwindonsignal
18634 Show the current setting of stack unwinding in the functions called by
18637 @item set unwind-on-terminating-exception
18638 @kindex set unwind-on-terminating-exception
18639 @cindex unwind stack in called functions with unhandled exceptions
18640 @cindex call dummy stack unwinding on unhandled exception.
18641 Set unwinding of the stack if a C@t{++} exception is raised, but left
18642 unhandled while in a function that @value{GDBN} called in the program being
18643 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18644 it created for the call and restores the context to what it was before
18645 the call. If set to off, @value{GDBN} the exception is delivered to
18646 the default C@t{++} exception handler and the inferior terminated.
18648 @item show unwind-on-terminating-exception
18649 @kindex show unwind-on-terminating-exception
18650 Show the current setting of stack unwinding in the functions called by
18655 @subsection Calling functions with no debug info
18657 @cindex no debug info functions
18658 Sometimes, a function you wish to call is missing debug information.
18659 In such case, @value{GDBN} does not know the type of the function,
18660 including the types of the function's parameters. To avoid calling
18661 the inferior function incorrectly, which could result in the called
18662 function functioning erroneously and even crash, @value{GDBN} refuses
18663 to call the function unless you tell it the type of the function.
18665 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18666 to do that. The simplest is to cast the call to the function's
18667 declared return type. For example:
18670 (@value{GDBP}) p getenv ("PATH")
18671 'getenv' has unknown return type; cast the call to its declared return type
18672 (@value{GDBP}) p (char *) getenv ("PATH")
18673 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18676 Casting the return type of a no-debug function is equivalent to
18677 casting the function to a pointer to a prototyped function that has a
18678 prototype that matches the types of the passed-in arguments, and
18679 calling that. I.e., the call above is equivalent to:
18682 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18686 and given this prototyped C or C++ function with float parameters:
18689 float multiply (float v1, float v2) @{ return v1 * v2; @}
18693 these calls are equivalent:
18696 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18697 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18700 If the function you wish to call is declared as unprototyped (i.e.@:
18701 old K&R style), you must use the cast-to-function-pointer syntax, so
18702 that @value{GDBN} knows that it needs to apply default argument
18703 promotions (promote float arguments to double). @xref{ABI, float
18704 promotion}. For example, given this unprototyped C function with
18705 float parameters, and no debug info:
18709 multiply_noproto (v1, v2)
18717 you call it like this:
18720 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18724 @section Patching Programs
18726 @cindex patching binaries
18727 @cindex writing into executables
18728 @cindex writing into corefiles
18730 By default, @value{GDBN} opens the file containing your program's
18731 executable code (or the corefile) read-only. This prevents accidental
18732 alterations to machine code; but it also prevents you from intentionally
18733 patching your program's binary.
18735 If you'd like to be able to patch the binary, you can specify that
18736 explicitly with the @code{set write} command. For example, you might
18737 want to turn on internal debugging flags, or even to make emergency
18743 @itemx set write off
18744 If you specify @samp{set write on}, @value{GDBN} opens executable and
18745 core files for both reading and writing; if you specify @kbd{set write
18746 off} (the default), @value{GDBN} opens them read-only.
18748 If you have already loaded a file, you must load it again (using the
18749 @code{exec-file} or @code{core-file} command) after changing @code{set
18750 write}, for your new setting to take effect.
18754 Display whether executable files and core files are opened for writing
18755 as well as reading.
18758 @node Compiling and Injecting Code
18759 @section Compiling and injecting code in @value{GDBN}
18760 @cindex injecting code
18761 @cindex writing into executables
18762 @cindex compiling code
18764 @value{GDBN} supports on-demand compilation and code injection into
18765 programs running under @value{GDBN}. GCC 5.0 or higher built with
18766 @file{libcc1.so} must be installed for this functionality to be enabled.
18767 This functionality is implemented with the following commands.
18770 @kindex compile code
18771 @item compile code @var{source-code}
18772 @itemx compile code -raw @var{--} @var{source-code}
18773 Compile @var{source-code} with the compiler language found as the current
18774 language in @value{GDBN} (@pxref{Languages}). If compilation and
18775 injection is not supported with the current language specified in
18776 @value{GDBN}, or the compiler does not support this feature, an error
18777 message will be printed. If @var{source-code} compiles and links
18778 successfully, @value{GDBN} will load the object-code emitted,
18779 and execute it within the context of the currently selected inferior.
18780 It is important to note that the compiled code is executed immediately.
18781 After execution, the compiled code is removed from @value{GDBN} and any
18782 new types or variables you have defined will be deleted.
18784 The command allows you to specify @var{source-code} in two ways.
18785 The simplest method is to provide a single line of code to the command.
18789 compile code printf ("hello world\n");
18792 If you specify options on the command line as well as source code, they
18793 may conflict. The @samp{--} delimiter can be used to separate options
18794 from actual source code. E.g.:
18797 compile code -r -- printf ("hello world\n");
18800 Alternatively you can enter source code as multiple lines of text. To
18801 enter this mode, invoke the @samp{compile code} command without any text
18802 following the command. This will start the multiple-line editor and
18803 allow you to type as many lines of source code as required. When you
18804 have completed typing, enter @samp{end} on its own line to exit the
18809 >printf ("hello\n");
18810 >printf ("world\n");
18814 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18815 provided @var{source-code} in a callable scope. In this case, you must
18816 specify the entry point of the code by defining a function named
18817 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18818 inferior. Using @samp{-raw} option may be needed for example when
18819 @var{source-code} requires @samp{#include} lines which may conflict with
18820 inferior symbols otherwise.
18822 @kindex compile file
18823 @item compile file @var{filename}
18824 @itemx compile file -raw @var{filename}
18825 Like @code{compile code}, but take the source code from @var{filename}.
18828 compile file /home/user/example.c
18833 @item compile print @var{expr}
18834 @itemx compile print /@var{f} @var{expr}
18835 Compile and execute @var{expr} with the compiler language found as the
18836 current language in @value{GDBN} (@pxref{Languages}). By default the
18837 value of @var{expr} is printed in a format appropriate to its data type;
18838 you can choose a different format by specifying @samp{/@var{f}}, where
18839 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18842 @item compile print
18843 @itemx compile print /@var{f}
18844 @cindex reprint the last value
18845 Alternatively you can enter the expression (source code producing it) as
18846 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18847 command without any text following the command. This will start the
18848 multiple-line editor.
18852 The process of compiling and injecting the code can be inspected using:
18855 @anchor{set debug compile}
18856 @item set debug compile
18857 @cindex compile command debugging info
18858 Turns on or off display of @value{GDBN} process of compiling and
18859 injecting the code. The default is off.
18861 @item show debug compile
18862 Displays the current state of displaying @value{GDBN} process of
18863 compiling and injecting the code.
18865 @anchor{set debug compile-cplus-types}
18866 @item set debug compile-cplus-types
18867 @cindex compile C@t{++} type conversion
18868 Turns on or off the display of C@t{++} type conversion debugging information.
18869 The default is off.
18871 @item show debug compile-cplus-types
18872 Displays the current state of displaying debugging information for
18873 C@t{++} type conversion.
18876 @subsection Compilation options for the @code{compile} command
18878 @value{GDBN} needs to specify the right compilation options for the code
18879 to be injected, in part to make its ABI compatible with the inferior
18880 and in part to make the injected code compatible with @value{GDBN}'s
18884 The options used, in increasing precedence:
18887 @item target architecture and OS options (@code{gdbarch})
18888 These options depend on target processor type and target operating
18889 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18890 (@code{-m64}) compilation option.
18892 @item compilation options recorded in the target
18893 @value{NGCC} (since version 4.7) stores the options used for compilation
18894 into @code{DW_AT_producer} part of DWARF debugging information according
18895 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18896 explicitly specify @code{-g} during inferior compilation otherwise
18897 @value{NGCC} produces no DWARF. This feature is only relevant for
18898 platforms where @code{-g} produces DWARF by default, otherwise one may
18899 try to enforce DWARF by using @code{-gdwarf-4}.
18901 @item compilation options set by @code{set compile-args}
18905 You can override compilation options using the following command:
18908 @item set compile-args
18909 @cindex compile command options override
18910 Set compilation options used for compiling and injecting code with the
18911 @code{compile} commands. These options override any conflicting ones
18912 from the target architecture and/or options stored during inferior
18915 @item show compile-args
18916 Displays the current state of compilation options override.
18917 This does not show all the options actually used during compilation,
18918 use @ref{set debug compile} for that.
18921 @subsection Caveats when using the @code{compile} command
18923 There are a few caveats to keep in mind when using the @code{compile}
18924 command. As the caveats are different per language, the table below
18925 highlights specific issues on a per language basis.
18928 @item C code examples and caveats
18929 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18930 attempt to compile the source code with a @samp{C} compiler. The source
18931 code provided to the @code{compile} command will have much the same
18932 access to variables and types as it normally would if it were part of
18933 the program currently being debugged in @value{GDBN}.
18935 Below is a sample program that forms the basis of the examples that
18936 follow. This program has been compiled and loaded into @value{GDBN},
18937 much like any other normal debugging session.
18940 void function1 (void)
18943 printf ("function 1\n");
18946 void function2 (void)
18961 For the purposes of the examples in this section, the program above has
18962 been compiled, loaded into @value{GDBN}, stopped at the function
18963 @code{main}, and @value{GDBN} is awaiting input from the user.
18965 To access variables and types for any program in @value{GDBN}, the
18966 program must be compiled and packaged with debug information. The
18967 @code{compile} command is not an exception to this rule. Without debug
18968 information, you can still use the @code{compile} command, but you will
18969 be very limited in what variables and types you can access.
18971 So with that in mind, the example above has been compiled with debug
18972 information enabled. The @code{compile} command will have access to
18973 all variables and types (except those that may have been optimized
18974 out). Currently, as @value{GDBN} has stopped the program in the
18975 @code{main} function, the @code{compile} command would have access to
18976 the variable @code{k}. You could invoke the @code{compile} command
18977 and type some source code to set the value of @code{k}. You can also
18978 read it, or do anything with that variable you would normally do in
18979 @code{C}. Be aware that changes to inferior variables in the
18980 @code{compile} command are persistent. In the following example:
18983 compile code k = 3;
18987 the variable @code{k} is now 3. It will retain that value until
18988 something else in the example program changes it, or another
18989 @code{compile} command changes it.
18991 Normal scope and access rules apply to source code compiled and
18992 injected by the @code{compile} command. In the example, the variables
18993 @code{j} and @code{k} are not accessible yet, because the program is
18994 currently stopped in the @code{main} function, where these variables
18995 are not in scope. Therefore, the following command
18998 compile code j = 3;
19002 will result in a compilation error message.
19004 Once the program is continued, execution will bring these variables in
19005 scope, and they will become accessible; then the code you specify via
19006 the @code{compile} command will be able to access them.
19008 You can create variables and types with the @code{compile} command as
19009 part of your source code. Variables and types that are created as part
19010 of the @code{compile} command are not visible to the rest of the program for
19011 the duration of its run. This example is valid:
19014 compile code int ff = 5; printf ("ff is %d\n", ff);
19017 However, if you were to type the following into @value{GDBN} after that
19018 command has completed:
19021 compile code printf ("ff is %d\n'', ff);
19025 a compiler error would be raised as the variable @code{ff} no longer
19026 exists. Object code generated and injected by the @code{compile}
19027 command is removed when its execution ends. Caution is advised
19028 when assigning to program variables values of variables created by the
19029 code submitted to the @code{compile} command. This example is valid:
19032 compile code int ff = 5; k = ff;
19035 The value of the variable @code{ff} is assigned to @code{k}. The variable
19036 @code{k} does not require the existence of @code{ff} to maintain the value
19037 it has been assigned. However, pointers require particular care in
19038 assignment. If the source code compiled with the @code{compile} command
19039 changed the address of a pointer in the example program, perhaps to a
19040 variable created in the @code{compile} command, that pointer would point
19041 to an invalid location when the command exits. The following example
19042 would likely cause issues with your debugged program:
19045 compile code int ff = 5; p = &ff;
19048 In this example, @code{p} would point to @code{ff} when the
19049 @code{compile} command is executing the source code provided to it.
19050 However, as variables in the (example) program persist with their
19051 assigned values, the variable @code{p} would point to an invalid
19052 location when the command exists. A general rule should be followed
19053 in that you should either assign @code{NULL} to any assigned pointers,
19054 or restore a valid location to the pointer before the command exits.
19056 Similar caution must be exercised with any structs, unions, and typedefs
19057 defined in @code{compile} command. Types defined in the @code{compile}
19058 command will no longer be available in the next @code{compile} command.
19059 Therefore, if you cast a variable to a type defined in the
19060 @code{compile} command, care must be taken to ensure that any future
19061 need to resolve the type can be achieved.
19064 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19065 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19066 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19067 Compilation failed.
19068 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19072 Variables that have been optimized away by the compiler are not
19073 accessible to the code submitted to the @code{compile} command.
19074 Access to those variables will generate a compiler error which @value{GDBN}
19075 will print to the console.
19078 @subsection Compiler search for the @code{compile} command
19080 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19081 which may not be obvious for remote targets of different architecture
19082 than where @value{GDBN} is running. Environment variable @code{PATH} on
19083 @value{GDBN} host is searched for @value{NGCC} binary matching the
19084 target architecture and operating system. This search can be overriden
19085 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19086 taken from shell that executed @value{GDBN}, it is not the value set by
19087 @value{GDBN} command @code{set environment}). @xref{Environment}.
19090 Specifically @code{PATH} is searched for binaries matching regular expression
19091 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19092 debugged. @var{arch} is processor name --- multiarch is supported, so for
19093 example both @code{i386} and @code{x86_64} targets look for pattern
19094 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19095 for pattern @code{s390x?}. @var{os} is currently supported only for
19096 pattern @code{linux(-gnu)?}.
19098 On Posix hosts the compiler driver @value{GDBN} needs to find also
19099 shared library @file{libcc1.so} from the compiler. It is searched in
19100 default shared library search path (overridable with usual environment
19101 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19102 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19103 according to the installation of the found compiler --- as possibly
19104 specified by the @code{set compile-gcc} command.
19107 @item set compile-gcc
19108 @cindex compile command driver filename override
19109 Set compilation command used for compiling and injecting code with the
19110 @code{compile} commands. If this option is not set (it is set to
19111 an empty string), the search described above will occur --- that is the
19114 @item show compile-gcc
19115 Displays the current compile command @value{NGCC} driver filename.
19116 If set, it is the main command @command{gcc}, found usually for example
19117 under name @file{x86_64-linux-gnu-gcc}.
19121 @chapter @value{GDBN} Files
19123 @value{GDBN} needs to know the file name of the program to be debugged,
19124 both in order to read its symbol table and in order to start your
19125 program. To debug a core dump of a previous run, you must also tell
19126 @value{GDBN} the name of the core dump file.
19129 * Files:: Commands to specify files
19130 * File Caching:: Information about @value{GDBN}'s file caching
19131 * Separate Debug Files:: Debugging information in separate files
19132 * MiniDebugInfo:: Debugging information in a special section
19133 * Index Files:: Index files speed up GDB
19134 * Symbol Errors:: Errors reading symbol files
19135 * Data Files:: GDB data files
19139 @section Commands to Specify Files
19141 @cindex symbol table
19142 @cindex core dump file
19144 You may want to specify executable and core dump file names. The usual
19145 way to do this is at start-up time, using the arguments to
19146 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19147 Out of @value{GDBN}}).
19149 Occasionally it is necessary to change to a different file during a
19150 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19151 specify a file you want to use. Or you are debugging a remote target
19152 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19153 Program}). In these situations the @value{GDBN} commands to specify
19154 new files are useful.
19157 @cindex executable file
19159 @item file @var{filename}
19160 Use @var{filename} as the program to be debugged. It is read for its
19161 symbols and for the contents of pure memory. It is also the program
19162 executed when you use the @code{run} command. If you do not specify a
19163 directory and the file is not found in the @value{GDBN} working directory,
19164 @value{GDBN} uses the environment variable @code{PATH} as a list of
19165 directories to search, just as the shell does when looking for a program
19166 to run. You can change the value of this variable, for both @value{GDBN}
19167 and your program, using the @code{path} command.
19169 @cindex unlinked object files
19170 @cindex patching object files
19171 You can load unlinked object @file{.o} files into @value{GDBN} using
19172 the @code{file} command. You will not be able to ``run'' an object
19173 file, but you can disassemble functions and inspect variables. Also,
19174 if the underlying BFD functionality supports it, you could use
19175 @kbd{gdb -write} to patch object files using this technique. Note
19176 that @value{GDBN} can neither interpret nor modify relocations in this
19177 case, so branches and some initialized variables will appear to go to
19178 the wrong place. But this feature is still handy from time to time.
19181 @code{file} with no argument makes @value{GDBN} discard any information it
19182 has on both executable file and the symbol table.
19185 @item exec-file @r{[} @var{filename} @r{]}
19186 Specify that the program to be run (but not the symbol table) is found
19187 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19188 if necessary to locate your program. Omitting @var{filename} means to
19189 discard information on the executable file.
19191 @kindex symbol-file
19192 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19193 Read symbol table information from file @var{filename}. @code{PATH} is
19194 searched when necessary. Use the @code{file} command to get both symbol
19195 table and program to run from the same file.
19197 If an optional @var{offset} is specified, it is added to the start
19198 address of each section in the symbol file. This is useful if the
19199 program is relocated at runtime, such as the Linux kernel with kASLR
19202 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19203 program's symbol table.
19205 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19206 some breakpoints and auto-display expressions. This is because they may
19207 contain pointers to the internal data recording symbols and data types,
19208 which are part of the old symbol table data being discarded inside
19211 @code{symbol-file} does not repeat if you press @key{RET} again after
19214 When @value{GDBN} is configured for a particular environment, it
19215 understands debugging information in whatever format is the standard
19216 generated for that environment; you may use either a @sc{gnu} compiler, or
19217 other compilers that adhere to the local conventions.
19218 Best results are usually obtained from @sc{gnu} compilers; for example,
19219 using @code{@value{NGCC}} you can generate debugging information for
19222 For most kinds of object files, with the exception of old SVR3 systems
19223 using COFF, the @code{symbol-file} command does not normally read the
19224 symbol table in full right away. Instead, it scans the symbol table
19225 quickly to find which source files and which symbols are present. The
19226 details are read later, one source file at a time, as they are needed.
19228 The purpose of this two-stage reading strategy is to make @value{GDBN}
19229 start up faster. For the most part, it is invisible except for
19230 occasional pauses while the symbol table details for a particular source
19231 file are being read. (The @code{set verbose} command can turn these
19232 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19233 Warnings and Messages}.)
19235 We have not implemented the two-stage strategy for COFF yet. When the
19236 symbol table is stored in COFF format, @code{symbol-file} reads the
19237 symbol table data in full right away. Note that ``stabs-in-COFF''
19238 still does the two-stage strategy, since the debug info is actually
19242 @cindex reading symbols immediately
19243 @cindex symbols, reading immediately
19244 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19245 @itemx file @r{[} -readnow @r{]} @var{filename}
19246 You can override the @value{GDBN} two-stage strategy for reading symbol
19247 tables by using the @samp{-readnow} option with any of the commands that
19248 load symbol table information, if you want to be sure @value{GDBN} has the
19249 entire symbol table available.
19251 @cindex @code{-readnever}, option for symbol-file command
19252 @cindex never read symbols
19253 @cindex symbols, never read
19254 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19255 @itemx file @r{[} -readnever @r{]} @var{filename}
19256 You can instruct @value{GDBN} to never read the symbolic information
19257 contained in @var{filename} by using the @samp{-readnever} option.
19258 @xref{--readnever}.
19260 @c FIXME: for now no mention of directories, since this seems to be in
19261 @c flux. 13mar1992 status is that in theory GDB would look either in
19262 @c current dir or in same dir as myprog; but issues like competing
19263 @c GDB's, or clutter in system dirs, mean that in practice right now
19264 @c only current dir is used. FFish says maybe a special GDB hierarchy
19265 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19269 @item core-file @r{[}@var{filename}@r{]}
19271 Specify the whereabouts of a core dump file to be used as the ``contents
19272 of memory''. Traditionally, core files contain only some parts of the
19273 address space of the process that generated them; @value{GDBN} can access the
19274 executable file itself for other parts.
19276 @code{core-file} with no argument specifies that no core file is
19279 Note that the core file is ignored when your program is actually running
19280 under @value{GDBN}. So, if you have been running your program and you
19281 wish to debug a core file instead, you must kill the subprocess in which
19282 the program is running. To do this, use the @code{kill} command
19283 (@pxref{Kill Process, ,Killing the Child Process}).
19285 @kindex add-symbol-file
19286 @cindex dynamic linking
19287 @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{]}
19288 The @code{add-symbol-file} command reads additional symbol table
19289 information from the file @var{filename}. You would use this command
19290 when @var{filename} has been dynamically loaded (by some other means)
19291 into the program that is running. The @var{textaddress} parameter gives
19292 the memory address at which the file's text section has been loaded.
19293 You can additionally specify the base address of other sections using
19294 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19295 If a section is omitted, @value{GDBN} will use its default addresses
19296 as found in @var{filename}. Any @var{address} or @var{textaddress}
19297 can be given as an expression.
19299 If an optional @var{offset} is specified, it is added to the start
19300 address of each section, except those for which the address was
19301 specified explicitly.
19303 The symbol table of the file @var{filename} is added to the symbol table
19304 originally read with the @code{symbol-file} command. You can use the
19305 @code{add-symbol-file} command any number of times; the new symbol data
19306 thus read is kept in addition to the old.
19308 Changes can be reverted using the command @code{remove-symbol-file}.
19310 @cindex relocatable object files, reading symbols from
19311 @cindex object files, relocatable, reading symbols from
19312 @cindex reading symbols from relocatable object files
19313 @cindex symbols, reading from relocatable object files
19314 @cindex @file{.o} files, reading symbols from
19315 Although @var{filename} is typically a shared library file, an
19316 executable file, or some other object file which has been fully
19317 relocated for loading into a process, you can also load symbolic
19318 information from relocatable @file{.o} files, as long as:
19322 the file's symbolic information refers only to linker symbols defined in
19323 that file, not to symbols defined by other object files,
19325 every section the file's symbolic information refers to has actually
19326 been loaded into the inferior, as it appears in the file, and
19328 you can determine the address at which every section was loaded, and
19329 provide these to the @code{add-symbol-file} command.
19333 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19334 relocatable files into an already running program; such systems
19335 typically make the requirements above easy to meet. However, it's
19336 important to recognize that many native systems use complex link
19337 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19338 assembly, for example) that make the requirements difficult to meet. In
19339 general, one cannot assume that using @code{add-symbol-file} to read a
19340 relocatable object file's symbolic information will have the same effect
19341 as linking the relocatable object file into the program in the normal
19344 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19346 @kindex remove-symbol-file
19347 @item remove-symbol-file @var{filename}
19348 @item remove-symbol-file -a @var{address}
19349 Remove a symbol file added via the @code{add-symbol-file} command. The
19350 file to remove can be identified by its @var{filename} or by an @var{address}
19351 that lies within the boundaries of this symbol file in memory. Example:
19354 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19355 add symbol table from file "/home/user/gdb/mylib.so" at
19356 .text_addr = 0x7ffff7ff9480
19358 Reading symbols from /home/user/gdb/mylib.so...done.
19359 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19360 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19365 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19367 @kindex add-symbol-file-from-memory
19368 @cindex @code{syscall DSO}
19369 @cindex load symbols from memory
19370 @item add-symbol-file-from-memory @var{address}
19371 Load symbols from the given @var{address} in a dynamically loaded
19372 object file whose image is mapped directly into the inferior's memory.
19373 For example, the Linux kernel maps a @code{syscall DSO} into each
19374 process's address space; this DSO provides kernel-specific code for
19375 some system calls. The argument can be any expression whose
19376 evaluation yields the address of the file's shared object file header.
19377 For this command to work, you must have used @code{symbol-file} or
19378 @code{exec-file} commands in advance.
19381 @item section @var{section} @var{addr}
19382 The @code{section} command changes the base address of the named
19383 @var{section} of the exec file to @var{addr}. This can be used if the
19384 exec file does not contain section addresses, (such as in the
19385 @code{a.out} format), or when the addresses specified in the file
19386 itself are wrong. Each section must be changed separately. The
19387 @code{info files} command, described below, lists all the sections and
19391 @kindex info target
19394 @code{info files} and @code{info target} are synonymous; both print the
19395 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19396 including the names of the executable and core dump files currently in
19397 use by @value{GDBN}, and the files from which symbols were loaded. The
19398 command @code{help target} lists all possible targets rather than
19401 @kindex maint info sections
19402 @item maint info sections
19403 Another command that can give you extra information about program sections
19404 is @code{maint info sections}. In addition to the section information
19405 displayed by @code{info files}, this command displays the flags and file
19406 offset of each section in the executable and core dump files. In addition,
19407 @code{maint info sections} provides the following command options (which
19408 may be arbitrarily combined):
19412 Display sections for all loaded object files, including shared libraries.
19413 @item @var{sections}
19414 Display info only for named @var{sections}.
19415 @item @var{section-flags}
19416 Display info only for sections for which @var{section-flags} are true.
19417 The section flags that @value{GDBN} currently knows about are:
19420 Section will have space allocated in the process when loaded.
19421 Set for all sections except those containing debug information.
19423 Section will be loaded from the file into the child process memory.
19424 Set for pre-initialized code and data, clear for @code{.bss} sections.
19426 Section needs to be relocated before loading.
19428 Section cannot be modified by the child process.
19430 Section contains executable code only.
19432 Section contains data only (no executable code).
19434 Section will reside in ROM.
19436 Section contains data for constructor/destructor lists.
19438 Section is not empty.
19440 An instruction to the linker to not output the section.
19441 @item COFF_SHARED_LIBRARY
19442 A notification to the linker that the section contains
19443 COFF shared library information.
19445 Section contains common symbols.
19448 @kindex set trust-readonly-sections
19449 @cindex read-only sections
19450 @item set trust-readonly-sections on
19451 Tell @value{GDBN} that readonly sections in your object file
19452 really are read-only (i.e.@: that their contents will not change).
19453 In that case, @value{GDBN} can fetch values from these sections
19454 out of the object file, rather than from the target program.
19455 For some targets (notably embedded ones), this can be a significant
19456 enhancement to debugging performance.
19458 The default is off.
19460 @item set trust-readonly-sections off
19461 Tell @value{GDBN} not to trust readonly sections. This means that
19462 the contents of the section might change while the program is running,
19463 and must therefore be fetched from the target when needed.
19465 @item show trust-readonly-sections
19466 Show the current setting of trusting readonly sections.
19469 All file-specifying commands allow both absolute and relative file names
19470 as arguments. @value{GDBN} always converts the file name to an absolute file
19471 name and remembers it that way.
19473 @cindex shared libraries
19474 @anchor{Shared Libraries}
19475 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19476 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19477 DSBT (TIC6X) shared libraries.
19479 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19480 shared libraries. @xref{Expat}.
19482 @value{GDBN} automatically loads symbol definitions from shared libraries
19483 when you use the @code{run} command, or when you examine a core file.
19484 (Before you issue the @code{run} command, @value{GDBN} does not understand
19485 references to a function in a shared library, however---unless you are
19486 debugging a core file).
19488 @c FIXME: some @value{GDBN} release may permit some refs to undef
19489 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19490 @c FIXME...lib; check this from time to time when updating manual
19492 There are times, however, when you may wish to not automatically load
19493 symbol definitions from shared libraries, such as when they are
19494 particularly large or there are many of them.
19496 To control the automatic loading of shared library symbols, use the
19500 @kindex set auto-solib-add
19501 @item set auto-solib-add @var{mode}
19502 If @var{mode} is @code{on}, symbols from all shared object libraries
19503 will be loaded automatically when the inferior begins execution, you
19504 attach to an independently started inferior, or when the dynamic linker
19505 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19506 is @code{off}, symbols must be loaded manually, using the
19507 @code{sharedlibrary} command. The default value is @code{on}.
19509 @cindex memory used for symbol tables
19510 If your program uses lots of shared libraries with debug info that
19511 takes large amounts of memory, you can decrease the @value{GDBN}
19512 memory footprint by preventing it from automatically loading the
19513 symbols from shared libraries. To that end, type @kbd{set
19514 auto-solib-add off} before running the inferior, then load each
19515 library whose debug symbols you do need with @kbd{sharedlibrary
19516 @var{regexp}}, where @var{regexp} is a regular expression that matches
19517 the libraries whose symbols you want to be loaded.
19519 @kindex show auto-solib-add
19520 @item show auto-solib-add
19521 Display the current autoloading mode.
19524 @cindex load shared library
19525 To explicitly load shared library symbols, use the @code{sharedlibrary}
19529 @kindex info sharedlibrary
19531 @item info share @var{regex}
19532 @itemx info sharedlibrary @var{regex}
19533 Print the names of the shared libraries which are currently loaded
19534 that match @var{regex}. If @var{regex} is omitted then print
19535 all shared libraries that are loaded.
19538 @item info dll @var{regex}
19539 This is an alias of @code{info sharedlibrary}.
19541 @kindex sharedlibrary
19543 @item sharedlibrary @var{regex}
19544 @itemx share @var{regex}
19545 Load shared object library symbols for files matching a
19546 Unix regular expression.
19547 As with files loaded automatically, it only loads shared libraries
19548 required by your program for a core file or after typing @code{run}. If
19549 @var{regex} is omitted all shared libraries required by your program are
19552 @item nosharedlibrary
19553 @kindex nosharedlibrary
19554 @cindex unload symbols from shared libraries
19555 Unload all shared object library symbols. This discards all symbols
19556 that have been loaded from all shared libraries. Symbols from shared
19557 libraries that were loaded by explicit user requests are not
19561 Sometimes you may wish that @value{GDBN} stops and gives you control
19562 when any of shared library events happen. The best way to do this is
19563 to use @code{catch load} and @code{catch unload} (@pxref{Set
19566 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19567 command for this. This command exists for historical reasons. It is
19568 less useful than setting a catchpoint, because it does not allow for
19569 conditions or commands as a catchpoint does.
19572 @item set stop-on-solib-events
19573 @kindex set stop-on-solib-events
19574 This command controls whether @value{GDBN} should give you control
19575 when the dynamic linker notifies it about some shared library event.
19576 The most common event of interest is loading or unloading of a new
19579 @item show stop-on-solib-events
19580 @kindex show stop-on-solib-events
19581 Show whether @value{GDBN} stops and gives you control when shared
19582 library events happen.
19585 Shared libraries are also supported in many cross or remote debugging
19586 configurations. @value{GDBN} needs to have access to the target's libraries;
19587 this can be accomplished either by providing copies of the libraries
19588 on the host system, or by asking @value{GDBN} to automatically retrieve the
19589 libraries from the target. If copies of the target libraries are
19590 provided, they need to be the same as the target libraries, although the
19591 copies on the target can be stripped as long as the copies on the host are
19594 @cindex where to look for shared libraries
19595 For remote debugging, you need to tell @value{GDBN} where the target
19596 libraries are, so that it can load the correct copies---otherwise, it
19597 may try to load the host's libraries. @value{GDBN} has two variables
19598 to specify the search directories for target libraries.
19601 @cindex prefix for executable and shared library file names
19602 @cindex system root, alternate
19603 @kindex set solib-absolute-prefix
19604 @kindex set sysroot
19605 @item set sysroot @var{path}
19606 Use @var{path} as the system root for the program being debugged. Any
19607 absolute shared library paths will be prefixed with @var{path}; many
19608 runtime loaders store the absolute paths to the shared library in the
19609 target program's memory. When starting processes remotely, and when
19610 attaching to already-running processes (local or remote), their
19611 executable filenames will be prefixed with @var{path} if reported to
19612 @value{GDBN} as absolute by the operating system. If you use
19613 @code{set sysroot} to find executables and shared libraries, they need
19614 to be laid out in the same way that they are on the target, with
19615 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19618 If @var{path} starts with the sequence @file{target:} and the target
19619 system is remote then @value{GDBN} will retrieve the target binaries
19620 from the remote system. This is only supported when using a remote
19621 target that supports the @code{remote get} command (@pxref{File
19622 Transfer,,Sending files to a remote system}). The part of @var{path}
19623 following the initial @file{target:} (if present) is used as system
19624 root prefix on the remote file system. If @var{path} starts with the
19625 sequence @file{remote:} this is converted to the sequence
19626 @file{target:} by @code{set sysroot}@footnote{Historically the
19627 functionality to retrieve binaries from the remote system was
19628 provided by prefixing @var{path} with @file{remote:}}. If you want
19629 to specify a local system root using a directory that happens to be
19630 named @file{target:} or @file{remote:}, you need to use some
19631 equivalent variant of the name like @file{./target:}.
19633 For targets with an MS-DOS based filesystem, such as MS-Windows and
19634 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19635 absolute file name with @var{path}. But first, on Unix hosts,
19636 @value{GDBN} converts all backslash directory separators into forward
19637 slashes, because the backslash is not a directory separator on Unix:
19640 c:\foo\bar.dll @result{} c:/foo/bar.dll
19643 Then, @value{GDBN} attempts prefixing the target file name with
19644 @var{path}, and looks for the resulting file name in the host file
19648 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19651 If that does not find the binary, @value{GDBN} tries removing
19652 the @samp{:} character from the drive spec, both for convenience, and,
19653 for the case of the host file system not supporting file names with
19657 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19660 This makes it possible to have a system root that mirrors a target
19661 with more than one drive. E.g., you may want to setup your local
19662 copies of the target system shared libraries like so (note @samp{c} vs
19666 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19667 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19668 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19672 and point the system root at @file{/path/to/sysroot}, so that
19673 @value{GDBN} can find the correct copies of both
19674 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19676 If that still does not find the binary, @value{GDBN} tries
19677 removing the whole drive spec from the target file name:
19680 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19683 This last lookup makes it possible to not care about the drive name,
19684 if you don't want or need to.
19686 The @code{set solib-absolute-prefix} command is an alias for @code{set
19689 @cindex default system root
19690 @cindex @samp{--with-sysroot}
19691 You can set the default system root by using the configure-time
19692 @samp{--with-sysroot} option. If the system root is inside
19693 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19694 @samp{--exec-prefix}), then the default system root will be updated
19695 automatically if the installed @value{GDBN} is moved to a new
19698 @kindex show sysroot
19700 Display the current executable and shared library prefix.
19702 @kindex set solib-search-path
19703 @item set solib-search-path @var{path}
19704 If this variable is set, @var{path} is a colon-separated list of
19705 directories to search for shared libraries. @samp{solib-search-path}
19706 is used after @samp{sysroot} fails to locate the library, or if the
19707 path to the library is relative instead of absolute. If you want to
19708 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19709 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19710 finding your host's libraries. @samp{sysroot} is preferred; setting
19711 it to a nonexistent directory may interfere with automatic loading
19712 of shared library symbols.
19714 @kindex show solib-search-path
19715 @item show solib-search-path
19716 Display the current shared library search path.
19718 @cindex DOS file-name semantics of file names.
19719 @kindex set target-file-system-kind (unix|dos-based|auto)
19720 @kindex show target-file-system-kind
19721 @item set target-file-system-kind @var{kind}
19722 Set assumed file system kind for target reported file names.
19724 Shared library file names as reported by the target system may not
19725 make sense as is on the system @value{GDBN} is running on. For
19726 example, when remote debugging a target that has MS-DOS based file
19727 system semantics, from a Unix host, the target may be reporting to
19728 @value{GDBN} a list of loaded shared libraries with file names such as
19729 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19730 drive letters, so the @samp{c:\} prefix is not normally understood as
19731 indicating an absolute file name, and neither is the backslash
19732 normally considered a directory separator character. In that case,
19733 the native file system would interpret this whole absolute file name
19734 as a relative file name with no directory components. This would make
19735 it impossible to point @value{GDBN} at a copy of the remote target's
19736 shared libraries on the host using @code{set sysroot}, and impractical
19737 with @code{set solib-search-path}. Setting
19738 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19739 to interpret such file names similarly to how the target would, and to
19740 map them to file names valid on @value{GDBN}'s native file system
19741 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19742 to one of the supported file system kinds. In that case, @value{GDBN}
19743 tries to determine the appropriate file system variant based on the
19744 current target's operating system (@pxref{ABI, ,Configuring the
19745 Current ABI}). The supported file system settings are:
19749 Instruct @value{GDBN} to assume the target file system is of Unix
19750 kind. Only file names starting the forward slash (@samp{/}) character
19751 are considered absolute, and the directory separator character is also
19755 Instruct @value{GDBN} to assume the target file system is DOS based.
19756 File names starting with either a forward slash, or a drive letter
19757 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19758 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19759 considered directory separators.
19762 Instruct @value{GDBN} to use the file system kind associated with the
19763 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19764 This is the default.
19768 @cindex file name canonicalization
19769 @cindex base name differences
19770 When processing file names provided by the user, @value{GDBN}
19771 frequently needs to compare them to the file names recorded in the
19772 program's debug info. Normally, @value{GDBN} compares just the
19773 @dfn{base names} of the files as strings, which is reasonably fast
19774 even for very large programs. (The base name of a file is the last
19775 portion of its name, after stripping all the leading directories.)
19776 This shortcut in comparison is based upon the assumption that files
19777 cannot have more than one base name. This is usually true, but
19778 references to files that use symlinks or similar filesystem
19779 facilities violate that assumption. If your program records files
19780 using such facilities, or if you provide file names to @value{GDBN}
19781 using symlinks etc., you can set @code{basenames-may-differ} to
19782 @code{true} to instruct @value{GDBN} to completely canonicalize each
19783 pair of file names it needs to compare. This will make file-name
19784 comparisons accurate, but at a price of a significant slowdown.
19787 @item set basenames-may-differ
19788 @kindex set basenames-may-differ
19789 Set whether a source file may have multiple base names.
19791 @item show basenames-may-differ
19792 @kindex show basenames-may-differ
19793 Show whether a source file may have multiple base names.
19797 @section File Caching
19798 @cindex caching of opened files
19799 @cindex caching of bfd objects
19801 To speed up file loading, and reduce memory usage, @value{GDBN} will
19802 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19803 BFD, bfd, The Binary File Descriptor Library}. The following commands
19804 allow visibility and control of the caching behavior.
19807 @kindex maint info bfds
19808 @item maint info bfds
19809 This prints information about each @code{bfd} object that is known to
19812 @kindex maint set bfd-sharing
19813 @kindex maint show bfd-sharing
19814 @kindex bfd caching
19815 @item maint set bfd-sharing
19816 @item maint show bfd-sharing
19817 Control whether @code{bfd} objects can be shared. When sharing is
19818 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19819 than reopening the same file. Turning sharing off does not cause
19820 already shared @code{bfd} objects to be unshared, but all future files
19821 that are opened will create a new @code{bfd} object. Similarly,
19822 re-enabling sharing does not cause multiple existing @code{bfd}
19823 objects to be collapsed into a single shared @code{bfd} object.
19825 @kindex set debug bfd-cache @var{level}
19826 @kindex bfd caching
19827 @item set debug bfd-cache @var{level}
19828 Turns on debugging of the bfd cache, setting the level to @var{level}.
19830 @kindex show debug bfd-cache
19831 @kindex bfd caching
19832 @item show debug bfd-cache
19833 Show the current debugging level of the bfd cache.
19836 @node Separate Debug Files
19837 @section Debugging Information in Separate Files
19838 @cindex separate debugging information files
19839 @cindex debugging information in separate files
19840 @cindex @file{.debug} subdirectories
19841 @cindex debugging information directory, global
19842 @cindex global debugging information directories
19843 @cindex build ID, and separate debugging files
19844 @cindex @file{.build-id} directory
19846 @value{GDBN} allows you to put a program's debugging information in a
19847 file separate from the executable itself, in a way that allows
19848 @value{GDBN} to find and load the debugging information automatically.
19849 Since debugging information can be very large---sometimes larger
19850 than the executable code itself---some systems distribute debugging
19851 information for their executables in separate files, which users can
19852 install only when they need to debug a problem.
19854 @value{GDBN} supports two ways of specifying the separate debug info
19859 The executable contains a @dfn{debug link} that specifies the name of
19860 the separate debug info file. The separate debug file's name is
19861 usually @file{@var{executable}.debug}, where @var{executable} is the
19862 name of the corresponding executable file without leading directories
19863 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19864 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19865 checksum for the debug file, which @value{GDBN} uses to validate that
19866 the executable and the debug file came from the same build.
19869 The executable contains a @dfn{build ID}, a unique bit string that is
19870 also present in the corresponding debug info file. (This is supported
19871 only on some operating systems, when using the ELF or PE file formats
19872 for binary files and the @sc{gnu} Binutils.) For more details about
19873 this feature, see the description of the @option{--build-id}
19874 command-line option in @ref{Options, , Command Line Options, ld,
19875 The GNU Linker}. The debug info file's name is not specified
19876 explicitly by the build ID, but can be computed from the build ID, see
19880 Depending on the way the debug info file is specified, @value{GDBN}
19881 uses two different methods of looking for the debug file:
19885 For the ``debug link'' method, @value{GDBN} looks up the named file in
19886 the directory of the executable file, then in a subdirectory of that
19887 directory named @file{.debug}, and finally under each one of the global debug
19888 directories, in a subdirectory whose name is identical to the leading
19889 directories of the executable's absolute file name.
19892 For the ``build ID'' method, @value{GDBN} looks in the
19893 @file{.build-id} subdirectory of each one of the global debug directories for
19894 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19895 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19896 are the rest of the bit string. (Real build ID strings are 32 or more
19897 hex characters, not 10.)
19900 So, for example, suppose you ask @value{GDBN} to debug
19901 @file{/usr/bin/ls}, which has a debug link that specifies the
19902 file @file{ls.debug}, and a build ID whose value in hex is
19903 @code{abcdef1234}. If the list of the global debug directories includes
19904 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19905 debug information files, in the indicated order:
19909 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19911 @file{/usr/bin/ls.debug}
19913 @file{/usr/bin/.debug/ls.debug}
19915 @file{/usr/lib/debug/usr/bin/ls.debug}.
19918 @anchor{debug-file-directory}
19919 Global debugging info directories default to what is set by @value{GDBN}
19920 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19921 you can also set the global debugging info directories, and view the list
19922 @value{GDBN} is currently using.
19926 @kindex set debug-file-directory
19927 @item set debug-file-directory @var{directories}
19928 Set the directories which @value{GDBN} searches for separate debugging
19929 information files to @var{directory}. Multiple path components can be set
19930 concatenating them by a path separator.
19932 @kindex show debug-file-directory
19933 @item show debug-file-directory
19934 Show the directories @value{GDBN} searches for separate debugging
19939 @cindex @code{.gnu_debuglink} sections
19940 @cindex debug link sections
19941 A debug link is a special section of the executable file named
19942 @code{.gnu_debuglink}. The section must contain:
19946 A filename, with any leading directory components removed, followed by
19949 zero to three bytes of padding, as needed to reach the next four-byte
19950 boundary within the section, and
19952 a four-byte CRC checksum, stored in the same endianness used for the
19953 executable file itself. The checksum is computed on the debugging
19954 information file's full contents by the function given below, passing
19955 zero as the @var{crc} argument.
19958 Any executable file format can carry a debug link, as long as it can
19959 contain a section named @code{.gnu_debuglink} with the contents
19962 @cindex @code{.note.gnu.build-id} sections
19963 @cindex build ID sections
19964 The build ID is a special section in the executable file (and in other
19965 ELF binary files that @value{GDBN} may consider). This section is
19966 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19967 It contains unique identification for the built files---the ID remains
19968 the same across multiple builds of the same build tree. The default
19969 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19970 content for the build ID string. The same section with an identical
19971 value is present in the original built binary with symbols, in its
19972 stripped variant, and in the separate debugging information file.
19974 The debugging information file itself should be an ordinary
19975 executable, containing a full set of linker symbols, sections, and
19976 debugging information. The sections of the debugging information file
19977 should have the same names, addresses, and sizes as the original file,
19978 but they need not contain any data---much like a @code{.bss} section
19979 in an ordinary executable.
19981 The @sc{gnu} binary utilities (Binutils) package includes the
19982 @samp{objcopy} utility that can produce
19983 the separated executable / debugging information file pairs using the
19984 following commands:
19987 @kbd{objcopy --only-keep-debug foo foo.debug}
19992 These commands remove the debugging
19993 information from the executable file @file{foo} and place it in the file
19994 @file{foo.debug}. You can use the first, second or both methods to link the
19999 The debug link method needs the following additional command to also leave
20000 behind a debug link in @file{foo}:
20003 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20006 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20007 a version of the @code{strip} command such that the command @kbd{strip foo -f
20008 foo.debug} has the same functionality as the two @code{objcopy} commands and
20009 the @code{ln -s} command above, together.
20012 Build ID gets embedded into the main executable using @code{ld --build-id} or
20013 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20014 compatibility fixes for debug files separation are present in @sc{gnu} binary
20015 utilities (Binutils) package since version 2.18.
20020 @cindex CRC algorithm definition
20021 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20022 IEEE 802.3 using the polynomial:
20024 @c TexInfo requires naked braces for multi-digit exponents for Tex
20025 @c output, but this causes HTML output to barf. HTML has to be set using
20026 @c raw commands. So we end up having to specify this equation in 2
20031 <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>
20032 + <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
20038 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20039 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20043 The function is computed byte at a time, taking the least
20044 significant bit of each byte first. The initial pattern
20045 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20046 the final result is inverted to ensure trailing zeros also affect the
20049 @emph{Note:} This is the same CRC polynomial as used in handling the
20050 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20051 However in the case of the Remote Serial Protocol, the CRC is computed
20052 @emph{most} significant bit first, and the result is not inverted, so
20053 trailing zeros have no effect on the CRC value.
20055 To complete the description, we show below the code of the function
20056 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20057 initially supplied @code{crc} argument means that an initial call to
20058 this function passing in zero will start computing the CRC using
20061 @kindex gnu_debuglink_crc32
20064 gnu_debuglink_crc32 (unsigned long crc,
20065 unsigned char *buf, size_t len)
20067 static const unsigned long crc32_table[256] =
20069 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20070 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20071 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20072 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20073 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20074 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20075 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20076 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20077 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20078 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20079 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20080 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20081 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20082 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20083 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20084 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20085 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20086 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20087 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20088 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20089 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20090 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20091 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20092 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20093 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20094 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20095 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20096 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20097 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20098 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20099 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20100 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20101 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20102 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20103 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20104 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20105 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20106 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20107 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20108 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20109 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20110 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20111 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20112 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20113 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20114 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20115 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20116 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20117 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20118 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20119 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20122 unsigned char *end;
20124 crc = ~crc & 0xffffffff;
20125 for (end = buf + len; buf < end; ++buf)
20126 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20127 return ~crc & 0xffffffff;
20132 This computation does not apply to the ``build ID'' method.
20134 @node MiniDebugInfo
20135 @section Debugging information in a special section
20136 @cindex separate debug sections
20137 @cindex @samp{.gnu_debugdata} section
20139 Some systems ship pre-built executables and libraries that have a
20140 special @samp{.gnu_debugdata} section. This feature is called
20141 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20142 is used to supply extra symbols for backtraces.
20144 The intent of this section is to provide extra minimal debugging
20145 information for use in simple backtraces. It is not intended to be a
20146 replacement for full separate debugging information (@pxref{Separate
20147 Debug Files}). The example below shows the intended use; however,
20148 @value{GDBN} does not currently put restrictions on what sort of
20149 debugging information might be included in the section.
20151 @value{GDBN} has support for this extension. If the section exists,
20152 then it is used provided that no other source of debugging information
20153 can be found, and that @value{GDBN} was configured with LZMA support.
20155 This section can be easily created using @command{objcopy} and other
20156 standard utilities:
20159 # Extract the dynamic symbols from the main binary, there is no need
20160 # to also have these in the normal symbol table.
20161 nm -D @var{binary} --format=posix --defined-only \
20162 | awk '@{ print $1 @}' | sort > dynsyms
20164 # Extract all the text (i.e. function) symbols from the debuginfo.
20165 # (Note that we actually also accept "D" symbols, for the benefit
20166 # of platforms like PowerPC64 that use function descriptors.)
20167 nm @var{binary} --format=posix --defined-only \
20168 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20171 # Keep all the function symbols not already in the dynamic symbol
20173 comm -13 dynsyms funcsyms > keep_symbols
20175 # Separate full debug info into debug binary.
20176 objcopy --only-keep-debug @var{binary} debug
20178 # Copy the full debuginfo, keeping only a minimal set of symbols and
20179 # removing some unnecessary sections.
20180 objcopy -S --remove-section .gdb_index --remove-section .comment \
20181 --keep-symbols=keep_symbols debug mini_debuginfo
20183 # Drop the full debug info from the original binary.
20184 strip --strip-all -R .comment @var{binary}
20186 # Inject the compressed data into the .gnu_debugdata section of the
20189 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20193 @section Index Files Speed Up @value{GDBN}
20194 @cindex index files
20195 @cindex @samp{.gdb_index} section
20197 When @value{GDBN} finds a symbol file, it scans the symbols in the
20198 file in order to construct an internal symbol table. This lets most
20199 @value{GDBN} operations work quickly---at the cost of a delay early
20200 on. For large programs, this delay can be quite lengthy, so
20201 @value{GDBN} provides a way to build an index, which speeds up
20204 For convenience, @value{GDBN} comes with a program,
20205 @command{gdb-add-index}, which can be used to add the index to a
20206 symbol file. It takes the symbol file as its only argument:
20209 $ gdb-add-index symfile
20212 @xref{gdb-add-index}.
20214 It is also possible to do the work manually. Here is what
20215 @command{gdb-add-index} does behind the curtains.
20217 The index is stored as a section in the symbol file. @value{GDBN} can
20218 write the index to a file, then you can put it into the symbol file
20219 using @command{objcopy}.
20221 To create an index file, use the @code{save gdb-index} command:
20224 @item save gdb-index [-dwarf-5] @var{directory}
20225 @kindex save gdb-index
20226 Create index files for all symbol files currently known by
20227 @value{GDBN}. For each known @var{symbol-file}, this command by
20228 default creates it produces a single file
20229 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20230 the @option{-dwarf-5} option, it produces 2 files:
20231 @file{@var{symbol-file}.debug_names} and
20232 @file{@var{symbol-file}.debug_str}. The files are created in the
20233 given @var{directory}.
20236 Once you have created an index file you can merge it into your symbol
20237 file, here named @file{symfile}, using @command{objcopy}:
20240 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20241 --set-section-flags .gdb_index=readonly symfile symfile
20244 Or for @code{-dwarf-5}:
20247 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20248 $ cat symfile.debug_str >>symfile.debug_str.new
20249 $ objcopy --add-section .debug_names=symfile.gdb-index \
20250 --set-section-flags .debug_names=readonly \
20251 --update-section .debug_str=symfile.debug_str.new symfile symfile
20254 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20255 sections that have been deprecated. Usually they are deprecated because
20256 they are missing a new feature or have performance issues.
20257 To tell @value{GDBN} to use a deprecated index section anyway
20258 specify @code{set use-deprecated-index-sections on}.
20259 The default is @code{off}.
20260 This can speed up startup, but may result in some functionality being lost.
20261 @xref{Index Section Format}.
20263 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20264 must be done before gdb reads the file. The following will not work:
20267 $ gdb -ex "set use-deprecated-index-sections on" <program>
20270 Instead you must do, for example,
20273 $ gdb -iex "set use-deprecated-index-sections on" <program>
20276 There are currently some limitation on indices. They only work when
20277 for DWARF debugging information, not stabs. And, they do not
20278 currently work for programs using Ada.
20280 @subsection Automatic symbol index cache
20282 It is possible for @value{GDBN} to automatically save a copy of this index in a
20283 cache on disk and retrieve it from there when loading the same binary in the
20284 future. This feature can be turned on with @kbd{set index-cache on}. The
20285 following commands can be used to tweak the behavior of the index cache.
20289 @item set index-cache on
20290 @itemx set index-cache off
20291 Enable or disable the use of the symbol index cache.
20293 @item set index-cache directory @var{directory}
20294 @itemx show index-cache directory
20295 Set/show the directory where index files will be saved.
20297 The default value for this directory depends on the host platform. On
20298 most systems, the index is cached in the @file{gdb} subdirectory of
20299 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20300 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20301 of your home directory. However, on some systems, the default may
20302 differ according to local convention.
20304 There is no limit on the disk space used by index cache. It is perfectly safe
20305 to delete the content of that directory to free up disk space.
20307 @item show index-cache stats
20308 Print the number of cache hits and misses since the launch of @value{GDBN}.
20312 @node Symbol Errors
20313 @section Errors Reading Symbol Files
20315 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20316 such as symbol types it does not recognize, or known bugs in compiler
20317 output. By default, @value{GDBN} does not notify you of such problems, since
20318 they are relatively common and primarily of interest to people
20319 debugging compilers. If you are interested in seeing information
20320 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20321 only one message about each such type of problem, no matter how many
20322 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20323 to see how many times the problems occur, with the @code{set
20324 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20327 The messages currently printed, and their meanings, include:
20330 @item inner block not inside outer block in @var{symbol}
20332 The symbol information shows where symbol scopes begin and end
20333 (such as at the start of a function or a block of statements). This
20334 error indicates that an inner scope block is not fully contained
20335 in its outer scope blocks.
20337 @value{GDBN} circumvents the problem by treating the inner block as if it had
20338 the same scope as the outer block. In the error message, @var{symbol}
20339 may be shown as ``@code{(don't know)}'' if the outer block is not a
20342 @item block at @var{address} out of order
20344 The symbol information for symbol scope blocks should occur in
20345 order of increasing addresses. This error indicates that it does not
20348 @value{GDBN} does not circumvent this problem, and has trouble
20349 locating symbols in the source file whose symbols it is reading. (You
20350 can often determine what source file is affected by specifying
20351 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20354 @item bad block start address patched
20356 The symbol information for a symbol scope block has a start address
20357 smaller than the address of the preceding source line. This is known
20358 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20360 @value{GDBN} circumvents the problem by treating the symbol scope block as
20361 starting on the previous source line.
20363 @item bad string table offset in symbol @var{n}
20366 Symbol number @var{n} contains a pointer into the string table which is
20367 larger than the size of the string table.
20369 @value{GDBN} circumvents the problem by considering the symbol to have the
20370 name @code{foo}, which may cause other problems if many symbols end up
20373 @item unknown symbol type @code{0x@var{nn}}
20375 The symbol information contains new data types that @value{GDBN} does
20376 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20377 uncomprehended information, in hexadecimal.
20379 @value{GDBN} circumvents the error by ignoring this symbol information.
20380 This usually allows you to debug your program, though certain symbols
20381 are not accessible. If you encounter such a problem and feel like
20382 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20383 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20384 and examine @code{*bufp} to see the symbol.
20386 @item stub type has NULL name
20388 @value{GDBN} could not find the full definition for a struct or class.
20390 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20391 The symbol information for a C@t{++} member function is missing some
20392 information that recent versions of the compiler should have output for
20395 @item info mismatch between compiler and debugger
20397 @value{GDBN} could not parse a type specification output by the compiler.
20402 @section GDB Data Files
20404 @cindex prefix for data files
20405 @value{GDBN} will sometimes read an auxiliary data file. These files
20406 are kept in a directory known as the @dfn{data directory}.
20408 You can set the data directory's name, and view the name @value{GDBN}
20409 is currently using.
20412 @kindex set data-directory
20413 @item set data-directory @var{directory}
20414 Set the directory which @value{GDBN} searches for auxiliary data files
20415 to @var{directory}.
20417 @kindex show data-directory
20418 @item show data-directory
20419 Show the directory @value{GDBN} searches for auxiliary data files.
20422 @cindex default data directory
20423 @cindex @samp{--with-gdb-datadir}
20424 You can set the default data directory by using the configure-time
20425 @samp{--with-gdb-datadir} option. If the data directory is inside
20426 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20427 @samp{--exec-prefix}), then the default data directory will be updated
20428 automatically if the installed @value{GDBN} is moved to a new
20431 The data directory may also be specified with the
20432 @code{--data-directory} command line option.
20433 @xref{Mode Options}.
20436 @chapter Specifying a Debugging Target
20438 @cindex debugging target
20439 A @dfn{target} is the execution environment occupied by your program.
20441 Often, @value{GDBN} runs in the same host environment as your program;
20442 in that case, the debugging target is specified as a side effect when
20443 you use the @code{file} or @code{core} commands. When you need more
20444 flexibility---for example, running @value{GDBN} on a physically separate
20445 host, or controlling a standalone system over a serial port or a
20446 realtime system over a TCP/IP connection---you can use the @code{target}
20447 command to specify one of the target types configured for @value{GDBN}
20448 (@pxref{Target Commands, ,Commands for Managing Targets}).
20450 @cindex target architecture
20451 It is possible to build @value{GDBN} for several different @dfn{target
20452 architectures}. When @value{GDBN} is built like that, you can choose
20453 one of the available architectures with the @kbd{set architecture}
20457 @kindex set architecture
20458 @kindex show architecture
20459 @item set architecture @var{arch}
20460 This command sets the current target architecture to @var{arch}. The
20461 value of @var{arch} can be @code{"auto"}, in addition to one of the
20462 supported architectures.
20464 @item show architecture
20465 Show the current target architecture.
20467 @item set processor
20469 @kindex set processor
20470 @kindex show processor
20471 These are alias commands for, respectively, @code{set architecture}
20472 and @code{show architecture}.
20476 * Active Targets:: Active targets
20477 * Target Commands:: Commands for managing targets
20478 * Byte Order:: Choosing target byte order
20481 @node Active Targets
20482 @section Active Targets
20484 @cindex stacking targets
20485 @cindex active targets
20486 @cindex multiple targets
20488 There are multiple classes of targets such as: processes, executable files or
20489 recording sessions. Core files belong to the process class, making core file
20490 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20491 on multiple active targets, one in each class. This allows you to (for
20492 example) start a process and inspect its activity, while still having access to
20493 the executable file after the process finishes. Or if you start process
20494 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20495 presented a virtual layer of the recording target, while the process target
20496 remains stopped at the chronologically last point of the process execution.
20498 Use the @code{core-file} and @code{exec-file} commands to select a new core
20499 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20500 specify as a target a process that is already running, use the @code{attach}
20501 command (@pxref{Attach, ,Debugging an Already-running Process}).
20503 @node Target Commands
20504 @section Commands for Managing Targets
20507 @item target @var{type} @var{parameters}
20508 Connects the @value{GDBN} host environment to a target machine or
20509 process. A target is typically a protocol for talking to debugging
20510 facilities. You use the argument @var{type} to specify the type or
20511 protocol of the target machine.
20513 Further @var{parameters} are interpreted by the target protocol, but
20514 typically include things like device names or host names to connect
20515 with, process numbers, and baud rates.
20517 The @code{target} command does not repeat if you press @key{RET} again
20518 after executing the command.
20520 @kindex help target
20522 Displays the names of all targets available. To display targets
20523 currently selected, use either @code{info target} or @code{info files}
20524 (@pxref{Files, ,Commands to Specify Files}).
20526 @item help target @var{name}
20527 Describe a particular target, including any parameters necessary to
20530 @kindex set gnutarget
20531 @item set gnutarget @var{args}
20532 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20533 knows whether it is reading an @dfn{executable},
20534 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20535 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20536 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20539 @emph{Warning:} To specify a file format with @code{set gnutarget},
20540 you must know the actual BFD name.
20544 @xref{Files, , Commands to Specify Files}.
20546 @kindex show gnutarget
20547 @item show gnutarget
20548 Use the @code{show gnutarget} command to display what file format
20549 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20550 @value{GDBN} will determine the file format for each file automatically,
20551 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20554 @cindex common targets
20555 Here are some common targets (available, or not, depending on the GDB
20560 @item target exec @var{program}
20561 @cindex executable file target
20562 An executable file. @samp{target exec @var{program}} is the same as
20563 @samp{exec-file @var{program}}.
20565 @item target core @var{filename}
20566 @cindex core dump file target
20567 A core dump file. @samp{target core @var{filename}} is the same as
20568 @samp{core-file @var{filename}}.
20570 @item target remote @var{medium}
20571 @cindex remote target
20572 A remote system connected to @value{GDBN} via a serial line or network
20573 connection. This command tells @value{GDBN} to use its own remote
20574 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20576 For example, if you have a board connected to @file{/dev/ttya} on the
20577 machine running @value{GDBN}, you could say:
20580 target remote /dev/ttya
20583 @code{target remote} supports the @code{load} command. This is only
20584 useful if you have some other way of getting the stub to the target
20585 system, and you can put it somewhere in memory where it won't get
20586 clobbered by the download.
20588 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20589 @cindex built-in simulator target
20590 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20598 works; however, you cannot assume that a specific memory map, device
20599 drivers, or even basic I/O is available, although some simulators do
20600 provide these. For info about any processor-specific simulator details,
20601 see the appropriate section in @ref{Embedded Processors, ,Embedded
20604 @item target native
20605 @cindex native target
20606 Setup for local/native process debugging. Useful to make the
20607 @code{run} command spawn native processes (likewise @code{attach},
20608 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20609 (@pxref{set auto-connect-native-target}).
20613 Different targets are available on different configurations of @value{GDBN};
20614 your configuration may have more or fewer targets.
20616 Many remote targets require you to download the executable's code once
20617 you've successfully established a connection. You may wish to control
20618 various aspects of this process.
20623 @kindex set hash@r{, for remote monitors}
20624 @cindex hash mark while downloading
20625 This command controls whether a hash mark @samp{#} is displayed while
20626 downloading a file to the remote monitor. If on, a hash mark is
20627 displayed after each S-record is successfully downloaded to the
20631 @kindex show hash@r{, for remote monitors}
20632 Show the current status of displaying the hash mark.
20634 @item set debug monitor
20635 @kindex set debug monitor
20636 @cindex display remote monitor communications
20637 Enable or disable display of communications messages between
20638 @value{GDBN} and the remote monitor.
20640 @item show debug monitor
20641 @kindex show debug monitor
20642 Show the current status of displaying communications between
20643 @value{GDBN} and the remote monitor.
20648 @kindex load @var{filename} @var{offset}
20649 @item load @var{filename} @var{offset}
20651 Depending on what remote debugging facilities are configured into
20652 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20653 is meant to make @var{filename} (an executable) available for debugging
20654 on the remote system---by downloading, or dynamic linking, for example.
20655 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20656 the @code{add-symbol-file} command.
20658 If your @value{GDBN} does not have a @code{load} command, attempting to
20659 execute it gets the error message ``@code{You can't do that when your
20660 target is @dots{}}''
20662 The file is loaded at whatever address is specified in the executable.
20663 For some object file formats, you can specify the load address when you
20664 link the program; for other formats, like a.out, the object file format
20665 specifies a fixed address.
20666 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20668 It is also possible to tell @value{GDBN} to load the executable file at a
20669 specific offset described by the optional argument @var{offset}. When
20670 @var{offset} is provided, @var{filename} must also be provided.
20672 Depending on the remote side capabilities, @value{GDBN} may be able to
20673 load programs into flash memory.
20675 @code{load} does not repeat if you press @key{RET} again after using it.
20680 @kindex flash-erase
20682 @anchor{flash-erase}
20684 Erases all known flash memory regions on the target.
20689 @section Choosing Target Byte Order
20691 @cindex choosing target byte order
20692 @cindex target byte order
20694 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20695 offer the ability to run either big-endian or little-endian byte
20696 orders. Usually the executable or symbol will include a bit to
20697 designate the endian-ness, and you will not need to worry about
20698 which to use. However, you may still find it useful to adjust
20699 @value{GDBN}'s idea of processor endian-ness manually.
20703 @item set endian big
20704 Instruct @value{GDBN} to assume the target is big-endian.
20706 @item set endian little
20707 Instruct @value{GDBN} to assume the target is little-endian.
20709 @item set endian auto
20710 Instruct @value{GDBN} to use the byte order associated with the
20714 Display @value{GDBN}'s current idea of the target byte order.
20718 If the @code{set endian auto} mode is in effect and no executable has
20719 been selected, then the endianness used is the last one chosen either
20720 by one of the @code{set endian big} and @code{set endian little}
20721 commands or by inferring from the last executable used. If no
20722 endianness has been previously chosen, then the default for this mode
20723 is inferred from the target @value{GDBN} has been built for, and is
20724 @code{little} if the name of the target CPU has an @code{el} suffix
20725 and @code{big} otherwise.
20727 Note that these commands merely adjust interpretation of symbolic
20728 data on the host, and that they have absolutely no effect on the
20732 @node Remote Debugging
20733 @chapter Debugging Remote Programs
20734 @cindex remote debugging
20736 If you are trying to debug a program running on a machine that cannot run
20737 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20738 For example, you might use remote debugging on an operating system kernel,
20739 or on a small system which does not have a general purpose operating system
20740 powerful enough to run a full-featured debugger.
20742 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20743 to make this work with particular debugging targets. In addition,
20744 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20745 but not specific to any particular target system) which you can use if you
20746 write the remote stubs---the code that runs on the remote system to
20747 communicate with @value{GDBN}.
20749 Other remote targets may be available in your
20750 configuration of @value{GDBN}; use @code{help target} to list them.
20753 * Connecting:: Connecting to a remote target
20754 * File Transfer:: Sending files to a remote system
20755 * Server:: Using the gdbserver program
20756 * Remote Configuration:: Remote configuration
20757 * Remote Stub:: Implementing a remote stub
20761 @section Connecting to a Remote Target
20762 @cindex remote debugging, connecting
20763 @cindex @code{gdbserver}, connecting
20764 @cindex remote debugging, types of connections
20765 @cindex @code{gdbserver}, types of connections
20766 @cindex @code{gdbserver}, @code{target remote} mode
20767 @cindex @code{gdbserver}, @code{target extended-remote} mode
20769 This section describes how to connect to a remote target, including the
20770 types of connections and their differences, how to set up executable and
20771 symbol files on the host and target, and the commands used for
20772 connecting to and disconnecting from the remote target.
20774 @subsection Types of Remote Connections
20776 @value{GDBN} supports two types of remote connections, @code{target remote}
20777 mode and @code{target extended-remote} mode. Note that many remote targets
20778 support only @code{target remote} mode. There are several major
20779 differences between the two types of connections, enumerated here:
20783 @cindex remote debugging, detach and program exit
20784 @item Result of detach or program exit
20785 @strong{With target remote mode:} When the debugged program exits or you
20786 detach from it, @value{GDBN} disconnects from the target. When using
20787 @code{gdbserver}, @code{gdbserver} will exit.
20789 @strong{With target extended-remote mode:} When the debugged program exits or
20790 you detach from it, @value{GDBN} remains connected to the target, even
20791 though no program is running. You can rerun the program, attach to a
20792 running program, or use @code{monitor} commands specific to the target.
20794 When using @code{gdbserver} in this case, it does not exit unless it was
20795 invoked using the @option{--once} option. If the @option{--once} option
20796 was not used, you can ask @code{gdbserver} to exit using the
20797 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20799 @item Specifying the program to debug
20800 For both connection types you use the @code{file} command to specify the
20801 program on the host system. If you are using @code{gdbserver} there are
20802 some differences in how to specify the location of the program on the
20805 @strong{With target remote mode:} You must either specify the program to debug
20806 on the @code{gdbserver} command line or use the @option{--attach} option
20807 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20809 @cindex @option{--multi}, @code{gdbserver} option
20810 @strong{With target extended-remote mode:} You may specify the program to debug
20811 on the @code{gdbserver} command line, or you can load the program or attach
20812 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20814 @anchor{--multi Option in Types of Remote Connnections}
20815 You can start @code{gdbserver} without supplying an initial command to run
20816 or process ID to attach. To do this, use the @option{--multi} command line
20817 option. Then you can connect using @code{target extended-remote} and start
20818 the program you want to debug (see below for details on using the
20819 @code{run} command in this scenario). Note that the conditions under which
20820 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20821 (@code{target remote} or @code{target extended-remote}). The
20822 @option{--multi} option to @code{gdbserver} has no influence on that.
20824 @item The @code{run} command
20825 @strong{With target remote mode:} The @code{run} command is not
20826 supported. Once a connection has been established, you can use all
20827 the usual @value{GDBN} commands to examine and change data. The
20828 remote program is already running, so you can use commands like
20829 @kbd{step} and @kbd{continue}.
20831 @strong{With target extended-remote mode:} The @code{run} command is
20832 supported. The @code{run} command uses the value set by
20833 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20834 the program to run. Command line arguments are supported, except for
20835 wildcard expansion and I/O redirection (@pxref{Arguments}).
20837 If you specify the program to debug on the command line, then the
20838 @code{run} command is not required to start execution, and you can
20839 resume using commands like @kbd{step} and @kbd{continue} as with
20840 @code{target remote} mode.
20842 @anchor{Attaching in Types of Remote Connections}
20844 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20845 not supported. To attach to a running program using @code{gdbserver}, you
20846 must use the @option{--attach} option (@pxref{Running gdbserver}).
20848 @strong{With target extended-remote mode:} To attach to a running program,
20849 you may use the @code{attach} command after the connection has been
20850 established. If you are using @code{gdbserver}, you may also invoke
20851 @code{gdbserver} using the @option{--attach} option
20852 (@pxref{Running gdbserver}).
20856 @anchor{Host and target files}
20857 @subsection Host and Target Files
20858 @cindex remote debugging, symbol files
20859 @cindex symbol files, remote debugging
20861 @value{GDBN}, running on the host, needs access to symbol and debugging
20862 information for your program running on the target. This requires
20863 access to an unstripped copy of your program, and possibly any associated
20864 symbol files. Note that this section applies equally to both @code{target
20865 remote} mode and @code{target extended-remote} mode.
20867 Some remote targets (@pxref{qXfer executable filename read}, and
20868 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20869 the same connection used to communicate with @value{GDBN}. With such a
20870 target, if the remote program is unstripped, the only command you need is
20871 @code{target remote} (or @code{target extended-remote}).
20873 If the remote program is stripped, or the target does not support remote
20874 program file access, start up @value{GDBN} using the name of the local
20875 unstripped copy of your program as the first argument, or use the
20876 @code{file} command. Use @code{set sysroot} to specify the location (on
20877 the host) of target libraries (unless your @value{GDBN} was compiled with
20878 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20879 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20882 The symbol file and target libraries must exactly match the executable
20883 and libraries on the target, with one exception: the files on the host
20884 system should not be stripped, even if the files on the target system
20885 are. Mismatched or missing files will lead to confusing results
20886 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20887 files may also prevent @code{gdbserver} from debugging multi-threaded
20890 @subsection Remote Connection Commands
20891 @cindex remote connection commands
20892 @value{GDBN} can communicate with the target over a serial line, a
20893 local Unix domain socket, or
20894 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20895 each case, @value{GDBN} uses the same protocol for debugging your
20896 program; only the medium carrying the debugging packets varies. The
20897 @code{target remote} and @code{target extended-remote} commands
20898 establish a connection to the target. Both commands accept the same
20899 arguments, which indicate the medium to use:
20903 @item target remote @var{serial-device}
20904 @itemx target extended-remote @var{serial-device}
20905 @cindex serial line, @code{target remote}
20906 Use @var{serial-device} to communicate with the target. For example,
20907 to use a serial line connected to the device named @file{/dev/ttyb}:
20910 target remote /dev/ttyb
20913 If you're using a serial line, you may want to give @value{GDBN} the
20914 @samp{--baud} option, or use the @code{set serial baud} command
20915 (@pxref{Remote Configuration, set serial baud}) before the
20916 @code{target} command.
20918 @item target remote @var{local-socket}
20919 @itemx target extended-remote @var{local-socket}
20920 @cindex local socket, @code{target remote}
20921 @cindex Unix domain socket
20922 Use @var{local-socket} to communicate with the target. For example,
20923 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20926 target remote /tmp/gdb-socket0
20929 Note that this command has the same form as the command to connect
20930 to a serial line. @value{GDBN} will automatically determine which
20931 kind of file you have specified and will make the appropriate kind
20933 The above command is identical to the command:
20936 target remote unix::/tmp/gdb-socket1
20940 See below for the explanation of this syntax.
20942 This feature is not available if the host system does not support
20943 Unix domain sockets.
20945 @item target remote @code{@var{host}:@var{port}}
20946 @itemx target remote @code{@var{[host]}:@var{port}}
20947 @itemx target remote @code{tcp:@var{host}:@var{port}}
20948 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20949 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20950 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20951 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20952 @itemx target remote @code{unix::@var{local-socket}}
20953 @itemx target extended-remote @code{@var{host}:@var{port}}
20954 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20955 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20956 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20957 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20958 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20959 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20960 @itemx target extended-remote @code{unix::@var{local-socket}}
20961 @cindex @acronym{TCP} port, @code{target remote}
20962 Debug using a @acronym{TCP} connection to @var{port} on @var{host}
20963 or using the Unix domain socket @var{local-socket} on the local machine.
20964 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20965 address, or a numeric @acronym{IPv6} address (with or without the
20966 square brackets to separate the address from the port); @var{port}
20967 must be a decimal number. The @var{host} could be the target machine
20968 itself, if it is directly connected to the net, or it might be a
20969 terminal server which in turn has a serial line to the target.
20971 For example, to connect to port 2828 on a terminal server named
20975 target remote manyfarms:2828
20978 To connect to port 2828 on a terminal server whose address is
20979 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20980 square bracket syntax:
20983 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
20987 or explicitly specify the @acronym{IPv6} protocol:
20990 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
20993 This last example may be confusing to the reader, because there is no
20994 visible separation between the hostname and the port number.
20995 Therefore, we recommend the user to provide @acronym{IPv6} addresses
20996 using square brackets for clarity. However, it is important to
20997 mention that for @value{GDBN} there is no ambiguity: the number after
20998 the last colon is considered to be the port number.
21000 If your remote target is actually running on the same machine as your
21001 debugger session (e.g.@: a simulator for your target running on the
21002 same host), you can omit the hostname. For example, to connect to
21003 port 1234 on your local machine:
21006 target remote :1234
21010 Note that the colon is still required here.
21011 Alternatively you can use a Unix domain socket:
21014 target remote unix::/tmp/gdb-socket1
21018 This has the advantage that it'll not fail if the port number is already
21022 @item target remote @code{udp:@var{host}:@var{port}}
21023 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21024 @itemx target remote @code{udp4:@var{host}:@var{port}}
21025 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21026 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21027 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21028 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21029 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21030 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21031 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21032 @cindex @acronym{UDP} port, @code{target remote}
21033 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21034 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21037 target remote udp:manyfarms:2828
21040 When using a @acronym{UDP} connection for remote debugging, you should
21041 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21042 can silently drop packets on busy or unreliable networks, which will
21043 cause havoc with your debugging session.
21045 @item target remote | @var{command}
21046 @itemx target extended-remote | @var{command}
21047 @cindex pipe, @code{target remote} to
21048 Run @var{command} in the background and communicate with it using a
21049 pipe. The @var{command} is a shell command, to be parsed and expanded
21050 by the system's command shell, @code{/bin/sh}; it should expect remote
21051 protocol packets on its standard input, and send replies on its
21052 standard output. You could use this to run a stand-alone simulator
21053 that speaks the remote debugging protocol, to make net connections
21054 using programs like @code{ssh}, or for other similar tricks.
21056 If @var{command} closes its standard output (perhaps by exiting),
21057 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21058 program has already exited, this will have no effect.)
21062 @cindex interrupting remote programs
21063 @cindex remote programs, interrupting
21064 Whenever @value{GDBN} is waiting for the remote program, if you type the
21065 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21066 program. This may or may not succeed, depending in part on the hardware
21067 and the serial drivers the remote system uses. If you type the
21068 interrupt character once again, @value{GDBN} displays this prompt:
21071 Interrupted while waiting for the program.
21072 Give up (and stop debugging it)? (y or n)
21075 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21076 the remote debugging session. (If you decide you want to try again later,
21077 you can use @kbd{target remote} again to connect once more.) If you type
21078 @kbd{n}, @value{GDBN} goes back to waiting.
21080 In @code{target extended-remote} mode, typing @kbd{n} will leave
21081 @value{GDBN} connected to the target.
21084 @kindex detach (remote)
21086 When you have finished debugging the remote program, you can use the
21087 @code{detach} command to release it from @value{GDBN} control.
21088 Detaching from the target normally resumes its execution, but the results
21089 will depend on your particular remote stub. After the @code{detach}
21090 command in @code{target remote} mode, @value{GDBN} is free to connect to
21091 another target. In @code{target extended-remote} mode, @value{GDBN} is
21092 still connected to the target.
21096 The @code{disconnect} command closes the connection to the target, and
21097 the target is generally not resumed. It will wait for @value{GDBN}
21098 (this instance or another one) to connect and continue debugging. After
21099 the @code{disconnect} command, @value{GDBN} is again free to connect to
21102 @cindex send command to remote monitor
21103 @cindex extend @value{GDBN} for remote targets
21104 @cindex add new commands for external monitor
21106 @item monitor @var{cmd}
21107 This command allows you to send arbitrary commands directly to the
21108 remote monitor. Since @value{GDBN} doesn't care about the commands it
21109 sends like this, this command is the way to extend @value{GDBN}---you
21110 can add new commands that only the external monitor will understand
21114 @node File Transfer
21115 @section Sending files to a remote system
21116 @cindex remote target, file transfer
21117 @cindex file transfer
21118 @cindex sending files to remote systems
21120 Some remote targets offer the ability to transfer files over the same
21121 connection used to communicate with @value{GDBN}. This is convenient
21122 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21123 running @code{gdbserver} over a network interface. For other targets,
21124 e.g.@: embedded devices with only a single serial port, this may be
21125 the only way to upload or download files.
21127 Not all remote targets support these commands.
21131 @item remote put @var{hostfile} @var{targetfile}
21132 Copy file @var{hostfile} from the host system (the machine running
21133 @value{GDBN}) to @var{targetfile} on the target system.
21136 @item remote get @var{targetfile} @var{hostfile}
21137 Copy file @var{targetfile} from the target system to @var{hostfile}
21138 on the host system.
21140 @kindex remote delete
21141 @item remote delete @var{targetfile}
21142 Delete @var{targetfile} from the target system.
21147 @section Using the @code{gdbserver} Program
21150 @cindex remote connection without stubs
21151 @code{gdbserver} is a control program for Unix-like systems, which
21152 allows you to connect your program with a remote @value{GDBN} via
21153 @code{target remote} or @code{target extended-remote}---but without
21154 linking in the usual debugging stub.
21156 @code{gdbserver} is not a complete replacement for the debugging stubs,
21157 because it requires essentially the same operating-system facilities
21158 that @value{GDBN} itself does. In fact, a system that can run
21159 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21160 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21161 because it is a much smaller program than @value{GDBN} itself. It is
21162 also easier to port than all of @value{GDBN}, so you may be able to get
21163 started more quickly on a new system by using @code{gdbserver}.
21164 Finally, if you develop code for real-time systems, you may find that
21165 the tradeoffs involved in real-time operation make it more convenient to
21166 do as much development work as possible on another system, for example
21167 by cross-compiling. You can use @code{gdbserver} to make a similar
21168 choice for debugging.
21170 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21171 or a TCP connection, using the standard @value{GDBN} remote serial
21175 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21176 Do not run @code{gdbserver} connected to any public network; a
21177 @value{GDBN} connection to @code{gdbserver} provides access to the
21178 target system with the same privileges as the user running
21182 @anchor{Running gdbserver}
21183 @subsection Running @code{gdbserver}
21184 @cindex arguments, to @code{gdbserver}
21185 @cindex @code{gdbserver}, command-line arguments
21187 Run @code{gdbserver} on the target system. You need a copy of the
21188 program you want to debug, including any libraries it requires.
21189 @code{gdbserver} does not need your program's symbol table, so you can
21190 strip the program if necessary to save space. @value{GDBN} on the host
21191 system does all the symbol handling.
21193 To use the server, you must tell it how to communicate with @value{GDBN};
21194 the name of your program; and the arguments for your program. The usual
21198 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21201 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21204 @var{comm} may take several forms:
21208 A serial line device.
21212 To use the stdin/stdout of @code{gdbserver}.
21214 For example, to debug Emacs with the argument
21215 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21219 target> gdbserver /dev/com1 emacs foo.txt
21222 The @code{stdio} connection is useful when starting @code{gdbserver}
21226 (gdb) target remote | ssh -T hostname gdbserver - hello
21229 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21230 and we don't want escape-character handling. Ssh does this by default when
21231 a command is provided, the flag is provided to make it explicit.
21232 You could elide it if you want to.
21234 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21235 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21236 display through a pipe connected to gdbserver.
21237 Both @code{stdout} and @code{stderr} use the same pipe.
21239 @item @var{host}:@var{port}
21240 @itemx tcp:@var{host}:@var{port}
21241 @itemx tcp4:@var{host}:@var{port}
21242 To use a @acronym{TCP} @acronym{IPv4} socket connection on port number @var{port}.
21244 To use a TCP connection instead of a serial line:
21247 target> gdbserver host:2345 emacs foo.txt
21250 The only difference from the previous example is the first argument,
21251 specifying that you are communicating with the host @value{GDBN} via
21252 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21253 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21254 (Currently, the @samp{host} part is ignored.) You can choose any number
21255 you want for the port number as long as it does not conflict with any
21256 TCP ports already in use on the target system (for example, @code{23} is
21257 reserved for @code{telnet}).@footnote{If you choose a port number that
21258 conflicts with another service, @code{gdbserver} prints an error message
21259 and exits.} You must use the same port number with the host @value{GDBN}
21260 @code{target remote} command.
21263 @item tcp6:@var{host}:@var{port}
21264 To use a @acronym{TCP} @acronym{IPv6} socket connection on port number @var{port}.
21266 @item unix:@var{host}:@var{local-socket}
21267 To use a Unix domain socket. This will create a socket with the file
21268 system entry @var{local-socket} and listen on that. For example:
21271 target> gdbserver unix:localhost:/tmp/gdb-socket0 emacs foo.txt
21274 @var{host} must either be the empty string or the literal string @code{localhost}.
21278 @anchor{Attaching to a program}
21279 @subsubsection Attaching to a Running Program
21280 @cindex attach to a program, @code{gdbserver}
21281 @cindex @option{--attach}, @code{gdbserver} option
21283 On some targets, @code{gdbserver} can also attach to running programs.
21284 This is accomplished via the @code{--attach} argument. The syntax is:
21287 target> gdbserver --attach @var{comm} @var{pid}
21290 @var{pid} is the process ID of a currently running process. It isn't
21291 necessary to point @code{gdbserver} at a binary for the running process.
21293 In @code{target extended-remote} mode, you can also attach using the
21294 @value{GDBN} attach command
21295 (@pxref{Attaching in Types of Remote Connections}).
21298 You can debug processes by name instead of process ID if your target has the
21299 @code{pidof} utility:
21302 target> gdbserver --attach @var{comm} `pidof @var{program}`
21305 In case more than one copy of @var{program} is running, or @var{program}
21306 has multiple threads, most versions of @code{pidof} support the
21307 @code{-s} option to only return the first process ID.
21309 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21311 This section applies only when @code{gdbserver} is run to listen on a TCP
21314 @code{gdbserver} normally terminates after all of its debugged processes have
21315 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21316 extended-remote}, @code{gdbserver} stays running even with no processes left.
21317 @value{GDBN} normally terminates the spawned debugged process on its exit,
21318 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21319 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21320 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21321 stays running even in the @kbd{target remote} mode.
21323 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21324 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21325 completeness, at most one @value{GDBN} can be connected at a time.
21327 @cindex @option{--once}, @code{gdbserver} option
21328 By default, @code{gdbserver} keeps the listening TCP port open, so that
21329 subsequent connections are possible. However, if you start @code{gdbserver}
21330 with the @option{--once} option, it will stop listening for any further
21331 connection attempts after connecting to the first @value{GDBN} session. This
21332 means no further connections to @code{gdbserver} will be possible after the
21333 first one. It also means @code{gdbserver} will terminate after the first
21334 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21335 connections and even in the @kbd{target extended-remote} mode. The
21336 @option{--once} option allows reusing the same port number for connecting to
21337 multiple instances of @code{gdbserver} running on the same host, since each
21338 instance closes its port after the first connection.
21340 @anchor{Other Command-Line Arguments for gdbserver}
21341 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21343 You can use the @option{--multi} option to start @code{gdbserver} without
21344 specifying a program to debug or a process to attach to. Then you can
21345 attach in @code{target extended-remote} mode and run or attach to a
21346 program. For more information,
21347 @pxref{--multi Option in Types of Remote Connnections}.
21349 @cindex @option{--debug}, @code{gdbserver} option
21350 The @option{--debug} option tells @code{gdbserver} to display extra
21351 status information about the debugging process.
21352 @cindex @option{--remote-debug}, @code{gdbserver} option
21353 The @option{--remote-debug} option tells @code{gdbserver} to display
21354 remote protocol debug output. These options are intended for
21355 @code{gdbserver} development and for bug reports to the developers.
21357 @cindex @option{--debug-format}, @code{gdbserver} option
21358 The @option{--debug-format=option1[,option2,...]} option tells
21359 @code{gdbserver} to include additional information in each output.
21360 Possible options are:
21364 Turn off all extra information in debugging output.
21366 Turn on all extra information in debugging output.
21368 Include a timestamp in each line of debugging output.
21371 Options are processed in order. Thus, for example, if @option{none}
21372 appears last then no additional information is added to debugging output.
21374 @cindex @option{--wrapper}, @code{gdbserver} option
21375 The @option{--wrapper} option specifies a wrapper to launch programs
21376 for debugging. The option should be followed by the name of the
21377 wrapper, then any command-line arguments to pass to the wrapper, then
21378 @kbd{--} indicating the end of the wrapper arguments.
21380 @code{gdbserver} runs the specified wrapper program with a combined
21381 command line including the wrapper arguments, then the name of the
21382 program to debug, then any arguments to the program. The wrapper
21383 runs until it executes your program, and then @value{GDBN} gains control.
21385 You can use any program that eventually calls @code{execve} with
21386 its arguments as a wrapper. Several standard Unix utilities do
21387 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21388 with @code{exec "$@@"} will also work.
21390 For example, you can use @code{env} to pass an environment variable to
21391 the debugged program, without setting the variable in @code{gdbserver}'s
21395 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21398 @cindex @option{--selftest}
21399 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21402 $ gdbserver --selftest
21403 Ran 2 unit tests, 0 failed
21406 These tests are disabled in release.
21407 @subsection Connecting to @code{gdbserver}
21409 The basic procedure for connecting to the remote target is:
21413 Run @value{GDBN} on the host system.
21416 Make sure you have the necessary symbol files
21417 (@pxref{Host and target files}).
21418 Load symbols for your application using the @code{file} command before you
21419 connect. Use @code{set sysroot} to locate target libraries (unless your
21420 @value{GDBN} was compiled with the correct sysroot using
21421 @code{--with-sysroot}).
21424 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21425 For TCP connections, you must start up @code{gdbserver} prior to using
21426 the @code{target} command. Otherwise you may get an error whose
21427 text depends on the host system, but which usually looks something like
21428 @samp{Connection refused}. Don't use the @code{load}
21429 command in @value{GDBN} when using @code{target remote} mode, since the
21430 program is already on the target.
21434 @anchor{Monitor Commands for gdbserver}
21435 @subsection Monitor Commands for @code{gdbserver}
21436 @cindex monitor commands, for @code{gdbserver}
21438 During a @value{GDBN} session using @code{gdbserver}, you can use the
21439 @code{monitor} command to send special requests to @code{gdbserver}.
21440 Here are the available commands.
21444 List the available monitor commands.
21446 @item monitor set debug 0
21447 @itemx monitor set debug 1
21448 Disable or enable general debugging messages.
21450 @item monitor set remote-debug 0
21451 @itemx monitor set remote-debug 1
21452 Disable or enable specific debugging messages associated with the remote
21453 protocol (@pxref{Remote Protocol}).
21455 @item monitor set debug-format option1@r{[},option2,...@r{]}
21456 Specify additional text to add to debugging messages.
21457 Possible options are:
21461 Turn off all extra information in debugging output.
21463 Turn on all extra information in debugging output.
21465 Include a timestamp in each line of debugging output.
21468 Options are processed in order. Thus, for example, if @option{none}
21469 appears last then no additional information is added to debugging output.
21471 @item monitor set libthread-db-search-path [PATH]
21472 @cindex gdbserver, search path for @code{libthread_db}
21473 When this command is issued, @var{path} is a colon-separated list of
21474 directories to search for @code{libthread_db} (@pxref{Threads,,set
21475 libthread-db-search-path}). If you omit @var{path},
21476 @samp{libthread-db-search-path} will be reset to its default value.
21478 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21479 not supported in @code{gdbserver}.
21482 Tell gdbserver to exit immediately. This command should be followed by
21483 @code{disconnect} to close the debugging session. @code{gdbserver} will
21484 detach from any attached processes and kill any processes it created.
21485 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21486 of a multi-process mode debug session.
21490 @subsection Tracepoints support in @code{gdbserver}
21491 @cindex tracepoints support in @code{gdbserver}
21493 On some targets, @code{gdbserver} supports tracepoints, fast
21494 tracepoints and static tracepoints.
21496 For fast or static tracepoints to work, a special library called the
21497 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21498 This library is built and distributed as an integral part of
21499 @code{gdbserver}. In addition, support for static tracepoints
21500 requires building the in-process agent library with static tracepoints
21501 support. At present, the UST (LTTng Userspace Tracer,
21502 @url{http://lttng.org/ust}) tracing engine is supported. This support
21503 is automatically available if UST development headers are found in the
21504 standard include path when @code{gdbserver} is built, or if
21505 @code{gdbserver} was explicitly configured using @option{--with-ust}
21506 to point at such headers. You can explicitly disable the support
21507 using @option{--with-ust=no}.
21509 There are several ways to load the in-process agent in your program:
21512 @item Specifying it as dependency at link time
21514 You can link your program dynamically with the in-process agent
21515 library. On most systems, this is accomplished by adding
21516 @code{-linproctrace} to the link command.
21518 @item Using the system's preloading mechanisms
21520 You can force loading the in-process agent at startup time by using
21521 your system's support for preloading shared libraries. Many Unixes
21522 support the concept of preloading user defined libraries. In most
21523 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21524 in the environment. See also the description of @code{gdbserver}'s
21525 @option{--wrapper} command line option.
21527 @item Using @value{GDBN} to force loading the agent at run time
21529 On some systems, you can force the inferior to load a shared library,
21530 by calling a dynamic loader function in the inferior that takes care
21531 of dynamically looking up and loading a shared library. On most Unix
21532 systems, the function is @code{dlopen}. You'll use the @code{call}
21533 command for that. For example:
21536 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21539 Note that on most Unix systems, for the @code{dlopen} function to be
21540 available, the program needs to be linked with @code{-ldl}.
21543 On systems that have a userspace dynamic loader, like most Unix
21544 systems, when you connect to @code{gdbserver} using @code{target
21545 remote}, you'll find that the program is stopped at the dynamic
21546 loader's entry point, and no shared library has been loaded in the
21547 program's address space yet, including the in-process agent. In that
21548 case, before being able to use any of the fast or static tracepoints
21549 features, you need to let the loader run and load the shared
21550 libraries. The simplest way to do that is to run the program to the
21551 main procedure. E.g., if debugging a C or C@t{++} program, start
21552 @code{gdbserver} like so:
21555 $ gdbserver :9999 myprogram
21558 Start GDB and connect to @code{gdbserver} like so, and run to main:
21562 (@value{GDBP}) target remote myhost:9999
21563 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21564 (@value{GDBP}) b main
21565 (@value{GDBP}) continue
21568 The in-process tracing agent library should now be loaded into the
21569 process; you can confirm it with the @code{info sharedlibrary}
21570 command, which will list @file{libinproctrace.so} as loaded in the
21571 process. You are now ready to install fast tracepoints, list static
21572 tracepoint markers, probe static tracepoints markers, and start
21575 @node Remote Configuration
21576 @section Remote Configuration
21579 @kindex show remote
21580 This section documents the configuration options available when
21581 debugging remote programs. For the options related to the File I/O
21582 extensions of the remote protocol, see @ref{system,
21583 system-call-allowed}.
21586 @item set remoteaddresssize @var{bits}
21587 @cindex address size for remote targets
21588 @cindex bits in remote address
21589 Set the maximum size of address in a memory packet to the specified
21590 number of bits. @value{GDBN} will mask off the address bits above
21591 that number, when it passes addresses to the remote target. The
21592 default value is the number of bits in the target's address.
21594 @item show remoteaddresssize
21595 Show the current value of remote address size in bits.
21597 @item set serial baud @var{n}
21598 @cindex baud rate for remote targets
21599 Set the baud rate for the remote serial I/O to @var{n} baud. The
21600 value is used to set the speed of the serial port used for debugging
21603 @item show serial baud
21604 Show the current speed of the remote connection.
21606 @item set serial parity @var{parity}
21607 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21608 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21610 @item show serial parity
21611 Show the current parity of the serial port.
21613 @item set remotebreak
21614 @cindex interrupt remote programs
21615 @cindex BREAK signal instead of Ctrl-C
21616 @anchor{set remotebreak}
21617 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21618 when you type @kbd{Ctrl-c} to interrupt the program running
21619 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21620 character instead. The default is off, since most remote systems
21621 expect to see @samp{Ctrl-C} as the interrupt signal.
21623 @item show remotebreak
21624 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21625 interrupt the remote program.
21627 @item set remoteflow on
21628 @itemx set remoteflow off
21629 @kindex set remoteflow
21630 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21631 on the serial port used to communicate to the remote target.
21633 @item show remoteflow
21634 @kindex show remoteflow
21635 Show the current setting of hardware flow control.
21637 @item set remotelogbase @var{base}
21638 Set the base (a.k.a.@: radix) of logging serial protocol
21639 communications to @var{base}. Supported values of @var{base} are:
21640 @code{ascii}, @code{octal}, and @code{hex}. The default is
21643 @item show remotelogbase
21644 Show the current setting of the radix for logging remote serial
21647 @item set remotelogfile @var{file}
21648 @cindex record serial communications on file
21649 Record remote serial communications on the named @var{file}. The
21650 default is not to record at all.
21652 @item show remotelogfile.
21653 Show the current setting of the file name on which to record the
21654 serial communications.
21656 @item set remotetimeout @var{num}
21657 @cindex timeout for serial communications
21658 @cindex remote timeout
21659 Set the timeout limit to wait for the remote target to respond to
21660 @var{num} seconds. The default is 2 seconds.
21662 @item show remotetimeout
21663 Show the current number of seconds to wait for the remote target
21666 @cindex limit hardware breakpoints and watchpoints
21667 @cindex remote target, limit break- and watchpoints
21668 @anchor{set remote hardware-watchpoint-limit}
21669 @anchor{set remote hardware-breakpoint-limit}
21670 @item set remote hardware-watchpoint-limit @var{limit}
21671 @itemx set remote hardware-breakpoint-limit @var{limit}
21672 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21673 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21674 watchpoints or breakpoints, and @code{unlimited} for unlimited
21675 watchpoints or breakpoints.
21677 @item show remote hardware-watchpoint-limit
21678 @itemx show remote hardware-breakpoint-limit
21679 Show the current limit for the number of hardware watchpoints or
21680 breakpoints that @value{GDBN} can use.
21682 @cindex limit hardware watchpoints length
21683 @cindex remote target, limit watchpoints length
21684 @anchor{set remote hardware-watchpoint-length-limit}
21685 @item set remote hardware-watchpoint-length-limit @var{limit}
21686 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21687 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21688 hardware watchpoints and @code{unlimited} allows watchpoints of any
21691 @item show remote hardware-watchpoint-length-limit
21692 Show the current limit (in bytes) of the maximum length of
21693 a remote hardware watchpoint.
21695 @item set remote exec-file @var{filename}
21696 @itemx show remote exec-file
21697 @anchor{set remote exec-file}
21698 @cindex executable file, for remote target
21699 Select the file used for @code{run} with @code{target
21700 extended-remote}. This should be set to a filename valid on the
21701 target system. If it is not set, the target will use a default
21702 filename (e.g.@: the last program run).
21704 @item set remote interrupt-sequence
21705 @cindex interrupt remote programs
21706 @cindex select Ctrl-C, BREAK or BREAK-g
21707 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21708 @samp{BREAK-g} as the
21709 sequence to the remote target in order to interrupt the execution.
21710 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21711 is high level of serial line for some certain time.
21712 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21713 It is @code{BREAK} signal followed by character @code{g}.
21715 @item show interrupt-sequence
21716 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21717 is sent by @value{GDBN} to interrupt the remote program.
21718 @code{BREAK-g} is BREAK signal followed by @code{g} and
21719 also known as Magic SysRq g.
21721 @item set remote interrupt-on-connect
21722 @cindex send interrupt-sequence on start
21723 Specify whether interrupt-sequence is sent to remote target when
21724 @value{GDBN} connects to it. This is mostly needed when you debug
21725 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21726 which is known as Magic SysRq g in order to connect @value{GDBN}.
21728 @item show interrupt-on-connect
21729 Show whether interrupt-sequence is sent
21730 to remote target when @value{GDBN} connects to it.
21734 @item set tcp auto-retry on
21735 @cindex auto-retry, for remote TCP target
21736 Enable auto-retry for remote TCP connections. This is useful if the remote
21737 debugging agent is launched in parallel with @value{GDBN}; there is a race
21738 condition because the agent may not become ready to accept the connection
21739 before @value{GDBN} attempts to connect. When auto-retry is
21740 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21741 to establish the connection using the timeout specified by
21742 @code{set tcp connect-timeout}.
21744 @item set tcp auto-retry off
21745 Do not auto-retry failed TCP connections.
21747 @item show tcp auto-retry
21748 Show the current auto-retry setting.
21750 @item set tcp connect-timeout @var{seconds}
21751 @itemx set tcp connect-timeout unlimited
21752 @cindex connection timeout, for remote TCP target
21753 @cindex timeout, for remote target connection
21754 Set the timeout for establishing a TCP connection to the remote target to
21755 @var{seconds}. The timeout affects both polling to retry failed connections
21756 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21757 that are merely slow to complete, and represents an approximate cumulative
21758 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21759 @value{GDBN} will keep attempting to establish a connection forever,
21760 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21762 @item show tcp connect-timeout
21763 Show the current connection timeout setting.
21766 @cindex remote packets, enabling and disabling
21767 The @value{GDBN} remote protocol autodetects the packets supported by
21768 your debugging stub. If you need to override the autodetection, you
21769 can use these commands to enable or disable individual packets. Each
21770 packet can be set to @samp{on} (the remote target supports this
21771 packet), @samp{off} (the remote target does not support this packet),
21772 or @samp{auto} (detect remote target support for this packet). They
21773 all default to @samp{auto}. For more information about each packet,
21774 see @ref{Remote Protocol}.
21776 During normal use, you should not have to use any of these commands.
21777 If you do, that may be a bug in your remote debugging stub, or a bug
21778 in @value{GDBN}. You may want to report the problem to the
21779 @value{GDBN} developers.
21781 For each packet @var{name}, the command to enable or disable the
21782 packet is @code{set remote @var{name}-packet}. The available settings
21785 @multitable @columnfractions 0.28 0.32 0.25
21788 @tab Related Features
21790 @item @code{fetch-register}
21792 @tab @code{info registers}
21794 @item @code{set-register}
21798 @item @code{binary-download}
21800 @tab @code{load}, @code{set}
21802 @item @code{read-aux-vector}
21803 @tab @code{qXfer:auxv:read}
21804 @tab @code{info auxv}
21806 @item @code{symbol-lookup}
21807 @tab @code{qSymbol}
21808 @tab Detecting multiple threads
21810 @item @code{attach}
21811 @tab @code{vAttach}
21814 @item @code{verbose-resume}
21816 @tab Stepping or resuming multiple threads
21822 @item @code{software-breakpoint}
21826 @item @code{hardware-breakpoint}
21830 @item @code{write-watchpoint}
21834 @item @code{read-watchpoint}
21838 @item @code{access-watchpoint}
21842 @item @code{pid-to-exec-file}
21843 @tab @code{qXfer:exec-file:read}
21844 @tab @code{attach}, @code{run}
21846 @item @code{target-features}
21847 @tab @code{qXfer:features:read}
21848 @tab @code{set architecture}
21850 @item @code{library-info}
21851 @tab @code{qXfer:libraries:read}
21852 @tab @code{info sharedlibrary}
21854 @item @code{memory-map}
21855 @tab @code{qXfer:memory-map:read}
21856 @tab @code{info mem}
21858 @item @code{read-sdata-object}
21859 @tab @code{qXfer:sdata:read}
21860 @tab @code{print $_sdata}
21862 @item @code{read-spu-object}
21863 @tab @code{qXfer:spu:read}
21864 @tab @code{info spu}
21866 @item @code{write-spu-object}
21867 @tab @code{qXfer:spu:write}
21868 @tab @code{info spu}
21870 @item @code{read-siginfo-object}
21871 @tab @code{qXfer:siginfo:read}
21872 @tab @code{print $_siginfo}
21874 @item @code{write-siginfo-object}
21875 @tab @code{qXfer:siginfo:write}
21876 @tab @code{set $_siginfo}
21878 @item @code{threads}
21879 @tab @code{qXfer:threads:read}
21880 @tab @code{info threads}
21882 @item @code{get-thread-local-@*storage-address}
21883 @tab @code{qGetTLSAddr}
21884 @tab Displaying @code{__thread} variables
21886 @item @code{get-thread-information-block-address}
21887 @tab @code{qGetTIBAddr}
21888 @tab Display MS-Windows Thread Information Block.
21890 @item @code{search-memory}
21891 @tab @code{qSearch:memory}
21894 @item @code{supported-packets}
21895 @tab @code{qSupported}
21896 @tab Remote communications parameters
21898 @item @code{catch-syscalls}
21899 @tab @code{QCatchSyscalls}
21900 @tab @code{catch syscall}
21902 @item @code{pass-signals}
21903 @tab @code{QPassSignals}
21904 @tab @code{handle @var{signal}}
21906 @item @code{program-signals}
21907 @tab @code{QProgramSignals}
21908 @tab @code{handle @var{signal}}
21910 @item @code{hostio-close-packet}
21911 @tab @code{vFile:close}
21912 @tab @code{remote get}, @code{remote put}
21914 @item @code{hostio-open-packet}
21915 @tab @code{vFile:open}
21916 @tab @code{remote get}, @code{remote put}
21918 @item @code{hostio-pread-packet}
21919 @tab @code{vFile:pread}
21920 @tab @code{remote get}, @code{remote put}
21922 @item @code{hostio-pwrite-packet}
21923 @tab @code{vFile:pwrite}
21924 @tab @code{remote get}, @code{remote put}
21926 @item @code{hostio-unlink-packet}
21927 @tab @code{vFile:unlink}
21928 @tab @code{remote delete}
21930 @item @code{hostio-readlink-packet}
21931 @tab @code{vFile:readlink}
21934 @item @code{hostio-fstat-packet}
21935 @tab @code{vFile:fstat}
21938 @item @code{hostio-setfs-packet}
21939 @tab @code{vFile:setfs}
21942 @item @code{noack-packet}
21943 @tab @code{QStartNoAckMode}
21944 @tab Packet acknowledgment
21946 @item @code{osdata}
21947 @tab @code{qXfer:osdata:read}
21948 @tab @code{info os}
21950 @item @code{query-attached}
21951 @tab @code{qAttached}
21952 @tab Querying remote process attach state.
21954 @item @code{trace-buffer-size}
21955 @tab @code{QTBuffer:size}
21956 @tab @code{set trace-buffer-size}
21958 @item @code{trace-status}
21959 @tab @code{qTStatus}
21960 @tab @code{tstatus}
21962 @item @code{traceframe-info}
21963 @tab @code{qXfer:traceframe-info:read}
21964 @tab Traceframe info
21966 @item @code{install-in-trace}
21967 @tab @code{InstallInTrace}
21968 @tab Install tracepoint in tracing
21970 @item @code{disable-randomization}
21971 @tab @code{QDisableRandomization}
21972 @tab @code{set disable-randomization}
21974 @item @code{startup-with-shell}
21975 @tab @code{QStartupWithShell}
21976 @tab @code{set startup-with-shell}
21978 @item @code{environment-hex-encoded}
21979 @tab @code{QEnvironmentHexEncoded}
21980 @tab @code{set environment}
21982 @item @code{environment-unset}
21983 @tab @code{QEnvironmentUnset}
21984 @tab @code{unset environment}
21986 @item @code{environment-reset}
21987 @tab @code{QEnvironmentReset}
21988 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21990 @item @code{set-working-dir}
21991 @tab @code{QSetWorkingDir}
21992 @tab @code{set cwd}
21994 @item @code{conditional-breakpoints-packet}
21995 @tab @code{Z0 and Z1}
21996 @tab @code{Support for target-side breakpoint condition evaluation}
21998 @item @code{multiprocess-extensions}
21999 @tab @code{multiprocess extensions}
22000 @tab Debug multiple processes and remote process PID awareness
22002 @item @code{swbreak-feature}
22003 @tab @code{swbreak stop reason}
22006 @item @code{hwbreak-feature}
22007 @tab @code{hwbreak stop reason}
22010 @item @code{fork-event-feature}
22011 @tab @code{fork stop reason}
22014 @item @code{vfork-event-feature}
22015 @tab @code{vfork stop reason}
22018 @item @code{exec-event-feature}
22019 @tab @code{exec stop reason}
22022 @item @code{thread-events}
22023 @tab @code{QThreadEvents}
22024 @tab Tracking thread lifetime.
22026 @item @code{no-resumed-stop-reply}
22027 @tab @code{no resumed thread left stop reply}
22028 @tab Tracking thread lifetime.
22033 @section Implementing a Remote Stub
22035 @cindex debugging stub, example
22036 @cindex remote stub, example
22037 @cindex stub example, remote debugging
22038 The stub files provided with @value{GDBN} implement the target side of the
22039 communication protocol, and the @value{GDBN} side is implemented in the
22040 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22041 these subroutines to communicate, and ignore the details. (If you're
22042 implementing your own stub file, you can still ignore the details: start
22043 with one of the existing stub files. @file{sparc-stub.c} is the best
22044 organized, and therefore the easiest to read.)
22046 @cindex remote serial debugging, overview
22047 To debug a program running on another machine (the debugging
22048 @dfn{target} machine), you must first arrange for all the usual
22049 prerequisites for the program to run by itself. For example, for a C
22054 A startup routine to set up the C runtime environment; these usually
22055 have a name like @file{crt0}. The startup routine may be supplied by
22056 your hardware supplier, or you may have to write your own.
22059 A C subroutine library to support your program's
22060 subroutine calls, notably managing input and output.
22063 A way of getting your program to the other machine---for example, a
22064 download program. These are often supplied by the hardware
22065 manufacturer, but you may have to write your own from hardware
22069 The next step is to arrange for your program to use a serial port to
22070 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22071 machine). In general terms, the scheme looks like this:
22075 @value{GDBN} already understands how to use this protocol; when everything
22076 else is set up, you can simply use the @samp{target remote} command
22077 (@pxref{Targets,,Specifying a Debugging Target}).
22079 @item On the target,
22080 you must link with your program a few special-purpose subroutines that
22081 implement the @value{GDBN} remote serial protocol. The file containing these
22082 subroutines is called a @dfn{debugging stub}.
22084 On certain remote targets, you can use an auxiliary program
22085 @code{gdbserver} instead of linking a stub into your program.
22086 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22089 The debugging stub is specific to the architecture of the remote
22090 machine; for example, use @file{sparc-stub.c} to debug programs on
22093 @cindex remote serial stub list
22094 These working remote stubs are distributed with @value{GDBN}:
22099 @cindex @file{i386-stub.c}
22102 For Intel 386 and compatible architectures.
22105 @cindex @file{m68k-stub.c}
22106 @cindex Motorola 680x0
22108 For Motorola 680x0 architectures.
22111 @cindex @file{sh-stub.c}
22114 For Renesas SH architectures.
22117 @cindex @file{sparc-stub.c}
22119 For @sc{sparc} architectures.
22121 @item sparcl-stub.c
22122 @cindex @file{sparcl-stub.c}
22125 For Fujitsu @sc{sparclite} architectures.
22129 The @file{README} file in the @value{GDBN} distribution may list other
22130 recently added stubs.
22133 * Stub Contents:: What the stub can do for you
22134 * Bootstrapping:: What you must do for the stub
22135 * Debug Session:: Putting it all together
22138 @node Stub Contents
22139 @subsection What the Stub Can Do for You
22141 @cindex remote serial stub
22142 The debugging stub for your architecture supplies these three
22146 @item set_debug_traps
22147 @findex set_debug_traps
22148 @cindex remote serial stub, initialization
22149 This routine arranges for @code{handle_exception} to run when your
22150 program stops. You must call this subroutine explicitly in your
22151 program's startup code.
22153 @item handle_exception
22154 @findex handle_exception
22155 @cindex remote serial stub, main routine
22156 This is the central workhorse, but your program never calls it
22157 explicitly---the setup code arranges for @code{handle_exception} to
22158 run when a trap is triggered.
22160 @code{handle_exception} takes control when your program stops during
22161 execution (for example, on a breakpoint), and mediates communications
22162 with @value{GDBN} on the host machine. This is where the communications
22163 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22164 representative on the target machine. It begins by sending summary
22165 information on the state of your program, then continues to execute,
22166 retrieving and transmitting any information @value{GDBN} needs, until you
22167 execute a @value{GDBN} command that makes your program resume; at that point,
22168 @code{handle_exception} returns control to your own code on the target
22172 @cindex @code{breakpoint} subroutine, remote
22173 Use this auxiliary subroutine to make your program contain a
22174 breakpoint. Depending on the particular situation, this may be the only
22175 way for @value{GDBN} to get control. For instance, if your target
22176 machine has some sort of interrupt button, you won't need to call this;
22177 pressing the interrupt button transfers control to
22178 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22179 simply receiving characters on the serial port may also trigger a trap;
22180 again, in that situation, you don't need to call @code{breakpoint} from
22181 your own program---simply running @samp{target remote} from the host
22182 @value{GDBN} session gets control.
22184 Call @code{breakpoint} if none of these is true, or if you simply want
22185 to make certain your program stops at a predetermined point for the
22186 start of your debugging session.
22189 @node Bootstrapping
22190 @subsection What You Must Do for the Stub
22192 @cindex remote stub, support routines
22193 The debugging stubs that come with @value{GDBN} are set up for a particular
22194 chip architecture, but they have no information about the rest of your
22195 debugging target machine.
22197 First of all you need to tell the stub how to communicate with the
22201 @item int getDebugChar()
22202 @findex getDebugChar
22203 Write this subroutine to read a single character from the serial port.
22204 It may be identical to @code{getchar} for your target system; a
22205 different name is used to allow you to distinguish the two if you wish.
22207 @item void putDebugChar(int)
22208 @findex putDebugChar
22209 Write this subroutine to write a single character to the serial port.
22210 It may be identical to @code{putchar} for your target system; a
22211 different name is used to allow you to distinguish the two if you wish.
22214 @cindex control C, and remote debugging
22215 @cindex interrupting remote targets
22216 If you want @value{GDBN} to be able to stop your program while it is
22217 running, you need to use an interrupt-driven serial driver, and arrange
22218 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22219 character). That is the character which @value{GDBN} uses to tell the
22220 remote system to stop.
22222 Getting the debugging target to return the proper status to @value{GDBN}
22223 probably requires changes to the standard stub; one quick and dirty way
22224 is to just execute a breakpoint instruction (the ``dirty'' part is that
22225 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22227 Other routines you need to supply are:
22230 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22231 @findex exceptionHandler
22232 Write this function to install @var{exception_address} in the exception
22233 handling tables. You need to do this because the stub does not have any
22234 way of knowing what the exception handling tables on your target system
22235 are like (for example, the processor's table might be in @sc{rom},
22236 containing entries which point to a table in @sc{ram}).
22237 The @var{exception_number} specifies the exception which should be changed;
22238 its meaning is architecture-dependent (for example, different numbers
22239 might represent divide by zero, misaligned access, etc). When this
22240 exception occurs, control should be transferred directly to
22241 @var{exception_address}, and the processor state (stack, registers,
22242 and so on) should be just as it is when a processor exception occurs. So if
22243 you want to use a jump instruction to reach @var{exception_address}, it
22244 should be a simple jump, not a jump to subroutine.
22246 For the 386, @var{exception_address} should be installed as an interrupt
22247 gate so that interrupts are masked while the handler runs. The gate
22248 should be at privilege level 0 (the most privileged level). The
22249 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22250 help from @code{exceptionHandler}.
22252 @item void flush_i_cache()
22253 @findex flush_i_cache
22254 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22255 instruction cache, if any, on your target machine. If there is no
22256 instruction cache, this subroutine may be a no-op.
22258 On target machines that have instruction caches, @value{GDBN} requires this
22259 function to make certain that the state of your program is stable.
22263 You must also make sure this library routine is available:
22266 @item void *memset(void *, int, int)
22268 This is the standard library function @code{memset} that sets an area of
22269 memory to a known value. If you have one of the free versions of
22270 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22271 either obtain it from your hardware manufacturer, or write your own.
22274 If you do not use the GNU C compiler, you may need other standard
22275 library subroutines as well; this varies from one stub to another,
22276 but in general the stubs are likely to use any of the common library
22277 subroutines which @code{@value{NGCC}} generates as inline code.
22280 @node Debug Session
22281 @subsection Putting it All Together
22283 @cindex remote serial debugging summary
22284 In summary, when your program is ready to debug, you must follow these
22289 Make sure you have defined the supporting low-level routines
22290 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22292 @code{getDebugChar}, @code{putDebugChar},
22293 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22297 Insert these lines in your program's startup code, before the main
22298 procedure is called:
22305 On some machines, when a breakpoint trap is raised, the hardware
22306 automatically makes the PC point to the instruction after the
22307 breakpoint. If your machine doesn't do that, you may need to adjust
22308 @code{handle_exception} to arrange for it to return to the instruction
22309 after the breakpoint on this first invocation, so that your program
22310 doesn't keep hitting the initial breakpoint instead of making
22314 For the 680x0 stub only, you need to provide a variable called
22315 @code{exceptionHook}. Normally you just use:
22318 void (*exceptionHook)() = 0;
22322 but if before calling @code{set_debug_traps}, you set it to point to a
22323 function in your program, that function is called when
22324 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22325 error). The function indicated by @code{exceptionHook} is called with
22326 one parameter: an @code{int} which is the exception number.
22329 Compile and link together: your program, the @value{GDBN} debugging stub for
22330 your target architecture, and the supporting subroutines.
22333 Make sure you have a serial connection between your target machine and
22334 the @value{GDBN} host, and identify the serial port on the host.
22337 @c The "remote" target now provides a `load' command, so we should
22338 @c document that. FIXME.
22339 Download your program to your target machine (or get it there by
22340 whatever means the manufacturer provides), and start it.
22343 Start @value{GDBN} on the host, and connect to the target
22344 (@pxref{Connecting,,Connecting to a Remote Target}).
22348 @node Configurations
22349 @chapter Configuration-Specific Information
22351 While nearly all @value{GDBN} commands are available for all native and
22352 cross versions of the debugger, there are some exceptions. This chapter
22353 describes things that are only available in certain configurations.
22355 There are three major categories of configurations: native
22356 configurations, where the host and target are the same, embedded
22357 operating system configurations, which are usually the same for several
22358 different processor architectures, and bare embedded processors, which
22359 are quite different from each other.
22364 * Embedded Processors::
22371 This section describes details specific to particular native
22375 * BSD libkvm Interface:: Debugging BSD kernel memory images
22376 * Process Information:: Process information
22377 * DJGPP Native:: Features specific to the DJGPP port
22378 * Cygwin Native:: Features specific to the Cygwin port
22379 * Hurd Native:: Features specific to @sc{gnu} Hurd
22380 * Darwin:: Features specific to Darwin
22383 @node BSD libkvm Interface
22384 @subsection BSD libkvm Interface
22387 @cindex kernel memory image
22388 @cindex kernel crash dump
22390 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22391 interface that provides a uniform interface for accessing kernel virtual
22392 memory images, including live systems and crash dumps. @value{GDBN}
22393 uses this interface to allow you to debug live kernels and kernel crash
22394 dumps on many native BSD configurations. This is implemented as a
22395 special @code{kvm} debugging target. For debugging a live system, load
22396 the currently running kernel into @value{GDBN} and connect to the
22400 (@value{GDBP}) @b{target kvm}
22403 For debugging crash dumps, provide the file name of the crash dump as an
22407 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22410 Once connected to the @code{kvm} target, the following commands are
22416 Set current context from the @dfn{Process Control Block} (PCB) address.
22419 Set current context from proc address. This command isn't available on
22420 modern FreeBSD systems.
22423 @node Process Information
22424 @subsection Process Information
22426 @cindex examine process image
22427 @cindex process info via @file{/proc}
22429 Some operating systems provide interfaces to fetch additional
22430 information about running processes beyond memory and per-thread
22431 register state. If @value{GDBN} is configured for an operating system
22432 with a supported interface, the command @code{info proc} is available
22433 to report information about the process running your program, or about
22434 any process running on your system.
22436 One supported interface is a facility called @samp{/proc} that can be
22437 used to examine the image of a running process using file-system
22438 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22441 On FreeBSD systems, system control nodes are used to query process
22444 In addition, some systems may provide additional process information
22445 in core files. Note that a core file may include a subset of the
22446 information available from a live process. Process information is
22447 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22454 @itemx info proc @var{process-id}
22455 Summarize available information about a process. If a
22456 process ID is specified by @var{process-id}, display information about
22457 that process; otherwise display information about the program being
22458 debugged. The summary includes the debugged process ID, the command
22459 line used to invoke it, its current working directory, and its
22460 executable file's absolute file name.
22462 On some systems, @var{process-id} can be of the form
22463 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22464 within a process. If the optional @var{pid} part is missing, it means
22465 a thread from the process being debugged (the leading @samp{/} still
22466 needs to be present, or else @value{GDBN} will interpret the number as
22467 a process ID rather than a thread ID).
22469 @item info proc cmdline
22470 @cindex info proc cmdline
22471 Show the original command line of the process. This command is
22472 supported on @sc{gnu}/Linux and FreeBSD.
22474 @item info proc cwd
22475 @cindex info proc cwd
22476 Show the current working directory of the process. This command is
22477 supported on @sc{gnu}/Linux and FreeBSD.
22479 @item info proc exe
22480 @cindex info proc exe
22481 Show the name of executable of the process. This command is supported
22482 on @sc{gnu}/Linux and FreeBSD.
22484 @item info proc files
22485 @cindex info proc files
22486 Show the file descriptors open by the process. For each open file
22487 descriptor, @value{GDBN} shows its number, type (file, directory,
22488 character device, socket), file pointer offset, and the name of the
22489 resource open on the descriptor. The resource name can be a file name
22490 (for files, directories, and devices) or a protocol followed by socket
22491 address (for network connections). This command is supported on
22494 This example shows the open file descriptors for a process using a
22495 tty for standard input and output as well as two network sockets:
22498 (gdb) info proc files 22136
22502 FD Type Offset Flags Name
22503 text file - r-------- /usr/bin/ssh
22504 ctty chr - rw------- /dev/pts/20
22505 cwd dir - r-------- /usr/home/john
22506 root dir - r-------- /
22507 0 chr 0x32933a4 rw------- /dev/pts/20
22508 1 chr 0x32933a4 rw------- /dev/pts/20
22509 2 chr 0x32933a4 rw------- /dev/pts/20
22510 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22511 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22514 @item info proc mappings
22515 @cindex memory address space mappings
22516 Report the memory address space ranges accessible in a process. On
22517 Solaris and FreeBSD systems, each memory range includes information on
22518 whether the process has read, write, or execute access rights to each
22519 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22520 includes the object file which is mapped to that range.
22522 @item info proc stat
22523 @itemx info proc status
22524 @cindex process detailed status information
22525 Show additional process-related information, including the user ID and
22526 group ID; virtual memory usage; the signals that are pending, blocked,
22527 and ignored; its TTY; its consumption of system and user time; its
22528 stack size; its @samp{nice} value; etc. These commands are supported
22529 on @sc{gnu}/Linux and FreeBSD.
22531 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22532 information (type @kbd{man 5 proc} from your shell prompt).
22534 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22537 @item info proc all
22538 Show all the information about the process described under all of the
22539 above @code{info proc} subcommands.
22542 @comment These sub-options of 'info proc' were not included when
22543 @comment procfs.c was re-written. Keep their descriptions around
22544 @comment against the day when someone finds the time to put them back in.
22545 @kindex info proc times
22546 @item info proc times
22547 Starting time, user CPU time, and system CPU time for your program and
22550 @kindex info proc id
22552 Report on the process IDs related to your program: its own process ID,
22553 the ID of its parent, the process group ID, and the session ID.
22556 @item set procfs-trace
22557 @kindex set procfs-trace
22558 @cindex @code{procfs} API calls
22559 This command enables and disables tracing of @code{procfs} API calls.
22561 @item show procfs-trace
22562 @kindex show procfs-trace
22563 Show the current state of @code{procfs} API call tracing.
22565 @item set procfs-file @var{file}
22566 @kindex set procfs-file
22567 Tell @value{GDBN} to write @code{procfs} API trace to the named
22568 @var{file}. @value{GDBN} appends the trace info to the previous
22569 contents of the file. The default is to display the trace on the
22572 @item show procfs-file
22573 @kindex show procfs-file
22574 Show the file to which @code{procfs} API trace is written.
22576 @item proc-trace-entry
22577 @itemx proc-trace-exit
22578 @itemx proc-untrace-entry
22579 @itemx proc-untrace-exit
22580 @kindex proc-trace-entry
22581 @kindex proc-trace-exit
22582 @kindex proc-untrace-entry
22583 @kindex proc-untrace-exit
22584 These commands enable and disable tracing of entries into and exits
22585 from the @code{syscall} interface.
22588 @kindex info pidlist
22589 @cindex process list, QNX Neutrino
22590 For QNX Neutrino only, this command displays the list of all the
22591 processes and all the threads within each process.
22594 @kindex info meminfo
22595 @cindex mapinfo list, QNX Neutrino
22596 For QNX Neutrino only, this command displays the list of all mapinfos.
22600 @subsection Features for Debugging @sc{djgpp} Programs
22601 @cindex @sc{djgpp} debugging
22602 @cindex native @sc{djgpp} debugging
22603 @cindex MS-DOS-specific commands
22606 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22607 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22608 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22609 top of real-mode DOS systems and their emulations.
22611 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22612 defines a few commands specific to the @sc{djgpp} port. This
22613 subsection describes those commands.
22618 This is a prefix of @sc{djgpp}-specific commands which print
22619 information about the target system and important OS structures.
22622 @cindex MS-DOS system info
22623 @cindex free memory information (MS-DOS)
22624 @item info dos sysinfo
22625 This command displays assorted information about the underlying
22626 platform: the CPU type and features, the OS version and flavor, the
22627 DPMI version, and the available conventional and DPMI memory.
22632 @cindex segment descriptor tables
22633 @cindex descriptor tables display
22635 @itemx info dos ldt
22636 @itemx info dos idt
22637 These 3 commands display entries from, respectively, Global, Local,
22638 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22639 tables are data structures which store a descriptor for each segment
22640 that is currently in use. The segment's selector is an index into a
22641 descriptor table; the table entry for that index holds the
22642 descriptor's base address and limit, and its attributes and access
22645 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22646 segment (used for both data and the stack), and a DOS segment (which
22647 allows access to DOS/BIOS data structures and absolute addresses in
22648 conventional memory). However, the DPMI host will usually define
22649 additional segments in order to support the DPMI environment.
22651 @cindex garbled pointers
22652 These commands allow to display entries from the descriptor tables.
22653 Without an argument, all entries from the specified table are
22654 displayed. An argument, which should be an integer expression, means
22655 display a single entry whose index is given by the argument. For
22656 example, here's a convenient way to display information about the
22657 debugged program's data segment:
22660 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22661 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22665 This comes in handy when you want to see whether a pointer is outside
22666 the data segment's limit (i.e.@: @dfn{garbled}).
22668 @cindex page tables display (MS-DOS)
22670 @itemx info dos pte
22671 These two commands display entries from, respectively, the Page
22672 Directory and the Page Tables. Page Directories and Page Tables are
22673 data structures which control how virtual memory addresses are mapped
22674 into physical addresses. A Page Table includes an entry for every
22675 page of memory that is mapped into the program's address space; there
22676 may be several Page Tables, each one holding up to 4096 entries. A
22677 Page Directory has up to 4096 entries, one each for every Page Table
22678 that is currently in use.
22680 Without an argument, @kbd{info dos pde} displays the entire Page
22681 Directory, and @kbd{info dos pte} displays all the entries in all of
22682 the Page Tables. An argument, an integer expression, given to the
22683 @kbd{info dos pde} command means display only that entry from the Page
22684 Directory table. An argument given to the @kbd{info dos pte} command
22685 means display entries from a single Page Table, the one pointed to by
22686 the specified entry in the Page Directory.
22688 @cindex direct memory access (DMA) on MS-DOS
22689 These commands are useful when your program uses @dfn{DMA} (Direct
22690 Memory Access), which needs physical addresses to program the DMA
22693 These commands are supported only with some DPMI servers.
22695 @cindex physical address from linear address
22696 @item info dos address-pte @var{addr}
22697 This command displays the Page Table entry for a specified linear
22698 address. The argument @var{addr} is a linear address which should
22699 already have the appropriate segment's base address added to it,
22700 because this command accepts addresses which may belong to @emph{any}
22701 segment. For example, here's how to display the Page Table entry for
22702 the page where a variable @code{i} is stored:
22705 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22706 @exdent @code{Page Table entry for address 0x11a00d30:}
22707 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22711 This says that @code{i} is stored at offset @code{0xd30} from the page
22712 whose physical base address is @code{0x02698000}, and shows all the
22713 attributes of that page.
22715 Note that you must cast the addresses of variables to a @code{char *},
22716 since otherwise the value of @code{__djgpp_base_address}, the base
22717 address of all variables and functions in a @sc{djgpp} program, will
22718 be added using the rules of C pointer arithmetics: if @code{i} is
22719 declared an @code{int}, @value{GDBN} will add 4 times the value of
22720 @code{__djgpp_base_address} to the address of @code{i}.
22722 Here's another example, it displays the Page Table entry for the
22726 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22727 @exdent @code{Page Table entry for address 0x29110:}
22728 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22732 (The @code{+ 3} offset is because the transfer buffer's address is the
22733 3rd member of the @code{_go32_info_block} structure.) The output
22734 clearly shows that this DPMI server maps the addresses in conventional
22735 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22736 linear (@code{0x29110}) addresses are identical.
22738 This command is supported only with some DPMI servers.
22741 @cindex DOS serial data link, remote debugging
22742 In addition to native debugging, the DJGPP port supports remote
22743 debugging via a serial data link. The following commands are specific
22744 to remote serial debugging in the DJGPP port of @value{GDBN}.
22747 @kindex set com1base
22748 @kindex set com1irq
22749 @kindex set com2base
22750 @kindex set com2irq
22751 @kindex set com3base
22752 @kindex set com3irq
22753 @kindex set com4base
22754 @kindex set com4irq
22755 @item set com1base @var{addr}
22756 This command sets the base I/O port address of the @file{COM1} serial
22759 @item set com1irq @var{irq}
22760 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22761 for the @file{COM1} serial port.
22763 There are similar commands @samp{set com2base}, @samp{set com3irq},
22764 etc.@: for setting the port address and the @code{IRQ} lines for the
22767 @kindex show com1base
22768 @kindex show com1irq
22769 @kindex show com2base
22770 @kindex show com2irq
22771 @kindex show com3base
22772 @kindex show com3irq
22773 @kindex show com4base
22774 @kindex show com4irq
22775 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22776 display the current settings of the base address and the @code{IRQ}
22777 lines used by the COM ports.
22780 @kindex info serial
22781 @cindex DOS serial port status
22782 This command prints the status of the 4 DOS serial ports. For each
22783 port, it prints whether it's active or not, its I/O base address and
22784 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22785 counts of various errors encountered so far.
22789 @node Cygwin Native
22790 @subsection Features for Debugging MS Windows PE Executables
22791 @cindex MS Windows debugging
22792 @cindex native Cygwin debugging
22793 @cindex Cygwin-specific commands
22795 @value{GDBN} supports native debugging of MS Windows programs, including
22796 DLLs with and without symbolic debugging information.
22798 @cindex Ctrl-BREAK, MS-Windows
22799 @cindex interrupt debuggee on MS-Windows
22800 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22801 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22802 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22803 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22804 sequence, which can be used to interrupt the debuggee even if it
22807 There are various additional Cygwin-specific commands, described in
22808 this section. Working with DLLs that have no debugging symbols is
22809 described in @ref{Non-debug DLL Symbols}.
22814 This is a prefix of MS Windows-specific commands which print
22815 information about the target system and important OS structures.
22817 @item info w32 selector
22818 This command displays information returned by
22819 the Win32 API @code{GetThreadSelectorEntry} function.
22820 It takes an optional argument that is evaluated to
22821 a long value to give the information about this given selector.
22822 Without argument, this command displays information
22823 about the six segment registers.
22825 @item info w32 thread-information-block
22826 This command displays thread specific information stored in the
22827 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22828 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22830 @kindex signal-event
22831 @item signal-event @var{id}
22832 This command signals an event with user-provided @var{id}. Used to resume
22833 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22835 To use it, create or edit the following keys in
22836 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22837 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22838 (for x86_64 versions):
22842 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22843 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22844 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22846 The first @code{%ld} will be replaced by the process ID of the
22847 crashing process, the second @code{%ld} will be replaced by the ID of
22848 the event that blocks the crashing process, waiting for @value{GDBN}
22852 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22853 make the system run debugger specified by the Debugger key
22854 automatically, @code{0} will cause a dialog box with ``OK'' and
22855 ``Cancel'' buttons to appear, which allows the user to either
22856 terminate the crashing process (OK) or debug it (Cancel).
22859 @kindex set cygwin-exceptions
22860 @cindex debugging the Cygwin DLL
22861 @cindex Cygwin DLL, debugging
22862 @item set cygwin-exceptions @var{mode}
22863 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22864 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22865 @value{GDBN} will delay recognition of exceptions, and may ignore some
22866 exceptions which seem to be caused by internal Cygwin DLL
22867 ``bookkeeping''. This option is meant primarily for debugging the
22868 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22869 @value{GDBN} users with false @code{SIGSEGV} signals.
22871 @kindex show cygwin-exceptions
22872 @item show cygwin-exceptions
22873 Displays whether @value{GDBN} will break on exceptions that happen
22874 inside the Cygwin DLL itself.
22876 @kindex set new-console
22877 @item set new-console @var{mode}
22878 If @var{mode} is @code{on} the debuggee will
22879 be started in a new console on next start.
22880 If @var{mode} is @code{off}, the debuggee will
22881 be started in the same console as the debugger.
22883 @kindex show new-console
22884 @item show new-console
22885 Displays whether a new console is used
22886 when the debuggee is started.
22888 @kindex set new-group
22889 @item set new-group @var{mode}
22890 This boolean value controls whether the debuggee should
22891 start a new group or stay in the same group as the debugger.
22892 This affects the way the Windows OS handles
22895 @kindex show new-group
22896 @item show new-group
22897 Displays current value of new-group boolean.
22899 @kindex set debugevents
22900 @item set debugevents
22901 This boolean value adds debug output concerning kernel events related
22902 to the debuggee seen by the debugger. This includes events that
22903 signal thread and process creation and exit, DLL loading and
22904 unloading, console interrupts, and debugging messages produced by the
22905 Windows @code{OutputDebugString} API call.
22907 @kindex set debugexec
22908 @item set debugexec
22909 This boolean value adds debug output concerning execute events
22910 (such as resume thread) seen by the debugger.
22912 @kindex set debugexceptions
22913 @item set debugexceptions
22914 This boolean value adds debug output concerning exceptions in the
22915 debuggee seen by the debugger.
22917 @kindex set debugmemory
22918 @item set debugmemory
22919 This boolean value adds debug output concerning debuggee memory reads
22920 and writes by the debugger.
22924 This boolean values specifies whether the debuggee is called
22925 via a shell or directly (default value is on).
22929 Displays if the debuggee will be started with a shell.
22934 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22937 @node Non-debug DLL Symbols
22938 @subsubsection Support for DLLs without Debugging Symbols
22939 @cindex DLLs with no debugging symbols
22940 @cindex Minimal symbols and DLLs
22942 Very often on windows, some of the DLLs that your program relies on do
22943 not include symbolic debugging information (for example,
22944 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22945 symbols in a DLL, it relies on the minimal amount of symbolic
22946 information contained in the DLL's export table. This section
22947 describes working with such symbols, known internally to @value{GDBN} as
22948 ``minimal symbols''.
22950 Note that before the debugged program has started execution, no DLLs
22951 will have been loaded. The easiest way around this problem is simply to
22952 start the program --- either by setting a breakpoint or letting the
22953 program run once to completion.
22955 @subsubsection DLL Name Prefixes
22957 In keeping with the naming conventions used by the Microsoft debugging
22958 tools, DLL export symbols are made available with a prefix based on the
22959 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22960 also entered into the symbol table, so @code{CreateFileA} is often
22961 sufficient. In some cases there will be name clashes within a program
22962 (particularly if the executable itself includes full debugging symbols)
22963 necessitating the use of the fully qualified name when referring to the
22964 contents of the DLL. Use single-quotes around the name to avoid the
22965 exclamation mark (``!'') being interpreted as a language operator.
22967 Note that the internal name of the DLL may be all upper-case, even
22968 though the file name of the DLL is lower-case, or vice-versa. Since
22969 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22970 some confusion. If in doubt, try the @code{info functions} and
22971 @code{info variables} commands or even @code{maint print msymbols}
22972 (@pxref{Symbols}). Here's an example:
22975 (@value{GDBP}) info function CreateFileA
22976 All functions matching regular expression "CreateFileA":
22978 Non-debugging symbols:
22979 0x77e885f4 CreateFileA
22980 0x77e885f4 KERNEL32!CreateFileA
22984 (@value{GDBP}) info function !
22985 All functions matching regular expression "!":
22987 Non-debugging symbols:
22988 0x6100114c cygwin1!__assert
22989 0x61004034 cygwin1!_dll_crt0@@0
22990 0x61004240 cygwin1!dll_crt0(per_process *)
22994 @subsubsection Working with Minimal Symbols
22996 Symbols extracted from a DLL's export table do not contain very much
22997 type information. All that @value{GDBN} can do is guess whether a symbol
22998 refers to a function or variable depending on the linker section that
22999 contains the symbol. Also note that the actual contents of the memory
23000 contained in a DLL are not available unless the program is running. This
23001 means that you cannot examine the contents of a variable or disassemble
23002 a function within a DLL without a running program.
23004 Variables are generally treated as pointers and dereferenced
23005 automatically. For this reason, it is often necessary to prefix a
23006 variable name with the address-of operator (``&'') and provide explicit
23007 type information in the command. Here's an example of the type of
23011 (@value{GDBP}) print 'cygwin1!__argv'
23012 'cygwin1!__argv' has unknown type; cast it to its declared type
23016 (@value{GDBP}) x 'cygwin1!__argv'
23017 'cygwin1!__argv' has unknown type; cast it to its declared type
23020 And two possible solutions:
23023 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23024 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23028 (@value{GDBP}) x/2x &'cygwin1!__argv'
23029 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23030 (@value{GDBP}) x/x 0x10021608
23031 0x10021608: 0x0022fd98
23032 (@value{GDBP}) x/s 0x0022fd98
23033 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23036 Setting a break point within a DLL is possible even before the program
23037 starts execution. However, under these circumstances, @value{GDBN} can't
23038 examine the initial instructions of the function in order to skip the
23039 function's frame set-up code. You can work around this by using ``*&''
23040 to set the breakpoint at a raw memory address:
23043 (@value{GDBP}) break *&'python22!PyOS_Readline'
23044 Breakpoint 1 at 0x1e04eff0
23047 The author of these extensions is not entirely convinced that setting a
23048 break point within a shared DLL like @file{kernel32.dll} is completely
23052 @subsection Commands Specific to @sc{gnu} Hurd Systems
23053 @cindex @sc{gnu} Hurd debugging
23055 This subsection describes @value{GDBN} commands specific to the
23056 @sc{gnu} Hurd native debugging.
23061 @kindex set signals@r{, Hurd command}
23062 @kindex set sigs@r{, Hurd command}
23063 This command toggles the state of inferior signal interception by
23064 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23065 affected by this command. @code{sigs} is a shorthand alias for
23070 @kindex show signals@r{, Hurd command}
23071 @kindex show sigs@r{, Hurd command}
23072 Show the current state of intercepting inferior's signals.
23074 @item set signal-thread
23075 @itemx set sigthread
23076 @kindex set signal-thread
23077 @kindex set sigthread
23078 This command tells @value{GDBN} which thread is the @code{libc} signal
23079 thread. That thread is run when a signal is delivered to a running
23080 process. @code{set sigthread} is the shorthand alias of @code{set
23083 @item show signal-thread
23084 @itemx show sigthread
23085 @kindex show signal-thread
23086 @kindex show sigthread
23087 These two commands show which thread will run when the inferior is
23088 delivered a signal.
23091 @kindex set stopped@r{, Hurd command}
23092 This commands tells @value{GDBN} that the inferior process is stopped,
23093 as with the @code{SIGSTOP} signal. The stopped process can be
23094 continued by delivering a signal to it.
23097 @kindex show stopped@r{, Hurd command}
23098 This command shows whether @value{GDBN} thinks the debuggee is
23101 @item set exceptions
23102 @kindex set exceptions@r{, Hurd command}
23103 Use this command to turn off trapping of exceptions in the inferior.
23104 When exception trapping is off, neither breakpoints nor
23105 single-stepping will work. To restore the default, set exception
23108 @item show exceptions
23109 @kindex show exceptions@r{, Hurd command}
23110 Show the current state of trapping exceptions in the inferior.
23112 @item set task pause
23113 @kindex set task@r{, Hurd commands}
23114 @cindex task attributes (@sc{gnu} Hurd)
23115 @cindex pause current task (@sc{gnu} Hurd)
23116 This command toggles task suspension when @value{GDBN} has control.
23117 Setting it to on takes effect immediately, and the task is suspended
23118 whenever @value{GDBN} gets control. Setting it to off will take
23119 effect the next time the inferior is continued. If this option is set
23120 to off, you can use @code{set thread default pause on} or @code{set
23121 thread pause on} (see below) to pause individual threads.
23123 @item show task pause
23124 @kindex show task@r{, Hurd commands}
23125 Show the current state of task suspension.
23127 @item set task detach-suspend-count
23128 @cindex task suspend count
23129 @cindex detach from task, @sc{gnu} Hurd
23130 This command sets the suspend count the task will be left with when
23131 @value{GDBN} detaches from it.
23133 @item show task detach-suspend-count
23134 Show the suspend count the task will be left with when detaching.
23136 @item set task exception-port
23137 @itemx set task excp
23138 @cindex task exception port, @sc{gnu} Hurd
23139 This command sets the task exception port to which @value{GDBN} will
23140 forward exceptions. The argument should be the value of the @dfn{send
23141 rights} of the task. @code{set task excp} is a shorthand alias.
23143 @item set noninvasive
23144 @cindex noninvasive task options
23145 This command switches @value{GDBN} to a mode that is the least
23146 invasive as far as interfering with the inferior is concerned. This
23147 is the same as using @code{set task pause}, @code{set exceptions}, and
23148 @code{set signals} to values opposite to the defaults.
23150 @item info send-rights
23151 @itemx info receive-rights
23152 @itemx info port-rights
23153 @itemx info port-sets
23154 @itemx info dead-names
23157 @cindex send rights, @sc{gnu} Hurd
23158 @cindex receive rights, @sc{gnu} Hurd
23159 @cindex port rights, @sc{gnu} Hurd
23160 @cindex port sets, @sc{gnu} Hurd
23161 @cindex dead names, @sc{gnu} Hurd
23162 These commands display information about, respectively, send rights,
23163 receive rights, port rights, port sets, and dead names of a task.
23164 There are also shorthand aliases: @code{info ports} for @code{info
23165 port-rights} and @code{info psets} for @code{info port-sets}.
23167 @item set thread pause
23168 @kindex set thread@r{, Hurd command}
23169 @cindex thread properties, @sc{gnu} Hurd
23170 @cindex pause current thread (@sc{gnu} Hurd)
23171 This command toggles current thread suspension when @value{GDBN} has
23172 control. Setting it to on takes effect immediately, and the current
23173 thread is suspended whenever @value{GDBN} gets control. Setting it to
23174 off will take effect the next time the inferior is continued.
23175 Normally, this command has no effect, since when @value{GDBN} has
23176 control, the whole task is suspended. However, if you used @code{set
23177 task pause off} (see above), this command comes in handy to suspend
23178 only the current thread.
23180 @item show thread pause
23181 @kindex show thread@r{, Hurd command}
23182 This command shows the state of current thread suspension.
23184 @item set thread run
23185 This command sets whether the current thread is allowed to run.
23187 @item show thread run
23188 Show whether the current thread is allowed to run.
23190 @item set thread detach-suspend-count
23191 @cindex thread suspend count, @sc{gnu} Hurd
23192 @cindex detach from thread, @sc{gnu} Hurd
23193 This command sets the suspend count @value{GDBN} will leave on a
23194 thread when detaching. This number is relative to the suspend count
23195 found by @value{GDBN} when it notices the thread; use @code{set thread
23196 takeover-suspend-count} to force it to an absolute value.
23198 @item show thread detach-suspend-count
23199 Show the suspend count @value{GDBN} will leave on the thread when
23202 @item set thread exception-port
23203 @itemx set thread excp
23204 Set the thread exception port to which to forward exceptions. This
23205 overrides the port set by @code{set task exception-port} (see above).
23206 @code{set thread excp} is the shorthand alias.
23208 @item set thread takeover-suspend-count
23209 Normally, @value{GDBN}'s thread suspend counts are relative to the
23210 value @value{GDBN} finds when it notices each thread. This command
23211 changes the suspend counts to be absolute instead.
23213 @item set thread default
23214 @itemx show thread default
23215 @cindex thread default settings, @sc{gnu} Hurd
23216 Each of the above @code{set thread} commands has a @code{set thread
23217 default} counterpart (e.g., @code{set thread default pause}, @code{set
23218 thread default exception-port}, etc.). The @code{thread default}
23219 variety of commands sets the default thread properties for all
23220 threads; you can then change the properties of individual threads with
23221 the non-default commands.
23228 @value{GDBN} provides the following commands specific to the Darwin target:
23231 @item set debug darwin @var{num}
23232 @kindex set debug darwin
23233 When set to a non zero value, enables debugging messages specific to
23234 the Darwin support. Higher values produce more verbose output.
23236 @item show debug darwin
23237 @kindex show debug darwin
23238 Show the current state of Darwin messages.
23240 @item set debug mach-o @var{num}
23241 @kindex set debug mach-o
23242 When set to a non zero value, enables debugging messages while
23243 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23244 file format used on Darwin for object and executable files.) Higher
23245 values produce more verbose output. This is a command to diagnose
23246 problems internal to @value{GDBN} and should not be needed in normal
23249 @item show debug mach-o
23250 @kindex show debug mach-o
23251 Show the current state of Mach-O file messages.
23253 @item set mach-exceptions on
23254 @itemx set mach-exceptions off
23255 @kindex set mach-exceptions
23256 On Darwin, faults are first reported as a Mach exception and are then
23257 mapped to a Posix signal. Use this command to turn on trapping of
23258 Mach exceptions in the inferior. This might be sometimes useful to
23259 better understand the cause of a fault. The default is off.
23261 @item show mach-exceptions
23262 @kindex show mach-exceptions
23263 Show the current state of exceptions trapping.
23268 @section Embedded Operating Systems
23270 This section describes configurations involving the debugging of
23271 embedded operating systems that are available for several different
23274 @value{GDBN} includes the ability to debug programs running on
23275 various real-time operating systems.
23277 @node Embedded Processors
23278 @section Embedded Processors
23280 This section goes into details specific to particular embedded
23283 @cindex send command to simulator
23284 Whenever a specific embedded processor has a simulator, @value{GDBN}
23285 allows to send an arbitrary command to the simulator.
23288 @item sim @var{command}
23289 @kindex sim@r{, a command}
23290 Send an arbitrary @var{command} string to the simulator. Consult the
23291 documentation for the specific simulator in use for information about
23292 acceptable commands.
23297 * ARC:: Synopsys ARC
23299 * M68K:: Motorola M68K
23300 * MicroBlaze:: Xilinx MicroBlaze
23301 * MIPS Embedded:: MIPS Embedded
23302 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23303 * PowerPC Embedded:: PowerPC Embedded
23306 * Super-H:: Renesas Super-H
23310 @subsection Synopsys ARC
23311 @cindex Synopsys ARC
23312 @cindex ARC specific commands
23318 @value{GDBN} provides the following ARC-specific commands:
23321 @item set debug arc
23322 @kindex set debug arc
23323 Control the level of ARC specific debug messages. Use 0 for no messages (the
23324 default), 1 for debug messages, and 2 for even more debug messages.
23326 @item show debug arc
23327 @kindex show debug arc
23328 Show the level of ARC specific debugging in operation.
23330 @item maint print arc arc-instruction @var{address}
23331 @kindex maint print arc arc-instruction
23332 Print internal disassembler information about instruction at a given address.
23339 @value{GDBN} provides the following ARM-specific commands:
23342 @item set arm disassembler
23344 This commands selects from a list of disassembly styles. The
23345 @code{"std"} style is the standard style.
23347 @item show arm disassembler
23349 Show the current disassembly style.
23351 @item set arm apcs32
23352 @cindex ARM 32-bit mode
23353 This command toggles ARM operation mode between 32-bit and 26-bit.
23355 @item show arm apcs32
23356 Display the current usage of the ARM 32-bit mode.
23358 @item set arm fpu @var{fputype}
23359 This command sets the ARM floating-point unit (FPU) type. The
23360 argument @var{fputype} can be one of these:
23364 Determine the FPU type by querying the OS ABI.
23366 Software FPU, with mixed-endian doubles on little-endian ARM
23369 GCC-compiled FPA co-processor.
23371 Software FPU with pure-endian doubles.
23377 Show the current type of the FPU.
23380 This command forces @value{GDBN} to use the specified ABI.
23383 Show the currently used ABI.
23385 @item set arm fallback-mode (arm|thumb|auto)
23386 @value{GDBN} uses the symbol table, when available, to determine
23387 whether instructions are ARM or Thumb. This command controls
23388 @value{GDBN}'s default behavior when the symbol table is not
23389 available. The default is @samp{auto}, which causes @value{GDBN} to
23390 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23393 @item show arm fallback-mode
23394 Show the current fallback instruction mode.
23396 @item set arm force-mode (arm|thumb|auto)
23397 This command overrides use of the symbol table to determine whether
23398 instructions are ARM or Thumb. The default is @samp{auto}, which
23399 causes @value{GDBN} to use the symbol table and then the setting
23400 of @samp{set arm fallback-mode}.
23402 @item show arm force-mode
23403 Show the current forced instruction mode.
23405 @item set debug arm
23406 Toggle whether to display ARM-specific debugging messages from the ARM
23407 target support subsystem.
23409 @item show debug arm
23410 Show whether ARM-specific debugging messages are enabled.
23414 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23415 The @value{GDBN} ARM simulator accepts the following optional arguments.
23418 @item --swi-support=@var{type}
23419 Tell the simulator which SWI interfaces to support. The argument
23420 @var{type} may be a comma separated list of the following values.
23421 The default value is @code{all}.
23436 The Motorola m68k configuration includes ColdFire support.
23439 @subsection MicroBlaze
23440 @cindex Xilinx MicroBlaze
23441 @cindex XMD, Xilinx Microprocessor Debugger
23443 The MicroBlaze is a soft-core processor supported on various Xilinx
23444 FPGAs, such as Spartan or Virtex series. Boards with these processors
23445 usually have JTAG ports which connect to a host system running the Xilinx
23446 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23447 This host system is used to download the configuration bitstream to
23448 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23449 communicates with the target board using the JTAG interface and
23450 presents a @code{gdbserver} interface to the board. By default
23451 @code{xmd} uses port @code{1234}. (While it is possible to change
23452 this default port, it requires the use of undocumented @code{xmd}
23453 commands. Contact Xilinx support if you need to do this.)
23455 Use these GDB commands to connect to the MicroBlaze target processor.
23458 @item target remote :1234
23459 Use this command to connect to the target if you are running @value{GDBN}
23460 on the same system as @code{xmd}.
23462 @item target remote @var{xmd-host}:1234
23463 Use this command to connect to the target if it is connected to @code{xmd}
23464 running on a different system named @var{xmd-host}.
23467 Use this command to download a program to the MicroBlaze target.
23469 @item set debug microblaze @var{n}
23470 Enable MicroBlaze-specific debugging messages if non-zero.
23472 @item show debug microblaze @var{n}
23473 Show MicroBlaze-specific debugging level.
23476 @node MIPS Embedded
23477 @subsection @acronym{MIPS} Embedded
23480 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23483 @item set mipsfpu double
23484 @itemx set mipsfpu single
23485 @itemx set mipsfpu none
23486 @itemx set mipsfpu auto
23487 @itemx show mipsfpu
23488 @kindex set mipsfpu
23489 @kindex show mipsfpu
23490 @cindex @acronym{MIPS} remote floating point
23491 @cindex floating point, @acronym{MIPS} remote
23492 If your target board does not support the @acronym{MIPS} floating point
23493 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23494 need this, you may wish to put the command in your @value{GDBN} init
23495 file). This tells @value{GDBN} how to find the return value of
23496 functions which return floating point values. It also allows
23497 @value{GDBN} to avoid saving the floating point registers when calling
23498 functions on the board. If you are using a floating point coprocessor
23499 with only single precision floating point support, as on the @sc{r4650}
23500 processor, use the command @samp{set mipsfpu single}. The default
23501 double precision floating point coprocessor may be selected using
23502 @samp{set mipsfpu double}.
23504 In previous versions the only choices were double precision or no
23505 floating point, so @samp{set mipsfpu on} will select double precision
23506 and @samp{set mipsfpu off} will select no floating point.
23508 As usual, you can inquire about the @code{mipsfpu} variable with
23509 @samp{show mipsfpu}.
23512 @node OpenRISC 1000
23513 @subsection OpenRISC 1000
23514 @cindex OpenRISC 1000
23517 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23518 mainly provided as a soft-core which can run on Xilinx, Altera and other
23521 @value{GDBN} for OpenRISC supports the below commands when connecting to
23529 Runs the builtin CPU simulator which can run very basic
23530 programs but does not support most hardware functions like MMU.
23531 For more complex use cases the user is advised to run an external
23532 target, and connect using @samp{target remote}.
23534 Example: @code{target sim}
23536 @item set debug or1k
23537 Toggle whether to display OpenRISC-specific debugging messages from the
23538 OpenRISC target support subsystem.
23540 @item show debug or1k
23541 Show whether OpenRISC-specific debugging messages are enabled.
23544 @node PowerPC Embedded
23545 @subsection PowerPC Embedded
23547 @cindex DVC register
23548 @value{GDBN} supports using the DVC (Data Value Compare) register to
23549 implement in hardware simple hardware watchpoint conditions of the form:
23552 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23553 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23556 The DVC register will be automatically used when @value{GDBN} detects
23557 such pattern in a condition expression, and the created watchpoint uses one
23558 debug register (either the @code{exact-watchpoints} option is on and the
23559 variable is scalar, or the variable has a length of one byte). This feature
23560 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23563 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23564 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23565 in which case watchpoints using only one debug register are created when
23566 watching variables of scalar types.
23568 You can create an artificial array to watch an arbitrary memory
23569 region using one of the following commands (@pxref{Expressions}):
23572 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23573 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23576 PowerPC embedded processors support masked watchpoints. See the discussion
23577 about the @code{mask} argument in @ref{Set Watchpoints}.
23579 @cindex ranged breakpoint
23580 PowerPC embedded processors support hardware accelerated
23581 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23582 the inferior whenever it executes an instruction at any address within
23583 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23584 use the @code{break-range} command.
23586 @value{GDBN} provides the following PowerPC-specific commands:
23589 @kindex break-range
23590 @item break-range @var{start-location}, @var{end-location}
23591 Set a breakpoint for an address range given by
23592 @var{start-location} and @var{end-location}, which can specify a function name,
23593 a line number, an offset of lines from the current line or from the start
23594 location, or an address of an instruction (see @ref{Specify Location},
23595 for a list of all the possible ways to specify a @var{location}.)
23596 The breakpoint will stop execution of the inferior whenever it
23597 executes an instruction at any address within the specified range,
23598 (including @var{start-location} and @var{end-location}.)
23600 @kindex set powerpc
23601 @item set powerpc soft-float
23602 @itemx show powerpc soft-float
23603 Force @value{GDBN} to use (or not use) a software floating point calling
23604 convention. By default, @value{GDBN} selects the calling convention based
23605 on the selected architecture and the provided executable file.
23607 @item set powerpc vector-abi
23608 @itemx show powerpc vector-abi
23609 Force @value{GDBN} to use the specified calling convention for vector
23610 arguments and return values. The valid options are @samp{auto};
23611 @samp{generic}, to avoid vector registers even if they are present;
23612 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23613 registers. By default, @value{GDBN} selects the calling convention
23614 based on the selected architecture and the provided executable file.
23616 @item set powerpc exact-watchpoints
23617 @itemx show powerpc exact-watchpoints
23618 Allow @value{GDBN} to use only one debug register when watching a variable
23619 of scalar type, thus assuming that the variable is accessed through the
23620 address of its first byte.
23625 @subsection Atmel AVR
23628 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23629 following AVR-specific commands:
23632 @item info io_registers
23633 @kindex info io_registers@r{, AVR}
23634 @cindex I/O registers (Atmel AVR)
23635 This command displays information about the AVR I/O registers. For
23636 each register, @value{GDBN} prints its number and value.
23643 When configured for debugging CRIS, @value{GDBN} provides the
23644 following CRIS-specific commands:
23647 @item set cris-version @var{ver}
23648 @cindex CRIS version
23649 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23650 The CRIS version affects register names and sizes. This command is useful in
23651 case autodetection of the CRIS version fails.
23653 @item show cris-version
23654 Show the current CRIS version.
23656 @item set cris-dwarf2-cfi
23657 @cindex DWARF-2 CFI and CRIS
23658 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23659 Change to @samp{off} when using @code{gcc-cris} whose version is below
23662 @item show cris-dwarf2-cfi
23663 Show the current state of using DWARF-2 CFI.
23665 @item set cris-mode @var{mode}
23667 Set the current CRIS mode to @var{mode}. It should only be changed when
23668 debugging in guru mode, in which case it should be set to
23669 @samp{guru} (the default is @samp{normal}).
23671 @item show cris-mode
23672 Show the current CRIS mode.
23676 @subsection Renesas Super-H
23679 For the Renesas Super-H processor, @value{GDBN} provides these
23683 @item set sh calling-convention @var{convention}
23684 @kindex set sh calling-convention
23685 Set the calling-convention used when calling functions from @value{GDBN}.
23686 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23687 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23688 convention. If the DWARF-2 information of the called function specifies
23689 that the function follows the Renesas calling convention, the function
23690 is called using the Renesas calling convention. If the calling convention
23691 is set to @samp{renesas}, the Renesas calling convention is always used,
23692 regardless of the DWARF-2 information. This can be used to override the
23693 default of @samp{gcc} if debug information is missing, or the compiler
23694 does not emit the DWARF-2 calling convention entry for a function.
23696 @item show sh calling-convention
23697 @kindex show sh calling-convention
23698 Show the current calling convention setting.
23703 @node Architectures
23704 @section Architectures
23706 This section describes characteristics of architectures that affect
23707 all uses of @value{GDBN} with the architecture, both native and cross.
23714 * HPPA:: HP PA architecture
23715 * SPU:: Cell Broadband Engine SPU architecture
23723 @subsection AArch64
23724 @cindex AArch64 support
23726 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23727 following special commands:
23730 @item set debug aarch64
23731 @kindex set debug aarch64
23732 This command determines whether AArch64 architecture-specific debugging
23733 messages are to be displayed.
23735 @item show debug aarch64
23736 Show whether AArch64 debugging messages are displayed.
23740 @subsubsection AArch64 SVE.
23741 @cindex AArch64 SVE.
23743 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23744 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23745 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23746 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23747 @code{$vg} will be provided. This is the vector granule for the current thread
23748 and represents the number of 64-bit chunks in an SVE @code{z} register.
23750 If the vector length changes, then the @code{$vg} register will be updated,
23751 but the lengths of the @code{z} and @code{p} registers will not change. This
23752 is a known limitation of @value{GDBN} and does not affect the execution of the
23757 @subsection x86 Architecture-specific Issues
23760 @item set struct-convention @var{mode}
23761 @kindex set struct-convention
23762 @cindex struct return convention
23763 @cindex struct/union returned in registers
23764 Set the convention used by the inferior to return @code{struct}s and
23765 @code{union}s from functions to @var{mode}. Possible values of
23766 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23767 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23768 are returned on the stack, while @code{"reg"} means that a
23769 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23770 be returned in a register.
23772 @item show struct-convention
23773 @kindex show struct-convention
23774 Show the current setting of the convention to return @code{struct}s
23779 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23780 @cindex Intel Memory Protection Extensions (MPX).
23782 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23783 @footnote{The register named with capital letters represent the architecture
23784 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23785 which are the lower bound and upper bound. Bounds are effective addresses or
23786 memory locations. The upper bounds are architecturally represented in 1's
23787 complement form. A bound having lower bound = 0, and upper bound = 0
23788 (1's complement of all bits set) will allow access to the entire address space.
23790 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23791 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23792 display the upper bound performing the complement of one operation on the
23793 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23794 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23795 can also be noted that the upper bounds are inclusive.
23797 As an example, assume that the register BND0 holds bounds for a pointer having
23798 access allowed for the range between 0x32 and 0x71. The values present on
23799 bnd0raw and bnd registers are presented as follows:
23802 bnd0raw = @{0x32, 0xffffffff8e@}
23803 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23806 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23807 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23808 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23809 Python, the display includes the memory size, in bits, accessible to
23812 Bounds can also be stored in bounds tables, which are stored in
23813 application memory. These tables store bounds for pointers by specifying
23814 the bounds pointer's value along with its bounds. Evaluating and changing
23815 bounds located in bound tables is therefore interesting while investigating
23816 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23819 @item show mpx bound @var{pointer}
23820 @kindex show mpx bound
23821 Display bounds of the given @var{pointer}.
23823 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23824 @kindex set mpx bound
23825 Set the bounds of a pointer in the bound table.
23826 This command takes three parameters: @var{pointer} is the pointers
23827 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23828 for lower and upper bounds respectively.
23831 When you call an inferior function on an Intel MPX enabled program,
23832 GDB sets the inferior's bound registers to the init (disabled) state
23833 before calling the function. As a consequence, bounds checks for the
23834 pointer arguments passed to the function will always pass.
23836 This is necessary because when you call an inferior function, the
23837 program is usually in the middle of the execution of other function.
23838 Since at that point bound registers are in an arbitrary state, not
23839 clearing them would lead to random bound violations in the called
23842 You can still examine the influence of the bound registers on the
23843 execution of the called function by stopping the execution of the
23844 called function at its prologue, setting bound registers, and
23845 continuing the execution. For example:
23849 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23850 $ print upper (a, b, c, d, 1)
23851 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23853 @{lbound = 0x0, ubound = ffffffff@} : size -1
23856 At this last step the value of bnd0 can be changed for investigation of bound
23857 violations caused along the execution of the call. In order to know how to
23858 set the bound registers or bound table for the call consult the ABI.
23863 See the following section.
23866 @subsection @acronym{MIPS}
23868 @cindex stack on Alpha
23869 @cindex stack on @acronym{MIPS}
23870 @cindex Alpha stack
23871 @cindex @acronym{MIPS} stack
23872 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23873 sometimes requires @value{GDBN} to search backward in the object code to
23874 find the beginning of a function.
23876 @cindex response time, @acronym{MIPS} debugging
23877 To improve response time (especially for embedded applications, where
23878 @value{GDBN} may be restricted to a slow serial line for this search)
23879 you may want to limit the size of this search, using one of these
23883 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23884 @item set heuristic-fence-post @var{limit}
23885 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23886 search for the beginning of a function. A value of @var{0} (the
23887 default) means there is no limit. However, except for @var{0}, the
23888 larger the limit the more bytes @code{heuristic-fence-post} must search
23889 and therefore the longer it takes to run. You should only need to use
23890 this command when debugging a stripped executable.
23892 @item show heuristic-fence-post
23893 Display the current limit.
23897 These commands are available @emph{only} when @value{GDBN} is configured
23898 for debugging programs on Alpha or @acronym{MIPS} processors.
23900 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23904 @item set mips abi @var{arg}
23905 @kindex set mips abi
23906 @cindex set ABI for @acronym{MIPS}
23907 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23908 values of @var{arg} are:
23912 The default ABI associated with the current binary (this is the
23922 @item show mips abi
23923 @kindex show mips abi
23924 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23926 @item set mips compression @var{arg}
23927 @kindex set mips compression
23928 @cindex code compression, @acronym{MIPS}
23929 Tell @value{GDBN} which @acronym{MIPS} compressed
23930 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23931 inferior. @value{GDBN} uses this for code disassembly and other
23932 internal interpretation purposes. This setting is only referred to
23933 when no executable has been associated with the debugging session or
23934 the executable does not provide information about the encoding it uses.
23935 Otherwise this setting is automatically updated from information
23936 provided by the executable.
23938 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23939 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23940 executables containing @acronym{MIPS16} code frequently are not
23941 identified as such.
23943 This setting is ``sticky''; that is, it retains its value across
23944 debugging sessions until reset either explicitly with this command or
23945 implicitly from an executable.
23947 The compiler and/or assembler typically add symbol table annotations to
23948 identify functions compiled for the @acronym{MIPS16} or
23949 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23950 are present, @value{GDBN} uses them in preference to the global
23951 compressed @acronym{ISA} encoding setting.
23953 @item show mips compression
23954 @kindex show mips compression
23955 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23956 @value{GDBN} to debug the inferior.
23959 @itemx show mipsfpu
23960 @xref{MIPS Embedded, set mipsfpu}.
23962 @item set mips mask-address @var{arg}
23963 @kindex set mips mask-address
23964 @cindex @acronym{MIPS} addresses, masking
23965 This command determines whether the most-significant 32 bits of 64-bit
23966 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23967 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23968 setting, which lets @value{GDBN} determine the correct value.
23970 @item show mips mask-address
23971 @kindex show mips mask-address
23972 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23975 @item set remote-mips64-transfers-32bit-regs
23976 @kindex set remote-mips64-transfers-32bit-regs
23977 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23978 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23979 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23980 and 64 bits for other registers, set this option to @samp{on}.
23982 @item show remote-mips64-transfers-32bit-regs
23983 @kindex show remote-mips64-transfers-32bit-regs
23984 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23986 @item set debug mips
23987 @kindex set debug mips
23988 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23989 target code in @value{GDBN}.
23991 @item show debug mips
23992 @kindex show debug mips
23993 Show the current setting of @acronym{MIPS} debugging messages.
23999 @cindex HPPA support
24001 When @value{GDBN} is debugging the HP PA architecture, it provides the
24002 following special commands:
24005 @item set debug hppa
24006 @kindex set debug hppa
24007 This command determines whether HPPA architecture-specific debugging
24008 messages are to be displayed.
24010 @item show debug hppa
24011 Show whether HPPA debugging messages are displayed.
24013 @item maint print unwind @var{address}
24014 @kindex maint print unwind@r{, HPPA}
24015 This command displays the contents of the unwind table entry at the
24016 given @var{address}.
24022 @subsection Cell Broadband Engine SPU architecture
24023 @cindex Cell Broadband Engine
24026 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24027 it provides the following special commands:
24030 @item info spu event
24032 Display SPU event facility status. Shows current event mask
24033 and pending event status.
24035 @item info spu signal
24036 Display SPU signal notification facility status. Shows pending
24037 signal-control word and signal notification mode of both signal
24038 notification channels.
24040 @item info spu mailbox
24041 Display SPU mailbox facility status. Shows all pending entries,
24042 in order of processing, in each of the SPU Write Outbound,
24043 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24046 Display MFC DMA status. Shows all pending commands in the MFC
24047 DMA queue. For each entry, opcode, tag, class IDs, effective
24048 and local store addresses and transfer size are shown.
24050 @item info spu proxydma
24051 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24052 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24053 and local store addresses and transfer size are shown.
24057 When @value{GDBN} is debugging a combined PowerPC/SPU application
24058 on the Cell Broadband Engine, it provides in addition the following
24062 @item set spu stop-on-load @var{arg}
24064 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24065 will give control to the user when a new SPE thread enters its @code{main}
24066 function. The default is @code{off}.
24068 @item show spu stop-on-load
24070 Show whether to stop for new SPE threads.
24072 @item set spu auto-flush-cache @var{arg}
24073 Set whether to automatically flush the software-managed cache. When set to
24074 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24075 cache to be flushed whenever SPE execution stops. This provides a consistent
24076 view of PowerPC memory that is accessed via the cache. If an application
24077 does not use the software-managed cache, this option has no effect.
24079 @item show spu auto-flush-cache
24080 Show whether to automatically flush the software-managed cache.
24085 @subsection PowerPC
24086 @cindex PowerPC architecture
24088 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24089 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24090 numbers stored in the floating point registers. These values must be stored
24091 in two consecutive registers, always starting at an even register like
24092 @code{f0} or @code{f2}.
24094 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24095 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24096 @code{f2} and @code{f3} for @code{$dl1} and so on.
24098 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24099 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24102 @subsection Nios II
24103 @cindex Nios II architecture
24105 When @value{GDBN} is debugging the Nios II architecture,
24106 it provides the following special commands:
24110 @item set debug nios2
24111 @kindex set debug nios2
24112 This command turns on and off debugging messages for the Nios II
24113 target code in @value{GDBN}.
24115 @item show debug nios2
24116 @kindex show debug nios2
24117 Show the current setting of Nios II debugging messages.
24121 @subsection Sparc64
24122 @cindex Sparc64 support
24123 @cindex Application Data Integrity
24124 @subsubsection ADI Support
24126 The M7 processor supports an Application Data Integrity (ADI) feature that
24127 detects invalid data accesses. When software allocates memory and enables
24128 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24129 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24130 the 4-bit version in every cacheline of that data. Hardware saves the latter
24131 in spare bits in the cache and memory hierarchy. On each load and store,
24132 the processor compares the upper 4 VA (virtual address) bits to the
24133 cacheline's version. If there is a mismatch, the processor generates a
24134 version mismatch trap which can be either precise or disrupting. The trap
24135 is an error condition which the kernel delivers to the process as a SIGSEGV
24138 Note that only 64-bit applications can use ADI and need to be built with
24141 Values of the ADI version tags, which are in granularity of a
24142 cacheline (64 bytes), can be viewed or modified.
24146 @kindex adi examine
24147 @item adi (examine | x) [ / @var{n} ] @var{addr}
24149 The @code{adi examine} command displays the value of one ADI version tag per
24152 @var{n} is a decimal integer specifying the number in bytes; the default
24153 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24154 block size, to display.
24156 @var{addr} is the address in user address space where you want @value{GDBN}
24157 to begin displaying the ADI version tags.
24159 Below is an example of displaying ADI versions of variable "shmaddr".
24162 (@value{GDBP}) adi x/100 shmaddr
24163 0xfff800010002c000: 0 0
24167 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24169 The @code{adi assign} command is used to assign new ADI version tag
24172 @var{n} is a decimal integer specifying the number in bytes;
24173 the default is 1. It specifies how much ADI version information, at the
24174 ratio of 1:ADI block size, to modify.
24176 @var{addr} is the address in user address space where you want @value{GDBN}
24177 to begin modifying the ADI version tags.
24179 @var{tag} is the new ADI version tag.
24181 For example, do the following to modify then verify ADI versions of
24182 variable "shmaddr":
24185 (@value{GDBP}) adi a/100 shmaddr = 7
24186 (@value{GDBP}) adi x/100 shmaddr
24187 0xfff800010002c000: 7 7
24194 @cindex S12Z support
24196 When @value{GDBN} is debugging the S12Z architecture,
24197 it provides the following special command:
24200 @item maint info bdccsr
24201 @kindex maint info bdccsr@r{, S12Z}
24202 This command displays the current value of the microprocessor's
24207 @node Controlling GDB
24208 @chapter Controlling @value{GDBN}
24210 You can alter the way @value{GDBN} interacts with you by using the
24211 @code{set} command. For commands controlling how @value{GDBN} displays
24212 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24217 * Editing:: Command editing
24218 * Command History:: Command history
24219 * Screen Size:: Screen size
24220 * Numbers:: Numbers
24221 * ABI:: Configuring the current ABI
24222 * Auto-loading:: Automatically loading associated files
24223 * Messages/Warnings:: Optional warnings and messages
24224 * Debugging Output:: Optional messages about internal happenings
24225 * Other Misc Settings:: Other Miscellaneous Settings
24233 @value{GDBN} indicates its readiness to read a command by printing a string
24234 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24235 can change the prompt string with the @code{set prompt} command. For
24236 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24237 the prompt in one of the @value{GDBN} sessions so that you can always tell
24238 which one you are talking to.
24240 @emph{Note:} @code{set prompt} does not add a space for you after the
24241 prompt you set. This allows you to set a prompt which ends in a space
24242 or a prompt that does not.
24246 @item set prompt @var{newprompt}
24247 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24249 @kindex show prompt
24251 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24254 Versions of @value{GDBN} that ship with Python scripting enabled have
24255 prompt extensions. The commands for interacting with these extensions
24259 @kindex set extended-prompt
24260 @item set extended-prompt @var{prompt}
24261 Set an extended prompt that allows for substitutions.
24262 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24263 substitution. Any escape sequences specified as part of the prompt
24264 string are replaced with the corresponding strings each time the prompt
24270 set extended-prompt Current working directory: \w (gdb)
24273 Note that when an extended-prompt is set, it takes control of the
24274 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24276 @kindex show extended-prompt
24277 @item show extended-prompt
24278 Prints the extended prompt. Any escape sequences specified as part of
24279 the prompt string with @code{set extended-prompt}, are replaced with the
24280 corresponding strings each time the prompt is displayed.
24284 @section Command Editing
24286 @cindex command line editing
24288 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24289 @sc{gnu} library provides consistent behavior for programs which provide a
24290 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24291 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24292 substitution, and a storage and recall of command history across
24293 debugging sessions.
24295 You may control the behavior of command line editing in @value{GDBN} with the
24296 command @code{set}.
24299 @kindex set editing
24302 @itemx set editing on
24303 Enable command line editing (enabled by default).
24305 @item set editing off
24306 Disable command line editing.
24308 @kindex show editing
24310 Show whether command line editing is enabled.
24313 @ifset SYSTEM_READLINE
24314 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24316 @ifclear SYSTEM_READLINE
24317 @xref{Command Line Editing},
24319 for more details about the Readline
24320 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24321 encouraged to read that chapter.
24323 @node Command History
24324 @section Command History
24325 @cindex command history
24327 @value{GDBN} can keep track of the commands you type during your
24328 debugging sessions, so that you can be certain of precisely what
24329 happened. Use these commands to manage the @value{GDBN} command
24332 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24333 package, to provide the history facility.
24334 @ifset SYSTEM_READLINE
24335 @xref{Using History Interactively, , , history, GNU History Library},
24337 @ifclear SYSTEM_READLINE
24338 @xref{Using History Interactively},
24340 for the detailed description of the History library.
24342 To issue a command to @value{GDBN} without affecting certain aspects of
24343 the state which is seen by users, prefix it with @samp{server }
24344 (@pxref{Server Prefix}). This
24345 means that this command will not affect the command history, nor will it
24346 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24347 pressed on a line by itself.
24349 @cindex @code{server}, command prefix
24350 The server prefix does not affect the recording of values into the value
24351 history; to print a value without recording it into the value history,
24352 use the @code{output} command instead of the @code{print} command.
24354 Here is the description of @value{GDBN} commands related to command
24358 @cindex history substitution
24359 @cindex history file
24360 @kindex set history filename
24361 @cindex @env{GDBHISTFILE}, environment variable
24362 @item set history filename @var{fname}
24363 Set the name of the @value{GDBN} command history file to @var{fname}.
24364 This is the file where @value{GDBN} reads an initial command history
24365 list, and where it writes the command history from this session when it
24366 exits. You can access this list through history expansion or through
24367 the history command editing characters listed below. This file defaults
24368 to the value of the environment variable @code{GDBHISTFILE}, or to
24369 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24372 @cindex save command history
24373 @kindex set history save
24374 @item set history save
24375 @itemx set history save on
24376 Record command history in a file, whose name may be specified with the
24377 @code{set history filename} command. By default, this option is disabled.
24379 @item set history save off
24380 Stop recording command history in a file.
24382 @cindex history size
24383 @kindex set history size
24384 @cindex @env{GDBHISTSIZE}, environment variable
24385 @item set history size @var{size}
24386 @itemx set history size unlimited
24387 Set the number of commands which @value{GDBN} keeps in its history list.
24388 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24389 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24390 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24391 either a negative number or the empty string, then the number of commands
24392 @value{GDBN} keeps in the history list is unlimited.
24394 @cindex remove duplicate history
24395 @kindex set history remove-duplicates
24396 @item set history remove-duplicates @var{count}
24397 @itemx set history remove-duplicates unlimited
24398 Control the removal of duplicate history entries in the command history list.
24399 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24400 history entries and remove the first entry that is a duplicate of the current
24401 entry being added to the command history list. If @var{count} is
24402 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24403 removal of duplicate history entries is disabled.
24405 Only history entries added during the current session are considered for
24406 removal. This option is set to 0 by default.
24410 History expansion assigns special meaning to the character @kbd{!}.
24411 @ifset SYSTEM_READLINE
24412 @xref{Event Designators, , , history, GNU History Library},
24414 @ifclear SYSTEM_READLINE
24415 @xref{Event Designators},
24419 @cindex history expansion, turn on/off
24420 Since @kbd{!} is also the logical not operator in C, history expansion
24421 is off by default. If you decide to enable history expansion with the
24422 @code{set history expansion on} command, you may sometimes need to
24423 follow @kbd{!} (when it is used as logical not, in an expression) with
24424 a space or a tab to prevent it from being expanded. The readline
24425 history facilities do not attempt substitution on the strings
24426 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24428 The commands to control history expansion are:
24431 @item set history expansion on
24432 @itemx set history expansion
24433 @kindex set history expansion
24434 Enable history expansion. History expansion is off by default.
24436 @item set history expansion off
24437 Disable history expansion.
24440 @kindex show history
24442 @itemx show history filename
24443 @itemx show history save
24444 @itemx show history size
24445 @itemx show history expansion
24446 These commands display the state of the @value{GDBN} history parameters.
24447 @code{show history} by itself displays all four states.
24452 @kindex show commands
24453 @cindex show last commands
24454 @cindex display command history
24455 @item show commands
24456 Display the last ten commands in the command history.
24458 @item show commands @var{n}
24459 Print ten commands centered on command number @var{n}.
24461 @item show commands +
24462 Print ten commands just after the commands last printed.
24466 @section Screen Size
24467 @cindex size of screen
24468 @cindex screen size
24471 @cindex pauses in output
24473 Certain commands to @value{GDBN} may produce large amounts of
24474 information output to the screen. To help you read all of it,
24475 @value{GDBN} pauses and asks you for input at the end of each page of
24476 output. Type @key{RET} when you want to see one more page of output,
24477 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24478 without paging for the rest of the current command. Also, the screen
24479 width setting determines when to wrap lines of output. Depending on
24480 what is being printed, @value{GDBN} tries to break the line at a
24481 readable place, rather than simply letting it overflow onto the
24484 Normally @value{GDBN} knows the size of the screen from the terminal
24485 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24486 together with the value of the @code{TERM} environment variable and the
24487 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24488 you can override it with the @code{set height} and @code{set
24495 @kindex show height
24496 @item set height @var{lpp}
24497 @itemx set height unlimited
24499 @itemx set width @var{cpl}
24500 @itemx set width unlimited
24502 These @code{set} commands specify a screen height of @var{lpp} lines and
24503 a screen width of @var{cpl} characters. The associated @code{show}
24504 commands display the current settings.
24506 If you specify a height of either @code{unlimited} or zero lines,
24507 @value{GDBN} does not pause during output no matter how long the
24508 output is. This is useful if output is to a file or to an editor
24511 Likewise, you can specify @samp{set width unlimited} or @samp{set
24512 width 0} to prevent @value{GDBN} from wrapping its output.
24514 @item set pagination on
24515 @itemx set pagination off
24516 @kindex set pagination
24517 Turn the output pagination on or off; the default is on. Turning
24518 pagination off is the alternative to @code{set height unlimited}. Note that
24519 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24520 Options, -batch}) also automatically disables pagination.
24522 @item show pagination
24523 @kindex show pagination
24524 Show the current pagination mode.
24529 @cindex number representation
24530 @cindex entering numbers
24532 You can always enter numbers in octal, decimal, or hexadecimal in
24533 @value{GDBN} by the usual conventions: octal numbers begin with
24534 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24535 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24536 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24537 10; likewise, the default display for numbers---when no particular
24538 format is specified---is base 10. You can change the default base for
24539 both input and output with the commands described below.
24542 @kindex set input-radix
24543 @item set input-radix @var{base}
24544 Set the default base for numeric input. 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; for
24550 set input-radix 012
24551 set input-radix 10.
24552 set input-radix 0xa
24556 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24557 leaves the input radix unchanged, no matter what it was, since
24558 @samp{10}, being without any leading or trailing signs of its base, is
24559 interpreted in the current radix. Thus, if the current radix is 16,
24560 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24563 @kindex set output-radix
24564 @item set output-radix @var{base}
24565 Set the default base for numeric display. Supported choices
24566 for @var{base} are decimal 8, 10, or 16. The base must itself be
24567 specified either unambiguously or using the current input radix.
24569 @kindex show input-radix
24570 @item show input-radix
24571 Display the current default base for numeric input.
24573 @kindex show output-radix
24574 @item show output-radix
24575 Display the current default base for numeric display.
24577 @item set radix @r{[}@var{base}@r{]}
24581 These commands set and show the default base for both input and output
24582 of numbers. @code{set radix} sets the radix of input and output to
24583 the same base; without an argument, it resets the radix back to its
24584 default value of 10.
24589 @section Configuring the Current ABI
24591 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24592 application automatically. However, sometimes you need to override its
24593 conclusions. Use these commands to manage @value{GDBN}'s view of the
24599 @cindex Newlib OS ABI and its influence on the longjmp handling
24601 One @value{GDBN} configuration can debug binaries for multiple operating
24602 system targets, either via remote debugging or native emulation.
24603 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24604 but you can override its conclusion using the @code{set osabi} command.
24605 One example where this is useful is in debugging of binaries which use
24606 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24607 not have the same identifying marks that the standard C library for your
24610 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24611 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24612 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24613 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24617 Show the OS ABI currently in use.
24620 With no argument, show the list of registered available OS ABI's.
24622 @item set osabi @var{abi}
24623 Set the current OS ABI to @var{abi}.
24626 @cindex float promotion
24628 Generally, the way that an argument of type @code{float} is passed to a
24629 function depends on whether the function is prototyped. For a prototyped
24630 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24631 according to the architecture's convention for @code{float}. For unprototyped
24632 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24633 @code{double} and then passed.
24635 Unfortunately, some forms of debug information do not reliably indicate whether
24636 a function is prototyped. If @value{GDBN} calls a function that is not marked
24637 as prototyped, it consults @kbd{set coerce-float-to-double}.
24640 @kindex set coerce-float-to-double
24641 @item set coerce-float-to-double
24642 @itemx set coerce-float-to-double on
24643 Arguments of type @code{float} will be promoted to @code{double} when passed
24644 to an unprototyped function. This is the default setting.
24646 @item set coerce-float-to-double off
24647 Arguments of type @code{float} will be passed directly to unprototyped
24650 @kindex show coerce-float-to-double
24651 @item show coerce-float-to-double
24652 Show the current setting of promoting @code{float} to @code{double}.
24656 @kindex show cp-abi
24657 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24658 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24659 used to build your application. @value{GDBN} only fully supports
24660 programs with a single C@t{++} ABI; if your program contains code using
24661 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24662 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24663 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24664 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24665 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24666 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24671 Show the C@t{++} ABI currently in use.
24674 With no argument, show the list of supported C@t{++} ABI's.
24676 @item set cp-abi @var{abi}
24677 @itemx set cp-abi auto
24678 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24682 @section Automatically loading associated files
24683 @cindex auto-loading
24685 @value{GDBN} sometimes reads files with commands and settings automatically,
24686 without being explicitly told so by the user. We call this feature
24687 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24688 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24689 results or introduce security risks (e.g., if the file comes from untrusted
24693 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24694 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24696 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24697 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24700 There are various kinds of files @value{GDBN} can automatically load.
24701 In addition to these files, @value{GDBN} supports auto-loading code written
24702 in various extension languages. @xref{Auto-loading extensions}.
24704 Note that loading of these associated files (including the local @file{.gdbinit}
24705 file) requires accordingly configured @code{auto-load safe-path}
24706 (@pxref{Auto-loading safe path}).
24708 For these reasons, @value{GDBN} includes commands and options to let you
24709 control when to auto-load files and which files should be auto-loaded.
24712 @anchor{set auto-load off}
24713 @kindex set auto-load off
24714 @item set auto-load off
24715 Globally disable loading of all auto-loaded files.
24716 You may want to use this command with the @samp{-iex} option
24717 (@pxref{Option -init-eval-command}) such as:
24719 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24722 Be aware that system init file (@pxref{System-wide configuration})
24723 and init files from your home directory (@pxref{Home Directory Init File})
24724 still get read (as they come from generally trusted directories).
24725 To prevent @value{GDBN} from auto-loading even those init files, use the
24726 @option{-nx} option (@pxref{Mode Options}), in addition to
24727 @code{set auto-load no}.
24729 @anchor{show auto-load}
24730 @kindex show auto-load
24731 @item show auto-load
24732 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24736 (gdb) show auto-load
24737 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24738 libthread-db: Auto-loading of inferior specific libthread_db is on.
24739 local-gdbinit: Auto-loading of .gdbinit script from current directory
24741 python-scripts: Auto-loading of Python scripts is on.
24742 safe-path: List of directories from which it is safe to auto-load files
24743 is $debugdir:$datadir/auto-load.
24744 scripts-directory: List of directories from which to load auto-loaded scripts
24745 is $debugdir:$datadir/auto-load.
24748 @anchor{info auto-load}
24749 @kindex info auto-load
24750 @item info auto-load
24751 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24755 (gdb) info auto-load
24758 Yes /home/user/gdb/gdb-gdb.gdb
24759 libthread-db: No auto-loaded libthread-db.
24760 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24764 Yes /home/user/gdb/gdb-gdb.py
24768 These are @value{GDBN} control commands for the auto-loading:
24770 @multitable @columnfractions .5 .5
24771 @item @xref{set auto-load off}.
24772 @tab Disable auto-loading globally.
24773 @item @xref{show auto-load}.
24774 @tab Show setting of all kinds of files.
24775 @item @xref{info auto-load}.
24776 @tab Show state of all kinds of files.
24777 @item @xref{set auto-load gdb-scripts}.
24778 @tab Control for @value{GDBN} command scripts.
24779 @item @xref{show auto-load gdb-scripts}.
24780 @tab Show setting of @value{GDBN} command scripts.
24781 @item @xref{info auto-load gdb-scripts}.
24782 @tab Show state of @value{GDBN} command scripts.
24783 @item @xref{set auto-load python-scripts}.
24784 @tab Control for @value{GDBN} Python scripts.
24785 @item @xref{show auto-load python-scripts}.
24786 @tab Show setting of @value{GDBN} Python scripts.
24787 @item @xref{info auto-load python-scripts}.
24788 @tab Show state of @value{GDBN} Python scripts.
24789 @item @xref{set auto-load guile-scripts}.
24790 @tab Control for @value{GDBN} Guile scripts.
24791 @item @xref{show auto-load guile-scripts}.
24792 @tab Show setting of @value{GDBN} Guile scripts.
24793 @item @xref{info auto-load guile-scripts}.
24794 @tab Show state of @value{GDBN} Guile scripts.
24795 @item @xref{set auto-load scripts-directory}.
24796 @tab Control for @value{GDBN} auto-loaded scripts location.
24797 @item @xref{show auto-load scripts-directory}.
24798 @tab Show @value{GDBN} auto-loaded scripts location.
24799 @item @xref{add-auto-load-scripts-directory}.
24800 @tab Add directory for auto-loaded scripts location list.
24801 @item @xref{set auto-load local-gdbinit}.
24802 @tab Control for init file in the current directory.
24803 @item @xref{show auto-load local-gdbinit}.
24804 @tab Show setting of init file in the current directory.
24805 @item @xref{info auto-load local-gdbinit}.
24806 @tab Show state of init file in the current directory.
24807 @item @xref{set auto-load libthread-db}.
24808 @tab Control for thread debugging library.
24809 @item @xref{show auto-load libthread-db}.
24810 @tab Show setting of thread debugging library.
24811 @item @xref{info auto-load libthread-db}.
24812 @tab Show state of thread debugging library.
24813 @item @xref{set auto-load safe-path}.
24814 @tab Control directories trusted for automatic loading.
24815 @item @xref{show auto-load safe-path}.
24816 @tab Show directories trusted for automatic loading.
24817 @item @xref{add-auto-load-safe-path}.
24818 @tab Add directory trusted for automatic loading.
24821 @node Init File in the Current Directory
24822 @subsection Automatically loading init file in the current directory
24823 @cindex auto-loading init file in the current directory
24825 By default, @value{GDBN} reads and executes the canned sequences of commands
24826 from init file (if any) in the current working directory,
24827 see @ref{Init File in the Current Directory during Startup}.
24829 Note that loading of this local @file{.gdbinit} file also requires accordingly
24830 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24833 @anchor{set auto-load local-gdbinit}
24834 @kindex set auto-load local-gdbinit
24835 @item set auto-load local-gdbinit [on|off]
24836 Enable or disable the auto-loading of canned sequences of commands
24837 (@pxref{Sequences}) found in init file in the current directory.
24839 @anchor{show auto-load local-gdbinit}
24840 @kindex show auto-load local-gdbinit
24841 @item show auto-load local-gdbinit
24842 Show whether auto-loading of canned sequences of commands from init file in the
24843 current directory is enabled or disabled.
24845 @anchor{info auto-load local-gdbinit}
24846 @kindex info auto-load local-gdbinit
24847 @item info auto-load local-gdbinit
24848 Print whether canned sequences of commands from init file in the
24849 current directory have been auto-loaded.
24852 @node libthread_db.so.1 file
24853 @subsection Automatically loading thread debugging library
24854 @cindex auto-loading libthread_db.so.1
24856 This feature is currently present only on @sc{gnu}/Linux native hosts.
24858 @value{GDBN} reads in some cases thread debugging library from places specific
24859 to the inferior (@pxref{set libthread-db-search-path}).
24861 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24862 without checking this @samp{set auto-load libthread-db} switch as system
24863 libraries have to be trusted in general. In all other cases of
24864 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24865 auto-load libthread-db} is enabled before trying to open such thread debugging
24868 Note that loading of this debugging library also requires accordingly configured
24869 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24872 @anchor{set auto-load libthread-db}
24873 @kindex set auto-load libthread-db
24874 @item set auto-load libthread-db [on|off]
24875 Enable or disable the auto-loading of inferior specific thread debugging library.
24877 @anchor{show auto-load libthread-db}
24878 @kindex show auto-load libthread-db
24879 @item show auto-load libthread-db
24880 Show whether auto-loading of inferior specific thread debugging library is
24881 enabled or disabled.
24883 @anchor{info auto-load libthread-db}
24884 @kindex info auto-load libthread-db
24885 @item info auto-load libthread-db
24886 Print the list of all loaded inferior specific thread debugging libraries and
24887 for each such library print list of inferior @var{pid}s using it.
24890 @node Auto-loading safe path
24891 @subsection Security restriction for auto-loading
24892 @cindex auto-loading safe-path
24894 As the files of inferior can come from untrusted source (such as submitted by
24895 an application user) @value{GDBN} does not always load any files automatically.
24896 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24897 directories trusted for loading files not explicitly requested by user.
24898 Each directory can also be a shell wildcard pattern.
24900 If the path is not set properly you will see a warning and the file will not
24905 Reading symbols from /home/user/gdb/gdb...done.
24906 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24907 declined by your `auto-load safe-path' set
24908 to "$debugdir:$datadir/auto-load".
24909 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24910 declined by your `auto-load safe-path' set
24911 to "$debugdir:$datadir/auto-load".
24915 To instruct @value{GDBN} to go ahead and use the init files anyway,
24916 invoke @value{GDBN} like this:
24919 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24922 The list of trusted directories is controlled by the following commands:
24925 @anchor{set auto-load safe-path}
24926 @kindex set auto-load safe-path
24927 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24928 Set the list of directories (and their subdirectories) trusted for automatic
24929 loading and execution of scripts. You can also enter a specific trusted file.
24930 Each directory can also be a shell wildcard pattern; wildcards do not match
24931 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24932 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24933 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24934 its default value as specified during @value{GDBN} compilation.
24936 The list of directories uses path separator (@samp{:} on GNU and Unix
24937 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24938 to the @env{PATH} environment variable.
24940 @anchor{show auto-load safe-path}
24941 @kindex show auto-load safe-path
24942 @item show auto-load safe-path
24943 Show the list of directories trusted for automatic loading and execution of
24946 @anchor{add-auto-load-safe-path}
24947 @kindex add-auto-load-safe-path
24948 @item add-auto-load-safe-path
24949 Add an entry (or list of entries) to the list of directories trusted for
24950 automatic loading and execution of scripts. Multiple entries may be delimited
24951 by the host platform path separator in use.
24954 This variable defaults to what @code{--with-auto-load-dir} has been configured
24955 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24956 substitution applies the same as for @ref{set auto-load scripts-directory}.
24957 The default @code{set auto-load safe-path} value can be also overriden by
24958 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24960 Setting this variable to @file{/} disables this security protection,
24961 corresponding @value{GDBN} configuration option is
24962 @option{--without-auto-load-safe-path}.
24963 This variable is supposed to be set to the system directories writable by the
24964 system superuser only. Users can add their source directories in init files in
24965 their home directories (@pxref{Home Directory Init File}). See also deprecated
24966 init file in the current directory
24967 (@pxref{Init File in the Current Directory during Startup}).
24969 To force @value{GDBN} to load the files it declined to load in the previous
24970 example, you could use one of the following ways:
24973 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24974 Specify this trusted directory (or a file) as additional component of the list.
24975 You have to specify also any existing directories displayed by
24976 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24978 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24979 Specify this directory as in the previous case but just for a single
24980 @value{GDBN} session.
24982 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24983 Disable auto-loading safety for a single @value{GDBN} session.
24984 This assumes all the files you debug during this @value{GDBN} session will come
24985 from trusted sources.
24987 @item @kbd{./configure --without-auto-load-safe-path}
24988 During compilation of @value{GDBN} you may disable any auto-loading safety.
24989 This assumes all the files you will ever debug with this @value{GDBN} come from
24993 On the other hand you can also explicitly forbid automatic files loading which
24994 also suppresses any such warning messages:
24997 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24998 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25000 @item @file{~/.gdbinit}: @samp{set auto-load no}
25001 Disable auto-loading globally for the user
25002 (@pxref{Home Directory Init File}). While it is improbable, you could also
25003 use system init file instead (@pxref{System-wide configuration}).
25006 This setting applies to the file names as entered by user. If no entry matches
25007 @value{GDBN} tries as a last resort to also resolve all the file names into
25008 their canonical form (typically resolving symbolic links) and compare the
25009 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25010 own before starting the comparison so a canonical form of directories is
25011 recommended to be entered.
25013 @node Auto-loading verbose mode
25014 @subsection Displaying files tried for auto-load
25015 @cindex auto-loading verbose mode
25017 For better visibility of all the file locations where you can place scripts to
25018 be auto-loaded with inferior --- or to protect yourself against accidental
25019 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25020 all the files attempted to be loaded. Both existing and non-existing files may
25023 For example the list of directories from which it is safe to auto-load files
25024 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25025 may not be too obvious while setting it up.
25028 (gdb) set debug auto-load on
25029 (gdb) file ~/src/t/true
25030 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25031 for objfile "/tmp/true".
25032 auto-load: Updating directories of "/usr:/opt".
25033 auto-load: Using directory "/usr".
25034 auto-load: Using directory "/opt".
25035 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25036 by your `auto-load safe-path' set to "/usr:/opt".
25040 @anchor{set debug auto-load}
25041 @kindex set debug auto-load
25042 @item set debug auto-load [on|off]
25043 Set whether to print the filenames attempted to be auto-loaded.
25045 @anchor{show debug auto-load}
25046 @kindex show debug auto-load
25047 @item show debug auto-load
25048 Show whether printing of the filenames attempted to be auto-loaded is turned
25052 @node Messages/Warnings
25053 @section Optional Warnings and Messages
25055 @cindex verbose operation
25056 @cindex optional warnings
25057 By default, @value{GDBN} is silent about its inner workings. If you are
25058 running on a slow machine, you may want to use the @code{set verbose}
25059 command. This makes @value{GDBN} tell you when it does a lengthy
25060 internal operation, so you will not think it has crashed.
25062 Currently, the messages controlled by @code{set verbose} are those
25063 which announce that the symbol table for a source file is being read;
25064 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25067 @kindex set verbose
25068 @item set verbose on
25069 Enables @value{GDBN} output of certain informational messages.
25071 @item set verbose off
25072 Disables @value{GDBN} output of certain informational messages.
25074 @kindex show verbose
25076 Displays whether @code{set verbose} is on or off.
25079 By default, if @value{GDBN} encounters bugs in the symbol table of an
25080 object file, it is silent; but if you are debugging a compiler, you may
25081 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25086 @kindex set complaints
25087 @item set complaints @var{limit}
25088 Permits @value{GDBN} to output @var{limit} complaints about each type of
25089 unusual symbols before becoming silent about the problem. Set
25090 @var{limit} to zero to suppress all complaints; set it to a large number
25091 to prevent complaints from being suppressed.
25093 @kindex show complaints
25094 @item show complaints
25095 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25099 @anchor{confirmation requests}
25100 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25101 lot of stupid questions to confirm certain commands. For example, if
25102 you try to run a program which is already running:
25106 The program being debugged has been started already.
25107 Start it from the beginning? (y or n)
25110 If you are willing to unflinchingly face the consequences of your own
25111 commands, you can disable this ``feature'':
25115 @kindex set confirm
25117 @cindex confirmation
25118 @cindex stupid questions
25119 @item set confirm off
25120 Disables confirmation requests. Note that running @value{GDBN} with
25121 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25122 automatically disables confirmation requests.
25124 @item set confirm on
25125 Enables confirmation requests (the default).
25127 @kindex show confirm
25129 Displays state of confirmation requests.
25133 @cindex command tracing
25134 If you need to debug user-defined commands or sourced files you may find it
25135 useful to enable @dfn{command tracing}. In this mode each command will be
25136 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25137 quantity denoting the call depth of each command.
25140 @kindex set trace-commands
25141 @cindex command scripts, debugging
25142 @item set trace-commands on
25143 Enable command tracing.
25144 @item set trace-commands off
25145 Disable command tracing.
25146 @item show trace-commands
25147 Display the current state of command tracing.
25150 @node Debugging Output
25151 @section Optional Messages about Internal Happenings
25152 @cindex optional debugging messages
25154 @value{GDBN} has commands that enable optional debugging messages from
25155 various @value{GDBN} subsystems; normally these commands are of
25156 interest to @value{GDBN} maintainers, or when reporting a bug. This
25157 section documents those commands.
25160 @kindex set exec-done-display
25161 @item set exec-done-display
25162 Turns on or off the notification of asynchronous commands'
25163 completion. When on, @value{GDBN} will print a message when an
25164 asynchronous command finishes its execution. The default is off.
25165 @kindex show exec-done-display
25166 @item show exec-done-display
25167 Displays the current setting of asynchronous command completion
25170 @cindex ARM AArch64
25171 @item set debug aarch64
25172 Turns on or off display of debugging messages related to ARM AArch64.
25173 The default is off.
25175 @item show debug aarch64
25176 Displays the current state of displaying debugging messages related to
25178 @cindex gdbarch debugging info
25179 @cindex architecture debugging info
25180 @item set debug arch
25181 Turns on or off display of gdbarch debugging info. The default is off
25182 @item show debug arch
25183 Displays the current state of displaying gdbarch debugging info.
25184 @item set debug aix-solib
25185 @cindex AIX shared library debugging
25186 Control display of debugging messages from the AIX shared library
25187 support module. The default is off.
25188 @item show debug aix-thread
25189 Show the current state of displaying AIX shared library debugging messages.
25190 @item set debug aix-thread
25191 @cindex AIX threads
25192 Display debugging messages about inner workings of the AIX thread
25194 @item show debug aix-thread
25195 Show the current state of AIX thread debugging info display.
25196 @item set debug check-physname
25198 Check the results of the ``physname'' computation. When reading DWARF
25199 debugging information for C@t{++}, @value{GDBN} attempts to compute
25200 each entity's name. @value{GDBN} can do this computation in two
25201 different ways, depending on exactly what information is present.
25202 When enabled, this setting causes @value{GDBN} to compute the names
25203 both ways and display any discrepancies.
25204 @item show debug check-physname
25205 Show the current state of ``physname'' checking.
25206 @item set debug coff-pe-read
25207 @cindex COFF/PE exported symbols
25208 Control display of debugging messages related to reading of COFF/PE
25209 exported symbols. The default is off.
25210 @item show debug coff-pe-read
25211 Displays the current state of displaying debugging messages related to
25212 reading of COFF/PE exported symbols.
25213 @item set debug dwarf-die
25215 Dump DWARF DIEs after they are read in.
25216 The value is the number of nesting levels to print.
25217 A value of zero turns off the display.
25218 @item show debug dwarf-die
25219 Show the current state of DWARF DIE debugging.
25220 @item set debug dwarf-line
25221 @cindex DWARF Line Tables
25222 Turns on or off display of debugging messages related to reading
25223 DWARF line tables. The default is 0 (off).
25224 A value of 1 provides basic information.
25225 A value greater than 1 provides more verbose information.
25226 @item show debug dwarf-line
25227 Show the current state of DWARF line table debugging.
25228 @item set debug dwarf-read
25229 @cindex DWARF Reading
25230 Turns on or off display of debugging messages related to reading
25231 DWARF debug info. The default is 0 (off).
25232 A value of 1 provides basic information.
25233 A value greater than 1 provides more verbose information.
25234 @item show debug dwarf-read
25235 Show the current state of DWARF reader debugging.
25236 @item set debug displaced
25237 @cindex displaced stepping debugging info
25238 Turns on or off display of @value{GDBN} debugging info for the
25239 displaced stepping support. The default is off.
25240 @item show debug displaced
25241 Displays the current state of displaying @value{GDBN} debugging info
25242 related to displaced stepping.
25243 @item set debug event
25244 @cindex event debugging info
25245 Turns on or off display of @value{GDBN} event debugging info. The
25247 @item show debug event
25248 Displays the current state of displaying @value{GDBN} event debugging
25250 @item set debug expression
25251 @cindex expression debugging info
25252 Turns on or off display of debugging info about @value{GDBN}
25253 expression parsing. The default is off.
25254 @item show debug expression
25255 Displays the current state of displaying debugging info about
25256 @value{GDBN} expression parsing.
25257 @item set debug fbsd-lwp
25258 @cindex FreeBSD LWP debug messages
25259 Turns on or off debugging messages from the FreeBSD LWP debug support.
25260 @item show debug fbsd-lwp
25261 Show the current state of FreeBSD LWP debugging messages.
25262 @item set debug fbsd-nat
25263 @cindex FreeBSD native target debug messages
25264 Turns on or off debugging messages from the FreeBSD native target.
25265 @item show debug fbsd-nat
25266 Show the current state of FreeBSD native target debugging messages.
25267 @item set debug frame
25268 @cindex frame debugging info
25269 Turns on or off display of @value{GDBN} frame debugging info. The
25271 @item show debug frame
25272 Displays the current state of displaying @value{GDBN} frame debugging
25274 @item set debug gnu-nat
25275 @cindex @sc{gnu}/Hurd debug messages
25276 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25277 @item show debug gnu-nat
25278 Show the current state of @sc{gnu}/Hurd debugging messages.
25279 @item set debug infrun
25280 @cindex inferior debugging info
25281 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25282 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25283 for implementing operations such as single-stepping the inferior.
25284 @item show debug infrun
25285 Displays the current state of @value{GDBN} inferior debugging.
25286 @item set debug jit
25287 @cindex just-in-time compilation, debugging messages
25288 Turn on or off debugging messages from JIT debug support.
25289 @item show debug jit
25290 Displays the current state of @value{GDBN} JIT debugging.
25291 @item set debug lin-lwp
25292 @cindex @sc{gnu}/Linux LWP debug messages
25293 @cindex Linux lightweight processes
25294 Turn on or off debugging messages from the Linux LWP debug support.
25295 @item show debug lin-lwp
25296 Show the current state of Linux LWP debugging messages.
25297 @item set debug linux-namespaces
25298 @cindex @sc{gnu}/Linux namespaces debug messages
25299 Turn on or off debugging messages from the Linux namespaces debug support.
25300 @item show debug linux-namespaces
25301 Show the current state of Linux namespaces debugging messages.
25302 @item set debug mach-o
25303 @cindex Mach-O symbols processing
25304 Control display of debugging messages related to Mach-O symbols
25305 processing. The default is off.
25306 @item show debug mach-o
25307 Displays the current state of displaying debugging messages related to
25308 reading of COFF/PE exported symbols.
25309 @item set debug notification
25310 @cindex remote async notification debugging info
25311 Turn on or off debugging messages about remote async notification.
25312 The default is off.
25313 @item show debug notification
25314 Displays the current state of remote async notification debugging messages.
25315 @item set debug observer
25316 @cindex observer debugging info
25317 Turns on or off display of @value{GDBN} observer debugging. This
25318 includes info such as the notification of observable events.
25319 @item show debug observer
25320 Displays the current state of observer debugging.
25321 @item set debug overload
25322 @cindex C@t{++} overload debugging info
25323 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25324 info. This includes info such as ranking of functions, etc. The default
25326 @item show debug overload
25327 Displays the current state of displaying @value{GDBN} C@t{++} overload
25329 @cindex expression parser, debugging info
25330 @cindex debug expression parser
25331 @item set debug parser
25332 Turns on or off the display of expression parser debugging output.
25333 Internally, this sets the @code{yydebug} variable in the expression
25334 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25335 details. The default is off.
25336 @item show debug parser
25337 Show the current state of expression parser debugging.
25338 @cindex packets, reporting on stdout
25339 @cindex serial connections, debugging
25340 @cindex debug remote protocol
25341 @cindex remote protocol debugging
25342 @cindex display remote packets
25343 @item set debug remote
25344 Turns on or off display of reports on all packets sent back and forth across
25345 the serial line to the remote machine. The info is printed on the
25346 @value{GDBN} standard output stream. The default is off.
25347 @item show debug remote
25348 Displays the state of display of remote packets.
25350 @item set debug separate-debug-file
25351 Turns on or off display of debug output about separate debug file search.
25352 @item show debug separate-debug-file
25353 Displays the state of separate debug file search debug output.
25355 @item set debug serial
25356 Turns on or off display of @value{GDBN} serial debugging info. The
25358 @item show debug serial
25359 Displays the current state of displaying @value{GDBN} serial debugging
25361 @item set debug solib-frv
25362 @cindex FR-V shared-library debugging
25363 Turn on or off debugging messages for FR-V shared-library code.
25364 @item show debug solib-frv
25365 Display the current state of FR-V shared-library code debugging
25367 @item set debug symbol-lookup
25368 @cindex symbol lookup
25369 Turns on or off display of debugging messages related to symbol lookup.
25370 The default is 0 (off).
25371 A value of 1 provides basic information.
25372 A value greater than 1 provides more verbose information.
25373 @item show debug symbol-lookup
25374 Show the current state of symbol lookup debugging messages.
25375 @item set debug symfile
25376 @cindex symbol file functions
25377 Turns on or off display of debugging messages related to symbol file functions.
25378 The default is off. @xref{Files}.
25379 @item show debug symfile
25380 Show the current state of symbol file debugging messages.
25381 @item set debug symtab-create
25382 @cindex symbol table creation
25383 Turns on or off display of debugging messages related to symbol table creation.
25384 The default is 0 (off).
25385 A value of 1 provides basic information.
25386 A value greater than 1 provides more verbose information.
25387 @item show debug symtab-create
25388 Show the current state of symbol table creation debugging.
25389 @item set debug target
25390 @cindex target debugging info
25391 Turns on or off display of @value{GDBN} target debugging info. This info
25392 includes what is going on at the target level of GDB, as it happens. The
25393 default is 0. Set it to 1 to track events, and to 2 to also track the
25394 value of large memory transfers.
25395 @item show debug target
25396 Displays the current state of displaying @value{GDBN} target debugging
25398 @item set debug timestamp
25399 @cindex timestampping debugging info
25400 Turns on or off display of timestamps with @value{GDBN} debugging info.
25401 When enabled, seconds and microseconds are displayed before each debugging
25403 @item show debug timestamp
25404 Displays the current state of displaying timestamps with @value{GDBN}
25406 @item set debug varobj
25407 @cindex variable object debugging info
25408 Turns on or off display of @value{GDBN} variable object debugging
25409 info. The default is off.
25410 @item show debug varobj
25411 Displays the current state of displaying @value{GDBN} variable object
25413 @item set debug xml
25414 @cindex XML parser debugging
25415 Turn on or off debugging messages for built-in XML parsers.
25416 @item show debug xml
25417 Displays the current state of XML debugging messages.
25420 @node Other Misc Settings
25421 @section Other Miscellaneous Settings
25422 @cindex miscellaneous settings
25425 @kindex set interactive-mode
25426 @item set interactive-mode
25427 If @code{on}, forces @value{GDBN} to assume that GDB was started
25428 in a terminal. In practice, this means that @value{GDBN} should wait
25429 for the user to answer queries generated by commands entered at
25430 the command prompt. If @code{off}, forces @value{GDBN} to operate
25431 in the opposite mode, and it uses the default answers to all queries.
25432 If @code{auto} (the default), @value{GDBN} tries to determine whether
25433 its standard input is a terminal, and works in interactive-mode if it
25434 is, non-interactively otherwise.
25436 In the vast majority of cases, the debugger should be able to guess
25437 correctly which mode should be used. But this setting can be useful
25438 in certain specific cases, such as running a MinGW @value{GDBN}
25439 inside a cygwin window.
25441 @kindex show interactive-mode
25442 @item show interactive-mode
25443 Displays whether the debugger is operating in interactive mode or not.
25446 @node Extending GDB
25447 @chapter Extending @value{GDBN}
25448 @cindex extending GDB
25450 @value{GDBN} provides several mechanisms for extension.
25451 @value{GDBN} also provides the ability to automatically load
25452 extensions when it reads a file for debugging. This allows the
25453 user to automatically customize @value{GDBN} for the program
25457 * Sequences:: Canned Sequences of @value{GDBN} Commands
25458 * Python:: Extending @value{GDBN} using Python
25459 * Guile:: Extending @value{GDBN} using Guile
25460 * Auto-loading extensions:: Automatically loading extensions
25461 * Multiple Extension Languages:: Working with multiple extension languages
25462 * Aliases:: Creating new spellings of existing commands
25465 To facilitate the use of extension languages, @value{GDBN} is capable
25466 of evaluating the contents of a file. When doing so, @value{GDBN}
25467 can recognize which extension language is being used by looking at
25468 the filename extension. Files with an unrecognized filename extension
25469 are always treated as a @value{GDBN} Command Files.
25470 @xref{Command Files,, Command files}.
25472 You can control how @value{GDBN} evaluates these files with the following
25476 @kindex set script-extension
25477 @kindex show script-extension
25478 @item set script-extension off
25479 All scripts are always evaluated as @value{GDBN} Command Files.
25481 @item set script-extension soft
25482 The debugger determines the scripting language based on filename
25483 extension. If this scripting language is supported, @value{GDBN}
25484 evaluates the script using that language. Otherwise, it evaluates
25485 the file as a @value{GDBN} Command File.
25487 @item set script-extension strict
25488 The debugger determines the scripting language based on filename
25489 extension, and evaluates the script using that language. If the
25490 language is not supported, then the evaluation fails.
25492 @item show script-extension
25493 Display the current value of the @code{script-extension} option.
25498 @section Canned Sequences of Commands
25500 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25501 Command Lists}), @value{GDBN} provides two ways to store sequences of
25502 commands for execution as a unit: user-defined commands and command
25506 * Define:: How to define your own commands
25507 * Hooks:: Hooks for user-defined commands
25508 * Command Files:: How to write scripts of commands to be stored in a file
25509 * Output:: Commands for controlled output
25510 * Auto-loading sequences:: Controlling auto-loaded command files
25514 @subsection User-defined Commands
25516 @cindex user-defined command
25517 @cindex arguments, to user-defined commands
25518 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25519 which you assign a new name as a command. This is done with the
25520 @code{define} command. User commands may accept an unlimited number of arguments
25521 separated by whitespace. Arguments are accessed within the user command
25522 via @code{$arg0@dots{}$argN}. A trivial example:
25526 print $arg0 + $arg1 + $arg2
25531 To execute the command use:
25538 This defines the command @code{adder}, which prints the sum of
25539 its three arguments. Note the arguments are text substitutions, so they may
25540 reference variables, use complex expressions, or even perform inferior
25543 @cindex argument count in user-defined commands
25544 @cindex how many arguments (user-defined commands)
25545 In addition, @code{$argc} may be used to find out how many arguments have
25551 print $arg0 + $arg1
25554 print $arg0 + $arg1 + $arg2
25559 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25560 to process a variable number of arguments:
25567 eval "set $sum = $sum + $arg%d", $i
25577 @item define @var{commandname}
25578 Define a command named @var{commandname}. If there is already a command
25579 by that name, you are asked to confirm that you want to redefine it.
25580 The argument @var{commandname} may be a bare command name consisting of letters,
25581 numbers, dashes, and underscores. It may also start with any predefined
25582 prefix command. For example, @samp{define target my-target} creates
25583 a user-defined @samp{target my-target} command.
25585 The definition of the command is made up of other @value{GDBN} command lines,
25586 which are given following the @code{define} command. The end of these
25587 commands is marked by a line containing @code{end}.
25590 @kindex end@r{ (user-defined commands)}
25591 @item document @var{commandname}
25592 Document the user-defined command @var{commandname}, so that it can be
25593 accessed by @code{help}. The command @var{commandname} must already be
25594 defined. This command reads lines of documentation just as @code{define}
25595 reads the lines of the command definition, ending with @code{end}.
25596 After the @code{document} command is finished, @code{help} on command
25597 @var{commandname} displays the documentation you have written.
25599 You may use the @code{document} command again to change the
25600 documentation of a command. Redefining the command with @code{define}
25601 does not change the documentation.
25603 @kindex dont-repeat
25604 @cindex don't repeat command
25606 Used inside a user-defined command, this tells @value{GDBN} that this
25607 command should not be repeated when the user hits @key{RET}
25608 (@pxref{Command Syntax, repeat last command}).
25610 @kindex help user-defined
25611 @item help user-defined
25612 List all user-defined commands and all python commands defined in class
25613 COMAND_USER. The first line of the documentation or docstring is
25618 @itemx show user @var{commandname}
25619 Display the @value{GDBN} commands used to define @var{commandname} (but
25620 not its documentation). If no @var{commandname} is given, display the
25621 definitions for all user-defined commands.
25622 This does not work for user-defined python commands.
25624 @cindex infinite recursion in user-defined commands
25625 @kindex show max-user-call-depth
25626 @kindex set max-user-call-depth
25627 @item show max-user-call-depth
25628 @itemx set max-user-call-depth
25629 The value of @code{max-user-call-depth} controls how many recursion
25630 levels are allowed in user-defined commands before @value{GDBN} suspects an
25631 infinite recursion and aborts the command.
25632 This does not apply to user-defined python commands.
25635 In addition to the above commands, user-defined commands frequently
25636 use control flow commands, described in @ref{Command Files}.
25638 When user-defined commands are executed, the
25639 commands of the definition are not printed. An error in any command
25640 stops execution of the user-defined command.
25642 If used interactively, commands that would ask for confirmation proceed
25643 without asking when used inside a user-defined command. Many @value{GDBN}
25644 commands that normally print messages to say what they are doing omit the
25645 messages when used in a user-defined command.
25648 @subsection User-defined Command Hooks
25649 @cindex command hooks
25650 @cindex hooks, for commands
25651 @cindex hooks, pre-command
25654 You may define @dfn{hooks}, which are a special kind of user-defined
25655 command. Whenever you run the command @samp{foo}, if the user-defined
25656 command @samp{hook-foo} exists, it is executed (with no arguments)
25657 before that command.
25659 @cindex hooks, post-command
25661 A hook may also be defined which is run after the command you executed.
25662 Whenever you run the command @samp{foo}, if the user-defined command
25663 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25664 that command. Post-execution hooks may exist simultaneously with
25665 pre-execution hooks, for the same command.
25667 It is valid for a hook to call the command which it hooks. If this
25668 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25670 @c It would be nice if hookpost could be passed a parameter indicating
25671 @c if the command it hooks executed properly or not. FIXME!
25673 @kindex stop@r{, a pseudo-command}
25674 In addition, a pseudo-command, @samp{stop} exists. Defining
25675 (@samp{hook-stop}) makes the associated commands execute every time
25676 execution stops in your program: before breakpoint commands are run,
25677 displays are printed, or the stack frame is printed.
25679 For example, to ignore @code{SIGALRM} signals while
25680 single-stepping, but treat them normally during normal execution,
25685 handle SIGALRM nopass
25689 handle SIGALRM pass
25692 define hook-continue
25693 handle SIGALRM pass
25697 As a further example, to hook at the beginning and end of the @code{echo}
25698 command, and to add extra text to the beginning and end of the message,
25706 define hookpost-echo
25710 (@value{GDBP}) echo Hello World
25711 <<<---Hello World--->>>
25716 You can define a hook for any single-word command in @value{GDBN}, but
25717 not for command aliases; you should define a hook for the basic command
25718 name, e.g.@: @code{backtrace} rather than @code{bt}.
25719 @c FIXME! So how does Joe User discover whether a command is an alias
25721 You can hook a multi-word command by adding @code{hook-} or
25722 @code{hookpost-} to the last word of the command, e.g.@:
25723 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25725 If an error occurs during the execution of your hook, execution of
25726 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25727 (before the command that you actually typed had a chance to run).
25729 If you try to define a hook which does not match any known command, you
25730 get a warning from the @code{define} command.
25732 @node Command Files
25733 @subsection Command Files
25735 @cindex command files
25736 @cindex scripting commands
25737 A command file for @value{GDBN} is a text file made of lines that are
25738 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25739 also be included. An empty line in a command file does nothing; it
25740 does not mean to repeat the last command, as it would from the
25743 You can request the execution of a command file with the @code{source}
25744 command. Note that the @code{source} command is also used to evaluate
25745 scripts that are not Command Files. The exact behavior can be configured
25746 using the @code{script-extension} setting.
25747 @xref{Extending GDB,, Extending GDB}.
25751 @cindex execute commands from a file
25752 @item source [-s] [-v] @var{filename}
25753 Execute the command file @var{filename}.
25756 The lines in a command file are generally executed sequentially,
25757 unless the order of execution is changed by one of the
25758 @emph{flow-control commands} described below. The commands are not
25759 printed as they are executed. An error in any command terminates
25760 execution of the command file and control is returned to the console.
25762 @value{GDBN} first searches for @var{filename} in the current directory.
25763 If the file is not found there, and @var{filename} does not specify a
25764 directory, then @value{GDBN} also looks for the file on the source search path
25765 (specified with the @samp{directory} command);
25766 except that @file{$cdir} is not searched because the compilation directory
25767 is not relevant to scripts.
25769 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25770 on the search path even if @var{filename} specifies a directory.
25771 The search is done by appending @var{filename} to each element of the
25772 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25773 and the search path contains @file{/home/user} then @value{GDBN} will
25774 look for the script @file{/home/user/mylib/myscript}.
25775 The search is also done if @var{filename} is an absolute path.
25776 For example, if @var{filename} is @file{/tmp/myscript} and
25777 the search path contains @file{/home/user} then @value{GDBN} will
25778 look for the script @file{/home/user/tmp/myscript}.
25779 For DOS-like systems, if @var{filename} contains a drive specification,
25780 it is stripped before concatenation. For example, if @var{filename} is
25781 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25782 will look for the script @file{c:/tmp/myscript}.
25784 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25785 each command as it is executed. The option must be given before
25786 @var{filename}, and is interpreted as part of the filename anywhere else.
25788 Commands that would ask for confirmation if used interactively proceed
25789 without asking when used in a command file. Many @value{GDBN} commands that
25790 normally print messages to say what they are doing omit the messages
25791 when called from command files.
25793 @value{GDBN} also accepts command input from standard input. In this
25794 mode, normal output goes to standard output and error output goes to
25795 standard error. Errors in a command file supplied on standard input do
25796 not terminate execution of the command file---execution continues with
25800 gdb < cmds > log 2>&1
25803 (The syntax above will vary depending on the shell used.) This example
25804 will execute commands from the file @file{cmds}. All output and errors
25805 would be directed to @file{log}.
25807 Since commands stored on command files tend to be more general than
25808 commands typed interactively, they frequently need to deal with
25809 complicated situations, such as different or unexpected values of
25810 variables and symbols, changes in how the program being debugged is
25811 built, etc. @value{GDBN} provides a set of flow-control commands to
25812 deal with these complexities. Using these commands, you can write
25813 complex scripts that loop over data structures, execute commands
25814 conditionally, etc.
25821 This command allows to include in your script conditionally executed
25822 commands. The @code{if} command takes a single argument, which is an
25823 expression to evaluate. It is followed by a series of commands that
25824 are executed only if the expression is true (its value is nonzero).
25825 There can then optionally be an @code{else} line, followed by a series
25826 of commands that are only executed if the expression was false. The
25827 end of the list is marked by a line containing @code{end}.
25831 This command allows to write loops. Its syntax is similar to
25832 @code{if}: the command takes a single argument, which is an expression
25833 to evaluate, and must be followed by the commands to execute, one per
25834 line, terminated by an @code{end}. These commands are called the
25835 @dfn{body} of the loop. The commands in the body of @code{while} are
25836 executed repeatedly as long as the expression evaluates to true.
25840 This command exits the @code{while} loop in whose body it is included.
25841 Execution of the script continues after that @code{while}s @code{end}
25844 @kindex loop_continue
25845 @item loop_continue
25846 This command skips the execution of the rest of the body of commands
25847 in the @code{while} loop in whose body it is included. Execution
25848 branches to the beginning of the @code{while} loop, where it evaluates
25849 the controlling expression.
25851 @kindex end@r{ (if/else/while commands)}
25853 Terminate the block of commands that are the body of @code{if},
25854 @code{else}, or @code{while} flow-control commands.
25859 @subsection Commands for Controlled Output
25861 During the execution of a command file or a user-defined command, normal
25862 @value{GDBN} output is suppressed; the only output that appears is what is
25863 explicitly printed by the commands in the definition. This section
25864 describes three commands useful for generating exactly the output you
25869 @item echo @var{text}
25870 @c I do not consider backslash-space a standard C escape sequence
25871 @c because it is not in ANSI.
25872 Print @var{text}. Nonprinting characters can be included in
25873 @var{text} using C escape sequences, such as @samp{\n} to print a
25874 newline. @strong{No newline is printed unless you specify one.}
25875 In addition to the standard C escape sequences, a backslash followed
25876 by a space stands for a space. This is useful for displaying a
25877 string with spaces at the beginning or the end, since leading and
25878 trailing spaces are otherwise trimmed from all arguments.
25879 To print @samp{@w{ }and foo =@w{ }}, use the command
25880 @samp{echo \@w{ }and foo = \@w{ }}.
25882 A backslash at the end of @var{text} can be used, as in C, to continue
25883 the command onto subsequent lines. For example,
25886 echo This is some text\n\
25887 which is continued\n\
25888 onto several lines.\n
25891 produces the same output as
25894 echo This is some text\n
25895 echo which is continued\n
25896 echo onto several lines.\n
25900 @item output @var{expression}
25901 Print the value of @var{expression} and nothing but that value: no
25902 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25903 value history either. @xref{Expressions, ,Expressions}, for more information
25906 @item output/@var{fmt} @var{expression}
25907 Print the value of @var{expression} in format @var{fmt}. You can use
25908 the same formats as for @code{print}. @xref{Output Formats,,Output
25909 Formats}, for more information.
25912 @item printf @var{template}, @var{expressions}@dots{}
25913 Print the values of one or more @var{expressions} under the control of
25914 the string @var{template}. To print several values, make
25915 @var{expressions} be a comma-separated list of individual expressions,
25916 which may be either numbers or pointers. Their values are printed as
25917 specified by @var{template}, exactly as a C program would do by
25918 executing the code below:
25921 printf (@var{template}, @var{expressions}@dots{});
25924 As in @code{C} @code{printf}, ordinary characters in @var{template}
25925 are printed verbatim, while @dfn{conversion specification} introduced
25926 by the @samp{%} character cause subsequent @var{expressions} to be
25927 evaluated, their values converted and formatted according to type and
25928 style information encoded in the conversion specifications, and then
25931 For example, you can print two values in hex like this:
25934 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25937 @code{printf} supports all the standard @code{C} conversion
25938 specifications, including the flags and modifiers between the @samp{%}
25939 character and the conversion letter, with the following exceptions:
25943 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25946 The modifier @samp{*} is not supported for specifying precision or
25950 The @samp{'} flag (for separation of digits into groups according to
25951 @code{LC_NUMERIC'}) is not supported.
25954 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25958 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25961 The conversion letters @samp{a} and @samp{A} are not supported.
25965 Note that the @samp{ll} type modifier is supported only if the
25966 underlying @code{C} implementation used to build @value{GDBN} supports
25967 the @code{long long int} type, and the @samp{L} type modifier is
25968 supported only if @code{long double} type is available.
25970 As in @code{C}, @code{printf} supports simple backslash-escape
25971 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25972 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25973 single character. Octal and hexadecimal escape sequences are not
25976 Additionally, @code{printf} supports conversion specifications for DFP
25977 (@dfn{Decimal Floating Point}) types using the following length modifiers
25978 together with a floating point specifier.
25983 @samp{H} for printing @code{Decimal32} types.
25986 @samp{D} for printing @code{Decimal64} types.
25989 @samp{DD} for printing @code{Decimal128} types.
25992 If the underlying @code{C} implementation used to build @value{GDBN} has
25993 support for the three length modifiers for DFP types, other modifiers
25994 such as width and precision will also be available for @value{GDBN} to use.
25996 In case there is no such @code{C} support, no additional modifiers will be
25997 available and the value will be printed in the standard way.
25999 Here's an example of printing DFP types using the above conversion letters:
26001 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26006 @item eval @var{template}, @var{expressions}@dots{}
26007 Convert the values of one or more @var{expressions} under the control of
26008 the string @var{template} to a command line, and call it.
26012 @node Auto-loading sequences
26013 @subsection Controlling auto-loading native @value{GDBN} scripts
26014 @cindex native script auto-loading
26016 When a new object file is read (for example, due to the @code{file}
26017 command, or because the inferior has loaded a shared library),
26018 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26019 @xref{Auto-loading extensions}.
26021 Auto-loading can be enabled or disabled,
26022 and the list of auto-loaded scripts can be printed.
26025 @anchor{set auto-load gdb-scripts}
26026 @kindex set auto-load gdb-scripts
26027 @item set auto-load gdb-scripts [on|off]
26028 Enable or disable the auto-loading of canned sequences of commands scripts.
26030 @anchor{show auto-load gdb-scripts}
26031 @kindex show auto-load gdb-scripts
26032 @item show auto-load gdb-scripts
26033 Show whether auto-loading of canned sequences of commands scripts is enabled or
26036 @anchor{info auto-load gdb-scripts}
26037 @kindex info auto-load gdb-scripts
26038 @cindex print list of auto-loaded canned sequences of commands scripts
26039 @item info auto-load gdb-scripts [@var{regexp}]
26040 Print the list of all canned sequences of commands scripts that @value{GDBN}
26044 If @var{regexp} is supplied only canned sequences of commands scripts with
26045 matching names are printed.
26047 @c Python docs live in a separate file.
26048 @include python.texi
26050 @c Guile docs live in a separate file.
26051 @include guile.texi
26053 @node Auto-loading extensions
26054 @section Auto-loading extensions
26055 @cindex auto-loading extensions
26057 @value{GDBN} provides two mechanisms for automatically loading extensions
26058 when a new object file is read (for example, due to the @code{file}
26059 command, or because the inferior has loaded a shared library):
26060 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26061 section of modern file formats like ELF.
26064 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26065 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26066 * Which flavor to choose?::
26069 The auto-loading feature is useful for supplying application-specific
26070 debugging commands and features.
26072 Auto-loading can be enabled or disabled,
26073 and the list of auto-loaded scripts can be printed.
26074 See the @samp{auto-loading} section of each extension language
26075 for more information.
26076 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26077 For Python files see @ref{Python Auto-loading}.
26079 Note that loading of this script file also requires accordingly configured
26080 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26082 @node objfile-gdbdotext file
26083 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26084 @cindex @file{@var{objfile}-gdb.gdb}
26085 @cindex @file{@var{objfile}-gdb.py}
26086 @cindex @file{@var{objfile}-gdb.scm}
26088 When a new object file is read, @value{GDBN} looks for a file named
26089 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26090 where @var{objfile} is the object file's name and
26091 where @var{ext} is the file extension for the extension language:
26094 @item @file{@var{objfile}-gdb.gdb}
26095 GDB's own command language
26096 @item @file{@var{objfile}-gdb.py}
26098 @item @file{@var{objfile}-gdb.scm}
26102 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26103 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26104 components, and appending the @file{-gdb.@var{ext}} suffix.
26105 If this file exists and is readable, @value{GDBN} will evaluate it as a
26106 script in the specified extension language.
26108 If this file does not exist, then @value{GDBN} will look for
26109 @var{script-name} file in all of the directories as specified below.
26111 Note that loading of these files requires an accordingly configured
26112 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26114 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26115 scripts normally according to its @file{.exe} filename. But if no scripts are
26116 found @value{GDBN} also tries script filenames matching the object file without
26117 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26118 is attempted on any platform. This makes the script filenames compatible
26119 between Unix and MS-Windows hosts.
26122 @anchor{set auto-load scripts-directory}
26123 @kindex set auto-load scripts-directory
26124 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26125 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26126 may be delimited by the host platform path separator in use
26127 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26129 Each entry here needs to be covered also by the security setting
26130 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26132 @anchor{with-auto-load-dir}
26133 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26134 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26135 configuration option @option{--with-auto-load-dir}.
26137 Any reference to @file{$debugdir} will get replaced by
26138 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26139 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26140 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26141 @file{$datadir} must be placed as a directory component --- either alone or
26142 delimited by @file{/} or @file{\} directory separators, depending on the host
26145 The list of directories uses path separator (@samp{:} on GNU and Unix
26146 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26147 to the @env{PATH} environment variable.
26149 @anchor{show auto-load scripts-directory}
26150 @kindex show auto-load scripts-directory
26151 @item show auto-load scripts-directory
26152 Show @value{GDBN} auto-loaded scripts location.
26154 @anchor{add-auto-load-scripts-directory}
26155 @kindex add-auto-load-scripts-directory
26156 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26157 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26158 Multiple entries may be delimited by the host platform path separator in use.
26161 @value{GDBN} does not track which files it has already auto-loaded this way.
26162 @value{GDBN} will load the associated script every time the corresponding
26163 @var{objfile} is opened.
26164 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26165 is evaluated more than once.
26167 @node dotdebug_gdb_scripts section
26168 @subsection The @code{.debug_gdb_scripts} section
26169 @cindex @code{.debug_gdb_scripts} section
26171 For systems using file formats like ELF and COFF,
26172 when @value{GDBN} loads a new object file
26173 it will look for a special section named @code{.debug_gdb_scripts}.
26174 If this section exists, its contents is a list of null-terminated entries
26175 specifying scripts to load. Each entry begins with a non-null prefix byte that
26176 specifies the kind of entry, typically the extension language and whether the
26177 script is in a file or inlined in @code{.debug_gdb_scripts}.
26179 The following entries are supported:
26182 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26183 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26184 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26185 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26188 @subsubsection Script File Entries
26190 If the entry specifies a file, @value{GDBN} will look for the file first
26191 in the current directory and then along the source search path
26192 (@pxref{Source Path, ,Specifying Source Directories}),
26193 except that @file{$cdir} is not searched, since the compilation
26194 directory is not relevant to scripts.
26196 File entries can be placed in section @code{.debug_gdb_scripts} with,
26197 for example, this GCC macro for Python scripts.
26200 /* Note: The "MS" section flags are to remove duplicates. */
26201 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26203 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26204 .byte 1 /* Python */\n\
26205 .asciz \"" script_name "\"\n\
26211 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26212 Then one can reference the macro in a header or source file like this:
26215 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26218 The script name may include directories if desired.
26220 Note that loading of this script file also requires accordingly configured
26221 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26223 If the macro invocation is put in a header, any application or library
26224 using this header will get a reference to the specified script,
26225 and with the use of @code{"MS"} attributes on the section, the linker
26226 will remove duplicates.
26228 @subsubsection Script Text Entries
26230 Script text entries allow to put the executable script in the entry
26231 itself instead of loading it from a file.
26232 The first line of the entry, everything after the prefix byte and up to
26233 the first newline (@code{0xa}) character, is the script name, and must not
26234 contain any kind of space character, e.g., spaces or tabs.
26235 The rest of the entry, up to the trailing null byte, is the script to
26236 execute in the specified language. The name needs to be unique among
26237 all script names, as @value{GDBN} executes each script only once based
26240 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26244 #include "symcat.h"
26245 #include "gdb/section-scripts.h"
26247 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26248 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26249 ".ascii \"gdb.inlined-script\\n\"\n"
26250 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26251 ".ascii \" def __init__ (self):\\n\"\n"
26252 ".ascii \" super (test_cmd, self).__init__ ("
26253 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26254 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26255 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26256 ".ascii \"test_cmd ()\\n\"\n"
26262 Loading of inlined scripts requires a properly configured
26263 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26264 The path to specify in @code{auto-load safe-path} is the path of the file
26265 containing the @code{.debug_gdb_scripts} section.
26267 @node Which flavor to choose?
26268 @subsection Which flavor to choose?
26270 Given the multiple ways of auto-loading extensions, it might not always
26271 be clear which one to choose. This section provides some guidance.
26274 Benefits of the @file{-gdb.@var{ext}} way:
26278 Can be used with file formats that don't support multiple sections.
26281 Ease of finding scripts for public libraries.
26283 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26284 in the source search path.
26285 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26286 isn't a source directory in which to find the script.
26289 Doesn't require source code additions.
26293 Benefits of the @code{.debug_gdb_scripts} way:
26297 Works with static linking.
26299 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26300 trigger their loading. When an application is statically linked the only
26301 objfile available is the executable, and it is cumbersome to attach all the
26302 scripts from all the input libraries to the executable's
26303 @file{-gdb.@var{ext}} script.
26306 Works with classes that are entirely inlined.
26308 Some classes can be entirely inlined, and thus there may not be an associated
26309 shared library to attach a @file{-gdb.@var{ext}} script to.
26312 Scripts needn't be copied out of the source tree.
26314 In some circumstances, apps can be built out of large collections of internal
26315 libraries, and the build infrastructure necessary to install the
26316 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26317 cumbersome. It may be easier to specify the scripts in the
26318 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26319 top of the source tree to the source search path.
26322 @node Multiple Extension Languages
26323 @section Multiple Extension Languages
26325 The Guile and Python extension languages do not share any state,
26326 and generally do not interfere with each other.
26327 There are some things to be aware of, however.
26329 @subsection Python comes first
26331 Python was @value{GDBN}'s first extension language, and to avoid breaking
26332 existing behaviour Python comes first. This is generally solved by the
26333 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26334 extension languages, and when it makes a call to an extension language,
26335 (say to pretty-print a value), it tries each in turn until an extension
26336 language indicates it has performed the request (e.g., has returned the
26337 pretty-printed form of a value).
26338 This extends to errors while performing such requests: If an error happens
26339 while, for example, trying to pretty-print an object then the error is
26340 reported and any following extension languages are not tried.
26343 @section Creating new spellings of existing commands
26344 @cindex aliases for commands
26346 It is often useful to define alternate spellings of existing commands.
26347 For example, if a new @value{GDBN} command defined in Python has
26348 a long name to type, it is handy to have an abbreviated version of it
26349 that involves less typing.
26351 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26352 of the @samp{step} command even though it is otherwise an ambiguous
26353 abbreviation of other commands like @samp{set} and @samp{show}.
26355 Aliases are also used to provide shortened or more common versions
26356 of multi-word commands. For example, @value{GDBN} provides the
26357 @samp{tty} alias of the @samp{set inferior-tty} command.
26359 You can define a new alias with the @samp{alias} command.
26364 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26368 @var{ALIAS} specifies the name of the new alias.
26369 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26372 @var{COMMAND} specifies the name of an existing command
26373 that is being aliased.
26375 The @samp{-a} option specifies that the new alias is an abbreviation
26376 of the command. Abbreviations are not shown in command
26377 lists displayed by the @samp{help} command.
26379 The @samp{--} option specifies the end of options,
26380 and is useful when @var{ALIAS} begins with a dash.
26382 Here is a simple example showing how to make an abbreviation
26383 of a command so that there is less to type.
26384 Suppose you were tired of typing @samp{disas}, the current
26385 shortest unambiguous abbreviation of the @samp{disassemble} command
26386 and you wanted an even shorter version named @samp{di}.
26387 The following will accomplish this.
26390 (gdb) alias -a di = disas
26393 Note that aliases are different from user-defined commands.
26394 With a user-defined command, you also need to write documentation
26395 for it with the @samp{document} command.
26396 An alias automatically picks up the documentation of the existing command.
26398 Here is an example where we make @samp{elms} an abbreviation of
26399 @samp{elements} in the @samp{set print elements} command.
26400 This is to show that you can make an abbreviation of any part
26404 (gdb) alias -a set print elms = set print elements
26405 (gdb) alias -a show print elms = show print elements
26406 (gdb) set p elms 20
26408 Limit on string chars or array elements to print is 200.
26411 Note that if you are defining an alias of a @samp{set} command,
26412 and you want to have an alias for the corresponding @samp{show}
26413 command, then you need to define the latter separately.
26415 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26416 @var{ALIAS}, just as they are normally.
26419 (gdb) alias -a set pr elms = set p ele
26422 Finally, here is an example showing the creation of a one word
26423 alias for a more complex command.
26424 This creates alias @samp{spe} of the command @samp{set print elements}.
26427 (gdb) alias spe = set print elements
26432 @chapter Command Interpreters
26433 @cindex command interpreters
26435 @value{GDBN} supports multiple command interpreters, and some command
26436 infrastructure to allow users or user interface writers to switch
26437 between interpreters or run commands in other interpreters.
26439 @value{GDBN} currently supports two command interpreters, the console
26440 interpreter (sometimes called the command-line interpreter or @sc{cli})
26441 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26442 describes both of these interfaces in great detail.
26444 By default, @value{GDBN} will start with the console interpreter.
26445 However, the user may choose to start @value{GDBN} with another
26446 interpreter by specifying the @option{-i} or @option{--interpreter}
26447 startup options. Defined interpreters include:
26451 @cindex console interpreter
26452 The traditional console or command-line interpreter. This is the most often
26453 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26454 @value{GDBN} will use this interpreter.
26457 @cindex mi interpreter
26458 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26459 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26460 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26464 @cindex mi2 interpreter
26465 The current @sc{gdb/mi} interface.
26468 @cindex mi1 interpreter
26469 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26473 @cindex invoke another interpreter
26475 @kindex interpreter-exec
26476 You may execute commands in any interpreter from the current
26477 interpreter using the appropriate command. If you are running the
26478 console interpreter, simply use the @code{interpreter-exec} command:
26481 interpreter-exec mi "-data-list-register-names"
26484 @sc{gdb/mi} has a similar command, although it is only available in versions of
26485 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26487 Note that @code{interpreter-exec} only changes the interpreter for the
26488 duration of the specified command. It does not change the interpreter
26491 @cindex start a new independent interpreter
26493 Although you may only choose a single interpreter at startup, it is
26494 possible to run an independent interpreter on a specified input/output
26495 device (usually a tty).
26497 For example, consider a debugger GUI or IDE that wants to provide a
26498 @value{GDBN} console view. It may do so by embedding a terminal
26499 emulator widget in its GUI, starting @value{GDBN} in the traditional
26500 command-line mode with stdin/stdout/stderr redirected to that
26501 terminal, and then creating an MI interpreter running on a specified
26502 input/output device. The console interpreter created by @value{GDBN}
26503 at startup handles commands the user types in the terminal widget,
26504 while the GUI controls and synchronizes state with @value{GDBN} using
26505 the separate MI interpreter.
26507 To start a new secondary @dfn{user interface} running MI, use the
26508 @code{new-ui} command:
26511 @cindex new user interface
26513 new-ui @var{interpreter} @var{tty}
26516 The @var{interpreter} parameter specifies the interpreter to run.
26517 This accepts the same values as the @code{interpreter-exec} command.
26518 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26519 @var{tty} parameter specifies the name of the bidirectional file the
26520 interpreter uses for input/output, usually the name of a
26521 pseudoterminal slave on Unix systems. For example:
26524 (@value{GDBP}) new-ui mi /dev/pts/9
26528 runs an MI interpreter on @file{/dev/pts/9}.
26531 @chapter @value{GDBN} Text User Interface
26533 @cindex Text User Interface
26536 * TUI Overview:: TUI overview
26537 * TUI Keys:: TUI key bindings
26538 * TUI Single Key Mode:: TUI single key mode
26539 * TUI Commands:: TUI-specific commands
26540 * TUI Configuration:: TUI configuration variables
26543 The @value{GDBN} Text User Interface (TUI) is a terminal
26544 interface which uses the @code{curses} library to show the source
26545 file, the assembly output, the program registers and @value{GDBN}
26546 commands in separate text windows. The TUI mode is supported only
26547 on platforms where a suitable version of the @code{curses} library
26550 The TUI mode is enabled by default when you invoke @value{GDBN} as
26551 @samp{@value{GDBP} -tui}.
26552 You can also switch in and out of TUI mode while @value{GDBN} runs by
26553 using various TUI commands and key bindings, such as @command{tui
26554 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26555 @ref{TUI Keys, ,TUI Key Bindings}.
26558 @section TUI Overview
26560 In TUI mode, @value{GDBN} can display several text windows:
26564 This window is the @value{GDBN} command window with the @value{GDBN}
26565 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26566 managed using readline.
26569 The source window shows the source file of the program. The current
26570 line and active breakpoints are displayed in this window.
26573 The assembly window shows the disassembly output of the program.
26576 This window shows the processor registers. Registers are highlighted
26577 when their values change.
26580 The source and assembly windows show the current program position
26581 by highlighting the current line and marking it with a @samp{>} marker.
26582 Breakpoints are indicated with two markers. The first marker
26583 indicates the breakpoint type:
26587 Breakpoint which was hit at least once.
26590 Breakpoint which was never hit.
26593 Hardware breakpoint which was hit at least once.
26596 Hardware breakpoint which was never hit.
26599 The second marker indicates whether the breakpoint is enabled or not:
26603 Breakpoint is enabled.
26606 Breakpoint is disabled.
26609 The source, assembly and register windows are updated when the current
26610 thread changes, when the frame changes, or when the program counter
26613 These windows are not all visible at the same time. The command
26614 window is always visible. The others can be arranged in several
26625 source and assembly,
26628 source and registers, or
26631 assembly and registers.
26634 A status line above the command window shows the following information:
26638 Indicates the current @value{GDBN} target.
26639 (@pxref{Targets, ,Specifying a Debugging Target}).
26642 Gives the current process or thread number.
26643 When no process is being debugged, this field is set to @code{No process}.
26646 Gives the current function name for the selected frame.
26647 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26648 When there is no symbol corresponding to the current program counter,
26649 the string @code{??} is displayed.
26652 Indicates the current line number for the selected frame.
26653 When the current line number is not known, the string @code{??} is displayed.
26656 Indicates the current program counter address.
26660 @section TUI Key Bindings
26661 @cindex TUI key bindings
26663 The TUI installs several key bindings in the readline keymaps
26664 @ifset SYSTEM_READLINE
26665 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26667 @ifclear SYSTEM_READLINE
26668 (@pxref{Command Line Editing}).
26670 The following key bindings are installed for both TUI mode and the
26671 @value{GDBN} standard mode.
26680 Enter or leave the TUI mode. When leaving the TUI mode,
26681 the curses window management stops and @value{GDBN} operates using
26682 its standard mode, writing on the terminal directly. When reentering
26683 the TUI mode, control is given back to the curses windows.
26684 The screen is then refreshed.
26688 Use a TUI layout with only one window. The layout will
26689 either be @samp{source} or @samp{assembly}. When the TUI mode
26690 is not active, it will switch to the TUI mode.
26692 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26696 Use a TUI layout with at least two windows. When the current
26697 layout already has two windows, the next layout with two windows is used.
26698 When a new layout is chosen, one window will always be common to the
26699 previous layout and the new one.
26701 Think of it as the Emacs @kbd{C-x 2} binding.
26705 Change the active window. The TUI associates several key bindings
26706 (like scrolling and arrow keys) with the active window. This command
26707 gives the focus to the next TUI window.
26709 Think of it as the Emacs @kbd{C-x o} binding.
26713 Switch in and out of the TUI SingleKey mode that binds single
26714 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26717 The following key bindings only work in the TUI mode:
26722 Scroll the active window one page up.
26726 Scroll the active window one page down.
26730 Scroll the active window one line up.
26734 Scroll the active window one line down.
26738 Scroll the active window one column left.
26742 Scroll the active window one column right.
26746 Refresh the screen.
26749 Because the arrow keys scroll the active window in the TUI mode, they
26750 are not available for their normal use by readline unless the command
26751 window has the focus. When another window is active, you must use
26752 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26753 and @kbd{C-f} to control the command window.
26755 @node TUI Single Key Mode
26756 @section TUI Single Key Mode
26757 @cindex TUI single key mode
26759 The TUI also provides a @dfn{SingleKey} mode, which binds several
26760 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26761 switch into this mode, where the following key bindings are used:
26764 @kindex c @r{(SingleKey TUI key)}
26768 @kindex d @r{(SingleKey TUI key)}
26772 @kindex f @r{(SingleKey TUI key)}
26776 @kindex n @r{(SingleKey TUI key)}
26780 @kindex o @r{(SingleKey TUI key)}
26782 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26784 @kindex q @r{(SingleKey TUI key)}
26786 exit the SingleKey mode.
26788 @kindex r @r{(SingleKey TUI key)}
26792 @kindex s @r{(SingleKey TUI key)}
26796 @kindex i @r{(SingleKey TUI key)}
26798 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26800 @kindex u @r{(SingleKey TUI key)}
26804 @kindex v @r{(SingleKey TUI key)}
26808 @kindex w @r{(SingleKey TUI key)}
26813 Other keys temporarily switch to the @value{GDBN} command prompt.
26814 The key that was pressed is inserted in the editing buffer so that
26815 it is possible to type most @value{GDBN} commands without interaction
26816 with the TUI SingleKey mode. Once the command is entered the TUI
26817 SingleKey mode is restored. The only way to permanently leave
26818 this mode is by typing @kbd{q} or @kbd{C-x s}.
26822 @section TUI-specific Commands
26823 @cindex TUI commands
26825 The TUI has specific commands to control the text windows.
26826 These commands are always available, even when @value{GDBN} is not in
26827 the TUI mode. When @value{GDBN} is in the standard mode, most
26828 of these commands will automatically switch to the TUI mode.
26830 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26831 terminal, or @value{GDBN} has been started with the machine interface
26832 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26833 these commands will fail with an error, because it would not be
26834 possible or desirable to enable curses window management.
26839 Activate TUI mode. The last active TUI window layout will be used if
26840 TUI mode has prevsiouly been used in the current debugging session,
26841 otherwise a default layout is used.
26844 @kindex tui disable
26845 Disable TUI mode, returning to the console interpreter.
26849 List and give the size of all displayed windows.
26851 @item layout @var{name}
26853 Changes which TUI windows are displayed. In each layout the command
26854 window is always displayed, the @var{name} parameter controls which
26855 additional windows are displayed, and can be any of the following:
26859 Display the next layout.
26862 Display the previous layout.
26865 Display the source and command windows.
26868 Display the assembly and command windows.
26871 Display the source, assembly, and command windows.
26874 When in @code{src} layout display the register, source, and command
26875 windows. When in @code{asm} or @code{split} layout display the
26876 register, assembler, and command windows.
26879 @item focus @var{name}
26881 Changes which TUI window is currently active for scrolling. The
26882 @var{name} parameter can be any of the following:
26886 Make the next window active for scrolling.
26889 Make the previous window active for scrolling.
26892 Make the source window active for scrolling.
26895 Make the assembly window active for scrolling.
26898 Make the register window active for scrolling.
26901 Make the command window active for scrolling.
26906 Refresh the screen. This is similar to typing @kbd{C-L}.
26908 @item tui reg @var{group}
26910 Changes the register group displayed in the tui register window to
26911 @var{group}. If the register window is not currently displayed this
26912 command will cause the register window to be displayed. The list of
26913 register groups, as well as their order is target specific. The
26914 following groups are available on most targets:
26917 Repeatedly selecting this group will cause the display to cycle
26918 through all of the available register groups.
26921 Repeatedly selecting this group will cause the display to cycle
26922 through all of the available register groups in the reverse order to
26926 Display the general registers.
26928 Display the floating point registers.
26930 Display the system registers.
26932 Display the vector registers.
26934 Display all registers.
26939 Update the source window and the current execution point.
26941 @item winheight @var{name} +@var{count}
26942 @itemx winheight @var{name} -@var{count}
26944 Change the height of the window @var{name} by @var{count}
26945 lines. Positive counts increase the height, while negative counts
26946 decrease it. The @var{name} parameter can be one of @code{src} (the
26947 source window), @code{cmd} (the command window), @code{asm} (the
26948 disassembly window), or @code{regs} (the register display window).
26951 @node TUI Configuration
26952 @section TUI Configuration Variables
26953 @cindex TUI configuration variables
26955 Several configuration variables control the appearance of TUI windows.
26958 @item set tui border-kind @var{kind}
26959 @kindex set tui border-kind
26960 Select the border appearance for the source, assembly and register windows.
26961 The possible values are the following:
26964 Use a space character to draw the border.
26967 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26970 Use the Alternate Character Set to draw the border. The border is
26971 drawn using character line graphics if the terminal supports them.
26974 @item set tui border-mode @var{mode}
26975 @kindex set tui border-mode
26976 @itemx set tui active-border-mode @var{mode}
26977 @kindex set tui active-border-mode
26978 Select the display attributes for the borders of the inactive windows
26979 or the active window. The @var{mode} can be one of the following:
26982 Use normal attributes to display the border.
26988 Use reverse video mode.
26991 Use half bright mode.
26993 @item half-standout
26994 Use half bright and standout mode.
26997 Use extra bright or bold mode.
26999 @item bold-standout
27000 Use extra bright or bold and standout mode.
27003 @item set tui tab-width @var{nchars}
27004 @kindex set tui tab-width
27006 Set the width of tab stops to be @var{nchars} characters. This
27007 setting affects the display of TAB characters in the source and
27012 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27015 @cindex @sc{gnu} Emacs
27016 A special interface allows you to use @sc{gnu} Emacs to view (and
27017 edit) the source files for the program you are debugging with
27020 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27021 executable file you want to debug as an argument. This command starts
27022 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27023 created Emacs buffer.
27024 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27026 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27031 All ``terminal'' input and output goes through an Emacs buffer, called
27034 This applies both to @value{GDBN} commands and their output, and to the input
27035 and output done by the program you are debugging.
27037 This is useful because it means that you can copy the text of previous
27038 commands and input them again; you can even use parts of the output
27041 All the facilities of Emacs' Shell mode are available for interacting
27042 with your program. In particular, you can send signals the usual
27043 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27047 @value{GDBN} displays source code through Emacs.
27049 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27050 source file for that frame and puts an arrow (@samp{=>}) at the
27051 left margin of the current line. Emacs uses a separate buffer for
27052 source display, and splits the screen to show both your @value{GDBN} session
27055 Explicit @value{GDBN} @code{list} or search commands still produce output as
27056 usual, but you probably have no reason to use them from Emacs.
27059 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27060 a graphical mode, enabled by default, which provides further buffers
27061 that can control the execution and describe the state of your program.
27062 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27064 If you specify an absolute file name when prompted for the @kbd{M-x
27065 gdb} argument, then Emacs sets your current working directory to where
27066 your program resides. If you only specify the file name, then Emacs
27067 sets your current working directory to the directory associated
27068 with the previous buffer. In this case, @value{GDBN} may find your
27069 program by searching your environment's @code{PATH} variable, but on
27070 some operating systems it might not find the source. So, although the
27071 @value{GDBN} input and output session proceeds normally, the auxiliary
27072 buffer does not display the current source and line of execution.
27074 The initial working directory of @value{GDBN} is printed on the top
27075 line of the GUD buffer and this serves as a default for the commands
27076 that specify files for @value{GDBN} to operate on. @xref{Files,
27077 ,Commands to Specify Files}.
27079 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27080 need to call @value{GDBN} by a different name (for example, if you
27081 keep several configurations around, with different names) you can
27082 customize the Emacs variable @code{gud-gdb-command-name} to run the
27085 In the GUD buffer, you can use these special Emacs commands in
27086 addition to the standard Shell mode commands:
27090 Describe the features of Emacs' GUD Mode.
27093 Execute to another source line, like the @value{GDBN} @code{step} command; also
27094 update the display window to show the current file and location.
27097 Execute to next source line in this function, skipping all function
27098 calls, like the @value{GDBN} @code{next} command. Then update the display window
27099 to show the current file and location.
27102 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27103 display window accordingly.
27106 Execute until exit from the selected stack frame, like the @value{GDBN}
27107 @code{finish} command.
27110 Continue execution of your program, like the @value{GDBN} @code{continue}
27114 Go up the number of frames indicated by the numeric argument
27115 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27116 like the @value{GDBN} @code{up} command.
27119 Go down the number of frames indicated by the numeric argument, like the
27120 @value{GDBN} @code{down} command.
27123 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27124 tells @value{GDBN} to set a breakpoint on the source line point is on.
27126 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27127 separate frame which shows a backtrace when the GUD buffer is current.
27128 Move point to any frame in the stack and type @key{RET} to make it
27129 become the current frame and display the associated source in the
27130 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27131 selected frame become the current one. In graphical mode, the
27132 speedbar displays watch expressions.
27134 If you accidentally delete the source-display buffer, an easy way to get
27135 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27136 request a frame display; when you run under Emacs, this recreates
27137 the source buffer if necessary to show you the context of the current
27140 The source files displayed in Emacs are in ordinary Emacs buffers
27141 which are visiting the source files in the usual way. You can edit
27142 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27143 communicates with Emacs in terms of line numbers. If you add or
27144 delete lines from the text, the line numbers that @value{GDBN} knows cease
27145 to correspond properly with the code.
27147 A more detailed description of Emacs' interaction with @value{GDBN} is
27148 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27152 @chapter The @sc{gdb/mi} Interface
27154 @unnumberedsec Function and Purpose
27156 @cindex @sc{gdb/mi}, its purpose
27157 @sc{gdb/mi} is a line based machine oriented text interface to
27158 @value{GDBN} and is activated by specifying using the
27159 @option{--interpreter} command line option (@pxref{Mode Options}). It
27160 is specifically intended to support the development of systems which
27161 use the debugger as just one small component of a larger system.
27163 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27164 in the form of a reference manual.
27166 Note that @sc{gdb/mi} is still under construction, so some of the
27167 features described below are incomplete and subject to change
27168 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27170 @unnumberedsec Notation and Terminology
27172 @cindex notational conventions, for @sc{gdb/mi}
27173 This chapter uses the following notation:
27177 @code{|} separates two alternatives.
27180 @code{[ @var{something} ]} indicates that @var{something} is optional:
27181 it may or may not be given.
27184 @code{( @var{group} )*} means that @var{group} inside the parentheses
27185 may repeat zero or more times.
27188 @code{( @var{group} )+} means that @var{group} inside the parentheses
27189 may repeat one or more times.
27192 @code{"@var{string}"} means a literal @var{string}.
27196 @heading Dependencies
27200 * GDB/MI General Design::
27201 * GDB/MI Command Syntax::
27202 * GDB/MI Compatibility with CLI::
27203 * GDB/MI Development and Front Ends::
27204 * GDB/MI Output Records::
27205 * GDB/MI Simple Examples::
27206 * GDB/MI Command Description Format::
27207 * GDB/MI Breakpoint Commands::
27208 * GDB/MI Catchpoint Commands::
27209 * GDB/MI Program Context::
27210 * GDB/MI Thread Commands::
27211 * GDB/MI Ada Tasking Commands::
27212 * GDB/MI Program Execution::
27213 * GDB/MI Stack Manipulation::
27214 * GDB/MI Variable Objects::
27215 * GDB/MI Data Manipulation::
27216 * GDB/MI Tracepoint Commands::
27217 * GDB/MI Symbol Query::
27218 * GDB/MI File Commands::
27220 * GDB/MI Kod Commands::
27221 * GDB/MI Memory Overlay Commands::
27222 * GDB/MI Signal Handling Commands::
27224 * GDB/MI Target Manipulation::
27225 * GDB/MI File Transfer Commands::
27226 * GDB/MI Ada Exceptions Commands::
27227 * GDB/MI Support Commands::
27228 * GDB/MI Miscellaneous Commands::
27231 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27232 @node GDB/MI General Design
27233 @section @sc{gdb/mi} General Design
27234 @cindex GDB/MI General Design
27236 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27237 parts---commands sent to @value{GDBN}, responses to those commands
27238 and notifications. Each command results in exactly one response,
27239 indicating either successful completion of the command, or an error.
27240 For the commands that do not resume the target, the response contains the
27241 requested information. For the commands that resume the target, the
27242 response only indicates whether the target was successfully resumed.
27243 Notifications is the mechanism for reporting changes in the state of the
27244 target, or in @value{GDBN} state, that cannot conveniently be associated with
27245 a command and reported as part of that command response.
27247 The important examples of notifications are:
27251 Exec notifications. These are used to report changes in
27252 target state---when a target is resumed, or stopped. It would not
27253 be feasible to include this information in response of resuming
27254 commands, because one resume commands can result in multiple events in
27255 different threads. Also, quite some time may pass before any event
27256 happens in the target, while a frontend needs to know whether the resuming
27257 command itself was successfully executed.
27260 Console output, and status notifications. Console output
27261 notifications are used to report output of CLI commands, as well as
27262 diagnostics for other commands. Status notifications are used to
27263 report the progress of a long-running operation. Naturally, including
27264 this information in command response would mean no output is produced
27265 until the command is finished, which is undesirable.
27268 General notifications. Commands may have various side effects on
27269 the @value{GDBN} or target state beyond their official purpose. For example,
27270 a command may change the selected thread. Although such changes can
27271 be included in command response, using notification allows for more
27272 orthogonal frontend design.
27276 There's no guarantee that whenever an MI command reports an error,
27277 @value{GDBN} or the target are in any specific state, and especially,
27278 the state is not reverted to the state before the MI command was
27279 processed. Therefore, whenever an MI command results in an error,
27280 we recommend that the frontend refreshes all the information shown in
27281 the user interface.
27285 * Context management::
27286 * Asynchronous and non-stop modes::
27290 @node Context management
27291 @subsection Context management
27293 @subsubsection Threads and Frames
27295 In most cases when @value{GDBN} accesses the target, this access is
27296 done in context of a specific thread and frame (@pxref{Frames}).
27297 Often, even when accessing global data, the target requires that a thread
27298 be specified. The CLI interface maintains the selected thread and frame,
27299 and supplies them to target on each command. This is convenient,
27300 because a command line user would not want to specify that information
27301 explicitly on each command, and because user interacts with
27302 @value{GDBN} via a single terminal, so no confusion is possible as
27303 to what thread and frame are the current ones.
27305 In the case of MI, the concept of selected thread and frame is less
27306 useful. First, a frontend can easily remember this information
27307 itself. Second, a graphical frontend can have more than one window,
27308 each one used for debugging a different thread, and the frontend might
27309 want to access additional threads for internal purposes. This
27310 increases the risk that by relying on implicitly selected thread, the
27311 frontend may be operating on a wrong one. Therefore, each MI command
27312 should explicitly specify which thread and frame to operate on. To
27313 make it possible, each MI command accepts the @samp{--thread} and
27314 @samp{--frame} options, the value to each is @value{GDBN} global
27315 identifier for thread and frame to operate on.
27317 Usually, each top-level window in a frontend allows the user to select
27318 a thread and a frame, and remembers the user selection for further
27319 operations. However, in some cases @value{GDBN} may suggest that the
27320 current thread or frame be changed. For example, when stopping on a
27321 breakpoint it is reasonable to switch to the thread where breakpoint is
27322 hit. For another example, if the user issues the CLI @samp{thread} or
27323 @samp{frame} commands via the frontend, it is desirable to change the
27324 frontend's selection to the one specified by user. @value{GDBN}
27325 communicates the suggestion to change current thread and frame using the
27326 @samp{=thread-selected} notification.
27328 Note that historically, MI shares the selected thread with CLI, so
27329 frontends used the @code{-thread-select} to execute commands in the
27330 right context. However, getting this to work right is cumbersome. The
27331 simplest way is for frontend to emit @code{-thread-select} command
27332 before every command. This doubles the number of commands that need
27333 to be sent. The alternative approach is to suppress @code{-thread-select}
27334 if the selected thread in @value{GDBN} is supposed to be identical to the
27335 thread the frontend wants to operate on. However, getting this
27336 optimization right can be tricky. In particular, if the frontend
27337 sends several commands to @value{GDBN}, and one of the commands changes the
27338 selected thread, then the behaviour of subsequent commands will
27339 change. So, a frontend should either wait for response from such
27340 problematic commands, or explicitly add @code{-thread-select} for
27341 all subsequent commands. No frontend is known to do this exactly
27342 right, so it is suggested to just always pass the @samp{--thread} and
27343 @samp{--frame} options.
27345 @subsubsection Language
27347 The execution of several commands depends on which language is selected.
27348 By default, the current language (@pxref{show language}) is used.
27349 But for commands known to be language-sensitive, it is recommended
27350 to use the @samp{--language} option. This option takes one argument,
27351 which is the name of the language to use while executing the command.
27355 -data-evaluate-expression --language c "sizeof (void*)"
27360 The valid language names are the same names accepted by the
27361 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27362 @samp{local} or @samp{unknown}.
27364 @node Asynchronous and non-stop modes
27365 @subsection Asynchronous command execution and non-stop mode
27367 On some targets, @value{GDBN} is capable of processing MI commands
27368 even while the target is running. This is called @dfn{asynchronous
27369 command execution} (@pxref{Background Execution}). The frontend may
27370 specify a preferrence for asynchronous execution using the
27371 @code{-gdb-set mi-async 1} command, which should be emitted before
27372 either running the executable or attaching to the target. After the
27373 frontend has started the executable or attached to the target, it can
27374 find if asynchronous execution is enabled using the
27375 @code{-list-target-features} command.
27378 @item -gdb-set mi-async on
27379 @item -gdb-set mi-async off
27380 Set whether MI is in asynchronous mode.
27382 When @code{off}, which is the default, MI execution commands (e.g.,
27383 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27384 for the program to stop before processing further commands.
27386 When @code{on}, MI execution commands are background execution
27387 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27388 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27389 MI commands even while the target is running.
27391 @item -gdb-show mi-async
27392 Show whether MI asynchronous mode is enabled.
27395 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27396 @code{target-async} instead of @code{mi-async}, and it had the effect
27397 of both putting MI in asynchronous mode and making CLI background
27398 commands possible. CLI background commands are now always possible
27399 ``out of the box'' if the target supports them. The old spelling is
27400 kept as a deprecated alias for backwards compatibility.
27402 Even if @value{GDBN} can accept a command while target is running,
27403 many commands that access the target do not work when the target is
27404 running. Therefore, asynchronous command execution is most useful
27405 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27406 it is possible to examine the state of one thread, while other threads
27409 When a given thread is running, MI commands that try to access the
27410 target in the context of that thread may not work, or may work only on
27411 some targets. In particular, commands that try to operate on thread's
27412 stack will not work, on any target. Commands that read memory, or
27413 modify breakpoints, may work or not work, depending on the target. Note
27414 that even commands that operate on global state, such as @code{print},
27415 @code{set}, and breakpoint commands, still access the target in the
27416 context of a specific thread, so frontend should try to find a
27417 stopped thread and perform the operation on that thread (using the
27418 @samp{--thread} option).
27420 Which commands will work in the context of a running thread is
27421 highly target dependent. However, the two commands
27422 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27423 to find the state of a thread, will always work.
27425 @node Thread groups
27426 @subsection Thread groups
27427 @value{GDBN} may be used to debug several processes at the same time.
27428 On some platfroms, @value{GDBN} may support debugging of several
27429 hardware systems, each one having several cores with several different
27430 processes running on each core. This section describes the MI
27431 mechanism to support such debugging scenarios.
27433 The key observation is that regardless of the structure of the
27434 target, MI can have a global list of threads, because most commands that
27435 accept the @samp{--thread} option do not need to know what process that
27436 thread belongs to. Therefore, it is not necessary to introduce
27437 neither additional @samp{--process} option, nor an notion of the
27438 current process in the MI interface. The only strictly new feature
27439 that is required is the ability to find how the threads are grouped
27442 To allow the user to discover such grouping, and to support arbitrary
27443 hierarchy of machines/cores/processes, MI introduces the concept of a
27444 @dfn{thread group}. Thread group is a collection of threads and other
27445 thread groups. A thread group always has a string identifier, a type,
27446 and may have additional attributes specific to the type. A new
27447 command, @code{-list-thread-groups}, returns the list of top-level
27448 thread groups, which correspond to processes that @value{GDBN} is
27449 debugging at the moment. By passing an identifier of a thread group
27450 to the @code{-list-thread-groups} command, it is possible to obtain
27451 the members of specific thread group.
27453 To allow the user to easily discover processes, and other objects, he
27454 wishes to debug, a concept of @dfn{available thread group} is
27455 introduced. Available thread group is an thread group that
27456 @value{GDBN} is not debugging, but that can be attached to, using the
27457 @code{-target-attach} command. The list of available top-level thread
27458 groups can be obtained using @samp{-list-thread-groups --available}.
27459 In general, the content of a thread group may be only retrieved only
27460 after attaching to that thread group.
27462 Thread groups are related to inferiors (@pxref{Inferiors and
27463 Programs}). Each inferior corresponds to a thread group of a special
27464 type @samp{process}, and some additional operations are permitted on
27465 such thread groups.
27467 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27468 @node GDB/MI Command Syntax
27469 @section @sc{gdb/mi} Command Syntax
27472 * GDB/MI Input Syntax::
27473 * GDB/MI Output Syntax::
27476 @node GDB/MI Input Syntax
27477 @subsection @sc{gdb/mi} Input Syntax
27479 @cindex input syntax for @sc{gdb/mi}
27480 @cindex @sc{gdb/mi}, input syntax
27482 @item @var{command} @expansion{}
27483 @code{@var{cli-command} | @var{mi-command}}
27485 @item @var{cli-command} @expansion{}
27486 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27487 @var{cli-command} is any existing @value{GDBN} CLI command.
27489 @item @var{mi-command} @expansion{}
27490 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27491 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27493 @item @var{token} @expansion{}
27494 "any sequence of digits"
27496 @item @var{option} @expansion{}
27497 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27499 @item @var{parameter} @expansion{}
27500 @code{@var{non-blank-sequence} | @var{c-string}}
27502 @item @var{operation} @expansion{}
27503 @emph{any of the operations described in this chapter}
27505 @item @var{non-blank-sequence} @expansion{}
27506 @emph{anything, provided it doesn't contain special characters such as
27507 "-", @var{nl}, """ and of course " "}
27509 @item @var{c-string} @expansion{}
27510 @code{""" @var{seven-bit-iso-c-string-content} """}
27512 @item @var{nl} @expansion{}
27521 The CLI commands are still handled by the @sc{mi} interpreter; their
27522 output is described below.
27525 The @code{@var{token}}, when present, is passed back when the command
27529 Some @sc{mi} commands accept optional arguments as part of the parameter
27530 list. Each option is identified by a leading @samp{-} (dash) and may be
27531 followed by an optional argument parameter. Options occur first in the
27532 parameter list and can be delimited from normal parameters using
27533 @samp{--} (this is useful when some parameters begin with a dash).
27540 We want easy access to the existing CLI syntax (for debugging).
27543 We want it to be easy to spot a @sc{mi} operation.
27546 @node GDB/MI Output Syntax
27547 @subsection @sc{gdb/mi} Output Syntax
27549 @cindex output syntax of @sc{gdb/mi}
27550 @cindex @sc{gdb/mi}, output syntax
27551 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27552 followed, optionally, by a single result record. This result record
27553 is for the most recent command. The sequence of output records is
27554 terminated by @samp{(gdb)}.
27556 If an input command was prefixed with a @code{@var{token}} then the
27557 corresponding output for that command will also be prefixed by that same
27561 @item @var{output} @expansion{}
27562 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27564 @item @var{result-record} @expansion{}
27565 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27567 @item @var{out-of-band-record} @expansion{}
27568 @code{@var{async-record} | @var{stream-record}}
27570 @item @var{async-record} @expansion{}
27571 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27573 @item @var{exec-async-output} @expansion{}
27574 @code{[ @var{token} ] "*" @var{async-output nl}}
27576 @item @var{status-async-output} @expansion{}
27577 @code{[ @var{token} ] "+" @var{async-output nl}}
27579 @item @var{notify-async-output} @expansion{}
27580 @code{[ @var{token} ] "=" @var{async-output nl}}
27582 @item @var{async-output} @expansion{}
27583 @code{@var{async-class} ( "," @var{result} )*}
27585 @item @var{result-class} @expansion{}
27586 @code{"done" | "running" | "connected" | "error" | "exit"}
27588 @item @var{async-class} @expansion{}
27589 @code{"stopped" | @var{others}} (where @var{others} will be added
27590 depending on the needs---this is still in development).
27592 @item @var{result} @expansion{}
27593 @code{ @var{variable} "=" @var{value}}
27595 @item @var{variable} @expansion{}
27596 @code{ @var{string} }
27598 @item @var{value} @expansion{}
27599 @code{ @var{const} | @var{tuple} | @var{list} }
27601 @item @var{const} @expansion{}
27602 @code{@var{c-string}}
27604 @item @var{tuple} @expansion{}
27605 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27607 @item @var{list} @expansion{}
27608 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27609 @var{result} ( "," @var{result} )* "]" }
27611 @item @var{stream-record} @expansion{}
27612 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27614 @item @var{console-stream-output} @expansion{}
27615 @code{"~" @var{c-string nl}}
27617 @item @var{target-stream-output} @expansion{}
27618 @code{"@@" @var{c-string nl}}
27620 @item @var{log-stream-output} @expansion{}
27621 @code{"&" @var{c-string nl}}
27623 @item @var{nl} @expansion{}
27626 @item @var{token} @expansion{}
27627 @emph{any sequence of digits}.
27635 All output sequences end in a single line containing a period.
27638 The @code{@var{token}} is from the corresponding request. Note that
27639 for all async output, while the token is allowed by the grammar and
27640 may be output by future versions of @value{GDBN} for select async
27641 output messages, it is generally omitted. Frontends should treat
27642 all async output as reporting general changes in the state of the
27643 target and there should be no need to associate async output to any
27647 @cindex status output in @sc{gdb/mi}
27648 @var{status-async-output} contains on-going status information about the
27649 progress of a slow operation. It can be discarded. All status output is
27650 prefixed by @samp{+}.
27653 @cindex async output in @sc{gdb/mi}
27654 @var{exec-async-output} contains asynchronous state change on the target
27655 (stopped, started, disappeared). All async output is prefixed by
27659 @cindex notify output in @sc{gdb/mi}
27660 @var{notify-async-output} contains supplementary information that the
27661 client should handle (e.g., a new breakpoint information). All notify
27662 output is prefixed by @samp{=}.
27665 @cindex console output in @sc{gdb/mi}
27666 @var{console-stream-output} is output that should be displayed as is in the
27667 console. It is the textual response to a CLI command. All the console
27668 output is prefixed by @samp{~}.
27671 @cindex target output in @sc{gdb/mi}
27672 @var{target-stream-output} is the output produced by the target program.
27673 All the target output is prefixed by @samp{@@}.
27676 @cindex log output in @sc{gdb/mi}
27677 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27678 instance messages that should be displayed as part of an error log. All
27679 the log output is prefixed by @samp{&}.
27682 @cindex list output in @sc{gdb/mi}
27683 New @sc{gdb/mi} commands should only output @var{lists} containing
27689 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27690 details about the various output records.
27692 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27693 @node GDB/MI Compatibility with CLI
27694 @section @sc{gdb/mi} Compatibility with CLI
27696 @cindex compatibility, @sc{gdb/mi} and CLI
27697 @cindex @sc{gdb/mi}, compatibility with CLI
27699 For the developers convenience CLI commands can be entered directly,
27700 but there may be some unexpected behaviour. For example, commands
27701 that query the user will behave as if the user replied yes, breakpoint
27702 command lists are not executed and some CLI commands, such as
27703 @code{if}, @code{when} and @code{define}, prompt for further input with
27704 @samp{>}, which is not valid MI output.
27706 This feature may be removed at some stage in the future and it is
27707 recommended that front ends use the @code{-interpreter-exec} command
27708 (@pxref{-interpreter-exec}).
27710 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27711 @node GDB/MI Development and Front Ends
27712 @section @sc{gdb/mi} Development and Front Ends
27713 @cindex @sc{gdb/mi} development
27715 The application which takes the MI output and presents the state of the
27716 program being debugged to the user is called a @dfn{front end}.
27718 Although @sc{gdb/mi} is still incomplete, it is currently being used
27719 by a variety of front ends to @value{GDBN}. This makes it difficult
27720 to introduce new functionality without breaking existing usage. This
27721 section tries to minimize the problems by describing how the protocol
27724 Some changes in MI need not break a carefully designed front end, and
27725 for these the MI version will remain unchanged. The following is a
27726 list of changes that may occur within one level, so front ends should
27727 parse MI output in a way that can handle them:
27731 New MI commands may be added.
27734 New fields may be added to the output of any MI command.
27737 The range of values for fields with specified values, e.g.,
27738 @code{in_scope} (@pxref{-var-update}) may be extended.
27740 @c The format of field's content e.g type prefix, may change so parse it
27741 @c at your own risk. Yes, in general?
27743 @c The order of fields may change? Shouldn't really matter but it might
27744 @c resolve inconsistencies.
27747 If the changes are likely to break front ends, the MI version level
27748 will be increased by one. This will allow the front end to parse the
27749 output according to the MI version. Apart from mi0, new versions of
27750 @value{GDBN} will not support old versions of MI and it will be the
27751 responsibility of the front end to work with the new one.
27753 @c Starting with mi3, add a new command -mi-version that prints the MI
27756 The best way to avoid unexpected changes in MI that might break your front
27757 end is to make your project known to @value{GDBN} developers and
27758 follow development on @email{gdb@@sourceware.org} and
27759 @email{gdb-patches@@sourceware.org}.
27760 @cindex mailing lists
27762 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27763 @node GDB/MI Output Records
27764 @section @sc{gdb/mi} Output Records
27767 * GDB/MI Result Records::
27768 * GDB/MI Stream Records::
27769 * GDB/MI Async Records::
27770 * GDB/MI Breakpoint Information::
27771 * GDB/MI Frame Information::
27772 * GDB/MI Thread Information::
27773 * GDB/MI Ada Exception Information::
27776 @node GDB/MI Result Records
27777 @subsection @sc{gdb/mi} Result Records
27779 @cindex result records in @sc{gdb/mi}
27780 @cindex @sc{gdb/mi}, result records
27781 In addition to a number of out-of-band notifications, the response to a
27782 @sc{gdb/mi} command includes one of the following result indications:
27786 @item "^done" [ "," @var{results} ]
27787 The synchronous operation was successful, @code{@var{results}} are the return
27792 This result record is equivalent to @samp{^done}. Historically, it
27793 was output instead of @samp{^done} if the command has resumed the
27794 target. This behaviour is maintained for backward compatibility, but
27795 all frontends should treat @samp{^done} and @samp{^running}
27796 identically and rely on the @samp{*running} output record to determine
27797 which threads are resumed.
27801 @value{GDBN} has connected to a remote target.
27803 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27805 The operation failed. The @code{msg=@var{c-string}} variable contains
27806 the corresponding error message.
27808 If present, the @code{code=@var{c-string}} variable provides an error
27809 code on which consumers can rely on to detect the corresponding
27810 error condition. At present, only one error code is defined:
27813 @item "undefined-command"
27814 Indicates that the command causing the error does not exist.
27819 @value{GDBN} has terminated.
27823 @node GDB/MI Stream Records
27824 @subsection @sc{gdb/mi} Stream Records
27826 @cindex @sc{gdb/mi}, stream records
27827 @cindex stream records in @sc{gdb/mi}
27828 @value{GDBN} internally maintains a number of output streams: the console, the
27829 target, and the log. The output intended for each of these streams is
27830 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27832 Each stream record begins with a unique @dfn{prefix character} which
27833 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27834 Syntax}). In addition to the prefix, each stream record contains a
27835 @code{@var{string-output}}. This is either raw text (with an implicit new
27836 line) or a quoted C string (which does not contain an implicit newline).
27839 @item "~" @var{string-output}
27840 The console output stream contains text that should be displayed in the
27841 CLI console window. It contains the textual responses to CLI commands.
27843 @item "@@" @var{string-output}
27844 The target output stream contains any textual output from the running
27845 target. This is only present when GDB's event loop is truly
27846 asynchronous, which is currently only the case for remote targets.
27848 @item "&" @var{string-output}
27849 The log stream contains debugging messages being produced by @value{GDBN}'s
27853 @node GDB/MI Async Records
27854 @subsection @sc{gdb/mi} Async Records
27856 @cindex async records in @sc{gdb/mi}
27857 @cindex @sc{gdb/mi}, async records
27858 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27859 additional changes that have occurred. Those changes can either be a
27860 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27861 target activity (e.g., target stopped).
27863 The following is the list of possible async records:
27867 @item *running,thread-id="@var{thread}"
27868 The target is now running. The @var{thread} field can be the global
27869 thread ID of the the thread that is now running, and it can be
27870 @samp{all} if all threads are running. The frontend should assume
27871 that no interaction with a running thread is possible after this
27872 notification is produced. The frontend should not assume that this
27873 notification is output only once for any command. @value{GDBN} may
27874 emit this notification several times, either for different threads,
27875 because it cannot resume all threads together, or even for a single
27876 thread, if the thread must be stepped though some code before letting
27879 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27880 The target has stopped. The @var{reason} field can have one of the
27884 @item breakpoint-hit
27885 A breakpoint was reached.
27886 @item watchpoint-trigger
27887 A watchpoint was triggered.
27888 @item read-watchpoint-trigger
27889 A read watchpoint was triggered.
27890 @item access-watchpoint-trigger
27891 An access watchpoint was triggered.
27892 @item function-finished
27893 An -exec-finish or similar CLI command was accomplished.
27894 @item location-reached
27895 An -exec-until or similar CLI command was accomplished.
27896 @item watchpoint-scope
27897 A watchpoint has gone out of scope.
27898 @item end-stepping-range
27899 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27900 similar CLI command was accomplished.
27901 @item exited-signalled
27902 The inferior exited because of a signal.
27904 The inferior exited.
27905 @item exited-normally
27906 The inferior exited normally.
27907 @item signal-received
27908 A signal was received by the inferior.
27910 The inferior has stopped due to a library being loaded or unloaded.
27911 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27912 set or when a @code{catch load} or @code{catch unload} catchpoint is
27913 in use (@pxref{Set Catchpoints}).
27915 The inferior has forked. This is reported when @code{catch fork}
27916 (@pxref{Set Catchpoints}) has been used.
27918 The inferior has vforked. This is reported in when @code{catch vfork}
27919 (@pxref{Set Catchpoints}) has been used.
27920 @item syscall-entry
27921 The inferior entered a system call. This is reported when @code{catch
27922 syscall} (@pxref{Set Catchpoints}) has been used.
27923 @item syscall-return
27924 The inferior returned from a system call. This is reported when
27925 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27927 The inferior called @code{exec}. This is reported when @code{catch exec}
27928 (@pxref{Set Catchpoints}) has been used.
27931 The @var{id} field identifies the global thread ID of the thread
27932 that directly caused the stop -- for example by hitting a breakpoint.
27933 Depending on whether all-stop
27934 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27935 stop all threads, or only the thread that directly triggered the stop.
27936 If all threads are stopped, the @var{stopped} field will have the
27937 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27938 field will be a list of thread identifiers. Presently, this list will
27939 always include a single thread, but frontend should be prepared to see
27940 several threads in the list. The @var{core} field reports the
27941 processor core on which the stop event has happened. This field may be absent
27942 if such information is not available.
27944 @item =thread-group-added,id="@var{id}"
27945 @itemx =thread-group-removed,id="@var{id}"
27946 A thread group was either added or removed. The @var{id} field
27947 contains the @value{GDBN} identifier of the thread group. When a thread
27948 group is added, it generally might not be associated with a running
27949 process. When a thread group is removed, its id becomes invalid and
27950 cannot be used in any way.
27952 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27953 A thread group became associated with a running program,
27954 either because the program was just started or the thread group
27955 was attached to a program. The @var{id} field contains the
27956 @value{GDBN} identifier of the thread group. The @var{pid} field
27957 contains process identifier, specific to the operating system.
27959 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27960 A thread group is no longer associated with a running program,
27961 either because the program has exited, or because it was detached
27962 from. The @var{id} field contains the @value{GDBN} identifier of the
27963 thread group. The @var{code} field is the exit code of the inferior; it exists
27964 only when the inferior exited with some code.
27966 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27967 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27968 A thread either was created, or has exited. The @var{id} field
27969 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27970 field identifies the thread group this thread belongs to.
27972 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27973 Informs that the selected thread or frame were changed. This notification
27974 is not emitted as result of the @code{-thread-select} or
27975 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27976 that is not documented to change the selected thread and frame actually
27977 changes them. In particular, invoking, directly or indirectly
27978 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27979 will generate this notification. Changing the thread or frame from another
27980 user interface (see @ref{Interpreters}) will also generate this notification.
27982 The @var{frame} field is only present if the newly selected thread is
27983 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27985 We suggest that in response to this notification, front ends
27986 highlight the selected thread and cause subsequent commands to apply to
27989 @item =library-loaded,...
27990 Reports that a new library file was loaded by the program. This
27991 notification has 5 fields---@var{id}, @var{target-name},
27992 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27993 opaque identifier of the library. For remote debugging case,
27994 @var{target-name} and @var{host-name} fields give the name of the
27995 library file on the target, and on the host respectively. For native
27996 debugging, both those fields have the same value. The
27997 @var{symbols-loaded} field is emitted only for backward compatibility
27998 and should not be relied on to convey any useful information. The
27999 @var{thread-group} field, if present, specifies the id of the thread
28000 group in whose context the library was loaded. If the field is
28001 absent, it means the library was loaded in the context of all present
28002 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28005 @item =library-unloaded,...
28006 Reports that a library was unloaded by the program. This notification
28007 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28008 the same meaning as for the @code{=library-loaded} notification.
28009 The @var{thread-group} field, if present, specifies the id of the
28010 thread group in whose context the library was unloaded. If the field is
28011 absent, it means the library was unloaded in the context of all present
28014 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28015 @itemx =traceframe-changed,end
28016 Reports that the trace frame was changed and its new number is
28017 @var{tfnum}. The number of the tracepoint associated with this trace
28018 frame is @var{tpnum}.
28020 @item =tsv-created,name=@var{name},initial=@var{initial}
28021 Reports that the new trace state variable @var{name} is created with
28022 initial value @var{initial}.
28024 @item =tsv-deleted,name=@var{name}
28025 @itemx =tsv-deleted
28026 Reports that the trace state variable @var{name} is deleted or all
28027 trace state variables are deleted.
28029 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28030 Reports that the trace state variable @var{name} is modified with
28031 the initial value @var{initial}. The current value @var{current} of
28032 trace state variable is optional and is reported if the current
28033 value of trace state variable is known.
28035 @item =breakpoint-created,bkpt=@{...@}
28036 @itemx =breakpoint-modified,bkpt=@{...@}
28037 @itemx =breakpoint-deleted,id=@var{number}
28038 Reports that a breakpoint was created, modified, or deleted,
28039 respectively. Only user-visible breakpoints are reported to the MI
28042 The @var{bkpt} argument is of the same form as returned by the various
28043 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28044 @var{number} is the ordinal number of the breakpoint.
28046 Note that if a breakpoint is emitted in the result record of a
28047 command, then it will not also be emitted in an async record.
28049 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28050 @itemx =record-stopped,thread-group="@var{id}"
28051 Execution log recording was either started or stopped on an
28052 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28053 group corresponding to the affected inferior.
28055 The @var{method} field indicates the method used to record execution. If the
28056 method in use supports multiple recording formats, @var{format} will be present
28057 and contain the currently used format. @xref{Process Record and Replay},
28058 for existing method and format values.
28060 @item =cmd-param-changed,param=@var{param},value=@var{value}
28061 Reports that a parameter of the command @code{set @var{param}} is
28062 changed to @var{value}. In the multi-word @code{set} command,
28063 the @var{param} is the whole parameter list to @code{set} command.
28064 For example, In command @code{set check type on}, @var{param}
28065 is @code{check type} and @var{value} is @code{on}.
28067 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28068 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28069 written in an inferior. The @var{id} is the identifier of the
28070 thread group corresponding to the affected inferior. The optional
28071 @code{type="code"} part is reported if the memory written to holds
28075 @node GDB/MI Breakpoint Information
28076 @subsection @sc{gdb/mi} Breakpoint Information
28078 When @value{GDBN} reports information about a breakpoint, a
28079 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28084 The breakpoint number. For a breakpoint that represents one location
28085 of a multi-location breakpoint, this will be a dotted pair, like
28089 The type of the breakpoint. For ordinary breakpoints this will be
28090 @samp{breakpoint}, but many values are possible.
28093 If the type of the breakpoint is @samp{catchpoint}, then this
28094 indicates the exact type of catchpoint.
28097 This is the breakpoint disposition---either @samp{del}, meaning that
28098 the breakpoint will be deleted at the next stop, or @samp{keep},
28099 meaning that the breakpoint will not be deleted.
28102 This indicates whether the breakpoint is enabled, in which case the
28103 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28104 Note that this is not the same as the field @code{enable}.
28107 The address of the breakpoint. This may be a hexidecimal number,
28108 giving the address; or the string @samp{<PENDING>}, for a pending
28109 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28110 multiple locations. This field will not be present if no address can
28111 be determined. For example, a watchpoint does not have an address.
28114 If known, the function in which the breakpoint appears.
28115 If not known, this field is not present.
28118 The name of the source file which contains this function, if known.
28119 If not known, this field is not present.
28122 The full file name of the source file which contains this function, if
28123 known. If not known, this field is not present.
28126 The line number at which this breakpoint appears, if known.
28127 If not known, this field is not present.
28130 If the source file is not known, this field may be provided. If
28131 provided, this holds the address of the breakpoint, possibly followed
28135 If this breakpoint is pending, this field is present and holds the
28136 text used to set the breakpoint, as entered by the user.
28139 Where this breakpoint's condition is evaluated, either @samp{host} or
28143 If this is a thread-specific breakpoint, then this identifies the
28144 thread in which the breakpoint can trigger.
28147 If this breakpoint is restricted to a particular Ada task, then this
28148 field will hold the task identifier.
28151 If the breakpoint is conditional, this is the condition expression.
28154 The ignore count of the breakpoint.
28157 The enable count of the breakpoint.
28159 @item traceframe-usage
28162 @item static-tracepoint-marker-string-id
28163 For a static tracepoint, the name of the static tracepoint marker.
28166 For a masked watchpoint, this is the mask.
28169 A tracepoint's pass count.
28171 @item original-location
28172 The location of the breakpoint as originally specified by the user.
28173 This field is optional.
28176 The number of times the breakpoint has been hit.
28179 This field is only given for tracepoints. This is either @samp{y},
28180 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28184 Some extra data, the exact contents of which are type-dependent.
28188 For example, here is what the output of @code{-break-insert}
28189 (@pxref{GDB/MI Breakpoint Commands}) might be:
28192 -> -break-insert main
28193 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28194 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28195 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28200 @node GDB/MI Frame Information
28201 @subsection @sc{gdb/mi} Frame Information
28203 Response from many MI commands includes an information about stack
28204 frame. This information is a tuple that may have the following
28209 The level of the stack frame. The innermost frame has the level of
28210 zero. This field is always present.
28213 The name of the function corresponding to the frame. This field may
28214 be absent if @value{GDBN} is unable to determine the function name.
28217 The code address for the frame. This field is always present.
28220 The name of the source files that correspond to the frame's code
28221 address. This field may be absent.
28224 The source line corresponding to the frames' code address. This field
28228 The name of the binary file (either executable or shared library) the
28229 corresponds to the frame's code address. This field may be absent.
28233 @node GDB/MI Thread Information
28234 @subsection @sc{gdb/mi} Thread Information
28236 Whenever @value{GDBN} has to report an information about a thread, it
28237 uses a tuple with the following fields. The fields are always present unless
28242 The global numeric id assigned to the thread by @value{GDBN}.
28245 The target-specific string identifying the thread.
28248 Additional information about the thread provided by the target.
28249 It is supposed to be human-readable and not interpreted by the
28250 frontend. This field is optional.
28253 The name of the thread. If the user specified a name using the
28254 @code{thread name} command, then this name is given. Otherwise, if
28255 @value{GDBN} can extract the thread name from the target, then that
28256 name is given. If @value{GDBN} cannot find the thread name, then this
28260 The execution state of the thread, either @samp{stopped} or @samp{running},
28261 depending on whether the thread is presently running.
28264 The stack frame currently executing in the thread. This field is only present
28265 if the thread is stopped. Its format is documented in
28266 @ref{GDB/MI Frame Information}.
28269 The value of this field is an integer number of the processor core the
28270 thread was last seen on. This field is optional.
28273 @node GDB/MI Ada Exception Information
28274 @subsection @sc{gdb/mi} Ada Exception Information
28276 Whenever a @code{*stopped} record is emitted because the program
28277 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28278 @value{GDBN} provides the name of the exception that was raised via
28279 the @code{exception-name} field. Also, for exceptions that were raised
28280 with an exception message, @value{GDBN} provides that message via
28281 the @code{exception-message} field.
28283 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28284 @node GDB/MI Simple Examples
28285 @section Simple Examples of @sc{gdb/mi} Interaction
28286 @cindex @sc{gdb/mi}, simple examples
28288 This subsection presents several simple examples of interaction using
28289 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28290 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28291 the output received from @sc{gdb/mi}.
28293 Note the line breaks shown in the examples are here only for
28294 readability, they don't appear in the real output.
28296 @subheading Setting a Breakpoint
28298 Setting a breakpoint generates synchronous output which contains detailed
28299 information of the breakpoint.
28302 -> -break-insert main
28303 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28304 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28305 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28310 @subheading Program Execution
28312 Program execution generates asynchronous records and MI gives the
28313 reason that execution stopped.
28319 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28320 frame=@{addr="0x08048564",func="main",
28321 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28322 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28323 arch="i386:x86_64"@}
28328 <- *stopped,reason="exited-normally"
28332 @subheading Quitting @value{GDBN}
28334 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28342 Please note that @samp{^exit} is printed immediately, but it might
28343 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28344 performs necessary cleanups, including killing programs being debugged
28345 or disconnecting from debug hardware, so the frontend should wait till
28346 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28347 fails to exit in reasonable time.
28349 @subheading A Bad Command
28351 Here's what happens if you pass a non-existent command:
28355 <- ^error,msg="Undefined MI command: rubbish"
28360 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28361 @node GDB/MI Command Description Format
28362 @section @sc{gdb/mi} Command Description Format
28364 The remaining sections describe blocks of commands. Each block of
28365 commands is laid out in a fashion similar to this section.
28367 @subheading Motivation
28369 The motivation for this collection of commands.
28371 @subheading Introduction
28373 A brief introduction to this collection of commands as a whole.
28375 @subheading Commands
28377 For each command in the block, the following is described:
28379 @subsubheading Synopsis
28382 -command @var{args}@dots{}
28385 @subsubheading Result
28387 @subsubheading @value{GDBN} Command
28389 The corresponding @value{GDBN} CLI command(s), if any.
28391 @subsubheading Example
28393 Example(s) formatted for readability. Some of the described commands have
28394 not been implemented yet and these are labeled N.A.@: (not available).
28397 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28398 @node GDB/MI Breakpoint Commands
28399 @section @sc{gdb/mi} Breakpoint Commands
28401 @cindex breakpoint commands for @sc{gdb/mi}
28402 @cindex @sc{gdb/mi}, breakpoint commands
28403 This section documents @sc{gdb/mi} commands for manipulating
28406 @subheading The @code{-break-after} Command
28407 @findex -break-after
28409 @subsubheading Synopsis
28412 -break-after @var{number} @var{count}
28415 The breakpoint number @var{number} is not in effect until it has been
28416 hit @var{count} times. To see how this is reflected in the output of
28417 the @samp{-break-list} command, see the description of the
28418 @samp{-break-list} command below.
28420 @subsubheading @value{GDBN} Command
28422 The corresponding @value{GDBN} command is @samp{ignore}.
28424 @subsubheading Example
28429 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28430 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28431 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28439 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28440 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28441 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28442 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28443 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28444 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28445 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28446 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28447 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28448 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28453 @subheading The @code{-break-catch} Command
28454 @findex -break-catch
28457 @subheading The @code{-break-commands} Command
28458 @findex -break-commands
28460 @subsubheading Synopsis
28463 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28466 Specifies the CLI commands that should be executed when breakpoint
28467 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28468 are the commands. If no command is specified, any previously-set
28469 commands are cleared. @xref{Break Commands}. Typical use of this
28470 functionality is tracing a program, that is, printing of values of
28471 some variables whenever breakpoint is hit and then continuing.
28473 @subsubheading @value{GDBN} Command
28475 The corresponding @value{GDBN} command is @samp{commands}.
28477 @subsubheading Example
28482 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28483 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28484 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28487 -break-commands 1 "print v" "continue"
28492 @subheading The @code{-break-condition} Command
28493 @findex -break-condition
28495 @subsubheading Synopsis
28498 -break-condition @var{number} @var{expr}
28501 Breakpoint @var{number} will stop the program only if the condition in
28502 @var{expr} is true. The condition becomes part of the
28503 @samp{-break-list} output (see the description of the @samp{-break-list}
28506 @subsubheading @value{GDBN} Command
28508 The corresponding @value{GDBN} command is @samp{condition}.
28510 @subsubheading Example
28514 -break-condition 1 1
28518 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28519 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28520 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28521 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28522 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28523 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28524 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28525 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28526 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28527 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28531 @subheading The @code{-break-delete} Command
28532 @findex -break-delete
28534 @subsubheading Synopsis
28537 -break-delete ( @var{breakpoint} )+
28540 Delete the breakpoint(s) whose number(s) are specified in the argument
28541 list. This is obviously reflected in the breakpoint list.
28543 @subsubheading @value{GDBN} Command
28545 The corresponding @value{GDBN} command is @samp{delete}.
28547 @subsubheading Example
28555 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28556 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28557 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28558 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28559 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28560 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28561 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28566 @subheading The @code{-break-disable} Command
28567 @findex -break-disable
28569 @subsubheading Synopsis
28572 -break-disable ( @var{breakpoint} )+
28575 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28576 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28578 @subsubheading @value{GDBN} Command
28580 The corresponding @value{GDBN} command is @samp{disable}.
28582 @subsubheading Example
28590 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28591 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28592 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28593 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28594 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28595 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28596 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28597 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28598 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28599 line="5",thread-groups=["i1"],times="0"@}]@}
28603 @subheading The @code{-break-enable} Command
28604 @findex -break-enable
28606 @subsubheading Synopsis
28609 -break-enable ( @var{breakpoint} )+
28612 Enable (previously disabled) @var{breakpoint}(s).
28614 @subsubheading @value{GDBN} Command
28616 The corresponding @value{GDBN} command is @samp{enable}.
28618 @subsubheading Example
28626 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28627 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28628 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28629 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28630 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28631 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28632 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28633 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28634 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28635 line="5",thread-groups=["i1"],times="0"@}]@}
28639 @subheading The @code{-break-info} Command
28640 @findex -break-info
28642 @subsubheading Synopsis
28645 -break-info @var{breakpoint}
28649 Get information about a single breakpoint.
28651 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28652 Information}, for details on the format of each breakpoint in the
28655 @subsubheading @value{GDBN} Command
28657 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28659 @subsubheading Example
28662 @subheading The @code{-break-insert} Command
28663 @findex -break-insert
28664 @anchor{-break-insert}
28666 @subsubheading Synopsis
28669 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28670 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28671 [ -p @var{thread-id} ] [ @var{location} ]
28675 If specified, @var{location}, can be one of:
28678 @item linespec location
28679 A linespec location. @xref{Linespec Locations}.
28681 @item explicit location
28682 An explicit location. @sc{gdb/mi} explicit locations are
28683 analogous to the CLI's explicit locations using the option names
28684 listed below. @xref{Explicit Locations}.
28687 @item --source @var{filename}
28688 The source file name of the location. This option requires the use
28689 of either @samp{--function} or @samp{--line}.
28691 @item --function @var{function}
28692 The name of a function or method.
28694 @item --label @var{label}
28695 The name of a label.
28697 @item --line @var{lineoffset}
28698 An absolute or relative line offset from the start of the location.
28701 @item address location
28702 An address location, *@var{address}. @xref{Address Locations}.
28706 The possible optional parameters of this command are:
28710 Insert a temporary breakpoint.
28712 Insert a hardware breakpoint.
28714 If @var{location} cannot be parsed (for example if it
28715 refers to unknown files or functions), create a pending
28716 breakpoint. Without this flag, @value{GDBN} will report
28717 an error, and won't create a breakpoint, if @var{location}
28720 Create a disabled breakpoint.
28722 Create a tracepoint. @xref{Tracepoints}. When this parameter
28723 is used together with @samp{-h}, a fast tracepoint is created.
28724 @item -c @var{condition}
28725 Make the breakpoint conditional on @var{condition}.
28726 @item -i @var{ignore-count}
28727 Initialize the @var{ignore-count}.
28728 @item -p @var{thread-id}
28729 Restrict the breakpoint to the thread with the specified global
28733 @subsubheading Result
28735 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28736 resulting breakpoint.
28738 Note: this format is open to change.
28739 @c An out-of-band breakpoint instead of part of the result?
28741 @subsubheading @value{GDBN} Command
28743 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28744 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28746 @subsubheading Example
28751 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28752 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28755 -break-insert -t foo
28756 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28757 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28761 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28768 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28769 addr="0x0001072c", func="main",file="recursive2.c",
28770 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28772 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28773 addr="0x00010774",func="foo",file="recursive2.c",
28774 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28777 @c -break-insert -r foo.*
28778 @c ~int foo(int, int);
28779 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28780 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28785 @subheading The @code{-dprintf-insert} Command
28786 @findex -dprintf-insert
28788 @subsubheading Synopsis
28791 -dprintf-insert [ -t ] [ -f ] [ -d ]
28792 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28793 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28798 If supplied, @var{location} may be specified the same way as for
28799 the @code{-break-insert} command. @xref{-break-insert}.
28801 The possible optional parameters of this command are:
28805 Insert a temporary breakpoint.
28807 If @var{location} cannot be parsed (for example, if it
28808 refers to unknown files or functions), create a pending
28809 breakpoint. Without this flag, @value{GDBN} will report
28810 an error, and won't create a breakpoint, if @var{location}
28813 Create a disabled breakpoint.
28814 @item -c @var{condition}
28815 Make the breakpoint conditional on @var{condition}.
28816 @item -i @var{ignore-count}
28817 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28818 to @var{ignore-count}.
28819 @item -p @var{thread-id}
28820 Restrict the breakpoint to the thread with the specified global
28824 @subsubheading Result
28826 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28827 resulting breakpoint.
28829 @c An out-of-band breakpoint instead of part of the result?
28831 @subsubheading @value{GDBN} Command
28833 The corresponding @value{GDBN} command is @samp{dprintf}.
28835 @subsubheading Example
28839 4-dprintf-insert foo "At foo entry\n"
28840 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28841 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28842 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28843 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28844 original-location="foo"@}
28846 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28847 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28848 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28849 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28850 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28851 original-location="mi-dprintf.c:26"@}
28855 @subheading The @code{-break-list} Command
28856 @findex -break-list
28858 @subsubheading Synopsis
28864 Displays the list of inserted breakpoints, showing the following fields:
28868 number of the breakpoint
28870 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28872 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28875 is the breakpoint enabled or no: @samp{y} or @samp{n}
28877 memory location at which the breakpoint is set
28879 logical location of the breakpoint, expressed by function name, file
28881 @item Thread-groups
28882 list of thread groups to which this breakpoint applies
28884 number of times the breakpoint has been hit
28887 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28888 @code{body} field is an empty list.
28890 @subsubheading @value{GDBN} Command
28892 The corresponding @value{GDBN} command is @samp{info break}.
28894 @subsubheading Example
28899 ^done,BreakpointTable=@{nr_rows="2",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"@}],
28906 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28907 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28909 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28910 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28911 line="13",thread-groups=["i1"],times="0"@}]@}
28915 Here's an example of the result when there are no breakpoints:
28920 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28921 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28922 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28923 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28924 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28925 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28926 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28931 @subheading The @code{-break-passcount} Command
28932 @findex -break-passcount
28934 @subsubheading Synopsis
28937 -break-passcount @var{tracepoint-number} @var{passcount}
28940 Set the passcount for tracepoint @var{tracepoint-number} to
28941 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28942 is not a tracepoint, error is emitted. This corresponds to CLI
28943 command @samp{passcount}.
28945 @subheading The @code{-break-watch} Command
28946 @findex -break-watch
28948 @subsubheading Synopsis
28951 -break-watch [ -a | -r ]
28954 Create a watchpoint. With the @samp{-a} option it will create an
28955 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28956 read from or on a write to the memory location. With the @samp{-r}
28957 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28958 trigger only when the memory location is accessed for reading. Without
28959 either of the options, the watchpoint created is a regular watchpoint,
28960 i.e., it will trigger when the memory location is accessed for writing.
28961 @xref{Set Watchpoints, , Setting Watchpoints}.
28963 Note that @samp{-break-list} will report a single list of watchpoints and
28964 breakpoints inserted.
28966 @subsubheading @value{GDBN} Command
28968 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28971 @subsubheading Example
28973 Setting a watchpoint on a variable in the @code{main} function:
28978 ^done,wpt=@{number="2",exp="x"@}
28983 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28984 value=@{old="-268439212",new="55"@},
28985 frame=@{func="main",args=[],file="recursive2.c",
28986 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
28990 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28991 the program execution twice: first for the variable changing value, then
28992 for the watchpoint going out of scope.
28997 ^done,wpt=@{number="5",exp="C"@}
29002 *stopped,reason="watchpoint-trigger",
29003 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29004 frame=@{func="callee4",args=[],
29005 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29006 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29007 arch="i386:x86_64"@}
29012 *stopped,reason="watchpoint-scope",wpnum="5",
29013 frame=@{func="callee3",args=[@{name="strarg",
29014 value="0x11940 \"A string argument.\""@}],
29015 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29016 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29017 arch="i386:x86_64"@}
29021 Listing breakpoints and watchpoints, at different points in the program
29022 execution. Note that once the watchpoint goes out of scope, it is
29028 ^done,wpt=@{number="2",exp="C"@}
29031 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29032 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29033 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29034 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29035 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29036 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29037 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29038 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29039 addr="0x00010734",func="callee4",
29040 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29041 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29043 bkpt=@{number="2",type="watchpoint",disp="keep",
29044 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29049 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29050 value=@{old="-276895068",new="3"@},
29051 frame=@{func="callee4",args=[],
29052 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29053 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29054 arch="i386:x86_64"@}
29057 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29058 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29059 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29060 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29061 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29062 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29063 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29064 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29065 addr="0x00010734",func="callee4",
29066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29067 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29069 bkpt=@{number="2",type="watchpoint",disp="keep",
29070 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29074 ^done,reason="watchpoint-scope",wpnum="2",
29075 frame=@{func="callee3",args=[@{name="strarg",
29076 value="0x11940 \"A string argument.\""@}],
29077 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29078 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29079 arch="i386:x86_64"@}
29082 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29083 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29084 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29085 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29086 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29087 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29088 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29089 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29090 addr="0x00010734",func="callee4",
29091 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29092 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29093 thread-groups=["i1"],times="1"@}]@}
29098 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29099 @node GDB/MI Catchpoint Commands
29100 @section @sc{gdb/mi} Catchpoint Commands
29102 This section documents @sc{gdb/mi} commands for manipulating
29106 * Shared Library GDB/MI Catchpoint Commands::
29107 * Ada Exception GDB/MI Catchpoint Commands::
29110 @node Shared Library GDB/MI Catchpoint Commands
29111 @subsection Shared Library @sc{gdb/mi} Catchpoints
29113 @subheading The @code{-catch-load} Command
29114 @findex -catch-load
29116 @subsubheading Synopsis
29119 -catch-load [ -t ] [ -d ] @var{regexp}
29122 Add a catchpoint for library load events. If the @samp{-t} option is used,
29123 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29124 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29125 in a disabled state. The @samp{regexp} argument is a regular
29126 expression used to match the name of the loaded library.
29129 @subsubheading @value{GDBN} Command
29131 The corresponding @value{GDBN} command is @samp{catch load}.
29133 @subsubheading Example
29136 -catch-load -t foo.so
29137 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29138 what="load of library matching foo.so",catch-type="load",times="0"@}
29143 @subheading The @code{-catch-unload} Command
29144 @findex -catch-unload
29146 @subsubheading Synopsis
29149 -catch-unload [ -t ] [ -d ] @var{regexp}
29152 Add a catchpoint for library unload events. If the @samp{-t} option is
29153 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29154 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29155 created in a disabled state. The @samp{regexp} argument is a regular
29156 expression used to match the name of the unloaded library.
29158 @subsubheading @value{GDBN} Command
29160 The corresponding @value{GDBN} command is @samp{catch unload}.
29162 @subsubheading Example
29165 -catch-unload -d bar.so
29166 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29167 what="load of library matching bar.so",catch-type="unload",times="0"@}
29171 @node Ada Exception GDB/MI Catchpoint Commands
29172 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29174 The following @sc{gdb/mi} commands can be used to create catchpoints
29175 that stop the execution when Ada exceptions are being raised.
29177 @subheading The @code{-catch-assert} Command
29178 @findex -catch-assert
29180 @subsubheading Synopsis
29183 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29186 Add a catchpoint for failed Ada assertions.
29188 The possible optional parameters for this command are:
29191 @item -c @var{condition}
29192 Make the catchpoint conditional on @var{condition}.
29194 Create a disabled catchpoint.
29196 Create a temporary catchpoint.
29199 @subsubheading @value{GDBN} Command
29201 The corresponding @value{GDBN} command is @samp{catch assert}.
29203 @subsubheading Example
29207 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29208 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29209 thread-groups=["i1"],times="0",
29210 original-location="__gnat_debug_raise_assert_failure"@}
29214 @subheading The @code{-catch-exception} Command
29215 @findex -catch-exception
29217 @subsubheading Synopsis
29220 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29224 Add a catchpoint stopping when Ada exceptions are raised.
29225 By default, the command stops the program when any Ada exception
29226 gets raised. But it is also possible, by using some of the
29227 optional parameters described below, to create more selective
29230 The possible optional parameters for this command are:
29233 @item -c @var{condition}
29234 Make the catchpoint conditional on @var{condition}.
29236 Create a disabled catchpoint.
29237 @item -e @var{exception-name}
29238 Only stop when @var{exception-name} is raised. This option cannot
29239 be used combined with @samp{-u}.
29241 Create a temporary catchpoint.
29243 Stop only when an unhandled exception gets raised. This option
29244 cannot be used combined with @samp{-e}.
29247 @subsubheading @value{GDBN} Command
29249 The corresponding @value{GDBN} commands are @samp{catch exception}
29250 and @samp{catch exception unhandled}.
29252 @subsubheading Example
29255 -catch-exception -e Program_Error
29256 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29257 enabled="y",addr="0x0000000000404874",
29258 what="`Program_Error' Ada exception", thread-groups=["i1"],
29259 times="0",original-location="__gnat_debug_raise_exception"@}
29263 @subheading The @code{-catch-handlers} Command
29264 @findex -catch-handlers
29266 @subsubheading Synopsis
29269 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29273 Add a catchpoint stopping when Ada exceptions are handled.
29274 By default, the command stops the program when any Ada exception
29275 gets handled. But it is also possible, by using some of the
29276 optional parameters described below, to create more selective
29279 The possible optional parameters for this command are:
29282 @item -c @var{condition}
29283 Make the catchpoint conditional on @var{condition}.
29285 Create a disabled catchpoint.
29286 @item -e @var{exception-name}
29287 Only stop when @var{exception-name} is handled.
29289 Create a temporary catchpoint.
29292 @subsubheading @value{GDBN} Command
29294 The corresponding @value{GDBN} command is @samp{catch handlers}.
29296 @subsubheading Example
29299 -catch-handlers -e Constraint_Error
29300 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29301 enabled="y",addr="0x0000000000402f68",
29302 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29303 times="0",original-location="__gnat_begin_handler"@}
29307 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29308 @node GDB/MI Program Context
29309 @section @sc{gdb/mi} Program Context
29311 @subheading The @code{-exec-arguments} Command
29312 @findex -exec-arguments
29315 @subsubheading Synopsis
29318 -exec-arguments @var{args}
29321 Set the inferior program arguments, to be used in the next
29324 @subsubheading @value{GDBN} Command
29326 The corresponding @value{GDBN} command is @samp{set args}.
29328 @subsubheading Example
29332 -exec-arguments -v word
29339 @subheading The @code{-exec-show-arguments} Command
29340 @findex -exec-show-arguments
29342 @subsubheading Synopsis
29345 -exec-show-arguments
29348 Print the arguments of the program.
29350 @subsubheading @value{GDBN} Command
29352 The corresponding @value{GDBN} command is @samp{show args}.
29354 @subsubheading Example
29359 @subheading The @code{-environment-cd} Command
29360 @findex -environment-cd
29362 @subsubheading Synopsis
29365 -environment-cd @var{pathdir}
29368 Set @value{GDBN}'s working directory.
29370 @subsubheading @value{GDBN} Command
29372 The corresponding @value{GDBN} command is @samp{cd}.
29374 @subsubheading Example
29378 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29384 @subheading The @code{-environment-directory} Command
29385 @findex -environment-directory
29387 @subsubheading Synopsis
29390 -environment-directory [ -r ] [ @var{pathdir} ]+
29393 Add directories @var{pathdir} to beginning of search path for source files.
29394 If the @samp{-r} option is used, the search path is reset to the default
29395 search path. If directories @var{pathdir} are supplied in addition to the
29396 @samp{-r} option, the search path is first reset and then addition
29398 Multiple directories may be specified, separated by blanks. Specifying
29399 multiple directories in a single command
29400 results in the directories added to the beginning of the
29401 search path in the same order they were presented in the command.
29402 If blanks are needed as
29403 part of a directory name, double-quotes should be used around
29404 the name. In the command output, the path will show up separated
29405 by the system directory-separator character. The directory-separator
29406 character must not be used
29407 in any directory name.
29408 If no directories are specified, the current search path is displayed.
29410 @subsubheading @value{GDBN} Command
29412 The corresponding @value{GDBN} command is @samp{dir}.
29414 @subsubheading Example
29418 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29419 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29421 -environment-directory ""
29422 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29424 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29425 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29427 -environment-directory -r
29428 ^done,source-path="$cdir:$cwd"
29433 @subheading The @code{-environment-path} Command
29434 @findex -environment-path
29436 @subsubheading Synopsis
29439 -environment-path [ -r ] [ @var{pathdir} ]+
29442 Add directories @var{pathdir} to beginning of search path for object files.
29443 If the @samp{-r} option is used, the search path is reset to the original
29444 search path that existed at gdb start-up. If directories @var{pathdir} are
29445 supplied in addition to the
29446 @samp{-r} option, the search path is first reset and then addition
29448 Multiple directories may be specified, separated by blanks. Specifying
29449 multiple directories in a single command
29450 results in the directories added to the beginning of the
29451 search path in the same order they were presented in the command.
29452 If blanks are needed as
29453 part of a directory name, double-quotes should be used around
29454 the name. In the command output, the path will show up separated
29455 by the system directory-separator character. The directory-separator
29456 character must not be used
29457 in any directory name.
29458 If no directories are specified, the current path is displayed.
29461 @subsubheading @value{GDBN} Command
29463 The corresponding @value{GDBN} command is @samp{path}.
29465 @subsubheading Example
29470 ^done,path="/usr/bin"
29472 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29473 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29475 -environment-path -r /usr/local/bin
29476 ^done,path="/usr/local/bin:/usr/bin"
29481 @subheading The @code{-environment-pwd} Command
29482 @findex -environment-pwd
29484 @subsubheading Synopsis
29490 Show the current working directory.
29492 @subsubheading @value{GDBN} Command
29494 The corresponding @value{GDBN} command is @samp{pwd}.
29496 @subsubheading Example
29501 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29505 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29506 @node GDB/MI Thread Commands
29507 @section @sc{gdb/mi} Thread Commands
29510 @subheading The @code{-thread-info} Command
29511 @findex -thread-info
29513 @subsubheading Synopsis
29516 -thread-info [ @var{thread-id} ]
29519 Reports information about either a specific thread, if the
29520 @var{thread-id} parameter is present, or about all threads.
29521 @var{thread-id} is the thread's global thread ID. When printing
29522 information about all threads, also reports the global ID of the
29525 @subsubheading @value{GDBN} Command
29527 The @samp{info thread} command prints the same information
29530 @subsubheading Result
29532 The result contains the following attributes:
29536 A list of threads. The format of the elements of the list is described in
29537 @ref{GDB/MI Thread Information}.
29539 @item current-thread-id
29540 The global id of the currently selected thread. This field is omitted if there
29541 is no selected thread (for example, when the selected inferior is not running,
29542 and therefore has no threads) or if a @var{thread-id} argument was passed to
29547 @subsubheading Example
29552 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29553 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29554 args=[]@},state="running"@},
29555 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29556 frame=@{level="0",addr="0x0804891f",func="foo",
29557 args=[@{name="i",value="10"@}],
29558 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29559 state="running"@}],
29560 current-thread-id="1"
29564 @subheading The @code{-thread-list-ids} Command
29565 @findex -thread-list-ids
29567 @subsubheading Synopsis
29573 Produces a list of the currently known global @value{GDBN} thread ids.
29574 At the end of the list it also prints the total number of such
29577 This command is retained for historical reasons, the
29578 @code{-thread-info} command should be used instead.
29580 @subsubheading @value{GDBN} Command
29582 Part of @samp{info threads} supplies the same information.
29584 @subsubheading Example
29589 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29590 current-thread-id="1",number-of-threads="3"
29595 @subheading The @code{-thread-select} Command
29596 @findex -thread-select
29598 @subsubheading Synopsis
29601 -thread-select @var{thread-id}
29604 Make thread with global thread number @var{thread-id} the current
29605 thread. It prints the number of the new current thread, and the
29606 topmost frame for that thread.
29608 This command is deprecated in favor of explicitly using the
29609 @samp{--thread} option to each command.
29611 @subsubheading @value{GDBN} Command
29613 The corresponding @value{GDBN} command is @samp{thread}.
29615 @subsubheading Example
29622 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29623 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29627 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29628 number-of-threads="3"
29631 ^done,new-thread-id="3",
29632 frame=@{level="0",func="vprintf",
29633 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29634 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29639 @node GDB/MI Ada Tasking Commands
29640 @section @sc{gdb/mi} Ada Tasking Commands
29642 @subheading The @code{-ada-task-info} Command
29643 @findex -ada-task-info
29645 @subsubheading Synopsis
29648 -ada-task-info [ @var{task-id} ]
29651 Reports information about either a specific Ada task, if the
29652 @var{task-id} parameter is present, or about all Ada tasks.
29654 @subsubheading @value{GDBN} Command
29656 The @samp{info tasks} command prints the same information
29657 about all Ada tasks (@pxref{Ada Tasks}).
29659 @subsubheading Result
29661 The result is a table of Ada tasks. The following columns are
29662 defined for each Ada task:
29666 This field exists only for the current thread. It has the value @samp{*}.
29669 The identifier that @value{GDBN} uses to refer to the Ada task.
29672 The identifier that the target uses to refer to the Ada task.
29675 The global thread identifier of the thread corresponding to the Ada
29678 This field should always exist, as Ada tasks are always implemented
29679 on top of a thread. But if @value{GDBN} cannot find this corresponding
29680 thread for any reason, the field is omitted.
29683 This field exists only when the task was created by another task.
29684 In this case, it provides the ID of the parent task.
29687 The base priority of the task.
29690 The current state of the task. For a detailed description of the
29691 possible states, see @ref{Ada Tasks}.
29694 The name of the task.
29698 @subsubheading Example
29702 ^done,tasks=@{nr_rows="3",nr_cols="8",
29703 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29704 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29705 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29706 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29707 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29708 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29709 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29710 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29711 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29712 state="Child Termination Wait",name="main_task"@}]@}
29716 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29717 @node GDB/MI Program Execution
29718 @section @sc{gdb/mi} Program Execution
29720 These are the asynchronous commands which generate the out-of-band
29721 record @samp{*stopped}. Currently @value{GDBN} only really executes
29722 asynchronously with remote targets and this interaction is mimicked in
29725 @subheading The @code{-exec-continue} Command
29726 @findex -exec-continue
29728 @subsubheading Synopsis
29731 -exec-continue [--reverse] [--all|--thread-group N]
29734 Resumes the execution of the inferior program, which will continue
29735 to execute until it reaches a debugger stop event. If the
29736 @samp{--reverse} option is specified, execution resumes in reverse until
29737 it reaches a stop event. Stop events may include
29740 breakpoints or watchpoints
29742 signals or exceptions
29744 the end of the process (or its beginning under @samp{--reverse})
29746 the end or beginning of a replay log if one is being used.
29748 In all-stop mode (@pxref{All-Stop
29749 Mode}), may resume only one thread, or all threads, depending on the
29750 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29751 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29752 ignored in all-stop mode. If the @samp{--thread-group} options is
29753 specified, then all threads in that thread group are resumed.
29755 @subsubheading @value{GDBN} Command
29757 The corresponding @value{GDBN} corresponding is @samp{continue}.
29759 @subsubheading Example
29766 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29767 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29768 line="13",arch="i386:x86_64"@}
29773 @subheading The @code{-exec-finish} Command
29774 @findex -exec-finish
29776 @subsubheading Synopsis
29779 -exec-finish [--reverse]
29782 Resumes the execution of the inferior program until the current
29783 function is exited. Displays the results returned by the function.
29784 If the @samp{--reverse} option is specified, resumes the reverse
29785 execution of the inferior program until the point where current
29786 function was called.
29788 @subsubheading @value{GDBN} Command
29790 The corresponding @value{GDBN} command is @samp{finish}.
29792 @subsubheading Example
29794 Function returning @code{void}.
29801 *stopped,reason="function-finished",frame=@{func="main",args=[],
29802 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
29806 Function returning other than @code{void}. The name of the internal
29807 @value{GDBN} variable storing the result is printed, together with the
29814 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29815 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29816 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
29817 arch="i386:x86_64"@},
29818 gdb-result-var="$1",return-value="0"
29823 @subheading The @code{-exec-interrupt} Command
29824 @findex -exec-interrupt
29826 @subsubheading Synopsis
29829 -exec-interrupt [--all|--thread-group N]
29832 Interrupts the background execution of the target. Note how the token
29833 associated with the stop message is the one for the execution command
29834 that has been interrupted. The token for the interrupt itself only
29835 appears in the @samp{^done} output. If the user is trying to
29836 interrupt a non-running program, an error message will be printed.
29838 Note that when asynchronous execution is enabled, this command is
29839 asynchronous just like other execution commands. That is, first the
29840 @samp{^done} response will be printed, and the target stop will be
29841 reported after that using the @samp{*stopped} notification.
29843 In non-stop mode, only the context thread is interrupted by default.
29844 All threads (in all inferiors) will be interrupted if the
29845 @samp{--all} option is specified. If the @samp{--thread-group}
29846 option is specified, all threads in that group will be interrupted.
29848 @subsubheading @value{GDBN} Command
29850 The corresponding @value{GDBN} command is @samp{interrupt}.
29852 @subsubheading Example
29863 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29864 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29865 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
29870 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29874 @subheading The @code{-exec-jump} Command
29877 @subsubheading Synopsis
29880 -exec-jump @var{location}
29883 Resumes execution of the inferior program at the location specified by
29884 parameter. @xref{Specify Location}, for a description of the
29885 different forms of @var{location}.
29887 @subsubheading @value{GDBN} Command
29889 The corresponding @value{GDBN} command is @samp{jump}.
29891 @subsubheading Example
29894 -exec-jump foo.c:10
29895 *running,thread-id="all"
29900 @subheading The @code{-exec-next} Command
29903 @subsubheading Synopsis
29906 -exec-next [--reverse]
29909 Resumes execution of the inferior program, stopping when the beginning
29910 of the next source line is reached.
29912 If the @samp{--reverse} option is specified, resumes reverse execution
29913 of the inferior program, stopping at the beginning of the previous
29914 source line. If you issue this command on the first line of a
29915 function, it will take you back to the caller of that function, to the
29916 source line where the function was called.
29919 @subsubheading @value{GDBN} Command
29921 The corresponding @value{GDBN} command is @samp{next}.
29923 @subsubheading Example
29929 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29934 @subheading The @code{-exec-next-instruction} Command
29935 @findex -exec-next-instruction
29937 @subsubheading Synopsis
29940 -exec-next-instruction [--reverse]
29943 Executes one machine instruction. If the instruction is a function
29944 call, continues until the function returns. If the program stops at an
29945 instruction in the middle of a source line, the address will be
29948 If the @samp{--reverse} option is specified, resumes reverse execution
29949 of the inferior program, stopping at the previous instruction. If the
29950 previously executed instruction was a return from another function,
29951 it will continue to execute in reverse until the call to that function
29952 (from the current stack frame) is reached.
29954 @subsubheading @value{GDBN} Command
29956 The corresponding @value{GDBN} command is @samp{nexti}.
29958 @subsubheading Example
29962 -exec-next-instruction
29966 *stopped,reason="end-stepping-range",
29967 addr="0x000100d4",line="5",file="hello.c"
29972 @subheading The @code{-exec-return} Command
29973 @findex -exec-return
29975 @subsubheading Synopsis
29981 Makes current function return immediately. Doesn't execute the inferior.
29982 Displays the new current frame.
29984 @subsubheading @value{GDBN} Command
29986 The corresponding @value{GDBN} command is @samp{return}.
29988 @subsubheading Example
29992 200-break-insert callee4
29993 200^done,bkpt=@{number="1",addr="0x00010734",
29994 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29999 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30000 frame=@{func="callee4",args=[],
30001 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30002 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30003 arch="i386:x86_64"@}
30009 111^done,frame=@{level="0",func="callee3",
30010 args=[@{name="strarg",
30011 value="0x11940 \"A string argument.\""@}],
30012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30013 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30014 arch="i386:x86_64"@}
30019 @subheading The @code{-exec-run} Command
30022 @subsubheading Synopsis
30025 -exec-run [ --all | --thread-group N ] [ --start ]
30028 Starts execution of the inferior from the beginning. The inferior
30029 executes until either a breakpoint is encountered or the program
30030 exits. In the latter case the output will include an exit code, if
30031 the program has exited exceptionally.
30033 When neither the @samp{--all} nor the @samp{--thread-group} option
30034 is specified, the current inferior is started. If the
30035 @samp{--thread-group} option is specified, it should refer to a thread
30036 group of type @samp{process}, and that thread group will be started.
30037 If the @samp{--all} option is specified, then all inferiors will be started.
30039 Using the @samp{--start} option instructs the debugger to stop
30040 the execution at the start of the inferior's main subprogram,
30041 following the same behavior as the @code{start} command
30042 (@pxref{Starting}).
30044 @subsubheading @value{GDBN} Command
30046 The corresponding @value{GDBN} command is @samp{run}.
30048 @subsubheading Examples
30053 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30058 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30059 frame=@{func="main",args=[],file="recursive2.c",
30060 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30065 Program exited normally:
30073 *stopped,reason="exited-normally"
30078 Program exited exceptionally:
30086 *stopped,reason="exited",exit-code="01"
30090 Another way the program can terminate is if it receives a signal such as
30091 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30095 *stopped,reason="exited-signalled",signal-name="SIGINT",
30096 signal-meaning="Interrupt"
30100 @c @subheading -exec-signal
30103 @subheading The @code{-exec-step} Command
30106 @subsubheading Synopsis
30109 -exec-step [--reverse]
30112 Resumes execution of the inferior program, stopping when the beginning
30113 of the next source line is reached, if the next source line is not a
30114 function call. If it is, stop at the first instruction of the called
30115 function. If the @samp{--reverse} option is specified, resumes reverse
30116 execution of the inferior program, stopping at the beginning of the
30117 previously executed source line.
30119 @subsubheading @value{GDBN} Command
30121 The corresponding @value{GDBN} command is @samp{step}.
30123 @subsubheading Example
30125 Stepping into a function:
30131 *stopped,reason="end-stepping-range",
30132 frame=@{func="foo",args=[@{name="a",value="10"@},
30133 @{name="b",value="0"@}],file="recursive2.c",
30134 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30144 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30149 @subheading The @code{-exec-step-instruction} Command
30150 @findex -exec-step-instruction
30152 @subsubheading Synopsis
30155 -exec-step-instruction [--reverse]
30158 Resumes the inferior which executes one machine instruction. If the
30159 @samp{--reverse} option is specified, resumes reverse execution of the
30160 inferior program, stopping at the previously executed instruction.
30161 The output, once @value{GDBN} has stopped, will vary depending on
30162 whether we have stopped in the middle of a source line or not. In the
30163 former case, the address at which the program stopped will be printed
30166 @subsubheading @value{GDBN} Command
30168 The corresponding @value{GDBN} command is @samp{stepi}.
30170 @subsubheading Example
30174 -exec-step-instruction
30178 *stopped,reason="end-stepping-range",
30179 frame=@{func="foo",args=[],file="try.c",
30180 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30182 -exec-step-instruction
30186 *stopped,reason="end-stepping-range",
30187 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30188 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30193 @subheading The @code{-exec-until} Command
30194 @findex -exec-until
30196 @subsubheading Synopsis
30199 -exec-until [ @var{location} ]
30202 Executes the inferior until the @var{location} specified in the
30203 argument is reached. If there is no argument, the inferior executes
30204 until a source line greater than the current one is reached. The
30205 reason for stopping in this case will be @samp{location-reached}.
30207 @subsubheading @value{GDBN} Command
30209 The corresponding @value{GDBN} command is @samp{until}.
30211 @subsubheading Example
30215 -exec-until recursive2.c:6
30219 *stopped,reason="location-reached",frame=@{func="main",args=[],
30220 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30221 arch="i386:x86_64"@}
30226 @subheading -file-clear
30227 Is this going away????
30230 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30231 @node GDB/MI Stack Manipulation
30232 @section @sc{gdb/mi} Stack Manipulation Commands
30234 @subheading The @code{-enable-frame-filters} Command
30235 @findex -enable-frame-filters
30238 -enable-frame-filters
30241 @value{GDBN} allows Python-based frame filters to affect the output of
30242 the MI commands relating to stack traces. As there is no way to
30243 implement this in a fully backward-compatible way, a front end must
30244 request that this functionality be enabled.
30246 Once enabled, this feature cannot be disabled.
30248 Note that if Python support has not been compiled into @value{GDBN},
30249 this command will still succeed (and do nothing).
30251 @subheading The @code{-stack-info-frame} Command
30252 @findex -stack-info-frame
30254 @subsubheading Synopsis
30260 Get info on the selected frame.
30262 @subsubheading @value{GDBN} Command
30264 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30265 (without arguments).
30267 @subsubheading Example
30272 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30273 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30274 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30275 arch="i386:x86_64"@}
30279 @subheading The @code{-stack-info-depth} Command
30280 @findex -stack-info-depth
30282 @subsubheading Synopsis
30285 -stack-info-depth [ @var{max-depth} ]
30288 Return the depth of the stack. If the integer argument @var{max-depth}
30289 is specified, do not count beyond @var{max-depth} frames.
30291 @subsubheading @value{GDBN} Command
30293 There's no equivalent @value{GDBN} command.
30295 @subsubheading Example
30297 For a stack with frame levels 0 through 11:
30304 -stack-info-depth 4
30307 -stack-info-depth 12
30310 -stack-info-depth 11
30313 -stack-info-depth 13
30318 @anchor{-stack-list-arguments}
30319 @subheading The @code{-stack-list-arguments} Command
30320 @findex -stack-list-arguments
30322 @subsubheading Synopsis
30325 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30326 [ @var{low-frame} @var{high-frame} ]
30329 Display a list of the arguments for the frames between @var{low-frame}
30330 and @var{high-frame} (inclusive). If @var{low-frame} and
30331 @var{high-frame} are not provided, list the arguments for the whole
30332 call stack. If the two arguments are equal, show the single frame
30333 at the corresponding level. It is an error if @var{low-frame} is
30334 larger than the actual number of frames. On the other hand,
30335 @var{high-frame} may be larger than the actual number of frames, in
30336 which case only existing frames will be returned.
30338 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30339 the variables; if it is 1 or @code{--all-values}, print also their
30340 values; and if it is 2 or @code{--simple-values}, print the name,
30341 type and value for simple data types, and the name and type for arrays,
30342 structures and unions. If the option @code{--no-frame-filters} is
30343 supplied, then Python frame filters will not be executed.
30345 If the @code{--skip-unavailable} option is specified, arguments that
30346 are not available are not listed. Partially available arguments
30347 are still displayed, however.
30349 Use of this command to obtain arguments in a single frame is
30350 deprecated in favor of the @samp{-stack-list-variables} command.
30352 @subsubheading @value{GDBN} Command
30354 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30355 @samp{gdb_get_args} command which partially overlaps with the
30356 functionality of @samp{-stack-list-arguments}.
30358 @subsubheading Example
30365 frame=@{level="0",addr="0x00010734",func="callee4",
30366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30368 arch="i386:x86_64"@},
30369 frame=@{level="1",addr="0x0001076c",func="callee3",
30370 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30371 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30372 arch="i386:x86_64"@},
30373 frame=@{level="2",addr="0x0001078c",func="callee2",
30374 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30375 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30376 arch="i386:x86_64"@},
30377 frame=@{level="3",addr="0x000107b4",func="callee1",
30378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30379 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30380 arch="i386:x86_64"@},
30381 frame=@{level="4",addr="0x000107e0",func="main",
30382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30384 arch="i386:x86_64"@}]
30386 -stack-list-arguments 0
30389 frame=@{level="0",args=[]@},
30390 frame=@{level="1",args=[name="strarg"]@},
30391 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30392 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30393 frame=@{level="4",args=[]@}]
30395 -stack-list-arguments 1
30398 frame=@{level="0",args=[]@},
30400 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30401 frame=@{level="2",args=[
30402 @{name="intarg",value="2"@},
30403 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30404 @{frame=@{level="3",args=[
30405 @{name="intarg",value="2"@},
30406 @{name="strarg",value="0x11940 \"A string argument.\""@},
30407 @{name="fltarg",value="3.5"@}]@},
30408 frame=@{level="4",args=[]@}]
30410 -stack-list-arguments 0 2 2
30411 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30413 -stack-list-arguments 1 2 2
30414 ^done,stack-args=[frame=@{level="2",
30415 args=[@{name="intarg",value="2"@},
30416 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30420 @c @subheading -stack-list-exception-handlers
30423 @anchor{-stack-list-frames}
30424 @subheading The @code{-stack-list-frames} Command
30425 @findex -stack-list-frames
30427 @subsubheading Synopsis
30430 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30433 List the frames currently on the stack. For each frame it displays the
30438 The frame number, 0 being the topmost frame, i.e., the innermost function.
30440 The @code{$pc} value for that frame.
30444 File name of the source file where the function lives.
30445 @item @var{fullname}
30446 The full file name of the source file where the function lives.
30448 Line number corresponding to the @code{$pc}.
30450 The shared library where this function is defined. This is only given
30451 if the frame's function is not known.
30453 Frame's architecture.
30456 If invoked without arguments, this command prints a backtrace for the
30457 whole stack. If given two integer arguments, it shows the frames whose
30458 levels are between the two arguments (inclusive). If the two arguments
30459 are equal, it shows the single frame at the corresponding level. It is
30460 an error if @var{low-frame} is larger than the actual number of
30461 frames. On the other hand, @var{high-frame} may be larger than the
30462 actual number of frames, in which case only existing frames will be
30463 returned. If the option @code{--no-frame-filters} is supplied, then
30464 Python frame filters will not be executed.
30466 @subsubheading @value{GDBN} Command
30468 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30470 @subsubheading Example
30472 Full stack backtrace:
30478 [frame=@{level="0",addr="0x0001076c",func="foo",
30479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30480 arch="i386:x86_64"@},
30481 frame=@{level="1",addr="0x000107a4",func="foo",
30482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30483 arch="i386:x86_64"@},
30484 frame=@{level="2",addr="0x000107a4",func="foo",
30485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30486 arch="i386:x86_64"@},
30487 frame=@{level="3",addr="0x000107a4",func="foo",
30488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30489 arch="i386:x86_64"@},
30490 frame=@{level="4",addr="0x000107a4",func="foo",
30491 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30492 arch="i386:x86_64"@},
30493 frame=@{level="5",addr="0x000107a4",func="foo",
30494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30495 arch="i386:x86_64"@},
30496 frame=@{level="6",addr="0x000107a4",func="foo",
30497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30498 arch="i386:x86_64"@},
30499 frame=@{level="7",addr="0x000107a4",func="foo",
30500 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30501 arch="i386:x86_64"@},
30502 frame=@{level="8",addr="0x000107a4",func="foo",
30503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30504 arch="i386:x86_64"@},
30505 frame=@{level="9",addr="0x000107a4",func="foo",
30506 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30507 arch="i386:x86_64"@},
30508 frame=@{level="10",addr="0x000107a4",func="foo",
30509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30510 arch="i386:x86_64"@},
30511 frame=@{level="11",addr="0x00010738",func="main",
30512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30513 arch="i386:x86_64"@}]
30517 Show frames between @var{low_frame} and @var{high_frame}:
30521 -stack-list-frames 3 5
30523 [frame=@{level="3",addr="0x000107a4",func="foo",
30524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30525 arch="i386:x86_64"@},
30526 frame=@{level="4",addr="0x000107a4",func="foo",
30527 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30528 arch="i386:x86_64"@},
30529 frame=@{level="5",addr="0x000107a4",func="foo",
30530 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30531 arch="i386:x86_64"@}]
30535 Show a single frame:
30539 -stack-list-frames 3 3
30541 [frame=@{level="3",addr="0x000107a4",func="foo",
30542 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30543 arch="i386:x86_64"@}]
30548 @subheading The @code{-stack-list-locals} Command
30549 @findex -stack-list-locals
30550 @anchor{-stack-list-locals}
30552 @subsubheading Synopsis
30555 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30558 Display the local variable names for the selected frame. If
30559 @var{print-values} is 0 or @code{--no-values}, print only the names of
30560 the variables; if it is 1 or @code{--all-values}, print also their
30561 values; and if it is 2 or @code{--simple-values}, print the name,
30562 type and value for simple data types, and the name and type for arrays,
30563 structures and unions. In this last case, a frontend can immediately
30564 display the value of simple data types and create variable objects for
30565 other data types when the user wishes to explore their values in
30566 more detail. If the option @code{--no-frame-filters} is supplied, then
30567 Python frame filters will not be executed.
30569 If the @code{--skip-unavailable} option is specified, local variables
30570 that are not available are not listed. Partially available local
30571 variables are still displayed, however.
30573 This command is deprecated in favor of the
30574 @samp{-stack-list-variables} command.
30576 @subsubheading @value{GDBN} Command
30578 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30580 @subsubheading Example
30584 -stack-list-locals 0
30585 ^done,locals=[name="A",name="B",name="C"]
30587 -stack-list-locals --all-values
30588 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30589 @{name="C",value="@{1, 2, 3@}"@}]
30590 -stack-list-locals --simple-values
30591 ^done,locals=[@{name="A",type="int",value="1"@},
30592 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30596 @anchor{-stack-list-variables}
30597 @subheading The @code{-stack-list-variables} Command
30598 @findex -stack-list-variables
30600 @subsubheading Synopsis
30603 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30606 Display the names of local variables and function arguments for the selected frame. If
30607 @var{print-values} is 0 or @code{--no-values}, print only the names of
30608 the variables; if it is 1 or @code{--all-values}, print also their
30609 values; and if it is 2 or @code{--simple-values}, print the name,
30610 type and value for simple data types, and the name and type for arrays,
30611 structures and unions. If the option @code{--no-frame-filters} is
30612 supplied, then Python frame filters will not be executed.
30614 If the @code{--skip-unavailable} option is specified, local variables
30615 and arguments that are not available are not listed. Partially
30616 available arguments and local variables are still displayed, however.
30618 @subsubheading Example
30622 -stack-list-variables --thread 1 --frame 0 --all-values
30623 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30628 @subheading The @code{-stack-select-frame} Command
30629 @findex -stack-select-frame
30631 @subsubheading Synopsis
30634 -stack-select-frame @var{framenum}
30637 Change the selected frame. Select a different frame @var{framenum} on
30640 This command in deprecated in favor of passing the @samp{--frame}
30641 option to every command.
30643 @subsubheading @value{GDBN} Command
30645 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30646 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30648 @subsubheading Example
30652 -stack-select-frame 2
30657 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30658 @node GDB/MI Variable Objects
30659 @section @sc{gdb/mi} Variable Objects
30663 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30665 For the implementation of a variable debugger window (locals, watched
30666 expressions, etc.), we are proposing the adaptation of the existing code
30667 used by @code{Insight}.
30669 The two main reasons for that are:
30673 It has been proven in practice (it is already on its second generation).
30676 It will shorten development time (needless to say how important it is
30680 The original interface was designed to be used by Tcl code, so it was
30681 slightly changed so it could be used through @sc{gdb/mi}. This section
30682 describes the @sc{gdb/mi} operations that will be available and gives some
30683 hints about their use.
30685 @emph{Note}: In addition to the set of operations described here, we
30686 expect the @sc{gui} implementation of a variable window to require, at
30687 least, the following operations:
30690 @item @code{-gdb-show} @code{output-radix}
30691 @item @code{-stack-list-arguments}
30692 @item @code{-stack-list-locals}
30693 @item @code{-stack-select-frame}
30698 @subheading Introduction to Variable Objects
30700 @cindex variable objects in @sc{gdb/mi}
30702 Variable objects are "object-oriented" MI interface for examining and
30703 changing values of expressions. Unlike some other MI interfaces that
30704 work with expressions, variable objects are specifically designed for
30705 simple and efficient presentation in the frontend. A variable object
30706 is identified by string name. When a variable object is created, the
30707 frontend specifies the expression for that variable object. The
30708 expression can be a simple variable, or it can be an arbitrary complex
30709 expression, and can even involve CPU registers. After creating a
30710 variable object, the frontend can invoke other variable object
30711 operations---for example to obtain or change the value of a variable
30712 object, or to change display format.
30714 Variable objects have hierarchical tree structure. Any variable object
30715 that corresponds to a composite type, such as structure in C, has
30716 a number of child variable objects, for example corresponding to each
30717 element of a structure. A child variable object can itself have
30718 children, recursively. Recursion ends when we reach
30719 leaf variable objects, which always have built-in types. Child variable
30720 objects are created only by explicit request, so if a frontend
30721 is not interested in the children of a particular variable object, no
30722 child will be created.
30724 For a leaf variable object it is possible to obtain its value as a
30725 string, or set the value from a string. String value can be also
30726 obtained for a non-leaf variable object, but it's generally a string
30727 that only indicates the type of the object, and does not list its
30728 contents. Assignment to a non-leaf variable object is not allowed.
30730 A frontend does not need to read the values of all variable objects each time
30731 the program stops. Instead, MI provides an update command that lists all
30732 variable objects whose values has changed since the last update
30733 operation. This considerably reduces the amount of data that must
30734 be transferred to the frontend. As noted above, children variable
30735 objects are created on demand, and only leaf variable objects have a
30736 real value. As result, gdb will read target memory only for leaf
30737 variables that frontend has created.
30739 The automatic update is not always desirable. For example, a frontend
30740 might want to keep a value of some expression for future reference,
30741 and never update it. For another example, fetching memory is
30742 relatively slow for embedded targets, so a frontend might want
30743 to disable automatic update for the variables that are either not
30744 visible on the screen, or ``closed''. This is possible using so
30745 called ``frozen variable objects''. Such variable objects are never
30746 implicitly updated.
30748 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30749 fixed variable object, the expression is parsed when the variable
30750 object is created, including associating identifiers to specific
30751 variables. The meaning of expression never changes. For a floating
30752 variable object the values of variables whose names appear in the
30753 expressions are re-evaluated every time in the context of the current
30754 frame. Consider this example:
30759 struct work_state state;
30766 If a fixed variable object for the @code{state} variable is created in
30767 this function, and we enter the recursive call, the variable
30768 object will report the value of @code{state} in the top-level
30769 @code{do_work} invocation. On the other hand, a floating variable
30770 object will report the value of @code{state} in the current frame.
30772 If an expression specified when creating a fixed variable object
30773 refers to a local variable, the variable object becomes bound to the
30774 thread and frame in which the variable object is created. When such
30775 variable object is updated, @value{GDBN} makes sure that the
30776 thread/frame combination the variable object is bound to still exists,
30777 and re-evaluates the variable object in context of that thread/frame.
30779 The following is the complete set of @sc{gdb/mi} operations defined to
30780 access this functionality:
30782 @multitable @columnfractions .4 .6
30783 @item @strong{Operation}
30784 @tab @strong{Description}
30786 @item @code{-enable-pretty-printing}
30787 @tab enable Python-based pretty-printing
30788 @item @code{-var-create}
30789 @tab create a variable object
30790 @item @code{-var-delete}
30791 @tab delete the variable object and/or its children
30792 @item @code{-var-set-format}
30793 @tab set the display format of this variable
30794 @item @code{-var-show-format}
30795 @tab show the display format of this variable
30796 @item @code{-var-info-num-children}
30797 @tab tells how many children this object has
30798 @item @code{-var-list-children}
30799 @tab return a list of the object's children
30800 @item @code{-var-info-type}
30801 @tab show the type of this variable object
30802 @item @code{-var-info-expression}
30803 @tab print parent-relative expression that this variable object represents
30804 @item @code{-var-info-path-expression}
30805 @tab print full expression that this variable object represents
30806 @item @code{-var-show-attributes}
30807 @tab is this variable editable? does it exist here?
30808 @item @code{-var-evaluate-expression}
30809 @tab get the value of this variable
30810 @item @code{-var-assign}
30811 @tab set the value of this variable
30812 @item @code{-var-update}
30813 @tab update the variable and its children
30814 @item @code{-var-set-frozen}
30815 @tab set frozeness attribute
30816 @item @code{-var-set-update-range}
30817 @tab set range of children to display on update
30820 In the next subsection we describe each operation in detail and suggest
30821 how it can be used.
30823 @subheading Description And Use of Operations on Variable Objects
30825 @subheading The @code{-enable-pretty-printing} Command
30826 @findex -enable-pretty-printing
30829 -enable-pretty-printing
30832 @value{GDBN} allows Python-based visualizers to affect the output of the
30833 MI variable object commands. However, because there was no way to
30834 implement this in a fully backward-compatible way, a front end must
30835 request that this functionality be enabled.
30837 Once enabled, this feature cannot be disabled.
30839 Note that if Python support has not been compiled into @value{GDBN},
30840 this command will still succeed (and do nothing).
30842 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30843 may work differently in future versions of @value{GDBN}.
30845 @subheading The @code{-var-create} Command
30846 @findex -var-create
30848 @subsubheading Synopsis
30851 -var-create @{@var{name} | "-"@}
30852 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30855 This operation creates a variable object, which allows the monitoring of
30856 a variable, the result of an expression, a memory cell or a CPU
30859 The @var{name} parameter is the string by which the object can be
30860 referenced. It must be unique. If @samp{-} is specified, the varobj
30861 system will generate a string ``varNNNNNN'' automatically. It will be
30862 unique provided that one does not specify @var{name} of that format.
30863 The command fails if a duplicate name is found.
30865 The frame under which the expression should be evaluated can be
30866 specified by @var{frame-addr}. A @samp{*} indicates that the current
30867 frame should be used. A @samp{@@} indicates that a floating variable
30868 object must be created.
30870 @var{expression} is any expression valid on the current language set (must not
30871 begin with a @samp{*}), or one of the following:
30875 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30878 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30881 @samp{$@var{regname}} --- a CPU register name
30884 @cindex dynamic varobj
30885 A varobj's contents may be provided by a Python-based pretty-printer. In this
30886 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30887 have slightly different semantics in some cases. If the
30888 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30889 will never create a dynamic varobj. This ensures backward
30890 compatibility for existing clients.
30892 @subsubheading Result
30894 This operation returns attributes of the newly-created varobj. These
30899 The name of the varobj.
30902 The number of children of the varobj. This number is not necessarily
30903 reliable for a dynamic varobj. Instead, you must examine the
30904 @samp{has_more} attribute.
30907 The varobj's scalar value. For a varobj whose type is some sort of
30908 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30909 will not be interesting.
30912 The varobj's type. This is a string representation of the type, as
30913 would be printed by the @value{GDBN} CLI. If @samp{print object}
30914 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30915 @emph{actual} (derived) type of the object is shown rather than the
30916 @emph{declared} one.
30919 If a variable object is bound to a specific thread, then this is the
30920 thread's global identifier.
30923 For a dynamic varobj, this indicates whether there appear to be any
30924 children available. For a non-dynamic varobj, this will be 0.
30927 This attribute will be present and have the value @samp{1} if the
30928 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30929 then this attribute will not be present.
30932 A dynamic varobj can supply a display hint to the front end. The
30933 value comes directly from the Python pretty-printer object's
30934 @code{display_hint} method. @xref{Pretty Printing API}.
30937 Typical output will look like this:
30940 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30941 has_more="@var{has_more}"
30945 @subheading The @code{-var-delete} Command
30946 @findex -var-delete
30948 @subsubheading Synopsis
30951 -var-delete [ -c ] @var{name}
30954 Deletes a previously created variable object and all of its children.
30955 With the @samp{-c} option, just deletes the children.
30957 Returns an error if the object @var{name} is not found.
30960 @subheading The @code{-var-set-format} Command
30961 @findex -var-set-format
30963 @subsubheading Synopsis
30966 -var-set-format @var{name} @var{format-spec}
30969 Sets the output format for the value of the object @var{name} to be
30972 @anchor{-var-set-format}
30973 The syntax for the @var{format-spec} is as follows:
30976 @var{format-spec} @expansion{}
30977 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30980 The natural format is the default format choosen automatically
30981 based on the variable type (like decimal for an @code{int}, hex
30982 for pointers, etc.).
30984 The zero-hexadecimal format has a representation similar to hexadecimal
30985 but with padding zeroes to the left of the value. For example, a 32-bit
30986 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30987 zero-hexadecimal format.
30989 For a variable with children, the format is set only on the
30990 variable itself, and the children are not affected.
30992 @subheading The @code{-var-show-format} Command
30993 @findex -var-show-format
30995 @subsubheading Synopsis
30998 -var-show-format @var{name}
31001 Returns the format used to display the value of the object @var{name}.
31004 @var{format} @expansion{}
31009 @subheading The @code{-var-info-num-children} Command
31010 @findex -var-info-num-children
31012 @subsubheading Synopsis
31015 -var-info-num-children @var{name}
31018 Returns the number of children of a variable object @var{name}:
31024 Note that this number is not completely reliable for a dynamic varobj.
31025 It will return the current number of children, but more children may
31029 @subheading The @code{-var-list-children} Command
31030 @findex -var-list-children
31032 @subsubheading Synopsis
31035 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31037 @anchor{-var-list-children}
31039 Return a list of the children of the specified variable object and
31040 create variable objects for them, if they do not already exist. With
31041 a single argument or if @var{print-values} has a value of 0 or
31042 @code{--no-values}, print only the names of the variables; if
31043 @var{print-values} is 1 or @code{--all-values}, also print their
31044 values; and if it is 2 or @code{--simple-values} print the name and
31045 value for simple data types and just the name for arrays, structures
31048 @var{from} and @var{to}, if specified, indicate the range of children
31049 to report. If @var{from} or @var{to} is less than zero, the range is
31050 reset and all children will be reported. Otherwise, children starting
31051 at @var{from} (zero-based) and up to and excluding @var{to} will be
31054 If a child range is requested, it will only affect the current call to
31055 @code{-var-list-children}, but not future calls to @code{-var-update}.
31056 For this, you must instead use @code{-var-set-update-range}. The
31057 intent of this approach is to enable a front end to implement any
31058 update approach it likes; for example, scrolling a view may cause the
31059 front end to request more children with @code{-var-list-children}, and
31060 then the front end could call @code{-var-set-update-range} with a
31061 different range to ensure that future updates are restricted to just
31064 For each child the following results are returned:
31069 Name of the variable object created for this child.
31072 The expression to be shown to the user by the front end to designate this child.
31073 For example this may be the name of a structure member.
31075 For a dynamic varobj, this value cannot be used to form an
31076 expression. There is no way to do this at all with a dynamic varobj.
31078 For C/C@t{++} structures there are several pseudo children returned to
31079 designate access qualifiers. For these pseudo children @var{exp} is
31080 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31081 type and value are not present.
31083 A dynamic varobj will not report the access qualifying
31084 pseudo-children, regardless of the language. This information is not
31085 available at all with a dynamic varobj.
31088 Number of children this child has. For a dynamic varobj, this will be
31092 The type of the child. If @samp{print object}
31093 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31094 @emph{actual} (derived) type of the object is shown rather than the
31095 @emph{declared} one.
31098 If values were requested, this is the value.
31101 If this variable object is associated with a thread, this is the
31102 thread's global thread id. Otherwise this result is not present.
31105 If the variable object is frozen, this variable will be present with a value of 1.
31108 A dynamic varobj can supply a display hint to the front end. The
31109 value comes directly from the Python pretty-printer object's
31110 @code{display_hint} method. @xref{Pretty Printing API}.
31113 This attribute will be present and have the value @samp{1} if the
31114 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31115 then this attribute will not be present.
31119 The result may have its own attributes:
31123 A dynamic varobj can supply a display hint to the front end. The
31124 value comes directly from the Python pretty-printer object's
31125 @code{display_hint} method. @xref{Pretty Printing API}.
31128 This is an integer attribute which is nonzero if there are children
31129 remaining after the end of the selected range.
31132 @subsubheading Example
31136 -var-list-children n
31137 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31138 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31140 -var-list-children --all-values n
31141 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31142 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31146 @subheading The @code{-var-info-type} Command
31147 @findex -var-info-type
31149 @subsubheading Synopsis
31152 -var-info-type @var{name}
31155 Returns the type of the specified variable @var{name}. The type is
31156 returned as a string in the same format as it is output by the
31160 type=@var{typename}
31164 @subheading The @code{-var-info-expression} Command
31165 @findex -var-info-expression
31167 @subsubheading Synopsis
31170 -var-info-expression @var{name}
31173 Returns a string that is suitable for presenting this
31174 variable object in user interface. The string is generally
31175 not valid expression in the current language, and cannot be evaluated.
31177 For example, if @code{a} is an array, and variable object
31178 @code{A} was created for @code{a}, then we'll get this output:
31181 (gdb) -var-info-expression A.1
31182 ^done,lang="C",exp="1"
31186 Here, the value of @code{lang} is the language name, which can be
31187 found in @ref{Supported Languages}.
31189 Note that the output of the @code{-var-list-children} command also
31190 includes those expressions, so the @code{-var-info-expression} command
31193 @subheading The @code{-var-info-path-expression} Command
31194 @findex -var-info-path-expression
31196 @subsubheading Synopsis
31199 -var-info-path-expression @var{name}
31202 Returns an expression that can be evaluated in the current
31203 context and will yield the same value that a variable object has.
31204 Compare this with the @code{-var-info-expression} command, which
31205 result can be used only for UI presentation. Typical use of
31206 the @code{-var-info-path-expression} command is creating a
31207 watchpoint from a variable object.
31209 This command is currently not valid for children of a dynamic varobj,
31210 and will give an error when invoked on one.
31212 For example, suppose @code{C} is a C@t{++} class, derived from class
31213 @code{Base}, and that the @code{Base} class has a member called
31214 @code{m_size}. Assume a variable @code{c} is has the type of
31215 @code{C} and a variable object @code{C} was created for variable
31216 @code{c}. Then, we'll get this output:
31218 (gdb) -var-info-path-expression C.Base.public.m_size
31219 ^done,path_expr=((Base)c).m_size)
31222 @subheading The @code{-var-show-attributes} Command
31223 @findex -var-show-attributes
31225 @subsubheading Synopsis
31228 -var-show-attributes @var{name}
31231 List attributes of the specified variable object @var{name}:
31234 status=@var{attr} [ ( ,@var{attr} )* ]
31238 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31240 @subheading The @code{-var-evaluate-expression} Command
31241 @findex -var-evaluate-expression
31243 @subsubheading Synopsis
31246 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31249 Evaluates the expression that is represented by the specified variable
31250 object and returns its value as a string. The format of the string
31251 can be specified with the @samp{-f} option. The possible values of
31252 this option are the same as for @code{-var-set-format}
31253 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31254 the current display format will be used. The current display format
31255 can be changed using the @code{-var-set-format} command.
31261 Note that one must invoke @code{-var-list-children} for a variable
31262 before the value of a child variable can be evaluated.
31264 @subheading The @code{-var-assign} Command
31265 @findex -var-assign
31267 @subsubheading Synopsis
31270 -var-assign @var{name} @var{expression}
31273 Assigns the value of @var{expression} to the variable object specified
31274 by @var{name}. The object must be @samp{editable}. If the variable's
31275 value is altered by the assign, the variable will show up in any
31276 subsequent @code{-var-update} list.
31278 @subsubheading Example
31286 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31290 @subheading The @code{-var-update} Command
31291 @findex -var-update
31293 @subsubheading Synopsis
31296 -var-update [@var{print-values}] @{@var{name} | "*"@}
31299 Reevaluate the expressions corresponding to the variable object
31300 @var{name} and all its direct and indirect children, and return the
31301 list of variable objects whose values have changed; @var{name} must
31302 be a root variable object. Here, ``changed'' means that the result of
31303 @code{-var-evaluate-expression} before and after the
31304 @code{-var-update} is different. If @samp{*} is used as the variable
31305 object names, all existing variable objects are updated, except
31306 for frozen ones (@pxref{-var-set-frozen}). The option
31307 @var{print-values} determines whether both names and values, or just
31308 names are printed. The possible values of this option are the same
31309 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31310 recommended to use the @samp{--all-values} option, to reduce the
31311 number of MI commands needed on each program stop.
31313 With the @samp{*} parameter, if a variable object is bound to a
31314 currently running thread, it will not be updated, without any
31317 If @code{-var-set-update-range} was previously used on a varobj, then
31318 only the selected range of children will be reported.
31320 @code{-var-update} reports all the changed varobjs in a tuple named
31323 Each item in the change list is itself a tuple holding:
31327 The name of the varobj.
31330 If values were requested for this update, then this field will be
31331 present and will hold the value of the varobj.
31334 @anchor{-var-update}
31335 This field is a string which may take one of three values:
31339 The variable object's current value is valid.
31342 The variable object does not currently hold a valid value but it may
31343 hold one in the future if its associated expression comes back into
31347 The variable object no longer holds a valid value.
31348 This can occur when the executable file being debugged has changed,
31349 either through recompilation or by using the @value{GDBN} @code{file}
31350 command. The front end should normally choose to delete these variable
31354 In the future new values may be added to this list so the front should
31355 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31358 This is only present if the varobj is still valid. If the type
31359 changed, then this will be the string @samp{true}; otherwise it will
31362 When a varobj's type changes, its children are also likely to have
31363 become incorrect. Therefore, the varobj's children are automatically
31364 deleted when this attribute is @samp{true}. Also, the varobj's update
31365 range, when set using the @code{-var-set-update-range} command, is
31369 If the varobj's type changed, then this field will be present and will
31372 @item new_num_children
31373 For a dynamic varobj, if the number of children changed, or if the
31374 type changed, this will be the new number of children.
31376 The @samp{numchild} field in other varobj responses is generally not
31377 valid for a dynamic varobj -- it will show the number of children that
31378 @value{GDBN} knows about, but because dynamic varobjs lazily
31379 instantiate their children, this will not reflect the number of
31380 children which may be available.
31382 The @samp{new_num_children} attribute only reports changes to the
31383 number of children known by @value{GDBN}. This is the only way to
31384 detect whether an update has removed children (which necessarily can
31385 only happen at the end of the update range).
31388 The display hint, if any.
31391 This is an integer value, which will be 1 if there are more children
31392 available outside the varobj's update range.
31395 This attribute will be present and have the value @samp{1} if the
31396 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31397 then this attribute will not be present.
31400 If new children were added to a dynamic varobj within the selected
31401 update range (as set by @code{-var-set-update-range}), then they will
31402 be listed in this attribute.
31405 @subsubheading Example
31412 -var-update --all-values var1
31413 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31414 type_changed="false"@}]
31418 @subheading The @code{-var-set-frozen} Command
31419 @findex -var-set-frozen
31420 @anchor{-var-set-frozen}
31422 @subsubheading Synopsis
31425 -var-set-frozen @var{name} @var{flag}
31428 Set the frozenness flag on the variable object @var{name}. The
31429 @var{flag} parameter should be either @samp{1} to make the variable
31430 frozen or @samp{0} to make it unfrozen. If a variable object is
31431 frozen, then neither itself, nor any of its children, are
31432 implicitly updated by @code{-var-update} of
31433 a parent variable or by @code{-var-update *}. Only
31434 @code{-var-update} of the variable itself will update its value and
31435 values of its children. After a variable object is unfrozen, it is
31436 implicitly updated by all subsequent @code{-var-update} operations.
31437 Unfreezing a variable does not update it, only subsequent
31438 @code{-var-update} does.
31440 @subsubheading Example
31444 -var-set-frozen V 1
31449 @subheading The @code{-var-set-update-range} command
31450 @findex -var-set-update-range
31451 @anchor{-var-set-update-range}
31453 @subsubheading Synopsis
31456 -var-set-update-range @var{name} @var{from} @var{to}
31459 Set the range of children to be returned by future invocations of
31460 @code{-var-update}.
31462 @var{from} and @var{to} indicate the range of children to report. If
31463 @var{from} or @var{to} is less than zero, the range is reset and all
31464 children will be reported. Otherwise, children starting at @var{from}
31465 (zero-based) and up to and excluding @var{to} will be reported.
31467 @subsubheading Example
31471 -var-set-update-range V 1 2
31475 @subheading The @code{-var-set-visualizer} command
31476 @findex -var-set-visualizer
31477 @anchor{-var-set-visualizer}
31479 @subsubheading Synopsis
31482 -var-set-visualizer @var{name} @var{visualizer}
31485 Set a visualizer for the variable object @var{name}.
31487 @var{visualizer} is the visualizer to use. The special value
31488 @samp{None} means to disable any visualizer in use.
31490 If not @samp{None}, @var{visualizer} must be a Python expression.
31491 This expression must evaluate to a callable object which accepts a
31492 single argument. @value{GDBN} will call this object with the value of
31493 the varobj @var{name} as an argument (this is done so that the same
31494 Python pretty-printing code can be used for both the CLI and MI).
31495 When called, this object must return an object which conforms to the
31496 pretty-printing interface (@pxref{Pretty Printing API}).
31498 The pre-defined function @code{gdb.default_visualizer} may be used to
31499 select a visualizer by following the built-in process
31500 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31501 a varobj is created, and so ordinarily is not needed.
31503 This feature is only available if Python support is enabled. The MI
31504 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31505 can be used to check this.
31507 @subsubheading Example
31509 Resetting the visualizer:
31513 -var-set-visualizer V None
31517 Reselecting the default (type-based) visualizer:
31521 -var-set-visualizer V gdb.default_visualizer
31525 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31526 can be used to instantiate this class for a varobj:
31530 -var-set-visualizer V "lambda val: SomeClass()"
31534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31535 @node GDB/MI Data Manipulation
31536 @section @sc{gdb/mi} Data Manipulation
31538 @cindex data manipulation, in @sc{gdb/mi}
31539 @cindex @sc{gdb/mi}, data manipulation
31540 This section describes the @sc{gdb/mi} commands that manipulate data:
31541 examine memory and registers, evaluate expressions, etc.
31543 For details about what an addressable memory unit is,
31544 @pxref{addressable memory unit}.
31546 @c REMOVED FROM THE INTERFACE.
31547 @c @subheading -data-assign
31548 @c Change the value of a program variable. Plenty of side effects.
31549 @c @subsubheading GDB Command
31551 @c @subsubheading Example
31554 @subheading The @code{-data-disassemble} Command
31555 @findex -data-disassemble
31557 @subsubheading Synopsis
31561 [ -s @var{start-addr} -e @var{end-addr} ]
31562 | [ -a @var{addr} ]
31563 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31571 @item @var{start-addr}
31572 is the beginning address (or @code{$pc})
31573 @item @var{end-addr}
31576 is an address anywhere within (or the name of) the function to
31577 disassemble. If an address is specified, the whole function
31578 surrounding that address will be disassembled. If a name is
31579 specified, the whole function with that name will be disassembled.
31580 @item @var{filename}
31581 is the name of the file to disassemble
31582 @item @var{linenum}
31583 is the line number to disassemble around
31585 is the number of disassembly lines to be produced. If it is -1,
31586 the whole function will be disassembled, in case no @var{end-addr} is
31587 specified. If @var{end-addr} is specified as a non-zero value, and
31588 @var{lines} is lower than the number of disassembly lines between
31589 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31590 displayed; if @var{lines} is higher than the number of lines between
31591 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31596 @item 0 disassembly only
31597 @item 1 mixed source and disassembly (deprecated)
31598 @item 2 disassembly with raw opcodes
31599 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31600 @item 4 mixed source and disassembly
31601 @item 5 mixed source and disassembly with raw opcodes
31604 Modes 1 and 3 are deprecated. The output is ``source centric''
31605 which hasn't proved useful in practice.
31606 @xref{Machine Code}, for a discussion of the difference between
31607 @code{/m} and @code{/s} output of the @code{disassemble} command.
31610 @subsubheading Result
31612 The result of the @code{-data-disassemble} command will be a list named
31613 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31614 used with the @code{-data-disassemble} command.
31616 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31621 The address at which this instruction was disassembled.
31624 The name of the function this instruction is within.
31627 The decimal offset in bytes from the start of @samp{func-name}.
31630 The text disassembly for this @samp{address}.
31633 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31634 bytes for the @samp{inst} field.
31638 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31639 @samp{src_and_asm_line}, each of which has the following fields:
31643 The line number within @samp{file}.
31646 The file name from the compilation unit. This might be an absolute
31647 file name or a relative file name depending on the compile command
31651 Absolute file name of @samp{file}. It is converted to a canonical form
31652 using the source file search path
31653 (@pxref{Source Path, ,Specifying Source Directories})
31654 and after resolving all the symbolic links.
31656 If the source file is not found this field will contain the path as
31657 present in the debug information.
31659 @item line_asm_insn
31660 This is a list of tuples containing the disassembly for @samp{line} in
31661 @samp{file}. The fields of each tuple are the same as for
31662 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31663 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31668 Note that whatever included in the @samp{inst} field, is not
31669 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31672 @subsubheading @value{GDBN} Command
31674 The corresponding @value{GDBN} command is @samp{disassemble}.
31676 @subsubheading Example
31678 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31682 -data-disassemble -s $pc -e "$pc + 20" -- 0
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"@},
31689 @{address="0x000107c8",func-name="main",offset="12",
31690 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31691 @{address="0x000107cc",func-name="main",offset="16",
31692 inst="sethi %hi(0x11800), %o2"@},
31693 @{address="0x000107d0",func-name="main",offset="20",
31694 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31698 Disassemble the whole @code{main} function. Line 32 is part of
31702 -data-disassemble -f basics.c -l 32 -- 0
31704 @{address="0x000107bc",func-name="main",offset="0",
31705 inst="save %sp, -112, %sp"@},
31706 @{address="0x000107c0",func-name="main",offset="4",
31707 inst="mov 2, %o0"@},
31708 @{address="0x000107c4",func-name="main",offset="8",
31709 inst="sethi %hi(0x11800), %o2"@},
31711 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31712 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31716 Disassemble 3 instructions from the start of @code{main}:
31720 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31722 @{address="0x000107bc",func-name="main",offset="0",
31723 inst="save %sp, -112, %sp"@},
31724 @{address="0x000107c0",func-name="main",offset="4",
31725 inst="mov 2, %o0"@},
31726 @{address="0x000107c4",func-name="main",offset="8",
31727 inst="sethi %hi(0x11800), %o2"@}]
31731 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31735 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31737 src_and_asm_line=@{line="31",
31738 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31739 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31740 line_asm_insn=[@{address="0x000107bc",
31741 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31742 src_and_asm_line=@{line="32",
31743 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31744 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31745 line_asm_insn=[@{address="0x000107c0",
31746 func-name="main",offset="4",inst="mov 2, %o0"@},
31747 @{address="0x000107c4",func-name="main",offset="8",
31748 inst="sethi %hi(0x11800), %o2"@}]@}]
31753 @subheading The @code{-data-evaluate-expression} Command
31754 @findex -data-evaluate-expression
31756 @subsubheading Synopsis
31759 -data-evaluate-expression @var{expr}
31762 Evaluate @var{expr} as an expression. The expression could contain an
31763 inferior function call. The function call will execute synchronously.
31764 If the expression contains spaces, it must be enclosed in double quotes.
31766 @subsubheading @value{GDBN} Command
31768 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31769 @samp{call}. In @code{gdbtk} only, there's a corresponding
31770 @samp{gdb_eval} command.
31772 @subsubheading Example
31774 In the following example, the numbers that precede the commands are the
31775 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31776 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31780 211-data-evaluate-expression A
31783 311-data-evaluate-expression &A
31784 311^done,value="0xefffeb7c"
31786 411-data-evaluate-expression A+3
31789 511-data-evaluate-expression "A + 3"
31795 @subheading The @code{-data-list-changed-registers} Command
31796 @findex -data-list-changed-registers
31798 @subsubheading Synopsis
31801 -data-list-changed-registers
31804 Display a list of the registers that have changed.
31806 @subsubheading @value{GDBN} Command
31808 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31809 has the corresponding command @samp{gdb_changed_register_list}.
31811 @subsubheading Example
31813 On a PPC MBX board:
31821 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31822 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31823 line="5",arch="powerpc"@}
31825 -data-list-changed-registers
31826 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31827 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31828 "24","25","26","27","28","30","31","64","65","66","67","69"]
31833 @subheading The @code{-data-list-register-names} Command
31834 @findex -data-list-register-names
31836 @subsubheading Synopsis
31839 -data-list-register-names [ ( @var{regno} )+ ]
31842 Show a list of register names for the current target. If no arguments
31843 are given, it shows a list of the names of all the registers. If
31844 integer numbers are given as arguments, it will print a list of the
31845 names of the registers corresponding to the arguments. To ensure
31846 consistency between a register name and its number, the output list may
31847 include empty register names.
31849 @subsubheading @value{GDBN} Command
31851 @value{GDBN} does not have a command which corresponds to
31852 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31853 corresponding command @samp{gdb_regnames}.
31855 @subsubheading Example
31857 For the PPC MBX board:
31860 -data-list-register-names
31861 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31862 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31863 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31864 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31865 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31866 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31867 "", "pc","ps","cr","lr","ctr","xer"]
31869 -data-list-register-names 1 2 3
31870 ^done,register-names=["r1","r2","r3"]
31874 @subheading The @code{-data-list-register-values} Command
31875 @findex -data-list-register-values
31877 @subsubheading Synopsis
31880 -data-list-register-values
31881 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31884 Display the registers' contents. The format according to which the
31885 registers' contents are to be returned is given by @var{fmt}, followed
31886 by an optional list of numbers specifying the registers to display. A
31887 missing list of numbers indicates that the contents of all the
31888 registers must be returned. The @code{--skip-unavailable} option
31889 indicates that only the available registers are to be returned.
31891 Allowed formats for @var{fmt} are:
31908 @subsubheading @value{GDBN} Command
31910 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31911 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31913 @subsubheading Example
31915 For a PPC MBX board (note: line breaks are for readability only, they
31916 don't appear in the actual output):
31920 -data-list-register-values r 64 65
31921 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31922 @{number="65",value="0x00029002"@}]
31924 -data-list-register-values x
31925 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31926 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31927 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31928 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31929 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31930 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31931 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31932 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31933 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31934 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31935 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31936 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31937 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31938 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31939 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31940 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31941 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31942 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31943 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31944 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31945 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31946 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31947 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31948 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31949 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31950 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31951 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31952 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31953 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31954 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31955 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31956 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31957 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31958 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31959 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31960 @{number="69",value="0x20002b03"@}]
31965 @subheading The @code{-data-read-memory} Command
31966 @findex -data-read-memory
31968 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31970 @subsubheading Synopsis
31973 -data-read-memory [ -o @var{byte-offset} ]
31974 @var{address} @var{word-format} @var{word-size}
31975 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31982 @item @var{address}
31983 An expression specifying the address of the first memory word to be
31984 read. Complex expressions containing embedded white space should be
31985 quoted using the C convention.
31987 @item @var{word-format}
31988 The format to be used to print the memory words. The notation is the
31989 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31992 @item @var{word-size}
31993 The size of each memory word in bytes.
31995 @item @var{nr-rows}
31996 The number of rows in the output table.
31998 @item @var{nr-cols}
31999 The number of columns in the output table.
32002 If present, indicates that each row should include an @sc{ascii} dump. The
32003 value of @var{aschar} is used as a padding character when a byte is not a
32004 member of the printable @sc{ascii} character set (printable @sc{ascii}
32005 characters are those whose code is between 32 and 126, inclusively).
32007 @item @var{byte-offset}
32008 An offset to add to the @var{address} before fetching memory.
32011 This command displays memory contents as a table of @var{nr-rows} by
32012 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32013 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32014 (returned as @samp{total-bytes}). Should less than the requested number
32015 of bytes be returned by the target, the missing words are identified
32016 using @samp{N/A}. The number of bytes read from the target is returned
32017 in @samp{nr-bytes} and the starting address used to read memory in
32020 The address of the next/previous row or page is available in
32021 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32024 @subsubheading @value{GDBN} Command
32026 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32027 @samp{gdb_get_mem} memory read command.
32029 @subsubheading Example
32031 Read six bytes of memory starting at @code{bytes+6} but then offset by
32032 @code{-6} bytes. Format as three rows of two columns. One byte per
32033 word. Display each word in hex.
32037 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32038 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32039 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32040 prev-page="0x0000138a",memory=[
32041 @{addr="0x00001390",data=["0x00","0x01"]@},
32042 @{addr="0x00001392",data=["0x02","0x03"]@},
32043 @{addr="0x00001394",data=["0x04","0x05"]@}]
32047 Read two bytes of memory starting at address @code{shorts + 64} and
32048 display as a single word formatted in decimal.
32052 5-data-read-memory shorts+64 d 2 1 1
32053 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32054 next-row="0x00001512",prev-row="0x0000150e",
32055 next-page="0x00001512",prev-page="0x0000150e",memory=[
32056 @{addr="0x00001510",data=["128"]@}]
32060 Read thirty two bytes of memory starting at @code{bytes+16} and format
32061 as eight rows of four columns. Include a string encoding with @samp{x}
32062 used as the non-printable character.
32066 4-data-read-memory bytes+16 x 1 8 4 x
32067 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32068 next-row="0x000013c0",prev-row="0x0000139c",
32069 next-page="0x000013c0",prev-page="0x00001380",memory=[
32070 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32071 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32072 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32073 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32074 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32075 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32076 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32077 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32081 @subheading The @code{-data-read-memory-bytes} Command
32082 @findex -data-read-memory-bytes
32084 @subsubheading Synopsis
32087 -data-read-memory-bytes [ -o @var{offset} ]
32088 @var{address} @var{count}
32095 @item @var{address}
32096 An expression specifying the address of the first addressable memory unit
32097 to be read. Complex expressions containing embedded white space should be
32098 quoted using the C convention.
32101 The number of addressable memory units to read. This should be an integer
32105 The offset relative to @var{address} at which to start reading. This
32106 should be an integer literal. This option is provided so that a frontend
32107 is not required to first evaluate address and then perform address
32108 arithmetics itself.
32112 This command attempts to read all accessible memory regions in the
32113 specified range. First, all regions marked as unreadable in the memory
32114 map (if one is defined) will be skipped. @xref{Memory Region
32115 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32116 regions. For each one, if reading full region results in an errors,
32117 @value{GDBN} will try to read a subset of the region.
32119 In general, every single memory unit in the region may be readable or not,
32120 and the only way to read every readable unit is to try a read at
32121 every address, which is not practical. Therefore, @value{GDBN} will
32122 attempt to read all accessible memory units at either beginning or the end
32123 of the region, using a binary division scheme. This heuristic works
32124 well for reading accross a memory map boundary. Note that if a region
32125 has a readable range that is neither at the beginning or the end,
32126 @value{GDBN} will not read it.
32128 The result record (@pxref{GDB/MI Result Records}) that is output of
32129 the command includes a field named @samp{memory} whose content is a
32130 list of tuples. Each tuple represent a successfully read memory block
32131 and has the following fields:
32135 The start address of the memory block, as hexadecimal literal.
32138 The end address of the memory block, as hexadecimal literal.
32141 The offset of the memory block, as hexadecimal literal, relative to
32142 the start address passed to @code{-data-read-memory-bytes}.
32145 The contents of the memory block, in hex.
32151 @subsubheading @value{GDBN} Command
32153 The corresponding @value{GDBN} command is @samp{x}.
32155 @subsubheading Example
32159 -data-read-memory-bytes &a 10
32160 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32162 contents="01000000020000000300"@}]
32167 @subheading The @code{-data-write-memory-bytes} Command
32168 @findex -data-write-memory-bytes
32170 @subsubheading Synopsis
32173 -data-write-memory-bytes @var{address} @var{contents}
32174 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32181 @item @var{address}
32182 An expression specifying the address of the first addressable memory unit
32183 to be written. Complex expressions containing embedded white space should
32184 be quoted using the C convention.
32186 @item @var{contents}
32187 The hex-encoded data to write. It is an error if @var{contents} does
32188 not represent an integral number of addressable memory units.
32191 Optional argument indicating the number of addressable memory units to be
32192 written. If @var{count} is greater than @var{contents}' length,
32193 @value{GDBN} will repeatedly write @var{contents} until it fills
32194 @var{count} memory units.
32198 @subsubheading @value{GDBN} Command
32200 There's no corresponding @value{GDBN} command.
32202 @subsubheading Example
32206 -data-write-memory-bytes &a "aabbccdd"
32213 -data-write-memory-bytes &a "aabbccdd" 16e
32218 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32219 @node GDB/MI Tracepoint Commands
32220 @section @sc{gdb/mi} Tracepoint Commands
32222 The commands defined in this section implement MI support for
32223 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32225 @subheading The @code{-trace-find} Command
32226 @findex -trace-find
32228 @subsubheading Synopsis
32231 -trace-find @var{mode} [@var{parameters}@dots{}]
32234 Find a trace frame using criteria defined by @var{mode} and
32235 @var{parameters}. The following table lists permissible
32236 modes and their parameters. For details of operation, see @ref{tfind}.
32241 No parameters are required. Stops examining trace frames.
32244 An integer is required as parameter. Selects tracepoint frame with
32247 @item tracepoint-number
32248 An integer is required as parameter. Finds next
32249 trace frame that corresponds to tracepoint with the specified number.
32252 An address is required as parameter. Finds
32253 next trace frame that corresponds to any tracepoint at the specified
32256 @item pc-inside-range
32257 Two addresses are required as parameters. Finds next trace
32258 frame that corresponds to a tracepoint at an address inside the
32259 specified range. Both bounds are considered to be inside the range.
32261 @item pc-outside-range
32262 Two addresses are required as parameters. Finds
32263 next trace frame that corresponds to a tracepoint at an address outside
32264 the specified range. Both bounds are considered to be inside the range.
32267 Line specification is required as parameter. @xref{Specify Location}.
32268 Finds next trace frame that corresponds to a tracepoint at
32269 the specified location.
32273 If @samp{none} was passed as @var{mode}, the response does not
32274 have fields. Otherwise, the response may have the following fields:
32278 This field has either @samp{0} or @samp{1} as the value, depending
32279 on whether a matching tracepoint was found.
32282 The index of the found traceframe. This field is present iff
32283 the @samp{found} field has value of @samp{1}.
32286 The index of the found tracepoint. This field is present iff
32287 the @samp{found} field has value of @samp{1}.
32290 The information about the frame corresponding to the found trace
32291 frame. This field is present only if a trace frame was found.
32292 @xref{GDB/MI Frame Information}, for description of this field.
32296 @subsubheading @value{GDBN} Command
32298 The corresponding @value{GDBN} command is @samp{tfind}.
32300 @subheading -trace-define-variable
32301 @findex -trace-define-variable
32303 @subsubheading Synopsis
32306 -trace-define-variable @var{name} [ @var{value} ]
32309 Create trace variable @var{name} if it does not exist. If
32310 @var{value} is specified, sets the initial value of the specified
32311 trace variable to that value. Note that the @var{name} should start
32312 with the @samp{$} character.
32314 @subsubheading @value{GDBN} Command
32316 The corresponding @value{GDBN} command is @samp{tvariable}.
32318 @subheading The @code{-trace-frame-collected} Command
32319 @findex -trace-frame-collected
32321 @subsubheading Synopsis
32324 -trace-frame-collected
32325 [--var-print-values @var{var_pval}]
32326 [--comp-print-values @var{comp_pval}]
32327 [--registers-format @var{regformat}]
32328 [--memory-contents]
32331 This command returns the set of collected objects, register names,
32332 trace state variable names, memory ranges and computed expressions
32333 that have been collected at a particular trace frame. The optional
32334 parameters to the command affect the output format in different ways.
32335 See the output description table below for more details.
32337 The reported names can be used in the normal manner to create
32338 varobjs and inspect the objects themselves. The items returned by
32339 this command are categorized so that it is clear which is a variable,
32340 which is a register, which is a trace state variable, which is a
32341 memory range and which is a computed expression.
32343 For instance, if the actions were
32345 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32346 collect *(int*)0xaf02bef0@@40
32350 the object collected in its entirety would be @code{myVar}. The
32351 object @code{myArray} would be partially collected, because only the
32352 element at index @code{myIndex} would be collected. The remaining
32353 objects would be computed expressions.
32355 An example output would be:
32359 -trace-frame-collected
32361 explicit-variables=[@{name="myVar",value="1"@}],
32362 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32363 @{name="myObj.field",value="0"@},
32364 @{name="myPtr->field",value="1"@},
32365 @{name="myCount + 2",value="3"@},
32366 @{name="$tvar1 + 1",value="43970027"@}],
32367 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32368 @{number="1",value="0x0"@},
32369 @{number="2",value="0x4"@},
32371 @{number="125",value="0x0"@}],
32372 tvars=[@{name="$tvar1",current="43970026"@}],
32373 memory=[@{address="0x0000000000602264",length="4"@},
32374 @{address="0x0000000000615bc0",length="4"@}]
32381 @item explicit-variables
32382 The set of objects that have been collected in their entirety (as
32383 opposed to collecting just a few elements of an array or a few struct
32384 members). For each object, its name and value are printed.
32385 The @code{--var-print-values} option affects how or whether the value
32386 field is output. If @var{var_pval} is 0, then print only the names;
32387 if it is 1, print also their values; and if it is 2, print the name,
32388 type and value for simple data types, and the name and type for
32389 arrays, structures and unions.
32391 @item computed-expressions
32392 The set of computed expressions that have been collected at the
32393 current trace frame. The @code{--comp-print-values} option affects
32394 this set like the @code{--var-print-values} option affects the
32395 @code{explicit-variables} set. See above.
32398 The registers that have been collected at the current trace frame.
32399 For each register collected, the name and current value are returned.
32400 The value is formatted according to the @code{--registers-format}
32401 option. See the @command{-data-list-register-values} command for a
32402 list of the allowed formats. The default is @samp{x}.
32405 The trace state variables that have been collected at the current
32406 trace frame. For each trace state variable collected, the name and
32407 current value are returned.
32410 The set of memory ranges that have been collected at the current trace
32411 frame. Its content is a list of tuples. Each tuple represents a
32412 collected memory range and has the following fields:
32416 The start address of the memory range, as hexadecimal literal.
32419 The length of the memory range, as decimal literal.
32422 The contents of the memory block, in hex. This field is only present
32423 if the @code{--memory-contents} option is specified.
32429 @subsubheading @value{GDBN} Command
32431 There is no corresponding @value{GDBN} command.
32433 @subsubheading Example
32435 @subheading -trace-list-variables
32436 @findex -trace-list-variables
32438 @subsubheading Synopsis
32441 -trace-list-variables
32444 Return a table of all defined trace variables. Each element of the
32445 table has the following fields:
32449 The name of the trace variable. This field is always present.
32452 The initial value. This is a 64-bit signed integer. This
32453 field is always present.
32456 The value the trace variable has at the moment. This is a 64-bit
32457 signed integer. This field is absent iff current value is
32458 not defined, for example if the trace was never run, or is
32463 @subsubheading @value{GDBN} Command
32465 The corresponding @value{GDBN} command is @samp{tvariables}.
32467 @subsubheading Example
32471 -trace-list-variables
32472 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32473 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32474 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32475 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32476 body=[variable=@{name="$trace_timestamp",initial="0"@}
32477 variable=@{name="$foo",initial="10",current="15"@}]@}
32481 @subheading -trace-save
32482 @findex -trace-save
32484 @subsubheading Synopsis
32487 -trace-save [ -r ] [ -ctf ] @var{filename}
32490 Saves the collected trace data to @var{filename}. Without the
32491 @samp{-r} option, the data is downloaded from the target and saved
32492 in a local file. With the @samp{-r} option the target is asked
32493 to perform the save.
32495 By default, this command will save the trace in the tfile format. You can
32496 supply the optional @samp{-ctf} argument to save it the CTF format. See
32497 @ref{Trace Files} for more information about CTF.
32499 @subsubheading @value{GDBN} Command
32501 The corresponding @value{GDBN} command is @samp{tsave}.
32504 @subheading -trace-start
32505 @findex -trace-start
32507 @subsubheading Synopsis
32513 Starts a tracing experiment. The result of this command does not
32516 @subsubheading @value{GDBN} Command
32518 The corresponding @value{GDBN} command is @samp{tstart}.
32520 @subheading -trace-status
32521 @findex -trace-status
32523 @subsubheading Synopsis
32529 Obtains the status of a tracing experiment. The result may include
32530 the following fields:
32535 May have a value of either @samp{0}, when no tracing operations are
32536 supported, @samp{1}, when all tracing operations are supported, or
32537 @samp{file} when examining trace file. In the latter case, examining
32538 of trace frame is possible but new tracing experiement cannot be
32539 started. This field is always present.
32542 May have a value of either @samp{0} or @samp{1} depending on whether
32543 tracing experiement is in progress on target. This field is present
32544 if @samp{supported} field is not @samp{0}.
32547 Report the reason why the tracing was stopped last time. This field
32548 may be absent iff tracing was never stopped on target yet. The
32549 value of @samp{request} means the tracing was stopped as result of
32550 the @code{-trace-stop} command. The value of @samp{overflow} means
32551 the tracing buffer is full. The value of @samp{disconnection} means
32552 tracing was automatically stopped when @value{GDBN} has disconnected.
32553 The value of @samp{passcount} means tracing was stopped when a
32554 tracepoint was passed a maximal number of times for that tracepoint.
32555 This field is present if @samp{supported} field is not @samp{0}.
32557 @item stopping-tracepoint
32558 The number of tracepoint whose passcount as exceeded. This field is
32559 present iff the @samp{stop-reason} field has the value of
32563 @itemx frames-created
32564 The @samp{frames} field is a count of the total number of trace frames
32565 in the trace buffer, while @samp{frames-created} is the total created
32566 during the run, including ones that were discarded, such as when a
32567 circular trace buffer filled up. Both fields are optional.
32571 These fields tell the current size of the tracing buffer and the
32572 remaining space. These fields are optional.
32575 The value of the circular trace buffer flag. @code{1} means that the
32576 trace buffer is circular and old trace frames will be discarded if
32577 necessary to make room, @code{0} means that the trace buffer is linear
32581 The value of the disconnected tracing flag. @code{1} means that
32582 tracing will continue after @value{GDBN} disconnects, @code{0} means
32583 that the trace run will stop.
32586 The filename of the trace file being examined. This field is
32587 optional, and only present when examining a trace file.
32591 @subsubheading @value{GDBN} Command
32593 The corresponding @value{GDBN} command is @samp{tstatus}.
32595 @subheading -trace-stop
32596 @findex -trace-stop
32598 @subsubheading Synopsis
32604 Stops a tracing experiment. The result of this command has the same
32605 fields as @code{-trace-status}, except that the @samp{supported} and
32606 @samp{running} fields are not output.
32608 @subsubheading @value{GDBN} Command
32610 The corresponding @value{GDBN} command is @samp{tstop}.
32613 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32614 @node GDB/MI Symbol Query
32615 @section @sc{gdb/mi} Symbol Query Commands
32619 @subheading The @code{-symbol-info-address} Command
32620 @findex -symbol-info-address
32622 @subsubheading Synopsis
32625 -symbol-info-address @var{symbol}
32628 Describe where @var{symbol} is stored.
32630 @subsubheading @value{GDBN} Command
32632 The corresponding @value{GDBN} command is @samp{info address}.
32634 @subsubheading Example
32638 @subheading The @code{-symbol-info-file} Command
32639 @findex -symbol-info-file
32641 @subsubheading Synopsis
32647 Show the file for the symbol.
32649 @subsubheading @value{GDBN} Command
32651 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32652 @samp{gdb_find_file}.
32654 @subsubheading Example
32658 @subheading The @code{-symbol-info-function} Command
32659 @findex -symbol-info-function
32661 @subsubheading Synopsis
32664 -symbol-info-function
32667 Show which function the symbol lives in.
32669 @subsubheading @value{GDBN} Command
32671 @samp{gdb_get_function} in @code{gdbtk}.
32673 @subsubheading Example
32677 @subheading The @code{-symbol-info-line} Command
32678 @findex -symbol-info-line
32680 @subsubheading Synopsis
32686 Show the core addresses of the code for a source line.
32688 @subsubheading @value{GDBN} Command
32690 The corresponding @value{GDBN} command is @samp{info line}.
32691 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32693 @subsubheading Example
32697 @subheading The @code{-symbol-info-symbol} Command
32698 @findex -symbol-info-symbol
32700 @subsubheading Synopsis
32703 -symbol-info-symbol @var{addr}
32706 Describe what symbol is at location @var{addr}.
32708 @subsubheading @value{GDBN} Command
32710 The corresponding @value{GDBN} command is @samp{info symbol}.
32712 @subsubheading Example
32716 @subheading The @code{-symbol-list-functions} Command
32717 @findex -symbol-list-functions
32719 @subsubheading Synopsis
32722 -symbol-list-functions
32725 List the functions in the executable.
32727 @subsubheading @value{GDBN} Command
32729 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32730 @samp{gdb_search} in @code{gdbtk}.
32732 @subsubheading Example
32737 @subheading The @code{-symbol-list-lines} Command
32738 @findex -symbol-list-lines
32740 @subsubheading Synopsis
32743 -symbol-list-lines @var{filename}
32746 Print the list of lines that contain code and their associated program
32747 addresses for the given source filename. The entries are sorted in
32748 ascending PC order.
32750 @subsubheading @value{GDBN} Command
32752 There is no corresponding @value{GDBN} command.
32754 @subsubheading Example
32757 -symbol-list-lines basics.c
32758 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32764 @subheading The @code{-symbol-list-types} Command
32765 @findex -symbol-list-types
32767 @subsubheading Synopsis
32773 List all the type names.
32775 @subsubheading @value{GDBN} Command
32777 The corresponding commands are @samp{info types} in @value{GDBN},
32778 @samp{gdb_search} in @code{gdbtk}.
32780 @subsubheading Example
32784 @subheading The @code{-symbol-list-variables} Command
32785 @findex -symbol-list-variables
32787 @subsubheading Synopsis
32790 -symbol-list-variables
32793 List all the global and static variable names.
32795 @subsubheading @value{GDBN} Command
32797 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32799 @subsubheading Example
32803 @subheading The @code{-symbol-locate} Command
32804 @findex -symbol-locate
32806 @subsubheading Synopsis
32812 @subsubheading @value{GDBN} Command
32814 @samp{gdb_loc} in @code{gdbtk}.
32816 @subsubheading Example
32820 @subheading The @code{-symbol-type} Command
32821 @findex -symbol-type
32823 @subsubheading Synopsis
32826 -symbol-type @var{variable}
32829 Show type of @var{variable}.
32831 @subsubheading @value{GDBN} Command
32833 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32834 @samp{gdb_obj_variable}.
32836 @subsubheading Example
32841 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32842 @node GDB/MI File Commands
32843 @section @sc{gdb/mi} File Commands
32845 This section describes the GDB/MI commands to specify executable file names
32846 and to read in and obtain symbol table information.
32848 @subheading The @code{-file-exec-and-symbols} Command
32849 @findex -file-exec-and-symbols
32851 @subsubheading Synopsis
32854 -file-exec-and-symbols @var{file}
32857 Specify the executable file to be debugged. This file is the one from
32858 which the symbol table is also read. If no file is specified, the
32859 command clears the executable and symbol information. If breakpoints
32860 are set when using this command with no arguments, @value{GDBN} will produce
32861 error messages. Otherwise, no output is produced, except a completion
32864 @subsubheading @value{GDBN} Command
32866 The corresponding @value{GDBN} command is @samp{file}.
32868 @subsubheading Example
32872 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32878 @subheading The @code{-file-exec-file} Command
32879 @findex -file-exec-file
32881 @subsubheading Synopsis
32884 -file-exec-file @var{file}
32887 Specify the executable file to be debugged. Unlike
32888 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32889 from this file. If used without argument, @value{GDBN} clears the information
32890 about the executable file. No output is produced, except a completion
32893 @subsubheading @value{GDBN} Command
32895 The corresponding @value{GDBN} command is @samp{exec-file}.
32897 @subsubheading Example
32901 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32908 @subheading The @code{-file-list-exec-sections} Command
32909 @findex -file-list-exec-sections
32911 @subsubheading Synopsis
32914 -file-list-exec-sections
32917 List the sections of the current executable file.
32919 @subsubheading @value{GDBN} Command
32921 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32922 information as this command. @code{gdbtk} has a corresponding command
32923 @samp{gdb_load_info}.
32925 @subsubheading Example
32930 @subheading The @code{-file-list-exec-source-file} Command
32931 @findex -file-list-exec-source-file
32933 @subsubheading Synopsis
32936 -file-list-exec-source-file
32939 List the line number, the current source file, and the absolute path
32940 to the current source file for the current executable. The macro
32941 information field has a value of @samp{1} or @samp{0} depending on
32942 whether or not the file includes preprocessor macro information.
32944 @subsubheading @value{GDBN} Command
32946 The @value{GDBN} equivalent is @samp{info source}
32948 @subsubheading Example
32952 123-file-list-exec-source-file
32953 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32958 @subheading The @code{-file-list-exec-source-files} Command
32959 @findex -file-list-exec-source-files
32961 @subsubheading Synopsis
32964 -file-list-exec-source-files
32967 List the source files for the current executable.
32969 It will always output both the filename and fullname (absolute file
32970 name) of a source file.
32972 @subsubheading @value{GDBN} Command
32974 The @value{GDBN} equivalent is @samp{info sources}.
32975 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32977 @subsubheading Example
32980 -file-list-exec-source-files
32982 @{file=foo.c,fullname=/home/foo.c@},
32983 @{file=/home/bar.c,fullname=/home/bar.c@},
32984 @{file=gdb_could_not_find_fullpath.c@}]
32988 @subheading The @code{-file-list-shared-libraries} Command
32989 @findex -file-list-shared-libraries
32991 @subsubheading Synopsis
32994 -file-list-shared-libraries [ @var{regexp} ]
32997 List the shared libraries in the program.
32998 With a regular expression @var{regexp}, only those libraries whose
32999 names match @var{regexp} are listed.
33001 @subsubheading @value{GDBN} Command
33003 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33004 have a similar meaning to the @code{=library-loaded} notification.
33005 The @code{ranges} field specifies the multiple segments belonging to this
33006 library. Each range has the following fields:
33010 The address defining the inclusive lower bound of the segment.
33012 The address defining the exclusive upper bound of the segment.
33015 @subsubheading Example
33018 -file-list-exec-source-files
33019 ^done,shared-libraries=[
33020 @{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"@}]@},
33021 @{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"@}]@}]
33027 @subheading The @code{-file-list-symbol-files} Command
33028 @findex -file-list-symbol-files
33030 @subsubheading Synopsis
33033 -file-list-symbol-files
33038 @subsubheading @value{GDBN} Command
33040 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33042 @subsubheading Example
33047 @subheading The @code{-file-symbol-file} Command
33048 @findex -file-symbol-file
33050 @subsubheading Synopsis
33053 -file-symbol-file @var{file}
33056 Read symbol table info from the specified @var{file} argument. When
33057 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33058 produced, except for a completion notification.
33060 @subsubheading @value{GDBN} Command
33062 The corresponding @value{GDBN} command is @samp{symbol-file}.
33064 @subsubheading Example
33068 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33074 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33075 @node GDB/MI Memory Overlay Commands
33076 @section @sc{gdb/mi} Memory Overlay Commands
33078 The memory overlay commands are not implemented.
33080 @c @subheading -overlay-auto
33082 @c @subheading -overlay-list-mapping-state
33084 @c @subheading -overlay-list-overlays
33086 @c @subheading -overlay-map
33088 @c @subheading -overlay-off
33090 @c @subheading -overlay-on
33092 @c @subheading -overlay-unmap
33094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33095 @node GDB/MI Signal Handling Commands
33096 @section @sc{gdb/mi} Signal Handling Commands
33098 Signal handling commands are not implemented.
33100 @c @subheading -signal-handle
33102 @c @subheading -signal-list-handle-actions
33104 @c @subheading -signal-list-signal-types
33108 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33109 @node GDB/MI Target Manipulation
33110 @section @sc{gdb/mi} Target Manipulation Commands
33113 @subheading The @code{-target-attach} Command
33114 @findex -target-attach
33116 @subsubheading Synopsis
33119 -target-attach @var{pid} | @var{gid} | @var{file}
33122 Attach to a process @var{pid} or a file @var{file} outside of
33123 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33124 group, the id previously returned by
33125 @samp{-list-thread-groups --available} must be used.
33127 @subsubheading @value{GDBN} Command
33129 The corresponding @value{GDBN} command is @samp{attach}.
33131 @subsubheading Example
33135 =thread-created,id="1"
33136 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33142 @subheading The @code{-target-compare-sections} Command
33143 @findex -target-compare-sections
33145 @subsubheading Synopsis
33148 -target-compare-sections [ @var{section} ]
33151 Compare data of section @var{section} on target to the exec file.
33152 Without the argument, all sections are compared.
33154 @subsubheading @value{GDBN} Command
33156 The @value{GDBN} equivalent is @samp{compare-sections}.
33158 @subsubheading Example
33163 @subheading The @code{-target-detach} Command
33164 @findex -target-detach
33166 @subsubheading Synopsis
33169 -target-detach [ @var{pid} | @var{gid} ]
33172 Detach from the remote target which normally resumes its execution.
33173 If either @var{pid} or @var{gid} is specified, detaches from either
33174 the specified process, or specified thread group. There's no output.
33176 @subsubheading @value{GDBN} Command
33178 The corresponding @value{GDBN} command is @samp{detach}.
33180 @subsubheading Example
33190 @subheading The @code{-target-disconnect} Command
33191 @findex -target-disconnect
33193 @subsubheading Synopsis
33199 Disconnect from the remote target. There's no output and the target is
33200 generally not resumed.
33202 @subsubheading @value{GDBN} Command
33204 The corresponding @value{GDBN} command is @samp{disconnect}.
33206 @subsubheading Example
33216 @subheading The @code{-target-download} Command
33217 @findex -target-download
33219 @subsubheading Synopsis
33225 Loads the executable onto the remote target.
33226 It prints out an update message every half second, which includes the fields:
33230 The name of the section.
33232 The size of what has been sent so far for that section.
33234 The size of the section.
33236 The total size of what was sent so far (the current and the previous sections).
33238 The size of the overall executable to download.
33242 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33243 @sc{gdb/mi} Output Syntax}).
33245 In addition, it prints the name and size of the sections, as they are
33246 downloaded. These messages include the following fields:
33250 The name of the section.
33252 The size of the section.
33254 The size of the overall executable to download.
33258 At the end, a summary is printed.
33260 @subsubheading @value{GDBN} Command
33262 The corresponding @value{GDBN} command is @samp{load}.
33264 @subsubheading Example
33266 Note: each status message appears on a single line. Here the messages
33267 have been broken down so that they can fit onto a page.
33272 +download,@{section=".text",section-size="6668",total-size="9880"@}
33273 +download,@{section=".text",section-sent="512",section-size="6668",
33274 total-sent="512",total-size="9880"@}
33275 +download,@{section=".text",section-sent="1024",section-size="6668",
33276 total-sent="1024",total-size="9880"@}
33277 +download,@{section=".text",section-sent="1536",section-size="6668",
33278 total-sent="1536",total-size="9880"@}
33279 +download,@{section=".text",section-sent="2048",section-size="6668",
33280 total-sent="2048",total-size="9880"@}
33281 +download,@{section=".text",section-sent="2560",section-size="6668",
33282 total-sent="2560",total-size="9880"@}
33283 +download,@{section=".text",section-sent="3072",section-size="6668",
33284 total-sent="3072",total-size="9880"@}
33285 +download,@{section=".text",section-sent="3584",section-size="6668",
33286 total-sent="3584",total-size="9880"@}
33287 +download,@{section=".text",section-sent="4096",section-size="6668",
33288 total-sent="4096",total-size="9880"@}
33289 +download,@{section=".text",section-sent="4608",section-size="6668",
33290 total-sent="4608",total-size="9880"@}
33291 +download,@{section=".text",section-sent="5120",section-size="6668",
33292 total-sent="5120",total-size="9880"@}
33293 +download,@{section=".text",section-sent="5632",section-size="6668",
33294 total-sent="5632",total-size="9880"@}
33295 +download,@{section=".text",section-sent="6144",section-size="6668",
33296 total-sent="6144",total-size="9880"@}
33297 +download,@{section=".text",section-sent="6656",section-size="6668",
33298 total-sent="6656",total-size="9880"@}
33299 +download,@{section=".init",section-size="28",total-size="9880"@}
33300 +download,@{section=".fini",section-size="28",total-size="9880"@}
33301 +download,@{section=".data",section-size="3156",total-size="9880"@}
33302 +download,@{section=".data",section-sent="512",section-size="3156",
33303 total-sent="7236",total-size="9880"@}
33304 +download,@{section=".data",section-sent="1024",section-size="3156",
33305 total-sent="7748",total-size="9880"@}
33306 +download,@{section=".data",section-sent="1536",section-size="3156",
33307 total-sent="8260",total-size="9880"@}
33308 +download,@{section=".data",section-sent="2048",section-size="3156",
33309 total-sent="8772",total-size="9880"@}
33310 +download,@{section=".data",section-sent="2560",section-size="3156",
33311 total-sent="9284",total-size="9880"@}
33312 +download,@{section=".data",section-sent="3072",section-size="3156",
33313 total-sent="9796",total-size="9880"@}
33314 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33321 @subheading The @code{-target-exec-status} Command
33322 @findex -target-exec-status
33324 @subsubheading Synopsis
33327 -target-exec-status
33330 Provide information on the state of the target (whether it is running or
33331 not, for instance).
33333 @subsubheading @value{GDBN} Command
33335 There's no equivalent @value{GDBN} command.
33337 @subsubheading Example
33341 @subheading The @code{-target-list-available-targets} Command
33342 @findex -target-list-available-targets
33344 @subsubheading Synopsis
33347 -target-list-available-targets
33350 List the possible targets to connect to.
33352 @subsubheading @value{GDBN} Command
33354 The corresponding @value{GDBN} command is @samp{help target}.
33356 @subsubheading Example
33360 @subheading The @code{-target-list-current-targets} Command
33361 @findex -target-list-current-targets
33363 @subsubheading Synopsis
33366 -target-list-current-targets
33369 Describe the current target.
33371 @subsubheading @value{GDBN} Command
33373 The corresponding information is printed by @samp{info file} (among
33376 @subsubheading Example
33380 @subheading The @code{-target-list-parameters} Command
33381 @findex -target-list-parameters
33383 @subsubheading Synopsis
33386 -target-list-parameters
33392 @subsubheading @value{GDBN} Command
33396 @subsubheading Example
33399 @subheading The @code{-target-flash-erase} Command
33400 @findex -target-flash-erase
33402 @subsubheading Synopsis
33405 -target-flash-erase
33408 Erases all known flash memory regions on the target.
33410 The corresponding @value{GDBN} command is @samp{flash-erase}.
33412 The output is a list of flash regions that have been erased, with starting
33413 addresses and memory region sizes.
33417 -target-flash-erase
33418 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33422 @subheading The @code{-target-select} Command
33423 @findex -target-select
33425 @subsubheading Synopsis
33428 -target-select @var{type} @var{parameters @dots{}}
33431 Connect @value{GDBN} to the remote target. This command takes two args:
33435 The type of target, for instance @samp{remote}, etc.
33436 @item @var{parameters}
33437 Device names, host names and the like. @xref{Target Commands, ,
33438 Commands for Managing Targets}, for more details.
33441 The output is a connection notification, followed by the address at
33442 which the target program is, in the following form:
33445 ^connected,addr="@var{address}",func="@var{function name}",
33446 args=[@var{arg list}]
33449 @subsubheading @value{GDBN} Command
33451 The corresponding @value{GDBN} command is @samp{target}.
33453 @subsubheading Example
33457 -target-select remote /dev/ttya
33458 ^connected,addr="0xfe00a300",func="??",args=[]
33462 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33463 @node GDB/MI File Transfer Commands
33464 @section @sc{gdb/mi} File Transfer Commands
33467 @subheading The @code{-target-file-put} Command
33468 @findex -target-file-put
33470 @subsubheading Synopsis
33473 -target-file-put @var{hostfile} @var{targetfile}
33476 Copy file @var{hostfile} from the host system (the machine running
33477 @value{GDBN}) to @var{targetfile} on the target system.
33479 @subsubheading @value{GDBN} Command
33481 The corresponding @value{GDBN} command is @samp{remote put}.
33483 @subsubheading Example
33487 -target-file-put localfile remotefile
33493 @subheading The @code{-target-file-get} Command
33494 @findex -target-file-get
33496 @subsubheading Synopsis
33499 -target-file-get @var{targetfile} @var{hostfile}
33502 Copy file @var{targetfile} from the target system to @var{hostfile}
33503 on the host system.
33505 @subsubheading @value{GDBN} Command
33507 The corresponding @value{GDBN} command is @samp{remote get}.
33509 @subsubheading Example
33513 -target-file-get remotefile localfile
33519 @subheading The @code{-target-file-delete} Command
33520 @findex -target-file-delete
33522 @subsubheading Synopsis
33525 -target-file-delete @var{targetfile}
33528 Delete @var{targetfile} from the target system.
33530 @subsubheading @value{GDBN} Command
33532 The corresponding @value{GDBN} command is @samp{remote delete}.
33534 @subsubheading Example
33538 -target-file-delete remotefile
33544 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33545 @node GDB/MI Ada Exceptions Commands
33546 @section Ada Exceptions @sc{gdb/mi} Commands
33548 @subheading The @code{-info-ada-exceptions} Command
33549 @findex -info-ada-exceptions
33551 @subsubheading Synopsis
33554 -info-ada-exceptions [ @var{regexp}]
33557 List all Ada exceptions defined within the program being debugged.
33558 With a regular expression @var{regexp}, only those exceptions whose
33559 names match @var{regexp} are listed.
33561 @subsubheading @value{GDBN} Command
33563 The corresponding @value{GDBN} command is @samp{info exceptions}.
33565 @subsubheading Result
33567 The result is a table of Ada exceptions. The following columns are
33568 defined for each exception:
33572 The name of the exception.
33575 The address of the exception.
33579 @subsubheading Example
33582 -info-ada-exceptions aint
33583 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33584 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33585 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33586 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33587 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33590 @subheading Catching Ada Exceptions
33592 The commands describing how to ask @value{GDBN} to stop when a program
33593 raises an exception are described at @ref{Ada Exception GDB/MI
33594 Catchpoint Commands}.
33597 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33598 @node GDB/MI Support Commands
33599 @section @sc{gdb/mi} Support Commands
33601 Since new commands and features get regularly added to @sc{gdb/mi},
33602 some commands are available to help front-ends query the debugger
33603 about support for these capabilities. Similarly, it is also possible
33604 to query @value{GDBN} about target support of certain features.
33606 @subheading The @code{-info-gdb-mi-command} Command
33607 @cindex @code{-info-gdb-mi-command}
33608 @findex -info-gdb-mi-command
33610 @subsubheading Synopsis
33613 -info-gdb-mi-command @var{cmd_name}
33616 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33618 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33619 is technically not part of the command name (@pxref{GDB/MI Input
33620 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33621 for ease of use, this command also accepts the form with the leading
33624 @subsubheading @value{GDBN} Command
33626 There is no corresponding @value{GDBN} command.
33628 @subsubheading Result
33630 The result is a tuple. There is currently only one field:
33634 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33635 @code{"false"} otherwise.
33639 @subsubheading Example
33641 Here is an example where the @sc{gdb/mi} command does not exist:
33644 -info-gdb-mi-command unsupported-command
33645 ^done,command=@{exists="false"@}
33649 And here is an example where the @sc{gdb/mi} command is known
33653 -info-gdb-mi-command symbol-list-lines
33654 ^done,command=@{exists="true"@}
33657 @subheading The @code{-list-features} Command
33658 @findex -list-features
33659 @cindex supported @sc{gdb/mi} features, list
33661 Returns a list of particular features of the MI protocol that
33662 this version of gdb implements. A feature can be a command,
33663 or a new field in an output of some command, or even an
33664 important bugfix. While a frontend can sometimes detect presence
33665 of a feature at runtime, it is easier to perform detection at debugger
33668 The command returns a list of strings, with each string naming an
33669 available feature. Each returned string is just a name, it does not
33670 have any internal structure. The list of possible feature names
33676 (gdb) -list-features
33677 ^done,result=["feature1","feature2"]
33680 The current list of features is:
33683 @item frozen-varobjs
33684 Indicates support for the @code{-var-set-frozen} command, as well
33685 as possible presense of the @code{frozen} field in the output
33686 of @code{-varobj-create}.
33687 @item pending-breakpoints
33688 Indicates support for the @option{-f} option to the @code{-break-insert}
33691 Indicates Python scripting support, Python-based
33692 pretty-printing commands, and possible presence of the
33693 @samp{display_hint} field in the output of @code{-var-list-children}
33695 Indicates support for the @code{-thread-info} command.
33696 @item data-read-memory-bytes
33697 Indicates support for the @code{-data-read-memory-bytes} and the
33698 @code{-data-write-memory-bytes} commands.
33699 @item breakpoint-notifications
33700 Indicates that changes to breakpoints and breakpoints created via the
33701 CLI will be announced via async records.
33702 @item ada-task-info
33703 Indicates support for the @code{-ada-task-info} command.
33704 @item language-option
33705 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33706 option (@pxref{Context management}).
33707 @item info-gdb-mi-command
33708 Indicates support for the @code{-info-gdb-mi-command} command.
33709 @item undefined-command-error-code
33710 Indicates support for the "undefined-command" error code in error result
33711 records, produced when trying to execute an undefined @sc{gdb/mi} command
33712 (@pxref{GDB/MI Result Records}).
33713 @item exec-run-start-option
33714 Indicates that the @code{-exec-run} command supports the @option{--start}
33715 option (@pxref{GDB/MI Program Execution}).
33716 @item data-disassemble-a-option
33717 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33718 option (@pxref{GDB/MI Data Manipulation}).
33721 @subheading The @code{-list-target-features} Command
33722 @findex -list-target-features
33724 Returns a list of particular features that are supported by the
33725 target. Those features affect the permitted MI commands, but
33726 unlike the features reported by the @code{-list-features} command, the
33727 features depend on which target GDB is using at the moment. Whenever
33728 a target can change, due to commands such as @code{-target-select},
33729 @code{-target-attach} or @code{-exec-run}, the list of target features
33730 may change, and the frontend should obtain it again.
33734 (gdb) -list-target-features
33735 ^done,result=["async"]
33738 The current list of features is:
33742 Indicates that the target is capable of asynchronous command
33743 execution, which means that @value{GDBN} will accept further commands
33744 while the target is running.
33747 Indicates that the target is capable of reverse execution.
33748 @xref{Reverse Execution}, for more information.
33752 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33753 @node GDB/MI Miscellaneous Commands
33754 @section Miscellaneous @sc{gdb/mi} Commands
33756 @c @subheading -gdb-complete
33758 @subheading The @code{-gdb-exit} Command
33761 @subsubheading Synopsis
33767 Exit @value{GDBN} immediately.
33769 @subsubheading @value{GDBN} Command
33771 Approximately corresponds to @samp{quit}.
33773 @subsubheading Example
33783 @subheading The @code{-exec-abort} Command
33784 @findex -exec-abort
33786 @subsubheading Synopsis
33792 Kill the inferior running program.
33794 @subsubheading @value{GDBN} Command
33796 The corresponding @value{GDBN} command is @samp{kill}.
33798 @subsubheading Example
33803 @subheading The @code{-gdb-set} Command
33806 @subsubheading Synopsis
33812 Set an internal @value{GDBN} variable.
33813 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33815 @subsubheading @value{GDBN} Command
33817 The corresponding @value{GDBN} command is @samp{set}.
33819 @subsubheading Example
33829 @subheading The @code{-gdb-show} Command
33832 @subsubheading Synopsis
33838 Show the current value of a @value{GDBN} variable.
33840 @subsubheading @value{GDBN} Command
33842 The corresponding @value{GDBN} command is @samp{show}.
33844 @subsubheading Example
33853 @c @subheading -gdb-source
33856 @subheading The @code{-gdb-version} Command
33857 @findex -gdb-version
33859 @subsubheading Synopsis
33865 Show version information for @value{GDBN}. Used mostly in testing.
33867 @subsubheading @value{GDBN} Command
33869 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33870 default shows this information when you start an interactive session.
33872 @subsubheading Example
33874 @c This example modifies the actual output from GDB to avoid overfull
33880 ~Copyright 2000 Free Software Foundation, Inc.
33881 ~GDB is free software, covered by the GNU General Public License, and
33882 ~you are welcome to change it and/or distribute copies of it under
33883 ~ certain conditions.
33884 ~Type "show copying" to see the conditions.
33885 ~There is absolutely no warranty for GDB. Type "show warranty" for
33887 ~This GDB was configured as
33888 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33893 @subheading The @code{-list-thread-groups} Command
33894 @findex -list-thread-groups
33896 @subheading Synopsis
33899 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33902 Lists thread groups (@pxref{Thread groups}). When a single thread
33903 group is passed as the argument, lists the children of that group.
33904 When several thread group are passed, lists information about those
33905 thread groups. Without any parameters, lists information about all
33906 top-level thread groups.
33908 Normally, thread groups that are being debugged are reported.
33909 With the @samp{--available} option, @value{GDBN} reports thread groups
33910 available on the target.
33912 The output of this command may have either a @samp{threads} result or
33913 a @samp{groups} result. The @samp{thread} result has a list of tuples
33914 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33915 Information}). The @samp{groups} result has a list of tuples as value,
33916 each tuple describing a thread group. If top-level groups are
33917 requested (that is, no parameter is passed), or when several groups
33918 are passed, the output always has a @samp{groups} result. The format
33919 of the @samp{group} result is described below.
33921 To reduce the number of roundtrips it's possible to list thread groups
33922 together with their children, by passing the @samp{--recurse} option
33923 and the recursion depth. Presently, only recursion depth of 1 is
33924 permitted. If this option is present, then every reported thread group
33925 will also include its children, either as @samp{group} or
33926 @samp{threads} field.
33928 In general, any combination of option and parameters is permitted, with
33929 the following caveats:
33933 When a single thread group is passed, the output will typically
33934 be the @samp{threads} result. Because threads may not contain
33935 anything, the @samp{recurse} option will be ignored.
33938 When the @samp{--available} option is passed, limited information may
33939 be available. In particular, the list of threads of a process might
33940 be inaccessible. Further, specifying specific thread groups might
33941 not give any performance advantage over listing all thread groups.
33942 The frontend should assume that @samp{-list-thread-groups --available}
33943 is always an expensive operation and cache the results.
33947 The @samp{groups} result is a list of tuples, where each tuple may
33948 have the following fields:
33952 Identifier of the thread group. This field is always present.
33953 The identifier is an opaque string; frontends should not try to
33954 convert it to an integer, even though it might look like one.
33957 The type of the thread group. At present, only @samp{process} is a
33961 The target-specific process identifier. This field is only present
33962 for thread groups of type @samp{process} and only if the process exists.
33965 The exit code of this group's last exited thread, formatted in octal.
33966 This field is only present for thread groups of type @samp{process} and
33967 only if the process is not running.
33970 The number of children this thread group has. This field may be
33971 absent for an available thread group.
33974 This field has a list of tuples as value, each tuple describing a
33975 thread. It may be present if the @samp{--recurse} option is
33976 specified, and it's actually possible to obtain the threads.
33979 This field is a list of integers, each identifying a core that one
33980 thread of the group is running on. This field may be absent if
33981 such information is not available.
33984 The name of the executable file that corresponds to this thread group.
33985 The field is only present for thread groups of type @samp{process},
33986 and only if there is a corresponding executable file.
33990 @subheading Example
33994 -list-thread-groups
33995 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33996 -list-thread-groups 17
33997 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33998 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33999 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34000 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34001 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34002 -list-thread-groups --available
34003 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34004 -list-thread-groups --available --recurse 1
34005 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34006 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34007 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34008 -list-thread-groups --available --recurse 1 17 18
34009 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34010 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34011 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34014 @subheading The @code{-info-os} Command
34017 @subsubheading Synopsis
34020 -info-os [ @var{type} ]
34023 If no argument is supplied, the command returns a table of available
34024 operating-system-specific information types. If one of these types is
34025 supplied as an argument @var{type}, then the command returns a table
34026 of data of that type.
34028 The types of information available depend on the target operating
34031 @subsubheading @value{GDBN} Command
34033 The corresponding @value{GDBN} command is @samp{info os}.
34035 @subsubheading Example
34037 When run on a @sc{gnu}/Linux system, the output will look something
34043 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34044 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34045 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34046 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34047 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34049 item=@{col0="files",col1="Listing of all file descriptors",
34050 col2="File descriptors"@},
34051 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34052 col2="Kernel modules"@},
34053 item=@{col0="msg",col1="Listing of all message queues",
34054 col2="Message queues"@},
34055 item=@{col0="processes",col1="Listing of all processes",
34056 col2="Processes"@},
34057 item=@{col0="procgroups",col1="Listing of all process groups",
34058 col2="Process groups"@},
34059 item=@{col0="semaphores",col1="Listing of all semaphores",
34060 col2="Semaphores"@},
34061 item=@{col0="shm",col1="Listing of all shared-memory regions",
34062 col2="Shared-memory regions"@},
34063 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34065 item=@{col0="threads",col1="Listing of all threads",
34069 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34070 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34071 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34072 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34073 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34074 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34075 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34076 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34078 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34079 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34083 (Note that the MI output here includes a @code{"Title"} column that
34084 does not appear in command-line @code{info os}; this column is useful
34085 for MI clients that want to enumerate the types of data, such as in a
34086 popup menu, but is needless clutter on the command line, and
34087 @code{info os} omits it.)
34089 @subheading The @code{-add-inferior} Command
34090 @findex -add-inferior
34092 @subheading Synopsis
34098 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34099 inferior is not associated with any executable. Such association may
34100 be established with the @samp{-file-exec-and-symbols} command
34101 (@pxref{GDB/MI File Commands}). The command response has a single
34102 field, @samp{inferior}, whose value is the identifier of the
34103 thread group corresponding to the new inferior.
34105 @subheading Example
34110 ^done,inferior="i3"
34113 @subheading The @code{-interpreter-exec} Command
34114 @findex -interpreter-exec
34116 @subheading Synopsis
34119 -interpreter-exec @var{interpreter} @var{command}
34121 @anchor{-interpreter-exec}
34123 Execute the specified @var{command} in the given @var{interpreter}.
34125 @subheading @value{GDBN} Command
34127 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34129 @subheading Example
34133 -interpreter-exec console "break main"
34134 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34135 &"During symbol reading, bad structure-type format.\n"
34136 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34141 @subheading The @code{-inferior-tty-set} Command
34142 @findex -inferior-tty-set
34144 @subheading Synopsis
34147 -inferior-tty-set /dev/pts/1
34150 Set terminal for future runs of the program being debugged.
34152 @subheading @value{GDBN} Command
34154 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34156 @subheading Example
34160 -inferior-tty-set /dev/pts/1
34165 @subheading The @code{-inferior-tty-show} Command
34166 @findex -inferior-tty-show
34168 @subheading Synopsis
34174 Show terminal for future runs of program being debugged.
34176 @subheading @value{GDBN} Command
34178 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34180 @subheading Example
34184 -inferior-tty-set /dev/pts/1
34188 ^done,inferior_tty_terminal="/dev/pts/1"
34192 @subheading The @code{-enable-timings} Command
34193 @findex -enable-timings
34195 @subheading Synopsis
34198 -enable-timings [yes | no]
34201 Toggle the printing of the wallclock, user and system times for an MI
34202 command as a field in its output. This command is to help frontend
34203 developers optimize the performance of their code. No argument is
34204 equivalent to @samp{yes}.
34206 @subheading @value{GDBN} Command
34210 @subheading Example
34218 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34219 addr="0x080484ed",func="main",file="myprog.c",
34220 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34222 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34230 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34231 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34232 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34233 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34238 @chapter @value{GDBN} Annotations
34240 This chapter describes annotations in @value{GDBN}. Annotations were
34241 designed to interface @value{GDBN} to graphical user interfaces or other
34242 similar programs which want to interact with @value{GDBN} at a
34243 relatively high level.
34245 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34249 This is Edition @value{EDITION}, @value{DATE}.
34253 * Annotations Overview:: What annotations are; the general syntax.
34254 * Server Prefix:: Issuing a command without affecting user state.
34255 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34256 * Errors:: Annotations for error messages.
34257 * Invalidation:: Some annotations describe things now invalid.
34258 * Annotations for Running::
34259 Whether the program is running, how it stopped, etc.
34260 * Source Annotations:: Annotations describing source code.
34263 @node Annotations Overview
34264 @section What is an Annotation?
34265 @cindex annotations
34267 Annotations start with a newline character, two @samp{control-z}
34268 characters, and the name of the annotation. If there is no additional
34269 information associated with this annotation, the name of the annotation
34270 is followed immediately by a newline. If there is additional
34271 information, the name of the annotation is followed by a space, the
34272 additional information, and a newline. The additional information
34273 cannot contain newline characters.
34275 Any output not beginning with a newline and two @samp{control-z}
34276 characters denotes literal output from @value{GDBN}. Currently there is
34277 no need for @value{GDBN} to output a newline followed by two
34278 @samp{control-z} characters, but if there was such a need, the
34279 annotations could be extended with an @samp{escape} annotation which
34280 means those three characters as output.
34282 The annotation @var{level}, which is specified using the
34283 @option{--annotate} command line option (@pxref{Mode Options}), controls
34284 how much information @value{GDBN} prints together with its prompt,
34285 values of expressions, source lines, and other types of output. Level 0
34286 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34287 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34288 for programs that control @value{GDBN}, and level 2 annotations have
34289 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34290 Interface, annotate, GDB's Obsolete Annotations}).
34293 @kindex set annotate
34294 @item set annotate @var{level}
34295 The @value{GDBN} command @code{set annotate} sets the level of
34296 annotations to the specified @var{level}.
34298 @item show annotate
34299 @kindex show annotate
34300 Show the current annotation level.
34303 This chapter describes level 3 annotations.
34305 A simple example of starting up @value{GDBN} with annotations is:
34308 $ @kbd{gdb --annotate=3}
34310 Copyright 2003 Free Software Foundation, Inc.
34311 GDB is free software, covered by the GNU General Public License,
34312 and you are welcome to change it and/or distribute copies of it
34313 under certain conditions.
34314 Type "show copying" to see the conditions.
34315 There is absolutely no warranty for GDB. Type "show warranty"
34317 This GDB was configured as "i386-pc-linux-gnu"
34328 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34329 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34330 denotes a @samp{control-z} character) are annotations; the rest is
34331 output from @value{GDBN}.
34333 @node Server Prefix
34334 @section The Server Prefix
34335 @cindex server prefix
34337 If you prefix a command with @samp{server } then it will not affect
34338 the command history, nor will it affect @value{GDBN}'s notion of which
34339 command to repeat if @key{RET} is pressed on a line by itself. This
34340 means that commands can be run behind a user's back by a front-end in
34341 a transparent manner.
34343 The @code{server } prefix does not affect the recording of values into
34344 the value history; to print a value without recording it into the
34345 value history, use the @code{output} command instead of the
34346 @code{print} command.
34348 Using this prefix also disables confirmation requests
34349 (@pxref{confirmation requests}).
34352 @section Annotation for @value{GDBN} Input
34354 @cindex annotations for prompts
34355 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34356 to know when to send output, when the output from a given command is
34359 Different kinds of input each have a different @dfn{input type}. Each
34360 input type has three annotations: a @code{pre-} annotation, which
34361 denotes the beginning of any prompt which is being output, a plain
34362 annotation, which denotes the end of the prompt, and then a @code{post-}
34363 annotation which denotes the end of any echo which may (or may not) be
34364 associated with the input. For example, the @code{prompt} input type
34365 features the following annotations:
34373 The input types are
34376 @findex pre-prompt annotation
34377 @findex prompt annotation
34378 @findex post-prompt annotation
34380 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34382 @findex pre-commands annotation
34383 @findex commands annotation
34384 @findex post-commands annotation
34386 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34387 command. The annotations are repeated for each command which is input.
34389 @findex pre-overload-choice annotation
34390 @findex overload-choice annotation
34391 @findex post-overload-choice annotation
34392 @item overload-choice
34393 When @value{GDBN} wants the user to select between various overloaded functions.
34395 @findex pre-query annotation
34396 @findex query annotation
34397 @findex post-query annotation
34399 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34401 @findex pre-prompt-for-continue annotation
34402 @findex prompt-for-continue annotation
34403 @findex post-prompt-for-continue annotation
34404 @item prompt-for-continue
34405 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34406 expect this to work well; instead use @code{set height 0} to disable
34407 prompting. This is because the counting of lines is buggy in the
34408 presence of annotations.
34413 @cindex annotations for errors, warnings and interrupts
34415 @findex quit annotation
34420 This annotation occurs right before @value{GDBN} responds to an interrupt.
34422 @findex error annotation
34427 This annotation occurs right before @value{GDBN} responds to an error.
34429 Quit and error annotations indicate that any annotations which @value{GDBN} was
34430 in the middle of may end abruptly. For example, if a
34431 @code{value-history-begin} annotation is followed by a @code{error}, one
34432 cannot expect to receive the matching @code{value-history-end}. One
34433 cannot expect not to receive it either, however; an error annotation
34434 does not necessarily mean that @value{GDBN} is immediately returning all the way
34437 @findex error-begin annotation
34438 A quit or error annotation may be preceded by
34444 Any output between that and the quit or error annotation is the error
34447 Warning messages are not yet annotated.
34448 @c If we want to change that, need to fix warning(), type_error(),
34449 @c range_error(), and possibly other places.
34452 @section Invalidation Notices
34454 @cindex annotations for invalidation messages
34455 The following annotations say that certain pieces of state may have
34459 @findex frames-invalid annotation
34460 @item ^Z^Zframes-invalid
34462 The frames (for example, output from the @code{backtrace} command) may
34465 @findex breakpoints-invalid annotation
34466 @item ^Z^Zbreakpoints-invalid
34468 The breakpoints may have changed. For example, the user just added or
34469 deleted a breakpoint.
34472 @node Annotations for Running
34473 @section Running the Program
34474 @cindex annotations for running programs
34476 @findex starting annotation
34477 @findex stopping annotation
34478 When the program starts executing due to a @value{GDBN} command such as
34479 @code{step} or @code{continue},
34485 is output. When the program stops,
34491 is output. Before the @code{stopped} annotation, a variety of
34492 annotations describe how the program stopped.
34495 @findex exited annotation
34496 @item ^Z^Zexited @var{exit-status}
34497 The program exited, and @var{exit-status} is the exit status (zero for
34498 successful exit, otherwise nonzero).
34500 @findex signalled annotation
34501 @findex signal-name annotation
34502 @findex signal-name-end annotation
34503 @findex signal-string annotation
34504 @findex signal-string-end annotation
34505 @item ^Z^Zsignalled
34506 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34507 annotation continues:
34513 ^Z^Zsignal-name-end
34517 ^Z^Zsignal-string-end
34522 where @var{name} is the name of the signal, such as @code{SIGILL} or
34523 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34524 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34525 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34526 user's benefit and have no particular format.
34528 @findex signal annotation
34530 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34531 just saying that the program received the signal, not that it was
34532 terminated with it.
34534 @findex breakpoint annotation
34535 @item ^Z^Zbreakpoint @var{number}
34536 The program hit breakpoint number @var{number}.
34538 @findex watchpoint annotation
34539 @item ^Z^Zwatchpoint @var{number}
34540 The program hit watchpoint number @var{number}.
34543 @node Source Annotations
34544 @section Displaying Source
34545 @cindex annotations for source display
34547 @findex source annotation
34548 The following annotation is used instead of displaying source code:
34551 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34554 where @var{filename} is an absolute file name indicating which source
34555 file, @var{line} is the line number within that file (where 1 is the
34556 first line in the file), @var{character} is the character position
34557 within the file (where 0 is the first character in the file) (for most
34558 debug formats this will necessarily point to the beginning of a line),
34559 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34560 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34561 @var{addr} is the address in the target program associated with the
34562 source which is being displayed. The @var{addr} is in the form @samp{0x}
34563 followed by one or more lowercase hex digits (note that this does not
34564 depend on the language).
34566 @node JIT Interface
34567 @chapter JIT Compilation Interface
34568 @cindex just-in-time compilation
34569 @cindex JIT compilation interface
34571 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34572 interface. A JIT compiler is a program or library that generates native
34573 executable code at runtime and executes it, usually in order to achieve good
34574 performance while maintaining platform independence.
34576 Programs that use JIT compilation are normally difficult to debug because
34577 portions of their code are generated at runtime, instead of being loaded from
34578 object files, which is where @value{GDBN} normally finds the program's symbols
34579 and debug information. In order to debug programs that use JIT compilation,
34580 @value{GDBN} has an interface that allows the program to register in-memory
34581 symbol files with @value{GDBN} at runtime.
34583 If you are using @value{GDBN} to debug a program that uses this interface, then
34584 it should work transparently so long as you have not stripped the binary. If
34585 you are developing a JIT compiler, then the interface is documented in the rest
34586 of this chapter. At this time, the only known client of this interface is the
34589 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34590 JIT compiler communicates with @value{GDBN} by writing data into a global
34591 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34592 attaches, it reads a linked list of symbol files from the global variable to
34593 find existing code, and puts a breakpoint in the function so that it can find
34594 out about additional code.
34597 * Declarations:: Relevant C struct declarations
34598 * Registering Code:: Steps to register code
34599 * Unregistering Code:: Steps to unregister code
34600 * Custom Debug Info:: Emit debug information in a custom format
34604 @section JIT Declarations
34606 These are the relevant struct declarations that a C program should include to
34607 implement the interface:
34617 struct jit_code_entry
34619 struct jit_code_entry *next_entry;
34620 struct jit_code_entry *prev_entry;
34621 const char *symfile_addr;
34622 uint64_t symfile_size;
34625 struct jit_descriptor
34628 /* This type should be jit_actions_t, but we use uint32_t
34629 to be explicit about the bitwidth. */
34630 uint32_t action_flag;
34631 struct jit_code_entry *relevant_entry;
34632 struct jit_code_entry *first_entry;
34635 /* GDB puts a breakpoint in this function. */
34636 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34638 /* Make sure to specify the version statically, because the
34639 debugger may check the version before we can set it. */
34640 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34643 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34644 modifications to this global data properly, which can easily be done by putting
34645 a global mutex around modifications to these structures.
34647 @node Registering Code
34648 @section Registering Code
34650 To register code with @value{GDBN}, the JIT should follow this protocol:
34654 Generate an object file in memory with symbols and other desired debug
34655 information. The file must include the virtual addresses of the sections.
34658 Create a code entry for the file, which gives the start and size of the symbol
34662 Add it to the linked list in the JIT descriptor.
34665 Point the relevant_entry field of the descriptor at the entry.
34668 Set @code{action_flag} to @code{JIT_REGISTER} and call
34669 @code{__jit_debug_register_code}.
34672 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34673 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34674 new code. However, the linked list must still be maintained in order to allow
34675 @value{GDBN} to attach to a running process and still find the symbol files.
34677 @node Unregistering Code
34678 @section Unregistering Code
34680 If code is freed, then the JIT should use the following protocol:
34684 Remove the code entry corresponding to the code from the linked list.
34687 Point the @code{relevant_entry} field of the descriptor at the code entry.
34690 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34691 @code{__jit_debug_register_code}.
34694 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34695 and the JIT will leak the memory used for the associated symbol files.
34697 @node Custom Debug Info
34698 @section Custom Debug Info
34699 @cindex custom JIT debug info
34700 @cindex JIT debug info reader
34702 Generating debug information in platform-native file formats (like ELF
34703 or COFF) may be an overkill for JIT compilers; especially if all the
34704 debug info is used for is displaying a meaningful backtrace. The
34705 issue can be resolved by having the JIT writers decide on a debug info
34706 format and also provide a reader that parses the debug info generated
34707 by the JIT compiler. This section gives a brief overview on writing
34708 such a parser. More specific details can be found in the source file
34709 @file{gdb/jit-reader.in}, which is also installed as a header at
34710 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34712 The reader is implemented as a shared object (so this functionality is
34713 not available on platforms which don't allow loading shared objects at
34714 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34715 @code{jit-reader-unload} are provided, to be used to load and unload
34716 the readers from a preconfigured directory. Once loaded, the shared
34717 object is used the parse the debug information emitted by the JIT
34721 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34722 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34725 @node Using JIT Debug Info Readers
34726 @subsection Using JIT Debug Info Readers
34727 @kindex jit-reader-load
34728 @kindex jit-reader-unload
34730 Readers can be loaded and unloaded using the @code{jit-reader-load}
34731 and @code{jit-reader-unload} commands.
34734 @item jit-reader-load @var{reader}
34735 Load the JIT reader named @var{reader}, which is a shared
34736 object specified as either an absolute or a relative file name. In
34737 the latter case, @value{GDBN} will try to load the reader from a
34738 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34739 system (here @var{libdir} is the system library directory, often
34740 @file{/usr/local/lib}).
34742 Only one reader can be active at a time; trying to load a second
34743 reader when one is already loaded will result in @value{GDBN}
34744 reporting an error. A new JIT reader can be loaded by first unloading
34745 the current one using @code{jit-reader-unload} and then invoking
34746 @code{jit-reader-load}.
34748 @item jit-reader-unload
34749 Unload the currently loaded JIT reader.
34753 @node Writing JIT Debug Info Readers
34754 @subsection Writing JIT Debug Info Readers
34755 @cindex writing JIT debug info readers
34757 As mentioned, a reader is essentially a shared object conforming to a
34758 certain ABI. This ABI is described in @file{jit-reader.h}.
34760 @file{jit-reader.h} defines the structures, macros and functions
34761 required to write a reader. It is installed (along with
34762 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34763 the system include directory.
34765 Readers need to be released under a GPL compatible license. A reader
34766 can be declared as released under such a license by placing the macro
34767 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34769 The entry point for readers is the symbol @code{gdb_init_reader},
34770 which is expected to be a function with the prototype
34772 @findex gdb_init_reader
34774 extern struct gdb_reader_funcs *gdb_init_reader (void);
34777 @cindex @code{struct gdb_reader_funcs}
34779 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34780 functions. These functions are executed to read the debug info
34781 generated by the JIT compiler (@code{read}), to unwind stack frames
34782 (@code{unwind}) and to create canonical frame IDs
34783 (@code{get_Frame_id}). It also has a callback that is called when the
34784 reader is being unloaded (@code{destroy}). The struct looks like this
34787 struct gdb_reader_funcs
34789 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34790 int reader_version;
34792 /* For use by the reader. */
34795 gdb_read_debug_info *read;
34796 gdb_unwind_frame *unwind;
34797 gdb_get_frame_id *get_frame_id;
34798 gdb_destroy_reader *destroy;
34802 @cindex @code{struct gdb_symbol_callbacks}
34803 @cindex @code{struct gdb_unwind_callbacks}
34805 The callbacks are provided with another set of callbacks by
34806 @value{GDBN} to do their job. For @code{read}, these callbacks are
34807 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34808 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34809 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34810 files and new symbol tables inside those object files. @code{struct
34811 gdb_unwind_callbacks} has callbacks to read registers off the current
34812 frame and to write out the values of the registers in the previous
34813 frame. Both have a callback (@code{target_read}) to read bytes off the
34814 target's address space.
34816 @node In-Process Agent
34817 @chapter In-Process Agent
34818 @cindex debugging agent
34819 The traditional debugging model is conceptually low-speed, but works fine,
34820 because most bugs can be reproduced in debugging-mode execution. However,
34821 as multi-core or many-core processors are becoming mainstream, and
34822 multi-threaded programs become more and more popular, there should be more
34823 and more bugs that only manifest themselves at normal-mode execution, for
34824 example, thread races, because debugger's interference with the program's
34825 timing may conceal the bugs. On the other hand, in some applications,
34826 it is not feasible for the debugger to interrupt the program's execution
34827 long enough for the developer to learn anything helpful about its behavior.
34828 If the program's correctness depends on its real-time behavior, delays
34829 introduced by a debugger might cause the program to fail, even when the
34830 code itself is correct. It is useful to be able to observe the program's
34831 behavior without interrupting it.
34833 Therefore, traditional debugging model is too intrusive to reproduce
34834 some bugs. In order to reduce the interference with the program, we can
34835 reduce the number of operations performed by debugger. The
34836 @dfn{In-Process Agent}, a shared library, is running within the same
34837 process with inferior, and is able to perform some debugging operations
34838 itself. As a result, debugger is only involved when necessary, and
34839 performance of debugging can be improved accordingly. Note that
34840 interference with program can be reduced but can't be removed completely,
34841 because the in-process agent will still stop or slow down the program.
34843 The in-process agent can interpret and execute Agent Expressions
34844 (@pxref{Agent Expressions}) during performing debugging operations. The
34845 agent expressions can be used for different purposes, such as collecting
34846 data in tracepoints, and condition evaluation in breakpoints.
34848 @anchor{Control Agent}
34849 You can control whether the in-process agent is used as an aid for
34850 debugging with the following commands:
34853 @kindex set agent on
34855 Causes the in-process agent to perform some operations on behalf of the
34856 debugger. Just which operations requested by the user will be done
34857 by the in-process agent depends on the its capabilities. For example,
34858 if you request to evaluate breakpoint conditions in the in-process agent,
34859 and the in-process agent has such capability as well, then breakpoint
34860 conditions will be evaluated in the in-process agent.
34862 @kindex set agent off
34863 @item set agent off
34864 Disables execution of debugging operations by the in-process agent. All
34865 of the operations will be performed by @value{GDBN}.
34869 Display the current setting of execution of debugging operations by
34870 the in-process agent.
34874 * In-Process Agent Protocol::
34877 @node In-Process Agent Protocol
34878 @section In-Process Agent Protocol
34879 @cindex in-process agent protocol
34881 The in-process agent is able to communicate with both @value{GDBN} and
34882 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34883 used for communications between @value{GDBN} or GDBserver and the IPA.
34884 In general, @value{GDBN} or GDBserver sends commands
34885 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34886 in-process agent replies back with the return result of the command, or
34887 some other information. The data sent to in-process agent is composed
34888 of primitive data types, such as 4-byte or 8-byte type, and composite
34889 types, which are called objects (@pxref{IPA Protocol Objects}).
34892 * IPA Protocol Objects::
34893 * IPA Protocol Commands::
34896 @node IPA Protocol Objects
34897 @subsection IPA Protocol Objects
34898 @cindex ipa protocol objects
34900 The commands sent to and results received from agent may contain some
34901 complex data types called @dfn{objects}.
34903 The in-process agent is running on the same machine with @value{GDBN}
34904 or GDBserver, so it doesn't have to handle as much differences between
34905 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34906 However, there are still some differences of two ends in two processes:
34910 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34911 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34913 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34914 GDBserver is compiled with one, and in-process agent is compiled with
34918 Here are the IPA Protocol Objects:
34922 agent expression object. It represents an agent expression
34923 (@pxref{Agent Expressions}).
34924 @anchor{agent expression object}
34926 tracepoint action object. It represents a tracepoint action
34927 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34928 memory, static trace data and to evaluate expression.
34929 @anchor{tracepoint action object}
34931 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34932 @anchor{tracepoint object}
34936 The following table describes important attributes of each IPA protocol
34939 @multitable @columnfractions .30 .20 .50
34940 @headitem Name @tab Size @tab Description
34941 @item @emph{agent expression object} @tab @tab
34942 @item length @tab 4 @tab length of bytes code
34943 @item byte code @tab @var{length} @tab contents of byte code
34944 @item @emph{tracepoint action for collecting memory} @tab @tab
34945 @item 'M' @tab 1 @tab type of tracepoint action
34946 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34947 address of the lowest byte to collect, otherwise @var{addr} is the offset
34948 of @var{basereg} for memory collecting.
34949 @item len @tab 8 @tab length of memory for collecting
34950 @item basereg @tab 4 @tab the register number containing the starting
34951 memory address for collecting.
34952 @item @emph{tracepoint action for collecting registers} @tab @tab
34953 @item 'R' @tab 1 @tab type of tracepoint action
34954 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34955 @item 'L' @tab 1 @tab type of tracepoint action
34956 @item @emph{tracepoint action for expression evaluation} @tab @tab
34957 @item 'X' @tab 1 @tab type of tracepoint action
34958 @item agent expression @tab length of @tab @ref{agent expression object}
34959 @item @emph{tracepoint object} @tab @tab
34960 @item number @tab 4 @tab number of tracepoint
34961 @item address @tab 8 @tab address of tracepoint inserted on
34962 @item type @tab 4 @tab type of tracepoint
34963 @item enabled @tab 1 @tab enable or disable of tracepoint
34964 @item step_count @tab 8 @tab step
34965 @item pass_count @tab 8 @tab pass
34966 @item numactions @tab 4 @tab number of tracepoint actions
34967 @item hit count @tab 8 @tab hit count
34968 @item trace frame usage @tab 8 @tab trace frame usage
34969 @item compiled_cond @tab 8 @tab compiled condition
34970 @item orig_size @tab 8 @tab orig size
34971 @item condition @tab 4 if condition is NULL otherwise length of
34972 @ref{agent expression object}
34973 @tab zero if condition is NULL, otherwise is
34974 @ref{agent expression object}
34975 @item actions @tab variable
34976 @tab numactions number of @ref{tracepoint action object}
34979 @node IPA Protocol Commands
34980 @subsection IPA Protocol Commands
34981 @cindex ipa protocol commands
34983 The spaces in each command are delimiters to ease reading this commands
34984 specification. They don't exist in real commands.
34988 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34989 Installs a new fast tracepoint described by @var{tracepoint_object}
34990 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34991 head of @dfn{jumppad}, which is used to jump to data collection routine
34996 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34997 @var{target_address} is address of tracepoint in the inferior.
34998 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34999 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35000 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35001 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35008 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35009 is about to kill inferiors.
35017 @item probe_marker_at:@var{address}
35018 Asks in-process agent to probe the marker at @var{address}.
35025 @item unprobe_marker_at:@var{address}
35026 Asks in-process agent to unprobe the marker at @var{address}.
35030 @chapter Reporting Bugs in @value{GDBN}
35031 @cindex bugs in @value{GDBN}
35032 @cindex reporting bugs in @value{GDBN}
35034 Your bug reports play an essential role in making @value{GDBN} reliable.
35036 Reporting a bug may help you by bringing a solution to your problem, or it
35037 may not. But in any case the principal function of a bug report is to help
35038 the entire community by making the next version of @value{GDBN} work better. Bug
35039 reports are your contribution to the maintenance of @value{GDBN}.
35041 In order for a bug report to serve its purpose, you must include the
35042 information that enables us to fix the bug.
35045 * Bug Criteria:: Have you found a bug?
35046 * Bug Reporting:: How to report bugs
35050 @section Have You Found a Bug?
35051 @cindex bug criteria
35053 If you are not sure whether you have found a bug, here are some guidelines:
35056 @cindex fatal signal
35057 @cindex debugger crash
35058 @cindex crash of debugger
35060 If the debugger gets a fatal signal, for any input whatever, that is a
35061 @value{GDBN} bug. Reliable debuggers never crash.
35063 @cindex error on valid input
35065 If @value{GDBN} produces an error message for valid input, that is a
35066 bug. (Note that if you're cross debugging, the problem may also be
35067 somewhere in the connection to the target.)
35069 @cindex invalid input
35071 If @value{GDBN} does not produce an error message for invalid input,
35072 that is a bug. However, you should note that your idea of
35073 ``invalid input'' might be our idea of ``an extension'' or ``support
35074 for traditional practice''.
35077 If you are an experienced user of debugging tools, your suggestions
35078 for improvement of @value{GDBN} are welcome in any case.
35081 @node Bug Reporting
35082 @section How to Report Bugs
35083 @cindex bug reports
35084 @cindex @value{GDBN} bugs, reporting
35086 A number of companies and individuals offer support for @sc{gnu} products.
35087 If you obtained @value{GDBN} from a support organization, we recommend you
35088 contact that organization first.
35090 You can find contact information for many support companies and
35091 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35093 @c should add a web page ref...
35096 @ifset BUGURL_DEFAULT
35097 In any event, we also recommend that you submit bug reports for
35098 @value{GDBN}. The preferred method is to submit them directly using
35099 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35100 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35103 @strong{Do not send bug reports to @samp{info-gdb}, or to
35104 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35105 not want to receive bug reports. Those that do have arranged to receive
35108 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35109 serves as a repeater. The mailing list and the newsgroup carry exactly
35110 the same messages. Often people think of posting bug reports to the
35111 newsgroup instead of mailing them. This appears to work, but it has one
35112 problem which can be crucial: a newsgroup posting often lacks a mail
35113 path back to the sender. Thus, if we need to ask for more information,
35114 we may be unable to reach you. For this reason, it is better to send
35115 bug reports to the mailing list.
35117 @ifclear BUGURL_DEFAULT
35118 In any event, we also recommend that you submit bug reports for
35119 @value{GDBN} to @value{BUGURL}.
35123 The fundamental principle of reporting bugs usefully is this:
35124 @strong{report all the facts}. If you are not sure whether to state a
35125 fact or leave it out, state it!
35127 Often people omit facts because they think they know what causes the
35128 problem and assume that some details do not matter. Thus, you might
35129 assume that the name of the variable you use in an example does not matter.
35130 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35131 stray memory reference which happens to fetch from the location where that
35132 name is stored in memory; perhaps, if the name were different, the contents
35133 of that location would fool the debugger into doing the right thing despite
35134 the bug. Play it safe and give a specific, complete example. That is the
35135 easiest thing for you to do, and the most helpful.
35137 Keep in mind that the purpose of a bug report is to enable us to fix the
35138 bug. It may be that the bug has been reported previously, but neither
35139 you nor we can know that unless your bug report is complete and
35142 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35143 bell?'' Those bug reports are useless, and we urge everyone to
35144 @emph{refuse to respond to them} except to chide the sender to report
35147 To enable us to fix the bug, you should include all these things:
35151 The version of @value{GDBN}. @value{GDBN} announces it if you start
35152 with no arguments; you can also print it at any time using @code{show
35155 Without this, we will not know whether there is any point in looking for
35156 the bug in the current version of @value{GDBN}.
35159 The type of machine you are using, and the operating system name and
35163 The details of the @value{GDBN} build-time configuration.
35164 @value{GDBN} shows these details if you invoke it with the
35165 @option{--configuration} command-line option, or if you type
35166 @code{show configuration} at @value{GDBN}'s prompt.
35169 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35170 ``@value{GCC}--2.8.1''.
35173 What compiler (and its version) was used to compile the program you are
35174 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35175 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35176 to get this information; for other compilers, see the documentation for
35180 The command arguments you gave the compiler to compile your example and
35181 observe the bug. For example, did you use @samp{-O}? To guarantee
35182 you will not omit something important, list them all. A copy of the
35183 Makefile (or the output from make) is sufficient.
35185 If we were to try to guess the arguments, we would probably guess wrong
35186 and then we might not encounter the bug.
35189 A complete input script, and all necessary source files, that will
35193 A description of what behavior you observe that you believe is
35194 incorrect. For example, ``It gets a fatal signal.''
35196 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35197 will certainly notice it. But if the bug is incorrect output, we might
35198 not notice unless it is glaringly wrong. You might as well not give us
35199 a chance to make a mistake.
35201 Even if the problem you experience is a fatal signal, you should still
35202 say so explicitly. Suppose something strange is going on, such as, your
35203 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35204 the C library on your system. (This has happened!) Your copy might
35205 crash and ours would not. If you told us to expect a crash, then when
35206 ours fails to crash, we would know that the bug was not happening for
35207 us. If you had not told us to expect a crash, then we would not be able
35208 to draw any conclusion from our observations.
35211 @cindex recording a session script
35212 To collect all this information, you can use a session recording program
35213 such as @command{script}, which is available on many Unix systems.
35214 Just run your @value{GDBN} session inside @command{script} and then
35215 include the @file{typescript} file with your bug report.
35217 Another way to record a @value{GDBN} session is to run @value{GDBN}
35218 inside Emacs and then save the entire buffer to a file.
35221 If you wish to suggest changes to the @value{GDBN} source, send us context
35222 diffs. If you even discuss something in the @value{GDBN} source, refer to
35223 it by context, not by line number.
35225 The line numbers in our development sources will not match those in your
35226 sources. Your line numbers would convey no useful information to us.
35230 Here are some things that are not necessary:
35234 A description of the envelope of the bug.
35236 Often people who encounter a bug spend a lot of time investigating
35237 which changes to the input file will make the bug go away and which
35238 changes will not affect it.
35240 This is often time consuming and not very useful, because the way we
35241 will find the bug is by running a single example under the debugger
35242 with breakpoints, not by pure deduction from a series of examples.
35243 We recommend that you save your time for something else.
35245 Of course, if you can find a simpler example to report @emph{instead}
35246 of the original one, that is a convenience for us. Errors in the
35247 output will be easier to spot, running under the debugger will take
35248 less time, and so on.
35250 However, simplification is not vital; if you do not want to do this,
35251 report the bug anyway and send us the entire test case you used.
35254 A patch for the bug.
35256 A patch for the bug does help us if it is a good one. But do not omit
35257 the necessary information, such as the test case, on the assumption that
35258 a patch is all we need. We might see problems with your patch and decide
35259 to fix the problem another way, or we might not understand it at all.
35261 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35262 construct an example that will make the program follow a certain path
35263 through the code. If you do not send us the example, we will not be able
35264 to construct one, so we will not be able to verify that the bug is fixed.
35266 And if we cannot understand what bug you are trying to fix, or why your
35267 patch should be an improvement, we will not install it. A test case will
35268 help us to understand.
35271 A guess about what the bug is or what it depends on.
35273 Such guesses are usually wrong. Even we cannot guess right about such
35274 things without first using the debugger to find the facts.
35277 @c The readline documentation is distributed with the readline code
35278 @c and consists of the two following files:
35281 @c Use -I with makeinfo to point to the appropriate directory,
35282 @c environment var TEXINPUTS with TeX.
35283 @ifclear SYSTEM_READLINE
35284 @include rluser.texi
35285 @include hsuser.texi
35289 @appendix In Memoriam
35291 The @value{GDBN} project mourns the loss of the following long-time
35296 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35297 to Free Software in general. Outside of @value{GDBN}, he was known in
35298 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35300 @item Michael Snyder
35301 Michael was one of the Global Maintainers of the @value{GDBN} project,
35302 with contributions recorded as early as 1996, until 2011. In addition
35303 to his day to day participation, he was a large driving force behind
35304 adding Reverse Debugging to @value{GDBN}.
35307 Beyond their technical contributions to the project, they were also
35308 enjoyable members of the Free Software Community. We will miss them.
35310 @node Formatting Documentation
35311 @appendix Formatting Documentation
35313 @cindex @value{GDBN} reference card
35314 @cindex reference card
35315 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35316 for printing with PostScript or Ghostscript, in the @file{gdb}
35317 subdirectory of the main source directory@footnote{In
35318 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35319 release.}. If you can use PostScript or Ghostscript with your printer,
35320 you can print the reference card immediately with @file{refcard.ps}.
35322 The release also includes the source for the reference card. You
35323 can format it, using @TeX{}, by typing:
35329 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35330 mode on US ``letter'' size paper;
35331 that is, on a sheet 11 inches wide by 8.5 inches
35332 high. You will need to specify this form of printing as an option to
35333 your @sc{dvi} output program.
35335 @cindex documentation
35337 All the documentation for @value{GDBN} comes as part of the machine-readable
35338 distribution. The documentation is written in Texinfo format, which is
35339 a documentation system that uses a single source file to produce both
35340 on-line information and a printed manual. You can use one of the Info
35341 formatting commands to create the on-line version of the documentation
35342 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35344 @value{GDBN} includes an already formatted copy of the on-line Info
35345 version of this manual in the @file{gdb} subdirectory. The main Info
35346 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35347 subordinate files matching @samp{gdb.info*} in the same directory. If
35348 necessary, you can print out these files, or read them with any editor;
35349 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35350 Emacs or the standalone @code{info} program, available as part of the
35351 @sc{gnu} Texinfo distribution.
35353 If you want to format these Info files yourself, you need one of the
35354 Info formatting programs, such as @code{texinfo-format-buffer} or
35357 If you have @code{makeinfo} installed, and are in the top level
35358 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35359 version @value{GDBVN}), you can make the Info file by typing:
35366 If you want to typeset and print copies of this manual, you need @TeX{},
35367 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35368 Texinfo definitions file.
35370 @TeX{} is a typesetting program; it does not print files directly, but
35371 produces output files called @sc{dvi} files. To print a typeset
35372 document, you need a program to print @sc{dvi} files. If your system
35373 has @TeX{} installed, chances are it has such a program. The precise
35374 command to use depends on your system; @kbd{lpr -d} is common; another
35375 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35376 require a file name without any extension or a @samp{.dvi} extension.
35378 @TeX{} also requires a macro definitions file called
35379 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35380 written in Texinfo format. On its own, @TeX{} cannot either read or
35381 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35382 and is located in the @file{gdb-@var{version-number}/texinfo}
35385 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35386 typeset and print this manual. First switch to the @file{gdb}
35387 subdirectory of the main source directory (for example, to
35388 @file{gdb-@value{GDBVN}/gdb}) and type:
35394 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35396 @node Installing GDB
35397 @appendix Installing @value{GDBN}
35398 @cindex installation
35401 * Requirements:: Requirements for building @value{GDBN}
35402 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35403 * Separate Objdir:: Compiling @value{GDBN} in another directory
35404 * Config Names:: Specifying names for hosts and targets
35405 * Configure Options:: Summary of options for configure
35406 * System-wide configuration:: Having a system-wide init file
35410 @section Requirements for Building @value{GDBN}
35411 @cindex building @value{GDBN}, requirements for
35413 Building @value{GDBN} requires various tools and packages to be available.
35414 Other packages will be used only if they are found.
35416 @heading Tools/Packages Necessary for Building @value{GDBN}
35418 @item C@t{++}11 compiler
35419 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35420 recent C@t{++}11 compiler, e.g.@: GCC.
35423 @value{GDBN}'s build system relies on features only found in the GNU
35424 make program. Other variants of @code{make} will not work.
35427 @heading Tools/Packages Optional for Building @value{GDBN}
35431 @value{GDBN} can use the Expat XML parsing library. This library may be
35432 included with your operating system distribution; if it is not, you
35433 can get the latest version from @url{http://expat.sourceforge.net}.
35434 The @file{configure} script will search for this library in several
35435 standard locations; if it is installed in an unusual path, you can
35436 use the @option{--with-libexpat-prefix} option to specify its location.
35442 Remote protocol memory maps (@pxref{Memory Map Format})
35444 Target descriptions (@pxref{Target Descriptions})
35446 Remote shared library lists (@xref{Library List Format},
35447 or alternatively @pxref{Library List Format for SVR4 Targets})
35449 MS-Windows shared libraries (@pxref{Shared Libraries})
35451 Traceframe info (@pxref{Traceframe Info Format})
35453 Branch trace (@pxref{Branch Trace Format},
35454 @pxref{Branch Trace Configuration Format})
35458 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35459 default, @value{GDBN} will be compiled if the Guile libraries are
35460 installed and are found by @file{configure}. You can use the
35461 @code{--with-guile} option to request Guile, and pass either the Guile
35462 version number or the file name of the relevant @code{pkg-config}
35463 program to choose a particular version of Guile.
35466 @value{GDBN}'s features related to character sets (@pxref{Character
35467 Sets}) require a functioning @code{iconv} implementation. If you are
35468 on a GNU system, then this is provided by the GNU C Library. Some
35469 other systems also provide a working @code{iconv}.
35471 If @value{GDBN} is using the @code{iconv} program which is installed
35472 in a non-standard place, you will need to tell @value{GDBN} where to
35473 find it. This is done with @option{--with-iconv-bin} which specifies
35474 the directory that contains the @code{iconv} program. This program is
35475 run in order to make a list of the available character sets.
35477 On systems without @code{iconv}, you can install GNU Libiconv. If
35478 Libiconv is installed in a standard place, @value{GDBN} will
35479 automatically use it if it is needed. If you have previously
35480 installed Libiconv in a non-standard place, you can use the
35481 @option{--with-libiconv-prefix} option to @file{configure}.
35483 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35484 arrange to build Libiconv if a directory named @file{libiconv} appears
35485 in the top-most source directory. If Libiconv is built this way, and
35486 if the operating system does not provide a suitable @code{iconv}
35487 implementation, then the just-built library will automatically be used
35488 by @value{GDBN}. One easy way to set this up is to download GNU
35489 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35490 source tree, and then rename the directory holding the Libiconv source
35491 code to @samp{libiconv}.
35494 @value{GDBN} can support debugging sections that are compressed with
35495 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35496 included with your operating system, you can find it in the xz package
35497 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35498 the usual place, then the @file{configure} script will use it
35499 automatically. If it is installed in an unusual path, you can use the
35500 @option{--with-lzma-prefix} option to specify its location.
35504 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35505 library. This library may be included with your operating system
35506 distribution; if it is not, you can get the latest version from
35507 @url{http://www.mpfr.org}. The @file{configure} script will search
35508 for this library in several standard locations; if it is installed
35509 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35510 option to specify its location.
35512 GNU MPFR is used to emulate target floating-point arithmetic during
35513 expression evaluation when the target uses different floating-point
35514 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35515 will fall back to using host floating-point arithmetic.
35518 @value{GDBN} can be scripted using Python language. @xref{Python}.
35519 By default, @value{GDBN} will be compiled if the Python libraries are
35520 installed and are found by @file{configure}. You can use the
35521 @code{--with-python} option to request Python, and pass either the
35522 file name of the relevant @code{python} executable, or the name of the
35523 directory in which Python is installed, to choose a particular
35524 installation of Python.
35527 @cindex compressed debug sections
35528 @value{GDBN} will use the @samp{zlib} library, if available, to read
35529 compressed debug sections. Some linkers, such as GNU gold, are capable
35530 of producing binaries with compressed debug sections. If @value{GDBN}
35531 is compiled with @samp{zlib}, it will be able to read the debug
35532 information in such binaries.
35534 The @samp{zlib} library is likely included with your operating system
35535 distribution; if it is not, you can get the latest version from
35536 @url{http://zlib.net}.
35539 @node Running Configure
35540 @section Invoking the @value{GDBN} @file{configure} Script
35541 @cindex configuring @value{GDBN}
35542 @value{GDBN} comes with a @file{configure} script that automates the process
35543 of preparing @value{GDBN} for installation; you can then use @code{make} to
35544 build the @code{gdb} program.
35546 @c irrelevant in info file; it's as current as the code it lives with.
35547 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35548 look at the @file{README} file in the sources; we may have improved the
35549 installation procedures since publishing this manual.}
35552 The @value{GDBN} distribution includes all the source code you need for
35553 @value{GDBN} in a single directory, whose name is usually composed by
35554 appending the version number to @samp{gdb}.
35556 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35557 @file{gdb-@value{GDBVN}} directory. That directory contains:
35560 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35561 script for configuring @value{GDBN} and all its supporting libraries
35563 @item gdb-@value{GDBVN}/gdb
35564 the source specific to @value{GDBN} itself
35566 @item gdb-@value{GDBVN}/bfd
35567 source for the Binary File Descriptor library
35569 @item gdb-@value{GDBVN}/include
35570 @sc{gnu} include files
35572 @item gdb-@value{GDBVN}/libiberty
35573 source for the @samp{-liberty} free software library
35575 @item gdb-@value{GDBVN}/opcodes
35576 source for the library of opcode tables and disassemblers
35578 @item gdb-@value{GDBVN}/readline
35579 source for the @sc{gnu} command-line interface
35582 There may be other subdirectories as well.
35584 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35585 from the @file{gdb-@var{version-number}} source directory, which in
35586 this example is the @file{gdb-@value{GDBVN}} directory.
35588 First switch to the @file{gdb-@var{version-number}} source directory
35589 if you are not already in it; then run @file{configure}. Pass the
35590 identifier for the platform on which @value{GDBN} will run as an
35596 cd gdb-@value{GDBVN}
35601 Running @samp{configure} and then running @code{make} builds the
35602 included supporting libraries, then @code{gdb} itself. The configured
35603 source files, and the binaries, are left in the corresponding source
35607 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35608 system does not recognize this automatically when you run a different
35609 shell, you may need to run @code{sh} on it explicitly:
35615 You should run the @file{configure} script from the top directory in the
35616 source tree, the @file{gdb-@var{version-number}} directory. If you run
35617 @file{configure} from one of the subdirectories, you will configure only
35618 that subdirectory. That is usually not what you want. In particular,
35619 if you run the first @file{configure} from the @file{gdb} subdirectory
35620 of the @file{gdb-@var{version-number}} directory, you will omit the
35621 configuration of @file{bfd}, @file{readline}, and other sibling
35622 directories of the @file{gdb} subdirectory. This leads to build errors
35623 about missing include files such as @file{bfd/bfd.h}.
35625 You can install @code{@value{GDBN}} anywhere. The best way to do this
35626 is to pass the @code{--prefix} option to @code{configure}, and then
35627 install it with @code{make install}.
35629 @node Separate Objdir
35630 @section Compiling @value{GDBN} in Another Directory
35632 If you want to run @value{GDBN} versions for several host or target machines,
35633 you need a different @code{gdb} compiled for each combination of
35634 host and target. @file{configure} is designed to make this easy by
35635 allowing you to generate each configuration in a separate subdirectory,
35636 rather than in the source directory. If your @code{make} program
35637 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35638 @code{make} in each of these directories builds the @code{gdb}
35639 program specified there.
35641 To build @code{gdb} in a separate directory, run @file{configure}
35642 with the @samp{--srcdir} option to specify where to find the source.
35643 (You also need to specify a path to find @file{configure}
35644 itself from your working directory. If the path to @file{configure}
35645 would be the same as the argument to @samp{--srcdir}, you can leave out
35646 the @samp{--srcdir} option; it is assumed.)
35648 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35649 separate directory for a Sun 4 like this:
35653 cd gdb-@value{GDBVN}
35656 ../gdb-@value{GDBVN}/configure
35661 When @file{configure} builds a configuration using a remote source
35662 directory, it creates a tree for the binaries with the same structure
35663 (and using the same names) as the tree under the source directory. In
35664 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35665 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35666 @file{gdb-sun4/gdb}.
35668 Make sure that your path to the @file{configure} script has just one
35669 instance of @file{gdb} in it. If your path to @file{configure} looks
35670 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35671 one subdirectory of @value{GDBN}, not the whole package. This leads to
35672 build errors about missing include files such as @file{bfd/bfd.h}.
35674 One popular reason to build several @value{GDBN} configurations in separate
35675 directories is to configure @value{GDBN} for cross-compiling (where
35676 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35677 programs that run on another machine---the @dfn{target}).
35678 You specify a cross-debugging target by
35679 giving the @samp{--target=@var{target}} option to @file{configure}.
35681 When you run @code{make} to build a program or library, you must run
35682 it in a configured directory---whatever directory you were in when you
35683 called @file{configure} (or one of its subdirectories).
35685 The @code{Makefile} that @file{configure} generates in each source
35686 directory also runs recursively. If you type @code{make} in a source
35687 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35688 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35689 will build all the required libraries, and then build GDB.
35691 When you have multiple hosts or targets configured in separate
35692 directories, you can run @code{make} on them in parallel (for example,
35693 if they are NFS-mounted on each of the hosts); they will not interfere
35697 @section Specifying Names for Hosts and Targets
35699 The specifications used for hosts and targets in the @file{configure}
35700 script are based on a three-part naming scheme, but some short predefined
35701 aliases are also supported. The full naming scheme encodes three pieces
35702 of information in the following pattern:
35705 @var{architecture}-@var{vendor}-@var{os}
35708 For example, you can use the alias @code{sun4} as a @var{host} argument,
35709 or as the value for @var{target} in a @code{--target=@var{target}}
35710 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35712 The @file{configure} script accompanying @value{GDBN} does not provide
35713 any query facility to list all supported host and target names or
35714 aliases. @file{configure} calls the Bourne shell script
35715 @code{config.sub} to map abbreviations to full names; you can read the
35716 script, if you wish, or you can use it to test your guesses on
35717 abbreviations---for example:
35720 % sh config.sub i386-linux
35722 % sh config.sub alpha-linux
35723 alpha-unknown-linux-gnu
35724 % sh config.sub hp9k700
35726 % sh config.sub sun4
35727 sparc-sun-sunos4.1.1
35728 % sh config.sub sun3
35729 m68k-sun-sunos4.1.1
35730 % sh config.sub i986v
35731 Invalid configuration `i986v': machine `i986v' not recognized
35735 @code{config.sub} is also distributed in the @value{GDBN} source
35736 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35738 @node Configure Options
35739 @section @file{configure} Options
35741 Here is a summary of the @file{configure} options and arguments that
35742 are most often useful for building @value{GDBN}. @file{configure}
35743 also has several other options not listed here. @inforef{Running
35744 configure scripts,,autoconf.info}, for a full
35745 explanation of @file{configure}.
35748 configure @r{[}--help@r{]}
35749 @r{[}--prefix=@var{dir}@r{]}
35750 @r{[}--exec-prefix=@var{dir}@r{]}
35751 @r{[}--srcdir=@var{dirname}@r{]}
35752 @r{[}--target=@var{target}@r{]}
35756 You may introduce options with a single @samp{-} rather than
35757 @samp{--} if you prefer; but you may abbreviate option names if you use
35762 Display a quick summary of how to invoke @file{configure}.
35764 @item --prefix=@var{dir}
35765 Configure the source to install programs and files under directory
35768 @item --exec-prefix=@var{dir}
35769 Configure the source to install programs under directory
35772 @c avoid splitting the warning from the explanation:
35774 @item --srcdir=@var{dirname}
35775 Use this option to make configurations in directories separate from the
35776 @value{GDBN} source directories. Among other things, you can use this to
35777 build (or maintain) several configurations simultaneously, in separate
35778 directories. @file{configure} writes configuration-specific files in
35779 the current directory, but arranges for them to use the source in the
35780 directory @var{dirname}. @file{configure} creates directories under
35781 the working directory in parallel to the source directories below
35784 @item --target=@var{target}
35785 Configure @value{GDBN} for cross-debugging programs running on the specified
35786 @var{target}. Without this option, @value{GDBN} is configured to debug
35787 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35789 There is no convenient way to generate a list of all available
35790 targets. Also see the @code{--enable-targets} option, below.
35793 There are many other options that are specific to @value{GDBN}. This
35794 lists just the most common ones; there are some very specialized
35795 options not described here.
35798 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
35799 @itemx --enable-targets=all
35800 Configure @value{GDBN} for cross-debugging programs running on the
35801 specified list of targets. The special value @samp{all} configures
35802 @value{GDBN} for debugging programs running on any target it supports.
35804 @item --with-gdb-datadir=@var{path}
35805 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
35806 here for certain supporting files or scripts. This defaults to the
35807 @file{gdb} subdirectory of @samp{datadi} (which can be set using
35810 @item --with-relocated-sources=@var{dir}
35811 Sets up the default source path substitution rule so that directory
35812 names recorded in debug information will be automatically adjusted for
35813 any directory under @var{dir}. @var{dir} should be a subdirectory of
35814 @value{GDBN}'s configured prefix, the one mentioned in the
35815 @code{--prefix} or @code{--exec-prefix} options to configure. This
35816 option is useful if GDB is supposed to be moved to a different place
35819 @item --enable-64-bit-bfd
35820 Enable 64-bit support in BFD on 32-bit hosts.
35822 @item --disable-gdbmi
35823 Build @value{GDBN} without the GDB/MI machine interface
35827 Build @value{GDBN} with the text-mode full-screen user interface
35828 (TUI). Requires a curses library (ncurses and cursesX are also
35831 @item --with-curses
35832 Use the curses library instead of the termcap library, for text-mode
35833 terminal operations.
35835 @item --with-libunwind-ia64
35836 Use the libunwind library for unwinding function call stack on ia64
35837 target platforms. See http://www.nongnu.org/libunwind/index.html for
35840 @item --with-system-readline
35841 Use the readline library installed on the host, rather than the
35842 library supplied as part of @value{GDBN}.
35844 @item --with-system-zlib
35845 Use the zlib library installed on the host, rather than the library
35846 supplied as part of @value{GDBN}.
35849 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
35850 default if libexpat is installed and found at configure time.) This
35851 library is used to read XML files supplied with @value{GDBN}. If it
35852 is unavailable, some features, such as remote protocol memory maps,
35853 target descriptions, and shared library lists, that are based on XML
35854 files, will not be available in @value{GDBN}. If your host does not
35855 have libexpat installed, you can get the latest version from
35856 `http://expat.sourceforge.net'.
35858 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
35860 Build @value{GDBN} with GNU libiconv, a character set encoding
35861 conversion library. This is not done by default, as on GNU systems
35862 the @code{iconv} that is built in to the C library is sufficient. If
35863 your host does not have a working @code{iconv}, you can get the latest
35864 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
35866 @value{GDBN}'s build system also supports building GNU libiconv as
35867 part of the overall build. @xref{Requirements}.
35870 Build @value{GDBN} with LZMA, a compression library. (Done by default
35871 if liblzma is installed and found at configure time.) LZMA is used by
35872 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
35873 platforms using the ELF object file format. If your host does not
35874 have liblzma installed, you can get the latest version from
35875 `https://tukaani.org/xz/'.
35878 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
35879 floating-point computation with correct rounding. (Done by default if
35880 GNU MPFR is installed and found at configure time.) This library is
35881 used to emulate target floating-point arithmetic during expression
35882 evaluation when the target uses different floating-point formats than
35883 the host. If GNU MPFR is not available, @value{GDBN} will fall back
35884 to using host floating-point arithmetic. If your host does not have
35885 GNU MPFR installed, you can get the latest version from
35886 `http://www.mpfr.org'.
35888 @item --with-python@r{[}=@var{python}@r{]}
35889 Build @value{GDBN} with Python scripting support. (Done by default if
35890 libpython is present and found at configure time.) Python makes
35891 @value{GDBN} scripting much more powerful than the restricted CLI
35892 scripting language. If your host does not have Python installed, you
35893 can find it on `http://www.python.org/download/'. The oldest version
35894 of Python supported by GDB is 2.4. The optional argument @var{python}
35895 is used to find the Python headers and libraries. It can be either
35896 the name of a Python executable, or the name of the directory in which
35897 Python is installed.
35899 @item --with-guile[=GUILE]'
35900 Build @value{GDBN} with GNU Guile scripting support. (Done by default
35901 if libguile is present and found at configure time.) If your host
35902 does not have Guile installed, you can find it at
35903 `https://www.gnu.org/software/guile/'. The optional argument GUILE
35904 can be a version number, which will cause @code{configure} to try to
35905 use that version of Guile; or the file name of a @code{pkg-config}
35906 executable, which will be queried to find the information needed to
35907 compile and link against Guile.
35909 @item --without-included-regex
35910 Don't use the regex library included with @value{GDBN} (as part of the
35911 libiberty library). This is the default on hosts with version 2 of
35914 @item --with-sysroot=@var{dir}
35915 Use @var{dir} as the default system root directory for libraries whose
35916 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
35917 @var{dir} can be modified at run time by using the @command{set
35918 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
35919 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
35920 default system root will be automatically adjusted if and when
35921 @value{GDBN} is moved to a different location.
35923 @item --with-system-gdbinit=@var{file}
35924 Configure @value{GDBN} to automatically load a system-wide init file.
35925 @var{file} should be an absolute file name. If @var{file} is in a
35926 directory under the configured prefix, and @value{GDBN} is moved to
35927 another location after being built, the location of the system-wide
35928 init file will be adjusted accordingly.
35930 @item --enable-build-warnings
35931 When building the @value{GDBN} sources, ask the compiler to warn about
35932 any code which looks even vaguely suspicious. It passes many
35933 different warning flags, depending on the exact version of the
35934 compiler you are using.
35936 @item --enable-werror
35937 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
35938 to the compiler, which will fail the compilation if the compiler
35939 outputs any warning messages.
35941 @item --enable-ubsan
35942 Enable the GCC undefined behavior sanitizer. This is disabled by
35943 default, but passing @code{--enable-ubsan=yes} or
35944 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
35945 undefined behavior sanitizer checks for C@t{++} undefined behavior.
35946 It has a performance cost, so if you are looking at @value{GDBN}'s
35947 performance, you should disable it. The undefined behavior sanitizer
35948 was first introduced in GCC 4.9.
35951 @node System-wide configuration
35952 @section System-wide configuration and settings
35953 @cindex system-wide init file
35955 @value{GDBN} can be configured to have a system-wide init file;
35956 this file will be read and executed at startup (@pxref{Startup, , What
35957 @value{GDBN} does during startup}).
35959 Here is the corresponding configure option:
35962 @item --with-system-gdbinit=@var{file}
35963 Specify that the default location of the system-wide init file is
35967 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35968 it may be subject to relocation. Two possible cases:
35972 If the default location of this init file contains @file{$prefix},
35973 it will be subject to relocation. Suppose that the configure options
35974 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35975 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35976 init file is looked for as @file{$install/etc/gdbinit} instead of
35977 @file{$prefix/etc/gdbinit}.
35980 By contrast, if the default location does not contain the prefix,
35981 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35982 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35983 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35984 wherever @value{GDBN} is installed.
35987 If the configured location of the system-wide init file (as given by the
35988 @option{--with-system-gdbinit} option at configure time) is in the
35989 data-directory (as specified by @option{--with-gdb-datadir} at configure
35990 time) or in one of its subdirectories, then @value{GDBN} will look for the
35991 system-wide init file in the directory specified by the
35992 @option{--data-directory} command-line option.
35993 Note that the system-wide init file is only read once, during @value{GDBN}
35994 initialization. If the data-directory is changed after @value{GDBN} has
35995 started with the @code{set data-directory} command, the file will not be
35999 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36002 @node System-wide Configuration Scripts
36003 @subsection Installed System-wide Configuration Scripts
36004 @cindex system-wide configuration scripts
36006 The @file{system-gdbinit} directory, located inside the data-directory
36007 (as specified by @option{--with-gdb-datadir} at configure time) contains
36008 a number of scripts which can be used as system-wide init files. To
36009 automatically source those scripts at startup, @value{GDBN} should be
36010 configured with @option{--with-system-gdbinit}. Otherwise, any user
36011 should be able to source them by hand as needed.
36013 The following scripts are currently available:
36016 @item @file{elinos.py}
36018 @cindex ELinOS system-wide configuration script
36019 This script is useful when debugging a program on an ELinOS target.
36020 It takes advantage of the environment variables defined in a standard
36021 ELinOS environment in order to determine the location of the system
36022 shared libraries, and then sets the @samp{solib-absolute-prefix}
36023 and @samp{solib-search-path} variables appropriately.
36025 @item @file{wrs-linux.py}
36026 @pindex wrs-linux.py
36027 @cindex Wind River Linux system-wide configuration script
36028 This script is useful when debugging a program on a target running
36029 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36030 the host-side sysroot used by the target system.
36034 @node Maintenance Commands
36035 @appendix Maintenance Commands
36036 @cindex maintenance commands
36037 @cindex internal commands
36039 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36040 includes a number of commands intended for @value{GDBN} developers,
36041 that are not documented elsewhere in this manual. These commands are
36042 provided here for reference. (For commands that turn on debugging
36043 messages, see @ref{Debugging Output}.)
36046 @kindex maint agent
36047 @kindex maint agent-eval
36048 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36049 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36050 Translate the given @var{expression} into remote agent bytecodes.
36051 This command is useful for debugging the Agent Expression mechanism
36052 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36053 expression useful for data collection, such as by tracepoints, while
36054 @samp{maint agent-eval} produces an expression that evaluates directly
36055 to a result. For instance, a collection expression for @code{globa +
36056 globb} will include bytecodes to record four bytes of memory at each
36057 of the addresses of @code{globa} and @code{globb}, while discarding
36058 the result of the addition, while an evaluation expression will do the
36059 addition and return the sum.
36060 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36061 If not, generate remote agent bytecode for current frame PC address.
36063 @kindex maint agent-printf
36064 @item maint agent-printf @var{format},@var{expr},...
36065 Translate the given format string and list of argument expressions
36066 into remote agent bytecodes and display them as a disassembled list.
36067 This command is useful for debugging the agent version of dynamic
36068 printf (@pxref{Dynamic Printf}).
36070 @kindex maint info breakpoints
36071 @item @anchor{maint info breakpoints}maint info breakpoints
36072 Using the same format as @samp{info breakpoints}, display both the
36073 breakpoints you've set explicitly, and those @value{GDBN} is using for
36074 internal purposes. Internal breakpoints are shown with negative
36075 breakpoint numbers. The type column identifies what kind of breakpoint
36080 Normal, explicitly set breakpoint.
36083 Normal, explicitly set watchpoint.
36086 Internal breakpoint, used to handle correctly stepping through
36087 @code{longjmp} calls.
36089 @item longjmp resume
36090 Internal breakpoint at the target of a @code{longjmp}.
36093 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36096 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36099 Shared library events.
36103 @kindex maint info btrace
36104 @item maint info btrace
36105 Pint information about raw branch tracing data.
36107 @kindex maint btrace packet-history
36108 @item maint btrace packet-history
36109 Print the raw branch trace packets that are used to compute the
36110 execution history for the @samp{record btrace} command. Both the
36111 information and the format in which it is printed depend on the btrace
36116 For the BTS recording format, print a list of blocks of sequential
36117 code. For each block, the following information is printed:
36121 Newer blocks have higher numbers. The oldest block has number zero.
36122 @item Lowest @samp{PC}
36123 @item Highest @samp{PC}
36127 For the Intel Processor Trace recording format, print a list of
36128 Intel Processor Trace packets. For each packet, the following
36129 information is printed:
36132 @item Packet number
36133 Newer packets have higher numbers. The oldest packet has number zero.
36135 The packet's offset in the trace stream.
36136 @item Packet opcode and payload
36140 @kindex maint btrace clear-packet-history
36141 @item maint btrace clear-packet-history
36142 Discards the cached packet history printed by the @samp{maint btrace
36143 packet-history} command. The history will be computed again when
36146 @kindex maint btrace clear
36147 @item maint btrace clear
36148 Discard the branch trace data. The data will be fetched anew and the
36149 branch trace will be recomputed when needed.
36151 This implicitly truncates the branch trace to a single branch trace
36152 buffer. When updating branch trace incrementally, the branch trace
36153 available to @value{GDBN} may be bigger than a single branch trace
36156 @kindex maint set btrace pt skip-pad
36157 @item maint set btrace pt skip-pad
36158 @kindex maint show btrace pt skip-pad
36159 @item maint show btrace pt skip-pad
36160 Control whether @value{GDBN} will skip PAD packets when computing the
36163 @kindex set displaced-stepping
36164 @kindex show displaced-stepping
36165 @cindex displaced stepping support
36166 @cindex out-of-line single-stepping
36167 @item set displaced-stepping
36168 @itemx show displaced-stepping
36169 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36170 if the target supports it. Displaced stepping is a way to single-step
36171 over breakpoints without removing them from the inferior, by executing
36172 an out-of-line copy of the instruction that was originally at the
36173 breakpoint location. It is also known as out-of-line single-stepping.
36176 @item set displaced-stepping on
36177 If the target architecture supports it, @value{GDBN} will use
36178 displaced stepping to step over breakpoints.
36180 @item set displaced-stepping off
36181 @value{GDBN} will not use displaced stepping to step over breakpoints,
36182 even if such is supported by the target architecture.
36184 @cindex non-stop mode, and @samp{set displaced-stepping}
36185 @item set displaced-stepping auto
36186 This is the default mode. @value{GDBN} will use displaced stepping
36187 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36188 architecture supports displaced stepping.
36191 @kindex maint check-psymtabs
36192 @item maint check-psymtabs
36193 Check the consistency of currently expanded psymtabs versus symtabs.
36194 Use this to check, for example, whether a symbol is in one but not the other.
36196 @kindex maint check-symtabs
36197 @item maint check-symtabs
36198 Check the consistency of currently expanded symtabs.
36200 @kindex maint expand-symtabs
36201 @item maint expand-symtabs [@var{regexp}]
36202 Expand symbol tables.
36203 If @var{regexp} is specified, only expand symbol tables for file
36204 names matching @var{regexp}.
36206 @kindex maint set catch-demangler-crashes
36207 @kindex maint show catch-demangler-crashes
36208 @cindex demangler crashes
36209 @item maint set catch-demangler-crashes [on|off]
36210 @itemx maint show catch-demangler-crashes
36211 Control whether @value{GDBN} should attempt to catch crashes in the
36212 symbol name demangler. The default is to attempt to catch crashes.
36213 If enabled, the first time a crash is caught, a core file is created,
36214 the offending symbol is displayed and the user is presented with the
36215 option to terminate the current session.
36217 @kindex maint cplus first_component
36218 @item maint cplus first_component @var{name}
36219 Print the first C@t{++} class/namespace component of @var{name}.
36221 @kindex maint cplus namespace
36222 @item maint cplus namespace
36223 Print the list of possible C@t{++} namespaces.
36225 @kindex maint deprecate
36226 @kindex maint undeprecate
36227 @cindex deprecated commands
36228 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36229 @itemx maint undeprecate @var{command}
36230 Deprecate or undeprecate the named @var{command}. Deprecated commands
36231 cause @value{GDBN} to issue a warning when you use them. The optional
36232 argument @var{replacement} says which newer command should be used in
36233 favor of the deprecated one; if it is given, @value{GDBN} will mention
36234 the replacement as part of the warning.
36236 @kindex maint dump-me
36237 @item maint dump-me
36238 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36239 Cause a fatal signal in the debugger and force it to dump its core.
36240 This is supported only on systems which support aborting a program
36241 with the @code{SIGQUIT} signal.
36243 @kindex maint internal-error
36244 @kindex maint internal-warning
36245 @kindex maint demangler-warning
36246 @cindex demangler crashes
36247 @item maint internal-error @r{[}@var{message-text}@r{]}
36248 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36249 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36251 Cause @value{GDBN} to call the internal function @code{internal_error},
36252 @code{internal_warning} or @code{demangler_warning} and hence behave
36253 as though an internal problem has been detected. In addition to
36254 reporting the internal problem, these functions give the user the
36255 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36256 and @code{internal_warning}) create a core file of the current
36257 @value{GDBN} session.
36259 These commands take an optional parameter @var{message-text} that is
36260 used as the text of the error or warning message.
36262 Here's an example of using @code{internal-error}:
36265 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36266 @dots{}/maint.c:121: internal-error: testing, 1, 2
36267 A problem internal to GDB has been detected. Further
36268 debugging may prove unreliable.
36269 Quit this debugging session? (y or n) @kbd{n}
36270 Create a core file? (y or n) @kbd{n}
36274 @cindex @value{GDBN} internal error
36275 @cindex internal errors, control of @value{GDBN} behavior
36276 @cindex demangler crashes
36278 @kindex maint set internal-error
36279 @kindex maint show internal-error
36280 @kindex maint set internal-warning
36281 @kindex maint show internal-warning
36282 @kindex maint set demangler-warning
36283 @kindex maint show demangler-warning
36284 @item maint set internal-error @var{action} [ask|yes|no]
36285 @itemx maint show internal-error @var{action}
36286 @itemx maint set internal-warning @var{action} [ask|yes|no]
36287 @itemx maint show internal-warning @var{action}
36288 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36289 @itemx maint show demangler-warning @var{action}
36290 When @value{GDBN} reports an internal problem (error or warning) it
36291 gives the user the opportunity to both quit @value{GDBN} and create a
36292 core file of the current @value{GDBN} session. These commands let you
36293 override the default behaviour for each particular @var{action},
36294 described in the table below.
36298 You can specify that @value{GDBN} should always (yes) or never (no)
36299 quit. The default is to ask the user what to do.
36302 You can specify that @value{GDBN} should always (yes) or never (no)
36303 create a core file. The default is to ask the user what to do. Note
36304 that there is no @code{corefile} option for @code{demangler-warning}:
36305 demangler warnings always create a core file and this cannot be
36309 @kindex maint packet
36310 @item maint packet @var{text}
36311 If @value{GDBN} is talking to an inferior via the serial protocol,
36312 then this command sends the string @var{text} to the inferior, and
36313 displays the response packet. @value{GDBN} supplies the initial
36314 @samp{$} character, the terminating @samp{#} character, and the
36317 @kindex maint print architecture
36318 @item maint print architecture @r{[}@var{file}@r{]}
36319 Print the entire architecture configuration. The optional argument
36320 @var{file} names the file where the output goes.
36322 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36323 @item maint print c-tdesc
36324 Print the target description (@pxref{Target Descriptions}) as
36325 a C source file. By default, the target description is for the current
36326 target, but if the optional argument @var{file} is provided, that file
36327 is used to produce the description. The @var{file} should be an XML
36328 document, of the form described in @ref{Target Description Format}.
36329 The created source file is built into @value{GDBN} when @value{GDBN} is
36330 built again. This command is used by developers after they add or
36331 modify XML target descriptions.
36333 @kindex maint check xml-descriptions
36334 @item maint check xml-descriptions @var{dir}
36335 Check that the target descriptions dynamically created by @value{GDBN}
36336 equal the descriptions created from XML files found in @var{dir}.
36338 @anchor{maint check libthread-db}
36339 @kindex maint check libthread-db
36340 @item maint check libthread-db
36341 Run integrity checks on the current inferior's thread debugging
36342 library. This exercises all @code{libthread_db} functionality used by
36343 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36344 @code{proc_service} functions provided by @value{GDBN} that
36345 @code{libthread_db} uses. Note that parts of the test may be skipped
36346 on some platforms when debugging core files.
36348 @kindex maint print dummy-frames
36349 @item maint print dummy-frames
36350 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36353 (@value{GDBP}) @kbd{b add}
36355 (@value{GDBP}) @kbd{print add(2,3)}
36356 Breakpoint 2, add (a=2, b=3) at @dots{}
36358 The program being debugged stopped while in a function called from GDB.
36360 (@value{GDBP}) @kbd{maint print dummy-frames}
36361 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36365 Takes an optional file parameter.
36367 @kindex maint print registers
36368 @kindex maint print raw-registers
36369 @kindex maint print cooked-registers
36370 @kindex maint print register-groups
36371 @kindex maint print remote-registers
36372 @item maint print registers @r{[}@var{file}@r{]}
36373 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36374 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36375 @itemx maint print register-groups @r{[}@var{file}@r{]}
36376 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36377 Print @value{GDBN}'s internal register data structures.
36379 The command @code{maint print raw-registers} includes the contents of
36380 the raw register cache; the command @code{maint print
36381 cooked-registers} includes the (cooked) value of all registers,
36382 including registers which aren't available on the target nor visible
36383 to user; the command @code{maint print register-groups} includes the
36384 groups that each register is a member of; and the command @code{maint
36385 print remote-registers} includes the remote target's register numbers
36386 and offsets in the `G' packets.
36388 These commands take an optional parameter, a file name to which to
36389 write the information.
36391 @kindex maint print reggroups
36392 @item maint print reggroups @r{[}@var{file}@r{]}
36393 Print @value{GDBN}'s internal register group data structures. The
36394 optional argument @var{file} tells to what file to write the
36397 The register groups info looks like this:
36400 (@value{GDBP}) @kbd{maint print reggroups}
36413 This command forces @value{GDBN} to flush its internal register cache.
36415 @kindex maint print objfiles
36416 @cindex info for known object files
36417 @item maint print objfiles @r{[}@var{regexp}@r{]}
36418 Print a dump of all known object files.
36419 If @var{regexp} is specified, only print object files whose names
36420 match @var{regexp}. For each object file, this command prints its name,
36421 address in memory, and all of its psymtabs and symtabs.
36423 @kindex maint print user-registers
36424 @cindex user registers
36425 @item maint print user-registers
36426 List all currently available @dfn{user registers}. User registers
36427 typically provide alternate names for actual hardware registers. They
36428 include the four ``standard'' registers @code{$fp}, @code{$pc},
36429 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36430 registers can be used in expressions in the same way as the canonical
36431 register names, but only the latter are listed by the @code{info
36432 registers} and @code{maint print registers} commands.
36434 @kindex maint print section-scripts
36435 @cindex info for known .debug_gdb_scripts-loaded scripts
36436 @item maint print section-scripts [@var{regexp}]
36437 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36438 If @var{regexp} is specified, only print scripts loaded by object files
36439 matching @var{regexp}.
36440 For each script, this command prints its name as specified in the objfile,
36441 and the full path if known.
36442 @xref{dotdebug_gdb_scripts section}.
36444 @kindex maint print statistics
36445 @cindex bcache statistics
36446 @item maint print statistics
36447 This command prints, for each object file in the program, various data
36448 about that object file followed by the byte cache (@dfn{bcache})
36449 statistics for the object file. The objfile data includes the number
36450 of minimal, partial, full, and stabs symbols, the number of types
36451 defined by the objfile, the number of as yet unexpanded psym tables,
36452 the number of line tables and string tables, and the amount of memory
36453 used by the various tables. The bcache statistics include the counts,
36454 sizes, and counts of duplicates of all and unique objects, max,
36455 average, and median entry size, total memory used and its overhead and
36456 savings, and various measures of the hash table size and chain
36459 @kindex maint print target-stack
36460 @cindex target stack description
36461 @item maint print target-stack
36462 A @dfn{target} is an interface between the debugger and a particular
36463 kind of file or process. Targets can be stacked in @dfn{strata},
36464 so that more than one target can potentially respond to a request.
36465 In particular, memory accesses will walk down the stack of targets
36466 until they find a target that is interested in handling that particular
36469 This command prints a short description of each layer that was pushed on
36470 the @dfn{target stack}, starting from the top layer down to the bottom one.
36472 @kindex maint print type
36473 @cindex type chain of a data type
36474 @item maint print type @var{expr}
36475 Print the type chain for a type specified by @var{expr}. The argument
36476 can be either a type name or a symbol. If it is a symbol, the type of
36477 that symbol is described. The type chain produced by this command is
36478 a recursive definition of the data type as stored in @value{GDBN}'s
36479 data structures, including its flags and contained types.
36481 @kindex maint selftest
36483 @item maint selftest @r{[}@var{filter}@r{]}
36484 Run any self tests that were compiled in to @value{GDBN}. This will
36485 print a message showing how many tests were run, and how many failed.
36486 If a @var{filter} is passed, only the tests with @var{filter} in their
36489 @kindex "maint info selftests"
36491 @item maint info selftests
36492 List the selftests compiled in to @value{GDBN}.
36494 @kindex maint set dwarf always-disassemble
36495 @kindex maint show dwarf always-disassemble
36496 @item maint set dwarf always-disassemble
36497 @item maint show dwarf always-disassemble
36498 Control the behavior of @code{info address} when using DWARF debugging
36501 The default is @code{off}, which means that @value{GDBN} should try to
36502 describe a variable's location in an easily readable format. When
36503 @code{on}, @value{GDBN} will instead display the DWARF location
36504 expression in an assembly-like format. Note that some locations are
36505 too complex for @value{GDBN} to describe simply; in this case you will
36506 always see the disassembly form.
36508 Here is an example of the resulting disassembly:
36511 (gdb) info addr argc
36512 Symbol "argc" is a complex DWARF expression:
36516 For more information on these expressions, see
36517 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36519 @kindex maint set dwarf max-cache-age
36520 @kindex maint show dwarf max-cache-age
36521 @item maint set dwarf max-cache-age
36522 @itemx maint show dwarf max-cache-age
36523 Control the DWARF compilation unit cache.
36525 @cindex DWARF compilation units cache
36526 In object files with inter-compilation-unit references, such as those
36527 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36528 reader needs to frequently refer to previously read compilation units.
36529 This setting controls how long a compilation unit will remain in the
36530 cache if it is not referenced. A higher limit means that cached
36531 compilation units will be stored in memory longer, and more total
36532 memory will be used. Setting it to zero disables caching, which will
36533 slow down @value{GDBN} startup, but reduce memory consumption.
36535 @kindex maint set dwarf unwinders
36536 @kindex maint show dwarf unwinders
36537 @item maint set dwarf unwinders
36538 @itemx maint show dwarf unwinders
36539 Control use of the DWARF frame unwinders.
36541 @cindex DWARF frame unwinders
36542 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36543 frame unwinders to build the backtrace. Many of these targets will
36544 also have a second mechanism for building the backtrace for use in
36545 cases where DWARF information is not available, this second mechanism
36546 is often an analysis of a function's prologue.
36548 In order to extend testing coverage of the second level stack
36549 unwinding mechanisms it is helpful to be able to disable the DWARF
36550 stack unwinders, this can be done with this switch.
36552 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36553 advisable, there are cases that are better handled through DWARF than
36554 prologue analysis, and the debug experience is likely to be better
36555 with the DWARF frame unwinders enabled.
36557 If DWARF frame unwinders are not supported for a particular target
36558 architecture, then enabling this flag does not cause them to be used.
36559 @kindex maint set profile
36560 @kindex maint show profile
36561 @cindex profiling GDB
36562 @item maint set profile
36563 @itemx maint show profile
36564 Control profiling of @value{GDBN}.
36566 Profiling will be disabled until you use the @samp{maint set profile}
36567 command to enable it. When you enable profiling, the system will begin
36568 collecting timing and execution count data; when you disable profiling or
36569 exit @value{GDBN}, the results will be written to a log file. Remember that
36570 if you use profiling, @value{GDBN} will overwrite the profiling log file
36571 (often called @file{gmon.out}). If you have a record of important profiling
36572 data in a @file{gmon.out} file, be sure to move it to a safe location.
36574 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36575 compiled with the @samp{-pg} compiler option.
36577 @kindex maint set show-debug-regs
36578 @kindex maint show show-debug-regs
36579 @cindex hardware debug registers
36580 @item maint set show-debug-regs
36581 @itemx maint show show-debug-regs
36582 Control whether to show variables that mirror the hardware debug
36583 registers. Use @code{on} to enable, @code{off} to disable. If
36584 enabled, the debug registers values are shown when @value{GDBN} inserts or
36585 removes a hardware breakpoint or watchpoint, and when the inferior
36586 triggers a hardware-assisted breakpoint or watchpoint.
36588 @kindex maint set show-all-tib
36589 @kindex maint show show-all-tib
36590 @item maint set show-all-tib
36591 @itemx maint show show-all-tib
36592 Control whether to show all non zero areas within a 1k block starting
36593 at thread local base, when using the @samp{info w32 thread-information-block}
36596 @kindex maint set target-async
36597 @kindex maint show target-async
36598 @item maint set target-async
36599 @itemx maint show target-async
36600 This controls whether @value{GDBN} targets operate in synchronous or
36601 asynchronous mode (@pxref{Background Execution}). Normally the
36602 default is asynchronous, if it is available; but this can be changed
36603 to more easily debug problems occurring only in synchronous mode.
36605 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36606 @kindex maint show target-non-stop
36607 @item maint set target-non-stop
36608 @itemx maint show target-non-stop
36610 This controls whether @value{GDBN} targets always operate in non-stop
36611 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36612 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36613 if supported by the target.
36616 @item maint set target-non-stop auto
36617 This is the default mode. @value{GDBN} controls the target in
36618 non-stop mode if the target supports it.
36620 @item maint set target-non-stop on
36621 @value{GDBN} controls the target in non-stop mode even if the target
36622 does not indicate support.
36624 @item maint set target-non-stop off
36625 @value{GDBN} does not control the target in non-stop mode even if the
36626 target supports it.
36629 @kindex maint set per-command
36630 @kindex maint show per-command
36631 @item maint set per-command
36632 @itemx maint show per-command
36633 @cindex resources used by commands
36635 @value{GDBN} can display the resources used by each command.
36636 This is useful in debugging performance problems.
36639 @item maint set per-command space [on|off]
36640 @itemx maint show per-command space
36641 Enable or disable the printing of the memory used by GDB for each command.
36642 If enabled, @value{GDBN} will display how much memory each command
36643 took, following the command's own output.
36644 This can also be requested by invoking @value{GDBN} with the
36645 @option{--statistics} command-line switch (@pxref{Mode Options}).
36647 @item maint set per-command time [on|off]
36648 @itemx maint show per-command time
36649 Enable or disable the printing of the execution time of @value{GDBN}
36651 If enabled, @value{GDBN} will display how much time it
36652 took to execute each command, following the command's own output.
36653 Both CPU time and wallclock time are printed.
36654 Printing both is useful when trying to determine whether the cost is
36655 CPU or, e.g., disk/network latency.
36656 Note that the CPU time printed is for @value{GDBN} only, it does not include
36657 the execution time of the inferior because there's no mechanism currently
36658 to compute how much time was spent by @value{GDBN} and how much time was
36659 spent by the program been debugged.
36660 This can also be requested by invoking @value{GDBN} with the
36661 @option{--statistics} command-line switch (@pxref{Mode Options}).
36663 @item maint set per-command symtab [on|off]
36664 @itemx maint show per-command symtab
36665 Enable or disable the printing of basic symbol table statistics
36667 If enabled, @value{GDBN} will display the following information:
36671 number of symbol tables
36673 number of primary symbol tables
36675 number of blocks in the blockvector
36679 @kindex maint set check-libthread-db
36680 @kindex maint show check-libthread-db
36681 @item maint set check-libthread-db [on|off]
36682 @itemx maint show check-libthread-db
36683 Control whether @value{GDBN} should run integrity checks on inferior
36684 specific thread debugging libraries as they are loaded. The default
36685 is not to perform such checks. If any check fails @value{GDBN} will
36686 unload the library and continue searching for a suitable candidate as
36687 described in @ref{set libthread-db-search-path}. For more information
36688 about the tests, see @ref{maint check libthread-db}.
36690 @kindex maint space
36691 @cindex memory used by commands
36692 @item maint space @var{value}
36693 An alias for @code{maint set per-command space}.
36694 A non-zero value enables it, zero disables it.
36697 @cindex time of command execution
36698 @item maint time @var{value}
36699 An alias for @code{maint set per-command time}.
36700 A non-zero value enables it, zero disables it.
36702 @kindex maint translate-address
36703 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36704 Find the symbol stored at the location specified by the address
36705 @var{addr} and an optional section name @var{section}. If found,
36706 @value{GDBN} prints the name of the closest symbol and an offset from
36707 the symbol's location to the specified address. This is similar to
36708 the @code{info address} command (@pxref{Symbols}), except that this
36709 command also allows to find symbols in other sections.
36711 If section was not specified, the section in which the symbol was found
36712 is also printed. For dynamically linked executables, the name of
36713 executable or shared library containing the symbol is printed as well.
36717 The following command is useful for non-interactive invocations of
36718 @value{GDBN}, such as in the test suite.
36721 @item set watchdog @var{nsec}
36722 @kindex set watchdog
36723 @cindex watchdog timer
36724 @cindex timeout for commands
36725 Set the maximum number of seconds @value{GDBN} will wait for the
36726 target operation to finish. If this time expires, @value{GDBN}
36727 reports and error and the command is aborted.
36729 @item show watchdog
36730 Show the current setting of the target wait timeout.
36733 @node Remote Protocol
36734 @appendix @value{GDBN} Remote Serial Protocol
36739 * Stop Reply Packets::
36740 * General Query Packets::
36741 * Architecture-Specific Protocol Details::
36742 * Tracepoint Packets::
36743 * Host I/O Packets::
36745 * Notification Packets::
36746 * Remote Non-Stop::
36747 * Packet Acknowledgment::
36749 * File-I/O Remote Protocol Extension::
36750 * Library List Format::
36751 * Library List Format for SVR4 Targets::
36752 * Memory Map Format::
36753 * Thread List Format::
36754 * Traceframe Info Format::
36755 * Branch Trace Format::
36756 * Branch Trace Configuration Format::
36762 There may be occasions when you need to know something about the
36763 protocol---for example, if there is only one serial port to your target
36764 machine, you might want your program to do something special if it
36765 recognizes a packet meant for @value{GDBN}.
36767 In the examples below, @samp{->} and @samp{<-} are used to indicate
36768 transmitted and received data, respectively.
36770 @cindex protocol, @value{GDBN} remote serial
36771 @cindex serial protocol, @value{GDBN} remote
36772 @cindex remote serial protocol
36773 All @value{GDBN} commands and responses (other than acknowledgments
36774 and notifications, see @ref{Notification Packets}) are sent as a
36775 @var{packet}. A @var{packet} is introduced with the character
36776 @samp{$}, the actual @var{packet-data}, and the terminating character
36777 @samp{#} followed by a two-digit @var{checksum}:
36780 @code{$}@var{packet-data}@code{#}@var{checksum}
36784 @cindex checksum, for @value{GDBN} remote
36786 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36787 characters between the leading @samp{$} and the trailing @samp{#} (an
36788 eight bit unsigned checksum).
36790 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36791 specification also included an optional two-digit @var{sequence-id}:
36794 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36797 @cindex sequence-id, for @value{GDBN} remote
36799 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36800 has never output @var{sequence-id}s. Stubs that handle packets added
36801 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36803 When either the host or the target machine receives a packet, the first
36804 response expected is an acknowledgment: either @samp{+} (to indicate
36805 the package was received correctly) or @samp{-} (to request
36809 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36814 The @samp{+}/@samp{-} acknowledgments can be disabled
36815 once a connection is established.
36816 @xref{Packet Acknowledgment}, for details.
36818 The host (@value{GDBN}) sends @var{command}s, and the target (the
36819 debugging stub incorporated in your program) sends a @var{response}. In
36820 the case of step and continue @var{command}s, the response is only sent
36821 when the operation has completed, and the target has again stopped all
36822 threads in all attached processes. This is the default all-stop mode
36823 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36824 execution mode; see @ref{Remote Non-Stop}, for details.
36826 @var{packet-data} consists of a sequence of characters with the
36827 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
36830 @cindex remote protocol, field separator
36831 Fields within the packet should be separated using @samp{,} @samp{;} or
36832 @samp{:}. Except where otherwise noted all numbers are represented in
36833 @sc{hex} with leading zeros suppressed.
36835 Implementors should note that prior to @value{GDBN} 5.0, the character
36836 @samp{:} could not appear as the third character in a packet (as it
36837 would potentially conflict with the @var{sequence-id}).
36839 @cindex remote protocol, binary data
36840 @anchor{Binary Data}
36841 Binary data in most packets is encoded either as two hexadecimal
36842 digits per byte of binary data. This allowed the traditional remote
36843 protocol to work over connections which were only seven-bit clean.
36844 Some packets designed more recently assume an eight-bit clean
36845 connection, and use a more efficient encoding to send and receive
36848 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36849 as an escape character. Any escaped byte is transmitted as the escape
36850 character followed by the original character XORed with @code{0x20}.
36851 For example, the byte @code{0x7d} would be transmitted as the two
36852 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36853 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36854 @samp{@}}) must always be escaped. Responses sent by the stub
36855 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36856 is not interpreted as the start of a run-length encoded sequence
36859 Response @var{data} can be run-length encoded to save space.
36860 Run-length encoding replaces runs of identical characters with one
36861 instance of the repeated character, followed by a @samp{*} and a
36862 repeat count. The repeat count is itself sent encoded, to avoid
36863 binary characters in @var{data}: a value of @var{n} is sent as
36864 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36865 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36866 code 32) for a repeat count of 3. (This is because run-length
36867 encoding starts to win for counts 3 or more.) Thus, for example,
36868 @samp{0* } is a run-length encoding of ``0000'': the space character
36869 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36872 The printable characters @samp{#} and @samp{$} or with a numeric value
36873 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36874 seven repeats (@samp{$}) can be expanded using a repeat count of only
36875 five (@samp{"}). For example, @samp{00000000} can be encoded as
36878 The error response returned for some packets includes a two character
36879 error number. That number is not well defined.
36881 @cindex empty response, for unsupported packets
36882 For any @var{command} not supported by the stub, an empty response
36883 (@samp{$#00}) should be returned. That way it is possible to extend the
36884 protocol. A newer @value{GDBN} can tell if a packet is supported based
36887 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36888 commands for register access, and the @samp{m} and @samp{M} commands
36889 for memory access. Stubs that only control single-threaded targets
36890 can implement run control with the @samp{c} (continue), and @samp{s}
36891 (step) commands. Stubs that support multi-threading targets should
36892 support the @samp{vCont} command. All other commands are optional.
36897 The following table provides a complete list of all currently defined
36898 @var{command}s and their corresponding response @var{data}.
36899 @xref{File-I/O Remote Protocol Extension}, for details about the File
36900 I/O extension of the remote protocol.
36902 Each packet's description has a template showing the packet's overall
36903 syntax, followed by an explanation of the packet's meaning. We
36904 include spaces in some of the templates for clarity; these are not
36905 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36906 separate its components. For example, a template like @samp{foo
36907 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36908 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36909 @var{baz}. @value{GDBN} does not transmit a space character between the
36910 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36913 @cindex @var{thread-id}, in remote protocol
36914 @anchor{thread-id syntax}
36915 Several packets and replies include a @var{thread-id} field to identify
36916 a thread. Normally these are positive numbers with a target-specific
36917 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36918 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36921 In addition, the remote protocol supports a multiprocess feature in
36922 which the @var{thread-id} syntax is extended to optionally include both
36923 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36924 The @var{pid} (process) and @var{tid} (thread) components each have the
36925 format described above: a positive number with target-specific
36926 interpretation formatted as a big-endian hex string, literal @samp{-1}
36927 to indicate all processes or threads (respectively), or @samp{0} to
36928 indicate an arbitrary process or thread. Specifying just a process, as
36929 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36930 error to specify all processes but a specific thread, such as
36931 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36932 for those packets and replies explicitly documented to include a process
36933 ID, rather than a @var{thread-id}.
36935 The multiprocess @var{thread-id} syntax extensions are only used if both
36936 @value{GDBN} and the stub report support for the @samp{multiprocess}
36937 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36940 Note that all packet forms beginning with an upper- or lower-case
36941 letter, other than those described here, are reserved for future use.
36943 Here are the packet descriptions.
36948 @cindex @samp{!} packet
36949 @anchor{extended mode}
36950 Enable extended mode. In extended mode, the remote server is made
36951 persistent. The @samp{R} packet is used to restart the program being
36957 The remote target both supports and has enabled extended mode.
36961 @cindex @samp{?} packet
36963 Indicate the reason the target halted. The reply is the same as for
36964 step and continue. This packet has a special interpretation when the
36965 target is in non-stop mode; see @ref{Remote Non-Stop}.
36968 @xref{Stop Reply Packets}, for the reply specifications.
36970 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36971 @cindex @samp{A} packet
36972 Initialized @code{argv[]} array passed into program. @var{arglen}
36973 specifies the number of bytes in the hex encoded byte stream
36974 @var{arg}. See @code{gdbserver} for more details.
36979 The arguments were set.
36985 @cindex @samp{b} packet
36986 (Don't use this packet; its behavior is not well-defined.)
36987 Change the serial line speed to @var{baud}.
36989 JTC: @emph{When does the transport layer state change? When it's
36990 received, or after the ACK is transmitted. In either case, there are
36991 problems if the command or the acknowledgment packet is dropped.}
36993 Stan: @emph{If people really wanted to add something like this, and get
36994 it working for the first time, they ought to modify ser-unix.c to send
36995 some kind of out-of-band message to a specially-setup stub and have the
36996 switch happen "in between" packets, so that from remote protocol's point
36997 of view, nothing actually happened.}
36999 @item B @var{addr},@var{mode}
37000 @cindex @samp{B} packet
37001 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37002 breakpoint at @var{addr}.
37004 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37005 (@pxref{insert breakpoint or watchpoint packet}).
37007 @cindex @samp{bc} packet
37010 Backward continue. Execute the target system in reverse. No parameter.
37011 @xref{Reverse Execution}, for more information.
37014 @xref{Stop Reply Packets}, for the reply specifications.
37016 @cindex @samp{bs} packet
37019 Backward single step. Execute one instruction in reverse. No parameter.
37020 @xref{Reverse Execution}, for more information.
37023 @xref{Stop Reply Packets}, for the reply specifications.
37025 @item c @r{[}@var{addr}@r{]}
37026 @cindex @samp{c} packet
37027 Continue at @var{addr}, which is the address to resume. If @var{addr}
37028 is omitted, resume at current address.
37030 This packet is deprecated for multi-threading support. @xref{vCont
37034 @xref{Stop Reply Packets}, for the reply specifications.
37036 @item C @var{sig}@r{[};@var{addr}@r{]}
37037 @cindex @samp{C} packet
37038 Continue with signal @var{sig} (hex signal number). If
37039 @samp{;@var{addr}} is omitted, resume at same address.
37041 This packet is deprecated for multi-threading support. @xref{vCont
37045 @xref{Stop Reply Packets}, for the reply specifications.
37048 @cindex @samp{d} packet
37051 Don't use this packet; instead, define a general set packet
37052 (@pxref{General Query Packets}).
37056 @cindex @samp{D} packet
37057 The first form of the packet is used to detach @value{GDBN} from the
37058 remote system. It is sent to the remote target
37059 before @value{GDBN} disconnects via the @code{detach} command.
37061 The second form, including a process ID, is used when multiprocess
37062 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37063 detach only a specific process. The @var{pid} is specified as a
37064 big-endian hex string.
37074 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37075 @cindex @samp{F} packet
37076 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37077 This is part of the File-I/O protocol extension. @xref{File-I/O
37078 Remote Protocol Extension}, for the specification.
37081 @anchor{read registers packet}
37082 @cindex @samp{g} packet
37083 Read general registers.
37087 @item @var{XX@dots{}}
37088 Each byte of register data is described by two hex digits. The bytes
37089 with the register are transmitted in target byte order. The size of
37090 each register and their position within the @samp{g} packet are
37091 determined by the @value{GDBN} internal gdbarch functions
37092 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37094 When reading registers from a trace frame (@pxref{Analyze Collected
37095 Data,,Using the Collected Data}), the stub may also return a string of
37096 literal @samp{x}'s in place of the register data digits, to indicate
37097 that the corresponding register has not been collected, thus its value
37098 is unavailable. For example, for an architecture with 4 registers of
37099 4 bytes each, the following reply indicates to @value{GDBN} that
37100 registers 0 and 2 have not been collected, while registers 1 and 3
37101 have been collected, and both have zero value:
37105 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37112 @item G @var{XX@dots{}}
37113 @cindex @samp{G} packet
37114 Write general registers. @xref{read registers packet}, for a
37115 description of the @var{XX@dots{}} data.
37125 @item H @var{op} @var{thread-id}
37126 @cindex @samp{H} packet
37127 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37128 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37129 should be @samp{c} for step and continue operations (note that this
37130 is deprecated, supporting the @samp{vCont} command is a better
37131 option), and @samp{g} for other operations. The thread designator
37132 @var{thread-id} has the format and interpretation described in
37133 @ref{thread-id syntax}.
37144 @c 'H': How restrictive (or permissive) is the thread model. If a
37145 @c thread is selected and stopped, are other threads allowed
37146 @c to continue to execute? As I mentioned above, I think the
37147 @c semantics of each command when a thread is selected must be
37148 @c described. For example:
37150 @c 'g': If the stub supports threads and a specific thread is
37151 @c selected, returns the register block from that thread;
37152 @c otherwise returns current registers.
37154 @c 'G' If the stub supports threads and a specific thread is
37155 @c selected, sets the registers of the register block of
37156 @c that thread; otherwise sets current registers.
37158 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37159 @anchor{cycle step packet}
37160 @cindex @samp{i} packet
37161 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37162 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37163 step starting at that address.
37166 @cindex @samp{I} packet
37167 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37171 @cindex @samp{k} packet
37174 The exact effect of this packet is not specified.
37176 For a bare-metal target, it may power cycle or reset the target
37177 system. For that reason, the @samp{k} packet has no reply.
37179 For a single-process target, it may kill that process if possible.
37181 A multiple-process target may choose to kill just one process, or all
37182 that are under @value{GDBN}'s control. For more precise control, use
37183 the vKill packet (@pxref{vKill packet}).
37185 If the target system immediately closes the connection in response to
37186 @samp{k}, @value{GDBN} does not consider the lack of packet
37187 acknowledgment to be an error, and assumes the kill was successful.
37189 If connected using @kbd{target extended-remote}, and the target does
37190 not close the connection in response to a kill request, @value{GDBN}
37191 probes the target state as if a new connection was opened
37192 (@pxref{? packet}).
37194 @item m @var{addr},@var{length}
37195 @cindex @samp{m} packet
37196 Read @var{length} addressable memory units starting at address @var{addr}
37197 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37198 any particular boundary.
37200 The stub need not use any particular size or alignment when gathering
37201 data from memory for the response; even if @var{addr} is word-aligned
37202 and @var{length} is a multiple of the word size, the stub is free to
37203 use byte accesses, or not. For this reason, this packet may not be
37204 suitable for accessing memory-mapped I/O devices.
37205 @cindex alignment of remote memory accesses
37206 @cindex size of remote memory accesses
37207 @cindex memory, alignment and size of remote accesses
37211 @item @var{XX@dots{}}
37212 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37213 The reply may contain fewer addressable memory units than requested if the
37214 server was able to read only part of the region of memory.
37219 @item M @var{addr},@var{length}:@var{XX@dots{}}
37220 @cindex @samp{M} packet
37221 Write @var{length} addressable memory units starting at address @var{addr}
37222 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37223 byte is transmitted as a two-digit hexadecimal number.
37230 for an error (this includes the case where only part of the data was
37235 @cindex @samp{p} packet
37236 Read the value of register @var{n}; @var{n} is in hex.
37237 @xref{read registers packet}, for a description of how the returned
37238 register value is encoded.
37242 @item @var{XX@dots{}}
37243 the register's value
37247 Indicating an unrecognized @var{query}.
37250 @item P @var{n@dots{}}=@var{r@dots{}}
37251 @anchor{write register packet}
37252 @cindex @samp{P} packet
37253 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37254 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37255 digits for each byte in the register (target byte order).
37265 @item q @var{name} @var{params}@dots{}
37266 @itemx Q @var{name} @var{params}@dots{}
37267 @cindex @samp{q} packet
37268 @cindex @samp{Q} packet
37269 General query (@samp{q}) and set (@samp{Q}). These packets are
37270 described fully in @ref{General Query Packets}.
37273 @cindex @samp{r} packet
37274 Reset the entire system.
37276 Don't use this packet; use the @samp{R} packet instead.
37279 @cindex @samp{R} packet
37280 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37281 This packet is only available in extended mode (@pxref{extended mode}).
37283 The @samp{R} packet has no reply.
37285 @item s @r{[}@var{addr}@r{]}
37286 @cindex @samp{s} packet
37287 Single step, resuming at @var{addr}. If
37288 @var{addr} is omitted, resume at same address.
37290 This packet is deprecated for multi-threading support. @xref{vCont
37294 @xref{Stop Reply Packets}, for the reply specifications.
37296 @item S @var{sig}@r{[};@var{addr}@r{]}
37297 @anchor{step with signal packet}
37298 @cindex @samp{S} packet
37299 Step with signal. This is analogous to the @samp{C} packet, but
37300 requests a single-step, rather than a normal resumption of execution.
37302 This packet is deprecated for multi-threading support. @xref{vCont
37306 @xref{Stop Reply Packets}, for the reply specifications.
37308 @item t @var{addr}:@var{PP},@var{MM}
37309 @cindex @samp{t} packet
37310 Search backwards starting at address @var{addr} for a match with pattern
37311 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37312 There must be at least 3 digits in @var{addr}.
37314 @item T @var{thread-id}
37315 @cindex @samp{T} packet
37316 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37321 thread is still alive
37327 Packets starting with @samp{v} are identified by a multi-letter name,
37328 up to the first @samp{;} or @samp{?} (or the end of the packet).
37330 @item vAttach;@var{pid}
37331 @cindex @samp{vAttach} packet
37332 Attach to a new process with the specified process ID @var{pid}.
37333 The process ID is a
37334 hexadecimal integer identifying the process. In all-stop mode, all
37335 threads in the attached process are stopped; in non-stop mode, it may be
37336 attached without being stopped if that is supported by the target.
37338 @c In non-stop mode, on a successful vAttach, the stub should set the
37339 @c current thread to a thread of the newly-attached process. After
37340 @c attaching, GDB queries for the attached process's thread ID with qC.
37341 @c Also note that, from a user perspective, whether or not the
37342 @c target is stopped on attach in non-stop mode depends on whether you
37343 @c use the foreground or background version of the attach command, not
37344 @c on what vAttach does; GDB does the right thing with respect to either
37345 @c stopping or restarting threads.
37347 This packet is only available in extended mode (@pxref{extended mode}).
37353 @item @r{Any stop packet}
37354 for success in all-stop mode (@pxref{Stop Reply Packets})
37356 for success in non-stop mode (@pxref{Remote Non-Stop})
37359 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37360 @cindex @samp{vCont} packet
37361 @anchor{vCont packet}
37362 Resume the inferior, specifying different actions for each thread.
37364 For each inferior thread, the leftmost action with a matching
37365 @var{thread-id} is applied. Threads that don't match any action
37366 remain in their current state. Thread IDs are specified using the
37367 syntax described in @ref{thread-id syntax}. If multiprocess
37368 extensions (@pxref{multiprocess extensions}) are supported, actions
37369 can be specified to match all threads in a process by using the
37370 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37371 @var{thread-id} matches all threads. Specifying no actions is an
37374 Currently supported actions are:
37380 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37384 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37387 @item r @var{start},@var{end}
37388 Step once, and then keep stepping as long as the thread stops at
37389 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37390 The remote stub reports a stop reply when either the thread goes out
37391 of the range or is stopped due to an unrelated reason, such as hitting
37392 a breakpoint. @xref{range stepping}.
37394 If the range is empty (@var{start} == @var{end}), then the action
37395 becomes equivalent to the @samp{s} action. In other words,
37396 single-step once, and report the stop (even if the stepped instruction
37397 jumps to @var{start}).
37399 (A stop reply may be sent at any point even if the PC is still within
37400 the stepping range; for example, it is valid to implement this packet
37401 in a degenerate way as a single instruction step operation.)
37405 The optional argument @var{addr} normally associated with the
37406 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37407 not supported in @samp{vCont}.
37409 The @samp{t} action is only relevant in non-stop mode
37410 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37411 A stop reply should be generated for any affected thread not already stopped.
37412 When a thread is stopped by means of a @samp{t} action,
37413 the corresponding stop reply should indicate that the thread has stopped with
37414 signal @samp{0}, regardless of whether the target uses some other signal
37415 as an implementation detail.
37417 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37418 @samp{r} actions for threads that are already running. Conversely,
37419 the server must ignore @samp{t} actions for threads that are already
37422 @emph{Note:} In non-stop mode, a thread is considered running until
37423 @value{GDBN} acknowleges an asynchronous stop notification for it with
37424 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37426 The stub must support @samp{vCont} if it reports support for
37427 multiprocess extensions (@pxref{multiprocess extensions}).
37430 @xref{Stop Reply Packets}, for the reply specifications.
37433 @cindex @samp{vCont?} packet
37434 Request a list of actions supported by the @samp{vCont} packet.
37438 @item vCont@r{[};@var{action}@dots{}@r{]}
37439 The @samp{vCont} packet is supported. Each @var{action} is a supported
37440 command in the @samp{vCont} packet.
37442 The @samp{vCont} packet is not supported.
37445 @anchor{vCtrlC packet}
37447 @cindex @samp{vCtrlC} packet
37448 Interrupt remote target as if a control-C was pressed on the remote
37449 terminal. This is the equivalent to reacting to the @code{^C}
37450 (@samp{\003}, the control-C character) character in all-stop mode
37451 while the target is running, except this works in non-stop mode.
37452 @xref{interrupting remote targets}, for more info on the all-stop
37463 @item vFile:@var{operation}:@var{parameter}@dots{}
37464 @cindex @samp{vFile} packet
37465 Perform a file operation on the target system. For details,
37466 see @ref{Host I/O Packets}.
37468 @item vFlashErase:@var{addr},@var{length}
37469 @cindex @samp{vFlashErase} packet
37470 Direct the stub to erase @var{length} bytes of flash starting at
37471 @var{addr}. The region may enclose any number of flash blocks, but
37472 its start and end must fall on block boundaries, as indicated by the
37473 flash block size appearing in the memory map (@pxref{Memory Map
37474 Format}). @value{GDBN} groups flash memory programming operations
37475 together, and sends a @samp{vFlashDone} request after each group; the
37476 stub is allowed to delay erase operation until the @samp{vFlashDone}
37477 packet is received.
37487 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37488 @cindex @samp{vFlashWrite} packet
37489 Direct the stub to write data to flash address @var{addr}. The data
37490 is passed in binary form using the same encoding as for the @samp{X}
37491 packet (@pxref{Binary Data}). The memory ranges specified by
37492 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37493 not overlap, and must appear in order of increasing addresses
37494 (although @samp{vFlashErase} packets for higher addresses may already
37495 have been received; the ordering is guaranteed only between
37496 @samp{vFlashWrite} packets). If a packet writes to an address that was
37497 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37498 target-specific method, the results are unpredictable.
37506 for vFlashWrite addressing non-flash memory
37512 @cindex @samp{vFlashDone} packet
37513 Indicate to the stub that flash programming operation is finished.
37514 The stub is permitted to delay or batch the effects of a group of
37515 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37516 @samp{vFlashDone} packet is received. The contents of the affected
37517 regions of flash memory are unpredictable until the @samp{vFlashDone}
37518 request is completed.
37520 @item vKill;@var{pid}
37521 @cindex @samp{vKill} packet
37522 @anchor{vKill packet}
37523 Kill the process with the specified process ID @var{pid}, which is a
37524 hexadecimal integer identifying the process. This packet is used in
37525 preference to @samp{k} when multiprocess protocol extensions are
37526 supported; see @ref{multiprocess extensions}.
37536 @item vMustReplyEmpty
37537 @cindex @samp{vMustReplyEmpty} packet
37538 The correct reply to an unknown @samp{v} packet is to return the empty
37539 string, however, some older versions of @command{gdbserver} would
37540 incorrectly return @samp{OK} for unknown @samp{v} packets.
37542 The @samp{vMustReplyEmpty} is used as a feature test to check how
37543 @command{gdbserver} handles unknown packets, it is important that this
37544 packet be handled in the same way as other unknown @samp{v} packets.
37545 If this packet is handled differently to other unknown @samp{v}
37546 packets then it is possile that @value{GDBN} may run into problems in
37547 other areas, specifically around use of @samp{vFile:setfs:}.
37549 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37550 @cindex @samp{vRun} packet
37551 Run the program @var{filename}, passing it each @var{argument} on its
37552 command line. The file and arguments are hex-encoded strings. If
37553 @var{filename} is an empty string, the stub may use a default program
37554 (e.g.@: the last program run). The program is created in the stopped
37557 @c FIXME: What about non-stop mode?
37559 This packet is only available in extended mode (@pxref{extended mode}).
37565 @item @r{Any stop packet}
37566 for success (@pxref{Stop Reply Packets})
37570 @cindex @samp{vStopped} packet
37571 @xref{Notification Packets}.
37573 @item X @var{addr},@var{length}:@var{XX@dots{}}
37575 @cindex @samp{X} packet
37576 Write data to memory, where the data is transmitted in binary.
37577 Memory is specified by its address @var{addr} and number of addressable memory
37578 units @var{length} (@pxref{addressable memory unit});
37579 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37589 @item z @var{type},@var{addr},@var{kind}
37590 @itemx Z @var{type},@var{addr},@var{kind}
37591 @anchor{insert breakpoint or watchpoint packet}
37592 @cindex @samp{z} packet
37593 @cindex @samp{Z} packets
37594 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37595 watchpoint starting at address @var{address} of kind @var{kind}.
37597 Each breakpoint and watchpoint packet @var{type} is documented
37600 @emph{Implementation notes: A remote target shall return an empty string
37601 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37602 remote target shall support either both or neither of a given
37603 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37604 avoid potential problems with duplicate packets, the operations should
37605 be implemented in an idempotent way.}
37607 @item z0,@var{addr},@var{kind}
37608 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37609 @cindex @samp{z0} packet
37610 @cindex @samp{Z0} packet
37611 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37612 @var{addr} of type @var{kind}.
37614 A software breakpoint is implemented by replacing the instruction at
37615 @var{addr} with a software breakpoint or trap instruction. The
37616 @var{kind} is target-specific and typically indicates the size of the
37617 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37618 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37619 architectures have additional meanings for @var{kind}
37620 (@pxref{Architecture-Specific Protocol Details}); if no
37621 architecture-specific value is being used, it should be @samp{0}.
37622 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37623 conditional expressions in bytecode form that should be evaluated on
37624 the target's side. These are the conditions that should be taken into
37625 consideration when deciding if the breakpoint trigger should be
37626 reported back to @value{GDBN}.
37628 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37629 for how to best report a software breakpoint event to @value{GDBN}.
37631 The @var{cond_list} parameter is comprised of a series of expressions,
37632 concatenated without separators. Each expression has the following form:
37636 @item X @var{len},@var{expr}
37637 @var{len} is the length of the bytecode expression and @var{expr} is the
37638 actual conditional expression in bytecode form.
37642 The optional @var{cmd_list} parameter introduces commands that may be
37643 run on the target, rather than being reported back to @value{GDBN}.
37644 The parameter starts with a numeric flag @var{persist}; if the flag is
37645 nonzero, then the breakpoint may remain active and the commands
37646 continue to be run even when @value{GDBN} disconnects from the target.
37647 Following this flag is a series of expressions concatenated with no
37648 separators. Each expression has the following form:
37652 @item X @var{len},@var{expr}
37653 @var{len} is the length of the bytecode expression and @var{expr} is the
37654 actual commands expression in bytecode form.
37658 @emph{Implementation note: It is possible for a target to copy or move
37659 code that contains software breakpoints (e.g., when implementing
37660 overlays). The behavior of this packet, in the presence of such a
37661 target, is not defined.}
37673 @item z1,@var{addr},@var{kind}
37674 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37675 @cindex @samp{z1} packet
37676 @cindex @samp{Z1} packet
37677 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37678 address @var{addr}.
37680 A hardware breakpoint is implemented using a mechanism that is not
37681 dependent on being able to modify the target's memory. The
37682 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37683 same meaning as in @samp{Z0} packets.
37685 @emph{Implementation note: A hardware breakpoint is not affected by code
37698 @item z2,@var{addr},@var{kind}
37699 @itemx Z2,@var{addr},@var{kind}
37700 @cindex @samp{z2} packet
37701 @cindex @samp{Z2} packet
37702 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37703 The number of bytes to watch is specified by @var{kind}.
37715 @item z3,@var{addr},@var{kind}
37716 @itemx Z3,@var{addr},@var{kind}
37717 @cindex @samp{z3} packet
37718 @cindex @samp{Z3} packet
37719 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37720 The number of bytes to watch is specified by @var{kind}.
37732 @item z4,@var{addr},@var{kind}
37733 @itemx Z4,@var{addr},@var{kind}
37734 @cindex @samp{z4} packet
37735 @cindex @samp{Z4} packet
37736 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37737 The number of bytes to watch is specified by @var{kind}.
37751 @node Stop Reply Packets
37752 @section Stop Reply Packets
37753 @cindex stop reply packets
37755 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37756 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37757 receive any of the below as a reply. Except for @samp{?}
37758 and @samp{vStopped}, that reply is only returned
37759 when the target halts. In the below the exact meaning of @dfn{signal
37760 number} is defined by the header @file{include/gdb/signals.h} in the
37761 @value{GDBN} source code.
37763 In non-stop mode, the server will simply reply @samp{OK} to commands
37764 such as @samp{vCont}; any stop will be the subject of a future
37765 notification. @xref{Remote Non-Stop}.
37767 As in the description of request packets, we include spaces in the
37768 reply templates for clarity; these are not part of the reply packet's
37769 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37775 The program received signal number @var{AA} (a two-digit hexadecimal
37776 number). This is equivalent to a @samp{T} response with no
37777 @var{n}:@var{r} pairs.
37779 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37780 @cindex @samp{T} packet reply
37781 The program received signal number @var{AA} (a two-digit hexadecimal
37782 number). This is equivalent to an @samp{S} response, except that the
37783 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37784 and other information directly in the stop reply packet, reducing
37785 round-trip latency. Single-step and breakpoint traps are reported
37786 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37790 If @var{n} is a hexadecimal number, it is a register number, and the
37791 corresponding @var{r} gives that register's value. The data @var{r} is a
37792 series of bytes in target byte order, with each byte given by a
37793 two-digit hex number.
37796 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37797 the stopped thread, as specified in @ref{thread-id syntax}.
37800 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37801 the core on which the stop event was detected.
37804 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37805 specific event that stopped the target. The currently defined stop
37806 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37807 signal. At most one stop reason should be present.
37810 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37811 and go on to the next; this allows us to extend the protocol in the
37815 The currently defined stop reasons are:
37821 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37824 @item syscall_entry
37825 @itemx syscall_return
37826 The packet indicates a syscall entry or return, and @var{r} is the
37827 syscall number, in hex.
37829 @cindex shared library events, remote reply
37831 The packet indicates that the loaded libraries have changed.
37832 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
37833 list of loaded libraries. The @var{r} part is ignored.
37835 @cindex replay log events, remote reply
37837 The packet indicates that the target cannot continue replaying
37838 logged execution events, because it has reached the end (or the
37839 beginning when executing backward) of the log. The value of @var{r}
37840 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
37841 for more information.
37844 @anchor{swbreak stop reason}
37845 The packet indicates a software breakpoint instruction was executed,
37846 irrespective of whether it was @value{GDBN} that planted the
37847 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37848 part must be left empty.
37850 On some architectures, such as x86, at the architecture level, when a
37851 breakpoint instruction executes the program counter points at the
37852 breakpoint address plus an offset. On such targets, the stub is
37853 responsible for adjusting the PC to point back at the breakpoint
37856 This packet should not be sent by default; older @value{GDBN} versions
37857 did not support it. @value{GDBN} requests it, by supplying an
37858 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37859 remote stub must also supply the appropriate @samp{qSupported} feature
37860 indicating support.
37862 This packet is required for correct non-stop mode operation.
37865 The packet indicates the target stopped for a hardware breakpoint.
37866 The @var{r} part must be left empty.
37868 The same remarks about @samp{qSupported} and non-stop mode above
37871 @cindex fork events, remote reply
37873 The packet indicates that @code{fork} was called, and @var{r}
37874 is the thread ID of the new child process. Refer to
37875 @ref{thread-id syntax} for the format of the @var{thread-id}
37876 field. This packet is only applicable to targets that support
37879 This packet should not be sent by default; older @value{GDBN} versions
37880 did not support it. @value{GDBN} requests it, by supplying an
37881 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37882 remote stub must also supply the appropriate @samp{qSupported} feature
37883 indicating support.
37885 @cindex vfork events, remote reply
37887 The packet indicates that @code{vfork} was called, and @var{r}
37888 is the thread ID of the new child process. Refer to
37889 @ref{thread-id syntax} for the format of the @var{thread-id}
37890 field. This packet is only applicable to targets that support
37893 This packet should not be sent by default; older @value{GDBN} versions
37894 did not support it. @value{GDBN} requests it, by supplying an
37895 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37896 remote stub must also supply the appropriate @samp{qSupported} feature
37897 indicating support.
37899 @cindex vforkdone events, remote reply
37901 The packet indicates that a child process created by a vfork
37902 has either called @code{exec} or terminated, so that the
37903 address spaces of the parent and child process are no longer
37904 shared. The @var{r} part is ignored. This packet is only
37905 applicable to targets that support vforkdone events.
37907 This packet should not be sent by default; older @value{GDBN} versions
37908 did not support it. @value{GDBN} requests it, by supplying an
37909 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37910 remote stub must also supply the appropriate @samp{qSupported} feature
37911 indicating support.
37913 @cindex exec events, remote reply
37915 The packet indicates that @code{execve} was called, and @var{r}
37916 is the absolute pathname of the file that was executed, in hex.
37917 This packet is only applicable to targets that support exec events.
37919 This packet should not be sent by default; older @value{GDBN} versions
37920 did not support it. @value{GDBN} requests it, by supplying an
37921 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37922 remote stub must also supply the appropriate @samp{qSupported} feature
37923 indicating support.
37925 @cindex thread create event, remote reply
37926 @anchor{thread create event}
37928 The packet indicates that the thread was just created. The new thread
37929 is stopped until @value{GDBN} sets it running with a resumption packet
37930 (@pxref{vCont packet}). This packet should not be sent by default;
37931 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37932 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37933 @var{r} part is ignored.
37938 @itemx W @var{AA} ; process:@var{pid}
37939 The process exited, and @var{AA} is the exit status. This is only
37940 applicable to certain targets.
37942 The second form of the response, including the process ID of the
37943 exited process, can be used only when @value{GDBN} has reported
37944 support for multiprocess protocol extensions; see @ref{multiprocess
37945 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37949 @itemx X @var{AA} ; process:@var{pid}
37950 The process terminated with signal @var{AA}.
37952 The second form of the response, including the process ID of the
37953 terminated process, can be used only when @value{GDBN} has reported
37954 support for multiprocess protocol extensions; see @ref{multiprocess
37955 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37958 @anchor{thread exit event}
37959 @cindex thread exit event, remote reply
37960 @item w @var{AA} ; @var{tid}
37962 The thread exited, and @var{AA} is the exit status. This response
37963 should not be sent by default; @value{GDBN} requests it with the
37964 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37965 @var{AA} is formatted as a big-endian hex string.
37968 There are no resumed threads left in the target. In other words, even
37969 though the process is alive, the last resumed thread has exited. For
37970 example, say the target process has two threads: thread 1 and thread
37971 2. The client leaves thread 1 stopped, and resumes thread 2, which
37972 subsequently exits. At this point, even though the process is still
37973 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37974 executing either. The @samp{N} stop reply thus informs the client
37975 that it can stop waiting for stop replies. This packet should not be
37976 sent by default; older @value{GDBN} versions did not support it.
37977 @value{GDBN} requests it, by supplying an appropriate
37978 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37979 also supply the appropriate @samp{qSupported} feature indicating
37982 @item O @var{XX}@dots{}
37983 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37984 written as the program's console output. This can happen at any time
37985 while the program is running and the debugger should continue to wait
37986 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37988 @item F @var{call-id},@var{parameter}@dots{}
37989 @var{call-id} is the identifier which says which host system call should
37990 be called. This is just the name of the function. Translation into the
37991 correct system call is only applicable as it's defined in @value{GDBN}.
37992 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37995 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37996 this very system call.
37998 The target replies with this packet when it expects @value{GDBN} to
37999 call a host system call on behalf of the target. @value{GDBN} replies
38000 with an appropriate @samp{F} packet and keeps up waiting for the next
38001 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38002 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38003 Protocol Extension}, for more details.
38007 @node General Query Packets
38008 @section General Query Packets
38009 @cindex remote query requests
38011 Packets starting with @samp{q} are @dfn{general query packets};
38012 packets starting with @samp{Q} are @dfn{general set packets}. General
38013 query and set packets are a semi-unified form for retrieving and
38014 sending information to and from the stub.
38016 The initial letter of a query or set packet is followed by a name
38017 indicating what sort of thing the packet applies to. For example,
38018 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38019 definitions with the stub. These packet names follow some
38024 The name must not contain commas, colons or semicolons.
38026 Most @value{GDBN} query and set packets have a leading upper case
38029 The names of custom vendor packets should use a company prefix, in
38030 lower case, followed by a period. For example, packets designed at
38031 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38032 foos) or @samp{Qacme.bar} (for setting bars).
38035 The name of a query or set packet should be separated from any
38036 parameters by a @samp{:}; the parameters themselves should be
38037 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38038 full packet name, and check for a separator or the end of the packet,
38039 in case two packet names share a common prefix. New packets should not begin
38040 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38041 packets predate these conventions, and have arguments without any terminator
38042 for the packet name; we suspect they are in widespread use in places that
38043 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38044 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38047 Like the descriptions of the other packets, each description here
38048 has a template showing the packet's overall syntax, followed by an
38049 explanation of the packet's meaning. We include spaces in some of the
38050 templates for clarity; these are not part of the packet's syntax. No
38051 @value{GDBN} packet uses spaces to separate its components.
38053 Here are the currently defined query and set packets:
38059 Turn on or off the agent as a helper to perform some debugging operations
38060 delegated from @value{GDBN} (@pxref{Control Agent}).
38062 @item QAllow:@var{op}:@var{val}@dots{}
38063 @cindex @samp{QAllow} packet
38064 Specify which operations @value{GDBN} expects to request of the
38065 target, as a semicolon-separated list of operation name and value
38066 pairs. Possible values for @var{op} include @samp{WriteReg},
38067 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38068 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38069 indicating that @value{GDBN} will not request the operation, or 1,
38070 indicating that it may. (The target can then use this to set up its
38071 own internals optimally, for instance if the debugger never expects to
38072 insert breakpoints, it may not need to install its own trap handler.)
38075 @cindex current thread, remote request
38076 @cindex @samp{qC} packet
38077 Return the current thread ID.
38081 @item QC @var{thread-id}
38082 Where @var{thread-id} is a thread ID as documented in
38083 @ref{thread-id syntax}.
38084 @item @r{(anything else)}
38085 Any other reply implies the old thread ID.
38088 @item qCRC:@var{addr},@var{length}
38089 @cindex CRC of memory block, remote request
38090 @cindex @samp{qCRC} packet
38091 @anchor{qCRC packet}
38092 Compute the CRC checksum of a block of memory using CRC-32 defined in
38093 IEEE 802.3. The CRC is computed byte at a time, taking the most
38094 significant bit of each byte first. The initial pattern code
38095 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38097 @emph{Note:} This is the same CRC used in validating separate debug
38098 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38099 Files}). However the algorithm is slightly different. When validating
38100 separate debug files, the CRC is computed taking the @emph{least}
38101 significant bit of each byte first, and the final result is inverted to
38102 detect trailing zeros.
38107 An error (such as memory fault)
38108 @item C @var{crc32}
38109 The specified memory region's checksum is @var{crc32}.
38112 @item QDisableRandomization:@var{value}
38113 @cindex disable address space randomization, remote request
38114 @cindex @samp{QDisableRandomization} packet
38115 Some target operating systems will randomize the virtual address space
38116 of the inferior process as a security feature, but provide a feature
38117 to disable such randomization, e.g.@: to allow for a more deterministic
38118 debugging experience. On such systems, this packet with a @var{value}
38119 of 1 directs the target to disable address space randomization for
38120 processes subsequently started via @samp{vRun} packets, while a packet
38121 with a @var{value} of 0 tells the target to enable address space
38124 This packet is only available in extended mode (@pxref{extended mode}).
38129 The request succeeded.
38132 An error occurred. The error number @var{nn} is given as hex digits.
38135 An empty reply indicates that @samp{QDisableRandomization} is not supported
38139 This packet is not probed by default; the remote stub must request it,
38140 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38141 This should only be done on targets that actually support disabling
38142 address space randomization.
38144 @item QStartupWithShell:@var{value}
38145 @cindex startup with shell, remote request
38146 @cindex @samp{QStartupWithShell} packet
38147 On UNIX-like targets, it is possible to start the inferior using a
38148 shell program. This is the default behavior on both @value{GDBN} and
38149 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38150 used to inform @command{gdbserver} whether it should start the
38151 inferior using a shell or not.
38153 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38154 to start the inferior. If @var{value} is @samp{1},
38155 @command{gdbserver} will use a shell to start the inferior. All other
38156 values are considered an error.
38158 This packet is only available in extended mode (@pxref{extended
38164 The request succeeded.
38167 An error occurred. The error number @var{nn} is given as hex digits.
38170 This packet is not probed by default; the remote stub must request it,
38171 by supplying an appropriate @samp{qSupported} response
38172 (@pxref{qSupported}). This should only be done on targets that
38173 actually support starting the inferior using a shell.
38175 Use of this packet is controlled by the @code{set startup-with-shell}
38176 command; @pxref{set startup-with-shell}.
38178 @item QEnvironmentHexEncoded:@var{hex-value}
38179 @anchor{QEnvironmentHexEncoded}
38180 @cindex set environment variable, remote request
38181 @cindex @samp{QEnvironmentHexEncoded} packet
38182 On UNIX-like targets, it is possible to set environment variables that
38183 will be passed to the inferior during the startup process. This
38184 packet is used to inform @command{gdbserver} of an environment
38185 variable that has been defined by the user on @value{GDBN} (@pxref{set
38188 The packet is composed by @var{hex-value}, an hex encoded
38189 representation of the @var{name=value} format representing an
38190 environment variable. The name of the environment variable is
38191 represented by @var{name}, and the value to be assigned to the
38192 environment variable is represented by @var{value}. If the variable
38193 has no value (i.e., the value is @code{null}), then @var{value} will
38196 This packet is only available in extended mode (@pxref{extended
38202 The request succeeded.
38205 This packet is not probed by default; the remote stub must request it,
38206 by supplying an appropriate @samp{qSupported} response
38207 (@pxref{qSupported}). This should only be done on targets that
38208 actually support passing environment variables to the starting
38211 This packet is related to the @code{set environment} command;
38212 @pxref{set environment}.
38214 @item QEnvironmentUnset:@var{hex-value}
38215 @anchor{QEnvironmentUnset}
38216 @cindex unset environment variable, remote request
38217 @cindex @samp{QEnvironmentUnset} packet
38218 On UNIX-like targets, it is possible to unset environment variables
38219 before starting the inferior in the remote target. This packet is
38220 used to inform @command{gdbserver} of an environment variable that has
38221 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38223 The packet is composed by @var{hex-value}, an hex encoded
38224 representation of the name of the environment variable to be unset.
38226 This packet is only available in extended mode (@pxref{extended
38232 The request succeeded.
38235 This packet is not probed by default; the remote stub must request it,
38236 by supplying an appropriate @samp{qSupported} response
38237 (@pxref{qSupported}). This should only be done on targets that
38238 actually support passing environment variables to the starting
38241 This packet is related to the @code{unset environment} command;
38242 @pxref{unset environment}.
38244 @item QEnvironmentReset
38245 @anchor{QEnvironmentReset}
38246 @cindex reset environment, remote request
38247 @cindex @samp{QEnvironmentReset} packet
38248 On UNIX-like targets, this packet is used to reset the state of
38249 environment variables in the remote target before starting the
38250 inferior. In this context, reset means unsetting all environment
38251 variables that were previously set by the user (i.e., were not
38252 initially present in the environment). It is sent to
38253 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38254 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38255 (@pxref{QEnvironmentUnset}) packets.
38257 This packet is only available in extended mode (@pxref{extended
38263 The request succeeded.
38266 This packet is not probed by default; the remote stub must request it,
38267 by supplying an appropriate @samp{qSupported} response
38268 (@pxref{qSupported}). This should only be done on targets that
38269 actually support passing environment variables to the starting
38272 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38273 @anchor{QSetWorkingDir packet}
38274 @cindex set working directory, remote request
38275 @cindex @samp{QSetWorkingDir} packet
38276 This packet is used to inform the remote server of the intended
38277 current working directory for programs that are going to be executed.
38279 The packet is composed by @var{directory}, an hex encoded
38280 representation of the directory that the remote inferior will use as
38281 its current working directory. If @var{directory} is an empty string,
38282 the remote server should reset the inferior's current working
38283 directory to its original, empty value.
38285 This packet is only available in extended mode (@pxref{extended
38291 The request succeeded.
38295 @itemx qsThreadInfo
38296 @cindex list active threads, remote request
38297 @cindex @samp{qfThreadInfo} packet
38298 @cindex @samp{qsThreadInfo} packet
38299 Obtain a list of all active thread IDs from the target (OS). Since there
38300 may be too many active threads to fit into one reply packet, this query
38301 works iteratively: it may require more than one query/reply sequence to
38302 obtain the entire list of threads. The first query of the sequence will
38303 be the @samp{qfThreadInfo} query; subsequent queries in the
38304 sequence will be the @samp{qsThreadInfo} query.
38306 NOTE: This packet replaces the @samp{qL} query (see below).
38310 @item m @var{thread-id}
38312 @item m @var{thread-id},@var{thread-id}@dots{}
38313 a comma-separated list of thread IDs
38315 (lower case letter @samp{L}) denotes end of list.
38318 In response to each query, the target will reply with a list of one or
38319 more thread IDs, separated by commas.
38320 @value{GDBN} will respond to each reply with a request for more thread
38321 ids (using the @samp{qs} form of the query), until the target responds
38322 with @samp{l} (lower-case ell, for @dfn{last}).
38323 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38326 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38327 initial connection with the remote target, and the very first thread ID
38328 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38329 message. Therefore, the stub should ensure that the first thread ID in
38330 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38332 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38333 @cindex get thread-local storage address, remote request
38334 @cindex @samp{qGetTLSAddr} packet
38335 Fetch the address associated with thread local storage specified
38336 by @var{thread-id}, @var{offset}, and @var{lm}.
38338 @var{thread-id} is the thread ID associated with the
38339 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38341 @var{offset} is the (big endian, hex encoded) offset associated with the
38342 thread local variable. (This offset is obtained from the debug
38343 information associated with the variable.)
38345 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38346 load module associated with the thread local storage. For example,
38347 a @sc{gnu}/Linux system will pass the link map address of the shared
38348 object associated with the thread local storage under consideration.
38349 Other operating environments may choose to represent the load module
38350 differently, so the precise meaning of this parameter will vary.
38354 @item @var{XX}@dots{}
38355 Hex encoded (big endian) bytes representing the address of the thread
38356 local storage requested.
38359 An error occurred. The error number @var{nn} is given as hex digits.
38362 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38365 @item qGetTIBAddr:@var{thread-id}
38366 @cindex get thread information block address
38367 @cindex @samp{qGetTIBAddr} packet
38368 Fetch address of the Windows OS specific Thread Information Block.
38370 @var{thread-id} is the thread ID associated with the thread.
38374 @item @var{XX}@dots{}
38375 Hex encoded (big endian) bytes representing the linear address of the
38376 thread information block.
38379 An error occured. This means that either the thread was not found, or the
38380 address could not be retrieved.
38383 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38386 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38387 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38388 digit) is one to indicate the first query and zero to indicate a
38389 subsequent query; @var{threadcount} (two hex digits) is the maximum
38390 number of threads the response packet can contain; and @var{nextthread}
38391 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38392 returned in the response as @var{argthread}.
38394 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38398 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38399 Where: @var{count} (two hex digits) is the number of threads being
38400 returned; @var{done} (one hex digit) is zero to indicate more threads
38401 and one indicates no further threads; @var{argthreadid} (eight hex
38402 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38403 is a sequence of thread IDs, @var{threadid} (eight hex
38404 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38408 @cindex section offsets, remote request
38409 @cindex @samp{qOffsets} packet
38410 Get section offsets that the target used when relocating the downloaded
38415 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38416 Relocate the @code{Text} section by @var{xxx} from its original address.
38417 Relocate the @code{Data} section by @var{yyy} from its original address.
38418 If the object file format provides segment information (e.g.@: @sc{elf}
38419 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38420 segments by the supplied offsets.
38422 @emph{Note: while a @code{Bss} offset may be included in the response,
38423 @value{GDBN} ignores this and instead applies the @code{Data} offset
38424 to the @code{Bss} section.}
38426 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38427 Relocate the first segment of the object file, which conventionally
38428 contains program code, to a starting address of @var{xxx}. If
38429 @samp{DataSeg} is specified, relocate the second segment, which
38430 conventionally contains modifiable data, to a starting address of
38431 @var{yyy}. @value{GDBN} will report an error if the object file
38432 does not contain segment information, or does not contain at least
38433 as many segments as mentioned in the reply. Extra segments are
38434 kept at fixed offsets relative to the last relocated segment.
38437 @item qP @var{mode} @var{thread-id}
38438 @cindex thread information, remote request
38439 @cindex @samp{qP} packet
38440 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38441 encoded 32 bit mode; @var{thread-id} is a thread ID
38442 (@pxref{thread-id syntax}).
38444 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38447 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38451 @cindex non-stop mode, remote request
38452 @cindex @samp{QNonStop} packet
38454 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38455 @xref{Remote Non-Stop}, for more information.
38460 The request succeeded.
38463 An error occurred. The error number @var{nn} is given as hex digits.
38466 An empty reply indicates that @samp{QNonStop} is not supported by
38470 This packet is not probed by default; the remote stub must request it,
38471 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38472 Use of this packet is controlled by the @code{set non-stop} command;
38473 @pxref{Non-Stop Mode}.
38475 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38476 @itemx QCatchSyscalls:0
38477 @cindex catch syscalls from inferior, remote request
38478 @cindex @samp{QCatchSyscalls} packet
38479 @anchor{QCatchSyscalls}
38480 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38481 catching syscalls from the inferior process.
38483 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38484 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38485 is listed, every system call should be reported.
38487 Note that if a syscall not in the list is reported, @value{GDBN} will
38488 still filter the event according to its own list from all corresponding
38489 @code{catch syscall} commands. However, it is more efficient to only
38490 report the requested syscalls.
38492 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38493 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38495 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38496 kept for the new process too. On targets where exec may affect syscall
38497 numbers, for example with exec between 32 and 64-bit processes, the
38498 client should send a new packet with the new syscall list.
38503 The request succeeded.
38506 An error occurred. @var{nn} are hex digits.
38509 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38513 Use of this packet is controlled by the @code{set remote catch-syscalls}
38514 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38515 This packet is not probed by default; the remote stub must request it,
38516 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38518 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38519 @cindex pass signals to inferior, remote request
38520 @cindex @samp{QPassSignals} packet
38521 @anchor{QPassSignals}
38522 Each listed @var{signal} should be passed directly to the inferior process.
38523 Signals are numbered identically to continue packets and stop replies
38524 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38525 strictly greater than the previous item. These signals do not need to stop
38526 the inferior, or be reported to @value{GDBN}. All other signals should be
38527 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38528 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38529 new list. This packet improves performance when using @samp{handle
38530 @var{signal} nostop noprint pass}.
38535 The request succeeded.
38538 An error occurred. The error number @var{nn} is given as hex digits.
38541 An empty reply indicates that @samp{QPassSignals} is not supported by
38545 Use of this packet is controlled by the @code{set remote pass-signals}
38546 command (@pxref{Remote Configuration, set remote pass-signals}).
38547 This packet is not probed by default; the remote stub must request it,
38548 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38550 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38551 @cindex signals the inferior may see, remote request
38552 @cindex @samp{QProgramSignals} packet
38553 @anchor{QProgramSignals}
38554 Each listed @var{signal} may be delivered to the inferior process.
38555 Others should be silently discarded.
38557 In some cases, the remote stub may need to decide whether to deliver a
38558 signal to the program or not without @value{GDBN} involvement. One
38559 example of that is while detaching --- the program's threads may have
38560 stopped for signals that haven't yet had a chance of being reported to
38561 @value{GDBN}, and so the remote stub can use the signal list specified
38562 by this packet to know whether to deliver or ignore those pending
38565 This does not influence whether to deliver a signal as requested by a
38566 resumption packet (@pxref{vCont packet}).
38568 Signals are numbered identically to continue packets and stop replies
38569 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38570 strictly greater than the previous item. Multiple
38571 @samp{QProgramSignals} packets do not combine; any earlier
38572 @samp{QProgramSignals} list is completely replaced by the new list.
38577 The request succeeded.
38580 An error occurred. The error number @var{nn} is given as hex digits.
38583 An empty reply indicates that @samp{QProgramSignals} is not supported
38587 Use of this packet is controlled by the @code{set remote program-signals}
38588 command (@pxref{Remote Configuration, set remote program-signals}).
38589 This packet is not probed by default; the remote stub must request it,
38590 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38592 @anchor{QThreadEvents}
38593 @item QThreadEvents:1
38594 @itemx QThreadEvents:0
38595 @cindex thread create/exit events, remote request
38596 @cindex @samp{QThreadEvents} packet
38598 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38599 reporting of thread create and exit events. @xref{thread create
38600 event}, for the reply specifications. For example, this is used in
38601 non-stop mode when @value{GDBN} stops a set of threads and
38602 synchronously waits for the their corresponding stop replies. Without
38603 exit events, if one of the threads exits, @value{GDBN} would hang
38604 forever not knowing that it should no longer expect a stop for that
38605 same thread. @value{GDBN} does not enable this feature unless the
38606 stub reports that it supports it by including @samp{QThreadEvents+} in
38607 its @samp{qSupported} reply.
38612 The request succeeded.
38615 An error occurred. The error number @var{nn} is given as hex digits.
38618 An empty reply indicates that @samp{QThreadEvents} is not supported by
38622 Use of this packet is controlled by the @code{set remote thread-events}
38623 command (@pxref{Remote Configuration, set remote thread-events}).
38625 @item qRcmd,@var{command}
38626 @cindex execute remote command, remote request
38627 @cindex @samp{qRcmd} packet
38628 @var{command} (hex encoded) is passed to the local interpreter for
38629 execution. Invalid commands should be reported using the output
38630 string. Before the final result packet, the target may also respond
38631 with a number of intermediate @samp{O@var{output}} console output
38632 packets. @emph{Implementors should note that providing access to a
38633 stubs's interpreter may have security implications}.
38638 A command response with no output.
38640 A command response with the hex encoded output string @var{OUTPUT}.
38642 Indicate a badly formed request.
38644 An empty reply indicates that @samp{qRcmd} is not recognized.
38647 (Note that the @code{qRcmd} packet's name is separated from the
38648 command by a @samp{,}, not a @samp{:}, contrary to the naming
38649 conventions above. Please don't use this packet as a model for new
38652 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38653 @cindex searching memory, in remote debugging
38655 @cindex @samp{qSearch:memory} packet
38657 @cindex @samp{qSearch memory} packet
38658 @anchor{qSearch memory}
38659 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38660 Both @var{address} and @var{length} are encoded in hex;
38661 @var{search-pattern} is a sequence of bytes, also hex encoded.
38666 The pattern was not found.
38668 The pattern was found at @var{address}.
38670 A badly formed request or an error was encountered while searching memory.
38672 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38675 @item QStartNoAckMode
38676 @cindex @samp{QStartNoAckMode} packet
38677 @anchor{QStartNoAckMode}
38678 Request that the remote stub disable the normal @samp{+}/@samp{-}
38679 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38684 The stub has switched to no-acknowledgment mode.
38685 @value{GDBN} acknowledges this reponse,
38686 but neither the stub nor @value{GDBN} shall send or expect further
38687 @samp{+}/@samp{-} acknowledgments in the current connection.
38689 An empty reply indicates that the stub does not support no-acknowledgment mode.
38692 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38693 @cindex supported packets, remote query
38694 @cindex features of the remote protocol
38695 @cindex @samp{qSupported} packet
38696 @anchor{qSupported}
38697 Tell the remote stub about features supported by @value{GDBN}, and
38698 query the stub for features it supports. This packet allows
38699 @value{GDBN} and the remote stub to take advantage of each others'
38700 features. @samp{qSupported} also consolidates multiple feature probes
38701 at startup, to improve @value{GDBN} performance---a single larger
38702 packet performs better than multiple smaller probe packets on
38703 high-latency links. Some features may enable behavior which must not
38704 be on by default, e.g.@: because it would confuse older clients or
38705 stubs. Other features may describe packets which could be
38706 automatically probed for, but are not. These features must be
38707 reported before @value{GDBN} will use them. This ``default
38708 unsupported'' behavior is not appropriate for all packets, but it
38709 helps to keep the initial connection time under control with new
38710 versions of @value{GDBN} which support increasing numbers of packets.
38714 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38715 The stub supports or does not support each returned @var{stubfeature},
38716 depending on the form of each @var{stubfeature} (see below for the
38719 An empty reply indicates that @samp{qSupported} is not recognized,
38720 or that no features needed to be reported to @value{GDBN}.
38723 The allowed forms for each feature (either a @var{gdbfeature} in the
38724 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38728 @item @var{name}=@var{value}
38729 The remote protocol feature @var{name} is supported, and associated
38730 with the specified @var{value}. The format of @var{value} depends
38731 on the feature, but it must not include a semicolon.
38733 The remote protocol feature @var{name} is supported, and does not
38734 need an associated value.
38736 The remote protocol feature @var{name} is not supported.
38738 The remote protocol feature @var{name} may be supported, and
38739 @value{GDBN} should auto-detect support in some other way when it is
38740 needed. This form will not be used for @var{gdbfeature} notifications,
38741 but may be used for @var{stubfeature} responses.
38744 Whenever the stub receives a @samp{qSupported} request, the
38745 supplied set of @value{GDBN} features should override any previous
38746 request. This allows @value{GDBN} to put the stub in a known
38747 state, even if the stub had previously been communicating with
38748 a different version of @value{GDBN}.
38750 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38755 This feature indicates whether @value{GDBN} supports multiprocess
38756 extensions to the remote protocol. @value{GDBN} does not use such
38757 extensions unless the stub also reports that it supports them by
38758 including @samp{multiprocess+} in its @samp{qSupported} reply.
38759 @xref{multiprocess extensions}, for details.
38762 This feature indicates that @value{GDBN} supports the XML target
38763 description. If the stub sees @samp{xmlRegisters=} with target
38764 specific strings separated by a comma, it will report register
38768 This feature indicates whether @value{GDBN} supports the
38769 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38770 instruction reply packet}).
38773 This feature indicates whether @value{GDBN} supports the swbreak stop
38774 reason in stop replies. @xref{swbreak stop reason}, for details.
38777 This feature indicates whether @value{GDBN} supports the hwbreak stop
38778 reason in stop replies. @xref{swbreak stop reason}, for details.
38781 This feature indicates whether @value{GDBN} supports fork event
38782 extensions to the remote protocol. @value{GDBN} does not use such
38783 extensions unless the stub also reports that it supports them by
38784 including @samp{fork-events+} in its @samp{qSupported} reply.
38787 This feature indicates whether @value{GDBN} supports vfork event
38788 extensions to the remote protocol. @value{GDBN} does not use such
38789 extensions unless the stub also reports that it supports them by
38790 including @samp{vfork-events+} in its @samp{qSupported} reply.
38793 This feature indicates whether @value{GDBN} supports exec event
38794 extensions to the remote protocol. @value{GDBN} does not use such
38795 extensions unless the stub also reports that it supports them by
38796 including @samp{exec-events+} in its @samp{qSupported} reply.
38798 @item vContSupported
38799 This feature indicates whether @value{GDBN} wants to know the
38800 supported actions in the reply to @samp{vCont?} packet.
38803 Stubs should ignore any unknown values for
38804 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38805 packet supports receiving packets of unlimited length (earlier
38806 versions of @value{GDBN} may reject overly long responses). Additional values
38807 for @var{gdbfeature} may be defined in the future to let the stub take
38808 advantage of new features in @value{GDBN}, e.g.@: incompatible
38809 improvements in the remote protocol---the @samp{multiprocess} feature is
38810 an example of such a feature. The stub's reply should be independent
38811 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38812 describes all the features it supports, and then the stub replies with
38813 all the features it supports.
38815 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38816 responses, as long as each response uses one of the standard forms.
38818 Some features are flags. A stub which supports a flag feature
38819 should respond with a @samp{+} form response. Other features
38820 require values, and the stub should respond with an @samp{=}
38823 Each feature has a default value, which @value{GDBN} will use if
38824 @samp{qSupported} is not available or if the feature is not mentioned
38825 in the @samp{qSupported} response. The default values are fixed; a
38826 stub is free to omit any feature responses that match the defaults.
38828 Not all features can be probed, but for those which can, the probing
38829 mechanism is useful: in some cases, a stub's internal
38830 architecture may not allow the protocol layer to know some information
38831 about the underlying target in advance. This is especially common in
38832 stubs which may be configured for multiple targets.
38834 These are the currently defined stub features and their properties:
38836 @multitable @columnfractions 0.35 0.2 0.12 0.2
38837 @c NOTE: The first row should be @headitem, but we do not yet require
38838 @c a new enough version of Texinfo (4.7) to use @headitem.
38840 @tab Value Required
38844 @item @samp{PacketSize}
38849 @item @samp{qXfer:auxv:read}
38854 @item @samp{qXfer:btrace:read}
38859 @item @samp{qXfer:btrace-conf:read}
38864 @item @samp{qXfer:exec-file:read}
38869 @item @samp{qXfer:features:read}
38874 @item @samp{qXfer:libraries:read}
38879 @item @samp{qXfer:libraries-svr4:read}
38884 @item @samp{augmented-libraries-svr4-read}
38889 @item @samp{qXfer:memory-map:read}
38894 @item @samp{qXfer:sdata:read}
38899 @item @samp{qXfer:spu:read}
38904 @item @samp{qXfer:spu:write}
38909 @item @samp{qXfer:siginfo:read}
38914 @item @samp{qXfer:siginfo:write}
38919 @item @samp{qXfer:threads:read}
38924 @item @samp{qXfer:traceframe-info:read}
38929 @item @samp{qXfer:uib:read}
38934 @item @samp{qXfer:fdpic:read}
38939 @item @samp{Qbtrace:off}
38944 @item @samp{Qbtrace:bts}
38949 @item @samp{Qbtrace:pt}
38954 @item @samp{Qbtrace-conf:bts:size}
38959 @item @samp{Qbtrace-conf:pt:size}
38964 @item @samp{QNonStop}
38969 @item @samp{QCatchSyscalls}
38974 @item @samp{QPassSignals}
38979 @item @samp{QStartNoAckMode}
38984 @item @samp{multiprocess}
38989 @item @samp{ConditionalBreakpoints}
38994 @item @samp{ConditionalTracepoints}
38999 @item @samp{ReverseContinue}
39004 @item @samp{ReverseStep}
39009 @item @samp{TracepointSource}
39014 @item @samp{QAgent}
39019 @item @samp{QAllow}
39024 @item @samp{QDisableRandomization}
39029 @item @samp{EnableDisableTracepoints}
39034 @item @samp{QTBuffer:size}
39039 @item @samp{tracenz}
39044 @item @samp{BreakpointCommands}
39049 @item @samp{swbreak}
39054 @item @samp{hwbreak}
39059 @item @samp{fork-events}
39064 @item @samp{vfork-events}
39069 @item @samp{exec-events}
39074 @item @samp{QThreadEvents}
39079 @item @samp{no-resumed}
39086 These are the currently defined stub features, in more detail:
39089 @cindex packet size, remote protocol
39090 @item PacketSize=@var{bytes}
39091 The remote stub can accept packets up to at least @var{bytes} in
39092 length. @value{GDBN} will send packets up to this size for bulk
39093 transfers, and will never send larger packets. This is a limit on the
39094 data characters in the packet, including the frame and checksum.
39095 There is no trailing NUL byte in a remote protocol packet; if the stub
39096 stores packets in a NUL-terminated format, it should allow an extra
39097 byte in its buffer for the NUL. If this stub feature is not supported,
39098 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39100 @item qXfer:auxv:read
39101 The remote stub understands the @samp{qXfer:auxv:read} packet
39102 (@pxref{qXfer auxiliary vector read}).
39104 @item qXfer:btrace:read
39105 The remote stub understands the @samp{qXfer:btrace:read}
39106 packet (@pxref{qXfer btrace read}).
39108 @item qXfer:btrace-conf:read
39109 The remote stub understands the @samp{qXfer:btrace-conf:read}
39110 packet (@pxref{qXfer btrace-conf read}).
39112 @item qXfer:exec-file:read
39113 The remote stub understands the @samp{qXfer:exec-file:read} packet
39114 (@pxref{qXfer executable filename read}).
39116 @item qXfer:features:read
39117 The remote stub understands the @samp{qXfer:features:read} packet
39118 (@pxref{qXfer target description read}).
39120 @item qXfer:libraries:read
39121 The remote stub understands the @samp{qXfer:libraries:read} packet
39122 (@pxref{qXfer library list read}).
39124 @item qXfer:libraries-svr4:read
39125 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39126 (@pxref{qXfer svr4 library list read}).
39128 @item augmented-libraries-svr4-read
39129 The remote stub understands the augmented form of the
39130 @samp{qXfer:libraries-svr4:read} packet
39131 (@pxref{qXfer svr4 library list read}).
39133 @item qXfer:memory-map:read
39134 The remote stub understands the @samp{qXfer:memory-map:read} packet
39135 (@pxref{qXfer memory map read}).
39137 @item qXfer:sdata:read
39138 The remote stub understands the @samp{qXfer:sdata:read} packet
39139 (@pxref{qXfer sdata read}).
39141 @item qXfer:spu:read
39142 The remote stub understands the @samp{qXfer:spu:read} packet
39143 (@pxref{qXfer spu read}).
39145 @item qXfer:spu:write
39146 The remote stub understands the @samp{qXfer:spu:write} packet
39147 (@pxref{qXfer spu write}).
39149 @item qXfer:siginfo:read
39150 The remote stub understands the @samp{qXfer:siginfo:read} packet
39151 (@pxref{qXfer siginfo read}).
39153 @item qXfer:siginfo:write
39154 The remote stub understands the @samp{qXfer:siginfo:write} packet
39155 (@pxref{qXfer siginfo write}).
39157 @item qXfer:threads:read
39158 The remote stub understands the @samp{qXfer:threads:read} packet
39159 (@pxref{qXfer threads read}).
39161 @item qXfer:traceframe-info:read
39162 The remote stub understands the @samp{qXfer:traceframe-info:read}
39163 packet (@pxref{qXfer traceframe info read}).
39165 @item qXfer:uib:read
39166 The remote stub understands the @samp{qXfer:uib:read}
39167 packet (@pxref{qXfer unwind info block}).
39169 @item qXfer:fdpic:read
39170 The remote stub understands the @samp{qXfer:fdpic:read}
39171 packet (@pxref{qXfer fdpic loadmap read}).
39174 The remote stub understands the @samp{QNonStop} packet
39175 (@pxref{QNonStop}).
39177 @item QCatchSyscalls
39178 The remote stub understands the @samp{QCatchSyscalls} packet
39179 (@pxref{QCatchSyscalls}).
39182 The remote stub understands the @samp{QPassSignals} packet
39183 (@pxref{QPassSignals}).
39185 @item QStartNoAckMode
39186 The remote stub understands the @samp{QStartNoAckMode} packet and
39187 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39190 @anchor{multiprocess extensions}
39191 @cindex multiprocess extensions, in remote protocol
39192 The remote stub understands the multiprocess extensions to the remote
39193 protocol syntax. The multiprocess extensions affect the syntax of
39194 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39195 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39196 replies. Note that reporting this feature indicates support for the
39197 syntactic extensions only, not that the stub necessarily supports
39198 debugging of more than one process at a time. The stub must not use
39199 multiprocess extensions in packet replies unless @value{GDBN} has also
39200 indicated it supports them in its @samp{qSupported} request.
39202 @item qXfer:osdata:read
39203 The remote stub understands the @samp{qXfer:osdata:read} packet
39204 ((@pxref{qXfer osdata read}).
39206 @item ConditionalBreakpoints
39207 The target accepts and implements evaluation of conditional expressions
39208 defined for breakpoints. The target will only report breakpoint triggers
39209 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39211 @item ConditionalTracepoints
39212 The remote stub accepts and implements conditional expressions defined
39213 for tracepoints (@pxref{Tracepoint Conditions}).
39215 @item ReverseContinue
39216 The remote stub accepts and implements the reverse continue packet
39220 The remote stub accepts and implements the reverse step packet
39223 @item TracepointSource
39224 The remote stub understands the @samp{QTDPsrc} packet that supplies
39225 the source form of tracepoint definitions.
39228 The remote stub understands the @samp{QAgent} packet.
39231 The remote stub understands the @samp{QAllow} packet.
39233 @item QDisableRandomization
39234 The remote stub understands the @samp{QDisableRandomization} packet.
39236 @item StaticTracepoint
39237 @cindex static tracepoints, in remote protocol
39238 The remote stub supports static tracepoints.
39240 @item InstallInTrace
39241 @anchor{install tracepoint in tracing}
39242 The remote stub supports installing tracepoint in tracing.
39244 @item EnableDisableTracepoints
39245 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39246 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39247 to be enabled and disabled while a trace experiment is running.
39249 @item QTBuffer:size
39250 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39251 packet that allows to change the size of the trace buffer.
39254 @cindex string tracing, in remote protocol
39255 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39256 See @ref{Bytecode Descriptions} for details about the bytecode.
39258 @item BreakpointCommands
39259 @cindex breakpoint commands, in remote protocol
39260 The remote stub supports running a breakpoint's command list itself,
39261 rather than reporting the hit to @value{GDBN}.
39264 The remote stub understands the @samp{Qbtrace:off} packet.
39267 The remote stub understands the @samp{Qbtrace:bts} packet.
39270 The remote stub understands the @samp{Qbtrace:pt} packet.
39272 @item Qbtrace-conf:bts:size
39273 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39275 @item Qbtrace-conf:pt:size
39276 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39279 The remote stub reports the @samp{swbreak} stop reason for memory
39283 The remote stub reports the @samp{hwbreak} stop reason for hardware
39287 The remote stub reports the @samp{fork} stop reason for fork events.
39290 The remote stub reports the @samp{vfork} stop reason for vfork events
39291 and vforkdone events.
39294 The remote stub reports the @samp{exec} stop reason for exec events.
39296 @item vContSupported
39297 The remote stub reports the supported actions in the reply to
39298 @samp{vCont?} packet.
39300 @item QThreadEvents
39301 The remote stub understands the @samp{QThreadEvents} packet.
39304 The remote stub reports the @samp{N} stop reply.
39309 @cindex symbol lookup, remote request
39310 @cindex @samp{qSymbol} packet
39311 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39312 requests. Accept requests from the target for the values of symbols.
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 symbol @var{sym_name} (hex encoded).
39320 @value{GDBN} may provide the value by using the
39321 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39325 @item qSymbol:@var{sym_value}:@var{sym_name}
39326 Set the value of @var{sym_name} to @var{sym_value}.
39328 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39329 target has previously requested.
39331 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39332 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39338 The target does not need to look up any (more) symbols.
39339 @item qSymbol:@var{sym_name}
39340 The target requests the value of a new symbol @var{sym_name} (hex
39341 encoded). @value{GDBN} will continue to supply the values of symbols
39342 (if available), until the target ceases to request them.
39347 @itemx QTDisconnected
39354 @itemx qTMinFTPILen
39356 @xref{Tracepoint Packets}.
39358 @item qThreadExtraInfo,@var{thread-id}
39359 @cindex thread attributes info, remote request
39360 @cindex @samp{qThreadExtraInfo} packet
39361 Obtain from the target OS a printable string description of thread
39362 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39363 for the forms of @var{thread-id}. This
39364 string may contain anything that the target OS thinks is interesting
39365 for @value{GDBN} to tell the user about the thread. The string is
39366 displayed in @value{GDBN}'s @code{info threads} display. Some
39367 examples of possible thread extra info strings are @samp{Runnable}, or
39368 @samp{Blocked on Mutex}.
39372 @item @var{XX}@dots{}
39373 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39374 comprising the printable string containing the extra information about
39375 the thread's attributes.
39378 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39379 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39380 conventions above. Please don't use this packet as a model for new
39399 @xref{Tracepoint Packets}.
39401 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39402 @cindex read special object, remote request
39403 @cindex @samp{qXfer} packet
39404 @anchor{qXfer read}
39405 Read uninterpreted bytes from the target's special data area
39406 identified by the keyword @var{object}. Request @var{length} bytes
39407 starting at @var{offset} bytes into the data. The content and
39408 encoding of @var{annex} is specific to @var{object}; it can supply
39409 additional details about what data to access.
39414 Data @var{data} (@pxref{Binary Data}) has been read from the
39415 target. There may be more data at a higher address (although
39416 it is permitted to return @samp{m} even for the last valid
39417 block of data, as long as at least one byte of data was read).
39418 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39422 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39423 There is no more data to be read. It is possible for @var{data} to
39424 have fewer bytes than the @var{length} in the request.
39427 The @var{offset} in the request is at the end of the data.
39428 There is no more data to be read.
39431 The request was malformed, or @var{annex} was invalid.
39434 The offset was invalid, or there was an error encountered reading the data.
39435 The @var{nn} part is a hex-encoded @code{errno} value.
39438 An empty reply indicates the @var{object} string was not recognized by
39439 the stub, or that the object does not support reading.
39442 Here are the specific requests of this form defined so far. All the
39443 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39444 formats, listed above.
39447 @item qXfer:auxv:read::@var{offset},@var{length}
39448 @anchor{qXfer auxiliary vector read}
39449 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39450 auxiliary vector}. Note @var{annex} must be empty.
39452 This packet is not probed by default; the remote stub must request it,
39453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39455 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39456 @anchor{qXfer btrace read}
39458 Return a description of the current branch trace.
39459 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39460 packet may have one of the following values:
39464 Returns all available branch trace.
39467 Returns all available branch trace if the branch trace changed since
39468 the last read request.
39471 Returns the new branch trace since the last read request. Adds a new
39472 block to the end of the trace that begins at zero and ends at the source
39473 location of the first branch in the trace buffer. This extra block is
39474 used to stitch traces together.
39476 If the trace buffer overflowed, returns an error indicating the overflow.
39479 This packet is not probed by default; the remote stub must request it
39480 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39482 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39483 @anchor{qXfer btrace-conf read}
39485 Return a description of the current branch trace configuration.
39486 @xref{Branch Trace Configuration Format}.
39488 This packet is not probed by default; the remote stub must request it
39489 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39491 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39492 @anchor{qXfer executable filename read}
39493 Return the full absolute name of the file that was executed to create
39494 a process running on the remote system. The annex specifies the
39495 numeric process ID of the process to query, encoded as a hexadecimal
39496 number. If the annex part is empty the remote stub should return the
39497 filename corresponding to the currently executing process.
39499 This packet is not probed by default; the remote stub must request it,
39500 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39502 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39503 @anchor{qXfer target description read}
39504 Access the @dfn{target description}. @xref{Target Descriptions}. The
39505 annex specifies which XML document to access. The main description is
39506 always loaded from the @samp{target.xml} annex.
39508 This packet is not probed by default; the remote stub must request it,
39509 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39511 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39512 @anchor{qXfer library list read}
39513 Access the target's list of loaded libraries. @xref{Library List Format}.
39514 The annex part of the generic @samp{qXfer} packet must be empty
39515 (@pxref{qXfer read}).
39517 Targets which maintain a list of libraries in the program's memory do
39518 not need to implement this packet; it is designed for platforms where
39519 the operating system manages the list of loaded libraries.
39521 This packet is not probed by default; the remote stub must request it,
39522 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39524 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39525 @anchor{qXfer svr4 library list read}
39526 Access the target's list of loaded libraries when the target is an SVR4
39527 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39528 of the generic @samp{qXfer} packet must be empty unless the remote
39529 stub indicated it supports the augmented form of this packet
39530 by supplying an appropriate @samp{qSupported} response
39531 (@pxref{qXfer read}, @ref{qSupported}).
39533 This packet is optional for better performance on SVR4 targets.
39534 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39536 This packet is not probed by default; the remote stub must request it,
39537 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39539 If the remote stub indicates it supports the augmented form of this
39540 packet then the annex part of the generic @samp{qXfer} packet may
39541 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39542 arguments. The currently supported arguments are:
39545 @item start=@var{address}
39546 A hexadecimal number specifying the address of the @samp{struct
39547 link_map} to start reading the library list from. If unset or zero
39548 then the first @samp{struct link_map} in the library list will be
39549 chosen as the starting point.
39551 @item prev=@var{address}
39552 A hexadecimal number specifying the address of the @samp{struct
39553 link_map} immediately preceding the @samp{struct link_map}
39554 specified by the @samp{start} argument. If unset or zero then
39555 the remote stub will expect that no @samp{struct link_map}
39556 exists prior to the starting point.
39560 Arguments that are not understood by the remote stub will be silently
39563 @item qXfer:memory-map:read::@var{offset},@var{length}
39564 @anchor{qXfer memory map read}
39565 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39566 annex part of the generic @samp{qXfer} packet must be empty
39567 (@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 (@pxref{qSupported}).
39572 @item qXfer:sdata:read::@var{offset},@var{length}
39573 @anchor{qXfer sdata read}
39575 Read contents of the extra collected static tracepoint marker
39576 information. The annex part of the generic @samp{qXfer} packet must
39577 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39580 This packet is not probed by default; the remote stub must request it,
39581 by supplying an appropriate @samp{qSupported} response
39582 (@pxref{qSupported}).
39584 @item qXfer:siginfo:read::@var{offset},@var{length}
39585 @anchor{qXfer siginfo read}
39586 Read contents of the extra signal information on the target
39587 system. The annex part of the generic @samp{qXfer} packet must be
39588 empty (@pxref{qXfer read}).
39590 This packet is not probed by default; the remote stub must request it,
39591 by supplying an appropriate @samp{qSupported} response
39592 (@pxref{qSupported}).
39594 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39595 @anchor{qXfer spu read}
39596 Read contents of an @code{spufs} file on the target system. The
39597 annex specifies which file to read; it must be of the form
39598 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39599 in the target process, and @var{name} identifes the @code{spufs} file
39600 in that context to be accessed.
39602 This packet is not probed by default; the remote stub must request it,
39603 by supplying an appropriate @samp{qSupported} response
39604 (@pxref{qSupported}).
39606 @item qXfer:threads:read::@var{offset},@var{length}
39607 @anchor{qXfer threads read}
39608 Access the list of threads on target. @xref{Thread List Format}. The
39609 annex part of the generic @samp{qXfer} packet must be empty
39610 (@pxref{qXfer read}).
39612 This packet is not probed by default; the remote stub must request it,
39613 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39615 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39616 @anchor{qXfer traceframe info read}
39618 Return a description of the current traceframe's contents.
39619 @xref{Traceframe Info Format}. The annex part of the generic
39620 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39622 This packet is not probed by default; the remote stub must request it,
39623 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39625 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39626 @anchor{qXfer unwind info block}
39628 Return the unwind information block for @var{pc}. This packet is used
39629 on OpenVMS/ia64 to ask the kernel unwind information.
39631 This packet is not probed by default.
39633 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39634 @anchor{qXfer fdpic loadmap read}
39635 Read contents of @code{loadmap}s on the target system. The
39636 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39637 executable @code{loadmap} or interpreter @code{loadmap} to read.
39639 This packet is not probed by default; the remote stub must request it,
39640 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39642 @item qXfer:osdata:read::@var{offset},@var{length}
39643 @anchor{qXfer osdata read}
39644 Access the target's @dfn{operating system information}.
39645 @xref{Operating System Information}.
39649 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39650 @cindex write data into object, remote request
39651 @anchor{qXfer write}
39652 Write uninterpreted bytes into the target's special data area
39653 identified by the keyword @var{object}, starting at @var{offset} bytes
39654 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39655 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39656 is specific to @var{object}; it can supply additional details about what data
39662 @var{nn} (hex encoded) is the number of bytes written.
39663 This may be fewer bytes than supplied in the request.
39666 The request was malformed, or @var{annex} was invalid.
39669 The offset was invalid, or there was an error encountered writing the data.
39670 The @var{nn} part is a hex-encoded @code{errno} value.
39673 An empty reply indicates the @var{object} string was not
39674 recognized by the stub, or that the object does not support writing.
39677 Here are the specific requests of this form defined so far. All the
39678 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39679 formats, listed above.
39682 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39683 @anchor{qXfer siginfo write}
39684 Write @var{data} to the extra signal information on the target system.
39685 The annex part of the generic @samp{qXfer} packet must be
39686 empty (@pxref{qXfer write}).
39688 This packet is not probed by default; the remote stub must request it,
39689 by supplying an appropriate @samp{qSupported} response
39690 (@pxref{qSupported}).
39692 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39693 @anchor{qXfer spu write}
39694 Write @var{data} to an @code{spufs} file on the target system. The
39695 annex specifies which file to write; it must be of the form
39696 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39697 in the target process, and @var{name} identifes the @code{spufs} file
39698 in that context to be accessed.
39700 This packet is not probed by default; the remote stub must request it,
39701 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39704 @item qXfer:@var{object}:@var{operation}:@dots{}
39705 Requests of this form may be added in the future. When a stub does
39706 not recognize the @var{object} keyword, or its support for
39707 @var{object} does not recognize the @var{operation} keyword, the stub
39708 must respond with an empty packet.
39710 @item qAttached:@var{pid}
39711 @cindex query attached, remote request
39712 @cindex @samp{qAttached} packet
39713 Return an indication of whether the remote server attached to an
39714 existing process or created a new process. When the multiprocess
39715 protocol extensions are supported (@pxref{multiprocess extensions}),
39716 @var{pid} is an integer in hexadecimal format identifying the target
39717 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39718 the query packet will be simplified as @samp{qAttached}.
39720 This query is used, for example, to know whether the remote process
39721 should be detached or killed when a @value{GDBN} session is ended with
39722 the @code{quit} command.
39727 The remote server attached to an existing process.
39729 The remote server created a new process.
39731 A badly formed request or an error was encountered.
39735 Enable branch tracing for the current thread using Branch Trace Store.
39740 Branch tracing has been enabled.
39742 A badly formed request or an error was encountered.
39746 Enable branch tracing for the current thread using Intel Processor Trace.
39751 Branch tracing has been enabled.
39753 A badly formed request or an error was encountered.
39757 Disable branch tracing for the current thread.
39762 Branch tracing has been disabled.
39764 A badly formed request or an error was encountered.
39767 @item Qbtrace-conf:bts:size=@var{value}
39768 Set the requested ring buffer size for new threads that use the
39769 btrace recording method in bts format.
39774 The ring buffer size has been set.
39776 A badly formed request or an error was encountered.
39779 @item Qbtrace-conf:pt:size=@var{value}
39780 Set the requested ring buffer size for new threads that use the
39781 btrace recording method in pt format.
39786 The ring buffer size has been set.
39788 A badly formed request or an error was encountered.
39793 @node Architecture-Specific Protocol Details
39794 @section Architecture-Specific Protocol Details
39796 This section describes how the remote protocol is applied to specific
39797 target architectures. Also see @ref{Standard Target Features}, for
39798 details of XML target descriptions for each architecture.
39801 * ARM-Specific Protocol Details::
39802 * MIPS-Specific Protocol Details::
39805 @node ARM-Specific Protocol Details
39806 @subsection @acronym{ARM}-specific Protocol Details
39809 * ARM Breakpoint Kinds::
39812 @node ARM Breakpoint Kinds
39813 @subsubsection @acronym{ARM} Breakpoint Kinds
39814 @cindex breakpoint kinds, @acronym{ARM}
39816 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39821 16-bit Thumb mode breakpoint.
39824 32-bit Thumb mode (Thumb-2) breakpoint.
39827 32-bit @acronym{ARM} mode breakpoint.
39831 @node MIPS-Specific Protocol Details
39832 @subsection @acronym{MIPS}-specific Protocol Details
39835 * MIPS Register packet Format::
39836 * MIPS Breakpoint Kinds::
39839 @node MIPS Register packet Format
39840 @subsubsection @acronym{MIPS} Register Packet Format
39841 @cindex register packet format, @acronym{MIPS}
39843 The following @code{g}/@code{G} packets have previously been defined.
39844 In the below, some thirty-two bit registers are transferred as
39845 sixty-four bits. Those registers should be zero/sign extended (which?)
39846 to fill the space allocated. Register bytes are transferred in target
39847 byte order. The two nibbles within a register byte are transferred
39848 most-significant -- least-significant.
39853 All registers are transferred as thirty-two bit quantities in the order:
39854 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39855 registers; fsr; fir; fp.
39858 All registers are transferred as sixty-four bit quantities (including
39859 thirty-two bit registers such as @code{sr}). The ordering is the same
39864 @node MIPS Breakpoint Kinds
39865 @subsubsection @acronym{MIPS} Breakpoint Kinds
39866 @cindex breakpoint kinds, @acronym{MIPS}
39868 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39873 16-bit @acronym{MIPS16} mode breakpoint.
39876 16-bit @acronym{microMIPS} mode breakpoint.
39879 32-bit standard @acronym{MIPS} mode breakpoint.
39882 32-bit @acronym{microMIPS} mode breakpoint.
39886 @node Tracepoint Packets
39887 @section Tracepoint Packets
39888 @cindex tracepoint packets
39889 @cindex packets, tracepoint
39891 Here we describe the packets @value{GDBN} uses to implement
39892 tracepoints (@pxref{Tracepoints}).
39896 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39897 @cindex @samp{QTDP} packet
39898 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39899 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39900 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39901 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39902 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39903 the number of bytes that the target should copy elsewhere to make room
39904 for the tracepoint. If an @samp{X} is present, it introduces a
39905 tracepoint condition, which consists of a hexadecimal length, followed
39906 by a comma and hex-encoded bytes, in a manner similar to action
39907 encodings as described below. If the trailing @samp{-} is present,
39908 further @samp{QTDP} packets will follow to specify this tracepoint's
39914 The packet was understood and carried out.
39916 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39918 The packet was not recognized.
39921 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39922 Define actions to be taken when a tracepoint is hit. The @var{n} and
39923 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39924 this tracepoint. This packet may only be sent immediately after
39925 another @samp{QTDP} packet that ended with a @samp{-}. If the
39926 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39927 specifying more actions for this tracepoint.
39929 In the series of action packets for a given tracepoint, at most one
39930 can have an @samp{S} before its first @var{action}. If such a packet
39931 is sent, it and the following packets define ``while-stepping''
39932 actions. Any prior packets define ordinary actions --- that is, those
39933 taken when the tracepoint is first hit. If no action packet has an
39934 @samp{S}, then all the packets in the series specify ordinary
39935 tracepoint actions.
39937 The @samp{@var{action}@dots{}} portion of the packet is a series of
39938 actions, concatenated without separators. Each action has one of the
39944 Collect the registers whose bits are set in @var{mask},
39945 a hexadecimal number whose @var{i}'th bit is set if register number
39946 @var{i} should be collected. (The least significant bit is numbered
39947 zero.) Note that @var{mask} may be any number of digits long; it may
39948 not fit in a 32-bit word.
39950 @item M @var{basereg},@var{offset},@var{len}
39951 Collect @var{len} bytes of memory starting at the address in register
39952 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39953 @samp{-1}, then the range has a fixed address: @var{offset} is the
39954 address of the lowest byte to collect. The @var{basereg},
39955 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39956 values (the @samp{-1} value for @var{basereg} is a special case).
39958 @item X @var{len},@var{expr}
39959 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39960 it directs. The agent expression @var{expr} is as described in
39961 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39962 two-digit hex number in the packet; @var{len} is the number of bytes
39963 in the expression (and thus one-half the number of hex digits in the
39968 Any number of actions may be packed together in a single @samp{QTDP}
39969 packet, as long as the packet does not exceed the maximum packet
39970 length (400 bytes, for many stubs). There may be only one @samp{R}
39971 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39972 actions. Any registers referred to by @samp{M} and @samp{X} actions
39973 must be collected by a preceding @samp{R} action. (The
39974 ``while-stepping'' actions are treated as if they were attached to a
39975 separate tracepoint, as far as these restrictions are concerned.)
39980 The packet was understood and carried out.
39982 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39984 The packet was not recognized.
39987 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39988 @cindex @samp{QTDPsrc} packet
39989 Specify a source string of tracepoint @var{n} at address @var{addr}.
39990 This is useful to get accurate reproduction of the tracepoints
39991 originally downloaded at the beginning of the trace run. The @var{type}
39992 is the name of the tracepoint part, such as @samp{cond} for the
39993 tracepoint's conditional expression (see below for a list of types), while
39994 @var{bytes} is the string, encoded in hexadecimal.
39996 @var{start} is the offset of the @var{bytes} within the overall source
39997 string, while @var{slen} is the total length of the source string.
39998 This is intended for handling source strings that are longer than will
39999 fit in a single packet.
40000 @c Add detailed example when this info is moved into a dedicated
40001 @c tracepoint descriptions section.
40003 The available string types are @samp{at} for the location,
40004 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40005 @value{GDBN} sends a separate packet for each command in the action
40006 list, in the same order in which the commands are stored in the list.
40008 The target does not need to do anything with source strings except
40009 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40012 Although this packet is optional, and @value{GDBN} will only send it
40013 if the target replies with @samp{TracepointSource} @xref{General
40014 Query Packets}, it makes both disconnected tracing and trace files
40015 much easier to use. Otherwise the user must be careful that the
40016 tracepoints in effect while looking at trace frames are identical to
40017 the ones in effect during the trace run; even a small discrepancy
40018 could cause @samp{tdump} not to work, or a particular trace frame not
40021 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40022 @cindex define trace state variable, remote request
40023 @cindex @samp{QTDV} packet
40024 Create a new trace state variable, number @var{n}, with an initial
40025 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40026 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40027 the option of not using this packet for initial values of zero; the
40028 target should simply create the trace state variables as they are
40029 mentioned in expressions. The value @var{builtin} should be 1 (one)
40030 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40031 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40032 @samp{qTsV} packet had it set. The contents of @var{name} is the
40033 hex-encoded name (without the leading @samp{$}) of the trace state
40036 @item QTFrame:@var{n}
40037 @cindex @samp{QTFrame} packet
40038 Select the @var{n}'th tracepoint frame from the buffer, and use the
40039 register and memory contents recorded there to answer subsequent
40040 request packets from @value{GDBN}.
40042 A successful reply from the stub indicates that the stub has found the
40043 requested frame. The response is a series of parts, concatenated
40044 without separators, describing the frame we selected. Each part has
40045 one of the following forms:
40049 The selected frame is number @var{n} in the trace frame buffer;
40050 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40051 was no frame matching the criteria in the request packet.
40054 The selected trace frame records a hit of tracepoint number @var{t};
40055 @var{t} is a hexadecimal number.
40059 @item QTFrame:pc:@var{addr}
40060 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40061 currently selected frame whose PC is @var{addr};
40062 @var{addr} is a hexadecimal number.
40064 @item QTFrame:tdp:@var{t}
40065 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40066 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40067 is a hexadecimal number.
40069 @item QTFrame:range:@var{start}:@var{end}
40070 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40071 currently selected frame whose PC is between @var{start} (inclusive)
40072 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40075 @item QTFrame:outside:@var{start}:@var{end}
40076 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40077 frame @emph{outside} the given range of addresses (exclusive).
40080 @cindex @samp{qTMinFTPILen} packet
40081 This packet requests the minimum length of instruction at which a fast
40082 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40083 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40084 it depends on the target system being able to create trampolines in
40085 the first 64K of memory, which might or might not be possible for that
40086 system. So the reply to this packet will be 4 if it is able to
40093 The minimum instruction length is currently unknown.
40095 The minimum instruction length is @var{length}, where @var{length}
40096 is a hexadecimal number greater or equal to 1. A reply
40097 of 1 means that a fast tracepoint may be placed on any instruction
40098 regardless of size.
40100 An error has occurred.
40102 An empty reply indicates that the request is not supported by the stub.
40106 @cindex @samp{QTStart} packet
40107 Begin the tracepoint experiment. Begin collecting data from
40108 tracepoint hits in the trace frame buffer. This packet supports the
40109 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40110 instruction reply packet}).
40113 @cindex @samp{QTStop} packet
40114 End the tracepoint experiment. Stop collecting trace frames.
40116 @item QTEnable:@var{n}:@var{addr}
40118 @cindex @samp{QTEnable} packet
40119 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40120 experiment. If the tracepoint was previously disabled, then collection
40121 of data from it will resume.
40123 @item QTDisable:@var{n}:@var{addr}
40125 @cindex @samp{QTDisable} packet
40126 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40127 experiment. No more data will be collected from the tracepoint unless
40128 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40131 @cindex @samp{QTinit} packet
40132 Clear the table of tracepoints, and empty the trace frame buffer.
40134 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40135 @cindex @samp{QTro} packet
40136 Establish the given ranges of memory as ``transparent''. The stub
40137 will answer requests for these ranges from memory's current contents,
40138 if they were not collected as part of the tracepoint hit.
40140 @value{GDBN} uses this to mark read-only regions of memory, like those
40141 containing program code. Since these areas never change, they should
40142 still have the same contents they did when the tracepoint was hit, so
40143 there's no reason for the stub to refuse to provide their contents.
40145 @item QTDisconnected:@var{value}
40146 @cindex @samp{QTDisconnected} packet
40147 Set the choice to what to do with the tracing run when @value{GDBN}
40148 disconnects from the target. A @var{value} of 1 directs the target to
40149 continue the tracing run, while 0 tells the target to stop tracing if
40150 @value{GDBN} is no longer in the picture.
40153 @cindex @samp{qTStatus} packet
40154 Ask the stub if there is a trace experiment running right now.
40156 The reply has the form:
40160 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40161 @var{running} is a single digit @code{1} if the trace is presently
40162 running, or @code{0} if not. It is followed by semicolon-separated
40163 optional fields that an agent may use to report additional status.
40167 If the trace is not running, the agent may report any of several
40168 explanations as one of the optional fields:
40173 No trace has been run yet.
40175 @item tstop[:@var{text}]:0
40176 The trace was stopped by a user-originated stop command. The optional
40177 @var{text} field is a user-supplied string supplied as part of the
40178 stop command (for instance, an explanation of why the trace was
40179 stopped manually). It is hex-encoded.
40182 The trace stopped because the trace buffer filled up.
40184 @item tdisconnected:0
40185 The trace stopped because @value{GDBN} disconnected from the target.
40187 @item tpasscount:@var{tpnum}
40188 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40190 @item terror:@var{text}:@var{tpnum}
40191 The trace stopped because tracepoint @var{tpnum} had an error. The
40192 string @var{text} is available to describe the nature of the error
40193 (for instance, a divide by zero in the condition expression); it
40197 The trace stopped for some other reason.
40201 Additional optional fields supply statistical and other information.
40202 Although not required, they are extremely useful for users monitoring
40203 the progress of a trace run. If a trace has stopped, and these
40204 numbers are reported, they must reflect the state of the just-stopped
40209 @item tframes:@var{n}
40210 The number of trace frames in the buffer.
40212 @item tcreated:@var{n}
40213 The total number of trace frames created during the run. This may
40214 be larger than the trace frame count, if the buffer is circular.
40216 @item tsize:@var{n}
40217 The total size of the trace buffer, in bytes.
40219 @item tfree:@var{n}
40220 The number of bytes still unused in the buffer.
40222 @item circular:@var{n}
40223 The value of the circular trace buffer flag. @code{1} means that the
40224 trace buffer is circular and old trace frames will be discarded if
40225 necessary to make room, @code{0} means that the trace buffer is linear
40228 @item disconn:@var{n}
40229 The value of the disconnected tracing flag. @code{1} means that
40230 tracing will continue after @value{GDBN} disconnects, @code{0} means
40231 that the trace run will stop.
40235 @item qTP:@var{tp}:@var{addr}
40236 @cindex tracepoint status, remote request
40237 @cindex @samp{qTP} packet
40238 Ask the stub for the current state of tracepoint number @var{tp} at
40239 address @var{addr}.
40243 @item V@var{hits}:@var{usage}
40244 The tracepoint has been hit @var{hits} times so far during the trace
40245 run, and accounts for @var{usage} in the trace buffer. Note that
40246 @code{while-stepping} steps are not counted as separate hits, but the
40247 steps' space consumption is added into the usage number.
40251 @item qTV:@var{var}
40252 @cindex trace state variable value, remote request
40253 @cindex @samp{qTV} packet
40254 Ask the stub for the value of the trace state variable number @var{var}.
40259 The value of the variable is @var{value}. This will be the current
40260 value of the variable if the user is examining a running target, or a
40261 saved value if the variable was collected in the trace frame that the
40262 user is looking at. Note that multiple requests may result in
40263 different reply values, such as when requesting values while the
40264 program is running.
40267 The value of the variable is unknown. This would occur, for example,
40268 if the user is examining a trace frame in which the requested variable
40273 @cindex @samp{qTfP} packet
40275 @cindex @samp{qTsP} packet
40276 These packets request data about tracepoints that are being used by
40277 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40278 of data, and multiple @code{qTsP} to get additional pieces. Replies
40279 to these packets generally take the form of the @code{QTDP} packets
40280 that define tracepoints. (FIXME add detailed syntax)
40283 @cindex @samp{qTfV} packet
40285 @cindex @samp{qTsV} packet
40286 These packets request data about trace state variables that are on the
40287 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40288 and multiple @code{qTsV} to get additional variables. Replies to
40289 these packets follow the syntax of the @code{QTDV} packets that define
40290 trace state variables.
40296 @cindex @samp{qTfSTM} packet
40297 @cindex @samp{qTsSTM} packet
40298 These packets request data about static tracepoint markers that exist
40299 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40300 first piece of data, and multiple @code{qTsSTM} to get additional
40301 pieces. Replies to these packets take the following form:
40305 @item m @var{address}:@var{id}:@var{extra}
40307 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40308 a comma-separated list of markers
40310 (lower case letter @samp{L}) denotes end of list.
40312 An error occurred. The error number @var{nn} is given as hex digits.
40314 An empty reply indicates that the request is not supported by the
40318 The @var{address} is encoded in hex;
40319 @var{id} and @var{extra} are strings encoded in hex.
40321 In response to each query, the target will reply with a list of one or
40322 more markers, separated by commas. @value{GDBN} will respond to each
40323 reply with a request for more markers (using the @samp{qs} form of the
40324 query), until the target responds with @samp{l} (lower-case ell, for
40327 @item qTSTMat:@var{address}
40329 @cindex @samp{qTSTMat} packet
40330 This packets requests data about static tracepoint markers in the
40331 target program at @var{address}. Replies to this packet follow the
40332 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40333 tracepoint markers.
40335 @item QTSave:@var{filename}
40336 @cindex @samp{QTSave} packet
40337 This packet directs the target to save trace data to the file name
40338 @var{filename} in the target's filesystem. The @var{filename} is encoded
40339 as a hex string; the interpretation of the file name (relative vs
40340 absolute, wild cards, etc) is up to the target.
40342 @item qTBuffer:@var{offset},@var{len}
40343 @cindex @samp{qTBuffer} packet
40344 Return up to @var{len} bytes of the current contents of trace buffer,
40345 starting at @var{offset}. The trace buffer is treated as if it were
40346 a contiguous collection of traceframes, as per the trace file format.
40347 The reply consists as many hex-encoded bytes as the target can deliver
40348 in a packet; it is not an error to return fewer than were asked for.
40349 A reply consisting of just @code{l} indicates that no bytes are
40352 @item QTBuffer:circular:@var{value}
40353 This packet directs the target to use a circular trace buffer if
40354 @var{value} is 1, or a linear buffer if the value is 0.
40356 @item QTBuffer:size:@var{size}
40357 @anchor{QTBuffer-size}
40358 @cindex @samp{QTBuffer size} packet
40359 This packet directs the target to make the trace buffer be of size
40360 @var{size} if possible. A value of @code{-1} tells the target to
40361 use whatever size it prefers.
40363 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40364 @cindex @samp{QTNotes} packet
40365 This packet adds optional textual notes to the trace run. Allowable
40366 types include @code{user}, @code{notes}, and @code{tstop}, the
40367 @var{text} fields are arbitrary strings, hex-encoded.
40371 @subsection Relocate instruction reply packet
40372 When installing fast tracepoints in memory, the target may need to
40373 relocate the instruction currently at the tracepoint address to a
40374 different address in memory. For most instructions, a simple copy is
40375 enough, but, for example, call instructions that implicitly push the
40376 return address on the stack, and relative branches or other
40377 PC-relative instructions require offset adjustment, so that the effect
40378 of executing the instruction at a different address is the same as if
40379 it had executed in the original location.
40381 In response to several of the tracepoint packets, the target may also
40382 respond with a number of intermediate @samp{qRelocInsn} request
40383 packets before the final result packet, to have @value{GDBN} handle
40384 this relocation operation. If a packet supports this mechanism, its
40385 documentation will explicitly say so. See for example the above
40386 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40387 format of the request is:
40390 @item qRelocInsn:@var{from};@var{to}
40392 This requests @value{GDBN} to copy instruction at address @var{from}
40393 to address @var{to}, possibly adjusted so that executing the
40394 instruction at @var{to} has the same effect as executing it at
40395 @var{from}. @value{GDBN} writes the adjusted instruction to target
40396 memory starting at @var{to}.
40401 @item qRelocInsn:@var{adjusted_size}
40402 Informs the stub the relocation is complete. The @var{adjusted_size} is
40403 the length in bytes of resulting relocated instruction sequence.
40405 A badly formed request was detected, or an error was encountered while
40406 relocating the instruction.
40409 @node Host I/O Packets
40410 @section Host I/O Packets
40411 @cindex Host I/O, remote protocol
40412 @cindex file transfer, remote protocol
40414 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40415 operations on the far side of a remote link. For example, Host I/O is
40416 used to upload and download files to a remote target with its own
40417 filesystem. Host I/O uses the same constant values and data structure
40418 layout as the target-initiated File-I/O protocol. However, the
40419 Host I/O packets are structured differently. The target-initiated
40420 protocol relies on target memory to store parameters and buffers.
40421 Host I/O requests are initiated by @value{GDBN}, and the
40422 target's memory is not involved. @xref{File-I/O Remote Protocol
40423 Extension}, for more details on the target-initiated protocol.
40425 The Host I/O request packets all encode a single operation along with
40426 its arguments. They have this format:
40430 @item vFile:@var{operation}: @var{parameter}@dots{}
40431 @var{operation} is the name of the particular request; the target
40432 should compare the entire packet name up to the second colon when checking
40433 for a supported operation. The format of @var{parameter} depends on
40434 the operation. Numbers are always passed in hexadecimal. Negative
40435 numbers have an explicit minus sign (i.e.@: two's complement is not
40436 used). Strings (e.g.@: filenames) are encoded as a series of
40437 hexadecimal bytes. The last argument to a system call may be a
40438 buffer of escaped binary data (@pxref{Binary Data}).
40442 The valid responses to Host I/O packets are:
40446 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40447 @var{result} is the integer value returned by this operation, usually
40448 non-negative for success and -1 for errors. If an error has occured,
40449 @var{errno} will be included in the result specifying a
40450 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40451 operations which return data, @var{attachment} supplies the data as a
40452 binary buffer. Binary buffers in response packets are escaped in the
40453 normal way (@pxref{Binary Data}). See the individual packet
40454 documentation for the interpretation of @var{result} and
40458 An empty response indicates that this operation is not recognized.
40462 These are the supported Host I/O operations:
40465 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40466 Open a file at @var{filename} and return a file descriptor for it, or
40467 return -1 if an error occurs. The @var{filename} is a string,
40468 @var{flags} is an integer indicating a mask of open flags
40469 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40470 of mode bits to use if the file is created (@pxref{mode_t Values}).
40471 @xref{open}, for details of the open flags and mode values.
40473 @item vFile:close: @var{fd}
40474 Close the open file corresponding to @var{fd} and return 0, or
40475 -1 if an error occurs.
40477 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40478 Read data from the open file corresponding to @var{fd}. Up to
40479 @var{count} bytes will be read from the file, starting at @var{offset}
40480 relative to the start of the file. The target may read fewer bytes;
40481 common reasons include packet size limits and an end-of-file
40482 condition. The number of bytes read is returned. Zero should only be
40483 returned for a successful read at the end of the file, or if
40484 @var{count} was zero.
40486 The data read should be returned as a binary attachment on success.
40487 If zero bytes were read, the response should include an empty binary
40488 attachment (i.e.@: a trailing semicolon). The return value is the
40489 number of target bytes read; the binary attachment may be longer if
40490 some characters were escaped.
40492 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40493 Write @var{data} (a binary buffer) to the open file corresponding
40494 to @var{fd}. Start the write at @var{offset} from the start of the
40495 file. Unlike many @code{write} system calls, there is no
40496 separate @var{count} argument; the length of @var{data} in the
40497 packet is used. @samp{vFile:write} returns the number of bytes written,
40498 which may be shorter than the length of @var{data}, or -1 if an
40501 @item vFile:fstat: @var{fd}
40502 Get information about the open file corresponding to @var{fd}.
40503 On success the information is returned as a binary attachment
40504 and the return value is the size of this attachment in bytes.
40505 If an error occurs the return value is -1. The format of the
40506 returned binary attachment is as described in @ref{struct stat}.
40508 @item vFile:unlink: @var{filename}
40509 Delete the file at @var{filename} on the target. Return 0,
40510 or -1 if an error occurs. The @var{filename} is a string.
40512 @item vFile:readlink: @var{filename}
40513 Read value of symbolic link @var{filename} on the target. Return
40514 the number of bytes read, or -1 if an error occurs.
40516 The data read should be returned as a binary attachment on success.
40517 If zero bytes were read, the response should include an empty binary
40518 attachment (i.e.@: a trailing semicolon). The return value is the
40519 number of target bytes read; the binary attachment may be longer if
40520 some characters were escaped.
40522 @item vFile:setfs: @var{pid}
40523 Select the filesystem on which @code{vFile} operations with
40524 @var{filename} arguments will operate. This is required for
40525 @value{GDBN} to be able to access files on remote targets where
40526 the remote stub does not share a common filesystem with the
40529 If @var{pid} is nonzero, select the filesystem as seen by process
40530 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40531 the remote stub. Return 0 on success, or -1 if an error occurs.
40532 If @code{vFile:setfs:} indicates success, the selected filesystem
40533 remains selected until the next successful @code{vFile:setfs:}
40539 @section Interrupts
40540 @cindex interrupts (remote protocol)
40541 @anchor{interrupting remote targets}
40543 In all-stop mode, when a program on the remote target is running,
40544 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40545 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40546 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40548 The precise meaning of @code{BREAK} is defined by the transport
40549 mechanism and may, in fact, be undefined. @value{GDBN} does not
40550 currently define a @code{BREAK} mechanism for any of the network
40551 interfaces except for TCP, in which case @value{GDBN} sends the
40552 @code{telnet} BREAK sequence.
40554 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40555 transport mechanisms. It is represented by sending the single byte
40556 @code{0x03} without any of the usual packet overhead described in
40557 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40558 transmitted as part of a packet, it is considered to be packet data
40559 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40560 (@pxref{X packet}), used for binary downloads, may include an unescaped
40561 @code{0x03} as part of its packet.
40563 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40564 When Linux kernel receives this sequence from serial port,
40565 it stops execution and connects to gdb.
40567 In non-stop mode, because packet resumptions are asynchronous
40568 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40569 command to the remote stub, even when the target is running. For that
40570 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40571 packet}) with the usual packet framing instead of the single byte
40574 Stubs are not required to recognize these interrupt mechanisms and the
40575 precise meaning associated with receipt of the interrupt is
40576 implementation defined. If the target supports debugging of multiple
40577 threads and/or processes, it should attempt to interrupt all
40578 currently-executing threads and processes.
40579 If the stub is successful at interrupting the
40580 running program, it should send one of the stop
40581 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40582 of successfully stopping the program in all-stop mode, and a stop reply
40583 for each stopped thread in non-stop mode.
40584 Interrupts received while the
40585 program is stopped are queued and the program will be interrupted when
40586 it is resumed next time.
40588 @node Notification Packets
40589 @section Notification Packets
40590 @cindex notification packets
40591 @cindex packets, notification
40593 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40594 packets that require no acknowledgment. Both the GDB and the stub
40595 may send notifications (although the only notifications defined at
40596 present are sent by the stub). Notifications carry information
40597 without incurring the round-trip latency of an acknowledgment, and so
40598 are useful for low-impact communications where occasional packet loss
40601 A notification packet has the form @samp{% @var{data} #
40602 @var{checksum}}, where @var{data} is the content of the notification,
40603 and @var{checksum} is a checksum of @var{data}, computed and formatted
40604 as for ordinary @value{GDBN} packets. A notification's @var{data}
40605 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40606 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40607 to acknowledge the notification's receipt or to report its corruption.
40609 Every notification's @var{data} begins with a name, which contains no
40610 colon characters, followed by a colon character.
40612 Recipients should silently ignore corrupted notifications and
40613 notifications they do not understand. Recipients should restart
40614 timeout periods on receipt of a well-formed notification, whether or
40615 not they understand it.
40617 Senders should only send the notifications described here when this
40618 protocol description specifies that they are permitted. In the
40619 future, we may extend the protocol to permit existing notifications in
40620 new contexts; this rule helps older senders avoid confusing newer
40623 (Older versions of @value{GDBN} ignore bytes received until they see
40624 the @samp{$} byte that begins an ordinary packet, so new stubs may
40625 transmit notifications without fear of confusing older clients. There
40626 are no notifications defined for @value{GDBN} to send at the moment, but we
40627 assume that most older stubs would ignore them, as well.)
40629 Each notification is comprised of three parts:
40631 @item @var{name}:@var{event}
40632 The notification packet is sent by the side that initiates the
40633 exchange (currently, only the stub does that), with @var{event}
40634 carrying the specific information about the notification, and
40635 @var{name} specifying the name of the notification.
40637 The acknowledge sent by the other side, usually @value{GDBN}, to
40638 acknowledge the exchange and request the event.
40641 The purpose of an asynchronous notification mechanism is to report to
40642 @value{GDBN} that something interesting happened in the remote stub.
40644 The remote stub may send notification @var{name}:@var{event}
40645 at any time, but @value{GDBN} acknowledges the notification when
40646 appropriate. The notification event is pending before @value{GDBN}
40647 acknowledges. Only one notification at a time may be pending; if
40648 additional events occur before @value{GDBN} has acknowledged the
40649 previous notification, they must be queued by the stub for later
40650 synchronous transmission in response to @var{ack} packets from
40651 @value{GDBN}. Because the notification mechanism is unreliable,
40652 the stub is permitted to resend a notification if it believes
40653 @value{GDBN} may not have received it.
40655 Specifically, notifications may appear when @value{GDBN} is not
40656 otherwise reading input from the stub, or when @value{GDBN} is
40657 expecting to read a normal synchronous response or a
40658 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40659 Notification packets are distinct from any other communication from
40660 the stub so there is no ambiguity.
40662 After receiving a notification, @value{GDBN} shall acknowledge it by
40663 sending a @var{ack} packet as a regular, synchronous request to the
40664 stub. Such acknowledgment is not required to happen immediately, as
40665 @value{GDBN} is permitted to send other, unrelated packets to the
40666 stub first, which the stub should process normally.
40668 Upon receiving a @var{ack} packet, if the stub has other queued
40669 events to report to @value{GDBN}, it shall respond by sending a
40670 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40671 packet to solicit further responses; again, it is permitted to send
40672 other, unrelated packets as well which the stub should process
40675 If the stub receives a @var{ack} packet and there are no additional
40676 @var{event} to report, the stub shall return an @samp{OK} response.
40677 At this point, @value{GDBN} has finished processing a notification
40678 and the stub has completed sending any queued events. @value{GDBN}
40679 won't accept any new notifications until the final @samp{OK} is
40680 received . If further notification events occur, the stub shall send
40681 a new notification, @value{GDBN} shall accept the notification, and
40682 the process shall be repeated.
40684 The process of asynchronous notification can be illustrated by the
40687 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40690 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40692 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40697 The following notifications are defined:
40698 @multitable @columnfractions 0.12 0.12 0.38 0.38
40707 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40708 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40709 for information on how these notifications are acknowledged by
40711 @tab Report an asynchronous stop event in non-stop mode.
40715 @node Remote Non-Stop
40716 @section Remote Protocol Support for Non-Stop Mode
40718 @value{GDBN}'s remote protocol supports non-stop debugging of
40719 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40720 supports non-stop mode, it should report that to @value{GDBN} by including
40721 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40723 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40724 establishing a new connection with the stub. Entering non-stop mode
40725 does not alter the state of any currently-running threads, but targets
40726 must stop all threads in any already-attached processes when entering
40727 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40728 probe the target state after a mode change.
40730 In non-stop mode, when an attached process encounters an event that
40731 would otherwise be reported with a stop reply, it uses the
40732 asynchronous notification mechanism (@pxref{Notification Packets}) to
40733 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40734 in all processes are stopped when a stop reply is sent, in non-stop
40735 mode only the thread reporting the stop event is stopped. That is,
40736 when reporting a @samp{S} or @samp{T} response to indicate completion
40737 of a step operation, hitting a breakpoint, or a fault, only the
40738 affected thread is stopped; any other still-running threads continue
40739 to run. When reporting a @samp{W} or @samp{X} response, all running
40740 threads belonging to other attached processes continue to run.
40742 In non-stop mode, the target shall respond to the @samp{?} packet as
40743 follows. First, any incomplete stop reply notification/@samp{vStopped}
40744 sequence in progress is abandoned. The target must begin a new
40745 sequence reporting stop events for all stopped threads, whether or not
40746 it has previously reported those events to @value{GDBN}. The first
40747 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40748 subsequent stop replies are sent as responses to @samp{vStopped} packets
40749 using the mechanism described above. The target must not send
40750 asynchronous stop reply notifications until the sequence is complete.
40751 If all threads are running when the target receives the @samp{?} packet,
40752 or if the target is not attached to any process, it shall respond
40755 If the stub supports non-stop mode, it should also support the
40756 @samp{swbreak} stop reason if software breakpoints are supported, and
40757 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40758 (@pxref{swbreak stop reason}). This is because given the asynchronous
40759 nature of non-stop mode, between the time a thread hits a breakpoint
40760 and the time the event is finally processed by @value{GDBN}, the
40761 breakpoint may have already been removed from the target. Due to
40762 this, @value{GDBN} needs to be able to tell whether a trap stop was
40763 caused by a delayed breakpoint event, which should be ignored, as
40764 opposed to a random trap signal, which should be reported to the user.
40765 Note the @samp{swbreak} feature implies that the target is responsible
40766 for adjusting the PC when a software breakpoint triggers, if
40767 necessary, such as on the x86 architecture.
40769 @node Packet Acknowledgment
40770 @section Packet Acknowledgment
40772 @cindex acknowledgment, for @value{GDBN} remote
40773 @cindex packet acknowledgment, for @value{GDBN} remote
40774 By default, when either the host or the target machine receives a packet,
40775 the first response expected is an acknowledgment: either @samp{+} (to indicate
40776 the package was received correctly) or @samp{-} (to request retransmission).
40777 This mechanism allows the @value{GDBN} remote protocol to operate over
40778 unreliable transport mechanisms, such as a serial line.
40780 In cases where the transport mechanism is itself reliable (such as a pipe or
40781 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40782 It may be desirable to disable them in that case to reduce communication
40783 overhead, or for other reasons. This can be accomplished by means of the
40784 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40786 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40787 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40788 and response format still includes the normal checksum, as described in
40789 @ref{Overview}, but the checksum may be ignored by the receiver.
40791 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40792 no-acknowledgment mode, it should report that to @value{GDBN}
40793 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40794 @pxref{qSupported}.
40795 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40796 disabled via the @code{set remote noack-packet off} command
40797 (@pxref{Remote Configuration}),
40798 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40799 Only then may the stub actually turn off packet acknowledgments.
40800 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40801 response, which can be safely ignored by the stub.
40803 Note that @code{set remote noack-packet} command only affects negotiation
40804 between @value{GDBN} and the stub when subsequent connections are made;
40805 it does not affect the protocol acknowledgment state for any current
40807 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40808 new connection is established,
40809 there is also no protocol request to re-enable the acknowledgments
40810 for the current connection, once disabled.
40815 Example sequence of a target being re-started. Notice how the restart
40816 does not get any direct output:
40821 @emph{target restarts}
40824 <- @code{T001:1234123412341234}
40828 Example sequence of a target being stepped by a single instruction:
40831 -> @code{G1445@dots{}}
40836 <- @code{T001:1234123412341234}
40840 <- @code{1455@dots{}}
40844 @node File-I/O Remote Protocol Extension
40845 @section File-I/O Remote Protocol Extension
40846 @cindex File-I/O remote protocol extension
40849 * File-I/O Overview::
40850 * Protocol Basics::
40851 * The F Request Packet::
40852 * The F Reply Packet::
40853 * The Ctrl-C Message::
40855 * List of Supported Calls::
40856 * Protocol-specific Representation of Datatypes::
40858 * File-I/O Examples::
40861 @node File-I/O Overview
40862 @subsection File-I/O Overview
40863 @cindex file-i/o overview
40865 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40866 target to use the host's file system and console I/O to perform various
40867 system calls. System calls on the target system are translated into a
40868 remote protocol packet to the host system, which then performs the needed
40869 actions and returns a response packet to the target system.
40870 This simulates file system operations even on targets that lack file systems.
40872 The protocol is defined to be independent of both the host and target systems.
40873 It uses its own internal representation of datatypes and values. Both
40874 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40875 translating the system-dependent value representations into the internal
40876 protocol representations when data is transmitted.
40878 The communication is synchronous. A system call is possible only when
40879 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40880 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40881 the target is stopped to allow deterministic access to the target's
40882 memory. Therefore File-I/O is not interruptible by target signals. On
40883 the other hand, it is possible to interrupt File-I/O by a user interrupt
40884 (@samp{Ctrl-C}) within @value{GDBN}.
40886 The target's request to perform a host system call does not finish
40887 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40888 after finishing the system call, the target returns to continuing the
40889 previous activity (continue, step). No additional continue or step
40890 request from @value{GDBN} is required.
40893 (@value{GDBP}) continue
40894 <- target requests 'system call X'
40895 target is stopped, @value{GDBN} executes system call
40896 -> @value{GDBN} returns result
40897 ... target continues, @value{GDBN} returns to wait for the target
40898 <- target hits breakpoint and sends a Txx packet
40901 The protocol only supports I/O on the console and to regular files on
40902 the host file system. Character or block special devices, pipes,
40903 named pipes, sockets or any other communication method on the host
40904 system are not supported by this protocol.
40906 File I/O is not supported in non-stop mode.
40908 @node Protocol Basics
40909 @subsection Protocol Basics
40910 @cindex protocol basics, file-i/o
40912 The File-I/O protocol uses the @code{F} packet as the request as well
40913 as reply packet. Since a File-I/O system call can only occur when
40914 @value{GDBN} is waiting for a response from the continuing or stepping target,
40915 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40916 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40917 This @code{F} packet contains all information needed to allow @value{GDBN}
40918 to call the appropriate host system call:
40922 A unique identifier for the requested system call.
40925 All parameters to the system call. Pointers are given as addresses
40926 in the target memory address space. Pointers to strings are given as
40927 pointer/length pair. Numerical values are given as they are.
40928 Numerical control flags are given in a protocol-specific representation.
40932 At this point, @value{GDBN} has to perform the following actions.
40936 If the parameters include pointer values to data needed as input to a
40937 system call, @value{GDBN} requests this data from the target with a
40938 standard @code{m} packet request. This additional communication has to be
40939 expected by the target implementation and is handled as any other @code{m}
40943 @value{GDBN} translates all value from protocol representation to host
40944 representation as needed. Datatypes are coerced into the host types.
40947 @value{GDBN} calls the system call.
40950 It then coerces datatypes back to protocol representation.
40953 If the system call is expected to return data in buffer space specified
40954 by pointer parameters to the call, the data is transmitted to the
40955 target using a @code{M} or @code{X} packet. This packet has to be expected
40956 by the target implementation and is handled as any other @code{M} or @code{X}
40961 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40962 necessary information for the target to continue. This at least contains
40969 @code{errno}, if has been changed by the system call.
40976 After having done the needed type and value coercion, the target continues
40977 the latest continue or step action.
40979 @node The F Request Packet
40980 @subsection The @code{F} Request Packet
40981 @cindex file-i/o request packet
40982 @cindex @code{F} request packet
40984 The @code{F} request packet has the following format:
40987 @item F@var{call-id},@var{parameter@dots{}}
40989 @var{call-id} is the identifier to indicate the host system call to be called.
40990 This is just the name of the function.
40992 @var{parameter@dots{}} are the parameters to the system call.
40993 Parameters are hexadecimal integer values, either the actual values in case
40994 of scalar datatypes, pointers to target buffer space in case of compound
40995 datatypes and unspecified memory areas, or pointer/length pairs in case
40996 of string parameters. These are appended to the @var{call-id} as a
40997 comma-delimited list. All values are transmitted in ASCII
40998 string representation, pointer/length pairs separated by a slash.
41004 @node The F Reply Packet
41005 @subsection The @code{F} Reply Packet
41006 @cindex file-i/o reply packet
41007 @cindex @code{F} reply packet
41009 The @code{F} reply packet has the following format:
41013 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41015 @var{retcode} is the return code of the system call as hexadecimal value.
41017 @var{errno} is the @code{errno} set by the call, in protocol-specific
41019 This parameter can be omitted if the call was successful.
41021 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41022 case, @var{errno} must be sent as well, even if the call was successful.
41023 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41030 or, if the call was interrupted before the host call has been performed:
41037 assuming 4 is the protocol-specific representation of @code{EINTR}.
41042 @node The Ctrl-C Message
41043 @subsection The @samp{Ctrl-C} Message
41044 @cindex ctrl-c message, in file-i/o protocol
41046 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41047 reply packet (@pxref{The F Reply Packet}),
41048 the target should behave as if it had
41049 gotten a break message. The meaning for the target is ``system call
41050 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41051 (as with a break message) and return to @value{GDBN} with a @code{T02}
41054 It's important for the target to know in which
41055 state the system call was interrupted. There are two possible cases:
41059 The system call hasn't been performed on the host yet.
41062 The system call on the host has been finished.
41066 These two states can be distinguished by the target by the value of the
41067 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41068 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41069 on POSIX systems. In any other case, the target may presume that the
41070 system call has been finished --- successfully or not --- and should behave
41071 as if the break message arrived right after the system call.
41073 @value{GDBN} must behave reliably. If the system call has not been called
41074 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41075 @code{errno} in the packet. If the system call on the host has been finished
41076 before the user requests a break, the full action must be finished by
41077 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41078 The @code{F} packet may only be sent when either nothing has happened
41079 or the full action has been completed.
41082 @subsection Console I/O
41083 @cindex console i/o as part of file-i/o
41085 By default and if not explicitly closed by the target system, the file
41086 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41087 on the @value{GDBN} console is handled as any other file output operation
41088 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41089 by @value{GDBN} so that after the target read request from file descriptor
41090 0 all following typing is buffered until either one of the following
41095 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41097 system call is treated as finished.
41100 The user presses @key{RET}. This is treated as end of input with a trailing
41104 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41105 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41109 If the user has typed more characters than fit in the buffer given to
41110 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41111 either another @code{read(0, @dots{})} is requested by the target, or debugging
41112 is stopped at the user's request.
41115 @node List of Supported Calls
41116 @subsection List of Supported Calls
41117 @cindex list of supported file-i/o calls
41134 @unnumberedsubsubsec open
41135 @cindex open, file-i/o system call
41140 int open(const char *pathname, int flags);
41141 int open(const char *pathname, int flags, mode_t mode);
41145 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41148 @var{flags} is the bitwise @code{OR} of the following values:
41152 If the file does not exist it will be created. The host
41153 rules apply as far as file ownership and time stamps
41157 When used with @code{O_CREAT}, if the file already exists it is
41158 an error and open() fails.
41161 If the file already exists and the open mode allows
41162 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41163 truncated to zero length.
41166 The file is opened in append mode.
41169 The file is opened for reading only.
41172 The file is opened for writing only.
41175 The file is opened for reading and writing.
41179 Other bits are silently ignored.
41183 @var{mode} is the bitwise @code{OR} of the following values:
41187 User has read permission.
41190 User has write permission.
41193 Group has read permission.
41196 Group has write permission.
41199 Others have read permission.
41202 Others have write permission.
41206 Other bits are silently ignored.
41209 @item Return value:
41210 @code{open} returns the new file descriptor or -1 if an error
41217 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41220 @var{pathname} refers to a directory.
41223 The requested access is not allowed.
41226 @var{pathname} was too long.
41229 A directory component in @var{pathname} does not exist.
41232 @var{pathname} refers to a device, pipe, named pipe or socket.
41235 @var{pathname} refers to a file on a read-only filesystem and
41236 write access was requested.
41239 @var{pathname} is an invalid pointer value.
41242 No space on device to create the file.
41245 The process already has the maximum number of files open.
41248 The limit on the total number of files open on the system
41252 The call was interrupted by the user.
41258 @unnumberedsubsubsec close
41259 @cindex close, file-i/o system call
41268 @samp{Fclose,@var{fd}}
41270 @item Return value:
41271 @code{close} returns zero on success, or -1 if an error occurred.
41277 @var{fd} isn't a valid open file descriptor.
41280 The call was interrupted by the user.
41286 @unnumberedsubsubsec read
41287 @cindex read, file-i/o system call
41292 int read(int fd, void *buf, unsigned int count);
41296 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41298 @item Return value:
41299 On success, the number of bytes read is returned.
41300 Zero indicates end of file. If count is zero, read
41301 returns zero as well. On error, -1 is returned.
41307 @var{fd} is not a valid file descriptor or is not open for
41311 @var{bufptr} is an invalid pointer value.
41314 The call was interrupted by the user.
41320 @unnumberedsubsubsec write
41321 @cindex write, file-i/o system call
41326 int write(int fd, const void *buf, unsigned int count);
41330 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41332 @item Return value:
41333 On success, the number of bytes written are returned.
41334 Zero indicates nothing was written. On error, -1
41341 @var{fd} is not a valid file descriptor or is not open for
41345 @var{bufptr} is an invalid pointer value.
41348 An attempt was made to write a file that exceeds the
41349 host-specific maximum file size allowed.
41352 No space on device to write the data.
41355 The call was interrupted by the user.
41361 @unnumberedsubsubsec lseek
41362 @cindex lseek, file-i/o system call
41367 long lseek (int fd, long offset, int flag);
41371 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41373 @var{flag} is one of:
41377 The offset is set to @var{offset} bytes.
41380 The offset is set to its current location plus @var{offset}
41384 The offset is set to the size of the file plus @var{offset}
41388 @item Return value:
41389 On success, the resulting unsigned offset in bytes from
41390 the beginning of the file is returned. Otherwise, a
41391 value of -1 is returned.
41397 @var{fd} is not a valid open file descriptor.
41400 @var{fd} is associated with the @value{GDBN} console.
41403 @var{flag} is not a proper value.
41406 The call was interrupted by the user.
41412 @unnumberedsubsubsec rename
41413 @cindex rename, file-i/o system call
41418 int rename(const char *oldpath, const char *newpath);
41422 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41424 @item Return value:
41425 On success, zero is returned. On error, -1 is returned.
41431 @var{newpath} is an existing directory, but @var{oldpath} is not a
41435 @var{newpath} is a non-empty directory.
41438 @var{oldpath} or @var{newpath} is a directory that is in use by some
41442 An attempt was made to make a directory a subdirectory
41446 A component used as a directory in @var{oldpath} or new
41447 path is not a directory. Or @var{oldpath} is a directory
41448 and @var{newpath} exists but is not a directory.
41451 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41454 No access to the file or the path of the file.
41458 @var{oldpath} or @var{newpath} was too long.
41461 A directory component in @var{oldpath} or @var{newpath} does not exist.
41464 The file is on a read-only filesystem.
41467 The device containing the file has no room for the new
41471 The call was interrupted by the user.
41477 @unnumberedsubsubsec unlink
41478 @cindex unlink, file-i/o system call
41483 int unlink(const char *pathname);
41487 @samp{Funlink,@var{pathnameptr}/@var{len}}
41489 @item Return value:
41490 On success, zero is returned. On error, -1 is returned.
41496 No access to the file or the path of the file.
41499 The system does not allow unlinking of directories.
41502 The file @var{pathname} cannot be unlinked because it's
41503 being used by another process.
41506 @var{pathnameptr} is an invalid pointer value.
41509 @var{pathname} was too long.
41512 A directory component in @var{pathname} does not exist.
41515 A component of the path is not a directory.
41518 The file is on a read-only filesystem.
41521 The call was interrupted by the user.
41527 @unnumberedsubsubsec stat/fstat
41528 @cindex fstat, file-i/o system call
41529 @cindex stat, file-i/o system call
41534 int stat(const char *pathname, struct stat *buf);
41535 int fstat(int fd, struct stat *buf);
41539 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41540 @samp{Ffstat,@var{fd},@var{bufptr}}
41542 @item Return value:
41543 On success, zero is returned. On error, -1 is returned.
41549 @var{fd} is not a valid open file.
41552 A directory component in @var{pathname} does not exist or the
41553 path is an empty string.
41556 A component of the path is not a directory.
41559 @var{pathnameptr} is an invalid pointer value.
41562 No access to the file or the path of the file.
41565 @var{pathname} was too long.
41568 The call was interrupted by the user.
41574 @unnumberedsubsubsec gettimeofday
41575 @cindex gettimeofday, file-i/o system call
41580 int gettimeofday(struct timeval *tv, void *tz);
41584 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41586 @item Return value:
41587 On success, 0 is returned, -1 otherwise.
41593 @var{tz} is a non-NULL pointer.
41596 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41602 @unnumberedsubsubsec isatty
41603 @cindex isatty, file-i/o system call
41608 int isatty(int fd);
41612 @samp{Fisatty,@var{fd}}
41614 @item Return value:
41615 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41621 The call was interrupted by the user.
41626 Note that the @code{isatty} call is treated as a special case: it returns
41627 1 to the target if the file descriptor is attached
41628 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41629 would require implementing @code{ioctl} and would be more complex than
41634 @unnumberedsubsubsec system
41635 @cindex system, file-i/o system call
41640 int system(const char *command);
41644 @samp{Fsystem,@var{commandptr}/@var{len}}
41646 @item Return value:
41647 If @var{len} is zero, the return value indicates whether a shell is
41648 available. A zero return value indicates a shell is not available.
41649 For non-zero @var{len}, the value returned is -1 on error and the
41650 return status of the command otherwise. Only the exit status of the
41651 command is returned, which is extracted from the host's @code{system}
41652 return value by calling @code{WEXITSTATUS(retval)}. In case
41653 @file{/bin/sh} could not be executed, 127 is returned.
41659 The call was interrupted by the user.
41664 @value{GDBN} takes over the full task of calling the necessary host calls
41665 to perform the @code{system} call. The return value of @code{system} on
41666 the host is simplified before it's returned
41667 to the target. Any termination signal information from the child process
41668 is discarded, and the return value consists
41669 entirely of the exit status of the called command.
41671 Due to security concerns, the @code{system} call is by default refused
41672 by @value{GDBN}. The user has to allow this call explicitly with the
41673 @code{set remote system-call-allowed 1} command.
41676 @item set remote system-call-allowed
41677 @kindex set remote system-call-allowed
41678 Control whether to allow the @code{system} calls in the File I/O
41679 protocol for the remote target. The default is zero (disabled).
41681 @item show remote system-call-allowed
41682 @kindex show remote system-call-allowed
41683 Show whether the @code{system} calls are allowed in the File I/O
41687 @node Protocol-specific Representation of Datatypes
41688 @subsection Protocol-specific Representation of Datatypes
41689 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41692 * Integral Datatypes::
41694 * Memory Transfer::
41699 @node Integral Datatypes
41700 @unnumberedsubsubsec Integral Datatypes
41701 @cindex integral datatypes, in file-i/o protocol
41703 The integral datatypes used in the system calls are @code{int},
41704 @code{unsigned int}, @code{long}, @code{unsigned long},
41705 @code{mode_t}, and @code{time_t}.
41707 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41708 implemented as 32 bit values in this protocol.
41710 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41712 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41713 in @file{limits.h}) to allow range checking on host and target.
41715 @code{time_t} datatypes are defined as seconds since the Epoch.
41717 All integral datatypes transferred as part of a memory read or write of a
41718 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41721 @node Pointer Values
41722 @unnumberedsubsubsec Pointer Values
41723 @cindex pointer values, in file-i/o protocol
41725 Pointers to target data are transmitted as they are. An exception
41726 is made for pointers to buffers for which the length isn't
41727 transmitted as part of the function call, namely strings. Strings
41728 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41735 which is a pointer to data of length 18 bytes at position 0x1aaf.
41736 The length is defined as the full string length in bytes, including
41737 the trailing null byte. For example, the string @code{"hello world"}
41738 at address 0x123456 is transmitted as
41744 @node Memory Transfer
41745 @unnumberedsubsubsec Memory Transfer
41746 @cindex memory transfer, in file-i/o protocol
41748 Structured data which is transferred using a memory read or write (for
41749 example, a @code{struct stat}) is expected to be in a protocol-specific format
41750 with all scalar multibyte datatypes being big endian. Translation to
41751 this representation needs to be done both by the target before the @code{F}
41752 packet is sent, and by @value{GDBN} before
41753 it transfers memory to the target. Transferred pointers to structured
41754 data should point to the already-coerced data at any time.
41758 @unnumberedsubsubsec struct stat
41759 @cindex struct stat, in file-i/o protocol
41761 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41762 is defined as follows:
41766 unsigned int st_dev; /* device */
41767 unsigned int st_ino; /* inode */
41768 mode_t st_mode; /* protection */
41769 unsigned int st_nlink; /* number of hard links */
41770 unsigned int st_uid; /* user ID of owner */
41771 unsigned int st_gid; /* group ID of owner */
41772 unsigned int st_rdev; /* device type (if inode device) */
41773 unsigned long st_size; /* total size, in bytes */
41774 unsigned long st_blksize; /* blocksize for filesystem I/O */
41775 unsigned long st_blocks; /* number of blocks allocated */
41776 time_t st_atime; /* time of last access */
41777 time_t st_mtime; /* time of last modification */
41778 time_t st_ctime; /* time of last change */
41782 The integral datatypes conform to the definitions given in the
41783 appropriate section (see @ref{Integral Datatypes}, for details) so this
41784 structure is of size 64 bytes.
41786 The values of several fields have a restricted meaning and/or
41792 A value of 0 represents a file, 1 the console.
41795 No valid meaning for the target. Transmitted unchanged.
41798 Valid mode bits are described in @ref{Constants}. Any other
41799 bits have currently no meaning for the target.
41804 No valid meaning for the target. Transmitted unchanged.
41809 These values have a host and file system dependent
41810 accuracy. Especially on Windows hosts, the file system may not
41811 support exact timing values.
41814 The target gets a @code{struct stat} of the above representation and is
41815 responsible for coercing it to the target representation before
41818 Note that due to size differences between the host, target, and protocol
41819 representations of @code{struct stat} members, these members could eventually
41820 get truncated on the target.
41822 @node struct timeval
41823 @unnumberedsubsubsec struct timeval
41824 @cindex struct timeval, in file-i/o protocol
41826 The buffer of type @code{struct timeval} used by the File-I/O protocol
41827 is defined as follows:
41831 time_t tv_sec; /* second */
41832 long tv_usec; /* microsecond */
41836 The integral datatypes conform to the definitions given in the
41837 appropriate section (see @ref{Integral Datatypes}, for details) so this
41838 structure is of size 8 bytes.
41841 @subsection Constants
41842 @cindex constants, in file-i/o protocol
41844 The following values are used for the constants inside of the
41845 protocol. @value{GDBN} and target are responsible for translating these
41846 values before and after the call as needed.
41857 @unnumberedsubsubsec Open Flags
41858 @cindex open flags, in file-i/o protocol
41860 All values are given in hexadecimal representation.
41872 @node mode_t Values
41873 @unnumberedsubsubsec mode_t Values
41874 @cindex mode_t values, in file-i/o protocol
41876 All values are given in octal representation.
41893 @unnumberedsubsubsec Errno Values
41894 @cindex errno values, in file-i/o protocol
41896 All values are given in decimal representation.
41921 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41922 any error value not in the list of supported error numbers.
41925 @unnumberedsubsubsec Lseek Flags
41926 @cindex lseek flags, in file-i/o protocol
41935 @unnumberedsubsubsec Limits
41936 @cindex limits, in file-i/o protocol
41938 All values are given in decimal representation.
41941 INT_MIN -2147483648
41943 UINT_MAX 4294967295
41944 LONG_MIN -9223372036854775808
41945 LONG_MAX 9223372036854775807
41946 ULONG_MAX 18446744073709551615
41949 @node File-I/O Examples
41950 @subsection File-I/O Examples
41951 @cindex file-i/o examples
41953 Example sequence of a write call, file descriptor 3, buffer is at target
41954 address 0x1234, 6 bytes should be written:
41957 <- @code{Fwrite,3,1234,6}
41958 @emph{request memory read from target}
41961 @emph{return "6 bytes written"}
41965 Example sequence of a read call, file descriptor 3, buffer is at target
41966 address 0x1234, 6 bytes should be read:
41969 <- @code{Fread,3,1234,6}
41970 @emph{request memory write to target}
41971 -> @code{X1234,6:XXXXXX}
41972 @emph{return "6 bytes read"}
41976 Example sequence of a read call, call fails on the host due to invalid
41977 file descriptor (@code{EBADF}):
41980 <- @code{Fread,3,1234,6}
41984 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41988 <- @code{Fread,3,1234,6}
41993 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41997 <- @code{Fread,3,1234,6}
41998 -> @code{X1234,6:XXXXXX}
42002 @node Library List Format
42003 @section Library List Format
42004 @cindex library list format, remote protocol
42006 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42007 same process as your application to manage libraries. In this case,
42008 @value{GDBN} can use the loader's symbol table and normal memory
42009 operations to maintain a list of shared libraries. On other
42010 platforms, the operating system manages loaded libraries.
42011 @value{GDBN} can not retrieve the list of currently loaded libraries
42012 through memory operations, so it uses the @samp{qXfer:libraries:read}
42013 packet (@pxref{qXfer library list read}) instead. The remote stub
42014 queries the target's operating system and reports which libraries
42017 The @samp{qXfer:libraries:read} packet returns an XML document which
42018 lists loaded libraries and their offsets. Each library has an
42019 associated name and one or more segment or section base addresses,
42020 which report where the library was loaded in memory.
42022 For the common case of libraries that are fully linked binaries, the
42023 library should have a list of segments. If the target supports
42024 dynamic linking of a relocatable object file, its library XML element
42025 should instead include a list of allocated sections. The segment or
42026 section bases are start addresses, not relocation offsets; they do not
42027 depend on the library's link-time base addresses.
42029 @value{GDBN} must be linked with the Expat library to support XML
42030 library lists. @xref{Expat}.
42032 A simple memory map, with one loaded library relocated by a single
42033 offset, looks like this:
42037 <library name="/lib/libc.so.6">
42038 <segment address="0x10000000"/>
42043 Another simple memory map, with one loaded library with three
42044 allocated sections (.text, .data, .bss), looks like this:
42048 <library name="sharedlib.o">
42049 <section address="0x10000000"/>
42050 <section address="0x20000000"/>
42051 <section address="0x30000000"/>
42056 The format of a library list is described by this DTD:
42059 <!-- library-list: Root element with versioning -->
42060 <!ELEMENT library-list (library)*>
42061 <!ATTLIST library-list version CDATA #FIXED "1.0">
42062 <!ELEMENT library (segment*, section*)>
42063 <!ATTLIST library name CDATA #REQUIRED>
42064 <!ELEMENT segment EMPTY>
42065 <!ATTLIST segment address CDATA #REQUIRED>
42066 <!ELEMENT section EMPTY>
42067 <!ATTLIST section address CDATA #REQUIRED>
42070 In addition, segments and section descriptors cannot be mixed within a
42071 single library element, and you must supply at least one segment or
42072 section for each library.
42074 @node Library List Format for SVR4 Targets
42075 @section Library List Format for SVR4 Targets
42076 @cindex library list format, remote protocol
42078 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42079 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42080 shared libraries. Still a special library list provided by this packet is
42081 more efficient for the @value{GDBN} remote protocol.
42083 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42084 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42085 target, the following parameters are reported:
42089 @code{name}, the absolute file name from the @code{l_name} field of
42090 @code{struct link_map}.
42092 @code{lm} with address of @code{struct link_map} used for TLS
42093 (Thread Local Storage) access.
42095 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42096 @code{struct link_map}. For prelinked libraries this is not an absolute
42097 memory address. It is a displacement of absolute memory address against
42098 address the file was prelinked to during the library load.
42100 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42103 Additionally the single @code{main-lm} attribute specifies address of
42104 @code{struct link_map} used for the main executable. This parameter is used
42105 for TLS access and its presence is optional.
42107 @value{GDBN} must be linked with the Expat library to support XML
42108 SVR4 library lists. @xref{Expat}.
42110 A simple memory map, with two loaded libraries (which do not use prelink),
42114 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42115 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42117 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42119 </library-list-svr>
42122 The format of an SVR4 library list is described by this DTD:
42125 <!-- library-list-svr4: Root element with versioning -->
42126 <!ELEMENT library-list-svr4 (library)*>
42127 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42128 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42129 <!ELEMENT library EMPTY>
42130 <!ATTLIST library name CDATA #REQUIRED>
42131 <!ATTLIST library lm CDATA #REQUIRED>
42132 <!ATTLIST library l_addr CDATA #REQUIRED>
42133 <!ATTLIST library l_ld CDATA #REQUIRED>
42136 @node Memory Map Format
42137 @section Memory Map Format
42138 @cindex memory map format
42140 To be able to write into flash memory, @value{GDBN} needs to obtain a
42141 memory map from the target. This section describes the format of the
42144 The memory map is obtained using the @samp{qXfer:memory-map:read}
42145 (@pxref{qXfer memory map read}) packet and is an XML document that
42146 lists memory regions.
42148 @value{GDBN} must be linked with the Expat library to support XML
42149 memory maps. @xref{Expat}.
42151 The top-level structure of the document is shown below:
42154 <?xml version="1.0"?>
42155 <!DOCTYPE memory-map
42156 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42157 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42163 Each region can be either:
42168 A region of RAM starting at @var{addr} and extending for @var{length}
42172 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42177 A region of read-only memory:
42180 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42185 A region of flash memory, with erasure blocks @var{blocksize}
42189 <memory type="flash" start="@var{addr}" length="@var{length}">
42190 <property name="blocksize">@var{blocksize}</property>
42196 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42197 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42198 packets to write to addresses in such ranges.
42200 The formal DTD for memory map format is given below:
42203 <!-- ................................................... -->
42204 <!-- Memory Map XML DTD ................................ -->
42205 <!-- File: memory-map.dtd .............................. -->
42206 <!-- .................................... .............. -->
42207 <!-- memory-map.dtd -->
42208 <!-- memory-map: Root element with versioning -->
42209 <!ELEMENT memory-map (memory)*>
42210 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42211 <!ELEMENT memory (property)*>
42212 <!-- memory: Specifies a memory region,
42213 and its type, or device. -->
42214 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42215 start CDATA #REQUIRED
42216 length CDATA #REQUIRED>
42217 <!-- property: Generic attribute tag -->
42218 <!ELEMENT property (#PCDATA | property)*>
42219 <!ATTLIST property name (blocksize) #REQUIRED>
42222 @node Thread List Format
42223 @section Thread List Format
42224 @cindex thread list format
42226 To efficiently update the list of threads and their attributes,
42227 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42228 (@pxref{qXfer threads read}) and obtains the XML document with
42229 the following structure:
42232 <?xml version="1.0"?>
42234 <thread id="id" core="0" name="name">
42235 ... description ...
42240 Each @samp{thread} element must have the @samp{id} attribute that
42241 identifies the thread (@pxref{thread-id syntax}). The
42242 @samp{core} attribute, if present, specifies which processor core
42243 the thread was last executing on. The @samp{name} attribute, if
42244 present, specifies the human-readable name of the thread. The content
42245 of the of @samp{thread} element is interpreted as human-readable
42246 auxiliary information. The @samp{handle} attribute, if present,
42247 is a hex encoded representation of the thread handle.
42250 @node Traceframe Info Format
42251 @section Traceframe Info Format
42252 @cindex traceframe info format
42254 To be able to know which objects in the inferior can be examined when
42255 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42256 memory ranges, registers and trace state variables that have been
42257 collected in a traceframe.
42259 This list is obtained using the @samp{qXfer:traceframe-info:read}
42260 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42262 @value{GDBN} must be linked with the Expat library to support XML
42263 traceframe info discovery. @xref{Expat}.
42265 The top-level structure of the document is shown below:
42268 <?xml version="1.0"?>
42269 <!DOCTYPE traceframe-info
42270 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42271 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42277 Each traceframe block can be either:
42282 A region of collected memory starting at @var{addr} and extending for
42283 @var{length} bytes from there:
42286 <memory start="@var{addr}" length="@var{length}"/>
42290 A block indicating trace state variable numbered @var{number} has been
42294 <tvar id="@var{number}"/>
42299 The formal DTD for the traceframe info format is given below:
42302 <!ELEMENT traceframe-info (memory | tvar)* >
42303 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42305 <!ELEMENT memory EMPTY>
42306 <!ATTLIST memory start CDATA #REQUIRED
42307 length CDATA #REQUIRED>
42309 <!ATTLIST tvar id CDATA #REQUIRED>
42312 @node Branch Trace Format
42313 @section Branch Trace Format
42314 @cindex branch trace format
42316 In order to display the branch trace of an inferior thread,
42317 @value{GDBN} needs to obtain the list of branches. This list is
42318 represented as list of sequential code blocks that are connected via
42319 branches. The code in each block has been executed sequentially.
42321 This list is obtained using the @samp{qXfer:btrace:read}
42322 (@pxref{qXfer btrace read}) packet and is an XML document.
42324 @value{GDBN} must be linked with the Expat library to support XML
42325 traceframe info discovery. @xref{Expat}.
42327 The top-level structure of the document is shown below:
42330 <?xml version="1.0"?>
42332 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42333 "http://sourceware.org/gdb/gdb-btrace.dtd">
42342 A block of sequentially executed instructions starting at @var{begin}
42343 and ending at @var{end}:
42346 <block begin="@var{begin}" end="@var{end}"/>
42351 The formal DTD for the branch trace format is given below:
42354 <!ELEMENT btrace (block* | pt) >
42355 <!ATTLIST btrace version CDATA #FIXED "1.0">
42357 <!ELEMENT block EMPTY>
42358 <!ATTLIST block begin CDATA #REQUIRED
42359 end CDATA #REQUIRED>
42361 <!ELEMENT pt (pt-config?, raw?)>
42363 <!ELEMENT pt-config (cpu?)>
42365 <!ELEMENT cpu EMPTY>
42366 <!ATTLIST cpu vendor CDATA #REQUIRED
42367 family CDATA #REQUIRED
42368 model CDATA #REQUIRED
42369 stepping CDATA #REQUIRED>
42371 <!ELEMENT raw (#PCDATA)>
42374 @node Branch Trace Configuration Format
42375 @section Branch Trace Configuration Format
42376 @cindex branch trace configuration format
42378 For each inferior thread, @value{GDBN} can obtain the branch trace
42379 configuration using the @samp{qXfer:btrace-conf:read}
42380 (@pxref{qXfer btrace-conf read}) packet.
42382 The configuration describes the branch trace format and configuration
42383 settings for that format. The following information is described:
42387 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42390 The size of the @acronym{BTS} ring buffer in bytes.
42393 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42397 The size of the @acronym{Intel PT} ring buffer in bytes.
42401 @value{GDBN} must be linked with the Expat library to support XML
42402 branch trace configuration discovery. @xref{Expat}.
42404 The formal DTD for the branch trace configuration format is given below:
42407 <!ELEMENT btrace-conf (bts?, pt?)>
42408 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42410 <!ELEMENT bts EMPTY>
42411 <!ATTLIST bts size CDATA #IMPLIED>
42413 <!ELEMENT pt EMPTY>
42414 <!ATTLIST pt size CDATA #IMPLIED>
42417 @include agentexpr.texi
42419 @node Target Descriptions
42420 @appendix Target Descriptions
42421 @cindex target descriptions
42423 One of the challenges of using @value{GDBN} to debug embedded systems
42424 is that there are so many minor variants of each processor
42425 architecture in use. It is common practice for vendors to start with
42426 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42427 and then make changes to adapt it to a particular market niche. Some
42428 architectures have hundreds of variants, available from dozens of
42429 vendors. This leads to a number of problems:
42433 With so many different customized processors, it is difficult for
42434 the @value{GDBN} maintainers to keep up with the changes.
42436 Since individual variants may have short lifetimes or limited
42437 audiences, it may not be worthwhile to carry information about every
42438 variant in the @value{GDBN} source tree.
42440 When @value{GDBN} does support the architecture of the embedded system
42441 at hand, the task of finding the correct architecture name to give the
42442 @command{set architecture} command can be error-prone.
42445 To address these problems, the @value{GDBN} remote protocol allows a
42446 target system to not only identify itself to @value{GDBN}, but to
42447 actually describe its own features. This lets @value{GDBN} support
42448 processor variants it has never seen before --- to the extent that the
42449 descriptions are accurate, and that @value{GDBN} understands them.
42451 @value{GDBN} must be linked with the Expat library to support XML
42452 target descriptions. @xref{Expat}.
42455 * Retrieving Descriptions:: How descriptions are fetched from a target.
42456 * Target Description Format:: The contents of a target description.
42457 * Predefined Target Types:: Standard types available for target
42459 * Enum Target Types:: How to define enum target types.
42460 * Standard Target Features:: Features @value{GDBN} knows about.
42463 @node Retrieving Descriptions
42464 @section Retrieving Descriptions
42466 Target descriptions can be read from the target automatically, or
42467 specified by the user manually. The default behavior is to read the
42468 description from the target. @value{GDBN} retrieves it via the remote
42469 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42470 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42471 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42472 XML document, of the form described in @ref{Target Description
42475 Alternatively, you can specify a file to read for the target description.
42476 If a file is set, the target will not be queried. The commands to
42477 specify a file are:
42480 @cindex set tdesc filename
42481 @item set tdesc filename @var{path}
42482 Read the target description from @var{path}.
42484 @cindex unset tdesc filename
42485 @item unset tdesc filename
42486 Do not read the XML target description from a file. @value{GDBN}
42487 will use the description supplied by the current target.
42489 @cindex show tdesc filename
42490 @item show tdesc filename
42491 Show the filename to read for a target description, if any.
42495 @node Target Description Format
42496 @section Target Description Format
42497 @cindex target descriptions, XML format
42499 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42500 document which complies with the Document Type Definition provided in
42501 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42502 means you can use generally available tools like @command{xmllint} to
42503 check that your feature descriptions are well-formed and valid.
42504 However, to help people unfamiliar with XML write descriptions for
42505 their targets, we also describe the grammar here.
42507 Target descriptions can identify the architecture of the remote target
42508 and (for some architectures) provide information about custom register
42509 sets. They can also identify the OS ABI of the remote target.
42510 @value{GDBN} can use this information to autoconfigure for your
42511 target, or to warn you if you connect to an unsupported target.
42513 Here is a simple target description:
42516 <target version="1.0">
42517 <architecture>i386:x86-64</architecture>
42522 This minimal description only says that the target uses
42523 the x86-64 architecture.
42525 A target description has the following overall form, with [ ] marking
42526 optional elements and @dots{} marking repeatable elements. The elements
42527 are explained further below.
42530 <?xml version="1.0"?>
42531 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42532 <target version="1.0">
42533 @r{[}@var{architecture}@r{]}
42534 @r{[}@var{osabi}@r{]}
42535 @r{[}@var{compatible}@r{]}
42536 @r{[}@var{feature}@dots{}@r{]}
42541 The description is generally insensitive to whitespace and line
42542 breaks, under the usual common-sense rules. The XML version
42543 declaration and document type declaration can generally be omitted
42544 (@value{GDBN} does not require them), but specifying them may be
42545 useful for XML validation tools. The @samp{version} attribute for
42546 @samp{<target>} may also be omitted, but we recommend
42547 including it; if future versions of @value{GDBN} use an incompatible
42548 revision of @file{gdb-target.dtd}, they will detect and report
42549 the version mismatch.
42551 @subsection Inclusion
42552 @cindex target descriptions, inclusion
42555 @cindex <xi:include>
42558 It can sometimes be valuable to split a target description up into
42559 several different annexes, either for organizational purposes, or to
42560 share files between different possible target descriptions. You can
42561 divide a description into multiple files by replacing any element of
42562 the target description with an inclusion directive of the form:
42565 <xi:include href="@var{document}"/>
42569 When @value{GDBN} encounters an element of this form, it will retrieve
42570 the named XML @var{document}, and replace the inclusion directive with
42571 the contents of that document. If the current description was read
42572 using @samp{qXfer}, then so will be the included document;
42573 @var{document} will be interpreted as the name of an annex. If the
42574 current description was read from a file, @value{GDBN} will look for
42575 @var{document} as a file in the same directory where it found the
42576 original description.
42578 @subsection Architecture
42579 @cindex <architecture>
42581 An @samp{<architecture>} element has this form:
42584 <architecture>@var{arch}</architecture>
42587 @var{arch} is one of the architectures from the set accepted by
42588 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42591 @cindex @code{<osabi>}
42593 This optional field was introduced in @value{GDBN} version 7.0.
42594 Previous versions of @value{GDBN} ignore it.
42596 An @samp{<osabi>} element has this form:
42599 <osabi>@var{abi-name}</osabi>
42602 @var{abi-name} is an OS ABI name from the same selection accepted by
42603 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42605 @subsection Compatible Architecture
42606 @cindex @code{<compatible>}
42608 This optional field was introduced in @value{GDBN} version 7.0.
42609 Previous versions of @value{GDBN} ignore it.
42611 A @samp{<compatible>} element has this form:
42614 <compatible>@var{arch}</compatible>
42617 @var{arch} is one of the architectures from the set accepted by
42618 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42620 A @samp{<compatible>} element is used to specify that the target
42621 is able to run binaries in some other than the main target architecture
42622 given by the @samp{<architecture>} element. For example, on the
42623 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42624 or @code{powerpc:common64}, but the system is able to run binaries
42625 in the @code{spu} architecture as well. The way to describe this
42626 capability with @samp{<compatible>} is as follows:
42629 <architecture>powerpc:common</architecture>
42630 <compatible>spu</compatible>
42633 @subsection Features
42636 Each @samp{<feature>} describes some logical portion of the target
42637 system. Features are currently used to describe available CPU
42638 registers and the types of their contents. A @samp{<feature>} element
42642 <feature name="@var{name}">
42643 @r{[}@var{type}@dots{}@r{]}
42649 Each feature's name should be unique within the description. The name
42650 of a feature does not matter unless @value{GDBN} has some special
42651 knowledge of the contents of that feature; if it does, the feature
42652 should have its standard name. @xref{Standard Target Features}.
42656 Any register's value is a collection of bits which @value{GDBN} must
42657 interpret. The default interpretation is a two's complement integer,
42658 but other types can be requested by name in the register description.
42659 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42660 Target Types}), and the description can define additional composite
42663 Each type element must have an @samp{id} attribute, which gives
42664 a unique (within the containing @samp{<feature>}) name to the type.
42665 Types must be defined before they are used.
42668 Some targets offer vector registers, which can be treated as arrays
42669 of scalar elements. These types are written as @samp{<vector>} elements,
42670 specifying the array element type, @var{type}, and the number of elements,
42674 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42678 If a register's value is usefully viewed in multiple ways, define it
42679 with a union type containing the useful representations. The
42680 @samp{<union>} element contains one or more @samp{<field>} elements,
42681 each of which has a @var{name} and a @var{type}:
42684 <union id="@var{id}">
42685 <field name="@var{name}" type="@var{type}"/>
42692 If a register's value is composed from several separate values, define
42693 it with either a structure type or a flags type.
42694 A flags type may only contain bitfields.
42695 A structure type may either contain only bitfields or contain no bitfields.
42696 If the value contains only bitfields, its total size in bytes must be
42699 Non-bitfield values have a @var{name} and @var{type}.
42702 <struct id="@var{id}">
42703 <field name="@var{name}" type="@var{type}"/>
42708 Both @var{name} and @var{type} values are required.
42709 No implicit padding is added.
42711 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42714 <struct id="@var{id}" size="@var{size}">
42715 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42721 <flags id="@var{id}" size="@var{size}">
42722 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42727 The @var{name} value is required.
42728 Bitfield values may be named with the empty string, @samp{""},
42729 in which case the field is ``filler'' and its value is not printed.
42730 Not all bits need to be specified, so ``filler'' fields are optional.
42732 The @var{start} and @var{end} values are required, and @var{type}
42734 The field's @var{start} must be less than or equal to its @var{end},
42735 and zero represents the least significant bit.
42737 The default value of @var{type} is @code{bool} for single bit fields,
42738 and an unsigned integer otherwise.
42740 Which to choose? Structures or flags?
42742 Registers defined with @samp{flags} have these advantages over
42743 defining them with @samp{struct}:
42747 Arithmetic may be performed on them as if they were integers.
42749 They are printed in a more readable fashion.
42752 Registers defined with @samp{struct} have one advantage over
42753 defining them with @samp{flags}:
42757 One can fetch individual fields like in @samp{C}.
42760 (gdb) print $my_struct_reg.field3
42766 @subsection Registers
42769 Each register is represented as an element with this form:
42772 <reg name="@var{name}"
42773 bitsize="@var{size}"
42774 @r{[}regnum="@var{num}"@r{]}
42775 @r{[}save-restore="@var{save-restore}"@r{]}
42776 @r{[}type="@var{type}"@r{]}
42777 @r{[}group="@var{group}"@r{]}/>
42781 The components are as follows:
42786 The register's name; it must be unique within the target description.
42789 The register's size, in bits.
42792 The register's number. If omitted, a register's number is one greater
42793 than that of the previous register (either in the current feature or in
42794 a preceding feature); the first register in the target description
42795 defaults to zero. This register number is used to read or write
42796 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42797 packets, and registers appear in the @code{g} and @code{G} packets
42798 in order of increasing register number.
42801 Whether the register should be preserved across inferior function
42802 calls; this must be either @code{yes} or @code{no}. The default is
42803 @code{yes}, which is appropriate for most registers except for
42804 some system control registers; this is not related to the target's
42808 The type of the register. It may be a predefined type, a type
42809 defined in the current feature, or one of the special types @code{int}
42810 and @code{float}. @code{int} is an integer type of the correct size
42811 for @var{bitsize}, and @code{float} is a floating point type (in the
42812 architecture's normal floating point format) of the correct size for
42813 @var{bitsize}. The default is @code{int}.
42816 The register group to which this register belongs. It can be one of the
42817 standard register groups @code{general}, @code{float}, @code{vector} or an
42818 arbitrary string. Group names should be limited to alphanumeric characters.
42819 If a group name is made up of multiple words the words may be separated by
42820 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42821 @var{group} is specified, @value{GDBN} will not display the register in
42822 @code{info registers}.
42826 @node Predefined Target Types
42827 @section Predefined Target Types
42828 @cindex target descriptions, predefined types
42830 Type definitions in the self-description can build up composite types
42831 from basic building blocks, but can not define fundamental types. Instead,
42832 standard identifiers are provided by @value{GDBN} for the fundamental
42833 types. The currently supported types are:
42838 Boolean type, occupying a single bit.
42846 Signed integer types holding the specified number of bits.
42854 Unsigned integer types holding the specified number of bits.
42858 Pointers to unspecified code and data. The program counter and
42859 any dedicated return address register may be marked as code
42860 pointers; printing a code pointer converts it into a symbolic
42861 address. The stack pointer and any dedicated address registers
42862 may be marked as data pointers.
42865 Single precision IEEE floating point.
42868 Double precision IEEE floating point.
42871 The 12-byte extended precision format used by ARM FPA registers.
42874 The 10-byte extended precision format used by x87 registers.
42877 32bit @sc{eflags} register used by x86.
42880 32bit @sc{mxcsr} register used by x86.
42884 @node Enum Target Types
42885 @section Enum Target Types
42886 @cindex target descriptions, enum types
42888 Enum target types are useful in @samp{struct} and @samp{flags}
42889 register descriptions. @xref{Target Description Format}.
42891 Enum types have a name, size and a list of name/value pairs.
42894 <enum id="@var{id}" size="@var{size}">
42895 <evalue name="@var{name}" value="@var{value}"/>
42900 Enums must be defined before they are used.
42903 <enum id="levels_type" size="4">
42904 <evalue name="low" value="0"/>
42905 <evalue name="high" value="1"/>
42907 <flags id="flags_type" size="4">
42908 <field name="X" start="0"/>
42909 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42911 <reg name="flags" bitsize="32" type="flags_type"/>
42914 Given that description, a value of 3 for the @samp{flags} register
42915 would be printed as:
42918 (gdb) info register flags
42919 flags 0x3 [ X LEVEL=high ]
42922 @node Standard Target Features
42923 @section Standard Target Features
42924 @cindex target descriptions, standard features
42926 A target description must contain either no registers or all the
42927 target's registers. If the description contains no registers, then
42928 @value{GDBN} will assume a default register layout, selected based on
42929 the architecture. If the description contains any registers, the
42930 default layout will not be used; the standard registers must be
42931 described in the target description, in such a way that @value{GDBN}
42932 can recognize them.
42934 This is accomplished by giving specific names to feature elements
42935 which contain standard registers. @value{GDBN} will look for features
42936 with those names and verify that they contain the expected registers;
42937 if any known feature is missing required registers, or if any required
42938 feature is missing, @value{GDBN} will reject the target
42939 description. You can add additional registers to any of the
42940 standard features --- @value{GDBN} will display them just as if
42941 they were added to an unrecognized feature.
42943 This section lists the known features and their expected contents.
42944 Sample XML documents for these features are included in the
42945 @value{GDBN} source tree, in the directory @file{gdb/features}.
42947 Names recognized by @value{GDBN} should include the name of the
42948 company or organization which selected the name, and the overall
42949 architecture to which the feature applies; so e.g.@: the feature
42950 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42952 The names of registers are not case sensitive for the purpose
42953 of recognizing standard features, but @value{GDBN} will only display
42954 registers using the capitalization used in the description.
42957 * AArch64 Features::
42961 * MicroBlaze Features::
42965 * Nios II Features::
42966 * OpenRISC 1000 Features::
42967 * PowerPC Features::
42968 * S/390 and System z Features::
42974 @node AArch64 Features
42975 @subsection AArch64 Features
42976 @cindex target descriptions, AArch64 features
42978 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42979 targets. It should contain registers @samp{x0} through @samp{x30},
42980 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42982 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42983 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42986 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42987 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42988 through @samp{p15}, @samp{ffr} and @samp{vg}.
42991 @subsection ARC Features
42992 @cindex target descriptions, ARC Features
42994 ARC processors are highly configurable, so even core registers and their number
42995 are not completely predetermined. In addition flags and PC registers which are
42996 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42997 that one of the core registers features is present.
42998 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43000 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43001 targets with a normal register file. It should contain registers @samp{r0}
43002 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43003 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43004 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43005 @samp{ilink} and extension core registers are not available to read/write, when
43006 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43008 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43009 ARC HS targets with a reduced register file. It should contain registers
43010 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43011 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43012 This feature may contain register @samp{ilink} and any of extension core
43013 registers @samp{r32} through @samp{r59/acch}.
43015 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43016 targets with a normal register file. It should contain registers @samp{r0}
43017 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43018 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43019 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43020 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43021 registers are not available when debugging GNU/Linux applications. The only
43022 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43023 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43024 ARC v2, but @samp{ilink2} is optional on ARCompact.
43026 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43027 targets. It should contain registers @samp{pc} and @samp{status32}.
43030 @subsection ARM Features
43031 @cindex target descriptions, ARM features
43033 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43035 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43036 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43038 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43039 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43040 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43043 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43044 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43046 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43047 it should contain at least registers @samp{wR0} through @samp{wR15} and
43048 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43049 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43051 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43052 should contain at least registers @samp{d0} through @samp{d15}. If
43053 they are present, @samp{d16} through @samp{d31} should also be included.
43054 @value{GDBN} will synthesize the single-precision registers from
43055 halves of the double-precision registers.
43057 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43058 need to contain registers; it instructs @value{GDBN} to display the
43059 VFP double-precision registers as vectors and to synthesize the
43060 quad-precision registers from pairs of double-precision registers.
43061 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43062 be present and include 32 double-precision registers.
43064 @node i386 Features
43065 @subsection i386 Features
43066 @cindex target descriptions, i386 features
43068 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43069 targets. It should describe the following registers:
43073 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43075 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43077 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43078 @samp{fs}, @samp{gs}
43080 @samp{st0} through @samp{st7}
43082 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43083 @samp{foseg}, @samp{fooff} and @samp{fop}
43086 The register sets may be different, depending on the target.
43088 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43089 describe registers:
43093 @samp{xmm0} through @samp{xmm7} for i386
43095 @samp{xmm0} through @samp{xmm15} for amd64
43100 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43101 @samp{org.gnu.gdb.i386.sse} feature. It should
43102 describe the upper 128 bits of @sc{ymm} registers:
43106 @samp{ymm0h} through @samp{ymm7h} for i386
43108 @samp{ymm0h} through @samp{ymm15h} for amd64
43111 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43112 Memory Protection Extension (MPX). It should describe the following registers:
43116 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43118 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43121 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43122 describe a single register, @samp{orig_eax}.
43124 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43125 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43127 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43128 @samp{org.gnu.gdb.i386.avx} feature. It should
43129 describe additional @sc{xmm} registers:
43133 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43136 It should describe the upper 128 bits of additional @sc{ymm} registers:
43140 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43144 describe the upper 256 bits of @sc{zmm} registers:
43148 @samp{zmm0h} through @samp{zmm7h} for i386.
43150 @samp{zmm0h} through @samp{zmm15h} for amd64.
43154 describe the additional @sc{zmm} registers:
43158 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43161 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43162 describe a single register, @samp{pkru}. It is a 32-bit register
43163 valid for i386 and amd64.
43165 @node MicroBlaze Features
43166 @subsection MicroBlaze Features
43167 @cindex target descriptions, MicroBlaze features
43169 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43170 targets. It should contain registers @samp{r0} through @samp{r31},
43171 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43172 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43173 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43175 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43176 If present, it should contain registers @samp{rshr} and @samp{rslr}
43178 @node MIPS Features
43179 @subsection @acronym{MIPS} Features
43180 @cindex target descriptions, @acronym{MIPS} features
43182 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43183 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43184 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43187 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43188 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43189 registers. They may be 32-bit or 64-bit depending on the target.
43191 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43192 it may be optional in a future version of @value{GDBN}. It should
43193 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43194 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43196 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43197 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43198 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43199 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43201 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43202 contain a single register, @samp{restart}, which is used by the
43203 Linux kernel to control restartable syscalls.
43205 @node M68K Features
43206 @subsection M68K Features
43207 @cindex target descriptions, M68K features
43210 @item @samp{org.gnu.gdb.m68k.core}
43211 @itemx @samp{org.gnu.gdb.coldfire.core}
43212 @itemx @samp{org.gnu.gdb.fido.core}
43213 One of those features must be always present.
43214 The feature that is present determines which flavor of m68k is
43215 used. The feature that is present should contain registers
43216 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43217 @samp{sp}, @samp{ps} and @samp{pc}.
43219 @item @samp{org.gnu.gdb.coldfire.fp}
43220 This feature is optional. If present, it should contain registers
43221 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43225 @node NDS32 Features
43226 @subsection NDS32 Features
43227 @cindex target descriptions, NDS32 features
43229 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43230 targets. It should contain at least registers @samp{r0} through
43231 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43234 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43235 it should contain 64-bit double-precision floating-point registers
43236 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43237 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43239 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43240 registers are overlapped with the thirty-two 32-bit single-precision
43241 floating-point registers. The 32-bit single-precision registers, if
43242 not being listed explicitly, will be synthesized from halves of the
43243 overlapping 64-bit double-precision registers. Listing 32-bit
43244 single-precision registers explicitly is deprecated, and the
43245 support to it could be totally removed some day.
43247 @node Nios II Features
43248 @subsection Nios II Features
43249 @cindex target descriptions, Nios II features
43251 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43252 targets. It should contain the 32 core registers (@samp{zero},
43253 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43254 @samp{pc}, and the 16 control registers (@samp{status} through
43257 @node OpenRISC 1000 Features
43258 @subsection Openrisc 1000 Features
43259 @cindex target descriptions, OpenRISC 1000 features
43261 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43262 targets. It should contain the 32 general purpose registers (@samp{r0}
43263 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43265 @node PowerPC Features
43266 @subsection PowerPC Features
43267 @cindex target descriptions, PowerPC features
43269 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43270 targets. It should contain registers @samp{r0} through @samp{r31},
43271 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43272 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43274 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43275 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43277 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43278 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43281 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43282 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43283 will combine these registers with the floating point registers
43284 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43285 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43286 through @samp{vs63}, the set of vector registers for POWER7.
43288 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43289 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43290 @samp{spefscr}. SPE targets should provide 32-bit registers in
43291 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43292 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43293 these to present registers @samp{ev0} through @samp{ev31} to the
43296 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43297 contain the 64-bit register @samp{ppr}.
43299 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43300 contain the 64-bit register @samp{dscr}.
43302 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43303 contain the 64-bit register @samp{tar}.
43305 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43306 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43309 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43310 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43311 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43312 server PMU registers provided by @sc{gnu}/Linux.
43314 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43315 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43318 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43319 contain the checkpointed general-purpose registers @samp{cr0} through
43320 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43321 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43322 depending on the target. It should also contain the checkpointed
43323 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43326 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43327 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43328 through @samp{cf31}, as well as the checkpointed 64-bit register
43331 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43332 should contain the checkpointed altivec registers @samp{cvr0} through
43333 @samp{cvr31}, all 128-bit wide. It should also contain the
43334 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43337 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43338 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43339 will combine these registers with the checkpointed floating point
43340 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43341 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43342 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43343 @samp{cvs63}. Therefore, this feature requires both
43344 @samp{org.gnu.gdb.power.htm.altivec} and
43345 @samp{org.gnu.gdb.power.htm.fpu}.
43347 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43348 contain the 64-bit checkpointed register @samp{cppr}.
43350 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43351 contain the 64-bit checkpointed register @samp{cdscr}.
43353 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43354 contain the 64-bit checkpointed register @samp{ctar}.
43356 @node S/390 and System z Features
43357 @subsection S/390 and System z Features
43358 @cindex target descriptions, S/390 features
43359 @cindex target descriptions, System z features
43361 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43362 System z targets. It should contain the PSW and the 16 general
43363 registers. In particular, System z targets should provide the 64-bit
43364 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43365 S/390 targets should provide the 32-bit versions of these registers.
43366 A System z target that runs in 31-bit addressing mode should provide
43367 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43368 register's upper halves @samp{r0h} through @samp{r15h}, and their
43369 lower halves @samp{r0l} through @samp{r15l}.
43371 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43372 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43375 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43376 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43378 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43379 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43380 targets and 32-bit otherwise. In addition, the feature may contain
43381 the @samp{last_break} register, whose width depends on the addressing
43382 mode, as well as the @samp{system_call} register, which is always
43385 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43386 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43387 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43389 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43390 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43391 combined by @value{GDBN} with the floating point registers @samp{f0}
43392 through @samp{f15} to present the 128-bit wide vector registers
43393 @samp{v0} through @samp{v15}. In addition, this feature should
43394 contain the 128-bit wide vector registers @samp{v16} through
43397 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43398 the 64-bit wide guarded-storage-control registers @samp{gsd},
43399 @samp{gssm}, and @samp{gsepla}.
43401 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43402 the 64-bit wide guarded-storage broadcast control registers
43403 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43405 @node Sparc Features
43406 @subsection Sparc Features
43407 @cindex target descriptions, sparc32 features
43408 @cindex target descriptions, sparc64 features
43409 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43410 targets. It should describe the following registers:
43414 @samp{g0} through @samp{g7}
43416 @samp{o0} through @samp{o7}
43418 @samp{l0} through @samp{l7}
43420 @samp{i0} through @samp{i7}
43423 They may be 32-bit or 64-bit depending on the target.
43425 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43426 targets. It should describe the following registers:
43430 @samp{f0} through @samp{f31}
43432 @samp{f32} through @samp{f62} for sparc64
43435 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43436 targets. It should describe the following registers:
43440 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43441 @samp{fsr}, and @samp{csr} for sparc32
43443 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43447 @node TIC6x Features
43448 @subsection TMS320C6x Features
43449 @cindex target descriptions, TIC6x features
43450 @cindex target descriptions, TMS320C6x features
43451 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43452 targets. It should contain registers @samp{A0} through @samp{A15},
43453 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43455 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43456 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43457 through @samp{B31}.
43459 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43460 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43462 @node Operating System Information
43463 @appendix Operating System Information
43464 @cindex operating system information
43470 Users of @value{GDBN} often wish to obtain information about the state of
43471 the operating system running on the target---for example the list of
43472 processes, or the list of open files. This section describes the
43473 mechanism that makes it possible. This mechanism is similar to the
43474 target features mechanism (@pxref{Target Descriptions}), but focuses
43475 on a different aspect of target.
43477 Operating system information is retrived from the target via the
43478 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43479 read}). The object name in the request should be @samp{osdata}, and
43480 the @var{annex} identifies the data to be fetched.
43483 @appendixsection Process list
43484 @cindex operating system information, process list
43486 When requesting the process list, the @var{annex} field in the
43487 @samp{qXfer} request should be @samp{processes}. The returned data is
43488 an XML document. The formal syntax of this document is defined in
43489 @file{gdb/features/osdata.dtd}.
43491 An example document is:
43494 <?xml version="1.0"?>
43495 <!DOCTYPE target SYSTEM "osdata.dtd">
43496 <osdata type="processes">
43498 <column name="pid">1</column>
43499 <column name="user">root</column>
43500 <column name="command">/sbin/init</column>
43501 <column name="cores">1,2,3</column>
43506 Each item should include a column whose name is @samp{pid}. The value
43507 of that column should identify the process on the target. The
43508 @samp{user} and @samp{command} columns are optional, and will be
43509 displayed by @value{GDBN}. The @samp{cores} column, if present,
43510 should contain a comma-separated list of cores that this process
43511 is running on. Target may provide additional columns,
43512 which @value{GDBN} currently ignores.
43514 @node Trace File Format
43515 @appendix Trace File Format
43516 @cindex trace file format
43518 The trace file comes in three parts: a header, a textual description
43519 section, and a trace frame section with binary data.
43521 The header has the form @code{\x7fTRACE0\n}. The first byte is
43522 @code{0x7f} so as to indicate that the file contains binary data,
43523 while the @code{0} is a version number that may have different values
43526 The description section consists of multiple lines of @sc{ascii} text
43527 separated by newline characters (@code{0xa}). The lines may include a
43528 variety of optional descriptive or context-setting information, such
43529 as tracepoint definitions or register set size. @value{GDBN} will
43530 ignore any line that it does not recognize. An empty line marks the end
43535 Specifies the size of a register block in bytes. This is equal to the
43536 size of a @code{g} packet payload in the remote protocol. @var{size}
43537 is an ascii decimal number. There should be only one such line in
43538 a single trace file.
43540 @item status @var{status}
43541 Trace status. @var{status} has the same format as a @code{qTStatus}
43542 remote packet reply. There should be only one such line in a single trace
43545 @item tp @var{payload}
43546 Tracepoint definition. The @var{payload} has the same format as
43547 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43548 may take multiple lines of definition, corresponding to the multiple
43551 @item tsv @var{payload}
43552 Trace state variable definition. The @var{payload} has the same format as
43553 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43554 may take multiple lines of definition, corresponding to the multiple
43557 @item tdesc @var{payload}
43558 Target description in XML format. The @var{payload} is a single line of
43559 the XML file. All such lines should be concatenated together to get
43560 the original XML file. This file is in the same format as @code{qXfer}
43561 @code{features} payload, and corresponds to the main @code{target.xml}
43562 file. Includes are not allowed.
43566 The trace frame section consists of a number of consecutive frames.
43567 Each frame begins with a two-byte tracepoint number, followed by a
43568 four-byte size giving the amount of data in the frame. The data in
43569 the frame consists of a number of blocks, each introduced by a
43570 character indicating its type (at least register, memory, and trace
43571 state variable). The data in this section is raw binary, not a
43572 hexadecimal or other encoding; its endianness matches the target's
43575 @c FIXME bi-arch may require endianness/arch info in description section
43578 @item R @var{bytes}
43579 Register block. The number and ordering of bytes matches that of a
43580 @code{g} packet in the remote protocol. Note that these are the
43581 actual bytes, in target order, not a hexadecimal encoding.
43583 @item M @var{address} @var{length} @var{bytes}...
43584 Memory block. This is a contiguous block of memory, at the 8-byte
43585 address @var{address}, with a 2-byte length @var{length}, followed by
43586 @var{length} bytes.
43588 @item V @var{number} @var{value}
43589 Trace state variable block. This records the 8-byte signed value
43590 @var{value} of trace state variable numbered @var{number}.
43594 Future enhancements of the trace file format may include additional types
43597 @node Index Section Format
43598 @appendix @code{.gdb_index} section format
43599 @cindex .gdb_index section format
43600 @cindex index section format
43602 This section documents the index section that is created by @code{save
43603 gdb-index} (@pxref{Index Files}). The index section is
43604 DWARF-specific; some knowledge of DWARF is assumed in this
43607 The mapped index file format is designed to be directly
43608 @code{mmap}able on any architecture. In most cases, a datum is
43609 represented using a little-endian 32-bit integer value, called an
43610 @code{offset_type}. Big endian machines must byte-swap the values
43611 before using them. Exceptions to this rule are noted. The data is
43612 laid out such that alignment is always respected.
43614 A mapped index consists of several areas, laid out in order.
43618 The file header. This is a sequence of values, of @code{offset_type}
43619 unless otherwise noted:
43623 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43624 Version 4 uses a different hashing function from versions 5 and 6.
43625 Version 6 includes symbols for inlined functions, whereas versions 4
43626 and 5 do not. Version 7 adds attributes to the CU indices in the
43627 symbol table. Version 8 specifies that symbols from DWARF type units
43628 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43629 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43631 @value{GDBN} will only read version 4, 5, or 6 indices
43632 by specifying @code{set use-deprecated-index-sections on}.
43633 GDB has a workaround for potentially broken version 7 indices so it is
43634 currently not flagged as deprecated.
43637 The offset, from the start of the file, of the CU list.
43640 The offset, from the start of the file, of the types CU list. Note
43641 that this area can be empty, in which case this offset will be equal
43642 to the next offset.
43645 The offset, from the start of the file, of the address area.
43648 The offset, from the start of the file, of the symbol table.
43651 The offset, from the start of the file, of the constant pool.
43655 The CU list. This is a sequence of pairs of 64-bit little-endian
43656 values, sorted by the CU offset. The first element in each pair is
43657 the offset of a CU in the @code{.debug_info} section. The second
43658 element in each pair is the length of that CU. References to a CU
43659 elsewhere in the map are done using a CU index, which is just the
43660 0-based index into this table. Note that if there are type CUs, then
43661 conceptually CUs and type CUs form a single list for the purposes of
43665 The types CU list. This is a sequence of triplets of 64-bit
43666 little-endian values. In a triplet, the first value is the CU offset,
43667 the second value is the type offset in the CU, and the third value is
43668 the type signature. The types CU list is not sorted.
43671 The address area. The address area consists of a sequence of address
43672 entries. Each address entry has three elements:
43676 The low address. This is a 64-bit little-endian value.
43679 The high address. This is a 64-bit little-endian value. Like
43680 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43683 The CU index. This is an @code{offset_type} value.
43687 The symbol table. This is an open-addressed hash table. The size of
43688 the hash table is always a power of 2.
43690 Each slot in the hash table consists of a pair of @code{offset_type}
43691 values. The first value is the offset of the symbol's name in the
43692 constant pool. The second value is the offset of the CU vector in the
43695 If both values are 0, then this slot in the hash table is empty. This
43696 is ok because while 0 is a valid constant pool index, it cannot be a
43697 valid index for both a string and a CU vector.
43699 The hash value for a table entry is computed by applying an
43700 iterative hash function to the symbol's name. Starting with an
43701 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43702 the string is incorporated into the hash using the formula depending on the
43707 The formula is @code{r = r * 67 + c - 113}.
43709 @item Versions 5 to 7
43710 The formula is @code{r = r * 67 + tolower (c) - 113}.
43713 The terminating @samp{\0} is not incorporated into the hash.
43715 The step size used in the hash table is computed via
43716 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43717 value, and @samp{size} is the size of the hash table. The step size
43718 is used to find the next candidate slot when handling a hash
43721 The names of C@t{++} symbols in the hash table are canonicalized. We
43722 don't currently have a simple description of the canonicalization
43723 algorithm; if you intend to create new index sections, you must read
43727 The constant pool. This is simply a bunch of bytes. It is organized
43728 so that alignment is correct: CU vectors are stored first, followed by
43731 A CU vector in the constant pool is a sequence of @code{offset_type}
43732 values. The first value is the number of CU indices in the vector.
43733 Each subsequent value is the index and symbol attributes of a CU in
43734 the CU list. This element in the hash table is used to indicate which
43735 CUs define the symbol and how the symbol is used.
43736 See below for the format of each CU index+attributes entry.
43738 A string in the constant pool is zero-terminated.
43741 Attributes were added to CU index values in @code{.gdb_index} version 7.
43742 If a symbol has multiple uses within a CU then there is one
43743 CU index+attributes value for each use.
43745 The format of each CU index+attributes entry is as follows
43751 This is the index of the CU in the CU list.
43753 These bits are reserved for future purposes and must be zero.
43755 The kind of the symbol in the CU.
43759 This value is reserved and should not be used.
43760 By reserving zero the full @code{offset_type} value is backwards compatible
43761 with previous versions of the index.
43763 The symbol is a type.
43765 The symbol is a variable or an enum value.
43767 The symbol is a function.
43769 Any other kind of symbol.
43771 These values are reserved.
43775 This bit is zero if the value is global and one if it is static.
43777 The determination of whether a symbol is global or static is complicated.
43778 The authorative reference is the file @file{dwarf2read.c} in
43779 @value{GDBN} sources.
43783 This pseudo-code describes the computation of a symbol's kind and
43784 global/static attributes in the index.
43787 is_external = get_attribute (die, DW_AT_external);
43788 language = get_attribute (cu_die, DW_AT_language);
43791 case DW_TAG_typedef:
43792 case DW_TAG_base_type:
43793 case DW_TAG_subrange_type:
43797 case DW_TAG_enumerator:
43799 is_static = language != CPLUS;
43801 case DW_TAG_subprogram:
43803 is_static = ! (is_external || language == ADA);
43805 case DW_TAG_constant:
43807 is_static = ! is_external;
43809 case DW_TAG_variable:
43811 is_static = ! is_external;
43813 case DW_TAG_namespace:
43817 case DW_TAG_class_type:
43818 case DW_TAG_interface_type:
43819 case DW_TAG_structure_type:
43820 case DW_TAG_union_type:
43821 case DW_TAG_enumeration_type:
43823 is_static = language != CPLUS;
43831 @appendix Manual pages
43835 * gdb man:: The GNU Debugger man page
43836 * gdbserver man:: Remote Server for the GNU Debugger man page
43837 * gcore man:: Generate a core file of a running program
43838 * gdbinit man:: gdbinit scripts
43839 * gdb-add-index man:: Add index files to speed up GDB
43845 @c man title gdb The GNU Debugger
43847 @c man begin SYNOPSIS gdb
43848 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43849 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43850 [@option{-b}@w{ }@var{bps}]
43851 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43852 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43853 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43854 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43855 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43858 @c man begin DESCRIPTION gdb
43859 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43860 going on ``inside'' another program while it executes -- or what another
43861 program was doing at the moment it crashed.
43863 @value{GDBN} can do four main kinds of things (plus other things in support of
43864 these) to help you catch bugs in the act:
43868 Start your program, specifying anything that might affect its behavior.
43871 Make your program stop on specified conditions.
43874 Examine what has happened, when your program has stopped.
43877 Change things in your program, so you can experiment with correcting the
43878 effects of one bug and go on to learn about another.
43881 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43884 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43885 commands from the terminal until you tell it to exit with the @value{GDBN}
43886 command @code{quit}. You can get online help from @value{GDBN} itself
43887 by using the command @code{help}.
43889 You can run @code{gdb} with no arguments or options; but the most
43890 usual way to start @value{GDBN} is with one argument or two, specifying an
43891 executable program as the argument:
43897 You can also start with both an executable program and a core file specified:
43903 You can, instead, specify a process ID as a second argument, if you want
43904 to debug a running process:
43912 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43913 named @file{1234}; @value{GDBN} does check for a core file first).
43914 With option @option{-p} you can omit the @var{program} filename.
43916 Here are some of the most frequently needed @value{GDBN} commands:
43918 @c pod2man highlights the right hand side of the @item lines.
43920 @item break [@var{file}:]@var{function}
43921 Set a breakpoint at @var{function} (in @var{file}).
43923 @item run [@var{arglist}]
43924 Start your program (with @var{arglist}, if specified).
43927 Backtrace: display the program stack.
43929 @item print @var{expr}
43930 Display the value of an expression.
43933 Continue running your program (after stopping, e.g. at a breakpoint).
43936 Execute next program line (after stopping); step @emph{over} any
43937 function calls in the line.
43939 @item edit [@var{file}:]@var{function}
43940 look at the program line where it is presently stopped.
43942 @item list [@var{file}:]@var{function}
43943 type the text of the program in the vicinity of where it is presently stopped.
43946 Execute next program line (after stopping); step @emph{into} any
43947 function calls in the line.
43949 @item help [@var{name}]
43950 Show information about @value{GDBN} command @var{name}, or general information
43951 about using @value{GDBN}.
43954 Exit from @value{GDBN}.
43958 For full details on @value{GDBN},
43959 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43960 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43961 as the @code{gdb} entry in the @code{info} program.
43965 @c man begin OPTIONS gdb
43966 Any arguments other than options specify an executable
43967 file and core file (or process ID); that is, the first argument
43968 encountered with no
43969 associated option flag is equivalent to a @option{-se} option, and the second,
43970 if any, is equivalent to a @option{-c} option if it's the name of a file.
43972 both long and short forms; both are shown here. The long forms are also
43973 recognized if you truncate them, so long as enough of the option is
43974 present to be unambiguous. (If you prefer, you can flag option
43975 arguments with @option{+} rather than @option{-}, though we illustrate the
43976 more usual convention.)
43978 All the options and command line arguments you give are processed
43979 in sequential order. The order makes a difference when the @option{-x}
43985 List all options, with brief explanations.
43987 @item -symbols=@var{file}
43988 @itemx -s @var{file}
43989 Read symbol table from file @var{file}.
43992 Enable writing into executable and core files.
43994 @item -exec=@var{file}
43995 @itemx -e @var{file}
43996 Use file @var{file} as the executable file to execute when
43997 appropriate, and for examining pure data in conjunction with a core
44000 @item -se=@var{file}
44001 Read symbol table from file @var{file} and use it as the executable
44004 @item -core=@var{file}
44005 @itemx -c @var{file}
44006 Use file @var{file} as a core dump to examine.
44008 @item -command=@var{file}
44009 @itemx -x @var{file}
44010 Execute @value{GDBN} commands from file @var{file}.
44012 @item -ex @var{command}
44013 Execute given @value{GDBN} @var{command}.
44015 @item -directory=@var{directory}
44016 @itemx -d @var{directory}
44017 Add @var{directory} to the path to search for source files.
44020 Do not execute commands from @file{~/.gdbinit}.
44024 Do not execute commands from any @file{.gdbinit} initialization files.
44028 ``Quiet''. Do not print the introductory and copyright messages. These
44029 messages are also suppressed in batch mode.
44032 Run in batch mode. Exit with status @code{0} after processing all the command
44033 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44034 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44035 commands in the command files.
44037 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44038 download and run a program on another computer; in order to make this
44039 more useful, the message
44042 Program exited normally.
44046 (which is ordinarily issued whenever a program running under @value{GDBN} control
44047 terminates) is not issued when running in batch mode.
44049 @item -cd=@var{directory}
44050 Run @value{GDBN} using @var{directory} as its working directory,
44051 instead of the current directory.
44055 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44056 @value{GDBN} to output the full file name and line number in a standard,
44057 recognizable fashion each time a stack frame is displayed (which
44058 includes each time the program stops). This recognizable format looks
44059 like two @samp{\032} characters, followed by the file name, line number
44060 and character position separated by colons, and a newline. The
44061 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44062 characters as a signal to display the source code for the frame.
44065 Set the line speed (baud rate or bits per second) of any serial
44066 interface used by @value{GDBN} for remote debugging.
44068 @item -tty=@var{device}
44069 Run using @var{device} for your program's standard input and output.
44073 @c man begin SEEALSO gdb
44075 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44076 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44077 documentation are properly installed at your site, the command
44084 should give you access to the complete manual.
44086 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44087 Richard M. Stallman and Roland H. Pesch, July 1991.
44091 @node gdbserver man
44092 @heading gdbserver man
44094 @c man title gdbserver Remote Server for the GNU Debugger
44096 @c man begin SYNOPSIS gdbserver
44097 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44099 gdbserver --attach @var{comm} @var{pid}
44101 gdbserver --multi @var{comm}
44105 @c man begin DESCRIPTION gdbserver
44106 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44107 than the one which is running the program being debugged.
44110 @subheading Usage (server (target) side)
44113 Usage (server (target) side):
44116 First, you need to have a copy of the program you want to debug put onto
44117 the target system. The program can be stripped to save space if needed, as
44118 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44119 the @value{GDBN} running on the host system.
44121 To use the server, you log on to the target system, and run the @command{gdbserver}
44122 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44123 your program, and (c) its arguments. The general syntax is:
44126 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44129 For example, using a serial port, you might say:
44133 @c @file would wrap it as F</dev/com1>.
44134 target> gdbserver /dev/com1 emacs foo.txt
44137 target> gdbserver @file{/dev/com1} emacs foo.txt
44141 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44142 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44143 waits patiently for the host @value{GDBN} to communicate with it.
44145 To use a TCP connection, you could say:
44148 target> gdbserver host:2345 emacs foo.txt
44151 This says pretty much the same thing as the last example, except that we are
44152 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44153 that we are expecting to see a TCP connection from @code{host} to local TCP port
44154 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44155 want for the port number as long as it does not conflict with any existing TCP
44156 ports on the target system. This same port number must be used in the host
44157 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44158 you chose a port number that conflicts with another service, @command{gdbserver} will
44159 print an error message and exit.
44161 @command{gdbserver} can also attach to running programs.
44162 This is accomplished via the @option{--attach} argument. The syntax is:
44165 target> gdbserver --attach @var{comm} @var{pid}
44168 @var{pid} is the process ID of a currently running process. It isn't
44169 necessary to point @command{gdbserver} at a binary for the running process.
44171 To start @code{gdbserver} without supplying an initial command to run
44172 or process ID to attach, use the @option{--multi} command line option.
44173 In such case you should connect using @kbd{target extended-remote} to start
44174 the program you want to debug.
44177 target> gdbserver --multi @var{comm}
44181 @subheading Usage (host side)
44187 You need an unstripped copy of the target program on your host system, since
44188 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44189 would, with the target program as the first argument. (You may need to use the
44190 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44191 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44192 new command you need to know about is @code{target remote}
44193 (or @code{target extended-remote}). Its argument is either
44194 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44195 descriptor. For example:
44199 @c @file would wrap it as F</dev/ttyb>.
44200 (gdb) target remote /dev/ttyb
44203 (gdb) target remote @file{/dev/ttyb}
44208 communicates with the server via serial line @file{/dev/ttyb}, and:
44211 (gdb) target remote the-target:2345
44215 communicates via a TCP connection to port 2345 on host `the-target', where
44216 you previously started up @command{gdbserver} with the same port number. Note that for
44217 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44218 command, otherwise you may get an error that looks something like
44219 `Connection refused'.
44221 @command{gdbserver} can also debug multiple inferiors at once,
44224 the @value{GDBN} manual in node @code{Inferiors and Programs}
44225 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44228 @ref{Inferiors and Programs}.
44230 In such case use the @code{extended-remote} @value{GDBN} command variant:
44233 (gdb) target extended-remote the-target:2345
44236 The @command{gdbserver} option @option{--multi} may or may not be used in such
44240 @c man begin OPTIONS gdbserver
44241 There are three different modes for invoking @command{gdbserver}:
44246 Debug a specific program specified by its program name:
44249 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44252 The @var{comm} parameter specifies how should the server communicate
44253 with @value{GDBN}; it is either a device name (to use a serial line),
44254 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44255 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44256 debug in @var{prog}. Any remaining arguments will be passed to the
44257 program verbatim. When the program exits, @value{GDBN} will close the
44258 connection, and @code{gdbserver} will exit.
44261 Debug a specific program by specifying the process ID of a running
44265 gdbserver --attach @var{comm} @var{pid}
44268 The @var{comm} parameter is as described above. Supply the process ID
44269 of a running program in @var{pid}; @value{GDBN} will do everything
44270 else. Like with the previous mode, when the process @var{pid} exits,
44271 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44274 Multi-process mode -- debug more than one program/process:
44277 gdbserver --multi @var{comm}
44280 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44281 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44282 close the connection when a process being debugged exits, so you can
44283 debug several processes in the same session.
44286 In each of the modes you may specify these options:
44291 List all options, with brief explanations.
44294 This option causes @command{gdbserver} to print its version number and exit.
44297 @command{gdbserver} will attach to a running program. The syntax is:
44300 target> gdbserver --attach @var{comm} @var{pid}
44303 @var{pid} is the process ID of a currently running process. It isn't
44304 necessary to point @command{gdbserver} at a binary for the running process.
44307 To start @code{gdbserver} without supplying an initial command to run
44308 or process ID to attach, use this command line option.
44309 Then you can connect using @kbd{target extended-remote} and start
44310 the program you want to debug. The syntax is:
44313 target> gdbserver --multi @var{comm}
44317 Instruct @code{gdbserver} to display extra status information about the debugging
44319 This option is intended for @code{gdbserver} development and for bug reports to
44322 @item --remote-debug
44323 Instruct @code{gdbserver} to display remote protocol debug output.
44324 This option is intended for @code{gdbserver} development and for bug reports to
44327 @item --debug-format=option1@r{[},option2,...@r{]}
44328 Instruct @code{gdbserver} to include extra information in each line
44329 of debugging output.
44330 @xref{Other Command-Line Arguments for gdbserver}.
44333 Specify a wrapper to launch programs
44334 for debugging. The option should be followed by the name of the
44335 wrapper, then any command-line arguments to pass to the wrapper, then
44336 @kbd{--} indicating the end of the wrapper arguments.
44339 By default, @command{gdbserver} keeps the listening TCP port open, so that
44340 additional connections are possible. However, if you start @code{gdbserver}
44341 with the @option{--once} option, it will stop listening for any further
44342 connection attempts after connecting to the first @value{GDBN} session.
44344 @c --disable-packet is not documented for users.
44346 @c --disable-randomization and --no-disable-randomization are superseded by
44347 @c QDisableRandomization.
44352 @c man begin SEEALSO gdbserver
44354 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44355 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44356 documentation are properly installed at your site, the command
44362 should give you access to the complete manual.
44364 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44365 Richard M. Stallman and Roland H. Pesch, July 1991.
44372 @c man title gcore Generate a core file of a running program
44375 @c man begin SYNOPSIS gcore
44376 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44380 @c man begin DESCRIPTION gcore
44381 Generate core dumps of one or more running programs with process IDs
44382 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44383 is equivalent to one produced by the kernel when the process crashes
44384 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44385 limit). However, unlike after a crash, after @command{gcore} finishes
44386 its job the program remains running without any change.
44389 @c man begin OPTIONS gcore
44392 Dump all memory mappings. The actual effect of this option depends on
44393 the Operating System. On @sc{gnu}/Linux, it will disable
44394 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44395 enable @code{dump-excluded-mappings} (@pxref{set
44396 dump-excluded-mappings}).
44398 @item -o @var{prefix}
44399 The optional argument @var{prefix} specifies the prefix to be used
44400 when composing the file names of the core dumps. The file name is
44401 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44402 process ID of the running program being analyzed by @command{gcore}.
44403 If not specified, @var{prefix} defaults to @var{gcore}.
44407 @c man begin SEEALSO gcore
44409 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44410 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44411 documentation are properly installed at your site, the command
44418 should give you access to the complete manual.
44420 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44421 Richard M. Stallman and Roland H. Pesch, July 1991.
44428 @c man title gdbinit GDB initialization scripts
44431 @c man begin SYNOPSIS gdbinit
44432 @ifset SYSTEM_GDBINIT
44433 @value{SYSTEM_GDBINIT}
44442 @c man begin DESCRIPTION gdbinit
44443 These files contain @value{GDBN} commands to automatically execute during
44444 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44447 the @value{GDBN} manual in node @code{Sequences}
44448 -- shell command @code{info -f gdb -n Sequences}.
44454 Please read more in
44456 the @value{GDBN} manual in node @code{Startup}
44457 -- shell command @code{info -f gdb -n Startup}.
44464 @ifset SYSTEM_GDBINIT
44465 @item @value{SYSTEM_GDBINIT}
44467 @ifclear SYSTEM_GDBINIT
44468 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44470 System-wide initialization file. It is executed unless user specified
44471 @value{GDBN} option @code{-nx} or @code{-n}.
44474 the @value{GDBN} manual in node @code{System-wide configuration}
44475 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44478 @ref{System-wide configuration}.
44482 User initialization file. It is executed unless user specified
44483 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44486 Initialization file for current directory. It may need to be enabled with
44487 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44490 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44491 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44494 @ref{Init File in the Current Directory}.
44499 @c man begin SEEALSO gdbinit
44501 gdb(1), @code{info -f gdb -n Startup}
44503 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44504 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44505 documentation are properly installed at your site, the command
44511 should give you access to the complete manual.
44513 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44514 Richard M. Stallman and Roland H. Pesch, July 1991.
44518 @node gdb-add-index man
44519 @heading gdb-add-index
44520 @pindex gdb-add-index
44521 @anchor{gdb-add-index}
44523 @c man title gdb-add-index Add index files to speed up GDB
44525 @c man begin SYNOPSIS gdb-add-index
44526 gdb-add-index @var{filename}
44529 @c man begin DESCRIPTION gdb-add-index
44530 When @value{GDBN} finds a symbol file, it scans the symbols in the
44531 file in order to construct an internal symbol table. This lets most
44532 @value{GDBN} operations work quickly--at the cost of a delay early on.
44533 For large programs, this delay can be quite lengthy, so @value{GDBN}
44534 provides a way to build an index, which speeds up startup.
44536 To determine whether a file contains such an index, use the command
44537 @kbd{readelf -S filename}: the index is stored in a section named
44538 @code{.gdb_index}. The index file can only be produced on systems
44539 which use ELF binaries and DWARF debug information (i.e., sections
44540 named @code{.debug_*}).
44542 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44543 in the @env{PATH} environment variable. If you want to use different
44544 versions of these programs, you can specify them through the
44545 @env{GDB} and @env{OBJDUMP} environment variables.
44549 the @value{GDBN} manual in node @code{Index Files}
44550 -- shell command @kbd{info -f gdb -n "Index Files"}.
44557 @c man begin SEEALSO gdb-add-index
44559 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44560 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44561 documentation are properly installed at your site, the command
44567 should give you access to the complete manual.
44569 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44570 Richard M. Stallman and Roland H. Pesch, July 1991.
44576 @node GNU Free Documentation License
44577 @appendix GNU Free Documentation License
44580 @node Concept Index
44581 @unnumbered Concept Index
44585 @node Command and Variable Index
44586 @unnumbered Command, Variable, and Function Index
44591 % I think something like @@colophon should be in texinfo. In the
44593 \long\def\colophon{\hbox to0pt{}\vfill
44594 \centerline{The body of this manual is set in}
44595 \centerline{\fontname\tenrm,}
44596 \centerline{with headings in {\bf\fontname\tenbf}}
44597 \centerline{and examples in {\tt\fontname\tentt}.}
44598 \centerline{{\it\fontname\tenit\/},}
44599 \centerline{{\bf\fontname\tenbf}, and}
44600 \centerline{{\sl\fontname\tensl\/}}
44601 \centerline{are used for emphasis.}\vfill}
44603 % Blame: doc@@cygnus.com, 1991.