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 The original port to the OpenRISC 1000 is believed to be due to
550 Alessandro Forin and Per Bothner. More recent ports have been the work
551 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
555 @chapter A Sample @value{GDBN} Session
557 You can use this manual at your leisure to read all about @value{GDBN}.
558 However, a handful of commands are enough to get started using the
559 debugger. This chapter illustrates those commands.
562 In this sample session, we emphasize user input like this: @b{input},
563 to make it easier to pick out from the surrounding output.
566 @c FIXME: this example may not be appropriate for some configs, where
567 @c FIXME...primary interest is in remote use.
569 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
570 processor) exhibits the following bug: sometimes, when we change its
571 quote strings from the default, the commands used to capture one macro
572 definition within another stop working. In the following short @code{m4}
573 session, we define a macro @code{foo} which expands to @code{0000}; we
574 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
575 same thing. However, when we change the open quote string to
576 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
577 procedure fails to define a new synonym @code{baz}:
586 @b{define(bar,defn(`foo'))}
590 @b{changequote(<QUOTE>,<UNQUOTE>)}
592 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
595 m4: End of input: 0: fatal error: EOF in string
599 Let us use @value{GDBN} to try to see what is going on.
602 $ @b{@value{GDBP} m4}
603 @c FIXME: this falsifies the exact text played out, to permit smallbook
604 @c FIXME... format to come out better.
605 @value{GDBN} is free software and you are welcome to distribute copies
606 of it under certain conditions; type "show copying" to see
608 There is absolutely no warranty for @value{GDBN}; type "show warranty"
611 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
616 @value{GDBN} reads only enough symbol data to know where to find the
617 rest when needed; as a result, the first prompt comes up very quickly.
618 We now tell @value{GDBN} to use a narrower display width than usual, so
619 that examples fit in this manual.
622 (@value{GDBP}) @b{set width 70}
626 We need to see how the @code{m4} built-in @code{changequote} works.
627 Having looked at the source, we know the relevant subroutine is
628 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
629 @code{break} command.
632 (@value{GDBP}) @b{break m4_changequote}
633 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
637 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
638 control; as long as control does not reach the @code{m4_changequote}
639 subroutine, the program runs as usual:
642 (@value{GDBP}) @b{run}
643 Starting program: /work/Editorial/gdb/gnu/m4/m4
651 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
652 suspends execution of @code{m4}, displaying information about the
653 context where it stops.
656 @b{changequote(<QUOTE>,<UNQUOTE>)}
658 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
660 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
664 Now we use the command @code{n} (@code{next}) to advance execution to
665 the next line of the current function.
669 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
674 @code{set_quotes} looks like a promising subroutine. We can go into it
675 by using the command @code{s} (@code{step}) instead of @code{next}.
676 @code{step} goes to the next line to be executed in @emph{any}
677 subroutine, so it steps into @code{set_quotes}.
681 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 530 if (lquote != def_lquote)
687 The display that shows the subroutine where @code{m4} is now
688 suspended (and its arguments) is called a stack frame display. It
689 shows a summary of the stack. We can use the @code{backtrace}
690 command (which can also be spelled @code{bt}), to see where we are
691 in the stack as a whole: the @code{backtrace} command displays a
692 stack frame for each active subroutine.
695 (@value{GDBP}) @b{bt}
696 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
698 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
700 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
701 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
703 #4 0x79dc in expand_input () at macro.c:40
704 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
708 We step through a few more lines to see what happens. The first two
709 times, we can use @samp{s}; the next two times we use @code{n} to avoid
710 falling into the @code{xstrdup} subroutine.
714 0x3b5c 532 if (rquote != def_rquote)
716 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
717 def_lquote : xstrdup(lq);
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
726 The last line displayed looks a little odd; we can examine the variables
727 @code{lquote} and @code{rquote} to see if they are in fact the new left
728 and right quotes we specified. We use the command @code{p}
729 (@code{print}) to see their values.
732 (@value{GDBP}) @b{p lquote}
733 $1 = 0x35d40 "<QUOTE>"
734 (@value{GDBP}) @b{p rquote}
735 $2 = 0x35d50 "<UNQUOTE>"
739 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
740 To look at some context, we can display ten lines of source
741 surrounding the current line with the @code{l} (@code{list}) command.
747 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
749 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
752 538 len_lquote = strlen(rquote);
753 539 len_rquote = strlen(lquote);
760 Let us step past the two lines that set @code{len_lquote} and
761 @code{len_rquote}, and then examine the values of those variables.
765 539 len_rquote = strlen(lquote);
768 (@value{GDBP}) @b{p len_lquote}
770 (@value{GDBP}) @b{p len_rquote}
775 That certainly looks wrong, assuming @code{len_lquote} and
776 @code{len_rquote} are meant to be the lengths of @code{lquote} and
777 @code{rquote} respectively. We can set them to better values using
778 the @code{p} command, since it can print the value of
779 any expression---and that expression can include subroutine calls and
783 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
785 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
790 Is that enough to fix the problem of using the new quotes with the
791 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
792 executing with the @code{c} (@code{continue}) command, and then try the
793 example that caused trouble initially:
799 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
806 Success! The new quotes now work just as well as the default ones. The
807 problem seems to have been just the two typos defining the wrong
808 lengths. We allow @code{m4} exit by giving it an EOF as input:
812 Program exited normally.
816 The message @samp{Program exited normally.} is from @value{GDBN}; it
817 indicates @code{m4} has finished executing. We can end our @value{GDBN}
818 session with the @value{GDBN} @code{quit} command.
821 (@value{GDBP}) @b{quit}
825 @chapter Getting In and Out of @value{GDBN}
827 This chapter discusses how to start @value{GDBN}, and how to get out of it.
831 type @samp{@value{GDBP}} to start @value{GDBN}.
833 type @kbd{quit} or @kbd{Ctrl-d} to exit.
837 * Invoking GDB:: How to start @value{GDBN}
838 * Quitting GDB:: How to quit @value{GDBN}
839 * Shell Commands:: How to use shell commands inside @value{GDBN}
840 * Logging Output:: How to log @value{GDBN}'s output to a file
844 @section Invoking @value{GDBN}
846 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
847 @value{GDBN} reads commands from the terminal until you tell it to exit.
849 You can also run @code{@value{GDBP}} with a variety of arguments and options,
850 to specify more of your debugging environment at the outset.
852 The command-line options described here are designed
853 to cover a variety of situations; in some environments, some of these
854 options may effectively be unavailable.
856 The most usual way to start @value{GDBN} is with one argument,
857 specifying an executable program:
860 @value{GDBP} @var{program}
864 You can also start with both an executable program and a core file
868 @value{GDBP} @var{program} @var{core}
871 You can, instead, specify a process ID as a second argument, if you want
872 to debug a running process:
875 @value{GDBP} @var{program} 1234
879 would attach @value{GDBN} to process @code{1234} (unless you also have a file
880 named @file{1234}; @value{GDBN} does check for a core file first).
882 Taking advantage of the second command-line argument requires a fairly
883 complete operating system; when you use @value{GDBN} as a remote
884 debugger attached to a bare board, there may not be any notion of
885 ``process'', and there is often no way to get a core dump. @value{GDBN}
886 will warn you if it is unable to attach or to read core dumps.
888 You can optionally have @code{@value{GDBP}} pass any arguments after the
889 executable file to the inferior using @code{--args}. This option stops
892 @value{GDBP} --args gcc -O2 -c foo.c
894 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
895 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
897 You can run @code{@value{GDBP}} without printing the front material, which describes
898 @value{GDBN}'s non-warranty, by specifying @code{--silent}
899 (or @code{-q}/@code{--quiet}):
902 @value{GDBP} --silent
906 You can further control how @value{GDBN} starts up by using command-line
907 options. @value{GDBN} itself can remind you of the options available.
917 to display all available options and briefly describe their use
918 (@samp{@value{GDBP} -h} is a shorter equivalent).
920 All options and command line arguments you give are processed
921 in sequential order. The order makes a difference when the
922 @samp{-x} option is used.
926 * File Options:: Choosing files
927 * Mode Options:: Choosing modes
928 * Startup:: What @value{GDBN} does during startup
932 @subsection Choosing Files
934 When @value{GDBN} starts, it reads any arguments other than options as
935 specifying an executable file and core file (or process ID). This is
936 the same as if the arguments were specified by the @samp{-se} and
937 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
938 first argument that does not have an associated option flag as
939 equivalent to the @samp{-se} option followed by that argument; and the
940 second argument that does not have an associated option flag, if any, as
941 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
942 If the second argument begins with a decimal digit, @value{GDBN} will
943 first attempt to attach to it as a process, and if that fails, attempt
944 to open it as a corefile. If you have a corefile whose name begins with
945 a digit, you can prevent @value{GDBN} from treating it as a pid by
946 prefixing it with @file{./}, e.g.@: @file{./12345}.
948 If @value{GDBN} has not been configured to included core file support,
949 such as for most embedded targets, then it will complain about a second
950 argument and ignore it.
952 Many options have both long and short forms; both are shown in the
953 following list. @value{GDBN} also recognizes the long forms if you truncate
954 them, so long as enough of the option is present to be unambiguous.
955 (If you prefer, you can flag option arguments with @samp{--} rather
956 than @samp{-}, though we illustrate the more usual convention.)
958 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
959 @c way, both those who look for -foo and --foo in the index, will find
963 @item -symbols @var{file}
965 @cindex @code{--symbols}
967 Read symbol table from file @var{file}.
969 @item -exec @var{file}
971 @cindex @code{--exec}
973 Use file @var{file} as the executable file to execute when appropriate,
974 and for examining pure data in conjunction with a core dump.
978 Read symbol table from file @var{file} and use it as the executable
981 @item -core @var{file}
983 @cindex @code{--core}
985 Use file @var{file} as a core dump to examine.
987 @item -pid @var{number}
988 @itemx -p @var{number}
991 Connect to process ID @var{number}, as with the @code{attach} command.
993 @item -command @var{file}
995 @cindex @code{--command}
997 Execute commands from file @var{file}. The contents of this file is
998 evaluated exactly as the @code{source} command would.
999 @xref{Command Files,, Command files}.
1001 @item -eval-command @var{command}
1002 @itemx -ex @var{command}
1003 @cindex @code{--eval-command}
1005 Execute a single @value{GDBN} command.
1007 This option may be used multiple times to call multiple commands. It may
1008 also be interleaved with @samp{-command} as required.
1011 @value{GDBP} -ex 'target sim' -ex 'load' \
1012 -x setbreakpoints -ex 'run' a.out
1015 @item -init-command @var{file}
1016 @itemx -ix @var{file}
1017 @cindex @code{--init-command}
1019 Execute commands from file @var{file} before loading the inferior (but
1020 after loading gdbinit files).
1023 @item -init-eval-command @var{command}
1024 @itemx -iex @var{command}
1025 @cindex @code{--init-eval-command}
1027 Execute a single @value{GDBN} command before loading the inferior (but
1028 after loading gdbinit files).
1031 @item -directory @var{directory}
1032 @itemx -d @var{directory}
1033 @cindex @code{--directory}
1035 Add @var{directory} to the path to search for source and script files.
1039 @cindex @code{--readnow}
1041 Read each symbol file's entire symbol table immediately, rather than
1042 the default, which is to read it incrementally as it is needed.
1043 This makes startup slower, but makes future operations faster.
1046 @anchor{--readnever}
1047 @cindex @code{--readnever}, command-line option
1048 Do not read each symbol file's symbolic debug information. This makes
1049 startup faster but at the expense of not being able to perform
1050 symbolic debugging. DWARF unwind information is also not read,
1051 meaning backtraces may become incomplete or inaccurate. One use of
1052 this is when a user simply wants to do the following sequence: attach,
1053 dump core, detach. Loading the debugging information in this case is
1054 an unnecessary cause of delay.
1058 @subsection Choosing Modes
1060 You can run @value{GDBN} in various alternative modes---for example, in
1061 batch mode or quiet mode.
1069 Do not execute commands found in any initialization file.
1070 There are three init files, loaded in the following order:
1073 @item @file{system.gdbinit}
1074 This is the system-wide init file.
1075 Its location is specified with the @code{--with-system-gdbinit}
1076 configure option (@pxref{System-wide configuration}).
1077 It is loaded first when @value{GDBN} starts, before command line options
1078 have been processed.
1079 @item @file{~/.gdbinit}
1080 This is the init file in your home directory.
1081 It is loaded next, after @file{system.gdbinit}, and before
1082 command options have been processed.
1083 @item @file{./.gdbinit}
1084 This is the init file in the current directory.
1085 It is loaded last, after command line options other than @code{-x} and
1086 @code{-ex} have been processed. Command line options @code{-x} and
1087 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1090 For further documentation on startup processing, @xref{Startup}.
1091 For documentation on how to write command files,
1092 @xref{Command Files,,Command Files}.
1097 Do not execute commands found in @file{~/.gdbinit}, the init file
1098 in your home directory.
1104 @cindex @code{--quiet}
1105 @cindex @code{--silent}
1107 ``Quiet''. Do not print the introductory and copyright messages. These
1108 messages are also suppressed in batch mode.
1111 @cindex @code{--batch}
1112 Run in batch mode. Exit with status @code{0} after processing all the
1113 command files specified with @samp{-x} (and all commands from
1114 initialization files, if not inhibited with @samp{-n}). Exit with
1115 nonzero status if an error occurs in executing the @value{GDBN} commands
1116 in the command files. Batch mode also disables pagination, sets unlimited
1117 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1118 off} were in effect (@pxref{Messages/Warnings}).
1120 Batch mode may be useful for running @value{GDBN} as a filter, for
1121 example to download and run a program on another computer; in order to
1122 make this more useful, the message
1125 Program exited normally.
1129 (which is ordinarily issued whenever a program running under
1130 @value{GDBN} control terminates) is not issued when running in batch
1134 @cindex @code{--batch-silent}
1135 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1136 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1137 unaffected). This is much quieter than @samp{-silent} and would be useless
1138 for an interactive session.
1140 This is particularly useful when using targets that give @samp{Loading section}
1141 messages, for example.
1143 Note that targets that give their output via @value{GDBN}, as opposed to
1144 writing directly to @code{stdout}, will also be made silent.
1146 @item -return-child-result
1147 @cindex @code{--return-child-result}
1148 The return code from @value{GDBN} will be the return code from the child
1149 process (the process being debugged), with the following exceptions:
1153 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1154 internal error. In this case the exit code is the same as it would have been
1155 without @samp{-return-child-result}.
1157 The user quits with an explicit value. E.g., @samp{quit 1}.
1159 The child process never runs, or is not allowed to terminate, in which case
1160 the exit code will be -1.
1163 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1164 when @value{GDBN} is being used as a remote program loader or simulator
1169 @cindex @code{--nowindows}
1171 ``No windows''. If @value{GDBN} comes with a graphical user interface
1172 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1173 interface. If no GUI is available, this option has no effect.
1177 @cindex @code{--windows}
1179 If @value{GDBN} includes a GUI, then this option requires it to be
1182 @item -cd @var{directory}
1184 Run @value{GDBN} using @var{directory} as its working directory,
1185 instead of the current directory.
1187 @item -data-directory @var{directory}
1188 @itemx -D @var{directory}
1189 @cindex @code{--data-directory}
1191 Run @value{GDBN} using @var{directory} as its data directory.
1192 The data directory is where @value{GDBN} searches for its
1193 auxiliary files. @xref{Data Files}.
1197 @cindex @code{--fullname}
1199 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1200 subprocess. It tells @value{GDBN} to output the full file name and line
1201 number in a standard, recognizable fashion each time a stack frame is
1202 displayed (which includes each time your program stops). This
1203 recognizable format looks like two @samp{\032} characters, followed by
1204 the file name, line number and character position separated by colons,
1205 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1206 @samp{\032} characters as a signal to display the source code for the
1209 @item -annotate @var{level}
1210 @cindex @code{--annotate}
1211 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1212 effect is identical to using @samp{set annotate @var{level}}
1213 (@pxref{Annotations}). The annotation @var{level} controls how much
1214 information @value{GDBN} prints together with its prompt, values of
1215 expressions, source lines, and other types of output. Level 0 is the
1216 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1217 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1218 that control @value{GDBN}, and level 2 has been deprecated.
1220 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1224 @cindex @code{--args}
1225 Change interpretation of command line so that arguments following the
1226 executable file are passed as command line arguments to the inferior.
1227 This option stops option processing.
1229 @item -baud @var{bps}
1231 @cindex @code{--baud}
1233 Set the line speed (baud rate or bits per second) of any serial
1234 interface used by @value{GDBN} for remote debugging.
1236 @item -l @var{timeout}
1238 Set the timeout (in seconds) of any communication used by @value{GDBN}
1239 for remote debugging.
1241 @item -tty @var{device}
1242 @itemx -t @var{device}
1243 @cindex @code{--tty}
1245 Run using @var{device} for your program's standard input and output.
1246 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1248 @c resolve the situation of these eventually
1250 @cindex @code{--tui}
1251 Activate the @dfn{Text User Interface} when starting. The Text User
1252 Interface manages several text windows on the terminal, showing
1253 source, assembly, registers and @value{GDBN} command outputs
1254 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1255 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1256 Using @value{GDBN} under @sc{gnu} Emacs}).
1258 @item -interpreter @var{interp}
1259 @cindex @code{--interpreter}
1260 Use the interpreter @var{interp} for interface with the controlling
1261 program or device. This option is meant to be set by programs which
1262 communicate with @value{GDBN} using it as a back end.
1263 @xref{Interpreters, , Command Interpreters}.
1265 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1266 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1267 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1268 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1269 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1270 @sc{gdb/mi} interfaces are no longer supported.
1273 @cindex @code{--write}
1274 Open the executable and core files for both reading and writing. This
1275 is equivalent to the @samp{set write on} command inside @value{GDBN}
1279 @cindex @code{--statistics}
1280 This option causes @value{GDBN} to print statistics about time and
1281 memory usage after it completes each command and returns to the prompt.
1284 @cindex @code{--version}
1285 This option causes @value{GDBN} to print its version number and
1286 no-warranty blurb, and exit.
1288 @item -configuration
1289 @cindex @code{--configuration}
1290 This option causes @value{GDBN} to print details about its build-time
1291 configuration parameters, and then exit. These details can be
1292 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1297 @subsection What @value{GDBN} Does During Startup
1298 @cindex @value{GDBN} startup
1300 Here's the description of what @value{GDBN} does during session startup:
1304 Sets up the command interpreter as specified by the command line
1305 (@pxref{Mode Options, interpreter}).
1309 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1310 used when building @value{GDBN}; @pxref{System-wide configuration,
1311 ,System-wide configuration and settings}) and executes all the commands in
1314 @anchor{Home Directory Init File}
1316 Reads the init file (if any) in your home directory@footnote{On
1317 DOS/Windows systems, the home directory is the one pointed to by the
1318 @code{HOME} environment variable.} and executes all the commands in
1321 @anchor{Option -init-eval-command}
1323 Executes commands and command files specified by the @samp{-iex} and
1324 @samp{-ix} options in their specified order. Usually you should use the
1325 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1326 settings before @value{GDBN} init files get executed and before inferior
1330 Processes command line options and operands.
1332 @anchor{Init File in the Current Directory during Startup}
1334 Reads and executes the commands from init file (if any) in the current
1335 working directory as long as @samp{set auto-load local-gdbinit} is set to
1336 @samp{on} (@pxref{Init File in the Current Directory}).
1337 This is only done if the current directory is
1338 different from your home directory. Thus, you can have more than one
1339 init file, one generic in your home directory, and another, specific
1340 to the program you are debugging, in the directory where you invoke
1344 If the command line specified a program to debug, or a process to
1345 attach to, or a core file, @value{GDBN} loads any auto-loaded
1346 scripts provided for the program or for its loaded shared libraries.
1347 @xref{Auto-loading}.
1349 If you wish to disable the auto-loading during startup,
1350 you must do something like the following:
1353 $ gdb -iex "set auto-load python-scripts off" myprogram
1356 Option @samp{-ex} does not work because the auto-loading is then turned
1360 Executes commands and command files specified by the @samp{-ex} and
1361 @samp{-x} options in their specified order. @xref{Command Files}, for
1362 more details about @value{GDBN} command files.
1365 Reads the command history recorded in the @dfn{history file}.
1366 @xref{Command History}, for more details about the command history and the
1367 files where @value{GDBN} records it.
1370 Init files use the same syntax as @dfn{command files} (@pxref{Command
1371 Files}) and are processed by @value{GDBN} in the same way. The init
1372 file in your home directory can set options (such as @samp{set
1373 complaints}) that affect subsequent processing of command line options
1374 and operands. Init files are not executed if you use the @samp{-nx}
1375 option (@pxref{Mode Options, ,Choosing Modes}).
1377 To display the list of init files loaded by gdb at startup, you
1378 can use @kbd{gdb --help}.
1380 @cindex init file name
1381 @cindex @file{.gdbinit}
1382 @cindex @file{gdb.ini}
1383 The @value{GDBN} init files are normally called @file{.gdbinit}.
1384 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1385 the limitations of file names imposed by DOS filesystems. The Windows
1386 port of @value{GDBN} uses the standard name, but if it finds a
1387 @file{gdb.ini} file in your home directory, it warns you about that
1388 and suggests to rename the file to the standard name.
1392 @section Quitting @value{GDBN}
1393 @cindex exiting @value{GDBN}
1394 @cindex leaving @value{GDBN}
1397 @kindex quit @r{[}@var{expression}@r{]}
1398 @kindex q @r{(@code{quit})}
1399 @item quit @r{[}@var{expression}@r{]}
1401 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1402 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1403 do not supply @var{expression}, @value{GDBN} will terminate normally;
1404 otherwise it will terminate using the result of @var{expression} as the
1409 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1410 terminates the action of any @value{GDBN} command that is in progress and
1411 returns to @value{GDBN} command level. It is safe to type the interrupt
1412 character at any time because @value{GDBN} does not allow it to take effect
1413 until a time when it is safe.
1415 If you have been using @value{GDBN} to control an attached process or
1416 device, you can release it with the @code{detach} command
1417 (@pxref{Attach, ,Debugging an Already-running Process}).
1419 @node Shell Commands
1420 @section Shell Commands
1422 If you need to execute occasional shell commands during your
1423 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1424 just use the @code{shell} command.
1429 @cindex shell escape
1430 @item shell @var{command-string}
1431 @itemx !@var{command-string}
1432 Invoke a standard shell to execute @var{command-string}.
1433 Note that no space is needed between @code{!} and @var{command-string}.
1434 If it exists, the environment variable @code{SHELL} determines which
1435 shell to run. Otherwise @value{GDBN} uses the default shell
1436 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1439 The utility @code{make} is often needed in development environments.
1440 You do not have to use the @code{shell} command for this purpose in
1445 @cindex calling make
1446 @item make @var{make-args}
1447 Execute the @code{make} program with the specified
1448 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1451 @node Logging Output
1452 @section Logging Output
1453 @cindex logging @value{GDBN} output
1454 @cindex save @value{GDBN} output to a file
1456 You may want to save the output of @value{GDBN} commands to a file.
1457 There are several commands to control @value{GDBN}'s logging.
1461 @item set logging on
1463 @item set logging off
1465 @cindex logging file name
1466 @item set logging file @var{file}
1467 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1468 @item set logging overwrite [on|off]
1469 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1470 you want @code{set logging on} to overwrite the logfile instead.
1471 @item set logging redirect [on|off]
1472 By default, @value{GDBN} output will go to both the terminal and the logfile.
1473 Set @code{redirect} if you want output to go only to the log file.
1474 @kindex show logging
1476 Show the current values of the logging settings.
1480 @chapter @value{GDBN} Commands
1482 You can abbreviate a @value{GDBN} command to the first few letters of the command
1483 name, if that abbreviation is unambiguous; and you can repeat certain
1484 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1485 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1486 show you the alternatives available, if there is more than one possibility).
1489 * Command Syntax:: How to give commands to @value{GDBN}
1490 * Completion:: Command completion
1491 * Help:: How to ask @value{GDBN} for help
1494 @node Command Syntax
1495 @section Command Syntax
1497 A @value{GDBN} command is a single line of input. There is no limit on
1498 how long it can be. It starts with a command name, which is followed by
1499 arguments whose meaning depends on the command name. For example, the
1500 command @code{step} accepts an argument which is the number of times to
1501 step, as in @samp{step 5}. You can also use the @code{step} command
1502 with no arguments. Some commands do not allow any arguments.
1504 @cindex abbreviation
1505 @value{GDBN} command names may always be truncated if that abbreviation is
1506 unambiguous. Other possible command abbreviations are listed in the
1507 documentation for individual commands. In some cases, even ambiguous
1508 abbreviations are allowed; for example, @code{s} is specially defined as
1509 equivalent to @code{step} even though there are other commands whose
1510 names start with @code{s}. You can test abbreviations by using them as
1511 arguments to the @code{help} command.
1513 @cindex repeating commands
1514 @kindex RET @r{(repeat last command)}
1515 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1516 repeat the previous command. Certain commands (for example, @code{run})
1517 will not repeat this way; these are commands whose unintentional
1518 repetition might cause trouble and which you are unlikely to want to
1519 repeat. User-defined commands can disable this feature; see
1520 @ref{Define, dont-repeat}.
1522 The @code{list} and @code{x} commands, when you repeat them with
1523 @key{RET}, construct new arguments rather than repeating
1524 exactly as typed. This permits easy scanning of source or memory.
1526 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1527 output, in a way similar to the common utility @code{more}
1528 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1529 @key{RET} too many in this situation, @value{GDBN} disables command
1530 repetition after any command that generates this sort of display.
1532 @kindex # @r{(a comment)}
1534 Any text from a @kbd{#} to the end of the line is a comment; it does
1535 nothing. This is useful mainly in command files (@pxref{Command
1536 Files,,Command Files}).
1538 @cindex repeating command sequences
1539 @kindex Ctrl-o @r{(operate-and-get-next)}
1540 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1541 commands. This command accepts the current line, like @key{RET}, and
1542 then fetches the next line relative to the current line from the history
1546 @section Command Completion
1549 @cindex word completion
1550 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1551 only one possibility; it can also show you what the valid possibilities
1552 are for the next word in a command, at any time. This works for @value{GDBN}
1553 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1555 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1556 of a word. If there is only one possibility, @value{GDBN} fills in the
1557 word, and waits for you to finish the command (or press @key{RET} to
1558 enter it). For example, if you type
1560 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1561 @c complete accuracy in these examples; space introduced for clarity.
1562 @c If texinfo enhancements make it unnecessary, it would be nice to
1563 @c replace " @key" by "@key" in the following...
1565 (@value{GDBP}) info bre @key{TAB}
1569 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1570 the only @code{info} subcommand beginning with @samp{bre}:
1573 (@value{GDBP}) info breakpoints
1577 You can either press @key{RET} at this point, to run the @code{info
1578 breakpoints} command, or backspace and enter something else, if
1579 @samp{breakpoints} does not look like the command you expected. (If you
1580 were sure you wanted @code{info breakpoints} in the first place, you
1581 might as well just type @key{RET} immediately after @samp{info bre},
1582 to exploit command abbreviations rather than command completion).
1584 If there is more than one possibility for the next word when you press
1585 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1586 characters and try again, or just press @key{TAB} a second time;
1587 @value{GDBN} displays all the possible completions for that word. For
1588 example, you might want to set a breakpoint on a subroutine whose name
1589 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1590 just sounds the bell. Typing @key{TAB} again displays all the
1591 function names in your program that begin with those characters, for
1595 (@value{GDBP}) b make_ @key{TAB}
1596 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1597 make_a_section_from_file make_environ
1598 make_abs_section make_function_type
1599 make_blockvector make_pointer_type
1600 make_cleanup make_reference_type
1601 make_command make_symbol_completion_list
1602 (@value{GDBP}) b make_
1606 After displaying the available possibilities, @value{GDBN} copies your
1607 partial input (@samp{b make_} in the example) so you can finish the
1610 If you just want to see the list of alternatives in the first place, you
1611 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1612 means @kbd{@key{META} ?}. You can type this either by holding down a
1613 key designated as the @key{META} shift on your keyboard (if there is
1614 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1616 If the number of possible completions is large, @value{GDBN} will
1617 print as much of the list as it has collected, as well as a message
1618 indicating that the list may be truncated.
1621 (@value{GDBP}) b m@key{TAB}@key{TAB}
1623 <... the rest of the possible completions ...>
1624 *** List may be truncated, max-completions reached. ***
1629 This behavior can be controlled with the following commands:
1632 @kindex set max-completions
1633 @item set max-completions @var{limit}
1634 @itemx set max-completions unlimited
1635 Set the maximum number of completion candidates. @value{GDBN} will
1636 stop looking for more completions once it collects this many candidates.
1637 This is useful when completing on things like function names as collecting
1638 all the possible candidates can be time consuming.
1639 The default value is 200. A value of zero disables tab-completion.
1640 Note that setting either no limit or a very large limit can make
1642 @kindex show max-completions
1643 @item show max-completions
1644 Show the maximum number of candidates that @value{GDBN} will collect and show
1648 @cindex quotes in commands
1649 @cindex completion of quoted strings
1650 Sometimes the string you need, while logically a ``word'', may contain
1651 parentheses or other characters that @value{GDBN} normally excludes from
1652 its notion of a word. To permit word completion to work in this
1653 situation, you may enclose words in @code{'} (single quote marks) in
1654 @value{GDBN} commands.
1656 A likely situation where you might need this is in typing an
1657 expression that involves a C@t{++} symbol name with template
1658 parameters. This is because when completing expressions, GDB treats
1659 the @samp{<} character as word delimiter, assuming that it's the
1660 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1663 For example, when you want to call a C@t{++} template function
1664 interactively using the @code{print} or @code{call} commands, you may
1665 need to distinguish whether you mean the version of @code{name} that
1666 was specialized for @code{int}, @code{name<int>()}, or the version
1667 that was specialized for @code{float}, @code{name<float>()}. To use
1668 the word-completion facilities in this situation, type a single quote
1669 @code{'} at the beginning of the function name. This alerts
1670 @value{GDBN} that it may need to consider more information than usual
1671 when you press @key{TAB} or @kbd{M-?} to request word completion:
1674 (@value{GDBP}) p 'func< @kbd{M-?}
1675 func<int>() func<float>()
1676 (@value{GDBP}) p 'func<
1679 When setting breakpoints however (@pxref{Specify Location}), you don't
1680 usually need to type a quote before the function name, because
1681 @value{GDBN} understands that you want to set a breakpoint on a
1685 (@value{GDBP}) b func< @kbd{M-?}
1686 func<int>() func<float>()
1687 (@value{GDBP}) b func<
1690 This is true even in the case of typing the name of C@t{++} overloaded
1691 functions (multiple definitions of the same function, distinguished by
1692 argument type). For example, when you want to set a breakpoint you
1693 don't need to distinguish whether you mean the version of @code{name}
1694 that takes an @code{int} parameter, @code{name(int)}, or the version
1695 that takes a @code{float} parameter, @code{name(float)}.
1698 (@value{GDBP}) b bubble( @kbd{M-?}
1699 bubble(int) bubble(double)
1700 (@value{GDBP}) b bubble(dou @kbd{M-?}
1704 See @ref{quoting names} for a description of other scenarios that
1707 For more information about overloaded functions, see @ref{C Plus Plus
1708 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1709 overload-resolution off} to disable overload resolution;
1710 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1712 @cindex completion of structure field names
1713 @cindex structure field name completion
1714 @cindex completion of union field names
1715 @cindex union field name completion
1716 When completing in an expression which looks up a field in a
1717 structure, @value{GDBN} also tries@footnote{The completer can be
1718 confused by certain kinds of invalid expressions. Also, it only
1719 examines the static type of the expression, not the dynamic type.} to
1720 limit completions to the field names available in the type of the
1724 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1725 magic to_fputs to_rewind
1726 to_data to_isatty to_write
1727 to_delete to_put to_write_async_safe
1732 This is because the @code{gdb_stdout} is a variable of the type
1733 @code{struct ui_file} that is defined in @value{GDBN} sources as
1740 ui_file_flush_ftype *to_flush;
1741 ui_file_write_ftype *to_write;
1742 ui_file_write_async_safe_ftype *to_write_async_safe;
1743 ui_file_fputs_ftype *to_fputs;
1744 ui_file_read_ftype *to_read;
1745 ui_file_delete_ftype *to_delete;
1746 ui_file_isatty_ftype *to_isatty;
1747 ui_file_rewind_ftype *to_rewind;
1748 ui_file_put_ftype *to_put;
1755 @section Getting Help
1756 @cindex online documentation
1759 You can always ask @value{GDBN} itself for information on its commands,
1760 using the command @code{help}.
1763 @kindex h @r{(@code{help})}
1766 You can use @code{help} (abbreviated @code{h}) with no arguments to
1767 display a short list of named classes of commands:
1771 List of classes of commands:
1773 aliases -- Aliases of other commands
1774 breakpoints -- Making program stop at certain points
1775 data -- Examining data
1776 files -- Specifying and examining files
1777 internals -- Maintenance commands
1778 obscure -- Obscure features
1779 running -- Running the program
1780 stack -- Examining the stack
1781 status -- Status inquiries
1782 support -- Support facilities
1783 tracepoints -- Tracing of program execution without
1784 stopping the program
1785 user-defined -- User-defined commands
1787 Type "help" followed by a class name for a list of
1788 commands in that class.
1789 Type "help" followed by command name for full
1791 Command name abbreviations are allowed if unambiguous.
1794 @c the above line break eliminates huge line overfull...
1796 @item help @var{class}
1797 Using one of the general help classes as an argument, you can get a
1798 list of the individual commands in that class. For example, here is the
1799 help display for the class @code{status}:
1802 (@value{GDBP}) help status
1807 @c Line break in "show" line falsifies real output, but needed
1808 @c to fit in smallbook page size.
1809 info -- Generic command for showing things
1810 about the program being debugged
1811 show -- Generic command for showing things
1814 Type "help" followed by command name for full
1816 Command name abbreviations are allowed if unambiguous.
1820 @item help @var{command}
1821 With a command name as @code{help} argument, @value{GDBN} displays a
1822 short paragraph on how to use that command.
1825 @item apropos @var{args}
1826 The @code{apropos} command searches through all of the @value{GDBN}
1827 commands, and their documentation, for the regular expression specified in
1828 @var{args}. It prints out all matches found. For example:
1839 alias -- Define a new command that is an alias of an existing command
1840 aliases -- Aliases of other commands
1841 d -- Delete some breakpoints or auto-display expressions
1842 del -- Delete some breakpoints or auto-display expressions
1843 delete -- Delete some breakpoints or auto-display expressions
1848 @item complete @var{args}
1849 The @code{complete @var{args}} command lists all the possible completions
1850 for the beginning of a command. Use @var{args} to specify the beginning of the
1851 command you want completed. For example:
1857 @noindent results in:
1868 @noindent This is intended for use by @sc{gnu} Emacs.
1871 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1872 and @code{show} to inquire about the state of your program, or the state
1873 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1874 manual introduces each of them in the appropriate context. The listings
1875 under @code{info} and under @code{show} in the Command, Variable, and
1876 Function Index point to all the sub-commands. @xref{Command and Variable
1882 @kindex i @r{(@code{info})}
1884 This command (abbreviated @code{i}) is for describing the state of your
1885 program. For example, you can show the arguments passed to a function
1886 with @code{info args}, list the registers currently in use with @code{info
1887 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1888 You can get a complete list of the @code{info} sub-commands with
1889 @w{@code{help info}}.
1893 You can assign the result of an expression to an environment variable with
1894 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1895 @code{set prompt $}.
1899 In contrast to @code{info}, @code{show} is for describing the state of
1900 @value{GDBN} itself.
1901 You can change most of the things you can @code{show}, by using the
1902 related command @code{set}; for example, you can control what number
1903 system is used for displays with @code{set radix}, or simply inquire
1904 which is currently in use with @code{show radix}.
1907 To display all the settable parameters and their current
1908 values, you can use @code{show} with no arguments; you may also use
1909 @code{info set}. Both commands produce the same display.
1910 @c FIXME: "info set" violates the rule that "info" is for state of
1911 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1912 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1916 Here are several miscellaneous @code{show} subcommands, all of which are
1917 exceptional in lacking corresponding @code{set} commands:
1920 @kindex show version
1921 @cindex @value{GDBN} version number
1923 Show what version of @value{GDBN} is running. You should include this
1924 information in @value{GDBN} bug-reports. If multiple versions of
1925 @value{GDBN} are in use at your site, you may need to determine which
1926 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1927 commands are introduced, and old ones may wither away. Also, many
1928 system vendors ship variant versions of @value{GDBN}, and there are
1929 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1930 The version number is the same as the one announced when you start
1933 @kindex show copying
1934 @kindex info copying
1935 @cindex display @value{GDBN} copyright
1938 Display information about permission for copying @value{GDBN}.
1940 @kindex show warranty
1941 @kindex info warranty
1943 @itemx info warranty
1944 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1945 if your version of @value{GDBN} comes with one.
1947 @kindex show configuration
1948 @item show configuration
1949 Display detailed information about the way @value{GDBN} was configured
1950 when it was built. This displays the optional arguments passed to the
1951 @file{configure} script and also configuration parameters detected
1952 automatically by @command{configure}. When reporting a @value{GDBN}
1953 bug (@pxref{GDB Bugs}), it is important to include this information in
1959 @chapter Running Programs Under @value{GDBN}
1961 When you run a program under @value{GDBN}, you must first generate
1962 debugging information when you compile it.
1964 You may start @value{GDBN} with its arguments, if any, in an environment
1965 of your choice. If you are doing native debugging, you may redirect
1966 your program's input and output, debug an already running process, or
1967 kill a child process.
1970 * Compilation:: Compiling for debugging
1971 * Starting:: Starting your program
1972 * Arguments:: Your program's arguments
1973 * Environment:: Your program's environment
1975 * Working Directory:: Your program's working directory
1976 * Input/Output:: Your program's input and output
1977 * Attach:: Debugging an already-running process
1978 * Kill Process:: Killing the child process
1980 * Inferiors and Programs:: Debugging multiple inferiors and programs
1981 * Threads:: Debugging programs with multiple threads
1982 * Forks:: Debugging forks
1983 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1987 @section Compiling for Debugging
1989 In order to debug a program effectively, you need to generate
1990 debugging information when you compile it. This debugging information
1991 is stored in the object file; it describes the data type of each
1992 variable or function and the correspondence between source line numbers
1993 and addresses in the executable code.
1995 To request debugging information, specify the @samp{-g} option when you run
1998 Programs that are to be shipped to your customers are compiled with
1999 optimizations, using the @samp{-O} compiler option. However, some
2000 compilers are unable to handle the @samp{-g} and @samp{-O} options
2001 together. Using those compilers, you cannot generate optimized
2002 executables containing debugging information.
2004 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2005 without @samp{-O}, making it possible to debug optimized code. We
2006 recommend that you @emph{always} use @samp{-g} whenever you compile a
2007 program. You may think your program is correct, but there is no sense
2008 in pushing your luck. For more information, see @ref{Optimized Code}.
2010 Older versions of the @sc{gnu} C compiler permitted a variant option
2011 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2012 format; if your @sc{gnu} C compiler has this option, do not use it.
2014 @value{GDBN} knows about preprocessor macros and can show you their
2015 expansion (@pxref{Macros}). Most compilers do not include information
2016 about preprocessor macros in the debugging information if you specify
2017 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2018 the @sc{gnu} C compiler, provides macro information if you are using
2019 the DWARF debugging format, and specify the option @option{-g3}.
2021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2023 information on @value{NGCC} options affecting debug information.
2025 You will have the best debugging experience if you use the latest
2026 version of the DWARF debugging format that your compiler supports.
2027 DWARF is currently the most expressive and best supported debugging
2028 format in @value{GDBN}.
2032 @section Starting your Program
2038 @kindex r @r{(@code{run})}
2041 Use the @code{run} command to start your program under @value{GDBN}.
2042 You must first specify the program name with an argument to
2043 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2044 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2045 command (@pxref{Files, ,Commands to Specify Files}).
2049 If you are running your program in an execution environment that
2050 supports processes, @code{run} creates an inferior process and makes
2051 that process run your program. In some environments without processes,
2052 @code{run} jumps to the start of your program. Other targets,
2053 like @samp{remote}, are always running. If you get an error
2054 message like this one:
2057 The "remote" target does not support "run".
2058 Try "help target" or "continue".
2062 then use @code{continue} to run your program. You may need @code{load}
2063 first (@pxref{load}).
2065 The execution of a program is affected by certain information it
2066 receives from its superior. @value{GDBN} provides ways to specify this
2067 information, which you must do @emph{before} starting your program. (You
2068 can change it after starting your program, but such changes only affect
2069 your program the next time you start it.) This information may be
2070 divided into four categories:
2073 @item The @emph{arguments.}
2074 Specify the arguments to give your program as the arguments of the
2075 @code{run} command. If a shell is available on your target, the shell
2076 is used to pass the arguments, so that you may use normal conventions
2077 (such as wildcard expansion or variable substitution) in describing
2079 In Unix systems, you can control which shell is used with the
2080 @code{SHELL} environment variable. If you do not define @code{SHELL},
2081 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2082 use of any shell with the @code{set startup-with-shell} command (see
2085 @item The @emph{environment.}
2086 Your program normally inherits its environment from @value{GDBN}, but you can
2087 use the @value{GDBN} commands @code{set environment} and @code{unset
2088 environment} to change parts of the environment that affect
2089 your program. @xref{Environment, ,Your Program's Environment}.
2091 @item The @emph{working directory.}
2092 You can set your program's working directory with the command
2093 @kbd{set cwd}. If you do not set any working directory with this
2094 command, your program will inherit @value{GDBN}'s working directory if
2095 native debugging, or the remote server's working directory if remote
2096 debugging. @xref{Working Directory, ,Your Program's Working
2099 @item The @emph{standard input and output.}
2100 Your program normally uses the same device for standard input and
2101 standard output as @value{GDBN} is using. You can redirect input and output
2102 in the @code{run} command line, or you can use the @code{tty} command to
2103 set a different device for your program.
2104 @xref{Input/Output, ,Your Program's Input and Output}.
2107 @emph{Warning:} While input and output redirection work, you cannot use
2108 pipes to pass the output of the program you are debugging to another
2109 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2113 When you issue the @code{run} command, your program begins to execute
2114 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2115 of how to arrange for your program to stop. Once your program has
2116 stopped, you may call functions in your program, using the @code{print}
2117 or @code{call} commands. @xref{Data, ,Examining Data}.
2119 If the modification time of your symbol file has changed since the last
2120 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2121 table, and reads it again. When it does this, @value{GDBN} tries to retain
2122 your current breakpoints.
2127 @cindex run to main procedure
2128 The name of the main procedure can vary from language to language.
2129 With C or C@t{++}, the main procedure name is always @code{main}, but
2130 other languages such as Ada do not require a specific name for their
2131 main procedure. The debugger provides a convenient way to start the
2132 execution of the program and to stop at the beginning of the main
2133 procedure, depending on the language used.
2135 The @samp{start} command does the equivalent of setting a temporary
2136 breakpoint at the beginning of the main procedure and then invoking
2137 the @samp{run} command.
2139 @cindex elaboration phase
2140 Some programs contain an @dfn{elaboration} phase where some startup code is
2141 executed before the main procedure is called. This depends on the
2142 languages used to write your program. In C@t{++}, for instance,
2143 constructors for static and global objects are executed before
2144 @code{main} is called. It is therefore possible that the debugger stops
2145 before reaching the main procedure. However, the temporary breakpoint
2146 will remain to halt execution.
2148 Specify the arguments to give to your program as arguments to the
2149 @samp{start} command. These arguments will be given verbatim to the
2150 underlying @samp{run} command. Note that the same arguments will be
2151 reused if no argument is provided during subsequent calls to
2152 @samp{start} or @samp{run}.
2154 It is sometimes necessary to debug the program during elaboration. In
2155 these cases, using the @code{start} command would stop the execution
2156 of your program too late, as the program would have already completed
2157 the elaboration phase. Under these circumstances, either insert
2158 breakpoints in your elaboration code before running your program or
2159 use the @code{starti} command.
2163 @cindex run to first instruction
2164 The @samp{starti} command does the equivalent of setting a temporary
2165 breakpoint at the first instruction of a program's execution and then
2166 invoking the @samp{run} command. For programs containing an
2167 elaboration phase, the @code{starti} command will stop execution at
2168 the start of the elaboration phase.
2170 @anchor{set exec-wrapper}
2171 @kindex set exec-wrapper
2172 @item set exec-wrapper @var{wrapper}
2173 @itemx show exec-wrapper
2174 @itemx unset exec-wrapper
2175 When @samp{exec-wrapper} is set, the specified wrapper is used to
2176 launch programs for debugging. @value{GDBN} starts your program
2177 with a shell command of the form @kbd{exec @var{wrapper}
2178 @var{program}}. Quoting is added to @var{program} and its
2179 arguments, but not to @var{wrapper}, so you should add quotes if
2180 appropriate for your shell. The wrapper runs until it executes
2181 your program, and then @value{GDBN} takes control.
2183 You can use any program that eventually calls @code{execve} with
2184 its arguments as a wrapper. Several standard Unix utilities do
2185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2186 with @code{exec "$@@"} will also work.
2188 For example, you can use @code{env} to pass an environment variable to
2189 the debugged program, without setting the variable in your shell's
2193 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2197 This command is available when debugging locally on most targets, excluding
2198 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2200 @kindex set startup-with-shell
2201 @anchor{set startup-with-shell}
2202 @item set startup-with-shell
2203 @itemx set startup-with-shell on
2204 @itemx set startup-with-shell off
2205 @itemx show startup-with-shell
2206 On Unix systems, by default, if a shell is available on your target,
2207 @value{GDBN}) uses it to start your program. Arguments of the
2208 @code{run} command are passed to the shell, which does variable
2209 substitution, expands wildcard characters and performs redirection of
2210 I/O. In some circumstances, it may be useful to disable such use of a
2211 shell, for example, when debugging the shell itself or diagnosing
2212 startup failures such as:
2216 Starting program: ./a.out
2217 During startup program terminated with signal SIGSEGV, Segmentation fault.
2221 which indicates the shell or the wrapper specified with
2222 @samp{exec-wrapper} crashed, not your program. Most often, this is
2223 caused by something odd in your shell's non-interactive mode
2224 initialization file---such as @file{.cshrc} for C-shell,
2225 $@file{.zshenv} for the Z shell, or the file specified in the
2226 @samp{BASH_ENV} environment variable for BASH.
2228 @anchor{set auto-connect-native-target}
2229 @kindex set auto-connect-native-target
2230 @item set auto-connect-native-target
2231 @itemx set auto-connect-native-target on
2232 @itemx set auto-connect-native-target off
2233 @itemx show auto-connect-native-target
2235 By default, if not connected to any target yet (e.g., with
2236 @code{target remote}), the @code{run} command starts your program as a
2237 native process under @value{GDBN}, on your local machine. If you're
2238 sure you don't want to debug programs on your local machine, you can
2239 tell @value{GDBN} to not connect to the native target automatically
2240 with the @code{set auto-connect-native-target off} command.
2242 If @code{on}, which is the default, and if @value{GDBN} is not
2243 connected to a target already, the @code{run} command automaticaly
2244 connects to the native target, if one is available.
2246 If @code{off}, and if @value{GDBN} is not connected to a target
2247 already, the @code{run} command fails with an error:
2251 Don't know how to run. Try "help target".
2254 If @value{GDBN} is already connected to a target, @value{GDBN} always
2255 uses it with the @code{run} command.
2257 In any case, you can explicitly connect to the native target with the
2258 @code{target native} command. For example,
2261 (@value{GDBP}) set auto-connect-native-target off
2263 Don't know how to run. Try "help target".
2264 (@value{GDBP}) target native
2266 Starting program: ./a.out
2267 [Inferior 1 (process 10421) exited normally]
2270 In case you connected explicitly to the @code{native} target,
2271 @value{GDBN} remains connected even if all inferiors exit, ready for
2272 the next @code{run} command. Use the @code{disconnect} command to
2275 Examples of other commands that likewise respect the
2276 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2277 proc}, @code{info os}.
2279 @kindex set disable-randomization
2280 @item set disable-randomization
2281 @itemx set disable-randomization on
2282 This option (enabled by default in @value{GDBN}) will turn off the native
2283 randomization of the virtual address space of the started program. This option
2284 is useful for multiple debugging sessions to make the execution better
2285 reproducible and memory addresses reusable across debugging sessions.
2287 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2288 On @sc{gnu}/Linux you can get the same behavior using
2291 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2294 @item set disable-randomization off
2295 Leave the behavior of the started executable unchanged. Some bugs rear their
2296 ugly heads only when the program is loaded at certain addresses. If your bug
2297 disappears when you run the program under @value{GDBN}, that might be because
2298 @value{GDBN} by default disables the address randomization on platforms, such
2299 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2300 disable-randomization off} to try to reproduce such elusive bugs.
2302 On targets where it is available, virtual address space randomization
2303 protects the programs against certain kinds of security attacks. In these
2304 cases the attacker needs to know the exact location of a concrete executable
2305 code. Randomizing its location makes it impossible to inject jumps misusing
2306 a code at its expected addresses.
2308 Prelinking shared libraries provides a startup performance advantage but it
2309 makes addresses in these libraries predictable for privileged processes by
2310 having just unprivileged access at the target system. Reading the shared
2311 library binary gives enough information for assembling the malicious code
2312 misusing it. Still even a prelinked shared library can get loaded at a new
2313 random address just requiring the regular relocation process during the
2314 startup. Shared libraries not already prelinked are always loaded at
2315 a randomly chosen address.
2317 Position independent executables (PIE) contain position independent code
2318 similar to the shared libraries and therefore such executables get loaded at
2319 a randomly chosen address upon startup. PIE executables always load even
2320 already prelinked shared libraries at a random address. You can build such
2321 executable using @command{gcc -fPIE -pie}.
2323 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2324 (as long as the randomization is enabled).
2326 @item show disable-randomization
2327 Show the current setting of the explicit disable of the native randomization of
2328 the virtual address space of the started program.
2333 @section Your Program's Arguments
2335 @cindex arguments (to your program)
2336 The arguments to your program can be specified by the arguments of the
2338 They are passed to a shell, which expands wildcard characters and
2339 performs redirection of I/O, and thence to your program. Your
2340 @code{SHELL} environment variable (if it exists) specifies what shell
2341 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2342 the default shell (@file{/bin/sh} on Unix).
2344 On non-Unix systems, the program is usually invoked directly by
2345 @value{GDBN}, which emulates I/O redirection via the appropriate system
2346 calls, and the wildcard characters are expanded by the startup code of
2347 the program, not by the shell.
2349 @code{run} with no arguments uses the same arguments used by the previous
2350 @code{run}, or those set by the @code{set args} command.
2355 Specify the arguments to be used the next time your program is run. If
2356 @code{set args} has no arguments, @code{run} executes your program
2357 with no arguments. Once you have run your program with arguments,
2358 using @code{set args} before the next @code{run} is the only way to run
2359 it again without arguments.
2363 Show the arguments to give your program when it is started.
2367 @section Your Program's Environment
2369 @cindex environment (of your program)
2370 The @dfn{environment} consists of a set of environment variables and
2371 their values. Environment variables conventionally record such things as
2372 your user name, your home directory, your terminal type, and your search
2373 path for programs to run. Usually you set up environment variables with
2374 the shell and they are inherited by all the other programs you run. When
2375 debugging, it can be useful to try running your program with a modified
2376 environment without having to start @value{GDBN} over again.
2380 @item path @var{directory}
2381 Add @var{directory} to the front of the @code{PATH} environment variable
2382 (the search path for executables) that will be passed to your program.
2383 The value of @code{PATH} used by @value{GDBN} does not change.
2384 You may specify several directory names, separated by whitespace or by a
2385 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2386 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2387 is moved to the front, so it is searched sooner.
2389 You can use the string @samp{$cwd} to refer to whatever is the current
2390 working directory at the time @value{GDBN} searches the path. If you
2391 use @samp{.} instead, it refers to the directory where you executed the
2392 @code{path} command. @value{GDBN} replaces @samp{.} in the
2393 @var{directory} argument (with the current path) before adding
2394 @var{directory} to the search path.
2395 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2396 @c document that, since repeating it would be a no-op.
2400 Display the list of search paths for executables (the @code{PATH}
2401 environment variable).
2403 @kindex show environment
2404 @item show environment @r{[}@var{varname}@r{]}
2405 Print the value of environment variable @var{varname} to be given to
2406 your program when it starts. If you do not supply @var{varname},
2407 print the names and values of all environment variables to be given to
2408 your program. You can abbreviate @code{environment} as @code{env}.
2410 @kindex set environment
2411 @anchor{set environment}
2412 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2413 Set environment variable @var{varname} to @var{value}. The value
2414 changes for your program (and the shell @value{GDBN} uses to launch
2415 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2416 values of environment variables are just strings, and any
2417 interpretation is supplied by your program itself. The @var{value}
2418 parameter is optional; if it is eliminated, the variable is set to a
2420 @c "any string" here does not include leading, trailing
2421 @c blanks. Gnu asks: does anyone care?
2423 For example, this command:
2430 tells the debugged program, when subsequently run, that its user is named
2431 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2432 are not actually required.)
2434 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2435 which also inherits the environment set with @code{set environment}.
2436 If necessary, you can avoid that by using the @samp{env} program as a
2437 wrapper instead of using @code{set environment}. @xref{set
2438 exec-wrapper}, for an example doing just that.
2440 Environment variables that are set by the user are also transmitted to
2441 @command{gdbserver} to be used when starting the remote inferior.
2442 @pxref{QEnvironmentHexEncoded}.
2444 @kindex unset environment
2445 @anchor{unset environment}
2446 @item unset environment @var{varname}
2447 Remove variable @var{varname} from the environment to be passed to your
2448 program. This is different from @samp{set env @var{varname} =};
2449 @code{unset environment} removes the variable from the environment,
2450 rather than assigning it an empty value.
2452 Environment variables that are unset by the user are also unset on
2453 @command{gdbserver} when starting the remote inferior.
2454 @pxref{QEnvironmentUnset}.
2457 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2458 the shell indicated by your @code{SHELL} environment variable if it
2459 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2460 names a shell that runs an initialization file when started
2461 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2462 for the Z shell, or the file specified in the @samp{BASH_ENV}
2463 environment variable for BASH---any variables you set in that file
2464 affect your program. You may wish to move setting of environment
2465 variables to files that are only run when you sign on, such as
2466 @file{.login} or @file{.profile}.
2468 @node Working Directory
2469 @section Your Program's Working Directory
2471 @cindex working directory (of your program)
2472 Each time you start your program with @code{run}, the inferior will be
2473 initialized with the current working directory specified by the
2474 @kbd{set cwd} command. If no directory has been specified by this
2475 command, then the inferior will inherit @value{GDBN}'s current working
2476 directory as its working directory if native debugging, or it will
2477 inherit the remote server's current working directory if remote
2482 @cindex change inferior's working directory
2483 @anchor{set cwd command}
2484 @item set cwd @r{[}@var{directory}@r{]}
2485 Set the inferior's working directory to @var{directory}, which will be
2486 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2487 argument has been specified, the command clears the setting and resets
2488 it to an empty state. This setting has no effect on @value{GDBN}'s
2489 working directory, and it only takes effect the next time you start
2490 the inferior. The @file{~} in @var{directory} is a short for the
2491 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2492 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2493 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2496 You can also change @value{GDBN}'s current working directory by using
2497 the @code{cd} command.
2501 @cindex show inferior's working directory
2503 Show the inferior's working directory. If no directory has been
2504 specified by @kbd{set cwd}, then the default inferior's working
2505 directory is the same as @value{GDBN}'s working directory.
2508 @cindex change @value{GDBN}'s working directory
2510 @item cd @r{[}@var{directory}@r{]}
2511 Set the @value{GDBN} working directory to @var{directory}. If not
2512 given, @var{directory} uses @file{'~'}.
2514 The @value{GDBN} working directory serves as a default for the
2515 commands that specify files for @value{GDBN} to operate on.
2516 @xref{Files, ,Commands to Specify Files}.
2517 @xref{set cwd command}.
2521 Print the @value{GDBN} working directory.
2524 It is generally impossible to find the current working directory of
2525 the process being debugged (since a program can change its directory
2526 during its run). If you work on a system where @value{GDBN} supports
2527 the @code{info proc} command (@pxref{Process Information}), you can
2528 use the @code{info proc} command to find out the
2529 current working directory of the debuggee.
2532 @section Your Program's Input and Output
2537 By default, the program you run under @value{GDBN} does input and output to
2538 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2539 to its own terminal modes to interact with you, but it records the terminal
2540 modes your program was using and switches back to them when you continue
2541 running your program.
2544 @kindex info terminal
2546 Displays information recorded by @value{GDBN} about the terminal modes your
2550 You can redirect your program's input and/or output using shell
2551 redirection with the @code{run} command. For example,
2558 starts your program, diverting its output to the file @file{outfile}.
2561 @cindex controlling terminal
2562 Another way to specify where your program should do input and output is
2563 with the @code{tty} command. This command accepts a file name as
2564 argument, and causes this file to be the default for future @code{run}
2565 commands. It also resets the controlling terminal for the child
2566 process, for future @code{run} commands. For example,
2573 directs that processes started with subsequent @code{run} commands
2574 default to do input and output on the terminal @file{/dev/ttyb} and have
2575 that as their controlling terminal.
2577 An explicit redirection in @code{run} overrides the @code{tty} command's
2578 effect on the input/output device, but not its effect on the controlling
2581 When you use the @code{tty} command or redirect input in the @code{run}
2582 command, only the input @emph{for your program} is affected. The input
2583 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2584 for @code{set inferior-tty}.
2586 @cindex inferior tty
2587 @cindex set inferior controlling terminal
2588 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2589 display the name of the terminal that will be used for future runs of your
2593 @item set inferior-tty [ @var{tty} ]
2594 @kindex set inferior-tty
2595 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2596 restores the default behavior, which is to use the same terminal as
2599 @item show inferior-tty
2600 @kindex show inferior-tty
2601 Show the current tty for the program being debugged.
2605 @section Debugging an Already-running Process
2610 @item attach @var{process-id}
2611 This command attaches to a running process---one that was started
2612 outside @value{GDBN}. (@code{info files} shows your active
2613 targets.) The command takes as argument a process ID. The usual way to
2614 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2615 or with the @samp{jobs -l} shell command.
2617 @code{attach} does not repeat if you press @key{RET} a second time after
2618 executing the command.
2621 To use @code{attach}, your program must be running in an environment
2622 which supports processes; for example, @code{attach} does not work for
2623 programs on bare-board targets that lack an operating system. You must
2624 also have permission to send the process a signal.
2626 When you use @code{attach}, the debugger finds the program running in
2627 the process first by looking in the current working directory, then (if
2628 the program is not found) by using the source file search path
2629 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2630 the @code{file} command to load the program. @xref{Files, ,Commands to
2633 The first thing @value{GDBN} does after arranging to debug the specified
2634 process is to stop it. You can examine and modify an attached process
2635 with all the @value{GDBN} commands that are ordinarily available when
2636 you start processes with @code{run}. You can insert breakpoints; you
2637 can step and continue; you can modify storage. If you would rather the
2638 process continue running, you may use the @code{continue} command after
2639 attaching @value{GDBN} to the process.
2644 When you have finished debugging the attached process, you can use the
2645 @code{detach} command to release it from @value{GDBN} control. Detaching
2646 the process continues its execution. After the @code{detach} command,
2647 that process and @value{GDBN} become completely independent once more, and you
2648 are ready to @code{attach} another process or start one with @code{run}.
2649 @code{detach} does not repeat if you press @key{RET} again after
2650 executing the command.
2653 If you exit @value{GDBN} while you have an attached process, you detach
2654 that process. If you use the @code{run} command, you kill that process.
2655 By default, @value{GDBN} asks for confirmation if you try to do either of these
2656 things; you can control whether or not you need to confirm by using the
2657 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2661 @section Killing the Child Process
2666 Kill the child process in which your program is running under @value{GDBN}.
2669 This command is useful if you wish to debug a core dump instead of a
2670 running process. @value{GDBN} ignores any core dump file while your program
2673 On some operating systems, a program cannot be executed outside @value{GDBN}
2674 while you have breakpoints set on it inside @value{GDBN}. You can use the
2675 @code{kill} command in this situation to permit running your program
2676 outside the debugger.
2678 The @code{kill} command is also useful if you wish to recompile and
2679 relink your program, since on many systems it is impossible to modify an
2680 executable file while it is running in a process. In this case, when you
2681 next type @code{run}, @value{GDBN} notices that the file has changed, and
2682 reads the symbol table again (while trying to preserve your current
2683 breakpoint settings).
2685 @node Inferiors and Programs
2686 @section Debugging Multiple Inferiors and Programs
2688 @value{GDBN} lets you run and debug multiple programs in a single
2689 session. In addition, @value{GDBN} on some systems may let you run
2690 several programs simultaneously (otherwise you have to exit from one
2691 before starting another). In the most general case, you can have
2692 multiple threads of execution in each of multiple processes, launched
2693 from multiple executables.
2696 @value{GDBN} represents the state of each program execution with an
2697 object called an @dfn{inferior}. An inferior typically corresponds to
2698 a process, but is more general and applies also to targets that do not
2699 have processes. Inferiors may be created before a process runs, and
2700 may be retained after a process exits. Inferiors have unique
2701 identifiers that are different from process ids. Usually each
2702 inferior will also have its own distinct address space, although some
2703 embedded targets may have several inferiors running in different parts
2704 of a single address space. Each inferior may in turn have multiple
2705 threads running in it.
2707 To find out what inferiors exist at any moment, use @w{@code{info
2711 @kindex info inferiors [ @var{id}@dots{} ]
2712 @item info inferiors
2713 Print a list of all inferiors currently being managed by @value{GDBN}.
2714 By default all inferiors are printed, but the argument @var{id}@dots{}
2715 -- a space separated list of inferior numbers -- can be used to limit
2716 the display to just the requested inferiors.
2718 @value{GDBN} displays for each inferior (in this order):
2722 the inferior number assigned by @value{GDBN}
2725 the target system's inferior identifier
2728 the name of the executable the inferior is running.
2733 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2734 indicates the current inferior.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info inferiors
2742 Num Description Executable
2743 2 process 2307 hello
2744 * 1 process 3401 goodbye
2747 To switch focus between inferiors, use the @code{inferior} command:
2750 @kindex inferior @var{infno}
2751 @item inferior @var{infno}
2752 Make inferior number @var{infno} the current inferior. The argument
2753 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2754 in the first field of the @samp{info inferiors} display.
2757 @vindex $_inferior@r{, convenience variable}
2758 The debugger convenience variable @samp{$_inferior} contains the
2759 number of the current inferior. You may find this useful in writing
2760 breakpoint conditional expressions, command scripts, and so forth.
2761 @xref{Convenience Vars,, Convenience Variables}, for general
2762 information on convenience variables.
2764 You can get multiple executables into a debugging session via the
2765 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2766 systems @value{GDBN} can add inferiors to the debug session
2767 automatically by following calls to @code{fork} and @code{exec}. To
2768 remove inferiors from the debugging session use the
2769 @w{@code{remove-inferiors}} command.
2772 @kindex add-inferior
2773 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2774 Adds @var{n} inferiors to be run using @var{executable} as the
2775 executable; @var{n} defaults to 1. If no executable is specified,
2776 the inferiors begins empty, with no program. You can still assign or
2777 change the program assigned to the inferior at any time by using the
2778 @code{file} command with the executable name as its argument.
2780 @kindex clone-inferior
2781 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2782 Adds @var{n} inferiors ready to execute the same program as inferior
2783 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2784 number of the current inferior. This is a convenient command when you
2785 want to run another instance of the inferior you are debugging.
2788 (@value{GDBP}) info inferiors
2789 Num Description Executable
2790 * 1 process 29964 helloworld
2791 (@value{GDBP}) clone-inferior
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2797 * 1 process 29964 helloworld
2800 You can now simply switch focus to inferior 2 and run it.
2802 @kindex remove-inferiors
2803 @item remove-inferiors @var{infno}@dots{}
2804 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2805 possible to remove an inferior that is running with this command. For
2806 those, use the @code{kill} or @code{detach} command first.
2810 To quit debugging one of the running inferiors that is not the current
2811 inferior, you can either detach from it by using the @w{@code{detach
2812 inferior}} command (allowing it to run independently), or kill it
2813 using the @w{@code{kill inferiors}} command:
2816 @kindex detach inferiors @var{infno}@dots{}
2817 @item detach inferior @var{infno}@dots{}
2818 Detach from the inferior or inferiors identified by @value{GDBN}
2819 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2820 still stays on the list of inferiors shown by @code{info inferiors},
2821 but its Description will show @samp{<null>}.
2823 @kindex kill inferiors @var{infno}@dots{}
2824 @item kill inferiors @var{infno}@dots{}
2825 Kill the inferior or inferiors identified by @value{GDBN} inferior
2826 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2827 stays on the list of inferiors shown by @code{info inferiors}, but its
2828 Description will show @samp{<null>}.
2831 After the successful completion of a command such as @code{detach},
2832 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2833 a normal process exit, the inferior is still valid and listed with
2834 @code{info inferiors}, ready to be restarted.
2837 To be notified when inferiors are started or exit under @value{GDBN}'s
2838 control use @w{@code{set print inferior-events}}:
2841 @kindex set print inferior-events
2842 @cindex print messages on inferior start and exit
2843 @item set print inferior-events
2844 @itemx set print inferior-events on
2845 @itemx set print inferior-events off
2846 The @code{set print inferior-events} command allows you to enable or
2847 disable printing of messages when @value{GDBN} notices that new
2848 inferiors have started or that inferiors have exited or have been
2849 detached. By default, these messages will not be printed.
2851 @kindex show print inferior-events
2852 @item show print inferior-events
2853 Show whether messages will be printed when @value{GDBN} detects that
2854 inferiors have started, exited or have been detached.
2857 Many commands will work the same with multiple programs as with a
2858 single program: e.g., @code{print myglobal} will simply display the
2859 value of @code{myglobal} in the current inferior.
2862 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2863 get more info about the relationship of inferiors, programs, address
2864 spaces in a debug session. You can do that with the @w{@code{maint
2865 info program-spaces}} command.
2868 @kindex maint info program-spaces
2869 @item maint info program-spaces
2870 Print a list of all program spaces currently being managed by
2873 @value{GDBN} displays for each program space (in this order):
2877 the program space number assigned by @value{GDBN}
2880 the name of the executable loaded into the program space, with e.g.,
2881 the @code{file} command.
2886 An asterisk @samp{*} preceding the @value{GDBN} program space number
2887 indicates the current program space.
2889 In addition, below each program space line, @value{GDBN} prints extra
2890 information that isn't suitable to display in tabular form. For
2891 example, the list of inferiors bound to the program space.
2894 (@value{GDBP}) maint info program-spaces
2898 Bound inferiors: ID 1 (process 21561)
2901 Here we can see that no inferior is running the program @code{hello},
2902 while @code{process 21561} is running the program @code{goodbye}. On
2903 some targets, it is possible that multiple inferiors are bound to the
2904 same program space. The most common example is that of debugging both
2905 the parent and child processes of a @code{vfork} call. For example,
2908 (@value{GDBP}) maint info program-spaces
2911 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2914 Here, both inferior 2 and inferior 1 are running in the same program
2915 space as a result of inferior 1 having executed a @code{vfork} call.
2919 @section Debugging Programs with Multiple Threads
2921 @cindex threads of execution
2922 @cindex multiple threads
2923 @cindex switching threads
2924 In some operating systems, such as GNU/Linux and Solaris, a single program
2925 may have more than one @dfn{thread} of execution. The precise semantics
2926 of threads differ from one operating system to another, but in general
2927 the threads of a single program are akin to multiple processes---except
2928 that they share one address space (that is, they can all examine and
2929 modify the same variables). On the other hand, each thread has its own
2930 registers and execution stack, and perhaps private memory.
2932 @value{GDBN} provides these facilities for debugging multi-thread
2936 @item automatic notification of new threads
2937 @item @samp{thread @var{thread-id}}, a command to switch among threads
2938 @item @samp{info threads}, a command to inquire about existing threads
2939 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2940 a command to apply a command to a list of threads
2941 @item thread-specific breakpoints
2942 @item @samp{set print thread-events}, which controls printing of
2943 messages on thread start and exit.
2944 @item @samp{set libthread-db-search-path @var{path}}, which lets
2945 the user specify which @code{libthread_db} to use if the default choice
2946 isn't compatible with the program.
2949 @cindex focus of debugging
2950 @cindex current thread
2951 The @value{GDBN} thread debugging facility allows you to observe all
2952 threads while your program runs---but whenever @value{GDBN} takes
2953 control, one thread in particular is always the focus of debugging.
2954 This thread is called the @dfn{current thread}. Debugging commands show
2955 program information from the perspective of the current thread.
2957 @cindex @code{New} @var{systag} message
2958 @cindex thread identifier (system)
2959 @c FIXME-implementors!! It would be more helpful if the [New...] message
2960 @c included GDB's numeric thread handle, so you could just go to that
2961 @c thread without first checking `info threads'.
2962 Whenever @value{GDBN} detects a new thread in your program, it displays
2963 the target system's identification for the thread with a message in the
2964 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2965 whose form varies depending on the particular system. For example, on
2966 @sc{gnu}/Linux, you might see
2969 [New Thread 0x41e02940 (LWP 25582)]
2973 when @value{GDBN} notices a new thread. In contrast, on other systems,
2974 the @var{systag} is simply something like @samp{process 368}, with no
2977 @c FIXME!! (1) Does the [New...] message appear even for the very first
2978 @c thread of a program, or does it only appear for the
2979 @c second---i.e.@: when it becomes obvious we have a multithread
2981 @c (2) *Is* there necessarily a first thread always? Or do some
2982 @c multithread systems permit starting a program with multiple
2983 @c threads ab initio?
2985 @anchor{thread numbers}
2986 @cindex thread number, per inferior
2987 @cindex thread identifier (GDB)
2988 For debugging purposes, @value{GDBN} associates its own thread number
2989 ---always a single integer---with each thread of an inferior. This
2990 number is unique between all threads of an inferior, but not unique
2991 between threads of different inferiors.
2993 @cindex qualified thread ID
2994 You can refer to a given thread in an inferior using the qualified
2995 @var{inferior-num}.@var{thread-num} syntax, also known as
2996 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2997 number and @var{thread-num} being the thread number of the given
2998 inferior. For example, thread @code{2.3} refers to thread number 3 of
2999 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3000 then @value{GDBN} infers you're referring to a thread of the current
3003 Until you create a second inferior, @value{GDBN} does not show the
3004 @var{inferior-num} part of thread IDs, even though you can always use
3005 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3006 of inferior 1, the initial inferior.
3008 @anchor{thread ID lists}
3009 @cindex thread ID lists
3010 Some commands accept a space-separated @dfn{thread ID list} as
3011 argument. A list element can be:
3015 A thread ID as shown in the first field of the @samp{info threads}
3016 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3020 A range of thread numbers, again with or without an inferior
3021 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3022 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3025 All threads of an inferior, specified with a star wildcard, with or
3026 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3027 @samp{1.*}) or @code{*}. The former refers to all threads of the
3028 given inferior, and the latter form without an inferior qualifier
3029 refers to all threads of the current inferior.
3033 For example, if the current inferior is 1, and inferior 7 has one
3034 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3035 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3036 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3037 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3041 @anchor{global thread numbers}
3042 @cindex global thread number
3043 @cindex global thread identifier (GDB)
3044 In addition to a @emph{per-inferior} number, each thread is also
3045 assigned a unique @emph{global} number, also known as @dfn{global
3046 thread ID}, a single integer. Unlike the thread number component of
3047 the thread ID, no two threads have the same global ID, even when
3048 you're debugging multiple inferiors.
3050 From @value{GDBN}'s perspective, a process always has at least one
3051 thread. In other words, @value{GDBN} assigns a thread number to the
3052 program's ``main thread'' even if the program is not multi-threaded.
3054 @vindex $_thread@r{, convenience variable}
3055 @vindex $_gthread@r{, convenience variable}
3056 The debugger convenience variables @samp{$_thread} and
3057 @samp{$_gthread} contain, respectively, the per-inferior thread number
3058 and the global thread number of the current thread. You may find this
3059 useful in writing breakpoint conditional expressions, command scripts,
3060 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3061 general information on convenience variables.
3063 If @value{GDBN} detects the program is multi-threaded, it augments the
3064 usual message about stopping at a breakpoint with the ID and name of
3065 the thread that hit the breakpoint.
3068 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3071 Likewise when the program receives a signal:
3074 Thread 1 "main" received signal SIGINT, Interrupt.
3078 @kindex info threads
3079 @item info threads @r{[}@var{thread-id-list}@r{]}
3081 Display information about one or more threads. With no arguments
3082 displays information about all threads. You can specify the list of
3083 threads that you want to display using the thread ID list syntax
3084 (@pxref{thread ID lists}).
3086 @value{GDBN} displays for each thread (in this order):
3090 the per-inferior thread number assigned by @value{GDBN}
3093 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3094 option was specified
3097 the target system's thread identifier (@var{systag})
3100 the thread's name, if one is known. A thread can either be named by
3101 the user (see @code{thread name}, below), or, in some cases, by the
3105 the current stack frame summary for that thread
3109 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3110 indicates the current thread.
3114 @c end table here to get a little more width for example
3117 (@value{GDBP}) info threads
3119 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3120 2 process 35 thread 23 0x34e5 in sigpause ()
3121 3 process 35 thread 27 0x34e5 in sigpause ()
3125 If you're debugging multiple inferiors, @value{GDBN} displays thread
3126 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3127 Otherwise, only @var{thread-num} is shown.
3129 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3130 indicating each thread's global thread ID:
3133 (@value{GDBP}) info threads
3134 Id GId Target Id Frame
3135 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3136 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3137 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3138 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3141 On Solaris, you can display more information about user threads with a
3142 Solaris-specific command:
3145 @item maint info sol-threads
3146 @kindex maint info sol-threads
3147 @cindex thread info (Solaris)
3148 Display info on Solaris user threads.
3152 @kindex thread @var{thread-id}
3153 @item thread @var{thread-id}
3154 Make thread ID @var{thread-id} the current thread. The command
3155 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3156 the first field of the @samp{info threads} display, with or without an
3157 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3159 @value{GDBN} responds by displaying the system identifier of the
3160 thread you selected, and its current stack frame summary:
3163 (@value{GDBP}) thread 2
3164 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3165 #0 some_function (ignore=0x0) at example.c:8
3166 8 printf ("hello\n");
3170 As with the @samp{[New @dots{}]} message, the form of the text after
3171 @samp{Switching to} depends on your system's conventions for identifying
3174 @kindex thread apply
3175 @cindex apply command to several threads
3176 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3177 The @code{thread apply} command allows you to apply the named
3178 @var{command} to one or more threads. Specify the threads that you
3179 want affected using the thread ID list syntax (@pxref{thread ID
3180 lists}), or specify @code{all} to apply to all threads. To apply a
3181 command to all threads in descending order, type @kbd{thread apply all
3182 @var{command}}. To apply a command to all threads in ascending order,
3183 type @kbd{thread apply all -ascending @var{command}}.
3185 The @var{flag} arguments control what output to produce and how to handle
3186 errors raised when applying @var{command} to a thread. @var{flag}
3187 must start with a @code{-} directly followed by one letter in
3188 @code{qcs}. If several flags are provided, they must be given
3189 individually, such as @code{-c -q}.
3191 By default, @value{GDBN} displays some thread information before the
3192 output produced by @var{command}, and an error raised during the
3193 execution of a @var{command} will abort @code{thread apply}. The
3194 following flags can be used to fine-tune this behavior:
3198 The flag @code{-c}, which stands for @samp{continue}, causes any
3199 errors in @var{command} to be displayed, and the execution of
3200 @code{thread apply} then continues.
3202 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3203 or empty output produced by a @var{command} to be silently ignored.
3204 That is, the execution continues, but the thread information and errors
3207 The flag @code{-q} (@samp{quiet}) disables printing the thread
3211 Flags @code{-c} and @code{-s} cannot be used together.
3214 @cindex apply command to all threads (ignoring errors and empty output)
3215 @item taas @var{command}
3216 Shortcut for @code{thread apply all -s @var{command}}.
3217 Applies @var{command} on all threads, ignoring errors and empty output.
3220 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3221 @item tfaas @var{command}
3222 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3223 Applies @var{command} on all frames of all threads, ignoring errors
3224 and empty output. Note that the flag @code{-s} is specified twice:
3225 The first @code{-s} ensures that @code{thread apply} only shows the thread
3226 information of the threads for which @code{frame apply} produces
3227 some output. The second @code{-s} is needed to ensure that @code{frame
3228 apply} shows the frame information of a frame only if the
3229 @var{command} successfully produced some output.
3231 It can for example be used to print a local variable or a function
3232 argument without knowing the thread or frame where this variable or argument
3235 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3240 @cindex name a thread
3241 @item thread name [@var{name}]
3242 This command assigns a name to the current thread. If no argument is
3243 given, any existing user-specified name is removed. The thread name
3244 appears in the @samp{info threads} display.
3246 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3247 determine the name of the thread as given by the OS. On these
3248 systems, a name specified with @samp{thread name} will override the
3249 system-give name, and removing the user-specified name will cause
3250 @value{GDBN} to once again display the system-specified name.
3253 @cindex search for a thread
3254 @item thread find [@var{regexp}]
3255 Search for and display thread ids whose name or @var{systag}
3256 matches the supplied regular expression.
3258 As well as being the complement to the @samp{thread name} command,
3259 this command also allows you to identify a thread by its target
3260 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3264 (@value{GDBN}) thread find 26688
3265 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3266 (@value{GDBN}) info thread 4
3268 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3271 @kindex set print thread-events
3272 @cindex print messages on thread start and exit
3273 @item set print thread-events
3274 @itemx set print thread-events on
3275 @itemx set print thread-events off
3276 The @code{set print thread-events} command allows you to enable or
3277 disable printing of messages when @value{GDBN} notices that new threads have
3278 started or that threads have exited. By default, these messages will
3279 be printed if detection of these events is supported by the target.
3280 Note that these messages cannot be disabled on all targets.
3282 @kindex show print thread-events
3283 @item show print thread-events
3284 Show whether messages will be printed when @value{GDBN} detects that threads
3285 have started and exited.
3288 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3289 more information about how @value{GDBN} behaves when you stop and start
3290 programs with multiple threads.
3292 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3293 watchpoints in programs with multiple threads.
3295 @anchor{set libthread-db-search-path}
3297 @kindex set libthread-db-search-path
3298 @cindex search path for @code{libthread_db}
3299 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3300 If this variable is set, @var{path} is a colon-separated list of
3301 directories @value{GDBN} will use to search for @code{libthread_db}.
3302 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3303 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3304 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3307 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3308 @code{libthread_db} library to obtain information about threads in the
3309 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3310 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3311 specific thread debugging library loading is enabled
3312 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3314 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3315 refers to the default system directories that are
3316 normally searched for loading shared libraries. The @samp{$sdir} entry
3317 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3318 (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3321 refers to the directory from which @code{libpthread}
3322 was loaded in the inferior process.
3324 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3325 @value{GDBN} attempts to initialize it with the current inferior process.
3326 If this initialization fails (which could happen because of a version
3327 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3328 will unload @code{libthread_db}, and continue with the next directory.
3329 If none of @code{libthread_db} libraries initialize successfully,
3330 @value{GDBN} will issue a warning and thread debugging will be disabled.
3332 Setting @code{libthread-db-search-path} is currently implemented
3333 only on some platforms.
3335 @kindex show libthread-db-search-path
3336 @item show libthread-db-search-path
3337 Display current libthread_db search path.
3339 @kindex set debug libthread-db
3340 @kindex show debug libthread-db
3341 @cindex debugging @code{libthread_db}
3342 @item set debug libthread-db
3343 @itemx show debug libthread-db
3344 Turns on or off display of @code{libthread_db}-related events.
3345 Use @code{1} to enable, @code{0} to disable.
3349 @section Debugging Forks
3351 @cindex fork, debugging programs which call
3352 @cindex multiple processes
3353 @cindex processes, multiple
3354 On most systems, @value{GDBN} has no special support for debugging
3355 programs which create additional processes using the @code{fork}
3356 function. When a program forks, @value{GDBN} will continue to debug the
3357 parent process and the child process will run unimpeded. If you have
3358 set a breakpoint in any code which the child then executes, the child
3359 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3360 will cause it to terminate.
3362 However, if you want to debug the child process there is a workaround
3363 which isn't too painful. Put a call to @code{sleep} in the code which
3364 the child process executes after the fork. It may be useful to sleep
3365 only if a certain environment variable is set, or a certain file exists,
3366 so that the delay need not occur when you don't want to run @value{GDBN}
3367 on the child. While the child is sleeping, use the @code{ps} program to
3368 get its process ID. Then tell @value{GDBN} (a new invocation of
3369 @value{GDBN} if you are also debugging the parent process) to attach to
3370 the child process (@pxref{Attach}). From that point on you can debug
3371 the child process just like any other process which you attached to.
3373 On some systems, @value{GDBN} provides support for debugging programs
3374 that create additional processes using the @code{fork} or @code{vfork}
3375 functions. On @sc{gnu}/Linux platforms, this feature is supported
3376 with kernel version 2.5.46 and later.
3378 The fork debugging commands are supported in native mode and when
3379 connected to @code{gdbserver} in either @code{target remote} mode or
3380 @code{target extended-remote} mode.
3382 By default, when a program forks, @value{GDBN} will continue to debug
3383 the parent process and the child process will run unimpeded.
3385 If you want to follow the child process instead of the parent process,
3386 use the command @w{@code{set follow-fork-mode}}.
3389 @kindex set follow-fork-mode
3390 @item set follow-fork-mode @var{mode}
3391 Set the debugger response to a program call of @code{fork} or
3392 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3393 process. The @var{mode} argument can be:
3397 The original process is debugged after a fork. The child process runs
3398 unimpeded. This is the default.
3401 The new process is debugged after a fork. The parent process runs
3406 @kindex show follow-fork-mode
3407 @item show follow-fork-mode
3408 Display the current debugger response to a @code{fork} or @code{vfork} call.
3411 @cindex debugging multiple processes
3412 On Linux, if you want to debug both the parent and child processes, use the
3413 command @w{@code{set detach-on-fork}}.
3416 @kindex set detach-on-fork
3417 @item set detach-on-fork @var{mode}
3418 Tells gdb whether to detach one of the processes after a fork, or
3419 retain debugger control over them both.
3423 The child process (or parent process, depending on the value of
3424 @code{follow-fork-mode}) will be detached and allowed to run
3425 independently. This is the default.
3428 Both processes will be held under the control of @value{GDBN}.
3429 One process (child or parent, depending on the value of
3430 @code{follow-fork-mode}) is debugged as usual, while the other
3435 @kindex show detach-on-fork
3436 @item show detach-on-fork
3437 Show whether detach-on-fork mode is on/off.
3440 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3441 will retain control of all forked processes (including nested forks).
3442 You can list the forked processes under the control of @value{GDBN} by
3443 using the @w{@code{info inferiors}} command, and switch from one fork
3444 to another by using the @code{inferior} command (@pxref{Inferiors and
3445 Programs, ,Debugging Multiple Inferiors and Programs}).
3447 To quit debugging one of the forked processes, you can either detach
3448 from it by using the @w{@code{detach inferiors}} command (allowing it
3449 to run independently), or kill it using the @w{@code{kill inferiors}}
3450 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3453 If you ask to debug a child process and a @code{vfork} is followed by an
3454 @code{exec}, @value{GDBN} executes the new target up to the first
3455 breakpoint in the new target. If you have a breakpoint set on
3456 @code{main} in your original program, the breakpoint will also be set on
3457 the child process's @code{main}.
3459 On some systems, when a child process is spawned by @code{vfork}, you
3460 cannot debug the child or parent until an @code{exec} call completes.
3462 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3463 call executes, the new target restarts. To restart the parent
3464 process, use the @code{file} command with the parent executable name
3465 as its argument. By default, after an @code{exec} call executes,
3466 @value{GDBN} discards the symbols of the previous executable image.
3467 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3471 @kindex set follow-exec-mode
3472 @item set follow-exec-mode @var{mode}
3474 Set debugger response to a program call of @code{exec}. An
3475 @code{exec} call replaces the program image of a process.
3477 @code{follow-exec-mode} can be:
3481 @value{GDBN} creates a new inferior and rebinds the process to this
3482 new inferior. The program the process was running before the
3483 @code{exec} call can be restarted afterwards by restarting the
3489 (@value{GDBP}) info inferiors
3491 Id Description Executable
3494 process 12020 is executing new program: prog2
3495 Program exited normally.
3496 (@value{GDBP}) info inferiors
3497 Id Description Executable
3503 @value{GDBN} keeps the process bound to the same inferior. The new
3504 executable image replaces the previous executable loaded in the
3505 inferior. Restarting the inferior after the @code{exec} call, with
3506 e.g., the @code{run} command, restarts the executable the process was
3507 running after the @code{exec} call. This is the default mode.
3512 (@value{GDBP}) info inferiors
3513 Id Description Executable
3516 process 12020 is executing new program: prog2
3517 Program exited normally.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3526 @code{follow-exec-mode} is supported in native mode and
3527 @code{target extended-remote} mode.
3529 You can use the @code{catch} command to make @value{GDBN} stop whenever
3530 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3531 Catchpoints, ,Setting Catchpoints}.
3533 @node Checkpoint/Restart
3534 @section Setting a @emph{Bookmark} to Return to Later
3539 @cindex snapshot of a process
3540 @cindex rewind program state
3542 On certain operating systems@footnote{Currently, only
3543 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3544 program's state, called a @dfn{checkpoint}, and come back to it
3547 Returning to a checkpoint effectively undoes everything that has
3548 happened in the program since the @code{checkpoint} was saved. This
3549 includes changes in memory, registers, and even (within some limits)
3550 system state. Effectively, it is like going back in time to the
3551 moment when the checkpoint was saved.
3553 Thus, if you're stepping thru a program and you think you're
3554 getting close to the point where things go wrong, you can save
3555 a checkpoint. Then, if you accidentally go too far and miss
3556 the critical statement, instead of having to restart your program
3557 from the beginning, you can just go back to the checkpoint and
3558 start again from there.
3560 This can be especially useful if it takes a lot of time or
3561 steps to reach the point where you think the bug occurs.
3563 To use the @code{checkpoint}/@code{restart} method of debugging:
3568 Save a snapshot of the debugged program's current execution state.
3569 The @code{checkpoint} command takes no arguments, but each checkpoint
3570 is assigned a small integer id, similar to a breakpoint id.
3572 @kindex info checkpoints
3573 @item info checkpoints
3574 List the checkpoints that have been saved in the current debugging
3575 session. For each checkpoint, the following information will be
3582 @item Source line, or label
3585 @kindex restart @var{checkpoint-id}
3586 @item restart @var{checkpoint-id}
3587 Restore the program state that was saved as checkpoint number
3588 @var{checkpoint-id}. All program variables, registers, stack frames
3589 etc.@: will be returned to the values that they had when the checkpoint
3590 was saved. In essence, gdb will ``wind back the clock'' to the point
3591 in time when the checkpoint was saved.
3593 Note that breakpoints, @value{GDBN} variables, command history etc.
3594 are not affected by restoring a checkpoint. In general, a checkpoint
3595 only restores things that reside in the program being debugged, not in
3598 @kindex delete checkpoint @var{checkpoint-id}
3599 @item delete checkpoint @var{checkpoint-id}
3600 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3604 Returning to a previously saved checkpoint will restore the user state
3605 of the program being debugged, plus a significant subset of the system
3606 (OS) state, including file pointers. It won't ``un-write'' data from
3607 a file, but it will rewind the file pointer to the previous location,
3608 so that the previously written data can be overwritten. For files
3609 opened in read mode, the pointer will also be restored so that the
3610 previously read data can be read again.
3612 Of course, characters that have been sent to a printer (or other
3613 external device) cannot be ``snatched back'', and characters received
3614 from eg.@: a serial device can be removed from internal program buffers,
3615 but they cannot be ``pushed back'' into the serial pipeline, ready to
3616 be received again. Similarly, the actual contents of files that have
3617 been changed cannot be restored (at this time).
3619 However, within those constraints, you actually can ``rewind'' your
3620 program to a previously saved point in time, and begin debugging it
3621 again --- and you can change the course of events so as to debug a
3622 different execution path this time.
3624 @cindex checkpoints and process id
3625 Finally, there is one bit of internal program state that will be
3626 different when you return to a checkpoint --- the program's process
3627 id. Each checkpoint will have a unique process id (or @var{pid}),
3628 and each will be different from the program's original @var{pid}.
3629 If your program has saved a local copy of its process id, this could
3630 potentially pose a problem.
3632 @subsection A Non-obvious Benefit of Using Checkpoints
3634 On some systems such as @sc{gnu}/Linux, address space randomization
3635 is performed on new processes for security reasons. This makes it
3636 difficult or impossible to set a breakpoint, or watchpoint, on an
3637 absolute address if you have to restart the program, since the
3638 absolute location of a symbol will change from one execution to the
3641 A checkpoint, however, is an @emph{identical} copy of a process.
3642 Therefore if you create a checkpoint at (eg.@:) the start of main,
3643 and simply return to that checkpoint instead of restarting the
3644 process, you can avoid the effects of address randomization and
3645 your symbols will all stay in the same place.
3648 @chapter Stopping and Continuing
3650 The principal purposes of using a debugger are so that you can stop your
3651 program before it terminates; or so that, if your program runs into
3652 trouble, you can investigate and find out why.
3654 Inside @value{GDBN}, your program may stop for any of several reasons,
3655 such as a signal, a breakpoint, or reaching a new line after a
3656 @value{GDBN} command such as @code{step}. You may then examine and
3657 change variables, set new breakpoints or remove old ones, and then
3658 continue execution. Usually, the messages shown by @value{GDBN} provide
3659 ample explanation of the status of your program---but you can also
3660 explicitly request this information at any time.
3663 @kindex info program
3665 Display information about the status of your program: whether it is
3666 running or not, what process it is, and why it stopped.
3670 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3671 * Continuing and Stepping:: Resuming execution
3672 * Skipping Over Functions and Files::
3673 Skipping over functions and files
3675 * Thread Stops:: Stopping and starting multi-thread programs
3679 @section Breakpoints, Watchpoints, and Catchpoints
3682 A @dfn{breakpoint} makes your program stop whenever a certain point in
3683 the program is reached. For each breakpoint, you can add conditions to
3684 control in finer detail whether your program stops. You can set
3685 breakpoints with the @code{break} command and its variants (@pxref{Set
3686 Breaks, ,Setting Breakpoints}), to specify the place where your program
3687 should stop by line number, function name or exact address in the
3690 On some systems, you can set breakpoints in shared libraries before
3691 the executable is run.
3694 @cindex data breakpoints
3695 @cindex memory tracing
3696 @cindex breakpoint on memory address
3697 @cindex breakpoint on variable modification
3698 A @dfn{watchpoint} is a special breakpoint that stops your program
3699 when the value of an expression changes. The expression may be a value
3700 of a variable, or it could involve values of one or more variables
3701 combined by operators, such as @samp{a + b}. This is sometimes called
3702 @dfn{data breakpoints}. You must use a different command to set
3703 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3704 from that, you can manage a watchpoint like any other breakpoint: you
3705 enable, disable, and delete both breakpoints and watchpoints using the
3708 You can arrange to have values from your program displayed automatically
3709 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3713 @cindex breakpoint on events
3714 A @dfn{catchpoint} is another special breakpoint that stops your program
3715 when a certain kind of event occurs, such as the throwing of a C@t{++}
3716 exception or the loading of a library. As with watchpoints, you use a
3717 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3718 Catchpoints}), but aside from that, you can manage a catchpoint like any
3719 other breakpoint. (To stop when your program receives a signal, use the
3720 @code{handle} command; see @ref{Signals, ,Signals}.)
3722 @cindex breakpoint numbers
3723 @cindex numbers for breakpoints
3724 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3725 catchpoint when you create it; these numbers are successive integers
3726 starting with one. In many of the commands for controlling various
3727 features of breakpoints you use the breakpoint number to say which
3728 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3729 @dfn{disabled}; if disabled, it has no effect on your program until you
3732 @cindex breakpoint ranges
3733 @cindex breakpoint lists
3734 @cindex ranges of breakpoints
3735 @cindex lists of breakpoints
3736 Some @value{GDBN} commands accept a space-separated list of breakpoints
3737 on which to operate. A list element can be either a single breakpoint number,
3738 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3739 When a breakpoint list is given to a command, all breakpoints in that list
3743 * Set Breaks:: Setting breakpoints
3744 * Set Watchpoints:: Setting watchpoints
3745 * Set Catchpoints:: Setting catchpoints
3746 * Delete Breaks:: Deleting breakpoints
3747 * Disabling:: Disabling breakpoints
3748 * Conditions:: Break conditions
3749 * Break Commands:: Breakpoint command lists
3750 * Dynamic Printf:: Dynamic printf
3751 * Save Breakpoints:: How to save breakpoints in a file
3752 * Static Probe Points:: Listing static probe points
3753 * Error in Breakpoints:: ``Cannot insert breakpoints''
3754 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3758 @subsection Setting Breakpoints
3760 @c FIXME LMB what does GDB do if no code on line of breakpt?
3761 @c consider in particular declaration with/without initialization.
3763 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3766 @kindex b @r{(@code{break})}
3767 @vindex $bpnum@r{, convenience variable}
3768 @cindex latest breakpoint
3769 Breakpoints are set with the @code{break} command (abbreviated
3770 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3771 number of the breakpoint you've set most recently; see @ref{Convenience
3772 Vars,, Convenience Variables}, for a discussion of what you can do with
3773 convenience variables.
3776 @item break @var{location}
3777 Set a breakpoint at the given @var{location}, which can specify a
3778 function name, a line number, or an address of an instruction.
3779 (@xref{Specify Location}, for a list of all the possible ways to
3780 specify a @var{location}.) The breakpoint will stop your program just
3781 before it executes any of the code in the specified @var{location}.
3783 When using source languages that permit overloading of symbols, such as
3784 C@t{++}, a function name may refer to more than one possible place to break.
3785 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3788 It is also possible to insert a breakpoint that will stop the program
3789 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3790 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3793 When called without any arguments, @code{break} sets a breakpoint at
3794 the next instruction to be executed in the selected stack frame
3795 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3796 innermost, this makes your program stop as soon as control
3797 returns to that frame. This is similar to the effect of a
3798 @code{finish} command in the frame inside the selected frame---except
3799 that @code{finish} does not leave an active breakpoint. If you use
3800 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3801 the next time it reaches the current location; this may be useful
3804 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3805 least one instruction has been executed. If it did not do this, you
3806 would be unable to proceed past a breakpoint without first disabling the
3807 breakpoint. This rule applies whether or not the breakpoint already
3808 existed when your program stopped.
3810 @item break @dots{} if @var{cond}
3811 Set a breakpoint with condition @var{cond}; evaluate the expression
3812 @var{cond} each time the breakpoint is reached, and stop only if the
3813 value is nonzero---that is, if @var{cond} evaluates as true.
3814 @samp{@dots{}} stands for one of the possible arguments described
3815 above (or no argument) specifying where to break. @xref{Conditions,
3816 ,Break Conditions}, for more information on breakpoint conditions.
3819 @item tbreak @var{args}
3820 Set a breakpoint enabled only for one stop. The @var{args} are the
3821 same as for the @code{break} command, and the breakpoint is set in the same
3822 way, but the breakpoint is automatically deleted after the first time your
3823 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3826 @cindex hardware breakpoints
3827 @item hbreak @var{args}
3828 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3829 @code{break} command and the breakpoint is set in the same way, but the
3830 breakpoint requires hardware support and some target hardware may not
3831 have this support. The main purpose of this is EPROM/ROM code
3832 debugging, so you can set a breakpoint at an instruction without
3833 changing the instruction. This can be used with the new trap-generation
3834 provided by SPARClite DSU and most x86-based targets. These targets
3835 will generate traps when a program accesses some data or instruction
3836 address that is assigned to the debug registers. However the hardware
3837 breakpoint registers can take a limited number of breakpoints. For
3838 example, on the DSU, only two data breakpoints can be set at a time, and
3839 @value{GDBN} will reject this command if more than two are used. Delete
3840 or disable unused hardware breakpoints before setting new ones
3841 (@pxref{Disabling, ,Disabling Breakpoints}).
3842 @xref{Conditions, ,Break Conditions}.
3843 For remote targets, you can restrict the number of hardware
3844 breakpoints @value{GDBN} will use, see @ref{set remote
3845 hardware-breakpoint-limit}.
3848 @item thbreak @var{args}
3849 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3850 are the same as for the @code{hbreak} command and the breakpoint is set in
3851 the same way. However, like the @code{tbreak} command,
3852 the breakpoint is automatically deleted after the
3853 first time your program stops there. Also, like the @code{hbreak}
3854 command, the breakpoint requires hardware support and some target hardware
3855 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3856 See also @ref{Conditions, ,Break Conditions}.
3859 @cindex regular expression
3860 @cindex breakpoints at functions matching a regexp
3861 @cindex set breakpoints in many functions
3862 @item rbreak @var{regex}
3863 Set breakpoints on all functions matching the regular expression
3864 @var{regex}. This command sets an unconditional breakpoint on all
3865 matches, printing a list of all breakpoints it set. Once these
3866 breakpoints are set, they are treated just like the breakpoints set with
3867 the @code{break} command. You can delete them, disable them, or make
3868 them conditional the same way as any other breakpoint.
3870 The syntax of the regular expression is the standard one used with tools
3871 like @file{grep}. Note that this is different from the syntax used by
3872 shells, so for instance @code{foo*} matches all functions that include
3873 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3874 @code{.*} leading and trailing the regular expression you supply, so to
3875 match only functions that begin with @code{foo}, use @code{^foo}.
3877 @cindex non-member C@t{++} functions, set breakpoint in
3878 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3879 breakpoints on overloaded functions that are not members of any special
3882 @cindex set breakpoints on all functions
3883 The @code{rbreak} command can be used to set breakpoints in
3884 @strong{all} the functions in a program, like this:
3887 (@value{GDBP}) rbreak .
3890 @item rbreak @var{file}:@var{regex}
3891 If @code{rbreak} is called with a filename qualification, it limits
3892 the search for functions matching the given regular expression to the
3893 specified @var{file}. This can be used, for example, to set breakpoints on
3894 every function in a given file:
3897 (@value{GDBP}) rbreak file.c:.
3900 The colon separating the filename qualifier from the regex may
3901 optionally be surrounded by spaces.
3903 @kindex info breakpoints
3904 @cindex @code{$_} and @code{info breakpoints}
3905 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3906 @itemx info break @r{[}@var{list}@dots{}@r{]}
3907 Print a table of all breakpoints, watchpoints, and catchpoints set and
3908 not deleted. Optional argument @var{n} means print information only
3909 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3910 For each breakpoint, following columns are printed:
3913 @item Breakpoint Numbers
3915 Breakpoint, watchpoint, or catchpoint.
3917 Whether the breakpoint is marked to be disabled or deleted when hit.
3918 @item Enabled or Disabled
3919 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3920 that are not enabled.
3922 Where the breakpoint is in your program, as a memory address. For a
3923 pending breakpoint whose address is not yet known, this field will
3924 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3925 library that has the symbol or line referred by breakpoint is loaded.
3926 See below for details. A breakpoint with several locations will
3927 have @samp{<MULTIPLE>} in this field---see below for details.
3929 Where the breakpoint is in the source for your program, as a file and
3930 line number. For a pending breakpoint, the original string passed to
3931 the breakpoint command will be listed as it cannot be resolved until
3932 the appropriate shared library is loaded in the future.
3936 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3937 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3938 @value{GDBN} on the host's side. If it is ``target'', then the condition
3939 is evaluated by the target. The @code{info break} command shows
3940 the condition on the line following the affected breakpoint, together with
3941 its condition evaluation mode in between parentheses.
3943 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3944 allowed to have a condition specified for it. The condition is not parsed for
3945 validity until a shared library is loaded that allows the pending
3946 breakpoint to resolve to a valid location.
3949 @code{info break} with a breakpoint
3950 number @var{n} as argument lists only that breakpoint. The
3951 convenience variable @code{$_} and the default examining-address for
3952 the @code{x} command are set to the address of the last breakpoint
3953 listed (@pxref{Memory, ,Examining Memory}).
3956 @code{info break} displays a count of the number of times the breakpoint
3957 has been hit. This is especially useful in conjunction with the
3958 @code{ignore} command. You can ignore a large number of breakpoint
3959 hits, look at the breakpoint info to see how many times the breakpoint
3960 was hit, and then run again, ignoring one less than that number. This
3961 will get you quickly to the last hit of that breakpoint.
3964 For a breakpoints with an enable count (xref) greater than 1,
3965 @code{info break} also displays that count.
3969 @value{GDBN} allows you to set any number of breakpoints at the same place in
3970 your program. There is nothing silly or meaningless about this. When
3971 the breakpoints are conditional, this is even useful
3972 (@pxref{Conditions, ,Break Conditions}).
3974 @cindex multiple locations, breakpoints
3975 @cindex breakpoints, multiple locations
3976 It is possible that a breakpoint corresponds to several locations
3977 in your program. Examples of this situation are:
3981 Multiple functions in the program may have the same name.
3984 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3985 instances of the function body, used in different cases.
3988 For a C@t{++} template function, a given line in the function can
3989 correspond to any number of instantiations.
3992 For an inlined function, a given source line can correspond to
3993 several places where that function is inlined.
3996 In all those cases, @value{GDBN} will insert a breakpoint at all
3997 the relevant locations.
3999 A breakpoint with multiple locations is displayed in the breakpoint
4000 table using several rows---one header row, followed by one row for
4001 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4002 address column. The rows for individual locations contain the actual
4003 addresses for locations, and show the functions to which those
4004 locations belong. The number column for a location is of the form
4005 @var{breakpoint-number}.@var{location-number}.
4010 Num Type Disp Enb Address What
4011 1 breakpoint keep y <MULTIPLE>
4013 breakpoint already hit 1 time
4014 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4015 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4018 You cannot delete the individual locations from a breakpoint. However,
4019 each location can be individually enabled or disabled by passing
4020 @var{breakpoint-number}.@var{location-number} as argument to the
4021 @code{enable} and @code{disable} commands. It's also possible to
4022 @code{enable} and @code{disable} a range of @var{location-number}
4023 locations using a @var{breakpoint-number} and two @var{location-number}s,
4024 in increasing order, separated by a hyphen, like
4025 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4026 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4027 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4028 all of the locations that belong to that breakpoint.
4030 @cindex pending breakpoints
4031 It's quite common to have a breakpoint inside a shared library.
4032 Shared libraries can be loaded and unloaded explicitly,
4033 and possibly repeatedly, as the program is executed. To support
4034 this use case, @value{GDBN} updates breakpoint locations whenever
4035 any shared library is loaded or unloaded. Typically, you would
4036 set a breakpoint in a shared library at the beginning of your
4037 debugging session, when the library is not loaded, and when the
4038 symbols from the library are not available. When you try to set
4039 breakpoint, @value{GDBN} will ask you if you want to set
4040 a so called @dfn{pending breakpoint}---breakpoint whose address
4041 is not yet resolved.
4043 After the program is run, whenever a new shared library is loaded,
4044 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4045 shared library contains the symbol or line referred to by some
4046 pending breakpoint, that breakpoint is resolved and becomes an
4047 ordinary breakpoint. When a library is unloaded, all breakpoints
4048 that refer to its symbols or source lines become pending again.
4050 This logic works for breakpoints with multiple locations, too. For
4051 example, if you have a breakpoint in a C@t{++} template function, and
4052 a newly loaded shared library has an instantiation of that template,
4053 a new location is added to the list of locations for the breakpoint.
4055 Except for having unresolved address, pending breakpoints do not
4056 differ from regular breakpoints. You can set conditions or commands,
4057 enable and disable them and perform other breakpoint operations.
4059 @value{GDBN} provides some additional commands for controlling what
4060 happens when the @samp{break} command cannot resolve breakpoint
4061 address specification to an address:
4063 @kindex set breakpoint pending
4064 @kindex show breakpoint pending
4066 @item set breakpoint pending auto
4067 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4068 location, it queries you whether a pending breakpoint should be created.
4070 @item set breakpoint pending on
4071 This indicates that an unrecognized breakpoint location should automatically
4072 result in a pending breakpoint being created.
4074 @item set breakpoint pending off
4075 This indicates that pending breakpoints are not to be created. Any
4076 unrecognized breakpoint location results in an error. This setting does
4077 not affect any pending breakpoints previously created.
4079 @item show breakpoint pending
4080 Show the current behavior setting for creating pending breakpoints.
4083 The settings above only affect the @code{break} command and its
4084 variants. Once breakpoint is set, it will be automatically updated
4085 as shared libraries are loaded and unloaded.
4087 @cindex automatic hardware breakpoints
4088 For some targets, @value{GDBN} can automatically decide if hardware or
4089 software breakpoints should be used, depending on whether the
4090 breakpoint address is read-only or read-write. This applies to
4091 breakpoints set with the @code{break} command as well as to internal
4092 breakpoints set by commands like @code{next} and @code{finish}. For
4093 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4096 You can control this automatic behaviour with the following commands:
4098 @kindex set breakpoint auto-hw
4099 @kindex show breakpoint auto-hw
4101 @item set breakpoint auto-hw on
4102 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4103 will try to use the target memory map to decide if software or hardware
4104 breakpoint must be used.
4106 @item set breakpoint auto-hw off
4107 This indicates @value{GDBN} should not automatically select breakpoint
4108 type. If the target provides a memory map, @value{GDBN} will warn when
4109 trying to set software breakpoint at a read-only address.
4112 @value{GDBN} normally implements breakpoints by replacing the program code
4113 at the breakpoint address with a special instruction, which, when
4114 executed, given control to the debugger. By default, the program
4115 code is so modified only when the program is resumed. As soon as
4116 the program stops, @value{GDBN} restores the original instructions. This
4117 behaviour guards against leaving breakpoints inserted in the
4118 target should gdb abrubptly disconnect. However, with slow remote
4119 targets, inserting and removing breakpoint can reduce the performance.
4120 This behavior can be controlled with the following commands::
4122 @kindex set breakpoint always-inserted
4123 @kindex show breakpoint always-inserted
4125 @item set breakpoint always-inserted off
4126 All breakpoints, including newly added by the user, are inserted in
4127 the target only when the target is resumed. All breakpoints are
4128 removed from the target when it stops. This is the default mode.
4130 @item set breakpoint always-inserted on
4131 Causes all breakpoints to be inserted in the target at all times. If
4132 the user adds a new breakpoint, or changes an existing breakpoint, the
4133 breakpoints in the target are updated immediately. A breakpoint is
4134 removed from the target only when breakpoint itself is deleted.
4137 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4138 when a breakpoint breaks. If the condition is true, then the process being
4139 debugged stops, otherwise the process is resumed.
4141 If the target supports evaluating conditions on its end, @value{GDBN} may
4142 download the breakpoint, together with its conditions, to it.
4144 This feature can be controlled via the following commands:
4146 @kindex set breakpoint condition-evaluation
4147 @kindex show breakpoint condition-evaluation
4149 @item set breakpoint condition-evaluation host
4150 This option commands @value{GDBN} to evaluate the breakpoint
4151 conditions on the host's side. Unconditional breakpoints are sent to
4152 the target which in turn receives the triggers and reports them back to GDB
4153 for condition evaluation. This is the standard evaluation mode.
4155 @item set breakpoint condition-evaluation target
4156 This option commands @value{GDBN} to download breakpoint conditions
4157 to the target at the moment of their insertion. The target
4158 is responsible for evaluating the conditional expression and reporting
4159 breakpoint stop events back to @value{GDBN} whenever the condition
4160 is true. Due to limitations of target-side evaluation, some conditions
4161 cannot be evaluated there, e.g., conditions that depend on local data
4162 that is only known to the host. Examples include
4163 conditional expressions involving convenience variables, complex types
4164 that cannot be handled by the agent expression parser and expressions
4165 that are too long to be sent over to the target, specially when the
4166 target is a remote system. In these cases, the conditions will be
4167 evaluated by @value{GDBN}.
4169 @item set breakpoint condition-evaluation auto
4170 This is the default mode. If the target supports evaluating breakpoint
4171 conditions on its end, @value{GDBN} will download breakpoint conditions to
4172 the target (limitations mentioned previously apply). If the target does
4173 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4174 to evaluating all these conditions on the host's side.
4178 @cindex negative breakpoint numbers
4179 @cindex internal @value{GDBN} breakpoints
4180 @value{GDBN} itself sometimes sets breakpoints in your program for
4181 special purposes, such as proper handling of @code{longjmp} (in C
4182 programs). These internal breakpoints are assigned negative numbers,
4183 starting with @code{-1}; @samp{info breakpoints} does not display them.
4184 You can see these breakpoints with the @value{GDBN} maintenance command
4185 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4188 @node Set Watchpoints
4189 @subsection Setting Watchpoints
4191 @cindex setting watchpoints
4192 You can use a watchpoint to stop execution whenever the value of an
4193 expression changes, without having to predict a particular place where
4194 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4195 The expression may be as simple as the value of a single variable, or
4196 as complex as many variables combined by operators. Examples include:
4200 A reference to the value of a single variable.
4203 An address cast to an appropriate data type. For example,
4204 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4205 address (assuming an @code{int} occupies 4 bytes).
4208 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4209 expression can use any operators valid in the program's native
4210 language (@pxref{Languages}).
4213 You can set a watchpoint on an expression even if the expression can
4214 not be evaluated yet. For instance, you can set a watchpoint on
4215 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4216 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4217 the expression produces a valid value. If the expression becomes
4218 valid in some other way than changing a variable (e.g.@: if the memory
4219 pointed to by @samp{*global_ptr} becomes readable as the result of a
4220 @code{malloc} call), @value{GDBN} may not stop until the next time
4221 the expression changes.
4223 @cindex software watchpoints
4224 @cindex hardware watchpoints
4225 Depending on your system, watchpoints may be implemented in software or
4226 hardware. @value{GDBN} does software watchpointing by single-stepping your
4227 program and testing the variable's value each time, which is hundreds of
4228 times slower than normal execution. (But this may still be worth it, to
4229 catch errors where you have no clue what part of your program is the
4232 On some systems, such as most PowerPC or x86-based targets,
4233 @value{GDBN} includes support for hardware watchpoints, which do not
4234 slow down the running of your program.
4238 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4239 Set a watchpoint for an expression. @value{GDBN} will break when the
4240 expression @var{expr} is written into by the program and its value
4241 changes. The simplest (and the most popular) use of this command is
4242 to watch the value of a single variable:
4245 (@value{GDBP}) watch foo
4248 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4249 argument, @value{GDBN} breaks only when the thread identified by
4250 @var{thread-id} changes the value of @var{expr}. If any other threads
4251 change the value of @var{expr}, @value{GDBN} will not break. Note
4252 that watchpoints restricted to a single thread in this way only work
4253 with Hardware Watchpoints.
4255 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4256 (see below). The @code{-location} argument tells @value{GDBN} to
4257 instead watch the memory referred to by @var{expr}. In this case,
4258 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4259 and watch the memory at that address. The type of the result is used
4260 to determine the size of the watched memory. If the expression's
4261 result does not have an address, then @value{GDBN} will print an
4264 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4265 of masked watchpoints, if the current architecture supports this
4266 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4267 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4268 to an address to watch. The mask specifies that some bits of an address
4269 (the bits which are reset in the mask) should be ignored when matching
4270 the address accessed by the inferior against the watchpoint address.
4271 Thus, a masked watchpoint watches many addresses simultaneously---those
4272 addresses whose unmasked bits are identical to the unmasked bits in the
4273 watchpoint address. The @code{mask} argument implies @code{-location}.
4277 (@value{GDBP}) watch foo mask 0xffff00ff
4278 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4282 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4283 Set a watchpoint that will break when the value of @var{expr} is read
4287 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4288 Set a watchpoint that will break when @var{expr} is either read from
4289 or written into by the program.
4291 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4292 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4293 This command prints a list of watchpoints, using the same format as
4294 @code{info break} (@pxref{Set Breaks}).
4297 If you watch for a change in a numerically entered address you need to
4298 dereference it, as the address itself is just a constant number which will
4299 never change. @value{GDBN} refuses to create a watchpoint that watches
4300 a never-changing value:
4303 (@value{GDBP}) watch 0x600850
4304 Cannot watch constant value 0x600850.
4305 (@value{GDBP}) watch *(int *) 0x600850
4306 Watchpoint 1: *(int *) 6293584
4309 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4310 watchpoints execute very quickly, and the debugger reports a change in
4311 value at the exact instruction where the change occurs. If @value{GDBN}
4312 cannot set a hardware watchpoint, it sets a software watchpoint, which
4313 executes more slowly and reports the change in value at the next
4314 @emph{statement}, not the instruction, after the change occurs.
4316 @cindex use only software watchpoints
4317 You can force @value{GDBN} to use only software watchpoints with the
4318 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4319 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4320 the underlying system supports them. (Note that hardware-assisted
4321 watchpoints that were set @emph{before} setting
4322 @code{can-use-hw-watchpoints} to zero will still use the hardware
4323 mechanism of watching expression values.)
4326 @item set can-use-hw-watchpoints
4327 @kindex set can-use-hw-watchpoints
4328 Set whether or not to use hardware watchpoints.
4330 @item show can-use-hw-watchpoints
4331 @kindex show can-use-hw-watchpoints
4332 Show the current mode of using hardware watchpoints.
4335 For remote targets, you can restrict the number of hardware
4336 watchpoints @value{GDBN} will use, see @ref{set remote
4337 hardware-breakpoint-limit}.
4339 When you issue the @code{watch} command, @value{GDBN} reports
4342 Hardware watchpoint @var{num}: @var{expr}
4346 if it was able to set a hardware watchpoint.
4348 Currently, the @code{awatch} and @code{rwatch} commands can only set
4349 hardware watchpoints, because accesses to data that don't change the
4350 value of the watched expression cannot be detected without examining
4351 every instruction as it is being executed, and @value{GDBN} does not do
4352 that currently. If @value{GDBN} finds that it is unable to set a
4353 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4354 will print a message like this:
4357 Expression cannot be implemented with read/access watchpoint.
4360 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4361 data type of the watched expression is wider than what a hardware
4362 watchpoint on the target machine can handle. For example, some systems
4363 can only watch regions that are up to 4 bytes wide; on such systems you
4364 cannot set hardware watchpoints for an expression that yields a
4365 double-precision floating-point number (which is typically 8 bytes
4366 wide). As a work-around, it might be possible to break the large region
4367 into a series of smaller ones and watch them with separate watchpoints.
4369 If you set too many hardware watchpoints, @value{GDBN} might be unable
4370 to insert all of them when you resume the execution of your program.
4371 Since the precise number of active watchpoints is unknown until such
4372 time as the program is about to be resumed, @value{GDBN} might not be
4373 able to warn you about this when you set the watchpoints, and the
4374 warning will be printed only when the program is resumed:
4377 Hardware watchpoint @var{num}: Could not insert watchpoint
4381 If this happens, delete or disable some of the watchpoints.
4383 Watching complex expressions that reference many variables can also
4384 exhaust the resources available for hardware-assisted watchpoints.
4385 That's because @value{GDBN} needs to watch every variable in the
4386 expression with separately allocated resources.
4388 If you call a function interactively using @code{print} or @code{call},
4389 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4390 kind of breakpoint or the call completes.
4392 @value{GDBN} automatically deletes watchpoints that watch local
4393 (automatic) variables, or expressions that involve such variables, when
4394 they go out of scope, that is, when the execution leaves the block in
4395 which these variables were defined. In particular, when the program
4396 being debugged terminates, @emph{all} local variables go out of scope,
4397 and so only watchpoints that watch global variables remain set. If you
4398 rerun the program, you will need to set all such watchpoints again. One
4399 way of doing that would be to set a code breakpoint at the entry to the
4400 @code{main} function and when it breaks, set all the watchpoints.
4402 @cindex watchpoints and threads
4403 @cindex threads and watchpoints
4404 In multi-threaded programs, watchpoints will detect changes to the
4405 watched expression from every thread.
4408 @emph{Warning:} In multi-threaded programs, software watchpoints
4409 have only limited usefulness. If @value{GDBN} creates a software
4410 watchpoint, it can only watch the value of an expression @emph{in a
4411 single thread}. If you are confident that the expression can only
4412 change due to the current thread's activity (and if you are also
4413 confident that no other thread can become current), then you can use
4414 software watchpoints as usual. However, @value{GDBN} may not notice
4415 when a non-current thread's activity changes the expression. (Hardware
4416 watchpoints, in contrast, watch an expression in all threads.)
4419 @xref{set remote hardware-watchpoint-limit}.
4421 @node Set Catchpoints
4422 @subsection Setting Catchpoints
4423 @cindex catchpoints, setting
4424 @cindex exception handlers
4425 @cindex event handling
4427 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4428 kinds of program events, such as C@t{++} exceptions or the loading of a
4429 shared library. Use the @code{catch} command to set a catchpoint.
4433 @item catch @var{event}
4434 Stop when @var{event} occurs. The @var{event} can be any of the following:
4437 @item throw @r{[}@var{regexp}@r{]}
4438 @itemx rethrow @r{[}@var{regexp}@r{]}
4439 @itemx catch @r{[}@var{regexp}@r{]}
4441 @kindex catch rethrow
4443 @cindex stop on C@t{++} exceptions
4444 The throwing, re-throwing, or catching of a C@t{++} exception.
4446 If @var{regexp} is given, then only exceptions whose type matches the
4447 regular expression will be caught.
4449 @vindex $_exception@r{, convenience variable}
4450 The convenience variable @code{$_exception} is available at an
4451 exception-related catchpoint, on some systems. This holds the
4452 exception being thrown.
4454 There are currently some limitations to C@t{++} exception handling in
4459 The support for these commands is system-dependent. Currently, only
4460 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4464 The regular expression feature and the @code{$_exception} convenience
4465 variable rely on the presence of some SDT probes in @code{libstdc++}.
4466 If these probes are not present, then these features cannot be used.
4467 These probes were first available in the GCC 4.8 release, but whether
4468 or not they are available in your GCC also depends on how it was
4472 The @code{$_exception} convenience variable is only valid at the
4473 instruction at which an exception-related catchpoint is set.
4476 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4477 location in the system library which implements runtime exception
4478 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4479 (@pxref{Selection}) to get to your code.
4482 If you call a function interactively, @value{GDBN} normally returns
4483 control to you when the function has finished executing. If the call
4484 raises an exception, however, the call may bypass the mechanism that
4485 returns control to you and cause your program either to abort or to
4486 simply continue running until it hits a breakpoint, catches a signal
4487 that @value{GDBN} is listening for, or exits. This is the case even if
4488 you set a catchpoint for the exception; catchpoints on exceptions are
4489 disabled within interactive calls. @xref{Calling}, for information on
4490 controlling this with @code{set unwind-on-terminating-exception}.
4493 You cannot raise an exception interactively.
4496 You cannot install an exception handler interactively.
4500 @kindex catch exception
4501 @cindex Ada exception catching
4502 @cindex catch Ada exceptions
4503 An Ada exception being raised. If an exception name is specified
4504 at the end of the command (eg @code{catch exception Program_Error}),
4505 the debugger will stop only when this specific exception is raised.
4506 Otherwise, the debugger stops execution when any Ada exception is raised.
4508 When inserting an exception catchpoint on a user-defined exception whose
4509 name is identical to one of the exceptions defined by the language, the
4510 fully qualified name must be used as the exception name. Otherwise,
4511 @value{GDBN} will assume that it should stop on the pre-defined exception
4512 rather than the user-defined one. For instance, assuming an exception
4513 called @code{Constraint_Error} is defined in package @code{Pck}, then
4514 the command to use to catch such exceptions is @kbd{catch exception
4515 Pck.Constraint_Error}.
4518 @kindex catch handlers
4519 @cindex Ada exception handlers catching
4520 @cindex catch Ada exceptions when handled
4521 An Ada exception being handled. If an exception name is
4522 specified at the end of the command
4523 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4524 only when this specific exception is handled.
4525 Otherwise, the debugger stops execution when any Ada exception is handled.
4527 When inserting a handlers catchpoint on a user-defined
4528 exception whose name is identical to one of the exceptions
4529 defined by the language, the fully qualified name must be used
4530 as the exception name. Otherwise, @value{GDBN} will assume that it
4531 should stop on the pre-defined exception rather than the
4532 user-defined one. For instance, assuming an exception called
4533 @code{Constraint_Error} is defined in package @code{Pck}, then the
4534 command to use to catch such exceptions handling is
4535 @kbd{catch handlers Pck.Constraint_Error}.
4537 @item exception unhandled
4538 @kindex catch exception unhandled
4539 An exception that was raised but is not handled by the program.
4542 @kindex catch assert
4543 A failed Ada assertion.
4547 @cindex break on fork/exec
4548 A call to @code{exec}.
4551 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4552 @kindex catch syscall
4553 @cindex break on a system call.
4554 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4555 syscall is a mechanism for application programs to request a service
4556 from the operating system (OS) or one of the OS system services.
4557 @value{GDBN} can catch some or all of the syscalls issued by the
4558 debuggee, and show the related information for each syscall. If no
4559 argument is specified, calls to and returns from all system calls
4562 @var{name} can be any system call name that is valid for the
4563 underlying OS. Just what syscalls are valid depends on the OS. On
4564 GNU and Unix systems, you can find the full list of valid syscall
4565 names on @file{/usr/include/asm/unistd.h}.
4567 @c For MS-Windows, the syscall names and the corresponding numbers
4568 @c can be found, e.g., on this URL:
4569 @c http://www.metasploit.com/users/opcode/syscalls.html
4570 @c but we don't support Windows syscalls yet.
4572 Normally, @value{GDBN} knows in advance which syscalls are valid for
4573 each OS, so you can use the @value{GDBN} command-line completion
4574 facilities (@pxref{Completion,, command completion}) to list the
4577 You may also specify the system call numerically. A syscall's
4578 number is the value passed to the OS's syscall dispatcher to
4579 identify the requested service. When you specify the syscall by its
4580 name, @value{GDBN} uses its database of syscalls to convert the name
4581 into the corresponding numeric code, but using the number directly
4582 may be useful if @value{GDBN}'s database does not have the complete
4583 list of syscalls on your system (e.g., because @value{GDBN} lags
4584 behind the OS upgrades).
4586 You may specify a group of related syscalls to be caught at once using
4587 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4588 instance, on some platforms @value{GDBN} allows you to catch all
4589 network related syscalls, by passing the argument @code{group:network}
4590 to @code{catch syscall}. Note that not all syscall groups are
4591 available in every system. You can use the command completion
4592 facilities (@pxref{Completion,, command completion}) to list the
4593 syscall groups available on your environment.
4595 The example below illustrates how this command works if you don't provide
4599 (@value{GDBP}) catch syscall
4600 Catchpoint 1 (syscall)
4602 Starting program: /tmp/catch-syscall
4604 Catchpoint 1 (call to syscall 'close'), \
4605 0xffffe424 in __kernel_vsyscall ()
4609 Catchpoint 1 (returned from syscall 'close'), \
4610 0xffffe424 in __kernel_vsyscall ()
4614 Here is an example of catching a system call by name:
4617 (@value{GDBP}) catch syscall chroot
4618 Catchpoint 1 (syscall 'chroot' [61])
4620 Starting program: /tmp/catch-syscall
4622 Catchpoint 1 (call to syscall 'chroot'), \
4623 0xffffe424 in __kernel_vsyscall ()
4627 Catchpoint 1 (returned from syscall 'chroot'), \
4628 0xffffe424 in __kernel_vsyscall ()
4632 An example of specifying a system call numerically. In the case
4633 below, the syscall number has a corresponding entry in the XML
4634 file, so @value{GDBN} finds its name and prints it:
4637 (@value{GDBP}) catch syscall 252
4638 Catchpoint 1 (syscall(s) 'exit_group')
4640 Starting program: /tmp/catch-syscall
4642 Catchpoint 1 (call to syscall 'exit_group'), \
4643 0xffffe424 in __kernel_vsyscall ()
4647 Program exited normally.
4651 Here is an example of catching a syscall group:
4654 (@value{GDBP}) catch syscall group:process
4655 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4656 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4657 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4659 Starting program: /tmp/catch-syscall
4661 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4662 from /lib64/ld-linux-x86-64.so.2
4668 However, there can be situations when there is no corresponding name
4669 in XML file for that syscall number. In this case, @value{GDBN} prints
4670 a warning message saying that it was not able to find the syscall name,
4671 but the catchpoint will be set anyway. See the example below:
4674 (@value{GDBP}) catch syscall 764
4675 warning: The number '764' does not represent a known syscall.
4676 Catchpoint 2 (syscall 764)
4680 If you configure @value{GDBN} using the @samp{--without-expat} option,
4681 it will not be able to display syscall names. Also, if your
4682 architecture does not have an XML file describing its system calls,
4683 you will not be able to see the syscall names. It is important to
4684 notice that these two features are used for accessing the syscall
4685 name database. In either case, you will see a warning like this:
4688 (@value{GDBP}) catch syscall
4689 warning: Could not open "syscalls/i386-linux.xml"
4690 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4691 GDB will not be able to display syscall names.
4692 Catchpoint 1 (syscall)
4696 Of course, the file name will change depending on your architecture and system.
4698 Still using the example above, you can also try to catch a syscall by its
4699 number. In this case, you would see something like:
4702 (@value{GDBP}) catch syscall 252
4703 Catchpoint 1 (syscall(s) 252)
4706 Again, in this case @value{GDBN} would not be able to display syscall's names.
4710 A call to @code{fork}.
4714 A call to @code{vfork}.
4716 @item load @r{[}regexp@r{]}
4717 @itemx unload @r{[}regexp@r{]}
4719 @kindex catch unload
4720 The loading or unloading of a shared library. If @var{regexp} is
4721 given, then the catchpoint will stop only if the regular expression
4722 matches one of the affected libraries.
4724 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4725 @kindex catch signal
4726 The delivery of a signal.
4728 With no arguments, this catchpoint will catch any signal that is not
4729 used internally by @value{GDBN}, specifically, all signals except
4730 @samp{SIGTRAP} and @samp{SIGINT}.
4732 With the argument @samp{all}, all signals, including those used by
4733 @value{GDBN}, will be caught. This argument cannot be used with other
4736 Otherwise, the arguments are a list of signal names as given to
4737 @code{handle} (@pxref{Signals}). Only signals specified in this list
4740 One reason that @code{catch signal} can be more useful than
4741 @code{handle} is that you can attach commands and conditions to the
4744 When a signal is caught by a catchpoint, the signal's @code{stop} and
4745 @code{print} settings, as specified by @code{handle}, are ignored.
4746 However, whether the signal is still delivered to the inferior depends
4747 on the @code{pass} setting; this can be changed in the catchpoint's
4752 @item tcatch @var{event}
4754 Set a catchpoint that is enabled only for one stop. The catchpoint is
4755 automatically deleted after the first time the event is caught.
4759 Use the @code{info break} command to list the current catchpoints.
4763 @subsection Deleting Breakpoints
4765 @cindex clearing breakpoints, watchpoints, catchpoints
4766 @cindex deleting breakpoints, watchpoints, catchpoints
4767 It is often necessary to eliminate a breakpoint, watchpoint, or
4768 catchpoint once it has done its job and you no longer want your program
4769 to stop there. This is called @dfn{deleting} the breakpoint. A
4770 breakpoint that has been deleted no longer exists; it is forgotten.
4772 With the @code{clear} command you can delete breakpoints according to
4773 where they are in your program. With the @code{delete} command you can
4774 delete individual breakpoints, watchpoints, or catchpoints by specifying
4775 their breakpoint numbers.
4777 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4778 automatically ignores breakpoints on the first instruction to be executed
4779 when you continue execution without changing the execution address.
4784 Delete any breakpoints at the next instruction to be executed in the
4785 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4786 the innermost frame is selected, this is a good way to delete a
4787 breakpoint where your program just stopped.
4789 @item clear @var{location}
4790 Delete any breakpoints set at the specified @var{location}.
4791 @xref{Specify Location}, for the various forms of @var{location}; the
4792 most useful ones are listed below:
4795 @item clear @var{function}
4796 @itemx clear @var{filename}:@var{function}
4797 Delete any breakpoints set at entry to the named @var{function}.
4799 @item clear @var{linenum}
4800 @itemx clear @var{filename}:@var{linenum}
4801 Delete any breakpoints set at or within the code of the specified
4802 @var{linenum} of the specified @var{filename}.
4805 @cindex delete breakpoints
4807 @kindex d @r{(@code{delete})}
4808 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4809 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4810 list specified as argument. If no argument is specified, delete all
4811 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4812 confirm off}). You can abbreviate this command as @code{d}.
4816 @subsection Disabling Breakpoints
4818 @cindex enable/disable a breakpoint
4819 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4820 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4821 it had been deleted, but remembers the information on the breakpoint so
4822 that you can @dfn{enable} it again later.
4824 You disable and enable breakpoints, watchpoints, and catchpoints with
4825 the @code{enable} and @code{disable} commands, optionally specifying
4826 one or more breakpoint numbers as arguments. Use @code{info break} to
4827 print a list of all breakpoints, watchpoints, and catchpoints if you
4828 do not know which numbers to use.
4830 Disabling and enabling a breakpoint that has multiple locations
4831 affects all of its locations.
4833 A breakpoint, watchpoint, or catchpoint can have any of several
4834 different states of enablement:
4838 Enabled. The breakpoint stops your program. A breakpoint set
4839 with the @code{break} command starts out in this state.
4841 Disabled. The breakpoint has no effect on your program.
4843 Enabled once. The breakpoint stops your program, but then becomes
4846 Enabled for a count. The breakpoint stops your program for the next
4847 N times, then becomes disabled.
4849 Enabled for deletion. The breakpoint stops your program, but
4850 immediately after it does so it is deleted permanently. A breakpoint
4851 set with the @code{tbreak} command starts out in this state.
4854 You can use the following commands to enable or disable breakpoints,
4855 watchpoints, and catchpoints:
4859 @kindex dis @r{(@code{disable})}
4860 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4861 Disable the specified breakpoints---or all breakpoints, if none are
4862 listed. A disabled breakpoint has no effect but is not forgotten. All
4863 options such as ignore-counts, conditions and commands are remembered in
4864 case the breakpoint is enabled again later. You may abbreviate
4865 @code{disable} as @code{dis}.
4868 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4869 Enable the specified breakpoints (or all defined breakpoints). They
4870 become effective once again in stopping your program.
4872 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4873 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4874 of these breakpoints immediately after stopping your program.
4876 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4877 Enable the specified breakpoints temporarily. @value{GDBN} records
4878 @var{count} with each of the specified breakpoints, and decrements a
4879 breakpoint's count when it is hit. When any count reaches 0,
4880 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4881 count (@pxref{Conditions, ,Break Conditions}), that will be
4882 decremented to 0 before @var{count} is affected.
4884 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4885 Enable the specified breakpoints to work once, then die. @value{GDBN}
4886 deletes any of these breakpoints as soon as your program stops there.
4887 Breakpoints set by the @code{tbreak} command start out in this state.
4890 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4891 @c confusing: tbreak is also initially enabled.
4892 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4893 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4894 subsequently, they become disabled or enabled only when you use one of
4895 the commands above. (The command @code{until} can set and delete a
4896 breakpoint of its own, but it does not change the state of your other
4897 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4901 @subsection Break Conditions
4902 @cindex conditional breakpoints
4903 @cindex breakpoint conditions
4905 @c FIXME what is scope of break condition expr? Context where wanted?
4906 @c in particular for a watchpoint?
4907 The simplest sort of breakpoint breaks every time your program reaches a
4908 specified place. You can also specify a @dfn{condition} for a
4909 breakpoint. A condition is just a Boolean expression in your
4910 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4911 a condition evaluates the expression each time your program reaches it,
4912 and your program stops only if the condition is @emph{true}.
4914 This is the converse of using assertions for program validation; in that
4915 situation, you want to stop when the assertion is violated---that is,
4916 when the condition is false. In C, if you want to test an assertion expressed
4917 by the condition @var{assert}, you should set the condition
4918 @samp{! @var{assert}} on the appropriate breakpoint.
4920 Conditions are also accepted for watchpoints; you may not need them,
4921 since a watchpoint is inspecting the value of an expression anyhow---but
4922 it might be simpler, say, to just set a watchpoint on a variable name,
4923 and specify a condition that tests whether the new value is an interesting
4926 Break conditions can have side effects, and may even call functions in
4927 your program. This can be useful, for example, to activate functions
4928 that log program progress, or to use your own print functions to
4929 format special data structures. The effects are completely predictable
4930 unless there is another enabled breakpoint at the same address. (In
4931 that case, @value{GDBN} might see the other breakpoint first and stop your
4932 program without checking the condition of this one.) Note that
4933 breakpoint commands are usually more convenient and flexible than break
4935 purpose of performing side effects when a breakpoint is reached
4936 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4938 Breakpoint conditions can also be evaluated on the target's side if
4939 the target supports it. Instead of evaluating the conditions locally,
4940 @value{GDBN} encodes the expression into an agent expression
4941 (@pxref{Agent Expressions}) suitable for execution on the target,
4942 independently of @value{GDBN}. Global variables become raw memory
4943 locations, locals become stack accesses, and so forth.
4945 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4946 when its condition evaluates to true. This mechanism may provide faster
4947 response times depending on the performance characteristics of the target
4948 since it does not need to keep @value{GDBN} informed about
4949 every breakpoint trigger, even those with false conditions.
4951 Break conditions can be specified when a breakpoint is set, by using
4952 @samp{if} in the arguments to the @code{break} command. @xref{Set
4953 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4954 with the @code{condition} command.
4956 You can also use the @code{if} keyword with the @code{watch} command.
4957 The @code{catch} command does not recognize the @code{if} keyword;
4958 @code{condition} is the only way to impose a further condition on a
4963 @item condition @var{bnum} @var{expression}
4964 Specify @var{expression} as the break condition for breakpoint,
4965 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4966 breakpoint @var{bnum} stops your program only if the value of
4967 @var{expression} is true (nonzero, in C). When you use
4968 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4969 syntactic correctness, and to determine whether symbols in it have
4970 referents in the context of your breakpoint. If @var{expression} uses
4971 symbols not referenced in the context of the breakpoint, @value{GDBN}
4972 prints an error message:
4975 No symbol "foo" in current context.
4980 not actually evaluate @var{expression} at the time the @code{condition}
4981 command (or a command that sets a breakpoint with a condition, like
4982 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4984 @item condition @var{bnum}
4985 Remove the condition from breakpoint number @var{bnum}. It becomes
4986 an ordinary unconditional breakpoint.
4989 @cindex ignore count (of breakpoint)
4990 A special case of a breakpoint condition is to stop only when the
4991 breakpoint has been reached a certain number of times. This is so
4992 useful that there is a special way to do it, using the @dfn{ignore
4993 count} of the breakpoint. Every breakpoint has an ignore count, which
4994 is an integer. Most of the time, the ignore count is zero, and
4995 therefore has no effect. But if your program reaches a breakpoint whose
4996 ignore count is positive, then instead of stopping, it just decrements
4997 the ignore count by one and continues. As a result, if the ignore count
4998 value is @var{n}, the breakpoint does not stop the next @var{n} times
4999 your program reaches it.
5003 @item ignore @var{bnum} @var{count}
5004 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5005 The next @var{count} times the breakpoint is reached, your program's
5006 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5009 To make the breakpoint stop the next time it is reached, specify
5012 When you use @code{continue} to resume execution of your program from a
5013 breakpoint, you can specify an ignore count directly as an argument to
5014 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5015 Stepping,,Continuing and Stepping}.
5017 If a breakpoint has a positive ignore count and a condition, the
5018 condition is not checked. Once the ignore count reaches zero,
5019 @value{GDBN} resumes checking the condition.
5021 You could achieve the effect of the ignore count with a condition such
5022 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5023 is decremented each time. @xref{Convenience Vars, ,Convenience
5027 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5030 @node Break Commands
5031 @subsection Breakpoint Command Lists
5033 @cindex breakpoint commands
5034 You can give any breakpoint (or watchpoint or catchpoint) a series of
5035 commands to execute when your program stops due to that breakpoint. For
5036 example, you might want to print the values of certain expressions, or
5037 enable other breakpoints.
5041 @kindex end@r{ (breakpoint commands)}
5042 @item commands @r{[}@var{list}@dots{}@r{]}
5043 @itemx @dots{} @var{command-list} @dots{}
5045 Specify a list of commands for the given breakpoints. The commands
5046 themselves appear on the following lines. Type a line containing just
5047 @code{end} to terminate the commands.
5049 To remove all commands from a breakpoint, type @code{commands} and
5050 follow it immediately with @code{end}; that is, give no commands.
5052 With no argument, @code{commands} refers to the last breakpoint,
5053 watchpoint, or catchpoint set (not to the breakpoint most recently
5054 encountered). If the most recent breakpoints were set with a single
5055 command, then the @code{commands} will apply to all the breakpoints
5056 set by that command. This applies to breakpoints set by
5057 @code{rbreak}, and also applies when a single @code{break} command
5058 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5062 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5063 disabled within a @var{command-list}.
5065 You can use breakpoint commands to start your program up again. Simply
5066 use the @code{continue} command, or @code{step}, or any other command
5067 that resumes execution.
5069 Any other commands in the command list, after a command that resumes
5070 execution, are ignored. This is because any time you resume execution
5071 (even with a simple @code{next} or @code{step}), you may encounter
5072 another breakpoint---which could have its own command list, leading to
5073 ambiguities about which list to execute.
5076 If the first command you specify in a command list is @code{silent}, the
5077 usual message about stopping at a breakpoint is not printed. This may
5078 be desirable for breakpoints that are to print a specific message and
5079 then continue. If none of the remaining commands print anything, you
5080 see no sign that the breakpoint was reached. @code{silent} is
5081 meaningful only at the beginning of a breakpoint command list.
5083 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5084 print precisely controlled output, and are often useful in silent
5085 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5087 For example, here is how you could use breakpoint commands to print the
5088 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5094 printf "x is %d\n",x
5099 One application for breakpoint commands is to compensate for one bug so
5100 you can test for another. Put a breakpoint just after the erroneous line
5101 of code, give it a condition to detect the case in which something
5102 erroneous has been done, and give it commands to assign correct values
5103 to any variables that need them. End with the @code{continue} command
5104 so that your program does not stop, and start with the @code{silent}
5105 command so that no output is produced. Here is an example:
5116 @node Dynamic Printf
5117 @subsection Dynamic Printf
5119 @cindex dynamic printf
5121 The dynamic printf command @code{dprintf} combines a breakpoint with
5122 formatted printing of your program's data to give you the effect of
5123 inserting @code{printf} calls into your program on-the-fly, without
5124 having to recompile it.
5126 In its most basic form, the output goes to the GDB console. However,
5127 you can set the variable @code{dprintf-style} for alternate handling.
5128 For instance, you can ask to format the output by calling your
5129 program's @code{printf} function. This has the advantage that the
5130 characters go to the program's output device, so they can recorded in
5131 redirects to files and so forth.
5133 If you are doing remote debugging with a stub or agent, you can also
5134 ask to have the printf handled by the remote agent. In addition to
5135 ensuring that the output goes to the remote program's device along
5136 with any other output the program might produce, you can also ask that
5137 the dprintf remain active even after disconnecting from the remote
5138 target. Using the stub/agent is also more efficient, as it can do
5139 everything without needing to communicate with @value{GDBN}.
5143 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5144 Whenever execution reaches @var{location}, print the values of one or
5145 more @var{expressions} under the control of the string @var{template}.
5146 To print several values, separate them with commas.
5148 @item set dprintf-style @var{style}
5149 Set the dprintf output to be handled in one of several different
5150 styles enumerated below. A change of style affects all existing
5151 dynamic printfs immediately. (If you need individual control over the
5152 print commands, simply define normal breakpoints with
5153 explicitly-supplied command lists.)
5157 @kindex dprintf-style gdb
5158 Handle the output using the @value{GDBN} @code{printf} command.
5161 @kindex dprintf-style call
5162 Handle the output by calling a function in your program (normally
5166 @kindex dprintf-style agent
5167 Have the remote debugging agent (such as @code{gdbserver}) handle
5168 the output itself. This style is only available for agents that
5169 support running commands on the target.
5172 @item set dprintf-function @var{function}
5173 Set the function to call if the dprintf style is @code{call}. By
5174 default its value is @code{printf}. You may set it to any expression.
5175 that @value{GDBN} can evaluate to a function, as per the @code{call}
5178 @item set dprintf-channel @var{channel}
5179 Set a ``channel'' for dprintf. If set to a non-empty value,
5180 @value{GDBN} will evaluate it as an expression and pass the result as
5181 a first argument to the @code{dprintf-function}, in the manner of
5182 @code{fprintf} and similar functions. Otherwise, the dprintf format
5183 string will be the first argument, in the manner of @code{printf}.
5185 As an example, if you wanted @code{dprintf} output to go to a logfile
5186 that is a standard I/O stream assigned to the variable @code{mylog},
5187 you could do the following:
5190 (gdb) set dprintf-style call
5191 (gdb) set dprintf-function fprintf
5192 (gdb) set dprintf-channel mylog
5193 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5194 Dprintf 1 at 0x123456: file main.c, line 25.
5196 1 dprintf keep y 0x00123456 in main at main.c:25
5197 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5202 Note that the @code{info break} displays the dynamic printf commands
5203 as normal breakpoint commands; you can thus easily see the effect of
5204 the variable settings.
5206 @item set disconnected-dprintf on
5207 @itemx set disconnected-dprintf off
5208 @kindex set disconnected-dprintf
5209 Choose whether @code{dprintf} commands should continue to run if
5210 @value{GDBN} has disconnected from the target. This only applies
5211 if the @code{dprintf-style} is @code{agent}.
5213 @item show disconnected-dprintf off
5214 @kindex show disconnected-dprintf
5215 Show the current choice for disconnected @code{dprintf}.
5219 @value{GDBN} does not check the validity of function and channel,
5220 relying on you to supply values that are meaningful for the contexts
5221 in which they are being used. For instance, the function and channel
5222 may be the values of local variables, but if that is the case, then
5223 all enabled dynamic prints must be at locations within the scope of
5224 those locals. If evaluation fails, @value{GDBN} will report an error.
5226 @node Save Breakpoints
5227 @subsection How to save breakpoints to a file
5229 To save breakpoint definitions to a file use the @w{@code{save
5230 breakpoints}} command.
5233 @kindex save breakpoints
5234 @cindex save breakpoints to a file for future sessions
5235 @item save breakpoints [@var{filename}]
5236 This command saves all current breakpoint definitions together with
5237 their commands and ignore counts, into a file @file{@var{filename}}
5238 suitable for use in a later debugging session. This includes all
5239 types of breakpoints (breakpoints, watchpoints, catchpoints,
5240 tracepoints). To read the saved breakpoint definitions, use the
5241 @code{source} command (@pxref{Command Files}). Note that watchpoints
5242 with expressions involving local variables may fail to be recreated
5243 because it may not be possible to access the context where the
5244 watchpoint is valid anymore. Because the saved breakpoint definitions
5245 are simply a sequence of @value{GDBN} commands that recreate the
5246 breakpoints, you can edit the file in your favorite editing program,
5247 and remove the breakpoint definitions you're not interested in, or
5248 that can no longer be recreated.
5251 @node Static Probe Points
5252 @subsection Static Probe Points
5254 @cindex static probe point, SystemTap
5255 @cindex static probe point, DTrace
5256 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5257 for Statically Defined Tracing, and the probes are designed to have a tiny
5258 runtime code and data footprint, and no dynamic relocations.
5260 Currently, the following types of probes are supported on
5261 ELF-compatible systems:
5265 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5266 @acronym{SDT} probes@footnote{See
5267 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5268 for more information on how to add @code{SystemTap} @acronym{SDT}
5269 probes in your applications.}. @code{SystemTap} probes are usable
5270 from assembly, C and C@t{++} languages@footnote{See
5271 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5272 for a good reference on how the @acronym{SDT} probes are implemented.}.
5274 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5275 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5279 @cindex semaphores on static probe points
5280 Some @code{SystemTap} probes have an associated semaphore variable;
5281 for instance, this happens automatically if you defined your probe
5282 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5283 @value{GDBN} will automatically enable it when you specify a
5284 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5285 breakpoint at a probe's location by some other method (e.g.,
5286 @code{break file:line}), then @value{GDBN} will not automatically set
5287 the semaphore. @code{DTrace} probes do not support semaphores.
5289 You can examine the available static static probes using @code{info
5290 probes}, with optional arguments:
5294 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5295 If given, @var{type} is either @code{stap} for listing
5296 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5297 probes. If omitted all probes are listed regardless of their types.
5299 If given, @var{provider} is a regular expression used to match against provider
5300 names when selecting which probes to list. If omitted, probes by all
5301 probes from all providers are listed.
5303 If given, @var{name} is a regular expression to match against probe names
5304 when selecting which probes to list. If omitted, probe names are not
5305 considered when deciding whether to display them.
5307 If given, @var{objfile} is a regular expression used to select which
5308 object files (executable or shared libraries) to examine. If not
5309 given, all object files are considered.
5311 @item info probes all
5312 List the available static probes, from all types.
5315 @cindex enabling and disabling probes
5316 Some probe points can be enabled and/or disabled. The effect of
5317 enabling or disabling a probe depends on the type of probe being
5318 handled. Some @code{DTrace} probes can be enabled or
5319 disabled, but @code{SystemTap} probes cannot be disabled.
5321 You can enable (or disable) one or more probes using the following
5322 commands, with optional arguments:
5325 @kindex enable probes
5326 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5327 If given, @var{provider} is a regular expression used to match against
5328 provider names when selecting which probes to enable. If omitted,
5329 all probes from all providers are enabled.
5331 If given, @var{name} is a regular expression to match against probe
5332 names when selecting which probes to enable. If omitted, probe names
5333 are not considered when deciding whether to enable them.
5335 If given, @var{objfile} is a regular expression used to select which
5336 object files (executable or shared libraries) to examine. If not
5337 given, all object files are considered.
5339 @kindex disable probes
5340 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5341 See the @code{enable probes} command above for a description of the
5342 optional arguments accepted by this command.
5345 @vindex $_probe_arg@r{, convenience variable}
5346 A probe may specify up to twelve arguments. These are available at the
5347 point at which the probe is defined---that is, when the current PC is
5348 at the probe's location. The arguments are available using the
5349 convenience variables (@pxref{Convenience Vars})
5350 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5351 probes each probe argument is an integer of the appropriate size;
5352 types are not preserved. In @code{DTrace} probes types are preserved
5353 provided that they are recognized as such by @value{GDBN}; otherwise
5354 the value of the probe argument will be a long integer. The
5355 convenience variable @code{$_probe_argc} holds the number of arguments
5356 at the current probe point.
5358 These variables are always available, but attempts to access them at
5359 any location other than a probe point will cause @value{GDBN} to give
5363 @c @ifclear BARETARGET
5364 @node Error in Breakpoints
5365 @subsection ``Cannot insert breakpoints''
5367 If you request too many active hardware-assisted breakpoints and
5368 watchpoints, you will see this error message:
5370 @c FIXME: the precise wording of this message may change; the relevant
5371 @c source change is not committed yet (Sep 3, 1999).
5373 Stopped; cannot insert breakpoints.
5374 You may have requested too many hardware breakpoints and watchpoints.
5378 This message is printed when you attempt to resume the program, since
5379 only then @value{GDBN} knows exactly how many hardware breakpoints and
5380 watchpoints it needs to insert.
5382 When this message is printed, you need to disable or remove some of the
5383 hardware-assisted breakpoints and watchpoints, and then continue.
5385 @node Breakpoint-related Warnings
5386 @subsection ``Breakpoint address adjusted...''
5387 @cindex breakpoint address adjusted
5389 Some processor architectures place constraints on the addresses at
5390 which breakpoints may be placed. For architectures thus constrained,
5391 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5392 with the constraints dictated by the architecture.
5394 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5395 a VLIW architecture in which a number of RISC-like instructions may be
5396 bundled together for parallel execution. The FR-V architecture
5397 constrains the location of a breakpoint instruction within such a
5398 bundle to the instruction with the lowest address. @value{GDBN}
5399 honors this constraint by adjusting a breakpoint's address to the
5400 first in the bundle.
5402 It is not uncommon for optimized code to have bundles which contain
5403 instructions from different source statements, thus it may happen that
5404 a breakpoint's address will be adjusted from one source statement to
5405 another. Since this adjustment may significantly alter @value{GDBN}'s
5406 breakpoint related behavior from what the user expects, a warning is
5407 printed when the breakpoint is first set and also when the breakpoint
5410 A warning like the one below is printed when setting a breakpoint
5411 that's been subject to address adjustment:
5414 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5417 Such warnings are printed both for user settable and @value{GDBN}'s
5418 internal breakpoints. If you see one of these warnings, you should
5419 verify that a breakpoint set at the adjusted address will have the
5420 desired affect. If not, the breakpoint in question may be removed and
5421 other breakpoints may be set which will have the desired behavior.
5422 E.g., it may be sufficient to place the breakpoint at a later
5423 instruction. A conditional breakpoint may also be useful in some
5424 cases to prevent the breakpoint from triggering too often.
5426 @value{GDBN} will also issue a warning when stopping at one of these
5427 adjusted breakpoints:
5430 warning: Breakpoint 1 address previously adjusted from 0x00010414
5434 When this warning is encountered, it may be too late to take remedial
5435 action except in cases where the breakpoint is hit earlier or more
5436 frequently than expected.
5438 @node Continuing and Stepping
5439 @section Continuing and Stepping
5443 @cindex resuming execution
5444 @dfn{Continuing} means resuming program execution until your program
5445 completes normally. In contrast, @dfn{stepping} means executing just
5446 one more ``step'' of your program, where ``step'' may mean either one
5447 line of source code, or one machine instruction (depending on what
5448 particular command you use). Either when continuing or when stepping,
5449 your program may stop even sooner, due to a breakpoint or a signal. (If
5450 it stops due to a signal, you may want to use @code{handle}, or use
5451 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5452 or you may step into the signal's handler (@pxref{stepping and signal
5457 @kindex c @r{(@code{continue})}
5458 @kindex fg @r{(resume foreground execution)}
5459 @item continue @r{[}@var{ignore-count}@r{]}
5460 @itemx c @r{[}@var{ignore-count}@r{]}
5461 @itemx fg @r{[}@var{ignore-count}@r{]}
5462 Resume program execution, at the address where your program last stopped;
5463 any breakpoints set at that address are bypassed. The optional argument
5464 @var{ignore-count} allows you to specify a further number of times to
5465 ignore a breakpoint at this location; its effect is like that of
5466 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5468 The argument @var{ignore-count} is meaningful only when your program
5469 stopped due to a breakpoint. At other times, the argument to
5470 @code{continue} is ignored.
5472 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5473 debugged program is deemed to be the foreground program) are provided
5474 purely for convenience, and have exactly the same behavior as
5478 To resume execution at a different place, you can use @code{return}
5479 (@pxref{Returning, ,Returning from a Function}) to go back to the
5480 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5481 Different Address}) to go to an arbitrary location in your program.
5483 A typical technique for using stepping is to set a breakpoint
5484 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5485 beginning of the function or the section of your program where a problem
5486 is believed to lie, run your program until it stops at that breakpoint,
5487 and then step through the suspect area, examining the variables that are
5488 interesting, until you see the problem happen.
5492 @kindex s @r{(@code{step})}
5494 Continue running your program until control reaches a different source
5495 line, then stop it and return control to @value{GDBN}. This command is
5496 abbreviated @code{s}.
5499 @c "without debugging information" is imprecise; actually "without line
5500 @c numbers in the debugging information". (gcc -g1 has debugging info but
5501 @c not line numbers). But it seems complex to try to make that
5502 @c distinction here.
5503 @emph{Warning:} If you use the @code{step} command while control is
5504 within a function that was compiled without debugging information,
5505 execution proceeds until control reaches a function that does have
5506 debugging information. Likewise, it will not step into a function which
5507 is compiled without debugging information. To step through functions
5508 without debugging information, use the @code{stepi} command, described
5512 The @code{step} command only stops at the first instruction of a source
5513 line. This prevents the multiple stops that could otherwise occur in
5514 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5515 to stop if a function that has debugging information is called within
5516 the line. In other words, @code{step} @emph{steps inside} any functions
5517 called within the line.
5519 Also, the @code{step} command only enters a function if there is line
5520 number information for the function. Otherwise it acts like the
5521 @code{next} command. This avoids problems when using @code{cc -gl}
5522 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5523 was any debugging information about the routine.
5525 @item step @var{count}
5526 Continue running as in @code{step}, but do so @var{count} times. If a
5527 breakpoint is reached, or a signal not related to stepping occurs before
5528 @var{count} steps, stepping stops right away.
5531 @kindex n @r{(@code{next})}
5532 @item next @r{[}@var{count}@r{]}
5533 Continue to the next source line in the current (innermost) stack frame.
5534 This is similar to @code{step}, but function calls that appear within
5535 the line of code are executed without stopping. Execution stops when
5536 control reaches a different line of code at the original stack level
5537 that was executing when you gave the @code{next} command. This command
5538 is abbreviated @code{n}.
5540 An argument @var{count} is a repeat count, as for @code{step}.
5543 @c FIX ME!! Do we delete this, or is there a way it fits in with
5544 @c the following paragraph? --- Vctoria
5546 @c @code{next} within a function that lacks debugging information acts like
5547 @c @code{step}, but any function calls appearing within the code of the
5548 @c function are executed without stopping.
5550 The @code{next} command only stops at the first instruction of a
5551 source line. This prevents multiple stops that could otherwise occur in
5552 @code{switch} statements, @code{for} loops, etc.
5554 @kindex set step-mode
5556 @cindex functions without line info, and stepping
5557 @cindex stepping into functions with no line info
5558 @itemx set step-mode on
5559 The @code{set step-mode on} command causes the @code{step} command to
5560 stop at the first instruction of a function which contains no debug line
5561 information rather than stepping over it.
5563 This is useful in cases where you may be interested in inspecting the
5564 machine instructions of a function which has no symbolic info and do not
5565 want @value{GDBN} to automatically skip over this function.
5567 @item set step-mode off
5568 Causes the @code{step} command to step over any functions which contains no
5569 debug information. This is the default.
5571 @item show step-mode
5572 Show whether @value{GDBN} will stop in or step over functions without
5573 source line debug information.
5576 @kindex fin @r{(@code{finish})}
5578 Continue running until just after function in the selected stack frame
5579 returns. Print the returned value (if any). This command can be
5580 abbreviated as @code{fin}.
5582 Contrast this with the @code{return} command (@pxref{Returning,
5583 ,Returning from a Function}).
5586 @kindex u @r{(@code{until})}
5587 @cindex run until specified location
5590 Continue running until a source line past the current line, in the
5591 current stack frame, is reached. This command is used to avoid single
5592 stepping through a loop more than once. It is like the @code{next}
5593 command, except that when @code{until} encounters a jump, it
5594 automatically continues execution until the program counter is greater
5595 than the address of the jump.
5597 This means that when you reach the end of a loop after single stepping
5598 though it, @code{until} makes your program continue execution until it
5599 exits the loop. In contrast, a @code{next} command at the end of a loop
5600 simply steps back to the beginning of the loop, which forces you to step
5601 through the next iteration.
5603 @code{until} always stops your program if it attempts to exit the current
5606 @code{until} may produce somewhat counterintuitive results if the order
5607 of machine code does not match the order of the source lines. For
5608 example, in the following excerpt from a debugging session, the @code{f}
5609 (@code{frame}) command shows that execution is stopped at line
5610 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5614 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5616 (@value{GDBP}) until
5617 195 for ( ; argc > 0; NEXTARG) @{
5620 This happened because, for execution efficiency, the compiler had
5621 generated code for the loop closure test at the end, rather than the
5622 start, of the loop---even though the test in a C @code{for}-loop is
5623 written before the body of the loop. The @code{until} command appeared
5624 to step back to the beginning of the loop when it advanced to this
5625 expression; however, it has not really gone to an earlier
5626 statement---not in terms of the actual machine code.
5628 @code{until} with no argument works by means of single
5629 instruction stepping, and hence is slower than @code{until} with an
5632 @item until @var{location}
5633 @itemx u @var{location}
5634 Continue running your program until either the specified @var{location} is
5635 reached, or the current stack frame returns. The location is any of
5636 the forms described in @ref{Specify Location}.
5637 This form of the command uses temporary breakpoints, and
5638 hence is quicker than @code{until} without an argument. The specified
5639 location is actually reached only if it is in the current frame. This
5640 implies that @code{until} can be used to skip over recursive function
5641 invocations. For instance in the code below, if the current location is
5642 line @code{96}, issuing @code{until 99} will execute the program up to
5643 line @code{99} in the same invocation of factorial, i.e., after the inner
5644 invocations have returned.
5647 94 int factorial (int value)
5649 96 if (value > 1) @{
5650 97 value *= factorial (value - 1);
5657 @kindex advance @var{location}
5658 @item advance @var{location}
5659 Continue running the program up to the given @var{location}. An argument is
5660 required, which should be of one of the forms described in
5661 @ref{Specify Location}.
5662 Execution will also stop upon exit from the current stack
5663 frame. This command is similar to @code{until}, but @code{advance} will
5664 not skip over recursive function calls, and the target location doesn't
5665 have to be in the same frame as the current one.
5669 @kindex si @r{(@code{stepi})}
5671 @itemx stepi @var{arg}
5673 Execute one machine instruction, then stop and return to the debugger.
5675 It is often useful to do @samp{display/i $pc} when stepping by machine
5676 instructions. This makes @value{GDBN} automatically display the next
5677 instruction to be executed, each time your program stops. @xref{Auto
5678 Display,, Automatic Display}.
5680 An argument is a repeat count, as in @code{step}.
5684 @kindex ni @r{(@code{nexti})}
5686 @itemx nexti @var{arg}
5688 Execute one machine instruction, but if it is a function call,
5689 proceed until the function returns.
5691 An argument is a repeat count, as in @code{next}.
5695 @anchor{range stepping}
5696 @cindex range stepping
5697 @cindex target-assisted range stepping
5698 By default, and if available, @value{GDBN} makes use of
5699 target-assisted @dfn{range stepping}. In other words, whenever you
5700 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5701 tells the target to step the corresponding range of instruction
5702 addresses instead of issuing multiple single-steps. This speeds up
5703 line stepping, particularly for remote targets. Ideally, there should
5704 be no reason you would want to turn range stepping off. However, it's
5705 possible that a bug in the debug info, a bug in the remote stub (for
5706 remote targets), or even a bug in @value{GDBN} could make line
5707 stepping behave incorrectly when target-assisted range stepping is
5708 enabled. You can use the following command to turn off range stepping
5712 @kindex set range-stepping
5713 @kindex show range-stepping
5714 @item set range-stepping
5715 @itemx show range-stepping
5716 Control whether range stepping is enabled.
5718 If @code{on}, and the target supports it, @value{GDBN} tells the
5719 target to step a range of addresses itself, instead of issuing
5720 multiple single-steps. If @code{off}, @value{GDBN} always issues
5721 single-steps, even if range stepping is supported by the target. The
5722 default is @code{on}.
5726 @node Skipping Over Functions and Files
5727 @section Skipping Over Functions and Files
5728 @cindex skipping over functions and files
5730 The program you are debugging may contain some functions which are
5731 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5732 skip a function, all functions in a file or a particular function in
5733 a particular file when stepping.
5735 For example, consider the following C function:
5746 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5747 are not interested in stepping through @code{boring}. If you run @code{step}
5748 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5749 step over both @code{foo} and @code{boring}!
5751 One solution is to @code{step} into @code{boring} and use the @code{finish}
5752 command to immediately exit it. But this can become tedious if @code{boring}
5753 is called from many places.
5755 A more flexible solution is to execute @kbd{skip boring}. This instructs
5756 @value{GDBN} never to step into @code{boring}. Now when you execute
5757 @code{step} at line 103, you'll step over @code{boring} and directly into
5760 Functions may be skipped by providing either a function name, linespec
5761 (@pxref{Specify Location}), regular expression that matches the function's
5762 name, file name or a @code{glob}-style pattern that matches the file name.
5764 On Posix systems the form of the regular expression is
5765 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5766 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5767 expression is whatever is provided by the @code{regcomp} function of
5768 the underlying system.
5769 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5770 description of @code{glob}-style patterns.
5774 @item skip @r{[}@var{options}@r{]}
5775 The basic form of the @code{skip} command takes zero or more options
5776 that specify what to skip.
5777 The @var{options} argument is any useful combination of the following:
5780 @item -file @var{file}
5781 @itemx -fi @var{file}
5782 Functions in @var{file} will be skipped over when stepping.
5784 @item -gfile @var{file-glob-pattern}
5785 @itemx -gfi @var{file-glob-pattern}
5786 @cindex skipping over files via glob-style patterns
5787 Functions in files matching @var{file-glob-pattern} will be skipped
5791 (gdb) skip -gfi utils/*.c
5794 @item -function @var{linespec}
5795 @itemx -fu @var{linespec}
5796 Functions named by @var{linespec} or the function containing the line
5797 named by @var{linespec} will be skipped over when stepping.
5798 @xref{Specify Location}.
5800 @item -rfunction @var{regexp}
5801 @itemx -rfu @var{regexp}
5802 @cindex skipping over functions via regular expressions
5803 Functions whose name matches @var{regexp} will be skipped over when stepping.
5805 This form is useful for complex function names.
5806 For example, there is generally no need to step into C@t{++} @code{std::string}
5807 constructors or destructors. Plus with C@t{++} templates it can be hard to
5808 write out the full name of the function, and often it doesn't matter what
5809 the template arguments are. Specifying the function to be skipped as a
5810 regular expression makes this easier.
5813 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5816 If you want to skip every templated C@t{++} constructor and destructor
5817 in the @code{std} namespace you can do:
5820 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5824 If no options are specified, the function you're currently debugging
5827 @kindex skip function
5828 @item skip function @r{[}@var{linespec}@r{]}
5829 After running this command, the function named by @var{linespec} or the
5830 function containing the line named by @var{linespec} will be skipped over when
5831 stepping. @xref{Specify Location}.
5833 If you do not specify @var{linespec}, the function you're currently debugging
5836 (If you have a function called @code{file} that you want to skip, use
5837 @kbd{skip function file}.)
5840 @item skip file @r{[}@var{filename}@r{]}
5841 After running this command, any function whose source lives in @var{filename}
5842 will be skipped over when stepping.
5845 (gdb) skip file boring.c
5846 File boring.c will be skipped when stepping.
5849 If you do not specify @var{filename}, functions whose source lives in the file
5850 you're currently debugging will be skipped.
5853 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5854 These are the commands for managing your list of skips:
5858 @item info skip @r{[}@var{range}@r{]}
5859 Print details about the specified skip(s). If @var{range} is not specified,
5860 print a table with details about all functions and files marked for skipping.
5861 @code{info skip} prints the following information about each skip:
5865 A number identifying this skip.
5866 @item Enabled or Disabled
5867 Enabled skips are marked with @samp{y}.
5868 Disabled skips are marked with @samp{n}.
5870 If the file name is a @samp{glob} pattern this is @samp{y}.
5871 Otherwise it is @samp{n}.
5873 The name or @samp{glob} pattern of the file to be skipped.
5874 If no file is specified this is @samp{<none>}.
5876 If the function name is a @samp{regular expression} this is @samp{y}.
5877 Otherwise it is @samp{n}.
5879 The name or regular expression of the function to skip.
5880 If no function is specified this is @samp{<none>}.
5884 @item skip delete @r{[}@var{range}@r{]}
5885 Delete the specified skip(s). If @var{range} is not specified, delete all
5889 @item skip enable @r{[}@var{range}@r{]}
5890 Enable the specified skip(s). If @var{range} is not specified, enable all
5893 @kindex skip disable
5894 @item skip disable @r{[}@var{range}@r{]}
5895 Disable the specified skip(s). If @var{range} is not specified, disable all
5904 A signal is an asynchronous event that can happen in a program. The
5905 operating system defines the possible kinds of signals, and gives each
5906 kind a name and a number. For example, in Unix @code{SIGINT} is the
5907 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5908 @code{SIGSEGV} is the signal a program gets from referencing a place in
5909 memory far away from all the areas in use; @code{SIGALRM} occurs when
5910 the alarm clock timer goes off (which happens only if your program has
5911 requested an alarm).
5913 @cindex fatal signals
5914 Some signals, including @code{SIGALRM}, are a normal part of the
5915 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5916 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5917 program has not specified in advance some other way to handle the signal.
5918 @code{SIGINT} does not indicate an error in your program, but it is normally
5919 fatal so it can carry out the purpose of the interrupt: to kill the program.
5921 @value{GDBN} has the ability to detect any occurrence of a signal in your
5922 program. You can tell @value{GDBN} in advance what to do for each kind of
5925 @cindex handling signals
5926 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5927 @code{SIGALRM} be silently passed to your program
5928 (so as not to interfere with their role in the program's functioning)
5929 but to stop your program immediately whenever an error signal happens.
5930 You can change these settings with the @code{handle} command.
5933 @kindex info signals
5937 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5938 handle each one. You can use this to see the signal numbers of all
5939 the defined types of signals.
5941 @item info signals @var{sig}
5942 Similar, but print information only about the specified signal number.
5944 @code{info handle} is an alias for @code{info signals}.
5946 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5947 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5948 for details about this command.
5951 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5952 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5953 can be the number of a signal or its name (with or without the
5954 @samp{SIG} at the beginning); a list of signal numbers of the form
5955 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5956 known signals. Optional arguments @var{keywords}, described below,
5957 say what change to make.
5961 The keywords allowed by the @code{handle} command can be abbreviated.
5962 Their full names are:
5966 @value{GDBN} should not stop your program when this signal happens. It may
5967 still print a message telling you that the signal has come in.
5970 @value{GDBN} should stop your program when this signal happens. This implies
5971 the @code{print} keyword as well.
5974 @value{GDBN} should print a message when this signal happens.
5977 @value{GDBN} should not mention the occurrence of the signal at all. This
5978 implies the @code{nostop} keyword as well.
5982 @value{GDBN} should allow your program to see this signal; your program
5983 can handle the signal, or else it may terminate if the signal is fatal
5984 and not handled. @code{pass} and @code{noignore} are synonyms.
5988 @value{GDBN} should not allow your program to see this signal.
5989 @code{nopass} and @code{ignore} are synonyms.
5993 When a signal stops your program, the signal is not visible to the
5995 continue. Your program sees the signal then, if @code{pass} is in
5996 effect for the signal in question @emph{at that time}. In other words,
5997 after @value{GDBN} reports a signal, you can use the @code{handle}
5998 command with @code{pass} or @code{nopass} to control whether your
5999 program sees that signal when you continue.
6001 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6002 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6003 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6006 You can also use the @code{signal} command to prevent your program from
6007 seeing a signal, or cause it to see a signal it normally would not see,
6008 or to give it any signal at any time. For example, if your program stopped
6009 due to some sort of memory reference error, you might store correct
6010 values into the erroneous variables and continue, hoping to see more
6011 execution; but your program would probably terminate immediately as
6012 a result of the fatal signal once it saw the signal. To prevent this,
6013 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6016 @cindex stepping and signal handlers
6017 @anchor{stepping and signal handlers}
6019 @value{GDBN} optimizes for stepping the mainline code. If a signal
6020 that has @code{handle nostop} and @code{handle pass} set arrives while
6021 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6022 in progress, @value{GDBN} lets the signal handler run and then resumes
6023 stepping the mainline code once the signal handler returns. In other
6024 words, @value{GDBN} steps over the signal handler. This prevents
6025 signals that you've specified as not interesting (with @code{handle
6026 nostop}) from changing the focus of debugging unexpectedly. Note that
6027 the signal handler itself may still hit a breakpoint, stop for another
6028 signal that has @code{handle stop} in effect, or for any other event
6029 that normally results in stopping the stepping command sooner. Also
6030 note that @value{GDBN} still informs you that the program received a
6031 signal if @code{handle print} is set.
6033 @anchor{stepping into signal handlers}
6035 If you set @code{handle pass} for a signal, and your program sets up a
6036 handler for it, then issuing a stepping command, such as @code{step}
6037 or @code{stepi}, when your program is stopped due to the signal will
6038 step @emph{into} the signal handler (if the target supports that).
6040 Likewise, if you use the @code{queue-signal} command to queue a signal
6041 to be delivered to the current thread when execution of the thread
6042 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6043 stepping command will step into the signal handler.
6045 Here's an example, using @code{stepi} to step to the first instruction
6046 of @code{SIGUSR1}'s handler:
6049 (@value{GDBP}) handle SIGUSR1
6050 Signal Stop Print Pass to program Description
6051 SIGUSR1 Yes Yes Yes User defined signal 1
6055 Program received signal SIGUSR1, User defined signal 1.
6056 main () sigusr1.c:28
6059 sigusr1_handler () at sigusr1.c:9
6063 The same, but using @code{queue-signal} instead of waiting for the
6064 program to receive the signal first:
6069 (@value{GDBP}) queue-signal SIGUSR1
6071 sigusr1_handler () at sigusr1.c:9
6076 @cindex extra signal information
6077 @anchor{extra signal information}
6079 On some targets, @value{GDBN} can inspect extra signal information
6080 associated with the intercepted signal, before it is actually
6081 delivered to the program being debugged. This information is exported
6082 by the convenience variable @code{$_siginfo}, and consists of data
6083 that is passed by the kernel to the signal handler at the time of the
6084 receipt of a signal. The data type of the information itself is
6085 target dependent. You can see the data type using the @code{ptype
6086 $_siginfo} command. On Unix systems, it typically corresponds to the
6087 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6090 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6091 referenced address that raised a segmentation fault.
6095 (@value{GDBP}) continue
6096 Program received signal SIGSEGV, Segmentation fault.
6097 0x0000000000400766 in main ()
6099 (@value{GDBP}) ptype $_siginfo
6106 struct @{...@} _kill;
6107 struct @{...@} _timer;
6109 struct @{...@} _sigchld;
6110 struct @{...@} _sigfault;
6111 struct @{...@} _sigpoll;
6114 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6118 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6119 $1 = (void *) 0x7ffff7ff7000
6123 Depending on target support, @code{$_siginfo} may also be writable.
6125 @cindex Intel MPX boundary violations
6126 @cindex boundary violations, Intel MPX
6127 On some targets, a @code{SIGSEGV} can be caused by a boundary
6128 violation, i.e., accessing an address outside of the allowed range.
6129 In those cases @value{GDBN} may displays additional information,
6130 depending on how @value{GDBN} has been told to handle the signal.
6131 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6132 kind: "Upper" or "Lower", the memory address accessed and the
6133 bounds, while with @code{handle nostop SIGSEGV} no additional
6134 information is displayed.
6136 The usual output of a segfault is:
6138 Program received signal SIGSEGV, Segmentation fault
6139 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6140 68 value = *(p + len);
6143 While a bound violation is presented as:
6145 Program received signal SIGSEGV, Segmentation fault
6146 Upper bound violation while accessing address 0x7fffffffc3b3
6147 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6148 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6149 68 value = *(p + len);
6153 @section Stopping and Starting Multi-thread Programs
6155 @cindex stopped threads
6156 @cindex threads, stopped
6158 @cindex continuing threads
6159 @cindex threads, continuing
6161 @value{GDBN} supports debugging programs with multiple threads
6162 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6163 are two modes of controlling execution of your program within the
6164 debugger. In the default mode, referred to as @dfn{all-stop mode},
6165 when any thread in your program stops (for example, at a breakpoint
6166 or while being stepped), all other threads in the program are also stopped by
6167 @value{GDBN}. On some targets, @value{GDBN} also supports
6168 @dfn{non-stop mode}, in which other threads can continue to run freely while
6169 you examine the stopped thread in the debugger.
6172 * All-Stop Mode:: All threads stop when GDB takes control
6173 * Non-Stop Mode:: Other threads continue to execute
6174 * Background Execution:: Running your program asynchronously
6175 * Thread-Specific Breakpoints:: Controlling breakpoints
6176 * Interrupted System Calls:: GDB may interfere with system calls
6177 * Observer Mode:: GDB does not alter program behavior
6181 @subsection All-Stop Mode
6183 @cindex all-stop mode
6185 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6186 @emph{all} threads of execution stop, not just the current thread. This
6187 allows you to examine the overall state of the program, including
6188 switching between threads, without worrying that things may change
6191 Conversely, whenever you restart the program, @emph{all} threads start
6192 executing. @emph{This is true even when single-stepping} with commands
6193 like @code{step} or @code{next}.
6195 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6196 Since thread scheduling is up to your debugging target's operating
6197 system (not controlled by @value{GDBN}), other threads may
6198 execute more than one statement while the current thread completes a
6199 single step. Moreover, in general other threads stop in the middle of a
6200 statement, rather than at a clean statement boundary, when the program
6203 You might even find your program stopped in another thread after
6204 continuing or even single-stepping. This happens whenever some other
6205 thread runs into a breakpoint, a signal, or an exception before the
6206 first thread completes whatever you requested.
6208 @cindex automatic thread selection
6209 @cindex switching threads automatically
6210 @cindex threads, automatic switching
6211 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6212 signal, it automatically selects the thread where that breakpoint or
6213 signal happened. @value{GDBN} alerts you to the context switch with a
6214 message such as @samp{[Switching to Thread @var{n}]} to identify the
6217 On some OSes, you can modify @value{GDBN}'s default behavior by
6218 locking the OS scheduler to allow only a single thread to run.
6221 @item set scheduler-locking @var{mode}
6222 @cindex scheduler locking mode
6223 @cindex lock scheduler
6224 Set the scheduler locking mode. It applies to normal execution,
6225 record mode, and replay mode. If it is @code{off}, then there is no
6226 locking and any thread may run at any time. If @code{on}, then only
6227 the current thread may run when the inferior is resumed. The
6228 @code{step} mode optimizes for single-stepping; it prevents other
6229 threads from preempting the current thread while you are stepping, so
6230 that the focus of debugging does not change unexpectedly. Other
6231 threads never get a chance to run when you step, and they are
6232 completely free to run when you use commands like @samp{continue},
6233 @samp{until}, or @samp{finish}. However, unless another thread hits a
6234 breakpoint during its timeslice, @value{GDBN} does not change the
6235 current thread away from the thread that you are debugging. The
6236 @code{replay} mode behaves like @code{off} in record mode and like
6237 @code{on} in replay mode.
6239 @item show scheduler-locking
6240 Display the current scheduler locking mode.
6243 @cindex resume threads of multiple processes simultaneously
6244 By default, when you issue one of the execution commands such as
6245 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6246 threads of the current inferior to run. For example, if @value{GDBN}
6247 is attached to two inferiors, each with two threads, the
6248 @code{continue} command resumes only the two threads of the current
6249 inferior. This is useful, for example, when you debug a program that
6250 forks and you want to hold the parent stopped (so that, for instance,
6251 it doesn't run to exit), while you debug the child. In other
6252 situations, you may not be interested in inspecting the current state
6253 of any of the processes @value{GDBN} is attached to, and you may want
6254 to resume them all until some breakpoint is hit. In the latter case,
6255 you can instruct @value{GDBN} to allow all threads of all the
6256 inferiors to run with the @w{@code{set schedule-multiple}} command.
6259 @kindex set schedule-multiple
6260 @item set schedule-multiple
6261 Set the mode for allowing threads of multiple processes to be resumed
6262 when an execution command is issued. When @code{on}, all threads of
6263 all processes are allowed to run. When @code{off}, only the threads
6264 of the current process are resumed. The default is @code{off}. The
6265 @code{scheduler-locking} mode takes precedence when set to @code{on},
6266 or while you are stepping and set to @code{step}.
6268 @item show schedule-multiple
6269 Display the current mode for resuming the execution of threads of
6274 @subsection Non-Stop Mode
6276 @cindex non-stop mode
6278 @c This section is really only a place-holder, and needs to be expanded
6279 @c with more details.
6281 For some multi-threaded targets, @value{GDBN} supports an optional
6282 mode of operation in which you can examine stopped program threads in
6283 the debugger while other threads continue to execute freely. This
6284 minimizes intrusion when debugging live systems, such as programs
6285 where some threads have real-time constraints or must continue to
6286 respond to external events. This is referred to as @dfn{non-stop} mode.
6288 In non-stop mode, when a thread stops to report a debugging event,
6289 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6290 threads as well, in contrast to the all-stop mode behavior. Additionally,
6291 execution commands such as @code{continue} and @code{step} apply by default
6292 only to the current thread in non-stop mode, rather than all threads as
6293 in all-stop mode. This allows you to control threads explicitly in
6294 ways that are not possible in all-stop mode --- for example, stepping
6295 one thread while allowing others to run freely, stepping
6296 one thread while holding all others stopped, or stepping several threads
6297 independently and simultaneously.
6299 To enter non-stop mode, use this sequence of commands before you run
6300 or attach to your program:
6303 # If using the CLI, pagination breaks non-stop.
6306 # Finally, turn it on!
6310 You can use these commands to manipulate the non-stop mode setting:
6313 @kindex set non-stop
6314 @item set non-stop on
6315 Enable selection of non-stop mode.
6316 @item set non-stop off
6317 Disable selection of non-stop mode.
6318 @kindex show non-stop
6320 Show the current non-stop enablement setting.
6323 Note these commands only reflect whether non-stop mode is enabled,
6324 not whether the currently-executing program is being run in non-stop mode.
6325 In particular, the @code{set non-stop} preference is only consulted when
6326 @value{GDBN} starts or connects to the target program, and it is generally
6327 not possible to switch modes once debugging has started. Furthermore,
6328 since not all targets support non-stop mode, even when you have enabled
6329 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6332 In non-stop mode, all execution commands apply only to the current thread
6333 by default. That is, @code{continue} only continues one thread.
6334 To continue all threads, issue @code{continue -a} or @code{c -a}.
6336 You can use @value{GDBN}'s background execution commands
6337 (@pxref{Background Execution}) to run some threads in the background
6338 while you continue to examine or step others from @value{GDBN}.
6339 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6340 always executed asynchronously in non-stop mode.
6342 Suspending execution is done with the @code{interrupt} command when
6343 running in the background, or @kbd{Ctrl-c} during foreground execution.
6344 In all-stop mode, this stops the whole process;
6345 but in non-stop mode the interrupt applies only to the current thread.
6346 To stop the whole program, use @code{interrupt -a}.
6348 Other execution commands do not currently support the @code{-a} option.
6350 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6351 that thread current, as it does in all-stop mode. This is because the
6352 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6353 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6354 changed to a different thread just as you entered a command to operate on the
6355 previously current thread.
6357 @node Background Execution
6358 @subsection Background Execution
6360 @cindex foreground execution
6361 @cindex background execution
6362 @cindex asynchronous execution
6363 @cindex execution, foreground, background and asynchronous
6365 @value{GDBN}'s execution commands have two variants: the normal
6366 foreground (synchronous) behavior, and a background
6367 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6368 the program to report that some thread has stopped before prompting for
6369 another command. In background execution, @value{GDBN} immediately gives
6370 a command prompt so that you can issue other commands while your program runs.
6372 If the target doesn't support async mode, @value{GDBN} issues an error
6373 message if you attempt to use the background execution commands.
6375 @cindex @code{&}, background execution of commands
6376 To specify background execution, add a @code{&} to the command. For example,
6377 the background form of the @code{continue} command is @code{continue&}, or
6378 just @code{c&}. The execution commands that accept background execution
6384 @xref{Starting, , Starting your Program}.
6388 @xref{Attach, , Debugging an Already-running Process}.
6392 @xref{Continuing and Stepping, step}.
6396 @xref{Continuing and Stepping, stepi}.
6400 @xref{Continuing and Stepping, next}.
6404 @xref{Continuing and Stepping, nexti}.
6408 @xref{Continuing and Stepping, continue}.
6412 @xref{Continuing and Stepping, finish}.
6416 @xref{Continuing and Stepping, until}.
6420 Background execution is especially useful in conjunction with non-stop
6421 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6422 However, you can also use these commands in the normal all-stop mode with
6423 the restriction that you cannot issue another execution command until the
6424 previous one finishes. Examples of commands that are valid in all-stop
6425 mode while the program is running include @code{help} and @code{info break}.
6427 You can interrupt your program while it is running in the background by
6428 using the @code{interrupt} command.
6435 Suspend execution of the running program. In all-stop mode,
6436 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6437 only the current thread. To stop the whole program in non-stop mode,
6438 use @code{interrupt -a}.
6441 @node Thread-Specific Breakpoints
6442 @subsection Thread-Specific Breakpoints
6444 When your program has multiple threads (@pxref{Threads,, Debugging
6445 Programs with Multiple Threads}), you can choose whether to set
6446 breakpoints on all threads, or on a particular thread.
6449 @cindex breakpoints and threads
6450 @cindex thread breakpoints
6451 @kindex break @dots{} thread @var{thread-id}
6452 @item break @var{location} thread @var{thread-id}
6453 @itemx break @var{location} thread @var{thread-id} if @dots{}
6454 @var{location} specifies source lines; there are several ways of
6455 writing them (@pxref{Specify Location}), but the effect is always to
6456 specify some source line.
6458 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6459 to specify that you only want @value{GDBN} to stop the program when a
6460 particular thread reaches this breakpoint. The @var{thread-id} specifier
6461 is one of the thread identifiers assigned by @value{GDBN}, shown
6462 in the first column of the @samp{info threads} display.
6464 If you do not specify @samp{thread @var{thread-id}} when you set a
6465 breakpoint, the breakpoint applies to @emph{all} threads of your
6468 You can use the @code{thread} qualifier on conditional breakpoints as
6469 well; in this case, place @samp{thread @var{thread-id}} before or
6470 after the breakpoint condition, like this:
6473 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6478 Thread-specific breakpoints are automatically deleted when
6479 @value{GDBN} detects the corresponding thread is no longer in the
6480 thread list. For example:
6484 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6487 There are several ways for a thread to disappear, such as a regular
6488 thread exit, but also when you detach from the process with the
6489 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6490 Process}), or if @value{GDBN} loses the remote connection
6491 (@pxref{Remote Debugging}), etc. Note that with some targets,
6492 @value{GDBN} is only able to detect a thread has exited when the user
6493 explictly asks for the thread list with the @code{info threads}
6496 @node Interrupted System Calls
6497 @subsection Interrupted System Calls
6499 @cindex thread breakpoints and system calls
6500 @cindex system calls and thread breakpoints
6501 @cindex premature return from system calls
6502 There is an unfortunate side effect when using @value{GDBN} to debug
6503 multi-threaded programs. If one thread stops for a
6504 breakpoint, or for some other reason, and another thread is blocked in a
6505 system call, then the system call may return prematurely. This is a
6506 consequence of the interaction between multiple threads and the signals
6507 that @value{GDBN} uses to implement breakpoints and other events that
6510 To handle this problem, your program should check the return value of
6511 each system call and react appropriately. This is good programming
6514 For example, do not write code like this:
6520 The call to @code{sleep} will return early if a different thread stops
6521 at a breakpoint or for some other reason.
6523 Instead, write this:
6528 unslept = sleep (unslept);
6531 A system call is allowed to return early, so the system is still
6532 conforming to its specification. But @value{GDBN} does cause your
6533 multi-threaded program to behave differently than it would without
6536 Also, @value{GDBN} uses internal breakpoints in the thread library to
6537 monitor certain events such as thread creation and thread destruction.
6538 When such an event happens, a system call in another thread may return
6539 prematurely, even though your program does not appear to stop.
6542 @subsection Observer Mode
6544 If you want to build on non-stop mode and observe program behavior
6545 without any chance of disruption by @value{GDBN}, you can set
6546 variables to disable all of the debugger's attempts to modify state,
6547 whether by writing memory, inserting breakpoints, etc. These operate
6548 at a low level, intercepting operations from all commands.
6550 When all of these are set to @code{off}, then @value{GDBN} is said to
6551 be @dfn{observer mode}. As a convenience, the variable
6552 @code{observer} can be set to disable these, plus enable non-stop
6555 Note that @value{GDBN} will not prevent you from making nonsensical
6556 combinations of these settings. For instance, if you have enabled
6557 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6558 then breakpoints that work by writing trap instructions into the code
6559 stream will still not be able to be placed.
6564 @item set observer on
6565 @itemx set observer off
6566 When set to @code{on}, this disables all the permission variables
6567 below (except for @code{insert-fast-tracepoints}), plus enables
6568 non-stop debugging. Setting this to @code{off} switches back to
6569 normal debugging, though remaining in non-stop mode.
6572 Show whether observer mode is on or off.
6574 @kindex may-write-registers
6575 @item set may-write-registers on
6576 @itemx set may-write-registers off
6577 This controls whether @value{GDBN} will attempt to alter the values of
6578 registers, such as with assignment expressions in @code{print}, or the
6579 @code{jump} command. It defaults to @code{on}.
6581 @item show may-write-registers
6582 Show the current permission to write registers.
6584 @kindex may-write-memory
6585 @item set may-write-memory on
6586 @itemx set may-write-memory off
6587 This controls whether @value{GDBN} will attempt to alter the contents
6588 of memory, such as with assignment expressions in @code{print}. It
6589 defaults to @code{on}.
6591 @item show may-write-memory
6592 Show the current permission to write memory.
6594 @kindex may-insert-breakpoints
6595 @item set may-insert-breakpoints on
6596 @itemx set may-insert-breakpoints off
6597 This controls whether @value{GDBN} will attempt to insert breakpoints.
6598 This affects all breakpoints, including internal breakpoints defined
6599 by @value{GDBN}. It defaults to @code{on}.
6601 @item show may-insert-breakpoints
6602 Show the current permission to insert breakpoints.
6604 @kindex may-insert-tracepoints
6605 @item set may-insert-tracepoints on
6606 @itemx set may-insert-tracepoints off
6607 This controls whether @value{GDBN} will attempt to insert (regular)
6608 tracepoints at the beginning of a tracing experiment. It affects only
6609 non-fast tracepoints, fast tracepoints being under the control of
6610 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6612 @item show may-insert-tracepoints
6613 Show the current permission to insert tracepoints.
6615 @kindex may-insert-fast-tracepoints
6616 @item set may-insert-fast-tracepoints on
6617 @itemx set may-insert-fast-tracepoints off
6618 This controls whether @value{GDBN} will attempt to insert fast
6619 tracepoints at the beginning of a tracing experiment. It affects only
6620 fast tracepoints, regular (non-fast) tracepoints being under the
6621 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6623 @item show may-insert-fast-tracepoints
6624 Show the current permission to insert fast tracepoints.
6626 @kindex may-interrupt
6627 @item set may-interrupt on
6628 @itemx set may-interrupt off
6629 This controls whether @value{GDBN} will attempt to interrupt or stop
6630 program execution. When this variable is @code{off}, the
6631 @code{interrupt} command will have no effect, nor will
6632 @kbd{Ctrl-c}. It defaults to @code{on}.
6634 @item show may-interrupt
6635 Show the current permission to interrupt or stop the program.
6639 @node Reverse Execution
6640 @chapter Running programs backward
6641 @cindex reverse execution
6642 @cindex running programs backward
6644 When you are debugging a program, it is not unusual to realize that
6645 you have gone too far, and some event of interest has already happened.
6646 If the target environment supports it, @value{GDBN} can allow you to
6647 ``rewind'' the program by running it backward.
6649 A target environment that supports reverse execution should be able
6650 to ``undo'' the changes in machine state that have taken place as the
6651 program was executing normally. Variables, registers etc.@: should
6652 revert to their previous values. Obviously this requires a great
6653 deal of sophistication on the part of the target environment; not
6654 all target environments can support reverse execution.
6656 When a program is executed in reverse, the instructions that
6657 have most recently been executed are ``un-executed'', in reverse
6658 order. The program counter runs backward, following the previous
6659 thread of execution in reverse. As each instruction is ``un-executed'',
6660 the values of memory and/or registers that were changed by that
6661 instruction are reverted to their previous states. After executing
6662 a piece of source code in reverse, all side effects of that code
6663 should be ``undone'', and all variables should be returned to their
6664 prior values@footnote{
6665 Note that some side effects are easier to undo than others. For instance,
6666 memory and registers are relatively easy, but device I/O is hard. Some
6667 targets may be able undo things like device I/O, and some may not.
6669 The contract between @value{GDBN} and the reverse executing target
6670 requires only that the target do something reasonable when
6671 @value{GDBN} tells it to execute backwards, and then report the
6672 results back to @value{GDBN}. Whatever the target reports back to
6673 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6674 assumes that the memory and registers that the target reports are in a
6675 consistant state, but @value{GDBN} accepts whatever it is given.
6678 If you are debugging in a target environment that supports
6679 reverse execution, @value{GDBN} provides the following commands.
6682 @kindex reverse-continue
6683 @kindex rc @r{(@code{reverse-continue})}
6684 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6685 @itemx rc @r{[}@var{ignore-count}@r{]}
6686 Beginning at the point where your program last stopped, start executing
6687 in reverse. Reverse execution will stop for breakpoints and synchronous
6688 exceptions (signals), just like normal execution. Behavior of
6689 asynchronous signals depends on the target environment.
6691 @kindex reverse-step
6692 @kindex rs @r{(@code{step})}
6693 @item reverse-step @r{[}@var{count}@r{]}
6694 Run the program backward until control reaches the start of a
6695 different source line; then stop it, and return control to @value{GDBN}.
6697 Like the @code{step} command, @code{reverse-step} will only stop
6698 at the beginning of a source line. It ``un-executes'' the previously
6699 executed source line. If the previous source line included calls to
6700 debuggable functions, @code{reverse-step} will step (backward) into
6701 the called function, stopping at the beginning of the @emph{last}
6702 statement in the called function (typically a return statement).
6704 Also, as with the @code{step} command, if non-debuggable functions are
6705 called, @code{reverse-step} will run thru them backward without stopping.
6707 @kindex reverse-stepi
6708 @kindex rsi @r{(@code{reverse-stepi})}
6709 @item reverse-stepi @r{[}@var{count}@r{]}
6710 Reverse-execute one machine instruction. Note that the instruction
6711 to be reverse-executed is @emph{not} the one pointed to by the program
6712 counter, but the instruction executed prior to that one. For instance,
6713 if the last instruction was a jump, @code{reverse-stepi} will take you
6714 back from the destination of the jump to the jump instruction itself.
6716 @kindex reverse-next
6717 @kindex rn @r{(@code{reverse-next})}
6718 @item reverse-next @r{[}@var{count}@r{]}
6719 Run backward to the beginning of the previous line executed in
6720 the current (innermost) stack frame. If the line contains function
6721 calls, they will be ``un-executed'' without stopping. Starting from
6722 the first line of a function, @code{reverse-next} will take you back
6723 to the caller of that function, @emph{before} the function was called,
6724 just as the normal @code{next} command would take you from the last
6725 line of a function back to its return to its caller
6726 @footnote{Unless the code is too heavily optimized.}.
6728 @kindex reverse-nexti
6729 @kindex rni @r{(@code{reverse-nexti})}
6730 @item reverse-nexti @r{[}@var{count}@r{]}
6731 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6732 in reverse, except that called functions are ``un-executed'' atomically.
6733 That is, if the previously executed instruction was a return from
6734 another function, @code{reverse-nexti} will continue to execute
6735 in reverse until the call to that function (from the current stack
6738 @kindex reverse-finish
6739 @item reverse-finish
6740 Just as the @code{finish} command takes you to the point where the
6741 current function returns, @code{reverse-finish} takes you to the point
6742 where it was called. Instead of ending up at the end of the current
6743 function invocation, you end up at the beginning.
6745 @kindex set exec-direction
6746 @item set exec-direction
6747 Set the direction of target execution.
6748 @item set exec-direction reverse
6749 @cindex execute forward or backward in time
6750 @value{GDBN} will perform all execution commands in reverse, until the
6751 exec-direction mode is changed to ``forward''. Affected commands include
6752 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6753 command cannot be used in reverse mode.
6754 @item set exec-direction forward
6755 @value{GDBN} will perform all execution commands in the normal fashion.
6756 This is the default.
6760 @node Process Record and Replay
6761 @chapter Recording Inferior's Execution and Replaying It
6762 @cindex process record and replay
6763 @cindex recording inferior's execution and replaying it
6765 On some platforms, @value{GDBN} provides a special @dfn{process record
6766 and replay} target that can record a log of the process execution, and
6767 replay it later with both forward and reverse execution commands.
6770 When this target is in use, if the execution log includes the record
6771 for the next instruction, @value{GDBN} will debug in @dfn{replay
6772 mode}. In the replay mode, the inferior does not really execute code
6773 instructions. Instead, all the events that normally happen during
6774 code execution are taken from the execution log. While code is not
6775 really executed in replay mode, the values of registers (including the
6776 program counter register) and the memory of the inferior are still
6777 changed as they normally would. Their contents are taken from the
6781 If the record for the next instruction is not in the execution log,
6782 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6783 inferior executes normally, and @value{GDBN} records the execution log
6786 The process record and replay target supports reverse execution
6787 (@pxref{Reverse Execution}), even if the platform on which the
6788 inferior runs does not. However, the reverse execution is limited in
6789 this case by the range of the instructions recorded in the execution
6790 log. In other words, reverse execution on platforms that don't
6791 support it directly can only be done in the replay mode.
6793 When debugging in the reverse direction, @value{GDBN} will work in
6794 replay mode as long as the execution log includes the record for the
6795 previous instruction; otherwise, it will work in record mode, if the
6796 platform supports reverse execution, or stop if not.
6798 For architecture environments that support process record and replay,
6799 @value{GDBN} provides the following commands:
6802 @kindex target record
6803 @kindex target record-full
6804 @kindex target record-btrace
6807 @kindex record btrace
6808 @kindex record btrace bts
6809 @kindex record btrace pt
6815 @kindex rec btrace bts
6816 @kindex rec btrace pt
6819 @item record @var{method}
6820 This command starts the process record and replay target. The
6821 recording method can be specified as parameter. Without a parameter
6822 the command uses the @code{full} recording method. The following
6823 recording methods are available:
6827 Full record/replay recording using @value{GDBN}'s software record and
6828 replay implementation. This method allows replaying and reverse
6831 @item btrace @var{format}
6832 Hardware-supported instruction recording. This method does not record
6833 data. Further, the data is collected in a ring buffer so old data will
6834 be overwritten when the buffer is full. It allows limited reverse
6835 execution. Variables and registers are not available during reverse
6836 execution. In remote debugging, recording continues on disconnect.
6837 Recorded data can be inspected after reconnecting. The recording may
6838 be stopped using @code{record stop}.
6840 The recording format can be specified as parameter. Without a parameter
6841 the command chooses the recording format. The following recording
6842 formats are available:
6846 @cindex branch trace store
6847 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6848 this format, the processor stores a from/to record for each executed
6849 branch in the btrace ring buffer.
6852 @cindex Intel Processor Trace
6853 Use the @dfn{Intel Processor Trace} recording format. In this
6854 format, the processor stores the execution trace in a compressed form
6855 that is afterwards decoded by @value{GDBN}.
6857 The trace can be recorded with very low overhead. The compressed
6858 trace format also allows small trace buffers to already contain a big
6859 number of instructions compared to @acronym{BTS}.
6861 Decoding the recorded execution trace, on the other hand, is more
6862 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6863 increased number of instructions to process. You should increase the
6864 buffer-size with care.
6867 Not all recording formats may be available on all processors.
6870 The process record and replay target can only debug a process that is
6871 already running. Therefore, you need first to start the process with
6872 the @kbd{run} or @kbd{start} commands, and then start the recording
6873 with the @kbd{record @var{method}} command.
6875 @cindex displaced stepping, and process record and replay
6876 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6877 will be automatically disabled when process record and replay target
6878 is started. That's because the process record and replay target
6879 doesn't support displaced stepping.
6881 @cindex non-stop mode, and process record and replay
6882 @cindex asynchronous execution, and process record and replay
6883 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6884 the asynchronous execution mode (@pxref{Background Execution}), not
6885 all recording methods are available. The @code{full} recording method
6886 does not support these two modes.
6891 Stop the process record and replay target. When process record and
6892 replay target stops, the entire execution log will be deleted and the
6893 inferior will either be terminated, or will remain in its final state.
6895 When you stop the process record and replay target in record mode (at
6896 the end of the execution log), the inferior will be stopped at the
6897 next instruction that would have been recorded. In other words, if
6898 you record for a while and then stop recording, the inferior process
6899 will be left in the same state as if the recording never happened.
6901 On the other hand, if the process record and replay target is stopped
6902 while in replay mode (that is, not at the end of the execution log,
6903 but at some earlier point), the inferior process will become ``live''
6904 at that earlier state, and it will then be possible to continue the
6905 usual ``live'' debugging of the process from that state.
6907 When the inferior process exits, or @value{GDBN} detaches from it,
6908 process record and replay target will automatically stop itself.
6912 Go to a specific location in the execution log. There are several
6913 ways to specify the location to go to:
6916 @item record goto begin
6917 @itemx record goto start
6918 Go to the beginning of the execution log.
6920 @item record goto end
6921 Go to the end of the execution log.
6923 @item record goto @var{n}
6924 Go to instruction number @var{n} in the execution log.
6928 @item record save @var{filename}
6929 Save the execution log to a file @file{@var{filename}}.
6930 Default filename is @file{gdb_record.@var{process_id}}, where
6931 @var{process_id} is the process ID of the inferior.
6933 This command may not be available for all recording methods.
6935 @kindex record restore
6936 @item record restore @var{filename}
6937 Restore the execution log from a file @file{@var{filename}}.
6938 File must have been created with @code{record save}.
6940 @kindex set record full
6941 @item set record full insn-number-max @var{limit}
6942 @itemx set record full insn-number-max unlimited
6943 Set the limit of instructions to be recorded for the @code{full}
6944 recording method. Default value is 200000.
6946 If @var{limit} is a positive number, then @value{GDBN} will start
6947 deleting instructions from the log once the number of the record
6948 instructions becomes greater than @var{limit}. For every new recorded
6949 instruction, @value{GDBN} will delete the earliest recorded
6950 instruction to keep the number of recorded instructions at the limit.
6951 (Since deleting recorded instructions loses information, @value{GDBN}
6952 lets you control what happens when the limit is reached, by means of
6953 the @code{stop-at-limit} option, described below.)
6955 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6956 delete recorded instructions from the execution log. The number of
6957 recorded instructions is limited only by the available memory.
6959 @kindex show record full
6960 @item show record full insn-number-max
6961 Show the limit of instructions to be recorded with the @code{full}
6964 @item set record full stop-at-limit
6965 Control the behavior of the @code{full} recording method when the
6966 number of recorded instructions reaches the limit. If ON (the
6967 default), @value{GDBN} will stop when the limit is reached for the
6968 first time and ask you whether you want to stop the inferior or
6969 continue running it and recording the execution log. If you decide
6970 to continue recording, each new recorded instruction will cause the
6971 oldest one to be deleted.
6973 If this option is OFF, @value{GDBN} will automatically delete the
6974 oldest record to make room for each new one, without asking.
6976 @item show record full stop-at-limit
6977 Show the current setting of @code{stop-at-limit}.
6979 @item set record full memory-query
6980 Control the behavior when @value{GDBN} is unable to record memory
6981 changes caused by an instruction for the @code{full} recording method.
6982 If ON, @value{GDBN} will query whether to stop the inferior in that
6985 If this option is OFF (the default), @value{GDBN} will automatically
6986 ignore the effect of such instructions on memory. Later, when
6987 @value{GDBN} replays this execution log, it will mark the log of this
6988 instruction as not accessible, and it will not affect the replay
6991 @item show record full memory-query
6992 Show the current setting of @code{memory-query}.
6994 @kindex set record btrace
6995 The @code{btrace} record target does not trace data. As a
6996 convenience, when replaying, @value{GDBN} reads read-only memory off
6997 the live program directly, assuming that the addresses of the
6998 read-only areas don't change. This for example makes it possible to
6999 disassemble code while replaying, but not to print variables.
7000 In some cases, being able to inspect variables might be useful.
7001 You can use the following command for that:
7003 @item set record btrace replay-memory-access
7004 Control the behavior of the @code{btrace} recording method when
7005 accessing memory during replay. If @code{read-only} (the default),
7006 @value{GDBN} will only allow accesses to read-only memory.
7007 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7008 and to read-write memory. Beware that the accessed memory corresponds
7009 to the live target and not necessarily to the current replay
7012 @item set record btrace cpu @var{identifier}
7013 Set the processor to be used for enabling workarounds for processor
7014 errata when decoding the trace.
7016 Processor errata are defects in processor operation, caused by its
7017 design or manufacture. They can cause a trace not to match the
7018 specification. This, in turn, may cause trace decode to fail.
7019 @value{GDBN} can detect erroneous trace packets and correct them, thus
7020 avoiding the decoding failures. These corrections are known as
7021 @dfn{errata workarounds}, and are enabled based on the processor on
7022 which the trace was recorded.
7024 By default, @value{GDBN} attempts to detect the processor
7025 automatically, and apply the necessary workarounds for it. However,
7026 you may need to specify the processor if @value{GDBN} does not yet
7027 support it. This command allows you to do that, and also allows to
7028 disable the workarounds.
7030 The argument @var{identifier} identifies the @sc{cpu} and is of the
7031 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7032 there are two special identifiers, @code{none} and @code{auto}
7035 The following vendor identifiers and corresponding processor
7036 identifiers are currently supported:
7038 @multitable @columnfractions .1 .9
7041 @tab @var{family}/@var{model}[/@var{stepping}]
7045 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7046 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7048 If @var{identifier} is @code{auto}, enable errata workarounds for the
7049 processor on which the trace was recorded. If @var{identifier} is
7050 @code{none}, errata workarounds are disabled.
7052 For example, when using an old @value{GDBN} on a new system, decode
7053 may fail because @value{GDBN} does not support the new processor. It
7054 often suffices to specify an older processor that @value{GDBN}
7059 Active record target: record-btrace
7060 Recording format: Intel Processor Trace.
7062 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7063 (gdb) set record btrace cpu intel:6/158
7065 Active record target: record-btrace
7066 Recording format: Intel Processor Trace.
7068 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7071 @kindex show record btrace
7072 @item show record btrace replay-memory-access
7073 Show the current setting of @code{replay-memory-access}.
7075 @item show record btrace cpu
7076 Show the processor to be used for enabling trace decode errata
7079 @kindex set record btrace bts
7080 @item set record btrace bts buffer-size @var{size}
7081 @itemx set record btrace bts buffer-size unlimited
7082 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7083 format. Default is 64KB.
7085 If @var{size} is a positive number, then @value{GDBN} will try to
7086 allocate a buffer of at least @var{size} bytes for each new thread
7087 that uses the btrace recording method and the @acronym{BTS} format.
7088 The actually obtained buffer size may differ from the requested
7089 @var{size}. Use the @code{info record} command to see the actual
7090 buffer size for each thread that uses the btrace recording method and
7091 the @acronym{BTS} format.
7093 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7094 allocate a buffer of 4MB.
7096 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7097 also need longer to process the branch trace data before it can be used.
7099 @item show record btrace bts buffer-size @var{size}
7100 Show the current setting of the requested ring buffer size for branch
7101 tracing in @acronym{BTS} format.
7103 @kindex set record btrace pt
7104 @item set record btrace pt buffer-size @var{size}
7105 @itemx set record btrace pt buffer-size unlimited
7106 Set the requested ring buffer size for branch tracing in Intel
7107 Processor Trace format. Default is 16KB.
7109 If @var{size} is a positive number, then @value{GDBN} will try to
7110 allocate a buffer of at least @var{size} bytes for each new thread
7111 that uses the btrace recording method and the Intel Processor Trace
7112 format. The actually obtained buffer size may differ from the
7113 requested @var{size}. Use the @code{info record} command to see the
7114 actual buffer size for each thread.
7116 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7117 allocate a buffer of 4MB.
7119 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7120 also need longer to process the branch trace data before it can be used.
7122 @item show record btrace pt buffer-size @var{size}
7123 Show the current setting of the requested ring buffer size for branch
7124 tracing in Intel Processor Trace format.
7128 Show various statistics about the recording depending on the recording
7133 For the @code{full} recording method, it shows the state of process
7134 record and its in-memory execution log buffer, including:
7138 Whether in record mode or replay mode.
7140 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7142 Highest recorded instruction number.
7144 Current instruction about to be replayed (if in replay mode).
7146 Number of instructions contained in the execution log.
7148 Maximum number of instructions that may be contained in the execution log.
7152 For the @code{btrace} recording method, it shows:
7158 Number of instructions that have been recorded.
7160 Number of blocks of sequential control-flow formed by the recorded
7163 Whether in record mode or replay mode.
7166 For the @code{bts} recording format, it also shows:
7169 Size of the perf ring buffer.
7172 For the @code{pt} recording format, it also shows:
7175 Size of the perf ring buffer.
7179 @kindex record delete
7182 When record target runs in replay mode (``in the past''), delete the
7183 subsequent execution log and begin to record a new execution log starting
7184 from the current address. This means you will abandon the previously
7185 recorded ``future'' and begin recording a new ``future''.
7187 @kindex record instruction-history
7188 @kindex rec instruction-history
7189 @item record instruction-history
7190 Disassembles instructions from the recorded execution log. By
7191 default, ten instructions are disassembled. This can be changed using
7192 the @code{set record instruction-history-size} command. Instructions
7193 are printed in execution order.
7195 It can also print mixed source+disassembly if you specify the the
7196 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7197 as well as in symbolic form by specifying the @code{/r} modifier.
7199 The current position marker is printed for the instruction at the
7200 current program counter value. This instruction can appear multiple
7201 times in the trace and the current position marker will be printed
7202 every time. To omit the current position marker, specify the
7205 To better align the printed instructions when the trace contains
7206 instructions from more than one function, the function name may be
7207 omitted by specifying the @code{/f} modifier.
7209 Speculatively executed instructions are prefixed with @samp{?}. This
7210 feature is not available for all recording formats.
7212 There are several ways to specify what part of the execution log to
7216 @item record instruction-history @var{insn}
7217 Disassembles ten instructions starting from instruction number
7220 @item record instruction-history @var{insn}, +/-@var{n}
7221 Disassembles @var{n} instructions around instruction number
7222 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7223 @var{n} instructions after instruction number @var{insn}. If
7224 @var{n} is preceded with @code{-}, disassembles @var{n}
7225 instructions before instruction number @var{insn}.
7227 @item record instruction-history
7228 Disassembles ten more instructions after the last disassembly.
7230 @item record instruction-history -
7231 Disassembles ten more instructions before the last disassembly.
7233 @item record instruction-history @var{begin}, @var{end}
7234 Disassembles instructions beginning with instruction number
7235 @var{begin} until instruction number @var{end}. The instruction
7236 number @var{end} is included.
7239 This command may not be available for all recording methods.
7242 @item set record instruction-history-size @var{size}
7243 @itemx set record instruction-history-size unlimited
7244 Define how many instructions to disassemble in the @code{record
7245 instruction-history} command. The default value is 10.
7246 A @var{size} of @code{unlimited} means unlimited instructions.
7249 @item show record instruction-history-size
7250 Show how many instructions to disassemble in the @code{record
7251 instruction-history} command.
7253 @kindex record function-call-history
7254 @kindex rec function-call-history
7255 @item record function-call-history
7256 Prints the execution history at function granularity. It prints one
7257 line for each sequence of instructions that belong to the same
7258 function giving the name of that function, the source lines
7259 for this instruction sequence (if the @code{/l} modifier is
7260 specified), and the instructions numbers that form the sequence (if
7261 the @code{/i} modifier is specified). The function names are indented
7262 to reflect the call stack depth if the @code{/c} modifier is
7263 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7267 (@value{GDBP}) @b{list 1, 10}
7278 (@value{GDBP}) @b{record function-call-history /ilc}
7279 1 bar inst 1,4 at foo.c:6,8
7280 2 foo inst 5,10 at foo.c:2,3
7281 3 bar inst 11,13 at foo.c:9,10
7284 By default, ten lines are printed. This can be changed using the
7285 @code{set record function-call-history-size} command. Functions are
7286 printed in execution order. There are several ways to specify what
7290 @item record function-call-history @var{func}
7291 Prints ten functions starting from function number @var{func}.
7293 @item record function-call-history @var{func}, +/-@var{n}
7294 Prints @var{n} functions around function number @var{func}. If
7295 @var{n} is preceded with @code{+}, prints @var{n} functions after
7296 function number @var{func}. If @var{n} is preceded with @code{-},
7297 prints @var{n} functions before function number @var{func}.
7299 @item record function-call-history
7300 Prints ten more functions after the last ten-line print.
7302 @item record function-call-history -
7303 Prints ten more functions before the last ten-line print.
7305 @item record function-call-history @var{begin}, @var{end}
7306 Prints functions beginning with function number @var{begin} until
7307 function number @var{end}. The function number @var{end} is included.
7310 This command may not be available for all recording methods.
7312 @item set record function-call-history-size @var{size}
7313 @itemx set record function-call-history-size unlimited
7314 Define how many lines to print in the
7315 @code{record function-call-history} command. The default value is 10.
7316 A size of @code{unlimited} means unlimited lines.
7318 @item show record function-call-history-size
7319 Show how many lines to print in the
7320 @code{record function-call-history} command.
7325 @chapter Examining the Stack
7327 When your program has stopped, the first thing you need to know is where it
7328 stopped and how it got there.
7331 Each time your program performs a function call, information about the call
7333 That information includes the location of the call in your program,
7334 the arguments of the call,
7335 and the local variables of the function being called.
7336 The information is saved in a block of data called a @dfn{stack frame}.
7337 The stack frames are allocated in a region of memory called the @dfn{call
7340 When your program stops, the @value{GDBN} commands for examining the
7341 stack allow you to see all of this information.
7343 @cindex selected frame
7344 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7345 @value{GDBN} commands refer implicitly to the selected frame. In
7346 particular, whenever you ask @value{GDBN} for the value of a variable in
7347 your program, the value is found in the selected frame. There are
7348 special @value{GDBN} commands to select whichever frame you are
7349 interested in. @xref{Selection, ,Selecting a Frame}.
7351 When your program stops, @value{GDBN} automatically selects the
7352 currently executing frame and describes it briefly, similar to the
7353 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7356 * Frames:: Stack frames
7357 * Backtrace:: Backtraces
7358 * Selection:: Selecting a frame
7359 * Frame Info:: Information on a frame
7360 * Frame Apply:: Applying a command to several frames
7361 * Frame Filter Management:: Managing frame filters
7366 @section Stack Frames
7368 @cindex frame, definition
7370 The call stack is divided up into contiguous pieces called @dfn{stack
7371 frames}, or @dfn{frames} for short; each frame is the data associated
7372 with one call to one function. The frame contains the arguments given
7373 to the function, the function's local variables, and the address at
7374 which the function is executing.
7376 @cindex initial frame
7377 @cindex outermost frame
7378 @cindex innermost frame
7379 When your program is started, the stack has only one frame, that of the
7380 function @code{main}. This is called the @dfn{initial} frame or the
7381 @dfn{outermost} frame. Each time a function is called, a new frame is
7382 made. Each time a function returns, the frame for that function invocation
7383 is eliminated. If a function is recursive, there can be many frames for
7384 the same function. The frame for the function in which execution is
7385 actually occurring is called the @dfn{innermost} frame. This is the most
7386 recently created of all the stack frames that still exist.
7388 @cindex frame pointer
7389 Inside your program, stack frames are identified by their addresses. A
7390 stack frame consists of many bytes, each of which has its own address; each
7391 kind of computer has a convention for choosing one byte whose
7392 address serves as the address of the frame. Usually this address is kept
7393 in a register called the @dfn{frame pointer register}
7394 (@pxref{Registers, $fp}) while execution is going on in that frame.
7396 @cindex frame number
7397 @value{GDBN} assigns numbers to all existing stack frames, starting with
7398 zero for the innermost frame, one for the frame that called it,
7399 and so on upward. These numbers do not really exist in your program;
7400 they are assigned by @value{GDBN} to give you a way of designating stack
7401 frames in @value{GDBN} commands.
7403 @c The -fomit-frame-pointer below perennially causes hbox overflow
7404 @c underflow problems.
7405 @cindex frameless execution
7406 Some compilers provide a way to compile functions so that they operate
7407 without stack frames. (For example, the @value{NGCC} option
7409 @samp{-fomit-frame-pointer}
7411 generates functions without a frame.)
7412 This is occasionally done with heavily used library functions to save
7413 the frame setup time. @value{GDBN} has limited facilities for dealing
7414 with these function invocations. If the innermost function invocation
7415 has no stack frame, @value{GDBN} nevertheless regards it as though
7416 it had a separate frame, which is numbered zero as usual, allowing
7417 correct tracing of the function call chain. However, @value{GDBN} has
7418 no provision for frameless functions elsewhere in the stack.
7424 @cindex call stack traces
7425 A backtrace is a summary of how your program got where it is. It shows one
7426 line per frame, for many frames, starting with the currently executing
7427 frame (frame zero), followed by its caller (frame one), and on up the
7430 @anchor{backtrace-command}
7432 @kindex bt @r{(@code{backtrace})}
7433 To print a backtrace of the entire stack, use the @code{backtrace}
7434 command, or its alias @code{bt}. This command will print one line per
7435 frame for frames in the stack. By default, all stack frames are
7436 printed. You can stop the backtrace at any time by typing the system
7437 interrupt character, normally @kbd{Ctrl-c}.
7440 @item backtrace [@var{args}@dots{}]
7441 @itemx bt [@var{args}@dots{}]
7442 Print the backtrace of the entire stack. The optional @var{args} can
7443 be one of the following:
7448 Print only the innermost @var{n} frames, where @var{n} is a positive
7453 Print only the outermost @var{n} frames, where @var{n} is a positive
7457 Print the values of the local variables also. This can be combined
7458 with a number to limit the number of frames shown.
7461 Do not run Python frame filters on this backtrace. @xref{Frame
7462 Filter API}, for more information. Additionally use @ref{disable
7463 frame-filter all} to turn off all frame filters. This is only
7464 relevant when @value{GDBN} has been configured with @code{Python}
7468 A Python frame filter might decide to ``elide'' some frames. Normally
7469 such elided frames are still printed, but they are indented relative
7470 to the filtered frames that cause them to be elided. The @code{hide}
7471 option causes elided frames to not be printed at all.
7477 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7478 are additional aliases for @code{backtrace}.
7480 @cindex multiple threads, backtrace
7481 In a multi-threaded program, @value{GDBN} by default shows the
7482 backtrace only for the current thread. To display the backtrace for
7483 several or all of the threads, use the command @code{thread apply}
7484 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7485 apply all backtrace}, @value{GDBN} will display the backtrace for all
7486 the threads; this is handy when you debug a core dump of a
7487 multi-threaded program.
7489 Each line in the backtrace shows the frame number and the function name.
7490 The program counter value is also shown---unless you use @code{set
7491 print address off}. The backtrace also shows the source file name and
7492 line number, as well as the arguments to the function. The program
7493 counter value is omitted if it is at the beginning of the code for that
7496 Here is an example of a backtrace. It was made with the command
7497 @samp{bt 3}, so it shows the innermost three frames.
7501 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7503 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7504 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7506 (More stack frames follow...)
7511 The display for frame zero does not begin with a program counter
7512 value, indicating that your program has stopped at the beginning of the
7513 code for line @code{993} of @code{builtin.c}.
7516 The value of parameter @code{data} in frame 1 has been replaced by
7517 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7518 only if it is a scalar (integer, pointer, enumeration, etc). See command
7519 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7520 on how to configure the way function parameter values are printed.
7522 @cindex optimized out, in backtrace
7523 @cindex function call arguments, optimized out
7524 If your program was compiled with optimizations, some compilers will
7525 optimize away arguments passed to functions if those arguments are
7526 never used after the call. Such optimizations generate code that
7527 passes arguments through registers, but doesn't store those arguments
7528 in the stack frame. @value{GDBN} has no way of displaying such
7529 arguments in stack frames other than the innermost one. Here's what
7530 such a backtrace might look like:
7534 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7536 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7537 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7539 (More stack frames follow...)
7544 The values of arguments that were not saved in their stack frames are
7545 shown as @samp{<optimized out>}.
7547 If you need to display the values of such optimized-out arguments,
7548 either deduce that from other variables whose values depend on the one
7549 you are interested in, or recompile without optimizations.
7551 @cindex backtrace beyond @code{main} function
7552 @cindex program entry point
7553 @cindex startup code, and backtrace
7554 Most programs have a standard user entry point---a place where system
7555 libraries and startup code transition into user code. For C this is
7556 @code{main}@footnote{
7557 Note that embedded programs (the so-called ``free-standing''
7558 environment) are not required to have a @code{main} function as the
7559 entry point. They could even have multiple entry points.}.
7560 When @value{GDBN} finds the entry function in a backtrace
7561 it will terminate the backtrace, to avoid tracing into highly
7562 system-specific (and generally uninteresting) code.
7564 If you need to examine the startup code, or limit the number of levels
7565 in a backtrace, you can change this behavior:
7568 @item set backtrace past-main
7569 @itemx set backtrace past-main on
7570 @kindex set backtrace
7571 Backtraces will continue past the user entry point.
7573 @item set backtrace past-main off
7574 Backtraces will stop when they encounter the user entry point. This is the
7577 @item show backtrace past-main
7578 @kindex show backtrace
7579 Display the current user entry point backtrace policy.
7581 @item set backtrace past-entry
7582 @itemx set backtrace past-entry on
7583 Backtraces will continue past the internal entry point of an application.
7584 This entry point is encoded by the linker when the application is built,
7585 and is likely before the user entry point @code{main} (or equivalent) is called.
7587 @item set backtrace past-entry off
7588 Backtraces will stop when they encounter the internal entry point of an
7589 application. This is the default.
7591 @item show backtrace past-entry
7592 Display the current internal entry point backtrace policy.
7594 @item set backtrace limit @var{n}
7595 @itemx set backtrace limit 0
7596 @itemx set backtrace limit unlimited
7597 @cindex backtrace limit
7598 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7599 or zero means unlimited levels.
7601 @item show backtrace limit
7602 Display the current limit on backtrace levels.
7605 You can control how file names are displayed.
7608 @item set filename-display
7609 @itemx set filename-display relative
7610 @cindex filename-display
7611 Display file names relative to the compilation directory. This is the default.
7613 @item set filename-display basename
7614 Display only basename of a filename.
7616 @item set filename-display absolute
7617 Display an absolute filename.
7619 @item show filename-display
7620 Show the current way to display filenames.
7624 @section Selecting a Frame
7626 Most commands for examining the stack and other data in your program work on
7627 whichever stack frame is selected at the moment. Here are the commands for
7628 selecting a stack frame; all of them finish by printing a brief description
7629 of the stack frame just selected.
7632 @kindex frame@r{, selecting}
7633 @kindex f @r{(@code{frame})}
7636 Select frame number @var{n}. Recall that frame zero is the innermost
7637 (currently executing) frame, frame one is the frame that called the
7638 innermost one, and so on. The highest-numbered frame is the one for
7641 @item frame @var{stack-addr} [ @var{pc-addr} ]
7642 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7643 Select the frame at address @var{stack-addr}. This is useful mainly if the
7644 chaining of stack frames has been damaged by a bug, making it
7645 impossible for @value{GDBN} to assign numbers properly to all frames. In
7646 addition, this can be useful when your program has multiple stacks and
7647 switches between them. The optional @var{pc-addr} can also be given to
7648 specify the value of PC for the stack frame.
7652 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7653 numbers @var{n}, this advances toward the outermost frame, to higher
7654 frame numbers, to frames that have existed longer.
7657 @kindex do @r{(@code{down})}
7659 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7660 positive numbers @var{n}, this advances toward the innermost frame, to
7661 lower frame numbers, to frames that were created more recently.
7662 You may abbreviate @code{down} as @code{do}.
7665 All of these commands end by printing two lines of output describing the
7666 frame. The first line shows the frame number, the function name, the
7667 arguments, and the source file and line number of execution in that
7668 frame. The second line shows the text of that source line.
7676 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7678 10 read_input_file (argv[i]);
7682 After such a printout, the @code{list} command with no arguments
7683 prints ten lines centered on the point of execution in the frame.
7684 You can also edit the program at the point of execution with your favorite
7685 editing program by typing @code{edit}.
7686 @xref{List, ,Printing Source Lines},
7690 @kindex select-frame
7692 The @code{select-frame} command is a variant of @code{frame} that does
7693 not display the new frame after selecting it. This command is
7694 intended primarily for use in @value{GDBN} command scripts, where the
7695 output might be unnecessary and distracting.
7697 @kindex down-silently
7699 @item up-silently @var{n}
7700 @itemx down-silently @var{n}
7701 These two commands are variants of @code{up} and @code{down},
7702 respectively; they differ in that they do their work silently, without
7703 causing display of the new frame. They are intended primarily for use
7704 in @value{GDBN} command scripts, where the output might be unnecessary and
7709 @section Information About a Frame
7711 There are several other commands to print information about the selected
7717 When used without any argument, this command does not change which
7718 frame is selected, but prints a brief description of the currently
7719 selected stack frame. It can be abbreviated @code{f}. With an
7720 argument, this command is used to select a stack frame.
7721 @xref{Selection, ,Selecting a Frame}.
7724 @kindex info f @r{(@code{info frame})}
7727 This command prints a verbose description of the selected stack frame,
7732 the address of the frame
7734 the address of the next frame down (called by this frame)
7736 the address of the next frame up (caller of this frame)
7738 the language in which the source code corresponding to this frame is written
7740 the address of the frame's arguments
7742 the address of the frame's local variables
7744 the program counter saved in it (the address of execution in the caller frame)
7746 which registers were saved in the frame
7749 @noindent The verbose description is useful when
7750 something has gone wrong that has made the stack format fail to fit
7751 the usual conventions.
7753 @item info frame @var{addr}
7754 @itemx info f @var{addr}
7755 Print a verbose description of the frame at address @var{addr}, without
7756 selecting that frame. The selected frame remains unchanged by this
7757 command. This requires the same kind of address (more than one for some
7758 architectures) that you specify in the @code{frame} command.
7759 @xref{Selection, ,Selecting a Frame}.
7763 Print the arguments of the selected frame, each on a separate line.
7767 Print the local variables of the selected frame, each on a separate
7768 line. These are all variables (declared either static or automatic)
7769 accessible at the point of execution of the selected frame.
7774 @section Applying a Command to Several Frames.
7776 @cindex apply command to several frames
7778 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7779 The @code{frame apply} command allows you to apply the named
7780 @var{command} to one or more frames.
7784 Specify @code{all} to apply @var{command} to all frames.
7787 Use @var{count} to apply @var{command} to the innermost @var{count}
7788 frames, where @var{count} is a positive number.
7791 Use @var{-count} to apply @var{command} to the outermost @var{count}
7792 frames, where @var{count} is a positive number.
7795 Use @code{level} to apply @var{command} to the set of frames identified
7796 by the @var{level} list. @var{level} is a frame level or a range of frame
7797 levels as @var{level1}-@var{level2}. The frame level is the number shown
7798 in the first field of the @samp{backtrace} command output.
7799 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7800 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7806 Note that the frames on which @code{frame apply} applies a command are
7807 also influenced by the @code{set backtrace} settings such as @code{set
7808 backtrace past-main} and @code{set backtrace limit N}. See
7809 @xref{Backtrace,,Backtraces}.
7811 The @var{flag} arguments control what output to produce and how to handle
7812 errors raised when applying @var{command} to a frame. @var{flag}
7813 must start with a @code{-} directly followed by one letter in
7814 @code{qcs}. If several flags are provided, they must be given
7815 individually, such as @code{-c -q}.
7817 By default, @value{GDBN} displays some frame information before the
7818 output produced by @var{command}, and an error raised during the
7819 execution of a @var{command} will abort @code{frame apply}. The
7820 following flags can be used to fine-tune this behavior:
7824 The flag @code{-c}, which stands for @samp{continue}, causes any
7825 errors in @var{command} to be displayed, and the execution of
7826 @code{frame apply} then continues.
7828 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7829 or empty output produced by a @var{command} to be silently ignored.
7830 That is, the execution continues, but the frame information and errors
7833 The flag @code{-q} (@samp{quiet}) disables printing the frame
7837 The following example shows how the flags @code{-c} and @code{-s} are
7838 working when applying the command @code{p j} to all frames, where
7839 variable @code{j} can only be successfully printed in the outermost
7840 @code{#1 main} frame.
7844 (gdb) frame apply all p j
7845 #0 some_function (i=5) at fun.c:4
7846 No symbol "j" in current context.
7847 (gdb) frame apply all -c p j
7848 #0 some_function (i=5) at fun.c:4
7849 No symbol "j" in current context.
7850 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7852 (gdb) frame apply all -s p j
7853 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7859 By default, @samp{frame apply}, prints the frame location
7860 information before the command output:
7864 (gdb) frame apply all p $sp
7865 #0 some_function (i=5) at fun.c:4
7866 $4 = (void *) 0xffffd1e0
7867 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7868 $5 = (void *) 0xffffd1f0
7873 If flag @code{-q} is given, no frame information is printed:
7876 (gdb) frame apply all -q p $sp
7877 $12 = (void *) 0xffffd1e0
7878 $13 = (void *) 0xffffd1f0
7886 @cindex apply a command to all frames (ignoring errors and empty output)
7887 @item faas @var{command}
7888 Shortcut for @code{frame apply all -s @var{command}}.
7889 Applies @var{command} on all frames, ignoring errors and empty output.
7891 It can for example be used to print a local variable or a function
7892 argument without knowing the frame where this variable or argument
7895 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
7898 Note that the command @code{tfaas @var{command}} applies @var{command}
7899 on all frames of all threads. See @xref{Threads,,Threads}.
7903 @node Frame Filter Management
7904 @section Management of Frame Filters.
7905 @cindex managing frame filters
7907 Frame filters are Python based utilities to manage and decorate the
7908 output of frames. @xref{Frame Filter API}, for further information.
7910 Managing frame filters is performed by several commands available
7911 within @value{GDBN}, detailed here.
7914 @kindex info frame-filter
7915 @item info frame-filter
7916 Print a list of installed frame filters from all dictionaries, showing
7917 their name, priority and enabled status.
7919 @kindex disable frame-filter
7920 @anchor{disable frame-filter all}
7921 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7922 Disable a frame filter in the dictionary matching
7923 @var{filter-dictionary} and @var{filter-name}. The
7924 @var{filter-dictionary} may be @code{all}, @code{global},
7925 @code{progspace}, or the name of the object file where the frame filter
7926 dictionary resides. When @code{all} is specified, all frame filters
7927 across all dictionaries are disabled. The @var{filter-name} is the name
7928 of the frame filter and is used when @code{all} is not the option for
7929 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7930 may be enabled again later.
7932 @kindex enable frame-filter
7933 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7934 Enable a frame filter in the dictionary matching
7935 @var{filter-dictionary} and @var{filter-name}. The
7936 @var{filter-dictionary} may be @code{all}, @code{global},
7937 @code{progspace} or the name of the object file where the frame filter
7938 dictionary resides. When @code{all} is specified, all frame filters across
7939 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7940 filter and is used when @code{all} is not the option for
7941 @var{filter-dictionary}.
7946 (gdb) info frame-filter
7948 global frame-filters:
7949 Priority Enabled Name
7950 1000 No PrimaryFunctionFilter
7953 progspace /build/test frame-filters:
7954 Priority Enabled Name
7955 100 Yes ProgspaceFilter
7957 objfile /build/test frame-filters:
7958 Priority Enabled Name
7959 999 Yes BuildProgra Filter
7961 (gdb) disable frame-filter /build/test BuildProgramFilter
7962 (gdb) info frame-filter
7964 global frame-filters:
7965 Priority Enabled Name
7966 1000 No PrimaryFunctionFilter
7969 progspace /build/test frame-filters:
7970 Priority Enabled Name
7971 100 Yes ProgspaceFilter
7973 objfile /build/test frame-filters:
7974 Priority Enabled Name
7975 999 No BuildProgramFilter
7977 (gdb) enable frame-filter global PrimaryFunctionFilter
7978 (gdb) info frame-filter
7980 global frame-filters:
7981 Priority Enabled Name
7982 1000 Yes PrimaryFunctionFilter
7985 progspace /build/test frame-filters:
7986 Priority Enabled Name
7987 100 Yes ProgspaceFilter
7989 objfile /build/test frame-filters:
7990 Priority Enabled Name
7991 999 No BuildProgramFilter
7994 @kindex set frame-filter priority
7995 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7996 Set the @var{priority} of a frame filter in the dictionary matching
7997 @var{filter-dictionary}, and the frame filter name matching
7998 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7999 @code{progspace} or the name of the object file where the frame filter
8000 dictionary resides. The @var{priority} is an integer.
8002 @kindex show frame-filter priority
8003 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8004 Show the @var{priority} of a frame filter in the dictionary matching
8005 @var{filter-dictionary}, and the frame filter name matching
8006 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8007 @code{progspace} or the name of the object file where the frame filter
8013 (gdb) info frame-filter
8015 global frame-filters:
8016 Priority Enabled Name
8017 1000 Yes PrimaryFunctionFilter
8020 progspace /build/test frame-filters:
8021 Priority Enabled Name
8022 100 Yes ProgspaceFilter
8024 objfile /build/test frame-filters:
8025 Priority Enabled Name
8026 999 No BuildProgramFilter
8028 (gdb) set frame-filter priority global Reverse 50
8029 (gdb) info frame-filter
8031 global frame-filters:
8032 Priority Enabled Name
8033 1000 Yes PrimaryFunctionFilter
8036 progspace /build/test frame-filters:
8037 Priority Enabled Name
8038 100 Yes ProgspaceFilter
8040 objfile /build/test frame-filters:
8041 Priority Enabled Name
8042 999 No BuildProgramFilter
8047 @chapter Examining Source Files
8049 @value{GDBN} can print parts of your program's source, since the debugging
8050 information recorded in the program tells @value{GDBN} what source files were
8051 used to build it. When your program stops, @value{GDBN} spontaneously prints
8052 the line where it stopped. Likewise, when you select a stack frame
8053 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8054 execution in that frame has stopped. You can print other portions of
8055 source files by explicit command.
8057 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8058 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8059 @value{GDBN} under @sc{gnu} Emacs}.
8062 * List:: Printing source lines
8063 * Specify Location:: How to specify code locations
8064 * Edit:: Editing source files
8065 * Search:: Searching source files
8066 * Source Path:: Specifying source directories
8067 * Machine Code:: Source and machine code
8071 @section Printing Source Lines
8074 @kindex l @r{(@code{list})}
8075 To print lines from a source file, use the @code{list} command
8076 (abbreviated @code{l}). By default, ten lines are printed.
8077 There are several ways to specify what part of the file you want to
8078 print; see @ref{Specify Location}, for the full list.
8080 Here are the forms of the @code{list} command most commonly used:
8083 @item list @var{linenum}
8084 Print lines centered around line number @var{linenum} in the
8085 current source file.
8087 @item list @var{function}
8088 Print lines centered around the beginning of function
8092 Print more lines. If the last lines printed were printed with a
8093 @code{list} command, this prints lines following the last lines
8094 printed; however, if the last line printed was a solitary line printed
8095 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8096 Stack}), this prints lines centered around that line.
8099 Print lines just before the lines last printed.
8102 @cindex @code{list}, how many lines to display
8103 By default, @value{GDBN} prints ten source lines with any of these forms of
8104 the @code{list} command. You can change this using @code{set listsize}:
8107 @kindex set listsize
8108 @item set listsize @var{count}
8109 @itemx set listsize unlimited
8110 Make the @code{list} command display @var{count} source lines (unless
8111 the @code{list} argument explicitly specifies some other number).
8112 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8114 @kindex show listsize
8116 Display the number of lines that @code{list} prints.
8119 Repeating a @code{list} command with @key{RET} discards the argument,
8120 so it is equivalent to typing just @code{list}. This is more useful
8121 than listing the same lines again. An exception is made for an
8122 argument of @samp{-}; that argument is preserved in repetition so that
8123 each repetition moves up in the source file.
8125 In general, the @code{list} command expects you to supply zero, one or two
8126 @dfn{locations}. Locations specify source lines; there are several ways
8127 of writing them (@pxref{Specify Location}), but the effect is always
8128 to specify some source line.
8130 Here is a complete description of the possible arguments for @code{list}:
8133 @item list @var{location}
8134 Print lines centered around the line specified by @var{location}.
8136 @item list @var{first},@var{last}
8137 Print lines from @var{first} to @var{last}. Both arguments are
8138 locations. When a @code{list} command has two locations, and the
8139 source file of the second location is omitted, this refers to
8140 the same source file as the first location.
8142 @item list ,@var{last}
8143 Print lines ending with @var{last}.
8145 @item list @var{first},
8146 Print lines starting with @var{first}.
8149 Print lines just after the lines last printed.
8152 Print lines just before the lines last printed.
8155 As described in the preceding table.
8158 @node Specify Location
8159 @section Specifying a Location
8160 @cindex specifying location
8162 @cindex source location
8165 * Linespec Locations:: Linespec locations
8166 * Explicit Locations:: Explicit locations
8167 * Address Locations:: Address locations
8170 Several @value{GDBN} commands accept arguments that specify a location
8171 of your program's code. Since @value{GDBN} is a source-level
8172 debugger, a location usually specifies some line in the source code.
8173 Locations may be specified using three different formats:
8174 linespec locations, explicit locations, or address locations.
8176 @node Linespec Locations
8177 @subsection Linespec Locations
8178 @cindex linespec locations
8180 A @dfn{linespec} is a colon-separated list of source location parameters such
8181 as file name, function name, etc. Here are all the different ways of
8182 specifying a linespec:
8186 Specifies the line number @var{linenum} of the current source file.
8189 @itemx +@var{offset}
8190 Specifies the line @var{offset} lines before or after the @dfn{current
8191 line}. For the @code{list} command, the current line is the last one
8192 printed; for the breakpoint commands, this is the line at which
8193 execution stopped in the currently selected @dfn{stack frame}
8194 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8195 used as the second of the two linespecs in a @code{list} command,
8196 this specifies the line @var{offset} lines up or down from the first
8199 @item @var{filename}:@var{linenum}
8200 Specifies the line @var{linenum} in the source file @var{filename}.
8201 If @var{filename} is a relative file name, then it will match any
8202 source file name with the same trailing components. For example, if
8203 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8204 name of @file{/build/trunk/gcc/expr.c}, but not
8205 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8207 @item @var{function}
8208 Specifies the line that begins the body of the function @var{function}.
8209 For example, in C, this is the line with the open brace.
8211 By default, in C@t{++} and Ada, @var{function} is interpreted as
8212 specifying all functions named @var{function} in all scopes. For
8213 C@t{++}, this means in all namespaces and classes. For Ada, this
8214 means in all packages.
8216 For example, assuming a program with C@t{++} symbols named
8217 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8218 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8220 Commands that accept a linespec let you override this with the
8221 @code{-qualified} option. For example, @w{@kbd{break -qualified
8222 func}} sets a breakpoint on a free-function named @code{func} ignoring
8223 any C@t{++} class methods and namespace functions called @code{func}.
8225 @xref{Explicit Locations}.
8227 @item @var{function}:@var{label}
8228 Specifies the line where @var{label} appears in @var{function}.
8230 @item @var{filename}:@var{function}
8231 Specifies the line that begins the body of the function @var{function}
8232 in the file @var{filename}. You only need the file name with a
8233 function name to avoid ambiguity when there are identically named
8234 functions in different source files.
8237 Specifies the line at which the label named @var{label} appears
8238 in the function corresponding to the currently selected stack frame.
8239 If there is no current selected stack frame (for instance, if the inferior
8240 is not running), then @value{GDBN} will not search for a label.
8242 @cindex breakpoint at static probe point
8243 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8244 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8245 applications to embed static probes. @xref{Static Probe Points}, for more
8246 information on finding and using static probes. This form of linespec
8247 specifies the location of such a static probe.
8249 If @var{objfile} is given, only probes coming from that shared library
8250 or executable matching @var{objfile} as a regular expression are considered.
8251 If @var{provider} is given, then only probes from that provider are considered.
8252 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8253 each one of those probes.
8256 @node Explicit Locations
8257 @subsection Explicit Locations
8258 @cindex explicit locations
8260 @dfn{Explicit locations} allow the user to directly specify the source
8261 location's parameters using option-value pairs.
8263 Explicit locations are useful when several functions, labels, or
8264 file names have the same name (base name for files) in the program's
8265 sources. In these cases, explicit locations point to the source
8266 line you meant more accurately and unambiguously. Also, using
8267 explicit locations might be faster in large programs.
8269 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8270 defined in the file named @file{foo} or the label @code{bar} in a function
8271 named @code{foo}. @value{GDBN} must search either the file system or
8272 the symbol table to know.
8274 The list of valid explicit location options is summarized in the
8278 @item -source @var{filename}
8279 The value specifies the source file name. To differentiate between
8280 files with the same base name, prepend as many directories as is necessary
8281 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8282 @value{GDBN} will use the first file it finds with the given base
8283 name. This option requires the use of either @code{-function} or @code{-line}.
8285 @item -function @var{function}
8286 The value specifies the name of a function. Operations
8287 on function locations unmodified by other options (such as @code{-label}
8288 or @code{-line}) refer to the line that begins the body of the function.
8289 In C, for example, this is the line with the open brace.
8291 By default, in C@t{++} and Ada, @var{function} is interpreted as
8292 specifying all functions named @var{function} in all scopes. For
8293 C@t{++}, this means in all namespaces and classes. For Ada, this
8294 means in all packages.
8296 For example, assuming a program with C@t{++} symbols named
8297 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8298 -function func}} and @w{@kbd{break -function B::func}} set a
8299 breakpoint on both symbols.
8301 You can use the @kbd{-qualified} flag to override this (see below).
8305 This flag makes @value{GDBN} interpret a function name specified with
8306 @kbd{-function} as a complete fully-qualified name.
8308 For example, assuming a C@t{++} program with symbols named
8309 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8310 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8312 (Note: the @kbd{-qualified} option can precede a linespec as well
8313 (@pxref{Linespec Locations}), so the particular example above could be
8314 simplified as @w{@kbd{break -qualified B::func}}.)
8316 @item -label @var{label}
8317 The value specifies the name of a label. When the function
8318 name is not specified, the label is searched in the function of the currently
8319 selected stack frame.
8321 @item -line @var{number}
8322 The value specifies a line offset for the location. The offset may either
8323 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8324 the command. When specified without any other options, the line offset is
8325 relative to the current line.
8328 Explicit location options may be abbreviated by omitting any non-unique
8329 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8331 @node Address Locations
8332 @subsection Address Locations
8333 @cindex address locations
8335 @dfn{Address locations} indicate a specific program address. They have
8336 the generalized form *@var{address}.
8338 For line-oriented commands, such as @code{list} and @code{edit}, this
8339 specifies a source line that contains @var{address}. For @code{break} and
8340 other breakpoint-oriented commands, this can be used to set breakpoints in
8341 parts of your program which do not have debugging information or
8344 Here @var{address} may be any expression valid in the current working
8345 language (@pxref{Languages, working language}) that specifies a code
8346 address. In addition, as a convenience, @value{GDBN} extends the
8347 semantics of expressions used in locations to cover several situations
8348 that frequently occur during debugging. Here are the various forms
8352 @item @var{expression}
8353 Any expression valid in the current working language.
8355 @item @var{funcaddr}
8356 An address of a function or procedure derived from its name. In C,
8357 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8358 simply the function's name @var{function} (and actually a special case
8359 of a valid expression). In Pascal and Modula-2, this is
8360 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8361 (although the Pascal form also works).
8363 This form specifies the address of the function's first instruction,
8364 before the stack frame and arguments have been set up.
8366 @item '@var{filename}':@var{funcaddr}
8367 Like @var{funcaddr} above, but also specifies the name of the source
8368 file explicitly. This is useful if the name of the function does not
8369 specify the function unambiguously, e.g., if there are several
8370 functions with identical names in different source files.
8374 @section Editing Source Files
8375 @cindex editing source files
8378 @kindex e @r{(@code{edit})}
8379 To edit the lines in a source file, use the @code{edit} command.
8380 The editing program of your choice
8381 is invoked with the current line set to
8382 the active line in the program.
8383 Alternatively, there are several ways to specify what part of the file you
8384 want to print if you want to see other parts of the program:
8387 @item edit @var{location}
8388 Edit the source file specified by @code{location}. Editing starts at
8389 that @var{location}, e.g., at the specified source line of the
8390 specified file. @xref{Specify Location}, for all the possible forms
8391 of the @var{location} argument; here are the forms of the @code{edit}
8392 command most commonly used:
8395 @item edit @var{number}
8396 Edit the current source file with @var{number} as the active line number.
8398 @item edit @var{function}
8399 Edit the file containing @var{function} at the beginning of its definition.
8404 @subsection Choosing your Editor
8405 You can customize @value{GDBN} to use any editor you want
8407 The only restriction is that your editor (say @code{ex}), recognizes the
8408 following command-line syntax:
8410 ex +@var{number} file
8412 The optional numeric value +@var{number} specifies the number of the line in
8413 the file where to start editing.}.
8414 By default, it is @file{@value{EDITOR}}, but you can change this
8415 by setting the environment variable @code{EDITOR} before using
8416 @value{GDBN}. For example, to configure @value{GDBN} to use the
8417 @code{vi} editor, you could use these commands with the @code{sh} shell:
8423 or in the @code{csh} shell,
8425 setenv EDITOR /usr/bin/vi
8430 @section Searching Source Files
8431 @cindex searching source files
8433 There are two commands for searching through the current source file for a
8438 @kindex forward-search
8439 @kindex fo @r{(@code{forward-search})}
8440 @item forward-search @var{regexp}
8441 @itemx search @var{regexp}
8442 The command @samp{forward-search @var{regexp}} checks each line,
8443 starting with the one following the last line listed, for a match for
8444 @var{regexp}. It lists the line that is found. You can use the
8445 synonym @samp{search @var{regexp}} or abbreviate the command name as
8448 @kindex reverse-search
8449 @item reverse-search @var{regexp}
8450 The command @samp{reverse-search @var{regexp}} checks each line, starting
8451 with the one before the last line listed and going backward, for a match
8452 for @var{regexp}. It lists the line that is found. You can abbreviate
8453 this command as @code{rev}.
8457 @section Specifying Source Directories
8460 @cindex directories for source files
8461 Executable programs sometimes do not record the directories of the source
8462 files from which they were compiled, just the names. Even when they do,
8463 the directories could be moved between the compilation and your debugging
8464 session. @value{GDBN} has a list of directories to search for source files;
8465 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8466 it tries all the directories in the list, in the order they are present
8467 in the list, until it finds a file with the desired name.
8469 For example, suppose an executable references the file
8470 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8471 @file{/mnt/cross}. The file is first looked up literally; if this
8472 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8473 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8474 message is printed. @value{GDBN} does not look up the parts of the
8475 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8476 Likewise, the subdirectories of the source path are not searched: if
8477 the source path is @file{/mnt/cross}, and the binary refers to
8478 @file{foo.c}, @value{GDBN} would not find it under
8479 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8481 Plain file names, relative file names with leading directories, file
8482 names containing dots, etc.@: are all treated as described above; for
8483 instance, if the source path is @file{/mnt/cross}, and the source file
8484 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8485 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8486 that---@file{/mnt/cross/foo.c}.
8488 Note that the executable search path is @emph{not} used to locate the
8491 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8492 any information it has cached about where source files are found and where
8493 each line is in the file.
8497 When you start @value{GDBN}, its source path includes only @samp{cdir}
8498 and @samp{cwd}, in that order.
8499 To add other directories, use the @code{directory} command.
8501 The search path is used to find both program source files and @value{GDBN}
8502 script files (read using the @samp{-command} option and @samp{source} command).
8504 In addition to the source path, @value{GDBN} provides a set of commands
8505 that manage a list of source path substitution rules. A @dfn{substitution
8506 rule} specifies how to rewrite source directories stored in the program's
8507 debug information in case the sources were moved to a different
8508 directory between compilation and debugging. A rule is made of
8509 two strings, the first specifying what needs to be rewritten in
8510 the path, and the second specifying how it should be rewritten.
8511 In @ref{set substitute-path}, we name these two parts @var{from} and
8512 @var{to} respectively. @value{GDBN} does a simple string replacement
8513 of @var{from} with @var{to} at the start of the directory part of the
8514 source file name, and uses that result instead of the original file
8515 name to look up the sources.
8517 Using the previous example, suppose the @file{foo-1.0} tree has been
8518 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8519 @value{GDBN} to replace @file{/usr/src} in all source path names with
8520 @file{/mnt/cross}. The first lookup will then be
8521 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8522 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8523 substitution rule, use the @code{set substitute-path} command
8524 (@pxref{set substitute-path}).
8526 To avoid unexpected substitution results, a rule is applied only if the
8527 @var{from} part of the directory name ends at a directory separator.
8528 For instance, a rule substituting @file{/usr/source} into
8529 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8530 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8531 is applied only at the beginning of the directory name, this rule will
8532 not be applied to @file{/root/usr/source/baz.c} either.
8534 In many cases, you can achieve the same result using the @code{directory}
8535 command. However, @code{set substitute-path} can be more efficient in
8536 the case where the sources are organized in a complex tree with multiple
8537 subdirectories. With the @code{directory} command, you need to add each
8538 subdirectory of your project. If you moved the entire tree while
8539 preserving its internal organization, then @code{set substitute-path}
8540 allows you to direct the debugger to all the sources with one single
8543 @code{set substitute-path} is also more than just a shortcut command.
8544 The source path is only used if the file at the original location no
8545 longer exists. On the other hand, @code{set substitute-path} modifies
8546 the debugger behavior to look at the rewritten location instead. So, if
8547 for any reason a source file that is not relevant to your executable is
8548 located at the original location, a substitution rule is the only
8549 method available to point @value{GDBN} at the new location.
8551 @cindex @samp{--with-relocated-sources}
8552 @cindex default source path substitution
8553 You can configure a default source path substitution rule by
8554 configuring @value{GDBN} with the
8555 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8556 should be the name of a directory under @value{GDBN}'s configured
8557 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8558 directory names in debug information under @var{dir} will be adjusted
8559 automatically if the installed @value{GDBN} is moved to a new
8560 location. This is useful if @value{GDBN}, libraries or executables
8561 with debug information and corresponding source code are being moved
8565 @item directory @var{dirname} @dots{}
8566 @item dir @var{dirname} @dots{}
8567 Add directory @var{dirname} to the front of the source path. Several
8568 directory names may be given to this command, separated by @samp{:}
8569 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8570 part of absolute file names) or
8571 whitespace. You may specify a directory that is already in the source
8572 path; this moves it forward, so @value{GDBN} searches it sooner.
8576 @vindex $cdir@r{, convenience variable}
8577 @vindex $cwd@r{, convenience variable}
8578 @cindex compilation directory
8579 @cindex current directory
8580 @cindex working directory
8581 @cindex directory, current
8582 @cindex directory, compilation
8583 You can use the string @samp{$cdir} to refer to the compilation
8584 directory (if one is recorded), and @samp{$cwd} to refer to the current
8585 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8586 tracks the current working directory as it changes during your @value{GDBN}
8587 session, while the latter is immediately expanded to the current
8588 directory at the time you add an entry to the source path.
8591 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8593 @c RET-repeat for @code{directory} is explicitly disabled, but since
8594 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8596 @item set directories @var{path-list}
8597 @kindex set directories
8598 Set the source path to @var{path-list}.
8599 @samp{$cdir:$cwd} are added if missing.
8601 @item show directories
8602 @kindex show directories
8603 Print the source path: show which directories it contains.
8605 @anchor{set substitute-path}
8606 @item set substitute-path @var{from} @var{to}
8607 @kindex set substitute-path
8608 Define a source path substitution rule, and add it at the end of the
8609 current list of existing substitution rules. If a rule with the same
8610 @var{from} was already defined, then the old rule is also deleted.
8612 For example, if the file @file{/foo/bar/baz.c} was moved to
8613 @file{/mnt/cross/baz.c}, then the command
8616 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8620 will tell @value{GDBN} to replace @samp{/foo/bar} with
8621 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8622 @file{baz.c} even though it was moved.
8624 In the case when more than one substitution rule have been defined,
8625 the rules are evaluated one by one in the order where they have been
8626 defined. The first one matching, if any, is selected to perform
8629 For instance, if we had entered the following commands:
8632 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8633 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8637 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8638 @file{/mnt/include/defs.h} by using the first rule. However, it would
8639 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8640 @file{/mnt/src/lib/foo.c}.
8643 @item unset substitute-path [path]
8644 @kindex unset substitute-path
8645 If a path is specified, search the current list of substitution rules
8646 for a rule that would rewrite that path. Delete that rule if found.
8647 A warning is emitted by the debugger if no rule could be found.
8649 If no path is specified, then all substitution rules are deleted.
8651 @item show substitute-path [path]
8652 @kindex show substitute-path
8653 If a path is specified, then print the source path substitution rule
8654 which would rewrite that path, if any.
8656 If no path is specified, then print all existing source path substitution
8661 If your source path is cluttered with directories that are no longer of
8662 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8663 versions of source. You can correct the situation as follows:
8667 Use @code{directory} with no argument to reset the source path to its default value.
8670 Use @code{directory} with suitable arguments to reinstall the
8671 directories you want in the source path. You can add all the
8672 directories in one command.
8676 @section Source and Machine Code
8677 @cindex source line and its code address
8679 You can use the command @code{info line} to map source lines to program
8680 addresses (and vice versa), and the command @code{disassemble} to display
8681 a range of addresses as machine instructions. You can use the command
8682 @code{set disassemble-next-line} to set whether to disassemble next
8683 source line when execution stops. When run under @sc{gnu} Emacs
8684 mode, the @code{info line} command causes the arrow to point to the
8685 line specified. Also, @code{info line} prints addresses in symbolic form as
8691 @itemx info line @var{location}
8692 Print the starting and ending addresses of the compiled code for
8693 source line @var{location}. You can specify source lines in any of
8694 the ways documented in @ref{Specify Location}. With no @var{location}
8695 information about the current source line is printed.
8698 For example, we can use @code{info line} to discover the location of
8699 the object code for the first line of function
8700 @code{m4_changequote}:
8703 (@value{GDBP}) info line m4_changequote
8704 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8705 ends at 0x6350 <m4_changequote+4>.
8709 @cindex code address and its source line
8710 We can also inquire (using @code{*@var{addr}} as the form for
8711 @var{location}) what source line covers a particular address:
8713 (@value{GDBP}) info line *0x63ff
8714 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8715 ends at 0x6404 <m4_changequote+184>.
8718 @cindex @code{$_} and @code{info line}
8719 @cindex @code{x} command, default address
8720 @kindex x@r{(examine), and} info line
8721 After @code{info line}, the default address for the @code{x} command
8722 is changed to the starting address of the line, so that @samp{x/i} is
8723 sufficient to begin examining the machine code (@pxref{Memory,
8724 ,Examining Memory}). Also, this address is saved as the value of the
8725 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8728 @cindex info line, repeated calls
8729 After @code{info line}, using @code{info line} again without
8730 specifying a location will display information about the next source
8735 @cindex assembly instructions
8736 @cindex instructions, assembly
8737 @cindex machine instructions
8738 @cindex listing machine instructions
8740 @itemx disassemble /m
8741 @itemx disassemble /s
8742 @itemx disassemble /r
8743 This specialized command dumps a range of memory as machine
8744 instructions. It can also print mixed source+disassembly by specifying
8745 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8746 as well as in symbolic form by specifying the @code{/r} modifier.
8747 The default memory range is the function surrounding the
8748 program counter of the selected frame. A single argument to this
8749 command is a program counter value; @value{GDBN} dumps the function
8750 surrounding this value. When two arguments are given, they should
8751 be separated by a comma, possibly surrounded by whitespace. The
8752 arguments specify a range of addresses to dump, in one of two forms:
8755 @item @var{start},@var{end}
8756 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8757 @item @var{start},+@var{length}
8758 the addresses from @var{start} (inclusive) to
8759 @code{@var{start}+@var{length}} (exclusive).
8763 When 2 arguments are specified, the name of the function is also
8764 printed (since there could be several functions in the given range).
8766 The argument(s) can be any expression yielding a numeric value, such as
8767 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8769 If the range of memory being disassembled contains current program counter,
8770 the instruction at that location is shown with a @code{=>} marker.
8773 The following example shows the disassembly of a range of addresses of
8774 HP PA-RISC 2.0 code:
8777 (@value{GDBP}) disas 0x32c4, 0x32e4
8778 Dump of assembler code from 0x32c4 to 0x32e4:
8779 0x32c4 <main+204>: addil 0,dp
8780 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8781 0x32cc <main+212>: ldil 0x3000,r31
8782 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8783 0x32d4 <main+220>: ldo 0(r31),rp
8784 0x32d8 <main+224>: addil -0x800,dp
8785 0x32dc <main+228>: ldo 0x588(r1),r26
8786 0x32e0 <main+232>: ldil 0x3000,r31
8787 End of assembler dump.
8790 Here is an example showing mixed source+assembly for Intel x86
8791 with @code{/m} or @code{/s}, when the program is stopped just after
8792 function prologue in a non-optimized function with no inline code.
8795 (@value{GDBP}) disas /m main
8796 Dump of assembler code for function main:
8798 0x08048330 <+0>: push %ebp
8799 0x08048331 <+1>: mov %esp,%ebp
8800 0x08048333 <+3>: sub $0x8,%esp
8801 0x08048336 <+6>: and $0xfffffff0,%esp
8802 0x08048339 <+9>: sub $0x10,%esp
8804 6 printf ("Hello.\n");
8805 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8806 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8810 0x08048348 <+24>: mov $0x0,%eax
8811 0x0804834d <+29>: leave
8812 0x0804834e <+30>: ret
8814 End of assembler dump.
8817 The @code{/m} option is deprecated as its output is not useful when
8818 there is either inlined code or re-ordered code.
8819 The @code{/s} option is the preferred choice.
8820 Here is an example for AMD x86-64 showing the difference between
8821 @code{/m} output and @code{/s} output.
8822 This example has one inline function defined in a header file,
8823 and the code is compiled with @samp{-O2} optimization.
8824 Note how the @code{/m} output is missing the disassembly of
8825 several instructions that are present in the @code{/s} output.
8855 (@value{GDBP}) disas /m main
8856 Dump of assembler code for function main:
8860 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8861 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8865 0x000000000040041d <+29>: xor %eax,%eax
8866 0x000000000040041f <+31>: retq
8867 0x0000000000400420 <+32>: add %eax,%eax
8868 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8870 End of assembler dump.
8871 (@value{GDBP}) disas /s main
8872 Dump of assembler code for function main:
8876 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8880 0x0000000000400406 <+6>: test %eax,%eax
8881 0x0000000000400408 <+8>: js 0x400420 <main+32>
8886 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8887 0x000000000040040d <+13>: test %eax,%eax
8888 0x000000000040040f <+15>: mov $0x1,%eax
8889 0x0000000000400414 <+20>: cmovne %edx,%eax
8893 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8897 0x000000000040041d <+29>: xor %eax,%eax
8898 0x000000000040041f <+31>: retq
8902 0x0000000000400420 <+32>: add %eax,%eax
8903 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8904 End of assembler dump.
8907 Here is another example showing raw instructions in hex for AMD x86-64,
8910 (gdb) disas /r 0x400281,+10
8911 Dump of assembler code from 0x400281 to 0x40028b:
8912 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8913 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8914 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8915 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8916 End of assembler dump.
8919 Addresses cannot be specified as a location (@pxref{Specify Location}).
8920 So, for example, if you want to disassemble function @code{bar}
8921 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8922 and not @samp{disassemble foo.c:bar}.
8924 Some architectures have more than one commonly-used set of instruction
8925 mnemonics or other syntax.
8927 For programs that were dynamically linked and use shared libraries,
8928 instructions that call functions or branch to locations in the shared
8929 libraries might show a seemingly bogus location---it's actually a
8930 location of the relocation table. On some architectures, @value{GDBN}
8931 might be able to resolve these to actual function names.
8934 @kindex set disassembler-options
8935 @cindex disassembler options
8936 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8937 This command controls the passing of target specific information to
8938 the disassembler. For a list of valid options, please refer to the
8939 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8940 manual and/or the output of @kbd{objdump --help}
8941 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8942 The default value is the empty string.
8944 If it is necessary to specify more than one disassembler option, then
8945 multiple options can be placed together into a comma separated list.
8946 Currently this command is only supported on targets ARM, MIPS, PowerPC
8949 @kindex show disassembler-options
8950 @item show disassembler-options
8951 Show the current setting of the disassembler options.
8955 @kindex set disassembly-flavor
8956 @cindex Intel disassembly flavor
8957 @cindex AT&T disassembly flavor
8958 @item set disassembly-flavor @var{instruction-set}
8959 Select the instruction set to use when disassembling the
8960 program via the @code{disassemble} or @code{x/i} commands.
8962 Currently this command is only defined for the Intel x86 family. You
8963 can set @var{instruction-set} to either @code{intel} or @code{att}.
8964 The default is @code{att}, the AT&T flavor used by default by Unix
8965 assemblers for x86-based targets.
8967 @kindex show disassembly-flavor
8968 @item show disassembly-flavor
8969 Show the current setting of the disassembly flavor.
8973 @kindex set disassemble-next-line
8974 @kindex show disassemble-next-line
8975 @item set disassemble-next-line
8976 @itemx show disassemble-next-line
8977 Control whether or not @value{GDBN} will disassemble the next source
8978 line or instruction when execution stops. If ON, @value{GDBN} will
8979 display disassembly of the next source line when execution of the
8980 program being debugged stops. This is @emph{in addition} to
8981 displaying the source line itself, which @value{GDBN} always does if
8982 possible. If the next source line cannot be displayed for some reason
8983 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8984 info in the debug info), @value{GDBN} will display disassembly of the
8985 next @emph{instruction} instead of showing the next source line. If
8986 AUTO, @value{GDBN} will display disassembly of next instruction only
8987 if the source line cannot be displayed. This setting causes
8988 @value{GDBN} to display some feedback when you step through a function
8989 with no line info or whose source file is unavailable. The default is
8990 OFF, which means never display the disassembly of the next line or
8996 @chapter Examining Data
8998 @cindex printing data
8999 @cindex examining data
9002 The usual way to examine data in your program is with the @code{print}
9003 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9004 evaluates and prints the value of an expression of the language your
9005 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9006 Different Languages}). It may also print the expression using a
9007 Python-based pretty-printer (@pxref{Pretty Printing}).
9010 @item print @var{expr}
9011 @itemx print /@var{f} @var{expr}
9012 @var{expr} is an expression (in the source language). By default the
9013 value of @var{expr} is printed in a format appropriate to its data type;
9014 you can choose a different format by specifying @samp{/@var{f}}, where
9015 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9019 @itemx print /@var{f}
9020 @cindex reprint the last value
9021 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9022 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9023 conveniently inspect the same value in an alternative format.
9026 A more low-level way of examining data is with the @code{x} command.
9027 It examines data in memory at a specified address and prints it in a
9028 specified format. @xref{Memory, ,Examining Memory}.
9030 If you are interested in information about types, or about how the
9031 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9032 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9035 @cindex exploring hierarchical data structures
9037 Another way of examining values of expressions and type information is
9038 through the Python extension command @code{explore} (available only if
9039 the @value{GDBN} build is configured with @code{--with-python}). It
9040 offers an interactive way to start at the highest level (or, the most
9041 abstract level) of the data type of an expression (or, the data type
9042 itself) and explore all the way down to leaf scalar values/fields
9043 embedded in the higher level data types.
9046 @item explore @var{arg}
9047 @var{arg} is either an expression (in the source language), or a type
9048 visible in the current context of the program being debugged.
9051 The working of the @code{explore} command can be illustrated with an
9052 example. If a data type @code{struct ComplexStruct} is defined in your
9062 struct ComplexStruct
9064 struct SimpleStruct *ss_p;
9070 followed by variable declarations as
9073 struct SimpleStruct ss = @{ 10, 1.11 @};
9074 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9078 then, the value of the variable @code{cs} can be explored using the
9079 @code{explore} command as follows.
9083 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9084 the following fields:
9086 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9087 arr = <Enter 1 to explore this field of type `int [10]'>
9089 Enter the field number of choice:
9093 Since the fields of @code{cs} are not scalar values, you are being
9094 prompted to chose the field you want to explore. Let's say you choose
9095 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9096 pointer, you will be asked if it is pointing to a single value. From
9097 the declaration of @code{cs} above, it is indeed pointing to a single
9098 value, hence you enter @code{y}. If you enter @code{n}, then you will
9099 be asked if it were pointing to an array of values, in which case this
9100 field will be explored as if it were an array.
9103 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9104 Continue exploring it as a pointer to a single value [y/n]: y
9105 The value of `*(cs.ss_p)' is a struct/class of type `struct
9106 SimpleStruct' with the following fields:
9108 i = 10 .. (Value of type `int')
9109 d = 1.1100000000000001 .. (Value of type `double')
9111 Press enter to return to parent value:
9115 If the field @code{arr} of @code{cs} was chosen for exploration by
9116 entering @code{1} earlier, then since it is as array, you will be
9117 prompted to enter the index of the element in the array that you want
9121 `cs.arr' is an array of `int'.
9122 Enter the index of the element you want to explore in `cs.arr': 5
9124 `(cs.arr)[5]' is a scalar value of type `int'.
9128 Press enter to return to parent value:
9131 In general, at any stage of exploration, you can go deeper towards the
9132 leaf values by responding to the prompts appropriately, or hit the
9133 return key to return to the enclosing data structure (the @i{higher}
9134 level data structure).
9136 Similar to exploring values, you can use the @code{explore} command to
9137 explore types. Instead of specifying a value (which is typically a
9138 variable name or an expression valid in the current context of the
9139 program being debugged), you specify a type name. If you consider the
9140 same example as above, your can explore the type
9141 @code{struct ComplexStruct} by passing the argument
9142 @code{struct ComplexStruct} to the @code{explore} command.
9145 (gdb) explore struct ComplexStruct
9149 By responding to the prompts appropriately in the subsequent interactive
9150 session, you can explore the type @code{struct ComplexStruct} in a
9151 manner similar to how the value @code{cs} was explored in the above
9154 The @code{explore} command also has two sub-commands,
9155 @code{explore value} and @code{explore type}. The former sub-command is
9156 a way to explicitly specify that value exploration of the argument is
9157 being invoked, while the latter is a way to explicitly specify that type
9158 exploration of the argument is being invoked.
9161 @item explore value @var{expr}
9162 @cindex explore value
9163 This sub-command of @code{explore} explores the value of the
9164 expression @var{expr} (if @var{expr} is an expression valid in the
9165 current context of the program being debugged). The behavior of this
9166 command is identical to that of the behavior of the @code{explore}
9167 command being passed the argument @var{expr}.
9169 @item explore type @var{arg}
9170 @cindex explore type
9171 This sub-command of @code{explore} explores the type of @var{arg} (if
9172 @var{arg} is a type visible in the current context of program being
9173 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9174 is an expression valid in the current context of the program being
9175 debugged). If @var{arg} is a type, then the behavior of this command is
9176 identical to that of the @code{explore} command being passed the
9177 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9178 this command will be identical to that of the @code{explore} command
9179 being passed the type of @var{arg} as the argument.
9183 * Expressions:: Expressions
9184 * Ambiguous Expressions:: Ambiguous Expressions
9185 * Variables:: Program variables
9186 * Arrays:: Artificial arrays
9187 * Output Formats:: Output formats
9188 * Memory:: Examining memory
9189 * Auto Display:: Automatic display
9190 * Print Settings:: Print settings
9191 * Pretty Printing:: Python pretty printing
9192 * Value History:: Value history
9193 * Convenience Vars:: Convenience variables
9194 * Convenience Funs:: Convenience functions
9195 * Registers:: Registers
9196 * Floating Point Hardware:: Floating point hardware
9197 * Vector Unit:: Vector Unit
9198 * OS Information:: Auxiliary data provided by operating system
9199 * Memory Region Attributes:: Memory region attributes
9200 * Dump/Restore Files:: Copy between memory and a file
9201 * Core File Generation:: Cause a program dump its core
9202 * Character Sets:: Debugging programs that use a different
9203 character set than GDB does
9204 * Caching Target Data:: Data caching for targets
9205 * Searching Memory:: Searching memory for a sequence of bytes
9206 * Value Sizes:: Managing memory allocated for values
9210 @section Expressions
9213 @code{print} and many other @value{GDBN} commands accept an expression and
9214 compute its value. Any kind of constant, variable or operator defined
9215 by the programming language you are using is valid in an expression in
9216 @value{GDBN}. This includes conditional expressions, function calls,
9217 casts, and string constants. It also includes preprocessor macros, if
9218 you compiled your program to include this information; see
9221 @cindex arrays in expressions
9222 @value{GDBN} supports array constants in expressions input by
9223 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9224 you can use the command @code{print @{1, 2, 3@}} to create an array
9225 of three integers. If you pass an array to a function or assign it
9226 to a program variable, @value{GDBN} copies the array to memory that
9227 is @code{malloc}ed in the target program.
9229 Because C is so widespread, most of the expressions shown in examples in
9230 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9231 Languages}, for information on how to use expressions in other
9234 In this section, we discuss operators that you can use in @value{GDBN}
9235 expressions regardless of your programming language.
9237 @cindex casts, in expressions
9238 Casts are supported in all languages, not just in C, because it is so
9239 useful to cast a number into a pointer in order to examine a structure
9240 at that address in memory.
9241 @c FIXME: casts supported---Mod2 true?
9243 @value{GDBN} supports these operators, in addition to those common
9244 to programming languages:
9248 @samp{@@} is a binary operator for treating parts of memory as arrays.
9249 @xref{Arrays, ,Artificial Arrays}, for more information.
9252 @samp{::} allows you to specify a variable in terms of the file or
9253 function where it is defined. @xref{Variables, ,Program Variables}.
9255 @cindex @{@var{type}@}
9256 @cindex type casting memory
9257 @cindex memory, viewing as typed object
9258 @cindex casts, to view memory
9259 @item @{@var{type}@} @var{addr}
9260 Refers to an object of type @var{type} stored at address @var{addr} in
9261 memory. The address @var{addr} may be any expression whose value is
9262 an integer or pointer (but parentheses are required around binary
9263 operators, just as in a cast). This construct is allowed regardless
9264 of what kind of data is normally supposed to reside at @var{addr}.
9267 @node Ambiguous Expressions
9268 @section Ambiguous Expressions
9269 @cindex ambiguous expressions
9271 Expressions can sometimes contain some ambiguous elements. For instance,
9272 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9273 a single function name to be defined several times, for application in
9274 different contexts. This is called @dfn{overloading}. Another example
9275 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9276 templates and is typically instantiated several times, resulting in
9277 the same function name being defined in different contexts.
9279 In some cases and depending on the language, it is possible to adjust
9280 the expression to remove the ambiguity. For instance in C@t{++}, you
9281 can specify the signature of the function you want to break on, as in
9282 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9283 qualified name of your function often makes the expression unambiguous
9286 When an ambiguity that needs to be resolved is detected, the debugger
9287 has the capability to display a menu of numbered choices for each
9288 possibility, and then waits for the selection with the prompt @samp{>}.
9289 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9290 aborts the current command. If the command in which the expression was
9291 used allows more than one choice to be selected, the next option in the
9292 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9295 For example, the following session excerpt shows an attempt to set a
9296 breakpoint at the overloaded symbol @code{String::after}.
9297 We choose three particular definitions of that function name:
9299 @c FIXME! This is likely to change to show arg type lists, at least
9302 (@value{GDBP}) b String::after
9305 [2] file:String.cc; line number:867
9306 [3] file:String.cc; line number:860
9307 [4] file:String.cc; line number:875
9308 [5] file:String.cc; line number:853
9309 [6] file:String.cc; line number:846
9310 [7] file:String.cc; line number:735
9312 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9313 Breakpoint 2 at 0xb344: file String.cc, line 875.
9314 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9315 Multiple breakpoints were set.
9316 Use the "delete" command to delete unwanted
9323 @kindex set multiple-symbols
9324 @item set multiple-symbols @var{mode}
9325 @cindex multiple-symbols menu
9327 This option allows you to adjust the debugger behavior when an expression
9330 By default, @var{mode} is set to @code{all}. If the command with which
9331 the expression is used allows more than one choice, then @value{GDBN}
9332 automatically selects all possible choices. For instance, inserting
9333 a breakpoint on a function using an ambiguous name results in a breakpoint
9334 inserted on each possible match. However, if a unique choice must be made,
9335 then @value{GDBN} uses the menu to help you disambiguate the expression.
9336 For instance, printing the address of an overloaded function will result
9337 in the use of the menu.
9339 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9340 when an ambiguity is detected.
9342 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9343 an error due to the ambiguity and the command is aborted.
9345 @kindex show multiple-symbols
9346 @item show multiple-symbols
9347 Show the current value of the @code{multiple-symbols} setting.
9351 @section Program Variables
9353 The most common kind of expression to use is the name of a variable
9356 Variables in expressions are understood in the selected stack frame
9357 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9361 global (or file-static)
9368 visible according to the scope rules of the
9369 programming language from the point of execution in that frame
9372 @noindent This means that in the function
9387 you can examine and use the variable @code{a} whenever your program is
9388 executing within the function @code{foo}, but you can only use or
9389 examine the variable @code{b} while your program is executing inside
9390 the block where @code{b} is declared.
9392 @cindex variable name conflict
9393 There is an exception: you can refer to a variable or function whose
9394 scope is a single source file even if the current execution point is not
9395 in this file. But it is possible to have more than one such variable or
9396 function with the same name (in different source files). If that
9397 happens, referring to that name has unpredictable effects. If you wish,
9398 you can specify a static variable in a particular function or file by
9399 using the colon-colon (@code{::}) notation:
9401 @cindex colon-colon, context for variables/functions
9403 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9404 @cindex @code{::}, context for variables/functions
9407 @var{file}::@var{variable}
9408 @var{function}::@var{variable}
9412 Here @var{file} or @var{function} is the name of the context for the
9413 static @var{variable}. In the case of file names, you can use quotes to
9414 make sure @value{GDBN} parses the file name as a single word---for example,
9415 to print a global value of @code{x} defined in @file{f2.c}:
9418 (@value{GDBP}) p 'f2.c'::x
9421 The @code{::} notation is normally used for referring to
9422 static variables, since you typically disambiguate uses of local variables
9423 in functions by selecting the appropriate frame and using the
9424 simple name of the variable. However, you may also use this notation
9425 to refer to local variables in frames enclosing the selected frame:
9434 process (a); /* Stop here */
9445 For example, if there is a breakpoint at the commented line,
9446 here is what you might see
9447 when the program stops after executing the call @code{bar(0)}:
9452 (@value{GDBP}) p bar::a
9455 #2 0x080483d0 in foo (a=5) at foobar.c:12
9458 (@value{GDBP}) p bar::a
9462 @cindex C@t{++} scope resolution
9463 These uses of @samp{::} are very rarely in conflict with the very
9464 similar use of the same notation in C@t{++}. When they are in
9465 conflict, the C@t{++} meaning takes precedence; however, this can be
9466 overridden by quoting the file or function name with single quotes.
9468 For example, suppose the program is stopped in a method of a class
9469 that has a field named @code{includefile}, and there is also an
9470 include file named @file{includefile} that defines a variable,
9474 (@value{GDBP}) p includefile
9476 (@value{GDBP}) p includefile::some_global
9477 A syntax error in expression, near `'.
9478 (@value{GDBP}) p 'includefile'::some_global
9482 @cindex wrong values
9483 @cindex variable values, wrong
9484 @cindex function entry/exit, wrong values of variables
9485 @cindex optimized code, wrong values of variables
9487 @emph{Warning:} Occasionally, a local variable may appear to have the
9488 wrong value at certain points in a function---just after entry to a new
9489 scope, and just before exit.
9491 You may see this problem when you are stepping by machine instructions.
9492 This is because, on most machines, it takes more than one instruction to
9493 set up a stack frame (including local variable definitions); if you are
9494 stepping by machine instructions, variables may appear to have the wrong
9495 values until the stack frame is completely built. On exit, it usually
9496 also takes more than one machine instruction to destroy a stack frame;
9497 after you begin stepping through that group of instructions, local
9498 variable definitions may be gone.
9500 This may also happen when the compiler does significant optimizations.
9501 To be sure of always seeing accurate values, turn off all optimization
9504 @cindex ``No symbol "foo" in current context''
9505 Another possible effect of compiler optimizations is to optimize
9506 unused variables out of existence, or assign variables to registers (as
9507 opposed to memory addresses). Depending on the support for such cases
9508 offered by the debug info format used by the compiler, @value{GDBN}
9509 might not be able to display values for such local variables. If that
9510 happens, @value{GDBN} will print a message like this:
9513 No symbol "foo" in current context.
9516 To solve such problems, either recompile without optimizations, or use a
9517 different debug info format, if the compiler supports several such
9518 formats. @xref{Compilation}, for more information on choosing compiler
9519 options. @xref{C, ,C and C@t{++}}, for more information about debug
9520 info formats that are best suited to C@t{++} programs.
9522 If you ask to print an object whose contents are unknown to
9523 @value{GDBN}, e.g., because its data type is not completely specified
9524 by the debug information, @value{GDBN} will say @samp{<incomplete
9525 type>}. @xref{Symbols, incomplete type}, for more about this.
9527 @cindex no debug info variables
9528 If you try to examine or use the value of a (global) variable for
9529 which @value{GDBN} has no type information, e.g., because the program
9530 includes no debug information, @value{GDBN} displays an error message.
9531 @xref{Symbols, unknown type}, for more about unknown types. If you
9532 cast the variable to its declared type, @value{GDBN} gets the
9533 variable's value using the cast-to type as the variable's type. For
9534 example, in a C program:
9537 (@value{GDBP}) p var
9538 'var' has unknown type; cast it to its declared type
9539 (@value{GDBP}) p (float) var
9543 If you append @kbd{@@entry} string to a function parameter name you get its
9544 value at the time the function got called. If the value is not available an
9545 error message is printed. Entry values are available only with some compilers.
9546 Entry values are normally also printed at the function parameter list according
9547 to @ref{set print entry-values}.
9550 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9556 (gdb) print i@@entry
9560 Strings are identified as arrays of @code{char} values without specified
9561 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9562 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9563 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9564 defines literal string type @code{"char"} as @code{char} without a sign.
9569 signed char var1[] = "A";
9572 You get during debugging
9577 $2 = @{65 'A', 0 '\0'@}
9581 @section Artificial Arrays
9583 @cindex artificial array
9585 @kindex @@@r{, referencing memory as an array}
9586 It is often useful to print out several successive objects of the
9587 same type in memory; a section of an array, or an array of
9588 dynamically determined size for which only a pointer exists in the
9591 You can do this by referring to a contiguous span of memory as an
9592 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9593 operand of @samp{@@} should be the first element of the desired array
9594 and be an individual object. The right operand should be the desired length
9595 of the array. The result is an array value whose elements are all of
9596 the type of the left argument. The first element is actually the left
9597 argument; the second element comes from bytes of memory immediately
9598 following those that hold the first element, and so on. Here is an
9599 example. If a program says
9602 int *array = (int *) malloc (len * sizeof (int));
9606 you can print the contents of @code{array} with
9612 The left operand of @samp{@@} must reside in memory. Array values made
9613 with @samp{@@} in this way behave just like other arrays in terms of
9614 subscripting, and are coerced to pointers when used in expressions.
9615 Artificial arrays most often appear in expressions via the value history
9616 (@pxref{Value History, ,Value History}), after printing one out.
9618 Another way to create an artificial array is to use a cast.
9619 This re-interprets a value as if it were an array.
9620 The value need not be in memory:
9622 (@value{GDBP}) p/x (short[2])0x12345678
9623 $1 = @{0x1234, 0x5678@}
9626 As a convenience, if you leave the array length out (as in
9627 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9628 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9630 (@value{GDBP}) p/x (short[])0x12345678
9631 $2 = @{0x1234, 0x5678@}
9634 Sometimes the artificial array mechanism is not quite enough; in
9635 moderately complex data structures, the elements of interest may not
9636 actually be adjacent---for example, if you are interested in the values
9637 of pointers in an array. One useful work-around in this situation is
9638 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9639 Variables}) as a counter in an expression that prints the first
9640 interesting value, and then repeat that expression via @key{RET}. For
9641 instance, suppose you have an array @code{dtab} of pointers to
9642 structures, and you are interested in the values of a field @code{fv}
9643 in each structure. Here is an example of what you might type:
9653 @node Output Formats
9654 @section Output Formats
9656 @cindex formatted output
9657 @cindex output formats
9658 By default, @value{GDBN} prints a value according to its data type. Sometimes
9659 this is not what you want. For example, you might want to print a number
9660 in hex, or a pointer in decimal. Or you might want to view data in memory
9661 at a certain address as a character string or as an instruction. To do
9662 these things, specify an @dfn{output format} when you print a value.
9664 The simplest use of output formats is to say how to print a value
9665 already computed. This is done by starting the arguments of the
9666 @code{print} command with a slash and a format letter. The format
9667 letters supported are:
9671 Regard the bits of the value as an integer, and print the integer in
9675 Print as integer in signed decimal.
9678 Print as integer in unsigned decimal.
9681 Print as integer in octal.
9684 Print as integer in binary. The letter @samp{t} stands for ``two''.
9685 @footnote{@samp{b} cannot be used because these format letters are also
9686 used with the @code{x} command, where @samp{b} stands for ``byte'';
9687 see @ref{Memory,,Examining Memory}.}
9690 @cindex unknown address, locating
9691 @cindex locate address
9692 Print as an address, both absolute in hexadecimal and as an offset from
9693 the nearest preceding symbol. You can use this format used to discover
9694 where (in what function) an unknown address is located:
9697 (@value{GDBP}) p/a 0x54320
9698 $3 = 0x54320 <_initialize_vx+396>
9702 The command @code{info symbol 0x54320} yields similar results.
9703 @xref{Symbols, info symbol}.
9706 Regard as an integer and print it as a character constant. This
9707 prints both the numerical value and its character representation. The
9708 character representation is replaced with the octal escape @samp{\nnn}
9709 for characters outside the 7-bit @sc{ascii} range.
9711 Without this format, @value{GDBN} displays @code{char},
9712 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9713 constants. Single-byte members of vectors are displayed as integer
9717 Regard the bits of the value as a floating point number and print
9718 using typical floating point syntax.
9721 @cindex printing strings
9722 @cindex printing byte arrays
9723 Regard as a string, if possible. With this format, pointers to single-byte
9724 data are displayed as null-terminated strings and arrays of single-byte data
9725 are displayed as fixed-length strings. Other values are displayed in their
9728 Without this format, @value{GDBN} displays pointers to and arrays of
9729 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9730 strings. Single-byte members of a vector are displayed as an integer
9734 Like @samp{x} formatting, the value is treated as an integer and
9735 printed as hexadecimal, but leading zeros are printed to pad the value
9736 to the size of the integer type.
9739 @cindex raw printing
9740 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9741 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9742 Printing}). This typically results in a higher-level display of the
9743 value's contents. The @samp{r} format bypasses any Python
9744 pretty-printer which might exist.
9747 For example, to print the program counter in hex (@pxref{Registers}), type
9754 Note that no space is required before the slash; this is because command
9755 names in @value{GDBN} cannot contain a slash.
9757 To reprint the last value in the value history with a different format,
9758 you can use the @code{print} command with just a format and no
9759 expression. For example, @samp{p/x} reprints the last value in hex.
9762 @section Examining Memory
9764 You can use the command @code{x} (for ``examine'') to examine memory in
9765 any of several formats, independently of your program's data types.
9767 @cindex examining memory
9769 @kindex x @r{(examine memory)}
9770 @item x/@var{nfu} @var{addr}
9773 Use the @code{x} command to examine memory.
9776 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9777 much memory to display and how to format it; @var{addr} is an
9778 expression giving the address where you want to start displaying memory.
9779 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9780 Several commands set convenient defaults for @var{addr}.
9783 @item @var{n}, the repeat count
9784 The repeat count is a decimal integer; the default is 1. It specifies
9785 how much memory (counting by units @var{u}) to display. If a negative
9786 number is specified, memory is examined backward from @var{addr}.
9787 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9790 @item @var{f}, the display format
9791 The display format is one of the formats used by @code{print}
9792 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9793 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9794 The default is @samp{x} (hexadecimal) initially. The default changes
9795 each time you use either @code{x} or @code{print}.
9797 @item @var{u}, the unit size
9798 The unit size is any of
9804 Halfwords (two bytes).
9806 Words (four bytes). This is the initial default.
9808 Giant words (eight bytes).
9811 Each time you specify a unit size with @code{x}, that size becomes the
9812 default unit the next time you use @code{x}. For the @samp{i} format,
9813 the unit size is ignored and is normally not written. For the @samp{s} format,
9814 the unit size defaults to @samp{b}, unless it is explicitly given.
9815 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9816 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9817 Note that the results depend on the programming language of the
9818 current compilation unit. If the language is C, the @samp{s}
9819 modifier will use the UTF-16 encoding while @samp{w} will use
9820 UTF-32. The encoding is set by the programming language and cannot
9823 @item @var{addr}, starting display address
9824 @var{addr} is the address where you want @value{GDBN} to begin displaying
9825 memory. The expression need not have a pointer value (though it may);
9826 it is always interpreted as an integer address of a byte of memory.
9827 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9828 @var{addr} is usually just after the last address examined---but several
9829 other commands also set the default address: @code{info breakpoints} (to
9830 the address of the last breakpoint listed), @code{info line} (to the
9831 starting address of a line), and @code{print} (if you use it to display
9832 a value from memory).
9835 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9836 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9837 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9838 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9839 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9841 You can also specify a negative repeat count to examine memory backward
9842 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9843 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9845 Since the letters indicating unit sizes are all distinct from the
9846 letters specifying output formats, you do not have to remember whether
9847 unit size or format comes first; either order works. The output
9848 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9849 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9851 Even though the unit size @var{u} is ignored for the formats @samp{s}
9852 and @samp{i}, you might still want to use a count @var{n}; for example,
9853 @samp{3i} specifies that you want to see three machine instructions,
9854 including any operands. For convenience, especially when used with
9855 the @code{display} command, the @samp{i} format also prints branch delay
9856 slot instructions, if any, beyond the count specified, which immediately
9857 follow the last instruction that is within the count. The command
9858 @code{disassemble} gives an alternative way of inspecting machine
9859 instructions; see @ref{Machine Code,,Source and Machine Code}.
9861 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9862 the command displays null-terminated strings or instructions before the given
9863 address as many as the absolute value of the given number. For the @samp{i}
9864 format, we use line number information in the debug info to accurately locate
9865 instruction boundaries while disassembling backward. If line info is not
9866 available, the command stops examining memory with an error message.
9868 All the defaults for the arguments to @code{x} are designed to make it
9869 easy to continue scanning memory with minimal specifications each time
9870 you use @code{x}. For example, after you have inspected three machine
9871 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9872 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9873 the repeat count @var{n} is used again; the other arguments default as
9874 for successive uses of @code{x}.
9876 When examining machine instructions, the instruction at current program
9877 counter is shown with a @code{=>} marker. For example:
9880 (@value{GDBP}) x/5i $pc-6
9881 0x804837f <main+11>: mov %esp,%ebp
9882 0x8048381 <main+13>: push %ecx
9883 0x8048382 <main+14>: sub $0x4,%esp
9884 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9885 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9888 @cindex @code{$_}, @code{$__}, and value history
9889 The addresses and contents printed by the @code{x} command are not saved
9890 in the value history because there is often too much of them and they
9891 would get in the way. Instead, @value{GDBN} makes these values available for
9892 subsequent use in expressions as values of the convenience variables
9893 @code{$_} and @code{$__}. After an @code{x} command, the last address
9894 examined is available for use in expressions in the convenience variable
9895 @code{$_}. The contents of that address, as examined, are available in
9896 the convenience variable @code{$__}.
9898 If the @code{x} command has a repeat count, the address and contents saved
9899 are from the last memory unit printed; this is not the same as the last
9900 address printed if several units were printed on the last line of output.
9902 @anchor{addressable memory unit}
9903 @cindex addressable memory unit
9904 Most targets have an addressable memory unit size of 8 bits. This means
9905 that to each memory address are associated 8 bits of data. Some
9906 targets, however, have other addressable memory unit sizes.
9907 Within @value{GDBN} and this document, the term
9908 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9909 when explicitly referring to a chunk of data of that size. The word
9910 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9911 the addressable memory unit size of the target. For most systems,
9912 addressable memory unit is a synonym of byte.
9914 @cindex remote memory comparison
9915 @cindex target memory comparison
9916 @cindex verify remote memory image
9917 @cindex verify target memory image
9918 When you are debugging a program running on a remote target machine
9919 (@pxref{Remote Debugging}), you may wish to verify the program's image
9920 in the remote machine's memory against the executable file you
9921 downloaded to the target. Or, on any target, you may want to check
9922 whether the program has corrupted its own read-only sections. The
9923 @code{compare-sections} command is provided for such situations.
9926 @kindex compare-sections
9927 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9928 Compare the data of a loadable section @var{section-name} in the
9929 executable file of the program being debugged with the same section in
9930 the target machine's memory, and report any mismatches. With no
9931 arguments, compares all loadable sections. With an argument of
9932 @code{-r}, compares all loadable read-only sections.
9934 Note: for remote targets, this command can be accelerated if the
9935 target supports computing the CRC checksum of a block of memory
9936 (@pxref{qCRC packet}).
9940 @section Automatic Display
9941 @cindex automatic display
9942 @cindex display of expressions
9944 If you find that you want to print the value of an expression frequently
9945 (to see how it changes), you might want to add it to the @dfn{automatic
9946 display list} so that @value{GDBN} prints its value each time your program stops.
9947 Each expression added to the list is given a number to identify it;
9948 to remove an expression from the list, you specify that number.
9949 The automatic display looks like this:
9953 3: bar[5] = (struct hack *) 0x3804
9957 This display shows item numbers, expressions and their current values. As with
9958 displays you request manually using @code{x} or @code{print}, you can
9959 specify the output format you prefer; in fact, @code{display} decides
9960 whether to use @code{print} or @code{x} depending your format
9961 specification---it uses @code{x} if you specify either the @samp{i}
9962 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9966 @item display @var{expr}
9967 Add the expression @var{expr} to the list of expressions to display
9968 each time your program stops. @xref{Expressions, ,Expressions}.
9970 @code{display} does not repeat if you press @key{RET} again after using it.
9972 @item display/@var{fmt} @var{expr}
9973 For @var{fmt} specifying only a display format and not a size or
9974 count, add the expression @var{expr} to the auto-display list but
9975 arrange to display it each time in the specified format @var{fmt}.
9976 @xref{Output Formats,,Output Formats}.
9978 @item display/@var{fmt} @var{addr}
9979 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9980 number of units, add the expression @var{addr} as a memory address to
9981 be examined each time your program stops. Examining means in effect
9982 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9985 For example, @samp{display/i $pc} can be helpful, to see the machine
9986 instruction about to be executed each time execution stops (@samp{$pc}
9987 is a common name for the program counter; @pxref{Registers, ,Registers}).
9990 @kindex delete display
9992 @item undisplay @var{dnums}@dots{}
9993 @itemx delete display @var{dnums}@dots{}
9994 Remove items from the list of expressions to display. Specify the
9995 numbers of the displays that you want affected with the command
9996 argument @var{dnums}. It can be a single display number, one of the
9997 numbers shown in the first field of the @samp{info display} display;
9998 or it could be a range of display numbers, as in @code{2-4}.
10000 @code{undisplay} does not repeat if you press @key{RET} after using it.
10001 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10003 @kindex disable display
10004 @item disable display @var{dnums}@dots{}
10005 Disable the display of item numbers @var{dnums}. A disabled display
10006 item is not printed automatically, but is not forgotten. It may be
10007 enabled again later. Specify the numbers of the displays that you
10008 want affected with the command argument @var{dnums}. It can be a
10009 single display number, one of the numbers shown in the first field of
10010 the @samp{info display} display; or it could be a range of display
10011 numbers, as in @code{2-4}.
10013 @kindex enable display
10014 @item enable display @var{dnums}@dots{}
10015 Enable display of item numbers @var{dnums}. It becomes effective once
10016 again in auto display of its expression, until you specify otherwise.
10017 Specify the numbers of the displays that you want affected with the
10018 command argument @var{dnums}. It can be a single display number, one
10019 of the numbers shown in the first field of the @samp{info display}
10020 display; or it could be a range of display numbers, as in @code{2-4}.
10023 Display the current values of the expressions on the list, just as is
10024 done when your program stops.
10026 @kindex info display
10028 Print the list of expressions previously set up to display
10029 automatically, each one with its item number, but without showing the
10030 values. This includes disabled expressions, which are marked as such.
10031 It also includes expressions which would not be displayed right now
10032 because they refer to automatic variables not currently available.
10035 @cindex display disabled out of scope
10036 If a display expression refers to local variables, then it does not make
10037 sense outside the lexical context for which it was set up. Such an
10038 expression is disabled when execution enters a context where one of its
10039 variables is not defined. For example, if you give the command
10040 @code{display last_char} while inside a function with an argument
10041 @code{last_char}, @value{GDBN} displays this argument while your program
10042 continues to stop inside that function. When it stops elsewhere---where
10043 there is no variable @code{last_char}---the display is disabled
10044 automatically. The next time your program stops where @code{last_char}
10045 is meaningful, you can enable the display expression once again.
10047 @node Print Settings
10048 @section Print Settings
10050 @cindex format options
10051 @cindex print settings
10052 @value{GDBN} provides the following ways to control how arrays, structures,
10053 and symbols are printed.
10056 These settings are useful for debugging programs in any language:
10060 @item set print address
10061 @itemx set print address on
10062 @cindex print/don't print memory addresses
10063 @value{GDBN} prints memory addresses showing the location of stack
10064 traces, structure values, pointer values, breakpoints, and so forth,
10065 even when it also displays the contents of those addresses. The default
10066 is @code{on}. For example, this is what a stack frame display looks like with
10067 @code{set print address on}:
10072 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10074 530 if (lquote != def_lquote)
10078 @item set print address off
10079 Do not print addresses when displaying their contents. For example,
10080 this is the same stack frame displayed with @code{set print address off}:
10084 (@value{GDBP}) set print addr off
10086 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10087 530 if (lquote != def_lquote)
10091 You can use @samp{set print address off} to eliminate all machine
10092 dependent displays from the @value{GDBN} interface. For example, with
10093 @code{print address off}, you should get the same text for backtraces on
10094 all machines---whether or not they involve pointer arguments.
10097 @item show print address
10098 Show whether or not addresses are to be printed.
10101 When @value{GDBN} prints a symbolic address, it normally prints the
10102 closest earlier symbol plus an offset. If that symbol does not uniquely
10103 identify the address (for example, it is a name whose scope is a single
10104 source file), you may need to clarify. One way to do this is with
10105 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10106 you can set @value{GDBN} to print the source file and line number when
10107 it prints a symbolic address:
10110 @item set print symbol-filename on
10111 @cindex source file and line of a symbol
10112 @cindex symbol, source file and line
10113 Tell @value{GDBN} to print the source file name and line number of a
10114 symbol in the symbolic form of an address.
10116 @item set print symbol-filename off
10117 Do not print source file name and line number of a symbol. This is the
10120 @item show print symbol-filename
10121 Show whether or not @value{GDBN} will print the source file name and
10122 line number of a symbol in the symbolic form of an address.
10125 Another situation where it is helpful to show symbol filenames and line
10126 numbers is when disassembling code; @value{GDBN} shows you the line
10127 number and source file that corresponds to each instruction.
10129 Also, you may wish to see the symbolic form only if the address being
10130 printed is reasonably close to the closest earlier symbol:
10133 @item set print max-symbolic-offset @var{max-offset}
10134 @itemx set print max-symbolic-offset unlimited
10135 @cindex maximum value for offset of closest symbol
10136 Tell @value{GDBN} to only display the symbolic form of an address if the
10137 offset between the closest earlier symbol and the address is less than
10138 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10139 to always print the symbolic form of an address if any symbol precedes
10140 it. Zero is equivalent to @code{unlimited}.
10142 @item show print max-symbolic-offset
10143 Ask how large the maximum offset is that @value{GDBN} prints in a
10147 @cindex wild pointer, interpreting
10148 @cindex pointer, finding referent
10149 If you have a pointer and you are not sure where it points, try
10150 @samp{set print symbol-filename on}. Then you can determine the name
10151 and source file location of the variable where it points, using
10152 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10153 For example, here @value{GDBN} shows that a variable @code{ptt} points
10154 at another variable @code{t}, defined in @file{hi2.c}:
10157 (@value{GDBP}) set print symbol-filename on
10158 (@value{GDBP}) p/a ptt
10159 $4 = 0xe008 <t in hi2.c>
10163 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10164 does not show the symbol name and filename of the referent, even with
10165 the appropriate @code{set print} options turned on.
10168 You can also enable @samp{/a}-like formatting all the time using
10169 @samp{set print symbol on}:
10172 @item set print symbol on
10173 Tell @value{GDBN} to print the symbol corresponding to an address, if
10176 @item set print symbol off
10177 Tell @value{GDBN} not to print the symbol corresponding to an
10178 address. In this mode, @value{GDBN} will still print the symbol
10179 corresponding to pointers to functions. This is the default.
10181 @item show print symbol
10182 Show whether @value{GDBN} will display the symbol corresponding to an
10186 Other settings control how different kinds of objects are printed:
10189 @item set print array
10190 @itemx set print array on
10191 @cindex pretty print arrays
10192 Pretty print arrays. This format is more convenient to read,
10193 but uses more space. The default is off.
10195 @item set print array off
10196 Return to compressed format for arrays.
10198 @item show print array
10199 Show whether compressed or pretty format is selected for displaying
10202 @cindex print array indexes
10203 @item set print array-indexes
10204 @itemx set print array-indexes on
10205 Print the index of each element when displaying arrays. May be more
10206 convenient to locate a given element in the array or quickly find the
10207 index of a given element in that printed array. The default is off.
10209 @item set print array-indexes off
10210 Stop printing element indexes when displaying arrays.
10212 @item show print array-indexes
10213 Show whether the index of each element is printed when displaying
10216 @item set print elements @var{number-of-elements}
10217 @itemx set print elements unlimited
10218 @cindex number of array elements to print
10219 @cindex limit on number of printed array elements
10220 Set a limit on how many elements of an array @value{GDBN} will print.
10221 If @value{GDBN} is printing a large array, it stops printing after it has
10222 printed the number of elements set by the @code{set print elements} command.
10223 This limit also applies to the display of strings.
10224 When @value{GDBN} starts, this limit is set to 200.
10225 Setting @var{number-of-elements} to @code{unlimited} or zero means
10226 that the number of elements to print is unlimited.
10228 @item show print elements
10229 Display the number of elements of a large array that @value{GDBN} will print.
10230 If the number is 0, then the printing is unlimited.
10232 @item set print frame-arguments @var{value}
10233 @kindex set print frame-arguments
10234 @cindex printing frame argument values
10235 @cindex print all frame argument values
10236 @cindex print frame argument values for scalars only
10237 @cindex do not print frame argument values
10238 This command allows to control how the values of arguments are printed
10239 when the debugger prints a frame (@pxref{Frames}). The possible
10244 The values of all arguments are printed.
10247 Print the value of an argument only if it is a scalar. The value of more
10248 complex arguments such as arrays, structures, unions, etc, is replaced
10249 by @code{@dots{}}. This is the default. Here is an example where
10250 only scalar arguments are shown:
10253 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10258 None of the argument values are printed. Instead, the value of each argument
10259 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10262 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10267 By default, only scalar arguments are printed. This command can be used
10268 to configure the debugger to print the value of all arguments, regardless
10269 of their type. However, it is often advantageous to not print the value
10270 of more complex parameters. For instance, it reduces the amount of
10271 information printed in each frame, making the backtrace more readable.
10272 Also, it improves performance when displaying Ada frames, because
10273 the computation of large arguments can sometimes be CPU-intensive,
10274 especially in large applications. Setting @code{print frame-arguments}
10275 to @code{scalars} (the default) or @code{none} avoids this computation,
10276 thus speeding up the display of each Ada frame.
10278 @item show print frame-arguments
10279 Show how the value of arguments should be displayed when printing a frame.
10281 @item set print raw frame-arguments on
10282 Print frame arguments in raw, non pretty-printed, form.
10284 @item set print raw frame-arguments off
10285 Print frame arguments in pretty-printed form, if there is a pretty-printer
10286 for the value (@pxref{Pretty Printing}),
10287 otherwise print the value in raw form.
10288 This is the default.
10290 @item show print raw frame-arguments
10291 Show whether to print frame arguments in raw form.
10293 @anchor{set print entry-values}
10294 @item set print entry-values @var{value}
10295 @kindex set print entry-values
10296 Set printing of frame argument values at function entry. In some cases
10297 @value{GDBN} can determine the value of function argument which was passed by
10298 the function caller, even if the value was modified inside the called function
10299 and therefore is different. With optimized code, the current value could be
10300 unavailable, but the entry value may still be known.
10302 The default value is @code{default} (see below for its description). Older
10303 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10304 this feature will behave in the @code{default} setting the same way as with the
10307 This functionality is currently supported only by DWARF 2 debugging format and
10308 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10309 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10312 The @var{value} parameter can be one of the following:
10316 Print only actual parameter values, never print values from function entry
10320 #0 different (val=6)
10321 #0 lost (val=<optimized out>)
10323 #0 invalid (val=<optimized out>)
10327 Print only parameter values from function entry point. The actual parameter
10328 values are never printed.
10330 #0 equal (val@@entry=5)
10331 #0 different (val@@entry=5)
10332 #0 lost (val@@entry=5)
10333 #0 born (val@@entry=<optimized out>)
10334 #0 invalid (val@@entry=<optimized out>)
10338 Print only parameter values from function entry point. If value from function
10339 entry point is not known while the actual value is known, print the actual
10340 value for such parameter.
10342 #0 equal (val@@entry=5)
10343 #0 different (val@@entry=5)
10344 #0 lost (val@@entry=5)
10346 #0 invalid (val@@entry=<optimized out>)
10350 Print actual parameter values. If actual parameter value is not known while
10351 value from function entry point is known, print the entry point value for such
10355 #0 different (val=6)
10356 #0 lost (val@@entry=5)
10358 #0 invalid (val=<optimized out>)
10362 Always print both the actual parameter value and its value from function entry
10363 point, even if values of one or both are not available due to compiler
10366 #0 equal (val=5, val@@entry=5)
10367 #0 different (val=6, val@@entry=5)
10368 #0 lost (val=<optimized out>, val@@entry=5)
10369 #0 born (val=10, val@@entry=<optimized out>)
10370 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10374 Print the actual parameter value if it is known and also its value from
10375 function entry point if it is known. If neither is known, print for the actual
10376 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10377 values are known and identical, print the shortened
10378 @code{param=param@@entry=VALUE} notation.
10380 #0 equal (val=val@@entry=5)
10381 #0 different (val=6, val@@entry=5)
10382 #0 lost (val@@entry=5)
10384 #0 invalid (val=<optimized out>)
10388 Always print the actual parameter value. Print also its value from function
10389 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10390 if both values are known and identical, print the shortened
10391 @code{param=param@@entry=VALUE} notation.
10393 #0 equal (val=val@@entry=5)
10394 #0 different (val=6, val@@entry=5)
10395 #0 lost (val=<optimized out>, val@@entry=5)
10397 #0 invalid (val=<optimized out>)
10401 For analysis messages on possible failures of frame argument values at function
10402 entry resolution see @ref{set debug entry-values}.
10404 @item show print entry-values
10405 Show the method being used for printing of frame argument values at function
10408 @item set print repeats @var{number-of-repeats}
10409 @itemx set print repeats unlimited
10410 @cindex repeated array elements
10411 Set the threshold for suppressing display of repeated array
10412 elements. When the number of consecutive identical elements of an
10413 array exceeds the threshold, @value{GDBN} prints the string
10414 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10415 identical repetitions, instead of displaying the identical elements
10416 themselves. Setting the threshold to @code{unlimited} or zero will
10417 cause all elements to be individually printed. The default threshold
10420 @item show print repeats
10421 Display the current threshold for printing repeated identical
10424 @item set print null-stop
10425 @cindex @sc{null} elements in arrays
10426 Cause @value{GDBN} to stop printing the characters of an array when the first
10427 @sc{null} is encountered. This is useful when large arrays actually
10428 contain only short strings.
10429 The default is off.
10431 @item show print null-stop
10432 Show whether @value{GDBN} stops printing an array on the first
10433 @sc{null} character.
10435 @item set print pretty on
10436 @cindex print structures in indented form
10437 @cindex indentation in structure display
10438 Cause @value{GDBN} to print structures in an indented format with one member
10439 per line, like this:
10454 @item set print pretty off
10455 Cause @value{GDBN} to print structures in a compact format, like this:
10459 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10460 meat = 0x54 "Pork"@}
10465 This is the default format.
10467 @item show print pretty
10468 Show which format @value{GDBN} is using to print structures.
10470 @item set print sevenbit-strings on
10471 @cindex eight-bit characters in strings
10472 @cindex octal escapes in strings
10473 Print using only seven-bit characters; if this option is set,
10474 @value{GDBN} displays any eight-bit characters (in strings or
10475 character values) using the notation @code{\}@var{nnn}. This setting is
10476 best if you are working in English (@sc{ascii}) and you use the
10477 high-order bit of characters as a marker or ``meta'' bit.
10479 @item set print sevenbit-strings off
10480 Print full eight-bit characters. This allows the use of more
10481 international character sets, and is the default.
10483 @item show print sevenbit-strings
10484 Show whether or not @value{GDBN} is printing only seven-bit characters.
10486 @item set print union on
10487 @cindex unions in structures, printing
10488 Tell @value{GDBN} to print unions which are contained in structures
10489 and other unions. This is the default setting.
10491 @item set print union off
10492 Tell @value{GDBN} not to print unions which are contained in
10493 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10496 @item show print union
10497 Ask @value{GDBN} whether or not it will print unions which are contained in
10498 structures and other unions.
10500 For example, given the declarations
10503 typedef enum @{Tree, Bug@} Species;
10504 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10505 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10516 struct thing foo = @{Tree, @{Acorn@}@};
10520 with @code{set print union on} in effect @samp{p foo} would print
10523 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10527 and with @code{set print union off} in effect it would print
10530 $1 = @{it = Tree, form = @{...@}@}
10534 @code{set print union} affects programs written in C-like languages
10540 These settings are of interest when debugging C@t{++} programs:
10543 @cindex demangling C@t{++} names
10544 @item set print demangle
10545 @itemx set print demangle on
10546 Print C@t{++} names in their source form rather than in the encoded
10547 (``mangled'') form passed to the assembler and linker for type-safe
10548 linkage. The default is on.
10550 @item show print demangle
10551 Show whether C@t{++} names are printed in mangled or demangled form.
10553 @item set print asm-demangle
10554 @itemx set print asm-demangle on
10555 Print C@t{++} names in their source form rather than their mangled form, even
10556 in assembler code printouts such as instruction disassemblies.
10557 The default is off.
10559 @item show print asm-demangle
10560 Show whether C@t{++} names in assembly listings are printed in mangled
10563 @cindex C@t{++} symbol decoding style
10564 @cindex symbol decoding style, C@t{++}
10565 @kindex set demangle-style
10566 @item set demangle-style @var{style}
10567 Choose among several encoding schemes used by different compilers to
10568 represent C@t{++} names. The choices for @var{style} are currently:
10572 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10573 This is the default.
10576 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10579 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10582 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10585 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10586 @strong{Warning:} this setting alone is not sufficient to allow
10587 debugging @code{cfront}-generated executables. @value{GDBN} would
10588 require further enhancement to permit that.
10591 If you omit @var{style}, you will see a list of possible formats.
10593 @item show demangle-style
10594 Display the encoding style currently in use for decoding C@t{++} symbols.
10596 @item set print object
10597 @itemx set print object on
10598 @cindex derived type of an object, printing
10599 @cindex display derived types
10600 When displaying a pointer to an object, identify the @emph{actual}
10601 (derived) type of the object rather than the @emph{declared} type, using
10602 the virtual function table. Note that the virtual function table is
10603 required---this feature can only work for objects that have run-time
10604 type identification; a single virtual method in the object's declared
10605 type is sufficient. Note that this setting is also taken into account when
10606 working with variable objects via MI (@pxref{GDB/MI}).
10608 @item set print object off
10609 Display only the declared type of objects, without reference to the
10610 virtual function table. This is the default setting.
10612 @item show print object
10613 Show whether actual, or declared, object types are displayed.
10615 @item set print static-members
10616 @itemx set print static-members on
10617 @cindex static members of C@t{++} objects
10618 Print static members when displaying a C@t{++} object. The default is on.
10620 @item set print static-members off
10621 Do not print static members when displaying a C@t{++} object.
10623 @item show print static-members
10624 Show whether C@t{++} static members are printed or not.
10626 @item set print pascal_static-members
10627 @itemx set print pascal_static-members on
10628 @cindex static members of Pascal objects
10629 @cindex Pascal objects, static members display
10630 Print static members when displaying a Pascal object. The default is on.
10632 @item set print pascal_static-members off
10633 Do not print static members when displaying a Pascal object.
10635 @item show print pascal_static-members
10636 Show whether Pascal static members are printed or not.
10638 @c These don't work with HP ANSI C++ yet.
10639 @item set print vtbl
10640 @itemx set print vtbl on
10641 @cindex pretty print C@t{++} virtual function tables
10642 @cindex virtual functions (C@t{++}) display
10643 @cindex VTBL display
10644 Pretty print C@t{++} virtual function tables. The default is off.
10645 (The @code{vtbl} commands do not work on programs compiled with the HP
10646 ANSI C@t{++} compiler (@code{aCC}).)
10648 @item set print vtbl off
10649 Do not pretty print C@t{++} virtual function tables.
10651 @item show print vtbl
10652 Show whether C@t{++} virtual function tables are pretty printed, or not.
10655 @node Pretty Printing
10656 @section Pretty Printing
10658 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10659 Python code. It greatly simplifies the display of complex objects. This
10660 mechanism works for both MI and the CLI.
10663 * Pretty-Printer Introduction:: Introduction to pretty-printers
10664 * Pretty-Printer Example:: An example pretty-printer
10665 * Pretty-Printer Commands:: Pretty-printer commands
10668 @node Pretty-Printer Introduction
10669 @subsection Pretty-Printer Introduction
10671 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10672 registered for the value. If there is then @value{GDBN} invokes the
10673 pretty-printer to print the value. Otherwise the value is printed normally.
10675 Pretty-printers are normally named. This makes them easy to manage.
10676 The @samp{info pretty-printer} command will list all the installed
10677 pretty-printers with their names.
10678 If a pretty-printer can handle multiple data types, then its
10679 @dfn{subprinters} are the printers for the individual data types.
10680 Each such subprinter has its own name.
10681 The format of the name is @var{printer-name};@var{subprinter-name}.
10683 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10684 Typically they are automatically loaded and registered when the corresponding
10685 debug information is loaded, thus making them available without having to
10686 do anything special.
10688 There are three places where a pretty-printer can be registered.
10692 Pretty-printers registered globally are available when debugging
10696 Pretty-printers registered with a program space are available only
10697 when debugging that program.
10698 @xref{Progspaces In Python}, for more details on program spaces in Python.
10701 Pretty-printers registered with an objfile are loaded and unloaded
10702 with the corresponding objfile (e.g., shared library).
10703 @xref{Objfiles In Python}, for more details on objfiles in Python.
10706 @xref{Selecting Pretty-Printers}, for further information on how
10707 pretty-printers are selected,
10709 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10712 @node Pretty-Printer Example
10713 @subsection Pretty-Printer Example
10715 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10718 (@value{GDBP}) print s
10720 static npos = 4294967295,
10722 <std::allocator<char>> = @{
10723 <__gnu_cxx::new_allocator<char>> = @{
10724 <No data fields>@}, <No data fields>
10726 members of std::basic_string<char, std::char_traits<char>,
10727 std::allocator<char> >::_Alloc_hider:
10728 _M_p = 0x804a014 "abcd"
10733 With a pretty-printer for @code{std::string} only the contents are printed:
10736 (@value{GDBP}) print s
10740 @node Pretty-Printer Commands
10741 @subsection Pretty-Printer Commands
10742 @cindex pretty-printer commands
10745 @kindex info pretty-printer
10746 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10747 Print the list of installed pretty-printers.
10748 This includes disabled pretty-printers, which are marked as such.
10750 @var{object-regexp} is a regular expression matching the objects
10751 whose pretty-printers to list.
10752 Objects can be @code{global}, the program space's file
10753 (@pxref{Progspaces In Python}),
10754 and the object files within that program space (@pxref{Objfiles In Python}).
10755 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10756 looks up a printer from these three objects.
10758 @var{name-regexp} is a regular expression matching the name of the printers
10761 @kindex disable pretty-printer
10762 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10763 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10764 A disabled pretty-printer is not forgotten, it may be enabled again later.
10766 @kindex enable pretty-printer
10767 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10768 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10773 Suppose we have three pretty-printers installed: one from library1.so
10774 named @code{foo} that prints objects of type @code{foo}, and
10775 another from library2.so named @code{bar} that prints two types of objects,
10776 @code{bar1} and @code{bar2}.
10779 (gdb) info pretty-printer
10786 (gdb) info pretty-printer library2
10791 (gdb) disable pretty-printer library1
10793 2 of 3 printers enabled
10794 (gdb) info pretty-printer
10801 (gdb) disable pretty-printer library2 bar:bar1
10803 1 of 3 printers enabled
10804 (gdb) info pretty-printer library2
10811 (gdb) disable pretty-printer library2 bar
10813 0 of 3 printers enabled
10814 (gdb) info pretty-printer library2
10823 Note that for @code{bar} the entire printer can be disabled,
10824 as can each individual subprinter.
10826 @node Value History
10827 @section Value History
10829 @cindex value history
10830 @cindex history of values printed by @value{GDBN}
10831 Values printed by the @code{print} command are saved in the @value{GDBN}
10832 @dfn{value history}. This allows you to refer to them in other expressions.
10833 Values are kept until the symbol table is re-read or discarded
10834 (for example with the @code{file} or @code{symbol-file} commands).
10835 When the symbol table changes, the value history is discarded,
10836 since the values may contain pointers back to the types defined in the
10841 @cindex history number
10842 The values printed are given @dfn{history numbers} by which you can
10843 refer to them. These are successive integers starting with one.
10844 @code{print} shows you the history number assigned to a value by
10845 printing @samp{$@var{num} = } before the value; here @var{num} is the
10848 To refer to any previous value, use @samp{$} followed by the value's
10849 history number. The way @code{print} labels its output is designed to
10850 remind you of this. Just @code{$} refers to the most recent value in
10851 the history, and @code{$$} refers to the value before that.
10852 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10853 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10854 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10856 For example, suppose you have just printed a pointer to a structure and
10857 want to see the contents of the structure. It suffices to type
10863 If you have a chain of structures where the component @code{next} points
10864 to the next one, you can print the contents of the next one with this:
10871 You can print successive links in the chain by repeating this
10872 command---which you can do by just typing @key{RET}.
10874 Note that the history records values, not expressions. If the value of
10875 @code{x} is 4 and you type these commands:
10883 then the value recorded in the value history by the @code{print} command
10884 remains 4 even though the value of @code{x} has changed.
10887 @kindex show values
10889 Print the last ten values in the value history, with their item numbers.
10890 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10891 values} does not change the history.
10893 @item show values @var{n}
10894 Print ten history values centered on history item number @var{n}.
10896 @item show values +
10897 Print ten history values just after the values last printed. If no more
10898 values are available, @code{show values +} produces no display.
10901 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10902 same effect as @samp{show values +}.
10904 @node Convenience Vars
10905 @section Convenience Variables
10907 @cindex convenience variables
10908 @cindex user-defined variables
10909 @value{GDBN} provides @dfn{convenience variables} that you can use within
10910 @value{GDBN} to hold on to a value and refer to it later. These variables
10911 exist entirely within @value{GDBN}; they are not part of your program, and
10912 setting a convenience variable has no direct effect on further execution
10913 of your program. That is why you can use them freely.
10915 Convenience variables are prefixed with @samp{$}. Any name preceded by
10916 @samp{$} can be used for a convenience variable, unless it is one of
10917 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10918 (Value history references, in contrast, are @emph{numbers} preceded
10919 by @samp{$}. @xref{Value History, ,Value History}.)
10921 You can save a value in a convenience variable with an assignment
10922 expression, just as you would set a variable in your program.
10926 set $foo = *object_ptr
10930 would save in @code{$foo} the value contained in the object pointed to by
10933 Using a convenience variable for the first time creates it, but its
10934 value is @code{void} until you assign a new value. You can alter the
10935 value with another assignment at any time.
10937 Convenience variables have no fixed types. You can assign a convenience
10938 variable any type of value, including structures and arrays, even if
10939 that variable already has a value of a different type. The convenience
10940 variable, when used as an expression, has the type of its current value.
10943 @kindex show convenience
10944 @cindex show all user variables and functions
10945 @item show convenience
10946 Print a list of convenience variables used so far, and their values,
10947 as well as a list of the convenience functions.
10948 Abbreviated @code{show conv}.
10950 @kindex init-if-undefined
10951 @cindex convenience variables, initializing
10952 @item init-if-undefined $@var{variable} = @var{expression}
10953 Set a convenience variable if it has not already been set. This is useful
10954 for user-defined commands that keep some state. It is similar, in concept,
10955 to using local static variables with initializers in C (except that
10956 convenience variables are global). It can also be used to allow users to
10957 override default values used in a command script.
10959 If the variable is already defined then the expression is not evaluated so
10960 any side-effects do not occur.
10963 One of the ways to use a convenience variable is as a counter to be
10964 incremented or a pointer to be advanced. For example, to print
10965 a field from successive elements of an array of structures:
10969 print bar[$i++]->contents
10973 Repeat that command by typing @key{RET}.
10975 Some convenience variables are created automatically by @value{GDBN} and given
10976 values likely to be useful.
10979 @vindex $_@r{, convenience variable}
10981 The variable @code{$_} is automatically set by the @code{x} command to
10982 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10983 commands which provide a default address for @code{x} to examine also
10984 set @code{$_} to that address; these commands include @code{info line}
10985 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10986 except when set by the @code{x} command, in which case it is a pointer
10987 to the type of @code{$__}.
10989 @vindex $__@r{, convenience variable}
10991 The variable @code{$__} is automatically set by the @code{x} command
10992 to the value found in the last address examined. Its type is chosen
10993 to match the format in which the data was printed.
10996 @vindex $_exitcode@r{, convenience variable}
10997 When the program being debugged terminates normally, @value{GDBN}
10998 automatically sets this variable to the exit code of the program, and
10999 resets @code{$_exitsignal} to @code{void}.
11002 @vindex $_exitsignal@r{, convenience variable}
11003 When the program being debugged dies due to an uncaught signal,
11004 @value{GDBN} automatically sets this variable to that signal's number,
11005 and resets @code{$_exitcode} to @code{void}.
11007 To distinguish between whether the program being debugged has exited
11008 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11009 @code{$_exitsignal} is not @code{void}), the convenience function
11010 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11011 Functions}). For example, considering the following source code:
11014 #include <signal.h>
11017 main (int argc, char *argv[])
11024 A valid way of telling whether the program being debugged has exited
11025 or signalled would be:
11028 (@value{GDBP}) define has_exited_or_signalled
11029 Type commands for definition of ``has_exited_or_signalled''.
11030 End with a line saying just ``end''.
11031 >if $_isvoid ($_exitsignal)
11032 >echo The program has exited\n
11034 >echo The program has signalled\n
11040 Program terminated with signal SIGALRM, Alarm clock.
11041 The program no longer exists.
11042 (@value{GDBP}) has_exited_or_signalled
11043 The program has signalled
11046 As can be seen, @value{GDBN} correctly informs that the program being
11047 debugged has signalled, since it calls @code{raise} and raises a
11048 @code{SIGALRM} signal. If the program being debugged had not called
11049 @code{raise}, then @value{GDBN} would report a normal exit:
11052 (@value{GDBP}) has_exited_or_signalled
11053 The program has exited
11057 The variable @code{$_exception} is set to the exception object being
11058 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11061 @itemx $_probe_arg0@dots{}$_probe_arg11
11062 Arguments to a static probe. @xref{Static Probe Points}.
11065 @vindex $_sdata@r{, inspect, convenience variable}
11066 The variable @code{$_sdata} contains extra collected static tracepoint
11067 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11068 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11069 if extra static tracepoint data has not been collected.
11072 @vindex $_siginfo@r{, convenience variable}
11073 The variable @code{$_siginfo} contains extra signal information
11074 (@pxref{extra signal information}). Note that @code{$_siginfo}
11075 could be empty, if the application has not yet received any signals.
11076 For example, it will be empty before you execute the @code{run} command.
11079 @vindex $_tlb@r{, convenience variable}
11080 The variable @code{$_tlb} is automatically set when debugging
11081 applications running on MS-Windows in native mode or connected to
11082 gdbserver that supports the @code{qGetTIBAddr} request.
11083 @xref{General Query Packets}.
11084 This variable contains the address of the thread information block.
11087 The number of the current inferior. @xref{Inferiors and
11088 Programs, ,Debugging Multiple Inferiors and Programs}.
11091 The thread number of the current thread. @xref{thread numbers}.
11094 The global number of the current thread. @xref{global thread numbers}.
11098 @node Convenience Funs
11099 @section Convenience Functions
11101 @cindex convenience functions
11102 @value{GDBN} also supplies some @dfn{convenience functions}. These
11103 have a syntax similar to convenience variables. A convenience
11104 function can be used in an expression just like an ordinary function;
11105 however, a convenience function is implemented internally to
11108 These functions do not require @value{GDBN} to be configured with
11109 @code{Python} support, which means that they are always available.
11113 @item $_isvoid (@var{expr})
11114 @findex $_isvoid@r{, convenience function}
11115 Return one if the expression @var{expr} is @code{void}. Otherwise it
11118 A @code{void} expression is an expression where the type of the result
11119 is @code{void}. For example, you can examine a convenience variable
11120 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11124 (@value{GDBP}) print $_exitcode
11126 (@value{GDBP}) print $_isvoid ($_exitcode)
11129 Starting program: ./a.out
11130 [Inferior 1 (process 29572) exited normally]
11131 (@value{GDBP}) print $_exitcode
11133 (@value{GDBP}) print $_isvoid ($_exitcode)
11137 In the example above, we used @code{$_isvoid} to check whether
11138 @code{$_exitcode} is @code{void} before and after the execution of the
11139 program being debugged. Before the execution there is no exit code to
11140 be examined, therefore @code{$_exitcode} is @code{void}. After the
11141 execution the program being debugged returned zero, therefore
11142 @code{$_exitcode} is zero, which means that it is not @code{void}
11145 The @code{void} expression can also be a call of a function from the
11146 program being debugged. For example, given the following function:
11155 The result of calling it inside @value{GDBN} is @code{void}:
11158 (@value{GDBP}) print foo ()
11160 (@value{GDBP}) print $_isvoid (foo ())
11162 (@value{GDBP}) set $v = foo ()
11163 (@value{GDBP}) print $v
11165 (@value{GDBP}) print $_isvoid ($v)
11171 These functions require @value{GDBN} to be configured with
11172 @code{Python} support.
11176 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11177 @findex $_memeq@r{, convenience function}
11178 Returns one if the @var{length} bytes at the addresses given by
11179 @var{buf1} and @var{buf2} are equal.
11180 Otherwise it returns zero.
11182 @item $_regex(@var{str}, @var{regex})
11183 @findex $_regex@r{, convenience function}
11184 Returns one if the string @var{str} matches the regular expression
11185 @var{regex}. Otherwise it returns zero.
11186 The syntax of the regular expression is that specified by @code{Python}'s
11187 regular expression support.
11189 @item $_streq(@var{str1}, @var{str2})
11190 @findex $_streq@r{, convenience function}
11191 Returns one if the strings @var{str1} and @var{str2} are equal.
11192 Otherwise it returns zero.
11194 @item $_strlen(@var{str})
11195 @findex $_strlen@r{, convenience function}
11196 Returns the length of string @var{str}.
11198 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11199 @findex $_caller_is@r{, convenience function}
11200 Returns one if the calling function's name is equal to @var{name}.
11201 Otherwise it returns zero.
11203 If the optional argument @var{number_of_frames} is provided,
11204 it is the number of frames up in the stack to look.
11212 at testsuite/gdb.python/py-caller-is.c:21
11213 #1 0x00000000004005a0 in middle_func ()
11214 at testsuite/gdb.python/py-caller-is.c:27
11215 #2 0x00000000004005ab in top_func ()
11216 at testsuite/gdb.python/py-caller-is.c:33
11217 #3 0x00000000004005b6 in main ()
11218 at testsuite/gdb.python/py-caller-is.c:39
11219 (gdb) print $_caller_is ("middle_func")
11221 (gdb) print $_caller_is ("top_func", 2)
11225 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11226 @findex $_caller_matches@r{, convenience function}
11227 Returns one if the calling function's name matches the regular expression
11228 @var{regexp}. Otherwise it returns zero.
11230 If the optional argument @var{number_of_frames} is provided,
11231 it is the number of frames up in the stack to look.
11234 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11235 @findex $_any_caller_is@r{, convenience function}
11236 Returns one if any calling function's name is equal to @var{name}.
11237 Otherwise it returns zero.
11239 If the optional argument @var{number_of_frames} is provided,
11240 it is the number of frames up in the stack to look.
11243 This function differs from @code{$_caller_is} in that this function
11244 checks all stack frames from the immediate caller to the frame specified
11245 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11246 frame specified by @var{number_of_frames}.
11248 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11249 @findex $_any_caller_matches@r{, convenience function}
11250 Returns one if any calling function's name matches the regular expression
11251 @var{regexp}. Otherwise it returns zero.
11253 If the optional argument @var{number_of_frames} is provided,
11254 it is the number of frames up in the stack to look.
11257 This function differs from @code{$_caller_matches} in that this function
11258 checks all stack frames from the immediate caller to the frame specified
11259 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11260 frame specified by @var{number_of_frames}.
11262 @item $_as_string(@var{value})
11263 @findex $_as_string@r{, convenience function}
11264 Return the string representation of @var{value}.
11266 This function is useful to obtain the textual label (enumerator) of an
11267 enumeration value. For example, assuming the variable @var{node} is of
11268 an enumerated type:
11271 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11272 Visiting node of type NODE_INTEGER
11277 @value{GDBN} provides the ability to list and get help on
11278 convenience functions.
11281 @item help function
11282 @kindex help function
11283 @cindex show all convenience functions
11284 Print a list of all convenience functions.
11291 You can refer to machine register contents, in expressions, as variables
11292 with names starting with @samp{$}. The names of registers are different
11293 for each machine; use @code{info registers} to see the names used on
11297 @kindex info registers
11298 @item info registers
11299 Print the names and values of all registers except floating-point
11300 and vector registers (in the selected stack frame).
11302 @kindex info all-registers
11303 @cindex floating point registers
11304 @item info all-registers
11305 Print the names and values of all registers, including floating-point
11306 and vector registers (in the selected stack frame).
11308 @item info registers @var{reggroup} @dots{}
11309 Print the name and value of the registers in each of the specified
11310 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11311 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11313 @item info registers @var{regname} @dots{}
11314 Print the @dfn{relativized} value of each specified register @var{regname}.
11315 As discussed in detail below, register values are normally relative to
11316 the selected stack frame. The @var{regname} may be any register name valid on
11317 the machine you are using, with or without the initial @samp{$}.
11320 @anchor{standard registers}
11321 @cindex stack pointer register
11322 @cindex program counter register
11323 @cindex process status register
11324 @cindex frame pointer register
11325 @cindex standard registers
11326 @value{GDBN} has four ``standard'' register names that are available (in
11327 expressions) on most machines---whenever they do not conflict with an
11328 architecture's canonical mnemonics for registers. The register names
11329 @code{$pc} and @code{$sp} are used for the program counter register and
11330 the stack pointer. @code{$fp} is used for a register that contains a
11331 pointer to the current stack frame, and @code{$ps} is used for a
11332 register that contains the processor status. For example,
11333 you could print the program counter in hex with
11340 or print the instruction to be executed next with
11347 or add four to the stack pointer@footnote{This is a way of removing
11348 one word from the stack, on machines where stacks grow downward in
11349 memory (most machines, nowadays). This assumes that the innermost
11350 stack frame is selected; setting @code{$sp} is not allowed when other
11351 stack frames are selected. To pop entire frames off the stack,
11352 regardless of machine architecture, use @code{return};
11353 see @ref{Returning, ,Returning from a Function}.} with
11359 Whenever possible, these four standard register names are available on
11360 your machine even though the machine has different canonical mnemonics,
11361 so long as there is no conflict. The @code{info registers} command
11362 shows the canonical names. For example, on the SPARC, @code{info
11363 registers} displays the processor status register as @code{$psr} but you
11364 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11365 is an alias for the @sc{eflags} register.
11367 @value{GDBN} always considers the contents of an ordinary register as an
11368 integer when the register is examined in this way. Some machines have
11369 special registers which can hold nothing but floating point; these
11370 registers are considered to have floating point values. There is no way
11371 to refer to the contents of an ordinary register as floating point value
11372 (although you can @emph{print} it as a floating point value with
11373 @samp{print/f $@var{regname}}).
11375 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11376 means that the data format in which the register contents are saved by
11377 the operating system is not the same one that your program normally
11378 sees. For example, the registers of the 68881 floating point
11379 coprocessor are always saved in ``extended'' (raw) format, but all C
11380 programs expect to work with ``double'' (virtual) format. In such
11381 cases, @value{GDBN} normally works with the virtual format only (the format
11382 that makes sense for your program), but the @code{info registers} command
11383 prints the data in both formats.
11385 @cindex SSE registers (x86)
11386 @cindex MMX registers (x86)
11387 Some machines have special registers whose contents can be interpreted
11388 in several different ways. For example, modern x86-based machines
11389 have SSE and MMX registers that can hold several values packed
11390 together in several different formats. @value{GDBN} refers to such
11391 registers in @code{struct} notation:
11394 (@value{GDBP}) print $xmm1
11396 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11397 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11398 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11399 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11400 v4_int32 = @{0, 20657912, 11, 13@},
11401 v2_int64 = @{88725056443645952, 55834574859@},
11402 uint128 = 0x0000000d0000000b013b36f800000000
11407 To set values of such registers, you need to tell @value{GDBN} which
11408 view of the register you wish to change, as if you were assigning
11409 value to a @code{struct} member:
11412 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11415 Normally, register values are relative to the selected stack frame
11416 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11417 value that the register would contain if all stack frames farther in
11418 were exited and their saved registers restored. In order to see the
11419 true contents of hardware registers, you must select the innermost
11420 frame (with @samp{frame 0}).
11422 @cindex caller-saved registers
11423 @cindex call-clobbered registers
11424 @cindex volatile registers
11425 @cindex <not saved> values
11426 Usually ABIs reserve some registers as not needed to be saved by the
11427 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11428 registers). It may therefore not be possible for @value{GDBN} to know
11429 the value a register had before the call (in other words, in the outer
11430 frame), if the register value has since been changed by the callee.
11431 @value{GDBN} tries to deduce where the inner frame saved
11432 (``callee-saved'') registers, from the debug info, unwind info, or the
11433 machine code generated by your compiler. If some register is not
11434 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11435 its own knowledge of the ABI, or because the debug/unwind info
11436 explicitly says the register's value is undefined), @value{GDBN}
11437 displays @w{@samp{<not saved>}} as the register's value. With targets
11438 that @value{GDBN} has no knowledge of the register saving convention,
11439 if a register was not saved by the callee, then its value and location
11440 in the outer frame are assumed to be the same of the inner frame.
11441 This is usually harmless, because if the register is call-clobbered,
11442 the caller either does not care what is in the register after the
11443 call, or has code to restore the value that it does care about. Note,
11444 however, that if you change such a register in the outer frame, you
11445 may also be affecting the inner frame. Also, the more ``outer'' the
11446 frame is you're looking at, the more likely a call-clobbered
11447 register's value is to be wrong, in the sense that it doesn't actually
11448 represent the value the register had just before the call.
11450 @node Floating Point Hardware
11451 @section Floating Point Hardware
11452 @cindex floating point
11454 Depending on the configuration, @value{GDBN} may be able to give
11455 you more information about the status of the floating point hardware.
11460 Display hardware-dependent information about the floating
11461 point unit. The exact contents and layout vary depending on the
11462 floating point chip. Currently, @samp{info float} is supported on
11463 the ARM and x86 machines.
11467 @section Vector Unit
11468 @cindex vector unit
11470 Depending on the configuration, @value{GDBN} may be able to give you
11471 more information about the status of the vector unit.
11474 @kindex info vector
11476 Display information about the vector unit. The exact contents and
11477 layout vary depending on the hardware.
11480 @node OS Information
11481 @section Operating System Auxiliary Information
11482 @cindex OS information
11484 @value{GDBN} provides interfaces to useful OS facilities that can help
11485 you debug your program.
11487 @cindex auxiliary vector
11488 @cindex vector, auxiliary
11489 Some operating systems supply an @dfn{auxiliary vector} to programs at
11490 startup. This is akin to the arguments and environment that you
11491 specify for a program, but contains a system-dependent variety of
11492 binary values that tell system libraries important details about the
11493 hardware, operating system, and process. Each value's purpose is
11494 identified by an integer tag; the meanings are well-known but system-specific.
11495 Depending on the configuration and operating system facilities,
11496 @value{GDBN} may be able to show you this information. For remote
11497 targets, this functionality may further depend on the remote stub's
11498 support of the @samp{qXfer:auxv:read} packet, see
11499 @ref{qXfer auxiliary vector read}.
11504 Display the auxiliary vector of the inferior, which can be either a
11505 live process or a core dump file. @value{GDBN} prints each tag value
11506 numerically, and also shows names and text descriptions for recognized
11507 tags. Some values in the vector are numbers, some bit masks, and some
11508 pointers to strings or other data. @value{GDBN} displays each value in the
11509 most appropriate form for a recognized tag, and in hexadecimal for
11510 an unrecognized tag.
11513 On some targets, @value{GDBN} can access operating system-specific
11514 information and show it to you. The types of information available
11515 will differ depending on the type of operating system running on the
11516 target. The mechanism used to fetch the data is described in
11517 @ref{Operating System Information}. For remote targets, this
11518 functionality depends on the remote stub's support of the
11519 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11523 @item info os @var{infotype}
11525 Display OS information of the requested type.
11527 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11529 @anchor{linux info os infotypes}
11531 @kindex info os cpus
11533 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11534 the available fields from /proc/cpuinfo. For each supported architecture
11535 different fields are available. Two common entries are processor which gives
11536 CPU number and bogomips; a system constant that is calculated during
11537 kernel initialization.
11539 @kindex info os files
11541 Display the list of open file descriptors on the target. For each
11542 file descriptor, @value{GDBN} prints the identifier of the process
11543 owning the descriptor, the command of the owning process, the value
11544 of the descriptor, and the target of the descriptor.
11546 @kindex info os modules
11548 Display the list of all loaded kernel modules on the target. For each
11549 module, @value{GDBN} prints the module name, the size of the module in
11550 bytes, the number of times the module is used, the dependencies of the
11551 module, the status of the module, and the address of the loaded module
11554 @kindex info os msg
11556 Display the list of all System V message queues on the target. For each
11557 message queue, @value{GDBN} prints the message queue key, the message
11558 queue identifier, the access permissions, the current number of bytes
11559 on the queue, the current number of messages on the queue, the processes
11560 that last sent and received a message on the queue, the user and group
11561 of the owner and creator of the message queue, the times at which a
11562 message was last sent and received on the queue, and the time at which
11563 the message queue was last changed.
11565 @kindex info os processes
11567 Display the list of processes on the target. For each process,
11568 @value{GDBN} prints the process identifier, the name of the user, the
11569 command corresponding to the process, and the list of processor cores
11570 that the process is currently running on. (To understand what these
11571 properties mean, for this and the following info types, please consult
11572 the general @sc{gnu}/Linux documentation.)
11574 @kindex info os procgroups
11576 Display the list of process groups on the target. For each process,
11577 @value{GDBN} prints the identifier of the process group that it belongs
11578 to, the command corresponding to the process group leader, the process
11579 identifier, and the command line of the process. The list is sorted
11580 first by the process group identifier, then by the process identifier,
11581 so that processes belonging to the same process group are grouped together
11582 and the process group leader is listed first.
11584 @kindex info os semaphores
11586 Display the list of all System V semaphore sets on the target. For each
11587 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11588 set identifier, the access permissions, the number of semaphores in the
11589 set, the user and group of the owner and creator of the semaphore set,
11590 and the times at which the semaphore set was operated upon and changed.
11592 @kindex info os shm
11594 Display the list of all System V shared-memory regions on the target.
11595 For each shared-memory region, @value{GDBN} prints the region key,
11596 the shared-memory identifier, the access permissions, the size of the
11597 region, the process that created the region, the process that last
11598 attached to or detached from the region, the current number of live
11599 attaches to the region, and the times at which the region was last
11600 attached to, detach from, and changed.
11602 @kindex info os sockets
11604 Display the list of Internet-domain sockets on the target. For each
11605 socket, @value{GDBN} prints the address and port of the local and
11606 remote endpoints, the current state of the connection, the creator of
11607 the socket, the IP address family of the socket, and the type of the
11610 @kindex info os threads
11612 Display the list of threads running on the target. For each thread,
11613 @value{GDBN} prints the identifier of the process that the thread
11614 belongs to, the command of the process, the thread identifier, and the
11615 processor core that it is currently running on. The main thread of a
11616 process is not listed.
11620 If @var{infotype} is omitted, then list the possible values for
11621 @var{infotype} and the kind of OS information available for each
11622 @var{infotype}. If the target does not return a list of possible
11623 types, this command will report an error.
11626 @node Memory Region Attributes
11627 @section Memory Region Attributes
11628 @cindex memory region attributes
11630 @dfn{Memory region attributes} allow you to describe special handling
11631 required by regions of your target's memory. @value{GDBN} uses
11632 attributes to determine whether to allow certain types of memory
11633 accesses; whether to use specific width accesses; and whether to cache
11634 target memory. By default the description of memory regions is
11635 fetched from the target (if the current target supports this), but the
11636 user can override the fetched regions.
11638 Defined memory regions can be individually enabled and disabled. When a
11639 memory region is disabled, @value{GDBN} uses the default attributes when
11640 accessing memory in that region. Similarly, if no memory regions have
11641 been defined, @value{GDBN} uses the default attributes when accessing
11644 When a memory region is defined, it is given a number to identify it;
11645 to enable, disable, or remove a memory region, you specify that number.
11649 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11650 Define a memory region bounded by @var{lower} and @var{upper} with
11651 attributes @var{attributes}@dots{}, and add it to the list of regions
11652 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11653 case: it is treated as the target's maximum memory address.
11654 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11657 Discard any user changes to the memory regions and use target-supplied
11658 regions, if available, or no regions if the target does not support.
11661 @item delete mem @var{nums}@dots{}
11662 Remove memory regions @var{nums}@dots{} from the list of regions
11663 monitored by @value{GDBN}.
11665 @kindex disable mem
11666 @item disable mem @var{nums}@dots{}
11667 Disable monitoring of memory regions @var{nums}@dots{}.
11668 A disabled memory region is not forgotten.
11669 It may be enabled again later.
11672 @item enable mem @var{nums}@dots{}
11673 Enable monitoring of memory regions @var{nums}@dots{}.
11677 Print a table of all defined memory regions, with the following columns
11681 @item Memory Region Number
11682 @item Enabled or Disabled.
11683 Enabled memory regions are marked with @samp{y}.
11684 Disabled memory regions are marked with @samp{n}.
11687 The address defining the inclusive lower bound of the memory region.
11690 The address defining the exclusive upper bound of the memory region.
11693 The list of attributes set for this memory region.
11698 @subsection Attributes
11700 @subsubsection Memory Access Mode
11701 The access mode attributes set whether @value{GDBN} may make read or
11702 write accesses to a memory region.
11704 While these attributes prevent @value{GDBN} from performing invalid
11705 memory accesses, they do nothing to prevent the target system, I/O DMA,
11706 etc.@: from accessing memory.
11710 Memory is read only.
11712 Memory is write only.
11714 Memory is read/write. This is the default.
11717 @subsubsection Memory Access Size
11718 The access size attribute tells @value{GDBN} to use specific sized
11719 accesses in the memory region. Often memory mapped device registers
11720 require specific sized accesses. If no access size attribute is
11721 specified, @value{GDBN} may use accesses of any size.
11725 Use 8 bit memory accesses.
11727 Use 16 bit memory accesses.
11729 Use 32 bit memory accesses.
11731 Use 64 bit memory accesses.
11734 @c @subsubsection Hardware/Software Breakpoints
11735 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11736 @c will use hardware or software breakpoints for the internal breakpoints
11737 @c used by the step, next, finish, until, etc. commands.
11741 @c Always use hardware breakpoints
11742 @c @item swbreak (default)
11745 @subsubsection Data Cache
11746 The data cache attributes set whether @value{GDBN} will cache target
11747 memory. While this generally improves performance by reducing debug
11748 protocol overhead, it can lead to incorrect results because @value{GDBN}
11749 does not know about volatile variables or memory mapped device
11754 Enable @value{GDBN} to cache target memory.
11756 Disable @value{GDBN} from caching target memory. This is the default.
11759 @subsection Memory Access Checking
11760 @value{GDBN} can be instructed to refuse accesses to memory that is
11761 not explicitly described. This can be useful if accessing such
11762 regions has undesired effects for a specific target, or to provide
11763 better error checking. The following commands control this behaviour.
11766 @kindex set mem inaccessible-by-default
11767 @item set mem inaccessible-by-default [on|off]
11768 If @code{on} is specified, make @value{GDBN} treat memory not
11769 explicitly described by the memory ranges as non-existent and refuse accesses
11770 to such memory. The checks are only performed if there's at least one
11771 memory range defined. If @code{off} is specified, make @value{GDBN}
11772 treat the memory not explicitly described by the memory ranges as RAM.
11773 The default value is @code{on}.
11774 @kindex show mem inaccessible-by-default
11775 @item show mem inaccessible-by-default
11776 Show the current handling of accesses to unknown memory.
11780 @c @subsubsection Memory Write Verification
11781 @c The memory write verification attributes set whether @value{GDBN}
11782 @c will re-reads data after each write to verify the write was successful.
11786 @c @item noverify (default)
11789 @node Dump/Restore Files
11790 @section Copy Between Memory and a File
11791 @cindex dump/restore files
11792 @cindex append data to a file
11793 @cindex dump data to a file
11794 @cindex restore data from a file
11796 You can use the commands @code{dump}, @code{append}, and
11797 @code{restore} to copy data between target memory and a file. The
11798 @code{dump} and @code{append} commands write data to a file, and the
11799 @code{restore} command reads data from a file back into the inferior's
11800 memory. Files may be in binary, Motorola S-record, Intel hex,
11801 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11802 append to binary files, and cannot read from Verilog Hex files.
11807 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11808 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11809 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11810 or the value of @var{expr}, to @var{filename} in the given format.
11812 The @var{format} parameter may be any one of:
11819 Motorola S-record format.
11821 Tektronix Hex format.
11823 Verilog Hex format.
11826 @value{GDBN} uses the same definitions of these formats as the
11827 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11828 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11832 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11833 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11834 Append the contents of memory from @var{start_addr} to @var{end_addr},
11835 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11836 (@value{GDBN} can only append data to files in raw binary form.)
11839 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11840 Restore the contents of file @var{filename} into memory. The
11841 @code{restore} command can automatically recognize any known @sc{bfd}
11842 file format, except for raw binary. To restore a raw binary file you
11843 must specify the optional keyword @code{binary} after the filename.
11845 If @var{bias} is non-zero, its value will be added to the addresses
11846 contained in the file. Binary files always start at address zero, so
11847 they will be restored at address @var{bias}. Other bfd files have
11848 a built-in location; they will be restored at offset @var{bias}
11849 from that location.
11851 If @var{start} and/or @var{end} are non-zero, then only data between
11852 file offset @var{start} and file offset @var{end} will be restored.
11853 These offsets are relative to the addresses in the file, before
11854 the @var{bias} argument is applied.
11858 @node Core File Generation
11859 @section How to Produce a Core File from Your Program
11860 @cindex dump core from inferior
11862 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11863 image of a running process and its process status (register values
11864 etc.). Its primary use is post-mortem debugging of a program that
11865 crashed while it ran outside a debugger. A program that crashes
11866 automatically produces a core file, unless this feature is disabled by
11867 the user. @xref{Files}, for information on invoking @value{GDBN} in
11868 the post-mortem debugging mode.
11870 Occasionally, you may wish to produce a core file of the program you
11871 are debugging in order to preserve a snapshot of its state.
11872 @value{GDBN} has a special command for that.
11876 @kindex generate-core-file
11877 @item generate-core-file [@var{file}]
11878 @itemx gcore [@var{file}]
11879 Produce a core dump of the inferior process. The optional argument
11880 @var{file} specifies the file name where to put the core dump. If not
11881 specified, the file name defaults to @file{core.@var{pid}}, where
11882 @var{pid} is the inferior process ID.
11884 Note that this command is implemented only for some systems (as of
11885 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11887 On @sc{gnu}/Linux, this command can take into account the value of the
11888 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11889 dump (@pxref{set use-coredump-filter}), and by default honors the
11890 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11891 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11893 @kindex set use-coredump-filter
11894 @anchor{set use-coredump-filter}
11895 @item set use-coredump-filter on
11896 @itemx set use-coredump-filter off
11897 Enable or disable the use of the file
11898 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11899 files. This file is used by the Linux kernel to decide what types of
11900 memory mappings will be dumped or ignored when generating a core dump
11901 file. @var{pid} is the process ID of a currently running process.
11903 To make use of this feature, you have to write in the
11904 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11905 which is a bit mask representing the memory mapping types. If a bit
11906 is set in the bit mask, then the memory mappings of the corresponding
11907 types will be dumped; otherwise, they will be ignored. This
11908 configuration is inherited by child processes. For more information
11909 about the bits that can be set in the
11910 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11911 manpage of @code{core(5)}.
11913 By default, this option is @code{on}. If this option is turned
11914 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11915 and instead uses the same default value as the Linux kernel in order
11916 to decide which pages will be dumped in the core dump file. This
11917 value is currently @code{0x33}, which means that bits @code{0}
11918 (anonymous private mappings), @code{1} (anonymous shared mappings),
11919 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11920 This will cause these memory mappings to be dumped automatically.
11922 @kindex set dump-excluded-mappings
11923 @anchor{set dump-excluded-mappings}
11924 @item set dump-excluded-mappings on
11925 @itemx set dump-excluded-mappings off
11926 If @code{on} is specified, @value{GDBN} will dump memory mappings
11927 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11928 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11930 The default value is @code{off}.
11933 @node Character Sets
11934 @section Character Sets
11935 @cindex character sets
11937 @cindex translating between character sets
11938 @cindex host character set
11939 @cindex target character set
11941 If the program you are debugging uses a different character set to
11942 represent characters and strings than the one @value{GDBN} uses itself,
11943 @value{GDBN} can automatically translate between the character sets for
11944 you. The character set @value{GDBN} uses we call the @dfn{host
11945 character set}; the one the inferior program uses we call the
11946 @dfn{target character set}.
11948 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11949 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11950 remote protocol (@pxref{Remote Debugging}) to debug a program
11951 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11952 then the host character set is Latin-1, and the target character set is
11953 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11954 target-charset EBCDIC-US}, then @value{GDBN} translates between
11955 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11956 character and string literals in expressions.
11958 @value{GDBN} has no way to automatically recognize which character set
11959 the inferior program uses; you must tell it, using the @code{set
11960 target-charset} command, described below.
11962 Here are the commands for controlling @value{GDBN}'s character set
11966 @item set target-charset @var{charset}
11967 @kindex set target-charset
11968 Set the current target character set to @var{charset}. To display the
11969 list of supported target character sets, type
11970 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11972 @item set host-charset @var{charset}
11973 @kindex set host-charset
11974 Set the current host character set to @var{charset}.
11976 By default, @value{GDBN} uses a host character set appropriate to the
11977 system it is running on; you can override that default using the
11978 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11979 automatically determine the appropriate host character set. In this
11980 case, @value{GDBN} uses @samp{UTF-8}.
11982 @value{GDBN} can only use certain character sets as its host character
11983 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11984 @value{GDBN} will list the host character sets it supports.
11986 @item set charset @var{charset}
11987 @kindex set charset
11988 Set the current host and target character sets to @var{charset}. As
11989 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11990 @value{GDBN} will list the names of the character sets that can be used
11991 for both host and target.
11994 @kindex show charset
11995 Show the names of the current host and target character sets.
11997 @item show host-charset
11998 @kindex show host-charset
11999 Show the name of the current host character set.
12001 @item show target-charset
12002 @kindex show target-charset
12003 Show the name of the current target character set.
12005 @item set target-wide-charset @var{charset}
12006 @kindex set target-wide-charset
12007 Set the current target's wide character set to @var{charset}. This is
12008 the character set used by the target's @code{wchar_t} type. To
12009 display the list of supported wide character sets, type
12010 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12012 @item show target-wide-charset
12013 @kindex show target-wide-charset
12014 Show the name of the current target's wide character set.
12017 Here is an example of @value{GDBN}'s character set support in action.
12018 Assume that the following source code has been placed in the file
12019 @file{charset-test.c}:
12025 = @{72, 101, 108, 108, 111, 44, 32, 119,
12026 111, 114, 108, 100, 33, 10, 0@};
12027 char ibm1047_hello[]
12028 = @{200, 133, 147, 147, 150, 107, 64, 166,
12029 150, 153, 147, 132, 90, 37, 0@};
12033 printf ("Hello, world!\n");
12037 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12038 containing the string @samp{Hello, world!} followed by a newline,
12039 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12041 We compile the program, and invoke the debugger on it:
12044 $ gcc -g charset-test.c -o charset-test
12045 $ gdb -nw charset-test
12046 GNU gdb 2001-12-19-cvs
12047 Copyright 2001 Free Software Foundation, Inc.
12052 We can use the @code{show charset} command to see what character sets
12053 @value{GDBN} is currently using to interpret and display characters and
12057 (@value{GDBP}) show charset
12058 The current host and target character set is `ISO-8859-1'.
12062 For the sake of printing this manual, let's use @sc{ascii} as our
12063 initial character set:
12065 (@value{GDBP}) set charset ASCII
12066 (@value{GDBP}) show charset
12067 The current host and target character set is `ASCII'.
12071 Let's assume that @sc{ascii} is indeed the correct character set for our
12072 host system --- in other words, let's assume that if @value{GDBN} prints
12073 characters using the @sc{ascii} character set, our terminal will display
12074 them properly. Since our current target character set is also
12075 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12078 (@value{GDBP}) print ascii_hello
12079 $1 = 0x401698 "Hello, world!\n"
12080 (@value{GDBP}) print ascii_hello[0]
12085 @value{GDBN} uses the target character set for character and string
12086 literals you use in expressions:
12089 (@value{GDBP}) print '+'
12094 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12097 @value{GDBN} relies on the user to tell it which character set the
12098 target program uses. If we print @code{ibm1047_hello} while our target
12099 character set is still @sc{ascii}, we get jibberish:
12102 (@value{GDBP}) print ibm1047_hello
12103 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12104 (@value{GDBP}) print ibm1047_hello[0]
12109 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12110 @value{GDBN} tells us the character sets it supports:
12113 (@value{GDBP}) set target-charset
12114 ASCII EBCDIC-US IBM1047 ISO-8859-1
12115 (@value{GDBP}) set target-charset
12118 We can select @sc{ibm1047} as our target character set, and examine the
12119 program's strings again. Now the @sc{ascii} string is wrong, but
12120 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12121 target character set, @sc{ibm1047}, to the host character set,
12122 @sc{ascii}, and they display correctly:
12125 (@value{GDBP}) set target-charset IBM1047
12126 (@value{GDBP}) show charset
12127 The current host character set is `ASCII'.
12128 The current target character set is `IBM1047'.
12129 (@value{GDBP}) print ascii_hello
12130 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12131 (@value{GDBP}) print ascii_hello[0]
12133 (@value{GDBP}) print ibm1047_hello
12134 $8 = 0x4016a8 "Hello, world!\n"
12135 (@value{GDBP}) print ibm1047_hello[0]
12140 As above, @value{GDBN} uses the target character set for character and
12141 string literals you use in expressions:
12144 (@value{GDBP}) print '+'
12149 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12152 @node Caching Target Data
12153 @section Caching Data of Targets
12154 @cindex caching data of targets
12156 @value{GDBN} caches data exchanged between the debugger and a target.
12157 Each cache is associated with the address space of the inferior.
12158 @xref{Inferiors and Programs}, about inferior and address space.
12159 Such caching generally improves performance in remote debugging
12160 (@pxref{Remote Debugging}), because it reduces the overhead of the
12161 remote protocol by bundling memory reads and writes into large chunks.
12162 Unfortunately, simply caching everything would lead to incorrect results,
12163 since @value{GDBN} does not necessarily know anything about volatile
12164 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12165 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12167 Therefore, by default, @value{GDBN} only caches data
12168 known to be on the stack@footnote{In non-stop mode, it is moderately
12169 rare for a running thread to modify the stack of a stopped thread
12170 in a way that would interfere with a backtrace, and caching of
12171 stack reads provides a significant speed up of remote backtraces.} or
12172 in the code segment.
12173 Other regions of memory can be explicitly marked as
12174 cacheable; @pxref{Memory Region Attributes}.
12177 @kindex set remotecache
12178 @item set remotecache on
12179 @itemx set remotecache off
12180 This option no longer does anything; it exists for compatibility
12183 @kindex show remotecache
12184 @item show remotecache
12185 Show the current state of the obsolete remotecache flag.
12187 @kindex set stack-cache
12188 @item set stack-cache on
12189 @itemx set stack-cache off
12190 Enable or disable caching of stack accesses. When @code{on}, use
12191 caching. By default, this option is @code{on}.
12193 @kindex show stack-cache
12194 @item show stack-cache
12195 Show the current state of data caching for memory accesses.
12197 @kindex set code-cache
12198 @item set code-cache on
12199 @itemx set code-cache off
12200 Enable or disable caching of code segment accesses. When @code{on},
12201 use caching. By default, this option is @code{on}. This improves
12202 performance of disassembly in remote debugging.
12204 @kindex show code-cache
12205 @item show code-cache
12206 Show the current state of target memory cache for code segment
12209 @kindex info dcache
12210 @item info dcache @r{[}line@r{]}
12211 Print the information about the performance of data cache of the
12212 current inferior's address space. The information displayed
12213 includes the dcache width and depth, and for each cache line, its
12214 number, address, and how many times it was referenced. This
12215 command is useful for debugging the data cache operation.
12217 If a line number is specified, the contents of that line will be
12220 @item set dcache size @var{size}
12221 @cindex dcache size
12222 @kindex set dcache size
12223 Set maximum number of entries in dcache (dcache depth above).
12225 @item set dcache line-size @var{line-size}
12226 @cindex dcache line-size
12227 @kindex set dcache line-size
12228 Set number of bytes each dcache entry caches (dcache width above).
12229 Must be a power of 2.
12231 @item show dcache size
12232 @kindex show dcache size
12233 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12235 @item show dcache line-size
12236 @kindex show dcache line-size
12237 Show default size of dcache lines.
12241 @node Searching Memory
12242 @section Search Memory
12243 @cindex searching memory
12245 Memory can be searched for a particular sequence of bytes with the
12246 @code{find} command.
12250 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12251 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12252 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12253 etc. The search begins at address @var{start_addr} and continues for either
12254 @var{len} bytes or through to @var{end_addr} inclusive.
12257 @var{s} and @var{n} are optional parameters.
12258 They may be specified in either order, apart or together.
12261 @item @var{s}, search query size
12262 The size of each search query value.
12268 halfwords (two bytes)
12272 giant words (eight bytes)
12275 All values are interpreted in the current language.
12276 This means, for example, that if the current source language is C/C@t{++}
12277 then searching for the string ``hello'' includes the trailing '\0'.
12278 The null terminator can be removed from searching by using casts,
12279 e.g.: @samp{@{char[5]@}"hello"}.
12281 If the value size is not specified, it is taken from the
12282 value's type in the current language.
12283 This is useful when one wants to specify the search
12284 pattern as a mixture of types.
12285 Note that this means, for example, that in the case of C-like languages
12286 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12287 which is typically four bytes.
12289 @item @var{n}, maximum number of finds
12290 The maximum number of matches to print. The default is to print all finds.
12293 You can use strings as search values. Quote them with double-quotes
12295 The string value is copied into the search pattern byte by byte,
12296 regardless of the endianness of the target and the size specification.
12298 The address of each match found is printed as well as a count of the
12299 number of matches found.
12301 The address of the last value found is stored in convenience variable
12303 A count of the number of matches is stored in @samp{$numfound}.
12305 For example, if stopped at the @code{printf} in this function:
12311 static char hello[] = "hello-hello";
12312 static struct @{ char c; short s; int i; @}
12313 __attribute__ ((packed)) mixed
12314 = @{ 'c', 0x1234, 0x87654321 @};
12315 printf ("%s\n", hello);
12320 you get during debugging:
12323 (gdb) find &hello[0], +sizeof(hello), "hello"
12324 0x804956d <hello.1620+6>
12326 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12327 0x8049567 <hello.1620>
12328 0x804956d <hello.1620+6>
12330 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12331 0x8049567 <hello.1620>
12332 0x804956d <hello.1620+6>
12334 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12335 0x8049567 <hello.1620>
12337 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12338 0x8049560 <mixed.1625>
12340 (gdb) print $numfound
12343 $2 = (void *) 0x8049560
12347 @section Value Sizes
12349 Whenever @value{GDBN} prints a value memory will be allocated within
12350 @value{GDBN} to hold the contents of the value. It is possible in
12351 some languages with dynamic typing systems, that an invalid program
12352 may indicate a value that is incorrectly large, this in turn may cause
12353 @value{GDBN} to try and allocate an overly large ammount of memory.
12356 @kindex set max-value-size
12357 @item set max-value-size @var{bytes}
12358 @itemx set max-value-size unlimited
12359 Set the maximum size of memory that @value{GDBN} will allocate for the
12360 contents of a value to @var{bytes}, trying to display a value that
12361 requires more memory than that will result in an error.
12363 Setting this variable does not effect values that have already been
12364 allocated within @value{GDBN}, only future allocations.
12366 There's a minimum size that @code{max-value-size} can be set to in
12367 order that @value{GDBN} can still operate correctly, this minimum is
12368 currently 16 bytes.
12370 The limit applies to the results of some subexpressions as well as to
12371 complete expressions. For example, an expression denoting a simple
12372 integer component, such as @code{x.y.z}, may fail if the size of
12373 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12374 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12375 @var{A} is an array variable with non-constant size, will generally
12376 succeed regardless of the bounds on @var{A}, as long as the component
12377 size is less than @var{bytes}.
12379 The default value of @code{max-value-size} is currently 64k.
12381 @kindex show max-value-size
12382 @item show max-value-size
12383 Show the maximum size of memory, in bytes, that @value{GDBN} will
12384 allocate for the contents of a value.
12387 @node Optimized Code
12388 @chapter Debugging Optimized Code
12389 @cindex optimized code, debugging
12390 @cindex debugging optimized code
12392 Almost all compilers support optimization. With optimization
12393 disabled, the compiler generates assembly code that corresponds
12394 directly to your source code, in a simplistic way. As the compiler
12395 applies more powerful optimizations, the generated assembly code
12396 diverges from your original source code. With help from debugging
12397 information generated by the compiler, @value{GDBN} can map from
12398 the running program back to constructs from your original source.
12400 @value{GDBN} is more accurate with optimization disabled. If you
12401 can recompile without optimization, it is easier to follow the
12402 progress of your program during debugging. But, there are many cases
12403 where you may need to debug an optimized version.
12405 When you debug a program compiled with @samp{-g -O}, remember that the
12406 optimizer has rearranged your code; the debugger shows you what is
12407 really there. Do not be too surprised when the execution path does not
12408 exactly match your source file! An extreme example: if you define a
12409 variable, but never use it, @value{GDBN} never sees that
12410 variable---because the compiler optimizes it out of existence.
12412 Some things do not work as well with @samp{-g -O} as with just
12413 @samp{-g}, particularly on machines with instruction scheduling. If in
12414 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12415 please report it to us as a bug (including a test case!).
12416 @xref{Variables}, for more information about debugging optimized code.
12419 * Inline Functions:: How @value{GDBN} presents inlining
12420 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12423 @node Inline Functions
12424 @section Inline Functions
12425 @cindex inline functions, debugging
12427 @dfn{Inlining} is an optimization that inserts a copy of the function
12428 body directly at each call site, instead of jumping to a shared
12429 routine. @value{GDBN} displays inlined functions just like
12430 non-inlined functions. They appear in backtraces. You can view their
12431 arguments and local variables, step into them with @code{step}, skip
12432 them with @code{next}, and escape from them with @code{finish}.
12433 You can check whether a function was inlined by using the
12434 @code{info frame} command.
12436 For @value{GDBN} to support inlined functions, the compiler must
12437 record information about inlining in the debug information ---
12438 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12439 other compilers do also. @value{GDBN} only supports inlined functions
12440 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12441 do not emit two required attributes (@samp{DW_AT_call_file} and
12442 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12443 function calls with earlier versions of @value{NGCC}. It instead
12444 displays the arguments and local variables of inlined functions as
12445 local variables in the caller.
12447 The body of an inlined function is directly included at its call site;
12448 unlike a non-inlined function, there are no instructions devoted to
12449 the call. @value{GDBN} still pretends that the call site and the
12450 start of the inlined function are different instructions. Stepping to
12451 the call site shows the call site, and then stepping again shows
12452 the first line of the inlined function, even though no additional
12453 instructions are executed.
12455 This makes source-level debugging much clearer; you can see both the
12456 context of the call and then the effect of the call. Only stepping by
12457 a single instruction using @code{stepi} or @code{nexti} does not do
12458 this; single instruction steps always show the inlined body.
12460 There are some ways that @value{GDBN} does not pretend that inlined
12461 function calls are the same as normal calls:
12465 Setting breakpoints at the call site of an inlined function may not
12466 work, because the call site does not contain any code. @value{GDBN}
12467 may incorrectly move the breakpoint to the next line of the enclosing
12468 function, after the call. This limitation will be removed in a future
12469 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12470 or inside the inlined function instead.
12473 @value{GDBN} cannot locate the return value of inlined calls after
12474 using the @code{finish} command. This is a limitation of compiler-generated
12475 debugging information; after @code{finish}, you can step to the next line
12476 and print a variable where your program stored the return value.
12480 @node Tail Call Frames
12481 @section Tail Call Frames
12482 @cindex tail call frames, debugging
12484 Function @code{B} can call function @code{C} in its very last statement. In
12485 unoptimized compilation the call of @code{C} is immediately followed by return
12486 instruction at the end of @code{B} code. Optimizing compiler may replace the
12487 call and return in function @code{B} into one jump to function @code{C}
12488 instead. Such use of a jump instruction is called @dfn{tail call}.
12490 During execution of function @code{C}, there will be no indication in the
12491 function call stack frames that it was tail-called from @code{B}. If function
12492 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12493 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12494 some cases @value{GDBN} can determine that @code{C} was tail-called from
12495 @code{B}, and it will then create fictitious call frame for that, with the
12496 return address set up as if @code{B} called @code{C} normally.
12498 This functionality is currently supported only by DWARF 2 debugging format and
12499 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12500 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12503 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12504 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12508 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12510 Stack level 1, frame at 0x7fffffffda30:
12511 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12512 tail call frame, caller of frame at 0x7fffffffda30
12513 source language c++.
12514 Arglist at unknown address.
12515 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12518 The detection of all the possible code path executions can find them ambiguous.
12519 There is no execution history stored (possible @ref{Reverse Execution} is never
12520 used for this purpose) and the last known caller could have reached the known
12521 callee by multiple different jump sequences. In such case @value{GDBN} still
12522 tries to show at least all the unambiguous top tail callers and all the
12523 unambiguous bottom tail calees, if any.
12526 @anchor{set debug entry-values}
12527 @item set debug entry-values
12528 @kindex set debug entry-values
12529 When set to on, enables printing of analysis messages for both frame argument
12530 values at function entry and tail calls. It will show all the possible valid
12531 tail calls code paths it has considered. It will also print the intersection
12532 of them with the final unambiguous (possibly partial or even empty) code path
12535 @item show debug entry-values
12536 @kindex show debug entry-values
12537 Show the current state of analysis messages printing for both frame argument
12538 values at function entry and tail calls.
12541 The analysis messages for tail calls can for example show why the virtual tail
12542 call frame for function @code{c} has not been recognized (due to the indirect
12543 reference by variable @code{x}):
12546 static void __attribute__((noinline, noclone)) c (void);
12547 void (*x) (void) = c;
12548 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12549 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12550 int main (void) @{ x (); return 0; @}
12552 Breakpoint 1, DW_OP_entry_value resolving cannot find
12553 DW_TAG_call_site 0x40039a in main
12555 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12558 #1 0x000000000040039a in main () at t.c:5
12561 Another possibility is an ambiguous virtual tail call frames resolution:
12565 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12566 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12567 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12568 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12569 static void __attribute__((noinline, noclone)) b (void)
12570 @{ if (i) c (); else e (); @}
12571 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12572 int main (void) @{ a (); return 0; @}
12574 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12575 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12576 tailcall: reduced: 0x4004d2(a) |
12579 #1 0x00000000004004d2 in a () at t.c:8
12580 #2 0x0000000000400395 in main () at t.c:9
12583 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12584 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12586 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12587 @ifset HAVE_MAKEINFO_CLICK
12588 @set ARROW @click{}
12589 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12590 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12592 @ifclear HAVE_MAKEINFO_CLICK
12594 @set CALLSEQ1B @value{CALLSEQ1A}
12595 @set CALLSEQ2B @value{CALLSEQ2A}
12598 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12599 The code can have possible execution paths @value{CALLSEQ1B} or
12600 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12602 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12603 has found. It then finds another possible calling sequcen - that one is
12604 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12605 printed as the @code{reduced:} calling sequence. That one could have many
12606 futher @code{compare:} and @code{reduced:} statements as long as there remain
12607 any non-ambiguous sequence entries.
12609 For the frame of function @code{b} in both cases there are different possible
12610 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12611 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12612 therefore this one is displayed to the user while the ambiguous frames are
12615 There can be also reasons why printing of frame argument values at function
12620 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12621 static void __attribute__((noinline, noclone)) a (int i);
12622 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12623 static void __attribute__((noinline, noclone)) a (int i)
12624 @{ if (i) b (i - 1); else c (0); @}
12625 int main (void) @{ a (5); return 0; @}
12628 #0 c (i=i@@entry=0) at t.c:2
12629 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12630 function "a" at 0x400420 can call itself via tail calls
12631 i=<optimized out>) at t.c:6
12632 #2 0x000000000040036e in main () at t.c:7
12635 @value{GDBN} cannot find out from the inferior state if and how many times did
12636 function @code{a} call itself (via function @code{b}) as these calls would be
12637 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12638 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12639 prints @code{<optimized out>} instead.
12642 @chapter C Preprocessor Macros
12644 Some languages, such as C and C@t{++}, provide a way to define and invoke
12645 ``preprocessor macros'' which expand into strings of tokens.
12646 @value{GDBN} can evaluate expressions containing macro invocations, show
12647 the result of macro expansion, and show a macro's definition, including
12648 where it was defined.
12650 You may need to compile your program specially to provide @value{GDBN}
12651 with information about preprocessor macros. Most compilers do not
12652 include macros in their debugging information, even when you compile
12653 with the @option{-g} flag. @xref{Compilation}.
12655 A program may define a macro at one point, remove that definition later,
12656 and then provide a different definition after that. Thus, at different
12657 points in the program, a macro may have different definitions, or have
12658 no definition at all. If there is a current stack frame, @value{GDBN}
12659 uses the macros in scope at that frame's source code line. Otherwise,
12660 @value{GDBN} uses the macros in scope at the current listing location;
12663 Whenever @value{GDBN} evaluates an expression, it always expands any
12664 macro invocations present in the expression. @value{GDBN} also provides
12665 the following commands for working with macros explicitly.
12669 @kindex macro expand
12670 @cindex macro expansion, showing the results of preprocessor
12671 @cindex preprocessor macro expansion, showing the results of
12672 @cindex expanding preprocessor macros
12673 @item macro expand @var{expression}
12674 @itemx macro exp @var{expression}
12675 Show the results of expanding all preprocessor macro invocations in
12676 @var{expression}. Since @value{GDBN} simply expands macros, but does
12677 not parse the result, @var{expression} need not be a valid expression;
12678 it can be any string of tokens.
12681 @item macro expand-once @var{expression}
12682 @itemx macro exp1 @var{expression}
12683 @cindex expand macro once
12684 @i{(This command is not yet implemented.)} Show the results of
12685 expanding those preprocessor macro invocations that appear explicitly in
12686 @var{expression}. Macro invocations appearing in that expansion are
12687 left unchanged. This command allows you to see the effect of a
12688 particular macro more clearly, without being confused by further
12689 expansions. Since @value{GDBN} simply expands macros, but does not
12690 parse the result, @var{expression} need not be a valid expression; it
12691 can be any string of tokens.
12694 @cindex macro definition, showing
12695 @cindex definition of a macro, showing
12696 @cindex macros, from debug info
12697 @item info macro [-a|-all] [--] @var{macro}
12698 Show the current definition or all definitions of the named @var{macro},
12699 and describe the source location or compiler command-line where that
12700 definition was established. The optional double dash is to signify the end of
12701 argument processing and the beginning of @var{macro} for non C-like macros where
12702 the macro may begin with a hyphen.
12704 @kindex info macros
12705 @item info macros @var{location}
12706 Show all macro definitions that are in effect at the location specified
12707 by @var{location}, and describe the source location or compiler
12708 command-line where those definitions were established.
12710 @kindex macro define
12711 @cindex user-defined macros
12712 @cindex defining macros interactively
12713 @cindex macros, user-defined
12714 @item macro define @var{macro} @var{replacement-list}
12715 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12716 Introduce a definition for a preprocessor macro named @var{macro},
12717 invocations of which are replaced by the tokens given in
12718 @var{replacement-list}. The first form of this command defines an
12719 ``object-like'' macro, which takes no arguments; the second form
12720 defines a ``function-like'' macro, which takes the arguments given in
12723 A definition introduced by this command is in scope in every
12724 expression evaluated in @value{GDBN}, until it is removed with the
12725 @code{macro undef} command, described below. The definition overrides
12726 all definitions for @var{macro} present in the program being debugged,
12727 as well as any previous user-supplied definition.
12729 @kindex macro undef
12730 @item macro undef @var{macro}
12731 Remove any user-supplied definition for the macro named @var{macro}.
12732 This command only affects definitions provided with the @code{macro
12733 define} command, described above; it cannot remove definitions present
12734 in the program being debugged.
12738 List all the macros defined using the @code{macro define} command.
12741 @cindex macros, example of debugging with
12742 Here is a transcript showing the above commands in action. First, we
12743 show our source files:
12748 #include "sample.h"
12751 #define ADD(x) (M + x)
12756 printf ("Hello, world!\n");
12758 printf ("We're so creative.\n");
12760 printf ("Goodbye, world!\n");
12767 Now, we compile the program using the @sc{gnu} C compiler,
12768 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12769 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12770 and @option{-gdwarf-4}; we recommend always choosing the most recent
12771 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12772 includes information about preprocessor macros in the debugging
12776 $ gcc -gdwarf-2 -g3 sample.c -o sample
12780 Now, we start @value{GDBN} on our sample program:
12784 GNU gdb 2002-05-06-cvs
12785 Copyright 2002 Free Software Foundation, Inc.
12786 GDB is free software, @dots{}
12790 We can expand macros and examine their definitions, even when the
12791 program is not running. @value{GDBN} uses the current listing position
12792 to decide which macro definitions are in scope:
12795 (@value{GDBP}) list main
12798 5 #define ADD(x) (M + x)
12803 10 printf ("Hello, world!\n");
12805 12 printf ("We're so creative.\n");
12806 (@value{GDBP}) info macro ADD
12807 Defined at /home/jimb/gdb/macros/play/sample.c:5
12808 #define ADD(x) (M + x)
12809 (@value{GDBP}) info macro Q
12810 Defined at /home/jimb/gdb/macros/play/sample.h:1
12811 included at /home/jimb/gdb/macros/play/sample.c:2
12813 (@value{GDBP}) macro expand ADD(1)
12814 expands to: (42 + 1)
12815 (@value{GDBP}) macro expand-once ADD(1)
12816 expands to: once (M + 1)
12820 In the example above, note that @code{macro expand-once} expands only
12821 the macro invocation explicit in the original text --- the invocation of
12822 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12823 which was introduced by @code{ADD}.
12825 Once the program is running, @value{GDBN} uses the macro definitions in
12826 force at the source line of the current stack frame:
12829 (@value{GDBP}) break main
12830 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12832 Starting program: /home/jimb/gdb/macros/play/sample
12834 Breakpoint 1, main () at sample.c:10
12835 10 printf ("Hello, world!\n");
12839 At line 10, the definition of the macro @code{N} at line 9 is in force:
12842 (@value{GDBP}) info macro N
12843 Defined at /home/jimb/gdb/macros/play/sample.c:9
12845 (@value{GDBP}) macro expand N Q M
12846 expands to: 28 < 42
12847 (@value{GDBP}) print N Q M
12852 As we step over directives that remove @code{N}'s definition, and then
12853 give it a new definition, @value{GDBN} finds the definition (or lack
12854 thereof) in force at each point:
12857 (@value{GDBP}) next
12859 12 printf ("We're so creative.\n");
12860 (@value{GDBP}) info macro N
12861 The symbol `N' has no definition as a C/C++ preprocessor macro
12862 at /home/jimb/gdb/macros/play/sample.c:12
12863 (@value{GDBP}) next
12865 14 printf ("Goodbye, world!\n");
12866 (@value{GDBP}) info macro N
12867 Defined at /home/jimb/gdb/macros/play/sample.c:13
12869 (@value{GDBP}) macro expand N Q M
12870 expands to: 1729 < 42
12871 (@value{GDBP}) print N Q M
12876 In addition to source files, macros can be defined on the compilation command
12877 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12878 such a way, @value{GDBN} displays the location of their definition as line zero
12879 of the source file submitted to the compiler.
12882 (@value{GDBP}) info macro __STDC__
12883 Defined at /home/jimb/gdb/macros/play/sample.c:0
12890 @chapter Tracepoints
12891 @c This chapter is based on the documentation written by Michael
12892 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12894 @cindex tracepoints
12895 In some applications, it is not feasible for the debugger to interrupt
12896 the program's execution long enough for the developer to learn
12897 anything helpful about its behavior. If the program's correctness
12898 depends on its real-time behavior, delays introduced by a debugger
12899 might cause the program to change its behavior drastically, or perhaps
12900 fail, even when the code itself is correct. It is useful to be able
12901 to observe the program's behavior without interrupting it.
12903 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12904 specify locations in the program, called @dfn{tracepoints}, and
12905 arbitrary expressions to evaluate when those tracepoints are reached.
12906 Later, using the @code{tfind} command, you can examine the values
12907 those expressions had when the program hit the tracepoints. The
12908 expressions may also denote objects in memory---structures or arrays,
12909 for example---whose values @value{GDBN} should record; while visiting
12910 a particular tracepoint, you may inspect those objects as if they were
12911 in memory at that moment. However, because @value{GDBN} records these
12912 values without interacting with you, it can do so quickly and
12913 unobtrusively, hopefully not disturbing the program's behavior.
12915 The tracepoint facility is currently available only for remote
12916 targets. @xref{Targets}. In addition, your remote target must know
12917 how to collect trace data. This functionality is implemented in the
12918 remote stub; however, none of the stubs distributed with @value{GDBN}
12919 support tracepoints as of this writing. The format of the remote
12920 packets used to implement tracepoints are described in @ref{Tracepoint
12923 It is also possible to get trace data from a file, in a manner reminiscent
12924 of corefiles; you specify the filename, and use @code{tfind} to search
12925 through the file. @xref{Trace Files}, for more details.
12927 This chapter describes the tracepoint commands and features.
12930 * Set Tracepoints::
12931 * Analyze Collected Data::
12932 * Tracepoint Variables::
12936 @node Set Tracepoints
12937 @section Commands to Set Tracepoints
12939 Before running such a @dfn{trace experiment}, an arbitrary number of
12940 tracepoints can be set. A tracepoint is actually a special type of
12941 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12942 standard breakpoint commands. For instance, as with breakpoints,
12943 tracepoint numbers are successive integers starting from one, and many
12944 of the commands associated with tracepoints take the tracepoint number
12945 as their argument, to identify which tracepoint to work on.
12947 For each tracepoint, you can specify, in advance, some arbitrary set
12948 of data that you want the target to collect in the trace buffer when
12949 it hits that tracepoint. The collected data can include registers,
12950 local variables, or global data. Later, you can use @value{GDBN}
12951 commands to examine the values these data had at the time the
12952 tracepoint was hit.
12954 Tracepoints do not support every breakpoint feature. Ignore counts on
12955 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12956 commands when they are hit. Tracepoints may not be thread-specific
12959 @cindex fast tracepoints
12960 Some targets may support @dfn{fast tracepoints}, which are inserted in
12961 a different way (such as with a jump instead of a trap), that is
12962 faster but possibly restricted in where they may be installed.
12964 @cindex static tracepoints
12965 @cindex markers, static tracepoints
12966 @cindex probing markers, static tracepoints
12967 Regular and fast tracepoints are dynamic tracing facilities, meaning
12968 that they can be used to insert tracepoints at (almost) any location
12969 in the target. Some targets may also support controlling @dfn{static
12970 tracepoints} from @value{GDBN}. With static tracing, a set of
12971 instrumentation points, also known as @dfn{markers}, are embedded in
12972 the target program, and can be activated or deactivated by name or
12973 address. These are usually placed at locations which facilitate
12974 investigating what the target is actually doing. @value{GDBN}'s
12975 support for static tracing includes being able to list instrumentation
12976 points, and attach them with @value{GDBN} defined high level
12977 tracepoints that expose the whole range of convenience of
12978 @value{GDBN}'s tracepoints support. Namely, support for collecting
12979 registers values and values of global or local (to the instrumentation
12980 point) variables; tracepoint conditions and trace state variables.
12981 The act of installing a @value{GDBN} static tracepoint on an
12982 instrumentation point, or marker, is referred to as @dfn{probing} a
12983 static tracepoint marker.
12985 @code{gdbserver} supports tracepoints on some target systems.
12986 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12988 This section describes commands to set tracepoints and associated
12989 conditions and actions.
12992 * Create and Delete Tracepoints::
12993 * Enable and Disable Tracepoints::
12994 * Tracepoint Passcounts::
12995 * Tracepoint Conditions::
12996 * Trace State Variables::
12997 * Tracepoint Actions::
12998 * Listing Tracepoints::
12999 * Listing Static Tracepoint Markers::
13000 * Starting and Stopping Trace Experiments::
13001 * Tracepoint Restrictions::
13004 @node Create and Delete Tracepoints
13005 @subsection Create and Delete Tracepoints
13008 @cindex set tracepoint
13010 @item trace @var{location}
13011 The @code{trace} command is very similar to the @code{break} command.
13012 Its argument @var{location} can be any valid location.
13013 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13014 which is a point in the target program where the debugger will briefly stop,
13015 collect some data, and then allow the program to continue. Setting a tracepoint
13016 or changing its actions takes effect immediately if the remote stub
13017 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13019 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13020 these changes don't take effect until the next @code{tstart}
13021 command, and once a trace experiment is running, further changes will
13022 not have any effect until the next trace experiment starts. In addition,
13023 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13024 address is not yet resolved. (This is similar to pending breakpoints.)
13025 Pending tracepoints are not downloaded to the target and not installed
13026 until they are resolved. The resolution of pending tracepoints requires
13027 @value{GDBN} support---when debugging with the remote target, and
13028 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13029 tracing}), pending tracepoints can not be resolved (and downloaded to
13030 the remote stub) while @value{GDBN} is disconnected.
13032 Here are some examples of using the @code{trace} command:
13035 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13037 (@value{GDBP}) @b{trace +2} // 2 lines forward
13039 (@value{GDBP}) @b{trace my_function} // first source line of function
13041 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13043 (@value{GDBP}) @b{trace *0x2117c4} // an address
13047 You can abbreviate @code{trace} as @code{tr}.
13049 @item trace @var{location} if @var{cond}
13050 Set a tracepoint with condition @var{cond}; evaluate the expression
13051 @var{cond} each time the tracepoint is reached, and collect data only
13052 if the value is nonzero---that is, if @var{cond} evaluates as true.
13053 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13054 information on tracepoint conditions.
13056 @item ftrace @var{location} [ if @var{cond} ]
13057 @cindex set fast tracepoint
13058 @cindex fast tracepoints, setting
13060 The @code{ftrace} command sets a fast tracepoint. For targets that
13061 support them, fast tracepoints will use a more efficient but possibly
13062 less general technique to trigger data collection, such as a jump
13063 instruction instead of a trap, or some sort of hardware support. It
13064 may not be possible to create a fast tracepoint at the desired
13065 location, in which case the command will exit with an explanatory
13068 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13071 On 32-bit x86-architecture systems, fast tracepoints normally need to
13072 be placed at an instruction that is 5 bytes or longer, but can be
13073 placed at 4-byte instructions if the low 64K of memory of the target
13074 program is available to install trampolines. Some Unix-type systems,
13075 such as @sc{gnu}/Linux, exclude low addresses from the program's
13076 address space; but for instance with the Linux kernel it is possible
13077 to let @value{GDBN} use this area by doing a @command{sysctl} command
13078 to set the @code{mmap_min_addr} kernel parameter, as in
13081 sudo sysctl -w vm.mmap_min_addr=32768
13085 which sets the low address to 32K, which leaves plenty of room for
13086 trampolines. The minimum address should be set to a page boundary.
13088 @item strace @var{location} [ if @var{cond} ]
13089 @cindex set static tracepoint
13090 @cindex static tracepoints, setting
13091 @cindex probe static tracepoint marker
13093 The @code{strace} command sets a static tracepoint. For targets that
13094 support it, setting a static tracepoint probes a static
13095 instrumentation point, or marker, found at @var{location}. It may not
13096 be possible to set a static tracepoint at the desired location, in
13097 which case the command will exit with an explanatory message.
13099 @value{GDBN} handles arguments to @code{strace} exactly as for
13100 @code{trace}, with the addition that the user can also specify
13101 @code{-m @var{marker}} as @var{location}. This probes the marker
13102 identified by the @var{marker} string identifier. This identifier
13103 depends on the static tracepoint backend library your program is
13104 using. You can find all the marker identifiers in the @samp{ID} field
13105 of the @code{info static-tracepoint-markers} command output.
13106 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13107 Markers}. For example, in the following small program using the UST
13113 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13118 the marker id is composed of joining the first two arguments to the
13119 @code{trace_mark} call with a slash, which translates to:
13122 (@value{GDBP}) info static-tracepoint-markers
13123 Cnt Enb ID Address What
13124 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13130 so you may probe the marker above with:
13133 (@value{GDBP}) strace -m ust/bar33
13136 Static tracepoints accept an extra collect action --- @code{collect
13137 $_sdata}. This collects arbitrary user data passed in the probe point
13138 call to the tracing library. In the UST example above, you'll see
13139 that the third argument to @code{trace_mark} is a printf-like format
13140 string. The user data is then the result of running that formating
13141 string against the following arguments. Note that @code{info
13142 static-tracepoint-markers} command output lists that format string in
13143 the @samp{Data:} field.
13145 You can inspect this data when analyzing the trace buffer, by printing
13146 the $_sdata variable like any other variable available to
13147 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13150 @cindex last tracepoint number
13151 @cindex recent tracepoint number
13152 @cindex tracepoint number
13153 The convenience variable @code{$tpnum} records the tracepoint number
13154 of the most recently set tracepoint.
13156 @kindex delete tracepoint
13157 @cindex tracepoint deletion
13158 @item delete tracepoint @r{[}@var{num}@r{]}
13159 Permanently delete one or more tracepoints. With no argument, the
13160 default is to delete all tracepoints. Note that the regular
13161 @code{delete} command can remove tracepoints also.
13166 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13168 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13172 You can abbreviate this command as @code{del tr}.
13175 @node Enable and Disable Tracepoints
13176 @subsection Enable and Disable Tracepoints
13178 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13181 @kindex disable tracepoint
13182 @item disable tracepoint @r{[}@var{num}@r{]}
13183 Disable tracepoint @var{num}, or all tracepoints if no argument
13184 @var{num} is given. A disabled tracepoint will have no effect during
13185 a trace experiment, but it is not forgotten. You can re-enable
13186 a disabled tracepoint using the @code{enable tracepoint} command.
13187 If the command is issued during a trace experiment and the debug target
13188 has support for disabling tracepoints during a trace experiment, then the
13189 change will be effective immediately. Otherwise, it will be applied to the
13190 next trace experiment.
13192 @kindex enable tracepoint
13193 @item enable tracepoint @r{[}@var{num}@r{]}
13194 Enable tracepoint @var{num}, or all tracepoints. If this command is
13195 issued during a trace experiment and the debug target supports enabling
13196 tracepoints during a trace experiment, then the enabled tracepoints will
13197 become effective immediately. Otherwise, they will become effective the
13198 next time a trace experiment is run.
13201 @node Tracepoint Passcounts
13202 @subsection Tracepoint Passcounts
13206 @cindex tracepoint pass count
13207 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13208 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13209 automatically stop a trace experiment. If a tracepoint's passcount is
13210 @var{n}, then the trace experiment will be automatically stopped on
13211 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13212 @var{num} is not specified, the @code{passcount} command sets the
13213 passcount of the most recently defined tracepoint. If no passcount is
13214 given, the trace experiment will run until stopped explicitly by the
13220 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13221 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13223 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13224 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13225 (@value{GDBP}) @b{trace foo}
13226 (@value{GDBP}) @b{pass 3}
13227 (@value{GDBP}) @b{trace bar}
13228 (@value{GDBP}) @b{pass 2}
13229 (@value{GDBP}) @b{trace baz}
13230 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13231 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13232 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13233 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13237 @node Tracepoint Conditions
13238 @subsection Tracepoint Conditions
13239 @cindex conditional tracepoints
13240 @cindex tracepoint conditions
13242 The simplest sort of tracepoint collects data every time your program
13243 reaches a specified place. You can also specify a @dfn{condition} for
13244 a tracepoint. A condition is just a Boolean expression in your
13245 programming language (@pxref{Expressions, ,Expressions}). A
13246 tracepoint with a condition evaluates the expression each time your
13247 program reaches it, and data collection happens only if the condition
13250 Tracepoint conditions can be specified when a tracepoint is set, by
13251 using @samp{if} in the arguments to the @code{trace} command.
13252 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13253 also be set or changed at any time with the @code{condition} command,
13254 just as with breakpoints.
13256 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13257 the conditional expression itself. Instead, @value{GDBN} encodes the
13258 expression into an agent expression (@pxref{Agent Expressions})
13259 suitable for execution on the target, independently of @value{GDBN}.
13260 Global variables become raw memory locations, locals become stack
13261 accesses, and so forth.
13263 For instance, suppose you have a function that is usually called
13264 frequently, but should not be called after an error has occurred. You
13265 could use the following tracepoint command to collect data about calls
13266 of that function that happen while the error code is propagating
13267 through the program; an unconditional tracepoint could end up
13268 collecting thousands of useless trace frames that you would have to
13272 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13275 @node Trace State Variables
13276 @subsection Trace State Variables
13277 @cindex trace state variables
13279 A @dfn{trace state variable} is a special type of variable that is
13280 created and managed by target-side code. The syntax is the same as
13281 that for GDB's convenience variables (a string prefixed with ``$''),
13282 but they are stored on the target. They must be created explicitly,
13283 using a @code{tvariable} command. They are always 64-bit signed
13286 Trace state variables are remembered by @value{GDBN}, and downloaded
13287 to the target along with tracepoint information when the trace
13288 experiment starts. There are no intrinsic limits on the number of
13289 trace state variables, beyond memory limitations of the target.
13291 @cindex convenience variables, and trace state variables
13292 Although trace state variables are managed by the target, you can use
13293 them in print commands and expressions as if they were convenience
13294 variables; @value{GDBN} will get the current value from the target
13295 while the trace experiment is running. Trace state variables share
13296 the same namespace as other ``$'' variables, which means that you
13297 cannot have trace state variables with names like @code{$23} or
13298 @code{$pc}, nor can you have a trace state variable and a convenience
13299 variable with the same name.
13303 @item tvariable $@var{name} [ = @var{expression} ]
13305 The @code{tvariable} command creates a new trace state variable named
13306 @code{$@var{name}}, and optionally gives it an initial value of
13307 @var{expression}. The @var{expression} is evaluated when this command is
13308 entered; the result will be converted to an integer if possible,
13309 otherwise @value{GDBN} will report an error. A subsequent
13310 @code{tvariable} command specifying the same name does not create a
13311 variable, but instead assigns the supplied initial value to the
13312 existing variable of that name, overwriting any previous initial
13313 value. The default initial value is 0.
13315 @item info tvariables
13316 @kindex info tvariables
13317 List all the trace state variables along with their initial values.
13318 Their current values may also be displayed, if the trace experiment is
13321 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13322 @kindex delete tvariable
13323 Delete the given trace state variables, or all of them if no arguments
13328 @node Tracepoint Actions
13329 @subsection Tracepoint Action Lists
13333 @cindex tracepoint actions
13334 @item actions @r{[}@var{num}@r{]}
13335 This command will prompt for a list of actions to be taken when the
13336 tracepoint is hit. If the tracepoint number @var{num} is not
13337 specified, this command sets the actions for the one that was most
13338 recently defined (so that you can define a tracepoint and then say
13339 @code{actions} without bothering about its number). You specify the
13340 actions themselves on the following lines, one action at a time, and
13341 terminate the actions list with a line containing just @code{end}. So
13342 far, the only defined actions are @code{collect}, @code{teval}, and
13343 @code{while-stepping}.
13345 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13346 Commands, ,Breakpoint Command Lists}), except that only the defined
13347 actions are allowed; any other @value{GDBN} command is rejected.
13349 @cindex remove actions from a tracepoint
13350 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13351 and follow it immediately with @samp{end}.
13354 (@value{GDBP}) @b{collect @var{data}} // collect some data
13356 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13358 (@value{GDBP}) @b{end} // signals the end of actions.
13361 In the following example, the action list begins with @code{collect}
13362 commands indicating the things to be collected when the tracepoint is
13363 hit. Then, in order to single-step and collect additional data
13364 following the tracepoint, a @code{while-stepping} command is used,
13365 followed by the list of things to be collected after each step in a
13366 sequence of single steps. The @code{while-stepping} command is
13367 terminated by its own separate @code{end} command. Lastly, the action
13368 list is terminated by an @code{end} command.
13371 (@value{GDBP}) @b{trace foo}
13372 (@value{GDBP}) @b{actions}
13373 Enter actions for tracepoint 1, one per line:
13376 > while-stepping 12
13377 > collect $pc, arr[i]
13382 @kindex collect @r{(tracepoints)}
13383 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13384 Collect values of the given expressions when the tracepoint is hit.
13385 This command accepts a comma-separated list of any valid expressions.
13386 In addition to global, static, or local variables, the following
13387 special arguments are supported:
13391 Collect all registers.
13394 Collect all function arguments.
13397 Collect all local variables.
13400 Collect the return address. This is helpful if you want to see more
13403 @emph{Note:} The return address location can not always be reliably
13404 determined up front, and the wrong address / registers may end up
13405 collected instead. On some architectures the reliability is higher
13406 for tracepoints at function entry, while on others it's the opposite.
13407 When this happens, backtracing will stop because the return address is
13408 found unavailable (unless another collect rule happened to match it).
13411 Collects the number of arguments from the static probe at which the
13412 tracepoint is located.
13413 @xref{Static Probe Points}.
13415 @item $_probe_arg@var{n}
13416 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13417 from the static probe at which the tracepoint is located.
13418 @xref{Static Probe Points}.
13421 @vindex $_sdata@r{, collect}
13422 Collect static tracepoint marker specific data. Only available for
13423 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13424 Lists}. On the UST static tracepoints library backend, an
13425 instrumentation point resembles a @code{printf} function call. The
13426 tracing library is able to collect user specified data formatted to a
13427 character string using the format provided by the programmer that
13428 instrumented the program. Other backends have similar mechanisms.
13429 Here's an example of a UST marker call:
13432 const char master_name[] = "$your_name";
13433 trace_mark(channel1, marker1, "hello %s", master_name)
13436 In this case, collecting @code{$_sdata} collects the string
13437 @samp{hello $yourname}. When analyzing the trace buffer, you can
13438 inspect @samp{$_sdata} like any other variable available to
13442 You can give several consecutive @code{collect} commands, each one
13443 with a single argument, or one @code{collect} command with several
13444 arguments separated by commas; the effect is the same.
13446 The optional @var{mods} changes the usual handling of the arguments.
13447 @code{s} requests that pointers to chars be handled as strings, in
13448 particular collecting the contents of the memory being pointed at, up
13449 to the first zero. The upper bound is by default the value of the
13450 @code{print elements} variable; if @code{s} is followed by a decimal
13451 number, that is the upper bound instead. So for instance
13452 @samp{collect/s25 mystr} collects as many as 25 characters at
13455 The command @code{info scope} (@pxref{Symbols, info scope}) is
13456 particularly useful for figuring out what data to collect.
13458 @kindex teval @r{(tracepoints)}
13459 @item teval @var{expr1}, @var{expr2}, @dots{}
13460 Evaluate the given expressions when the tracepoint is hit. This
13461 command accepts a comma-separated list of expressions. The results
13462 are discarded, so this is mainly useful for assigning values to trace
13463 state variables (@pxref{Trace State Variables}) without adding those
13464 values to the trace buffer, as would be the case if the @code{collect}
13467 @kindex while-stepping @r{(tracepoints)}
13468 @item while-stepping @var{n}
13469 Perform @var{n} single-step instruction traces after the tracepoint,
13470 collecting new data after each step. The @code{while-stepping}
13471 command is followed by the list of what to collect while stepping
13472 (followed by its own @code{end} command):
13475 > while-stepping 12
13476 > collect $regs, myglobal
13482 Note that @code{$pc} is not automatically collected by
13483 @code{while-stepping}; you need to explicitly collect that register if
13484 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13487 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13488 @kindex set default-collect
13489 @cindex default collection action
13490 This variable is a list of expressions to collect at each tracepoint
13491 hit. It is effectively an additional @code{collect} action prepended
13492 to every tracepoint action list. The expressions are parsed
13493 individually for each tracepoint, so for instance a variable named
13494 @code{xyz} may be interpreted as a global for one tracepoint, and a
13495 local for another, as appropriate to the tracepoint's location.
13497 @item show default-collect
13498 @kindex show default-collect
13499 Show the list of expressions that are collected by default at each
13504 @node Listing Tracepoints
13505 @subsection Listing Tracepoints
13508 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13509 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13510 @cindex information about tracepoints
13511 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13512 Display information about the tracepoint @var{num}. If you don't
13513 specify a tracepoint number, displays information about all the
13514 tracepoints defined so far. The format is similar to that used for
13515 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13516 command, simply restricting itself to tracepoints.
13518 A tracepoint's listing may include additional information specific to
13523 its passcount as given by the @code{passcount @var{n}} command
13526 the state about installed on target of each location
13530 (@value{GDBP}) @b{info trace}
13531 Num Type Disp Enb Address What
13532 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13534 collect globfoo, $regs
13539 2 tracepoint keep y <MULTIPLE>
13541 2.1 y 0x0804859c in func4 at change-loc.h:35
13542 installed on target
13543 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13544 installed on target
13545 2.3 y <PENDING> set_tracepoint
13546 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13547 not installed on target
13552 This command can be abbreviated @code{info tp}.
13555 @node Listing Static Tracepoint Markers
13556 @subsection Listing Static Tracepoint Markers
13559 @kindex info static-tracepoint-markers
13560 @cindex information about static tracepoint markers
13561 @item info static-tracepoint-markers
13562 Display information about all static tracepoint markers defined in the
13565 For each marker, the following columns are printed:
13569 An incrementing counter, output to help readability. This is not a
13572 The marker ID, as reported by the target.
13573 @item Enabled or Disabled
13574 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13575 that are not enabled.
13577 Where the marker is in your program, as a memory address.
13579 Where the marker is in the source for your program, as a file and line
13580 number. If the debug information included in the program does not
13581 allow @value{GDBN} to locate the source of the marker, this column
13582 will be left blank.
13586 In addition, the following information may be printed for each marker:
13590 User data passed to the tracing library by the marker call. In the
13591 UST backend, this is the format string passed as argument to the
13593 @item Static tracepoints probing the marker
13594 The list of static tracepoints attached to the marker.
13598 (@value{GDBP}) info static-tracepoint-markers
13599 Cnt ID Enb Address What
13600 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13601 Data: number1 %d number2 %d
13602 Probed by static tracepoints: #2
13603 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13609 @node Starting and Stopping Trace Experiments
13610 @subsection Starting and Stopping Trace Experiments
13613 @kindex tstart [ @var{notes} ]
13614 @cindex start a new trace experiment
13615 @cindex collected data discarded
13617 This command starts the trace experiment, and begins collecting data.
13618 It has the side effect of discarding all the data collected in the
13619 trace buffer during the previous trace experiment. If any arguments
13620 are supplied, they are taken as a note and stored with the trace
13621 experiment's state. The notes may be arbitrary text, and are
13622 especially useful with disconnected tracing in a multi-user context;
13623 the notes can explain what the trace is doing, supply user contact
13624 information, and so forth.
13626 @kindex tstop [ @var{notes} ]
13627 @cindex stop a running trace experiment
13629 This command stops the trace experiment. If any arguments are
13630 supplied, they are recorded with the experiment as a note. This is
13631 useful if you are stopping a trace started by someone else, for
13632 instance if the trace is interfering with the system's behavior and
13633 needs to be stopped quickly.
13635 @strong{Note}: a trace experiment and data collection may stop
13636 automatically if any tracepoint's passcount is reached
13637 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13640 @cindex status of trace data collection
13641 @cindex trace experiment, status of
13643 This command displays the status of the current trace data
13647 Here is an example of the commands we described so far:
13650 (@value{GDBP}) @b{trace gdb_c_test}
13651 (@value{GDBP}) @b{actions}
13652 Enter actions for tracepoint #1, one per line.
13653 > collect $regs,$locals,$args
13654 > while-stepping 11
13658 (@value{GDBP}) @b{tstart}
13659 [time passes @dots{}]
13660 (@value{GDBP}) @b{tstop}
13663 @anchor{disconnected tracing}
13664 @cindex disconnected tracing
13665 You can choose to continue running the trace experiment even if
13666 @value{GDBN} disconnects from the target, voluntarily or
13667 involuntarily. For commands such as @code{detach}, the debugger will
13668 ask what you want to do with the trace. But for unexpected
13669 terminations (@value{GDBN} crash, network outage), it would be
13670 unfortunate to lose hard-won trace data, so the variable
13671 @code{disconnected-tracing} lets you decide whether the trace should
13672 continue running without @value{GDBN}.
13675 @item set disconnected-tracing on
13676 @itemx set disconnected-tracing off
13677 @kindex set disconnected-tracing
13678 Choose whether a tracing run should continue to run if @value{GDBN}
13679 has disconnected from the target. Note that @code{detach} or
13680 @code{quit} will ask you directly what to do about a running trace no
13681 matter what this variable's setting, so the variable is mainly useful
13682 for handling unexpected situations, such as loss of the network.
13684 @item show disconnected-tracing
13685 @kindex show disconnected-tracing
13686 Show the current choice for disconnected tracing.
13690 When you reconnect to the target, the trace experiment may or may not
13691 still be running; it might have filled the trace buffer in the
13692 meantime, or stopped for one of the other reasons. If it is running,
13693 it will continue after reconnection.
13695 Upon reconnection, the target will upload information about the
13696 tracepoints in effect. @value{GDBN} will then compare that
13697 information to the set of tracepoints currently defined, and attempt
13698 to match them up, allowing for the possibility that the numbers may
13699 have changed due to creation and deletion in the meantime. If one of
13700 the target's tracepoints does not match any in @value{GDBN}, the
13701 debugger will create a new tracepoint, so that you have a number with
13702 which to specify that tracepoint. This matching-up process is
13703 necessarily heuristic, and it may result in useless tracepoints being
13704 created; you may simply delete them if they are of no use.
13706 @cindex circular trace buffer
13707 If your target agent supports a @dfn{circular trace buffer}, then you
13708 can run a trace experiment indefinitely without filling the trace
13709 buffer; when space runs out, the agent deletes already-collected trace
13710 frames, oldest first, until there is enough room to continue
13711 collecting. This is especially useful if your tracepoints are being
13712 hit too often, and your trace gets terminated prematurely because the
13713 buffer is full. To ask for a circular trace buffer, simply set
13714 @samp{circular-trace-buffer} to on. You can set this at any time,
13715 including during tracing; if the agent can do it, it will change
13716 buffer handling on the fly, otherwise it will not take effect until
13720 @item set circular-trace-buffer on
13721 @itemx set circular-trace-buffer off
13722 @kindex set circular-trace-buffer
13723 Choose whether a tracing run should use a linear or circular buffer
13724 for trace data. A linear buffer will not lose any trace data, but may
13725 fill up prematurely, while a circular buffer will discard old trace
13726 data, but it will have always room for the latest tracepoint hits.
13728 @item show circular-trace-buffer
13729 @kindex show circular-trace-buffer
13730 Show the current choice for the trace buffer. Note that this may not
13731 match the agent's current buffer handling, nor is it guaranteed to
13732 match the setting that might have been in effect during a past run,
13733 for instance if you are looking at frames from a trace file.
13738 @item set trace-buffer-size @var{n}
13739 @itemx set trace-buffer-size unlimited
13740 @kindex set trace-buffer-size
13741 Request that the target use a trace buffer of @var{n} bytes. Not all
13742 targets will honor the request; they may have a compiled-in size for
13743 the trace buffer, or some other limitation. Set to a value of
13744 @code{unlimited} or @code{-1} to let the target use whatever size it
13745 likes. This is also the default.
13747 @item show trace-buffer-size
13748 @kindex show trace-buffer-size
13749 Show the current requested size for the trace buffer. Note that this
13750 will only match the actual size if the target supports size-setting,
13751 and was able to handle the requested size. For instance, if the
13752 target can only change buffer size between runs, this variable will
13753 not reflect the change until the next run starts. Use @code{tstatus}
13754 to get a report of the actual buffer size.
13758 @item set trace-user @var{text}
13759 @kindex set trace-user
13761 @item show trace-user
13762 @kindex show trace-user
13764 @item set trace-notes @var{text}
13765 @kindex set trace-notes
13766 Set the trace run's notes.
13768 @item show trace-notes
13769 @kindex show trace-notes
13770 Show the trace run's notes.
13772 @item set trace-stop-notes @var{text}
13773 @kindex set trace-stop-notes
13774 Set the trace run's stop notes. The handling of the note is as for
13775 @code{tstop} arguments; the set command is convenient way to fix a
13776 stop note that is mistaken or incomplete.
13778 @item show trace-stop-notes
13779 @kindex show trace-stop-notes
13780 Show the trace run's stop notes.
13784 @node Tracepoint Restrictions
13785 @subsection Tracepoint Restrictions
13787 @cindex tracepoint restrictions
13788 There are a number of restrictions on the use of tracepoints. As
13789 described above, tracepoint data gathering occurs on the target
13790 without interaction from @value{GDBN}. Thus the full capabilities of
13791 the debugger are not available during data gathering, and then at data
13792 examination time, you will be limited by only having what was
13793 collected. The following items describe some common problems, but it
13794 is not exhaustive, and you may run into additional difficulties not
13800 Tracepoint expressions are intended to gather objects (lvalues). Thus
13801 the full flexibility of GDB's expression evaluator is not available.
13802 You cannot call functions, cast objects to aggregate types, access
13803 convenience variables or modify values (except by assignment to trace
13804 state variables). Some language features may implicitly call
13805 functions (for instance Objective-C fields with accessors), and therefore
13806 cannot be collected either.
13809 Collection of local variables, either individually or in bulk with
13810 @code{$locals} or @code{$args}, during @code{while-stepping} may
13811 behave erratically. The stepping action may enter a new scope (for
13812 instance by stepping into a function), or the location of the variable
13813 may change (for instance it is loaded into a register). The
13814 tracepoint data recorded uses the location information for the
13815 variables that is correct for the tracepoint location. When the
13816 tracepoint is created, it is not possible, in general, to determine
13817 where the steps of a @code{while-stepping} sequence will advance the
13818 program---particularly if a conditional branch is stepped.
13821 Collection of an incompletely-initialized or partially-destroyed object
13822 may result in something that @value{GDBN} cannot display, or displays
13823 in a misleading way.
13826 When @value{GDBN} displays a pointer to character it automatically
13827 dereferences the pointer to also display characters of the string
13828 being pointed to. However, collecting the pointer during tracing does
13829 not automatically collect the string. You need to explicitly
13830 dereference the pointer and provide size information if you want to
13831 collect not only the pointer, but the memory pointed to. For example,
13832 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13836 It is not possible to collect a complete stack backtrace at a
13837 tracepoint. Instead, you may collect the registers and a few hundred
13838 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13839 (adjust to use the name of the actual stack pointer register on your
13840 target architecture, and the amount of stack you wish to capture).
13841 Then the @code{backtrace} command will show a partial backtrace when
13842 using a trace frame. The number of stack frames that can be examined
13843 depends on the sizes of the frames in the collected stack. Note that
13844 if you ask for a block so large that it goes past the bottom of the
13845 stack, the target agent may report an error trying to read from an
13849 If you do not collect registers at a tracepoint, @value{GDBN} can
13850 infer that the value of @code{$pc} must be the same as the address of
13851 the tracepoint and use that when you are looking at a trace frame
13852 for that tracepoint. However, this cannot work if the tracepoint has
13853 multiple locations (for instance if it was set in a function that was
13854 inlined), or if it has a @code{while-stepping} loop. In those cases
13855 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13860 @node Analyze Collected Data
13861 @section Using the Collected Data
13863 After the tracepoint experiment ends, you use @value{GDBN} commands
13864 for examining the trace data. The basic idea is that each tracepoint
13865 collects a trace @dfn{snapshot} every time it is hit and another
13866 snapshot every time it single-steps. All these snapshots are
13867 consecutively numbered from zero and go into a buffer, and you can
13868 examine them later. The way you examine them is to @dfn{focus} on a
13869 specific trace snapshot. When the remote stub is focused on a trace
13870 snapshot, it will respond to all @value{GDBN} requests for memory and
13871 registers by reading from the buffer which belongs to that snapshot,
13872 rather than from @emph{real} memory or registers of the program being
13873 debugged. This means that @strong{all} @value{GDBN} commands
13874 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13875 behave as if we were currently debugging the program state as it was
13876 when the tracepoint occurred. Any requests for data that are not in
13877 the buffer will fail.
13880 * tfind:: How to select a trace snapshot
13881 * tdump:: How to display all data for a snapshot
13882 * save tracepoints:: How to save tracepoints for a future run
13886 @subsection @code{tfind @var{n}}
13889 @cindex select trace snapshot
13890 @cindex find trace snapshot
13891 The basic command for selecting a trace snapshot from the buffer is
13892 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13893 counting from zero. If no argument @var{n} is given, the next
13894 snapshot is selected.
13896 Here are the various forms of using the @code{tfind} command.
13900 Find the first snapshot in the buffer. This is a synonym for
13901 @code{tfind 0} (since 0 is the number of the first snapshot).
13904 Stop debugging trace snapshots, resume @emph{live} debugging.
13907 Same as @samp{tfind none}.
13910 No argument means find the next trace snapshot or find the first
13911 one if no trace snapshot is selected.
13914 Find the previous trace snapshot before the current one. This permits
13915 retracing earlier steps.
13917 @item tfind tracepoint @var{num}
13918 Find the next snapshot associated with tracepoint @var{num}. Search
13919 proceeds forward from the last examined trace snapshot. If no
13920 argument @var{num} is given, it means find the next snapshot collected
13921 for the same tracepoint as the current snapshot.
13923 @item tfind pc @var{addr}
13924 Find the next snapshot associated with the value @var{addr} of the
13925 program counter. Search proceeds forward from the last examined trace
13926 snapshot. If no argument @var{addr} is given, it means find the next
13927 snapshot with the same value of PC as the current snapshot.
13929 @item tfind outside @var{addr1}, @var{addr2}
13930 Find the next snapshot whose PC is outside the given range of
13931 addresses (exclusive).
13933 @item tfind range @var{addr1}, @var{addr2}
13934 Find the next snapshot whose PC is between @var{addr1} and
13935 @var{addr2} (inclusive).
13937 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13938 Find the next snapshot associated with the source line @var{n}. If
13939 the optional argument @var{file} is given, refer to line @var{n} in
13940 that source file. Search proceeds forward from the last examined
13941 trace snapshot. If no argument @var{n} is given, it means find the
13942 next line other than the one currently being examined; thus saying
13943 @code{tfind line} repeatedly can appear to have the same effect as
13944 stepping from line to line in a @emph{live} debugging session.
13947 The default arguments for the @code{tfind} commands are specifically
13948 designed to make it easy to scan through the trace buffer. For
13949 instance, @code{tfind} with no argument selects the next trace
13950 snapshot, and @code{tfind -} with no argument selects the previous
13951 trace snapshot. So, by giving one @code{tfind} command, and then
13952 simply hitting @key{RET} repeatedly you can examine all the trace
13953 snapshots in order. Or, by saying @code{tfind -} and then hitting
13954 @key{RET} repeatedly you can examine the snapshots in reverse order.
13955 The @code{tfind line} command with no argument selects the snapshot
13956 for the next source line executed. The @code{tfind pc} command with
13957 no argument selects the next snapshot with the same program counter
13958 (PC) as the current frame. The @code{tfind tracepoint} command with
13959 no argument selects the next trace snapshot collected by the same
13960 tracepoint as the current one.
13962 In addition to letting you scan through the trace buffer manually,
13963 these commands make it easy to construct @value{GDBN} scripts that
13964 scan through the trace buffer and print out whatever collected data
13965 you are interested in. Thus, if we want to examine the PC, FP, and SP
13966 registers from each trace frame in the buffer, we can say this:
13969 (@value{GDBP}) @b{tfind start}
13970 (@value{GDBP}) @b{while ($trace_frame != -1)}
13971 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13972 $trace_frame, $pc, $sp, $fp
13976 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13977 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13978 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13979 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13980 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13981 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13982 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13983 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13984 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13985 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13986 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13989 Or, if we want to examine the variable @code{X} at each source line in
13993 (@value{GDBP}) @b{tfind start}
13994 (@value{GDBP}) @b{while ($trace_frame != -1)}
13995 > printf "Frame %d, X == %d\n", $trace_frame, X
14005 @subsection @code{tdump}
14007 @cindex dump all data collected at tracepoint
14008 @cindex tracepoint data, display
14010 This command takes no arguments. It prints all the data collected at
14011 the current trace snapshot.
14014 (@value{GDBP}) @b{trace 444}
14015 (@value{GDBP}) @b{actions}
14016 Enter actions for tracepoint #2, one per line:
14017 > collect $regs, $locals, $args, gdb_long_test
14020 (@value{GDBP}) @b{tstart}
14022 (@value{GDBP}) @b{tfind line 444}
14023 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14025 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14027 (@value{GDBP}) @b{tdump}
14028 Data collected at tracepoint 2, trace frame 1:
14029 d0 0xc4aa0085 -995491707
14033 d4 0x71aea3d 119204413
14036 d7 0x380035 3670069
14037 a0 0x19e24a 1696330
14038 a1 0x3000668 50333288
14040 a3 0x322000 3284992
14041 a4 0x3000698 50333336
14042 a5 0x1ad3cc 1758156
14043 fp 0x30bf3c 0x30bf3c
14044 sp 0x30bf34 0x30bf34
14046 pc 0x20b2c8 0x20b2c8
14050 p = 0x20e5b4 "gdb-test"
14057 gdb_long_test = 17 '\021'
14062 @code{tdump} works by scanning the tracepoint's current collection
14063 actions and printing the value of each expression listed. So
14064 @code{tdump} can fail, if after a run, you change the tracepoint's
14065 actions to mention variables that were not collected during the run.
14067 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14068 uses the collected value of @code{$pc} to distinguish between trace
14069 frames that were collected at the tracepoint hit, and frames that were
14070 collected while stepping. This allows it to correctly choose whether
14071 to display the basic list of collections, or the collections from the
14072 body of the while-stepping loop. However, if @code{$pc} was not collected,
14073 then @code{tdump} will always attempt to dump using the basic collection
14074 list, and may fail if a while-stepping frame does not include all the
14075 same data that is collected at the tracepoint hit.
14076 @c This is getting pretty arcane, example would be good.
14078 @node save tracepoints
14079 @subsection @code{save tracepoints @var{filename}}
14080 @kindex save tracepoints
14081 @kindex save-tracepoints
14082 @cindex save tracepoints for future sessions
14084 This command saves all current tracepoint definitions together with
14085 their actions and passcounts, into a file @file{@var{filename}}
14086 suitable for use in a later debugging session. To read the saved
14087 tracepoint definitions, use the @code{source} command (@pxref{Command
14088 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14089 alias for @w{@code{save tracepoints}}
14091 @node Tracepoint Variables
14092 @section Convenience Variables for Tracepoints
14093 @cindex tracepoint variables
14094 @cindex convenience variables for tracepoints
14097 @vindex $trace_frame
14098 @item (int) $trace_frame
14099 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14100 snapshot is selected.
14102 @vindex $tracepoint
14103 @item (int) $tracepoint
14104 The tracepoint for the current trace snapshot.
14106 @vindex $trace_line
14107 @item (int) $trace_line
14108 The line number for the current trace snapshot.
14110 @vindex $trace_file
14111 @item (char []) $trace_file
14112 The source file for the current trace snapshot.
14114 @vindex $trace_func
14115 @item (char []) $trace_func
14116 The name of the function containing @code{$tracepoint}.
14119 Note: @code{$trace_file} is not suitable for use in @code{printf},
14120 use @code{output} instead.
14122 Here's a simple example of using these convenience variables for
14123 stepping through all the trace snapshots and printing some of their
14124 data. Note that these are not the same as trace state variables,
14125 which are managed by the target.
14128 (@value{GDBP}) @b{tfind start}
14130 (@value{GDBP}) @b{while $trace_frame != -1}
14131 > output $trace_file
14132 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14138 @section Using Trace Files
14139 @cindex trace files
14141 In some situations, the target running a trace experiment may no
14142 longer be available; perhaps it crashed, or the hardware was needed
14143 for a different activity. To handle these cases, you can arrange to
14144 dump the trace data into a file, and later use that file as a source
14145 of trace data, via the @code{target tfile} command.
14150 @item tsave [ -r ] @var{filename}
14151 @itemx tsave [-ctf] @var{dirname}
14152 Save the trace data to @var{filename}. By default, this command
14153 assumes that @var{filename} refers to the host filesystem, so if
14154 necessary @value{GDBN} will copy raw trace data up from the target and
14155 then save it. If the target supports it, you can also supply the
14156 optional argument @code{-r} (``remote'') to direct the target to save
14157 the data directly into @var{filename} in its own filesystem, which may be
14158 more efficient if the trace buffer is very large. (Note, however, that
14159 @code{target tfile} can only read from files accessible to the host.)
14160 By default, this command will save trace frame in tfile format.
14161 You can supply the optional argument @code{-ctf} to save data in CTF
14162 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14163 that can be shared by multiple debugging and tracing tools. Please go to
14164 @indicateurl{http://www.efficios.com/ctf} to get more information.
14166 @kindex target tfile
14170 @item target tfile @var{filename}
14171 @itemx target ctf @var{dirname}
14172 Use the file named @var{filename} or directory named @var{dirname} as
14173 a source of trace data. Commands that examine data work as they do with
14174 a live target, but it is not possible to run any new trace experiments.
14175 @code{tstatus} will report the state of the trace run at the moment
14176 the data was saved, as well as the current trace frame you are examining.
14177 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14181 (@value{GDBP}) target ctf ctf.ctf
14182 (@value{GDBP}) tfind
14183 Found trace frame 0, tracepoint 2
14184 39 ++a; /* set tracepoint 1 here */
14185 (@value{GDBP}) tdump
14186 Data collected at tracepoint 2, trace frame 0:
14190 c = @{"123", "456", "789", "123", "456", "789"@}
14191 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14199 @chapter Debugging Programs That Use Overlays
14202 If your program is too large to fit completely in your target system's
14203 memory, you can sometimes use @dfn{overlays} to work around this
14204 problem. @value{GDBN} provides some support for debugging programs that
14208 * How Overlays Work:: A general explanation of overlays.
14209 * Overlay Commands:: Managing overlays in @value{GDBN}.
14210 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14211 mapped by asking the inferior.
14212 * Overlay Sample Program:: A sample program using overlays.
14215 @node How Overlays Work
14216 @section How Overlays Work
14217 @cindex mapped overlays
14218 @cindex unmapped overlays
14219 @cindex load address, overlay's
14220 @cindex mapped address
14221 @cindex overlay area
14223 Suppose you have a computer whose instruction address space is only 64
14224 kilobytes long, but which has much more memory which can be accessed by
14225 other means: special instructions, segment registers, or memory
14226 management hardware, for example. Suppose further that you want to
14227 adapt a program which is larger than 64 kilobytes to run on this system.
14229 One solution is to identify modules of your program which are relatively
14230 independent, and need not call each other directly; call these modules
14231 @dfn{overlays}. Separate the overlays from the main program, and place
14232 their machine code in the larger memory. Place your main program in
14233 instruction memory, but leave at least enough space there to hold the
14234 largest overlay as well.
14236 Now, to call a function located in an overlay, you must first copy that
14237 overlay's machine code from the large memory into the space set aside
14238 for it in the instruction memory, and then jump to its entry point
14241 @c NB: In the below the mapped area's size is greater or equal to the
14242 @c size of all overlays. This is intentional to remind the developer
14243 @c that overlays don't necessarily need to be the same size.
14247 Data Instruction Larger
14248 Address Space Address Space Address Space
14249 +-----------+ +-----------+ +-----------+
14251 +-----------+ +-----------+ +-----------+<-- overlay 1
14252 | program | | main | .----| overlay 1 | load address
14253 | variables | | program | | +-----------+
14254 | and heap | | | | | |
14255 +-----------+ | | | +-----------+<-- overlay 2
14256 | | +-----------+ | | | load address
14257 +-----------+ | | | .-| overlay 2 |
14259 mapped --->+-----------+ | | +-----------+
14260 address | | | | | |
14261 | overlay | <-' | | |
14262 | area | <---' +-----------+<-- overlay 3
14263 | | <---. | | load address
14264 +-----------+ `--| overlay 3 |
14271 @anchor{A code overlay}A code overlay
14275 The diagram (@pxref{A code overlay}) shows a system with separate data
14276 and instruction address spaces. To map an overlay, the program copies
14277 its code from the larger address space to the instruction address space.
14278 Since the overlays shown here all use the same mapped address, only one
14279 may be mapped at a time. For a system with a single address space for
14280 data and instructions, the diagram would be similar, except that the
14281 program variables and heap would share an address space with the main
14282 program and the overlay area.
14284 An overlay loaded into instruction memory and ready for use is called a
14285 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14286 instruction memory. An overlay not present (or only partially present)
14287 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14288 is its address in the larger memory. The mapped address is also called
14289 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14290 called the @dfn{load memory address}, or @dfn{LMA}.
14292 Unfortunately, overlays are not a completely transparent way to adapt a
14293 program to limited instruction memory. They introduce a new set of
14294 global constraints you must keep in mind as you design your program:
14299 Before calling or returning to a function in an overlay, your program
14300 must make sure that overlay is actually mapped. Otherwise, the call or
14301 return will transfer control to the right address, but in the wrong
14302 overlay, and your program will probably crash.
14305 If the process of mapping an overlay is expensive on your system, you
14306 will need to choose your overlays carefully to minimize their effect on
14307 your program's performance.
14310 The executable file you load onto your system must contain each
14311 overlay's instructions, appearing at the overlay's load address, not its
14312 mapped address. However, each overlay's instructions must be relocated
14313 and its symbols defined as if the overlay were at its mapped address.
14314 You can use GNU linker scripts to specify different load and relocation
14315 addresses for pieces of your program; see @ref{Overlay Description,,,
14316 ld.info, Using ld: the GNU linker}.
14319 The procedure for loading executable files onto your system must be able
14320 to load their contents into the larger address space as well as the
14321 instruction and data spaces.
14325 The overlay system described above is rather simple, and could be
14326 improved in many ways:
14331 If your system has suitable bank switch registers or memory management
14332 hardware, you could use those facilities to make an overlay's load area
14333 contents simply appear at their mapped address in instruction space.
14334 This would probably be faster than copying the overlay to its mapped
14335 area in the usual way.
14338 If your overlays are small enough, you could set aside more than one
14339 overlay area, and have more than one overlay mapped at a time.
14342 You can use overlays to manage data, as well as instructions. In
14343 general, data overlays are even less transparent to your design than
14344 code overlays: whereas code overlays only require care when you call or
14345 return to functions, data overlays require care every time you access
14346 the data. Also, if you change the contents of a data overlay, you
14347 must copy its contents back out to its load address before you can copy a
14348 different data overlay into the same mapped area.
14353 @node Overlay Commands
14354 @section Overlay Commands
14356 To use @value{GDBN}'s overlay support, each overlay in your program must
14357 correspond to a separate section of the executable file. The section's
14358 virtual memory address and load memory address must be the overlay's
14359 mapped and load addresses. Identifying overlays with sections allows
14360 @value{GDBN} to determine the appropriate address of a function or
14361 variable, depending on whether the overlay is mapped or not.
14363 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14364 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14369 Disable @value{GDBN}'s overlay support. When overlay support is
14370 disabled, @value{GDBN} assumes that all functions and variables are
14371 always present at their mapped addresses. By default, @value{GDBN}'s
14372 overlay support is disabled.
14374 @item overlay manual
14375 @cindex manual overlay debugging
14376 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14377 relies on you to tell it which overlays are mapped, and which are not,
14378 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14379 commands described below.
14381 @item overlay map-overlay @var{overlay}
14382 @itemx overlay map @var{overlay}
14383 @cindex map an overlay
14384 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14385 be the name of the object file section containing the overlay. When an
14386 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14387 functions and variables at their mapped addresses. @value{GDBN} assumes
14388 that any other overlays whose mapped ranges overlap that of
14389 @var{overlay} are now unmapped.
14391 @item overlay unmap-overlay @var{overlay}
14392 @itemx overlay unmap @var{overlay}
14393 @cindex unmap an overlay
14394 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14395 must be the name of the object file section containing the overlay.
14396 When an overlay is unmapped, @value{GDBN} assumes it can find the
14397 overlay's functions and variables at their load addresses.
14400 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14401 consults a data structure the overlay manager maintains in the inferior
14402 to see which overlays are mapped. For details, see @ref{Automatic
14403 Overlay Debugging}.
14405 @item overlay load-target
14406 @itemx overlay load
14407 @cindex reloading the overlay table
14408 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14409 re-reads the table @value{GDBN} automatically each time the inferior
14410 stops, so this command should only be necessary if you have changed the
14411 overlay mapping yourself using @value{GDBN}. This command is only
14412 useful when using automatic overlay debugging.
14414 @item overlay list-overlays
14415 @itemx overlay list
14416 @cindex listing mapped overlays
14417 Display a list of the overlays currently mapped, along with their mapped
14418 addresses, load addresses, and sizes.
14422 Normally, when @value{GDBN} prints a code address, it includes the name
14423 of the function the address falls in:
14426 (@value{GDBP}) print main
14427 $3 = @{int ()@} 0x11a0 <main>
14430 When overlay debugging is enabled, @value{GDBN} recognizes code in
14431 unmapped overlays, and prints the names of unmapped functions with
14432 asterisks around them. For example, if @code{foo} is a function in an
14433 unmapped overlay, @value{GDBN} prints it this way:
14436 (@value{GDBP}) overlay list
14437 No sections are mapped.
14438 (@value{GDBP}) print foo
14439 $5 = @{int (int)@} 0x100000 <*foo*>
14442 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14446 (@value{GDBP}) overlay list
14447 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14448 mapped at 0x1016 - 0x104a
14449 (@value{GDBP}) print foo
14450 $6 = @{int (int)@} 0x1016 <foo>
14453 When overlay debugging is enabled, @value{GDBN} can find the correct
14454 address for functions and variables in an overlay, whether or not the
14455 overlay is mapped. This allows most @value{GDBN} commands, like
14456 @code{break} and @code{disassemble}, to work normally, even on unmapped
14457 code. However, @value{GDBN}'s breakpoint support has some limitations:
14461 @cindex breakpoints in overlays
14462 @cindex overlays, setting breakpoints in
14463 You can set breakpoints in functions in unmapped overlays, as long as
14464 @value{GDBN} can write to the overlay at its load address.
14466 @value{GDBN} can not set hardware or simulator-based breakpoints in
14467 unmapped overlays. However, if you set a breakpoint at the end of your
14468 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14469 you are using manual overlay management), @value{GDBN} will re-set its
14470 breakpoints properly.
14474 @node Automatic Overlay Debugging
14475 @section Automatic Overlay Debugging
14476 @cindex automatic overlay debugging
14478 @value{GDBN} can automatically track which overlays are mapped and which
14479 are not, given some simple co-operation from the overlay manager in the
14480 inferior. If you enable automatic overlay debugging with the
14481 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14482 looks in the inferior's memory for certain variables describing the
14483 current state of the overlays.
14485 Here are the variables your overlay manager must define to support
14486 @value{GDBN}'s automatic overlay debugging:
14490 @item @code{_ovly_table}:
14491 This variable must be an array of the following structures:
14496 /* The overlay's mapped address. */
14499 /* The size of the overlay, in bytes. */
14500 unsigned long size;
14502 /* The overlay's load address. */
14505 /* Non-zero if the overlay is currently mapped;
14507 unsigned long mapped;
14511 @item @code{_novlys}:
14512 This variable must be a four-byte signed integer, holding the total
14513 number of elements in @code{_ovly_table}.
14517 To decide whether a particular overlay is mapped or not, @value{GDBN}
14518 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14519 @code{lma} members equal the VMA and LMA of the overlay's section in the
14520 executable file. When @value{GDBN} finds a matching entry, it consults
14521 the entry's @code{mapped} member to determine whether the overlay is
14524 In addition, your overlay manager may define a function called
14525 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14526 will silently set a breakpoint there. If the overlay manager then
14527 calls this function whenever it has changed the overlay table, this
14528 will enable @value{GDBN} to accurately keep track of which overlays
14529 are in program memory, and update any breakpoints that may be set
14530 in overlays. This will allow breakpoints to work even if the
14531 overlays are kept in ROM or other non-writable memory while they
14532 are not being executed.
14534 @node Overlay Sample Program
14535 @section Overlay Sample Program
14536 @cindex overlay example program
14538 When linking a program which uses overlays, you must place the overlays
14539 at their load addresses, while relocating them to run at their mapped
14540 addresses. To do this, you must write a linker script (@pxref{Overlay
14541 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14542 since linker scripts are specific to a particular host system, target
14543 architecture, and target memory layout, this manual cannot provide
14544 portable sample code demonstrating @value{GDBN}'s overlay support.
14546 However, the @value{GDBN} source distribution does contain an overlaid
14547 program, with linker scripts for a few systems, as part of its test
14548 suite. The program consists of the following files from
14549 @file{gdb/testsuite/gdb.base}:
14553 The main program file.
14555 A simple overlay manager, used by @file{overlays.c}.
14560 Overlay modules, loaded and used by @file{overlays.c}.
14563 Linker scripts for linking the test program on the @code{d10v-elf}
14564 and @code{m32r-elf} targets.
14567 You can build the test program using the @code{d10v-elf} GCC
14568 cross-compiler like this:
14571 $ d10v-elf-gcc -g -c overlays.c
14572 $ d10v-elf-gcc -g -c ovlymgr.c
14573 $ d10v-elf-gcc -g -c foo.c
14574 $ d10v-elf-gcc -g -c bar.c
14575 $ d10v-elf-gcc -g -c baz.c
14576 $ d10v-elf-gcc -g -c grbx.c
14577 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14578 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14581 The build process is identical for any other architecture, except that
14582 you must substitute the appropriate compiler and linker script for the
14583 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14587 @chapter Using @value{GDBN} with Different Languages
14590 Although programming languages generally have common aspects, they are
14591 rarely expressed in the same manner. For instance, in ANSI C,
14592 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14593 Modula-2, it is accomplished by @code{p^}. Values can also be
14594 represented (and displayed) differently. Hex numbers in C appear as
14595 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14597 @cindex working language
14598 Language-specific information is built into @value{GDBN} for some languages,
14599 allowing you to express operations like the above in your program's
14600 native language, and allowing @value{GDBN} to output values in a manner
14601 consistent with the syntax of your program's native language. The
14602 language you use to build expressions is called the @dfn{working
14606 * Setting:: Switching between source languages
14607 * Show:: Displaying the language
14608 * Checks:: Type and range checks
14609 * Supported Languages:: Supported languages
14610 * Unsupported Languages:: Unsupported languages
14614 @section Switching Between Source Languages
14616 There are two ways to control the working language---either have @value{GDBN}
14617 set it automatically, or select it manually yourself. You can use the
14618 @code{set language} command for either purpose. On startup, @value{GDBN}
14619 defaults to setting the language automatically. The working language is
14620 used to determine how expressions you type are interpreted, how values
14623 In addition to the working language, every source file that
14624 @value{GDBN} knows about has its own working language. For some object
14625 file formats, the compiler might indicate which language a particular
14626 source file is in. However, most of the time @value{GDBN} infers the
14627 language from the name of the file. The language of a source file
14628 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14629 show each frame appropriately for its own language. There is no way to
14630 set the language of a source file from within @value{GDBN}, but you can
14631 set the language associated with a filename extension. @xref{Show, ,
14632 Displaying the Language}.
14634 This is most commonly a problem when you use a program, such
14635 as @code{cfront} or @code{f2c}, that generates C but is written in
14636 another language. In that case, make the
14637 program use @code{#line} directives in its C output; that way
14638 @value{GDBN} will know the correct language of the source code of the original
14639 program, and will display that source code, not the generated C code.
14642 * Filenames:: Filename extensions and languages.
14643 * Manually:: Setting the working language manually
14644 * Automatically:: Having @value{GDBN} infer the source language
14648 @subsection List of Filename Extensions and Languages
14650 If a source file name ends in one of the following extensions, then
14651 @value{GDBN} infers that its language is the one indicated.
14669 C@t{++} source file
14675 Objective-C source file
14679 Fortran source file
14682 Modula-2 source file
14686 Assembler source file. This actually behaves almost like C, but
14687 @value{GDBN} does not skip over function prologues when stepping.
14690 In addition, you may set the language associated with a filename
14691 extension. @xref{Show, , Displaying the Language}.
14694 @subsection Setting the Working Language
14696 If you allow @value{GDBN} to set the language automatically,
14697 expressions are interpreted the same way in your debugging session and
14700 @kindex set language
14701 If you wish, you may set the language manually. To do this, issue the
14702 command @samp{set language @var{lang}}, where @var{lang} is the name of
14703 a language, such as
14704 @code{c} or @code{modula-2}.
14705 For a list of the supported languages, type @samp{set language}.
14707 Setting the language manually prevents @value{GDBN} from updating the working
14708 language automatically. This can lead to confusion if you try
14709 to debug a program when the working language is not the same as the
14710 source language, when an expression is acceptable to both
14711 languages---but means different things. For instance, if the current
14712 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14720 might not have the effect you intended. In C, this means to add
14721 @code{b} and @code{c} and place the result in @code{a}. The result
14722 printed would be the value of @code{a}. In Modula-2, this means to compare
14723 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14725 @node Automatically
14726 @subsection Having @value{GDBN} Infer the Source Language
14728 To have @value{GDBN} set the working language automatically, use
14729 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14730 then infers the working language. That is, when your program stops in a
14731 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14732 working language to the language recorded for the function in that
14733 frame. If the language for a frame is unknown (that is, if the function
14734 or block corresponding to the frame was defined in a source file that
14735 does not have a recognized extension), the current working language is
14736 not changed, and @value{GDBN} issues a warning.
14738 This may not seem necessary for most programs, which are written
14739 entirely in one source language. However, program modules and libraries
14740 written in one source language can be used by a main program written in
14741 a different source language. Using @samp{set language auto} in this
14742 case frees you from having to set the working language manually.
14745 @section Displaying the Language
14747 The following commands help you find out which language is the
14748 working language, and also what language source files were written in.
14751 @item show language
14752 @anchor{show language}
14753 @kindex show language
14754 Display the current working language. This is the
14755 language you can use with commands such as @code{print} to
14756 build and compute expressions that may involve variables in your program.
14759 @kindex info frame@r{, show the source language}
14760 Display the source language for this frame. This language becomes the
14761 working language if you use an identifier from this frame.
14762 @xref{Frame Info, ,Information about a Frame}, to identify the other
14763 information listed here.
14766 @kindex info source@r{, show the source language}
14767 Display the source language of this source file.
14768 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14769 information listed here.
14772 In unusual circumstances, you may have source files with extensions
14773 not in the standard list. You can then set the extension associated
14774 with a language explicitly:
14777 @item set extension-language @var{ext} @var{language}
14778 @kindex set extension-language
14779 Tell @value{GDBN} that source files with extension @var{ext} are to be
14780 assumed as written in the source language @var{language}.
14782 @item info extensions
14783 @kindex info extensions
14784 List all the filename extensions and the associated languages.
14788 @section Type and Range Checking
14790 Some languages are designed to guard you against making seemingly common
14791 errors through a series of compile- and run-time checks. These include
14792 checking the type of arguments to functions and operators and making
14793 sure mathematical overflows are caught at run time. Checks such as
14794 these help to ensure a program's correctness once it has been compiled
14795 by eliminating type mismatches and providing active checks for range
14796 errors when your program is running.
14798 By default @value{GDBN} checks for these errors according to the
14799 rules of the current source language. Although @value{GDBN} does not check
14800 the statements in your program, it can check expressions entered directly
14801 into @value{GDBN} for evaluation via the @code{print} command, for example.
14804 * Type Checking:: An overview of type checking
14805 * Range Checking:: An overview of range checking
14808 @cindex type checking
14809 @cindex checks, type
14810 @node Type Checking
14811 @subsection An Overview of Type Checking
14813 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14814 arguments to operators and functions have to be of the correct type,
14815 otherwise an error occurs. These checks prevent type mismatch
14816 errors from ever causing any run-time problems. For example,
14819 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14821 (@value{GDBP}) print obj.my_method (0)
14824 (@value{GDBP}) print obj.my_method (0x1234)
14825 Cannot resolve method klass::my_method to any overloaded instance
14828 The second example fails because in C@t{++} the integer constant
14829 @samp{0x1234} is not type-compatible with the pointer parameter type.
14831 For the expressions you use in @value{GDBN} commands, you can tell
14832 @value{GDBN} to not enforce strict type checking or
14833 to treat any mismatches as errors and abandon the expression;
14834 When type checking is disabled, @value{GDBN} successfully evaluates
14835 expressions like the second example above.
14837 Even if type checking is off, there may be other reasons
14838 related to type that prevent @value{GDBN} from evaluating an expression.
14839 For instance, @value{GDBN} does not know how to add an @code{int} and
14840 a @code{struct foo}. These particular type errors have nothing to do
14841 with the language in use and usually arise from expressions which make
14842 little sense to evaluate anyway.
14844 @value{GDBN} provides some additional commands for controlling type checking:
14846 @kindex set check type
14847 @kindex show check type
14849 @item set check type on
14850 @itemx set check type off
14851 Set strict type checking on or off. If any type mismatches occur in
14852 evaluating an expression while type checking is on, @value{GDBN} prints a
14853 message and aborts evaluation of the expression.
14855 @item show check type
14856 Show the current setting of type checking and whether @value{GDBN}
14857 is enforcing strict type checking rules.
14860 @cindex range checking
14861 @cindex checks, range
14862 @node Range Checking
14863 @subsection An Overview of Range Checking
14865 In some languages (such as Modula-2), it is an error to exceed the
14866 bounds of a type; this is enforced with run-time checks. Such range
14867 checking is meant to ensure program correctness by making sure
14868 computations do not overflow, or indices on an array element access do
14869 not exceed the bounds of the array.
14871 For expressions you use in @value{GDBN} commands, you can tell
14872 @value{GDBN} to treat range errors in one of three ways: ignore them,
14873 always treat them as errors and abandon the expression, or issue
14874 warnings but evaluate the expression anyway.
14876 A range error can result from numerical overflow, from exceeding an
14877 array index bound, or when you type a constant that is not a member
14878 of any type. Some languages, however, do not treat overflows as an
14879 error. In many implementations of C, mathematical overflow causes the
14880 result to ``wrap around'' to lower values---for example, if @var{m} is
14881 the largest integer value, and @var{s} is the smallest, then
14884 @var{m} + 1 @result{} @var{s}
14887 This, too, is specific to individual languages, and in some cases
14888 specific to individual compilers or machines. @xref{Supported Languages, ,
14889 Supported Languages}, for further details on specific languages.
14891 @value{GDBN} provides some additional commands for controlling the range checker:
14893 @kindex set check range
14894 @kindex show check range
14896 @item set check range auto
14897 Set range checking on or off based on the current working language.
14898 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14901 @item set check range on
14902 @itemx set check range off
14903 Set range checking on or off, overriding the default setting for the
14904 current working language. A warning is issued if the setting does not
14905 match the language default. If a range error occurs and range checking is on,
14906 then a message is printed and evaluation of the expression is aborted.
14908 @item set check range warn
14909 Output messages when the @value{GDBN} range checker detects a range error,
14910 but attempt to evaluate the expression anyway. Evaluating the
14911 expression may still be impossible for other reasons, such as accessing
14912 memory that the process does not own (a typical example from many Unix
14916 Show the current setting of the range checker, and whether or not it is
14917 being set automatically by @value{GDBN}.
14920 @node Supported Languages
14921 @section Supported Languages
14923 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14924 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14925 @c This is false ...
14926 Some @value{GDBN} features may be used in expressions regardless of the
14927 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14928 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14929 ,Expressions}) can be used with the constructs of any supported
14932 The following sections detail to what degree each source language is
14933 supported by @value{GDBN}. These sections are not meant to be language
14934 tutorials or references, but serve only as a reference guide to what the
14935 @value{GDBN} expression parser accepts, and what input and output
14936 formats should look like for different languages. There are many good
14937 books written on each of these languages; please look to these for a
14938 language reference or tutorial.
14941 * C:: C and C@t{++}
14944 * Objective-C:: Objective-C
14945 * OpenCL C:: OpenCL C
14946 * Fortran:: Fortran
14949 * Modula-2:: Modula-2
14954 @subsection C and C@t{++}
14956 @cindex C and C@t{++}
14957 @cindex expressions in C or C@t{++}
14959 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14960 to both languages. Whenever this is the case, we discuss those languages
14964 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14965 @cindex @sc{gnu} C@t{++}
14966 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14967 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14968 effectively, you must compile your C@t{++} programs with a supported
14969 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14970 compiler (@code{aCC}).
14973 * C Operators:: C and C@t{++} operators
14974 * C Constants:: C and C@t{++} constants
14975 * C Plus Plus Expressions:: C@t{++} expressions
14976 * C Defaults:: Default settings for C and C@t{++}
14977 * C Checks:: C and C@t{++} type and range checks
14978 * Debugging C:: @value{GDBN} and C
14979 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14980 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14984 @subsubsection C and C@t{++} Operators
14986 @cindex C and C@t{++} operators
14988 Operators must be defined on values of specific types. For instance,
14989 @code{+} is defined on numbers, but not on structures. Operators are
14990 often defined on groups of types.
14992 For the purposes of C and C@t{++}, the following definitions hold:
14997 @emph{Integral types} include @code{int} with any of its storage-class
14998 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15001 @emph{Floating-point types} include @code{float}, @code{double}, and
15002 @code{long double} (if supported by the target platform).
15005 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15008 @emph{Scalar types} include all of the above.
15013 The following operators are supported. They are listed here
15014 in order of increasing precedence:
15018 The comma or sequencing operator. Expressions in a comma-separated list
15019 are evaluated from left to right, with the result of the entire
15020 expression being the last expression evaluated.
15023 Assignment. The value of an assignment expression is the value
15024 assigned. Defined on scalar types.
15027 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15028 and translated to @w{@code{@var{a} = @var{a op b}}}.
15029 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15030 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15031 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15034 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15035 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15036 should be of an integral type.
15039 Logical @sc{or}. Defined on integral types.
15042 Logical @sc{and}. Defined on integral types.
15045 Bitwise @sc{or}. Defined on integral types.
15048 Bitwise exclusive-@sc{or}. Defined on integral types.
15051 Bitwise @sc{and}. Defined on integral types.
15054 Equality and inequality. Defined on scalar types. The value of these
15055 expressions is 0 for false and non-zero for true.
15057 @item <@r{, }>@r{, }<=@r{, }>=
15058 Less than, greater than, less than or equal, greater than or equal.
15059 Defined on scalar types. The value of these expressions is 0 for false
15060 and non-zero for true.
15063 left shift, and right shift. Defined on integral types.
15066 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15069 Addition and subtraction. Defined on integral types, floating-point types and
15072 @item *@r{, }/@r{, }%
15073 Multiplication, division, and modulus. Multiplication and division are
15074 defined on integral and floating-point types. Modulus is defined on
15078 Increment and decrement. When appearing before a variable, the
15079 operation is performed before the variable is used in an expression;
15080 when appearing after it, the variable's value is used before the
15081 operation takes place.
15084 Pointer dereferencing. Defined on pointer types. Same precedence as
15088 Address operator. Defined on variables. Same precedence as @code{++}.
15090 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15091 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15092 to examine the address
15093 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15097 Negative. Defined on integral and floating-point types. Same
15098 precedence as @code{++}.
15101 Logical negation. Defined on integral types. Same precedence as
15105 Bitwise complement operator. Defined on integral types. Same precedence as
15110 Structure member, and pointer-to-structure member. For convenience,
15111 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15112 pointer based on the stored type information.
15113 Defined on @code{struct} and @code{union} data.
15116 Dereferences of pointers to members.
15119 Array indexing. @code{@var{a}[@var{i}]} is defined as
15120 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15123 Function parameter list. Same precedence as @code{->}.
15126 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15127 and @code{class} types.
15130 Doubled colons also represent the @value{GDBN} scope operator
15131 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15135 If an operator is redefined in the user code, @value{GDBN} usually
15136 attempts to invoke the redefined version instead of using the operator's
15137 predefined meaning.
15140 @subsubsection C and C@t{++} Constants
15142 @cindex C and C@t{++} constants
15144 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15149 Integer constants are a sequence of digits. Octal constants are
15150 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15151 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15152 @samp{l}, specifying that the constant should be treated as a
15156 Floating point constants are a sequence of digits, followed by a decimal
15157 point, followed by a sequence of digits, and optionally followed by an
15158 exponent. An exponent is of the form:
15159 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15160 sequence of digits. The @samp{+} is optional for positive exponents.
15161 A floating-point constant may also end with a letter @samp{f} or
15162 @samp{F}, specifying that the constant should be treated as being of
15163 the @code{float} (as opposed to the default @code{double}) type; or with
15164 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15168 Enumerated constants consist of enumerated identifiers, or their
15169 integral equivalents.
15172 Character constants are a single character surrounded by single quotes
15173 (@code{'}), or a number---the ordinal value of the corresponding character
15174 (usually its @sc{ascii} value). Within quotes, the single character may
15175 be represented by a letter or by @dfn{escape sequences}, which are of
15176 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15177 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15178 @samp{@var{x}} is a predefined special character---for example,
15179 @samp{\n} for newline.
15181 Wide character constants can be written by prefixing a character
15182 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15183 form of @samp{x}. The target wide character set is used when
15184 computing the value of this constant (@pxref{Character Sets}).
15187 String constants are a sequence of character constants surrounded by
15188 double quotes (@code{"}). Any valid character constant (as described
15189 above) may appear. Double quotes within the string must be preceded by
15190 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15193 Wide string constants can be written by prefixing a string constant
15194 with @samp{L}, as in C. The target wide character set is used when
15195 computing the value of this constant (@pxref{Character Sets}).
15198 Pointer constants are an integral value. You can also write pointers
15199 to constants using the C operator @samp{&}.
15202 Array constants are comma-separated lists surrounded by braces @samp{@{}
15203 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15204 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15205 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15208 @node C Plus Plus Expressions
15209 @subsubsection C@t{++} Expressions
15211 @cindex expressions in C@t{++}
15212 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15214 @cindex debugging C@t{++} programs
15215 @cindex C@t{++} compilers
15216 @cindex debug formats and C@t{++}
15217 @cindex @value{NGCC} and C@t{++}
15219 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15220 the proper compiler and the proper debug format. Currently,
15221 @value{GDBN} works best when debugging C@t{++} code that is compiled
15222 with the most recent version of @value{NGCC} possible. The DWARF
15223 debugging format is preferred; @value{NGCC} defaults to this on most
15224 popular platforms. Other compilers and/or debug formats are likely to
15225 work badly or not at all when using @value{GDBN} to debug C@t{++}
15226 code. @xref{Compilation}.
15231 @cindex member functions
15233 Member function calls are allowed; you can use expressions like
15236 count = aml->GetOriginal(x, y)
15239 @vindex this@r{, inside C@t{++} member functions}
15240 @cindex namespace in C@t{++}
15242 While a member function is active (in the selected stack frame), your
15243 expressions have the same namespace available as the member function;
15244 that is, @value{GDBN} allows implicit references to the class instance
15245 pointer @code{this} following the same rules as C@t{++}. @code{using}
15246 declarations in the current scope are also respected by @value{GDBN}.
15248 @cindex call overloaded functions
15249 @cindex overloaded functions, calling
15250 @cindex type conversions in C@t{++}
15252 You can call overloaded functions; @value{GDBN} resolves the function
15253 call to the right definition, with some restrictions. @value{GDBN} does not
15254 perform overload resolution involving user-defined type conversions,
15255 calls to constructors, or instantiations of templates that do not exist
15256 in the program. It also cannot handle ellipsis argument lists or
15259 It does perform integral conversions and promotions, floating-point
15260 promotions, arithmetic conversions, pointer conversions, conversions of
15261 class objects to base classes, and standard conversions such as those of
15262 functions or arrays to pointers; it requires an exact match on the
15263 number of function arguments.
15265 Overload resolution is always performed, unless you have specified
15266 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15267 ,@value{GDBN} Features for C@t{++}}.
15269 You must specify @code{set overload-resolution off} in order to use an
15270 explicit function signature to call an overloaded function, as in
15272 p 'foo(char,int)'('x', 13)
15275 The @value{GDBN} command-completion facility can simplify this;
15276 see @ref{Completion, ,Command Completion}.
15278 @cindex reference declarations
15280 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15281 references; you can use them in expressions just as you do in C@t{++}
15282 source---they are automatically dereferenced.
15284 In the parameter list shown when @value{GDBN} displays a frame, the values of
15285 reference variables are not displayed (unlike other variables); this
15286 avoids clutter, since references are often used for large structures.
15287 The @emph{address} of a reference variable is always shown, unless
15288 you have specified @samp{set print address off}.
15291 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15292 expressions can use it just as expressions in your program do. Since
15293 one scope may be defined in another, you can use @code{::} repeatedly if
15294 necessary, for example in an expression like
15295 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15296 resolving name scope by reference to source files, in both C and C@t{++}
15297 debugging (@pxref{Variables, ,Program Variables}).
15300 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15305 @subsubsection C and C@t{++} Defaults
15307 @cindex C and C@t{++} defaults
15309 If you allow @value{GDBN} to set range checking automatically, it
15310 defaults to @code{off} whenever the working language changes to
15311 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15312 selects the working language.
15314 If you allow @value{GDBN} to set the language automatically, it
15315 recognizes source files whose names end with @file{.c}, @file{.C}, or
15316 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15317 these files, it sets the working language to C or C@t{++}.
15318 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15319 for further details.
15322 @subsubsection C and C@t{++} Type and Range Checks
15324 @cindex C and C@t{++} checks
15326 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15327 checking is used. However, if you turn type checking off, @value{GDBN}
15328 will allow certain non-standard conversions, such as promoting integer
15329 constants to pointers.
15331 Range checking, if turned on, is done on mathematical operations. Array
15332 indices are not checked, since they are often used to index a pointer
15333 that is not itself an array.
15336 @subsubsection @value{GDBN} and C
15338 The @code{set print union} and @code{show print union} commands apply to
15339 the @code{union} type. When set to @samp{on}, any @code{union} that is
15340 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15341 appears as @samp{@{...@}}.
15343 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15344 with pointers and a memory allocation function. @xref{Expressions,
15347 @node Debugging C Plus Plus
15348 @subsubsection @value{GDBN} Features for C@t{++}
15350 @cindex commands for C@t{++}
15352 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15353 designed specifically for use with C@t{++}. Here is a summary:
15356 @cindex break in overloaded functions
15357 @item @r{breakpoint menus}
15358 When you want a breakpoint in a function whose name is overloaded,
15359 @value{GDBN} has the capability to display a menu of possible breakpoint
15360 locations to help you specify which function definition you want.
15361 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15363 @cindex overloading in C@t{++}
15364 @item rbreak @var{regex}
15365 Setting breakpoints using regular expressions is helpful for setting
15366 breakpoints on overloaded functions that are not members of any special
15368 @xref{Set Breaks, ,Setting Breakpoints}.
15370 @cindex C@t{++} exception handling
15372 @itemx catch rethrow
15374 Debug C@t{++} exception handling using these commands. @xref{Set
15375 Catchpoints, , Setting Catchpoints}.
15377 @cindex inheritance
15378 @item ptype @var{typename}
15379 Print inheritance relationships as well as other information for type
15381 @xref{Symbols, ,Examining the Symbol Table}.
15383 @item info vtbl @var{expression}.
15384 The @code{info vtbl} command can be used to display the virtual
15385 method tables of the object computed by @var{expression}. This shows
15386 one entry per virtual table; there may be multiple virtual tables when
15387 multiple inheritance is in use.
15389 @cindex C@t{++} demangling
15390 @item demangle @var{name}
15391 Demangle @var{name}.
15392 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15394 @cindex C@t{++} symbol display
15395 @item set print demangle
15396 @itemx show print demangle
15397 @itemx set print asm-demangle
15398 @itemx show print asm-demangle
15399 Control whether C@t{++} symbols display in their source form, both when
15400 displaying code as C@t{++} source and when displaying disassemblies.
15401 @xref{Print Settings, ,Print Settings}.
15403 @item set print object
15404 @itemx show print object
15405 Choose whether to print derived (actual) or declared types of objects.
15406 @xref{Print Settings, ,Print Settings}.
15408 @item set print vtbl
15409 @itemx show print vtbl
15410 Control the format for printing virtual function tables.
15411 @xref{Print Settings, ,Print Settings}.
15412 (The @code{vtbl} commands do not work on programs compiled with the HP
15413 ANSI C@t{++} compiler (@code{aCC}).)
15415 @kindex set overload-resolution
15416 @cindex overloaded functions, overload resolution
15417 @item set overload-resolution on
15418 Enable overload resolution for C@t{++} expression evaluation. The default
15419 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15420 and searches for a function whose signature matches the argument types,
15421 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15422 Expressions, ,C@t{++} Expressions}, for details).
15423 If it cannot find a match, it emits a message.
15425 @item set overload-resolution off
15426 Disable overload resolution for C@t{++} expression evaluation. For
15427 overloaded functions that are not class member functions, @value{GDBN}
15428 chooses the first function of the specified name that it finds in the
15429 symbol table, whether or not its arguments are of the correct type. For
15430 overloaded functions that are class member functions, @value{GDBN}
15431 searches for a function whose signature @emph{exactly} matches the
15434 @kindex show overload-resolution
15435 @item show overload-resolution
15436 Show the current setting of overload resolution.
15438 @item @r{Overloaded symbol names}
15439 You can specify a particular definition of an overloaded symbol, using
15440 the same notation that is used to declare such symbols in C@t{++}: type
15441 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15442 also use the @value{GDBN} command-line word completion facilities to list the
15443 available choices, or to finish the type list for you.
15444 @xref{Completion,, Command Completion}, for details on how to do this.
15446 @item @r{Breakpoints in functions with ABI tags}
15448 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15449 correspond to changes in the ABI of a type, function, or variable that
15450 would not otherwise be reflected in a mangled name. See
15451 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15454 The ABI tags are visible in C@t{++} demangled names. For example, a
15455 function that returns a std::string:
15458 std::string function(int);
15462 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15463 tag, and @value{GDBN} displays the symbol like this:
15466 function[abi:cxx11](int)
15469 You can set a breakpoint on such functions simply as if they had no
15473 (gdb) b function(int)
15474 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15475 (gdb) info breakpoints
15476 Num Type Disp Enb Address What
15477 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15481 On the rare occasion you need to disambiguate between different ABI
15482 tags, you can do so by simply including the ABI tag in the function
15486 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15490 @node Decimal Floating Point
15491 @subsubsection Decimal Floating Point format
15492 @cindex decimal floating point format
15494 @value{GDBN} can examine, set and perform computations with numbers in
15495 decimal floating point format, which in the C language correspond to the
15496 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15497 specified by the extension to support decimal floating-point arithmetic.
15499 There are two encodings in use, depending on the architecture: BID (Binary
15500 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15501 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15504 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15505 to manipulate decimal floating point numbers, it is not possible to convert
15506 (using a cast, for example) integers wider than 32-bit to decimal float.
15508 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15509 point computations, error checking in decimal float operations ignores
15510 underflow, overflow and divide by zero exceptions.
15512 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15513 to inspect @code{_Decimal128} values stored in floating point registers.
15514 See @ref{PowerPC,,PowerPC} for more details.
15520 @value{GDBN} can be used to debug programs written in D and compiled with
15521 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15522 specific feature --- dynamic arrays.
15527 @cindex Go (programming language)
15528 @value{GDBN} can be used to debug programs written in Go and compiled with
15529 @file{gccgo} or @file{6g} compilers.
15531 Here is a summary of the Go-specific features and restrictions:
15534 @cindex current Go package
15535 @item The current Go package
15536 The name of the current package does not need to be specified when
15537 specifying global variables and functions.
15539 For example, given the program:
15543 var myglob = "Shall we?"
15549 When stopped inside @code{main} either of these work:
15553 (gdb) p main.myglob
15556 @cindex builtin Go types
15557 @item Builtin Go types
15558 The @code{string} type is recognized by @value{GDBN} and is printed
15561 @cindex builtin Go functions
15562 @item Builtin Go functions
15563 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15564 function and handles it internally.
15566 @cindex restrictions on Go expressions
15567 @item Restrictions on Go expressions
15568 All Go operators are supported except @code{&^}.
15569 The Go @code{_} ``blank identifier'' is not supported.
15570 Automatic dereferencing of pointers is not supported.
15574 @subsection Objective-C
15576 @cindex Objective-C
15577 This section provides information about some commands and command
15578 options that are useful for debugging Objective-C code. See also
15579 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15580 few more commands specific to Objective-C support.
15583 * Method Names in Commands::
15584 * The Print Command with Objective-C::
15587 @node Method Names in Commands
15588 @subsubsection Method Names in Commands
15590 The following commands have been extended to accept Objective-C method
15591 names as line specifications:
15593 @kindex clear@r{, and Objective-C}
15594 @kindex break@r{, and Objective-C}
15595 @kindex info line@r{, and Objective-C}
15596 @kindex jump@r{, and Objective-C}
15597 @kindex list@r{, and Objective-C}
15601 @item @code{info line}
15606 A fully qualified Objective-C method name is specified as
15609 -[@var{Class} @var{methodName}]
15612 where the minus sign is used to indicate an instance method and a
15613 plus sign (not shown) is used to indicate a class method. The class
15614 name @var{Class} and method name @var{methodName} are enclosed in
15615 brackets, similar to the way messages are specified in Objective-C
15616 source code. For example, to set a breakpoint at the @code{create}
15617 instance method of class @code{Fruit} in the program currently being
15621 break -[Fruit create]
15624 To list ten program lines around the @code{initialize} class method,
15628 list +[NSText initialize]
15631 In the current version of @value{GDBN}, the plus or minus sign is
15632 required. In future versions of @value{GDBN}, the plus or minus
15633 sign will be optional, but you can use it to narrow the search. It
15634 is also possible to specify just a method name:
15640 You must specify the complete method name, including any colons. If
15641 your program's source files contain more than one @code{create} method,
15642 you'll be presented with a numbered list of classes that implement that
15643 method. Indicate your choice by number, or type @samp{0} to exit if
15646 As another example, to clear a breakpoint established at the
15647 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15650 clear -[NSWindow makeKeyAndOrderFront:]
15653 @node The Print Command with Objective-C
15654 @subsubsection The Print Command With Objective-C
15655 @cindex Objective-C, print objects
15656 @kindex print-object
15657 @kindex po @r{(@code{print-object})}
15659 The print command has also been extended to accept methods. For example:
15662 print -[@var{object} hash]
15665 @cindex print an Objective-C object description
15666 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15668 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15669 and print the result. Also, an additional command has been added,
15670 @code{print-object} or @code{po} for short, which is meant to print
15671 the description of an object. However, this command may only work
15672 with certain Objective-C libraries that have a particular hook
15673 function, @code{_NSPrintForDebugger}, defined.
15676 @subsection OpenCL C
15679 This section provides information about @value{GDBN}s OpenCL C support.
15682 * OpenCL C Datatypes::
15683 * OpenCL C Expressions::
15684 * OpenCL C Operators::
15687 @node OpenCL C Datatypes
15688 @subsubsection OpenCL C Datatypes
15690 @cindex OpenCL C Datatypes
15691 @value{GDBN} supports the builtin scalar and vector datatypes specified
15692 by OpenCL 1.1. In addition the half- and double-precision floating point
15693 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15694 extensions are also known to @value{GDBN}.
15696 @node OpenCL C Expressions
15697 @subsubsection OpenCL C Expressions
15699 @cindex OpenCL C Expressions
15700 @value{GDBN} supports accesses to vector components including the access as
15701 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15702 supported by @value{GDBN} can be used as well.
15704 @node OpenCL C Operators
15705 @subsubsection OpenCL C Operators
15707 @cindex OpenCL C Operators
15708 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15712 @subsection Fortran
15713 @cindex Fortran-specific support in @value{GDBN}
15715 @value{GDBN} can be used to debug programs written in Fortran, but it
15716 currently supports only the features of Fortran 77 language.
15718 @cindex trailing underscore, in Fortran symbols
15719 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15720 among them) append an underscore to the names of variables and
15721 functions. When you debug programs compiled by those compilers, you
15722 will need to refer to variables and functions with a trailing
15726 * Fortran Operators:: Fortran operators and expressions
15727 * Fortran Defaults:: Default settings for Fortran
15728 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15731 @node Fortran Operators
15732 @subsubsection Fortran Operators and Expressions
15734 @cindex Fortran operators and expressions
15736 Operators must be defined on values of specific types. For instance,
15737 @code{+} is defined on numbers, but not on characters or other non-
15738 arithmetic types. Operators are often defined on groups of types.
15742 The exponentiation operator. It raises the first operand to the power
15746 The range operator. Normally used in the form of array(low:high) to
15747 represent a section of array.
15750 The access component operator. Normally used to access elements in derived
15751 types. Also suitable for unions. As unions aren't part of regular Fortran,
15752 this can only happen when accessing a register that uses a gdbarch-defined
15756 @node Fortran Defaults
15757 @subsubsection Fortran Defaults
15759 @cindex Fortran Defaults
15761 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15762 default uses case-insensitive matches for Fortran symbols. You can
15763 change that with the @samp{set case-insensitive} command, see
15764 @ref{Symbols}, for the details.
15766 @node Special Fortran Commands
15767 @subsubsection Special Fortran Commands
15769 @cindex Special Fortran commands
15771 @value{GDBN} has some commands to support Fortran-specific features,
15772 such as displaying common blocks.
15775 @cindex @code{COMMON} blocks, Fortran
15776 @kindex info common
15777 @item info common @r{[}@var{common-name}@r{]}
15778 This command prints the values contained in the Fortran @code{COMMON}
15779 block whose name is @var{common-name}. With no argument, the names of
15780 all @code{COMMON} blocks visible at the current program location are
15787 @cindex Pascal support in @value{GDBN}, limitations
15788 Debugging Pascal programs which use sets, subranges, file variables, or
15789 nested functions does not currently work. @value{GDBN} does not support
15790 entering expressions, printing values, or similar features using Pascal
15793 The Pascal-specific command @code{set print pascal_static-members}
15794 controls whether static members of Pascal objects are displayed.
15795 @xref{Print Settings, pascal_static-members}.
15800 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15801 Programming Language}. Type- and value-printing, and expression
15802 parsing, are reasonably complete. However, there are a few
15803 peculiarities and holes to be aware of.
15807 Linespecs (@pxref{Specify Location}) are never relative to the current
15808 crate. Instead, they act as if there were a global namespace of
15809 crates, somewhat similar to the way @code{extern crate} behaves.
15811 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15812 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15813 to set a breakpoint in a function named @samp{f} in a crate named
15816 As a consequence of this approach, linespecs also cannot refer to
15817 items using @samp{self::} or @samp{super::}.
15820 Because @value{GDBN} implements Rust name-lookup semantics in
15821 expressions, it will sometimes prepend the current crate to a name.
15822 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15823 @samp{K}, then @code{print ::x::y} will try to find the symbol
15826 However, since it is useful to be able to refer to other crates when
15827 debugging, @value{GDBN} provides the @code{extern} extension to
15828 circumvent this. To use the extension, just put @code{extern} before
15829 a path expression to refer to the otherwise unavailable ``global''
15832 In the above example, if you wanted to refer to the symbol @samp{y} in
15833 the crate @samp{x}, you would use @code{print extern x::y}.
15836 The Rust expression evaluator does not support ``statement-like''
15837 expressions such as @code{if} or @code{match}, or lambda expressions.
15840 Tuple expressions are not implemented.
15843 The Rust expression evaluator does not currently implement the
15844 @code{Drop} trait. Objects that may be created by the evaluator will
15845 never be destroyed.
15848 @value{GDBN} does not implement type inference for generics. In order
15849 to call generic functions or otherwise refer to generic items, you
15850 will have to specify the type parameters manually.
15853 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15854 cases this does not cause any problems. However, in an expression
15855 context, completing a generic function name will give syntactically
15856 invalid results. This happens because Rust requires the @samp{::}
15857 operator between the function name and its generic arguments. For
15858 example, @value{GDBN} might provide a completion like
15859 @code{crate::f<u32>}, where the parser would require
15860 @code{crate::f::<u32>}.
15863 As of this writing, the Rust compiler (version 1.8) has a few holes in
15864 the debugging information it generates. These holes prevent certain
15865 features from being implemented by @value{GDBN}:
15869 Method calls cannot be made via traits.
15872 Operator overloading is not implemented.
15875 When debugging in a monomorphized function, you cannot use the generic
15879 The type @code{Self} is not available.
15882 @code{use} statements are not available, so some names may not be
15883 available in the crate.
15888 @subsection Modula-2
15890 @cindex Modula-2, @value{GDBN} support
15892 The extensions made to @value{GDBN} to support Modula-2 only support
15893 output from the @sc{gnu} Modula-2 compiler (which is currently being
15894 developed). Other Modula-2 compilers are not currently supported, and
15895 attempting to debug executables produced by them is most likely
15896 to give an error as @value{GDBN} reads in the executable's symbol
15899 @cindex expressions in Modula-2
15901 * M2 Operators:: Built-in operators
15902 * Built-In Func/Proc:: Built-in functions and procedures
15903 * M2 Constants:: Modula-2 constants
15904 * M2 Types:: Modula-2 types
15905 * M2 Defaults:: Default settings for Modula-2
15906 * Deviations:: Deviations from standard Modula-2
15907 * M2 Checks:: Modula-2 type and range checks
15908 * M2 Scope:: The scope operators @code{::} and @code{.}
15909 * GDB/M2:: @value{GDBN} and Modula-2
15913 @subsubsection Operators
15914 @cindex Modula-2 operators
15916 Operators must be defined on values of specific types. For instance,
15917 @code{+} is defined on numbers, but not on structures. Operators are
15918 often defined on groups of types. For the purposes of Modula-2, the
15919 following definitions hold:
15924 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15928 @emph{Character types} consist of @code{CHAR} and its subranges.
15931 @emph{Floating-point types} consist of @code{REAL}.
15934 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15938 @emph{Scalar types} consist of all of the above.
15941 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15944 @emph{Boolean types} consist of @code{BOOLEAN}.
15948 The following operators are supported, and appear in order of
15949 increasing precedence:
15953 Function argument or array index separator.
15956 Assignment. The value of @var{var} @code{:=} @var{value} is
15960 Less than, greater than on integral, floating-point, or enumerated
15964 Less than or equal to, greater than or equal to
15965 on integral, floating-point and enumerated types, or set inclusion on
15966 set types. Same precedence as @code{<}.
15968 @item =@r{, }<>@r{, }#
15969 Equality and two ways of expressing inequality, valid on scalar types.
15970 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15971 available for inequality, since @code{#} conflicts with the script
15975 Set membership. Defined on set types and the types of their members.
15976 Same precedence as @code{<}.
15979 Boolean disjunction. Defined on boolean types.
15982 Boolean conjunction. Defined on boolean types.
15985 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15988 Addition and subtraction on integral and floating-point types, or union
15989 and difference on set types.
15992 Multiplication on integral and floating-point types, or set intersection
15996 Division on floating-point types, or symmetric set difference on set
15997 types. Same precedence as @code{*}.
16000 Integer division and remainder. Defined on integral types. Same
16001 precedence as @code{*}.
16004 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16007 Pointer dereferencing. Defined on pointer types.
16010 Boolean negation. Defined on boolean types. Same precedence as
16014 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16015 precedence as @code{^}.
16018 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16021 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16025 @value{GDBN} and Modula-2 scope operators.
16029 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16030 treats the use of the operator @code{IN}, or the use of operators
16031 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16032 @code{<=}, and @code{>=} on sets as an error.
16036 @node Built-In Func/Proc
16037 @subsubsection Built-in Functions and Procedures
16038 @cindex Modula-2 built-ins
16040 Modula-2 also makes available several built-in procedures and functions.
16041 In describing these, the following metavariables are used:
16046 represents an @code{ARRAY} variable.
16049 represents a @code{CHAR} constant or variable.
16052 represents a variable or constant of integral type.
16055 represents an identifier that belongs to a set. Generally used in the
16056 same function with the metavariable @var{s}. The type of @var{s} should
16057 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16060 represents a variable or constant of integral or floating-point type.
16063 represents a variable or constant of floating-point type.
16069 represents a variable.
16072 represents a variable or constant of one of many types. See the
16073 explanation of the function for details.
16076 All Modula-2 built-in procedures also return a result, described below.
16080 Returns the absolute value of @var{n}.
16083 If @var{c} is a lower case letter, it returns its upper case
16084 equivalent, otherwise it returns its argument.
16087 Returns the character whose ordinal value is @var{i}.
16090 Decrements the value in the variable @var{v} by one. Returns the new value.
16092 @item DEC(@var{v},@var{i})
16093 Decrements the value in the variable @var{v} by @var{i}. Returns the
16096 @item EXCL(@var{m},@var{s})
16097 Removes the element @var{m} from the set @var{s}. Returns the new
16100 @item FLOAT(@var{i})
16101 Returns the floating point equivalent of the integer @var{i}.
16103 @item HIGH(@var{a})
16104 Returns the index of the last member of @var{a}.
16107 Increments the value in the variable @var{v} by one. Returns the new value.
16109 @item INC(@var{v},@var{i})
16110 Increments the value in the variable @var{v} by @var{i}. Returns the
16113 @item INCL(@var{m},@var{s})
16114 Adds the element @var{m} to the set @var{s} if it is not already
16115 there. Returns the new set.
16118 Returns the maximum value of the type @var{t}.
16121 Returns the minimum value of the type @var{t}.
16124 Returns boolean TRUE if @var{i} is an odd number.
16127 Returns the ordinal value of its argument. For example, the ordinal
16128 value of a character is its @sc{ascii} value (on machines supporting
16129 the @sc{ascii} character set). The argument @var{x} must be of an
16130 ordered type, which include integral, character and enumerated types.
16132 @item SIZE(@var{x})
16133 Returns the size of its argument. The argument @var{x} can be a
16134 variable or a type.
16136 @item TRUNC(@var{r})
16137 Returns the integral part of @var{r}.
16139 @item TSIZE(@var{x})
16140 Returns the size of its argument. The argument @var{x} can be a
16141 variable or a type.
16143 @item VAL(@var{t},@var{i})
16144 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16148 @emph{Warning:} Sets and their operations are not yet supported, so
16149 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16153 @cindex Modula-2 constants
16155 @subsubsection Constants
16157 @value{GDBN} allows you to express the constants of Modula-2 in the following
16163 Integer constants are simply a sequence of digits. When used in an
16164 expression, a constant is interpreted to be type-compatible with the
16165 rest of the expression. Hexadecimal integers are specified by a
16166 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16169 Floating point constants appear as a sequence of digits, followed by a
16170 decimal point and another sequence of digits. An optional exponent can
16171 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16172 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16173 digits of the floating point constant must be valid decimal (base 10)
16177 Character constants consist of a single character enclosed by a pair of
16178 like quotes, either single (@code{'}) or double (@code{"}). They may
16179 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16180 followed by a @samp{C}.
16183 String constants consist of a sequence of characters enclosed by a
16184 pair of like quotes, either single (@code{'}) or double (@code{"}).
16185 Escape sequences in the style of C are also allowed. @xref{C
16186 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16190 Enumerated constants consist of an enumerated identifier.
16193 Boolean constants consist of the identifiers @code{TRUE} and
16197 Pointer constants consist of integral values only.
16200 Set constants are not yet supported.
16204 @subsubsection Modula-2 Types
16205 @cindex Modula-2 types
16207 Currently @value{GDBN} can print the following data types in Modula-2
16208 syntax: array types, record types, set types, pointer types, procedure
16209 types, enumerated types, subrange types and base types. You can also
16210 print the contents of variables declared using these type.
16211 This section gives a number of simple source code examples together with
16212 sample @value{GDBN} sessions.
16214 The first example contains the following section of code:
16223 and you can request @value{GDBN} to interrogate the type and value of
16224 @code{r} and @code{s}.
16227 (@value{GDBP}) print s
16229 (@value{GDBP}) ptype s
16231 (@value{GDBP}) print r
16233 (@value{GDBP}) ptype r
16238 Likewise if your source code declares @code{s} as:
16242 s: SET ['A'..'Z'] ;
16246 then you may query the type of @code{s} by:
16249 (@value{GDBP}) ptype s
16250 type = SET ['A'..'Z']
16254 Note that at present you cannot interactively manipulate set
16255 expressions using the debugger.
16257 The following example shows how you might declare an array in Modula-2
16258 and how you can interact with @value{GDBN} to print its type and contents:
16262 s: ARRAY [-10..10] OF CHAR ;
16266 (@value{GDBP}) ptype s
16267 ARRAY [-10..10] OF CHAR
16270 Note that the array handling is not yet complete and although the type
16271 is printed correctly, expression handling still assumes that all
16272 arrays have a lower bound of zero and not @code{-10} as in the example
16275 Here are some more type related Modula-2 examples:
16279 colour = (blue, red, yellow, green) ;
16280 t = [blue..yellow] ;
16288 The @value{GDBN} interaction shows how you can query the data type
16289 and value of a variable.
16292 (@value{GDBP}) print s
16294 (@value{GDBP}) ptype t
16295 type = [blue..yellow]
16299 In this example a Modula-2 array is declared and its contents
16300 displayed. Observe that the contents are written in the same way as
16301 their @code{C} counterparts.
16305 s: ARRAY [1..5] OF CARDINAL ;
16311 (@value{GDBP}) print s
16312 $1 = @{1, 0, 0, 0, 0@}
16313 (@value{GDBP}) ptype s
16314 type = ARRAY [1..5] OF CARDINAL
16317 The Modula-2 language interface to @value{GDBN} also understands
16318 pointer types as shown in this example:
16322 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16329 and you can request that @value{GDBN} describes the type of @code{s}.
16332 (@value{GDBP}) ptype s
16333 type = POINTER TO ARRAY [1..5] OF CARDINAL
16336 @value{GDBN} handles compound types as we can see in this example.
16337 Here we combine array types, record types, pointer types and subrange
16348 myarray = ARRAY myrange OF CARDINAL ;
16349 myrange = [-2..2] ;
16351 s: POINTER TO ARRAY myrange OF foo ;
16355 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16359 (@value{GDBP}) ptype s
16360 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16363 f3 : ARRAY [-2..2] OF CARDINAL;
16368 @subsubsection Modula-2 Defaults
16369 @cindex Modula-2 defaults
16371 If type and range checking are set automatically by @value{GDBN}, they
16372 both default to @code{on} whenever the working language changes to
16373 Modula-2. This happens regardless of whether you or @value{GDBN}
16374 selected the working language.
16376 If you allow @value{GDBN} to set the language automatically, then entering
16377 code compiled from a file whose name ends with @file{.mod} sets the
16378 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16379 Infer the Source Language}, for further details.
16382 @subsubsection Deviations from Standard Modula-2
16383 @cindex Modula-2, deviations from
16385 A few changes have been made to make Modula-2 programs easier to debug.
16386 This is done primarily via loosening its type strictness:
16390 Unlike in standard Modula-2, pointer constants can be formed by
16391 integers. This allows you to modify pointer variables during
16392 debugging. (In standard Modula-2, the actual address contained in a
16393 pointer variable is hidden from you; it can only be modified
16394 through direct assignment to another pointer variable or expression that
16395 returned a pointer.)
16398 C escape sequences can be used in strings and characters to represent
16399 non-printable characters. @value{GDBN} prints out strings with these
16400 escape sequences embedded. Single non-printable characters are
16401 printed using the @samp{CHR(@var{nnn})} format.
16404 The assignment operator (@code{:=}) returns the value of its right-hand
16408 All built-in procedures both modify @emph{and} return their argument.
16412 @subsubsection Modula-2 Type and Range Checks
16413 @cindex Modula-2 checks
16416 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16419 @c FIXME remove warning when type/range checks added
16421 @value{GDBN} considers two Modula-2 variables type equivalent if:
16425 They are of types that have been declared equivalent via a @code{TYPE
16426 @var{t1} = @var{t2}} statement
16429 They have been declared on the same line. (Note: This is true of the
16430 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16433 As long as type checking is enabled, any attempt to combine variables
16434 whose types are not equivalent is an error.
16436 Range checking is done on all mathematical operations, assignment, array
16437 index bounds, and all built-in functions and procedures.
16440 @subsubsection The Scope Operators @code{::} and @code{.}
16442 @cindex @code{.}, Modula-2 scope operator
16443 @cindex colon, doubled as scope operator
16445 @vindex colon-colon@r{, in Modula-2}
16446 @c Info cannot handle :: but TeX can.
16449 @vindex ::@r{, in Modula-2}
16452 There are a few subtle differences between the Modula-2 scope operator
16453 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16458 @var{module} . @var{id}
16459 @var{scope} :: @var{id}
16463 where @var{scope} is the name of a module or a procedure,
16464 @var{module} the name of a module, and @var{id} is any declared
16465 identifier within your program, except another module.
16467 Using the @code{::} operator makes @value{GDBN} search the scope
16468 specified by @var{scope} for the identifier @var{id}. If it is not
16469 found in the specified scope, then @value{GDBN} searches all scopes
16470 enclosing the one specified by @var{scope}.
16472 Using the @code{.} operator makes @value{GDBN} search the current scope for
16473 the identifier specified by @var{id} that was imported from the
16474 definition module specified by @var{module}. With this operator, it is
16475 an error if the identifier @var{id} was not imported from definition
16476 module @var{module}, or if @var{id} is not an identifier in
16480 @subsubsection @value{GDBN} and Modula-2
16482 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16483 Five subcommands of @code{set print} and @code{show print} apply
16484 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16485 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16486 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16487 analogue in Modula-2.
16489 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16490 with any language, is not useful with Modula-2. Its
16491 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16492 created in Modula-2 as they can in C or C@t{++}. However, because an
16493 address can be specified by an integral constant, the construct
16494 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16496 @cindex @code{#} in Modula-2
16497 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16498 interpreted as the beginning of a comment. Use @code{<>} instead.
16504 The extensions made to @value{GDBN} for Ada only support
16505 output from the @sc{gnu} Ada (GNAT) compiler.
16506 Other Ada compilers are not currently supported, and
16507 attempting to debug executables produced by them is most likely
16511 @cindex expressions in Ada
16513 * Ada Mode Intro:: General remarks on the Ada syntax
16514 and semantics supported by Ada mode
16516 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16517 * Additions to Ada:: Extensions of the Ada expression syntax.
16518 * Overloading support for Ada:: Support for expressions involving overloaded
16520 * Stopping Before Main Program:: Debugging the program during elaboration.
16521 * Ada Exceptions:: Ada Exceptions
16522 * Ada Tasks:: Listing and setting breakpoints in tasks.
16523 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16524 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16526 * Ada Settings:: New settable GDB parameters for Ada.
16527 * Ada Glitches:: Known peculiarities of Ada mode.
16530 @node Ada Mode Intro
16531 @subsubsection Introduction
16532 @cindex Ada mode, general
16534 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16535 syntax, with some extensions.
16536 The philosophy behind the design of this subset is
16540 That @value{GDBN} should provide basic literals and access to operations for
16541 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16542 leaving more sophisticated computations to subprograms written into the
16543 program (which therefore may be called from @value{GDBN}).
16546 That type safety and strict adherence to Ada language restrictions
16547 are not particularly important to the @value{GDBN} user.
16550 That brevity is important to the @value{GDBN} user.
16553 Thus, for brevity, the debugger acts as if all names declared in
16554 user-written packages are directly visible, even if they are not visible
16555 according to Ada rules, thus making it unnecessary to fully qualify most
16556 names with their packages, regardless of context. Where this causes
16557 ambiguity, @value{GDBN} asks the user's intent.
16559 The debugger will start in Ada mode if it detects an Ada main program.
16560 As for other languages, it will enter Ada mode when stopped in a program that
16561 was translated from an Ada source file.
16563 While in Ada mode, you may use `@t{--}' for comments. This is useful
16564 mostly for documenting command files. The standard @value{GDBN} comment
16565 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16566 middle (to allow based literals).
16568 @node Omissions from Ada
16569 @subsubsection Omissions from Ada
16570 @cindex Ada, omissions from
16572 Here are the notable omissions from the subset:
16576 Only a subset of the attributes are supported:
16580 @t{'First}, @t{'Last}, and @t{'Length}
16581 on array objects (not on types and subtypes).
16584 @t{'Min} and @t{'Max}.
16587 @t{'Pos} and @t{'Val}.
16593 @t{'Range} on array objects (not subtypes), but only as the right
16594 operand of the membership (@code{in}) operator.
16597 @t{'Access}, @t{'Unchecked_Access}, and
16598 @t{'Unrestricted_Access} (a GNAT extension).
16606 @code{Characters.Latin_1} are not available and
16607 concatenation is not implemented. Thus, escape characters in strings are
16608 not currently available.
16611 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16612 equality of representations. They will generally work correctly
16613 for strings and arrays whose elements have integer or enumeration types.
16614 They may not work correctly for arrays whose element
16615 types have user-defined equality, for arrays of real values
16616 (in particular, IEEE-conformant floating point, because of negative
16617 zeroes and NaNs), and for arrays whose elements contain unused bits with
16618 indeterminate values.
16621 The other component-by-component array operations (@code{and}, @code{or},
16622 @code{xor}, @code{not}, and relational tests other than equality)
16623 are not implemented.
16626 @cindex array aggregates (Ada)
16627 @cindex record aggregates (Ada)
16628 @cindex aggregates (Ada)
16629 There is limited support for array and record aggregates. They are
16630 permitted only on the right sides of assignments, as in these examples:
16633 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16634 (@value{GDBP}) set An_Array := (1, others => 0)
16635 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16636 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16637 (@value{GDBP}) set A_Record := (1, "Peter", True);
16638 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16642 discriminant's value by assigning an aggregate has an
16643 undefined effect if that discriminant is used within the record.
16644 However, you can first modify discriminants by directly assigning to
16645 them (which normally would not be allowed in Ada), and then performing an
16646 aggregate assignment. For example, given a variable @code{A_Rec}
16647 declared to have a type such as:
16650 type Rec (Len : Small_Integer := 0) is record
16652 Vals : IntArray (1 .. Len);
16656 you can assign a value with a different size of @code{Vals} with two
16660 (@value{GDBP}) set A_Rec.Len := 4
16661 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16664 As this example also illustrates, @value{GDBN} is very loose about the usual
16665 rules concerning aggregates. You may leave out some of the
16666 components of an array or record aggregate (such as the @code{Len}
16667 component in the assignment to @code{A_Rec} above); they will retain their
16668 original values upon assignment. You may freely use dynamic values as
16669 indices in component associations. You may even use overlapping or
16670 redundant component associations, although which component values are
16671 assigned in such cases is not defined.
16674 Calls to dispatching subprograms are not implemented.
16677 The overloading algorithm is much more limited (i.e., less selective)
16678 than that of real Ada. It makes only limited use of the context in
16679 which a subexpression appears to resolve its meaning, and it is much
16680 looser in its rules for allowing type matches. As a result, some
16681 function calls will be ambiguous, and the user will be asked to choose
16682 the proper resolution.
16685 The @code{new} operator is not implemented.
16688 Entry calls are not implemented.
16691 Aside from printing, arithmetic operations on the native VAX floating-point
16692 formats are not supported.
16695 It is not possible to slice a packed array.
16698 The names @code{True} and @code{False}, when not part of a qualified name,
16699 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16701 Should your program
16702 redefine these names in a package or procedure (at best a dubious practice),
16703 you will have to use fully qualified names to access their new definitions.
16706 @node Additions to Ada
16707 @subsubsection Additions to Ada
16708 @cindex Ada, deviations from
16710 As it does for other languages, @value{GDBN} makes certain generic
16711 extensions to Ada (@pxref{Expressions}):
16715 If the expression @var{E} is a variable residing in memory (typically
16716 a local variable or array element) and @var{N} is a positive integer,
16717 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16718 @var{N}-1 adjacent variables following it in memory as an array. In
16719 Ada, this operator is generally not necessary, since its prime use is
16720 in displaying parts of an array, and slicing will usually do this in
16721 Ada. However, there are occasional uses when debugging programs in
16722 which certain debugging information has been optimized away.
16725 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16726 appears in function or file @var{B}.'' When @var{B} is a file name,
16727 you must typically surround it in single quotes.
16730 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16731 @var{type} that appears at address @var{addr}.''
16734 A name starting with @samp{$} is a convenience variable
16735 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16738 In addition, @value{GDBN} provides a few other shortcuts and outright
16739 additions specific to Ada:
16743 The assignment statement is allowed as an expression, returning
16744 its right-hand operand as its value. Thus, you may enter
16747 (@value{GDBP}) set x := y + 3
16748 (@value{GDBP}) print A(tmp := y + 1)
16752 The semicolon is allowed as an ``operator,'' returning as its value
16753 the value of its right-hand operand.
16754 This allows, for example,
16755 complex conditional breaks:
16758 (@value{GDBP}) break f
16759 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16763 Rather than use catenation and symbolic character names to introduce special
16764 characters into strings, one may instead use a special bracket notation,
16765 which is also used to print strings. A sequence of characters of the form
16766 @samp{["@var{XX}"]} within a string or character literal denotes the
16767 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16768 sequence of characters @samp{["""]} also denotes a single quotation mark
16769 in strings. For example,
16771 "One line.["0a"]Next line.["0a"]"
16774 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16778 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16779 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16783 (@value{GDBP}) print 'max(x, y)
16787 When printing arrays, @value{GDBN} uses positional notation when the
16788 array has a lower bound of 1, and uses a modified named notation otherwise.
16789 For example, a one-dimensional array of three integers with a lower bound
16790 of 3 might print as
16797 That is, in contrast to valid Ada, only the first component has a @code{=>}
16801 You may abbreviate attributes in expressions with any unique,
16802 multi-character subsequence of
16803 their names (an exact match gets preference).
16804 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16805 in place of @t{a'length}.
16808 @cindex quoting Ada internal identifiers
16809 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16810 to lower case. The GNAT compiler uses upper-case characters for
16811 some of its internal identifiers, which are normally of no interest to users.
16812 For the rare occasions when you actually have to look at them,
16813 enclose them in angle brackets to avoid the lower-case mapping.
16816 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16820 Printing an object of class-wide type or dereferencing an
16821 access-to-class-wide value will display all the components of the object's
16822 specific type (as indicated by its run-time tag). Likewise, component
16823 selection on such a value will operate on the specific type of the
16828 @node Overloading support for Ada
16829 @subsubsection Overloading support for Ada
16830 @cindex overloading, Ada
16832 The debugger supports limited overloading. Given a subprogram call in which
16833 the function symbol has multiple definitions, it will use the number of
16834 actual parameters and some information about their types to attempt to narrow
16835 the set of definitions. It also makes very limited use of context, preferring
16836 procedures to functions in the context of the @code{call} command, and
16837 functions to procedures elsewhere.
16839 If, after narrowing, the set of matching definitions still contains more than
16840 one definition, @value{GDBN} will display a menu to query which one it should
16844 (@value{GDBP}) print f(1)
16845 Multiple matches for f
16847 [1] foo.f (integer) return boolean at foo.adb:23
16848 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16852 In this case, just select one menu entry either to cancel expression evaluation
16853 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16854 instance (type the corresponding number and press @key{RET}).
16856 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16861 @kindex set ada print-signatures
16862 @item set ada print-signatures
16863 Control whether parameter types and return types are displayed in overloads
16864 selection menus. It is @code{on} by default.
16865 @xref{Overloading support for Ada}.
16867 @kindex show ada print-signatures
16868 @item show ada print-signatures
16869 Show the current setting for displaying parameter types and return types in
16870 overloads selection menu.
16871 @xref{Overloading support for Ada}.
16875 @node Stopping Before Main Program
16876 @subsubsection Stopping at the Very Beginning
16878 @cindex breakpointing Ada elaboration code
16879 It is sometimes necessary to debug the program during elaboration, and
16880 before reaching the main procedure.
16881 As defined in the Ada Reference
16882 Manual, the elaboration code is invoked from a procedure called
16883 @code{adainit}. To run your program up to the beginning of
16884 elaboration, simply use the following two commands:
16885 @code{tbreak adainit} and @code{run}.
16887 @node Ada Exceptions
16888 @subsubsection Ada Exceptions
16890 A command is provided to list all Ada exceptions:
16893 @kindex info exceptions
16894 @item info exceptions
16895 @itemx info exceptions @var{regexp}
16896 The @code{info exceptions} command allows you to list all Ada exceptions
16897 defined within the program being debugged, as well as their addresses.
16898 With a regular expression, @var{regexp}, as argument, only those exceptions
16899 whose names match @var{regexp} are listed.
16902 Below is a small example, showing how the command can be used, first
16903 without argument, and next with a regular expression passed as an
16907 (@value{GDBP}) info exceptions
16908 All defined Ada exceptions:
16909 constraint_error: 0x613da0
16910 program_error: 0x613d20
16911 storage_error: 0x613ce0
16912 tasking_error: 0x613ca0
16913 const.aint_global_e: 0x613b00
16914 (@value{GDBP}) info exceptions const.aint
16915 All Ada exceptions matching regular expression "const.aint":
16916 constraint_error: 0x613da0
16917 const.aint_global_e: 0x613b00
16920 It is also possible to ask @value{GDBN} to stop your program's execution
16921 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16924 @subsubsection Extensions for Ada Tasks
16925 @cindex Ada, tasking
16927 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16928 @value{GDBN} provides the following task-related commands:
16933 This command shows a list of current Ada tasks, as in the following example:
16940 (@value{GDBP}) info tasks
16941 ID TID P-ID Pri State Name
16942 1 8088000 0 15 Child Activation Wait main_task
16943 2 80a4000 1 15 Accept Statement b
16944 3 809a800 1 15 Child Activation Wait a
16945 * 4 80ae800 3 15 Runnable c
16950 In this listing, the asterisk before the last task indicates it to be the
16951 task currently being inspected.
16955 Represents @value{GDBN}'s internal task number.
16961 The parent's task ID (@value{GDBN}'s internal task number).
16964 The base priority of the task.
16967 Current state of the task.
16971 The task has been created but has not been activated. It cannot be
16975 The task is not blocked for any reason known to Ada. (It may be waiting
16976 for a mutex, though.) It is conceptually "executing" in normal mode.
16979 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16980 that were waiting on terminate alternatives have been awakened and have
16981 terminated themselves.
16983 @item Child Activation Wait
16984 The task is waiting for created tasks to complete activation.
16986 @item Accept Statement
16987 The task is waiting on an accept or selective wait statement.
16989 @item Waiting on entry call
16990 The task is waiting on an entry call.
16992 @item Async Select Wait
16993 The task is waiting to start the abortable part of an asynchronous
16997 The task is waiting on a select statement with only a delay
17000 @item Child Termination Wait
17001 The task is sleeping having completed a master within itself, and is
17002 waiting for the tasks dependent on that master to become terminated or
17003 waiting on a terminate Phase.
17005 @item Wait Child in Term Alt
17006 The task is sleeping waiting for tasks on terminate alternatives to
17007 finish terminating.
17009 @item Accepting RV with @var{taskno}
17010 The task is accepting a rendez-vous with the task @var{taskno}.
17014 Name of the task in the program.
17018 @kindex info task @var{taskno}
17019 @item info task @var{taskno}
17020 This command shows detailled informations on the specified task, as in
17021 the following example:
17026 (@value{GDBP}) info tasks
17027 ID TID P-ID Pri State Name
17028 1 8077880 0 15 Child Activation Wait main_task
17029 * 2 807c468 1 15 Runnable task_1
17030 (@value{GDBP}) info task 2
17031 Ada Task: 0x807c468
17034 Parent: 1 (main_task)
17040 @kindex task@r{ (Ada)}
17041 @cindex current Ada task ID
17042 This command prints the ID of the current task.
17048 (@value{GDBP}) info tasks
17049 ID TID P-ID Pri State Name
17050 1 8077870 0 15 Child Activation Wait main_task
17051 * 2 807c458 1 15 Runnable t
17052 (@value{GDBP}) task
17053 [Current task is 2]
17056 @item task @var{taskno}
17057 @cindex Ada task switching
17058 This command is like the @code{thread @var{thread-id}}
17059 command (@pxref{Threads}). It switches the context of debugging
17060 from the current task to the given task.
17066 (@value{GDBP}) info tasks
17067 ID TID P-ID Pri State Name
17068 1 8077870 0 15 Child Activation Wait main_task
17069 * 2 807c458 1 15 Runnable t
17070 (@value{GDBP}) task 1
17071 [Switching to task 1]
17072 #0 0x8067726 in pthread_cond_wait ()
17074 #0 0x8067726 in pthread_cond_wait ()
17075 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17076 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17077 #3 0x806153e in system.tasking.stages.activate_tasks ()
17078 #4 0x804aacc in un () at un.adb:5
17081 @item break @var{location} task @var{taskno}
17082 @itemx break @var{location} task @var{taskno} if @dots{}
17083 @cindex breakpoints and tasks, in Ada
17084 @cindex task breakpoints, in Ada
17085 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17086 These commands are like the @code{break @dots{} thread @dots{}}
17087 command (@pxref{Thread Stops}). The
17088 @var{location} argument specifies source lines, as described
17089 in @ref{Specify Location}.
17091 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17092 to specify that you only want @value{GDBN} to stop the program when a
17093 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17094 numeric task identifiers assigned by @value{GDBN}, shown in the first
17095 column of the @samp{info tasks} display.
17097 If you do not specify @samp{task @var{taskno}} when you set a
17098 breakpoint, the breakpoint applies to @emph{all} tasks of your
17101 You can use the @code{task} qualifier on conditional breakpoints as
17102 well; in this case, place @samp{task @var{taskno}} before the
17103 breakpoint condition (before the @code{if}).
17111 (@value{GDBP}) info tasks
17112 ID TID P-ID Pri State Name
17113 1 140022020 0 15 Child Activation Wait main_task
17114 2 140045060 1 15 Accept/Select Wait t2
17115 3 140044840 1 15 Runnable t1
17116 * 4 140056040 1 15 Runnable t3
17117 (@value{GDBP}) b 15 task 2
17118 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17119 (@value{GDBP}) cont
17124 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17126 (@value{GDBP}) info tasks
17127 ID TID P-ID Pri State Name
17128 1 140022020 0 15 Child Activation Wait main_task
17129 * 2 140045060 1 15 Runnable t2
17130 3 140044840 1 15 Runnable t1
17131 4 140056040 1 15 Delay Sleep t3
17135 @node Ada Tasks and Core Files
17136 @subsubsection Tasking Support when Debugging Core Files
17137 @cindex Ada tasking and core file debugging
17139 When inspecting a core file, as opposed to debugging a live program,
17140 tasking support may be limited or even unavailable, depending on
17141 the platform being used.
17142 For instance, on x86-linux, the list of tasks is available, but task
17143 switching is not supported.
17145 On certain platforms, the debugger needs to perform some
17146 memory writes in order to provide Ada tasking support. When inspecting
17147 a core file, this means that the core file must be opened with read-write
17148 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17149 Under these circumstances, you should make a backup copy of the core
17150 file before inspecting it with @value{GDBN}.
17152 @node Ravenscar Profile
17153 @subsubsection Tasking Support when using the Ravenscar Profile
17154 @cindex Ravenscar Profile
17156 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17157 specifically designed for systems with safety-critical real-time
17161 @kindex set ravenscar task-switching on
17162 @cindex task switching with program using Ravenscar Profile
17163 @item set ravenscar task-switching on
17164 Allows task switching when debugging a program that uses the Ravenscar
17165 Profile. This is the default.
17167 @kindex set ravenscar task-switching off
17168 @item set ravenscar task-switching off
17169 Turn off task switching when debugging a program that uses the Ravenscar
17170 Profile. This is mostly intended to disable the code that adds support
17171 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17172 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17173 To be effective, this command should be run before the program is started.
17175 @kindex show ravenscar task-switching
17176 @item show ravenscar task-switching
17177 Show whether it is possible to switch from task to task in a program
17178 using the Ravenscar Profile.
17183 @subsubsection Ada Settings
17184 @cindex Ada settings
17187 @kindex set varsize-limit
17188 @item set varsize-limit @var{size}
17189 Prevent @value{GDBN} from attempting to evaluate objects whose size
17190 is above the given limit (@var{size}) when those sizes are computed
17191 from run-time quantities. This is typically the case when the object
17192 has a variable size, such as an array whose bounds are not known at
17193 compile time for example. Setting @var{size} to @code{unlimited}
17194 removes the size limitation. By default, the limit is about 65KB.
17196 The purpose of having such a limit is to prevent @value{GDBN} from
17197 trying to grab enormous chunks of virtual memory when asked to evaluate
17198 a quantity whose bounds have been corrupted or have not yet been fully
17199 initialized. The limit applies to the results of some subexpressions
17200 as well as to complete expressions. For example, an expression denoting
17201 a simple integer component, such as @code{x.y.z}, may fail if the size of
17202 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17203 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17204 @code{A} is an array variable with non-constant size, will generally
17205 succeed regardless of the bounds on @code{A}, as long as the component
17206 size is less than @var{size}.
17208 @kindex show varsize-limit
17209 @item show varsize-limit
17210 Show the limit on types whose size is determined by run-time quantities.
17214 @subsubsection Known Peculiarities of Ada Mode
17215 @cindex Ada, problems
17217 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17218 we know of several problems with and limitations of Ada mode in
17220 some of which will be fixed with planned future releases of the debugger
17221 and the GNU Ada compiler.
17225 Static constants that the compiler chooses not to materialize as objects in
17226 storage are invisible to the debugger.
17229 Named parameter associations in function argument lists are ignored (the
17230 argument lists are treated as positional).
17233 Many useful library packages are currently invisible to the debugger.
17236 Fixed-point arithmetic, conversions, input, and output is carried out using
17237 floating-point arithmetic, and may give results that only approximate those on
17241 The GNAT compiler never generates the prefix @code{Standard} for any of
17242 the standard symbols defined by the Ada language. @value{GDBN} knows about
17243 this: it will strip the prefix from names when you use it, and will never
17244 look for a name you have so qualified among local symbols, nor match against
17245 symbols in other packages or subprograms. If you have
17246 defined entities anywhere in your program other than parameters and
17247 local variables whose simple names match names in @code{Standard},
17248 GNAT's lack of qualification here can cause confusion. When this happens,
17249 you can usually resolve the confusion
17250 by qualifying the problematic names with package
17251 @code{Standard} explicitly.
17254 Older versions of the compiler sometimes generate erroneous debugging
17255 information, resulting in the debugger incorrectly printing the value
17256 of affected entities. In some cases, the debugger is able to work
17257 around an issue automatically. In other cases, the debugger is able
17258 to work around the issue, but the work-around has to be specifically
17261 @kindex set ada trust-PAD-over-XVS
17262 @kindex show ada trust-PAD-over-XVS
17265 @item set ada trust-PAD-over-XVS on
17266 Configure GDB to strictly follow the GNAT encoding when computing the
17267 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17268 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17269 a complete description of the encoding used by the GNAT compiler).
17270 This is the default.
17272 @item set ada trust-PAD-over-XVS off
17273 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17274 sometimes prints the wrong value for certain entities, changing @code{ada
17275 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17276 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17277 @code{off}, but this incurs a slight performance penalty, so it is
17278 recommended to leave this setting to @code{on} unless necessary.
17282 @cindex GNAT descriptive types
17283 @cindex GNAT encoding
17284 Internally, the debugger also relies on the compiler following a number
17285 of conventions known as the @samp{GNAT Encoding}, all documented in
17286 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17287 how the debugging information should be generated for certain types.
17288 In particular, this convention makes use of @dfn{descriptive types},
17289 which are artificial types generated purely to help the debugger.
17291 These encodings were defined at a time when the debugging information
17292 format used was not powerful enough to describe some of the more complex
17293 types available in Ada. Since DWARF allows us to express nearly all
17294 Ada features, the long-term goal is to slowly replace these descriptive
17295 types by their pure DWARF equivalent. To facilitate that transition,
17296 a new maintenance option is available to force the debugger to ignore
17297 those descriptive types. It allows the user to quickly evaluate how
17298 well @value{GDBN} works without them.
17302 @kindex maint ada set ignore-descriptive-types
17303 @item maintenance ada set ignore-descriptive-types [on|off]
17304 Control whether the debugger should ignore descriptive types.
17305 The default is not to ignore descriptives types (@code{off}).
17307 @kindex maint ada show ignore-descriptive-types
17308 @item maintenance ada show ignore-descriptive-types
17309 Show if descriptive types are ignored by @value{GDBN}.
17313 @node Unsupported Languages
17314 @section Unsupported Languages
17316 @cindex unsupported languages
17317 @cindex minimal language
17318 In addition to the other fully-supported programming languages,
17319 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17320 It does not represent a real programming language, but provides a set
17321 of capabilities close to what the C or assembly languages provide.
17322 This should allow most simple operations to be performed while debugging
17323 an application that uses a language currently not supported by @value{GDBN}.
17325 If the language is set to @code{auto}, @value{GDBN} will automatically
17326 select this language if the current frame corresponds to an unsupported
17330 @chapter Examining the Symbol Table
17332 The commands described in this chapter allow you to inquire about the
17333 symbols (names of variables, functions and types) defined in your
17334 program. This information is inherent in the text of your program and
17335 does not change as your program executes. @value{GDBN} finds it in your
17336 program's symbol table, in the file indicated when you started @value{GDBN}
17337 (@pxref{File Options, ,Choosing Files}), or by one of the
17338 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17340 @cindex symbol names
17341 @cindex names of symbols
17342 @cindex quoting names
17343 @anchor{quoting names}
17344 Occasionally, you may need to refer to symbols that contain unusual
17345 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17346 most frequent case is in referring to static variables in other
17347 source files (@pxref{Variables,,Program Variables}). File names
17348 are recorded in object files as debugging symbols, but @value{GDBN} would
17349 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17350 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17351 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17358 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17361 @cindex case-insensitive symbol names
17362 @cindex case sensitivity in symbol names
17363 @kindex set case-sensitive
17364 @item set case-sensitive on
17365 @itemx set case-sensitive off
17366 @itemx set case-sensitive auto
17367 Normally, when @value{GDBN} looks up symbols, it matches their names
17368 with case sensitivity determined by the current source language.
17369 Occasionally, you may wish to control that. The command @code{set
17370 case-sensitive} lets you do that by specifying @code{on} for
17371 case-sensitive matches or @code{off} for case-insensitive ones. If
17372 you specify @code{auto}, case sensitivity is reset to the default
17373 suitable for the source language. The default is case-sensitive
17374 matches for all languages except for Fortran, for which the default is
17375 case-insensitive matches.
17377 @kindex show case-sensitive
17378 @item show case-sensitive
17379 This command shows the current setting of case sensitivity for symbols
17382 @kindex set print type methods
17383 @item set print type methods
17384 @itemx set print type methods on
17385 @itemx set print type methods off
17386 Normally, when @value{GDBN} prints a class, it displays any methods
17387 declared in that class. You can control this behavior either by
17388 passing the appropriate flag to @code{ptype}, or using @command{set
17389 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17390 display the methods; this is the default. Specifying @code{off} will
17391 cause @value{GDBN} to omit the methods.
17393 @kindex show print type methods
17394 @item show print type methods
17395 This command shows the current setting of method display when printing
17398 @kindex set print type nested-type-limit
17399 @item set print type nested-type-limit @var{limit}
17400 @itemx set print type nested-type-limit unlimited
17401 Set the limit of displayed nested types that the type printer will
17402 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17403 nested definitions. By default, the type printer will not show any nested
17404 types defined in classes.
17406 @kindex show print type nested-type-limit
17407 @item show print type nested-type-limit
17408 This command shows the current display limit of nested types when
17411 @kindex set print type typedefs
17412 @item set print type typedefs
17413 @itemx set print type typedefs on
17414 @itemx set print type typedefs off
17416 Normally, when @value{GDBN} prints a class, it displays any typedefs
17417 defined in that class. You can control this behavior either by
17418 passing the appropriate flag to @code{ptype}, or using @command{set
17419 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17420 display the typedef definitions; this is the default. Specifying
17421 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17422 Note that this controls whether the typedef definition itself is
17423 printed, not whether typedef names are substituted when printing other
17426 @kindex show print type typedefs
17427 @item show print type typedefs
17428 This command shows the current setting of typedef display when
17431 @kindex info address
17432 @cindex address of a symbol
17433 @item info address @var{symbol}
17434 Describe where the data for @var{symbol} is stored. For a register
17435 variable, this says which register it is kept in. For a non-register
17436 local variable, this prints the stack-frame offset at which the variable
17439 Note the contrast with @samp{print &@var{symbol}}, which does not work
17440 at all for a register variable, and for a stack local variable prints
17441 the exact address of the current instantiation of the variable.
17443 @kindex info symbol
17444 @cindex symbol from address
17445 @cindex closest symbol and offset for an address
17446 @item info symbol @var{addr}
17447 Print the name of a symbol which is stored at the address @var{addr}.
17448 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17449 nearest symbol and an offset from it:
17452 (@value{GDBP}) info symbol 0x54320
17453 _initialize_vx + 396 in section .text
17457 This is the opposite of the @code{info address} command. You can use
17458 it to find out the name of a variable or a function given its address.
17460 For dynamically linked executables, the name of executable or shared
17461 library containing the symbol is also printed:
17464 (@value{GDBP}) info symbol 0x400225
17465 _start + 5 in section .text of /tmp/a.out
17466 (@value{GDBP}) info symbol 0x2aaaac2811cf
17467 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17472 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17473 Demangle @var{name}.
17474 If @var{language} is provided it is the name of the language to demangle
17475 @var{name} in. Otherwise @var{name} is demangled in the current language.
17477 The @samp{--} option specifies the end of options,
17478 and is useful when @var{name} begins with a dash.
17480 The parameter @code{demangle-style} specifies how to interpret the kind
17481 of mangling used. @xref{Print Settings}.
17484 @item whatis[/@var{flags}] [@var{arg}]
17485 Print the data type of @var{arg}, which can be either an expression
17486 or a name of a data type. With no argument, print the data type of
17487 @code{$}, the last value in the value history.
17489 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17490 is not actually evaluated, and any side-effecting operations (such as
17491 assignments or function calls) inside it do not take place.
17493 If @var{arg} is a variable or an expression, @code{whatis} prints its
17494 literal type as it is used in the source code. If the type was
17495 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17496 the data type underlying the @code{typedef}. If the type of the
17497 variable or the expression is a compound data type, such as
17498 @code{struct} or @code{class}, @code{whatis} never prints their
17499 fields or methods. It just prints the @code{struct}/@code{class}
17500 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17501 such a compound data type, use @code{ptype}.
17503 If @var{arg} is a type name that was defined using @code{typedef},
17504 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17505 Unrolling means that @code{whatis} will show the underlying type used
17506 in the @code{typedef} declaration of @var{arg}. However, if that
17507 underlying type is also a @code{typedef}, @code{whatis} will not
17510 For C code, the type names may also have the form @samp{class
17511 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17512 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17514 @var{flags} can be used to modify how the type is displayed.
17515 Available flags are:
17519 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17520 parameters and typedefs defined in a class when printing the class'
17521 members. The @code{/r} flag disables this.
17524 Do not print methods defined in the class.
17527 Print methods defined in the class. This is the default, but the flag
17528 exists in case you change the default with @command{set print type methods}.
17531 Do not print typedefs defined in the class. Note that this controls
17532 whether the typedef definition itself is printed, not whether typedef
17533 names are substituted when printing other types.
17536 Print typedefs defined in the class. This is the default, but the flag
17537 exists in case you change the default with @command{set print type typedefs}.
17540 Print the offsets and sizes of fields in a struct, similar to what the
17541 @command{pahole} tool does. This option implies the @code{/tm} flags.
17543 For example, given the following declarations:
17579 Issuing a @kbd{ptype /o struct tuv} command would print:
17582 (@value{GDBP}) ptype /o struct tuv
17583 /* offset | size */ type = struct tuv @{
17584 /* 0 | 4 */ int a1;
17585 /* XXX 4-byte hole */
17586 /* 8 | 8 */ char *a2;
17587 /* 16 | 4 */ int a3;
17589 /* total size (bytes): 24 */
17593 Notice the format of the first column of comments. There, you can
17594 find two parts separated by the @samp{|} character: the @emph{offset},
17595 which indicates where the field is located inside the struct, in
17596 bytes, and the @emph{size} of the field. Another interesting line is
17597 the marker of a @emph{hole} in the struct, indicating that it may be
17598 possible to pack the struct and make it use less space by reorganizing
17601 It is also possible to print offsets inside an union:
17604 (@value{GDBP}) ptype /o union qwe
17605 /* offset | size */ type = union qwe @{
17606 /* 24 */ struct tuv @{
17607 /* 0 | 4 */ int a1;
17608 /* XXX 4-byte hole */
17609 /* 8 | 8 */ char *a2;
17610 /* 16 | 4 */ int a3;
17612 /* total size (bytes): 24 */
17614 /* 40 */ struct xyz @{
17615 /* 0 | 4 */ int f1;
17616 /* 4 | 1 */ char f2;
17617 /* XXX 3-byte hole */
17618 /* 8 | 8 */ void *f3;
17619 /* 16 | 24 */ struct tuv @{
17620 /* 16 | 4 */ int a1;
17621 /* XXX 4-byte hole */
17622 /* 24 | 8 */ char *a2;
17623 /* 32 | 4 */ int a3;
17625 /* total size (bytes): 24 */
17628 /* total size (bytes): 40 */
17631 /* total size (bytes): 40 */
17635 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17636 same space (because we are dealing with an union), the offset is not
17637 printed for them. However, you can still examine the offset of each
17638 of these structures' fields.
17640 Another useful scenario is printing the offsets of a struct containing
17644 (@value{GDBP}) ptype /o struct tyu
17645 /* offset | size */ type = struct tyu @{
17646 /* 0:31 | 4 */ int a1 : 1;
17647 /* 0:28 | 4 */ int a2 : 3;
17648 /* 0: 5 | 4 */ int a3 : 23;
17649 /* 3: 3 | 1 */ signed char a4 : 2;
17650 /* XXX 3-bit hole */
17651 /* XXX 4-byte hole */
17652 /* 8 | 8 */ int64_t a5;
17653 /* 16:27 | 4 */ int a6 : 5;
17654 /* 16:56 | 8 */ int64_t a7 : 3;
17656 /* total size (bytes): 24 */
17660 Note how the offset information is now extended to also include how
17661 many bits are left to be used in each bitfield.
17665 @item ptype[/@var{flags}] [@var{arg}]
17666 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17667 detailed description of the type, instead of just the name of the type.
17668 @xref{Expressions, ,Expressions}.
17670 Contrary to @code{whatis}, @code{ptype} always unrolls any
17671 @code{typedef}s in its argument declaration, whether the argument is
17672 a variable, expression, or a data type. This means that @code{ptype}
17673 of a variable or an expression will not print literally its type as
17674 present in the source code---use @code{whatis} for that. @code{typedef}s at
17675 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17676 fields, methods and inner @code{class typedef}s of @code{struct}s,
17677 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17679 For example, for this variable declaration:
17682 typedef double real_t;
17683 struct complex @{ real_t real; double imag; @};
17684 typedef struct complex complex_t;
17686 real_t *real_pointer_var;
17690 the two commands give this output:
17694 (@value{GDBP}) whatis var
17696 (@value{GDBP}) ptype var
17697 type = struct complex @{
17701 (@value{GDBP}) whatis complex_t
17702 type = struct complex
17703 (@value{GDBP}) whatis struct complex
17704 type = struct complex
17705 (@value{GDBP}) ptype struct complex
17706 type = struct complex @{
17710 (@value{GDBP}) whatis real_pointer_var
17712 (@value{GDBP}) ptype real_pointer_var
17718 As with @code{whatis}, using @code{ptype} without an argument refers to
17719 the type of @code{$}, the last value in the value history.
17721 @cindex incomplete type
17722 Sometimes, programs use opaque data types or incomplete specifications
17723 of complex data structure. If the debug information included in the
17724 program does not allow @value{GDBN} to display a full declaration of
17725 the data type, it will say @samp{<incomplete type>}. For example,
17726 given these declarations:
17730 struct foo *fooptr;
17734 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17737 (@value{GDBP}) ptype foo
17738 $1 = <incomplete type>
17742 ``Incomplete type'' is C terminology for data types that are not
17743 completely specified.
17745 @cindex unknown type
17746 Othertimes, information about a variable's type is completely absent
17747 from the debug information included in the program. This most often
17748 happens when the program or library where the variable is defined
17749 includes no debug information at all. @value{GDBN} knows the variable
17750 exists from inspecting the linker/loader symbol table (e.g., the ELF
17751 dynamic symbol table), but such symbols do not contain type
17752 information. Inspecting the type of a (global) variable for which
17753 @value{GDBN} has no type information shows:
17756 (@value{GDBP}) ptype var
17757 type = <data variable, no debug info>
17760 @xref{Variables, no debug info variables}, for how to print the values
17764 @item info types @var{regexp}
17766 Print a brief description of all types whose names match the regular
17767 expression @var{regexp} (or all types in your program, if you supply
17768 no argument). Each complete typename is matched as though it were a
17769 complete line; thus, @samp{i type value} gives information on all
17770 types in your program whose names include the string @code{value}, but
17771 @samp{i type ^value$} gives information only on types whose complete
17772 name is @code{value}.
17774 This command differs from @code{ptype} in two ways: first, like
17775 @code{whatis}, it does not print a detailed description; second, it
17776 lists all source files and line numbers where a type is defined.
17778 @kindex info type-printers
17779 @item info type-printers
17780 Versions of @value{GDBN} that ship with Python scripting enabled may
17781 have ``type printers'' available. When using @command{ptype} or
17782 @command{whatis}, these printers are consulted when the name of a type
17783 is needed. @xref{Type Printing API}, for more information on writing
17786 @code{info type-printers} displays all the available type printers.
17788 @kindex enable type-printer
17789 @kindex disable type-printer
17790 @item enable type-printer @var{name}@dots{}
17791 @item disable type-printer @var{name}@dots{}
17792 These commands can be used to enable or disable type printers.
17795 @cindex local variables
17796 @item info scope @var{location}
17797 List all the variables local to a particular scope. This command
17798 accepts a @var{location} argument---a function name, a source line, or
17799 an address preceded by a @samp{*}, and prints all the variables local
17800 to the scope defined by that location. (@xref{Specify Location}, for
17801 details about supported forms of @var{location}.) For example:
17804 (@value{GDBP}) @b{info scope command_line_handler}
17805 Scope for command_line_handler:
17806 Symbol rl is an argument at stack/frame offset 8, length 4.
17807 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17808 Symbol linelength is in static storage at address 0x150a1c, length 4.
17809 Symbol p is a local variable in register $esi, length 4.
17810 Symbol p1 is a local variable in register $ebx, length 4.
17811 Symbol nline is a local variable in register $edx, length 4.
17812 Symbol repeat is a local variable at frame offset -8, length 4.
17816 This command is especially useful for determining what data to collect
17817 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17820 @kindex info source
17822 Show information about the current source file---that is, the source file for
17823 the function containing the current point of execution:
17826 the name of the source file, and the directory containing it,
17828 the directory it was compiled in,
17830 its length, in lines,
17832 which programming language it is written in,
17834 if the debug information provides it, the program that compiled the file
17835 (which may include, e.g., the compiler version and command line arguments),
17837 whether the executable includes debugging information for that file, and
17838 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17840 whether the debugging information includes information about
17841 preprocessor macros.
17845 @kindex info sources
17847 Print the names of all source files in your program for which there is
17848 debugging information, organized into two lists: files whose symbols
17849 have already been read, and files whose symbols will be read when needed.
17851 @kindex info functions
17852 @item info functions
17853 Print the names and data types of all defined functions.
17854 Similarly to @samp{info types}, this command groups its output by source
17855 files and annotates each function definition with its source line
17858 @item info functions @var{regexp}
17859 Like @samp{info functions}, but only print the names and data types of
17860 functions whose names contain a match for regular expression
17861 @var{regexp}. Thus, @samp{info fun step} finds all functions whose
17862 names include @code{step}; @samp{info fun ^step} finds those whose names
17863 start with @code{step}. If a function name contains characters that
17864 conflict with the regular expression language (e.g.@:
17865 @samp{operator*()}), they may be quoted with a backslash.
17867 @kindex info variables
17868 @item info variables
17869 Print the names and data types of all variables that are defined
17870 outside of functions (i.e.@: excluding local variables).
17871 The printed variables are grouped by source files and annotated with
17872 their respective source line numbers.
17874 @item info variables @var{regexp}
17875 Like @kbd{info variables}, but only print the names and data types of
17876 non-local variables whose names contain a match for regular expression
17879 @kindex info classes
17880 @cindex Objective-C, classes and selectors
17882 @itemx info classes @var{regexp}
17883 Display all Objective-C classes in your program, or
17884 (with the @var{regexp} argument) all those matching a particular regular
17887 @kindex info selectors
17888 @item info selectors
17889 @itemx info selectors @var{regexp}
17890 Display all Objective-C selectors in your program, or
17891 (with the @var{regexp} argument) all those matching a particular regular
17895 This was never implemented.
17896 @kindex info methods
17898 @itemx info methods @var{regexp}
17899 The @code{info methods} command permits the user to examine all defined
17900 methods within C@t{++} program, or (with the @var{regexp} argument) a
17901 specific set of methods found in the various C@t{++} classes. Many
17902 C@t{++} classes provide a large number of methods. Thus, the output
17903 from the @code{ptype} command can be overwhelming and hard to use. The
17904 @code{info-methods} command filters the methods, printing only those
17905 which match the regular-expression @var{regexp}.
17908 @cindex opaque data types
17909 @kindex set opaque-type-resolution
17910 @item set opaque-type-resolution on
17911 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17912 declared as a pointer to a @code{struct}, @code{class}, or
17913 @code{union}---for example, @code{struct MyType *}---that is used in one
17914 source file although the full declaration of @code{struct MyType} is in
17915 another source file. The default is on.
17917 A change in the setting of this subcommand will not take effect until
17918 the next time symbols for a file are loaded.
17920 @item set opaque-type-resolution off
17921 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17922 is printed as follows:
17924 @{<no data fields>@}
17927 @kindex show opaque-type-resolution
17928 @item show opaque-type-resolution
17929 Show whether opaque types are resolved or not.
17931 @kindex set print symbol-loading
17932 @cindex print messages when symbols are loaded
17933 @item set print symbol-loading
17934 @itemx set print symbol-loading full
17935 @itemx set print symbol-loading brief
17936 @itemx set print symbol-loading off
17937 The @code{set print symbol-loading} command allows you to control the
17938 printing of messages when @value{GDBN} loads symbol information.
17939 By default a message is printed for the executable and one for each
17940 shared library, and normally this is what you want. However, when
17941 debugging apps with large numbers of shared libraries these messages
17943 When set to @code{brief} a message is printed for each executable,
17944 and when @value{GDBN} loads a collection of shared libraries at once
17945 it will only print one message regardless of the number of shared
17946 libraries. When set to @code{off} no messages are printed.
17948 @kindex show print symbol-loading
17949 @item show print symbol-loading
17950 Show whether messages will be printed when a @value{GDBN} command
17951 entered from the keyboard causes symbol information to be loaded.
17953 @kindex maint print symbols
17954 @cindex symbol dump
17955 @kindex maint print psymbols
17956 @cindex partial symbol dump
17957 @kindex maint print msymbols
17958 @cindex minimal symbol dump
17959 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17960 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17961 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17962 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17963 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17964 Write a dump of debugging symbol data into the file @var{filename} or
17965 the terminal if @var{filename} is unspecified.
17966 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17968 If @code{-pc @var{address}} is specified, only dump symbols for the file
17969 with code at that address. Note that @var{address} may be a symbol like
17971 If @code{-source @var{source}} is specified, only dump symbols for that
17974 These commands are used to debug the @value{GDBN} symbol-reading code.
17975 These commands do not modify internal @value{GDBN} state, therefore
17976 @samp{maint print symbols} will only print symbols for already expanded symbol
17978 You can use the command @code{info sources} to find out which files these are.
17979 If you use @samp{maint print psymbols} instead, the dump shows information
17980 about symbols that @value{GDBN} only knows partially---that is, symbols
17981 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17982 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17985 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17986 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17988 @kindex maint info symtabs
17989 @kindex maint info psymtabs
17990 @cindex listing @value{GDBN}'s internal symbol tables
17991 @cindex symbol tables, listing @value{GDBN}'s internal
17992 @cindex full symbol tables, listing @value{GDBN}'s internal
17993 @cindex partial symbol tables, listing @value{GDBN}'s internal
17994 @item maint info symtabs @r{[} @var{regexp} @r{]}
17995 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17997 List the @code{struct symtab} or @code{struct partial_symtab}
17998 structures whose names match @var{regexp}. If @var{regexp} is not
17999 given, list them all. The output includes expressions which you can
18000 copy into a @value{GDBN} debugging this one to examine a particular
18001 structure in more detail. For example:
18004 (@value{GDBP}) maint info psymtabs dwarf2read
18005 @{ objfile /home/gnu/build/gdb/gdb
18006 ((struct objfile *) 0x82e69d0)
18007 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18008 ((struct partial_symtab *) 0x8474b10)
18011 text addresses 0x814d3c8 -- 0x8158074
18012 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18013 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18014 dependencies (none)
18017 (@value{GDBP}) maint info symtabs
18021 We see that there is one partial symbol table whose filename contains
18022 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18023 and we see that @value{GDBN} has not read in any symtabs yet at all.
18024 If we set a breakpoint on a function, that will cause @value{GDBN} to
18025 read the symtab for the compilation unit containing that function:
18028 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18029 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18031 (@value{GDBP}) maint info symtabs
18032 @{ objfile /home/gnu/build/gdb/gdb
18033 ((struct objfile *) 0x82e69d0)
18034 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18035 ((struct symtab *) 0x86c1f38)
18038 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18039 linetable ((struct linetable *) 0x8370fa0)
18040 debugformat DWARF 2
18046 @kindex maint info line-table
18047 @cindex listing @value{GDBN}'s internal line tables
18048 @cindex line tables, listing @value{GDBN}'s internal
18049 @item maint info line-table @r{[} @var{regexp} @r{]}
18051 List the @code{struct linetable} from all @code{struct symtab}
18052 instances whose name matches @var{regexp}. If @var{regexp} is not
18053 given, list the @code{struct linetable} from all @code{struct symtab}.
18055 @kindex maint set symbol-cache-size
18056 @cindex symbol cache size
18057 @item maint set symbol-cache-size @var{size}
18058 Set the size of the symbol cache to @var{size}.
18059 The default size is intended to be good enough for debugging
18060 most applications. This option exists to allow for experimenting
18061 with different sizes.
18063 @kindex maint show symbol-cache-size
18064 @item maint show symbol-cache-size
18065 Show the size of the symbol cache.
18067 @kindex maint print symbol-cache
18068 @cindex symbol cache, printing its contents
18069 @item maint print symbol-cache
18070 Print the contents of the symbol cache.
18071 This is useful when debugging symbol cache issues.
18073 @kindex maint print symbol-cache-statistics
18074 @cindex symbol cache, printing usage statistics
18075 @item maint print symbol-cache-statistics
18076 Print symbol cache usage statistics.
18077 This helps determine how well the cache is being utilized.
18079 @kindex maint flush-symbol-cache
18080 @cindex symbol cache, flushing
18081 @item maint flush-symbol-cache
18082 Flush the contents of the symbol cache, all entries are removed.
18083 This command is useful when debugging the symbol cache.
18084 It is also useful when collecting performance data.
18089 @chapter Altering Execution
18091 Once you think you have found an error in your program, you might want to
18092 find out for certain whether correcting the apparent error would lead to
18093 correct results in the rest of the run. You can find the answer by
18094 experiment, using the @value{GDBN} features for altering execution of the
18097 For example, you can store new values into variables or memory
18098 locations, give your program a signal, restart it at a different
18099 address, or even return prematurely from a function.
18102 * Assignment:: Assignment to variables
18103 * Jumping:: Continuing at a different address
18104 * Signaling:: Giving your program a signal
18105 * Returning:: Returning from a function
18106 * Calling:: Calling your program's functions
18107 * Patching:: Patching your program
18108 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18112 @section Assignment to Variables
18115 @cindex setting variables
18116 To alter the value of a variable, evaluate an assignment expression.
18117 @xref{Expressions, ,Expressions}. For example,
18124 stores the value 4 into the variable @code{x}, and then prints the
18125 value of the assignment expression (which is 4).
18126 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18127 information on operators in supported languages.
18129 @kindex set variable
18130 @cindex variables, setting
18131 If you are not interested in seeing the value of the assignment, use the
18132 @code{set} command instead of the @code{print} command. @code{set} is
18133 really the same as @code{print} except that the expression's value is
18134 not printed and is not put in the value history (@pxref{Value History,
18135 ,Value History}). The expression is evaluated only for its effects.
18137 If the beginning of the argument string of the @code{set} command
18138 appears identical to a @code{set} subcommand, use the @code{set
18139 variable} command instead of just @code{set}. This command is identical
18140 to @code{set} except for its lack of subcommands. For example, if your
18141 program has a variable @code{width}, you get an error if you try to set
18142 a new value with just @samp{set width=13}, because @value{GDBN} has the
18143 command @code{set width}:
18146 (@value{GDBP}) whatis width
18148 (@value{GDBP}) p width
18150 (@value{GDBP}) set width=47
18151 Invalid syntax in expression.
18155 The invalid expression, of course, is @samp{=47}. In
18156 order to actually set the program's variable @code{width}, use
18159 (@value{GDBP}) set var width=47
18162 Because the @code{set} command has many subcommands that can conflict
18163 with the names of program variables, it is a good idea to use the
18164 @code{set variable} command instead of just @code{set}. For example, if
18165 your program has a variable @code{g}, you run into problems if you try
18166 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18167 the command @code{set gnutarget}, abbreviated @code{set g}:
18171 (@value{GDBP}) whatis g
18175 (@value{GDBP}) set g=4
18179 The program being debugged has been started already.
18180 Start it from the beginning? (y or n) y
18181 Starting program: /home/smith/cc_progs/a.out
18182 "/home/smith/cc_progs/a.out": can't open to read symbols:
18183 Invalid bfd target.
18184 (@value{GDBP}) show g
18185 The current BFD target is "=4".
18190 The program variable @code{g} did not change, and you silently set the
18191 @code{gnutarget} to an invalid value. In order to set the variable
18195 (@value{GDBP}) set var g=4
18198 @value{GDBN} allows more implicit conversions in assignments than C; you can
18199 freely store an integer value into a pointer variable or vice versa,
18200 and you can convert any structure to any other structure that is the
18201 same length or shorter.
18202 @comment FIXME: how do structs align/pad in these conversions?
18203 @comment /doc@cygnus.com 18dec1990
18205 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18206 construct to generate a value of specified type at a specified address
18207 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18208 to memory location @code{0x83040} as an integer (which implies a certain size
18209 and representation in memory), and
18212 set @{int@}0x83040 = 4
18216 stores the value 4 into that memory location.
18219 @section Continuing at a Different Address
18221 Ordinarily, when you continue your program, you do so at the place where
18222 it stopped, with the @code{continue} command. You can instead continue at
18223 an address of your own choosing, with the following commands:
18227 @kindex j @r{(@code{jump})}
18228 @item jump @var{location}
18229 @itemx j @var{location}
18230 Resume execution at @var{location}. Execution stops again immediately
18231 if there is a breakpoint there. @xref{Specify Location}, for a description
18232 of the different forms of @var{location}. It is common
18233 practice to use the @code{tbreak} command in conjunction with
18234 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18236 The @code{jump} command does not change the current stack frame, or
18237 the stack pointer, or the contents of any memory location or any
18238 register other than the program counter. If @var{location} is in
18239 a different function from the one currently executing, the results may
18240 be bizarre if the two functions expect different patterns of arguments or
18241 of local variables. For this reason, the @code{jump} command requests
18242 confirmation if the specified line is not in the function currently
18243 executing. However, even bizarre results are predictable if you are
18244 well acquainted with the machine-language code of your program.
18247 On many systems, you can get much the same effect as the @code{jump}
18248 command by storing a new value into the register @code{$pc}. The
18249 difference is that this does not start your program running; it only
18250 changes the address of where it @emph{will} run when you continue. For
18258 makes the next @code{continue} command or stepping command execute at
18259 address @code{0x485}, rather than at the address where your program stopped.
18260 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18262 The most common occasion to use the @code{jump} command is to back
18263 up---perhaps with more breakpoints set---over a portion of a program
18264 that has already executed, in order to examine its execution in more
18269 @section Giving your Program a Signal
18270 @cindex deliver a signal to a program
18274 @item signal @var{signal}
18275 Resume execution where your program is stopped, but immediately give it the
18276 signal @var{signal}. The @var{signal} can be the name or the number of a
18277 signal. For example, on many systems @code{signal 2} and @code{signal
18278 SIGINT} are both ways of sending an interrupt signal.
18280 Alternatively, if @var{signal} is zero, continue execution without
18281 giving a signal. This is useful when your program stopped on account of
18282 a signal and would ordinarily see the signal when resumed with the
18283 @code{continue} command; @samp{signal 0} causes it to resume without a
18286 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18287 delivered to the currently selected thread, not the thread that last
18288 reported a stop. This includes the situation where a thread was
18289 stopped due to a signal. So if you want to continue execution
18290 suppressing the signal that stopped a thread, you should select that
18291 same thread before issuing the @samp{signal 0} command. If you issue
18292 the @samp{signal 0} command with another thread as the selected one,
18293 @value{GDBN} detects that and asks for confirmation.
18295 Invoking the @code{signal} command is not the same as invoking the
18296 @code{kill} utility from the shell. Sending a signal with @code{kill}
18297 causes @value{GDBN} to decide what to do with the signal depending on
18298 the signal handling tables (@pxref{Signals}). The @code{signal} command
18299 passes the signal directly to your program.
18301 @code{signal} does not repeat when you press @key{RET} a second time
18302 after executing the command.
18304 @kindex queue-signal
18305 @item queue-signal @var{signal}
18306 Queue @var{signal} to be delivered immediately to the current thread
18307 when execution of the thread resumes. The @var{signal} can be the name or
18308 the number of a signal. For example, on many systems @code{signal 2} and
18309 @code{signal SIGINT} are both ways of sending an interrupt signal.
18310 The handling of the signal must be set to pass the signal to the program,
18311 otherwise @value{GDBN} will report an error.
18312 You can control the handling of signals from @value{GDBN} with the
18313 @code{handle} command (@pxref{Signals}).
18315 Alternatively, if @var{signal} is zero, any currently queued signal
18316 for the current thread is discarded and when execution resumes no signal
18317 will be delivered. This is useful when your program stopped on account
18318 of a signal and would ordinarily see the signal when resumed with the
18319 @code{continue} command.
18321 This command differs from the @code{signal} command in that the signal
18322 is just queued, execution is not resumed. And @code{queue-signal} cannot
18323 be used to pass a signal whose handling state has been set to @code{nopass}
18328 @xref{stepping into signal handlers}, for information on how stepping
18329 commands behave when the thread has a signal queued.
18332 @section Returning from a Function
18335 @cindex returning from a function
18338 @itemx return @var{expression}
18339 You can cancel execution of a function call with the @code{return}
18340 command. If you give an
18341 @var{expression} argument, its value is used as the function's return
18345 When you use @code{return}, @value{GDBN} discards the selected stack frame
18346 (and all frames within it). You can think of this as making the
18347 discarded frame return prematurely. If you wish to specify a value to
18348 be returned, give that value as the argument to @code{return}.
18350 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18351 Frame}), and any other frames inside of it, leaving its caller as the
18352 innermost remaining frame. That frame becomes selected. The
18353 specified value is stored in the registers used for returning values
18356 The @code{return} command does not resume execution; it leaves the
18357 program stopped in the state that would exist if the function had just
18358 returned. In contrast, the @code{finish} command (@pxref{Continuing
18359 and Stepping, ,Continuing and Stepping}) resumes execution until the
18360 selected stack frame returns naturally.
18362 @value{GDBN} needs to know how the @var{expression} argument should be set for
18363 the inferior. The concrete registers assignment depends on the OS ABI and the
18364 type being returned by the selected stack frame. For example it is common for
18365 OS ABI to return floating point values in FPU registers while integer values in
18366 CPU registers. Still some ABIs return even floating point values in CPU
18367 registers. Larger integer widths (such as @code{long long int}) also have
18368 specific placement rules. @value{GDBN} already knows the OS ABI from its
18369 current target so it needs to find out also the type being returned to make the
18370 assignment into the right register(s).
18372 Normally, the selected stack frame has debug info. @value{GDBN} will always
18373 use the debug info instead of the implicit type of @var{expression} when the
18374 debug info is available. For example, if you type @kbd{return -1}, and the
18375 function in the current stack frame is declared to return a @code{long long
18376 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18377 into a @code{long long int}:
18380 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18382 (@value{GDBP}) return -1
18383 Make func return now? (y or n) y
18384 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18385 43 printf ("result=%lld\n", func ());
18389 However, if the selected stack frame does not have a debug info, e.g., if the
18390 function was compiled without debug info, @value{GDBN} has to find out the type
18391 to return from user. Specifying a different type by mistake may set the value
18392 in different inferior registers than the caller code expects. For example,
18393 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18394 of a @code{long long int} result for a debug info less function (on 32-bit
18395 architectures). Therefore the user is required to specify the return type by
18396 an appropriate cast explicitly:
18399 Breakpoint 2, 0x0040050b in func ()
18400 (@value{GDBP}) return -1
18401 Return value type not available for selected stack frame.
18402 Please use an explicit cast of the value to return.
18403 (@value{GDBP}) return (long long int) -1
18404 Make selected stack frame return now? (y or n) y
18405 #0 0x00400526 in main ()
18410 @section Calling Program Functions
18413 @cindex calling functions
18414 @cindex inferior functions, calling
18415 @item print @var{expr}
18416 Evaluate the expression @var{expr} and display the resulting value.
18417 The expression may include calls to functions in the program being
18421 @item call @var{expr}
18422 Evaluate the expression @var{expr} without displaying @code{void}
18425 You can use this variant of the @code{print} command if you want to
18426 execute a function from your program that does not return anything
18427 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18428 with @code{void} returned values that @value{GDBN} will otherwise
18429 print. If the result is not void, it is printed and saved in the
18433 It is possible for the function you call via the @code{print} or
18434 @code{call} command to generate a signal (e.g., if there's a bug in
18435 the function, or if you passed it incorrect arguments). What happens
18436 in that case is controlled by the @code{set unwindonsignal} command.
18438 Similarly, with a C@t{++} program it is possible for the function you
18439 call via the @code{print} or @code{call} command to generate an
18440 exception that is not handled due to the constraints of the dummy
18441 frame. In this case, any exception that is raised in the frame, but has
18442 an out-of-frame exception handler will not be found. GDB builds a
18443 dummy-frame for the inferior function call, and the unwinder cannot
18444 seek for exception handlers outside of this dummy-frame. What happens
18445 in that case is controlled by the
18446 @code{set unwind-on-terminating-exception} command.
18449 @item set unwindonsignal
18450 @kindex set unwindonsignal
18451 @cindex unwind stack in called functions
18452 @cindex call dummy stack unwinding
18453 Set unwinding of the stack if a signal is received while in a function
18454 that @value{GDBN} called in the program being debugged. If set to on,
18455 @value{GDBN} unwinds the stack it created for the call and restores
18456 the context to what it was before the call. If set to off (the
18457 default), @value{GDBN} stops in the frame where the signal was
18460 @item show unwindonsignal
18461 @kindex show unwindonsignal
18462 Show the current setting of stack unwinding in the functions called by
18465 @item set unwind-on-terminating-exception
18466 @kindex set unwind-on-terminating-exception
18467 @cindex unwind stack in called functions with unhandled exceptions
18468 @cindex call dummy stack unwinding on unhandled exception.
18469 Set unwinding of the stack if a C@t{++} exception is raised, but left
18470 unhandled while in a function that @value{GDBN} called in the program being
18471 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18472 it created for the call and restores the context to what it was before
18473 the call. If set to off, @value{GDBN} the exception is delivered to
18474 the default C@t{++} exception handler and the inferior terminated.
18476 @item show unwind-on-terminating-exception
18477 @kindex show unwind-on-terminating-exception
18478 Show the current setting of stack unwinding in the functions called by
18483 @subsection Calling functions with no debug info
18485 @cindex no debug info functions
18486 Sometimes, a function you wish to call is missing debug information.
18487 In such case, @value{GDBN} does not know the type of the function,
18488 including the types of the function's parameters. To avoid calling
18489 the inferior function incorrectly, which could result in the called
18490 function functioning erroneously and even crash, @value{GDBN} refuses
18491 to call the function unless you tell it the type of the function.
18493 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18494 to do that. The simplest is to cast the call to the function's
18495 declared return type. For example:
18498 (@value{GDBP}) p getenv ("PATH")
18499 'getenv' has unknown return type; cast the call to its declared return type
18500 (@value{GDBP}) p (char *) getenv ("PATH")
18501 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18504 Casting the return type of a no-debug function is equivalent to
18505 casting the function to a pointer to a prototyped function that has a
18506 prototype that matches the types of the passed-in arguments, and
18507 calling that. I.e., the call above is equivalent to:
18510 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18514 and given this prototyped C or C++ function with float parameters:
18517 float multiply (float v1, float v2) @{ return v1 * v2; @}
18521 these calls are equivalent:
18524 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18525 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18528 If the function you wish to call is declared as unprototyped (i.e.@:
18529 old K&R style), you must use the cast-to-function-pointer syntax, so
18530 that @value{GDBN} knows that it needs to apply default argument
18531 promotions (promote float arguments to double). @xref{ABI, float
18532 promotion}. For example, given this unprototyped C function with
18533 float parameters, and no debug info:
18537 multiply_noproto (v1, v2)
18545 you call it like this:
18548 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18552 @section Patching Programs
18554 @cindex patching binaries
18555 @cindex writing into executables
18556 @cindex writing into corefiles
18558 By default, @value{GDBN} opens the file containing your program's
18559 executable code (or the corefile) read-only. This prevents accidental
18560 alterations to machine code; but it also prevents you from intentionally
18561 patching your program's binary.
18563 If you'd like to be able to patch the binary, you can specify that
18564 explicitly with the @code{set write} command. For example, you might
18565 want to turn on internal debugging flags, or even to make emergency
18571 @itemx set write off
18572 If you specify @samp{set write on}, @value{GDBN} opens executable and
18573 core files for both reading and writing; if you specify @kbd{set write
18574 off} (the default), @value{GDBN} opens them read-only.
18576 If you have already loaded a file, you must load it again (using the
18577 @code{exec-file} or @code{core-file} command) after changing @code{set
18578 write}, for your new setting to take effect.
18582 Display whether executable files and core files are opened for writing
18583 as well as reading.
18586 @node Compiling and Injecting Code
18587 @section Compiling and injecting code in @value{GDBN}
18588 @cindex injecting code
18589 @cindex writing into executables
18590 @cindex compiling code
18592 @value{GDBN} supports on-demand compilation and code injection into
18593 programs running under @value{GDBN}. GCC 5.0 or higher built with
18594 @file{libcc1.so} must be installed for this functionality to be enabled.
18595 This functionality is implemented with the following commands.
18598 @kindex compile code
18599 @item compile code @var{source-code}
18600 @itemx compile code -raw @var{--} @var{source-code}
18601 Compile @var{source-code} with the compiler language found as the current
18602 language in @value{GDBN} (@pxref{Languages}). If compilation and
18603 injection is not supported with the current language specified in
18604 @value{GDBN}, or the compiler does not support this feature, an error
18605 message will be printed. If @var{source-code} compiles and links
18606 successfully, @value{GDBN} will load the object-code emitted,
18607 and execute it within the context of the currently selected inferior.
18608 It is important to note that the compiled code is executed immediately.
18609 After execution, the compiled code is removed from @value{GDBN} and any
18610 new types or variables you have defined will be deleted.
18612 The command allows you to specify @var{source-code} in two ways.
18613 The simplest method is to provide a single line of code to the command.
18617 compile code printf ("hello world\n");
18620 If you specify options on the command line as well as source code, they
18621 may conflict. The @samp{--} delimiter can be used to separate options
18622 from actual source code. E.g.:
18625 compile code -r -- printf ("hello world\n");
18628 Alternatively you can enter source code as multiple lines of text. To
18629 enter this mode, invoke the @samp{compile code} command without any text
18630 following the command. This will start the multiple-line editor and
18631 allow you to type as many lines of source code as required. When you
18632 have completed typing, enter @samp{end} on its own line to exit the
18637 >printf ("hello\n");
18638 >printf ("world\n");
18642 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18643 provided @var{source-code} in a callable scope. In this case, you must
18644 specify the entry point of the code by defining a function named
18645 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18646 inferior. Using @samp{-raw} option may be needed for example when
18647 @var{source-code} requires @samp{#include} lines which may conflict with
18648 inferior symbols otherwise.
18650 @kindex compile file
18651 @item compile file @var{filename}
18652 @itemx compile file -raw @var{filename}
18653 Like @code{compile code}, but take the source code from @var{filename}.
18656 compile file /home/user/example.c
18661 @item compile print @var{expr}
18662 @itemx compile print /@var{f} @var{expr}
18663 Compile and execute @var{expr} with the compiler language found as the
18664 current language in @value{GDBN} (@pxref{Languages}). By default the
18665 value of @var{expr} is printed in a format appropriate to its data type;
18666 you can choose a different format by specifying @samp{/@var{f}}, where
18667 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18670 @item compile print
18671 @itemx compile print /@var{f}
18672 @cindex reprint the last value
18673 Alternatively you can enter the expression (source code producing it) as
18674 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18675 command without any text following the command. This will start the
18676 multiple-line editor.
18680 The process of compiling and injecting the code can be inspected using:
18683 @anchor{set debug compile}
18684 @item set debug compile
18685 @cindex compile command debugging info
18686 Turns on or off display of @value{GDBN} process of compiling and
18687 injecting the code. The default is off.
18689 @item show debug compile
18690 Displays the current state of displaying @value{GDBN} process of
18691 compiling and injecting the code.
18694 @subsection Compilation options for the @code{compile} command
18696 @value{GDBN} needs to specify the right compilation options for the code
18697 to be injected, in part to make its ABI compatible with the inferior
18698 and in part to make the injected code compatible with @value{GDBN}'s
18702 The options used, in increasing precedence:
18705 @item target architecture and OS options (@code{gdbarch})
18706 These options depend on target processor type and target operating
18707 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18708 (@code{-m64}) compilation option.
18710 @item compilation options recorded in the target
18711 @value{NGCC} (since version 4.7) stores the options used for compilation
18712 into @code{DW_AT_producer} part of DWARF debugging information according
18713 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18714 explicitly specify @code{-g} during inferior compilation otherwise
18715 @value{NGCC} produces no DWARF. This feature is only relevant for
18716 platforms where @code{-g} produces DWARF by default, otherwise one may
18717 try to enforce DWARF by using @code{-gdwarf-4}.
18719 @item compilation options set by @code{set compile-args}
18723 You can override compilation options using the following command:
18726 @item set compile-args
18727 @cindex compile command options override
18728 Set compilation options used for compiling and injecting code with the
18729 @code{compile} commands. These options override any conflicting ones
18730 from the target architecture and/or options stored during inferior
18733 @item show compile-args
18734 Displays the current state of compilation options override.
18735 This does not show all the options actually used during compilation,
18736 use @ref{set debug compile} for that.
18739 @subsection Caveats when using the @code{compile} command
18741 There are a few caveats to keep in mind when using the @code{compile}
18742 command. As the caveats are different per language, the table below
18743 highlights specific issues on a per language basis.
18746 @item C code examples and caveats
18747 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18748 attempt to compile the source code with a @samp{C} compiler. The source
18749 code provided to the @code{compile} command will have much the same
18750 access to variables and types as it normally would if it were part of
18751 the program currently being debugged in @value{GDBN}.
18753 Below is a sample program that forms the basis of the examples that
18754 follow. This program has been compiled and loaded into @value{GDBN},
18755 much like any other normal debugging session.
18758 void function1 (void)
18761 printf ("function 1\n");
18764 void function2 (void)
18779 For the purposes of the examples in this section, the program above has
18780 been compiled, loaded into @value{GDBN}, stopped at the function
18781 @code{main}, and @value{GDBN} is awaiting input from the user.
18783 To access variables and types for any program in @value{GDBN}, the
18784 program must be compiled and packaged with debug information. The
18785 @code{compile} command is not an exception to this rule. Without debug
18786 information, you can still use the @code{compile} command, but you will
18787 be very limited in what variables and types you can access.
18789 So with that in mind, the example above has been compiled with debug
18790 information enabled. The @code{compile} command will have access to
18791 all variables and types (except those that may have been optimized
18792 out). Currently, as @value{GDBN} has stopped the program in the
18793 @code{main} function, the @code{compile} command would have access to
18794 the variable @code{k}. You could invoke the @code{compile} command
18795 and type some source code to set the value of @code{k}. You can also
18796 read it, or do anything with that variable you would normally do in
18797 @code{C}. Be aware that changes to inferior variables in the
18798 @code{compile} command are persistent. In the following example:
18801 compile code k = 3;
18805 the variable @code{k} is now 3. It will retain that value until
18806 something else in the example program changes it, or another
18807 @code{compile} command changes it.
18809 Normal scope and access rules apply to source code compiled and
18810 injected by the @code{compile} command. In the example, the variables
18811 @code{j} and @code{k} are not accessible yet, because the program is
18812 currently stopped in the @code{main} function, where these variables
18813 are not in scope. Therefore, the following command
18816 compile code j = 3;
18820 will result in a compilation error message.
18822 Once the program is continued, execution will bring these variables in
18823 scope, and they will become accessible; then the code you specify via
18824 the @code{compile} command will be able to access them.
18826 You can create variables and types with the @code{compile} command as
18827 part of your source code. Variables and types that are created as part
18828 of the @code{compile} command are not visible to the rest of the program for
18829 the duration of its run. This example is valid:
18832 compile code int ff = 5; printf ("ff is %d\n", ff);
18835 However, if you were to type the following into @value{GDBN} after that
18836 command has completed:
18839 compile code printf ("ff is %d\n'', ff);
18843 a compiler error would be raised as the variable @code{ff} no longer
18844 exists. Object code generated and injected by the @code{compile}
18845 command is removed when its execution ends. Caution is advised
18846 when assigning to program variables values of variables created by the
18847 code submitted to the @code{compile} command. This example is valid:
18850 compile code int ff = 5; k = ff;
18853 The value of the variable @code{ff} is assigned to @code{k}. The variable
18854 @code{k} does not require the existence of @code{ff} to maintain the value
18855 it has been assigned. However, pointers require particular care in
18856 assignment. If the source code compiled with the @code{compile} command
18857 changed the address of a pointer in the example program, perhaps to a
18858 variable created in the @code{compile} command, that pointer would point
18859 to an invalid location when the command exits. The following example
18860 would likely cause issues with your debugged program:
18863 compile code int ff = 5; p = &ff;
18866 In this example, @code{p} would point to @code{ff} when the
18867 @code{compile} command is executing the source code provided to it.
18868 However, as variables in the (example) program persist with their
18869 assigned values, the variable @code{p} would point to an invalid
18870 location when the command exists. A general rule should be followed
18871 in that you should either assign @code{NULL} to any assigned pointers,
18872 or restore a valid location to the pointer before the command exits.
18874 Similar caution must be exercised with any structs, unions, and typedefs
18875 defined in @code{compile} command. Types defined in the @code{compile}
18876 command will no longer be available in the next @code{compile} command.
18877 Therefore, if you cast a variable to a type defined in the
18878 @code{compile} command, care must be taken to ensure that any future
18879 need to resolve the type can be achieved.
18882 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18883 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18884 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18885 Compilation failed.
18886 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18890 Variables that have been optimized away by the compiler are not
18891 accessible to the code submitted to the @code{compile} command.
18892 Access to those variables will generate a compiler error which @value{GDBN}
18893 will print to the console.
18896 @subsection Compiler search for the @code{compile} command
18898 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18899 which may not be obvious for remote targets of different architecture
18900 than where @value{GDBN} is running. Environment variable @code{PATH} on
18901 @value{GDBN} host is searched for @value{NGCC} binary matching the
18902 target architecture and operating system. This search can be overriden
18903 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18904 taken from shell that executed @value{GDBN}, it is not the value set by
18905 @value{GDBN} command @code{set environment}). @xref{Environment}.
18908 Specifically @code{PATH} is searched for binaries matching regular expression
18909 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18910 debugged. @var{arch} is processor name --- multiarch is supported, so for
18911 example both @code{i386} and @code{x86_64} targets look for pattern
18912 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18913 for pattern @code{s390x?}. @var{os} is currently supported only for
18914 pattern @code{linux(-gnu)?}.
18916 On Posix hosts the compiler driver @value{GDBN} needs to find also
18917 shared library @file{libcc1.so} from the compiler. It is searched in
18918 default shared library search path (overridable with usual environment
18919 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18920 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18921 according to the installation of the found compiler --- as possibly
18922 specified by the @code{set compile-gcc} command.
18925 @item set compile-gcc
18926 @cindex compile command driver filename override
18927 Set compilation command used for compiling and injecting code with the
18928 @code{compile} commands. If this option is not set (it is set to
18929 an empty string), the search described above will occur --- that is the
18932 @item show compile-gcc
18933 Displays the current compile command @value{NGCC} driver filename.
18934 If set, it is the main command @command{gcc}, found usually for example
18935 under name @file{x86_64-linux-gnu-gcc}.
18939 @chapter @value{GDBN} Files
18941 @value{GDBN} needs to know the file name of the program to be debugged,
18942 both in order to read its symbol table and in order to start your
18943 program. To debug a core dump of a previous run, you must also tell
18944 @value{GDBN} the name of the core dump file.
18947 * Files:: Commands to specify files
18948 * File Caching:: Information about @value{GDBN}'s file caching
18949 * Separate Debug Files:: Debugging information in separate files
18950 * MiniDebugInfo:: Debugging information in a special section
18951 * Index Files:: Index files speed up GDB
18952 * Symbol Errors:: Errors reading symbol files
18953 * Data Files:: GDB data files
18957 @section Commands to Specify Files
18959 @cindex symbol table
18960 @cindex core dump file
18962 You may want to specify executable and core dump file names. The usual
18963 way to do this is at start-up time, using the arguments to
18964 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18965 Out of @value{GDBN}}).
18967 Occasionally it is necessary to change to a different file during a
18968 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18969 specify a file you want to use. Or you are debugging a remote target
18970 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18971 Program}). In these situations the @value{GDBN} commands to specify
18972 new files are useful.
18975 @cindex executable file
18977 @item file @var{filename}
18978 Use @var{filename} as the program to be debugged. It is read for its
18979 symbols and for the contents of pure memory. It is also the program
18980 executed when you use the @code{run} command. If you do not specify a
18981 directory and the file is not found in the @value{GDBN} working directory,
18982 @value{GDBN} uses the environment variable @code{PATH} as a list of
18983 directories to search, just as the shell does when looking for a program
18984 to run. You can change the value of this variable, for both @value{GDBN}
18985 and your program, using the @code{path} command.
18987 @cindex unlinked object files
18988 @cindex patching object files
18989 You can load unlinked object @file{.o} files into @value{GDBN} using
18990 the @code{file} command. You will not be able to ``run'' an object
18991 file, but you can disassemble functions and inspect variables. Also,
18992 if the underlying BFD functionality supports it, you could use
18993 @kbd{gdb -write} to patch object files using this technique. Note
18994 that @value{GDBN} can neither interpret nor modify relocations in this
18995 case, so branches and some initialized variables will appear to go to
18996 the wrong place. But this feature is still handy from time to time.
18999 @code{file} with no argument makes @value{GDBN} discard any information it
19000 has on both executable file and the symbol table.
19003 @item exec-file @r{[} @var{filename} @r{]}
19004 Specify that the program to be run (but not the symbol table) is found
19005 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19006 if necessary to locate your program. Omitting @var{filename} means to
19007 discard information on the executable file.
19009 @kindex symbol-file
19010 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19011 Read symbol table information from file @var{filename}. @code{PATH} is
19012 searched when necessary. Use the @code{file} command to get both symbol
19013 table and program to run from the same file.
19015 If an optional @var{offset} is specified, it is added to the start
19016 address of each section in the symbol file. This is useful if the
19017 program is relocated at runtime, such as the Linux kernel with kASLR
19020 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19021 program's symbol table.
19023 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19024 some breakpoints and auto-display expressions. This is because they may
19025 contain pointers to the internal data recording symbols and data types,
19026 which are part of the old symbol table data being discarded inside
19029 @code{symbol-file} does not repeat if you press @key{RET} again after
19032 When @value{GDBN} is configured for a particular environment, it
19033 understands debugging information in whatever format is the standard
19034 generated for that environment; you may use either a @sc{gnu} compiler, or
19035 other compilers that adhere to the local conventions.
19036 Best results are usually obtained from @sc{gnu} compilers; for example,
19037 using @code{@value{NGCC}} you can generate debugging information for
19040 For most kinds of object files, with the exception of old SVR3 systems
19041 using COFF, the @code{symbol-file} command does not normally read the
19042 symbol table in full right away. Instead, it scans the symbol table
19043 quickly to find which source files and which symbols are present. The
19044 details are read later, one source file at a time, as they are needed.
19046 The purpose of this two-stage reading strategy is to make @value{GDBN}
19047 start up faster. For the most part, it is invisible except for
19048 occasional pauses while the symbol table details for a particular source
19049 file are being read. (The @code{set verbose} command can turn these
19050 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19051 Warnings and Messages}.)
19053 We have not implemented the two-stage strategy for COFF yet. When the
19054 symbol table is stored in COFF format, @code{symbol-file} reads the
19055 symbol table data in full right away. Note that ``stabs-in-COFF''
19056 still does the two-stage strategy, since the debug info is actually
19060 @cindex reading symbols immediately
19061 @cindex symbols, reading immediately
19062 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19063 @itemx file @r{[} -readnow @r{]} @var{filename}
19064 You can override the @value{GDBN} two-stage strategy for reading symbol
19065 tables by using the @samp{-readnow} option with any of the commands that
19066 load symbol table information, if you want to be sure @value{GDBN} has the
19067 entire symbol table available.
19069 @cindex @code{-readnever}, option for symbol-file command
19070 @cindex never read symbols
19071 @cindex symbols, never read
19072 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19073 @itemx file @r{[} -readnever @r{]} @var{filename}
19074 You can instruct @value{GDBN} to never read the symbolic information
19075 contained in @var{filename} by using the @samp{-readnever} option.
19076 @xref{--readnever}.
19078 @c FIXME: for now no mention of directories, since this seems to be in
19079 @c flux. 13mar1992 status is that in theory GDB would look either in
19080 @c current dir or in same dir as myprog; but issues like competing
19081 @c GDB's, or clutter in system dirs, mean that in practice right now
19082 @c only current dir is used. FFish says maybe a special GDB hierarchy
19083 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19087 @item core-file @r{[}@var{filename}@r{]}
19089 Specify the whereabouts of a core dump file to be used as the ``contents
19090 of memory''. Traditionally, core files contain only some parts of the
19091 address space of the process that generated them; @value{GDBN} can access the
19092 executable file itself for other parts.
19094 @code{core-file} with no argument specifies that no core file is
19097 Note that the core file is ignored when your program is actually running
19098 under @value{GDBN}. So, if you have been running your program and you
19099 wish to debug a core file instead, you must kill the subprocess in which
19100 the program is running. To do this, use the @code{kill} command
19101 (@pxref{Kill Process, ,Killing the Child Process}).
19103 @kindex add-symbol-file
19104 @cindex dynamic linking
19105 @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{]}
19106 The @code{add-symbol-file} command reads additional symbol table
19107 information from the file @var{filename}. You would use this command
19108 when @var{filename} has been dynamically loaded (by some other means)
19109 into the program that is running. The @var{textaddress} parameter gives
19110 the memory address at which the file's text section has been loaded.
19111 You can additionally specify the base address of other sections using
19112 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19113 If a section is omitted, @value{GDBN} will use its default addresses
19114 as found in @var{filename}. Any @var{address} or @var{textaddress}
19115 can be given as an expression.
19117 If an optional @var{offset} is specified, it is added to the start
19118 address of each section, except those for which the address was
19119 specified explicitly.
19121 The symbol table of the file @var{filename} is added to the symbol table
19122 originally read with the @code{symbol-file} command. You can use the
19123 @code{add-symbol-file} command any number of times; the new symbol data
19124 thus read is kept in addition to the old.
19126 Changes can be reverted using the command @code{remove-symbol-file}.
19128 @cindex relocatable object files, reading symbols from
19129 @cindex object files, relocatable, reading symbols from
19130 @cindex reading symbols from relocatable object files
19131 @cindex symbols, reading from relocatable object files
19132 @cindex @file{.o} files, reading symbols from
19133 Although @var{filename} is typically a shared library file, an
19134 executable file, or some other object file which has been fully
19135 relocated for loading into a process, you can also load symbolic
19136 information from relocatable @file{.o} files, as long as:
19140 the file's symbolic information refers only to linker symbols defined in
19141 that file, not to symbols defined by other object files,
19143 every section the file's symbolic information refers to has actually
19144 been loaded into the inferior, as it appears in the file, and
19146 you can determine the address at which every section was loaded, and
19147 provide these to the @code{add-symbol-file} command.
19151 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19152 relocatable files into an already running program; such systems
19153 typically make the requirements above easy to meet. However, it's
19154 important to recognize that many native systems use complex link
19155 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19156 assembly, for example) that make the requirements difficult to meet. In
19157 general, one cannot assume that using @code{add-symbol-file} to read a
19158 relocatable object file's symbolic information will have the same effect
19159 as linking the relocatable object file into the program in the normal
19162 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19164 @kindex remove-symbol-file
19165 @item remove-symbol-file @var{filename}
19166 @item remove-symbol-file -a @var{address}
19167 Remove a symbol file added via the @code{add-symbol-file} command. The
19168 file to remove can be identified by its @var{filename} or by an @var{address}
19169 that lies within the boundaries of this symbol file in memory. Example:
19172 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19173 add symbol table from file "/home/user/gdb/mylib.so" at
19174 .text_addr = 0x7ffff7ff9480
19176 Reading symbols from /home/user/gdb/mylib.so...done.
19177 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19178 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19183 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19185 @kindex add-symbol-file-from-memory
19186 @cindex @code{syscall DSO}
19187 @cindex load symbols from memory
19188 @item add-symbol-file-from-memory @var{address}
19189 Load symbols from the given @var{address} in a dynamically loaded
19190 object file whose image is mapped directly into the inferior's memory.
19191 For example, the Linux kernel maps a @code{syscall DSO} into each
19192 process's address space; this DSO provides kernel-specific code for
19193 some system calls. The argument can be any expression whose
19194 evaluation yields the address of the file's shared object file header.
19195 For this command to work, you must have used @code{symbol-file} or
19196 @code{exec-file} commands in advance.
19199 @item section @var{section} @var{addr}
19200 The @code{section} command changes the base address of the named
19201 @var{section} of the exec file to @var{addr}. This can be used if the
19202 exec file does not contain section addresses, (such as in the
19203 @code{a.out} format), or when the addresses specified in the file
19204 itself are wrong. Each section must be changed separately. The
19205 @code{info files} command, described below, lists all the sections and
19209 @kindex info target
19212 @code{info files} and @code{info target} are synonymous; both print the
19213 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19214 including the names of the executable and core dump files currently in
19215 use by @value{GDBN}, and the files from which symbols were loaded. The
19216 command @code{help target} lists all possible targets rather than
19219 @kindex maint info sections
19220 @item maint info sections
19221 Another command that can give you extra information about program sections
19222 is @code{maint info sections}. In addition to the section information
19223 displayed by @code{info files}, this command displays the flags and file
19224 offset of each section in the executable and core dump files. In addition,
19225 @code{maint info sections} provides the following command options (which
19226 may be arbitrarily combined):
19230 Display sections for all loaded object files, including shared libraries.
19231 @item @var{sections}
19232 Display info only for named @var{sections}.
19233 @item @var{section-flags}
19234 Display info only for sections for which @var{section-flags} are true.
19235 The section flags that @value{GDBN} currently knows about are:
19238 Section will have space allocated in the process when loaded.
19239 Set for all sections except those containing debug information.
19241 Section will be loaded from the file into the child process memory.
19242 Set for pre-initialized code and data, clear for @code{.bss} sections.
19244 Section needs to be relocated before loading.
19246 Section cannot be modified by the child process.
19248 Section contains executable code only.
19250 Section contains data only (no executable code).
19252 Section will reside in ROM.
19254 Section contains data for constructor/destructor lists.
19256 Section is not empty.
19258 An instruction to the linker to not output the section.
19259 @item COFF_SHARED_LIBRARY
19260 A notification to the linker that the section contains
19261 COFF shared library information.
19263 Section contains common symbols.
19266 @kindex set trust-readonly-sections
19267 @cindex read-only sections
19268 @item set trust-readonly-sections on
19269 Tell @value{GDBN} that readonly sections in your object file
19270 really are read-only (i.e.@: that their contents will not change).
19271 In that case, @value{GDBN} can fetch values from these sections
19272 out of the object file, rather than from the target program.
19273 For some targets (notably embedded ones), this can be a significant
19274 enhancement to debugging performance.
19276 The default is off.
19278 @item set trust-readonly-sections off
19279 Tell @value{GDBN} not to trust readonly sections. This means that
19280 the contents of the section might change while the program is running,
19281 and must therefore be fetched from the target when needed.
19283 @item show trust-readonly-sections
19284 Show the current setting of trusting readonly sections.
19287 All file-specifying commands allow both absolute and relative file names
19288 as arguments. @value{GDBN} always converts the file name to an absolute file
19289 name and remembers it that way.
19291 @cindex shared libraries
19292 @anchor{Shared Libraries}
19293 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19294 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19295 DSBT (TIC6X) shared libraries.
19297 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19298 shared libraries. @xref{Expat}.
19300 @value{GDBN} automatically loads symbol definitions from shared libraries
19301 when you use the @code{run} command, or when you examine a core file.
19302 (Before you issue the @code{run} command, @value{GDBN} does not understand
19303 references to a function in a shared library, however---unless you are
19304 debugging a core file).
19306 @c FIXME: some @value{GDBN} release may permit some refs to undef
19307 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19308 @c FIXME...lib; check this from time to time when updating manual
19310 There are times, however, when you may wish to not automatically load
19311 symbol definitions from shared libraries, such as when they are
19312 particularly large or there are many of them.
19314 To control the automatic loading of shared library symbols, use the
19318 @kindex set auto-solib-add
19319 @item set auto-solib-add @var{mode}
19320 If @var{mode} is @code{on}, symbols from all shared object libraries
19321 will be loaded automatically when the inferior begins execution, you
19322 attach to an independently started inferior, or when the dynamic linker
19323 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19324 is @code{off}, symbols must be loaded manually, using the
19325 @code{sharedlibrary} command. The default value is @code{on}.
19327 @cindex memory used for symbol tables
19328 If your program uses lots of shared libraries with debug info that
19329 takes large amounts of memory, you can decrease the @value{GDBN}
19330 memory footprint by preventing it from automatically loading the
19331 symbols from shared libraries. To that end, type @kbd{set
19332 auto-solib-add off} before running the inferior, then load each
19333 library whose debug symbols you do need with @kbd{sharedlibrary
19334 @var{regexp}}, where @var{regexp} is a regular expression that matches
19335 the libraries whose symbols you want to be loaded.
19337 @kindex show auto-solib-add
19338 @item show auto-solib-add
19339 Display the current autoloading mode.
19342 @cindex load shared library
19343 To explicitly load shared library symbols, use the @code{sharedlibrary}
19347 @kindex info sharedlibrary
19349 @item info share @var{regex}
19350 @itemx info sharedlibrary @var{regex}
19351 Print the names of the shared libraries which are currently loaded
19352 that match @var{regex}. If @var{regex} is omitted then print
19353 all shared libraries that are loaded.
19356 @item info dll @var{regex}
19357 This is an alias of @code{info sharedlibrary}.
19359 @kindex sharedlibrary
19361 @item sharedlibrary @var{regex}
19362 @itemx share @var{regex}
19363 Load shared object library symbols for files matching a
19364 Unix regular expression.
19365 As with files loaded automatically, it only loads shared libraries
19366 required by your program for a core file or after typing @code{run}. If
19367 @var{regex} is omitted all shared libraries required by your program are
19370 @item nosharedlibrary
19371 @kindex nosharedlibrary
19372 @cindex unload symbols from shared libraries
19373 Unload all shared object library symbols. This discards all symbols
19374 that have been loaded from all shared libraries. Symbols from shared
19375 libraries that were loaded by explicit user requests are not
19379 Sometimes you may wish that @value{GDBN} stops and gives you control
19380 when any of shared library events happen. The best way to do this is
19381 to use @code{catch load} and @code{catch unload} (@pxref{Set
19384 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19385 command for this. This command exists for historical reasons. It is
19386 less useful than setting a catchpoint, because it does not allow for
19387 conditions or commands as a catchpoint does.
19390 @item set stop-on-solib-events
19391 @kindex set stop-on-solib-events
19392 This command controls whether @value{GDBN} should give you control
19393 when the dynamic linker notifies it about some shared library event.
19394 The most common event of interest is loading or unloading of a new
19397 @item show stop-on-solib-events
19398 @kindex show stop-on-solib-events
19399 Show whether @value{GDBN} stops and gives you control when shared
19400 library events happen.
19403 Shared libraries are also supported in many cross or remote debugging
19404 configurations. @value{GDBN} needs to have access to the target's libraries;
19405 this can be accomplished either by providing copies of the libraries
19406 on the host system, or by asking @value{GDBN} to automatically retrieve the
19407 libraries from the target. If copies of the target libraries are
19408 provided, they need to be the same as the target libraries, although the
19409 copies on the target can be stripped as long as the copies on the host are
19412 @cindex where to look for shared libraries
19413 For remote debugging, you need to tell @value{GDBN} where the target
19414 libraries are, so that it can load the correct copies---otherwise, it
19415 may try to load the host's libraries. @value{GDBN} has two variables
19416 to specify the search directories for target libraries.
19419 @cindex prefix for executable and shared library file names
19420 @cindex system root, alternate
19421 @kindex set solib-absolute-prefix
19422 @kindex set sysroot
19423 @item set sysroot @var{path}
19424 Use @var{path} as the system root for the program being debugged. Any
19425 absolute shared library paths will be prefixed with @var{path}; many
19426 runtime loaders store the absolute paths to the shared library in the
19427 target program's memory. When starting processes remotely, and when
19428 attaching to already-running processes (local or remote), their
19429 executable filenames will be prefixed with @var{path} if reported to
19430 @value{GDBN} as absolute by the operating system. If you use
19431 @code{set sysroot} to find executables and shared libraries, they need
19432 to be laid out in the same way that they are on the target, with
19433 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19436 If @var{path} starts with the sequence @file{target:} and the target
19437 system is remote then @value{GDBN} will retrieve the target binaries
19438 from the remote system. This is only supported when using a remote
19439 target that supports the @code{remote get} command (@pxref{File
19440 Transfer,,Sending files to a remote system}). The part of @var{path}
19441 following the initial @file{target:} (if present) is used as system
19442 root prefix on the remote file system. If @var{path} starts with the
19443 sequence @file{remote:} this is converted to the sequence
19444 @file{target:} by @code{set sysroot}@footnote{Historically the
19445 functionality to retrieve binaries from the remote system was
19446 provided by prefixing @var{path} with @file{remote:}}. If you want
19447 to specify a local system root using a directory that happens to be
19448 named @file{target:} or @file{remote:}, you need to use some
19449 equivalent variant of the name like @file{./target:}.
19451 For targets with an MS-DOS based filesystem, such as MS-Windows and
19452 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19453 absolute file name with @var{path}. But first, on Unix hosts,
19454 @value{GDBN} converts all backslash directory separators into forward
19455 slashes, because the backslash is not a directory separator on Unix:
19458 c:\foo\bar.dll @result{} c:/foo/bar.dll
19461 Then, @value{GDBN} attempts prefixing the target file name with
19462 @var{path}, and looks for the resulting file name in the host file
19466 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19469 If that does not find the binary, @value{GDBN} tries removing
19470 the @samp{:} character from the drive spec, both for convenience, and,
19471 for the case of the host file system not supporting file names with
19475 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19478 This makes it possible to have a system root that mirrors a target
19479 with more than one drive. E.g., you may want to setup your local
19480 copies of the target system shared libraries like so (note @samp{c} vs
19484 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19485 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19486 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19490 and point the system root at @file{/path/to/sysroot}, so that
19491 @value{GDBN} can find the correct copies of both
19492 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19494 If that still does not find the binary, @value{GDBN} tries
19495 removing the whole drive spec from the target file name:
19498 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19501 This last lookup makes it possible to not care about the drive name,
19502 if you don't want or need to.
19504 The @code{set solib-absolute-prefix} command is an alias for @code{set
19507 @cindex default system root
19508 @cindex @samp{--with-sysroot}
19509 You can set the default system root by using the configure-time
19510 @samp{--with-sysroot} option. If the system root is inside
19511 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19512 @samp{--exec-prefix}), then the default system root will be updated
19513 automatically if the installed @value{GDBN} is moved to a new
19516 @kindex show sysroot
19518 Display the current executable and shared library prefix.
19520 @kindex set solib-search-path
19521 @item set solib-search-path @var{path}
19522 If this variable is set, @var{path} is a colon-separated list of
19523 directories to search for shared libraries. @samp{solib-search-path}
19524 is used after @samp{sysroot} fails to locate the library, or if the
19525 path to the library is relative instead of absolute. If you want to
19526 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19527 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19528 finding your host's libraries. @samp{sysroot} is preferred; setting
19529 it to a nonexistent directory may interfere with automatic loading
19530 of shared library symbols.
19532 @kindex show solib-search-path
19533 @item show solib-search-path
19534 Display the current shared library search path.
19536 @cindex DOS file-name semantics of file names.
19537 @kindex set target-file-system-kind (unix|dos-based|auto)
19538 @kindex show target-file-system-kind
19539 @item set target-file-system-kind @var{kind}
19540 Set assumed file system kind for target reported file names.
19542 Shared library file names as reported by the target system may not
19543 make sense as is on the system @value{GDBN} is running on. For
19544 example, when remote debugging a target that has MS-DOS based file
19545 system semantics, from a Unix host, the target may be reporting to
19546 @value{GDBN} a list of loaded shared libraries with file names such as
19547 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19548 drive letters, so the @samp{c:\} prefix is not normally understood as
19549 indicating an absolute file name, and neither is the backslash
19550 normally considered a directory separator character. In that case,
19551 the native file system would interpret this whole absolute file name
19552 as a relative file name with no directory components. This would make
19553 it impossible to point @value{GDBN} at a copy of the remote target's
19554 shared libraries on the host using @code{set sysroot}, and impractical
19555 with @code{set solib-search-path}. Setting
19556 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19557 to interpret such file names similarly to how the target would, and to
19558 map them to file names valid on @value{GDBN}'s native file system
19559 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19560 to one of the supported file system kinds. In that case, @value{GDBN}
19561 tries to determine the appropriate file system variant based on the
19562 current target's operating system (@pxref{ABI, ,Configuring the
19563 Current ABI}). The supported file system settings are:
19567 Instruct @value{GDBN} to assume the target file system is of Unix
19568 kind. Only file names starting the forward slash (@samp{/}) character
19569 are considered absolute, and the directory separator character is also
19573 Instruct @value{GDBN} to assume the target file system is DOS based.
19574 File names starting with either a forward slash, or a drive letter
19575 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19576 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19577 considered directory separators.
19580 Instruct @value{GDBN} to use the file system kind associated with the
19581 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19582 This is the default.
19586 @cindex file name canonicalization
19587 @cindex base name differences
19588 When processing file names provided by the user, @value{GDBN}
19589 frequently needs to compare them to the file names recorded in the
19590 program's debug info. Normally, @value{GDBN} compares just the
19591 @dfn{base names} of the files as strings, which is reasonably fast
19592 even for very large programs. (The base name of a file is the last
19593 portion of its name, after stripping all the leading directories.)
19594 This shortcut in comparison is based upon the assumption that files
19595 cannot have more than one base name. This is usually true, but
19596 references to files that use symlinks or similar filesystem
19597 facilities violate that assumption. If your program records files
19598 using such facilities, or if you provide file names to @value{GDBN}
19599 using symlinks etc., you can set @code{basenames-may-differ} to
19600 @code{true} to instruct @value{GDBN} to completely canonicalize each
19601 pair of file names it needs to compare. This will make file-name
19602 comparisons accurate, but at a price of a significant slowdown.
19605 @item set basenames-may-differ
19606 @kindex set basenames-may-differ
19607 Set whether a source file may have multiple base names.
19609 @item show basenames-may-differ
19610 @kindex show basenames-may-differ
19611 Show whether a source file may have multiple base names.
19615 @section File Caching
19616 @cindex caching of opened files
19617 @cindex caching of bfd objects
19619 To speed up file loading, and reduce memory usage, @value{GDBN} will
19620 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19621 BFD, bfd, The Binary File Descriptor Library}. The following commands
19622 allow visibility and control of the caching behavior.
19625 @kindex maint info bfds
19626 @item maint info bfds
19627 This prints information about each @code{bfd} object that is known to
19630 @kindex maint set bfd-sharing
19631 @kindex maint show bfd-sharing
19632 @kindex bfd caching
19633 @item maint set bfd-sharing
19634 @item maint show bfd-sharing
19635 Control whether @code{bfd} objects can be shared. When sharing is
19636 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19637 than reopening the same file. Turning sharing off does not cause
19638 already shared @code{bfd} objects to be unshared, but all future files
19639 that are opened will create a new @code{bfd} object. Similarly,
19640 re-enabling sharing does not cause multiple existing @code{bfd}
19641 objects to be collapsed into a single shared @code{bfd} object.
19643 @kindex set debug bfd-cache @var{level}
19644 @kindex bfd caching
19645 @item set debug bfd-cache @var{level}
19646 Turns on debugging of the bfd cache, setting the level to @var{level}.
19648 @kindex show debug bfd-cache
19649 @kindex bfd caching
19650 @item show debug bfd-cache
19651 Show the current debugging level of the bfd cache.
19654 @node Separate Debug Files
19655 @section Debugging Information in Separate Files
19656 @cindex separate debugging information files
19657 @cindex debugging information in separate files
19658 @cindex @file{.debug} subdirectories
19659 @cindex debugging information directory, global
19660 @cindex global debugging information directories
19661 @cindex build ID, and separate debugging files
19662 @cindex @file{.build-id} directory
19664 @value{GDBN} allows you to put a program's debugging information in a
19665 file separate from the executable itself, in a way that allows
19666 @value{GDBN} to find and load the debugging information automatically.
19667 Since debugging information can be very large---sometimes larger
19668 than the executable code itself---some systems distribute debugging
19669 information for their executables in separate files, which users can
19670 install only when they need to debug a problem.
19672 @value{GDBN} supports two ways of specifying the separate debug info
19677 The executable contains a @dfn{debug link} that specifies the name of
19678 the separate debug info file. The separate debug file's name is
19679 usually @file{@var{executable}.debug}, where @var{executable} is the
19680 name of the corresponding executable file without leading directories
19681 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19682 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19683 checksum for the debug file, which @value{GDBN} uses to validate that
19684 the executable and the debug file came from the same build.
19687 The executable contains a @dfn{build ID}, a unique bit string that is
19688 also present in the corresponding debug info file. (This is supported
19689 only on some operating systems, when using the ELF or PE file formats
19690 for binary files and the @sc{gnu} Binutils.) For more details about
19691 this feature, see the description of the @option{--build-id}
19692 command-line option in @ref{Options, , Command Line Options, ld.info,
19693 The GNU Linker}. The debug info file's name is not specified
19694 explicitly by the build ID, but can be computed from the build ID, see
19698 Depending on the way the debug info file is specified, @value{GDBN}
19699 uses two different methods of looking for the debug file:
19703 For the ``debug link'' method, @value{GDBN} looks up the named file in
19704 the directory of the executable file, then in a subdirectory of that
19705 directory named @file{.debug}, and finally under each one of the global debug
19706 directories, in a subdirectory whose name is identical to the leading
19707 directories of the executable's absolute file name.
19710 For the ``build ID'' method, @value{GDBN} looks in the
19711 @file{.build-id} subdirectory of each one of the global debug directories for
19712 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19713 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19714 are the rest of the bit string. (Real build ID strings are 32 or more
19715 hex characters, not 10.)
19718 So, for example, suppose you ask @value{GDBN} to debug
19719 @file{/usr/bin/ls}, which has a debug link that specifies the
19720 file @file{ls.debug}, and a build ID whose value in hex is
19721 @code{abcdef1234}. If the list of the global debug directories includes
19722 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19723 debug information files, in the indicated order:
19727 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19729 @file{/usr/bin/ls.debug}
19731 @file{/usr/bin/.debug/ls.debug}
19733 @file{/usr/lib/debug/usr/bin/ls.debug}.
19736 @anchor{debug-file-directory}
19737 Global debugging info directories default to what is set by @value{GDBN}
19738 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19739 you can also set the global debugging info directories, and view the list
19740 @value{GDBN} is currently using.
19744 @kindex set debug-file-directory
19745 @item set debug-file-directory @var{directories}
19746 Set the directories which @value{GDBN} searches for separate debugging
19747 information files to @var{directory}. Multiple path components can be set
19748 concatenating them by a path separator.
19750 @kindex show debug-file-directory
19751 @item show debug-file-directory
19752 Show the directories @value{GDBN} searches for separate debugging
19757 @cindex @code{.gnu_debuglink} sections
19758 @cindex debug link sections
19759 A debug link is a special section of the executable file named
19760 @code{.gnu_debuglink}. The section must contain:
19764 A filename, with any leading directory components removed, followed by
19767 zero to three bytes of padding, as needed to reach the next four-byte
19768 boundary within the section, and
19770 a four-byte CRC checksum, stored in the same endianness used for the
19771 executable file itself. The checksum is computed on the debugging
19772 information file's full contents by the function given below, passing
19773 zero as the @var{crc} argument.
19776 Any executable file format can carry a debug link, as long as it can
19777 contain a section named @code{.gnu_debuglink} with the contents
19780 @cindex @code{.note.gnu.build-id} sections
19781 @cindex build ID sections
19782 The build ID is a special section in the executable file (and in other
19783 ELF binary files that @value{GDBN} may consider). This section is
19784 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19785 It contains unique identification for the built files---the ID remains
19786 the same across multiple builds of the same build tree. The default
19787 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19788 content for the build ID string. The same section with an identical
19789 value is present in the original built binary with symbols, in its
19790 stripped variant, and in the separate debugging information file.
19792 The debugging information file itself should be an ordinary
19793 executable, containing a full set of linker symbols, sections, and
19794 debugging information. The sections of the debugging information file
19795 should have the same names, addresses, and sizes as the original file,
19796 but they need not contain any data---much like a @code{.bss} section
19797 in an ordinary executable.
19799 The @sc{gnu} binary utilities (Binutils) package includes the
19800 @samp{objcopy} utility that can produce
19801 the separated executable / debugging information file pairs using the
19802 following commands:
19805 @kbd{objcopy --only-keep-debug foo foo.debug}
19810 These commands remove the debugging
19811 information from the executable file @file{foo} and place it in the file
19812 @file{foo.debug}. You can use the first, second or both methods to link the
19817 The debug link method needs the following additional command to also leave
19818 behind a debug link in @file{foo}:
19821 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19824 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19825 a version of the @code{strip} command such that the command @kbd{strip foo -f
19826 foo.debug} has the same functionality as the two @code{objcopy} commands and
19827 the @code{ln -s} command above, together.
19830 Build ID gets embedded into the main executable using @code{ld --build-id} or
19831 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19832 compatibility fixes for debug files separation are present in @sc{gnu} binary
19833 utilities (Binutils) package since version 2.18.
19838 @cindex CRC algorithm definition
19839 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19840 IEEE 802.3 using the polynomial:
19842 @c TexInfo requires naked braces for multi-digit exponents for Tex
19843 @c output, but this causes HTML output to barf. HTML has to be set using
19844 @c raw commands. So we end up having to specify this equation in 2
19849 <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>
19850 + <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
19856 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19857 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19861 The function is computed byte at a time, taking the least
19862 significant bit of each byte first. The initial pattern
19863 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19864 the final result is inverted to ensure trailing zeros also affect the
19867 @emph{Note:} This is the same CRC polynomial as used in handling the
19868 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19869 However in the case of the Remote Serial Protocol, the CRC is computed
19870 @emph{most} significant bit first, and the result is not inverted, so
19871 trailing zeros have no effect on the CRC value.
19873 To complete the description, we show below the code of the function
19874 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19875 initially supplied @code{crc} argument means that an initial call to
19876 this function passing in zero will start computing the CRC using
19879 @kindex gnu_debuglink_crc32
19882 gnu_debuglink_crc32 (unsigned long crc,
19883 unsigned char *buf, size_t len)
19885 static const unsigned long crc32_table[256] =
19887 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19888 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19889 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19890 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19891 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19892 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19893 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19894 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19895 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19896 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19897 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19898 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19899 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19900 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19901 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19902 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19903 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19904 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19905 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19906 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19907 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19908 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19909 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19910 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19911 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19912 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19913 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19914 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19915 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19916 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19917 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19918 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19919 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19920 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19921 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19922 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19923 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19924 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19925 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19926 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19927 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19928 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19929 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19930 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19931 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19932 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19933 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19934 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19935 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19936 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19937 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19940 unsigned char *end;
19942 crc = ~crc & 0xffffffff;
19943 for (end = buf + len; buf < end; ++buf)
19944 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19945 return ~crc & 0xffffffff;
19950 This computation does not apply to the ``build ID'' method.
19952 @node MiniDebugInfo
19953 @section Debugging information in a special section
19954 @cindex separate debug sections
19955 @cindex @samp{.gnu_debugdata} section
19957 Some systems ship pre-built executables and libraries that have a
19958 special @samp{.gnu_debugdata} section. This feature is called
19959 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19960 is used to supply extra symbols for backtraces.
19962 The intent of this section is to provide extra minimal debugging
19963 information for use in simple backtraces. It is not intended to be a
19964 replacement for full separate debugging information (@pxref{Separate
19965 Debug Files}). The example below shows the intended use; however,
19966 @value{GDBN} does not currently put restrictions on what sort of
19967 debugging information might be included in the section.
19969 @value{GDBN} has support for this extension. If the section exists,
19970 then it is used provided that no other source of debugging information
19971 can be found, and that @value{GDBN} was configured with LZMA support.
19973 This section can be easily created using @command{objcopy} and other
19974 standard utilities:
19977 # Extract the dynamic symbols from the main binary, there is no need
19978 # to also have these in the normal symbol table.
19979 nm -D @var{binary} --format=posix --defined-only \
19980 | awk '@{ print $1 @}' | sort > dynsyms
19982 # Extract all the text (i.e. function) symbols from the debuginfo.
19983 # (Note that we actually also accept "D" symbols, for the benefit
19984 # of platforms like PowerPC64 that use function descriptors.)
19985 nm @var{binary} --format=posix --defined-only \
19986 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19989 # Keep all the function symbols not already in the dynamic symbol
19991 comm -13 dynsyms funcsyms > keep_symbols
19993 # Separate full debug info into debug binary.
19994 objcopy --only-keep-debug @var{binary} debug
19996 # Copy the full debuginfo, keeping only a minimal set of symbols and
19997 # removing some unnecessary sections.
19998 objcopy -S --remove-section .gdb_index --remove-section .comment \
19999 --keep-symbols=keep_symbols debug mini_debuginfo
20001 # Drop the full debug info from the original binary.
20002 strip --strip-all -R .comment @var{binary}
20004 # Inject the compressed data into the .gnu_debugdata section of the
20007 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20011 @section Index Files Speed Up @value{GDBN}
20012 @cindex index files
20013 @cindex @samp{.gdb_index} section
20015 When @value{GDBN} finds a symbol file, it scans the symbols in the
20016 file in order to construct an internal symbol table. This lets most
20017 @value{GDBN} operations work quickly---at the cost of a delay early
20018 on. For large programs, this delay can be quite lengthy, so
20019 @value{GDBN} provides a way to build an index, which speeds up
20022 For convenience, @value{GDBN} comes with a program,
20023 @command{gdb-add-index}, which can be used to add the index to a
20024 symbol file. It takes the symbol file as its only argument:
20027 $ gdb-add-index symfile
20030 @xref{gdb-add-index}.
20032 It is also possible to do the work manually. Here is what
20033 @command{gdb-add-index} does behind the curtains.
20035 The index is stored as a section in the symbol file. @value{GDBN} can
20036 write the index to a file, then you can put it into the symbol file
20037 using @command{objcopy}.
20039 To create an index file, use the @code{save gdb-index} command:
20042 @item save gdb-index [-dwarf-5] @var{directory}
20043 @kindex save gdb-index
20044 Create index files for all symbol files currently known by
20045 @value{GDBN}. For each known @var{symbol-file}, this command by
20046 default creates it produces a single file
20047 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20048 the @option{-dwarf-5} option, it produces 2 files:
20049 @file{@var{symbol-file}.debug_names} and
20050 @file{@var{symbol-file}.debug_str}. The files are created in the
20051 given @var{directory}.
20054 Once you have created an index file you can merge it into your symbol
20055 file, here named @file{symfile}, using @command{objcopy}:
20058 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20059 --set-section-flags .gdb_index=readonly symfile symfile
20062 Or for @code{-dwarf-5}:
20065 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20066 $ cat symfile.debug_str >>symfile.debug_str.new
20067 $ objcopy --add-section .debug_names=symfile.gdb-index \
20068 --set-section-flags .debug_names=readonly \
20069 --update-section .debug_str=symfile.debug_str.new symfile symfile
20072 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20073 sections that have been deprecated. Usually they are deprecated because
20074 they are missing a new feature or have performance issues.
20075 To tell @value{GDBN} to use a deprecated index section anyway
20076 specify @code{set use-deprecated-index-sections on}.
20077 The default is @code{off}.
20078 This can speed up startup, but may result in some functionality being lost.
20079 @xref{Index Section Format}.
20081 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20082 must be done before gdb reads the file. The following will not work:
20085 $ gdb -ex "set use-deprecated-index-sections on" <program>
20088 Instead you must do, for example,
20091 $ gdb -iex "set use-deprecated-index-sections on" <program>
20094 There are currently some limitation on indices. They only work when
20095 for DWARF debugging information, not stabs. And, they do not
20096 currently work for programs using Ada.
20098 @subsection Automatic symbol index cache
20100 It is possible for @value{GDBN} to automatically save a copy of this index in a
20101 cache on disk and retrieve it from there when loading the same binary in the
20102 future. This feature can be turned on with @kbd{set index-cache on}. The
20103 following commands can be used to tweak the behavior of the index cache.
20107 @item set index-cache on
20108 @itemx set index-cache off
20109 Enable or disable the use of the symbol index cache.
20111 @item set index-cache directory @var{directory}
20112 @itemx show index-cache directory
20113 Set/show the directory where index files will be saved. By default, the index
20114 is cached in the @file{gdb} subdirectory of the directory pointed to by the
20115 @env{XDG_CACHE_HOME} environment variable, if it is defined, else in the
20116 @file{.cache/gdb} subdirectory of your home directory.
20118 There is no limit on the disk space used by index cache. It is perfectly safe
20119 to delete the content of that directory to free up disk space.
20121 @item show index-cache stats
20122 Print the number of cache hits and misses since the launch of @value{GDBN}.
20126 @node Symbol Errors
20127 @section Errors Reading Symbol Files
20129 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20130 such as symbol types it does not recognize, or known bugs in compiler
20131 output. By default, @value{GDBN} does not notify you of such problems, since
20132 they are relatively common and primarily of interest to people
20133 debugging compilers. If you are interested in seeing information
20134 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20135 only one message about each such type of problem, no matter how many
20136 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20137 to see how many times the problems occur, with the @code{set
20138 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20141 The messages currently printed, and their meanings, include:
20144 @item inner block not inside outer block in @var{symbol}
20146 The symbol information shows where symbol scopes begin and end
20147 (such as at the start of a function or a block of statements). This
20148 error indicates that an inner scope block is not fully contained
20149 in its outer scope blocks.
20151 @value{GDBN} circumvents the problem by treating the inner block as if it had
20152 the same scope as the outer block. In the error message, @var{symbol}
20153 may be shown as ``@code{(don't know)}'' if the outer block is not a
20156 @item block at @var{address} out of order
20158 The symbol information for symbol scope blocks should occur in
20159 order of increasing addresses. This error indicates that it does not
20162 @value{GDBN} does not circumvent this problem, and has trouble
20163 locating symbols in the source file whose symbols it is reading. (You
20164 can often determine what source file is affected by specifying
20165 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20168 @item bad block start address patched
20170 The symbol information for a symbol scope block has a start address
20171 smaller than the address of the preceding source line. This is known
20172 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20174 @value{GDBN} circumvents the problem by treating the symbol scope block as
20175 starting on the previous source line.
20177 @item bad string table offset in symbol @var{n}
20180 Symbol number @var{n} contains a pointer into the string table which is
20181 larger than the size of the string table.
20183 @value{GDBN} circumvents the problem by considering the symbol to have the
20184 name @code{foo}, which may cause other problems if many symbols end up
20187 @item unknown symbol type @code{0x@var{nn}}
20189 The symbol information contains new data types that @value{GDBN} does
20190 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20191 uncomprehended information, in hexadecimal.
20193 @value{GDBN} circumvents the error by ignoring this symbol information.
20194 This usually allows you to debug your program, though certain symbols
20195 are not accessible. If you encounter such a problem and feel like
20196 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20197 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20198 and examine @code{*bufp} to see the symbol.
20200 @item stub type has NULL name
20202 @value{GDBN} could not find the full definition for a struct or class.
20204 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20205 The symbol information for a C@t{++} member function is missing some
20206 information that recent versions of the compiler should have output for
20209 @item info mismatch between compiler and debugger
20211 @value{GDBN} could not parse a type specification output by the compiler.
20216 @section GDB Data Files
20218 @cindex prefix for data files
20219 @value{GDBN} will sometimes read an auxiliary data file. These files
20220 are kept in a directory known as the @dfn{data directory}.
20222 You can set the data directory's name, and view the name @value{GDBN}
20223 is currently using.
20226 @kindex set data-directory
20227 @item set data-directory @var{directory}
20228 Set the directory which @value{GDBN} searches for auxiliary data files
20229 to @var{directory}.
20231 @kindex show data-directory
20232 @item show data-directory
20233 Show the directory @value{GDBN} searches for auxiliary data files.
20236 @cindex default data directory
20237 @cindex @samp{--with-gdb-datadir}
20238 You can set the default data directory by using the configure-time
20239 @samp{--with-gdb-datadir} option. If the data directory is inside
20240 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20241 @samp{--exec-prefix}), then the default data directory will be updated
20242 automatically if the installed @value{GDBN} is moved to a new
20245 The data directory may also be specified with the
20246 @code{--data-directory} command line option.
20247 @xref{Mode Options}.
20250 @chapter Specifying a Debugging Target
20252 @cindex debugging target
20253 A @dfn{target} is the execution environment occupied by your program.
20255 Often, @value{GDBN} runs in the same host environment as your program;
20256 in that case, the debugging target is specified as a side effect when
20257 you use the @code{file} or @code{core} commands. When you need more
20258 flexibility---for example, running @value{GDBN} on a physically separate
20259 host, or controlling a standalone system over a serial port or a
20260 realtime system over a TCP/IP connection---you can use the @code{target}
20261 command to specify one of the target types configured for @value{GDBN}
20262 (@pxref{Target Commands, ,Commands for Managing Targets}).
20264 @cindex target architecture
20265 It is possible to build @value{GDBN} for several different @dfn{target
20266 architectures}. When @value{GDBN} is built like that, you can choose
20267 one of the available architectures with the @kbd{set architecture}
20271 @kindex set architecture
20272 @kindex show architecture
20273 @item set architecture @var{arch}
20274 This command sets the current target architecture to @var{arch}. The
20275 value of @var{arch} can be @code{"auto"}, in addition to one of the
20276 supported architectures.
20278 @item show architecture
20279 Show the current target architecture.
20281 @item set processor
20283 @kindex set processor
20284 @kindex show processor
20285 These are alias commands for, respectively, @code{set architecture}
20286 and @code{show architecture}.
20290 * Active Targets:: Active targets
20291 * Target Commands:: Commands for managing targets
20292 * Byte Order:: Choosing target byte order
20295 @node Active Targets
20296 @section Active Targets
20298 @cindex stacking targets
20299 @cindex active targets
20300 @cindex multiple targets
20302 There are multiple classes of targets such as: processes, executable files or
20303 recording sessions. Core files belong to the process class, making core file
20304 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20305 on multiple active targets, one in each class. This allows you to (for
20306 example) start a process and inspect its activity, while still having access to
20307 the executable file after the process finishes. Or if you start process
20308 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20309 presented a virtual layer of the recording target, while the process target
20310 remains stopped at the chronologically last point of the process execution.
20312 Use the @code{core-file} and @code{exec-file} commands to select a new core
20313 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20314 specify as a target a process that is already running, use the @code{attach}
20315 command (@pxref{Attach, ,Debugging an Already-running Process}).
20317 @node Target Commands
20318 @section Commands for Managing Targets
20321 @item target @var{type} @var{parameters}
20322 Connects the @value{GDBN} host environment to a target machine or
20323 process. A target is typically a protocol for talking to debugging
20324 facilities. You use the argument @var{type} to specify the type or
20325 protocol of the target machine.
20327 Further @var{parameters} are interpreted by the target protocol, but
20328 typically include things like device names or host names to connect
20329 with, process numbers, and baud rates.
20331 The @code{target} command does not repeat if you press @key{RET} again
20332 after executing the command.
20334 @kindex help target
20336 Displays the names of all targets available. To display targets
20337 currently selected, use either @code{info target} or @code{info files}
20338 (@pxref{Files, ,Commands to Specify Files}).
20340 @item help target @var{name}
20341 Describe a particular target, including any parameters necessary to
20344 @kindex set gnutarget
20345 @item set gnutarget @var{args}
20346 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20347 knows whether it is reading an @dfn{executable},
20348 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20349 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20350 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20353 @emph{Warning:} To specify a file format with @code{set gnutarget},
20354 you must know the actual BFD name.
20358 @xref{Files, , Commands to Specify Files}.
20360 @kindex show gnutarget
20361 @item show gnutarget
20362 Use the @code{show gnutarget} command to display what file format
20363 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20364 @value{GDBN} will determine the file format for each file automatically,
20365 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20368 @cindex common targets
20369 Here are some common targets (available, or not, depending on the GDB
20374 @item target exec @var{program}
20375 @cindex executable file target
20376 An executable file. @samp{target exec @var{program}} is the same as
20377 @samp{exec-file @var{program}}.
20379 @item target core @var{filename}
20380 @cindex core dump file target
20381 A core dump file. @samp{target core @var{filename}} is the same as
20382 @samp{core-file @var{filename}}.
20384 @item target remote @var{medium}
20385 @cindex remote target
20386 A remote system connected to @value{GDBN} via a serial line or network
20387 connection. This command tells @value{GDBN} to use its own remote
20388 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20390 For example, if you have a board connected to @file{/dev/ttya} on the
20391 machine running @value{GDBN}, you could say:
20394 target remote /dev/ttya
20397 @code{target remote} supports the @code{load} command. This is only
20398 useful if you have some other way of getting the stub to the target
20399 system, and you can put it somewhere in memory where it won't get
20400 clobbered by the download.
20402 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20403 @cindex built-in simulator target
20404 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20412 works; however, you cannot assume that a specific memory map, device
20413 drivers, or even basic I/O is available, although some simulators do
20414 provide these. For info about any processor-specific simulator details,
20415 see the appropriate section in @ref{Embedded Processors, ,Embedded
20418 @item target native
20419 @cindex native target
20420 Setup for local/native process debugging. Useful to make the
20421 @code{run} command spawn native processes (likewise @code{attach},
20422 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20423 (@pxref{set auto-connect-native-target}).
20427 Different targets are available on different configurations of @value{GDBN};
20428 your configuration may have more or fewer targets.
20430 Many remote targets require you to download the executable's code once
20431 you've successfully established a connection. You may wish to control
20432 various aspects of this process.
20437 @kindex set hash@r{, for remote monitors}
20438 @cindex hash mark while downloading
20439 This command controls whether a hash mark @samp{#} is displayed while
20440 downloading a file to the remote monitor. If on, a hash mark is
20441 displayed after each S-record is successfully downloaded to the
20445 @kindex show hash@r{, for remote monitors}
20446 Show the current status of displaying the hash mark.
20448 @item set debug monitor
20449 @kindex set debug monitor
20450 @cindex display remote monitor communications
20451 Enable or disable display of communications messages between
20452 @value{GDBN} and the remote monitor.
20454 @item show debug monitor
20455 @kindex show debug monitor
20456 Show the current status of displaying communications between
20457 @value{GDBN} and the remote monitor.
20462 @kindex load @var{filename} @var{offset}
20463 @item load @var{filename} @var{offset}
20465 Depending on what remote debugging facilities are configured into
20466 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20467 is meant to make @var{filename} (an executable) available for debugging
20468 on the remote system---by downloading, or dynamic linking, for example.
20469 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20470 the @code{add-symbol-file} command.
20472 If your @value{GDBN} does not have a @code{load} command, attempting to
20473 execute it gets the error message ``@code{You can't do that when your
20474 target is @dots{}}''
20476 The file is loaded at whatever address is specified in the executable.
20477 For some object file formats, you can specify the load address when you
20478 link the program; for other formats, like a.out, the object file format
20479 specifies a fixed address.
20480 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20482 It is also possible to tell @value{GDBN} to load the executable file at a
20483 specific offset described by the optional argument @var{offset}. When
20484 @var{offset} is provided, @var{filename} must also be provided.
20486 Depending on the remote side capabilities, @value{GDBN} may be able to
20487 load programs into flash memory.
20489 @code{load} does not repeat if you press @key{RET} again after using it.
20494 @kindex flash-erase
20496 @anchor{flash-erase}
20498 Erases all known flash memory regions on the target.
20503 @section Choosing Target Byte Order
20505 @cindex choosing target byte order
20506 @cindex target byte order
20508 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20509 offer the ability to run either big-endian or little-endian byte
20510 orders. Usually the executable or symbol will include a bit to
20511 designate the endian-ness, and you will not need to worry about
20512 which to use. However, you may still find it useful to adjust
20513 @value{GDBN}'s idea of processor endian-ness manually.
20517 @item set endian big
20518 Instruct @value{GDBN} to assume the target is big-endian.
20520 @item set endian little
20521 Instruct @value{GDBN} to assume the target is little-endian.
20523 @item set endian auto
20524 Instruct @value{GDBN} to use the byte order associated with the
20528 Display @value{GDBN}'s current idea of the target byte order.
20532 If the @code{set endian auto} mode is in effect and no executable has
20533 been selected, then the endianness used is the last one chosen either
20534 by one of the @code{set endian big} and @code{set endian little}
20535 commands or by inferring from the last executable used. If no
20536 endianness has been previously chosen, then the default for this mode
20537 is inferred from the target @value{GDBN} has been built for, and is
20538 @code{little} if the name of the target CPU has an @code{el} suffix
20539 and @code{big} otherwise.
20541 Note that these commands merely adjust interpretation of symbolic
20542 data on the host, and that they have absolutely no effect on the
20546 @node Remote Debugging
20547 @chapter Debugging Remote Programs
20548 @cindex remote debugging
20550 If you are trying to debug a program running on a machine that cannot run
20551 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20552 For example, you might use remote debugging on an operating system kernel,
20553 or on a small system which does not have a general purpose operating system
20554 powerful enough to run a full-featured debugger.
20556 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20557 to make this work with particular debugging targets. In addition,
20558 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20559 but not specific to any particular target system) which you can use if you
20560 write the remote stubs---the code that runs on the remote system to
20561 communicate with @value{GDBN}.
20563 Other remote targets may be available in your
20564 configuration of @value{GDBN}; use @code{help target} to list them.
20567 * Connecting:: Connecting to a remote target
20568 * File Transfer:: Sending files to a remote system
20569 * Server:: Using the gdbserver program
20570 * Remote Configuration:: Remote configuration
20571 * Remote Stub:: Implementing a remote stub
20575 @section Connecting to a Remote Target
20576 @cindex remote debugging, connecting
20577 @cindex @code{gdbserver}, connecting
20578 @cindex remote debugging, types of connections
20579 @cindex @code{gdbserver}, types of connections
20580 @cindex @code{gdbserver}, @code{target remote} mode
20581 @cindex @code{gdbserver}, @code{target extended-remote} mode
20583 This section describes how to connect to a remote target, including the
20584 types of connections and their differences, how to set up executable and
20585 symbol files on the host and target, and the commands used for
20586 connecting to and disconnecting from the remote target.
20588 @subsection Types of Remote Connections
20590 @value{GDBN} supports two types of remote connections, @code{target remote}
20591 mode and @code{target extended-remote} mode. Note that many remote targets
20592 support only @code{target remote} mode. There are several major
20593 differences between the two types of connections, enumerated here:
20597 @cindex remote debugging, detach and program exit
20598 @item Result of detach or program exit
20599 @strong{With target remote mode:} When the debugged program exits or you
20600 detach from it, @value{GDBN} disconnects from the target. When using
20601 @code{gdbserver}, @code{gdbserver} will exit.
20603 @strong{With target extended-remote mode:} When the debugged program exits or
20604 you detach from it, @value{GDBN} remains connected to the target, even
20605 though no program is running. You can rerun the program, attach to a
20606 running program, or use @code{monitor} commands specific to the target.
20608 When using @code{gdbserver} in this case, it does not exit unless it was
20609 invoked using the @option{--once} option. If the @option{--once} option
20610 was not used, you can ask @code{gdbserver} to exit using the
20611 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20613 @item Specifying the program to debug
20614 For both connection types you use the @code{file} command to specify the
20615 program on the host system. If you are using @code{gdbserver} there are
20616 some differences in how to specify the location of the program on the
20619 @strong{With target remote mode:} You must either specify the program to debug
20620 on the @code{gdbserver} command line or use the @option{--attach} option
20621 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20623 @cindex @option{--multi}, @code{gdbserver} option
20624 @strong{With target extended-remote mode:} You may specify the program to debug
20625 on the @code{gdbserver} command line, or you can load the program or attach
20626 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20628 @anchor{--multi Option in Types of Remote Connnections}
20629 You can start @code{gdbserver} without supplying an initial command to run
20630 or process ID to attach. To do this, use the @option{--multi} command line
20631 option. Then you can connect using @code{target extended-remote} and start
20632 the program you want to debug (see below for details on using the
20633 @code{run} command in this scenario). Note that the conditions under which
20634 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20635 (@code{target remote} or @code{target extended-remote}). The
20636 @option{--multi} option to @code{gdbserver} has no influence on that.
20638 @item The @code{run} command
20639 @strong{With target remote mode:} The @code{run} command is not
20640 supported. Once a connection has been established, you can use all
20641 the usual @value{GDBN} commands to examine and change data. The
20642 remote program is already running, so you can use commands like
20643 @kbd{step} and @kbd{continue}.
20645 @strong{With target extended-remote mode:} The @code{run} command is
20646 supported. The @code{run} command uses the value set by
20647 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20648 the program to run. Command line arguments are supported, except for
20649 wildcard expansion and I/O redirection (@pxref{Arguments}).
20651 If you specify the program to debug on the command line, then the
20652 @code{run} command is not required to start execution, and you can
20653 resume using commands like @kbd{step} and @kbd{continue} as with
20654 @code{target remote} mode.
20656 @anchor{Attaching in Types of Remote Connections}
20658 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20659 not supported. To attach to a running program using @code{gdbserver}, you
20660 must use the @option{--attach} option (@pxref{Running gdbserver}).
20662 @strong{With target extended-remote mode:} To attach to a running program,
20663 you may use the @code{attach} command after the connection has been
20664 established. If you are using @code{gdbserver}, you may also invoke
20665 @code{gdbserver} using the @option{--attach} option
20666 (@pxref{Running gdbserver}).
20670 @anchor{Host and target files}
20671 @subsection Host and Target Files
20672 @cindex remote debugging, symbol files
20673 @cindex symbol files, remote debugging
20675 @value{GDBN}, running on the host, needs access to symbol and debugging
20676 information for your program running on the target. This requires
20677 access to an unstripped copy of your program, and possibly any associated
20678 symbol files. Note that this section applies equally to both @code{target
20679 remote} mode and @code{target extended-remote} mode.
20681 Some remote targets (@pxref{qXfer executable filename read}, and
20682 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20683 the same connection used to communicate with @value{GDBN}. With such a
20684 target, if the remote program is unstripped, the only command you need is
20685 @code{target remote} (or @code{target extended-remote}).
20687 If the remote program is stripped, or the target does not support remote
20688 program file access, start up @value{GDBN} using the name of the local
20689 unstripped copy of your program as the first argument, or use the
20690 @code{file} command. Use @code{set sysroot} to specify the location (on
20691 the host) of target libraries (unless your @value{GDBN} was compiled with
20692 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20693 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20696 The symbol file and target libraries must exactly match the executable
20697 and libraries on the target, with one exception: the files on the host
20698 system should not be stripped, even if the files on the target system
20699 are. Mismatched or missing files will lead to confusing results
20700 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20701 files may also prevent @code{gdbserver} from debugging multi-threaded
20704 @subsection Remote Connection Commands
20705 @cindex remote connection commands
20706 @value{GDBN} can communicate with the target over a serial line, or
20707 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20708 each case, @value{GDBN} uses the same protocol for debugging your
20709 program; only the medium carrying the debugging packets varies. The
20710 @code{target remote} and @code{target extended-remote} commands
20711 establish a connection to the target. Both commands accept the same
20712 arguments, which indicate the medium to use:
20716 @item target remote @var{serial-device}
20717 @itemx target extended-remote @var{serial-device}
20718 @cindex serial line, @code{target remote}
20719 Use @var{serial-device} to communicate with the target. For example,
20720 to use a serial line connected to the device named @file{/dev/ttyb}:
20723 target remote /dev/ttyb
20726 If you're using a serial line, you may want to give @value{GDBN} the
20727 @samp{--baud} option, or use the @code{set serial baud} command
20728 (@pxref{Remote Configuration, set serial baud}) before the
20729 @code{target} command.
20731 @item target remote @code{@var{host}:@var{port}}
20732 @itemx target remote @code{@var{[host]}:@var{port}}
20733 @itemx target remote @code{tcp:@var{host}:@var{port}}
20734 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20735 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20736 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20737 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20738 @itemx target extended-remote @code{@var{host}:@var{port}}
20739 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20740 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20741 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20742 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20743 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20744 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20745 @cindex @acronym{TCP} port, @code{target remote}
20746 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20747 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20748 address, or a numeric @acronym{IPv6} address (with or without the
20749 square brackets to separate the address from the port); @var{port}
20750 must be a decimal number. The @var{host} could be the target machine
20751 itself, if it is directly connected to the net, or it might be a
20752 terminal server which in turn has a serial line to the target.
20754 For example, to connect to port 2828 on a terminal server named
20758 target remote manyfarms:2828
20761 To connect to port 2828 on a terminal server whose address is
20762 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20763 square bracket syntax:
20766 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
20770 or explicitly specify the @acronym{IPv6} protocol:
20773 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
20776 This last example may be confusing to the reader, because there is no
20777 visible separation between the hostname and the port number.
20778 Therefore, we recommend the user to provide @acronym{IPv6} addresses
20779 using square brackets for clarity. However, it is important to
20780 mention that for @value{GDBN} there is no ambiguity: the number after
20781 the last colon is considered to be the port number.
20783 If your remote target is actually running on the same machine as your
20784 debugger session (e.g.@: a simulator for your target running on the
20785 same host), you can omit the hostname. For example, to connect to
20786 port 1234 on your local machine:
20789 target remote :1234
20793 Note that the colon is still required here.
20795 @item target remote @code{udp:@var{host}:@var{port}}
20796 @itemx target remote @code{udp:@var{[host]}:@var{port}}
20797 @itemx target remote @code{udp4:@var{host}:@var{port}}
20798 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
20799 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20800 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20801 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
20802 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
20803 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
20804 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
20805 @cindex @acronym{UDP} port, @code{target remote}
20806 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20807 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20810 target remote udp:manyfarms:2828
20813 When using a @acronym{UDP} connection for remote debugging, you should
20814 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20815 can silently drop packets on busy or unreliable networks, which will
20816 cause havoc with your debugging session.
20818 @item target remote | @var{command}
20819 @itemx target extended-remote | @var{command}
20820 @cindex pipe, @code{target remote} to
20821 Run @var{command} in the background and communicate with it using a
20822 pipe. The @var{command} is a shell command, to be parsed and expanded
20823 by the system's command shell, @code{/bin/sh}; it should expect remote
20824 protocol packets on its standard input, and send replies on its
20825 standard output. You could use this to run a stand-alone simulator
20826 that speaks the remote debugging protocol, to make net connections
20827 using programs like @code{ssh}, or for other similar tricks.
20829 If @var{command} closes its standard output (perhaps by exiting),
20830 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20831 program has already exited, this will have no effect.)
20835 @cindex interrupting remote programs
20836 @cindex remote programs, interrupting
20837 Whenever @value{GDBN} is waiting for the remote program, if you type the
20838 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20839 program. This may or may not succeed, depending in part on the hardware
20840 and the serial drivers the remote system uses. If you type the
20841 interrupt character once again, @value{GDBN} displays this prompt:
20844 Interrupted while waiting for the program.
20845 Give up (and stop debugging it)? (y or n)
20848 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20849 the remote debugging session. (If you decide you want to try again later,
20850 you can use @kbd{target remote} again to connect once more.) If you type
20851 @kbd{n}, @value{GDBN} goes back to waiting.
20853 In @code{target extended-remote} mode, typing @kbd{n} will leave
20854 @value{GDBN} connected to the target.
20857 @kindex detach (remote)
20859 When you have finished debugging the remote program, you can use the
20860 @code{detach} command to release it from @value{GDBN} control.
20861 Detaching from the target normally resumes its execution, but the results
20862 will depend on your particular remote stub. After the @code{detach}
20863 command in @code{target remote} mode, @value{GDBN} is free to connect to
20864 another target. In @code{target extended-remote} mode, @value{GDBN} is
20865 still connected to the target.
20869 The @code{disconnect} command closes the connection to the target, and
20870 the target is generally not resumed. It will wait for @value{GDBN}
20871 (this instance or another one) to connect and continue debugging. After
20872 the @code{disconnect} command, @value{GDBN} is again free to connect to
20875 @cindex send command to remote monitor
20876 @cindex extend @value{GDBN} for remote targets
20877 @cindex add new commands for external monitor
20879 @item monitor @var{cmd}
20880 This command allows you to send arbitrary commands directly to the
20881 remote monitor. Since @value{GDBN} doesn't care about the commands it
20882 sends like this, this command is the way to extend @value{GDBN}---you
20883 can add new commands that only the external monitor will understand
20887 @node File Transfer
20888 @section Sending files to a remote system
20889 @cindex remote target, file transfer
20890 @cindex file transfer
20891 @cindex sending files to remote systems
20893 Some remote targets offer the ability to transfer files over the same
20894 connection used to communicate with @value{GDBN}. This is convenient
20895 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20896 running @code{gdbserver} over a network interface. For other targets,
20897 e.g.@: embedded devices with only a single serial port, this may be
20898 the only way to upload or download files.
20900 Not all remote targets support these commands.
20904 @item remote put @var{hostfile} @var{targetfile}
20905 Copy file @var{hostfile} from the host system (the machine running
20906 @value{GDBN}) to @var{targetfile} on the target system.
20909 @item remote get @var{targetfile} @var{hostfile}
20910 Copy file @var{targetfile} from the target system to @var{hostfile}
20911 on the host system.
20913 @kindex remote delete
20914 @item remote delete @var{targetfile}
20915 Delete @var{targetfile} from the target system.
20920 @section Using the @code{gdbserver} Program
20923 @cindex remote connection without stubs
20924 @code{gdbserver} is a control program for Unix-like systems, which
20925 allows you to connect your program with a remote @value{GDBN} via
20926 @code{target remote} or @code{target extended-remote}---but without
20927 linking in the usual debugging stub.
20929 @code{gdbserver} is not a complete replacement for the debugging stubs,
20930 because it requires essentially the same operating-system facilities
20931 that @value{GDBN} itself does. In fact, a system that can run
20932 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20933 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20934 because it is a much smaller program than @value{GDBN} itself. It is
20935 also easier to port than all of @value{GDBN}, so you may be able to get
20936 started more quickly on a new system by using @code{gdbserver}.
20937 Finally, if you develop code for real-time systems, you may find that
20938 the tradeoffs involved in real-time operation make it more convenient to
20939 do as much development work as possible on another system, for example
20940 by cross-compiling. You can use @code{gdbserver} to make a similar
20941 choice for debugging.
20943 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20944 or a TCP connection, using the standard @value{GDBN} remote serial
20948 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20949 Do not run @code{gdbserver} connected to any public network; a
20950 @value{GDBN} connection to @code{gdbserver} provides access to the
20951 target system with the same privileges as the user running
20955 @anchor{Running gdbserver}
20956 @subsection Running @code{gdbserver}
20957 @cindex arguments, to @code{gdbserver}
20958 @cindex @code{gdbserver}, command-line arguments
20960 Run @code{gdbserver} on the target system. You need a copy of the
20961 program you want to debug, including any libraries it requires.
20962 @code{gdbserver} does not need your program's symbol table, so you can
20963 strip the program if necessary to save space. @value{GDBN} on the host
20964 system does all the symbol handling.
20966 To use the server, you must tell it how to communicate with @value{GDBN};
20967 the name of your program; and the arguments for your program. The usual
20971 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20974 @var{comm} is either a device name (to use a serial line), or a TCP
20975 hostname and portnumber, or @code{-} or @code{stdio} to use
20976 stdin/stdout of @code{gdbserver}.
20977 For example, to debug Emacs with the argument
20978 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20982 target> gdbserver /dev/com1 emacs foo.txt
20985 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20988 To use a TCP connection instead of a serial line:
20991 target> gdbserver host:2345 emacs foo.txt
20994 The only difference from the previous example is the first argument,
20995 specifying that you are communicating with the host @value{GDBN} via
20996 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20997 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20998 (Currently, the @samp{host} part is ignored.) You can choose any number
20999 you want for the port number as long as it does not conflict with any
21000 TCP ports already in use on the target system (for example, @code{23} is
21001 reserved for @code{telnet}).@footnote{If you choose a port number that
21002 conflicts with another service, @code{gdbserver} prints an error message
21003 and exits.} You must use the same port number with the host @value{GDBN}
21004 @code{target remote} command.
21006 The @code{stdio} connection is useful when starting @code{gdbserver}
21010 (gdb) target remote | ssh -T hostname gdbserver - hello
21013 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21014 and we don't want escape-character handling. Ssh does this by default when
21015 a command is provided, the flag is provided to make it explicit.
21016 You could elide it if you want to.
21018 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21019 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21020 display through a pipe connected to gdbserver.
21021 Both @code{stdout} and @code{stderr} use the same pipe.
21023 @anchor{Attaching to a program}
21024 @subsubsection Attaching to a Running Program
21025 @cindex attach to a program, @code{gdbserver}
21026 @cindex @option{--attach}, @code{gdbserver} option
21028 On some targets, @code{gdbserver} can also attach to running programs.
21029 This is accomplished via the @code{--attach} argument. The syntax is:
21032 target> gdbserver --attach @var{comm} @var{pid}
21035 @var{pid} is the process ID of a currently running process. It isn't
21036 necessary to point @code{gdbserver} at a binary for the running process.
21038 In @code{target extended-remote} mode, you can also attach using the
21039 @value{GDBN} attach command
21040 (@pxref{Attaching in Types of Remote Connections}).
21043 You can debug processes by name instead of process ID if your target has the
21044 @code{pidof} utility:
21047 target> gdbserver --attach @var{comm} `pidof @var{program}`
21050 In case more than one copy of @var{program} is running, or @var{program}
21051 has multiple threads, most versions of @code{pidof} support the
21052 @code{-s} option to only return the first process ID.
21054 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21056 This section applies only when @code{gdbserver} is run to listen on a TCP
21059 @code{gdbserver} normally terminates after all of its debugged processes have
21060 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21061 extended-remote}, @code{gdbserver} stays running even with no processes left.
21062 @value{GDBN} normally terminates the spawned debugged process on its exit,
21063 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21064 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21065 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21066 stays running even in the @kbd{target remote} mode.
21068 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21069 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21070 completeness, at most one @value{GDBN} can be connected at a time.
21072 @cindex @option{--once}, @code{gdbserver} option
21073 By default, @code{gdbserver} keeps the listening TCP port open, so that
21074 subsequent connections are possible. However, if you start @code{gdbserver}
21075 with the @option{--once} option, it will stop listening for any further
21076 connection attempts after connecting to the first @value{GDBN} session. This
21077 means no further connections to @code{gdbserver} will be possible after the
21078 first one. It also means @code{gdbserver} will terminate after the first
21079 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21080 connections and even in the @kbd{target extended-remote} mode. The
21081 @option{--once} option allows reusing the same port number for connecting to
21082 multiple instances of @code{gdbserver} running on the same host, since each
21083 instance closes its port after the first connection.
21085 @anchor{Other Command-Line Arguments for gdbserver}
21086 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21088 You can use the @option{--multi} option to start @code{gdbserver} without
21089 specifying a program to debug or a process to attach to. Then you can
21090 attach in @code{target extended-remote} mode and run or attach to a
21091 program. For more information,
21092 @pxref{--multi Option in Types of Remote Connnections}.
21094 @cindex @option{--debug}, @code{gdbserver} option
21095 The @option{--debug} option tells @code{gdbserver} to display extra
21096 status information about the debugging process.
21097 @cindex @option{--remote-debug}, @code{gdbserver} option
21098 The @option{--remote-debug} option tells @code{gdbserver} to display
21099 remote protocol debug output. These options are intended for
21100 @code{gdbserver} development and for bug reports to the developers.
21102 @cindex @option{--debug-format}, @code{gdbserver} option
21103 The @option{--debug-format=option1[,option2,...]} option tells
21104 @code{gdbserver} to include additional information in each output.
21105 Possible options are:
21109 Turn off all extra information in debugging output.
21111 Turn on all extra information in debugging output.
21113 Include a timestamp in each line of debugging output.
21116 Options are processed in order. Thus, for example, if @option{none}
21117 appears last then no additional information is added to debugging output.
21119 @cindex @option{--wrapper}, @code{gdbserver} option
21120 The @option{--wrapper} option specifies a wrapper to launch programs
21121 for debugging. The option should be followed by the name of the
21122 wrapper, then any command-line arguments to pass to the wrapper, then
21123 @kbd{--} indicating the end of the wrapper arguments.
21125 @code{gdbserver} runs the specified wrapper program with a combined
21126 command line including the wrapper arguments, then the name of the
21127 program to debug, then any arguments to the program. The wrapper
21128 runs until it executes your program, and then @value{GDBN} gains control.
21130 You can use any program that eventually calls @code{execve} with
21131 its arguments as a wrapper. Several standard Unix utilities do
21132 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21133 with @code{exec "$@@"} will also work.
21135 For example, you can use @code{env} to pass an environment variable to
21136 the debugged program, without setting the variable in @code{gdbserver}'s
21140 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21143 @cindex @option{--selftest}
21144 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21147 $ gdbserver --selftest
21148 Ran 2 unit tests, 0 failed
21151 These tests are disabled in release.
21152 @subsection Connecting to @code{gdbserver}
21154 The basic procedure for connecting to the remote target is:
21158 Run @value{GDBN} on the host system.
21161 Make sure you have the necessary symbol files
21162 (@pxref{Host and target files}).
21163 Load symbols for your application using the @code{file} command before you
21164 connect. Use @code{set sysroot} to locate target libraries (unless your
21165 @value{GDBN} was compiled with the correct sysroot using
21166 @code{--with-sysroot}).
21169 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21170 For TCP connections, you must start up @code{gdbserver} prior to using
21171 the @code{target} command. Otherwise you may get an error whose
21172 text depends on the host system, but which usually looks something like
21173 @samp{Connection refused}. Don't use the @code{load}
21174 command in @value{GDBN} when using @code{target remote} mode, since the
21175 program is already on the target.
21179 @anchor{Monitor Commands for gdbserver}
21180 @subsection Monitor Commands for @code{gdbserver}
21181 @cindex monitor commands, for @code{gdbserver}
21183 During a @value{GDBN} session using @code{gdbserver}, you can use the
21184 @code{monitor} command to send special requests to @code{gdbserver}.
21185 Here are the available commands.
21189 List the available monitor commands.
21191 @item monitor set debug 0
21192 @itemx monitor set debug 1
21193 Disable or enable general debugging messages.
21195 @item monitor set remote-debug 0
21196 @itemx monitor set remote-debug 1
21197 Disable or enable specific debugging messages associated with the remote
21198 protocol (@pxref{Remote Protocol}).
21200 @item monitor set debug-format option1@r{[},option2,...@r{]}
21201 Specify additional text to add to debugging messages.
21202 Possible options are:
21206 Turn off all extra information in debugging output.
21208 Turn on all extra information in debugging output.
21210 Include a timestamp in each line of debugging output.
21213 Options are processed in order. Thus, for example, if @option{none}
21214 appears last then no additional information is added to debugging output.
21216 @item monitor set libthread-db-search-path [PATH]
21217 @cindex gdbserver, search path for @code{libthread_db}
21218 When this command is issued, @var{path} is a colon-separated list of
21219 directories to search for @code{libthread_db} (@pxref{Threads,,set
21220 libthread-db-search-path}). If you omit @var{path},
21221 @samp{libthread-db-search-path} will be reset to its default value.
21223 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21224 not supported in @code{gdbserver}.
21227 Tell gdbserver to exit immediately. This command should be followed by
21228 @code{disconnect} to close the debugging session. @code{gdbserver} will
21229 detach from any attached processes and kill any processes it created.
21230 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21231 of a multi-process mode debug session.
21235 @subsection Tracepoints support in @code{gdbserver}
21236 @cindex tracepoints support in @code{gdbserver}
21238 On some targets, @code{gdbserver} supports tracepoints, fast
21239 tracepoints and static tracepoints.
21241 For fast or static tracepoints to work, a special library called the
21242 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21243 This library is built and distributed as an integral part of
21244 @code{gdbserver}. In addition, support for static tracepoints
21245 requires building the in-process agent library with static tracepoints
21246 support. At present, the UST (LTTng Userspace Tracer,
21247 @url{http://lttng.org/ust}) tracing engine is supported. This support
21248 is automatically available if UST development headers are found in the
21249 standard include path when @code{gdbserver} is built, or if
21250 @code{gdbserver} was explicitly configured using @option{--with-ust}
21251 to point at such headers. You can explicitly disable the support
21252 using @option{--with-ust=no}.
21254 There are several ways to load the in-process agent in your program:
21257 @item Specifying it as dependency at link time
21259 You can link your program dynamically with the in-process agent
21260 library. On most systems, this is accomplished by adding
21261 @code{-linproctrace} to the link command.
21263 @item Using the system's preloading mechanisms
21265 You can force loading the in-process agent at startup time by using
21266 your system's support for preloading shared libraries. Many Unixes
21267 support the concept of preloading user defined libraries. In most
21268 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21269 in the environment. See also the description of @code{gdbserver}'s
21270 @option{--wrapper} command line option.
21272 @item Using @value{GDBN} to force loading the agent at run time
21274 On some systems, you can force the inferior to load a shared library,
21275 by calling a dynamic loader function in the inferior that takes care
21276 of dynamically looking up and loading a shared library. On most Unix
21277 systems, the function is @code{dlopen}. You'll use the @code{call}
21278 command for that. For example:
21281 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21284 Note that on most Unix systems, for the @code{dlopen} function to be
21285 available, the program needs to be linked with @code{-ldl}.
21288 On systems that have a userspace dynamic loader, like most Unix
21289 systems, when you connect to @code{gdbserver} using @code{target
21290 remote}, you'll find that the program is stopped at the dynamic
21291 loader's entry point, and no shared library has been loaded in the
21292 program's address space yet, including the in-process agent. In that
21293 case, before being able to use any of the fast or static tracepoints
21294 features, you need to let the loader run and load the shared
21295 libraries. The simplest way to do that is to run the program to the
21296 main procedure. E.g., if debugging a C or C@t{++} program, start
21297 @code{gdbserver} like so:
21300 $ gdbserver :9999 myprogram
21303 Start GDB and connect to @code{gdbserver} like so, and run to main:
21307 (@value{GDBP}) target remote myhost:9999
21308 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21309 (@value{GDBP}) b main
21310 (@value{GDBP}) continue
21313 The in-process tracing agent library should now be loaded into the
21314 process; you can confirm it with the @code{info sharedlibrary}
21315 command, which will list @file{libinproctrace.so} as loaded in the
21316 process. You are now ready to install fast tracepoints, list static
21317 tracepoint markers, probe static tracepoints markers, and start
21320 @node Remote Configuration
21321 @section Remote Configuration
21324 @kindex show remote
21325 This section documents the configuration options available when
21326 debugging remote programs. For the options related to the File I/O
21327 extensions of the remote protocol, see @ref{system,
21328 system-call-allowed}.
21331 @item set remoteaddresssize @var{bits}
21332 @cindex address size for remote targets
21333 @cindex bits in remote address
21334 Set the maximum size of address in a memory packet to the specified
21335 number of bits. @value{GDBN} will mask off the address bits above
21336 that number, when it passes addresses to the remote target. The
21337 default value is the number of bits in the target's address.
21339 @item show remoteaddresssize
21340 Show the current value of remote address size in bits.
21342 @item set serial baud @var{n}
21343 @cindex baud rate for remote targets
21344 Set the baud rate for the remote serial I/O to @var{n} baud. The
21345 value is used to set the speed of the serial port used for debugging
21348 @item show serial baud
21349 Show the current speed of the remote connection.
21351 @item set serial parity @var{parity}
21352 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21353 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21355 @item show serial parity
21356 Show the current parity of the serial port.
21358 @item set remotebreak
21359 @cindex interrupt remote programs
21360 @cindex BREAK signal instead of Ctrl-C
21361 @anchor{set remotebreak}
21362 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21363 when you type @kbd{Ctrl-c} to interrupt the program running
21364 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21365 character instead. The default is off, since most remote systems
21366 expect to see @samp{Ctrl-C} as the interrupt signal.
21368 @item show remotebreak
21369 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21370 interrupt the remote program.
21372 @item set remoteflow on
21373 @itemx set remoteflow off
21374 @kindex set remoteflow
21375 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21376 on the serial port used to communicate to the remote target.
21378 @item show remoteflow
21379 @kindex show remoteflow
21380 Show the current setting of hardware flow control.
21382 @item set remotelogbase @var{base}
21383 Set the base (a.k.a.@: radix) of logging serial protocol
21384 communications to @var{base}. Supported values of @var{base} are:
21385 @code{ascii}, @code{octal}, and @code{hex}. The default is
21388 @item show remotelogbase
21389 Show the current setting of the radix for logging remote serial
21392 @item set remotelogfile @var{file}
21393 @cindex record serial communications on file
21394 Record remote serial communications on the named @var{file}. The
21395 default is not to record at all.
21397 @item show remotelogfile.
21398 Show the current setting of the file name on which to record the
21399 serial communications.
21401 @item set remotetimeout @var{num}
21402 @cindex timeout for serial communications
21403 @cindex remote timeout
21404 Set the timeout limit to wait for the remote target to respond to
21405 @var{num} seconds. The default is 2 seconds.
21407 @item show remotetimeout
21408 Show the current number of seconds to wait for the remote target
21411 @cindex limit hardware breakpoints and watchpoints
21412 @cindex remote target, limit break- and watchpoints
21413 @anchor{set remote hardware-watchpoint-limit}
21414 @anchor{set remote hardware-breakpoint-limit}
21415 @item set remote hardware-watchpoint-limit @var{limit}
21416 @itemx set remote hardware-breakpoint-limit @var{limit}
21417 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21418 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21419 watchpoints or breakpoints, and @code{unlimited} for unlimited
21420 watchpoints or breakpoints.
21422 @item show remote hardware-watchpoint-limit
21423 @itemx show remote hardware-breakpoint-limit
21424 Show the current limit for the number of hardware watchpoints or
21425 breakpoints that @value{GDBN} can use.
21427 @cindex limit hardware watchpoints length
21428 @cindex remote target, limit watchpoints length
21429 @anchor{set remote hardware-watchpoint-length-limit}
21430 @item set remote hardware-watchpoint-length-limit @var{limit}
21431 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21432 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21433 hardware watchpoints and @code{unlimited} allows watchpoints of any
21436 @item show remote hardware-watchpoint-length-limit
21437 Show the current limit (in bytes) of the maximum length of
21438 a remote hardware watchpoint.
21440 @item set remote exec-file @var{filename}
21441 @itemx show remote exec-file
21442 @anchor{set remote exec-file}
21443 @cindex executable file, for remote target
21444 Select the file used for @code{run} with @code{target
21445 extended-remote}. This should be set to a filename valid on the
21446 target system. If it is not set, the target will use a default
21447 filename (e.g.@: the last program run).
21449 @item set remote interrupt-sequence
21450 @cindex interrupt remote programs
21451 @cindex select Ctrl-C, BREAK or BREAK-g
21452 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21453 @samp{BREAK-g} as the
21454 sequence to the remote target in order to interrupt the execution.
21455 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21456 is high level of serial line for some certain time.
21457 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21458 It is @code{BREAK} signal followed by character @code{g}.
21460 @item show interrupt-sequence
21461 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21462 is sent by @value{GDBN} to interrupt the remote program.
21463 @code{BREAK-g} is BREAK signal followed by @code{g} and
21464 also known as Magic SysRq g.
21466 @item set remote interrupt-on-connect
21467 @cindex send interrupt-sequence on start
21468 Specify whether interrupt-sequence is sent to remote target when
21469 @value{GDBN} connects to it. This is mostly needed when you debug
21470 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21471 which is known as Magic SysRq g in order to connect @value{GDBN}.
21473 @item show interrupt-on-connect
21474 Show whether interrupt-sequence is sent
21475 to remote target when @value{GDBN} connects to it.
21479 @item set tcp auto-retry on
21480 @cindex auto-retry, for remote TCP target
21481 Enable auto-retry for remote TCP connections. This is useful if the remote
21482 debugging agent is launched in parallel with @value{GDBN}; there is a race
21483 condition because the agent may not become ready to accept the connection
21484 before @value{GDBN} attempts to connect. When auto-retry is
21485 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21486 to establish the connection using the timeout specified by
21487 @code{set tcp connect-timeout}.
21489 @item set tcp auto-retry off
21490 Do not auto-retry failed TCP connections.
21492 @item show tcp auto-retry
21493 Show the current auto-retry setting.
21495 @item set tcp connect-timeout @var{seconds}
21496 @itemx set tcp connect-timeout unlimited
21497 @cindex connection timeout, for remote TCP target
21498 @cindex timeout, for remote target connection
21499 Set the timeout for establishing a TCP connection to the remote target to
21500 @var{seconds}. The timeout affects both polling to retry failed connections
21501 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21502 that are merely slow to complete, and represents an approximate cumulative
21503 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21504 @value{GDBN} will keep attempting to establish a connection forever,
21505 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21507 @item show tcp connect-timeout
21508 Show the current connection timeout setting.
21511 @cindex remote packets, enabling and disabling
21512 The @value{GDBN} remote protocol autodetects the packets supported by
21513 your debugging stub. If you need to override the autodetection, you
21514 can use these commands to enable or disable individual packets. Each
21515 packet can be set to @samp{on} (the remote target supports this
21516 packet), @samp{off} (the remote target does not support this packet),
21517 or @samp{auto} (detect remote target support for this packet). They
21518 all default to @samp{auto}. For more information about each packet,
21519 see @ref{Remote Protocol}.
21521 During normal use, you should not have to use any of these commands.
21522 If you do, that may be a bug in your remote debugging stub, or a bug
21523 in @value{GDBN}. You may want to report the problem to the
21524 @value{GDBN} developers.
21526 For each packet @var{name}, the command to enable or disable the
21527 packet is @code{set remote @var{name}-packet}. The available settings
21530 @multitable @columnfractions 0.28 0.32 0.25
21533 @tab Related Features
21535 @item @code{fetch-register}
21537 @tab @code{info registers}
21539 @item @code{set-register}
21543 @item @code{binary-download}
21545 @tab @code{load}, @code{set}
21547 @item @code{read-aux-vector}
21548 @tab @code{qXfer:auxv:read}
21549 @tab @code{info auxv}
21551 @item @code{symbol-lookup}
21552 @tab @code{qSymbol}
21553 @tab Detecting multiple threads
21555 @item @code{attach}
21556 @tab @code{vAttach}
21559 @item @code{verbose-resume}
21561 @tab Stepping or resuming multiple threads
21567 @item @code{software-breakpoint}
21571 @item @code{hardware-breakpoint}
21575 @item @code{write-watchpoint}
21579 @item @code{read-watchpoint}
21583 @item @code{access-watchpoint}
21587 @item @code{pid-to-exec-file}
21588 @tab @code{qXfer:exec-file:read}
21589 @tab @code{attach}, @code{run}
21591 @item @code{target-features}
21592 @tab @code{qXfer:features:read}
21593 @tab @code{set architecture}
21595 @item @code{library-info}
21596 @tab @code{qXfer:libraries:read}
21597 @tab @code{info sharedlibrary}
21599 @item @code{memory-map}
21600 @tab @code{qXfer:memory-map:read}
21601 @tab @code{info mem}
21603 @item @code{read-sdata-object}
21604 @tab @code{qXfer:sdata:read}
21605 @tab @code{print $_sdata}
21607 @item @code{read-spu-object}
21608 @tab @code{qXfer:spu:read}
21609 @tab @code{info spu}
21611 @item @code{write-spu-object}
21612 @tab @code{qXfer:spu:write}
21613 @tab @code{info spu}
21615 @item @code{read-siginfo-object}
21616 @tab @code{qXfer:siginfo:read}
21617 @tab @code{print $_siginfo}
21619 @item @code{write-siginfo-object}
21620 @tab @code{qXfer:siginfo:write}
21621 @tab @code{set $_siginfo}
21623 @item @code{threads}
21624 @tab @code{qXfer:threads:read}
21625 @tab @code{info threads}
21627 @item @code{get-thread-local-@*storage-address}
21628 @tab @code{qGetTLSAddr}
21629 @tab Displaying @code{__thread} variables
21631 @item @code{get-thread-information-block-address}
21632 @tab @code{qGetTIBAddr}
21633 @tab Display MS-Windows Thread Information Block.
21635 @item @code{search-memory}
21636 @tab @code{qSearch:memory}
21639 @item @code{supported-packets}
21640 @tab @code{qSupported}
21641 @tab Remote communications parameters
21643 @item @code{catch-syscalls}
21644 @tab @code{QCatchSyscalls}
21645 @tab @code{catch syscall}
21647 @item @code{pass-signals}
21648 @tab @code{QPassSignals}
21649 @tab @code{handle @var{signal}}
21651 @item @code{program-signals}
21652 @tab @code{QProgramSignals}
21653 @tab @code{handle @var{signal}}
21655 @item @code{hostio-close-packet}
21656 @tab @code{vFile:close}
21657 @tab @code{remote get}, @code{remote put}
21659 @item @code{hostio-open-packet}
21660 @tab @code{vFile:open}
21661 @tab @code{remote get}, @code{remote put}
21663 @item @code{hostio-pread-packet}
21664 @tab @code{vFile:pread}
21665 @tab @code{remote get}, @code{remote put}
21667 @item @code{hostio-pwrite-packet}
21668 @tab @code{vFile:pwrite}
21669 @tab @code{remote get}, @code{remote put}
21671 @item @code{hostio-unlink-packet}
21672 @tab @code{vFile:unlink}
21673 @tab @code{remote delete}
21675 @item @code{hostio-readlink-packet}
21676 @tab @code{vFile:readlink}
21679 @item @code{hostio-fstat-packet}
21680 @tab @code{vFile:fstat}
21683 @item @code{hostio-setfs-packet}
21684 @tab @code{vFile:setfs}
21687 @item @code{noack-packet}
21688 @tab @code{QStartNoAckMode}
21689 @tab Packet acknowledgment
21691 @item @code{osdata}
21692 @tab @code{qXfer:osdata:read}
21693 @tab @code{info os}
21695 @item @code{query-attached}
21696 @tab @code{qAttached}
21697 @tab Querying remote process attach state.
21699 @item @code{trace-buffer-size}
21700 @tab @code{QTBuffer:size}
21701 @tab @code{set trace-buffer-size}
21703 @item @code{trace-status}
21704 @tab @code{qTStatus}
21705 @tab @code{tstatus}
21707 @item @code{traceframe-info}
21708 @tab @code{qXfer:traceframe-info:read}
21709 @tab Traceframe info
21711 @item @code{install-in-trace}
21712 @tab @code{InstallInTrace}
21713 @tab Install tracepoint in tracing
21715 @item @code{disable-randomization}
21716 @tab @code{QDisableRandomization}
21717 @tab @code{set disable-randomization}
21719 @item @code{startup-with-shell}
21720 @tab @code{QStartupWithShell}
21721 @tab @code{set startup-with-shell}
21723 @item @code{environment-hex-encoded}
21724 @tab @code{QEnvironmentHexEncoded}
21725 @tab @code{set environment}
21727 @item @code{environment-unset}
21728 @tab @code{QEnvironmentUnset}
21729 @tab @code{unset environment}
21731 @item @code{environment-reset}
21732 @tab @code{QEnvironmentReset}
21733 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21735 @item @code{set-working-dir}
21736 @tab @code{QSetWorkingDir}
21737 @tab @code{set cwd}
21739 @item @code{conditional-breakpoints-packet}
21740 @tab @code{Z0 and Z1}
21741 @tab @code{Support for target-side breakpoint condition evaluation}
21743 @item @code{multiprocess-extensions}
21744 @tab @code{multiprocess extensions}
21745 @tab Debug multiple processes and remote process PID awareness
21747 @item @code{swbreak-feature}
21748 @tab @code{swbreak stop reason}
21751 @item @code{hwbreak-feature}
21752 @tab @code{hwbreak stop reason}
21755 @item @code{fork-event-feature}
21756 @tab @code{fork stop reason}
21759 @item @code{vfork-event-feature}
21760 @tab @code{vfork stop reason}
21763 @item @code{exec-event-feature}
21764 @tab @code{exec stop reason}
21767 @item @code{thread-events}
21768 @tab @code{QThreadEvents}
21769 @tab Tracking thread lifetime.
21771 @item @code{no-resumed-stop-reply}
21772 @tab @code{no resumed thread left stop reply}
21773 @tab Tracking thread lifetime.
21778 @section Implementing a Remote Stub
21780 @cindex debugging stub, example
21781 @cindex remote stub, example
21782 @cindex stub example, remote debugging
21783 The stub files provided with @value{GDBN} implement the target side of the
21784 communication protocol, and the @value{GDBN} side is implemented in the
21785 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21786 these subroutines to communicate, and ignore the details. (If you're
21787 implementing your own stub file, you can still ignore the details: start
21788 with one of the existing stub files. @file{sparc-stub.c} is the best
21789 organized, and therefore the easiest to read.)
21791 @cindex remote serial debugging, overview
21792 To debug a program running on another machine (the debugging
21793 @dfn{target} machine), you must first arrange for all the usual
21794 prerequisites for the program to run by itself. For example, for a C
21799 A startup routine to set up the C runtime environment; these usually
21800 have a name like @file{crt0}. The startup routine may be supplied by
21801 your hardware supplier, or you may have to write your own.
21804 A C subroutine library to support your program's
21805 subroutine calls, notably managing input and output.
21808 A way of getting your program to the other machine---for example, a
21809 download program. These are often supplied by the hardware
21810 manufacturer, but you may have to write your own from hardware
21814 The next step is to arrange for your program to use a serial port to
21815 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21816 machine). In general terms, the scheme looks like this:
21820 @value{GDBN} already understands how to use this protocol; when everything
21821 else is set up, you can simply use the @samp{target remote} command
21822 (@pxref{Targets,,Specifying a Debugging Target}).
21824 @item On the target,
21825 you must link with your program a few special-purpose subroutines that
21826 implement the @value{GDBN} remote serial protocol. The file containing these
21827 subroutines is called a @dfn{debugging stub}.
21829 On certain remote targets, you can use an auxiliary program
21830 @code{gdbserver} instead of linking a stub into your program.
21831 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21834 The debugging stub is specific to the architecture of the remote
21835 machine; for example, use @file{sparc-stub.c} to debug programs on
21838 @cindex remote serial stub list
21839 These working remote stubs are distributed with @value{GDBN}:
21844 @cindex @file{i386-stub.c}
21847 For Intel 386 and compatible architectures.
21850 @cindex @file{m68k-stub.c}
21851 @cindex Motorola 680x0
21853 For Motorola 680x0 architectures.
21856 @cindex @file{sh-stub.c}
21859 For Renesas SH architectures.
21862 @cindex @file{sparc-stub.c}
21864 For @sc{sparc} architectures.
21866 @item sparcl-stub.c
21867 @cindex @file{sparcl-stub.c}
21870 For Fujitsu @sc{sparclite} architectures.
21874 The @file{README} file in the @value{GDBN} distribution may list other
21875 recently added stubs.
21878 * Stub Contents:: What the stub can do for you
21879 * Bootstrapping:: What you must do for the stub
21880 * Debug Session:: Putting it all together
21883 @node Stub Contents
21884 @subsection What the Stub Can Do for You
21886 @cindex remote serial stub
21887 The debugging stub for your architecture supplies these three
21891 @item set_debug_traps
21892 @findex set_debug_traps
21893 @cindex remote serial stub, initialization
21894 This routine arranges for @code{handle_exception} to run when your
21895 program stops. You must call this subroutine explicitly in your
21896 program's startup code.
21898 @item handle_exception
21899 @findex handle_exception
21900 @cindex remote serial stub, main routine
21901 This is the central workhorse, but your program never calls it
21902 explicitly---the setup code arranges for @code{handle_exception} to
21903 run when a trap is triggered.
21905 @code{handle_exception} takes control when your program stops during
21906 execution (for example, on a breakpoint), and mediates communications
21907 with @value{GDBN} on the host machine. This is where the communications
21908 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21909 representative on the target machine. It begins by sending summary
21910 information on the state of your program, then continues to execute,
21911 retrieving and transmitting any information @value{GDBN} needs, until you
21912 execute a @value{GDBN} command that makes your program resume; at that point,
21913 @code{handle_exception} returns control to your own code on the target
21917 @cindex @code{breakpoint} subroutine, remote
21918 Use this auxiliary subroutine to make your program contain a
21919 breakpoint. Depending on the particular situation, this may be the only
21920 way for @value{GDBN} to get control. For instance, if your target
21921 machine has some sort of interrupt button, you won't need to call this;
21922 pressing the interrupt button transfers control to
21923 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21924 simply receiving characters on the serial port may also trigger a trap;
21925 again, in that situation, you don't need to call @code{breakpoint} from
21926 your own program---simply running @samp{target remote} from the host
21927 @value{GDBN} session gets control.
21929 Call @code{breakpoint} if none of these is true, or if you simply want
21930 to make certain your program stops at a predetermined point for the
21931 start of your debugging session.
21934 @node Bootstrapping
21935 @subsection What You Must Do for the Stub
21937 @cindex remote stub, support routines
21938 The debugging stubs that come with @value{GDBN} are set up for a particular
21939 chip architecture, but they have no information about the rest of your
21940 debugging target machine.
21942 First of all you need to tell the stub how to communicate with the
21946 @item int getDebugChar()
21947 @findex getDebugChar
21948 Write this subroutine to read a single character from the serial port.
21949 It may be identical to @code{getchar} for your target system; a
21950 different name is used to allow you to distinguish the two if you wish.
21952 @item void putDebugChar(int)
21953 @findex putDebugChar
21954 Write this subroutine to write a single character to the serial port.
21955 It may be identical to @code{putchar} for your target system; a
21956 different name is used to allow you to distinguish the two if you wish.
21959 @cindex control C, and remote debugging
21960 @cindex interrupting remote targets
21961 If you want @value{GDBN} to be able to stop your program while it is
21962 running, you need to use an interrupt-driven serial driver, and arrange
21963 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21964 character). That is the character which @value{GDBN} uses to tell the
21965 remote system to stop.
21967 Getting the debugging target to return the proper status to @value{GDBN}
21968 probably requires changes to the standard stub; one quick and dirty way
21969 is to just execute a breakpoint instruction (the ``dirty'' part is that
21970 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21972 Other routines you need to supply are:
21975 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21976 @findex exceptionHandler
21977 Write this function to install @var{exception_address} in the exception
21978 handling tables. You need to do this because the stub does not have any
21979 way of knowing what the exception handling tables on your target system
21980 are like (for example, the processor's table might be in @sc{rom},
21981 containing entries which point to a table in @sc{ram}).
21982 The @var{exception_number} specifies the exception which should be changed;
21983 its meaning is architecture-dependent (for example, different numbers
21984 might represent divide by zero, misaligned access, etc). When this
21985 exception occurs, control should be transferred directly to
21986 @var{exception_address}, and the processor state (stack, registers,
21987 and so on) should be just as it is when a processor exception occurs. So if
21988 you want to use a jump instruction to reach @var{exception_address}, it
21989 should be a simple jump, not a jump to subroutine.
21991 For the 386, @var{exception_address} should be installed as an interrupt
21992 gate so that interrupts are masked while the handler runs. The gate
21993 should be at privilege level 0 (the most privileged level). The
21994 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21995 help from @code{exceptionHandler}.
21997 @item void flush_i_cache()
21998 @findex flush_i_cache
21999 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22000 instruction cache, if any, on your target machine. If there is no
22001 instruction cache, this subroutine may be a no-op.
22003 On target machines that have instruction caches, @value{GDBN} requires this
22004 function to make certain that the state of your program is stable.
22008 You must also make sure this library routine is available:
22011 @item void *memset(void *, int, int)
22013 This is the standard library function @code{memset} that sets an area of
22014 memory to a known value. If you have one of the free versions of
22015 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22016 either obtain it from your hardware manufacturer, or write your own.
22019 If you do not use the GNU C compiler, you may need other standard
22020 library subroutines as well; this varies from one stub to another,
22021 but in general the stubs are likely to use any of the common library
22022 subroutines which @code{@value{NGCC}} generates as inline code.
22025 @node Debug Session
22026 @subsection Putting it All Together
22028 @cindex remote serial debugging summary
22029 In summary, when your program is ready to debug, you must follow these
22034 Make sure you have defined the supporting low-level routines
22035 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22037 @code{getDebugChar}, @code{putDebugChar},
22038 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22042 Insert these lines in your program's startup code, before the main
22043 procedure is called:
22050 On some machines, when a breakpoint trap is raised, the hardware
22051 automatically makes the PC point to the instruction after the
22052 breakpoint. If your machine doesn't do that, you may need to adjust
22053 @code{handle_exception} to arrange for it to return to the instruction
22054 after the breakpoint on this first invocation, so that your program
22055 doesn't keep hitting the initial breakpoint instead of making
22059 For the 680x0 stub only, you need to provide a variable called
22060 @code{exceptionHook}. Normally you just use:
22063 void (*exceptionHook)() = 0;
22067 but if before calling @code{set_debug_traps}, you set it to point to a
22068 function in your program, that function is called when
22069 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22070 error). The function indicated by @code{exceptionHook} is called with
22071 one parameter: an @code{int} which is the exception number.
22074 Compile and link together: your program, the @value{GDBN} debugging stub for
22075 your target architecture, and the supporting subroutines.
22078 Make sure you have a serial connection between your target machine and
22079 the @value{GDBN} host, and identify the serial port on the host.
22082 @c The "remote" target now provides a `load' command, so we should
22083 @c document that. FIXME.
22084 Download your program to your target machine (or get it there by
22085 whatever means the manufacturer provides), and start it.
22088 Start @value{GDBN} on the host, and connect to the target
22089 (@pxref{Connecting,,Connecting to a Remote Target}).
22093 @node Configurations
22094 @chapter Configuration-Specific Information
22096 While nearly all @value{GDBN} commands are available for all native and
22097 cross versions of the debugger, there are some exceptions. This chapter
22098 describes things that are only available in certain configurations.
22100 There are three major categories of configurations: native
22101 configurations, where the host and target are the same, embedded
22102 operating system configurations, which are usually the same for several
22103 different processor architectures, and bare embedded processors, which
22104 are quite different from each other.
22109 * Embedded Processors::
22116 This section describes details specific to particular native
22120 * BSD libkvm Interface:: Debugging BSD kernel memory images
22121 * Process Information:: Process information
22122 * DJGPP Native:: Features specific to the DJGPP port
22123 * Cygwin Native:: Features specific to the Cygwin port
22124 * Hurd Native:: Features specific to @sc{gnu} Hurd
22125 * Darwin:: Features specific to Darwin
22128 @node BSD libkvm Interface
22129 @subsection BSD libkvm Interface
22132 @cindex kernel memory image
22133 @cindex kernel crash dump
22135 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22136 interface that provides a uniform interface for accessing kernel virtual
22137 memory images, including live systems and crash dumps. @value{GDBN}
22138 uses this interface to allow you to debug live kernels and kernel crash
22139 dumps on many native BSD configurations. This is implemented as a
22140 special @code{kvm} debugging target. For debugging a live system, load
22141 the currently running kernel into @value{GDBN} and connect to the
22145 (@value{GDBP}) @b{target kvm}
22148 For debugging crash dumps, provide the file name of the crash dump as an
22152 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22155 Once connected to the @code{kvm} target, the following commands are
22161 Set current context from the @dfn{Process Control Block} (PCB) address.
22164 Set current context from proc address. This command isn't available on
22165 modern FreeBSD systems.
22168 @node Process Information
22169 @subsection Process Information
22171 @cindex examine process image
22172 @cindex process info via @file{/proc}
22174 Some operating systems provide interfaces to fetch additional
22175 information about running processes beyond memory and per-thread
22176 register state. If @value{GDBN} is configured for an operating system
22177 with a supported interface, the command @code{info proc} is available
22178 to report information about the process running your program, or about
22179 any process running on your system.
22181 One supported interface is a facility called @samp{/proc} that can be
22182 used to examine the image of a running process using file-system
22183 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22186 On FreeBSD systems, system control nodes are used to query process
22189 In addition, some systems may provide additional process information
22190 in core files. Note that a core file may include a subset of the
22191 information available from a live process. Process information is
22192 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22199 @itemx info proc @var{process-id}
22200 Summarize available information about any running process. If a
22201 process ID is specified by @var{process-id}, display information about
22202 that process; otherwise display information about the program being
22203 debugged. The summary includes the debugged process ID, the command
22204 line used to invoke it, its current working directory, and its
22205 executable file's absolute file name.
22207 On some systems, @var{process-id} can be of the form
22208 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22209 within a process. If the optional @var{pid} part is missing, it means
22210 a thread from the process being debugged (the leading @samp{/} still
22211 needs to be present, or else @value{GDBN} will interpret the number as
22212 a process ID rather than a thread ID).
22214 @item info proc cmdline
22215 @cindex info proc cmdline
22216 Show the original command line of the process. This command is
22217 supported on @sc{gnu}/Linux and FreeBSD.
22219 @item info proc cwd
22220 @cindex info proc cwd
22221 Show the current working directory of the process. This command is
22222 supported on @sc{gnu}/Linux and FreeBSD.
22224 @item info proc exe
22225 @cindex info proc exe
22226 Show the name of executable of the process. This command is supported
22227 on @sc{gnu}/Linux and FreeBSD.
22229 @item info proc mappings
22230 @cindex memory address space mappings
22231 Report the memory address space ranges accessible in the program. On
22232 Solaris and FreeBSD systems, each memory range includes information on
22233 whether the process has read, write, or execute access rights to each
22234 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22235 includes the object file which is mapped to that range.
22237 @item info proc stat
22238 @itemx info proc status
22239 @cindex process detailed status information
22240 Show additional process-related information, including the user ID and
22241 group ID; virtual memory usage; the signals that are pending, blocked,
22242 and ignored; its TTY; its consumption of system and user time; its
22243 stack size; its @samp{nice} value; etc. These commands are supported
22244 on @sc{gnu}/Linux and FreeBSD.
22246 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22247 information (type @kbd{man 5 proc} from your shell prompt).
22249 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22252 @item info proc all
22253 Show all the information about the process described under all of the
22254 above @code{info proc} subcommands.
22257 @comment These sub-options of 'info proc' were not included when
22258 @comment procfs.c was re-written. Keep their descriptions around
22259 @comment against the day when someone finds the time to put them back in.
22260 @kindex info proc times
22261 @item info proc times
22262 Starting time, user CPU time, and system CPU time for your program and
22265 @kindex info proc id
22267 Report on the process IDs related to your program: its own process ID,
22268 the ID of its parent, the process group ID, and the session ID.
22271 @item set procfs-trace
22272 @kindex set procfs-trace
22273 @cindex @code{procfs} API calls
22274 This command enables and disables tracing of @code{procfs} API calls.
22276 @item show procfs-trace
22277 @kindex show procfs-trace
22278 Show the current state of @code{procfs} API call tracing.
22280 @item set procfs-file @var{file}
22281 @kindex set procfs-file
22282 Tell @value{GDBN} to write @code{procfs} API trace to the named
22283 @var{file}. @value{GDBN} appends the trace info to the previous
22284 contents of the file. The default is to display the trace on the
22287 @item show procfs-file
22288 @kindex show procfs-file
22289 Show the file to which @code{procfs} API trace is written.
22291 @item proc-trace-entry
22292 @itemx proc-trace-exit
22293 @itemx proc-untrace-entry
22294 @itemx proc-untrace-exit
22295 @kindex proc-trace-entry
22296 @kindex proc-trace-exit
22297 @kindex proc-untrace-entry
22298 @kindex proc-untrace-exit
22299 These commands enable and disable tracing of entries into and exits
22300 from the @code{syscall} interface.
22303 @kindex info pidlist
22304 @cindex process list, QNX Neutrino
22305 For QNX Neutrino only, this command displays the list of all the
22306 processes and all the threads within each process.
22309 @kindex info meminfo
22310 @cindex mapinfo list, QNX Neutrino
22311 For QNX Neutrino only, this command displays the list of all mapinfos.
22315 @subsection Features for Debugging @sc{djgpp} Programs
22316 @cindex @sc{djgpp} debugging
22317 @cindex native @sc{djgpp} debugging
22318 @cindex MS-DOS-specific commands
22321 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22322 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22323 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22324 top of real-mode DOS systems and their emulations.
22326 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22327 defines a few commands specific to the @sc{djgpp} port. This
22328 subsection describes those commands.
22333 This is a prefix of @sc{djgpp}-specific commands which print
22334 information about the target system and important OS structures.
22337 @cindex MS-DOS system info
22338 @cindex free memory information (MS-DOS)
22339 @item info dos sysinfo
22340 This command displays assorted information about the underlying
22341 platform: the CPU type and features, the OS version and flavor, the
22342 DPMI version, and the available conventional and DPMI memory.
22347 @cindex segment descriptor tables
22348 @cindex descriptor tables display
22350 @itemx info dos ldt
22351 @itemx info dos idt
22352 These 3 commands display entries from, respectively, Global, Local,
22353 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22354 tables are data structures which store a descriptor for each segment
22355 that is currently in use. The segment's selector is an index into a
22356 descriptor table; the table entry for that index holds the
22357 descriptor's base address and limit, and its attributes and access
22360 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22361 segment (used for both data and the stack), and a DOS segment (which
22362 allows access to DOS/BIOS data structures and absolute addresses in
22363 conventional memory). However, the DPMI host will usually define
22364 additional segments in order to support the DPMI environment.
22366 @cindex garbled pointers
22367 These commands allow to display entries from the descriptor tables.
22368 Without an argument, all entries from the specified table are
22369 displayed. An argument, which should be an integer expression, means
22370 display a single entry whose index is given by the argument. For
22371 example, here's a convenient way to display information about the
22372 debugged program's data segment:
22375 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22376 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22380 This comes in handy when you want to see whether a pointer is outside
22381 the data segment's limit (i.e.@: @dfn{garbled}).
22383 @cindex page tables display (MS-DOS)
22385 @itemx info dos pte
22386 These two commands display entries from, respectively, the Page
22387 Directory and the Page Tables. Page Directories and Page Tables are
22388 data structures which control how virtual memory addresses are mapped
22389 into physical addresses. A Page Table includes an entry for every
22390 page of memory that is mapped into the program's address space; there
22391 may be several Page Tables, each one holding up to 4096 entries. A
22392 Page Directory has up to 4096 entries, one each for every Page Table
22393 that is currently in use.
22395 Without an argument, @kbd{info dos pde} displays the entire Page
22396 Directory, and @kbd{info dos pte} displays all the entries in all of
22397 the Page Tables. An argument, an integer expression, given to the
22398 @kbd{info dos pde} command means display only that entry from the Page
22399 Directory table. An argument given to the @kbd{info dos pte} command
22400 means display entries from a single Page Table, the one pointed to by
22401 the specified entry in the Page Directory.
22403 @cindex direct memory access (DMA) on MS-DOS
22404 These commands are useful when your program uses @dfn{DMA} (Direct
22405 Memory Access), which needs physical addresses to program the DMA
22408 These commands are supported only with some DPMI servers.
22410 @cindex physical address from linear address
22411 @item info dos address-pte @var{addr}
22412 This command displays the Page Table entry for a specified linear
22413 address. The argument @var{addr} is a linear address which should
22414 already have the appropriate segment's base address added to it,
22415 because this command accepts addresses which may belong to @emph{any}
22416 segment. For example, here's how to display the Page Table entry for
22417 the page where a variable @code{i} is stored:
22420 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22421 @exdent @code{Page Table entry for address 0x11a00d30:}
22422 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22426 This says that @code{i} is stored at offset @code{0xd30} from the page
22427 whose physical base address is @code{0x02698000}, and shows all the
22428 attributes of that page.
22430 Note that you must cast the addresses of variables to a @code{char *},
22431 since otherwise the value of @code{__djgpp_base_address}, the base
22432 address of all variables and functions in a @sc{djgpp} program, will
22433 be added using the rules of C pointer arithmetics: if @code{i} is
22434 declared an @code{int}, @value{GDBN} will add 4 times the value of
22435 @code{__djgpp_base_address} to the address of @code{i}.
22437 Here's another example, it displays the Page Table entry for the
22441 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22442 @exdent @code{Page Table entry for address 0x29110:}
22443 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22447 (The @code{+ 3} offset is because the transfer buffer's address is the
22448 3rd member of the @code{_go32_info_block} structure.) The output
22449 clearly shows that this DPMI server maps the addresses in conventional
22450 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22451 linear (@code{0x29110}) addresses are identical.
22453 This command is supported only with some DPMI servers.
22456 @cindex DOS serial data link, remote debugging
22457 In addition to native debugging, the DJGPP port supports remote
22458 debugging via a serial data link. The following commands are specific
22459 to remote serial debugging in the DJGPP port of @value{GDBN}.
22462 @kindex set com1base
22463 @kindex set com1irq
22464 @kindex set com2base
22465 @kindex set com2irq
22466 @kindex set com3base
22467 @kindex set com3irq
22468 @kindex set com4base
22469 @kindex set com4irq
22470 @item set com1base @var{addr}
22471 This command sets the base I/O port address of the @file{COM1} serial
22474 @item set com1irq @var{irq}
22475 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22476 for the @file{COM1} serial port.
22478 There are similar commands @samp{set com2base}, @samp{set com3irq},
22479 etc.@: for setting the port address and the @code{IRQ} lines for the
22482 @kindex show com1base
22483 @kindex show com1irq
22484 @kindex show com2base
22485 @kindex show com2irq
22486 @kindex show com3base
22487 @kindex show com3irq
22488 @kindex show com4base
22489 @kindex show com4irq
22490 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22491 display the current settings of the base address and the @code{IRQ}
22492 lines used by the COM ports.
22495 @kindex info serial
22496 @cindex DOS serial port status
22497 This command prints the status of the 4 DOS serial ports. For each
22498 port, it prints whether it's active or not, its I/O base address and
22499 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22500 counts of various errors encountered so far.
22504 @node Cygwin Native
22505 @subsection Features for Debugging MS Windows PE Executables
22506 @cindex MS Windows debugging
22507 @cindex native Cygwin debugging
22508 @cindex Cygwin-specific commands
22510 @value{GDBN} supports native debugging of MS Windows programs, including
22511 DLLs with and without symbolic debugging information.
22513 @cindex Ctrl-BREAK, MS-Windows
22514 @cindex interrupt debuggee on MS-Windows
22515 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22516 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22517 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22518 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22519 sequence, which can be used to interrupt the debuggee even if it
22522 There are various additional Cygwin-specific commands, described in
22523 this section. Working with DLLs that have no debugging symbols is
22524 described in @ref{Non-debug DLL Symbols}.
22529 This is a prefix of MS Windows-specific commands which print
22530 information about the target system and important OS structures.
22532 @item info w32 selector
22533 This command displays information returned by
22534 the Win32 API @code{GetThreadSelectorEntry} function.
22535 It takes an optional argument that is evaluated to
22536 a long value to give the information about this given selector.
22537 Without argument, this command displays information
22538 about the six segment registers.
22540 @item info w32 thread-information-block
22541 This command displays thread specific information stored in the
22542 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22543 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22545 @kindex signal-event
22546 @item signal-event @var{id}
22547 This command signals an event with user-provided @var{id}. Used to resume
22548 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22550 To use it, create or edit the following keys in
22551 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22552 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22553 (for x86_64 versions):
22557 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22558 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22559 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22561 The first @code{%ld} will be replaced by the process ID of the
22562 crashing process, the second @code{%ld} will be replaced by the ID of
22563 the event that blocks the crashing process, waiting for @value{GDBN}
22567 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22568 make the system run debugger specified by the Debugger key
22569 automatically, @code{0} will cause a dialog box with ``OK'' and
22570 ``Cancel'' buttons to appear, which allows the user to either
22571 terminate the crashing process (OK) or debug it (Cancel).
22574 @kindex set cygwin-exceptions
22575 @cindex debugging the Cygwin DLL
22576 @cindex Cygwin DLL, debugging
22577 @item set cygwin-exceptions @var{mode}
22578 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22579 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22580 @value{GDBN} will delay recognition of exceptions, and may ignore some
22581 exceptions which seem to be caused by internal Cygwin DLL
22582 ``bookkeeping''. This option is meant primarily for debugging the
22583 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22584 @value{GDBN} users with false @code{SIGSEGV} signals.
22586 @kindex show cygwin-exceptions
22587 @item show cygwin-exceptions
22588 Displays whether @value{GDBN} will break on exceptions that happen
22589 inside the Cygwin DLL itself.
22591 @kindex set new-console
22592 @item set new-console @var{mode}
22593 If @var{mode} is @code{on} the debuggee will
22594 be started in a new console on next start.
22595 If @var{mode} is @code{off}, the debuggee will
22596 be started in the same console as the debugger.
22598 @kindex show new-console
22599 @item show new-console
22600 Displays whether a new console is used
22601 when the debuggee is started.
22603 @kindex set new-group
22604 @item set new-group @var{mode}
22605 This boolean value controls whether the debuggee should
22606 start a new group or stay in the same group as the debugger.
22607 This affects the way the Windows OS handles
22610 @kindex show new-group
22611 @item show new-group
22612 Displays current value of new-group boolean.
22614 @kindex set debugevents
22615 @item set debugevents
22616 This boolean value adds debug output concerning kernel events related
22617 to the debuggee seen by the debugger. This includes events that
22618 signal thread and process creation and exit, DLL loading and
22619 unloading, console interrupts, and debugging messages produced by the
22620 Windows @code{OutputDebugString} API call.
22622 @kindex set debugexec
22623 @item set debugexec
22624 This boolean value adds debug output concerning execute events
22625 (such as resume thread) seen by the debugger.
22627 @kindex set debugexceptions
22628 @item set debugexceptions
22629 This boolean value adds debug output concerning exceptions in the
22630 debuggee seen by the debugger.
22632 @kindex set debugmemory
22633 @item set debugmemory
22634 This boolean value adds debug output concerning debuggee memory reads
22635 and writes by the debugger.
22639 This boolean values specifies whether the debuggee is called
22640 via a shell or directly (default value is on).
22644 Displays if the debuggee will be started with a shell.
22649 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22652 @node Non-debug DLL Symbols
22653 @subsubsection Support for DLLs without Debugging Symbols
22654 @cindex DLLs with no debugging symbols
22655 @cindex Minimal symbols and DLLs
22657 Very often on windows, some of the DLLs that your program relies on do
22658 not include symbolic debugging information (for example,
22659 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22660 symbols in a DLL, it relies on the minimal amount of symbolic
22661 information contained in the DLL's export table. This section
22662 describes working with such symbols, known internally to @value{GDBN} as
22663 ``minimal symbols''.
22665 Note that before the debugged program has started execution, no DLLs
22666 will have been loaded. The easiest way around this problem is simply to
22667 start the program --- either by setting a breakpoint or letting the
22668 program run once to completion.
22670 @subsubsection DLL Name Prefixes
22672 In keeping with the naming conventions used by the Microsoft debugging
22673 tools, DLL export symbols are made available with a prefix based on the
22674 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22675 also entered into the symbol table, so @code{CreateFileA} is often
22676 sufficient. In some cases there will be name clashes within a program
22677 (particularly if the executable itself includes full debugging symbols)
22678 necessitating the use of the fully qualified name when referring to the
22679 contents of the DLL. Use single-quotes around the name to avoid the
22680 exclamation mark (``!'') being interpreted as a language operator.
22682 Note that the internal name of the DLL may be all upper-case, even
22683 though the file name of the DLL is lower-case, or vice-versa. Since
22684 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22685 some confusion. If in doubt, try the @code{info functions} and
22686 @code{info variables} commands or even @code{maint print msymbols}
22687 (@pxref{Symbols}). Here's an example:
22690 (@value{GDBP}) info function CreateFileA
22691 All functions matching regular expression "CreateFileA":
22693 Non-debugging symbols:
22694 0x77e885f4 CreateFileA
22695 0x77e885f4 KERNEL32!CreateFileA
22699 (@value{GDBP}) info function !
22700 All functions matching regular expression "!":
22702 Non-debugging symbols:
22703 0x6100114c cygwin1!__assert
22704 0x61004034 cygwin1!_dll_crt0@@0
22705 0x61004240 cygwin1!dll_crt0(per_process *)
22709 @subsubsection Working with Minimal Symbols
22711 Symbols extracted from a DLL's export table do not contain very much
22712 type information. All that @value{GDBN} can do is guess whether a symbol
22713 refers to a function or variable depending on the linker section that
22714 contains the symbol. Also note that the actual contents of the memory
22715 contained in a DLL are not available unless the program is running. This
22716 means that you cannot examine the contents of a variable or disassemble
22717 a function within a DLL without a running program.
22719 Variables are generally treated as pointers and dereferenced
22720 automatically. For this reason, it is often necessary to prefix a
22721 variable name with the address-of operator (``&'') and provide explicit
22722 type information in the command. Here's an example of the type of
22726 (@value{GDBP}) print 'cygwin1!__argv'
22727 'cygwin1!__argv' has unknown type; cast it to its declared type
22731 (@value{GDBP}) x 'cygwin1!__argv'
22732 'cygwin1!__argv' has unknown type; cast it to its declared type
22735 And two possible solutions:
22738 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22739 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22743 (@value{GDBP}) x/2x &'cygwin1!__argv'
22744 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22745 (@value{GDBP}) x/x 0x10021608
22746 0x10021608: 0x0022fd98
22747 (@value{GDBP}) x/s 0x0022fd98
22748 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22751 Setting a break point within a DLL is possible even before the program
22752 starts execution. However, under these circumstances, @value{GDBN} can't
22753 examine the initial instructions of the function in order to skip the
22754 function's frame set-up code. You can work around this by using ``*&''
22755 to set the breakpoint at a raw memory address:
22758 (@value{GDBP}) break *&'python22!PyOS_Readline'
22759 Breakpoint 1 at 0x1e04eff0
22762 The author of these extensions is not entirely convinced that setting a
22763 break point within a shared DLL like @file{kernel32.dll} is completely
22767 @subsection Commands Specific to @sc{gnu} Hurd Systems
22768 @cindex @sc{gnu} Hurd debugging
22770 This subsection describes @value{GDBN} commands specific to the
22771 @sc{gnu} Hurd native debugging.
22776 @kindex set signals@r{, Hurd command}
22777 @kindex set sigs@r{, Hurd command}
22778 This command toggles the state of inferior signal interception by
22779 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22780 affected by this command. @code{sigs} is a shorthand alias for
22785 @kindex show signals@r{, Hurd command}
22786 @kindex show sigs@r{, Hurd command}
22787 Show the current state of intercepting inferior's signals.
22789 @item set signal-thread
22790 @itemx set sigthread
22791 @kindex set signal-thread
22792 @kindex set sigthread
22793 This command tells @value{GDBN} which thread is the @code{libc} signal
22794 thread. That thread is run when a signal is delivered to a running
22795 process. @code{set sigthread} is the shorthand alias of @code{set
22798 @item show signal-thread
22799 @itemx show sigthread
22800 @kindex show signal-thread
22801 @kindex show sigthread
22802 These two commands show which thread will run when the inferior is
22803 delivered a signal.
22806 @kindex set stopped@r{, Hurd command}
22807 This commands tells @value{GDBN} that the inferior process is stopped,
22808 as with the @code{SIGSTOP} signal. The stopped process can be
22809 continued by delivering a signal to it.
22812 @kindex show stopped@r{, Hurd command}
22813 This command shows whether @value{GDBN} thinks the debuggee is
22816 @item set exceptions
22817 @kindex set exceptions@r{, Hurd command}
22818 Use this command to turn off trapping of exceptions in the inferior.
22819 When exception trapping is off, neither breakpoints nor
22820 single-stepping will work. To restore the default, set exception
22823 @item show exceptions
22824 @kindex show exceptions@r{, Hurd command}
22825 Show the current state of trapping exceptions in the inferior.
22827 @item set task pause
22828 @kindex set task@r{, Hurd commands}
22829 @cindex task attributes (@sc{gnu} Hurd)
22830 @cindex pause current task (@sc{gnu} Hurd)
22831 This command toggles task suspension when @value{GDBN} has control.
22832 Setting it to on takes effect immediately, and the task is suspended
22833 whenever @value{GDBN} gets control. Setting it to off will take
22834 effect the next time the inferior is continued. If this option is set
22835 to off, you can use @code{set thread default pause on} or @code{set
22836 thread pause on} (see below) to pause individual threads.
22838 @item show task pause
22839 @kindex show task@r{, Hurd commands}
22840 Show the current state of task suspension.
22842 @item set task detach-suspend-count
22843 @cindex task suspend count
22844 @cindex detach from task, @sc{gnu} Hurd
22845 This command sets the suspend count the task will be left with when
22846 @value{GDBN} detaches from it.
22848 @item show task detach-suspend-count
22849 Show the suspend count the task will be left with when detaching.
22851 @item set task exception-port
22852 @itemx set task excp
22853 @cindex task exception port, @sc{gnu} Hurd
22854 This command sets the task exception port to which @value{GDBN} will
22855 forward exceptions. The argument should be the value of the @dfn{send
22856 rights} of the task. @code{set task excp} is a shorthand alias.
22858 @item set noninvasive
22859 @cindex noninvasive task options
22860 This command switches @value{GDBN} to a mode that is the least
22861 invasive as far as interfering with the inferior is concerned. This
22862 is the same as using @code{set task pause}, @code{set exceptions}, and
22863 @code{set signals} to values opposite to the defaults.
22865 @item info send-rights
22866 @itemx info receive-rights
22867 @itemx info port-rights
22868 @itemx info port-sets
22869 @itemx info dead-names
22872 @cindex send rights, @sc{gnu} Hurd
22873 @cindex receive rights, @sc{gnu} Hurd
22874 @cindex port rights, @sc{gnu} Hurd
22875 @cindex port sets, @sc{gnu} Hurd
22876 @cindex dead names, @sc{gnu} Hurd
22877 These commands display information about, respectively, send rights,
22878 receive rights, port rights, port sets, and dead names of a task.
22879 There are also shorthand aliases: @code{info ports} for @code{info
22880 port-rights} and @code{info psets} for @code{info port-sets}.
22882 @item set thread pause
22883 @kindex set thread@r{, Hurd command}
22884 @cindex thread properties, @sc{gnu} Hurd
22885 @cindex pause current thread (@sc{gnu} Hurd)
22886 This command toggles current thread suspension when @value{GDBN} has
22887 control. Setting it to on takes effect immediately, and the current
22888 thread is suspended whenever @value{GDBN} gets control. Setting it to
22889 off will take effect the next time the inferior is continued.
22890 Normally, this command has no effect, since when @value{GDBN} has
22891 control, the whole task is suspended. However, if you used @code{set
22892 task pause off} (see above), this command comes in handy to suspend
22893 only the current thread.
22895 @item show thread pause
22896 @kindex show thread@r{, Hurd command}
22897 This command shows the state of current thread suspension.
22899 @item set thread run
22900 This command sets whether the current thread is allowed to run.
22902 @item show thread run
22903 Show whether the current thread is allowed to run.
22905 @item set thread detach-suspend-count
22906 @cindex thread suspend count, @sc{gnu} Hurd
22907 @cindex detach from thread, @sc{gnu} Hurd
22908 This command sets the suspend count @value{GDBN} will leave on a
22909 thread when detaching. This number is relative to the suspend count
22910 found by @value{GDBN} when it notices the thread; use @code{set thread
22911 takeover-suspend-count} to force it to an absolute value.
22913 @item show thread detach-suspend-count
22914 Show the suspend count @value{GDBN} will leave on the thread when
22917 @item set thread exception-port
22918 @itemx set thread excp
22919 Set the thread exception port to which to forward exceptions. This
22920 overrides the port set by @code{set task exception-port} (see above).
22921 @code{set thread excp} is the shorthand alias.
22923 @item set thread takeover-suspend-count
22924 Normally, @value{GDBN}'s thread suspend counts are relative to the
22925 value @value{GDBN} finds when it notices each thread. This command
22926 changes the suspend counts to be absolute instead.
22928 @item set thread default
22929 @itemx show thread default
22930 @cindex thread default settings, @sc{gnu} Hurd
22931 Each of the above @code{set thread} commands has a @code{set thread
22932 default} counterpart (e.g., @code{set thread default pause}, @code{set
22933 thread default exception-port}, etc.). The @code{thread default}
22934 variety of commands sets the default thread properties for all
22935 threads; you can then change the properties of individual threads with
22936 the non-default commands.
22943 @value{GDBN} provides the following commands specific to the Darwin target:
22946 @item set debug darwin @var{num}
22947 @kindex set debug darwin
22948 When set to a non zero value, enables debugging messages specific to
22949 the Darwin support. Higher values produce more verbose output.
22951 @item show debug darwin
22952 @kindex show debug darwin
22953 Show the current state of Darwin messages.
22955 @item set debug mach-o @var{num}
22956 @kindex set debug mach-o
22957 When set to a non zero value, enables debugging messages while
22958 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22959 file format used on Darwin for object and executable files.) Higher
22960 values produce more verbose output. This is a command to diagnose
22961 problems internal to @value{GDBN} and should not be needed in normal
22964 @item show debug mach-o
22965 @kindex show debug mach-o
22966 Show the current state of Mach-O file messages.
22968 @item set mach-exceptions on
22969 @itemx set mach-exceptions off
22970 @kindex set mach-exceptions
22971 On Darwin, faults are first reported as a Mach exception and are then
22972 mapped to a Posix signal. Use this command to turn on trapping of
22973 Mach exceptions in the inferior. This might be sometimes useful to
22974 better understand the cause of a fault. The default is off.
22976 @item show mach-exceptions
22977 @kindex show mach-exceptions
22978 Show the current state of exceptions trapping.
22983 @section Embedded Operating Systems
22985 This section describes configurations involving the debugging of
22986 embedded operating systems that are available for several different
22989 @value{GDBN} includes the ability to debug programs running on
22990 various real-time operating systems.
22992 @node Embedded Processors
22993 @section Embedded Processors
22995 This section goes into details specific to particular embedded
22998 @cindex send command to simulator
22999 Whenever a specific embedded processor has a simulator, @value{GDBN}
23000 allows to send an arbitrary command to the simulator.
23003 @item sim @var{command}
23004 @kindex sim@r{, a command}
23005 Send an arbitrary @var{command} string to the simulator. Consult the
23006 documentation for the specific simulator in use for information about
23007 acceptable commands.
23012 * ARC:: Synopsys ARC
23014 * M68K:: Motorola M68K
23015 * MicroBlaze:: Xilinx MicroBlaze
23016 * MIPS Embedded:: MIPS Embedded
23017 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23018 * PowerPC Embedded:: PowerPC Embedded
23021 * Super-H:: Renesas Super-H
23025 @subsection Synopsys ARC
23026 @cindex Synopsys ARC
23027 @cindex ARC specific commands
23033 @value{GDBN} provides the following ARC-specific commands:
23036 @item set debug arc
23037 @kindex set debug arc
23038 Control the level of ARC specific debug messages. Use 0 for no messages (the
23039 default), 1 for debug messages, and 2 for even more debug messages.
23041 @item show debug arc
23042 @kindex show debug arc
23043 Show the level of ARC specific debugging in operation.
23045 @item maint print arc arc-instruction @var{address}
23046 @kindex maint print arc arc-instruction
23047 Print internal disassembler information about instruction at a given address.
23054 @value{GDBN} provides the following ARM-specific commands:
23057 @item set arm disassembler
23059 This commands selects from a list of disassembly styles. The
23060 @code{"std"} style is the standard style.
23062 @item show arm disassembler
23064 Show the current disassembly style.
23066 @item set arm apcs32
23067 @cindex ARM 32-bit mode
23068 This command toggles ARM operation mode between 32-bit and 26-bit.
23070 @item show arm apcs32
23071 Display the current usage of the ARM 32-bit mode.
23073 @item set arm fpu @var{fputype}
23074 This command sets the ARM floating-point unit (FPU) type. The
23075 argument @var{fputype} can be one of these:
23079 Determine the FPU type by querying the OS ABI.
23081 Software FPU, with mixed-endian doubles on little-endian ARM
23084 GCC-compiled FPA co-processor.
23086 Software FPU with pure-endian doubles.
23092 Show the current type of the FPU.
23095 This command forces @value{GDBN} to use the specified ABI.
23098 Show the currently used ABI.
23100 @item set arm fallback-mode (arm|thumb|auto)
23101 @value{GDBN} uses the symbol table, when available, to determine
23102 whether instructions are ARM or Thumb. This command controls
23103 @value{GDBN}'s default behavior when the symbol table is not
23104 available. The default is @samp{auto}, which causes @value{GDBN} to
23105 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23108 @item show arm fallback-mode
23109 Show the current fallback instruction mode.
23111 @item set arm force-mode (arm|thumb|auto)
23112 This command overrides use of the symbol table to determine whether
23113 instructions are ARM or Thumb. The default is @samp{auto}, which
23114 causes @value{GDBN} to use the symbol table and then the setting
23115 of @samp{set arm fallback-mode}.
23117 @item show arm force-mode
23118 Show the current forced instruction mode.
23120 @item set debug arm
23121 Toggle whether to display ARM-specific debugging messages from the ARM
23122 target support subsystem.
23124 @item show debug arm
23125 Show whether ARM-specific debugging messages are enabled.
23129 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23130 The @value{GDBN} ARM simulator accepts the following optional arguments.
23133 @item --swi-support=@var{type}
23134 Tell the simulator which SWI interfaces to support. The argument
23135 @var{type} may be a comma separated list of the following values.
23136 The default value is @code{all}.
23151 The Motorola m68k configuration includes ColdFire support.
23154 @subsection MicroBlaze
23155 @cindex Xilinx MicroBlaze
23156 @cindex XMD, Xilinx Microprocessor Debugger
23158 The MicroBlaze is a soft-core processor supported on various Xilinx
23159 FPGAs, such as Spartan or Virtex series. Boards with these processors
23160 usually have JTAG ports which connect to a host system running the Xilinx
23161 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23162 This host system is used to download the configuration bitstream to
23163 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23164 communicates with the target board using the JTAG interface and
23165 presents a @code{gdbserver} interface to the board. By default
23166 @code{xmd} uses port @code{1234}. (While it is possible to change
23167 this default port, it requires the use of undocumented @code{xmd}
23168 commands. Contact Xilinx support if you need to do this.)
23170 Use these GDB commands to connect to the MicroBlaze target processor.
23173 @item target remote :1234
23174 Use this command to connect to the target if you are running @value{GDBN}
23175 on the same system as @code{xmd}.
23177 @item target remote @var{xmd-host}:1234
23178 Use this command to connect to the target if it is connected to @code{xmd}
23179 running on a different system named @var{xmd-host}.
23182 Use this command to download a program to the MicroBlaze target.
23184 @item set debug microblaze @var{n}
23185 Enable MicroBlaze-specific debugging messages if non-zero.
23187 @item show debug microblaze @var{n}
23188 Show MicroBlaze-specific debugging level.
23191 @node MIPS Embedded
23192 @subsection @acronym{MIPS} Embedded
23195 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23198 @item set mipsfpu double
23199 @itemx set mipsfpu single
23200 @itemx set mipsfpu none
23201 @itemx set mipsfpu auto
23202 @itemx show mipsfpu
23203 @kindex set mipsfpu
23204 @kindex show mipsfpu
23205 @cindex @acronym{MIPS} remote floating point
23206 @cindex floating point, @acronym{MIPS} remote
23207 If your target board does not support the @acronym{MIPS} floating point
23208 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23209 need this, you may wish to put the command in your @value{GDBN} init
23210 file). This tells @value{GDBN} how to find the return value of
23211 functions which return floating point values. It also allows
23212 @value{GDBN} to avoid saving the floating point registers when calling
23213 functions on the board. If you are using a floating point coprocessor
23214 with only single precision floating point support, as on the @sc{r4650}
23215 processor, use the command @samp{set mipsfpu single}. The default
23216 double precision floating point coprocessor may be selected using
23217 @samp{set mipsfpu double}.
23219 In previous versions the only choices were double precision or no
23220 floating point, so @samp{set mipsfpu on} will select double precision
23221 and @samp{set mipsfpu off} will select no floating point.
23223 As usual, you can inquire about the @code{mipsfpu} variable with
23224 @samp{show mipsfpu}.
23227 @node OpenRISC 1000
23228 @subsection OpenRISC 1000
23229 @cindex OpenRISC 1000
23232 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23233 mainly provided as a soft-core which can run on Xilinx, Altera and other
23236 @value{GDBN} for OpenRISC supports the below commands when connecting to
23244 Runs the builtin CPU simulator which can run very basic
23245 programs but does not support most hardware functions like MMU.
23246 For more complex use cases the user is advised to run an external
23247 target, and connect using @samp{target remote}.
23249 Example: @code{target sim}
23251 @item set debug or1k
23252 Toggle whether to display OpenRISC-specific debugging messages from the
23253 OpenRISC target support subsystem.
23255 @item show debug or1k
23256 Show whether OpenRISC-specific debugging messages are enabled.
23259 @node PowerPC Embedded
23260 @subsection PowerPC Embedded
23262 @cindex DVC register
23263 @value{GDBN} supports using the DVC (Data Value Compare) register to
23264 implement in hardware simple hardware watchpoint conditions of the form:
23267 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23268 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23271 The DVC register will be automatically used when @value{GDBN} detects
23272 such pattern in a condition expression, and the created watchpoint uses one
23273 debug register (either the @code{exact-watchpoints} option is on and the
23274 variable is scalar, or the variable has a length of one byte). This feature
23275 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23278 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23279 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23280 in which case watchpoints using only one debug register are created when
23281 watching variables of scalar types.
23283 You can create an artificial array to watch an arbitrary memory
23284 region using one of the following commands (@pxref{Expressions}):
23287 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23288 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23291 PowerPC embedded processors support masked watchpoints. See the discussion
23292 about the @code{mask} argument in @ref{Set Watchpoints}.
23294 @cindex ranged breakpoint
23295 PowerPC embedded processors support hardware accelerated
23296 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23297 the inferior whenever it executes an instruction at any address within
23298 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23299 use the @code{break-range} command.
23301 @value{GDBN} provides the following PowerPC-specific commands:
23304 @kindex break-range
23305 @item break-range @var{start-location}, @var{end-location}
23306 Set a breakpoint for an address range given by
23307 @var{start-location} and @var{end-location}, which can specify a function name,
23308 a line number, an offset of lines from the current line or from the start
23309 location, or an address of an instruction (see @ref{Specify Location},
23310 for a list of all the possible ways to specify a @var{location}.)
23311 The breakpoint will stop execution of the inferior whenever it
23312 executes an instruction at any address within the specified range,
23313 (including @var{start-location} and @var{end-location}.)
23315 @kindex set powerpc
23316 @item set powerpc soft-float
23317 @itemx show powerpc soft-float
23318 Force @value{GDBN} to use (or not use) a software floating point calling
23319 convention. By default, @value{GDBN} selects the calling convention based
23320 on the selected architecture and the provided executable file.
23322 @item set powerpc vector-abi
23323 @itemx show powerpc vector-abi
23324 Force @value{GDBN} to use the specified calling convention for vector
23325 arguments and return values. The valid options are @samp{auto};
23326 @samp{generic}, to avoid vector registers even if they are present;
23327 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23328 registers. By default, @value{GDBN} selects the calling convention
23329 based on the selected architecture and the provided executable file.
23331 @item set powerpc exact-watchpoints
23332 @itemx show powerpc exact-watchpoints
23333 Allow @value{GDBN} to use only one debug register when watching a variable
23334 of scalar type, thus assuming that the variable is accessed through the
23335 address of its first byte.
23340 @subsection Atmel AVR
23343 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23344 following AVR-specific commands:
23347 @item info io_registers
23348 @kindex info io_registers@r{, AVR}
23349 @cindex I/O registers (Atmel AVR)
23350 This command displays information about the AVR I/O registers. For
23351 each register, @value{GDBN} prints its number and value.
23358 When configured for debugging CRIS, @value{GDBN} provides the
23359 following CRIS-specific commands:
23362 @item set cris-version @var{ver}
23363 @cindex CRIS version
23364 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23365 The CRIS version affects register names and sizes. This command is useful in
23366 case autodetection of the CRIS version fails.
23368 @item show cris-version
23369 Show the current CRIS version.
23371 @item set cris-dwarf2-cfi
23372 @cindex DWARF-2 CFI and CRIS
23373 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23374 Change to @samp{off} when using @code{gcc-cris} whose version is below
23377 @item show cris-dwarf2-cfi
23378 Show the current state of using DWARF-2 CFI.
23380 @item set cris-mode @var{mode}
23382 Set the current CRIS mode to @var{mode}. It should only be changed when
23383 debugging in guru mode, in which case it should be set to
23384 @samp{guru} (the default is @samp{normal}).
23386 @item show cris-mode
23387 Show the current CRIS mode.
23391 @subsection Renesas Super-H
23394 For the Renesas Super-H processor, @value{GDBN} provides these
23398 @item set sh calling-convention @var{convention}
23399 @kindex set sh calling-convention
23400 Set the calling-convention used when calling functions from @value{GDBN}.
23401 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23402 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23403 convention. If the DWARF-2 information of the called function specifies
23404 that the function follows the Renesas calling convention, the function
23405 is called using the Renesas calling convention. If the calling convention
23406 is set to @samp{renesas}, the Renesas calling convention is always used,
23407 regardless of the DWARF-2 information. This can be used to override the
23408 default of @samp{gcc} if debug information is missing, or the compiler
23409 does not emit the DWARF-2 calling convention entry for a function.
23411 @item show sh calling-convention
23412 @kindex show sh calling-convention
23413 Show the current calling convention setting.
23418 @node Architectures
23419 @section Architectures
23421 This section describes characteristics of architectures that affect
23422 all uses of @value{GDBN} with the architecture, both native and cross.
23429 * HPPA:: HP PA architecture
23430 * SPU:: Cell Broadband Engine SPU architecture
23437 @subsection AArch64
23438 @cindex AArch64 support
23440 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23441 following special commands:
23444 @item set debug aarch64
23445 @kindex set debug aarch64
23446 This command determines whether AArch64 architecture-specific debugging
23447 messages are to be displayed.
23449 @item show debug aarch64
23450 Show whether AArch64 debugging messages are displayed.
23454 @subsubsection AArch64 SVE.
23455 @cindex AArch64 SVE.
23457 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23458 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23459 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23460 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23461 @code{$vg} will be provided. This is the vector granule for the current thread
23462 and represents the number of 64-bit chunks in an SVE @code{z} register.
23464 If the vector length changes, then the @code{$vg} register will be updated,
23465 but the lengths of the @code{z} and @code{p} registers will not change. This
23466 is a known limitation of @value{GDBN} and does not affect the execution of the
23471 @subsection x86 Architecture-specific Issues
23474 @item set struct-convention @var{mode}
23475 @kindex set struct-convention
23476 @cindex struct return convention
23477 @cindex struct/union returned in registers
23478 Set the convention used by the inferior to return @code{struct}s and
23479 @code{union}s from functions to @var{mode}. Possible values of
23480 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23481 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23482 are returned on the stack, while @code{"reg"} means that a
23483 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23484 be returned in a register.
23486 @item show struct-convention
23487 @kindex show struct-convention
23488 Show the current setting of the convention to return @code{struct}s
23493 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23494 @cindex Intel Memory Protection Extensions (MPX).
23496 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23497 @footnote{The register named with capital letters represent the architecture
23498 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23499 which are the lower bound and upper bound. Bounds are effective addresses or
23500 memory locations. The upper bounds are architecturally represented in 1's
23501 complement form. A bound having lower bound = 0, and upper bound = 0
23502 (1's complement of all bits set) will allow access to the entire address space.
23504 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23505 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23506 display the upper bound performing the complement of one operation on the
23507 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23508 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23509 can also be noted that the upper bounds are inclusive.
23511 As an example, assume that the register BND0 holds bounds for a pointer having
23512 access allowed for the range between 0x32 and 0x71. The values present on
23513 bnd0raw and bnd registers are presented as follows:
23516 bnd0raw = @{0x32, 0xffffffff8e@}
23517 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23520 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23521 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23522 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23523 Python, the display includes the memory size, in bits, accessible to
23526 Bounds can also be stored in bounds tables, which are stored in
23527 application memory. These tables store bounds for pointers by specifying
23528 the bounds pointer's value along with its bounds. Evaluating and changing
23529 bounds located in bound tables is therefore interesting while investigating
23530 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23533 @item show mpx bound @var{pointer}
23534 @kindex show mpx bound
23535 Display bounds of the given @var{pointer}.
23537 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23538 @kindex set mpx bound
23539 Set the bounds of a pointer in the bound table.
23540 This command takes three parameters: @var{pointer} is the pointers
23541 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23542 for lower and upper bounds respectively.
23545 When you call an inferior function on an Intel MPX enabled program,
23546 GDB sets the inferior's bound registers to the init (disabled) state
23547 before calling the function. As a consequence, bounds checks for the
23548 pointer arguments passed to the function will always pass.
23550 This is necessary because when you call an inferior function, the
23551 program is usually in the middle of the execution of other function.
23552 Since at that point bound registers are in an arbitrary state, not
23553 clearing them would lead to random bound violations in the called
23556 You can still examine the influence of the bound registers on the
23557 execution of the called function by stopping the execution of the
23558 called function at its prologue, setting bound registers, and
23559 continuing the execution. For example:
23563 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23564 $ print upper (a, b, c, d, 1)
23565 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23567 @{lbound = 0x0, ubound = ffffffff@} : size -1
23570 At this last step the value of bnd0 can be changed for investigation of bound
23571 violations caused along the execution of the call. In order to know how to
23572 set the bound registers or bound table for the call consult the ABI.
23577 See the following section.
23580 @subsection @acronym{MIPS}
23582 @cindex stack on Alpha
23583 @cindex stack on @acronym{MIPS}
23584 @cindex Alpha stack
23585 @cindex @acronym{MIPS} stack
23586 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23587 sometimes requires @value{GDBN} to search backward in the object code to
23588 find the beginning of a function.
23590 @cindex response time, @acronym{MIPS} debugging
23591 To improve response time (especially for embedded applications, where
23592 @value{GDBN} may be restricted to a slow serial line for this search)
23593 you may want to limit the size of this search, using one of these
23597 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23598 @item set heuristic-fence-post @var{limit}
23599 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23600 search for the beginning of a function. A value of @var{0} (the
23601 default) means there is no limit. However, except for @var{0}, the
23602 larger the limit the more bytes @code{heuristic-fence-post} must search
23603 and therefore the longer it takes to run. You should only need to use
23604 this command when debugging a stripped executable.
23606 @item show heuristic-fence-post
23607 Display the current limit.
23611 These commands are available @emph{only} when @value{GDBN} is configured
23612 for debugging programs on Alpha or @acronym{MIPS} processors.
23614 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23618 @item set mips abi @var{arg}
23619 @kindex set mips abi
23620 @cindex set ABI for @acronym{MIPS}
23621 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23622 values of @var{arg} are:
23626 The default ABI associated with the current binary (this is the
23636 @item show mips abi
23637 @kindex show mips abi
23638 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23640 @item set mips compression @var{arg}
23641 @kindex set mips compression
23642 @cindex code compression, @acronym{MIPS}
23643 Tell @value{GDBN} which @acronym{MIPS} compressed
23644 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23645 inferior. @value{GDBN} uses this for code disassembly and other
23646 internal interpretation purposes. This setting is only referred to
23647 when no executable has been associated with the debugging session or
23648 the executable does not provide information about the encoding it uses.
23649 Otherwise this setting is automatically updated from information
23650 provided by the executable.
23652 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23653 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23654 executables containing @acronym{MIPS16} code frequently are not
23655 identified as such.
23657 This setting is ``sticky''; that is, it retains its value across
23658 debugging sessions until reset either explicitly with this command or
23659 implicitly from an executable.
23661 The compiler and/or assembler typically add symbol table annotations to
23662 identify functions compiled for the @acronym{MIPS16} or
23663 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23664 are present, @value{GDBN} uses them in preference to the global
23665 compressed @acronym{ISA} encoding setting.
23667 @item show mips compression
23668 @kindex show mips compression
23669 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23670 @value{GDBN} to debug the inferior.
23673 @itemx show mipsfpu
23674 @xref{MIPS Embedded, set mipsfpu}.
23676 @item set mips mask-address @var{arg}
23677 @kindex set mips mask-address
23678 @cindex @acronym{MIPS} addresses, masking
23679 This command determines whether the most-significant 32 bits of 64-bit
23680 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23681 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23682 setting, which lets @value{GDBN} determine the correct value.
23684 @item show mips mask-address
23685 @kindex show mips mask-address
23686 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23689 @item set remote-mips64-transfers-32bit-regs
23690 @kindex set remote-mips64-transfers-32bit-regs
23691 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23692 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23693 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23694 and 64 bits for other registers, set this option to @samp{on}.
23696 @item show remote-mips64-transfers-32bit-regs
23697 @kindex show remote-mips64-transfers-32bit-regs
23698 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23700 @item set debug mips
23701 @kindex set debug mips
23702 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23703 target code in @value{GDBN}.
23705 @item show debug mips
23706 @kindex show debug mips
23707 Show the current setting of @acronym{MIPS} debugging messages.
23713 @cindex HPPA support
23715 When @value{GDBN} is debugging the HP PA architecture, it provides the
23716 following special commands:
23719 @item set debug hppa
23720 @kindex set debug hppa
23721 This command determines whether HPPA architecture-specific debugging
23722 messages are to be displayed.
23724 @item show debug hppa
23725 Show whether HPPA debugging messages are displayed.
23727 @item maint print unwind @var{address}
23728 @kindex maint print unwind@r{, HPPA}
23729 This command displays the contents of the unwind table entry at the
23730 given @var{address}.
23736 @subsection Cell Broadband Engine SPU architecture
23737 @cindex Cell Broadband Engine
23740 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23741 it provides the following special commands:
23744 @item info spu event
23746 Display SPU event facility status. Shows current event mask
23747 and pending event status.
23749 @item info spu signal
23750 Display SPU signal notification facility status. Shows pending
23751 signal-control word and signal notification mode of both signal
23752 notification channels.
23754 @item info spu mailbox
23755 Display SPU mailbox facility status. Shows all pending entries,
23756 in order of processing, in each of the SPU Write Outbound,
23757 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23760 Display MFC DMA status. Shows all pending commands in the MFC
23761 DMA queue. For each entry, opcode, tag, class IDs, effective
23762 and local store addresses and transfer size are shown.
23764 @item info spu proxydma
23765 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23766 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23767 and local store addresses and transfer size are shown.
23771 When @value{GDBN} is debugging a combined PowerPC/SPU application
23772 on the Cell Broadband Engine, it provides in addition the following
23776 @item set spu stop-on-load @var{arg}
23778 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23779 will give control to the user when a new SPE thread enters its @code{main}
23780 function. The default is @code{off}.
23782 @item show spu stop-on-load
23784 Show whether to stop for new SPE threads.
23786 @item set spu auto-flush-cache @var{arg}
23787 Set whether to automatically flush the software-managed cache. When set to
23788 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23789 cache to be flushed whenever SPE execution stops. This provides a consistent
23790 view of PowerPC memory that is accessed via the cache. If an application
23791 does not use the software-managed cache, this option has no effect.
23793 @item show spu auto-flush-cache
23794 Show whether to automatically flush the software-managed cache.
23799 @subsection PowerPC
23800 @cindex PowerPC architecture
23802 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23803 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23804 numbers stored in the floating point registers. These values must be stored
23805 in two consecutive registers, always starting at an even register like
23806 @code{f0} or @code{f2}.
23808 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23809 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23810 @code{f2} and @code{f3} for @code{$dl1} and so on.
23812 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23813 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23816 @subsection Nios II
23817 @cindex Nios II architecture
23819 When @value{GDBN} is debugging the Nios II architecture,
23820 it provides the following special commands:
23824 @item set debug nios2
23825 @kindex set debug nios2
23826 This command turns on and off debugging messages for the Nios II
23827 target code in @value{GDBN}.
23829 @item show debug nios2
23830 @kindex show debug nios2
23831 Show the current setting of Nios II debugging messages.
23835 @subsection Sparc64
23836 @cindex Sparc64 support
23837 @cindex Application Data Integrity
23838 @subsubsection ADI Support
23840 The M7 processor supports an Application Data Integrity (ADI) feature that
23841 detects invalid data accesses. When software allocates memory and enables
23842 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23843 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23844 the 4-bit version in every cacheline of that data. Hardware saves the latter
23845 in spare bits in the cache and memory hierarchy. On each load and store,
23846 the processor compares the upper 4 VA (virtual address) bits to the
23847 cacheline's version. If there is a mismatch, the processor generates a
23848 version mismatch trap which can be either precise or disrupting. The trap
23849 is an error condition which the kernel delivers to the process as a SIGSEGV
23852 Note that only 64-bit applications can use ADI and need to be built with
23855 Values of the ADI version tags, which are in granularity of a
23856 cacheline (64 bytes), can be viewed or modified.
23860 @kindex adi examine
23861 @item adi (examine | x) [ / @var{n} ] @var{addr}
23863 The @code{adi examine} command displays the value of one ADI version tag per
23866 @var{n} is a decimal integer specifying the number in bytes; the default
23867 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23868 block size, to display.
23870 @var{addr} is the address in user address space where you want @value{GDBN}
23871 to begin displaying the ADI version tags.
23873 Below is an example of displaying ADI versions of variable "shmaddr".
23876 (@value{GDBP}) adi x/100 shmaddr
23877 0xfff800010002c000: 0 0
23881 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23883 The @code{adi assign} command is used to assign new ADI version tag
23886 @var{n} is a decimal integer specifying the number in bytes;
23887 the default is 1. It specifies how much ADI version information, at the
23888 ratio of 1:ADI block size, to modify.
23890 @var{addr} is the address in user address space where you want @value{GDBN}
23891 to begin modifying the ADI version tags.
23893 @var{tag} is the new ADI version tag.
23895 For example, do the following to modify then verify ADI versions of
23896 variable "shmaddr":
23899 (@value{GDBP}) adi a/100 shmaddr = 7
23900 (@value{GDBP}) adi x/100 shmaddr
23901 0xfff800010002c000: 7 7
23906 @node Controlling GDB
23907 @chapter Controlling @value{GDBN}
23909 You can alter the way @value{GDBN} interacts with you by using the
23910 @code{set} command. For commands controlling how @value{GDBN} displays
23911 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23916 * Editing:: Command editing
23917 * Command History:: Command history
23918 * Screen Size:: Screen size
23919 * Numbers:: Numbers
23920 * ABI:: Configuring the current ABI
23921 * Auto-loading:: Automatically loading associated files
23922 * Messages/Warnings:: Optional warnings and messages
23923 * Debugging Output:: Optional messages about internal happenings
23924 * Other Misc Settings:: Other Miscellaneous Settings
23932 @value{GDBN} indicates its readiness to read a command by printing a string
23933 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23934 can change the prompt string with the @code{set prompt} command. For
23935 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23936 the prompt in one of the @value{GDBN} sessions so that you can always tell
23937 which one you are talking to.
23939 @emph{Note:} @code{set prompt} does not add a space for you after the
23940 prompt you set. This allows you to set a prompt which ends in a space
23941 or a prompt that does not.
23945 @item set prompt @var{newprompt}
23946 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23948 @kindex show prompt
23950 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23953 Versions of @value{GDBN} that ship with Python scripting enabled have
23954 prompt extensions. The commands for interacting with these extensions
23958 @kindex set extended-prompt
23959 @item set extended-prompt @var{prompt}
23960 Set an extended prompt that allows for substitutions.
23961 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23962 substitution. Any escape sequences specified as part of the prompt
23963 string are replaced with the corresponding strings each time the prompt
23969 set extended-prompt Current working directory: \w (gdb)
23972 Note that when an extended-prompt is set, it takes control of the
23973 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23975 @kindex show extended-prompt
23976 @item show extended-prompt
23977 Prints the extended prompt. Any escape sequences specified as part of
23978 the prompt string with @code{set extended-prompt}, are replaced with the
23979 corresponding strings each time the prompt is displayed.
23983 @section Command Editing
23985 @cindex command line editing
23987 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23988 @sc{gnu} library provides consistent behavior for programs which provide a
23989 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23990 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23991 substitution, and a storage and recall of command history across
23992 debugging sessions.
23994 You may control the behavior of command line editing in @value{GDBN} with the
23995 command @code{set}.
23998 @kindex set editing
24001 @itemx set editing on
24002 Enable command line editing (enabled by default).
24004 @item set editing off
24005 Disable command line editing.
24007 @kindex show editing
24009 Show whether command line editing is enabled.
24012 @ifset SYSTEM_READLINE
24013 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24015 @ifclear SYSTEM_READLINE
24016 @xref{Command Line Editing},
24018 for more details about the Readline
24019 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24020 encouraged to read that chapter.
24022 @node Command History
24023 @section Command History
24024 @cindex command history
24026 @value{GDBN} can keep track of the commands you type during your
24027 debugging sessions, so that you can be certain of precisely what
24028 happened. Use these commands to manage the @value{GDBN} command
24031 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24032 package, to provide the history facility.
24033 @ifset SYSTEM_READLINE
24034 @xref{Using History Interactively, , , history, GNU History Library},
24036 @ifclear SYSTEM_READLINE
24037 @xref{Using History Interactively},
24039 for the detailed description of the History library.
24041 To issue a command to @value{GDBN} without affecting certain aspects of
24042 the state which is seen by users, prefix it with @samp{server }
24043 (@pxref{Server Prefix}). This
24044 means that this command will not affect the command history, nor will it
24045 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24046 pressed on a line by itself.
24048 @cindex @code{server}, command prefix
24049 The server prefix does not affect the recording of values into the value
24050 history; to print a value without recording it into the value history,
24051 use the @code{output} command instead of the @code{print} command.
24053 Here is the description of @value{GDBN} commands related to command
24057 @cindex history substitution
24058 @cindex history file
24059 @kindex set history filename
24060 @cindex @env{GDBHISTFILE}, environment variable
24061 @item set history filename @var{fname}
24062 Set the name of the @value{GDBN} command history file to @var{fname}.
24063 This is the file where @value{GDBN} reads an initial command history
24064 list, and where it writes the command history from this session when it
24065 exits. You can access this list through history expansion or through
24066 the history command editing characters listed below. This file defaults
24067 to the value of the environment variable @code{GDBHISTFILE}, or to
24068 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24071 @cindex save command history
24072 @kindex set history save
24073 @item set history save
24074 @itemx set history save on
24075 Record command history in a file, whose name may be specified with the
24076 @code{set history filename} command. By default, this option is disabled.
24078 @item set history save off
24079 Stop recording command history in a file.
24081 @cindex history size
24082 @kindex set history size
24083 @cindex @env{GDBHISTSIZE}, environment variable
24084 @item set history size @var{size}
24085 @itemx set history size unlimited
24086 Set the number of commands which @value{GDBN} keeps in its history list.
24087 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24088 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24089 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24090 either a negative number or the empty string, then the number of commands
24091 @value{GDBN} keeps in the history list is unlimited.
24093 @cindex remove duplicate history
24094 @kindex set history remove-duplicates
24095 @item set history remove-duplicates @var{count}
24096 @itemx set history remove-duplicates unlimited
24097 Control the removal of duplicate history entries in the command history list.
24098 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24099 history entries and remove the first entry that is a duplicate of the current
24100 entry being added to the command history list. If @var{count} is
24101 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24102 removal of duplicate history entries is disabled.
24104 Only history entries added during the current session are considered for
24105 removal. This option is set to 0 by default.
24109 History expansion assigns special meaning to the character @kbd{!}.
24110 @ifset SYSTEM_READLINE
24111 @xref{Event Designators, , , history, GNU History Library},
24113 @ifclear SYSTEM_READLINE
24114 @xref{Event Designators},
24118 @cindex history expansion, turn on/off
24119 Since @kbd{!} is also the logical not operator in C, history expansion
24120 is off by default. If you decide to enable history expansion with the
24121 @code{set history expansion on} command, you may sometimes need to
24122 follow @kbd{!} (when it is used as logical not, in an expression) with
24123 a space or a tab to prevent it from being expanded. The readline
24124 history facilities do not attempt substitution on the strings
24125 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24127 The commands to control history expansion are:
24130 @item set history expansion on
24131 @itemx set history expansion
24132 @kindex set history expansion
24133 Enable history expansion. History expansion is off by default.
24135 @item set history expansion off
24136 Disable history expansion.
24139 @kindex show history
24141 @itemx show history filename
24142 @itemx show history save
24143 @itemx show history size
24144 @itemx show history expansion
24145 These commands display the state of the @value{GDBN} history parameters.
24146 @code{show history} by itself displays all four states.
24151 @kindex show commands
24152 @cindex show last commands
24153 @cindex display command history
24154 @item show commands
24155 Display the last ten commands in the command history.
24157 @item show commands @var{n}
24158 Print ten commands centered on command number @var{n}.
24160 @item show commands +
24161 Print ten commands just after the commands last printed.
24165 @section Screen Size
24166 @cindex size of screen
24167 @cindex screen size
24170 @cindex pauses in output
24172 Certain commands to @value{GDBN} may produce large amounts of
24173 information output to the screen. To help you read all of it,
24174 @value{GDBN} pauses and asks you for input at the end of each page of
24175 output. Type @key{RET} when you want to see one more page of output,
24176 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24177 without paging for the rest of the current command. Also, the screen
24178 width setting determines when to wrap lines of output. Depending on
24179 what is being printed, @value{GDBN} tries to break the line at a
24180 readable place, rather than simply letting it overflow onto the
24183 Normally @value{GDBN} knows the size of the screen from the terminal
24184 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24185 together with the value of the @code{TERM} environment variable and the
24186 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24187 you can override it with the @code{set height} and @code{set
24194 @kindex show height
24195 @item set height @var{lpp}
24196 @itemx set height unlimited
24198 @itemx set width @var{cpl}
24199 @itemx set width unlimited
24201 These @code{set} commands specify a screen height of @var{lpp} lines and
24202 a screen width of @var{cpl} characters. The associated @code{show}
24203 commands display the current settings.
24205 If you specify a height of either @code{unlimited} or zero lines,
24206 @value{GDBN} does not pause during output no matter how long the
24207 output is. This is useful if output is to a file or to an editor
24210 Likewise, you can specify @samp{set width unlimited} or @samp{set
24211 width 0} to prevent @value{GDBN} from wrapping its output.
24213 @item set pagination on
24214 @itemx set pagination off
24215 @kindex set pagination
24216 Turn the output pagination on or off; the default is on. Turning
24217 pagination off is the alternative to @code{set height unlimited}. Note that
24218 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24219 Options, -batch}) also automatically disables pagination.
24221 @item show pagination
24222 @kindex show pagination
24223 Show the current pagination mode.
24228 @cindex number representation
24229 @cindex entering numbers
24231 You can always enter numbers in octal, decimal, or hexadecimal in
24232 @value{GDBN} by the usual conventions: octal numbers begin with
24233 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24234 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24235 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24236 10; likewise, the default display for numbers---when no particular
24237 format is specified---is base 10. You can change the default base for
24238 both input and output with the commands described below.
24241 @kindex set input-radix
24242 @item set input-radix @var{base}
24243 Set the default base for numeric input. Supported choices
24244 for @var{base} are decimal 8, 10, or 16. The base must itself be
24245 specified either unambiguously or using the current input radix; for
24249 set input-radix 012
24250 set input-radix 10.
24251 set input-radix 0xa
24255 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24256 leaves the input radix unchanged, no matter what it was, since
24257 @samp{10}, being without any leading or trailing signs of its base, is
24258 interpreted in the current radix. Thus, if the current radix is 16,
24259 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24262 @kindex set output-radix
24263 @item set output-radix @var{base}
24264 Set the default base for numeric display. Supported choices
24265 for @var{base} are decimal 8, 10, or 16. The base must itself be
24266 specified either unambiguously or using the current input radix.
24268 @kindex show input-radix
24269 @item show input-radix
24270 Display the current default base for numeric input.
24272 @kindex show output-radix
24273 @item show output-radix
24274 Display the current default base for numeric display.
24276 @item set radix @r{[}@var{base}@r{]}
24280 These commands set and show the default base for both input and output
24281 of numbers. @code{set radix} sets the radix of input and output to
24282 the same base; without an argument, it resets the radix back to its
24283 default value of 10.
24288 @section Configuring the Current ABI
24290 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24291 application automatically. However, sometimes you need to override its
24292 conclusions. Use these commands to manage @value{GDBN}'s view of the
24298 @cindex Newlib OS ABI and its influence on the longjmp handling
24300 One @value{GDBN} configuration can debug binaries for multiple operating
24301 system targets, either via remote debugging or native emulation.
24302 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24303 but you can override its conclusion using the @code{set osabi} command.
24304 One example where this is useful is in debugging of binaries which use
24305 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24306 not have the same identifying marks that the standard C library for your
24309 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24310 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24311 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24312 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24316 Show the OS ABI currently in use.
24319 With no argument, show the list of registered available OS ABI's.
24321 @item set osabi @var{abi}
24322 Set the current OS ABI to @var{abi}.
24325 @cindex float promotion
24327 Generally, the way that an argument of type @code{float} is passed to a
24328 function depends on whether the function is prototyped. For a prototyped
24329 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24330 according to the architecture's convention for @code{float}. For unprototyped
24331 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24332 @code{double} and then passed.
24334 Unfortunately, some forms of debug information do not reliably indicate whether
24335 a function is prototyped. If @value{GDBN} calls a function that is not marked
24336 as prototyped, it consults @kbd{set coerce-float-to-double}.
24339 @kindex set coerce-float-to-double
24340 @item set coerce-float-to-double
24341 @itemx set coerce-float-to-double on
24342 Arguments of type @code{float} will be promoted to @code{double} when passed
24343 to an unprototyped function. This is the default setting.
24345 @item set coerce-float-to-double off
24346 Arguments of type @code{float} will be passed directly to unprototyped
24349 @kindex show coerce-float-to-double
24350 @item show coerce-float-to-double
24351 Show the current setting of promoting @code{float} to @code{double}.
24355 @kindex show cp-abi
24356 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24357 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24358 used to build your application. @value{GDBN} only fully supports
24359 programs with a single C@t{++} ABI; if your program contains code using
24360 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24361 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24362 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24363 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24364 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24365 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24370 Show the C@t{++} ABI currently in use.
24373 With no argument, show the list of supported C@t{++} ABI's.
24375 @item set cp-abi @var{abi}
24376 @itemx set cp-abi auto
24377 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24381 @section Automatically loading associated files
24382 @cindex auto-loading
24384 @value{GDBN} sometimes reads files with commands and settings automatically,
24385 without being explicitly told so by the user. We call this feature
24386 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24387 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24388 results or introduce security risks (e.g., if the file comes from untrusted
24392 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24393 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24395 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24396 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24399 There are various kinds of files @value{GDBN} can automatically load.
24400 In addition to these files, @value{GDBN} supports auto-loading code written
24401 in various extension languages. @xref{Auto-loading extensions}.
24403 Note that loading of these associated files (including the local @file{.gdbinit}
24404 file) requires accordingly configured @code{auto-load safe-path}
24405 (@pxref{Auto-loading safe path}).
24407 For these reasons, @value{GDBN} includes commands and options to let you
24408 control when to auto-load files and which files should be auto-loaded.
24411 @anchor{set auto-load off}
24412 @kindex set auto-load off
24413 @item set auto-load off
24414 Globally disable loading of all auto-loaded files.
24415 You may want to use this command with the @samp{-iex} option
24416 (@pxref{Option -init-eval-command}) such as:
24418 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24421 Be aware that system init file (@pxref{System-wide configuration})
24422 and init files from your home directory (@pxref{Home Directory Init File})
24423 still get read (as they come from generally trusted directories).
24424 To prevent @value{GDBN} from auto-loading even those init files, use the
24425 @option{-nx} option (@pxref{Mode Options}), in addition to
24426 @code{set auto-load no}.
24428 @anchor{show auto-load}
24429 @kindex show auto-load
24430 @item show auto-load
24431 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24435 (gdb) show auto-load
24436 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24437 libthread-db: Auto-loading of inferior specific libthread_db is on.
24438 local-gdbinit: Auto-loading of .gdbinit script from current directory
24440 python-scripts: Auto-loading of Python scripts is on.
24441 safe-path: List of directories from which it is safe to auto-load files
24442 is $debugdir:$datadir/auto-load.
24443 scripts-directory: List of directories from which to load auto-loaded scripts
24444 is $debugdir:$datadir/auto-load.
24447 @anchor{info auto-load}
24448 @kindex info auto-load
24449 @item info auto-load
24450 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24454 (gdb) info auto-load
24457 Yes /home/user/gdb/gdb-gdb.gdb
24458 libthread-db: No auto-loaded libthread-db.
24459 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24463 Yes /home/user/gdb/gdb-gdb.py
24467 These are @value{GDBN} control commands for the auto-loading:
24469 @multitable @columnfractions .5 .5
24470 @item @xref{set auto-load off}.
24471 @tab Disable auto-loading globally.
24472 @item @xref{show auto-load}.
24473 @tab Show setting of all kinds of files.
24474 @item @xref{info auto-load}.
24475 @tab Show state of all kinds of files.
24476 @item @xref{set auto-load gdb-scripts}.
24477 @tab Control for @value{GDBN} command scripts.
24478 @item @xref{show auto-load gdb-scripts}.
24479 @tab Show setting of @value{GDBN} command scripts.
24480 @item @xref{info auto-load gdb-scripts}.
24481 @tab Show state of @value{GDBN} command scripts.
24482 @item @xref{set auto-load python-scripts}.
24483 @tab Control for @value{GDBN} Python scripts.
24484 @item @xref{show auto-load python-scripts}.
24485 @tab Show setting of @value{GDBN} Python scripts.
24486 @item @xref{info auto-load python-scripts}.
24487 @tab Show state of @value{GDBN} Python scripts.
24488 @item @xref{set auto-load guile-scripts}.
24489 @tab Control for @value{GDBN} Guile scripts.
24490 @item @xref{show auto-load guile-scripts}.
24491 @tab Show setting of @value{GDBN} Guile scripts.
24492 @item @xref{info auto-load guile-scripts}.
24493 @tab Show state of @value{GDBN} Guile scripts.
24494 @item @xref{set auto-load scripts-directory}.
24495 @tab Control for @value{GDBN} auto-loaded scripts location.
24496 @item @xref{show auto-load scripts-directory}.
24497 @tab Show @value{GDBN} auto-loaded scripts location.
24498 @item @xref{add-auto-load-scripts-directory}.
24499 @tab Add directory for auto-loaded scripts location list.
24500 @item @xref{set auto-load local-gdbinit}.
24501 @tab Control for init file in the current directory.
24502 @item @xref{show auto-load local-gdbinit}.
24503 @tab Show setting of init file in the current directory.
24504 @item @xref{info auto-load local-gdbinit}.
24505 @tab Show state of init file in the current directory.
24506 @item @xref{set auto-load libthread-db}.
24507 @tab Control for thread debugging library.
24508 @item @xref{show auto-load libthread-db}.
24509 @tab Show setting of thread debugging library.
24510 @item @xref{info auto-load libthread-db}.
24511 @tab Show state of thread debugging library.
24512 @item @xref{set auto-load safe-path}.
24513 @tab Control directories trusted for automatic loading.
24514 @item @xref{show auto-load safe-path}.
24515 @tab Show directories trusted for automatic loading.
24516 @item @xref{add-auto-load-safe-path}.
24517 @tab Add directory trusted for automatic loading.
24520 @node Init File in the Current Directory
24521 @subsection Automatically loading init file in the current directory
24522 @cindex auto-loading init file in the current directory
24524 By default, @value{GDBN} reads and executes the canned sequences of commands
24525 from init file (if any) in the current working directory,
24526 see @ref{Init File in the Current Directory during Startup}.
24528 Note that loading of this local @file{.gdbinit} file also requires accordingly
24529 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24532 @anchor{set auto-load local-gdbinit}
24533 @kindex set auto-load local-gdbinit
24534 @item set auto-load local-gdbinit [on|off]
24535 Enable or disable the auto-loading of canned sequences of commands
24536 (@pxref{Sequences}) found in init file in the current directory.
24538 @anchor{show auto-load local-gdbinit}
24539 @kindex show auto-load local-gdbinit
24540 @item show auto-load local-gdbinit
24541 Show whether auto-loading of canned sequences of commands from init file in the
24542 current directory is enabled or disabled.
24544 @anchor{info auto-load local-gdbinit}
24545 @kindex info auto-load local-gdbinit
24546 @item info auto-load local-gdbinit
24547 Print whether canned sequences of commands from init file in the
24548 current directory have been auto-loaded.
24551 @node libthread_db.so.1 file
24552 @subsection Automatically loading thread debugging library
24553 @cindex auto-loading libthread_db.so.1
24555 This feature is currently present only on @sc{gnu}/Linux native hosts.
24557 @value{GDBN} reads in some cases thread debugging library from places specific
24558 to the inferior (@pxref{set libthread-db-search-path}).
24560 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24561 without checking this @samp{set auto-load libthread-db} switch as system
24562 libraries have to be trusted in general. In all other cases of
24563 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24564 auto-load libthread-db} is enabled before trying to open such thread debugging
24567 Note that loading of this debugging library also requires accordingly configured
24568 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24571 @anchor{set auto-load libthread-db}
24572 @kindex set auto-load libthread-db
24573 @item set auto-load libthread-db [on|off]
24574 Enable or disable the auto-loading of inferior specific thread debugging library.
24576 @anchor{show auto-load libthread-db}
24577 @kindex show auto-load libthread-db
24578 @item show auto-load libthread-db
24579 Show whether auto-loading of inferior specific thread debugging library is
24580 enabled or disabled.
24582 @anchor{info auto-load libthread-db}
24583 @kindex info auto-load libthread-db
24584 @item info auto-load libthread-db
24585 Print the list of all loaded inferior specific thread debugging libraries and
24586 for each such library print list of inferior @var{pid}s using it.
24589 @node Auto-loading safe path
24590 @subsection Security restriction for auto-loading
24591 @cindex auto-loading safe-path
24593 As the files of inferior can come from untrusted source (such as submitted by
24594 an application user) @value{GDBN} does not always load any files automatically.
24595 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24596 directories trusted for loading files not explicitly requested by user.
24597 Each directory can also be a shell wildcard pattern.
24599 If the path is not set properly you will see a warning and the file will not
24604 Reading symbols from /home/user/gdb/gdb...done.
24605 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24606 declined by your `auto-load safe-path' set
24607 to "$debugdir:$datadir/auto-load".
24608 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24609 declined by your `auto-load safe-path' set
24610 to "$debugdir:$datadir/auto-load".
24614 To instruct @value{GDBN} to go ahead and use the init files anyway,
24615 invoke @value{GDBN} like this:
24618 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24621 The list of trusted directories is controlled by the following commands:
24624 @anchor{set auto-load safe-path}
24625 @kindex set auto-load safe-path
24626 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24627 Set the list of directories (and their subdirectories) trusted for automatic
24628 loading and execution of scripts. You can also enter a specific trusted file.
24629 Each directory can also be a shell wildcard pattern; wildcards do not match
24630 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24631 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24632 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24633 its default value as specified during @value{GDBN} compilation.
24635 The list of directories uses path separator (@samp{:} on GNU and Unix
24636 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24637 to the @env{PATH} environment variable.
24639 @anchor{show auto-load safe-path}
24640 @kindex show auto-load safe-path
24641 @item show auto-load safe-path
24642 Show the list of directories trusted for automatic loading and execution of
24645 @anchor{add-auto-load-safe-path}
24646 @kindex add-auto-load-safe-path
24647 @item add-auto-load-safe-path
24648 Add an entry (or list of entries) to the list of directories trusted for
24649 automatic loading and execution of scripts. Multiple entries may be delimited
24650 by the host platform path separator in use.
24653 This variable defaults to what @code{--with-auto-load-dir} has been configured
24654 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24655 substitution applies the same as for @ref{set auto-load scripts-directory}.
24656 The default @code{set auto-load safe-path} value can be also overriden by
24657 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24659 Setting this variable to @file{/} disables this security protection,
24660 corresponding @value{GDBN} configuration option is
24661 @option{--without-auto-load-safe-path}.
24662 This variable is supposed to be set to the system directories writable by the
24663 system superuser only. Users can add their source directories in init files in
24664 their home directories (@pxref{Home Directory Init File}). See also deprecated
24665 init file in the current directory
24666 (@pxref{Init File in the Current Directory during Startup}).
24668 To force @value{GDBN} to load the files it declined to load in the previous
24669 example, you could use one of the following ways:
24672 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24673 Specify this trusted directory (or a file) as additional component of the list.
24674 You have to specify also any existing directories displayed by
24675 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24677 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24678 Specify this directory as in the previous case but just for a single
24679 @value{GDBN} session.
24681 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24682 Disable auto-loading safety for a single @value{GDBN} session.
24683 This assumes all the files you debug during this @value{GDBN} session will come
24684 from trusted sources.
24686 @item @kbd{./configure --without-auto-load-safe-path}
24687 During compilation of @value{GDBN} you may disable any auto-loading safety.
24688 This assumes all the files you will ever debug with this @value{GDBN} come from
24692 On the other hand you can also explicitly forbid automatic files loading which
24693 also suppresses any such warning messages:
24696 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24697 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24699 @item @file{~/.gdbinit}: @samp{set auto-load no}
24700 Disable auto-loading globally for the user
24701 (@pxref{Home Directory Init File}). While it is improbable, you could also
24702 use system init file instead (@pxref{System-wide configuration}).
24705 This setting applies to the file names as entered by user. If no entry matches
24706 @value{GDBN} tries as a last resort to also resolve all the file names into
24707 their canonical form (typically resolving symbolic links) and compare the
24708 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24709 own before starting the comparison so a canonical form of directories is
24710 recommended to be entered.
24712 @node Auto-loading verbose mode
24713 @subsection Displaying files tried for auto-load
24714 @cindex auto-loading verbose mode
24716 For better visibility of all the file locations where you can place scripts to
24717 be auto-loaded with inferior --- or to protect yourself against accidental
24718 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24719 all the files attempted to be loaded. Both existing and non-existing files may
24722 For example the list of directories from which it is safe to auto-load files
24723 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24724 may not be too obvious while setting it up.
24727 (gdb) set debug auto-load on
24728 (gdb) file ~/src/t/true
24729 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24730 for objfile "/tmp/true".
24731 auto-load: Updating directories of "/usr:/opt".
24732 auto-load: Using directory "/usr".
24733 auto-load: Using directory "/opt".
24734 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24735 by your `auto-load safe-path' set to "/usr:/opt".
24739 @anchor{set debug auto-load}
24740 @kindex set debug auto-load
24741 @item set debug auto-load [on|off]
24742 Set whether to print the filenames attempted to be auto-loaded.
24744 @anchor{show debug auto-load}
24745 @kindex show debug auto-load
24746 @item show debug auto-load
24747 Show whether printing of the filenames attempted to be auto-loaded is turned
24751 @node Messages/Warnings
24752 @section Optional Warnings and Messages
24754 @cindex verbose operation
24755 @cindex optional warnings
24756 By default, @value{GDBN} is silent about its inner workings. If you are
24757 running on a slow machine, you may want to use the @code{set verbose}
24758 command. This makes @value{GDBN} tell you when it does a lengthy
24759 internal operation, so you will not think it has crashed.
24761 Currently, the messages controlled by @code{set verbose} are those
24762 which announce that the symbol table for a source file is being read;
24763 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24766 @kindex set verbose
24767 @item set verbose on
24768 Enables @value{GDBN} output of certain informational messages.
24770 @item set verbose off
24771 Disables @value{GDBN} output of certain informational messages.
24773 @kindex show verbose
24775 Displays whether @code{set verbose} is on or off.
24778 By default, if @value{GDBN} encounters bugs in the symbol table of an
24779 object file, it is silent; but if you are debugging a compiler, you may
24780 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24785 @kindex set complaints
24786 @item set complaints @var{limit}
24787 Permits @value{GDBN} to output @var{limit} complaints about each type of
24788 unusual symbols before becoming silent about the problem. Set
24789 @var{limit} to zero to suppress all complaints; set it to a large number
24790 to prevent complaints from being suppressed.
24792 @kindex show complaints
24793 @item show complaints
24794 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24798 @anchor{confirmation requests}
24799 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24800 lot of stupid questions to confirm certain commands. For example, if
24801 you try to run a program which is already running:
24805 The program being debugged has been started already.
24806 Start it from the beginning? (y or n)
24809 If you are willing to unflinchingly face the consequences of your own
24810 commands, you can disable this ``feature'':
24814 @kindex set confirm
24816 @cindex confirmation
24817 @cindex stupid questions
24818 @item set confirm off
24819 Disables confirmation requests. Note that running @value{GDBN} with
24820 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24821 automatically disables confirmation requests.
24823 @item set confirm on
24824 Enables confirmation requests (the default).
24826 @kindex show confirm
24828 Displays state of confirmation requests.
24832 @cindex command tracing
24833 If you need to debug user-defined commands or sourced files you may find it
24834 useful to enable @dfn{command tracing}. In this mode each command will be
24835 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24836 quantity denoting the call depth of each command.
24839 @kindex set trace-commands
24840 @cindex command scripts, debugging
24841 @item set trace-commands on
24842 Enable command tracing.
24843 @item set trace-commands off
24844 Disable command tracing.
24845 @item show trace-commands
24846 Display the current state of command tracing.
24849 @node Debugging Output
24850 @section Optional Messages about Internal Happenings
24851 @cindex optional debugging messages
24853 @value{GDBN} has commands that enable optional debugging messages from
24854 various @value{GDBN} subsystems; normally these commands are of
24855 interest to @value{GDBN} maintainers, or when reporting a bug. This
24856 section documents those commands.
24859 @kindex set exec-done-display
24860 @item set exec-done-display
24861 Turns on or off the notification of asynchronous commands'
24862 completion. When on, @value{GDBN} will print a message when an
24863 asynchronous command finishes its execution. The default is off.
24864 @kindex show exec-done-display
24865 @item show exec-done-display
24866 Displays the current setting of asynchronous command completion
24869 @cindex ARM AArch64
24870 @item set debug aarch64
24871 Turns on or off display of debugging messages related to ARM AArch64.
24872 The default is off.
24874 @item show debug aarch64
24875 Displays the current state of displaying debugging messages related to
24877 @cindex gdbarch debugging info
24878 @cindex architecture debugging info
24879 @item set debug arch
24880 Turns on or off display of gdbarch debugging info. The default is off
24881 @item show debug arch
24882 Displays the current state of displaying gdbarch debugging info.
24883 @item set debug aix-solib
24884 @cindex AIX shared library debugging
24885 Control display of debugging messages from the AIX shared library
24886 support module. The default is off.
24887 @item show debug aix-thread
24888 Show the current state of displaying AIX shared library debugging messages.
24889 @item set debug aix-thread
24890 @cindex AIX threads
24891 Display debugging messages about inner workings of the AIX thread
24893 @item show debug aix-thread
24894 Show the current state of AIX thread debugging info display.
24895 @item set debug check-physname
24897 Check the results of the ``physname'' computation. When reading DWARF
24898 debugging information for C@t{++}, @value{GDBN} attempts to compute
24899 each entity's name. @value{GDBN} can do this computation in two
24900 different ways, depending on exactly what information is present.
24901 When enabled, this setting causes @value{GDBN} to compute the names
24902 both ways and display any discrepancies.
24903 @item show debug check-physname
24904 Show the current state of ``physname'' checking.
24905 @item set debug coff-pe-read
24906 @cindex COFF/PE exported symbols
24907 Control display of debugging messages related to reading of COFF/PE
24908 exported symbols. The default is off.
24909 @item show debug coff-pe-read
24910 Displays the current state of displaying debugging messages related to
24911 reading of COFF/PE exported symbols.
24912 @item set debug dwarf-die
24914 Dump DWARF DIEs after they are read in.
24915 The value is the number of nesting levels to print.
24916 A value of zero turns off the display.
24917 @item show debug dwarf-die
24918 Show the current state of DWARF DIE debugging.
24919 @item set debug dwarf-line
24920 @cindex DWARF Line Tables
24921 Turns on or off display of debugging messages related to reading
24922 DWARF line tables. The default is 0 (off).
24923 A value of 1 provides basic information.
24924 A value greater than 1 provides more verbose information.
24925 @item show debug dwarf-line
24926 Show the current state of DWARF line table debugging.
24927 @item set debug dwarf-read
24928 @cindex DWARF Reading
24929 Turns on or off display of debugging messages related to reading
24930 DWARF debug info. The default is 0 (off).
24931 A value of 1 provides basic information.
24932 A value greater than 1 provides more verbose information.
24933 @item show debug dwarf-read
24934 Show the current state of DWARF reader debugging.
24935 @item set debug displaced
24936 @cindex displaced stepping debugging info
24937 Turns on or off display of @value{GDBN} debugging info for the
24938 displaced stepping support. The default is off.
24939 @item show debug displaced
24940 Displays the current state of displaying @value{GDBN} debugging info
24941 related to displaced stepping.
24942 @item set debug event
24943 @cindex event debugging info
24944 Turns on or off display of @value{GDBN} event debugging info. The
24946 @item show debug event
24947 Displays the current state of displaying @value{GDBN} event debugging
24949 @item set debug expression
24950 @cindex expression debugging info
24951 Turns on or off display of debugging info about @value{GDBN}
24952 expression parsing. The default is off.
24953 @item show debug expression
24954 Displays the current state of displaying debugging info about
24955 @value{GDBN} expression parsing.
24956 @item set debug fbsd-lwp
24957 @cindex FreeBSD LWP debug messages
24958 Turns on or off debugging messages from the FreeBSD LWP debug support.
24959 @item show debug fbsd-lwp
24960 Show the current state of FreeBSD LWP debugging messages.
24961 @item set debug fbsd-nat
24962 @cindex FreeBSD native target debug messages
24963 Turns on or off debugging messages from the FreeBSD native target.
24964 @item show debug fbsd-nat
24965 Show the current state of FreeBSD native target debugging messages.
24966 @item set debug frame
24967 @cindex frame debugging info
24968 Turns on or off display of @value{GDBN} frame debugging info. The
24970 @item show debug frame
24971 Displays the current state of displaying @value{GDBN} frame debugging
24973 @item set debug gnu-nat
24974 @cindex @sc{gnu}/Hurd debug messages
24975 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24976 @item show debug gnu-nat
24977 Show the current state of @sc{gnu}/Hurd debugging messages.
24978 @item set debug infrun
24979 @cindex inferior debugging info
24980 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24981 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24982 for implementing operations such as single-stepping the inferior.
24983 @item show debug infrun
24984 Displays the current state of @value{GDBN} inferior debugging.
24985 @item set debug jit
24986 @cindex just-in-time compilation, debugging messages
24987 Turn on or off debugging messages from JIT debug support.
24988 @item show debug jit
24989 Displays the current state of @value{GDBN} JIT debugging.
24990 @item set debug lin-lwp
24991 @cindex @sc{gnu}/Linux LWP debug messages
24992 @cindex Linux lightweight processes
24993 Turn on or off debugging messages from the Linux LWP debug support.
24994 @item show debug lin-lwp
24995 Show the current state of Linux LWP debugging messages.
24996 @item set debug linux-namespaces
24997 @cindex @sc{gnu}/Linux namespaces debug messages
24998 Turn on or off debugging messages from the Linux namespaces debug support.
24999 @item show debug linux-namespaces
25000 Show the current state of Linux namespaces debugging messages.
25001 @item set debug mach-o
25002 @cindex Mach-O symbols processing
25003 Control display of debugging messages related to Mach-O symbols
25004 processing. The default is off.
25005 @item show debug mach-o
25006 Displays the current state of displaying debugging messages related to
25007 reading of COFF/PE exported symbols.
25008 @item set debug notification
25009 @cindex remote async notification debugging info
25010 Turn on or off debugging messages about remote async notification.
25011 The default is off.
25012 @item show debug notification
25013 Displays the current state of remote async notification debugging messages.
25014 @item set debug observer
25015 @cindex observer debugging info
25016 Turns on or off display of @value{GDBN} observer debugging. This
25017 includes info such as the notification of observable events.
25018 @item show debug observer
25019 Displays the current state of observer debugging.
25020 @item set debug overload
25021 @cindex C@t{++} overload debugging info
25022 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25023 info. This includes info such as ranking of functions, etc. The default
25025 @item show debug overload
25026 Displays the current state of displaying @value{GDBN} C@t{++} overload
25028 @cindex expression parser, debugging info
25029 @cindex debug expression parser
25030 @item set debug parser
25031 Turns on or off the display of expression parser debugging output.
25032 Internally, this sets the @code{yydebug} variable in the expression
25033 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25034 details. The default is off.
25035 @item show debug parser
25036 Show the current state of expression parser debugging.
25037 @cindex packets, reporting on stdout
25038 @cindex serial connections, debugging
25039 @cindex debug remote protocol
25040 @cindex remote protocol debugging
25041 @cindex display remote packets
25042 @item set debug remote
25043 Turns on or off display of reports on all packets sent back and forth across
25044 the serial line to the remote machine. The info is printed on the
25045 @value{GDBN} standard output stream. The default is off.
25046 @item show debug remote
25047 Displays the state of display of remote packets.
25049 @item set debug separate-debug-file
25050 Turns on or off display of debug output about separate debug file search.
25051 @item show debug separate-debug-file
25052 Displays the state of separate debug file search debug output.
25054 @item set debug serial
25055 Turns on or off display of @value{GDBN} serial debugging info. The
25057 @item show debug serial
25058 Displays the current state of displaying @value{GDBN} serial debugging
25060 @item set debug solib-frv
25061 @cindex FR-V shared-library debugging
25062 Turn on or off debugging messages for FR-V shared-library code.
25063 @item show debug solib-frv
25064 Display the current state of FR-V shared-library code debugging
25066 @item set debug symbol-lookup
25067 @cindex symbol lookup
25068 Turns on or off display of debugging messages related to symbol lookup.
25069 The default is 0 (off).
25070 A value of 1 provides basic information.
25071 A value greater than 1 provides more verbose information.
25072 @item show debug symbol-lookup
25073 Show the current state of symbol lookup debugging messages.
25074 @item set debug symfile
25075 @cindex symbol file functions
25076 Turns on or off display of debugging messages related to symbol file functions.
25077 The default is off. @xref{Files}.
25078 @item show debug symfile
25079 Show the current state of symbol file debugging messages.
25080 @item set debug symtab-create
25081 @cindex symbol table creation
25082 Turns on or off display of debugging messages related to symbol table creation.
25083 The default is 0 (off).
25084 A value of 1 provides basic information.
25085 A value greater than 1 provides more verbose information.
25086 @item show debug symtab-create
25087 Show the current state of symbol table creation debugging.
25088 @item set debug target
25089 @cindex target debugging info
25090 Turns on or off display of @value{GDBN} target debugging info. This info
25091 includes what is going on at the target level of GDB, as it happens. The
25092 default is 0. Set it to 1 to track events, and to 2 to also track the
25093 value of large memory transfers.
25094 @item show debug target
25095 Displays the current state of displaying @value{GDBN} target debugging
25097 @item set debug timestamp
25098 @cindex timestampping debugging info
25099 Turns on or off display of timestamps with @value{GDBN} debugging info.
25100 When enabled, seconds and microseconds are displayed before each debugging
25102 @item show debug timestamp
25103 Displays the current state of displaying timestamps with @value{GDBN}
25105 @item set debug varobj
25106 @cindex variable object debugging info
25107 Turns on or off display of @value{GDBN} variable object debugging
25108 info. The default is off.
25109 @item show debug varobj
25110 Displays the current state of displaying @value{GDBN} variable object
25112 @item set debug xml
25113 @cindex XML parser debugging
25114 Turn on or off debugging messages for built-in XML parsers.
25115 @item show debug xml
25116 Displays the current state of XML debugging messages.
25119 @node Other Misc Settings
25120 @section Other Miscellaneous Settings
25121 @cindex miscellaneous settings
25124 @kindex set interactive-mode
25125 @item set interactive-mode
25126 If @code{on}, forces @value{GDBN} to assume that GDB was started
25127 in a terminal. In practice, this means that @value{GDBN} should wait
25128 for the user to answer queries generated by commands entered at
25129 the command prompt. If @code{off}, forces @value{GDBN} to operate
25130 in the opposite mode, and it uses the default answers to all queries.
25131 If @code{auto} (the default), @value{GDBN} tries to determine whether
25132 its standard input is a terminal, and works in interactive-mode if it
25133 is, non-interactively otherwise.
25135 In the vast majority of cases, the debugger should be able to guess
25136 correctly which mode should be used. But this setting can be useful
25137 in certain specific cases, such as running a MinGW @value{GDBN}
25138 inside a cygwin window.
25140 @kindex show interactive-mode
25141 @item show interactive-mode
25142 Displays whether the debugger is operating in interactive mode or not.
25145 @node Extending GDB
25146 @chapter Extending @value{GDBN}
25147 @cindex extending GDB
25149 @value{GDBN} provides several mechanisms for extension.
25150 @value{GDBN} also provides the ability to automatically load
25151 extensions when it reads a file for debugging. This allows the
25152 user to automatically customize @value{GDBN} for the program
25156 * Sequences:: Canned Sequences of @value{GDBN} Commands
25157 * Python:: Extending @value{GDBN} using Python
25158 * Guile:: Extending @value{GDBN} using Guile
25159 * Auto-loading extensions:: Automatically loading extensions
25160 * Multiple Extension Languages:: Working with multiple extension languages
25161 * Aliases:: Creating new spellings of existing commands
25164 To facilitate the use of extension languages, @value{GDBN} is capable
25165 of evaluating the contents of a file. When doing so, @value{GDBN}
25166 can recognize which extension language is being used by looking at
25167 the filename extension. Files with an unrecognized filename extension
25168 are always treated as a @value{GDBN} Command Files.
25169 @xref{Command Files,, Command files}.
25171 You can control how @value{GDBN} evaluates these files with the following
25175 @kindex set script-extension
25176 @kindex show script-extension
25177 @item set script-extension off
25178 All scripts are always evaluated as @value{GDBN} Command Files.
25180 @item set script-extension soft
25181 The debugger determines the scripting language based on filename
25182 extension. If this scripting language is supported, @value{GDBN}
25183 evaluates the script using that language. Otherwise, it evaluates
25184 the file as a @value{GDBN} Command File.
25186 @item set script-extension strict
25187 The debugger determines the scripting language based on filename
25188 extension, and evaluates the script using that language. If the
25189 language is not supported, then the evaluation fails.
25191 @item show script-extension
25192 Display the current value of the @code{script-extension} option.
25197 @section Canned Sequences of Commands
25199 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25200 Command Lists}), @value{GDBN} provides two ways to store sequences of
25201 commands for execution as a unit: user-defined commands and command
25205 * Define:: How to define your own commands
25206 * Hooks:: Hooks for user-defined commands
25207 * Command Files:: How to write scripts of commands to be stored in a file
25208 * Output:: Commands for controlled output
25209 * Auto-loading sequences:: Controlling auto-loaded command files
25213 @subsection User-defined Commands
25215 @cindex user-defined command
25216 @cindex arguments, to user-defined commands
25217 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25218 which you assign a new name as a command. This is done with the
25219 @code{define} command. User commands may accept an unlimited number of arguments
25220 separated by whitespace. Arguments are accessed within the user command
25221 via @code{$arg0@dots{}$argN}. A trivial example:
25225 print $arg0 + $arg1 + $arg2
25230 To execute the command use:
25237 This defines the command @code{adder}, which prints the sum of
25238 its three arguments. Note the arguments are text substitutions, so they may
25239 reference variables, use complex expressions, or even perform inferior
25242 @cindex argument count in user-defined commands
25243 @cindex how many arguments (user-defined commands)
25244 In addition, @code{$argc} may be used to find out how many arguments have
25250 print $arg0 + $arg1
25253 print $arg0 + $arg1 + $arg2
25258 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25259 to process a variable number of arguments:
25266 eval "set $sum = $sum + $arg%d", $i
25276 @item define @var{commandname}
25277 Define a command named @var{commandname}. If there is already a command
25278 by that name, you are asked to confirm that you want to redefine it.
25279 The argument @var{commandname} may be a bare command name consisting of letters,
25280 numbers, dashes, and underscores. It may also start with any predefined
25281 prefix command. For example, @samp{define target my-target} creates
25282 a user-defined @samp{target my-target} command.
25284 The definition of the command is made up of other @value{GDBN} command lines,
25285 which are given following the @code{define} command. The end of these
25286 commands is marked by a line containing @code{end}.
25289 @kindex end@r{ (user-defined commands)}
25290 @item document @var{commandname}
25291 Document the user-defined command @var{commandname}, so that it can be
25292 accessed by @code{help}. The command @var{commandname} must already be
25293 defined. This command reads lines of documentation just as @code{define}
25294 reads the lines of the command definition, ending with @code{end}.
25295 After the @code{document} command is finished, @code{help} on command
25296 @var{commandname} displays the documentation you have written.
25298 You may use the @code{document} command again to change the
25299 documentation of a command. Redefining the command with @code{define}
25300 does not change the documentation.
25302 @kindex dont-repeat
25303 @cindex don't repeat command
25305 Used inside a user-defined command, this tells @value{GDBN} that this
25306 command should not be repeated when the user hits @key{RET}
25307 (@pxref{Command Syntax, repeat last command}).
25309 @kindex help user-defined
25310 @item help user-defined
25311 List all user-defined commands and all python commands defined in class
25312 COMAND_USER. The first line of the documentation or docstring is
25317 @itemx show user @var{commandname}
25318 Display the @value{GDBN} commands used to define @var{commandname} (but
25319 not its documentation). If no @var{commandname} is given, display the
25320 definitions for all user-defined commands.
25321 This does not work for user-defined python commands.
25323 @cindex infinite recursion in user-defined commands
25324 @kindex show max-user-call-depth
25325 @kindex set max-user-call-depth
25326 @item show max-user-call-depth
25327 @itemx set max-user-call-depth
25328 The value of @code{max-user-call-depth} controls how many recursion
25329 levels are allowed in user-defined commands before @value{GDBN} suspects an
25330 infinite recursion and aborts the command.
25331 This does not apply to user-defined python commands.
25334 In addition to the above commands, user-defined commands frequently
25335 use control flow commands, described in @ref{Command Files}.
25337 When user-defined commands are executed, the
25338 commands of the definition are not printed. An error in any command
25339 stops execution of the user-defined command.
25341 If used interactively, commands that would ask for confirmation proceed
25342 without asking when used inside a user-defined command. Many @value{GDBN}
25343 commands that normally print messages to say what they are doing omit the
25344 messages when used in a user-defined command.
25347 @subsection User-defined Command Hooks
25348 @cindex command hooks
25349 @cindex hooks, for commands
25350 @cindex hooks, pre-command
25353 You may define @dfn{hooks}, which are a special kind of user-defined
25354 command. Whenever you run the command @samp{foo}, if the user-defined
25355 command @samp{hook-foo} exists, it is executed (with no arguments)
25356 before that command.
25358 @cindex hooks, post-command
25360 A hook may also be defined which is run after the command you executed.
25361 Whenever you run the command @samp{foo}, if the user-defined command
25362 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25363 that command. Post-execution hooks may exist simultaneously with
25364 pre-execution hooks, for the same command.
25366 It is valid for a hook to call the command which it hooks. If this
25367 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25369 @c It would be nice if hookpost could be passed a parameter indicating
25370 @c if the command it hooks executed properly or not. FIXME!
25372 @kindex stop@r{, a pseudo-command}
25373 In addition, a pseudo-command, @samp{stop} exists. Defining
25374 (@samp{hook-stop}) makes the associated commands execute every time
25375 execution stops in your program: before breakpoint commands are run,
25376 displays are printed, or the stack frame is printed.
25378 For example, to ignore @code{SIGALRM} signals while
25379 single-stepping, but treat them normally during normal execution,
25384 handle SIGALRM nopass
25388 handle SIGALRM pass
25391 define hook-continue
25392 handle SIGALRM pass
25396 As a further example, to hook at the beginning and end of the @code{echo}
25397 command, and to add extra text to the beginning and end of the message,
25405 define hookpost-echo
25409 (@value{GDBP}) echo Hello World
25410 <<<---Hello World--->>>
25415 You can define a hook for any single-word command in @value{GDBN}, but
25416 not for command aliases; you should define a hook for the basic command
25417 name, e.g.@: @code{backtrace} rather than @code{bt}.
25418 @c FIXME! So how does Joe User discover whether a command is an alias
25420 You can hook a multi-word command by adding @code{hook-} or
25421 @code{hookpost-} to the last word of the command, e.g.@:
25422 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25424 If an error occurs during the execution of your hook, execution of
25425 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25426 (before the command that you actually typed had a chance to run).
25428 If you try to define a hook which does not match any known command, you
25429 get a warning from the @code{define} command.
25431 @node Command Files
25432 @subsection Command Files
25434 @cindex command files
25435 @cindex scripting commands
25436 A command file for @value{GDBN} is a text file made of lines that are
25437 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25438 also be included. An empty line in a command file does nothing; it
25439 does not mean to repeat the last command, as it would from the
25442 You can request the execution of a command file with the @code{source}
25443 command. Note that the @code{source} command is also used to evaluate
25444 scripts that are not Command Files. The exact behavior can be configured
25445 using the @code{script-extension} setting.
25446 @xref{Extending GDB,, Extending GDB}.
25450 @cindex execute commands from a file
25451 @item source [-s] [-v] @var{filename}
25452 Execute the command file @var{filename}.
25455 The lines in a command file are generally executed sequentially,
25456 unless the order of execution is changed by one of the
25457 @emph{flow-control commands} described below. The commands are not
25458 printed as they are executed. An error in any command terminates
25459 execution of the command file and control is returned to the console.
25461 @value{GDBN} first searches for @var{filename} in the current directory.
25462 If the file is not found there, and @var{filename} does not specify a
25463 directory, then @value{GDBN} also looks for the file on the source search path
25464 (specified with the @samp{directory} command);
25465 except that @file{$cdir} is not searched because the compilation directory
25466 is not relevant to scripts.
25468 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25469 on the search path even if @var{filename} specifies a directory.
25470 The search is done by appending @var{filename} to each element of the
25471 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25472 and the search path contains @file{/home/user} then @value{GDBN} will
25473 look for the script @file{/home/user/mylib/myscript}.
25474 The search is also done if @var{filename} is an absolute path.
25475 For example, if @var{filename} is @file{/tmp/myscript} and
25476 the search path contains @file{/home/user} then @value{GDBN} will
25477 look for the script @file{/home/user/tmp/myscript}.
25478 For DOS-like systems, if @var{filename} contains a drive specification,
25479 it is stripped before concatenation. For example, if @var{filename} is
25480 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25481 will look for the script @file{c:/tmp/myscript}.
25483 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25484 each command as it is executed. The option must be given before
25485 @var{filename}, and is interpreted as part of the filename anywhere else.
25487 Commands that would ask for confirmation if used interactively proceed
25488 without asking when used in a command file. Many @value{GDBN} commands that
25489 normally print messages to say what they are doing omit the messages
25490 when called from command files.
25492 @value{GDBN} also accepts command input from standard input. In this
25493 mode, normal output goes to standard output and error output goes to
25494 standard error. Errors in a command file supplied on standard input do
25495 not terminate execution of the command file---execution continues with
25499 gdb < cmds > log 2>&1
25502 (The syntax above will vary depending on the shell used.) This example
25503 will execute commands from the file @file{cmds}. All output and errors
25504 would be directed to @file{log}.
25506 Since commands stored on command files tend to be more general than
25507 commands typed interactively, they frequently need to deal with
25508 complicated situations, such as different or unexpected values of
25509 variables and symbols, changes in how the program being debugged is
25510 built, etc. @value{GDBN} provides a set of flow-control commands to
25511 deal with these complexities. Using these commands, you can write
25512 complex scripts that loop over data structures, execute commands
25513 conditionally, etc.
25520 This command allows to include in your script conditionally executed
25521 commands. The @code{if} command takes a single argument, which is an
25522 expression to evaluate. It is followed by a series of commands that
25523 are executed only if the expression is true (its value is nonzero).
25524 There can then optionally be an @code{else} line, followed by a series
25525 of commands that are only executed if the expression was false. The
25526 end of the list is marked by a line containing @code{end}.
25530 This command allows to write loops. Its syntax is similar to
25531 @code{if}: the command takes a single argument, which is an expression
25532 to evaluate, and must be followed by the commands to execute, one per
25533 line, terminated by an @code{end}. These commands are called the
25534 @dfn{body} of the loop. The commands in the body of @code{while} are
25535 executed repeatedly as long as the expression evaluates to true.
25539 This command exits the @code{while} loop in whose body it is included.
25540 Execution of the script continues after that @code{while}s @code{end}
25543 @kindex loop_continue
25544 @item loop_continue
25545 This command skips the execution of the rest of the body of commands
25546 in the @code{while} loop in whose body it is included. Execution
25547 branches to the beginning of the @code{while} loop, where it evaluates
25548 the controlling expression.
25550 @kindex end@r{ (if/else/while commands)}
25552 Terminate the block of commands that are the body of @code{if},
25553 @code{else}, or @code{while} flow-control commands.
25558 @subsection Commands for Controlled Output
25560 During the execution of a command file or a user-defined command, normal
25561 @value{GDBN} output is suppressed; the only output that appears is what is
25562 explicitly printed by the commands in the definition. This section
25563 describes three commands useful for generating exactly the output you
25568 @item echo @var{text}
25569 @c I do not consider backslash-space a standard C escape sequence
25570 @c because it is not in ANSI.
25571 Print @var{text}. Nonprinting characters can be included in
25572 @var{text} using C escape sequences, such as @samp{\n} to print a
25573 newline. @strong{No newline is printed unless you specify one.}
25574 In addition to the standard C escape sequences, a backslash followed
25575 by a space stands for a space. This is useful for displaying a
25576 string with spaces at the beginning or the end, since leading and
25577 trailing spaces are otherwise trimmed from all arguments.
25578 To print @samp{@w{ }and foo =@w{ }}, use the command
25579 @samp{echo \@w{ }and foo = \@w{ }}.
25581 A backslash at the end of @var{text} can be used, as in C, to continue
25582 the command onto subsequent lines. For example,
25585 echo This is some text\n\
25586 which is continued\n\
25587 onto several lines.\n
25590 produces the same output as
25593 echo This is some text\n
25594 echo which is continued\n
25595 echo onto several lines.\n
25599 @item output @var{expression}
25600 Print the value of @var{expression} and nothing but that value: no
25601 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25602 value history either. @xref{Expressions, ,Expressions}, for more information
25605 @item output/@var{fmt} @var{expression}
25606 Print the value of @var{expression} in format @var{fmt}. You can use
25607 the same formats as for @code{print}. @xref{Output Formats,,Output
25608 Formats}, for more information.
25611 @item printf @var{template}, @var{expressions}@dots{}
25612 Print the values of one or more @var{expressions} under the control of
25613 the string @var{template}. To print several values, make
25614 @var{expressions} be a comma-separated list of individual expressions,
25615 which may be either numbers or pointers. Their values are printed as
25616 specified by @var{template}, exactly as a C program would do by
25617 executing the code below:
25620 printf (@var{template}, @var{expressions}@dots{});
25623 As in @code{C} @code{printf}, ordinary characters in @var{template}
25624 are printed verbatim, while @dfn{conversion specification} introduced
25625 by the @samp{%} character cause subsequent @var{expressions} to be
25626 evaluated, their values converted and formatted according to type and
25627 style information encoded in the conversion specifications, and then
25630 For example, you can print two values in hex like this:
25633 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25636 @code{printf} supports all the standard @code{C} conversion
25637 specifications, including the flags and modifiers between the @samp{%}
25638 character and the conversion letter, with the following exceptions:
25642 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25645 The modifier @samp{*} is not supported for specifying precision or
25649 The @samp{'} flag (for separation of digits into groups according to
25650 @code{LC_NUMERIC'}) is not supported.
25653 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25657 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25660 The conversion letters @samp{a} and @samp{A} are not supported.
25664 Note that the @samp{ll} type modifier is supported only if the
25665 underlying @code{C} implementation used to build @value{GDBN} supports
25666 the @code{long long int} type, and the @samp{L} type modifier is
25667 supported only if @code{long double} type is available.
25669 As in @code{C}, @code{printf} supports simple backslash-escape
25670 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25671 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25672 single character. Octal and hexadecimal escape sequences are not
25675 Additionally, @code{printf} supports conversion specifications for DFP
25676 (@dfn{Decimal Floating Point}) types using the following length modifiers
25677 together with a floating point specifier.
25682 @samp{H} for printing @code{Decimal32} types.
25685 @samp{D} for printing @code{Decimal64} types.
25688 @samp{DD} for printing @code{Decimal128} types.
25691 If the underlying @code{C} implementation used to build @value{GDBN} has
25692 support for the three length modifiers for DFP types, other modifiers
25693 such as width and precision will also be available for @value{GDBN} to use.
25695 In case there is no such @code{C} support, no additional modifiers will be
25696 available and the value will be printed in the standard way.
25698 Here's an example of printing DFP types using the above conversion letters:
25700 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25705 @item eval @var{template}, @var{expressions}@dots{}
25706 Convert the values of one or more @var{expressions} under the control of
25707 the string @var{template} to a command line, and call it.
25711 @node Auto-loading sequences
25712 @subsection Controlling auto-loading native @value{GDBN} scripts
25713 @cindex native script auto-loading
25715 When a new object file is read (for example, due to the @code{file}
25716 command, or because the inferior has loaded a shared library),
25717 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25718 @xref{Auto-loading extensions}.
25720 Auto-loading can be enabled or disabled,
25721 and the list of auto-loaded scripts can be printed.
25724 @anchor{set auto-load gdb-scripts}
25725 @kindex set auto-load gdb-scripts
25726 @item set auto-load gdb-scripts [on|off]
25727 Enable or disable the auto-loading of canned sequences of commands scripts.
25729 @anchor{show auto-load gdb-scripts}
25730 @kindex show auto-load gdb-scripts
25731 @item show auto-load gdb-scripts
25732 Show whether auto-loading of canned sequences of commands scripts is enabled or
25735 @anchor{info auto-load gdb-scripts}
25736 @kindex info auto-load gdb-scripts
25737 @cindex print list of auto-loaded canned sequences of commands scripts
25738 @item info auto-load gdb-scripts [@var{regexp}]
25739 Print the list of all canned sequences of commands scripts that @value{GDBN}
25743 If @var{regexp} is supplied only canned sequences of commands scripts with
25744 matching names are printed.
25746 @c Python docs live in a separate file.
25747 @include python.texi
25749 @c Guile docs live in a separate file.
25750 @include guile.texi
25752 @node Auto-loading extensions
25753 @section Auto-loading extensions
25754 @cindex auto-loading extensions
25756 @value{GDBN} provides two mechanisms for automatically loading extensions
25757 when a new object file is read (for example, due to the @code{file}
25758 command, or because the inferior has loaded a shared library):
25759 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25760 section of modern file formats like ELF.
25763 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25764 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25765 * Which flavor to choose?::
25768 The auto-loading feature is useful for supplying application-specific
25769 debugging commands and features.
25771 Auto-loading can be enabled or disabled,
25772 and the list of auto-loaded scripts can be printed.
25773 See the @samp{auto-loading} section of each extension language
25774 for more information.
25775 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25776 For Python files see @ref{Python Auto-loading}.
25778 Note that loading of this script file also requires accordingly configured
25779 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25781 @node objfile-gdbdotext file
25782 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25783 @cindex @file{@var{objfile}-gdb.gdb}
25784 @cindex @file{@var{objfile}-gdb.py}
25785 @cindex @file{@var{objfile}-gdb.scm}
25787 When a new object file is read, @value{GDBN} looks for a file named
25788 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25789 where @var{objfile} is the object file's name and
25790 where @var{ext} is the file extension for the extension language:
25793 @item @file{@var{objfile}-gdb.gdb}
25794 GDB's own command language
25795 @item @file{@var{objfile}-gdb.py}
25797 @item @file{@var{objfile}-gdb.scm}
25801 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25802 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25803 components, and appending the @file{-gdb.@var{ext}} suffix.
25804 If this file exists and is readable, @value{GDBN} will evaluate it as a
25805 script in the specified extension language.
25807 If this file does not exist, then @value{GDBN} will look for
25808 @var{script-name} file in all of the directories as specified below.
25810 Note that loading of these files requires an accordingly configured
25811 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25813 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25814 scripts normally according to its @file{.exe} filename. But if no scripts are
25815 found @value{GDBN} also tries script filenames matching the object file without
25816 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25817 is attempted on any platform. This makes the script filenames compatible
25818 between Unix and MS-Windows hosts.
25821 @anchor{set auto-load scripts-directory}
25822 @kindex set auto-load scripts-directory
25823 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25824 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25825 may be delimited by the host platform path separator in use
25826 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25828 Each entry here needs to be covered also by the security setting
25829 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25831 @anchor{with-auto-load-dir}
25832 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25833 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25834 configuration option @option{--with-auto-load-dir}.
25836 Any reference to @file{$debugdir} will get replaced by
25837 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25838 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25839 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25840 @file{$datadir} must be placed as a directory component --- either alone or
25841 delimited by @file{/} or @file{\} directory separators, depending on the host
25844 The list of directories uses path separator (@samp{:} on GNU and Unix
25845 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25846 to the @env{PATH} environment variable.
25848 @anchor{show auto-load scripts-directory}
25849 @kindex show auto-load scripts-directory
25850 @item show auto-load scripts-directory
25851 Show @value{GDBN} auto-loaded scripts location.
25853 @anchor{add-auto-load-scripts-directory}
25854 @kindex add-auto-load-scripts-directory
25855 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25856 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25857 Multiple entries may be delimited by the host platform path separator in use.
25860 @value{GDBN} does not track which files it has already auto-loaded this way.
25861 @value{GDBN} will load the associated script every time the corresponding
25862 @var{objfile} is opened.
25863 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25864 is evaluated more than once.
25866 @node dotdebug_gdb_scripts section
25867 @subsection The @code{.debug_gdb_scripts} section
25868 @cindex @code{.debug_gdb_scripts} section
25870 For systems using file formats like ELF and COFF,
25871 when @value{GDBN} loads a new object file
25872 it will look for a special section named @code{.debug_gdb_scripts}.
25873 If this section exists, its contents is a list of null-terminated entries
25874 specifying scripts to load. Each entry begins with a non-null prefix byte that
25875 specifies the kind of entry, typically the extension language and whether the
25876 script is in a file or inlined in @code{.debug_gdb_scripts}.
25878 The following entries are supported:
25881 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25882 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25883 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25884 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25887 @subsubsection Script File Entries
25889 If the entry specifies a file, @value{GDBN} will look for the file first
25890 in the current directory and then along the source search path
25891 (@pxref{Source Path, ,Specifying Source Directories}),
25892 except that @file{$cdir} is not searched, since the compilation
25893 directory is not relevant to scripts.
25895 File entries can be placed in section @code{.debug_gdb_scripts} with,
25896 for example, this GCC macro for Python scripts.
25899 /* Note: The "MS" section flags are to remove duplicates. */
25900 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25902 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25903 .byte 1 /* Python */\n\
25904 .asciz \"" script_name "\"\n\
25910 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25911 Then one can reference the macro in a header or source file like this:
25914 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25917 The script name may include directories if desired.
25919 Note that loading of this script file also requires accordingly configured
25920 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25922 If the macro invocation is put in a header, any application or library
25923 using this header will get a reference to the specified script,
25924 and with the use of @code{"MS"} attributes on the section, the linker
25925 will remove duplicates.
25927 @subsubsection Script Text Entries
25929 Script text entries allow to put the executable script in the entry
25930 itself instead of loading it from a file.
25931 The first line of the entry, everything after the prefix byte and up to
25932 the first newline (@code{0xa}) character, is the script name, and must not
25933 contain any kind of space character, e.g., spaces or tabs.
25934 The rest of the entry, up to the trailing null byte, is the script to
25935 execute in the specified language. The name needs to be unique among
25936 all script names, as @value{GDBN} executes each script only once based
25939 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25943 #include "symcat.h"
25944 #include "gdb/section-scripts.h"
25946 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25947 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25948 ".ascii \"gdb.inlined-script\\n\"\n"
25949 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25950 ".ascii \" def __init__ (self):\\n\"\n"
25951 ".ascii \" super (test_cmd, self).__init__ ("
25952 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25953 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25954 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25955 ".ascii \"test_cmd ()\\n\"\n"
25961 Loading of inlined scripts requires a properly configured
25962 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25963 The path to specify in @code{auto-load safe-path} is the path of the file
25964 containing the @code{.debug_gdb_scripts} section.
25966 @node Which flavor to choose?
25967 @subsection Which flavor to choose?
25969 Given the multiple ways of auto-loading extensions, it might not always
25970 be clear which one to choose. This section provides some guidance.
25973 Benefits of the @file{-gdb.@var{ext}} way:
25977 Can be used with file formats that don't support multiple sections.
25980 Ease of finding scripts for public libraries.
25982 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25983 in the source search path.
25984 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25985 isn't a source directory in which to find the script.
25988 Doesn't require source code additions.
25992 Benefits of the @code{.debug_gdb_scripts} way:
25996 Works with static linking.
25998 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25999 trigger their loading. When an application is statically linked the only
26000 objfile available is the executable, and it is cumbersome to attach all the
26001 scripts from all the input libraries to the executable's
26002 @file{-gdb.@var{ext}} script.
26005 Works with classes that are entirely inlined.
26007 Some classes can be entirely inlined, and thus there may not be an associated
26008 shared library to attach a @file{-gdb.@var{ext}} script to.
26011 Scripts needn't be copied out of the source tree.
26013 In some circumstances, apps can be built out of large collections of internal
26014 libraries, and the build infrastructure necessary to install the
26015 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26016 cumbersome. It may be easier to specify the scripts in the
26017 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26018 top of the source tree to the source search path.
26021 @node Multiple Extension Languages
26022 @section Multiple Extension Languages
26024 The Guile and Python extension languages do not share any state,
26025 and generally do not interfere with each other.
26026 There are some things to be aware of, however.
26028 @subsection Python comes first
26030 Python was @value{GDBN}'s first extension language, and to avoid breaking
26031 existing behaviour Python comes first. This is generally solved by the
26032 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26033 extension languages, and when it makes a call to an extension language,
26034 (say to pretty-print a value), it tries each in turn until an extension
26035 language indicates it has performed the request (e.g., has returned the
26036 pretty-printed form of a value).
26037 This extends to errors while performing such requests: If an error happens
26038 while, for example, trying to pretty-print an object then the error is
26039 reported and any following extension languages are not tried.
26042 @section Creating new spellings of existing commands
26043 @cindex aliases for commands
26045 It is often useful to define alternate spellings of existing commands.
26046 For example, if a new @value{GDBN} command defined in Python has
26047 a long name to type, it is handy to have an abbreviated version of it
26048 that involves less typing.
26050 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26051 of the @samp{step} command even though it is otherwise an ambiguous
26052 abbreviation of other commands like @samp{set} and @samp{show}.
26054 Aliases are also used to provide shortened or more common versions
26055 of multi-word commands. For example, @value{GDBN} provides the
26056 @samp{tty} alias of the @samp{set inferior-tty} command.
26058 You can define a new alias with the @samp{alias} command.
26063 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26067 @var{ALIAS} specifies the name of the new alias.
26068 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26071 @var{COMMAND} specifies the name of an existing command
26072 that is being aliased.
26074 The @samp{-a} option specifies that the new alias is an abbreviation
26075 of the command. Abbreviations are not shown in command
26076 lists displayed by the @samp{help} command.
26078 The @samp{--} option specifies the end of options,
26079 and is useful when @var{ALIAS} begins with a dash.
26081 Here is a simple example showing how to make an abbreviation
26082 of a command so that there is less to type.
26083 Suppose you were tired of typing @samp{disas}, the current
26084 shortest unambiguous abbreviation of the @samp{disassemble} command
26085 and you wanted an even shorter version named @samp{di}.
26086 The following will accomplish this.
26089 (gdb) alias -a di = disas
26092 Note that aliases are different from user-defined commands.
26093 With a user-defined command, you also need to write documentation
26094 for it with the @samp{document} command.
26095 An alias automatically picks up the documentation of the existing command.
26097 Here is an example where we make @samp{elms} an abbreviation of
26098 @samp{elements} in the @samp{set print elements} command.
26099 This is to show that you can make an abbreviation of any part
26103 (gdb) alias -a set print elms = set print elements
26104 (gdb) alias -a show print elms = show print elements
26105 (gdb) set p elms 20
26107 Limit on string chars or array elements to print is 200.
26110 Note that if you are defining an alias of a @samp{set} command,
26111 and you want to have an alias for the corresponding @samp{show}
26112 command, then you need to define the latter separately.
26114 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26115 @var{ALIAS}, just as they are normally.
26118 (gdb) alias -a set pr elms = set p ele
26121 Finally, here is an example showing the creation of a one word
26122 alias for a more complex command.
26123 This creates alias @samp{spe} of the command @samp{set print elements}.
26126 (gdb) alias spe = set print elements
26131 @chapter Command Interpreters
26132 @cindex command interpreters
26134 @value{GDBN} supports multiple command interpreters, and some command
26135 infrastructure to allow users or user interface writers to switch
26136 between interpreters or run commands in other interpreters.
26138 @value{GDBN} currently supports two command interpreters, the console
26139 interpreter (sometimes called the command-line interpreter or @sc{cli})
26140 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26141 describes both of these interfaces in great detail.
26143 By default, @value{GDBN} will start with the console interpreter.
26144 However, the user may choose to start @value{GDBN} with another
26145 interpreter by specifying the @option{-i} or @option{--interpreter}
26146 startup options. Defined interpreters include:
26150 @cindex console interpreter
26151 The traditional console or command-line interpreter. This is the most often
26152 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26153 @value{GDBN} will use this interpreter.
26156 @cindex mi interpreter
26157 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26158 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26159 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26163 @cindex mi2 interpreter
26164 The current @sc{gdb/mi} interface.
26167 @cindex mi1 interpreter
26168 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26172 @cindex invoke another interpreter
26174 @kindex interpreter-exec
26175 You may execute commands in any interpreter from the current
26176 interpreter using the appropriate command. If you are running the
26177 console interpreter, simply use the @code{interpreter-exec} command:
26180 interpreter-exec mi "-data-list-register-names"
26183 @sc{gdb/mi} has a similar command, although it is only available in versions of
26184 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26186 Note that @code{interpreter-exec} only changes the interpreter for the
26187 duration of the specified command. It does not change the interpreter
26190 @cindex start a new independent interpreter
26192 Although you may only choose a single interpreter at startup, it is
26193 possible to run an independent interpreter on a specified input/output
26194 device (usually a tty).
26196 For example, consider a debugger GUI or IDE that wants to provide a
26197 @value{GDBN} console view. It may do so by embedding a terminal
26198 emulator widget in its GUI, starting @value{GDBN} in the traditional
26199 command-line mode with stdin/stdout/stderr redirected to that
26200 terminal, and then creating an MI interpreter running on a specified
26201 input/output device. The console interpreter created by @value{GDBN}
26202 at startup handles commands the user types in the terminal widget,
26203 while the GUI controls and synchronizes state with @value{GDBN} using
26204 the separate MI interpreter.
26206 To start a new secondary @dfn{user interface} running MI, use the
26207 @code{new-ui} command:
26210 @cindex new user interface
26212 new-ui @var{interpreter} @var{tty}
26215 The @var{interpreter} parameter specifies the interpreter to run.
26216 This accepts the same values as the @code{interpreter-exec} command.
26217 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26218 @var{tty} parameter specifies the name of the bidirectional file the
26219 interpreter uses for input/output, usually the name of a
26220 pseudoterminal slave on Unix systems. For example:
26223 (@value{GDBP}) new-ui mi /dev/pts/9
26227 runs an MI interpreter on @file{/dev/pts/9}.
26230 @chapter @value{GDBN} Text User Interface
26232 @cindex Text User Interface
26235 * TUI Overview:: TUI overview
26236 * TUI Keys:: TUI key bindings
26237 * TUI Single Key Mode:: TUI single key mode
26238 * TUI Commands:: TUI-specific commands
26239 * TUI Configuration:: TUI configuration variables
26242 The @value{GDBN} Text User Interface (TUI) is a terminal
26243 interface which uses the @code{curses} library to show the source
26244 file, the assembly output, the program registers and @value{GDBN}
26245 commands in separate text windows. The TUI mode is supported only
26246 on platforms where a suitable version of the @code{curses} library
26249 The TUI mode is enabled by default when you invoke @value{GDBN} as
26250 @samp{@value{GDBP} -tui}.
26251 You can also switch in and out of TUI mode while @value{GDBN} runs by
26252 using various TUI commands and key bindings, such as @command{tui
26253 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26254 @ref{TUI Keys, ,TUI Key Bindings}.
26257 @section TUI Overview
26259 In TUI mode, @value{GDBN} can display several text windows:
26263 This window is the @value{GDBN} command window with the @value{GDBN}
26264 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26265 managed using readline.
26268 The source window shows the source file of the program. The current
26269 line and active breakpoints are displayed in this window.
26272 The assembly window shows the disassembly output of the program.
26275 This window shows the processor registers. Registers are highlighted
26276 when their values change.
26279 The source and assembly windows show the current program position
26280 by highlighting the current line and marking it with a @samp{>} marker.
26281 Breakpoints are indicated with two markers. The first marker
26282 indicates the breakpoint type:
26286 Breakpoint which was hit at least once.
26289 Breakpoint which was never hit.
26292 Hardware breakpoint which was hit at least once.
26295 Hardware breakpoint which was never hit.
26298 The second marker indicates whether the breakpoint is enabled or not:
26302 Breakpoint is enabled.
26305 Breakpoint is disabled.
26308 The source, assembly and register windows are updated when the current
26309 thread changes, when the frame changes, or when the program counter
26312 These windows are not all visible at the same time. The command
26313 window is always visible. The others can be arranged in several
26324 source and assembly,
26327 source and registers, or
26330 assembly and registers.
26333 A status line above the command window shows the following information:
26337 Indicates the current @value{GDBN} target.
26338 (@pxref{Targets, ,Specifying a Debugging Target}).
26341 Gives the current process or thread number.
26342 When no process is being debugged, this field is set to @code{No process}.
26345 Gives the current function name for the selected frame.
26346 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26347 When there is no symbol corresponding to the current program counter,
26348 the string @code{??} is displayed.
26351 Indicates the current line number for the selected frame.
26352 When the current line number is not known, the string @code{??} is displayed.
26355 Indicates the current program counter address.
26359 @section TUI Key Bindings
26360 @cindex TUI key bindings
26362 The TUI installs several key bindings in the readline keymaps
26363 @ifset SYSTEM_READLINE
26364 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26366 @ifclear SYSTEM_READLINE
26367 (@pxref{Command Line Editing}).
26369 The following key bindings are installed for both TUI mode and the
26370 @value{GDBN} standard mode.
26379 Enter or leave the TUI mode. When leaving the TUI mode,
26380 the curses window management stops and @value{GDBN} operates using
26381 its standard mode, writing on the terminal directly. When reentering
26382 the TUI mode, control is given back to the curses windows.
26383 The screen is then refreshed.
26387 Use a TUI layout with only one window. The layout will
26388 either be @samp{source} or @samp{assembly}. When the TUI mode
26389 is not active, it will switch to the TUI mode.
26391 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26395 Use a TUI layout with at least two windows. When the current
26396 layout already has two windows, the next layout with two windows is used.
26397 When a new layout is chosen, one window will always be common to the
26398 previous layout and the new one.
26400 Think of it as the Emacs @kbd{C-x 2} binding.
26404 Change the active window. The TUI associates several key bindings
26405 (like scrolling and arrow keys) with the active window. This command
26406 gives the focus to the next TUI window.
26408 Think of it as the Emacs @kbd{C-x o} binding.
26412 Switch in and out of the TUI SingleKey mode that binds single
26413 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26416 The following key bindings only work in the TUI mode:
26421 Scroll the active window one page up.
26425 Scroll the active window one page down.
26429 Scroll the active window one line up.
26433 Scroll the active window one line down.
26437 Scroll the active window one column left.
26441 Scroll the active window one column right.
26445 Refresh the screen.
26448 Because the arrow keys scroll the active window in the TUI mode, they
26449 are not available for their normal use by readline unless the command
26450 window has the focus. When another window is active, you must use
26451 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26452 and @kbd{C-f} to control the command window.
26454 @node TUI Single Key Mode
26455 @section TUI Single Key Mode
26456 @cindex TUI single key mode
26458 The TUI also provides a @dfn{SingleKey} mode, which binds several
26459 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26460 switch into this mode, where the following key bindings are used:
26463 @kindex c @r{(SingleKey TUI key)}
26467 @kindex d @r{(SingleKey TUI key)}
26471 @kindex f @r{(SingleKey TUI key)}
26475 @kindex n @r{(SingleKey TUI key)}
26479 @kindex o @r{(SingleKey TUI key)}
26481 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26483 @kindex q @r{(SingleKey TUI key)}
26485 exit the SingleKey mode.
26487 @kindex r @r{(SingleKey TUI key)}
26491 @kindex s @r{(SingleKey TUI key)}
26495 @kindex i @r{(SingleKey TUI key)}
26497 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26499 @kindex u @r{(SingleKey TUI key)}
26503 @kindex v @r{(SingleKey TUI key)}
26507 @kindex w @r{(SingleKey TUI key)}
26512 Other keys temporarily switch to the @value{GDBN} command prompt.
26513 The key that was pressed is inserted in the editing buffer so that
26514 it is possible to type most @value{GDBN} commands without interaction
26515 with the TUI SingleKey mode. Once the command is entered the TUI
26516 SingleKey mode is restored. The only way to permanently leave
26517 this mode is by typing @kbd{q} or @kbd{C-x s}.
26521 @section TUI-specific Commands
26522 @cindex TUI commands
26524 The TUI has specific commands to control the text windows.
26525 These commands are always available, even when @value{GDBN} is not in
26526 the TUI mode. When @value{GDBN} is in the standard mode, most
26527 of these commands will automatically switch to the TUI mode.
26529 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26530 terminal, or @value{GDBN} has been started with the machine interface
26531 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26532 these commands will fail with an error, because it would not be
26533 possible or desirable to enable curses window management.
26538 Activate TUI mode. The last active TUI window layout will be used if
26539 TUI mode has prevsiouly been used in the current debugging session,
26540 otherwise a default layout is used.
26543 @kindex tui disable
26544 Disable TUI mode, returning to the console interpreter.
26548 List and give the size of all displayed windows.
26550 @item layout @var{name}
26552 Changes which TUI windows are displayed. In each layout the command
26553 window is always displayed, the @var{name} parameter controls which
26554 additional windows are displayed, and can be any of the following:
26558 Display the next layout.
26561 Display the previous layout.
26564 Display the source and command windows.
26567 Display the assembly and command windows.
26570 Display the source, assembly, and command windows.
26573 When in @code{src} layout display the register, source, and command
26574 windows. When in @code{asm} or @code{split} layout display the
26575 register, assembler, and command windows.
26578 @item focus @var{name}
26580 Changes which TUI window is currently active for scrolling. The
26581 @var{name} parameter can be any of the following:
26585 Make the next window active for scrolling.
26588 Make the previous window active for scrolling.
26591 Make the source window active for scrolling.
26594 Make the assembly window active for scrolling.
26597 Make the register window active for scrolling.
26600 Make the command window active for scrolling.
26605 Refresh the screen. This is similar to typing @kbd{C-L}.
26607 @item tui reg @var{group}
26609 Changes the register group displayed in the tui register window to
26610 @var{group}. If the register window is not currently displayed this
26611 command will cause the register window to be displayed. The list of
26612 register groups, as well as their order is target specific. The
26613 following groups are available on most targets:
26616 Repeatedly selecting this group will cause the display to cycle
26617 through all of the available register groups.
26620 Repeatedly selecting this group will cause the display to cycle
26621 through all of the available register groups in the reverse order to
26625 Display the general registers.
26627 Display the floating point registers.
26629 Display the system registers.
26631 Display the vector registers.
26633 Display all registers.
26638 Update the source window and the current execution point.
26640 @item winheight @var{name} +@var{count}
26641 @itemx winheight @var{name} -@var{count}
26643 Change the height of the window @var{name} by @var{count}
26644 lines. Positive counts increase the height, while negative counts
26645 decrease it. The @var{name} parameter can be one of @code{src} (the
26646 source window), @code{cmd} (the command window), @code{asm} (the
26647 disassembly window), or @code{regs} (the register display window).
26649 @item tabset @var{nchars}
26651 Set the width of tab stops to be @var{nchars} characters. This
26652 setting affects the display of TAB characters in the source and
26656 @node TUI Configuration
26657 @section TUI Configuration Variables
26658 @cindex TUI configuration variables
26660 Several configuration variables control the appearance of TUI windows.
26663 @item set tui border-kind @var{kind}
26664 @kindex set tui border-kind
26665 Select the border appearance for the source, assembly and register windows.
26666 The possible values are the following:
26669 Use a space character to draw the border.
26672 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26675 Use the Alternate Character Set to draw the border. The border is
26676 drawn using character line graphics if the terminal supports them.
26679 @item set tui border-mode @var{mode}
26680 @kindex set tui border-mode
26681 @itemx set tui active-border-mode @var{mode}
26682 @kindex set tui active-border-mode
26683 Select the display attributes for the borders of the inactive windows
26684 or the active window. The @var{mode} can be one of the following:
26687 Use normal attributes to display the border.
26693 Use reverse video mode.
26696 Use half bright mode.
26698 @item half-standout
26699 Use half bright and standout mode.
26702 Use extra bright or bold mode.
26704 @item bold-standout
26705 Use extra bright or bold and standout mode.
26710 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26713 @cindex @sc{gnu} Emacs
26714 A special interface allows you to use @sc{gnu} Emacs to view (and
26715 edit) the source files for the program you are debugging with
26718 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26719 executable file you want to debug as an argument. This command starts
26720 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26721 created Emacs buffer.
26722 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26724 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26729 All ``terminal'' input and output goes through an Emacs buffer, called
26732 This applies both to @value{GDBN} commands and their output, and to the input
26733 and output done by the program you are debugging.
26735 This is useful because it means that you can copy the text of previous
26736 commands and input them again; you can even use parts of the output
26739 All the facilities of Emacs' Shell mode are available for interacting
26740 with your program. In particular, you can send signals the usual
26741 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26745 @value{GDBN} displays source code through Emacs.
26747 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26748 source file for that frame and puts an arrow (@samp{=>}) at the
26749 left margin of the current line. Emacs uses a separate buffer for
26750 source display, and splits the screen to show both your @value{GDBN} session
26753 Explicit @value{GDBN} @code{list} or search commands still produce output as
26754 usual, but you probably have no reason to use them from Emacs.
26757 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26758 a graphical mode, enabled by default, which provides further buffers
26759 that can control the execution and describe the state of your program.
26760 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26762 If you specify an absolute file name when prompted for the @kbd{M-x
26763 gdb} argument, then Emacs sets your current working directory to where
26764 your program resides. If you only specify the file name, then Emacs
26765 sets your current working directory to the directory associated
26766 with the previous buffer. In this case, @value{GDBN} may find your
26767 program by searching your environment's @code{PATH} variable, but on
26768 some operating systems it might not find the source. So, although the
26769 @value{GDBN} input and output session proceeds normally, the auxiliary
26770 buffer does not display the current source and line of execution.
26772 The initial working directory of @value{GDBN} is printed on the top
26773 line of the GUD buffer and this serves as a default for the commands
26774 that specify files for @value{GDBN} to operate on. @xref{Files,
26775 ,Commands to Specify Files}.
26777 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26778 need to call @value{GDBN} by a different name (for example, if you
26779 keep several configurations around, with different names) you can
26780 customize the Emacs variable @code{gud-gdb-command-name} to run the
26783 In the GUD buffer, you can use these special Emacs commands in
26784 addition to the standard Shell mode commands:
26788 Describe the features of Emacs' GUD Mode.
26791 Execute to another source line, like the @value{GDBN} @code{step} command; also
26792 update the display window to show the current file and location.
26795 Execute to next source line in this function, skipping all function
26796 calls, like the @value{GDBN} @code{next} command. Then update the display window
26797 to show the current file and location.
26800 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26801 display window accordingly.
26804 Execute until exit from the selected stack frame, like the @value{GDBN}
26805 @code{finish} command.
26808 Continue execution of your program, like the @value{GDBN} @code{continue}
26812 Go up the number of frames indicated by the numeric argument
26813 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26814 like the @value{GDBN} @code{up} command.
26817 Go down the number of frames indicated by the numeric argument, like the
26818 @value{GDBN} @code{down} command.
26821 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26822 tells @value{GDBN} to set a breakpoint on the source line point is on.
26824 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26825 separate frame which shows a backtrace when the GUD buffer is current.
26826 Move point to any frame in the stack and type @key{RET} to make it
26827 become the current frame and display the associated source in the
26828 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26829 selected frame become the current one. In graphical mode, the
26830 speedbar displays watch expressions.
26832 If you accidentally delete the source-display buffer, an easy way to get
26833 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26834 request a frame display; when you run under Emacs, this recreates
26835 the source buffer if necessary to show you the context of the current
26838 The source files displayed in Emacs are in ordinary Emacs buffers
26839 which are visiting the source files in the usual way. You can edit
26840 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26841 communicates with Emacs in terms of line numbers. If you add or
26842 delete lines from the text, the line numbers that @value{GDBN} knows cease
26843 to correspond properly with the code.
26845 A more detailed description of Emacs' interaction with @value{GDBN} is
26846 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26850 @chapter The @sc{gdb/mi} Interface
26852 @unnumberedsec Function and Purpose
26854 @cindex @sc{gdb/mi}, its purpose
26855 @sc{gdb/mi} is a line based machine oriented text interface to
26856 @value{GDBN} and is activated by specifying using the
26857 @option{--interpreter} command line option (@pxref{Mode Options}). It
26858 is specifically intended to support the development of systems which
26859 use the debugger as just one small component of a larger system.
26861 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26862 in the form of a reference manual.
26864 Note that @sc{gdb/mi} is still under construction, so some of the
26865 features described below are incomplete and subject to change
26866 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26868 @unnumberedsec Notation and Terminology
26870 @cindex notational conventions, for @sc{gdb/mi}
26871 This chapter uses the following notation:
26875 @code{|} separates two alternatives.
26878 @code{[ @var{something} ]} indicates that @var{something} is optional:
26879 it may or may not be given.
26882 @code{( @var{group} )*} means that @var{group} inside the parentheses
26883 may repeat zero or more times.
26886 @code{( @var{group} )+} means that @var{group} inside the parentheses
26887 may repeat one or more times.
26890 @code{"@var{string}"} means a literal @var{string}.
26894 @heading Dependencies
26898 * GDB/MI General Design::
26899 * GDB/MI Command Syntax::
26900 * GDB/MI Compatibility with CLI::
26901 * GDB/MI Development and Front Ends::
26902 * GDB/MI Output Records::
26903 * GDB/MI Simple Examples::
26904 * GDB/MI Command Description Format::
26905 * GDB/MI Breakpoint Commands::
26906 * GDB/MI Catchpoint Commands::
26907 * GDB/MI Program Context::
26908 * GDB/MI Thread Commands::
26909 * GDB/MI Ada Tasking Commands::
26910 * GDB/MI Program Execution::
26911 * GDB/MI Stack Manipulation::
26912 * GDB/MI Variable Objects::
26913 * GDB/MI Data Manipulation::
26914 * GDB/MI Tracepoint Commands::
26915 * GDB/MI Symbol Query::
26916 * GDB/MI File Commands::
26918 * GDB/MI Kod Commands::
26919 * GDB/MI Memory Overlay Commands::
26920 * GDB/MI Signal Handling Commands::
26922 * GDB/MI Target Manipulation::
26923 * GDB/MI File Transfer Commands::
26924 * GDB/MI Ada Exceptions Commands::
26925 * GDB/MI Support Commands::
26926 * GDB/MI Miscellaneous Commands::
26929 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26930 @node GDB/MI General Design
26931 @section @sc{gdb/mi} General Design
26932 @cindex GDB/MI General Design
26934 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26935 parts---commands sent to @value{GDBN}, responses to those commands
26936 and notifications. Each command results in exactly one response,
26937 indicating either successful completion of the command, or an error.
26938 For the commands that do not resume the target, the response contains the
26939 requested information. For the commands that resume the target, the
26940 response only indicates whether the target was successfully resumed.
26941 Notifications is the mechanism for reporting changes in the state of the
26942 target, or in @value{GDBN} state, that cannot conveniently be associated with
26943 a command and reported as part of that command response.
26945 The important examples of notifications are:
26949 Exec notifications. These are used to report changes in
26950 target state---when a target is resumed, or stopped. It would not
26951 be feasible to include this information in response of resuming
26952 commands, because one resume commands can result in multiple events in
26953 different threads. Also, quite some time may pass before any event
26954 happens in the target, while a frontend needs to know whether the resuming
26955 command itself was successfully executed.
26958 Console output, and status notifications. Console output
26959 notifications are used to report output of CLI commands, as well as
26960 diagnostics for other commands. Status notifications are used to
26961 report the progress of a long-running operation. Naturally, including
26962 this information in command response would mean no output is produced
26963 until the command is finished, which is undesirable.
26966 General notifications. Commands may have various side effects on
26967 the @value{GDBN} or target state beyond their official purpose. For example,
26968 a command may change the selected thread. Although such changes can
26969 be included in command response, using notification allows for more
26970 orthogonal frontend design.
26974 There's no guarantee that whenever an MI command reports an error,
26975 @value{GDBN} or the target are in any specific state, and especially,
26976 the state is not reverted to the state before the MI command was
26977 processed. Therefore, whenever an MI command results in an error,
26978 we recommend that the frontend refreshes all the information shown in
26979 the user interface.
26983 * Context management::
26984 * Asynchronous and non-stop modes::
26988 @node Context management
26989 @subsection Context management
26991 @subsubsection Threads and Frames
26993 In most cases when @value{GDBN} accesses the target, this access is
26994 done in context of a specific thread and frame (@pxref{Frames}).
26995 Often, even when accessing global data, the target requires that a thread
26996 be specified. The CLI interface maintains the selected thread and frame,
26997 and supplies them to target on each command. This is convenient,
26998 because a command line user would not want to specify that information
26999 explicitly on each command, and because user interacts with
27000 @value{GDBN} via a single terminal, so no confusion is possible as
27001 to what thread and frame are the current ones.
27003 In the case of MI, the concept of selected thread and frame is less
27004 useful. First, a frontend can easily remember this information
27005 itself. Second, a graphical frontend can have more than one window,
27006 each one used for debugging a different thread, and the frontend might
27007 want to access additional threads for internal purposes. This
27008 increases the risk that by relying on implicitly selected thread, the
27009 frontend may be operating on a wrong one. Therefore, each MI command
27010 should explicitly specify which thread and frame to operate on. To
27011 make it possible, each MI command accepts the @samp{--thread} and
27012 @samp{--frame} options, the value to each is @value{GDBN} global
27013 identifier for thread and frame to operate on.
27015 Usually, each top-level window in a frontend allows the user to select
27016 a thread and a frame, and remembers the user selection for further
27017 operations. However, in some cases @value{GDBN} may suggest that the
27018 current thread or frame be changed. For example, when stopping on a
27019 breakpoint it is reasonable to switch to the thread where breakpoint is
27020 hit. For another example, if the user issues the CLI @samp{thread} or
27021 @samp{frame} commands via the frontend, it is desirable to change the
27022 frontend's selection to the one specified by user. @value{GDBN}
27023 communicates the suggestion to change current thread and frame using the
27024 @samp{=thread-selected} notification.
27026 Note that historically, MI shares the selected thread with CLI, so
27027 frontends used the @code{-thread-select} to execute commands in the
27028 right context. However, getting this to work right is cumbersome. The
27029 simplest way is for frontend to emit @code{-thread-select} command
27030 before every command. This doubles the number of commands that need
27031 to be sent. The alternative approach is to suppress @code{-thread-select}
27032 if the selected thread in @value{GDBN} is supposed to be identical to the
27033 thread the frontend wants to operate on. However, getting this
27034 optimization right can be tricky. In particular, if the frontend
27035 sends several commands to @value{GDBN}, and one of the commands changes the
27036 selected thread, then the behaviour of subsequent commands will
27037 change. So, a frontend should either wait for response from such
27038 problematic commands, or explicitly add @code{-thread-select} for
27039 all subsequent commands. No frontend is known to do this exactly
27040 right, so it is suggested to just always pass the @samp{--thread} and
27041 @samp{--frame} options.
27043 @subsubsection Language
27045 The execution of several commands depends on which language is selected.
27046 By default, the current language (@pxref{show language}) is used.
27047 But for commands known to be language-sensitive, it is recommended
27048 to use the @samp{--language} option. This option takes one argument,
27049 which is the name of the language to use while executing the command.
27053 -data-evaluate-expression --language c "sizeof (void*)"
27058 The valid language names are the same names accepted by the
27059 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27060 @samp{local} or @samp{unknown}.
27062 @node Asynchronous and non-stop modes
27063 @subsection Asynchronous command execution and non-stop mode
27065 On some targets, @value{GDBN} is capable of processing MI commands
27066 even while the target is running. This is called @dfn{asynchronous
27067 command execution} (@pxref{Background Execution}). The frontend may
27068 specify a preferrence for asynchronous execution using the
27069 @code{-gdb-set mi-async 1} command, which should be emitted before
27070 either running the executable or attaching to the target. After the
27071 frontend has started the executable or attached to the target, it can
27072 find if asynchronous execution is enabled using the
27073 @code{-list-target-features} command.
27076 @item -gdb-set mi-async on
27077 @item -gdb-set mi-async off
27078 Set whether MI is in asynchronous mode.
27080 When @code{off}, which is the default, MI execution commands (e.g.,
27081 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27082 for the program to stop before processing further commands.
27084 When @code{on}, MI execution commands are background execution
27085 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27086 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27087 MI commands even while the target is running.
27089 @item -gdb-show mi-async
27090 Show whether MI asynchronous mode is enabled.
27093 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27094 @code{target-async} instead of @code{mi-async}, and it had the effect
27095 of both putting MI in asynchronous mode and making CLI background
27096 commands possible. CLI background commands are now always possible
27097 ``out of the box'' if the target supports them. The old spelling is
27098 kept as a deprecated alias for backwards compatibility.
27100 Even if @value{GDBN} can accept a command while target is running,
27101 many commands that access the target do not work when the target is
27102 running. Therefore, asynchronous command execution is most useful
27103 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27104 it is possible to examine the state of one thread, while other threads
27107 When a given thread is running, MI commands that try to access the
27108 target in the context of that thread may not work, or may work only on
27109 some targets. In particular, commands that try to operate on thread's
27110 stack will not work, on any target. Commands that read memory, or
27111 modify breakpoints, may work or not work, depending on the target. Note
27112 that even commands that operate on global state, such as @code{print},
27113 @code{set}, and breakpoint commands, still access the target in the
27114 context of a specific thread, so frontend should try to find a
27115 stopped thread and perform the operation on that thread (using the
27116 @samp{--thread} option).
27118 Which commands will work in the context of a running thread is
27119 highly target dependent. However, the two commands
27120 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27121 to find the state of a thread, will always work.
27123 @node Thread groups
27124 @subsection Thread groups
27125 @value{GDBN} may be used to debug several processes at the same time.
27126 On some platfroms, @value{GDBN} may support debugging of several
27127 hardware systems, each one having several cores with several different
27128 processes running on each core. This section describes the MI
27129 mechanism to support such debugging scenarios.
27131 The key observation is that regardless of the structure of the
27132 target, MI can have a global list of threads, because most commands that
27133 accept the @samp{--thread} option do not need to know what process that
27134 thread belongs to. Therefore, it is not necessary to introduce
27135 neither additional @samp{--process} option, nor an notion of the
27136 current process in the MI interface. The only strictly new feature
27137 that is required is the ability to find how the threads are grouped
27140 To allow the user to discover such grouping, and to support arbitrary
27141 hierarchy of machines/cores/processes, MI introduces the concept of a
27142 @dfn{thread group}. Thread group is a collection of threads and other
27143 thread groups. A thread group always has a string identifier, a type,
27144 and may have additional attributes specific to the type. A new
27145 command, @code{-list-thread-groups}, returns the list of top-level
27146 thread groups, which correspond to processes that @value{GDBN} is
27147 debugging at the moment. By passing an identifier of a thread group
27148 to the @code{-list-thread-groups} command, it is possible to obtain
27149 the members of specific thread group.
27151 To allow the user to easily discover processes, and other objects, he
27152 wishes to debug, a concept of @dfn{available thread group} is
27153 introduced. Available thread group is an thread group that
27154 @value{GDBN} is not debugging, but that can be attached to, using the
27155 @code{-target-attach} command. The list of available top-level thread
27156 groups can be obtained using @samp{-list-thread-groups --available}.
27157 In general, the content of a thread group may be only retrieved only
27158 after attaching to that thread group.
27160 Thread groups are related to inferiors (@pxref{Inferiors and
27161 Programs}). Each inferior corresponds to a thread group of a special
27162 type @samp{process}, and some additional operations are permitted on
27163 such thread groups.
27165 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27166 @node GDB/MI Command Syntax
27167 @section @sc{gdb/mi} Command Syntax
27170 * GDB/MI Input Syntax::
27171 * GDB/MI Output Syntax::
27174 @node GDB/MI Input Syntax
27175 @subsection @sc{gdb/mi} Input Syntax
27177 @cindex input syntax for @sc{gdb/mi}
27178 @cindex @sc{gdb/mi}, input syntax
27180 @item @var{command} @expansion{}
27181 @code{@var{cli-command} | @var{mi-command}}
27183 @item @var{cli-command} @expansion{}
27184 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27185 @var{cli-command} is any existing @value{GDBN} CLI command.
27187 @item @var{mi-command} @expansion{}
27188 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27189 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27191 @item @var{token} @expansion{}
27192 "any sequence of digits"
27194 @item @var{option} @expansion{}
27195 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27197 @item @var{parameter} @expansion{}
27198 @code{@var{non-blank-sequence} | @var{c-string}}
27200 @item @var{operation} @expansion{}
27201 @emph{any of the operations described in this chapter}
27203 @item @var{non-blank-sequence} @expansion{}
27204 @emph{anything, provided it doesn't contain special characters such as
27205 "-", @var{nl}, """ and of course " "}
27207 @item @var{c-string} @expansion{}
27208 @code{""" @var{seven-bit-iso-c-string-content} """}
27210 @item @var{nl} @expansion{}
27219 The CLI commands are still handled by the @sc{mi} interpreter; their
27220 output is described below.
27223 The @code{@var{token}}, when present, is passed back when the command
27227 Some @sc{mi} commands accept optional arguments as part of the parameter
27228 list. Each option is identified by a leading @samp{-} (dash) and may be
27229 followed by an optional argument parameter. Options occur first in the
27230 parameter list and can be delimited from normal parameters using
27231 @samp{--} (this is useful when some parameters begin with a dash).
27238 We want easy access to the existing CLI syntax (for debugging).
27241 We want it to be easy to spot a @sc{mi} operation.
27244 @node GDB/MI Output Syntax
27245 @subsection @sc{gdb/mi} Output Syntax
27247 @cindex output syntax of @sc{gdb/mi}
27248 @cindex @sc{gdb/mi}, output syntax
27249 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27250 followed, optionally, by a single result record. This result record
27251 is for the most recent command. The sequence of output records is
27252 terminated by @samp{(gdb)}.
27254 If an input command was prefixed with a @code{@var{token}} then the
27255 corresponding output for that command will also be prefixed by that same
27259 @item @var{output} @expansion{}
27260 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27262 @item @var{result-record} @expansion{}
27263 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27265 @item @var{out-of-band-record} @expansion{}
27266 @code{@var{async-record} | @var{stream-record}}
27268 @item @var{async-record} @expansion{}
27269 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27271 @item @var{exec-async-output} @expansion{}
27272 @code{[ @var{token} ] "*" @var{async-output nl}}
27274 @item @var{status-async-output} @expansion{}
27275 @code{[ @var{token} ] "+" @var{async-output nl}}
27277 @item @var{notify-async-output} @expansion{}
27278 @code{[ @var{token} ] "=" @var{async-output nl}}
27280 @item @var{async-output} @expansion{}
27281 @code{@var{async-class} ( "," @var{result} )*}
27283 @item @var{result-class} @expansion{}
27284 @code{"done" | "running" | "connected" | "error" | "exit"}
27286 @item @var{async-class} @expansion{}
27287 @code{"stopped" | @var{others}} (where @var{others} will be added
27288 depending on the needs---this is still in development).
27290 @item @var{result} @expansion{}
27291 @code{ @var{variable} "=" @var{value}}
27293 @item @var{variable} @expansion{}
27294 @code{ @var{string} }
27296 @item @var{value} @expansion{}
27297 @code{ @var{const} | @var{tuple} | @var{list} }
27299 @item @var{const} @expansion{}
27300 @code{@var{c-string}}
27302 @item @var{tuple} @expansion{}
27303 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27305 @item @var{list} @expansion{}
27306 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27307 @var{result} ( "," @var{result} )* "]" }
27309 @item @var{stream-record} @expansion{}
27310 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27312 @item @var{console-stream-output} @expansion{}
27313 @code{"~" @var{c-string nl}}
27315 @item @var{target-stream-output} @expansion{}
27316 @code{"@@" @var{c-string nl}}
27318 @item @var{log-stream-output} @expansion{}
27319 @code{"&" @var{c-string nl}}
27321 @item @var{nl} @expansion{}
27324 @item @var{token} @expansion{}
27325 @emph{any sequence of digits}.
27333 All output sequences end in a single line containing a period.
27336 The @code{@var{token}} is from the corresponding request. Note that
27337 for all async output, while the token is allowed by the grammar and
27338 may be output by future versions of @value{GDBN} for select async
27339 output messages, it is generally omitted. Frontends should treat
27340 all async output as reporting general changes in the state of the
27341 target and there should be no need to associate async output to any
27345 @cindex status output in @sc{gdb/mi}
27346 @var{status-async-output} contains on-going status information about the
27347 progress of a slow operation. It can be discarded. All status output is
27348 prefixed by @samp{+}.
27351 @cindex async output in @sc{gdb/mi}
27352 @var{exec-async-output} contains asynchronous state change on the target
27353 (stopped, started, disappeared). All async output is prefixed by
27357 @cindex notify output in @sc{gdb/mi}
27358 @var{notify-async-output} contains supplementary information that the
27359 client should handle (e.g., a new breakpoint information). All notify
27360 output is prefixed by @samp{=}.
27363 @cindex console output in @sc{gdb/mi}
27364 @var{console-stream-output} is output that should be displayed as is in the
27365 console. It is the textual response to a CLI command. All the console
27366 output is prefixed by @samp{~}.
27369 @cindex target output in @sc{gdb/mi}
27370 @var{target-stream-output} is the output produced by the target program.
27371 All the target output is prefixed by @samp{@@}.
27374 @cindex log output in @sc{gdb/mi}
27375 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27376 instance messages that should be displayed as part of an error log. All
27377 the log output is prefixed by @samp{&}.
27380 @cindex list output in @sc{gdb/mi}
27381 New @sc{gdb/mi} commands should only output @var{lists} containing
27387 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27388 details about the various output records.
27390 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27391 @node GDB/MI Compatibility with CLI
27392 @section @sc{gdb/mi} Compatibility with CLI
27394 @cindex compatibility, @sc{gdb/mi} and CLI
27395 @cindex @sc{gdb/mi}, compatibility with CLI
27397 For the developers convenience CLI commands can be entered directly,
27398 but there may be some unexpected behaviour. For example, commands
27399 that query the user will behave as if the user replied yes, breakpoint
27400 command lists are not executed and some CLI commands, such as
27401 @code{if}, @code{when} and @code{define}, prompt for further input with
27402 @samp{>}, which is not valid MI output.
27404 This feature may be removed at some stage in the future and it is
27405 recommended that front ends use the @code{-interpreter-exec} command
27406 (@pxref{-interpreter-exec}).
27408 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27409 @node GDB/MI Development and Front Ends
27410 @section @sc{gdb/mi} Development and Front Ends
27411 @cindex @sc{gdb/mi} development
27413 The application which takes the MI output and presents the state of the
27414 program being debugged to the user is called a @dfn{front end}.
27416 Although @sc{gdb/mi} is still incomplete, it is currently being used
27417 by a variety of front ends to @value{GDBN}. This makes it difficult
27418 to introduce new functionality without breaking existing usage. This
27419 section tries to minimize the problems by describing how the protocol
27422 Some changes in MI need not break a carefully designed front end, and
27423 for these the MI version will remain unchanged. The following is a
27424 list of changes that may occur within one level, so front ends should
27425 parse MI output in a way that can handle them:
27429 New MI commands may be added.
27432 New fields may be added to the output of any MI command.
27435 The range of values for fields with specified values, e.g.,
27436 @code{in_scope} (@pxref{-var-update}) may be extended.
27438 @c The format of field's content e.g type prefix, may change so parse it
27439 @c at your own risk. Yes, in general?
27441 @c The order of fields may change? Shouldn't really matter but it might
27442 @c resolve inconsistencies.
27445 If the changes are likely to break front ends, the MI version level
27446 will be increased by one. This will allow the front end to parse the
27447 output according to the MI version. Apart from mi0, new versions of
27448 @value{GDBN} will not support old versions of MI and it will be the
27449 responsibility of the front end to work with the new one.
27451 @c Starting with mi3, add a new command -mi-version that prints the MI
27454 The best way to avoid unexpected changes in MI that might break your front
27455 end is to make your project known to @value{GDBN} developers and
27456 follow development on @email{gdb@@sourceware.org} and
27457 @email{gdb-patches@@sourceware.org}.
27458 @cindex mailing lists
27460 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27461 @node GDB/MI Output Records
27462 @section @sc{gdb/mi} Output Records
27465 * GDB/MI Result Records::
27466 * GDB/MI Stream Records::
27467 * GDB/MI Async Records::
27468 * GDB/MI Breakpoint Information::
27469 * GDB/MI Frame Information::
27470 * GDB/MI Thread Information::
27471 * GDB/MI Ada Exception Information::
27474 @node GDB/MI Result Records
27475 @subsection @sc{gdb/mi} Result Records
27477 @cindex result records in @sc{gdb/mi}
27478 @cindex @sc{gdb/mi}, result records
27479 In addition to a number of out-of-band notifications, the response to a
27480 @sc{gdb/mi} command includes one of the following result indications:
27484 @item "^done" [ "," @var{results} ]
27485 The synchronous operation was successful, @code{@var{results}} are the return
27490 This result record is equivalent to @samp{^done}. Historically, it
27491 was output instead of @samp{^done} if the command has resumed the
27492 target. This behaviour is maintained for backward compatibility, but
27493 all frontends should treat @samp{^done} and @samp{^running}
27494 identically and rely on the @samp{*running} output record to determine
27495 which threads are resumed.
27499 @value{GDBN} has connected to a remote target.
27501 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27503 The operation failed. The @code{msg=@var{c-string}} variable contains
27504 the corresponding error message.
27506 If present, the @code{code=@var{c-string}} variable provides an error
27507 code on which consumers can rely on to detect the corresponding
27508 error condition. At present, only one error code is defined:
27511 @item "undefined-command"
27512 Indicates that the command causing the error does not exist.
27517 @value{GDBN} has terminated.
27521 @node GDB/MI Stream Records
27522 @subsection @sc{gdb/mi} Stream Records
27524 @cindex @sc{gdb/mi}, stream records
27525 @cindex stream records in @sc{gdb/mi}
27526 @value{GDBN} internally maintains a number of output streams: the console, the
27527 target, and the log. The output intended for each of these streams is
27528 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27530 Each stream record begins with a unique @dfn{prefix character} which
27531 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27532 Syntax}). In addition to the prefix, each stream record contains a
27533 @code{@var{string-output}}. This is either raw text (with an implicit new
27534 line) or a quoted C string (which does not contain an implicit newline).
27537 @item "~" @var{string-output}
27538 The console output stream contains text that should be displayed in the
27539 CLI console window. It contains the textual responses to CLI commands.
27541 @item "@@" @var{string-output}
27542 The target output stream contains any textual output from the running
27543 target. This is only present when GDB's event loop is truly
27544 asynchronous, which is currently only the case for remote targets.
27546 @item "&" @var{string-output}
27547 The log stream contains debugging messages being produced by @value{GDBN}'s
27551 @node GDB/MI Async Records
27552 @subsection @sc{gdb/mi} Async Records
27554 @cindex async records in @sc{gdb/mi}
27555 @cindex @sc{gdb/mi}, async records
27556 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27557 additional changes that have occurred. Those changes can either be a
27558 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27559 target activity (e.g., target stopped).
27561 The following is the list of possible async records:
27565 @item *running,thread-id="@var{thread}"
27566 The target is now running. The @var{thread} field can be the global
27567 thread ID of the the thread that is now running, and it can be
27568 @samp{all} if all threads are running. The frontend should assume
27569 that no interaction with a running thread is possible after this
27570 notification is produced. The frontend should not assume that this
27571 notification is output only once for any command. @value{GDBN} may
27572 emit this notification several times, either for different threads,
27573 because it cannot resume all threads together, or even for a single
27574 thread, if the thread must be stepped though some code before letting
27577 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27578 The target has stopped. The @var{reason} field can have one of the
27582 @item breakpoint-hit
27583 A breakpoint was reached.
27584 @item watchpoint-trigger
27585 A watchpoint was triggered.
27586 @item read-watchpoint-trigger
27587 A read watchpoint was triggered.
27588 @item access-watchpoint-trigger
27589 An access watchpoint was triggered.
27590 @item function-finished
27591 An -exec-finish or similar CLI command was accomplished.
27592 @item location-reached
27593 An -exec-until or similar CLI command was accomplished.
27594 @item watchpoint-scope
27595 A watchpoint has gone out of scope.
27596 @item end-stepping-range
27597 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27598 similar CLI command was accomplished.
27599 @item exited-signalled
27600 The inferior exited because of a signal.
27602 The inferior exited.
27603 @item exited-normally
27604 The inferior exited normally.
27605 @item signal-received
27606 A signal was received by the inferior.
27608 The inferior has stopped due to a library being loaded or unloaded.
27609 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27610 set or when a @code{catch load} or @code{catch unload} catchpoint is
27611 in use (@pxref{Set Catchpoints}).
27613 The inferior has forked. This is reported when @code{catch fork}
27614 (@pxref{Set Catchpoints}) has been used.
27616 The inferior has vforked. This is reported in when @code{catch vfork}
27617 (@pxref{Set Catchpoints}) has been used.
27618 @item syscall-entry
27619 The inferior entered a system call. This is reported when @code{catch
27620 syscall} (@pxref{Set Catchpoints}) has been used.
27621 @item syscall-return
27622 The inferior returned from a system call. This is reported when
27623 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27625 The inferior called @code{exec}. This is reported when @code{catch exec}
27626 (@pxref{Set Catchpoints}) has been used.
27629 The @var{id} field identifies the global thread ID of the thread
27630 that directly caused the stop -- for example by hitting a breakpoint.
27631 Depending on whether all-stop
27632 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27633 stop all threads, or only the thread that directly triggered the stop.
27634 If all threads are stopped, the @var{stopped} field will have the
27635 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27636 field will be a list of thread identifiers. Presently, this list will
27637 always include a single thread, but frontend should be prepared to see
27638 several threads in the list. The @var{core} field reports the
27639 processor core on which the stop event has happened. This field may be absent
27640 if such information is not available.
27642 @item =thread-group-added,id="@var{id}"
27643 @itemx =thread-group-removed,id="@var{id}"
27644 A thread group was either added or removed. The @var{id} field
27645 contains the @value{GDBN} identifier of the thread group. When a thread
27646 group is added, it generally might not be associated with a running
27647 process. When a thread group is removed, its id becomes invalid and
27648 cannot be used in any way.
27650 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27651 A thread group became associated with a running program,
27652 either because the program was just started or the thread group
27653 was attached to a program. The @var{id} field contains the
27654 @value{GDBN} identifier of the thread group. The @var{pid} field
27655 contains process identifier, specific to the operating system.
27657 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27658 A thread group is no longer associated with a running program,
27659 either because the program has exited, or because it was detached
27660 from. The @var{id} field contains the @value{GDBN} identifier of the
27661 thread group. The @var{code} field is the exit code of the inferior; it exists
27662 only when the inferior exited with some code.
27664 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27665 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27666 A thread either was created, or has exited. The @var{id} field
27667 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27668 field identifies the thread group this thread belongs to.
27670 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27671 Informs that the selected thread or frame were changed. This notification
27672 is not emitted as result of the @code{-thread-select} or
27673 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27674 that is not documented to change the selected thread and frame actually
27675 changes them. In particular, invoking, directly or indirectly
27676 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27677 will generate this notification. Changing the thread or frame from another
27678 user interface (see @ref{Interpreters}) will also generate this notification.
27680 The @var{frame} field is only present if the newly selected thread is
27681 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27683 We suggest that in response to this notification, front ends
27684 highlight the selected thread and cause subsequent commands to apply to
27687 @item =library-loaded,...
27688 Reports that a new library file was loaded by the program. This
27689 notification has 5 fields---@var{id}, @var{target-name},
27690 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27691 opaque identifier of the library. For remote debugging case,
27692 @var{target-name} and @var{host-name} fields give the name of the
27693 library file on the target, and on the host respectively. For native
27694 debugging, both those fields have the same value. The
27695 @var{symbols-loaded} field is emitted only for backward compatibility
27696 and should not be relied on to convey any useful information. The
27697 @var{thread-group} field, if present, specifies the id of the thread
27698 group in whose context the library was loaded. If the field is
27699 absent, it means the library was loaded in the context of all present
27700 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27703 @item =library-unloaded,...
27704 Reports that a library was unloaded by the program. This notification
27705 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27706 the same meaning as for the @code{=library-loaded} notification.
27707 The @var{thread-group} field, if present, specifies the id of the
27708 thread group in whose context the library was unloaded. If the field is
27709 absent, it means the library was unloaded in the context of all present
27712 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27713 @itemx =traceframe-changed,end
27714 Reports that the trace frame was changed and its new number is
27715 @var{tfnum}. The number of the tracepoint associated with this trace
27716 frame is @var{tpnum}.
27718 @item =tsv-created,name=@var{name},initial=@var{initial}
27719 Reports that the new trace state variable @var{name} is created with
27720 initial value @var{initial}.
27722 @item =tsv-deleted,name=@var{name}
27723 @itemx =tsv-deleted
27724 Reports that the trace state variable @var{name} is deleted or all
27725 trace state variables are deleted.
27727 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27728 Reports that the trace state variable @var{name} is modified with
27729 the initial value @var{initial}. The current value @var{current} of
27730 trace state variable is optional and is reported if the current
27731 value of trace state variable is known.
27733 @item =breakpoint-created,bkpt=@{...@}
27734 @itemx =breakpoint-modified,bkpt=@{...@}
27735 @itemx =breakpoint-deleted,id=@var{number}
27736 Reports that a breakpoint was created, modified, or deleted,
27737 respectively. Only user-visible breakpoints are reported to the MI
27740 The @var{bkpt} argument is of the same form as returned by the various
27741 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27742 @var{number} is the ordinal number of the breakpoint.
27744 Note that if a breakpoint is emitted in the result record of a
27745 command, then it will not also be emitted in an async record.
27747 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27748 @itemx =record-stopped,thread-group="@var{id}"
27749 Execution log recording was either started or stopped on an
27750 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27751 group corresponding to the affected inferior.
27753 The @var{method} field indicates the method used to record execution. If the
27754 method in use supports multiple recording formats, @var{format} will be present
27755 and contain the currently used format. @xref{Process Record and Replay},
27756 for existing method and format values.
27758 @item =cmd-param-changed,param=@var{param},value=@var{value}
27759 Reports that a parameter of the command @code{set @var{param}} is
27760 changed to @var{value}. In the multi-word @code{set} command,
27761 the @var{param} is the whole parameter list to @code{set} command.
27762 For example, In command @code{set check type on}, @var{param}
27763 is @code{check type} and @var{value} is @code{on}.
27765 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27766 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27767 written in an inferior. The @var{id} is the identifier of the
27768 thread group corresponding to the affected inferior. The optional
27769 @code{type="code"} part is reported if the memory written to holds
27773 @node GDB/MI Breakpoint Information
27774 @subsection @sc{gdb/mi} Breakpoint Information
27776 When @value{GDBN} reports information about a breakpoint, a
27777 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27782 The breakpoint number. For a breakpoint that represents one location
27783 of a multi-location breakpoint, this will be a dotted pair, like
27787 The type of the breakpoint. For ordinary breakpoints this will be
27788 @samp{breakpoint}, but many values are possible.
27791 If the type of the breakpoint is @samp{catchpoint}, then this
27792 indicates the exact type of catchpoint.
27795 This is the breakpoint disposition---either @samp{del}, meaning that
27796 the breakpoint will be deleted at the next stop, or @samp{keep},
27797 meaning that the breakpoint will not be deleted.
27800 This indicates whether the breakpoint is enabled, in which case the
27801 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27802 Note that this is not the same as the field @code{enable}.
27805 The address of the breakpoint. This may be a hexidecimal number,
27806 giving the address; or the string @samp{<PENDING>}, for a pending
27807 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27808 multiple locations. This field will not be present if no address can
27809 be determined. For example, a watchpoint does not have an address.
27812 If known, the function in which the breakpoint appears.
27813 If not known, this field is not present.
27816 The name of the source file which contains this function, if known.
27817 If not known, this field is not present.
27820 The full file name of the source file which contains this function, if
27821 known. If not known, this field is not present.
27824 The line number at which this breakpoint appears, if known.
27825 If not known, this field is not present.
27828 If the source file is not known, this field may be provided. If
27829 provided, this holds the address of the breakpoint, possibly followed
27833 If this breakpoint is pending, this field is present and holds the
27834 text used to set the breakpoint, as entered by the user.
27837 Where this breakpoint's condition is evaluated, either @samp{host} or
27841 If this is a thread-specific breakpoint, then this identifies the
27842 thread in which the breakpoint can trigger.
27845 If this breakpoint is restricted to a particular Ada task, then this
27846 field will hold the task identifier.
27849 If the breakpoint is conditional, this is the condition expression.
27852 The ignore count of the breakpoint.
27855 The enable count of the breakpoint.
27857 @item traceframe-usage
27860 @item static-tracepoint-marker-string-id
27861 For a static tracepoint, the name of the static tracepoint marker.
27864 For a masked watchpoint, this is the mask.
27867 A tracepoint's pass count.
27869 @item original-location
27870 The location of the breakpoint as originally specified by the user.
27871 This field is optional.
27874 The number of times the breakpoint has been hit.
27877 This field is only given for tracepoints. This is either @samp{y},
27878 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27882 Some extra data, the exact contents of which are type-dependent.
27886 For example, here is what the output of @code{-break-insert}
27887 (@pxref{GDB/MI Breakpoint Commands}) might be:
27890 -> -break-insert main
27891 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27892 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27893 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27898 @node GDB/MI Frame Information
27899 @subsection @sc{gdb/mi} Frame Information
27901 Response from many MI commands includes an information about stack
27902 frame. This information is a tuple that may have the following
27907 The level of the stack frame. The innermost frame has the level of
27908 zero. This field is always present.
27911 The name of the function corresponding to the frame. This field may
27912 be absent if @value{GDBN} is unable to determine the function name.
27915 The code address for the frame. This field is always present.
27918 The name of the source files that correspond to the frame's code
27919 address. This field may be absent.
27922 The source line corresponding to the frames' code address. This field
27926 The name of the binary file (either executable or shared library) the
27927 corresponds to the frame's code address. This field may be absent.
27931 @node GDB/MI Thread Information
27932 @subsection @sc{gdb/mi} Thread Information
27934 Whenever @value{GDBN} has to report an information about a thread, it
27935 uses a tuple with the following fields. The fields are always present unless
27940 The global numeric id assigned to the thread by @value{GDBN}.
27943 The target-specific string identifying the thread.
27946 Additional information about the thread provided by the target.
27947 It is supposed to be human-readable and not interpreted by the
27948 frontend. This field is optional.
27951 The name of the thread. If the user specified a name using the
27952 @code{thread name} command, then this name is given. Otherwise, if
27953 @value{GDBN} can extract the thread name from the target, then that
27954 name is given. If @value{GDBN} cannot find the thread name, then this
27958 The execution state of the thread, either @samp{stopped} or @samp{running},
27959 depending on whether the thread is presently running.
27962 The stack frame currently executing in the thread. This field is only present
27963 if the thread is stopped. Its format is documented in
27964 @ref{GDB/MI Frame Information}.
27967 The value of this field is an integer number of the processor core the
27968 thread was last seen on. This field is optional.
27971 @node GDB/MI Ada Exception Information
27972 @subsection @sc{gdb/mi} Ada Exception Information
27974 Whenever a @code{*stopped} record is emitted because the program
27975 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27976 @value{GDBN} provides the name of the exception that was raised via
27977 the @code{exception-name} field. Also, for exceptions that were raised
27978 with an exception message, @value{GDBN} provides that message via
27979 the @code{exception-message} field.
27981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27982 @node GDB/MI Simple Examples
27983 @section Simple Examples of @sc{gdb/mi} Interaction
27984 @cindex @sc{gdb/mi}, simple examples
27986 This subsection presents several simple examples of interaction using
27987 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27988 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27989 the output received from @sc{gdb/mi}.
27991 Note the line breaks shown in the examples are here only for
27992 readability, they don't appear in the real output.
27994 @subheading Setting a Breakpoint
27996 Setting a breakpoint generates synchronous output which contains detailed
27997 information of the breakpoint.
28000 -> -break-insert main
28001 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28002 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28003 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28008 @subheading Program Execution
28010 Program execution generates asynchronous records and MI gives the
28011 reason that execution stopped.
28017 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28018 frame=@{addr="0x08048564",func="main",
28019 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28020 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28025 <- *stopped,reason="exited-normally"
28029 @subheading Quitting @value{GDBN}
28031 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28039 Please note that @samp{^exit} is printed immediately, but it might
28040 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28041 performs necessary cleanups, including killing programs being debugged
28042 or disconnecting from debug hardware, so the frontend should wait till
28043 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28044 fails to exit in reasonable time.
28046 @subheading A Bad Command
28048 Here's what happens if you pass a non-existent command:
28052 <- ^error,msg="Undefined MI command: rubbish"
28057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28058 @node GDB/MI Command Description Format
28059 @section @sc{gdb/mi} Command Description Format
28061 The remaining sections describe blocks of commands. Each block of
28062 commands is laid out in a fashion similar to this section.
28064 @subheading Motivation
28066 The motivation for this collection of commands.
28068 @subheading Introduction
28070 A brief introduction to this collection of commands as a whole.
28072 @subheading Commands
28074 For each command in the block, the following is described:
28076 @subsubheading Synopsis
28079 -command @var{args}@dots{}
28082 @subsubheading Result
28084 @subsubheading @value{GDBN} Command
28086 The corresponding @value{GDBN} CLI command(s), if any.
28088 @subsubheading Example
28090 Example(s) formatted for readability. Some of the described commands have
28091 not been implemented yet and these are labeled N.A.@: (not available).
28094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28095 @node GDB/MI Breakpoint Commands
28096 @section @sc{gdb/mi} Breakpoint Commands
28098 @cindex breakpoint commands for @sc{gdb/mi}
28099 @cindex @sc{gdb/mi}, breakpoint commands
28100 This section documents @sc{gdb/mi} commands for manipulating
28103 @subheading The @code{-break-after} Command
28104 @findex -break-after
28106 @subsubheading Synopsis
28109 -break-after @var{number} @var{count}
28112 The breakpoint number @var{number} is not in effect until it has been
28113 hit @var{count} times. To see how this is reflected in the output of
28114 the @samp{-break-list} command, see the description of the
28115 @samp{-break-list} command below.
28117 @subsubheading @value{GDBN} Command
28119 The corresponding @value{GDBN} command is @samp{ignore}.
28121 @subsubheading Example
28126 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28127 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28128 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28136 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28137 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28138 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28139 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28140 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28141 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28142 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28143 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28144 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28145 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28150 @subheading The @code{-break-catch} Command
28151 @findex -break-catch
28154 @subheading The @code{-break-commands} Command
28155 @findex -break-commands
28157 @subsubheading Synopsis
28160 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28163 Specifies the CLI commands that should be executed when breakpoint
28164 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28165 are the commands. If no command is specified, any previously-set
28166 commands are cleared. @xref{Break Commands}. Typical use of this
28167 functionality is tracing a program, that is, printing of values of
28168 some variables whenever breakpoint is hit and then continuing.
28170 @subsubheading @value{GDBN} Command
28172 The corresponding @value{GDBN} command is @samp{commands}.
28174 @subsubheading Example
28179 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28180 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28181 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28184 -break-commands 1 "print v" "continue"
28189 @subheading The @code{-break-condition} Command
28190 @findex -break-condition
28192 @subsubheading Synopsis
28195 -break-condition @var{number} @var{expr}
28198 Breakpoint @var{number} will stop the program only if the condition in
28199 @var{expr} is true. The condition becomes part of the
28200 @samp{-break-list} output (see the description of the @samp{-break-list}
28203 @subsubheading @value{GDBN} Command
28205 The corresponding @value{GDBN} command is @samp{condition}.
28207 @subsubheading Example
28211 -break-condition 1 1
28215 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28216 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28217 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28218 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28219 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28220 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28221 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28222 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28223 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28224 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28228 @subheading The @code{-break-delete} Command
28229 @findex -break-delete
28231 @subsubheading Synopsis
28234 -break-delete ( @var{breakpoint} )+
28237 Delete the breakpoint(s) whose number(s) are specified in the argument
28238 list. This is obviously reflected in the breakpoint list.
28240 @subsubheading @value{GDBN} Command
28242 The corresponding @value{GDBN} command is @samp{delete}.
28244 @subsubheading Example
28252 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28253 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28254 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28255 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28256 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28257 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28258 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28263 @subheading The @code{-break-disable} Command
28264 @findex -break-disable
28266 @subsubheading Synopsis
28269 -break-disable ( @var{breakpoint} )+
28272 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28273 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28275 @subsubheading @value{GDBN} Command
28277 The corresponding @value{GDBN} command is @samp{disable}.
28279 @subsubheading Example
28287 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28288 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28289 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28290 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28291 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28292 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28293 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28294 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28295 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28296 line="5",thread-groups=["i1"],times="0"@}]@}
28300 @subheading The @code{-break-enable} Command
28301 @findex -break-enable
28303 @subsubheading Synopsis
28306 -break-enable ( @var{breakpoint} )+
28309 Enable (previously disabled) @var{breakpoint}(s).
28311 @subsubheading @value{GDBN} Command
28313 The corresponding @value{GDBN} command is @samp{enable}.
28315 @subsubheading Example
28323 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28324 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28325 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28326 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28327 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28328 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28329 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28330 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28331 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28332 line="5",thread-groups=["i1"],times="0"@}]@}
28336 @subheading The @code{-break-info} Command
28337 @findex -break-info
28339 @subsubheading Synopsis
28342 -break-info @var{breakpoint}
28346 Get information about a single breakpoint.
28348 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28349 Information}, for details on the format of each breakpoint in the
28352 @subsubheading @value{GDBN} Command
28354 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28356 @subsubheading Example
28359 @subheading The @code{-break-insert} Command
28360 @findex -break-insert
28361 @anchor{-break-insert}
28363 @subsubheading Synopsis
28366 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28367 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28368 [ -p @var{thread-id} ] [ @var{location} ]
28372 If specified, @var{location}, can be one of:
28375 @item linespec location
28376 A linespec location. @xref{Linespec Locations}.
28378 @item explicit location
28379 An explicit location. @sc{gdb/mi} explicit locations are
28380 analogous to the CLI's explicit locations using the option names
28381 listed below. @xref{Explicit Locations}.
28384 @item --source @var{filename}
28385 The source file name of the location. This option requires the use
28386 of either @samp{--function} or @samp{--line}.
28388 @item --function @var{function}
28389 The name of a function or method.
28391 @item --label @var{label}
28392 The name of a label.
28394 @item --line @var{lineoffset}
28395 An absolute or relative line offset from the start of the location.
28398 @item address location
28399 An address location, *@var{address}. @xref{Address Locations}.
28403 The possible optional parameters of this command are:
28407 Insert a temporary breakpoint.
28409 Insert a hardware breakpoint.
28411 If @var{location} cannot be parsed (for example if it
28412 refers to unknown files or functions), create a pending
28413 breakpoint. Without this flag, @value{GDBN} will report
28414 an error, and won't create a breakpoint, if @var{location}
28417 Create a disabled breakpoint.
28419 Create a tracepoint. @xref{Tracepoints}. When this parameter
28420 is used together with @samp{-h}, a fast tracepoint is created.
28421 @item -c @var{condition}
28422 Make the breakpoint conditional on @var{condition}.
28423 @item -i @var{ignore-count}
28424 Initialize the @var{ignore-count}.
28425 @item -p @var{thread-id}
28426 Restrict the breakpoint to the thread with the specified global
28430 @subsubheading Result
28432 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28433 resulting breakpoint.
28435 Note: this format is open to change.
28436 @c An out-of-band breakpoint instead of part of the result?
28438 @subsubheading @value{GDBN} Command
28440 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28441 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28443 @subsubheading Example
28448 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28449 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28452 -break-insert -t foo
28453 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28454 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28458 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28459 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28460 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28461 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28462 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28463 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28464 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28465 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28466 addr="0x0001072c", func="main",file="recursive2.c",
28467 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28469 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28470 addr="0x00010774",func="foo",file="recursive2.c",
28471 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28474 @c -break-insert -r foo.*
28475 @c ~int foo(int, int);
28476 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28477 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28482 @subheading The @code{-dprintf-insert} Command
28483 @findex -dprintf-insert
28485 @subsubheading Synopsis
28488 -dprintf-insert [ -t ] [ -f ] [ -d ]
28489 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28490 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28495 If supplied, @var{location} may be specified the same way as for
28496 the @code{-break-insert} command. @xref{-break-insert}.
28498 The possible optional parameters of this command are:
28502 Insert a temporary breakpoint.
28504 If @var{location} cannot be parsed (for example, if it
28505 refers to unknown files or functions), create a pending
28506 breakpoint. Without this flag, @value{GDBN} will report
28507 an error, and won't create a breakpoint, if @var{location}
28510 Create a disabled breakpoint.
28511 @item -c @var{condition}
28512 Make the breakpoint conditional on @var{condition}.
28513 @item -i @var{ignore-count}
28514 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28515 to @var{ignore-count}.
28516 @item -p @var{thread-id}
28517 Restrict the breakpoint to the thread with the specified global
28521 @subsubheading Result
28523 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28524 resulting breakpoint.
28526 @c An out-of-band breakpoint instead of part of the result?
28528 @subsubheading @value{GDBN} Command
28530 The corresponding @value{GDBN} command is @samp{dprintf}.
28532 @subsubheading Example
28536 4-dprintf-insert foo "At foo entry\n"
28537 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28538 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28539 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28540 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28541 original-location="foo"@}
28543 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28544 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28545 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28546 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28547 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28548 original-location="mi-dprintf.c:26"@}
28552 @subheading The @code{-break-list} Command
28553 @findex -break-list
28555 @subsubheading Synopsis
28561 Displays the list of inserted breakpoints, showing the following fields:
28565 number of the breakpoint
28567 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28569 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28572 is the breakpoint enabled or no: @samp{y} or @samp{n}
28574 memory location at which the breakpoint is set
28576 logical location of the breakpoint, expressed by function name, file
28578 @item Thread-groups
28579 list of thread groups to which this breakpoint applies
28581 number of times the breakpoint has been hit
28584 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28585 @code{body} field is an empty list.
28587 @subsubheading @value{GDBN} Command
28589 The corresponding @value{GDBN} command is @samp{info break}.
28591 @subsubheading Example
28596 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28597 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28598 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28599 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28600 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28601 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28602 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28603 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28604 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28606 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28607 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28608 line="13",thread-groups=["i1"],times="0"@}]@}
28612 Here's an example of the result when there are no breakpoints:
28617 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28618 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28619 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28620 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28621 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28622 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28623 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28628 @subheading The @code{-break-passcount} Command
28629 @findex -break-passcount
28631 @subsubheading Synopsis
28634 -break-passcount @var{tracepoint-number} @var{passcount}
28637 Set the passcount for tracepoint @var{tracepoint-number} to
28638 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28639 is not a tracepoint, error is emitted. This corresponds to CLI
28640 command @samp{passcount}.
28642 @subheading The @code{-break-watch} Command
28643 @findex -break-watch
28645 @subsubheading Synopsis
28648 -break-watch [ -a | -r ]
28651 Create a watchpoint. With the @samp{-a} option it will create an
28652 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28653 read from or on a write to the memory location. With the @samp{-r}
28654 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28655 trigger only when the memory location is accessed for reading. Without
28656 either of the options, the watchpoint created is a regular watchpoint,
28657 i.e., it will trigger when the memory location is accessed for writing.
28658 @xref{Set Watchpoints, , Setting Watchpoints}.
28660 Note that @samp{-break-list} will report a single list of watchpoints and
28661 breakpoints inserted.
28663 @subsubheading @value{GDBN} Command
28665 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28668 @subsubheading Example
28670 Setting a watchpoint on a variable in the @code{main} function:
28675 ^done,wpt=@{number="2",exp="x"@}
28680 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28681 value=@{old="-268439212",new="55"@},
28682 frame=@{func="main",args=[],file="recursive2.c",
28683 fullname="/home/foo/bar/recursive2.c",line="5"@}
28687 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28688 the program execution twice: first for the variable changing value, then
28689 for the watchpoint going out of scope.
28694 ^done,wpt=@{number="5",exp="C"@}
28699 *stopped,reason="watchpoint-trigger",
28700 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28701 frame=@{func="callee4",args=[],
28702 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28703 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28708 *stopped,reason="watchpoint-scope",wpnum="5",
28709 frame=@{func="callee3",args=[@{name="strarg",
28710 value="0x11940 \"A string argument.\""@}],
28711 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28712 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28716 Listing breakpoints and watchpoints, at different points in the program
28717 execution. Note that once the watchpoint goes out of scope, it is
28723 ^done,wpt=@{number="2",exp="C"@}
28726 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28727 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28728 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28729 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28730 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28731 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28732 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28733 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28734 addr="0x00010734",func="callee4",
28735 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28736 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28738 bkpt=@{number="2",type="watchpoint",disp="keep",
28739 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28744 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28745 value=@{old="-276895068",new="3"@},
28746 frame=@{func="callee4",args=[],
28747 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28748 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28751 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28752 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28753 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28754 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28755 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28756 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28757 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28758 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28759 addr="0x00010734",func="callee4",
28760 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28761 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28763 bkpt=@{number="2",type="watchpoint",disp="keep",
28764 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28768 ^done,reason="watchpoint-scope",wpnum="2",
28769 frame=@{func="callee3",args=[@{name="strarg",
28770 value="0x11940 \"A string argument.\""@}],
28771 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28772 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28775 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28776 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28777 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28778 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28779 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28780 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28781 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28782 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28783 addr="0x00010734",func="callee4",
28784 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28785 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28786 thread-groups=["i1"],times="1"@}]@}
28791 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28792 @node GDB/MI Catchpoint Commands
28793 @section @sc{gdb/mi} Catchpoint Commands
28795 This section documents @sc{gdb/mi} commands for manipulating
28799 * Shared Library GDB/MI Catchpoint Commands::
28800 * Ada Exception GDB/MI Catchpoint Commands::
28803 @node Shared Library GDB/MI Catchpoint Commands
28804 @subsection Shared Library @sc{gdb/mi} Catchpoints
28806 @subheading The @code{-catch-load} Command
28807 @findex -catch-load
28809 @subsubheading Synopsis
28812 -catch-load [ -t ] [ -d ] @var{regexp}
28815 Add a catchpoint for library load events. If the @samp{-t} option is used,
28816 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28817 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28818 in a disabled state. The @samp{regexp} argument is a regular
28819 expression used to match the name of the loaded library.
28822 @subsubheading @value{GDBN} Command
28824 The corresponding @value{GDBN} command is @samp{catch load}.
28826 @subsubheading Example
28829 -catch-load -t foo.so
28830 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28831 what="load of library matching foo.so",catch-type="load",times="0"@}
28836 @subheading The @code{-catch-unload} Command
28837 @findex -catch-unload
28839 @subsubheading Synopsis
28842 -catch-unload [ -t ] [ -d ] @var{regexp}
28845 Add a catchpoint for library unload events. If the @samp{-t} option is
28846 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28847 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28848 created in a disabled state. The @samp{regexp} argument is a regular
28849 expression used to match the name of the unloaded library.
28851 @subsubheading @value{GDBN} Command
28853 The corresponding @value{GDBN} command is @samp{catch unload}.
28855 @subsubheading Example
28858 -catch-unload -d bar.so
28859 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28860 what="load of library matching bar.so",catch-type="unload",times="0"@}
28864 @node Ada Exception GDB/MI Catchpoint Commands
28865 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28867 The following @sc{gdb/mi} commands can be used to create catchpoints
28868 that stop the execution when Ada exceptions are being raised.
28870 @subheading The @code{-catch-assert} Command
28871 @findex -catch-assert
28873 @subsubheading Synopsis
28876 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28879 Add a catchpoint for failed Ada assertions.
28881 The possible optional parameters for this command are:
28884 @item -c @var{condition}
28885 Make the catchpoint conditional on @var{condition}.
28887 Create a disabled catchpoint.
28889 Create a temporary catchpoint.
28892 @subsubheading @value{GDBN} Command
28894 The corresponding @value{GDBN} command is @samp{catch assert}.
28896 @subsubheading Example
28900 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28901 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28902 thread-groups=["i1"],times="0",
28903 original-location="__gnat_debug_raise_assert_failure"@}
28907 @subheading The @code{-catch-exception} Command
28908 @findex -catch-exception
28910 @subsubheading Synopsis
28913 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28917 Add a catchpoint stopping when Ada exceptions are raised.
28918 By default, the command stops the program when any Ada exception
28919 gets raised. But it is also possible, by using some of the
28920 optional parameters described below, to create more selective
28923 The possible optional parameters for this command are:
28926 @item -c @var{condition}
28927 Make the catchpoint conditional on @var{condition}.
28929 Create a disabled catchpoint.
28930 @item -e @var{exception-name}
28931 Only stop when @var{exception-name} is raised. This option cannot
28932 be used combined with @samp{-u}.
28934 Create a temporary catchpoint.
28936 Stop only when an unhandled exception gets raised. This option
28937 cannot be used combined with @samp{-e}.
28940 @subsubheading @value{GDBN} Command
28942 The corresponding @value{GDBN} commands are @samp{catch exception}
28943 and @samp{catch exception unhandled}.
28945 @subsubheading Example
28948 -catch-exception -e Program_Error
28949 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28950 enabled="y",addr="0x0000000000404874",
28951 what="`Program_Error' Ada exception", thread-groups=["i1"],
28952 times="0",original-location="__gnat_debug_raise_exception"@}
28956 @subheading The @code{-catch-handlers} Command
28957 @findex -catch-handlers
28959 @subsubheading Synopsis
28962 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28966 Add a catchpoint stopping when Ada exceptions are handled.
28967 By default, the command stops the program when any Ada exception
28968 gets handled. But it is also possible, by using some of the
28969 optional parameters described below, to create more selective
28972 The possible optional parameters for this command are:
28975 @item -c @var{condition}
28976 Make the catchpoint conditional on @var{condition}.
28978 Create a disabled catchpoint.
28979 @item -e @var{exception-name}
28980 Only stop when @var{exception-name} is handled.
28982 Create a temporary catchpoint.
28985 @subsubheading @value{GDBN} Command
28987 The corresponding @value{GDBN} command is @samp{catch handlers}.
28989 @subsubheading Example
28992 -catch-handlers -e Constraint_Error
28993 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28994 enabled="y",addr="0x0000000000402f68",
28995 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
28996 times="0",original-location="__gnat_begin_handler"@}
29000 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29001 @node GDB/MI Program Context
29002 @section @sc{gdb/mi} Program Context
29004 @subheading The @code{-exec-arguments} Command
29005 @findex -exec-arguments
29008 @subsubheading Synopsis
29011 -exec-arguments @var{args}
29014 Set the inferior program arguments, to be used in the next
29017 @subsubheading @value{GDBN} Command
29019 The corresponding @value{GDBN} command is @samp{set args}.
29021 @subsubheading Example
29025 -exec-arguments -v word
29032 @subheading The @code{-exec-show-arguments} Command
29033 @findex -exec-show-arguments
29035 @subsubheading Synopsis
29038 -exec-show-arguments
29041 Print the arguments of the program.
29043 @subsubheading @value{GDBN} Command
29045 The corresponding @value{GDBN} command is @samp{show args}.
29047 @subsubheading Example
29052 @subheading The @code{-environment-cd} Command
29053 @findex -environment-cd
29055 @subsubheading Synopsis
29058 -environment-cd @var{pathdir}
29061 Set @value{GDBN}'s working directory.
29063 @subsubheading @value{GDBN} Command
29065 The corresponding @value{GDBN} command is @samp{cd}.
29067 @subsubheading Example
29071 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29077 @subheading The @code{-environment-directory} Command
29078 @findex -environment-directory
29080 @subsubheading Synopsis
29083 -environment-directory [ -r ] [ @var{pathdir} ]+
29086 Add directories @var{pathdir} to beginning of search path for source files.
29087 If the @samp{-r} option is used, the search path is reset to the default
29088 search path. If directories @var{pathdir} are supplied in addition to the
29089 @samp{-r} option, the search path is first reset and then addition
29091 Multiple directories may be specified, separated by blanks. Specifying
29092 multiple directories in a single command
29093 results in the directories added to the beginning of the
29094 search path in the same order they were presented in the command.
29095 If blanks are needed as
29096 part of a directory name, double-quotes should be used around
29097 the name. In the command output, the path will show up separated
29098 by the system directory-separator character. The directory-separator
29099 character must not be used
29100 in any directory name.
29101 If no directories are specified, the current search path is displayed.
29103 @subsubheading @value{GDBN} Command
29105 The corresponding @value{GDBN} command is @samp{dir}.
29107 @subsubheading Example
29111 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29112 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29114 -environment-directory ""
29115 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29117 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29118 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29120 -environment-directory -r
29121 ^done,source-path="$cdir:$cwd"
29126 @subheading The @code{-environment-path} Command
29127 @findex -environment-path
29129 @subsubheading Synopsis
29132 -environment-path [ -r ] [ @var{pathdir} ]+
29135 Add directories @var{pathdir} to beginning of search path for object files.
29136 If the @samp{-r} option is used, the search path is reset to the original
29137 search path that existed at gdb start-up. If directories @var{pathdir} are
29138 supplied in addition to the
29139 @samp{-r} option, the search path is first reset and then addition
29141 Multiple directories may be specified, separated by blanks. Specifying
29142 multiple directories in a single command
29143 results in the directories added to the beginning of the
29144 search path in the same order they were presented in the command.
29145 If blanks are needed as
29146 part of a directory name, double-quotes should be used around
29147 the name. In the command output, the path will show up separated
29148 by the system directory-separator character. The directory-separator
29149 character must not be used
29150 in any directory name.
29151 If no directories are specified, the current path is displayed.
29154 @subsubheading @value{GDBN} Command
29156 The corresponding @value{GDBN} command is @samp{path}.
29158 @subsubheading Example
29163 ^done,path="/usr/bin"
29165 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29166 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29168 -environment-path -r /usr/local/bin
29169 ^done,path="/usr/local/bin:/usr/bin"
29174 @subheading The @code{-environment-pwd} Command
29175 @findex -environment-pwd
29177 @subsubheading Synopsis
29183 Show the current working directory.
29185 @subsubheading @value{GDBN} Command
29187 The corresponding @value{GDBN} command is @samp{pwd}.
29189 @subsubheading Example
29194 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29199 @node GDB/MI Thread Commands
29200 @section @sc{gdb/mi} Thread Commands
29203 @subheading The @code{-thread-info} Command
29204 @findex -thread-info
29206 @subsubheading Synopsis
29209 -thread-info [ @var{thread-id} ]
29212 Reports information about either a specific thread, if the
29213 @var{thread-id} parameter is present, or about all threads.
29214 @var{thread-id} is the thread's global thread ID. When printing
29215 information about all threads, also reports the global ID of the
29218 @subsubheading @value{GDBN} Command
29220 The @samp{info thread} command prints the same information
29223 @subsubheading Result
29225 The result contains the following attributes:
29229 A list of threads. The format of the elements of the list is described in
29230 @ref{GDB/MI Thread Information}.
29232 @item current-thread-id
29233 The global id of the currently selected thread. This field is omitted if there
29234 is no selected thread (for example, when the selected inferior is not running,
29235 and therefore has no threads) or if a @var{thread-id} argument was passed to
29240 @subsubheading Example
29245 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29246 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29247 args=[]@},state="running"@},
29248 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29249 frame=@{level="0",addr="0x0804891f",func="foo",
29250 args=[@{name="i",value="10"@}],
29251 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29252 state="running"@}],
29253 current-thread-id="1"
29257 @subheading The @code{-thread-list-ids} Command
29258 @findex -thread-list-ids
29260 @subsubheading Synopsis
29266 Produces a list of the currently known global @value{GDBN} thread ids.
29267 At the end of the list it also prints the total number of such
29270 This command is retained for historical reasons, the
29271 @code{-thread-info} command should be used instead.
29273 @subsubheading @value{GDBN} Command
29275 Part of @samp{info threads} supplies the same information.
29277 @subsubheading Example
29282 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29283 current-thread-id="1",number-of-threads="3"
29288 @subheading The @code{-thread-select} Command
29289 @findex -thread-select
29291 @subsubheading Synopsis
29294 -thread-select @var{thread-id}
29297 Make thread with global thread number @var{thread-id} the current
29298 thread. It prints the number of the new current thread, and the
29299 topmost frame for that thread.
29301 This command is deprecated in favor of explicitly using the
29302 @samp{--thread} option to each command.
29304 @subsubheading @value{GDBN} Command
29306 The corresponding @value{GDBN} command is @samp{thread}.
29308 @subsubheading Example
29315 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29316 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29320 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29321 number-of-threads="3"
29324 ^done,new-thread-id="3",
29325 frame=@{level="0",func="vprintf",
29326 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29327 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29331 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29332 @node GDB/MI Ada Tasking Commands
29333 @section @sc{gdb/mi} Ada Tasking Commands
29335 @subheading The @code{-ada-task-info} Command
29336 @findex -ada-task-info
29338 @subsubheading Synopsis
29341 -ada-task-info [ @var{task-id} ]
29344 Reports information about either a specific Ada task, if the
29345 @var{task-id} parameter is present, or about all Ada tasks.
29347 @subsubheading @value{GDBN} Command
29349 The @samp{info tasks} command prints the same information
29350 about all Ada tasks (@pxref{Ada Tasks}).
29352 @subsubheading Result
29354 The result is a table of Ada tasks. The following columns are
29355 defined for each Ada task:
29359 This field exists only for the current thread. It has the value @samp{*}.
29362 The identifier that @value{GDBN} uses to refer to the Ada task.
29365 The identifier that the target uses to refer to the Ada task.
29368 The global thread identifier of the thread corresponding to the Ada
29371 This field should always exist, as Ada tasks are always implemented
29372 on top of a thread. But if @value{GDBN} cannot find this corresponding
29373 thread for any reason, the field is omitted.
29376 This field exists only when the task was created by another task.
29377 In this case, it provides the ID of the parent task.
29380 The base priority of the task.
29383 The current state of the task. For a detailed description of the
29384 possible states, see @ref{Ada Tasks}.
29387 The name of the task.
29391 @subsubheading Example
29395 ^done,tasks=@{nr_rows="3",nr_cols="8",
29396 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29397 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29398 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29399 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29400 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29401 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29402 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29403 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29404 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29405 state="Child Termination Wait",name="main_task"@}]@}
29409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29410 @node GDB/MI Program Execution
29411 @section @sc{gdb/mi} Program Execution
29413 These are the asynchronous commands which generate the out-of-band
29414 record @samp{*stopped}. Currently @value{GDBN} only really executes
29415 asynchronously with remote targets and this interaction is mimicked in
29418 @subheading The @code{-exec-continue} Command
29419 @findex -exec-continue
29421 @subsubheading Synopsis
29424 -exec-continue [--reverse] [--all|--thread-group N]
29427 Resumes the execution of the inferior program, which will continue
29428 to execute until it reaches a debugger stop event. If the
29429 @samp{--reverse} option is specified, execution resumes in reverse until
29430 it reaches a stop event. Stop events may include
29433 breakpoints or watchpoints
29435 signals or exceptions
29437 the end of the process (or its beginning under @samp{--reverse})
29439 the end or beginning of a replay log if one is being used.
29441 In all-stop mode (@pxref{All-Stop
29442 Mode}), may resume only one thread, or all threads, depending on the
29443 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29444 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29445 ignored in all-stop mode. If the @samp{--thread-group} options is
29446 specified, then all threads in that thread group are resumed.
29448 @subsubheading @value{GDBN} Command
29450 The corresponding @value{GDBN} corresponding is @samp{continue}.
29452 @subsubheading Example
29459 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29460 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29466 @subheading The @code{-exec-finish} Command
29467 @findex -exec-finish
29469 @subsubheading Synopsis
29472 -exec-finish [--reverse]
29475 Resumes the execution of the inferior program until the current
29476 function is exited. Displays the results returned by the function.
29477 If the @samp{--reverse} option is specified, resumes the reverse
29478 execution of the inferior program until the point where current
29479 function was called.
29481 @subsubheading @value{GDBN} Command
29483 The corresponding @value{GDBN} command is @samp{finish}.
29485 @subsubheading Example
29487 Function returning @code{void}.
29494 *stopped,reason="function-finished",frame=@{func="main",args=[],
29495 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29499 Function returning other than @code{void}. The name of the internal
29500 @value{GDBN} variable storing the result is printed, together with the
29507 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29508 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29510 gdb-result-var="$1",return-value="0"
29515 @subheading The @code{-exec-interrupt} Command
29516 @findex -exec-interrupt
29518 @subsubheading Synopsis
29521 -exec-interrupt [--all|--thread-group N]
29524 Interrupts the background execution of the target. Note how the token
29525 associated with the stop message is the one for the execution command
29526 that has been interrupted. The token for the interrupt itself only
29527 appears in the @samp{^done} output. If the user is trying to
29528 interrupt a non-running program, an error message will be printed.
29530 Note that when asynchronous execution is enabled, this command is
29531 asynchronous just like other execution commands. That is, first the
29532 @samp{^done} response will be printed, and the target stop will be
29533 reported after that using the @samp{*stopped} notification.
29535 In non-stop mode, only the context thread is interrupted by default.
29536 All threads (in all inferiors) will be interrupted if the
29537 @samp{--all} option is specified. If the @samp{--thread-group}
29538 option is specified, all threads in that group will be interrupted.
29540 @subsubheading @value{GDBN} Command
29542 The corresponding @value{GDBN} command is @samp{interrupt}.
29544 @subsubheading Example
29555 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29556 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29557 fullname="/home/foo/bar/try.c",line="13"@}
29562 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29566 @subheading The @code{-exec-jump} Command
29569 @subsubheading Synopsis
29572 -exec-jump @var{location}
29575 Resumes execution of the inferior program at the location specified by
29576 parameter. @xref{Specify Location}, for a description of the
29577 different forms of @var{location}.
29579 @subsubheading @value{GDBN} Command
29581 The corresponding @value{GDBN} command is @samp{jump}.
29583 @subsubheading Example
29586 -exec-jump foo.c:10
29587 *running,thread-id="all"
29592 @subheading The @code{-exec-next} Command
29595 @subsubheading Synopsis
29598 -exec-next [--reverse]
29601 Resumes execution of the inferior program, stopping when the beginning
29602 of the next source line is reached.
29604 If the @samp{--reverse} option is specified, resumes reverse execution
29605 of the inferior program, stopping at the beginning of the previous
29606 source line. If you issue this command on the first line of a
29607 function, it will take you back to the caller of that function, to the
29608 source line where the function was called.
29611 @subsubheading @value{GDBN} Command
29613 The corresponding @value{GDBN} command is @samp{next}.
29615 @subsubheading Example
29621 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29626 @subheading The @code{-exec-next-instruction} Command
29627 @findex -exec-next-instruction
29629 @subsubheading Synopsis
29632 -exec-next-instruction [--reverse]
29635 Executes one machine instruction. If the instruction is a function
29636 call, continues until the function returns. If the program stops at an
29637 instruction in the middle of a source line, the address will be
29640 If the @samp{--reverse} option is specified, resumes reverse execution
29641 of the inferior program, stopping at the previous instruction. If the
29642 previously executed instruction was a return from another function,
29643 it will continue to execute in reverse until the call to that function
29644 (from the current stack frame) is reached.
29646 @subsubheading @value{GDBN} Command
29648 The corresponding @value{GDBN} command is @samp{nexti}.
29650 @subsubheading Example
29654 -exec-next-instruction
29658 *stopped,reason="end-stepping-range",
29659 addr="0x000100d4",line="5",file="hello.c"
29664 @subheading The @code{-exec-return} Command
29665 @findex -exec-return
29667 @subsubheading Synopsis
29673 Makes current function return immediately. Doesn't execute the inferior.
29674 Displays the new current frame.
29676 @subsubheading @value{GDBN} Command
29678 The corresponding @value{GDBN} command is @samp{return}.
29680 @subsubheading Example
29684 200-break-insert callee4
29685 200^done,bkpt=@{number="1",addr="0x00010734",
29686 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29691 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29692 frame=@{func="callee4",args=[],
29693 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29694 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29700 111^done,frame=@{level="0",func="callee3",
29701 args=[@{name="strarg",
29702 value="0x11940 \"A string argument.\""@}],
29703 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29704 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29709 @subheading The @code{-exec-run} Command
29712 @subsubheading Synopsis
29715 -exec-run [ --all | --thread-group N ] [ --start ]
29718 Starts execution of the inferior from the beginning. The inferior
29719 executes until either a breakpoint is encountered or the program
29720 exits. In the latter case the output will include an exit code, if
29721 the program has exited exceptionally.
29723 When neither the @samp{--all} nor the @samp{--thread-group} option
29724 is specified, the current inferior is started. If the
29725 @samp{--thread-group} option is specified, it should refer to a thread
29726 group of type @samp{process}, and that thread group will be started.
29727 If the @samp{--all} option is specified, then all inferiors will be started.
29729 Using the @samp{--start} option instructs the debugger to stop
29730 the execution at the start of the inferior's main subprogram,
29731 following the same behavior as the @code{start} command
29732 (@pxref{Starting}).
29734 @subsubheading @value{GDBN} Command
29736 The corresponding @value{GDBN} command is @samp{run}.
29738 @subsubheading Examples
29743 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29748 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29749 frame=@{func="main",args=[],file="recursive2.c",
29750 fullname="/home/foo/bar/recursive2.c",line="4"@}
29755 Program exited normally:
29763 *stopped,reason="exited-normally"
29768 Program exited exceptionally:
29776 *stopped,reason="exited",exit-code="01"
29780 Another way the program can terminate is if it receives a signal such as
29781 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29785 *stopped,reason="exited-signalled",signal-name="SIGINT",
29786 signal-meaning="Interrupt"
29790 @c @subheading -exec-signal
29793 @subheading The @code{-exec-step} Command
29796 @subsubheading Synopsis
29799 -exec-step [--reverse]
29802 Resumes execution of the inferior program, stopping when the beginning
29803 of the next source line is reached, if the next source line is not a
29804 function call. If it is, stop at the first instruction of the called
29805 function. If the @samp{--reverse} option is specified, resumes reverse
29806 execution of the inferior program, stopping at the beginning of the
29807 previously executed source line.
29809 @subsubheading @value{GDBN} Command
29811 The corresponding @value{GDBN} command is @samp{step}.
29813 @subsubheading Example
29815 Stepping into a function:
29821 *stopped,reason="end-stepping-range",
29822 frame=@{func="foo",args=[@{name="a",value="10"@},
29823 @{name="b",value="0"@}],file="recursive2.c",
29824 fullname="/home/foo/bar/recursive2.c",line="11"@}
29834 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29839 @subheading The @code{-exec-step-instruction} Command
29840 @findex -exec-step-instruction
29842 @subsubheading Synopsis
29845 -exec-step-instruction [--reverse]
29848 Resumes the inferior which executes one machine instruction. If the
29849 @samp{--reverse} option is specified, resumes reverse execution of the
29850 inferior program, stopping at the previously executed instruction.
29851 The output, once @value{GDBN} has stopped, will vary depending on
29852 whether we have stopped in the middle of a source line or not. In the
29853 former case, the address at which the program stopped will be printed
29856 @subsubheading @value{GDBN} Command
29858 The corresponding @value{GDBN} command is @samp{stepi}.
29860 @subsubheading Example
29864 -exec-step-instruction
29868 *stopped,reason="end-stepping-range",
29869 frame=@{func="foo",args=[],file="try.c",
29870 fullname="/home/foo/bar/try.c",line="10"@}
29872 -exec-step-instruction
29876 *stopped,reason="end-stepping-range",
29877 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29878 fullname="/home/foo/bar/try.c",line="10"@}
29883 @subheading The @code{-exec-until} Command
29884 @findex -exec-until
29886 @subsubheading Synopsis
29889 -exec-until [ @var{location} ]
29892 Executes the inferior until the @var{location} specified in the
29893 argument is reached. If there is no argument, the inferior executes
29894 until a source line greater than the current one is reached. The
29895 reason for stopping in this case will be @samp{location-reached}.
29897 @subsubheading @value{GDBN} Command
29899 The corresponding @value{GDBN} command is @samp{until}.
29901 @subsubheading Example
29905 -exec-until recursive2.c:6
29909 *stopped,reason="location-reached",frame=@{func="main",args=[],
29910 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29915 @subheading -file-clear
29916 Is this going away????
29919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29920 @node GDB/MI Stack Manipulation
29921 @section @sc{gdb/mi} Stack Manipulation Commands
29923 @subheading The @code{-enable-frame-filters} Command
29924 @findex -enable-frame-filters
29927 -enable-frame-filters
29930 @value{GDBN} allows Python-based frame filters to affect the output of
29931 the MI commands relating to stack traces. As there is no way to
29932 implement this in a fully backward-compatible way, a front end must
29933 request that this functionality be enabled.
29935 Once enabled, this feature cannot be disabled.
29937 Note that if Python support has not been compiled into @value{GDBN},
29938 this command will still succeed (and do nothing).
29940 @subheading The @code{-stack-info-frame} Command
29941 @findex -stack-info-frame
29943 @subsubheading Synopsis
29949 Get info on the selected frame.
29951 @subsubheading @value{GDBN} Command
29953 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29954 (without arguments).
29956 @subsubheading Example
29961 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29962 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29963 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29967 @subheading The @code{-stack-info-depth} Command
29968 @findex -stack-info-depth
29970 @subsubheading Synopsis
29973 -stack-info-depth [ @var{max-depth} ]
29976 Return the depth of the stack. If the integer argument @var{max-depth}
29977 is specified, do not count beyond @var{max-depth} frames.
29979 @subsubheading @value{GDBN} Command
29981 There's no equivalent @value{GDBN} command.
29983 @subsubheading Example
29985 For a stack with frame levels 0 through 11:
29992 -stack-info-depth 4
29995 -stack-info-depth 12
29998 -stack-info-depth 11
30001 -stack-info-depth 13
30006 @anchor{-stack-list-arguments}
30007 @subheading The @code{-stack-list-arguments} Command
30008 @findex -stack-list-arguments
30010 @subsubheading Synopsis
30013 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30014 [ @var{low-frame} @var{high-frame} ]
30017 Display a list of the arguments for the frames between @var{low-frame}
30018 and @var{high-frame} (inclusive). If @var{low-frame} and
30019 @var{high-frame} are not provided, list the arguments for the whole
30020 call stack. If the two arguments are equal, show the single frame
30021 at the corresponding level. It is an error if @var{low-frame} is
30022 larger than the actual number of frames. On the other hand,
30023 @var{high-frame} may be larger than the actual number of frames, in
30024 which case only existing frames will be returned.
30026 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30027 the variables; if it is 1 or @code{--all-values}, print also their
30028 values; and if it is 2 or @code{--simple-values}, print the name,
30029 type and value for simple data types, and the name and type for arrays,
30030 structures and unions. If the option @code{--no-frame-filters} is
30031 supplied, then Python frame filters will not be executed.
30033 If the @code{--skip-unavailable} option is specified, arguments that
30034 are not available are not listed. Partially available arguments
30035 are still displayed, however.
30037 Use of this command to obtain arguments in a single frame is
30038 deprecated in favor of the @samp{-stack-list-variables} command.
30040 @subsubheading @value{GDBN} Command
30042 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30043 @samp{gdb_get_args} command which partially overlaps with the
30044 functionality of @samp{-stack-list-arguments}.
30046 @subsubheading Example
30053 frame=@{level="0",addr="0x00010734",func="callee4",
30054 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30055 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30056 frame=@{level="1",addr="0x0001076c",func="callee3",
30057 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30058 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30059 frame=@{level="2",addr="0x0001078c",func="callee2",
30060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30061 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30062 frame=@{level="3",addr="0x000107b4",func="callee1",
30063 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30064 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30065 frame=@{level="4",addr="0x000107e0",func="main",
30066 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30067 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30069 -stack-list-arguments 0
30072 frame=@{level="0",args=[]@},
30073 frame=@{level="1",args=[name="strarg"]@},
30074 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30075 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30076 frame=@{level="4",args=[]@}]
30078 -stack-list-arguments 1
30081 frame=@{level="0",args=[]@},
30083 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30084 frame=@{level="2",args=[
30085 @{name="intarg",value="2"@},
30086 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30087 @{frame=@{level="3",args=[
30088 @{name="intarg",value="2"@},
30089 @{name="strarg",value="0x11940 \"A string argument.\""@},
30090 @{name="fltarg",value="3.5"@}]@},
30091 frame=@{level="4",args=[]@}]
30093 -stack-list-arguments 0 2 2
30094 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30096 -stack-list-arguments 1 2 2
30097 ^done,stack-args=[frame=@{level="2",
30098 args=[@{name="intarg",value="2"@},
30099 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30103 @c @subheading -stack-list-exception-handlers
30106 @anchor{-stack-list-frames}
30107 @subheading The @code{-stack-list-frames} Command
30108 @findex -stack-list-frames
30110 @subsubheading Synopsis
30113 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30116 List the frames currently on the stack. For each frame it displays the
30121 The frame number, 0 being the topmost frame, i.e., the innermost function.
30123 The @code{$pc} value for that frame.
30127 File name of the source file where the function lives.
30128 @item @var{fullname}
30129 The full file name of the source file where the function lives.
30131 Line number corresponding to the @code{$pc}.
30133 The shared library where this function is defined. This is only given
30134 if the frame's function is not known.
30137 If invoked without arguments, this command prints a backtrace for the
30138 whole stack. If given two integer arguments, it shows the frames whose
30139 levels are between the two arguments (inclusive). If the two arguments
30140 are equal, it shows the single frame at the corresponding level. It is
30141 an error if @var{low-frame} is larger than the actual number of
30142 frames. On the other hand, @var{high-frame} may be larger than the
30143 actual number of frames, in which case only existing frames will be
30144 returned. If the option @code{--no-frame-filters} is supplied, then
30145 Python frame filters will not be executed.
30147 @subsubheading @value{GDBN} Command
30149 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30151 @subsubheading Example
30153 Full stack backtrace:
30159 [frame=@{level="0",addr="0x0001076c",func="foo",
30160 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30161 frame=@{level="1",addr="0x000107a4",func="foo",
30162 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30163 frame=@{level="2",addr="0x000107a4",func="foo",
30164 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30165 frame=@{level="3",addr="0x000107a4",func="foo",
30166 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30167 frame=@{level="4",addr="0x000107a4",func="foo",
30168 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30169 frame=@{level="5",addr="0x000107a4",func="foo",
30170 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30171 frame=@{level="6",addr="0x000107a4",func="foo",
30172 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30173 frame=@{level="7",addr="0x000107a4",func="foo",
30174 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30175 frame=@{level="8",addr="0x000107a4",func="foo",
30176 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30177 frame=@{level="9",addr="0x000107a4",func="foo",
30178 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30179 frame=@{level="10",addr="0x000107a4",func="foo",
30180 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30181 frame=@{level="11",addr="0x00010738",func="main",
30182 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30186 Show frames between @var{low_frame} and @var{high_frame}:
30190 -stack-list-frames 3 5
30192 [frame=@{level="3",addr="0x000107a4",func="foo",
30193 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30194 frame=@{level="4",addr="0x000107a4",func="foo",
30195 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30196 frame=@{level="5",addr="0x000107a4",func="foo",
30197 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30201 Show a single frame:
30205 -stack-list-frames 3 3
30207 [frame=@{level="3",addr="0x000107a4",func="foo",
30208 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30213 @subheading The @code{-stack-list-locals} Command
30214 @findex -stack-list-locals
30215 @anchor{-stack-list-locals}
30217 @subsubheading Synopsis
30220 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30223 Display the local variable names for the selected frame. If
30224 @var{print-values} is 0 or @code{--no-values}, print only the names of
30225 the variables; if it is 1 or @code{--all-values}, print also their
30226 values; and if it is 2 or @code{--simple-values}, print the name,
30227 type and value for simple data types, and the name and type for arrays,
30228 structures and unions. In this last case, a frontend can immediately
30229 display the value of simple data types and create variable objects for
30230 other data types when the user wishes to explore their values in
30231 more detail. If the option @code{--no-frame-filters} is supplied, then
30232 Python frame filters will not be executed.
30234 If the @code{--skip-unavailable} option is specified, local variables
30235 that are not available are not listed. Partially available local
30236 variables are still displayed, however.
30238 This command is deprecated in favor of the
30239 @samp{-stack-list-variables} command.
30241 @subsubheading @value{GDBN} Command
30243 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30245 @subsubheading Example
30249 -stack-list-locals 0
30250 ^done,locals=[name="A",name="B",name="C"]
30252 -stack-list-locals --all-values
30253 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30254 @{name="C",value="@{1, 2, 3@}"@}]
30255 -stack-list-locals --simple-values
30256 ^done,locals=[@{name="A",type="int",value="1"@},
30257 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30261 @anchor{-stack-list-variables}
30262 @subheading The @code{-stack-list-variables} Command
30263 @findex -stack-list-variables
30265 @subsubheading Synopsis
30268 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30271 Display the names of local variables and function arguments for the selected frame. If
30272 @var{print-values} is 0 or @code{--no-values}, print only the names of
30273 the variables; if it is 1 or @code{--all-values}, print also their
30274 values; and if it is 2 or @code{--simple-values}, print the name,
30275 type and value for simple data types, and the name and type for arrays,
30276 structures and unions. If the option @code{--no-frame-filters} is
30277 supplied, then Python frame filters will not be executed.
30279 If the @code{--skip-unavailable} option is specified, local variables
30280 and arguments that are not available are not listed. Partially
30281 available arguments and local variables are still displayed, however.
30283 @subsubheading Example
30287 -stack-list-variables --thread 1 --frame 0 --all-values
30288 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30293 @subheading The @code{-stack-select-frame} Command
30294 @findex -stack-select-frame
30296 @subsubheading Synopsis
30299 -stack-select-frame @var{framenum}
30302 Change the selected frame. Select a different frame @var{framenum} on
30305 This command in deprecated in favor of passing the @samp{--frame}
30306 option to every command.
30308 @subsubheading @value{GDBN} Command
30310 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30311 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30313 @subsubheading Example
30317 -stack-select-frame 2
30322 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30323 @node GDB/MI Variable Objects
30324 @section @sc{gdb/mi} Variable Objects
30328 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30330 For the implementation of a variable debugger window (locals, watched
30331 expressions, etc.), we are proposing the adaptation of the existing code
30332 used by @code{Insight}.
30334 The two main reasons for that are:
30338 It has been proven in practice (it is already on its second generation).
30341 It will shorten development time (needless to say how important it is
30345 The original interface was designed to be used by Tcl code, so it was
30346 slightly changed so it could be used through @sc{gdb/mi}. This section
30347 describes the @sc{gdb/mi} operations that will be available and gives some
30348 hints about their use.
30350 @emph{Note}: In addition to the set of operations described here, we
30351 expect the @sc{gui} implementation of a variable window to require, at
30352 least, the following operations:
30355 @item @code{-gdb-show} @code{output-radix}
30356 @item @code{-stack-list-arguments}
30357 @item @code{-stack-list-locals}
30358 @item @code{-stack-select-frame}
30363 @subheading Introduction to Variable Objects
30365 @cindex variable objects in @sc{gdb/mi}
30367 Variable objects are "object-oriented" MI interface for examining and
30368 changing values of expressions. Unlike some other MI interfaces that
30369 work with expressions, variable objects are specifically designed for
30370 simple and efficient presentation in the frontend. A variable object
30371 is identified by string name. When a variable object is created, the
30372 frontend specifies the expression for that variable object. The
30373 expression can be a simple variable, or it can be an arbitrary complex
30374 expression, and can even involve CPU registers. After creating a
30375 variable object, the frontend can invoke other variable object
30376 operations---for example to obtain or change the value of a variable
30377 object, or to change display format.
30379 Variable objects have hierarchical tree structure. Any variable object
30380 that corresponds to a composite type, such as structure in C, has
30381 a number of child variable objects, for example corresponding to each
30382 element of a structure. A child variable object can itself have
30383 children, recursively. Recursion ends when we reach
30384 leaf variable objects, which always have built-in types. Child variable
30385 objects are created only by explicit request, so if a frontend
30386 is not interested in the children of a particular variable object, no
30387 child will be created.
30389 For a leaf variable object it is possible to obtain its value as a
30390 string, or set the value from a string. String value can be also
30391 obtained for a non-leaf variable object, but it's generally a string
30392 that only indicates the type of the object, and does not list its
30393 contents. Assignment to a non-leaf variable object is not allowed.
30395 A frontend does not need to read the values of all variable objects each time
30396 the program stops. Instead, MI provides an update command that lists all
30397 variable objects whose values has changed since the last update
30398 operation. This considerably reduces the amount of data that must
30399 be transferred to the frontend. As noted above, children variable
30400 objects are created on demand, and only leaf variable objects have a
30401 real value. As result, gdb will read target memory only for leaf
30402 variables that frontend has created.
30404 The automatic update is not always desirable. For example, a frontend
30405 might want to keep a value of some expression for future reference,
30406 and never update it. For another example, fetching memory is
30407 relatively slow for embedded targets, so a frontend might want
30408 to disable automatic update for the variables that are either not
30409 visible on the screen, or ``closed''. This is possible using so
30410 called ``frozen variable objects''. Such variable objects are never
30411 implicitly updated.
30413 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30414 fixed variable object, the expression is parsed when the variable
30415 object is created, including associating identifiers to specific
30416 variables. The meaning of expression never changes. For a floating
30417 variable object the values of variables whose names appear in the
30418 expressions are re-evaluated every time in the context of the current
30419 frame. Consider this example:
30424 struct work_state state;
30431 If a fixed variable object for the @code{state} variable is created in
30432 this function, and we enter the recursive call, the variable
30433 object will report the value of @code{state} in the top-level
30434 @code{do_work} invocation. On the other hand, a floating variable
30435 object will report the value of @code{state} in the current frame.
30437 If an expression specified when creating a fixed variable object
30438 refers to a local variable, the variable object becomes bound to the
30439 thread and frame in which the variable object is created. When such
30440 variable object is updated, @value{GDBN} makes sure that the
30441 thread/frame combination the variable object is bound to still exists,
30442 and re-evaluates the variable object in context of that thread/frame.
30444 The following is the complete set of @sc{gdb/mi} operations defined to
30445 access this functionality:
30447 @multitable @columnfractions .4 .6
30448 @item @strong{Operation}
30449 @tab @strong{Description}
30451 @item @code{-enable-pretty-printing}
30452 @tab enable Python-based pretty-printing
30453 @item @code{-var-create}
30454 @tab create a variable object
30455 @item @code{-var-delete}
30456 @tab delete the variable object and/or its children
30457 @item @code{-var-set-format}
30458 @tab set the display format of this variable
30459 @item @code{-var-show-format}
30460 @tab show the display format of this variable
30461 @item @code{-var-info-num-children}
30462 @tab tells how many children this object has
30463 @item @code{-var-list-children}
30464 @tab return a list of the object's children
30465 @item @code{-var-info-type}
30466 @tab show the type of this variable object
30467 @item @code{-var-info-expression}
30468 @tab print parent-relative expression that this variable object represents
30469 @item @code{-var-info-path-expression}
30470 @tab print full expression that this variable object represents
30471 @item @code{-var-show-attributes}
30472 @tab is this variable editable? does it exist here?
30473 @item @code{-var-evaluate-expression}
30474 @tab get the value of this variable
30475 @item @code{-var-assign}
30476 @tab set the value of this variable
30477 @item @code{-var-update}
30478 @tab update the variable and its children
30479 @item @code{-var-set-frozen}
30480 @tab set frozeness attribute
30481 @item @code{-var-set-update-range}
30482 @tab set range of children to display on update
30485 In the next subsection we describe each operation in detail and suggest
30486 how it can be used.
30488 @subheading Description And Use of Operations on Variable Objects
30490 @subheading The @code{-enable-pretty-printing} Command
30491 @findex -enable-pretty-printing
30494 -enable-pretty-printing
30497 @value{GDBN} allows Python-based visualizers to affect the output of the
30498 MI variable object commands. However, because there was no way to
30499 implement this in a fully backward-compatible way, a front end must
30500 request that this functionality be enabled.
30502 Once enabled, this feature cannot be disabled.
30504 Note that if Python support has not been compiled into @value{GDBN},
30505 this command will still succeed (and do nothing).
30507 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30508 may work differently in future versions of @value{GDBN}.
30510 @subheading The @code{-var-create} Command
30511 @findex -var-create
30513 @subsubheading Synopsis
30516 -var-create @{@var{name} | "-"@}
30517 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30520 This operation creates a variable object, which allows the monitoring of
30521 a variable, the result of an expression, a memory cell or a CPU
30524 The @var{name} parameter is the string by which the object can be
30525 referenced. It must be unique. If @samp{-} is specified, the varobj
30526 system will generate a string ``varNNNNNN'' automatically. It will be
30527 unique provided that one does not specify @var{name} of that format.
30528 The command fails if a duplicate name is found.
30530 The frame under which the expression should be evaluated can be
30531 specified by @var{frame-addr}. A @samp{*} indicates that the current
30532 frame should be used. A @samp{@@} indicates that a floating variable
30533 object must be created.
30535 @var{expression} is any expression valid on the current language set (must not
30536 begin with a @samp{*}), or one of the following:
30540 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30543 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30546 @samp{$@var{regname}} --- a CPU register name
30549 @cindex dynamic varobj
30550 A varobj's contents may be provided by a Python-based pretty-printer. In this
30551 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30552 have slightly different semantics in some cases. If the
30553 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30554 will never create a dynamic varobj. This ensures backward
30555 compatibility for existing clients.
30557 @subsubheading Result
30559 This operation returns attributes of the newly-created varobj. These
30564 The name of the varobj.
30567 The number of children of the varobj. This number is not necessarily
30568 reliable for a dynamic varobj. Instead, you must examine the
30569 @samp{has_more} attribute.
30572 The varobj's scalar value. For a varobj whose type is some sort of
30573 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30574 will not be interesting.
30577 The varobj's type. This is a string representation of the type, as
30578 would be printed by the @value{GDBN} CLI. If @samp{print object}
30579 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30580 @emph{actual} (derived) type of the object is shown rather than the
30581 @emph{declared} one.
30584 If a variable object is bound to a specific thread, then this is the
30585 thread's global identifier.
30588 For a dynamic varobj, this indicates whether there appear to be any
30589 children available. For a non-dynamic varobj, this will be 0.
30592 This attribute will be present and have the value @samp{1} if the
30593 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30594 then this attribute will not be present.
30597 A dynamic varobj can supply a display hint to the front end. The
30598 value comes directly from the Python pretty-printer object's
30599 @code{display_hint} method. @xref{Pretty Printing API}.
30602 Typical output will look like this:
30605 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30606 has_more="@var{has_more}"
30610 @subheading The @code{-var-delete} Command
30611 @findex -var-delete
30613 @subsubheading Synopsis
30616 -var-delete [ -c ] @var{name}
30619 Deletes a previously created variable object and all of its children.
30620 With the @samp{-c} option, just deletes the children.
30622 Returns an error if the object @var{name} is not found.
30625 @subheading The @code{-var-set-format} Command
30626 @findex -var-set-format
30628 @subsubheading Synopsis
30631 -var-set-format @var{name} @var{format-spec}
30634 Sets the output format for the value of the object @var{name} to be
30637 @anchor{-var-set-format}
30638 The syntax for the @var{format-spec} is as follows:
30641 @var{format-spec} @expansion{}
30642 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30645 The natural format is the default format choosen automatically
30646 based on the variable type (like decimal for an @code{int}, hex
30647 for pointers, etc.).
30649 The zero-hexadecimal format has a representation similar to hexadecimal
30650 but with padding zeroes to the left of the value. For example, a 32-bit
30651 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30652 zero-hexadecimal format.
30654 For a variable with children, the format is set only on the
30655 variable itself, and the children are not affected.
30657 @subheading The @code{-var-show-format} Command
30658 @findex -var-show-format
30660 @subsubheading Synopsis
30663 -var-show-format @var{name}
30666 Returns the format used to display the value of the object @var{name}.
30669 @var{format} @expansion{}
30674 @subheading The @code{-var-info-num-children} Command
30675 @findex -var-info-num-children
30677 @subsubheading Synopsis
30680 -var-info-num-children @var{name}
30683 Returns the number of children of a variable object @var{name}:
30689 Note that this number is not completely reliable for a dynamic varobj.
30690 It will return the current number of children, but more children may
30694 @subheading The @code{-var-list-children} Command
30695 @findex -var-list-children
30697 @subsubheading Synopsis
30700 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30702 @anchor{-var-list-children}
30704 Return a list of the children of the specified variable object and
30705 create variable objects for them, if they do not already exist. With
30706 a single argument or if @var{print-values} has a value of 0 or
30707 @code{--no-values}, print only the names of the variables; if
30708 @var{print-values} is 1 or @code{--all-values}, also print their
30709 values; and if it is 2 or @code{--simple-values} print the name and
30710 value for simple data types and just the name for arrays, structures
30713 @var{from} and @var{to}, if specified, indicate the range of children
30714 to report. If @var{from} or @var{to} is less than zero, the range is
30715 reset and all children will be reported. Otherwise, children starting
30716 at @var{from} (zero-based) and up to and excluding @var{to} will be
30719 If a child range is requested, it will only affect the current call to
30720 @code{-var-list-children}, but not future calls to @code{-var-update}.
30721 For this, you must instead use @code{-var-set-update-range}. The
30722 intent of this approach is to enable a front end to implement any
30723 update approach it likes; for example, scrolling a view may cause the
30724 front end to request more children with @code{-var-list-children}, and
30725 then the front end could call @code{-var-set-update-range} with a
30726 different range to ensure that future updates are restricted to just
30729 For each child the following results are returned:
30734 Name of the variable object created for this child.
30737 The expression to be shown to the user by the front end to designate this child.
30738 For example this may be the name of a structure member.
30740 For a dynamic varobj, this value cannot be used to form an
30741 expression. There is no way to do this at all with a dynamic varobj.
30743 For C/C@t{++} structures there are several pseudo children returned to
30744 designate access qualifiers. For these pseudo children @var{exp} is
30745 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30746 type and value are not present.
30748 A dynamic varobj will not report the access qualifying
30749 pseudo-children, regardless of the language. This information is not
30750 available at all with a dynamic varobj.
30753 Number of children this child has. For a dynamic varobj, this will be
30757 The type of the child. If @samp{print object}
30758 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30759 @emph{actual} (derived) type of the object is shown rather than the
30760 @emph{declared} one.
30763 If values were requested, this is the value.
30766 If this variable object is associated with a thread, this is the
30767 thread's global thread id. Otherwise this result is not present.
30770 If the variable object is frozen, this variable will be present with a value of 1.
30773 A dynamic varobj can supply a display hint to the front end. The
30774 value comes directly from the Python pretty-printer object's
30775 @code{display_hint} method. @xref{Pretty Printing API}.
30778 This attribute will be present and have the value @samp{1} if the
30779 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30780 then this attribute will not be present.
30784 The result may have its own attributes:
30788 A dynamic varobj can supply a display hint to the front end. The
30789 value comes directly from the Python pretty-printer object's
30790 @code{display_hint} method. @xref{Pretty Printing API}.
30793 This is an integer attribute which is nonzero if there are children
30794 remaining after the end of the selected range.
30797 @subsubheading Example
30801 -var-list-children n
30802 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30803 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30805 -var-list-children --all-values n
30806 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30807 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30811 @subheading The @code{-var-info-type} Command
30812 @findex -var-info-type
30814 @subsubheading Synopsis
30817 -var-info-type @var{name}
30820 Returns the type of the specified variable @var{name}. The type is
30821 returned as a string in the same format as it is output by the
30825 type=@var{typename}
30829 @subheading The @code{-var-info-expression} Command
30830 @findex -var-info-expression
30832 @subsubheading Synopsis
30835 -var-info-expression @var{name}
30838 Returns a string that is suitable for presenting this
30839 variable object in user interface. The string is generally
30840 not valid expression in the current language, and cannot be evaluated.
30842 For example, if @code{a} is an array, and variable object
30843 @code{A} was created for @code{a}, then we'll get this output:
30846 (gdb) -var-info-expression A.1
30847 ^done,lang="C",exp="1"
30851 Here, the value of @code{lang} is the language name, which can be
30852 found in @ref{Supported Languages}.
30854 Note that the output of the @code{-var-list-children} command also
30855 includes those expressions, so the @code{-var-info-expression} command
30858 @subheading The @code{-var-info-path-expression} Command
30859 @findex -var-info-path-expression
30861 @subsubheading Synopsis
30864 -var-info-path-expression @var{name}
30867 Returns an expression that can be evaluated in the current
30868 context and will yield the same value that a variable object has.
30869 Compare this with the @code{-var-info-expression} command, which
30870 result can be used only for UI presentation. Typical use of
30871 the @code{-var-info-path-expression} command is creating a
30872 watchpoint from a variable object.
30874 This command is currently not valid for children of a dynamic varobj,
30875 and will give an error when invoked on one.
30877 For example, suppose @code{C} is a C@t{++} class, derived from class
30878 @code{Base}, and that the @code{Base} class has a member called
30879 @code{m_size}. Assume a variable @code{c} is has the type of
30880 @code{C} and a variable object @code{C} was created for variable
30881 @code{c}. Then, we'll get this output:
30883 (gdb) -var-info-path-expression C.Base.public.m_size
30884 ^done,path_expr=((Base)c).m_size)
30887 @subheading The @code{-var-show-attributes} Command
30888 @findex -var-show-attributes
30890 @subsubheading Synopsis
30893 -var-show-attributes @var{name}
30896 List attributes of the specified variable object @var{name}:
30899 status=@var{attr} [ ( ,@var{attr} )* ]
30903 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30905 @subheading The @code{-var-evaluate-expression} Command
30906 @findex -var-evaluate-expression
30908 @subsubheading Synopsis
30911 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30914 Evaluates the expression that is represented by the specified variable
30915 object and returns its value as a string. The format of the string
30916 can be specified with the @samp{-f} option. The possible values of
30917 this option are the same as for @code{-var-set-format}
30918 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30919 the current display format will be used. The current display format
30920 can be changed using the @code{-var-set-format} command.
30926 Note that one must invoke @code{-var-list-children} for a variable
30927 before the value of a child variable can be evaluated.
30929 @subheading The @code{-var-assign} Command
30930 @findex -var-assign
30932 @subsubheading Synopsis
30935 -var-assign @var{name} @var{expression}
30938 Assigns the value of @var{expression} to the variable object specified
30939 by @var{name}. The object must be @samp{editable}. If the variable's
30940 value is altered by the assign, the variable will show up in any
30941 subsequent @code{-var-update} list.
30943 @subsubheading Example
30951 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30955 @subheading The @code{-var-update} Command
30956 @findex -var-update
30958 @subsubheading Synopsis
30961 -var-update [@var{print-values}] @{@var{name} | "*"@}
30964 Reevaluate the expressions corresponding to the variable object
30965 @var{name} and all its direct and indirect children, and return the
30966 list of variable objects whose values have changed; @var{name} must
30967 be a root variable object. Here, ``changed'' means that the result of
30968 @code{-var-evaluate-expression} before and after the
30969 @code{-var-update} is different. If @samp{*} is used as the variable
30970 object names, all existing variable objects are updated, except
30971 for frozen ones (@pxref{-var-set-frozen}). The option
30972 @var{print-values} determines whether both names and values, or just
30973 names are printed. The possible values of this option are the same
30974 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30975 recommended to use the @samp{--all-values} option, to reduce the
30976 number of MI commands needed on each program stop.
30978 With the @samp{*} parameter, if a variable object is bound to a
30979 currently running thread, it will not be updated, without any
30982 If @code{-var-set-update-range} was previously used on a varobj, then
30983 only the selected range of children will be reported.
30985 @code{-var-update} reports all the changed varobjs in a tuple named
30988 Each item in the change list is itself a tuple holding:
30992 The name of the varobj.
30995 If values were requested for this update, then this field will be
30996 present and will hold the value of the varobj.
30999 @anchor{-var-update}
31000 This field is a string which may take one of three values:
31004 The variable object's current value is valid.
31007 The variable object does not currently hold a valid value but it may
31008 hold one in the future if its associated expression comes back into
31012 The variable object no longer holds a valid value.
31013 This can occur when the executable file being debugged has changed,
31014 either through recompilation or by using the @value{GDBN} @code{file}
31015 command. The front end should normally choose to delete these variable
31019 In the future new values may be added to this list so the front should
31020 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31023 This is only present if the varobj is still valid. If the type
31024 changed, then this will be the string @samp{true}; otherwise it will
31027 When a varobj's type changes, its children are also likely to have
31028 become incorrect. Therefore, the varobj's children are automatically
31029 deleted when this attribute is @samp{true}. Also, the varobj's update
31030 range, when set using the @code{-var-set-update-range} command, is
31034 If the varobj's type changed, then this field will be present and will
31037 @item new_num_children
31038 For a dynamic varobj, if the number of children changed, or if the
31039 type changed, this will be the new number of children.
31041 The @samp{numchild} field in other varobj responses is generally not
31042 valid for a dynamic varobj -- it will show the number of children that
31043 @value{GDBN} knows about, but because dynamic varobjs lazily
31044 instantiate their children, this will not reflect the number of
31045 children which may be available.
31047 The @samp{new_num_children} attribute only reports changes to the
31048 number of children known by @value{GDBN}. This is the only way to
31049 detect whether an update has removed children (which necessarily can
31050 only happen at the end of the update range).
31053 The display hint, if any.
31056 This is an integer value, which will be 1 if there are more children
31057 available outside the varobj's update range.
31060 This attribute will be present and have the value @samp{1} if the
31061 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31062 then this attribute will not be present.
31065 If new children were added to a dynamic varobj within the selected
31066 update range (as set by @code{-var-set-update-range}), then they will
31067 be listed in this attribute.
31070 @subsubheading Example
31077 -var-update --all-values var1
31078 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31079 type_changed="false"@}]
31083 @subheading The @code{-var-set-frozen} Command
31084 @findex -var-set-frozen
31085 @anchor{-var-set-frozen}
31087 @subsubheading Synopsis
31090 -var-set-frozen @var{name} @var{flag}
31093 Set the frozenness flag on the variable object @var{name}. The
31094 @var{flag} parameter should be either @samp{1} to make the variable
31095 frozen or @samp{0} to make it unfrozen. If a variable object is
31096 frozen, then neither itself, nor any of its children, are
31097 implicitly updated by @code{-var-update} of
31098 a parent variable or by @code{-var-update *}. Only
31099 @code{-var-update} of the variable itself will update its value and
31100 values of its children. After a variable object is unfrozen, it is
31101 implicitly updated by all subsequent @code{-var-update} operations.
31102 Unfreezing a variable does not update it, only subsequent
31103 @code{-var-update} does.
31105 @subsubheading Example
31109 -var-set-frozen V 1
31114 @subheading The @code{-var-set-update-range} command
31115 @findex -var-set-update-range
31116 @anchor{-var-set-update-range}
31118 @subsubheading Synopsis
31121 -var-set-update-range @var{name} @var{from} @var{to}
31124 Set the range of children to be returned by future invocations of
31125 @code{-var-update}.
31127 @var{from} and @var{to} indicate the range of children to report. If
31128 @var{from} or @var{to} is less than zero, the range is reset and all
31129 children will be reported. Otherwise, children starting at @var{from}
31130 (zero-based) and up to and excluding @var{to} will be reported.
31132 @subsubheading Example
31136 -var-set-update-range V 1 2
31140 @subheading The @code{-var-set-visualizer} command
31141 @findex -var-set-visualizer
31142 @anchor{-var-set-visualizer}
31144 @subsubheading Synopsis
31147 -var-set-visualizer @var{name} @var{visualizer}
31150 Set a visualizer for the variable object @var{name}.
31152 @var{visualizer} is the visualizer to use. The special value
31153 @samp{None} means to disable any visualizer in use.
31155 If not @samp{None}, @var{visualizer} must be a Python expression.
31156 This expression must evaluate to a callable object which accepts a
31157 single argument. @value{GDBN} will call this object with the value of
31158 the varobj @var{name} as an argument (this is done so that the same
31159 Python pretty-printing code can be used for both the CLI and MI).
31160 When called, this object must return an object which conforms to the
31161 pretty-printing interface (@pxref{Pretty Printing API}).
31163 The pre-defined function @code{gdb.default_visualizer} may be used to
31164 select a visualizer by following the built-in process
31165 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31166 a varobj is created, and so ordinarily is not needed.
31168 This feature is only available if Python support is enabled. The MI
31169 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31170 can be used to check this.
31172 @subsubheading Example
31174 Resetting the visualizer:
31178 -var-set-visualizer V None
31182 Reselecting the default (type-based) visualizer:
31186 -var-set-visualizer V gdb.default_visualizer
31190 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31191 can be used to instantiate this class for a varobj:
31195 -var-set-visualizer V "lambda val: SomeClass()"
31199 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31200 @node GDB/MI Data Manipulation
31201 @section @sc{gdb/mi} Data Manipulation
31203 @cindex data manipulation, in @sc{gdb/mi}
31204 @cindex @sc{gdb/mi}, data manipulation
31205 This section describes the @sc{gdb/mi} commands that manipulate data:
31206 examine memory and registers, evaluate expressions, etc.
31208 For details about what an addressable memory unit is,
31209 @pxref{addressable memory unit}.
31211 @c REMOVED FROM THE INTERFACE.
31212 @c @subheading -data-assign
31213 @c Change the value of a program variable. Plenty of side effects.
31214 @c @subsubheading GDB Command
31216 @c @subsubheading Example
31219 @subheading The @code{-data-disassemble} Command
31220 @findex -data-disassemble
31222 @subsubheading Synopsis
31226 [ -s @var{start-addr} -e @var{end-addr} ]
31227 | [ -a @var{addr} ]
31228 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31236 @item @var{start-addr}
31237 is the beginning address (or @code{$pc})
31238 @item @var{end-addr}
31241 is an address anywhere within (or the name of) the function to
31242 disassemble. If an address is specified, the whole function
31243 surrounding that address will be disassembled. If a name is
31244 specified, the whole function with that name will be disassembled.
31245 @item @var{filename}
31246 is the name of the file to disassemble
31247 @item @var{linenum}
31248 is the line number to disassemble around
31250 is the number of disassembly lines to be produced. If it is -1,
31251 the whole function will be disassembled, in case no @var{end-addr} is
31252 specified. If @var{end-addr} is specified as a non-zero value, and
31253 @var{lines} is lower than the number of disassembly lines between
31254 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31255 displayed; if @var{lines} is higher than the number of lines between
31256 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31261 @item 0 disassembly only
31262 @item 1 mixed source and disassembly (deprecated)
31263 @item 2 disassembly with raw opcodes
31264 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31265 @item 4 mixed source and disassembly
31266 @item 5 mixed source and disassembly with raw opcodes
31269 Modes 1 and 3 are deprecated. The output is ``source centric''
31270 which hasn't proved useful in practice.
31271 @xref{Machine Code}, for a discussion of the difference between
31272 @code{/m} and @code{/s} output of the @code{disassemble} command.
31275 @subsubheading Result
31277 The result of the @code{-data-disassemble} command will be a list named
31278 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31279 used with the @code{-data-disassemble} command.
31281 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31286 The address at which this instruction was disassembled.
31289 The name of the function this instruction is within.
31292 The decimal offset in bytes from the start of @samp{func-name}.
31295 The text disassembly for this @samp{address}.
31298 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31299 bytes for the @samp{inst} field.
31303 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31304 @samp{src_and_asm_line}, each of which has the following fields:
31308 The line number within @samp{file}.
31311 The file name from the compilation unit. This might be an absolute
31312 file name or a relative file name depending on the compile command
31316 Absolute file name of @samp{file}. It is converted to a canonical form
31317 using the source file search path
31318 (@pxref{Source Path, ,Specifying Source Directories})
31319 and after resolving all the symbolic links.
31321 If the source file is not found this field will contain the path as
31322 present in the debug information.
31324 @item line_asm_insn
31325 This is a list of tuples containing the disassembly for @samp{line} in
31326 @samp{file}. The fields of each tuple are the same as for
31327 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31328 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31333 Note that whatever included in the @samp{inst} field, is not
31334 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31337 @subsubheading @value{GDBN} Command
31339 The corresponding @value{GDBN} command is @samp{disassemble}.
31341 @subsubheading Example
31343 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31347 -data-disassemble -s $pc -e "$pc + 20" -- 0
31350 @{address="0x000107c0",func-name="main",offset="4",
31351 inst="mov 2, %o0"@},
31352 @{address="0x000107c4",func-name="main",offset="8",
31353 inst="sethi %hi(0x11800), %o2"@},
31354 @{address="0x000107c8",func-name="main",offset="12",
31355 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31356 @{address="0x000107cc",func-name="main",offset="16",
31357 inst="sethi %hi(0x11800), %o2"@},
31358 @{address="0x000107d0",func-name="main",offset="20",
31359 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31363 Disassemble the whole @code{main} function. Line 32 is part of
31367 -data-disassemble -f basics.c -l 32 -- 0
31369 @{address="0x000107bc",func-name="main",offset="0",
31370 inst="save %sp, -112, %sp"@},
31371 @{address="0x000107c0",func-name="main",offset="4",
31372 inst="mov 2, %o0"@},
31373 @{address="0x000107c4",func-name="main",offset="8",
31374 inst="sethi %hi(0x11800), %o2"@},
31376 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31377 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31381 Disassemble 3 instructions from the start of @code{main}:
31385 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31387 @{address="0x000107bc",func-name="main",offset="0",
31388 inst="save %sp, -112, %sp"@},
31389 @{address="0x000107c0",func-name="main",offset="4",
31390 inst="mov 2, %o0"@},
31391 @{address="0x000107c4",func-name="main",offset="8",
31392 inst="sethi %hi(0x11800), %o2"@}]
31396 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31400 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31402 src_and_asm_line=@{line="31",
31403 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31404 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31405 line_asm_insn=[@{address="0x000107bc",
31406 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31407 src_and_asm_line=@{line="32",
31408 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31409 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31410 line_asm_insn=[@{address="0x000107c0",
31411 func-name="main",offset="4",inst="mov 2, %o0"@},
31412 @{address="0x000107c4",func-name="main",offset="8",
31413 inst="sethi %hi(0x11800), %o2"@}]@}]
31418 @subheading The @code{-data-evaluate-expression} Command
31419 @findex -data-evaluate-expression
31421 @subsubheading Synopsis
31424 -data-evaluate-expression @var{expr}
31427 Evaluate @var{expr} as an expression. The expression could contain an
31428 inferior function call. The function call will execute synchronously.
31429 If the expression contains spaces, it must be enclosed in double quotes.
31431 @subsubheading @value{GDBN} Command
31433 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31434 @samp{call}. In @code{gdbtk} only, there's a corresponding
31435 @samp{gdb_eval} command.
31437 @subsubheading Example
31439 In the following example, the numbers that precede the commands are the
31440 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31441 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31445 211-data-evaluate-expression A
31448 311-data-evaluate-expression &A
31449 311^done,value="0xefffeb7c"
31451 411-data-evaluate-expression A+3
31454 511-data-evaluate-expression "A + 3"
31460 @subheading The @code{-data-list-changed-registers} Command
31461 @findex -data-list-changed-registers
31463 @subsubheading Synopsis
31466 -data-list-changed-registers
31469 Display a list of the registers that have changed.
31471 @subsubheading @value{GDBN} Command
31473 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31474 has the corresponding command @samp{gdb_changed_register_list}.
31476 @subsubheading Example
31478 On a PPC MBX board:
31486 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31487 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31490 -data-list-changed-registers
31491 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31492 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31493 "24","25","26","27","28","30","31","64","65","66","67","69"]
31498 @subheading The @code{-data-list-register-names} Command
31499 @findex -data-list-register-names
31501 @subsubheading Synopsis
31504 -data-list-register-names [ ( @var{regno} )+ ]
31507 Show a list of register names for the current target. If no arguments
31508 are given, it shows a list of the names of all the registers. If
31509 integer numbers are given as arguments, it will print a list of the
31510 names of the registers corresponding to the arguments. To ensure
31511 consistency between a register name and its number, the output list may
31512 include empty register names.
31514 @subsubheading @value{GDBN} Command
31516 @value{GDBN} does not have a command which corresponds to
31517 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31518 corresponding command @samp{gdb_regnames}.
31520 @subsubheading Example
31522 For the PPC MBX board:
31525 -data-list-register-names
31526 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31527 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31528 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31529 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31530 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31531 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31532 "", "pc","ps","cr","lr","ctr","xer"]
31534 -data-list-register-names 1 2 3
31535 ^done,register-names=["r1","r2","r3"]
31539 @subheading The @code{-data-list-register-values} Command
31540 @findex -data-list-register-values
31542 @subsubheading Synopsis
31545 -data-list-register-values
31546 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31549 Display the registers' contents. The format according to which the
31550 registers' contents are to be returned is given by @var{fmt}, followed
31551 by an optional list of numbers specifying the registers to display. A
31552 missing list of numbers indicates that the contents of all the
31553 registers must be returned. The @code{--skip-unavailable} option
31554 indicates that only the available registers are to be returned.
31556 Allowed formats for @var{fmt} are:
31573 @subsubheading @value{GDBN} Command
31575 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31576 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31578 @subsubheading Example
31580 For a PPC MBX board (note: line breaks are for readability only, they
31581 don't appear in the actual output):
31585 -data-list-register-values r 64 65
31586 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31587 @{number="65",value="0x00029002"@}]
31589 -data-list-register-values x
31590 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31591 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31592 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31593 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31594 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31595 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31596 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31597 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31598 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31599 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31600 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31601 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31602 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31603 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31604 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31605 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31606 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31607 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31608 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31609 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31610 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31611 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31612 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31613 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31614 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31615 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31616 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31617 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31618 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31619 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31620 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31621 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31622 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31623 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31624 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31625 @{number="69",value="0x20002b03"@}]
31630 @subheading The @code{-data-read-memory} Command
31631 @findex -data-read-memory
31633 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31635 @subsubheading Synopsis
31638 -data-read-memory [ -o @var{byte-offset} ]
31639 @var{address} @var{word-format} @var{word-size}
31640 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31647 @item @var{address}
31648 An expression specifying the address of the first memory word to be
31649 read. Complex expressions containing embedded white space should be
31650 quoted using the C convention.
31652 @item @var{word-format}
31653 The format to be used to print the memory words. The notation is the
31654 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31657 @item @var{word-size}
31658 The size of each memory word in bytes.
31660 @item @var{nr-rows}
31661 The number of rows in the output table.
31663 @item @var{nr-cols}
31664 The number of columns in the output table.
31667 If present, indicates that each row should include an @sc{ascii} dump. The
31668 value of @var{aschar} is used as a padding character when a byte is not a
31669 member of the printable @sc{ascii} character set (printable @sc{ascii}
31670 characters are those whose code is between 32 and 126, inclusively).
31672 @item @var{byte-offset}
31673 An offset to add to the @var{address} before fetching memory.
31676 This command displays memory contents as a table of @var{nr-rows} by
31677 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31678 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31679 (returned as @samp{total-bytes}). Should less than the requested number
31680 of bytes be returned by the target, the missing words are identified
31681 using @samp{N/A}. The number of bytes read from the target is returned
31682 in @samp{nr-bytes} and the starting address used to read memory in
31685 The address of the next/previous row or page is available in
31686 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31689 @subsubheading @value{GDBN} Command
31691 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31692 @samp{gdb_get_mem} memory read command.
31694 @subsubheading Example
31696 Read six bytes of memory starting at @code{bytes+6} but then offset by
31697 @code{-6} bytes. Format as three rows of two columns. One byte per
31698 word. Display each word in hex.
31702 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31703 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31704 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31705 prev-page="0x0000138a",memory=[
31706 @{addr="0x00001390",data=["0x00","0x01"]@},
31707 @{addr="0x00001392",data=["0x02","0x03"]@},
31708 @{addr="0x00001394",data=["0x04","0x05"]@}]
31712 Read two bytes of memory starting at address @code{shorts + 64} and
31713 display as a single word formatted in decimal.
31717 5-data-read-memory shorts+64 d 2 1 1
31718 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31719 next-row="0x00001512",prev-row="0x0000150e",
31720 next-page="0x00001512",prev-page="0x0000150e",memory=[
31721 @{addr="0x00001510",data=["128"]@}]
31725 Read thirty two bytes of memory starting at @code{bytes+16} and format
31726 as eight rows of four columns. Include a string encoding with @samp{x}
31727 used as the non-printable character.
31731 4-data-read-memory bytes+16 x 1 8 4 x
31732 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31733 next-row="0x000013c0",prev-row="0x0000139c",
31734 next-page="0x000013c0",prev-page="0x00001380",memory=[
31735 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31736 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31737 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31738 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31739 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31740 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31741 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31742 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31746 @subheading The @code{-data-read-memory-bytes} Command
31747 @findex -data-read-memory-bytes
31749 @subsubheading Synopsis
31752 -data-read-memory-bytes [ -o @var{offset} ]
31753 @var{address} @var{count}
31760 @item @var{address}
31761 An expression specifying the address of the first addressable memory unit
31762 to be read. Complex expressions containing embedded white space should be
31763 quoted using the C convention.
31766 The number of addressable memory units to read. This should be an integer
31770 The offset relative to @var{address} at which to start reading. This
31771 should be an integer literal. This option is provided so that a frontend
31772 is not required to first evaluate address and then perform address
31773 arithmetics itself.
31777 This command attempts to read all accessible memory regions in the
31778 specified range. First, all regions marked as unreadable in the memory
31779 map (if one is defined) will be skipped. @xref{Memory Region
31780 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31781 regions. For each one, if reading full region results in an errors,
31782 @value{GDBN} will try to read a subset of the region.
31784 In general, every single memory unit in the region may be readable or not,
31785 and the only way to read every readable unit is to try a read at
31786 every address, which is not practical. Therefore, @value{GDBN} will
31787 attempt to read all accessible memory units at either beginning or the end
31788 of the region, using a binary division scheme. This heuristic works
31789 well for reading accross a memory map boundary. Note that if a region
31790 has a readable range that is neither at the beginning or the end,
31791 @value{GDBN} will not read it.
31793 The result record (@pxref{GDB/MI Result Records}) that is output of
31794 the command includes a field named @samp{memory} whose content is a
31795 list of tuples. Each tuple represent a successfully read memory block
31796 and has the following fields:
31800 The start address of the memory block, as hexadecimal literal.
31803 The end address of the memory block, as hexadecimal literal.
31806 The offset of the memory block, as hexadecimal literal, relative to
31807 the start address passed to @code{-data-read-memory-bytes}.
31810 The contents of the memory block, in hex.
31816 @subsubheading @value{GDBN} Command
31818 The corresponding @value{GDBN} command is @samp{x}.
31820 @subsubheading Example
31824 -data-read-memory-bytes &a 10
31825 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31827 contents="01000000020000000300"@}]
31832 @subheading The @code{-data-write-memory-bytes} Command
31833 @findex -data-write-memory-bytes
31835 @subsubheading Synopsis
31838 -data-write-memory-bytes @var{address} @var{contents}
31839 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31846 @item @var{address}
31847 An expression specifying the address of the first addressable memory unit
31848 to be written. Complex expressions containing embedded white space should
31849 be quoted using the C convention.
31851 @item @var{contents}
31852 The hex-encoded data to write. It is an error if @var{contents} does
31853 not represent an integral number of addressable memory units.
31856 Optional argument indicating the number of addressable memory units to be
31857 written. If @var{count} is greater than @var{contents}' length,
31858 @value{GDBN} will repeatedly write @var{contents} until it fills
31859 @var{count} memory units.
31863 @subsubheading @value{GDBN} Command
31865 There's no corresponding @value{GDBN} command.
31867 @subsubheading Example
31871 -data-write-memory-bytes &a "aabbccdd"
31878 -data-write-memory-bytes &a "aabbccdd" 16e
31883 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31884 @node GDB/MI Tracepoint Commands
31885 @section @sc{gdb/mi} Tracepoint Commands
31887 The commands defined in this section implement MI support for
31888 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31890 @subheading The @code{-trace-find} Command
31891 @findex -trace-find
31893 @subsubheading Synopsis
31896 -trace-find @var{mode} [@var{parameters}@dots{}]
31899 Find a trace frame using criteria defined by @var{mode} and
31900 @var{parameters}. The following table lists permissible
31901 modes and their parameters. For details of operation, see @ref{tfind}.
31906 No parameters are required. Stops examining trace frames.
31909 An integer is required as parameter. Selects tracepoint frame with
31912 @item tracepoint-number
31913 An integer is required as parameter. Finds next
31914 trace frame that corresponds to tracepoint with the specified number.
31917 An address is required as parameter. Finds
31918 next trace frame that corresponds to any tracepoint at the specified
31921 @item pc-inside-range
31922 Two addresses are required as parameters. Finds next trace
31923 frame that corresponds to a tracepoint at an address inside the
31924 specified range. Both bounds are considered to be inside the range.
31926 @item pc-outside-range
31927 Two addresses are required as parameters. Finds
31928 next trace frame that corresponds to a tracepoint at an address outside
31929 the specified range. Both bounds are considered to be inside the range.
31932 Line specification is required as parameter. @xref{Specify Location}.
31933 Finds next trace frame that corresponds to a tracepoint at
31934 the specified location.
31938 If @samp{none} was passed as @var{mode}, the response does not
31939 have fields. Otherwise, the response may have the following fields:
31943 This field has either @samp{0} or @samp{1} as the value, depending
31944 on whether a matching tracepoint was found.
31947 The index of the found traceframe. This field is present iff
31948 the @samp{found} field has value of @samp{1}.
31951 The index of the found tracepoint. This field is present iff
31952 the @samp{found} field has value of @samp{1}.
31955 The information about the frame corresponding to the found trace
31956 frame. This field is present only if a trace frame was found.
31957 @xref{GDB/MI Frame Information}, for description of this field.
31961 @subsubheading @value{GDBN} Command
31963 The corresponding @value{GDBN} command is @samp{tfind}.
31965 @subheading -trace-define-variable
31966 @findex -trace-define-variable
31968 @subsubheading Synopsis
31971 -trace-define-variable @var{name} [ @var{value} ]
31974 Create trace variable @var{name} if it does not exist. If
31975 @var{value} is specified, sets the initial value of the specified
31976 trace variable to that value. Note that the @var{name} should start
31977 with the @samp{$} character.
31979 @subsubheading @value{GDBN} Command
31981 The corresponding @value{GDBN} command is @samp{tvariable}.
31983 @subheading The @code{-trace-frame-collected} Command
31984 @findex -trace-frame-collected
31986 @subsubheading Synopsis
31989 -trace-frame-collected
31990 [--var-print-values @var{var_pval}]
31991 [--comp-print-values @var{comp_pval}]
31992 [--registers-format @var{regformat}]
31993 [--memory-contents]
31996 This command returns the set of collected objects, register names,
31997 trace state variable names, memory ranges and computed expressions
31998 that have been collected at a particular trace frame. The optional
31999 parameters to the command affect the output format in different ways.
32000 See the output description table below for more details.
32002 The reported names can be used in the normal manner to create
32003 varobjs and inspect the objects themselves. The items returned by
32004 this command are categorized so that it is clear which is a variable,
32005 which is a register, which is a trace state variable, which is a
32006 memory range and which is a computed expression.
32008 For instance, if the actions were
32010 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32011 collect *(int*)0xaf02bef0@@40
32015 the object collected in its entirety would be @code{myVar}. The
32016 object @code{myArray} would be partially collected, because only the
32017 element at index @code{myIndex} would be collected. The remaining
32018 objects would be computed expressions.
32020 An example output would be:
32024 -trace-frame-collected
32026 explicit-variables=[@{name="myVar",value="1"@}],
32027 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32028 @{name="myObj.field",value="0"@},
32029 @{name="myPtr->field",value="1"@},
32030 @{name="myCount + 2",value="3"@},
32031 @{name="$tvar1 + 1",value="43970027"@}],
32032 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32033 @{number="1",value="0x0"@},
32034 @{number="2",value="0x4"@},
32036 @{number="125",value="0x0"@}],
32037 tvars=[@{name="$tvar1",current="43970026"@}],
32038 memory=[@{address="0x0000000000602264",length="4"@},
32039 @{address="0x0000000000615bc0",length="4"@}]
32046 @item explicit-variables
32047 The set of objects that have been collected in their entirety (as
32048 opposed to collecting just a few elements of an array or a few struct
32049 members). For each object, its name and value are printed.
32050 The @code{--var-print-values} option affects how or whether the value
32051 field is output. If @var{var_pval} is 0, then print only the names;
32052 if it is 1, print also their values; and if it is 2, print the name,
32053 type and value for simple data types, and the name and type for
32054 arrays, structures and unions.
32056 @item computed-expressions
32057 The set of computed expressions that have been collected at the
32058 current trace frame. The @code{--comp-print-values} option affects
32059 this set like the @code{--var-print-values} option affects the
32060 @code{explicit-variables} set. See above.
32063 The registers that have been collected at the current trace frame.
32064 For each register collected, the name and current value are returned.
32065 The value is formatted according to the @code{--registers-format}
32066 option. See the @command{-data-list-register-values} command for a
32067 list of the allowed formats. The default is @samp{x}.
32070 The trace state variables that have been collected at the current
32071 trace frame. For each trace state variable collected, the name and
32072 current value are returned.
32075 The set of memory ranges that have been collected at the current trace
32076 frame. Its content is a list of tuples. Each tuple represents a
32077 collected memory range and has the following fields:
32081 The start address of the memory range, as hexadecimal literal.
32084 The length of the memory range, as decimal literal.
32087 The contents of the memory block, in hex. This field is only present
32088 if the @code{--memory-contents} option is specified.
32094 @subsubheading @value{GDBN} Command
32096 There is no corresponding @value{GDBN} command.
32098 @subsubheading Example
32100 @subheading -trace-list-variables
32101 @findex -trace-list-variables
32103 @subsubheading Synopsis
32106 -trace-list-variables
32109 Return a table of all defined trace variables. Each element of the
32110 table has the following fields:
32114 The name of the trace variable. This field is always present.
32117 The initial value. This is a 64-bit signed integer. This
32118 field is always present.
32121 The value the trace variable has at the moment. This is a 64-bit
32122 signed integer. This field is absent iff current value is
32123 not defined, for example if the trace was never run, or is
32128 @subsubheading @value{GDBN} Command
32130 The corresponding @value{GDBN} command is @samp{tvariables}.
32132 @subsubheading Example
32136 -trace-list-variables
32137 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32138 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32139 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32140 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32141 body=[variable=@{name="$trace_timestamp",initial="0"@}
32142 variable=@{name="$foo",initial="10",current="15"@}]@}
32146 @subheading -trace-save
32147 @findex -trace-save
32149 @subsubheading Synopsis
32152 -trace-save [ -r ] [ -ctf ] @var{filename}
32155 Saves the collected trace data to @var{filename}. Without the
32156 @samp{-r} option, the data is downloaded from the target and saved
32157 in a local file. With the @samp{-r} option the target is asked
32158 to perform the save.
32160 By default, this command will save the trace in the tfile format. You can
32161 supply the optional @samp{-ctf} argument to save it the CTF format. See
32162 @ref{Trace Files} for more information about CTF.
32164 @subsubheading @value{GDBN} Command
32166 The corresponding @value{GDBN} command is @samp{tsave}.
32169 @subheading -trace-start
32170 @findex -trace-start
32172 @subsubheading Synopsis
32178 Starts a tracing experiment. The result of this command does not
32181 @subsubheading @value{GDBN} Command
32183 The corresponding @value{GDBN} command is @samp{tstart}.
32185 @subheading -trace-status
32186 @findex -trace-status
32188 @subsubheading Synopsis
32194 Obtains the status of a tracing experiment. The result may include
32195 the following fields:
32200 May have a value of either @samp{0}, when no tracing operations are
32201 supported, @samp{1}, when all tracing operations are supported, or
32202 @samp{file} when examining trace file. In the latter case, examining
32203 of trace frame is possible but new tracing experiement cannot be
32204 started. This field is always present.
32207 May have a value of either @samp{0} or @samp{1} depending on whether
32208 tracing experiement is in progress on target. This field is present
32209 if @samp{supported} field is not @samp{0}.
32212 Report the reason why the tracing was stopped last time. This field
32213 may be absent iff tracing was never stopped on target yet. The
32214 value of @samp{request} means the tracing was stopped as result of
32215 the @code{-trace-stop} command. The value of @samp{overflow} means
32216 the tracing buffer is full. The value of @samp{disconnection} means
32217 tracing was automatically stopped when @value{GDBN} has disconnected.
32218 The value of @samp{passcount} means tracing was stopped when a
32219 tracepoint was passed a maximal number of times for that tracepoint.
32220 This field is present if @samp{supported} field is not @samp{0}.
32222 @item stopping-tracepoint
32223 The number of tracepoint whose passcount as exceeded. This field is
32224 present iff the @samp{stop-reason} field has the value of
32228 @itemx frames-created
32229 The @samp{frames} field is a count of the total number of trace frames
32230 in the trace buffer, while @samp{frames-created} is the total created
32231 during the run, including ones that were discarded, such as when a
32232 circular trace buffer filled up. Both fields are optional.
32236 These fields tell the current size of the tracing buffer and the
32237 remaining space. These fields are optional.
32240 The value of the circular trace buffer flag. @code{1} means that the
32241 trace buffer is circular and old trace frames will be discarded if
32242 necessary to make room, @code{0} means that the trace buffer is linear
32246 The value of the disconnected tracing flag. @code{1} means that
32247 tracing will continue after @value{GDBN} disconnects, @code{0} means
32248 that the trace run will stop.
32251 The filename of the trace file being examined. This field is
32252 optional, and only present when examining a trace file.
32256 @subsubheading @value{GDBN} Command
32258 The corresponding @value{GDBN} command is @samp{tstatus}.
32260 @subheading -trace-stop
32261 @findex -trace-stop
32263 @subsubheading Synopsis
32269 Stops a tracing experiment. The result of this command has the same
32270 fields as @code{-trace-status}, except that the @samp{supported} and
32271 @samp{running} fields are not output.
32273 @subsubheading @value{GDBN} Command
32275 The corresponding @value{GDBN} command is @samp{tstop}.
32278 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32279 @node GDB/MI Symbol Query
32280 @section @sc{gdb/mi} Symbol Query Commands
32284 @subheading The @code{-symbol-info-address} Command
32285 @findex -symbol-info-address
32287 @subsubheading Synopsis
32290 -symbol-info-address @var{symbol}
32293 Describe where @var{symbol} is stored.
32295 @subsubheading @value{GDBN} Command
32297 The corresponding @value{GDBN} command is @samp{info address}.
32299 @subsubheading Example
32303 @subheading The @code{-symbol-info-file} Command
32304 @findex -symbol-info-file
32306 @subsubheading Synopsis
32312 Show the file for the symbol.
32314 @subsubheading @value{GDBN} Command
32316 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32317 @samp{gdb_find_file}.
32319 @subsubheading Example
32323 @subheading The @code{-symbol-info-function} Command
32324 @findex -symbol-info-function
32326 @subsubheading Synopsis
32329 -symbol-info-function
32332 Show which function the symbol lives in.
32334 @subsubheading @value{GDBN} Command
32336 @samp{gdb_get_function} in @code{gdbtk}.
32338 @subsubheading Example
32342 @subheading The @code{-symbol-info-line} Command
32343 @findex -symbol-info-line
32345 @subsubheading Synopsis
32351 Show the core addresses of the code for a source line.
32353 @subsubheading @value{GDBN} Command
32355 The corresponding @value{GDBN} command is @samp{info line}.
32356 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32358 @subsubheading Example
32362 @subheading The @code{-symbol-info-symbol} Command
32363 @findex -symbol-info-symbol
32365 @subsubheading Synopsis
32368 -symbol-info-symbol @var{addr}
32371 Describe what symbol is at location @var{addr}.
32373 @subsubheading @value{GDBN} Command
32375 The corresponding @value{GDBN} command is @samp{info symbol}.
32377 @subsubheading Example
32381 @subheading The @code{-symbol-list-functions} Command
32382 @findex -symbol-list-functions
32384 @subsubheading Synopsis
32387 -symbol-list-functions
32390 List the functions in the executable.
32392 @subsubheading @value{GDBN} Command
32394 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32395 @samp{gdb_search} in @code{gdbtk}.
32397 @subsubheading Example
32402 @subheading The @code{-symbol-list-lines} Command
32403 @findex -symbol-list-lines
32405 @subsubheading Synopsis
32408 -symbol-list-lines @var{filename}
32411 Print the list of lines that contain code and their associated program
32412 addresses for the given source filename. The entries are sorted in
32413 ascending PC order.
32415 @subsubheading @value{GDBN} Command
32417 There is no corresponding @value{GDBN} command.
32419 @subsubheading Example
32422 -symbol-list-lines basics.c
32423 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32429 @subheading The @code{-symbol-list-types} Command
32430 @findex -symbol-list-types
32432 @subsubheading Synopsis
32438 List all the type names.
32440 @subsubheading @value{GDBN} Command
32442 The corresponding commands are @samp{info types} in @value{GDBN},
32443 @samp{gdb_search} in @code{gdbtk}.
32445 @subsubheading Example
32449 @subheading The @code{-symbol-list-variables} Command
32450 @findex -symbol-list-variables
32452 @subsubheading Synopsis
32455 -symbol-list-variables
32458 List all the global and static variable names.
32460 @subsubheading @value{GDBN} Command
32462 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32464 @subsubheading Example
32468 @subheading The @code{-symbol-locate} Command
32469 @findex -symbol-locate
32471 @subsubheading Synopsis
32477 @subsubheading @value{GDBN} Command
32479 @samp{gdb_loc} in @code{gdbtk}.
32481 @subsubheading Example
32485 @subheading The @code{-symbol-type} Command
32486 @findex -symbol-type
32488 @subsubheading Synopsis
32491 -symbol-type @var{variable}
32494 Show type of @var{variable}.
32496 @subsubheading @value{GDBN} Command
32498 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32499 @samp{gdb_obj_variable}.
32501 @subsubheading Example
32506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32507 @node GDB/MI File Commands
32508 @section @sc{gdb/mi} File Commands
32510 This section describes the GDB/MI commands to specify executable file names
32511 and to read in and obtain symbol table information.
32513 @subheading The @code{-file-exec-and-symbols} Command
32514 @findex -file-exec-and-symbols
32516 @subsubheading Synopsis
32519 -file-exec-and-symbols @var{file}
32522 Specify the executable file to be debugged. This file is the one from
32523 which the symbol table is also read. If no file is specified, the
32524 command clears the executable and symbol information. If breakpoints
32525 are set when using this command with no arguments, @value{GDBN} will produce
32526 error messages. Otherwise, no output is produced, except a completion
32529 @subsubheading @value{GDBN} Command
32531 The corresponding @value{GDBN} command is @samp{file}.
32533 @subsubheading Example
32537 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32543 @subheading The @code{-file-exec-file} Command
32544 @findex -file-exec-file
32546 @subsubheading Synopsis
32549 -file-exec-file @var{file}
32552 Specify the executable file to be debugged. Unlike
32553 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32554 from this file. If used without argument, @value{GDBN} clears the information
32555 about the executable file. No output is produced, except a completion
32558 @subsubheading @value{GDBN} Command
32560 The corresponding @value{GDBN} command is @samp{exec-file}.
32562 @subsubheading Example
32566 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32573 @subheading The @code{-file-list-exec-sections} Command
32574 @findex -file-list-exec-sections
32576 @subsubheading Synopsis
32579 -file-list-exec-sections
32582 List the sections of the current executable file.
32584 @subsubheading @value{GDBN} Command
32586 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32587 information as this command. @code{gdbtk} has a corresponding command
32588 @samp{gdb_load_info}.
32590 @subsubheading Example
32595 @subheading The @code{-file-list-exec-source-file} Command
32596 @findex -file-list-exec-source-file
32598 @subsubheading Synopsis
32601 -file-list-exec-source-file
32604 List the line number, the current source file, and the absolute path
32605 to the current source file for the current executable. The macro
32606 information field has a value of @samp{1} or @samp{0} depending on
32607 whether or not the file includes preprocessor macro information.
32609 @subsubheading @value{GDBN} Command
32611 The @value{GDBN} equivalent is @samp{info source}
32613 @subsubheading Example
32617 123-file-list-exec-source-file
32618 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32623 @subheading The @code{-file-list-exec-source-files} Command
32624 @findex -file-list-exec-source-files
32626 @subsubheading Synopsis
32629 -file-list-exec-source-files
32632 List the source files for the current executable.
32634 It will always output both the filename and fullname (absolute file
32635 name) of a source file.
32637 @subsubheading @value{GDBN} Command
32639 The @value{GDBN} equivalent is @samp{info sources}.
32640 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32642 @subsubheading Example
32645 -file-list-exec-source-files
32647 @{file=foo.c,fullname=/home/foo.c@},
32648 @{file=/home/bar.c,fullname=/home/bar.c@},
32649 @{file=gdb_could_not_find_fullpath.c@}]
32653 @subheading The @code{-file-list-shared-libraries} Command
32654 @findex -file-list-shared-libraries
32656 @subsubheading Synopsis
32659 -file-list-shared-libraries [ @var{regexp} ]
32662 List the shared libraries in the program.
32663 With a regular expression @var{regexp}, only those libraries whose
32664 names match @var{regexp} are listed.
32666 @subsubheading @value{GDBN} Command
32668 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32669 have a similar meaning to the @code{=library-loaded} notification.
32670 The @code{ranges} field specifies the multiple segments belonging to this
32671 library. Each range has the following fields:
32675 The address defining the inclusive lower bound of the segment.
32677 The address defining the exclusive upper bound of the segment.
32680 @subsubheading Example
32683 -file-list-exec-source-files
32684 ^done,shared-libraries=[
32685 @{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"@}]@},
32686 @{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"@}]@}]
32692 @subheading The @code{-file-list-symbol-files} Command
32693 @findex -file-list-symbol-files
32695 @subsubheading Synopsis
32698 -file-list-symbol-files
32703 @subsubheading @value{GDBN} Command
32705 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32707 @subsubheading Example
32712 @subheading The @code{-file-symbol-file} Command
32713 @findex -file-symbol-file
32715 @subsubheading Synopsis
32718 -file-symbol-file @var{file}
32721 Read symbol table info from the specified @var{file} argument. When
32722 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32723 produced, except for a completion notification.
32725 @subsubheading @value{GDBN} Command
32727 The corresponding @value{GDBN} command is @samp{symbol-file}.
32729 @subsubheading Example
32733 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32739 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32740 @node GDB/MI Memory Overlay Commands
32741 @section @sc{gdb/mi} Memory Overlay Commands
32743 The memory overlay commands are not implemented.
32745 @c @subheading -overlay-auto
32747 @c @subheading -overlay-list-mapping-state
32749 @c @subheading -overlay-list-overlays
32751 @c @subheading -overlay-map
32753 @c @subheading -overlay-off
32755 @c @subheading -overlay-on
32757 @c @subheading -overlay-unmap
32759 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32760 @node GDB/MI Signal Handling Commands
32761 @section @sc{gdb/mi} Signal Handling Commands
32763 Signal handling commands are not implemented.
32765 @c @subheading -signal-handle
32767 @c @subheading -signal-list-handle-actions
32769 @c @subheading -signal-list-signal-types
32773 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32774 @node GDB/MI Target Manipulation
32775 @section @sc{gdb/mi} Target Manipulation Commands
32778 @subheading The @code{-target-attach} Command
32779 @findex -target-attach
32781 @subsubheading Synopsis
32784 -target-attach @var{pid} | @var{gid} | @var{file}
32787 Attach to a process @var{pid} or a file @var{file} outside of
32788 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32789 group, the id previously returned by
32790 @samp{-list-thread-groups --available} must be used.
32792 @subsubheading @value{GDBN} Command
32794 The corresponding @value{GDBN} command is @samp{attach}.
32796 @subsubheading Example
32800 =thread-created,id="1"
32801 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32807 @subheading The @code{-target-compare-sections} Command
32808 @findex -target-compare-sections
32810 @subsubheading Synopsis
32813 -target-compare-sections [ @var{section} ]
32816 Compare data of section @var{section} on target to the exec file.
32817 Without the argument, all sections are compared.
32819 @subsubheading @value{GDBN} Command
32821 The @value{GDBN} equivalent is @samp{compare-sections}.
32823 @subsubheading Example
32828 @subheading The @code{-target-detach} Command
32829 @findex -target-detach
32831 @subsubheading Synopsis
32834 -target-detach [ @var{pid} | @var{gid} ]
32837 Detach from the remote target which normally resumes its execution.
32838 If either @var{pid} or @var{gid} is specified, detaches from either
32839 the specified process, or specified thread group. There's no output.
32841 @subsubheading @value{GDBN} Command
32843 The corresponding @value{GDBN} command is @samp{detach}.
32845 @subsubheading Example
32855 @subheading The @code{-target-disconnect} Command
32856 @findex -target-disconnect
32858 @subsubheading Synopsis
32864 Disconnect from the remote target. There's no output and the target is
32865 generally not resumed.
32867 @subsubheading @value{GDBN} Command
32869 The corresponding @value{GDBN} command is @samp{disconnect}.
32871 @subsubheading Example
32881 @subheading The @code{-target-download} Command
32882 @findex -target-download
32884 @subsubheading Synopsis
32890 Loads the executable onto the remote target.
32891 It prints out an update message every half second, which includes the fields:
32895 The name of the section.
32897 The size of what has been sent so far for that section.
32899 The size of the section.
32901 The total size of what was sent so far (the current and the previous sections).
32903 The size of the overall executable to download.
32907 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32908 @sc{gdb/mi} Output Syntax}).
32910 In addition, it prints the name and size of the sections, as they are
32911 downloaded. These messages include the following fields:
32915 The name of the section.
32917 The size of the section.
32919 The size of the overall executable to download.
32923 At the end, a summary is printed.
32925 @subsubheading @value{GDBN} Command
32927 The corresponding @value{GDBN} command is @samp{load}.
32929 @subsubheading Example
32931 Note: each status message appears on a single line. Here the messages
32932 have been broken down so that they can fit onto a page.
32937 +download,@{section=".text",section-size="6668",total-size="9880"@}
32938 +download,@{section=".text",section-sent="512",section-size="6668",
32939 total-sent="512",total-size="9880"@}
32940 +download,@{section=".text",section-sent="1024",section-size="6668",
32941 total-sent="1024",total-size="9880"@}
32942 +download,@{section=".text",section-sent="1536",section-size="6668",
32943 total-sent="1536",total-size="9880"@}
32944 +download,@{section=".text",section-sent="2048",section-size="6668",
32945 total-sent="2048",total-size="9880"@}
32946 +download,@{section=".text",section-sent="2560",section-size="6668",
32947 total-sent="2560",total-size="9880"@}
32948 +download,@{section=".text",section-sent="3072",section-size="6668",
32949 total-sent="3072",total-size="9880"@}
32950 +download,@{section=".text",section-sent="3584",section-size="6668",
32951 total-sent="3584",total-size="9880"@}
32952 +download,@{section=".text",section-sent="4096",section-size="6668",
32953 total-sent="4096",total-size="9880"@}
32954 +download,@{section=".text",section-sent="4608",section-size="6668",
32955 total-sent="4608",total-size="9880"@}
32956 +download,@{section=".text",section-sent="5120",section-size="6668",
32957 total-sent="5120",total-size="9880"@}
32958 +download,@{section=".text",section-sent="5632",section-size="6668",
32959 total-sent="5632",total-size="9880"@}
32960 +download,@{section=".text",section-sent="6144",section-size="6668",
32961 total-sent="6144",total-size="9880"@}
32962 +download,@{section=".text",section-sent="6656",section-size="6668",
32963 total-sent="6656",total-size="9880"@}
32964 +download,@{section=".init",section-size="28",total-size="9880"@}
32965 +download,@{section=".fini",section-size="28",total-size="9880"@}
32966 +download,@{section=".data",section-size="3156",total-size="9880"@}
32967 +download,@{section=".data",section-sent="512",section-size="3156",
32968 total-sent="7236",total-size="9880"@}
32969 +download,@{section=".data",section-sent="1024",section-size="3156",
32970 total-sent="7748",total-size="9880"@}
32971 +download,@{section=".data",section-sent="1536",section-size="3156",
32972 total-sent="8260",total-size="9880"@}
32973 +download,@{section=".data",section-sent="2048",section-size="3156",
32974 total-sent="8772",total-size="9880"@}
32975 +download,@{section=".data",section-sent="2560",section-size="3156",
32976 total-sent="9284",total-size="9880"@}
32977 +download,@{section=".data",section-sent="3072",section-size="3156",
32978 total-sent="9796",total-size="9880"@}
32979 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32986 @subheading The @code{-target-exec-status} Command
32987 @findex -target-exec-status
32989 @subsubheading Synopsis
32992 -target-exec-status
32995 Provide information on the state of the target (whether it is running or
32996 not, for instance).
32998 @subsubheading @value{GDBN} Command
33000 There's no equivalent @value{GDBN} command.
33002 @subsubheading Example
33006 @subheading The @code{-target-list-available-targets} Command
33007 @findex -target-list-available-targets
33009 @subsubheading Synopsis
33012 -target-list-available-targets
33015 List the possible targets to connect to.
33017 @subsubheading @value{GDBN} Command
33019 The corresponding @value{GDBN} command is @samp{help target}.
33021 @subsubheading Example
33025 @subheading The @code{-target-list-current-targets} Command
33026 @findex -target-list-current-targets
33028 @subsubheading Synopsis
33031 -target-list-current-targets
33034 Describe the current target.
33036 @subsubheading @value{GDBN} Command
33038 The corresponding information is printed by @samp{info file} (among
33041 @subsubheading Example
33045 @subheading The @code{-target-list-parameters} Command
33046 @findex -target-list-parameters
33048 @subsubheading Synopsis
33051 -target-list-parameters
33057 @subsubheading @value{GDBN} Command
33061 @subsubheading Example
33064 @subheading The @code{-target-flash-erase} Command
33065 @findex -target-flash-erase
33067 @subsubheading Synopsis
33070 -target-flash-erase
33073 Erases all known flash memory regions on the target.
33075 The corresponding @value{GDBN} command is @samp{flash-erase}.
33077 The output is a list of flash regions that have been erased, with starting
33078 addresses and memory region sizes.
33082 -target-flash-erase
33083 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33087 @subheading The @code{-target-select} Command
33088 @findex -target-select
33090 @subsubheading Synopsis
33093 -target-select @var{type} @var{parameters @dots{}}
33096 Connect @value{GDBN} to the remote target. This command takes two args:
33100 The type of target, for instance @samp{remote}, etc.
33101 @item @var{parameters}
33102 Device names, host names and the like. @xref{Target Commands, ,
33103 Commands for Managing Targets}, for more details.
33106 The output is a connection notification, followed by the address at
33107 which the target program is, in the following form:
33110 ^connected,addr="@var{address}",func="@var{function name}",
33111 args=[@var{arg list}]
33114 @subsubheading @value{GDBN} Command
33116 The corresponding @value{GDBN} command is @samp{target}.
33118 @subsubheading Example
33122 -target-select remote /dev/ttya
33123 ^connected,addr="0xfe00a300",func="??",args=[]
33127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33128 @node GDB/MI File Transfer Commands
33129 @section @sc{gdb/mi} File Transfer Commands
33132 @subheading The @code{-target-file-put} Command
33133 @findex -target-file-put
33135 @subsubheading Synopsis
33138 -target-file-put @var{hostfile} @var{targetfile}
33141 Copy file @var{hostfile} from the host system (the machine running
33142 @value{GDBN}) to @var{targetfile} on the target system.
33144 @subsubheading @value{GDBN} Command
33146 The corresponding @value{GDBN} command is @samp{remote put}.
33148 @subsubheading Example
33152 -target-file-put localfile remotefile
33158 @subheading The @code{-target-file-get} Command
33159 @findex -target-file-get
33161 @subsubheading Synopsis
33164 -target-file-get @var{targetfile} @var{hostfile}
33167 Copy file @var{targetfile} from the target system to @var{hostfile}
33168 on the host system.
33170 @subsubheading @value{GDBN} Command
33172 The corresponding @value{GDBN} command is @samp{remote get}.
33174 @subsubheading Example
33178 -target-file-get remotefile localfile
33184 @subheading The @code{-target-file-delete} Command
33185 @findex -target-file-delete
33187 @subsubheading Synopsis
33190 -target-file-delete @var{targetfile}
33193 Delete @var{targetfile} from the target system.
33195 @subsubheading @value{GDBN} Command
33197 The corresponding @value{GDBN} command is @samp{remote delete}.
33199 @subsubheading Example
33203 -target-file-delete remotefile
33209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33210 @node GDB/MI Ada Exceptions Commands
33211 @section Ada Exceptions @sc{gdb/mi} Commands
33213 @subheading The @code{-info-ada-exceptions} Command
33214 @findex -info-ada-exceptions
33216 @subsubheading Synopsis
33219 -info-ada-exceptions [ @var{regexp}]
33222 List all Ada exceptions defined within the program being debugged.
33223 With a regular expression @var{regexp}, only those exceptions whose
33224 names match @var{regexp} are listed.
33226 @subsubheading @value{GDBN} Command
33228 The corresponding @value{GDBN} command is @samp{info exceptions}.
33230 @subsubheading Result
33232 The result is a table of Ada exceptions. The following columns are
33233 defined for each exception:
33237 The name of the exception.
33240 The address of the exception.
33244 @subsubheading Example
33247 -info-ada-exceptions aint
33248 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33249 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33250 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33251 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33252 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33255 @subheading Catching Ada Exceptions
33257 The commands describing how to ask @value{GDBN} to stop when a program
33258 raises an exception are described at @ref{Ada Exception GDB/MI
33259 Catchpoint Commands}.
33262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33263 @node GDB/MI Support Commands
33264 @section @sc{gdb/mi} Support Commands
33266 Since new commands and features get regularly added to @sc{gdb/mi},
33267 some commands are available to help front-ends query the debugger
33268 about support for these capabilities. Similarly, it is also possible
33269 to query @value{GDBN} about target support of certain features.
33271 @subheading The @code{-info-gdb-mi-command} Command
33272 @cindex @code{-info-gdb-mi-command}
33273 @findex -info-gdb-mi-command
33275 @subsubheading Synopsis
33278 -info-gdb-mi-command @var{cmd_name}
33281 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33283 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33284 is technically not part of the command name (@pxref{GDB/MI Input
33285 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33286 for ease of use, this command also accepts the form with the leading
33289 @subsubheading @value{GDBN} Command
33291 There is no corresponding @value{GDBN} command.
33293 @subsubheading Result
33295 The result is a tuple. There is currently only one field:
33299 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33300 @code{"false"} otherwise.
33304 @subsubheading Example
33306 Here is an example where the @sc{gdb/mi} command does not exist:
33309 -info-gdb-mi-command unsupported-command
33310 ^done,command=@{exists="false"@}
33314 And here is an example where the @sc{gdb/mi} command is known
33318 -info-gdb-mi-command symbol-list-lines
33319 ^done,command=@{exists="true"@}
33322 @subheading The @code{-list-features} Command
33323 @findex -list-features
33324 @cindex supported @sc{gdb/mi} features, list
33326 Returns a list of particular features of the MI protocol that
33327 this version of gdb implements. A feature can be a command,
33328 or a new field in an output of some command, or even an
33329 important bugfix. While a frontend can sometimes detect presence
33330 of a feature at runtime, it is easier to perform detection at debugger
33333 The command returns a list of strings, with each string naming an
33334 available feature. Each returned string is just a name, it does not
33335 have any internal structure. The list of possible feature names
33341 (gdb) -list-features
33342 ^done,result=["feature1","feature2"]
33345 The current list of features is:
33348 @item frozen-varobjs
33349 Indicates support for the @code{-var-set-frozen} command, as well
33350 as possible presense of the @code{frozen} field in the output
33351 of @code{-varobj-create}.
33352 @item pending-breakpoints
33353 Indicates support for the @option{-f} option to the @code{-break-insert}
33356 Indicates Python scripting support, Python-based
33357 pretty-printing commands, and possible presence of the
33358 @samp{display_hint} field in the output of @code{-var-list-children}
33360 Indicates support for the @code{-thread-info} command.
33361 @item data-read-memory-bytes
33362 Indicates support for the @code{-data-read-memory-bytes} and the
33363 @code{-data-write-memory-bytes} commands.
33364 @item breakpoint-notifications
33365 Indicates that changes to breakpoints and breakpoints created via the
33366 CLI will be announced via async records.
33367 @item ada-task-info
33368 Indicates support for the @code{-ada-task-info} command.
33369 @item language-option
33370 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33371 option (@pxref{Context management}).
33372 @item info-gdb-mi-command
33373 Indicates support for the @code{-info-gdb-mi-command} command.
33374 @item undefined-command-error-code
33375 Indicates support for the "undefined-command" error code in error result
33376 records, produced when trying to execute an undefined @sc{gdb/mi} command
33377 (@pxref{GDB/MI Result Records}).
33378 @item exec-run-start-option
33379 Indicates that the @code{-exec-run} command supports the @option{--start}
33380 option (@pxref{GDB/MI Program Execution}).
33381 @item data-disassemble-a-option
33382 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33383 option (@pxref{GDB/MI Data Manipulation}).
33386 @subheading The @code{-list-target-features} Command
33387 @findex -list-target-features
33389 Returns a list of particular features that are supported by the
33390 target. Those features affect the permitted MI commands, but
33391 unlike the features reported by the @code{-list-features} command, the
33392 features depend on which target GDB is using at the moment. Whenever
33393 a target can change, due to commands such as @code{-target-select},
33394 @code{-target-attach} or @code{-exec-run}, the list of target features
33395 may change, and the frontend should obtain it again.
33399 (gdb) -list-target-features
33400 ^done,result=["async"]
33403 The current list of features is:
33407 Indicates that the target is capable of asynchronous command
33408 execution, which means that @value{GDBN} will accept further commands
33409 while the target is running.
33412 Indicates that the target is capable of reverse execution.
33413 @xref{Reverse Execution}, for more information.
33417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33418 @node GDB/MI Miscellaneous Commands
33419 @section Miscellaneous @sc{gdb/mi} Commands
33421 @c @subheading -gdb-complete
33423 @subheading The @code{-gdb-exit} Command
33426 @subsubheading Synopsis
33432 Exit @value{GDBN} immediately.
33434 @subsubheading @value{GDBN} Command
33436 Approximately corresponds to @samp{quit}.
33438 @subsubheading Example
33448 @subheading The @code{-exec-abort} Command
33449 @findex -exec-abort
33451 @subsubheading Synopsis
33457 Kill the inferior running program.
33459 @subsubheading @value{GDBN} Command
33461 The corresponding @value{GDBN} command is @samp{kill}.
33463 @subsubheading Example
33468 @subheading The @code{-gdb-set} Command
33471 @subsubheading Synopsis
33477 Set an internal @value{GDBN} variable.
33478 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33480 @subsubheading @value{GDBN} Command
33482 The corresponding @value{GDBN} command is @samp{set}.
33484 @subsubheading Example
33494 @subheading The @code{-gdb-show} Command
33497 @subsubheading Synopsis
33503 Show the current value of a @value{GDBN} variable.
33505 @subsubheading @value{GDBN} Command
33507 The corresponding @value{GDBN} command is @samp{show}.
33509 @subsubheading Example
33518 @c @subheading -gdb-source
33521 @subheading The @code{-gdb-version} Command
33522 @findex -gdb-version
33524 @subsubheading Synopsis
33530 Show version information for @value{GDBN}. Used mostly in testing.
33532 @subsubheading @value{GDBN} Command
33534 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33535 default shows this information when you start an interactive session.
33537 @subsubheading Example
33539 @c This example modifies the actual output from GDB to avoid overfull
33545 ~Copyright 2000 Free Software Foundation, Inc.
33546 ~GDB is free software, covered by the GNU General Public License, and
33547 ~you are welcome to change it and/or distribute copies of it under
33548 ~ certain conditions.
33549 ~Type "show copying" to see the conditions.
33550 ~There is absolutely no warranty for GDB. Type "show warranty" for
33552 ~This GDB was configured as
33553 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33558 @subheading The @code{-list-thread-groups} Command
33559 @findex -list-thread-groups
33561 @subheading Synopsis
33564 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33567 Lists thread groups (@pxref{Thread groups}). When a single thread
33568 group is passed as the argument, lists the children of that group.
33569 When several thread group are passed, lists information about those
33570 thread groups. Without any parameters, lists information about all
33571 top-level thread groups.
33573 Normally, thread groups that are being debugged are reported.
33574 With the @samp{--available} option, @value{GDBN} reports thread groups
33575 available on the target.
33577 The output of this command may have either a @samp{threads} result or
33578 a @samp{groups} result. The @samp{thread} result has a list of tuples
33579 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33580 Information}). The @samp{groups} result has a list of tuples as value,
33581 each tuple describing a thread group. If top-level groups are
33582 requested (that is, no parameter is passed), or when several groups
33583 are passed, the output always has a @samp{groups} result. The format
33584 of the @samp{group} result is described below.
33586 To reduce the number of roundtrips it's possible to list thread groups
33587 together with their children, by passing the @samp{--recurse} option
33588 and the recursion depth. Presently, only recursion depth of 1 is
33589 permitted. If this option is present, then every reported thread group
33590 will also include its children, either as @samp{group} or
33591 @samp{threads} field.
33593 In general, any combination of option and parameters is permitted, with
33594 the following caveats:
33598 When a single thread group is passed, the output will typically
33599 be the @samp{threads} result. Because threads may not contain
33600 anything, the @samp{recurse} option will be ignored.
33603 When the @samp{--available} option is passed, limited information may
33604 be available. In particular, the list of threads of a process might
33605 be inaccessible. Further, specifying specific thread groups might
33606 not give any performance advantage over listing all thread groups.
33607 The frontend should assume that @samp{-list-thread-groups --available}
33608 is always an expensive operation and cache the results.
33612 The @samp{groups} result is a list of tuples, where each tuple may
33613 have the following fields:
33617 Identifier of the thread group. This field is always present.
33618 The identifier is an opaque string; frontends should not try to
33619 convert it to an integer, even though it might look like one.
33622 The type of the thread group. At present, only @samp{process} is a
33626 The target-specific process identifier. This field is only present
33627 for thread groups of type @samp{process} and only if the process exists.
33630 The exit code of this group's last exited thread, formatted in octal.
33631 This field is only present for thread groups of type @samp{process} and
33632 only if the process is not running.
33635 The number of children this thread group has. This field may be
33636 absent for an available thread group.
33639 This field has a list of tuples as value, each tuple describing a
33640 thread. It may be present if the @samp{--recurse} option is
33641 specified, and it's actually possible to obtain the threads.
33644 This field is a list of integers, each identifying a core that one
33645 thread of the group is running on. This field may be absent if
33646 such information is not available.
33649 The name of the executable file that corresponds to this thread group.
33650 The field is only present for thread groups of type @samp{process},
33651 and only if there is a corresponding executable file.
33655 @subheading Example
33659 -list-thread-groups
33660 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33661 -list-thread-groups 17
33662 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33663 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33664 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33665 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33666 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33667 -list-thread-groups --available
33668 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33669 -list-thread-groups --available --recurse 1
33670 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33671 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33672 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33673 -list-thread-groups --available --recurse 1 17 18
33674 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33675 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33676 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33679 @subheading The @code{-info-os} Command
33682 @subsubheading Synopsis
33685 -info-os [ @var{type} ]
33688 If no argument is supplied, the command returns a table of available
33689 operating-system-specific information types. If one of these types is
33690 supplied as an argument @var{type}, then the command returns a table
33691 of data of that type.
33693 The types of information available depend on the target operating
33696 @subsubheading @value{GDBN} Command
33698 The corresponding @value{GDBN} command is @samp{info os}.
33700 @subsubheading Example
33702 When run on a @sc{gnu}/Linux system, the output will look something
33708 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33709 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33710 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33711 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33712 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33714 item=@{col0="files",col1="Listing of all file descriptors",
33715 col2="File descriptors"@},
33716 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33717 col2="Kernel modules"@},
33718 item=@{col0="msg",col1="Listing of all message queues",
33719 col2="Message queues"@},
33720 item=@{col0="processes",col1="Listing of all processes",
33721 col2="Processes"@},
33722 item=@{col0="procgroups",col1="Listing of all process groups",
33723 col2="Process groups"@},
33724 item=@{col0="semaphores",col1="Listing of all semaphores",
33725 col2="Semaphores"@},
33726 item=@{col0="shm",col1="Listing of all shared-memory regions",
33727 col2="Shared-memory regions"@},
33728 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33730 item=@{col0="threads",col1="Listing of all threads",
33734 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33735 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33736 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33737 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33738 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33739 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33740 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33741 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33743 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33744 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33748 (Note that the MI output here includes a @code{"Title"} column that
33749 does not appear in command-line @code{info os}; this column is useful
33750 for MI clients that want to enumerate the types of data, such as in a
33751 popup menu, but is needless clutter on the command line, and
33752 @code{info os} omits it.)
33754 @subheading The @code{-add-inferior} Command
33755 @findex -add-inferior
33757 @subheading Synopsis
33763 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33764 inferior is not associated with any executable. Such association may
33765 be established with the @samp{-file-exec-and-symbols} command
33766 (@pxref{GDB/MI File Commands}). The command response has a single
33767 field, @samp{inferior}, whose value is the identifier of the
33768 thread group corresponding to the new inferior.
33770 @subheading Example
33775 ^done,inferior="i3"
33778 @subheading The @code{-interpreter-exec} Command
33779 @findex -interpreter-exec
33781 @subheading Synopsis
33784 -interpreter-exec @var{interpreter} @var{command}
33786 @anchor{-interpreter-exec}
33788 Execute the specified @var{command} in the given @var{interpreter}.
33790 @subheading @value{GDBN} Command
33792 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33794 @subheading Example
33798 -interpreter-exec console "break main"
33799 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33800 &"During symbol reading, bad structure-type format.\n"
33801 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33806 @subheading The @code{-inferior-tty-set} Command
33807 @findex -inferior-tty-set
33809 @subheading Synopsis
33812 -inferior-tty-set /dev/pts/1
33815 Set terminal for future runs of the program being debugged.
33817 @subheading @value{GDBN} Command
33819 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33821 @subheading Example
33825 -inferior-tty-set /dev/pts/1
33830 @subheading The @code{-inferior-tty-show} Command
33831 @findex -inferior-tty-show
33833 @subheading Synopsis
33839 Show terminal for future runs of program being debugged.
33841 @subheading @value{GDBN} Command
33843 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33845 @subheading Example
33849 -inferior-tty-set /dev/pts/1
33853 ^done,inferior_tty_terminal="/dev/pts/1"
33857 @subheading The @code{-enable-timings} Command
33858 @findex -enable-timings
33860 @subheading Synopsis
33863 -enable-timings [yes | no]
33866 Toggle the printing of the wallclock, user and system times for an MI
33867 command as a field in its output. This command is to help frontend
33868 developers optimize the performance of their code. No argument is
33869 equivalent to @samp{yes}.
33871 @subheading @value{GDBN} Command
33875 @subheading Example
33883 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33884 addr="0x080484ed",func="main",file="myprog.c",
33885 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33887 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33895 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33896 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33897 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33898 fullname="/home/nickrob/myprog.c",line="73"@}
33903 @chapter @value{GDBN} Annotations
33905 This chapter describes annotations in @value{GDBN}. Annotations were
33906 designed to interface @value{GDBN} to graphical user interfaces or other
33907 similar programs which want to interact with @value{GDBN} at a
33908 relatively high level.
33910 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33914 This is Edition @value{EDITION}, @value{DATE}.
33918 * Annotations Overview:: What annotations are; the general syntax.
33919 * Server Prefix:: Issuing a command without affecting user state.
33920 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33921 * Errors:: Annotations for error messages.
33922 * Invalidation:: Some annotations describe things now invalid.
33923 * Annotations for Running::
33924 Whether the program is running, how it stopped, etc.
33925 * Source Annotations:: Annotations describing source code.
33928 @node Annotations Overview
33929 @section What is an Annotation?
33930 @cindex annotations
33932 Annotations start with a newline character, two @samp{control-z}
33933 characters, and the name of the annotation. If there is no additional
33934 information associated with this annotation, the name of the annotation
33935 is followed immediately by a newline. If there is additional
33936 information, the name of the annotation is followed by a space, the
33937 additional information, and a newline. The additional information
33938 cannot contain newline characters.
33940 Any output not beginning with a newline and two @samp{control-z}
33941 characters denotes literal output from @value{GDBN}. Currently there is
33942 no need for @value{GDBN} to output a newline followed by two
33943 @samp{control-z} characters, but if there was such a need, the
33944 annotations could be extended with an @samp{escape} annotation which
33945 means those three characters as output.
33947 The annotation @var{level}, which is specified using the
33948 @option{--annotate} command line option (@pxref{Mode Options}), controls
33949 how much information @value{GDBN} prints together with its prompt,
33950 values of expressions, source lines, and other types of output. Level 0
33951 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33952 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33953 for programs that control @value{GDBN}, and level 2 annotations have
33954 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33955 Interface, annotate, GDB's Obsolete Annotations}).
33958 @kindex set annotate
33959 @item set annotate @var{level}
33960 The @value{GDBN} command @code{set annotate} sets the level of
33961 annotations to the specified @var{level}.
33963 @item show annotate
33964 @kindex show annotate
33965 Show the current annotation level.
33968 This chapter describes level 3 annotations.
33970 A simple example of starting up @value{GDBN} with annotations is:
33973 $ @kbd{gdb --annotate=3}
33975 Copyright 2003 Free Software Foundation, Inc.
33976 GDB is free software, covered by the GNU General Public License,
33977 and you are welcome to change it and/or distribute copies of it
33978 under certain conditions.
33979 Type "show copying" to see the conditions.
33980 There is absolutely no warranty for GDB. Type "show warranty"
33982 This GDB was configured as "i386-pc-linux-gnu"
33993 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33994 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33995 denotes a @samp{control-z} character) are annotations; the rest is
33996 output from @value{GDBN}.
33998 @node Server Prefix
33999 @section The Server Prefix
34000 @cindex server prefix
34002 If you prefix a command with @samp{server } then it will not affect
34003 the command history, nor will it affect @value{GDBN}'s notion of which
34004 command to repeat if @key{RET} is pressed on a line by itself. This
34005 means that commands can be run behind a user's back by a front-end in
34006 a transparent manner.
34008 The @code{server } prefix does not affect the recording of values into
34009 the value history; to print a value without recording it into the
34010 value history, use the @code{output} command instead of the
34011 @code{print} command.
34013 Using this prefix also disables confirmation requests
34014 (@pxref{confirmation requests}).
34017 @section Annotation for @value{GDBN} Input
34019 @cindex annotations for prompts
34020 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34021 to know when to send output, when the output from a given command is
34024 Different kinds of input each have a different @dfn{input type}. Each
34025 input type has three annotations: a @code{pre-} annotation, which
34026 denotes the beginning of any prompt which is being output, a plain
34027 annotation, which denotes the end of the prompt, and then a @code{post-}
34028 annotation which denotes the end of any echo which may (or may not) be
34029 associated with the input. For example, the @code{prompt} input type
34030 features the following annotations:
34038 The input types are
34041 @findex pre-prompt annotation
34042 @findex prompt annotation
34043 @findex post-prompt annotation
34045 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34047 @findex pre-commands annotation
34048 @findex commands annotation
34049 @findex post-commands annotation
34051 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34052 command. The annotations are repeated for each command which is input.
34054 @findex pre-overload-choice annotation
34055 @findex overload-choice annotation
34056 @findex post-overload-choice annotation
34057 @item overload-choice
34058 When @value{GDBN} wants the user to select between various overloaded functions.
34060 @findex pre-query annotation
34061 @findex query annotation
34062 @findex post-query annotation
34064 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34066 @findex pre-prompt-for-continue annotation
34067 @findex prompt-for-continue annotation
34068 @findex post-prompt-for-continue annotation
34069 @item prompt-for-continue
34070 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34071 expect this to work well; instead use @code{set height 0} to disable
34072 prompting. This is because the counting of lines is buggy in the
34073 presence of annotations.
34078 @cindex annotations for errors, warnings and interrupts
34080 @findex quit annotation
34085 This annotation occurs right before @value{GDBN} responds to an interrupt.
34087 @findex error annotation
34092 This annotation occurs right before @value{GDBN} responds to an error.
34094 Quit and error annotations indicate that any annotations which @value{GDBN} was
34095 in the middle of may end abruptly. For example, if a
34096 @code{value-history-begin} annotation is followed by a @code{error}, one
34097 cannot expect to receive the matching @code{value-history-end}. One
34098 cannot expect not to receive it either, however; an error annotation
34099 does not necessarily mean that @value{GDBN} is immediately returning all the way
34102 @findex error-begin annotation
34103 A quit or error annotation may be preceded by
34109 Any output between that and the quit or error annotation is the error
34112 Warning messages are not yet annotated.
34113 @c If we want to change that, need to fix warning(), type_error(),
34114 @c range_error(), and possibly other places.
34117 @section Invalidation Notices
34119 @cindex annotations for invalidation messages
34120 The following annotations say that certain pieces of state may have
34124 @findex frames-invalid annotation
34125 @item ^Z^Zframes-invalid
34127 The frames (for example, output from the @code{backtrace} command) may
34130 @findex breakpoints-invalid annotation
34131 @item ^Z^Zbreakpoints-invalid
34133 The breakpoints may have changed. For example, the user just added or
34134 deleted a breakpoint.
34137 @node Annotations for Running
34138 @section Running the Program
34139 @cindex annotations for running programs
34141 @findex starting annotation
34142 @findex stopping annotation
34143 When the program starts executing due to a @value{GDBN} command such as
34144 @code{step} or @code{continue},
34150 is output. When the program stops,
34156 is output. Before the @code{stopped} annotation, a variety of
34157 annotations describe how the program stopped.
34160 @findex exited annotation
34161 @item ^Z^Zexited @var{exit-status}
34162 The program exited, and @var{exit-status} is the exit status (zero for
34163 successful exit, otherwise nonzero).
34165 @findex signalled annotation
34166 @findex signal-name annotation
34167 @findex signal-name-end annotation
34168 @findex signal-string annotation
34169 @findex signal-string-end annotation
34170 @item ^Z^Zsignalled
34171 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34172 annotation continues:
34178 ^Z^Zsignal-name-end
34182 ^Z^Zsignal-string-end
34187 where @var{name} is the name of the signal, such as @code{SIGILL} or
34188 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34189 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34190 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34191 user's benefit and have no particular format.
34193 @findex signal annotation
34195 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34196 just saying that the program received the signal, not that it was
34197 terminated with it.
34199 @findex breakpoint annotation
34200 @item ^Z^Zbreakpoint @var{number}
34201 The program hit breakpoint number @var{number}.
34203 @findex watchpoint annotation
34204 @item ^Z^Zwatchpoint @var{number}
34205 The program hit watchpoint number @var{number}.
34208 @node Source Annotations
34209 @section Displaying Source
34210 @cindex annotations for source display
34212 @findex source annotation
34213 The following annotation is used instead of displaying source code:
34216 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34219 where @var{filename} is an absolute file name indicating which source
34220 file, @var{line} is the line number within that file (where 1 is the
34221 first line in the file), @var{character} is the character position
34222 within the file (where 0 is the first character in the file) (for most
34223 debug formats this will necessarily point to the beginning of a line),
34224 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34225 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34226 @var{addr} is the address in the target program associated with the
34227 source which is being displayed. The @var{addr} is in the form @samp{0x}
34228 followed by one or more lowercase hex digits (note that this does not
34229 depend on the language).
34231 @node JIT Interface
34232 @chapter JIT Compilation Interface
34233 @cindex just-in-time compilation
34234 @cindex JIT compilation interface
34236 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34237 interface. A JIT compiler is a program or library that generates native
34238 executable code at runtime and executes it, usually in order to achieve good
34239 performance while maintaining platform independence.
34241 Programs that use JIT compilation are normally difficult to debug because
34242 portions of their code are generated at runtime, instead of being loaded from
34243 object files, which is where @value{GDBN} normally finds the program's symbols
34244 and debug information. In order to debug programs that use JIT compilation,
34245 @value{GDBN} has an interface that allows the program to register in-memory
34246 symbol files with @value{GDBN} at runtime.
34248 If you are using @value{GDBN} to debug a program that uses this interface, then
34249 it should work transparently so long as you have not stripped the binary. If
34250 you are developing a JIT compiler, then the interface is documented in the rest
34251 of this chapter. At this time, the only known client of this interface is the
34254 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34255 JIT compiler communicates with @value{GDBN} by writing data into a global
34256 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34257 attaches, it reads a linked list of symbol files from the global variable to
34258 find existing code, and puts a breakpoint in the function so that it can find
34259 out about additional code.
34262 * Declarations:: Relevant C struct declarations
34263 * Registering Code:: Steps to register code
34264 * Unregistering Code:: Steps to unregister code
34265 * Custom Debug Info:: Emit debug information in a custom format
34269 @section JIT Declarations
34271 These are the relevant struct declarations that a C program should include to
34272 implement the interface:
34282 struct jit_code_entry
34284 struct jit_code_entry *next_entry;
34285 struct jit_code_entry *prev_entry;
34286 const char *symfile_addr;
34287 uint64_t symfile_size;
34290 struct jit_descriptor
34293 /* This type should be jit_actions_t, but we use uint32_t
34294 to be explicit about the bitwidth. */
34295 uint32_t action_flag;
34296 struct jit_code_entry *relevant_entry;
34297 struct jit_code_entry *first_entry;
34300 /* GDB puts a breakpoint in this function. */
34301 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34303 /* Make sure to specify the version statically, because the
34304 debugger may check the version before we can set it. */
34305 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34308 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34309 modifications to this global data properly, which can easily be done by putting
34310 a global mutex around modifications to these structures.
34312 @node Registering Code
34313 @section Registering Code
34315 To register code with @value{GDBN}, the JIT should follow this protocol:
34319 Generate an object file in memory with symbols and other desired debug
34320 information. The file must include the virtual addresses of the sections.
34323 Create a code entry for the file, which gives the start and size of the symbol
34327 Add it to the linked list in the JIT descriptor.
34330 Point the relevant_entry field of the descriptor at the entry.
34333 Set @code{action_flag} to @code{JIT_REGISTER} and call
34334 @code{__jit_debug_register_code}.
34337 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34338 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34339 new code. However, the linked list must still be maintained in order to allow
34340 @value{GDBN} to attach to a running process and still find the symbol files.
34342 @node Unregistering Code
34343 @section Unregistering Code
34345 If code is freed, then the JIT should use the following protocol:
34349 Remove the code entry corresponding to the code from the linked list.
34352 Point the @code{relevant_entry} field of the descriptor at the code entry.
34355 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34356 @code{__jit_debug_register_code}.
34359 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34360 and the JIT will leak the memory used for the associated symbol files.
34362 @node Custom Debug Info
34363 @section Custom Debug Info
34364 @cindex custom JIT debug info
34365 @cindex JIT debug info reader
34367 Generating debug information in platform-native file formats (like ELF
34368 or COFF) may be an overkill for JIT compilers; especially if all the
34369 debug info is used for is displaying a meaningful backtrace. The
34370 issue can be resolved by having the JIT writers decide on a debug info
34371 format and also provide a reader that parses the debug info generated
34372 by the JIT compiler. This section gives a brief overview on writing
34373 such a parser. More specific details can be found in the source file
34374 @file{gdb/jit-reader.in}, which is also installed as a header at
34375 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34377 The reader is implemented as a shared object (so this functionality is
34378 not available on platforms which don't allow loading shared objects at
34379 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34380 @code{jit-reader-unload} are provided, to be used to load and unload
34381 the readers from a preconfigured directory. Once loaded, the shared
34382 object is used the parse the debug information emitted by the JIT
34386 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34387 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34390 @node Using JIT Debug Info Readers
34391 @subsection Using JIT Debug Info Readers
34392 @kindex jit-reader-load
34393 @kindex jit-reader-unload
34395 Readers can be loaded and unloaded using the @code{jit-reader-load}
34396 and @code{jit-reader-unload} commands.
34399 @item jit-reader-load @var{reader}
34400 Load the JIT reader named @var{reader}, which is a shared
34401 object specified as either an absolute or a relative file name. In
34402 the latter case, @value{GDBN} will try to load the reader from a
34403 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34404 system (here @var{libdir} is the system library directory, often
34405 @file{/usr/local/lib}).
34407 Only one reader can be active at a time; trying to load a second
34408 reader when one is already loaded will result in @value{GDBN}
34409 reporting an error. A new JIT reader can be loaded by first unloading
34410 the current one using @code{jit-reader-unload} and then invoking
34411 @code{jit-reader-load}.
34413 @item jit-reader-unload
34414 Unload the currently loaded JIT reader.
34418 @node Writing JIT Debug Info Readers
34419 @subsection Writing JIT Debug Info Readers
34420 @cindex writing JIT debug info readers
34422 As mentioned, a reader is essentially a shared object conforming to a
34423 certain ABI. This ABI is described in @file{jit-reader.h}.
34425 @file{jit-reader.h} defines the structures, macros and functions
34426 required to write a reader. It is installed (along with
34427 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34428 the system include directory.
34430 Readers need to be released under a GPL compatible license. A reader
34431 can be declared as released under such a license by placing the macro
34432 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34434 The entry point for readers is the symbol @code{gdb_init_reader},
34435 which is expected to be a function with the prototype
34437 @findex gdb_init_reader
34439 extern struct gdb_reader_funcs *gdb_init_reader (void);
34442 @cindex @code{struct gdb_reader_funcs}
34444 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34445 functions. These functions are executed to read the debug info
34446 generated by the JIT compiler (@code{read}), to unwind stack frames
34447 (@code{unwind}) and to create canonical frame IDs
34448 (@code{get_Frame_id}). It also has a callback that is called when the
34449 reader is being unloaded (@code{destroy}). The struct looks like this
34452 struct gdb_reader_funcs
34454 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34455 int reader_version;
34457 /* For use by the reader. */
34460 gdb_read_debug_info *read;
34461 gdb_unwind_frame *unwind;
34462 gdb_get_frame_id *get_frame_id;
34463 gdb_destroy_reader *destroy;
34467 @cindex @code{struct gdb_symbol_callbacks}
34468 @cindex @code{struct gdb_unwind_callbacks}
34470 The callbacks are provided with another set of callbacks by
34471 @value{GDBN} to do their job. For @code{read}, these callbacks are
34472 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34473 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34474 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34475 files and new symbol tables inside those object files. @code{struct
34476 gdb_unwind_callbacks} has callbacks to read registers off the current
34477 frame and to write out the values of the registers in the previous
34478 frame. Both have a callback (@code{target_read}) to read bytes off the
34479 target's address space.
34481 @node In-Process Agent
34482 @chapter In-Process Agent
34483 @cindex debugging agent
34484 The traditional debugging model is conceptually low-speed, but works fine,
34485 because most bugs can be reproduced in debugging-mode execution. However,
34486 as multi-core or many-core processors are becoming mainstream, and
34487 multi-threaded programs become more and more popular, there should be more
34488 and more bugs that only manifest themselves at normal-mode execution, for
34489 example, thread races, because debugger's interference with the program's
34490 timing may conceal the bugs. On the other hand, in some applications,
34491 it is not feasible for the debugger to interrupt the program's execution
34492 long enough for the developer to learn anything helpful about its behavior.
34493 If the program's correctness depends on its real-time behavior, delays
34494 introduced by a debugger might cause the program to fail, even when the
34495 code itself is correct. It is useful to be able to observe the program's
34496 behavior without interrupting it.
34498 Therefore, traditional debugging model is too intrusive to reproduce
34499 some bugs. In order to reduce the interference with the program, we can
34500 reduce the number of operations performed by debugger. The
34501 @dfn{In-Process Agent}, a shared library, is running within the same
34502 process with inferior, and is able to perform some debugging operations
34503 itself. As a result, debugger is only involved when necessary, and
34504 performance of debugging can be improved accordingly. Note that
34505 interference with program can be reduced but can't be removed completely,
34506 because the in-process agent will still stop or slow down the program.
34508 The in-process agent can interpret and execute Agent Expressions
34509 (@pxref{Agent Expressions}) during performing debugging operations. The
34510 agent expressions can be used for different purposes, such as collecting
34511 data in tracepoints, and condition evaluation in breakpoints.
34513 @anchor{Control Agent}
34514 You can control whether the in-process agent is used as an aid for
34515 debugging with the following commands:
34518 @kindex set agent on
34520 Causes the in-process agent to perform some operations on behalf of the
34521 debugger. Just which operations requested by the user will be done
34522 by the in-process agent depends on the its capabilities. For example,
34523 if you request to evaluate breakpoint conditions in the in-process agent,
34524 and the in-process agent has such capability as well, then breakpoint
34525 conditions will be evaluated in the in-process agent.
34527 @kindex set agent off
34528 @item set agent off
34529 Disables execution of debugging operations by the in-process agent. All
34530 of the operations will be performed by @value{GDBN}.
34534 Display the current setting of execution of debugging operations by
34535 the in-process agent.
34539 * In-Process Agent Protocol::
34542 @node In-Process Agent Protocol
34543 @section In-Process Agent Protocol
34544 @cindex in-process agent protocol
34546 The in-process agent is able to communicate with both @value{GDBN} and
34547 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34548 used for communications between @value{GDBN} or GDBserver and the IPA.
34549 In general, @value{GDBN} or GDBserver sends commands
34550 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34551 in-process agent replies back with the return result of the command, or
34552 some other information. The data sent to in-process agent is composed
34553 of primitive data types, such as 4-byte or 8-byte type, and composite
34554 types, which are called objects (@pxref{IPA Protocol Objects}).
34557 * IPA Protocol Objects::
34558 * IPA Protocol Commands::
34561 @node IPA Protocol Objects
34562 @subsection IPA Protocol Objects
34563 @cindex ipa protocol objects
34565 The commands sent to and results received from agent may contain some
34566 complex data types called @dfn{objects}.
34568 The in-process agent is running on the same machine with @value{GDBN}
34569 or GDBserver, so it doesn't have to handle as much differences between
34570 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34571 However, there are still some differences of two ends in two processes:
34575 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34576 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34578 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34579 GDBserver is compiled with one, and in-process agent is compiled with
34583 Here are the IPA Protocol Objects:
34587 agent expression object. It represents an agent expression
34588 (@pxref{Agent Expressions}).
34589 @anchor{agent expression object}
34591 tracepoint action object. It represents a tracepoint action
34592 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34593 memory, static trace data and to evaluate expression.
34594 @anchor{tracepoint action object}
34596 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34597 @anchor{tracepoint object}
34601 The following table describes important attributes of each IPA protocol
34604 @multitable @columnfractions .30 .20 .50
34605 @headitem Name @tab Size @tab Description
34606 @item @emph{agent expression object} @tab @tab
34607 @item length @tab 4 @tab length of bytes code
34608 @item byte code @tab @var{length} @tab contents of byte code
34609 @item @emph{tracepoint action for collecting memory} @tab @tab
34610 @item 'M' @tab 1 @tab type of tracepoint action
34611 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34612 address of the lowest byte to collect, otherwise @var{addr} is the offset
34613 of @var{basereg} for memory collecting.
34614 @item len @tab 8 @tab length of memory for collecting
34615 @item basereg @tab 4 @tab the register number containing the starting
34616 memory address for collecting.
34617 @item @emph{tracepoint action for collecting registers} @tab @tab
34618 @item 'R' @tab 1 @tab type of tracepoint action
34619 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34620 @item 'L' @tab 1 @tab type of tracepoint action
34621 @item @emph{tracepoint action for expression evaluation} @tab @tab
34622 @item 'X' @tab 1 @tab type of tracepoint action
34623 @item agent expression @tab length of @tab @ref{agent expression object}
34624 @item @emph{tracepoint object} @tab @tab
34625 @item number @tab 4 @tab number of tracepoint
34626 @item address @tab 8 @tab address of tracepoint inserted on
34627 @item type @tab 4 @tab type of tracepoint
34628 @item enabled @tab 1 @tab enable or disable of tracepoint
34629 @item step_count @tab 8 @tab step
34630 @item pass_count @tab 8 @tab pass
34631 @item numactions @tab 4 @tab number of tracepoint actions
34632 @item hit count @tab 8 @tab hit count
34633 @item trace frame usage @tab 8 @tab trace frame usage
34634 @item compiled_cond @tab 8 @tab compiled condition
34635 @item orig_size @tab 8 @tab orig size
34636 @item condition @tab 4 if condition is NULL otherwise length of
34637 @ref{agent expression object}
34638 @tab zero if condition is NULL, otherwise is
34639 @ref{agent expression object}
34640 @item actions @tab variable
34641 @tab numactions number of @ref{tracepoint action object}
34644 @node IPA Protocol Commands
34645 @subsection IPA Protocol Commands
34646 @cindex ipa protocol commands
34648 The spaces in each command are delimiters to ease reading this commands
34649 specification. They don't exist in real commands.
34653 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34654 Installs a new fast tracepoint described by @var{tracepoint_object}
34655 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34656 head of @dfn{jumppad}, which is used to jump to data collection routine
34661 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34662 @var{target_address} is address of tracepoint in the inferior.
34663 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34664 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34665 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34666 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34673 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34674 is about to kill inferiors.
34682 @item probe_marker_at:@var{address}
34683 Asks in-process agent to probe the marker at @var{address}.
34690 @item unprobe_marker_at:@var{address}
34691 Asks in-process agent to unprobe the marker at @var{address}.
34695 @chapter Reporting Bugs in @value{GDBN}
34696 @cindex bugs in @value{GDBN}
34697 @cindex reporting bugs in @value{GDBN}
34699 Your bug reports play an essential role in making @value{GDBN} reliable.
34701 Reporting a bug may help you by bringing a solution to your problem, or it
34702 may not. But in any case the principal function of a bug report is to help
34703 the entire community by making the next version of @value{GDBN} work better. Bug
34704 reports are your contribution to the maintenance of @value{GDBN}.
34706 In order for a bug report to serve its purpose, you must include the
34707 information that enables us to fix the bug.
34710 * Bug Criteria:: Have you found a bug?
34711 * Bug Reporting:: How to report bugs
34715 @section Have You Found a Bug?
34716 @cindex bug criteria
34718 If you are not sure whether you have found a bug, here are some guidelines:
34721 @cindex fatal signal
34722 @cindex debugger crash
34723 @cindex crash of debugger
34725 If the debugger gets a fatal signal, for any input whatever, that is a
34726 @value{GDBN} bug. Reliable debuggers never crash.
34728 @cindex error on valid input
34730 If @value{GDBN} produces an error message for valid input, that is a
34731 bug. (Note that if you're cross debugging, the problem may also be
34732 somewhere in the connection to the target.)
34734 @cindex invalid input
34736 If @value{GDBN} does not produce an error message for invalid input,
34737 that is a bug. However, you should note that your idea of
34738 ``invalid input'' might be our idea of ``an extension'' or ``support
34739 for traditional practice''.
34742 If you are an experienced user of debugging tools, your suggestions
34743 for improvement of @value{GDBN} are welcome in any case.
34746 @node Bug Reporting
34747 @section How to Report Bugs
34748 @cindex bug reports
34749 @cindex @value{GDBN} bugs, reporting
34751 A number of companies and individuals offer support for @sc{gnu} products.
34752 If you obtained @value{GDBN} from a support organization, we recommend you
34753 contact that organization first.
34755 You can find contact information for many support companies and
34756 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34758 @c should add a web page ref...
34761 @ifset BUGURL_DEFAULT
34762 In any event, we also recommend that you submit bug reports for
34763 @value{GDBN}. The preferred method is to submit them directly using
34764 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34765 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34768 @strong{Do not send bug reports to @samp{info-gdb}, or to
34769 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34770 not want to receive bug reports. Those that do have arranged to receive
34773 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34774 serves as a repeater. The mailing list and the newsgroup carry exactly
34775 the same messages. Often people think of posting bug reports to the
34776 newsgroup instead of mailing them. This appears to work, but it has one
34777 problem which can be crucial: a newsgroup posting often lacks a mail
34778 path back to the sender. Thus, if we need to ask for more information,
34779 we may be unable to reach you. For this reason, it is better to send
34780 bug reports to the mailing list.
34782 @ifclear BUGURL_DEFAULT
34783 In any event, we also recommend that you submit bug reports for
34784 @value{GDBN} to @value{BUGURL}.
34788 The fundamental principle of reporting bugs usefully is this:
34789 @strong{report all the facts}. If you are not sure whether to state a
34790 fact or leave it out, state it!
34792 Often people omit facts because they think they know what causes the
34793 problem and assume that some details do not matter. Thus, you might
34794 assume that the name of the variable you use in an example does not matter.
34795 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34796 stray memory reference which happens to fetch from the location where that
34797 name is stored in memory; perhaps, if the name were different, the contents
34798 of that location would fool the debugger into doing the right thing despite
34799 the bug. Play it safe and give a specific, complete example. That is the
34800 easiest thing for you to do, and the most helpful.
34802 Keep in mind that the purpose of a bug report is to enable us to fix the
34803 bug. It may be that the bug has been reported previously, but neither
34804 you nor we can know that unless your bug report is complete and
34807 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34808 bell?'' Those bug reports are useless, and we urge everyone to
34809 @emph{refuse to respond to them} except to chide the sender to report
34812 To enable us to fix the bug, you should include all these things:
34816 The version of @value{GDBN}. @value{GDBN} announces it if you start
34817 with no arguments; you can also print it at any time using @code{show
34820 Without this, we will not know whether there is any point in looking for
34821 the bug in the current version of @value{GDBN}.
34824 The type of machine you are using, and the operating system name and
34828 The details of the @value{GDBN} build-time configuration.
34829 @value{GDBN} shows these details if you invoke it with the
34830 @option{--configuration} command-line option, or if you type
34831 @code{show configuration} at @value{GDBN}'s prompt.
34834 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34835 ``@value{GCC}--2.8.1''.
34838 What compiler (and its version) was used to compile the program you are
34839 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34840 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34841 to get this information; for other compilers, see the documentation for
34845 The command arguments you gave the compiler to compile your example and
34846 observe the bug. For example, did you use @samp{-O}? To guarantee
34847 you will not omit something important, list them all. A copy of the
34848 Makefile (or the output from make) is sufficient.
34850 If we were to try to guess the arguments, we would probably guess wrong
34851 and then we might not encounter the bug.
34854 A complete input script, and all necessary source files, that will
34858 A description of what behavior you observe that you believe is
34859 incorrect. For example, ``It gets a fatal signal.''
34861 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34862 will certainly notice it. But if the bug is incorrect output, we might
34863 not notice unless it is glaringly wrong. You might as well not give us
34864 a chance to make a mistake.
34866 Even if the problem you experience is a fatal signal, you should still
34867 say so explicitly. Suppose something strange is going on, such as, your
34868 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34869 the C library on your system. (This has happened!) Your copy might
34870 crash and ours would not. If you told us to expect a crash, then when
34871 ours fails to crash, we would know that the bug was not happening for
34872 us. If you had not told us to expect a crash, then we would not be able
34873 to draw any conclusion from our observations.
34876 @cindex recording a session script
34877 To collect all this information, you can use a session recording program
34878 such as @command{script}, which is available on many Unix systems.
34879 Just run your @value{GDBN} session inside @command{script} and then
34880 include the @file{typescript} file with your bug report.
34882 Another way to record a @value{GDBN} session is to run @value{GDBN}
34883 inside Emacs and then save the entire buffer to a file.
34886 If you wish to suggest changes to the @value{GDBN} source, send us context
34887 diffs. If you even discuss something in the @value{GDBN} source, refer to
34888 it by context, not by line number.
34890 The line numbers in our development sources will not match those in your
34891 sources. Your line numbers would convey no useful information to us.
34895 Here are some things that are not necessary:
34899 A description of the envelope of the bug.
34901 Often people who encounter a bug spend a lot of time investigating
34902 which changes to the input file will make the bug go away and which
34903 changes will not affect it.
34905 This is often time consuming and not very useful, because the way we
34906 will find the bug is by running a single example under the debugger
34907 with breakpoints, not by pure deduction from a series of examples.
34908 We recommend that you save your time for something else.
34910 Of course, if you can find a simpler example to report @emph{instead}
34911 of the original one, that is a convenience for us. Errors in the
34912 output will be easier to spot, running under the debugger will take
34913 less time, and so on.
34915 However, simplification is not vital; if you do not want to do this,
34916 report the bug anyway and send us the entire test case you used.
34919 A patch for the bug.
34921 A patch for the bug does help us if it is a good one. But do not omit
34922 the necessary information, such as the test case, on the assumption that
34923 a patch is all we need. We might see problems with your patch and decide
34924 to fix the problem another way, or we might not understand it at all.
34926 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34927 construct an example that will make the program follow a certain path
34928 through the code. If you do not send us the example, we will not be able
34929 to construct one, so we will not be able to verify that the bug is fixed.
34931 And if we cannot understand what bug you are trying to fix, or why your
34932 patch should be an improvement, we will not install it. A test case will
34933 help us to understand.
34936 A guess about what the bug is or what it depends on.
34938 Such guesses are usually wrong. Even we cannot guess right about such
34939 things without first using the debugger to find the facts.
34942 @c The readline documentation is distributed with the readline code
34943 @c and consists of the two following files:
34946 @c Use -I with makeinfo to point to the appropriate directory,
34947 @c environment var TEXINPUTS with TeX.
34948 @ifclear SYSTEM_READLINE
34949 @include rluser.texi
34950 @include hsuser.texi
34954 @appendix In Memoriam
34956 The @value{GDBN} project mourns the loss of the following long-time
34961 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34962 to Free Software in general. Outside of @value{GDBN}, he was known in
34963 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34965 @item Michael Snyder
34966 Michael was one of the Global Maintainers of the @value{GDBN} project,
34967 with contributions recorded as early as 1996, until 2011. In addition
34968 to his day to day participation, he was a large driving force behind
34969 adding Reverse Debugging to @value{GDBN}.
34972 Beyond their technical contributions to the project, they were also
34973 enjoyable members of the Free Software Community. We will miss them.
34975 @node Formatting Documentation
34976 @appendix Formatting Documentation
34978 @cindex @value{GDBN} reference card
34979 @cindex reference card
34980 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34981 for printing with PostScript or Ghostscript, in the @file{gdb}
34982 subdirectory of the main source directory@footnote{In
34983 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34984 release.}. If you can use PostScript or Ghostscript with your printer,
34985 you can print the reference card immediately with @file{refcard.ps}.
34987 The release also includes the source for the reference card. You
34988 can format it, using @TeX{}, by typing:
34994 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34995 mode on US ``letter'' size paper;
34996 that is, on a sheet 11 inches wide by 8.5 inches
34997 high. You will need to specify this form of printing as an option to
34998 your @sc{dvi} output program.
35000 @cindex documentation
35002 All the documentation for @value{GDBN} comes as part of the machine-readable
35003 distribution. The documentation is written in Texinfo format, which is
35004 a documentation system that uses a single source file to produce both
35005 on-line information and a printed manual. You can use one of the Info
35006 formatting commands to create the on-line version of the documentation
35007 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35009 @value{GDBN} includes an already formatted copy of the on-line Info
35010 version of this manual in the @file{gdb} subdirectory. The main Info
35011 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35012 subordinate files matching @samp{gdb.info*} in the same directory. If
35013 necessary, you can print out these files, or read them with any editor;
35014 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35015 Emacs or the standalone @code{info} program, available as part of the
35016 @sc{gnu} Texinfo distribution.
35018 If you want to format these Info files yourself, you need one of the
35019 Info formatting programs, such as @code{texinfo-format-buffer} or
35022 If you have @code{makeinfo} installed, and are in the top level
35023 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35024 version @value{GDBVN}), you can make the Info file by typing:
35031 If you want to typeset and print copies of this manual, you need @TeX{},
35032 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35033 Texinfo definitions file.
35035 @TeX{} is a typesetting program; it does not print files directly, but
35036 produces output files called @sc{dvi} files. To print a typeset
35037 document, you need a program to print @sc{dvi} files. If your system
35038 has @TeX{} installed, chances are it has such a program. The precise
35039 command to use depends on your system; @kbd{lpr -d} is common; another
35040 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35041 require a file name without any extension or a @samp{.dvi} extension.
35043 @TeX{} also requires a macro definitions file called
35044 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35045 written in Texinfo format. On its own, @TeX{} cannot either read or
35046 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35047 and is located in the @file{gdb-@var{version-number}/texinfo}
35050 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35051 typeset and print this manual. First switch to the @file{gdb}
35052 subdirectory of the main source directory (for example, to
35053 @file{gdb-@value{GDBVN}/gdb}) and type:
35059 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35061 @node Installing GDB
35062 @appendix Installing @value{GDBN}
35063 @cindex installation
35066 * Requirements:: Requirements for building @value{GDBN}
35067 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35068 * Separate Objdir:: Compiling @value{GDBN} in another directory
35069 * Config Names:: Specifying names for hosts and targets
35070 * Configure Options:: Summary of options for configure
35071 * System-wide configuration:: Having a system-wide init file
35075 @section Requirements for Building @value{GDBN}
35076 @cindex building @value{GDBN}, requirements for
35078 Building @value{GDBN} requires various tools and packages to be available.
35079 Other packages will be used only if they are found.
35081 @heading Tools/Packages Necessary for Building @value{GDBN}
35083 @item ISO C90 compiler
35084 @value{GDBN} is written in ISO C90. It should be buildable with any
35085 working C90 compiler, e.g.@: GCC.
35089 @heading Tools/Packages Optional for Building @value{GDBN}
35093 @value{GDBN} can use the Expat XML parsing library. This library may be
35094 included with your operating system distribution; if it is not, you
35095 can get the latest version from @url{http://expat.sourceforge.net}.
35096 The @file{configure} script will search for this library in several
35097 standard locations; if it is installed in an unusual path, you can
35098 use the @option{--with-libexpat-prefix} option to specify its location.
35104 Remote protocol memory maps (@pxref{Memory Map Format})
35106 Target descriptions (@pxref{Target Descriptions})
35108 Remote shared library lists (@xref{Library List Format},
35109 or alternatively @pxref{Library List Format for SVR4 Targets})
35111 MS-Windows shared libraries (@pxref{Shared Libraries})
35113 Traceframe info (@pxref{Traceframe Info Format})
35115 Branch trace (@pxref{Branch Trace Format},
35116 @pxref{Branch Trace Configuration Format})
35121 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35122 library. This library may be included with your operating system
35123 distribution; if it is not, you can get the latest version from
35124 @url{http://www.mpfr.org}. The @file{configure} script will search
35125 for this library in several standard locations; if it is installed
35126 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35127 option to specify its location.
35129 GNU MPFR is used to emulate target floating-point arithmetic during
35130 expression evaluation when the target uses different floating-point
35131 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35132 will fall back to using host floating-point arithmetic.
35135 @cindex compressed debug sections
35136 @value{GDBN} will use the @samp{zlib} library, if available, to read
35137 compressed debug sections. Some linkers, such as GNU gold, are capable
35138 of producing binaries with compressed debug sections. If @value{GDBN}
35139 is compiled with @samp{zlib}, it will be able to read the debug
35140 information in such binaries.
35142 The @samp{zlib} library is likely included with your operating system
35143 distribution; if it is not, you can get the latest version from
35144 @url{http://zlib.net}.
35147 @value{GDBN}'s features related to character sets (@pxref{Character
35148 Sets}) require a functioning @code{iconv} implementation. If you are
35149 on a GNU system, then this is provided by the GNU C Library. Some
35150 other systems also provide a working @code{iconv}.
35152 If @value{GDBN} is using the @code{iconv} program which is installed
35153 in a non-standard place, you will need to tell @value{GDBN} where to find it.
35154 This is done with @option{--with-iconv-bin} which specifies the
35155 directory that contains the @code{iconv} program.
35157 On systems without @code{iconv}, you can install GNU Libiconv. If you
35158 have previously installed Libiconv, you can use the
35159 @option{--with-libiconv-prefix} option to configure.
35161 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35162 arrange to build Libiconv if a directory named @file{libiconv} appears
35163 in the top-most source directory. If Libiconv is built this way, and
35164 if the operating system does not provide a suitable @code{iconv}
35165 implementation, then the just-built library will automatically be used
35166 by @value{GDBN}. One easy way to set this up is to download GNU
35167 Libiconv, unpack it, and then rename the directory holding the
35168 Libiconv source code to @samp{libiconv}.
35171 @node Running Configure
35172 @section Invoking the @value{GDBN} @file{configure} Script
35173 @cindex configuring @value{GDBN}
35174 @value{GDBN} comes with a @file{configure} script that automates the process
35175 of preparing @value{GDBN} for installation; you can then use @code{make} to
35176 build the @code{gdb} program.
35178 @c irrelevant in info file; it's as current as the code it lives with.
35179 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35180 look at the @file{README} file in the sources; we may have improved the
35181 installation procedures since publishing this manual.}
35184 The @value{GDBN} distribution includes all the source code you need for
35185 @value{GDBN} in a single directory, whose name is usually composed by
35186 appending the version number to @samp{gdb}.
35188 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35189 @file{gdb-@value{GDBVN}} directory. That directory contains:
35192 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35193 script for configuring @value{GDBN} and all its supporting libraries
35195 @item gdb-@value{GDBVN}/gdb
35196 the source specific to @value{GDBN} itself
35198 @item gdb-@value{GDBVN}/bfd
35199 source for the Binary File Descriptor library
35201 @item gdb-@value{GDBVN}/include
35202 @sc{gnu} include files
35204 @item gdb-@value{GDBVN}/libiberty
35205 source for the @samp{-liberty} free software library
35207 @item gdb-@value{GDBVN}/opcodes
35208 source for the library of opcode tables and disassemblers
35210 @item gdb-@value{GDBVN}/readline
35211 source for the @sc{gnu} command-line interface
35213 @item gdb-@value{GDBVN}/glob
35214 source for the @sc{gnu} filename pattern-matching subroutine
35216 @item gdb-@value{GDBVN}/mmalloc
35217 source for the @sc{gnu} memory-mapped malloc package
35220 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35221 from the @file{gdb-@var{version-number}} source directory, which in
35222 this example is the @file{gdb-@value{GDBVN}} directory.
35224 First switch to the @file{gdb-@var{version-number}} source directory
35225 if you are not already in it; then run @file{configure}. Pass the
35226 identifier for the platform on which @value{GDBN} will run as an
35232 cd gdb-@value{GDBVN}
35233 ./configure @var{host}
35238 where @var{host} is an identifier such as @samp{sun4} or
35239 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35240 (You can often leave off @var{host}; @file{configure} tries to guess the
35241 correct value by examining your system.)
35243 Running @samp{configure @var{host}} and then running @code{make} builds the
35244 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35245 libraries, then @code{gdb} itself. The configured source files, and the
35246 binaries, are left in the corresponding source directories.
35249 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35250 system does not recognize this automatically when you run a different
35251 shell, you may need to run @code{sh} on it explicitly:
35254 sh configure @var{host}
35257 If you run @file{configure} from a directory that contains source
35258 directories for multiple libraries or programs, such as the
35259 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35261 creates configuration files for every directory level underneath (unless
35262 you tell it not to, with the @samp{--norecursion} option).
35264 You should run the @file{configure} script from the top directory in the
35265 source tree, the @file{gdb-@var{version-number}} directory. If you run
35266 @file{configure} from one of the subdirectories, you will configure only
35267 that subdirectory. That is usually not what you want. In particular,
35268 if you run the first @file{configure} from the @file{gdb} subdirectory
35269 of the @file{gdb-@var{version-number}} directory, you will omit the
35270 configuration of @file{bfd}, @file{readline}, and other sibling
35271 directories of the @file{gdb} subdirectory. This leads to build errors
35272 about missing include files such as @file{bfd/bfd.h}.
35274 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35275 However, you should make sure that the shell on your path (named by
35276 the @samp{SHELL} environment variable) is publicly readable. Remember
35277 that @value{GDBN} uses the shell to start your program---some systems refuse to
35278 let @value{GDBN} debug child processes whose programs are not readable.
35280 @node Separate Objdir
35281 @section Compiling @value{GDBN} in Another Directory
35283 If you want to run @value{GDBN} versions for several host or target machines,
35284 you need a different @code{gdb} compiled for each combination of
35285 host and target. @file{configure} is designed to make this easy by
35286 allowing you to generate each configuration in a separate subdirectory,
35287 rather than in the source directory. If your @code{make} program
35288 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35289 @code{make} in each of these directories builds the @code{gdb}
35290 program specified there.
35292 To build @code{gdb} in a separate directory, run @file{configure}
35293 with the @samp{--srcdir} option to specify where to find the source.
35294 (You also need to specify a path to find @file{configure}
35295 itself from your working directory. If the path to @file{configure}
35296 would be the same as the argument to @samp{--srcdir}, you can leave out
35297 the @samp{--srcdir} option; it is assumed.)
35299 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35300 separate directory for a Sun 4 like this:
35304 cd gdb-@value{GDBVN}
35307 ../gdb-@value{GDBVN}/configure sun4
35312 When @file{configure} builds a configuration using a remote source
35313 directory, it creates a tree for the binaries with the same structure
35314 (and using the same names) as the tree under the source directory. In
35315 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35316 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35317 @file{gdb-sun4/gdb}.
35319 Make sure that your path to the @file{configure} script has just one
35320 instance of @file{gdb} in it. If your path to @file{configure} looks
35321 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35322 one subdirectory of @value{GDBN}, not the whole package. This leads to
35323 build errors about missing include files such as @file{bfd/bfd.h}.
35325 One popular reason to build several @value{GDBN} configurations in separate
35326 directories is to configure @value{GDBN} for cross-compiling (where
35327 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35328 programs that run on another machine---the @dfn{target}).
35329 You specify a cross-debugging target by
35330 giving the @samp{--target=@var{target}} option to @file{configure}.
35332 When you run @code{make} to build a program or library, you must run
35333 it in a configured directory---whatever directory you were in when you
35334 called @file{configure} (or one of its subdirectories).
35336 The @code{Makefile} that @file{configure} generates in each source
35337 directory also runs recursively. If you type @code{make} in a source
35338 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35339 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35340 will build all the required libraries, and then build GDB.
35342 When you have multiple hosts or targets configured in separate
35343 directories, you can run @code{make} on them in parallel (for example,
35344 if they are NFS-mounted on each of the hosts); they will not interfere
35348 @section Specifying Names for Hosts and Targets
35350 The specifications used for hosts and targets in the @file{configure}
35351 script are based on a three-part naming scheme, but some short predefined
35352 aliases are also supported. The full naming scheme encodes three pieces
35353 of information in the following pattern:
35356 @var{architecture}-@var{vendor}-@var{os}
35359 For example, you can use the alias @code{sun4} as a @var{host} argument,
35360 or as the value for @var{target} in a @code{--target=@var{target}}
35361 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35363 The @file{configure} script accompanying @value{GDBN} does not provide
35364 any query facility to list all supported host and target names or
35365 aliases. @file{configure} calls the Bourne shell script
35366 @code{config.sub} to map abbreviations to full names; you can read the
35367 script, if you wish, or you can use it to test your guesses on
35368 abbreviations---for example:
35371 % sh config.sub i386-linux
35373 % sh config.sub alpha-linux
35374 alpha-unknown-linux-gnu
35375 % sh config.sub hp9k700
35377 % sh config.sub sun4
35378 sparc-sun-sunos4.1.1
35379 % sh config.sub sun3
35380 m68k-sun-sunos4.1.1
35381 % sh config.sub i986v
35382 Invalid configuration `i986v': machine `i986v' not recognized
35386 @code{config.sub} is also distributed in the @value{GDBN} source
35387 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35389 @node Configure Options
35390 @section @file{configure} Options
35392 Here is a summary of the @file{configure} options and arguments that
35393 are most often useful for building @value{GDBN}. @file{configure} also has
35394 several other options not listed here. @inforef{What Configure
35395 Does,,configure.info}, for a full explanation of @file{configure}.
35398 configure @r{[}--help@r{]}
35399 @r{[}--prefix=@var{dir}@r{]}
35400 @r{[}--exec-prefix=@var{dir}@r{]}
35401 @r{[}--srcdir=@var{dirname}@r{]}
35402 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35403 @r{[}--target=@var{target}@r{]}
35408 You may introduce options with a single @samp{-} rather than
35409 @samp{--} if you prefer; but you may abbreviate option names if you use
35414 Display a quick summary of how to invoke @file{configure}.
35416 @item --prefix=@var{dir}
35417 Configure the source to install programs and files under directory
35420 @item --exec-prefix=@var{dir}
35421 Configure the source to install programs under directory
35424 @c avoid splitting the warning from the explanation:
35426 @item --srcdir=@var{dirname}
35427 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35428 @code{make} that implements the @code{VPATH} feature.}@*
35429 Use this option to make configurations in directories separate from the
35430 @value{GDBN} source directories. Among other things, you can use this to
35431 build (or maintain) several configurations simultaneously, in separate
35432 directories. @file{configure} writes configuration-specific files in
35433 the current directory, but arranges for them to use the source in the
35434 directory @var{dirname}. @file{configure} creates directories under
35435 the working directory in parallel to the source directories below
35438 @item --norecursion
35439 Configure only the directory level where @file{configure} is executed; do not
35440 propagate configuration to subdirectories.
35442 @item --target=@var{target}
35443 Configure @value{GDBN} for cross-debugging programs running on the specified
35444 @var{target}. Without this option, @value{GDBN} is configured to debug
35445 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35447 There is no convenient way to generate a list of all available targets.
35449 @item @var{host} @dots{}
35450 Configure @value{GDBN} to run on the specified @var{host}.
35452 There is no convenient way to generate a list of all available hosts.
35455 There are many other options available as well, but they are generally
35456 needed for special purposes only.
35458 @node System-wide configuration
35459 @section System-wide configuration and settings
35460 @cindex system-wide init file
35462 @value{GDBN} can be configured to have a system-wide init file;
35463 this file will be read and executed at startup (@pxref{Startup, , What
35464 @value{GDBN} does during startup}).
35466 Here is the corresponding configure option:
35469 @item --with-system-gdbinit=@var{file}
35470 Specify that the default location of the system-wide init file is
35474 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35475 it may be subject to relocation. Two possible cases:
35479 If the default location of this init file contains @file{$prefix},
35480 it will be subject to relocation. Suppose that the configure options
35481 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35482 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35483 init file is looked for as @file{$install/etc/gdbinit} instead of
35484 @file{$prefix/etc/gdbinit}.
35487 By contrast, if the default location does not contain the prefix,
35488 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35489 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35490 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35491 wherever @value{GDBN} is installed.
35494 If the configured location of the system-wide init file (as given by the
35495 @option{--with-system-gdbinit} option at configure time) is in the
35496 data-directory (as specified by @option{--with-gdb-datadir} at configure
35497 time) or in one of its subdirectories, then @value{GDBN} will look for the
35498 system-wide init file in the directory specified by the
35499 @option{--data-directory} command-line option.
35500 Note that the system-wide init file is only read once, during @value{GDBN}
35501 initialization. If the data-directory is changed after @value{GDBN} has
35502 started with the @code{set data-directory} command, the file will not be
35506 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35509 @node System-wide Configuration Scripts
35510 @subsection Installed System-wide Configuration Scripts
35511 @cindex system-wide configuration scripts
35513 The @file{system-gdbinit} directory, located inside the data-directory
35514 (as specified by @option{--with-gdb-datadir} at configure time) contains
35515 a number of scripts which can be used as system-wide init files. To
35516 automatically source those scripts at startup, @value{GDBN} should be
35517 configured with @option{--with-system-gdbinit}. Otherwise, any user
35518 should be able to source them by hand as needed.
35520 The following scripts are currently available:
35523 @item @file{elinos.py}
35525 @cindex ELinOS system-wide configuration script
35526 This script is useful when debugging a program on an ELinOS target.
35527 It takes advantage of the environment variables defined in a standard
35528 ELinOS environment in order to determine the location of the system
35529 shared libraries, and then sets the @samp{solib-absolute-prefix}
35530 and @samp{solib-search-path} variables appropriately.
35532 @item @file{wrs-linux.py}
35533 @pindex wrs-linux.py
35534 @cindex Wind River Linux system-wide configuration script
35535 This script is useful when debugging a program on a target running
35536 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35537 the host-side sysroot used by the target system.
35541 @node Maintenance Commands
35542 @appendix Maintenance Commands
35543 @cindex maintenance commands
35544 @cindex internal commands
35546 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35547 includes a number of commands intended for @value{GDBN} developers,
35548 that are not documented elsewhere in this manual. These commands are
35549 provided here for reference. (For commands that turn on debugging
35550 messages, see @ref{Debugging Output}.)
35553 @kindex maint agent
35554 @kindex maint agent-eval
35555 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35556 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35557 Translate the given @var{expression} into remote agent bytecodes.
35558 This command is useful for debugging the Agent Expression mechanism
35559 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35560 expression useful for data collection, such as by tracepoints, while
35561 @samp{maint agent-eval} produces an expression that evaluates directly
35562 to a result. For instance, a collection expression for @code{globa +
35563 globb} will include bytecodes to record four bytes of memory at each
35564 of the addresses of @code{globa} and @code{globb}, while discarding
35565 the result of the addition, while an evaluation expression will do the
35566 addition and return the sum.
35567 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35568 If not, generate remote agent bytecode for current frame PC address.
35570 @kindex maint agent-printf
35571 @item maint agent-printf @var{format},@var{expr},...
35572 Translate the given format string and list of argument expressions
35573 into remote agent bytecodes and display them as a disassembled list.
35574 This command is useful for debugging the agent version of dynamic
35575 printf (@pxref{Dynamic Printf}).
35577 @kindex maint info breakpoints
35578 @item @anchor{maint info breakpoints}maint info breakpoints
35579 Using the same format as @samp{info breakpoints}, display both the
35580 breakpoints you've set explicitly, and those @value{GDBN} is using for
35581 internal purposes. Internal breakpoints are shown with negative
35582 breakpoint numbers. The type column identifies what kind of breakpoint
35587 Normal, explicitly set breakpoint.
35590 Normal, explicitly set watchpoint.
35593 Internal breakpoint, used to handle correctly stepping through
35594 @code{longjmp} calls.
35596 @item longjmp resume
35597 Internal breakpoint at the target of a @code{longjmp}.
35600 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35603 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35606 Shared library events.
35610 @kindex maint info btrace
35611 @item maint info btrace
35612 Pint information about raw branch tracing data.
35614 @kindex maint btrace packet-history
35615 @item maint btrace packet-history
35616 Print the raw branch trace packets that are used to compute the
35617 execution history for the @samp{record btrace} command. Both the
35618 information and the format in which it is printed depend on the btrace
35623 For the BTS recording format, print a list of blocks of sequential
35624 code. For each block, the following information is printed:
35628 Newer blocks have higher numbers. The oldest block has number zero.
35629 @item Lowest @samp{PC}
35630 @item Highest @samp{PC}
35634 For the Intel Processor Trace recording format, print a list of
35635 Intel Processor Trace packets. For each packet, the following
35636 information is printed:
35639 @item Packet number
35640 Newer packets have higher numbers. The oldest packet has number zero.
35642 The packet's offset in the trace stream.
35643 @item Packet opcode and payload
35647 @kindex maint btrace clear-packet-history
35648 @item maint btrace clear-packet-history
35649 Discards the cached packet history printed by the @samp{maint btrace
35650 packet-history} command. The history will be computed again when
35653 @kindex maint btrace clear
35654 @item maint btrace clear
35655 Discard the branch trace data. The data will be fetched anew and the
35656 branch trace will be recomputed when needed.
35658 This implicitly truncates the branch trace to a single branch trace
35659 buffer. When updating branch trace incrementally, the branch trace
35660 available to @value{GDBN} may be bigger than a single branch trace
35663 @kindex maint set btrace pt skip-pad
35664 @item maint set btrace pt skip-pad
35665 @kindex maint show btrace pt skip-pad
35666 @item maint show btrace pt skip-pad
35667 Control whether @value{GDBN} will skip PAD packets when computing the
35670 @kindex set displaced-stepping
35671 @kindex show displaced-stepping
35672 @cindex displaced stepping support
35673 @cindex out-of-line single-stepping
35674 @item set displaced-stepping
35675 @itemx show displaced-stepping
35676 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35677 if the target supports it. Displaced stepping is a way to single-step
35678 over breakpoints without removing them from the inferior, by executing
35679 an out-of-line copy of the instruction that was originally at the
35680 breakpoint location. It is also known as out-of-line single-stepping.
35683 @item set displaced-stepping on
35684 If the target architecture supports it, @value{GDBN} will use
35685 displaced stepping to step over breakpoints.
35687 @item set displaced-stepping off
35688 @value{GDBN} will not use displaced stepping to step over breakpoints,
35689 even if such is supported by the target architecture.
35691 @cindex non-stop mode, and @samp{set displaced-stepping}
35692 @item set displaced-stepping auto
35693 This is the default mode. @value{GDBN} will use displaced stepping
35694 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35695 architecture supports displaced stepping.
35698 @kindex maint check-psymtabs
35699 @item maint check-psymtabs
35700 Check the consistency of currently expanded psymtabs versus symtabs.
35701 Use this to check, for example, whether a symbol is in one but not the other.
35703 @kindex maint check-symtabs
35704 @item maint check-symtabs
35705 Check the consistency of currently expanded symtabs.
35707 @kindex maint expand-symtabs
35708 @item maint expand-symtabs [@var{regexp}]
35709 Expand symbol tables.
35710 If @var{regexp} is specified, only expand symbol tables for file
35711 names matching @var{regexp}.
35713 @kindex maint set catch-demangler-crashes
35714 @kindex maint show catch-demangler-crashes
35715 @cindex demangler crashes
35716 @item maint set catch-demangler-crashes [on|off]
35717 @itemx maint show catch-demangler-crashes
35718 Control whether @value{GDBN} should attempt to catch crashes in the
35719 symbol name demangler. The default is to attempt to catch crashes.
35720 If enabled, the first time a crash is caught, a core file is created,
35721 the offending symbol is displayed and the user is presented with the
35722 option to terminate the current session.
35724 @kindex maint cplus first_component
35725 @item maint cplus first_component @var{name}
35726 Print the first C@t{++} class/namespace component of @var{name}.
35728 @kindex maint cplus namespace
35729 @item maint cplus namespace
35730 Print the list of possible C@t{++} namespaces.
35732 @kindex maint deprecate
35733 @kindex maint undeprecate
35734 @cindex deprecated commands
35735 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35736 @itemx maint undeprecate @var{command}
35737 Deprecate or undeprecate the named @var{command}. Deprecated commands
35738 cause @value{GDBN} to issue a warning when you use them. The optional
35739 argument @var{replacement} says which newer command should be used in
35740 favor of the deprecated one; if it is given, @value{GDBN} will mention
35741 the replacement as part of the warning.
35743 @kindex maint dump-me
35744 @item maint dump-me
35745 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35746 Cause a fatal signal in the debugger and force it to dump its core.
35747 This is supported only on systems which support aborting a program
35748 with the @code{SIGQUIT} signal.
35750 @kindex maint internal-error
35751 @kindex maint internal-warning
35752 @kindex maint demangler-warning
35753 @cindex demangler crashes
35754 @item maint internal-error @r{[}@var{message-text}@r{]}
35755 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35756 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35758 Cause @value{GDBN} to call the internal function @code{internal_error},
35759 @code{internal_warning} or @code{demangler_warning} and hence behave
35760 as though an internal problem has been detected. In addition to
35761 reporting the internal problem, these functions give the user the
35762 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35763 and @code{internal_warning}) create a core file of the current
35764 @value{GDBN} session.
35766 These commands take an optional parameter @var{message-text} that is
35767 used as the text of the error or warning message.
35769 Here's an example of using @code{internal-error}:
35772 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35773 @dots{}/maint.c:121: internal-error: testing, 1, 2
35774 A problem internal to GDB has been detected. Further
35775 debugging may prove unreliable.
35776 Quit this debugging session? (y or n) @kbd{n}
35777 Create a core file? (y or n) @kbd{n}
35781 @cindex @value{GDBN} internal error
35782 @cindex internal errors, control of @value{GDBN} behavior
35783 @cindex demangler crashes
35785 @kindex maint set internal-error
35786 @kindex maint show internal-error
35787 @kindex maint set internal-warning
35788 @kindex maint show internal-warning
35789 @kindex maint set demangler-warning
35790 @kindex maint show demangler-warning
35791 @item maint set internal-error @var{action} [ask|yes|no]
35792 @itemx maint show internal-error @var{action}
35793 @itemx maint set internal-warning @var{action} [ask|yes|no]
35794 @itemx maint show internal-warning @var{action}
35795 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35796 @itemx maint show demangler-warning @var{action}
35797 When @value{GDBN} reports an internal problem (error or warning) it
35798 gives the user the opportunity to both quit @value{GDBN} and create a
35799 core file of the current @value{GDBN} session. These commands let you
35800 override the default behaviour for each particular @var{action},
35801 described in the table below.
35805 You can specify that @value{GDBN} should always (yes) or never (no)
35806 quit. The default is to ask the user what to do.
35809 You can specify that @value{GDBN} should always (yes) or never (no)
35810 create a core file. The default is to ask the user what to do. Note
35811 that there is no @code{corefile} option for @code{demangler-warning}:
35812 demangler warnings always create a core file and this cannot be
35816 @kindex maint packet
35817 @item maint packet @var{text}
35818 If @value{GDBN} is talking to an inferior via the serial protocol,
35819 then this command sends the string @var{text} to the inferior, and
35820 displays the response packet. @value{GDBN} supplies the initial
35821 @samp{$} character, the terminating @samp{#} character, and the
35824 @kindex maint print architecture
35825 @item maint print architecture @r{[}@var{file}@r{]}
35826 Print the entire architecture configuration. The optional argument
35827 @var{file} names the file where the output goes.
35829 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35830 @item maint print c-tdesc
35831 Print the target description (@pxref{Target Descriptions}) as
35832 a C source file. By default, the target description is for the current
35833 target, but if the optional argument @var{file} is provided, that file
35834 is used to produce the description. The @var{file} should be an XML
35835 document, of the form described in @ref{Target Description Format}.
35836 The created source file is built into @value{GDBN} when @value{GDBN} is
35837 built again. This command is used by developers after they add or
35838 modify XML target descriptions.
35840 @kindex maint check xml-descriptions
35841 @item maint check xml-descriptions @var{dir}
35842 Check that the target descriptions dynamically created by @value{GDBN}
35843 equal the descriptions created from XML files found in @var{dir}.
35845 @anchor{maint check libthread-db}
35846 @kindex maint check libthread-db
35847 @item maint check libthread-db
35848 Run integrity checks on the current inferior's thread debugging
35849 library. This exercises all @code{libthread_db} functionality used by
35850 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
35851 @code{proc_service} functions provided by @value{GDBN} that
35852 @code{libthread_db} uses. Note that parts of the test may be skipped
35853 on some platforms when debugging core files.
35855 @kindex maint print dummy-frames
35856 @item maint print dummy-frames
35857 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35860 (@value{GDBP}) @kbd{b add}
35862 (@value{GDBP}) @kbd{print add(2,3)}
35863 Breakpoint 2, add (a=2, b=3) at @dots{}
35865 The program being debugged stopped while in a function called from GDB.
35867 (@value{GDBP}) @kbd{maint print dummy-frames}
35868 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35872 Takes an optional file parameter.
35874 @kindex maint print registers
35875 @kindex maint print raw-registers
35876 @kindex maint print cooked-registers
35877 @kindex maint print register-groups
35878 @kindex maint print remote-registers
35879 @item maint print registers @r{[}@var{file}@r{]}
35880 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35881 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35882 @itemx maint print register-groups @r{[}@var{file}@r{]}
35883 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35884 Print @value{GDBN}'s internal register data structures.
35886 The command @code{maint print raw-registers} includes the contents of
35887 the raw register cache; the command @code{maint print
35888 cooked-registers} includes the (cooked) value of all registers,
35889 including registers which aren't available on the target nor visible
35890 to user; the command @code{maint print register-groups} includes the
35891 groups that each register is a member of; and the command @code{maint
35892 print remote-registers} includes the remote target's register numbers
35893 and offsets in the `G' packets.
35895 These commands take an optional parameter, a file name to which to
35896 write the information.
35898 @kindex maint print reggroups
35899 @item maint print reggroups @r{[}@var{file}@r{]}
35900 Print @value{GDBN}'s internal register group data structures. The
35901 optional argument @var{file} tells to what file to write the
35904 The register groups info looks like this:
35907 (@value{GDBP}) @kbd{maint print reggroups}
35920 This command forces @value{GDBN} to flush its internal register cache.
35922 @kindex maint print objfiles
35923 @cindex info for known object files
35924 @item maint print objfiles @r{[}@var{regexp}@r{]}
35925 Print a dump of all known object files.
35926 If @var{regexp} is specified, only print object files whose names
35927 match @var{regexp}. For each object file, this command prints its name,
35928 address in memory, and all of its psymtabs and symtabs.
35930 @kindex maint print user-registers
35931 @cindex user registers
35932 @item maint print user-registers
35933 List all currently available @dfn{user registers}. User registers
35934 typically provide alternate names for actual hardware registers. They
35935 include the four ``standard'' registers @code{$fp}, @code{$pc},
35936 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35937 registers can be used in expressions in the same way as the canonical
35938 register names, but only the latter are listed by the @code{info
35939 registers} and @code{maint print registers} commands.
35941 @kindex maint print section-scripts
35942 @cindex info for known .debug_gdb_scripts-loaded scripts
35943 @item maint print section-scripts [@var{regexp}]
35944 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35945 If @var{regexp} is specified, only print scripts loaded by object files
35946 matching @var{regexp}.
35947 For each script, this command prints its name as specified in the objfile,
35948 and the full path if known.
35949 @xref{dotdebug_gdb_scripts section}.
35951 @kindex maint print statistics
35952 @cindex bcache statistics
35953 @item maint print statistics
35954 This command prints, for each object file in the program, various data
35955 about that object file followed by the byte cache (@dfn{bcache})
35956 statistics for the object file. The objfile data includes the number
35957 of minimal, partial, full, and stabs symbols, the number of types
35958 defined by the objfile, the number of as yet unexpanded psym tables,
35959 the number of line tables and string tables, and the amount of memory
35960 used by the various tables. The bcache statistics include the counts,
35961 sizes, and counts of duplicates of all and unique objects, max,
35962 average, and median entry size, total memory used and its overhead and
35963 savings, and various measures of the hash table size and chain
35966 @kindex maint print target-stack
35967 @cindex target stack description
35968 @item maint print target-stack
35969 A @dfn{target} is an interface between the debugger and a particular
35970 kind of file or process. Targets can be stacked in @dfn{strata},
35971 so that more than one target can potentially respond to a request.
35972 In particular, memory accesses will walk down the stack of targets
35973 until they find a target that is interested in handling that particular
35976 This command prints a short description of each layer that was pushed on
35977 the @dfn{target stack}, starting from the top layer down to the bottom one.
35979 @kindex maint print type
35980 @cindex type chain of a data type
35981 @item maint print type @var{expr}
35982 Print the type chain for a type specified by @var{expr}. The argument
35983 can be either a type name or a symbol. If it is a symbol, the type of
35984 that symbol is described. The type chain produced by this command is
35985 a recursive definition of the data type as stored in @value{GDBN}'s
35986 data structures, including its flags and contained types.
35988 @kindex maint selftest
35990 @item maint selftest @r{[}@var{filter}@r{]}
35991 Run any self tests that were compiled in to @value{GDBN}. This will
35992 print a message showing how many tests were run, and how many failed.
35993 If a @var{filter} is passed, only the tests with @var{filter} in their
35996 @kindex "maint info selftests"
35998 @item maint info selftests
35999 List the selftests compiled in to @value{GDBN}.
36001 @kindex maint set dwarf always-disassemble
36002 @kindex maint show dwarf always-disassemble
36003 @item maint set dwarf always-disassemble
36004 @item maint show dwarf always-disassemble
36005 Control the behavior of @code{info address} when using DWARF debugging
36008 The default is @code{off}, which means that @value{GDBN} should try to
36009 describe a variable's location in an easily readable format. When
36010 @code{on}, @value{GDBN} will instead display the DWARF location
36011 expression in an assembly-like format. Note that some locations are
36012 too complex for @value{GDBN} to describe simply; in this case you will
36013 always see the disassembly form.
36015 Here is an example of the resulting disassembly:
36018 (gdb) info addr argc
36019 Symbol "argc" is a complex DWARF expression:
36023 For more information on these expressions, see
36024 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36026 @kindex maint set dwarf max-cache-age
36027 @kindex maint show dwarf max-cache-age
36028 @item maint set dwarf max-cache-age
36029 @itemx maint show dwarf max-cache-age
36030 Control the DWARF compilation unit cache.
36032 @cindex DWARF compilation units cache
36033 In object files with inter-compilation-unit references, such as those
36034 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36035 reader needs to frequently refer to previously read compilation units.
36036 This setting controls how long a compilation unit will remain in the
36037 cache if it is not referenced. A higher limit means that cached
36038 compilation units will be stored in memory longer, and more total
36039 memory will be used. Setting it to zero disables caching, which will
36040 slow down @value{GDBN} startup, but reduce memory consumption.
36042 @kindex maint set dwarf unwinders
36043 @kindex maint show dwarf unwinders
36044 @item maint set dwarf unwinders
36045 @itemx maint show dwarf unwinders
36046 Control use of the DWARF frame unwinders.
36048 @cindex DWARF frame unwinders
36049 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36050 frame unwinders to build the backtrace. Many of these targets will
36051 also have a second mechanism for building the backtrace for use in
36052 cases where DWARF information is not available, this second mechanism
36053 is often an analysis of a function's prologue.
36055 In order to extend testing coverage of the second level stack
36056 unwinding mechanisms it is helpful to be able to disable the DWARF
36057 stack unwinders, this can be done with this switch.
36059 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36060 advisable, there are cases that are better handled through DWARF than
36061 prologue analysis, and the debug experience is likely to be better
36062 with the DWARF frame unwinders enabled.
36064 If DWARF frame unwinders are not supported for a particular target
36065 architecture, then enabling this flag does not cause them to be used.
36066 @kindex maint set profile
36067 @kindex maint show profile
36068 @cindex profiling GDB
36069 @item maint set profile
36070 @itemx maint show profile
36071 Control profiling of @value{GDBN}.
36073 Profiling will be disabled until you use the @samp{maint set profile}
36074 command to enable it. When you enable profiling, the system will begin
36075 collecting timing and execution count data; when you disable profiling or
36076 exit @value{GDBN}, the results will be written to a log file. Remember that
36077 if you use profiling, @value{GDBN} will overwrite the profiling log file
36078 (often called @file{gmon.out}). If you have a record of important profiling
36079 data in a @file{gmon.out} file, be sure to move it to a safe location.
36081 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36082 compiled with the @samp{-pg} compiler option.
36084 @kindex maint set show-debug-regs
36085 @kindex maint show show-debug-regs
36086 @cindex hardware debug registers
36087 @item maint set show-debug-regs
36088 @itemx maint show show-debug-regs
36089 Control whether to show variables that mirror the hardware debug
36090 registers. Use @code{on} to enable, @code{off} to disable. If
36091 enabled, the debug registers values are shown when @value{GDBN} inserts or
36092 removes a hardware breakpoint or watchpoint, and when the inferior
36093 triggers a hardware-assisted breakpoint or watchpoint.
36095 @kindex maint set show-all-tib
36096 @kindex maint show show-all-tib
36097 @item maint set show-all-tib
36098 @itemx maint show show-all-tib
36099 Control whether to show all non zero areas within a 1k block starting
36100 at thread local base, when using the @samp{info w32 thread-information-block}
36103 @kindex maint set target-async
36104 @kindex maint show target-async
36105 @item maint set target-async
36106 @itemx maint show target-async
36107 This controls whether @value{GDBN} targets operate in synchronous or
36108 asynchronous mode (@pxref{Background Execution}). Normally the
36109 default is asynchronous, if it is available; but this can be changed
36110 to more easily debug problems occurring only in synchronous mode.
36112 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36113 @kindex maint show target-non-stop
36114 @item maint set target-non-stop
36115 @itemx maint show target-non-stop
36117 This controls whether @value{GDBN} targets always operate in non-stop
36118 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36119 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36120 if supported by the target.
36123 @item maint set target-non-stop auto
36124 This is the default mode. @value{GDBN} controls the target in
36125 non-stop mode if the target supports it.
36127 @item maint set target-non-stop on
36128 @value{GDBN} controls the target in non-stop mode even if the target
36129 does not indicate support.
36131 @item maint set target-non-stop off
36132 @value{GDBN} does not control the target in non-stop mode even if the
36133 target supports it.
36136 @kindex maint set per-command
36137 @kindex maint show per-command
36138 @item maint set per-command
36139 @itemx maint show per-command
36140 @cindex resources used by commands
36142 @value{GDBN} can display the resources used by each command.
36143 This is useful in debugging performance problems.
36146 @item maint set per-command space [on|off]
36147 @itemx maint show per-command space
36148 Enable or disable the printing of the memory used by GDB for each command.
36149 If enabled, @value{GDBN} will display how much memory each command
36150 took, following the command's own output.
36151 This can also be requested by invoking @value{GDBN} with the
36152 @option{--statistics} command-line switch (@pxref{Mode Options}).
36154 @item maint set per-command time [on|off]
36155 @itemx maint show per-command time
36156 Enable or disable the printing of the execution time of @value{GDBN}
36158 If enabled, @value{GDBN} will display how much time it
36159 took to execute each command, following the command's own output.
36160 Both CPU time and wallclock time are printed.
36161 Printing both is useful when trying to determine whether the cost is
36162 CPU or, e.g., disk/network latency.
36163 Note that the CPU time printed is for @value{GDBN} only, it does not include
36164 the execution time of the inferior because there's no mechanism currently
36165 to compute how much time was spent by @value{GDBN} and how much time was
36166 spent by the program been debugged.
36167 This can also be requested by invoking @value{GDBN} with the
36168 @option{--statistics} command-line switch (@pxref{Mode Options}).
36170 @item maint set per-command symtab [on|off]
36171 @itemx maint show per-command symtab
36172 Enable or disable the printing of basic symbol table statistics
36174 If enabled, @value{GDBN} will display the following information:
36178 number of symbol tables
36180 number of primary symbol tables
36182 number of blocks in the blockvector
36186 @kindex maint set check-libthread-db
36187 @kindex maint show check-libthread-db
36188 @item maint set check-libthread-db [on|off]
36189 @itemx maint show check-libthread-db
36190 Control whether @value{GDBN} should run integrity checks on inferior
36191 specific thread debugging libraries as they are loaded. The default
36192 is not to perform such checks. If any check fails @value{GDBN} will
36193 unload the library and continue searching for a suitable candidate as
36194 described in @ref{set libthread-db-search-path}. For more information
36195 about the tests, see @ref{maint check libthread-db}.
36197 @kindex maint space
36198 @cindex memory used by commands
36199 @item maint space @var{value}
36200 An alias for @code{maint set per-command space}.
36201 A non-zero value enables it, zero disables it.
36204 @cindex time of command execution
36205 @item maint time @var{value}
36206 An alias for @code{maint set per-command time}.
36207 A non-zero value enables it, zero disables it.
36209 @kindex maint translate-address
36210 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36211 Find the symbol stored at the location specified by the address
36212 @var{addr} and an optional section name @var{section}. If found,
36213 @value{GDBN} prints the name of the closest symbol and an offset from
36214 the symbol's location to the specified address. This is similar to
36215 the @code{info address} command (@pxref{Symbols}), except that this
36216 command also allows to find symbols in other sections.
36218 If section was not specified, the section in which the symbol was found
36219 is also printed. For dynamically linked executables, the name of
36220 executable or shared library containing the symbol is printed as well.
36224 The following command is useful for non-interactive invocations of
36225 @value{GDBN}, such as in the test suite.
36228 @item set watchdog @var{nsec}
36229 @kindex set watchdog
36230 @cindex watchdog timer
36231 @cindex timeout for commands
36232 Set the maximum number of seconds @value{GDBN} will wait for the
36233 target operation to finish. If this time expires, @value{GDBN}
36234 reports and error and the command is aborted.
36236 @item show watchdog
36237 Show the current setting of the target wait timeout.
36240 @node Remote Protocol
36241 @appendix @value{GDBN} Remote Serial Protocol
36246 * Stop Reply Packets::
36247 * General Query Packets::
36248 * Architecture-Specific Protocol Details::
36249 * Tracepoint Packets::
36250 * Host I/O Packets::
36252 * Notification Packets::
36253 * Remote Non-Stop::
36254 * Packet Acknowledgment::
36256 * File-I/O Remote Protocol Extension::
36257 * Library List Format::
36258 * Library List Format for SVR4 Targets::
36259 * Memory Map Format::
36260 * Thread List Format::
36261 * Traceframe Info Format::
36262 * Branch Trace Format::
36263 * Branch Trace Configuration Format::
36269 There may be occasions when you need to know something about the
36270 protocol---for example, if there is only one serial port to your target
36271 machine, you might want your program to do something special if it
36272 recognizes a packet meant for @value{GDBN}.
36274 In the examples below, @samp{->} and @samp{<-} are used to indicate
36275 transmitted and received data, respectively.
36277 @cindex protocol, @value{GDBN} remote serial
36278 @cindex serial protocol, @value{GDBN} remote
36279 @cindex remote serial protocol
36280 All @value{GDBN} commands and responses (other than acknowledgments
36281 and notifications, see @ref{Notification Packets}) are sent as a
36282 @var{packet}. A @var{packet} is introduced with the character
36283 @samp{$}, the actual @var{packet-data}, and the terminating character
36284 @samp{#} followed by a two-digit @var{checksum}:
36287 @code{$}@var{packet-data}@code{#}@var{checksum}
36291 @cindex checksum, for @value{GDBN} remote
36293 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36294 characters between the leading @samp{$} and the trailing @samp{#} (an
36295 eight bit unsigned checksum).
36297 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36298 specification also included an optional two-digit @var{sequence-id}:
36301 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36304 @cindex sequence-id, for @value{GDBN} remote
36306 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36307 has never output @var{sequence-id}s. Stubs that handle packets added
36308 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36310 When either the host or the target machine receives a packet, the first
36311 response expected is an acknowledgment: either @samp{+} (to indicate
36312 the package was received correctly) or @samp{-} (to request
36316 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36321 The @samp{+}/@samp{-} acknowledgments can be disabled
36322 once a connection is established.
36323 @xref{Packet Acknowledgment}, for details.
36325 The host (@value{GDBN}) sends @var{command}s, and the target (the
36326 debugging stub incorporated in your program) sends a @var{response}. In
36327 the case of step and continue @var{command}s, the response is only sent
36328 when the operation has completed, and the target has again stopped all
36329 threads in all attached processes. This is the default all-stop mode
36330 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36331 execution mode; see @ref{Remote Non-Stop}, for details.
36333 @var{packet-data} consists of a sequence of characters with the
36334 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
36337 @cindex remote protocol, field separator
36338 Fields within the packet should be separated using @samp{,} @samp{;} or
36339 @samp{:}. Except where otherwise noted all numbers are represented in
36340 @sc{hex} with leading zeros suppressed.
36342 Implementors should note that prior to @value{GDBN} 5.0, the character
36343 @samp{:} could not appear as the third character in a packet (as it
36344 would potentially conflict with the @var{sequence-id}).
36346 @cindex remote protocol, binary data
36347 @anchor{Binary Data}
36348 Binary data in most packets is encoded either as two hexadecimal
36349 digits per byte of binary data. This allowed the traditional remote
36350 protocol to work over connections which were only seven-bit clean.
36351 Some packets designed more recently assume an eight-bit clean
36352 connection, and use a more efficient encoding to send and receive
36355 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36356 as an escape character. Any escaped byte is transmitted as the escape
36357 character followed by the original character XORed with @code{0x20}.
36358 For example, the byte @code{0x7d} would be transmitted as the two
36359 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36360 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36361 @samp{@}}) must always be escaped. Responses sent by the stub
36362 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36363 is not interpreted as the start of a run-length encoded sequence
36366 Response @var{data} can be run-length encoded to save space.
36367 Run-length encoding replaces runs of identical characters with one
36368 instance of the repeated character, followed by a @samp{*} and a
36369 repeat count. The repeat count is itself sent encoded, to avoid
36370 binary characters in @var{data}: a value of @var{n} is sent as
36371 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36372 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36373 code 32) for a repeat count of 3. (This is because run-length
36374 encoding starts to win for counts 3 or more.) Thus, for example,
36375 @samp{0* } is a run-length encoding of ``0000'': the space character
36376 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36379 The printable characters @samp{#} and @samp{$} or with a numeric value
36380 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36381 seven repeats (@samp{$}) can be expanded using a repeat count of only
36382 five (@samp{"}). For example, @samp{00000000} can be encoded as
36385 The error response returned for some packets includes a two character
36386 error number. That number is not well defined.
36388 @cindex empty response, for unsupported packets
36389 For any @var{command} not supported by the stub, an empty response
36390 (@samp{$#00}) should be returned. That way it is possible to extend the
36391 protocol. A newer @value{GDBN} can tell if a packet is supported based
36394 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36395 commands for register access, and the @samp{m} and @samp{M} commands
36396 for memory access. Stubs that only control single-threaded targets
36397 can implement run control with the @samp{c} (continue), and @samp{s}
36398 (step) commands. Stubs that support multi-threading targets should
36399 support the @samp{vCont} command. All other commands are optional.
36404 The following table provides a complete list of all currently defined
36405 @var{command}s and their corresponding response @var{data}.
36406 @xref{File-I/O Remote Protocol Extension}, for details about the File
36407 I/O extension of the remote protocol.
36409 Each packet's description has a template showing the packet's overall
36410 syntax, followed by an explanation of the packet's meaning. We
36411 include spaces in some of the templates for clarity; these are not
36412 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36413 separate its components. For example, a template like @samp{foo
36414 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36415 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36416 @var{baz}. @value{GDBN} does not transmit a space character between the
36417 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36420 @cindex @var{thread-id}, in remote protocol
36421 @anchor{thread-id syntax}
36422 Several packets and replies include a @var{thread-id} field to identify
36423 a thread. Normally these are positive numbers with a target-specific
36424 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36425 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36428 In addition, the remote protocol supports a multiprocess feature in
36429 which the @var{thread-id} syntax is extended to optionally include both
36430 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36431 The @var{pid} (process) and @var{tid} (thread) components each have the
36432 format described above: a positive number with target-specific
36433 interpretation formatted as a big-endian hex string, literal @samp{-1}
36434 to indicate all processes or threads (respectively), or @samp{0} to
36435 indicate an arbitrary process or thread. Specifying just a process, as
36436 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36437 error to specify all processes but a specific thread, such as
36438 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36439 for those packets and replies explicitly documented to include a process
36440 ID, rather than a @var{thread-id}.
36442 The multiprocess @var{thread-id} syntax extensions are only used if both
36443 @value{GDBN} and the stub report support for the @samp{multiprocess}
36444 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36447 Note that all packet forms beginning with an upper- or lower-case
36448 letter, other than those described here, are reserved for future use.
36450 Here are the packet descriptions.
36455 @cindex @samp{!} packet
36456 @anchor{extended mode}
36457 Enable extended mode. In extended mode, the remote server is made
36458 persistent. The @samp{R} packet is used to restart the program being
36464 The remote target both supports and has enabled extended mode.
36468 @cindex @samp{?} packet
36470 Indicate the reason the target halted. The reply is the same as for
36471 step and continue. This packet has a special interpretation when the
36472 target is in non-stop mode; see @ref{Remote Non-Stop}.
36475 @xref{Stop Reply Packets}, for the reply specifications.
36477 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36478 @cindex @samp{A} packet
36479 Initialized @code{argv[]} array passed into program. @var{arglen}
36480 specifies the number of bytes in the hex encoded byte stream
36481 @var{arg}. See @code{gdbserver} for more details.
36486 The arguments were set.
36492 @cindex @samp{b} packet
36493 (Don't use this packet; its behavior is not well-defined.)
36494 Change the serial line speed to @var{baud}.
36496 JTC: @emph{When does the transport layer state change? When it's
36497 received, or after the ACK is transmitted. In either case, there are
36498 problems if the command or the acknowledgment packet is dropped.}
36500 Stan: @emph{If people really wanted to add something like this, and get
36501 it working for the first time, they ought to modify ser-unix.c to send
36502 some kind of out-of-band message to a specially-setup stub and have the
36503 switch happen "in between" packets, so that from remote protocol's point
36504 of view, nothing actually happened.}
36506 @item B @var{addr},@var{mode}
36507 @cindex @samp{B} packet
36508 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36509 breakpoint at @var{addr}.
36511 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36512 (@pxref{insert breakpoint or watchpoint packet}).
36514 @cindex @samp{bc} packet
36517 Backward continue. Execute the target system in reverse. No parameter.
36518 @xref{Reverse Execution}, for more information.
36521 @xref{Stop Reply Packets}, for the reply specifications.
36523 @cindex @samp{bs} packet
36526 Backward single step. Execute one instruction in reverse. No parameter.
36527 @xref{Reverse Execution}, for more information.
36530 @xref{Stop Reply Packets}, for the reply specifications.
36532 @item c @r{[}@var{addr}@r{]}
36533 @cindex @samp{c} packet
36534 Continue at @var{addr}, which is the address to resume. If @var{addr}
36535 is omitted, resume at current address.
36537 This packet is deprecated for multi-threading support. @xref{vCont
36541 @xref{Stop Reply Packets}, for the reply specifications.
36543 @item C @var{sig}@r{[};@var{addr}@r{]}
36544 @cindex @samp{C} packet
36545 Continue with signal @var{sig} (hex signal number). If
36546 @samp{;@var{addr}} is omitted, resume at same address.
36548 This packet is deprecated for multi-threading support. @xref{vCont
36552 @xref{Stop Reply Packets}, for the reply specifications.
36555 @cindex @samp{d} packet
36558 Don't use this packet; instead, define a general set packet
36559 (@pxref{General Query Packets}).
36563 @cindex @samp{D} packet
36564 The first form of the packet is used to detach @value{GDBN} from the
36565 remote system. It is sent to the remote target
36566 before @value{GDBN} disconnects via the @code{detach} command.
36568 The second form, including a process ID, is used when multiprocess
36569 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36570 detach only a specific process. The @var{pid} is specified as a
36571 big-endian hex string.
36581 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36582 @cindex @samp{F} packet
36583 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36584 This is part of the File-I/O protocol extension. @xref{File-I/O
36585 Remote Protocol Extension}, for the specification.
36588 @anchor{read registers packet}
36589 @cindex @samp{g} packet
36590 Read general registers.
36594 @item @var{XX@dots{}}
36595 Each byte of register data is described by two hex digits. The bytes
36596 with the register are transmitted in target byte order. The size of
36597 each register and their position within the @samp{g} packet are
36598 determined by the @value{GDBN} internal gdbarch functions
36599 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36601 When reading registers from a trace frame (@pxref{Analyze Collected
36602 Data,,Using the Collected Data}), the stub may also return a string of
36603 literal @samp{x}'s in place of the register data digits, to indicate
36604 that the corresponding register has not been collected, thus its value
36605 is unavailable. For example, for an architecture with 4 registers of
36606 4 bytes each, the following reply indicates to @value{GDBN} that
36607 registers 0 and 2 have not been collected, while registers 1 and 3
36608 have been collected, and both have zero value:
36612 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36619 @item G @var{XX@dots{}}
36620 @cindex @samp{G} packet
36621 Write general registers. @xref{read registers packet}, for a
36622 description of the @var{XX@dots{}} data.
36632 @item H @var{op} @var{thread-id}
36633 @cindex @samp{H} packet
36634 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36635 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36636 should be @samp{c} for step and continue operations (note that this
36637 is deprecated, supporting the @samp{vCont} command is a better
36638 option), and @samp{g} for other operations. The thread designator
36639 @var{thread-id} has the format and interpretation described in
36640 @ref{thread-id syntax}.
36651 @c 'H': How restrictive (or permissive) is the thread model. If a
36652 @c thread is selected and stopped, are other threads allowed
36653 @c to continue to execute? As I mentioned above, I think the
36654 @c semantics of each command when a thread is selected must be
36655 @c described. For example:
36657 @c 'g': If the stub supports threads and a specific thread is
36658 @c selected, returns the register block from that thread;
36659 @c otherwise returns current registers.
36661 @c 'G' If the stub supports threads and a specific thread is
36662 @c selected, sets the registers of the register block of
36663 @c that thread; otherwise sets current registers.
36665 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36666 @anchor{cycle step packet}
36667 @cindex @samp{i} packet
36668 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36669 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36670 step starting at that address.
36673 @cindex @samp{I} packet
36674 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36678 @cindex @samp{k} packet
36681 The exact effect of this packet is not specified.
36683 For a bare-metal target, it may power cycle or reset the target
36684 system. For that reason, the @samp{k} packet has no reply.
36686 For a single-process target, it may kill that process if possible.
36688 A multiple-process target may choose to kill just one process, or all
36689 that are under @value{GDBN}'s control. For more precise control, use
36690 the vKill packet (@pxref{vKill packet}).
36692 If the target system immediately closes the connection in response to
36693 @samp{k}, @value{GDBN} does not consider the lack of packet
36694 acknowledgment to be an error, and assumes the kill was successful.
36696 If connected using @kbd{target extended-remote}, and the target does
36697 not close the connection in response to a kill request, @value{GDBN}
36698 probes the target state as if a new connection was opened
36699 (@pxref{? packet}).
36701 @item m @var{addr},@var{length}
36702 @cindex @samp{m} packet
36703 Read @var{length} addressable memory units starting at address @var{addr}
36704 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36705 any particular boundary.
36707 The stub need not use any particular size or alignment when gathering
36708 data from memory for the response; even if @var{addr} is word-aligned
36709 and @var{length} is a multiple of the word size, the stub is free to
36710 use byte accesses, or not. For this reason, this packet may not be
36711 suitable for accessing memory-mapped I/O devices.
36712 @cindex alignment of remote memory accesses
36713 @cindex size of remote memory accesses
36714 @cindex memory, alignment and size of remote accesses
36718 @item @var{XX@dots{}}
36719 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36720 The reply may contain fewer addressable memory units than requested if the
36721 server was able to read only part of the region of memory.
36726 @item M @var{addr},@var{length}:@var{XX@dots{}}
36727 @cindex @samp{M} packet
36728 Write @var{length} addressable memory units starting at address @var{addr}
36729 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36730 byte is transmitted as a two-digit hexadecimal number.
36737 for an error (this includes the case where only part of the data was
36742 @cindex @samp{p} packet
36743 Read the value of register @var{n}; @var{n} is in hex.
36744 @xref{read registers packet}, for a description of how the returned
36745 register value is encoded.
36749 @item @var{XX@dots{}}
36750 the register's value
36754 Indicating an unrecognized @var{query}.
36757 @item P @var{n@dots{}}=@var{r@dots{}}
36758 @anchor{write register packet}
36759 @cindex @samp{P} packet
36760 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36761 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36762 digits for each byte in the register (target byte order).
36772 @item q @var{name} @var{params}@dots{}
36773 @itemx Q @var{name} @var{params}@dots{}
36774 @cindex @samp{q} packet
36775 @cindex @samp{Q} packet
36776 General query (@samp{q}) and set (@samp{Q}). These packets are
36777 described fully in @ref{General Query Packets}.
36780 @cindex @samp{r} packet
36781 Reset the entire system.
36783 Don't use this packet; use the @samp{R} packet instead.
36786 @cindex @samp{R} packet
36787 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36788 This packet is only available in extended mode (@pxref{extended mode}).
36790 The @samp{R} packet has no reply.
36792 @item s @r{[}@var{addr}@r{]}
36793 @cindex @samp{s} packet
36794 Single step, resuming at @var{addr}. If
36795 @var{addr} is omitted, resume at same address.
36797 This packet is deprecated for multi-threading support. @xref{vCont
36801 @xref{Stop Reply Packets}, for the reply specifications.
36803 @item S @var{sig}@r{[};@var{addr}@r{]}
36804 @anchor{step with signal packet}
36805 @cindex @samp{S} packet
36806 Step with signal. This is analogous to the @samp{C} packet, but
36807 requests a single-step, rather than a normal resumption of execution.
36809 This packet is deprecated for multi-threading support. @xref{vCont
36813 @xref{Stop Reply Packets}, for the reply specifications.
36815 @item t @var{addr}:@var{PP},@var{MM}
36816 @cindex @samp{t} packet
36817 Search backwards starting at address @var{addr} for a match with pattern
36818 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36819 There must be at least 3 digits in @var{addr}.
36821 @item T @var{thread-id}
36822 @cindex @samp{T} packet
36823 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36828 thread is still alive
36834 Packets starting with @samp{v} are identified by a multi-letter name,
36835 up to the first @samp{;} or @samp{?} (or the end of the packet).
36837 @item vAttach;@var{pid}
36838 @cindex @samp{vAttach} packet
36839 Attach to a new process with the specified process ID @var{pid}.
36840 The process ID is a
36841 hexadecimal integer identifying the process. In all-stop mode, all
36842 threads in the attached process are stopped; in non-stop mode, it may be
36843 attached without being stopped if that is supported by the target.
36845 @c In non-stop mode, on a successful vAttach, the stub should set the
36846 @c current thread to a thread of the newly-attached process. After
36847 @c attaching, GDB queries for the attached process's thread ID with qC.
36848 @c Also note that, from a user perspective, whether or not the
36849 @c target is stopped on attach in non-stop mode depends on whether you
36850 @c use the foreground or background version of the attach command, not
36851 @c on what vAttach does; GDB does the right thing with respect to either
36852 @c stopping or restarting threads.
36854 This packet is only available in extended mode (@pxref{extended mode}).
36860 @item @r{Any stop packet}
36861 for success in all-stop mode (@pxref{Stop Reply Packets})
36863 for success in non-stop mode (@pxref{Remote Non-Stop})
36866 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36867 @cindex @samp{vCont} packet
36868 @anchor{vCont packet}
36869 Resume the inferior, specifying different actions for each thread.
36871 For each inferior thread, the leftmost action with a matching
36872 @var{thread-id} is applied. Threads that don't match any action
36873 remain in their current state. Thread IDs are specified using the
36874 syntax described in @ref{thread-id syntax}. If multiprocess
36875 extensions (@pxref{multiprocess extensions}) are supported, actions
36876 can be specified to match all threads in a process by using the
36877 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36878 @var{thread-id} matches all threads. Specifying no actions is an
36881 Currently supported actions are:
36887 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36891 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36894 @item r @var{start},@var{end}
36895 Step once, and then keep stepping as long as the thread stops at
36896 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36897 The remote stub reports a stop reply when either the thread goes out
36898 of the range or is stopped due to an unrelated reason, such as hitting
36899 a breakpoint. @xref{range stepping}.
36901 If the range is empty (@var{start} == @var{end}), then the action
36902 becomes equivalent to the @samp{s} action. In other words,
36903 single-step once, and report the stop (even if the stepped instruction
36904 jumps to @var{start}).
36906 (A stop reply may be sent at any point even if the PC is still within
36907 the stepping range; for example, it is valid to implement this packet
36908 in a degenerate way as a single instruction step operation.)
36912 The optional argument @var{addr} normally associated with the
36913 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36914 not supported in @samp{vCont}.
36916 The @samp{t} action is only relevant in non-stop mode
36917 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36918 A stop reply should be generated for any affected thread not already stopped.
36919 When a thread is stopped by means of a @samp{t} action,
36920 the corresponding stop reply should indicate that the thread has stopped with
36921 signal @samp{0}, regardless of whether the target uses some other signal
36922 as an implementation detail.
36924 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36925 @samp{r} actions for threads that are already running. Conversely,
36926 the server must ignore @samp{t} actions for threads that are already
36929 @emph{Note:} In non-stop mode, a thread is considered running until
36930 @value{GDBN} acknowleges an asynchronous stop notification for it with
36931 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36933 The stub must support @samp{vCont} if it reports support for
36934 multiprocess extensions (@pxref{multiprocess extensions}).
36937 @xref{Stop Reply Packets}, for the reply specifications.
36940 @cindex @samp{vCont?} packet
36941 Request a list of actions supported by the @samp{vCont} packet.
36945 @item vCont@r{[};@var{action}@dots{}@r{]}
36946 The @samp{vCont} packet is supported. Each @var{action} is a supported
36947 command in the @samp{vCont} packet.
36949 The @samp{vCont} packet is not supported.
36952 @anchor{vCtrlC packet}
36954 @cindex @samp{vCtrlC} packet
36955 Interrupt remote target as if a control-C was pressed on the remote
36956 terminal. This is the equivalent to reacting to the @code{^C}
36957 (@samp{\003}, the control-C character) character in all-stop mode
36958 while the target is running, except this works in non-stop mode.
36959 @xref{interrupting remote targets}, for more info on the all-stop
36970 @item vFile:@var{operation}:@var{parameter}@dots{}
36971 @cindex @samp{vFile} packet
36972 Perform a file operation on the target system. For details,
36973 see @ref{Host I/O Packets}.
36975 @item vFlashErase:@var{addr},@var{length}
36976 @cindex @samp{vFlashErase} packet
36977 Direct the stub to erase @var{length} bytes of flash starting at
36978 @var{addr}. The region may enclose any number of flash blocks, but
36979 its start and end must fall on block boundaries, as indicated by the
36980 flash block size appearing in the memory map (@pxref{Memory Map
36981 Format}). @value{GDBN} groups flash memory programming operations
36982 together, and sends a @samp{vFlashDone} request after each group; the
36983 stub is allowed to delay erase operation until the @samp{vFlashDone}
36984 packet is received.
36994 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36995 @cindex @samp{vFlashWrite} packet
36996 Direct the stub to write data to flash address @var{addr}. The data
36997 is passed in binary form using the same encoding as for the @samp{X}
36998 packet (@pxref{Binary Data}). The memory ranges specified by
36999 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37000 not overlap, and must appear in order of increasing addresses
37001 (although @samp{vFlashErase} packets for higher addresses may already
37002 have been received; the ordering is guaranteed only between
37003 @samp{vFlashWrite} packets). If a packet writes to an address that was
37004 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37005 target-specific method, the results are unpredictable.
37013 for vFlashWrite addressing non-flash memory
37019 @cindex @samp{vFlashDone} packet
37020 Indicate to the stub that flash programming operation is finished.
37021 The stub is permitted to delay or batch the effects of a group of
37022 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37023 @samp{vFlashDone} packet is received. The contents of the affected
37024 regions of flash memory are unpredictable until the @samp{vFlashDone}
37025 request is completed.
37027 @item vKill;@var{pid}
37028 @cindex @samp{vKill} packet
37029 @anchor{vKill packet}
37030 Kill the process with the specified process ID @var{pid}, which is a
37031 hexadecimal integer identifying the process. This packet is used in
37032 preference to @samp{k} when multiprocess protocol extensions are
37033 supported; see @ref{multiprocess extensions}.
37043 @item vMustReplyEmpty
37044 @cindex @samp{vMustReplyEmpty} packet
37045 The correct reply to an unknown @samp{v} packet is to return the empty
37046 string, however, some older versions of @command{gdbserver} would
37047 incorrectly return @samp{OK} for unknown @samp{v} packets.
37049 The @samp{vMustReplyEmpty} is used as a feature test to check how
37050 @command{gdbserver} handles unknown packets, it is important that this
37051 packet be handled in the same way as other unknown @samp{v} packets.
37052 If this packet is handled differently to other unknown @samp{v}
37053 packets then it is possile that @value{GDBN} may run into problems in
37054 other areas, specifically around use of @samp{vFile:setfs:}.
37056 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37057 @cindex @samp{vRun} packet
37058 Run the program @var{filename}, passing it each @var{argument} on its
37059 command line. The file and arguments are hex-encoded strings. If
37060 @var{filename} is an empty string, the stub may use a default program
37061 (e.g.@: the last program run). The program is created in the stopped
37064 @c FIXME: What about non-stop mode?
37066 This packet is only available in extended mode (@pxref{extended mode}).
37072 @item @r{Any stop packet}
37073 for success (@pxref{Stop Reply Packets})
37077 @cindex @samp{vStopped} packet
37078 @xref{Notification Packets}.
37080 @item X @var{addr},@var{length}:@var{XX@dots{}}
37082 @cindex @samp{X} packet
37083 Write data to memory, where the data is transmitted in binary.
37084 Memory is specified by its address @var{addr} and number of addressable memory
37085 units @var{length} (@pxref{addressable memory unit});
37086 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37096 @item z @var{type},@var{addr},@var{kind}
37097 @itemx Z @var{type},@var{addr},@var{kind}
37098 @anchor{insert breakpoint or watchpoint packet}
37099 @cindex @samp{z} packet
37100 @cindex @samp{Z} packets
37101 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37102 watchpoint starting at address @var{address} of kind @var{kind}.
37104 Each breakpoint and watchpoint packet @var{type} is documented
37107 @emph{Implementation notes: A remote target shall return an empty string
37108 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37109 remote target shall support either both or neither of a given
37110 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37111 avoid potential problems with duplicate packets, the operations should
37112 be implemented in an idempotent way.}
37114 @item z0,@var{addr},@var{kind}
37115 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37116 @cindex @samp{z0} packet
37117 @cindex @samp{Z0} packet
37118 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37119 @var{addr} of type @var{kind}.
37121 A software breakpoint is implemented by replacing the instruction at
37122 @var{addr} with a software breakpoint or trap instruction. The
37123 @var{kind} is target-specific and typically indicates the size of the
37124 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37125 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37126 architectures have additional meanings for @var{kind}
37127 (@pxref{Architecture-Specific Protocol Details}); if no
37128 architecture-specific value is being used, it should be @samp{0}.
37129 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37130 conditional expressions in bytecode form that should be evaluated on
37131 the target's side. These are the conditions that should be taken into
37132 consideration when deciding if the breakpoint trigger should be
37133 reported back to @value{GDBN}.
37135 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37136 for how to best report a software breakpoint event to @value{GDBN}.
37138 The @var{cond_list} parameter is comprised of a series of expressions,
37139 concatenated without separators. Each expression has the following form:
37143 @item X @var{len},@var{expr}
37144 @var{len} is the length of the bytecode expression and @var{expr} is the
37145 actual conditional expression in bytecode form.
37149 The optional @var{cmd_list} parameter introduces commands that may be
37150 run on the target, rather than being reported back to @value{GDBN}.
37151 The parameter starts with a numeric flag @var{persist}; if the flag is
37152 nonzero, then the breakpoint may remain active and the commands
37153 continue to be run even when @value{GDBN} disconnects from the target.
37154 Following this flag is a series of expressions concatenated with no
37155 separators. Each expression has the following form:
37159 @item X @var{len},@var{expr}
37160 @var{len} is the length of the bytecode expression and @var{expr} is the
37161 actual commands expression in bytecode form.
37165 @emph{Implementation note: It is possible for a target to copy or move
37166 code that contains software breakpoints (e.g., when implementing
37167 overlays). The behavior of this packet, in the presence of such a
37168 target, is not defined.}
37180 @item z1,@var{addr},@var{kind}
37181 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37182 @cindex @samp{z1} packet
37183 @cindex @samp{Z1} packet
37184 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37185 address @var{addr}.
37187 A hardware breakpoint is implemented using a mechanism that is not
37188 dependent on being able to modify the target's memory. The
37189 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37190 same meaning as in @samp{Z0} packets.
37192 @emph{Implementation note: A hardware breakpoint is not affected by code
37205 @item z2,@var{addr},@var{kind}
37206 @itemx Z2,@var{addr},@var{kind}
37207 @cindex @samp{z2} packet
37208 @cindex @samp{Z2} packet
37209 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37210 The number of bytes to watch is specified by @var{kind}.
37222 @item z3,@var{addr},@var{kind}
37223 @itemx Z3,@var{addr},@var{kind}
37224 @cindex @samp{z3} packet
37225 @cindex @samp{Z3} packet
37226 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37227 The number of bytes to watch is specified by @var{kind}.
37239 @item z4,@var{addr},@var{kind}
37240 @itemx Z4,@var{addr},@var{kind}
37241 @cindex @samp{z4} packet
37242 @cindex @samp{Z4} packet
37243 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37244 The number of bytes to watch is specified by @var{kind}.
37258 @node Stop Reply Packets
37259 @section Stop Reply Packets
37260 @cindex stop reply packets
37262 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37263 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37264 receive any of the below as a reply. Except for @samp{?}
37265 and @samp{vStopped}, that reply is only returned
37266 when the target halts. In the below the exact meaning of @dfn{signal
37267 number} is defined by the header @file{include/gdb/signals.h} in the
37268 @value{GDBN} source code.
37270 In non-stop mode, the server will simply reply @samp{OK} to commands
37271 such as @samp{vCont}; any stop will be the subject of a future
37272 notification. @xref{Remote Non-Stop}.
37274 As in the description of request packets, we include spaces in the
37275 reply templates for clarity; these are not part of the reply packet's
37276 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37282 The program received signal number @var{AA} (a two-digit hexadecimal
37283 number). This is equivalent to a @samp{T} response with no
37284 @var{n}:@var{r} pairs.
37286 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37287 @cindex @samp{T} packet reply
37288 The program received signal number @var{AA} (a two-digit hexadecimal
37289 number). This is equivalent to an @samp{S} response, except that the
37290 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37291 and other information directly in the stop reply packet, reducing
37292 round-trip latency. Single-step and breakpoint traps are reported
37293 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37297 If @var{n} is a hexadecimal number, it is a register number, and the
37298 corresponding @var{r} gives that register's value. The data @var{r} is a
37299 series of bytes in target byte order, with each byte given by a
37300 two-digit hex number.
37303 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37304 the stopped thread, as specified in @ref{thread-id syntax}.
37307 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37308 the core on which the stop event was detected.
37311 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37312 specific event that stopped the target. The currently defined stop
37313 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37314 signal. At most one stop reason should be present.
37317 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37318 and go on to the next; this allows us to extend the protocol in the
37322 The currently defined stop reasons are:
37328 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37331 @item syscall_entry
37332 @itemx syscall_return
37333 The packet indicates a syscall entry or return, and @var{r} is the
37334 syscall number, in hex.
37336 @cindex shared library events, remote reply
37338 The packet indicates that the loaded libraries have changed.
37339 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
37340 list of loaded libraries. The @var{r} part is ignored.
37342 @cindex replay log events, remote reply
37344 The packet indicates that the target cannot continue replaying
37345 logged execution events, because it has reached the end (or the
37346 beginning when executing backward) of the log. The value of @var{r}
37347 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
37348 for more information.
37351 @anchor{swbreak stop reason}
37352 The packet indicates a software breakpoint instruction was executed,
37353 irrespective of whether it was @value{GDBN} that planted the
37354 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37355 part must be left empty.
37357 On some architectures, such as x86, at the architecture level, when a
37358 breakpoint instruction executes the program counter points at the
37359 breakpoint address plus an offset. On such targets, the stub is
37360 responsible for adjusting the PC to point back at the breakpoint
37363 This packet should not be sent by default; older @value{GDBN} versions
37364 did not support it. @value{GDBN} requests it, by supplying an
37365 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37366 remote stub must also supply the appropriate @samp{qSupported} feature
37367 indicating support.
37369 This packet is required for correct non-stop mode operation.
37372 The packet indicates the target stopped for a hardware breakpoint.
37373 The @var{r} part must be left empty.
37375 The same remarks about @samp{qSupported} and non-stop mode above
37378 @cindex fork events, remote reply
37380 The packet indicates that @code{fork} was called, and @var{r}
37381 is the thread ID of the new child process. Refer to
37382 @ref{thread-id syntax} for the format of the @var{thread-id}
37383 field. This packet is only applicable to targets that support
37386 This packet should not be sent by default; older @value{GDBN} versions
37387 did not support it. @value{GDBN} requests it, by supplying an
37388 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37389 remote stub must also supply the appropriate @samp{qSupported} feature
37390 indicating support.
37392 @cindex vfork events, remote reply
37394 The packet indicates that @code{vfork} was called, and @var{r}
37395 is the thread ID of the new child process. Refer to
37396 @ref{thread-id syntax} for the format of the @var{thread-id}
37397 field. This packet is only applicable to targets that support
37400 This packet should not be sent by default; older @value{GDBN} versions
37401 did not support it. @value{GDBN} requests it, by supplying an
37402 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37403 remote stub must also supply the appropriate @samp{qSupported} feature
37404 indicating support.
37406 @cindex vforkdone events, remote reply
37408 The packet indicates that a child process created by a vfork
37409 has either called @code{exec} or terminated, so that the
37410 address spaces of the parent and child process are no longer
37411 shared. The @var{r} part is ignored. This packet is only
37412 applicable to targets that support vforkdone events.
37414 This packet should not be sent by default; older @value{GDBN} versions
37415 did not support it. @value{GDBN} requests it, by supplying an
37416 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37417 remote stub must also supply the appropriate @samp{qSupported} feature
37418 indicating support.
37420 @cindex exec events, remote reply
37422 The packet indicates that @code{execve} was called, and @var{r}
37423 is the absolute pathname of the file that was executed, in hex.
37424 This packet is only applicable to targets that support exec events.
37426 This packet should not be sent by default; older @value{GDBN} versions
37427 did not support it. @value{GDBN} requests it, by supplying an
37428 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37429 remote stub must also supply the appropriate @samp{qSupported} feature
37430 indicating support.
37432 @cindex thread create event, remote reply
37433 @anchor{thread create event}
37435 The packet indicates that the thread was just created. The new thread
37436 is stopped until @value{GDBN} sets it running with a resumption packet
37437 (@pxref{vCont packet}). This packet should not be sent by default;
37438 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37439 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37440 @var{r} part is ignored.
37445 @itemx W @var{AA} ; process:@var{pid}
37446 The process exited, and @var{AA} is the exit status. This is only
37447 applicable to certain targets.
37449 The second form of the response, including the process ID of the
37450 exited process, can be used only when @value{GDBN} has reported
37451 support for multiprocess protocol extensions; see @ref{multiprocess
37452 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37456 @itemx X @var{AA} ; process:@var{pid}
37457 The process terminated with signal @var{AA}.
37459 The second form of the response, including the process ID of the
37460 terminated process, can be used only when @value{GDBN} has reported
37461 support for multiprocess protocol extensions; see @ref{multiprocess
37462 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37465 @anchor{thread exit event}
37466 @cindex thread exit event, remote reply
37467 @item w @var{AA} ; @var{tid}
37469 The thread exited, and @var{AA} is the exit status. This response
37470 should not be sent by default; @value{GDBN} requests it with the
37471 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37472 @var{AA} is formatted as a big-endian hex string.
37475 There are no resumed threads left in the target. In other words, even
37476 though the process is alive, the last resumed thread has exited. For
37477 example, say the target process has two threads: thread 1 and thread
37478 2. The client leaves thread 1 stopped, and resumes thread 2, which
37479 subsequently exits. At this point, even though the process is still
37480 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37481 executing either. The @samp{N} stop reply thus informs the client
37482 that it can stop waiting for stop replies. This packet should not be
37483 sent by default; older @value{GDBN} versions did not support it.
37484 @value{GDBN} requests it, by supplying an appropriate
37485 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37486 also supply the appropriate @samp{qSupported} feature indicating
37489 @item O @var{XX}@dots{}
37490 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37491 written as the program's console output. This can happen at any time
37492 while the program is running and the debugger should continue to wait
37493 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37495 @item F @var{call-id},@var{parameter}@dots{}
37496 @var{call-id} is the identifier which says which host system call should
37497 be called. This is just the name of the function. Translation into the
37498 correct system call is only applicable as it's defined in @value{GDBN}.
37499 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37502 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37503 this very system call.
37505 The target replies with this packet when it expects @value{GDBN} to
37506 call a host system call on behalf of the target. @value{GDBN} replies
37507 with an appropriate @samp{F} packet and keeps up waiting for the next
37508 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37509 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37510 Protocol Extension}, for more details.
37514 @node General Query Packets
37515 @section General Query Packets
37516 @cindex remote query requests
37518 Packets starting with @samp{q} are @dfn{general query packets};
37519 packets starting with @samp{Q} are @dfn{general set packets}. General
37520 query and set packets are a semi-unified form for retrieving and
37521 sending information to and from the stub.
37523 The initial letter of a query or set packet is followed by a name
37524 indicating what sort of thing the packet applies to. For example,
37525 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37526 definitions with the stub. These packet names follow some
37531 The name must not contain commas, colons or semicolons.
37533 Most @value{GDBN} query and set packets have a leading upper case
37536 The names of custom vendor packets should use a company prefix, in
37537 lower case, followed by a period. For example, packets designed at
37538 the Acme Corporation might begin with @samp{qacme.foo} (for querying
37539 foos) or @samp{Qacme.bar} (for setting bars).
37542 The name of a query or set packet should be separated from any
37543 parameters by a @samp{:}; the parameters themselves should be
37544 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
37545 full packet name, and check for a separator or the end of the packet,
37546 in case two packet names share a common prefix. New packets should not begin
37547 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
37548 packets predate these conventions, and have arguments without any terminator
37549 for the packet name; we suspect they are in widespread use in places that
37550 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
37551 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
37554 Like the descriptions of the other packets, each description here
37555 has a template showing the packet's overall syntax, followed by an
37556 explanation of the packet's meaning. We include spaces in some of the
37557 templates for clarity; these are not part of the packet's syntax. No
37558 @value{GDBN} packet uses spaces to separate its components.
37560 Here are the currently defined query and set packets:
37566 Turn on or off the agent as a helper to perform some debugging operations
37567 delegated from @value{GDBN} (@pxref{Control Agent}).
37569 @item QAllow:@var{op}:@var{val}@dots{}
37570 @cindex @samp{QAllow} packet
37571 Specify which operations @value{GDBN} expects to request of the
37572 target, as a semicolon-separated list of operation name and value
37573 pairs. Possible values for @var{op} include @samp{WriteReg},
37574 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37575 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37576 indicating that @value{GDBN} will not request the operation, or 1,
37577 indicating that it may. (The target can then use this to set up its
37578 own internals optimally, for instance if the debugger never expects to
37579 insert breakpoints, it may not need to install its own trap handler.)
37582 @cindex current thread, remote request
37583 @cindex @samp{qC} packet
37584 Return the current thread ID.
37588 @item QC @var{thread-id}
37589 Where @var{thread-id} is a thread ID as documented in
37590 @ref{thread-id syntax}.
37591 @item @r{(anything else)}
37592 Any other reply implies the old thread ID.
37595 @item qCRC:@var{addr},@var{length}
37596 @cindex CRC of memory block, remote request
37597 @cindex @samp{qCRC} packet
37598 @anchor{qCRC packet}
37599 Compute the CRC checksum of a block of memory using CRC-32 defined in
37600 IEEE 802.3. The CRC is computed byte at a time, taking the most
37601 significant bit of each byte first. The initial pattern code
37602 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37604 @emph{Note:} This is the same CRC used in validating separate debug
37605 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37606 Files}). However the algorithm is slightly different. When validating
37607 separate debug files, the CRC is computed taking the @emph{least}
37608 significant bit of each byte first, and the final result is inverted to
37609 detect trailing zeros.
37614 An error (such as memory fault)
37615 @item C @var{crc32}
37616 The specified memory region's checksum is @var{crc32}.
37619 @item QDisableRandomization:@var{value}
37620 @cindex disable address space randomization, remote request
37621 @cindex @samp{QDisableRandomization} packet
37622 Some target operating systems will randomize the virtual address space
37623 of the inferior process as a security feature, but provide a feature
37624 to disable such randomization, e.g.@: to allow for a more deterministic
37625 debugging experience. On such systems, this packet with a @var{value}
37626 of 1 directs the target to disable address space randomization for
37627 processes subsequently started via @samp{vRun} packets, while a packet
37628 with a @var{value} of 0 tells the target to enable address space
37631 This packet is only available in extended mode (@pxref{extended mode}).
37636 The request succeeded.
37639 An error occurred. The error number @var{nn} is given as hex digits.
37642 An empty reply indicates that @samp{QDisableRandomization} is not supported
37646 This packet is not probed by default; the remote stub must request it,
37647 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37648 This should only be done on targets that actually support disabling
37649 address space randomization.
37651 @item QStartupWithShell:@var{value}
37652 @cindex startup with shell, remote request
37653 @cindex @samp{QStartupWithShell} packet
37654 On UNIX-like targets, it is possible to start the inferior using a
37655 shell program. This is the default behavior on both @value{GDBN} and
37656 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37657 used to inform @command{gdbserver} whether it should start the
37658 inferior using a shell or not.
37660 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37661 to start the inferior. If @var{value} is @samp{1},
37662 @command{gdbserver} will use a shell to start the inferior. All other
37663 values are considered an error.
37665 This packet is only available in extended mode (@pxref{extended
37671 The request succeeded.
37674 An error occurred. The error number @var{nn} is given as hex digits.
37677 This packet is not probed by default; the remote stub must request it,
37678 by supplying an appropriate @samp{qSupported} response
37679 (@pxref{qSupported}). This should only be done on targets that
37680 actually support starting the inferior using a shell.
37682 Use of this packet is controlled by the @code{set startup-with-shell}
37683 command; @pxref{set startup-with-shell}.
37685 @item QEnvironmentHexEncoded:@var{hex-value}
37686 @anchor{QEnvironmentHexEncoded}
37687 @cindex set environment variable, remote request
37688 @cindex @samp{QEnvironmentHexEncoded} packet
37689 On UNIX-like targets, it is possible to set environment variables that
37690 will be passed to the inferior during the startup process. This
37691 packet is used to inform @command{gdbserver} of an environment
37692 variable that has been defined by the user on @value{GDBN} (@pxref{set
37695 The packet is composed by @var{hex-value}, an hex encoded
37696 representation of the @var{name=value} format representing an
37697 environment variable. The name of the environment variable is
37698 represented by @var{name}, and the value to be assigned to the
37699 environment variable is represented by @var{value}. If the variable
37700 has no value (i.e., the value is @code{null}), then @var{value} will
37703 This packet is only available in extended mode (@pxref{extended
37709 The request succeeded.
37712 This packet is not probed by default; the remote stub must request it,
37713 by supplying an appropriate @samp{qSupported} response
37714 (@pxref{qSupported}). This should only be done on targets that
37715 actually support passing environment variables to the starting
37718 This packet is related to the @code{set environment} command;
37719 @pxref{set environment}.
37721 @item QEnvironmentUnset:@var{hex-value}
37722 @anchor{QEnvironmentUnset}
37723 @cindex unset environment variable, remote request
37724 @cindex @samp{QEnvironmentUnset} packet
37725 On UNIX-like targets, it is possible to unset environment variables
37726 before starting the inferior in the remote target. This packet is
37727 used to inform @command{gdbserver} of an environment variable that has
37728 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37730 The packet is composed by @var{hex-value}, an hex encoded
37731 representation of the name of the environment variable to be unset.
37733 This packet is only available in extended mode (@pxref{extended
37739 The request succeeded.
37742 This packet is not probed by default; the remote stub must request it,
37743 by supplying an appropriate @samp{qSupported} response
37744 (@pxref{qSupported}). This should only be done on targets that
37745 actually support passing environment variables to the starting
37748 This packet is related to the @code{unset environment} command;
37749 @pxref{unset environment}.
37751 @item QEnvironmentReset
37752 @anchor{QEnvironmentReset}
37753 @cindex reset environment, remote request
37754 @cindex @samp{QEnvironmentReset} packet
37755 On UNIX-like targets, this packet is used to reset the state of
37756 environment variables in the remote target before starting the
37757 inferior. In this context, reset means unsetting all environment
37758 variables that were previously set by the user (i.e., were not
37759 initially present in the environment). It is sent to
37760 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37761 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37762 (@pxref{QEnvironmentUnset}) packets.
37764 This packet is only available in extended mode (@pxref{extended
37770 The request succeeded.
37773 This packet is not probed by default; the remote stub must request it,
37774 by supplying an appropriate @samp{qSupported} response
37775 (@pxref{qSupported}). This should only be done on targets that
37776 actually support passing environment variables to the starting
37779 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37780 @anchor{QSetWorkingDir packet}
37781 @cindex set working directory, remote request
37782 @cindex @samp{QSetWorkingDir} packet
37783 This packet is used to inform the remote server of the intended
37784 current working directory for programs that are going to be executed.
37786 The packet is composed by @var{directory}, an hex encoded
37787 representation of the directory that the remote inferior will use as
37788 its current working directory. If @var{directory} is an empty string,
37789 the remote server should reset the inferior's current working
37790 directory to its original, empty value.
37792 This packet is only available in extended mode (@pxref{extended
37798 The request succeeded.
37802 @itemx qsThreadInfo
37803 @cindex list active threads, remote request
37804 @cindex @samp{qfThreadInfo} packet
37805 @cindex @samp{qsThreadInfo} packet
37806 Obtain a list of all active thread IDs from the target (OS). Since there
37807 may be too many active threads to fit into one reply packet, this query
37808 works iteratively: it may require more than one query/reply sequence to
37809 obtain the entire list of threads. The first query of the sequence will
37810 be the @samp{qfThreadInfo} query; subsequent queries in the
37811 sequence will be the @samp{qsThreadInfo} query.
37813 NOTE: This packet replaces the @samp{qL} query (see below).
37817 @item m @var{thread-id}
37819 @item m @var{thread-id},@var{thread-id}@dots{}
37820 a comma-separated list of thread IDs
37822 (lower case letter @samp{L}) denotes end of list.
37825 In response to each query, the target will reply with a list of one or
37826 more thread IDs, separated by commas.
37827 @value{GDBN} will respond to each reply with a request for more thread
37828 ids (using the @samp{qs} form of the query), until the target responds
37829 with @samp{l} (lower-case ell, for @dfn{last}).
37830 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37833 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37834 initial connection with the remote target, and the very first thread ID
37835 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37836 message. Therefore, the stub should ensure that the first thread ID in
37837 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37839 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37840 @cindex get thread-local storage address, remote request
37841 @cindex @samp{qGetTLSAddr} packet
37842 Fetch the address associated with thread local storage specified
37843 by @var{thread-id}, @var{offset}, and @var{lm}.
37845 @var{thread-id} is the thread ID associated with the
37846 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37848 @var{offset} is the (big endian, hex encoded) offset associated with the
37849 thread local variable. (This offset is obtained from the debug
37850 information associated with the variable.)
37852 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37853 load module associated with the thread local storage. For example,
37854 a @sc{gnu}/Linux system will pass the link map address of the shared
37855 object associated with the thread local storage under consideration.
37856 Other operating environments may choose to represent the load module
37857 differently, so the precise meaning of this parameter will vary.
37861 @item @var{XX}@dots{}
37862 Hex encoded (big endian) bytes representing the address of the thread
37863 local storage requested.
37866 An error occurred. The error number @var{nn} is given as hex digits.
37869 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37872 @item qGetTIBAddr:@var{thread-id}
37873 @cindex get thread information block address
37874 @cindex @samp{qGetTIBAddr} packet
37875 Fetch address of the Windows OS specific Thread Information Block.
37877 @var{thread-id} is the thread ID associated with the thread.
37881 @item @var{XX}@dots{}
37882 Hex encoded (big endian) bytes representing the linear address of the
37883 thread information block.
37886 An error occured. This means that either the thread was not found, or the
37887 address could not be retrieved.
37890 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37893 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37894 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37895 digit) is one to indicate the first query and zero to indicate a
37896 subsequent query; @var{threadcount} (two hex digits) is the maximum
37897 number of threads the response packet can contain; and @var{nextthread}
37898 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37899 returned in the response as @var{argthread}.
37901 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37905 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37906 Where: @var{count} (two hex digits) is the number of threads being
37907 returned; @var{done} (one hex digit) is zero to indicate more threads
37908 and one indicates no further threads; @var{argthreadid} (eight hex
37909 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37910 is a sequence of thread IDs, @var{threadid} (eight hex
37911 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37915 @cindex section offsets, remote request
37916 @cindex @samp{qOffsets} packet
37917 Get section offsets that the target used when relocating the downloaded
37922 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37923 Relocate the @code{Text} section by @var{xxx} from its original address.
37924 Relocate the @code{Data} section by @var{yyy} from its original address.
37925 If the object file format provides segment information (e.g.@: @sc{elf}
37926 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37927 segments by the supplied offsets.
37929 @emph{Note: while a @code{Bss} offset may be included in the response,
37930 @value{GDBN} ignores this and instead applies the @code{Data} offset
37931 to the @code{Bss} section.}
37933 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37934 Relocate the first segment of the object file, which conventionally
37935 contains program code, to a starting address of @var{xxx}. If
37936 @samp{DataSeg} is specified, relocate the second segment, which
37937 conventionally contains modifiable data, to a starting address of
37938 @var{yyy}. @value{GDBN} will report an error if the object file
37939 does not contain segment information, or does not contain at least
37940 as many segments as mentioned in the reply. Extra segments are
37941 kept at fixed offsets relative to the last relocated segment.
37944 @item qP @var{mode} @var{thread-id}
37945 @cindex thread information, remote request
37946 @cindex @samp{qP} packet
37947 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37948 encoded 32 bit mode; @var{thread-id} is a thread ID
37949 (@pxref{thread-id syntax}).
37951 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37954 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37958 @cindex non-stop mode, remote request
37959 @cindex @samp{QNonStop} packet
37961 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37962 @xref{Remote Non-Stop}, for more information.
37967 The request succeeded.
37970 An error occurred. The error number @var{nn} is given as hex digits.
37973 An empty reply indicates that @samp{QNonStop} is not supported by
37977 This packet is not probed by default; the remote stub must request it,
37978 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37979 Use of this packet is controlled by the @code{set non-stop} command;
37980 @pxref{Non-Stop Mode}.
37982 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37983 @itemx QCatchSyscalls:0
37984 @cindex catch syscalls from inferior, remote request
37985 @cindex @samp{QCatchSyscalls} packet
37986 @anchor{QCatchSyscalls}
37987 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37988 catching syscalls from the inferior process.
37990 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37991 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37992 is listed, every system call should be reported.
37994 Note that if a syscall not in the list is reported, @value{GDBN} will
37995 still filter the event according to its own list from all corresponding
37996 @code{catch syscall} commands. However, it is more efficient to only
37997 report the requested syscalls.
37999 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38000 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38002 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38003 kept for the new process too. On targets where exec may affect syscall
38004 numbers, for example with exec between 32 and 64-bit processes, the
38005 client should send a new packet with the new syscall list.
38010 The request succeeded.
38013 An error occurred. @var{nn} are hex digits.
38016 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38020 Use of this packet is controlled by the @code{set remote catch-syscalls}
38021 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38022 This packet is not probed by default; the remote stub must request it,
38023 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38025 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38026 @cindex pass signals to inferior, remote request
38027 @cindex @samp{QPassSignals} packet
38028 @anchor{QPassSignals}
38029 Each listed @var{signal} should be passed directly to the inferior process.
38030 Signals are numbered identically to continue packets and stop replies
38031 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38032 strictly greater than the previous item. These signals do not need to stop
38033 the inferior, or be reported to @value{GDBN}. All other signals should be
38034 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38035 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38036 new list. This packet improves performance when using @samp{handle
38037 @var{signal} nostop noprint pass}.
38042 The request succeeded.
38045 An error occurred. The error number @var{nn} is given as hex digits.
38048 An empty reply indicates that @samp{QPassSignals} is not supported by
38052 Use of this packet is controlled by the @code{set remote pass-signals}
38053 command (@pxref{Remote Configuration, set remote pass-signals}).
38054 This packet is not probed by default; the remote stub must request it,
38055 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38057 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38058 @cindex signals the inferior may see, remote request
38059 @cindex @samp{QProgramSignals} packet
38060 @anchor{QProgramSignals}
38061 Each listed @var{signal} may be delivered to the inferior process.
38062 Others should be silently discarded.
38064 In some cases, the remote stub may need to decide whether to deliver a
38065 signal to the program or not without @value{GDBN} involvement. One
38066 example of that is while detaching --- the program's threads may have
38067 stopped for signals that haven't yet had a chance of being reported to
38068 @value{GDBN}, and so the remote stub can use the signal list specified
38069 by this packet to know whether to deliver or ignore those pending
38072 This does not influence whether to deliver a signal as requested by a
38073 resumption packet (@pxref{vCont packet}).
38075 Signals are numbered identically to continue packets and stop replies
38076 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38077 strictly greater than the previous item. Multiple
38078 @samp{QProgramSignals} packets do not combine; any earlier
38079 @samp{QProgramSignals} list is completely replaced by the new list.
38084 The request succeeded.
38087 An error occurred. The error number @var{nn} is given as hex digits.
38090 An empty reply indicates that @samp{QProgramSignals} is not supported
38094 Use of this packet is controlled by the @code{set remote program-signals}
38095 command (@pxref{Remote Configuration, set remote program-signals}).
38096 This packet is not probed by default; the remote stub must request it,
38097 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38099 @anchor{QThreadEvents}
38100 @item QThreadEvents:1
38101 @itemx QThreadEvents:0
38102 @cindex thread create/exit events, remote request
38103 @cindex @samp{QThreadEvents} packet
38105 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38106 reporting of thread create and exit events. @xref{thread create
38107 event}, for the reply specifications. For example, this is used in
38108 non-stop mode when @value{GDBN} stops a set of threads and
38109 synchronously waits for the their corresponding stop replies. Without
38110 exit events, if one of the threads exits, @value{GDBN} would hang
38111 forever not knowing that it should no longer expect a stop for that
38112 same thread. @value{GDBN} does not enable this feature unless the
38113 stub reports that it supports it by including @samp{QThreadEvents+} in
38114 its @samp{qSupported} reply.
38119 The request succeeded.
38122 An error occurred. The error number @var{nn} is given as hex digits.
38125 An empty reply indicates that @samp{QThreadEvents} is not supported by
38129 Use of this packet is controlled by the @code{set remote thread-events}
38130 command (@pxref{Remote Configuration, set remote thread-events}).
38132 @item qRcmd,@var{command}
38133 @cindex execute remote command, remote request
38134 @cindex @samp{qRcmd} packet
38135 @var{command} (hex encoded) is passed to the local interpreter for
38136 execution. Invalid commands should be reported using the output
38137 string. Before the final result packet, the target may also respond
38138 with a number of intermediate @samp{O@var{output}} console output
38139 packets. @emph{Implementors should note that providing access to a
38140 stubs's interpreter may have security implications}.
38145 A command response with no output.
38147 A command response with the hex encoded output string @var{OUTPUT}.
38149 Indicate a badly formed request.
38151 An empty reply indicates that @samp{qRcmd} is not recognized.
38154 (Note that the @code{qRcmd} packet's name is separated from the
38155 command by a @samp{,}, not a @samp{:}, contrary to the naming
38156 conventions above. Please don't use this packet as a model for new
38159 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38160 @cindex searching memory, in remote debugging
38162 @cindex @samp{qSearch:memory} packet
38164 @cindex @samp{qSearch memory} packet
38165 @anchor{qSearch memory}
38166 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38167 Both @var{address} and @var{length} are encoded in hex;
38168 @var{search-pattern} is a sequence of bytes, also hex encoded.
38173 The pattern was not found.
38175 The pattern was found at @var{address}.
38177 A badly formed request or an error was encountered while searching memory.
38179 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38182 @item QStartNoAckMode
38183 @cindex @samp{QStartNoAckMode} packet
38184 @anchor{QStartNoAckMode}
38185 Request that the remote stub disable the normal @samp{+}/@samp{-}
38186 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38191 The stub has switched to no-acknowledgment mode.
38192 @value{GDBN} acknowledges this reponse,
38193 but neither the stub nor @value{GDBN} shall send or expect further
38194 @samp{+}/@samp{-} acknowledgments in the current connection.
38196 An empty reply indicates that the stub does not support no-acknowledgment mode.
38199 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38200 @cindex supported packets, remote query
38201 @cindex features of the remote protocol
38202 @cindex @samp{qSupported} packet
38203 @anchor{qSupported}
38204 Tell the remote stub about features supported by @value{GDBN}, and
38205 query the stub for features it supports. This packet allows
38206 @value{GDBN} and the remote stub to take advantage of each others'
38207 features. @samp{qSupported} also consolidates multiple feature probes
38208 at startup, to improve @value{GDBN} performance---a single larger
38209 packet performs better than multiple smaller probe packets on
38210 high-latency links. Some features may enable behavior which must not
38211 be on by default, e.g.@: because it would confuse older clients or
38212 stubs. Other features may describe packets which could be
38213 automatically probed for, but are not. These features must be
38214 reported before @value{GDBN} will use them. This ``default
38215 unsupported'' behavior is not appropriate for all packets, but it
38216 helps to keep the initial connection time under control with new
38217 versions of @value{GDBN} which support increasing numbers of packets.
38221 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38222 The stub supports or does not support each returned @var{stubfeature},
38223 depending on the form of each @var{stubfeature} (see below for the
38226 An empty reply indicates that @samp{qSupported} is not recognized,
38227 or that no features needed to be reported to @value{GDBN}.
38230 The allowed forms for each feature (either a @var{gdbfeature} in the
38231 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38235 @item @var{name}=@var{value}
38236 The remote protocol feature @var{name} is supported, and associated
38237 with the specified @var{value}. The format of @var{value} depends
38238 on the feature, but it must not include a semicolon.
38240 The remote protocol feature @var{name} is supported, and does not
38241 need an associated value.
38243 The remote protocol feature @var{name} is not supported.
38245 The remote protocol feature @var{name} may be supported, and
38246 @value{GDBN} should auto-detect support in some other way when it is
38247 needed. This form will not be used for @var{gdbfeature} notifications,
38248 but may be used for @var{stubfeature} responses.
38251 Whenever the stub receives a @samp{qSupported} request, the
38252 supplied set of @value{GDBN} features should override any previous
38253 request. This allows @value{GDBN} to put the stub in a known
38254 state, even if the stub had previously been communicating with
38255 a different version of @value{GDBN}.
38257 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38262 This feature indicates whether @value{GDBN} supports multiprocess
38263 extensions to the remote protocol. @value{GDBN} does not use such
38264 extensions unless the stub also reports that it supports them by
38265 including @samp{multiprocess+} in its @samp{qSupported} reply.
38266 @xref{multiprocess extensions}, for details.
38269 This feature indicates that @value{GDBN} supports the XML target
38270 description. If the stub sees @samp{xmlRegisters=} with target
38271 specific strings separated by a comma, it will report register
38275 This feature indicates whether @value{GDBN} supports the
38276 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38277 instruction reply packet}).
38280 This feature indicates whether @value{GDBN} supports the swbreak stop
38281 reason in stop replies. @xref{swbreak stop reason}, for details.
38284 This feature indicates whether @value{GDBN} supports the hwbreak stop
38285 reason in stop replies. @xref{swbreak stop reason}, for details.
38288 This feature indicates whether @value{GDBN} supports fork event
38289 extensions to the remote protocol. @value{GDBN} does not use such
38290 extensions unless the stub also reports that it supports them by
38291 including @samp{fork-events+} in its @samp{qSupported} reply.
38294 This feature indicates whether @value{GDBN} supports vfork event
38295 extensions to the remote protocol. @value{GDBN} does not use such
38296 extensions unless the stub also reports that it supports them by
38297 including @samp{vfork-events+} in its @samp{qSupported} reply.
38300 This feature indicates whether @value{GDBN} supports exec event
38301 extensions to the remote protocol. @value{GDBN} does not use such
38302 extensions unless the stub also reports that it supports them by
38303 including @samp{exec-events+} in its @samp{qSupported} reply.
38305 @item vContSupported
38306 This feature indicates whether @value{GDBN} wants to know the
38307 supported actions in the reply to @samp{vCont?} packet.
38310 Stubs should ignore any unknown values for
38311 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38312 packet supports receiving packets of unlimited length (earlier
38313 versions of @value{GDBN} may reject overly long responses). Additional values
38314 for @var{gdbfeature} may be defined in the future to let the stub take
38315 advantage of new features in @value{GDBN}, e.g.@: incompatible
38316 improvements in the remote protocol---the @samp{multiprocess} feature is
38317 an example of such a feature. The stub's reply should be independent
38318 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38319 describes all the features it supports, and then the stub replies with
38320 all the features it supports.
38322 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38323 responses, as long as each response uses one of the standard forms.
38325 Some features are flags. A stub which supports a flag feature
38326 should respond with a @samp{+} form response. Other features
38327 require values, and the stub should respond with an @samp{=}
38330 Each feature has a default value, which @value{GDBN} will use if
38331 @samp{qSupported} is not available or if the feature is not mentioned
38332 in the @samp{qSupported} response. The default values are fixed; a
38333 stub is free to omit any feature responses that match the defaults.
38335 Not all features can be probed, but for those which can, the probing
38336 mechanism is useful: in some cases, a stub's internal
38337 architecture may not allow the protocol layer to know some information
38338 about the underlying target in advance. This is especially common in
38339 stubs which may be configured for multiple targets.
38341 These are the currently defined stub features and their properties:
38343 @multitable @columnfractions 0.35 0.2 0.12 0.2
38344 @c NOTE: The first row should be @headitem, but we do not yet require
38345 @c a new enough version of Texinfo (4.7) to use @headitem.
38347 @tab Value Required
38351 @item @samp{PacketSize}
38356 @item @samp{qXfer:auxv:read}
38361 @item @samp{qXfer:btrace:read}
38366 @item @samp{qXfer:btrace-conf:read}
38371 @item @samp{qXfer:exec-file:read}
38376 @item @samp{qXfer:features:read}
38381 @item @samp{qXfer:libraries:read}
38386 @item @samp{qXfer:libraries-svr4:read}
38391 @item @samp{augmented-libraries-svr4-read}
38396 @item @samp{qXfer:memory-map:read}
38401 @item @samp{qXfer:sdata:read}
38406 @item @samp{qXfer:spu:read}
38411 @item @samp{qXfer:spu:write}
38416 @item @samp{qXfer:siginfo:read}
38421 @item @samp{qXfer:siginfo:write}
38426 @item @samp{qXfer:threads:read}
38431 @item @samp{qXfer:traceframe-info:read}
38436 @item @samp{qXfer:uib:read}
38441 @item @samp{qXfer:fdpic:read}
38446 @item @samp{Qbtrace:off}
38451 @item @samp{Qbtrace:bts}
38456 @item @samp{Qbtrace:pt}
38461 @item @samp{Qbtrace-conf:bts:size}
38466 @item @samp{Qbtrace-conf:pt:size}
38471 @item @samp{QNonStop}
38476 @item @samp{QCatchSyscalls}
38481 @item @samp{QPassSignals}
38486 @item @samp{QStartNoAckMode}
38491 @item @samp{multiprocess}
38496 @item @samp{ConditionalBreakpoints}
38501 @item @samp{ConditionalTracepoints}
38506 @item @samp{ReverseContinue}
38511 @item @samp{ReverseStep}
38516 @item @samp{TracepointSource}
38521 @item @samp{QAgent}
38526 @item @samp{QAllow}
38531 @item @samp{QDisableRandomization}
38536 @item @samp{EnableDisableTracepoints}
38541 @item @samp{QTBuffer:size}
38546 @item @samp{tracenz}
38551 @item @samp{BreakpointCommands}
38556 @item @samp{swbreak}
38561 @item @samp{hwbreak}
38566 @item @samp{fork-events}
38571 @item @samp{vfork-events}
38576 @item @samp{exec-events}
38581 @item @samp{QThreadEvents}
38586 @item @samp{no-resumed}
38593 These are the currently defined stub features, in more detail:
38596 @cindex packet size, remote protocol
38597 @item PacketSize=@var{bytes}
38598 The remote stub can accept packets up to at least @var{bytes} in
38599 length. @value{GDBN} will send packets up to this size for bulk
38600 transfers, and will never send larger packets. This is a limit on the
38601 data characters in the packet, including the frame and checksum.
38602 There is no trailing NUL byte in a remote protocol packet; if the stub
38603 stores packets in a NUL-terminated format, it should allow an extra
38604 byte in its buffer for the NUL. If this stub feature is not supported,
38605 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38607 @item qXfer:auxv:read
38608 The remote stub understands the @samp{qXfer:auxv:read} packet
38609 (@pxref{qXfer auxiliary vector read}).
38611 @item qXfer:btrace:read
38612 The remote stub understands the @samp{qXfer:btrace:read}
38613 packet (@pxref{qXfer btrace read}).
38615 @item qXfer:btrace-conf:read
38616 The remote stub understands the @samp{qXfer:btrace-conf:read}
38617 packet (@pxref{qXfer btrace-conf read}).
38619 @item qXfer:exec-file:read
38620 The remote stub understands the @samp{qXfer:exec-file:read} packet
38621 (@pxref{qXfer executable filename read}).
38623 @item qXfer:features:read
38624 The remote stub understands the @samp{qXfer:features:read} packet
38625 (@pxref{qXfer target description read}).
38627 @item qXfer:libraries:read
38628 The remote stub understands the @samp{qXfer:libraries:read} packet
38629 (@pxref{qXfer library list read}).
38631 @item qXfer:libraries-svr4:read
38632 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38633 (@pxref{qXfer svr4 library list read}).
38635 @item augmented-libraries-svr4-read
38636 The remote stub understands the augmented form of the
38637 @samp{qXfer:libraries-svr4:read} packet
38638 (@pxref{qXfer svr4 library list read}).
38640 @item qXfer:memory-map:read
38641 The remote stub understands the @samp{qXfer:memory-map:read} packet
38642 (@pxref{qXfer memory map read}).
38644 @item qXfer:sdata:read
38645 The remote stub understands the @samp{qXfer:sdata:read} packet
38646 (@pxref{qXfer sdata read}).
38648 @item qXfer:spu:read
38649 The remote stub understands the @samp{qXfer:spu:read} packet
38650 (@pxref{qXfer spu read}).
38652 @item qXfer:spu:write
38653 The remote stub understands the @samp{qXfer:spu:write} packet
38654 (@pxref{qXfer spu write}).
38656 @item qXfer:siginfo:read
38657 The remote stub understands the @samp{qXfer:siginfo:read} packet
38658 (@pxref{qXfer siginfo read}).
38660 @item qXfer:siginfo:write
38661 The remote stub understands the @samp{qXfer:siginfo:write} packet
38662 (@pxref{qXfer siginfo write}).
38664 @item qXfer:threads:read
38665 The remote stub understands the @samp{qXfer:threads:read} packet
38666 (@pxref{qXfer threads read}).
38668 @item qXfer:traceframe-info:read
38669 The remote stub understands the @samp{qXfer:traceframe-info:read}
38670 packet (@pxref{qXfer traceframe info read}).
38672 @item qXfer:uib:read
38673 The remote stub understands the @samp{qXfer:uib:read}
38674 packet (@pxref{qXfer unwind info block}).
38676 @item qXfer:fdpic:read
38677 The remote stub understands the @samp{qXfer:fdpic:read}
38678 packet (@pxref{qXfer fdpic loadmap read}).
38681 The remote stub understands the @samp{QNonStop} packet
38682 (@pxref{QNonStop}).
38684 @item QCatchSyscalls
38685 The remote stub understands the @samp{QCatchSyscalls} packet
38686 (@pxref{QCatchSyscalls}).
38689 The remote stub understands the @samp{QPassSignals} packet
38690 (@pxref{QPassSignals}).
38692 @item QStartNoAckMode
38693 The remote stub understands the @samp{QStartNoAckMode} packet and
38694 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38697 @anchor{multiprocess extensions}
38698 @cindex multiprocess extensions, in remote protocol
38699 The remote stub understands the multiprocess extensions to the remote
38700 protocol syntax. The multiprocess extensions affect the syntax of
38701 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38702 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38703 replies. Note that reporting this feature indicates support for the
38704 syntactic extensions only, not that the stub necessarily supports
38705 debugging of more than one process at a time. The stub must not use
38706 multiprocess extensions in packet replies unless @value{GDBN} has also
38707 indicated it supports them in its @samp{qSupported} request.
38709 @item qXfer:osdata:read
38710 The remote stub understands the @samp{qXfer:osdata:read} packet
38711 ((@pxref{qXfer osdata read}).
38713 @item ConditionalBreakpoints
38714 The target accepts and implements evaluation of conditional expressions
38715 defined for breakpoints. The target will only report breakpoint triggers
38716 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38718 @item ConditionalTracepoints
38719 The remote stub accepts and implements conditional expressions defined
38720 for tracepoints (@pxref{Tracepoint Conditions}).
38722 @item ReverseContinue
38723 The remote stub accepts and implements the reverse continue packet
38727 The remote stub accepts and implements the reverse step packet
38730 @item TracepointSource
38731 The remote stub understands the @samp{QTDPsrc} packet that supplies
38732 the source form of tracepoint definitions.
38735 The remote stub understands the @samp{QAgent} packet.
38738 The remote stub understands the @samp{QAllow} packet.
38740 @item QDisableRandomization
38741 The remote stub understands the @samp{QDisableRandomization} packet.
38743 @item StaticTracepoint
38744 @cindex static tracepoints, in remote protocol
38745 The remote stub supports static tracepoints.
38747 @item InstallInTrace
38748 @anchor{install tracepoint in tracing}
38749 The remote stub supports installing tracepoint in tracing.
38751 @item EnableDisableTracepoints
38752 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38753 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38754 to be enabled and disabled while a trace experiment is running.
38756 @item QTBuffer:size
38757 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38758 packet that allows to change the size of the trace buffer.
38761 @cindex string tracing, in remote protocol
38762 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38763 See @ref{Bytecode Descriptions} for details about the bytecode.
38765 @item BreakpointCommands
38766 @cindex breakpoint commands, in remote protocol
38767 The remote stub supports running a breakpoint's command list itself,
38768 rather than reporting the hit to @value{GDBN}.
38771 The remote stub understands the @samp{Qbtrace:off} packet.
38774 The remote stub understands the @samp{Qbtrace:bts} packet.
38777 The remote stub understands the @samp{Qbtrace:pt} packet.
38779 @item Qbtrace-conf:bts:size
38780 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38782 @item Qbtrace-conf:pt:size
38783 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38786 The remote stub reports the @samp{swbreak} stop reason for memory
38790 The remote stub reports the @samp{hwbreak} stop reason for hardware
38794 The remote stub reports the @samp{fork} stop reason for fork events.
38797 The remote stub reports the @samp{vfork} stop reason for vfork events
38798 and vforkdone events.
38801 The remote stub reports the @samp{exec} stop reason for exec events.
38803 @item vContSupported
38804 The remote stub reports the supported actions in the reply to
38805 @samp{vCont?} packet.
38807 @item QThreadEvents
38808 The remote stub understands the @samp{QThreadEvents} packet.
38811 The remote stub reports the @samp{N} stop reply.
38816 @cindex symbol lookup, remote request
38817 @cindex @samp{qSymbol} packet
38818 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38819 requests. Accept requests from the target for the values of symbols.
38824 The target does not need to look up any (more) symbols.
38825 @item qSymbol:@var{sym_name}
38826 The target requests the value of symbol @var{sym_name} (hex encoded).
38827 @value{GDBN} may provide the value by using the
38828 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38832 @item qSymbol:@var{sym_value}:@var{sym_name}
38833 Set the value of @var{sym_name} to @var{sym_value}.
38835 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38836 target has previously requested.
38838 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38839 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38845 The target does not need to look up any (more) symbols.
38846 @item qSymbol:@var{sym_name}
38847 The target requests the value of a new symbol @var{sym_name} (hex
38848 encoded). @value{GDBN} will continue to supply the values of symbols
38849 (if available), until the target ceases to request them.
38854 @itemx QTDisconnected
38861 @itemx qTMinFTPILen
38863 @xref{Tracepoint Packets}.
38865 @item qThreadExtraInfo,@var{thread-id}
38866 @cindex thread attributes info, remote request
38867 @cindex @samp{qThreadExtraInfo} packet
38868 Obtain from the target OS a printable string description of thread
38869 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38870 for the forms of @var{thread-id}. This
38871 string may contain anything that the target OS thinks is interesting
38872 for @value{GDBN} to tell the user about the thread. The string is
38873 displayed in @value{GDBN}'s @code{info threads} display. Some
38874 examples of possible thread extra info strings are @samp{Runnable}, or
38875 @samp{Blocked on Mutex}.
38879 @item @var{XX}@dots{}
38880 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38881 comprising the printable string containing the extra information about
38882 the thread's attributes.
38885 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38886 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38887 conventions above. Please don't use this packet as a model for new
38906 @xref{Tracepoint Packets}.
38908 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38909 @cindex read special object, remote request
38910 @cindex @samp{qXfer} packet
38911 @anchor{qXfer read}
38912 Read uninterpreted bytes from the target's special data area
38913 identified by the keyword @var{object}. Request @var{length} bytes
38914 starting at @var{offset} bytes into the data. The content and
38915 encoding of @var{annex} is specific to @var{object}; it can supply
38916 additional details about what data to access.
38921 Data @var{data} (@pxref{Binary Data}) has been read from the
38922 target. There may be more data at a higher address (although
38923 it is permitted to return @samp{m} even for the last valid
38924 block of data, as long as at least one byte of data was read).
38925 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38929 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38930 There is no more data to be read. It is possible for @var{data} to
38931 have fewer bytes than the @var{length} in the request.
38934 The @var{offset} in the request is at the end of the data.
38935 There is no more data to be read.
38938 The request was malformed, or @var{annex} was invalid.
38941 The offset was invalid, or there was an error encountered reading the data.
38942 The @var{nn} part is a hex-encoded @code{errno} value.
38945 An empty reply indicates the @var{object} string was not recognized by
38946 the stub, or that the object does not support reading.
38949 Here are the specific requests of this form defined so far. All the
38950 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38951 formats, listed above.
38954 @item qXfer:auxv:read::@var{offset},@var{length}
38955 @anchor{qXfer auxiliary vector read}
38956 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38957 auxiliary vector}. Note @var{annex} must be empty.
38959 This packet is not probed by default; the remote stub must request it,
38960 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38962 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38963 @anchor{qXfer btrace read}
38965 Return a description of the current branch trace.
38966 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38967 packet may have one of the following values:
38971 Returns all available branch trace.
38974 Returns all available branch trace if the branch trace changed since
38975 the last read request.
38978 Returns the new branch trace since the last read request. Adds a new
38979 block to the end of the trace that begins at zero and ends at the source
38980 location of the first branch in the trace buffer. This extra block is
38981 used to stitch traces together.
38983 If the trace buffer overflowed, returns an error indicating the overflow.
38986 This packet is not probed by default; the remote stub must request it
38987 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38989 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38990 @anchor{qXfer btrace-conf read}
38992 Return a description of the current branch trace configuration.
38993 @xref{Branch Trace Configuration Format}.
38995 This packet is not probed by default; the remote stub must request it
38996 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38998 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38999 @anchor{qXfer executable filename read}
39000 Return the full absolute name of the file that was executed to create
39001 a process running on the remote system. The annex specifies the
39002 numeric process ID of the process to query, encoded as a hexadecimal
39003 number. If the annex part is empty the remote stub should return the
39004 filename corresponding to the currently executing process.
39006 This packet is not probed by default; the remote stub must request it,
39007 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39009 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39010 @anchor{qXfer target description read}
39011 Access the @dfn{target description}. @xref{Target Descriptions}. The
39012 annex specifies which XML document to access. The main description is
39013 always loaded from the @samp{target.xml} annex.
39015 This packet is not probed by default; the remote stub must request it,
39016 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39018 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39019 @anchor{qXfer library list read}
39020 Access the target's list of loaded libraries. @xref{Library List Format}.
39021 The annex part of the generic @samp{qXfer} packet must be empty
39022 (@pxref{qXfer read}).
39024 Targets which maintain a list of libraries in the program's memory do
39025 not need to implement this packet; it is designed for platforms where
39026 the operating system manages the list of loaded libraries.
39028 This packet is not probed by default; the remote stub must request it,
39029 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39031 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39032 @anchor{qXfer svr4 library list read}
39033 Access the target's list of loaded libraries when the target is an SVR4
39034 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39035 of the generic @samp{qXfer} packet must be empty unless the remote
39036 stub indicated it supports the augmented form of this packet
39037 by supplying an appropriate @samp{qSupported} response
39038 (@pxref{qXfer read}, @ref{qSupported}).
39040 This packet is optional for better performance on SVR4 targets.
39041 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39043 This packet is not probed by default; the remote stub must request it,
39044 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39046 If the remote stub indicates it supports the augmented form of this
39047 packet then the annex part of the generic @samp{qXfer} packet may
39048 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39049 arguments. The currently supported arguments are:
39052 @item start=@var{address}
39053 A hexadecimal number specifying the address of the @samp{struct
39054 link_map} to start reading the library list from. If unset or zero
39055 then the first @samp{struct link_map} in the library list will be
39056 chosen as the starting point.
39058 @item prev=@var{address}
39059 A hexadecimal number specifying the address of the @samp{struct
39060 link_map} immediately preceding the @samp{struct link_map}
39061 specified by the @samp{start} argument. If unset or zero then
39062 the remote stub will expect that no @samp{struct link_map}
39063 exists prior to the starting point.
39067 Arguments that are not understood by the remote stub will be silently
39070 @item qXfer:memory-map:read::@var{offset},@var{length}
39071 @anchor{qXfer memory map read}
39072 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39073 annex part of the generic @samp{qXfer} packet must be empty
39074 (@pxref{qXfer read}).
39076 This packet is not probed by default; the remote stub must request it,
39077 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39079 @item qXfer:sdata:read::@var{offset},@var{length}
39080 @anchor{qXfer sdata read}
39082 Read contents of the extra collected static tracepoint marker
39083 information. The annex part of the generic @samp{qXfer} packet must
39084 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39087 This packet is not probed by default; the remote stub must request it,
39088 by supplying an appropriate @samp{qSupported} response
39089 (@pxref{qSupported}).
39091 @item qXfer:siginfo:read::@var{offset},@var{length}
39092 @anchor{qXfer siginfo read}
39093 Read contents of the extra signal information on the target
39094 system. The annex part of the generic @samp{qXfer} packet must be
39095 empty (@pxref{qXfer read}).
39097 This packet is not probed by default; the remote stub must request it,
39098 by supplying an appropriate @samp{qSupported} response
39099 (@pxref{qSupported}).
39101 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39102 @anchor{qXfer spu read}
39103 Read contents of an @code{spufs} file on the target system. The
39104 annex specifies which file to read; it must be of the form
39105 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39106 in the target process, and @var{name} identifes the @code{spufs} file
39107 in that context to be accessed.
39109 This packet is not probed by default; the remote stub must request it,
39110 by supplying an appropriate @samp{qSupported} response
39111 (@pxref{qSupported}).
39113 @item qXfer:threads:read::@var{offset},@var{length}
39114 @anchor{qXfer threads read}
39115 Access the list of threads on target. @xref{Thread List Format}. The
39116 annex part of the generic @samp{qXfer} packet must be empty
39117 (@pxref{qXfer read}).
39119 This packet is not probed by default; the remote stub must request it,
39120 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39122 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39123 @anchor{qXfer traceframe info read}
39125 Return a description of the current traceframe's contents.
39126 @xref{Traceframe Info Format}. The annex part of the generic
39127 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39129 This packet is not probed by default; the remote stub must request it,
39130 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39132 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39133 @anchor{qXfer unwind info block}
39135 Return the unwind information block for @var{pc}. This packet is used
39136 on OpenVMS/ia64 to ask the kernel unwind information.
39138 This packet is not probed by default.
39140 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39141 @anchor{qXfer fdpic loadmap read}
39142 Read contents of @code{loadmap}s on the target system. The
39143 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39144 executable @code{loadmap} or interpreter @code{loadmap} to read.
39146 This packet is not probed by default; the remote stub must request it,
39147 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39149 @item qXfer:osdata:read::@var{offset},@var{length}
39150 @anchor{qXfer osdata read}
39151 Access the target's @dfn{operating system information}.
39152 @xref{Operating System Information}.
39156 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39157 @cindex write data into object, remote request
39158 @anchor{qXfer write}
39159 Write uninterpreted bytes into the target's special data area
39160 identified by the keyword @var{object}, starting at @var{offset} bytes
39161 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39162 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39163 is specific to @var{object}; it can supply additional details about what data
39169 @var{nn} (hex encoded) is the number of bytes written.
39170 This may be fewer bytes than supplied in the request.
39173 The request was malformed, or @var{annex} was invalid.
39176 The offset was invalid, or there was an error encountered writing the data.
39177 The @var{nn} part is a hex-encoded @code{errno} value.
39180 An empty reply indicates the @var{object} string was not
39181 recognized by the stub, or that the object does not support writing.
39184 Here are the specific requests of this form defined so far. All the
39185 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39186 formats, listed above.
39189 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39190 @anchor{qXfer siginfo write}
39191 Write @var{data} to the extra signal information on the target system.
39192 The annex part of the generic @samp{qXfer} packet must be
39193 empty (@pxref{qXfer write}).
39195 This packet is not probed by default; the remote stub must request it,
39196 by supplying an appropriate @samp{qSupported} response
39197 (@pxref{qSupported}).
39199 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39200 @anchor{qXfer spu write}
39201 Write @var{data} to an @code{spufs} file on the target system. The
39202 annex specifies which file to write; it must be of the form
39203 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39204 in the target process, and @var{name} identifes the @code{spufs} file
39205 in that context to be accessed.
39207 This packet is not probed by default; the remote stub must request it,
39208 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39211 @item qXfer:@var{object}:@var{operation}:@dots{}
39212 Requests of this form may be added in the future. When a stub does
39213 not recognize the @var{object} keyword, or its support for
39214 @var{object} does not recognize the @var{operation} keyword, the stub
39215 must respond with an empty packet.
39217 @item qAttached:@var{pid}
39218 @cindex query attached, remote request
39219 @cindex @samp{qAttached} packet
39220 Return an indication of whether the remote server attached to an
39221 existing process or created a new process. When the multiprocess
39222 protocol extensions are supported (@pxref{multiprocess extensions}),
39223 @var{pid} is an integer in hexadecimal format identifying the target
39224 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39225 the query packet will be simplified as @samp{qAttached}.
39227 This query is used, for example, to know whether the remote process
39228 should be detached or killed when a @value{GDBN} session is ended with
39229 the @code{quit} command.
39234 The remote server attached to an existing process.
39236 The remote server created a new process.
39238 A badly formed request or an error was encountered.
39242 Enable branch tracing for the current thread using Branch Trace Store.
39247 Branch tracing has been enabled.
39249 A badly formed request or an error was encountered.
39253 Enable branch tracing for the current thread using Intel Processor Trace.
39258 Branch tracing has been enabled.
39260 A badly formed request or an error was encountered.
39264 Disable branch tracing for the current thread.
39269 Branch tracing has been disabled.
39271 A badly formed request or an error was encountered.
39274 @item Qbtrace-conf:bts:size=@var{value}
39275 Set the requested ring buffer size for new threads that use the
39276 btrace recording method in bts format.
39281 The ring buffer size has been set.
39283 A badly formed request or an error was encountered.
39286 @item Qbtrace-conf:pt:size=@var{value}
39287 Set the requested ring buffer size for new threads that use the
39288 btrace recording method in pt format.
39293 The ring buffer size has been set.
39295 A badly formed request or an error was encountered.
39300 @node Architecture-Specific Protocol Details
39301 @section Architecture-Specific Protocol Details
39303 This section describes how the remote protocol is applied to specific
39304 target architectures. Also see @ref{Standard Target Features}, for
39305 details of XML target descriptions for each architecture.
39308 * ARM-Specific Protocol Details::
39309 * MIPS-Specific Protocol Details::
39312 @node ARM-Specific Protocol Details
39313 @subsection @acronym{ARM}-specific Protocol Details
39316 * ARM Breakpoint Kinds::
39319 @node ARM Breakpoint Kinds
39320 @subsubsection @acronym{ARM} Breakpoint Kinds
39321 @cindex breakpoint kinds, @acronym{ARM}
39323 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39328 16-bit Thumb mode breakpoint.
39331 32-bit Thumb mode (Thumb-2) breakpoint.
39334 32-bit @acronym{ARM} mode breakpoint.
39338 @node MIPS-Specific Protocol Details
39339 @subsection @acronym{MIPS}-specific Protocol Details
39342 * MIPS Register packet Format::
39343 * MIPS Breakpoint Kinds::
39346 @node MIPS Register packet Format
39347 @subsubsection @acronym{MIPS} Register Packet Format
39348 @cindex register packet format, @acronym{MIPS}
39350 The following @code{g}/@code{G} packets have previously been defined.
39351 In the below, some thirty-two bit registers are transferred as
39352 sixty-four bits. Those registers should be zero/sign extended (which?)
39353 to fill the space allocated. Register bytes are transferred in target
39354 byte order. The two nibbles within a register byte are transferred
39355 most-significant -- least-significant.
39360 All registers are transferred as thirty-two bit quantities in the order:
39361 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39362 registers; fsr; fir; fp.
39365 All registers are transferred as sixty-four bit quantities (including
39366 thirty-two bit registers such as @code{sr}). The ordering is the same
39371 @node MIPS Breakpoint Kinds
39372 @subsubsection @acronym{MIPS} Breakpoint Kinds
39373 @cindex breakpoint kinds, @acronym{MIPS}
39375 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39380 16-bit @acronym{MIPS16} mode breakpoint.
39383 16-bit @acronym{microMIPS} mode breakpoint.
39386 32-bit standard @acronym{MIPS} mode breakpoint.
39389 32-bit @acronym{microMIPS} mode breakpoint.
39393 @node Tracepoint Packets
39394 @section Tracepoint Packets
39395 @cindex tracepoint packets
39396 @cindex packets, tracepoint
39398 Here we describe the packets @value{GDBN} uses to implement
39399 tracepoints (@pxref{Tracepoints}).
39403 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39404 @cindex @samp{QTDP} packet
39405 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39406 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39407 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39408 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39409 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39410 the number of bytes that the target should copy elsewhere to make room
39411 for the tracepoint. If an @samp{X} is present, it introduces a
39412 tracepoint condition, which consists of a hexadecimal length, followed
39413 by a comma and hex-encoded bytes, in a manner similar to action
39414 encodings as described below. If the trailing @samp{-} is present,
39415 further @samp{QTDP} packets will follow to specify this tracepoint's
39421 The packet was understood and carried out.
39423 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39425 The packet was not recognized.
39428 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39429 Define actions to be taken when a tracepoint is hit. The @var{n} and
39430 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39431 this tracepoint. This packet may only be sent immediately after
39432 another @samp{QTDP} packet that ended with a @samp{-}. If the
39433 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39434 specifying more actions for this tracepoint.
39436 In the series of action packets for a given tracepoint, at most one
39437 can have an @samp{S} before its first @var{action}. If such a packet
39438 is sent, it and the following packets define ``while-stepping''
39439 actions. Any prior packets define ordinary actions --- that is, those
39440 taken when the tracepoint is first hit. If no action packet has an
39441 @samp{S}, then all the packets in the series specify ordinary
39442 tracepoint actions.
39444 The @samp{@var{action}@dots{}} portion of the packet is a series of
39445 actions, concatenated without separators. Each action has one of the
39451 Collect the registers whose bits are set in @var{mask},
39452 a hexadecimal number whose @var{i}'th bit is set if register number
39453 @var{i} should be collected. (The least significant bit is numbered
39454 zero.) Note that @var{mask} may be any number of digits long; it may
39455 not fit in a 32-bit word.
39457 @item M @var{basereg},@var{offset},@var{len}
39458 Collect @var{len} bytes of memory starting at the address in register
39459 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39460 @samp{-1}, then the range has a fixed address: @var{offset} is the
39461 address of the lowest byte to collect. The @var{basereg},
39462 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39463 values (the @samp{-1} value for @var{basereg} is a special case).
39465 @item X @var{len},@var{expr}
39466 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39467 it directs. The agent expression @var{expr} is as described in
39468 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39469 two-digit hex number in the packet; @var{len} is the number of bytes
39470 in the expression (and thus one-half the number of hex digits in the
39475 Any number of actions may be packed together in a single @samp{QTDP}
39476 packet, as long as the packet does not exceed the maximum packet
39477 length (400 bytes, for many stubs). There may be only one @samp{R}
39478 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39479 actions. Any registers referred to by @samp{M} and @samp{X} actions
39480 must be collected by a preceding @samp{R} action. (The
39481 ``while-stepping'' actions are treated as if they were attached to a
39482 separate tracepoint, as far as these restrictions are concerned.)
39487 The packet was understood and carried out.
39489 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39491 The packet was not recognized.
39494 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39495 @cindex @samp{QTDPsrc} packet
39496 Specify a source string of tracepoint @var{n} at address @var{addr}.
39497 This is useful to get accurate reproduction of the tracepoints
39498 originally downloaded at the beginning of the trace run. The @var{type}
39499 is the name of the tracepoint part, such as @samp{cond} for the
39500 tracepoint's conditional expression (see below for a list of types), while
39501 @var{bytes} is the string, encoded in hexadecimal.
39503 @var{start} is the offset of the @var{bytes} within the overall source
39504 string, while @var{slen} is the total length of the source string.
39505 This is intended for handling source strings that are longer than will
39506 fit in a single packet.
39507 @c Add detailed example when this info is moved into a dedicated
39508 @c tracepoint descriptions section.
39510 The available string types are @samp{at} for the location,
39511 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39512 @value{GDBN} sends a separate packet for each command in the action
39513 list, in the same order in which the commands are stored in the list.
39515 The target does not need to do anything with source strings except
39516 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39519 Although this packet is optional, and @value{GDBN} will only send it
39520 if the target replies with @samp{TracepointSource} @xref{General
39521 Query Packets}, it makes both disconnected tracing and trace files
39522 much easier to use. Otherwise the user must be careful that the
39523 tracepoints in effect while looking at trace frames are identical to
39524 the ones in effect during the trace run; even a small discrepancy
39525 could cause @samp{tdump} not to work, or a particular trace frame not
39528 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39529 @cindex define trace state variable, remote request
39530 @cindex @samp{QTDV} packet
39531 Create a new trace state variable, number @var{n}, with an initial
39532 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39533 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39534 the option of not using this packet for initial values of zero; the
39535 target should simply create the trace state variables as they are
39536 mentioned in expressions. The value @var{builtin} should be 1 (one)
39537 if the trace state variable is builtin and 0 (zero) if it is not builtin.
39538 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
39539 @samp{qTsV} packet had it set. The contents of @var{name} is the
39540 hex-encoded name (without the leading @samp{$}) of the trace state
39543 @item QTFrame:@var{n}
39544 @cindex @samp{QTFrame} packet
39545 Select the @var{n}'th tracepoint frame from the buffer, and use the
39546 register and memory contents recorded there to answer subsequent
39547 request packets from @value{GDBN}.
39549 A successful reply from the stub indicates that the stub has found the
39550 requested frame. The response is a series of parts, concatenated
39551 without separators, describing the frame we selected. Each part has
39552 one of the following forms:
39556 The selected frame is number @var{n} in the trace frame buffer;
39557 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39558 was no frame matching the criteria in the request packet.
39561 The selected trace frame records a hit of tracepoint number @var{t};
39562 @var{t} is a hexadecimal number.
39566 @item QTFrame:pc:@var{addr}
39567 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39568 currently selected frame whose PC is @var{addr};
39569 @var{addr} is a hexadecimal number.
39571 @item QTFrame:tdp:@var{t}
39572 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39573 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39574 is a hexadecimal number.
39576 @item QTFrame:range:@var{start}:@var{end}
39577 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39578 currently selected frame whose PC is between @var{start} (inclusive)
39579 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39582 @item QTFrame:outside:@var{start}:@var{end}
39583 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39584 frame @emph{outside} the given range of addresses (exclusive).
39587 @cindex @samp{qTMinFTPILen} packet
39588 This packet requests the minimum length of instruction at which a fast
39589 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39590 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39591 it depends on the target system being able to create trampolines in
39592 the first 64K of memory, which might or might not be possible for that
39593 system. So the reply to this packet will be 4 if it is able to
39600 The minimum instruction length is currently unknown.
39602 The minimum instruction length is @var{length}, where @var{length}
39603 is a hexadecimal number greater or equal to 1. A reply
39604 of 1 means that a fast tracepoint may be placed on any instruction
39605 regardless of size.
39607 An error has occurred.
39609 An empty reply indicates that the request is not supported by the stub.
39613 @cindex @samp{QTStart} packet
39614 Begin the tracepoint experiment. Begin collecting data from
39615 tracepoint hits in the trace frame buffer. This packet supports the
39616 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39617 instruction reply packet}).
39620 @cindex @samp{QTStop} packet
39621 End the tracepoint experiment. Stop collecting trace frames.
39623 @item QTEnable:@var{n}:@var{addr}
39625 @cindex @samp{QTEnable} packet
39626 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39627 experiment. If the tracepoint was previously disabled, then collection
39628 of data from it will resume.
39630 @item QTDisable:@var{n}:@var{addr}
39632 @cindex @samp{QTDisable} packet
39633 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39634 experiment. No more data will be collected from the tracepoint unless
39635 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39638 @cindex @samp{QTinit} packet
39639 Clear the table of tracepoints, and empty the trace frame buffer.
39641 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39642 @cindex @samp{QTro} packet
39643 Establish the given ranges of memory as ``transparent''. The stub
39644 will answer requests for these ranges from memory's current contents,
39645 if they were not collected as part of the tracepoint hit.
39647 @value{GDBN} uses this to mark read-only regions of memory, like those
39648 containing program code. Since these areas never change, they should
39649 still have the same contents they did when the tracepoint was hit, so
39650 there's no reason for the stub to refuse to provide their contents.
39652 @item QTDisconnected:@var{value}
39653 @cindex @samp{QTDisconnected} packet
39654 Set the choice to what to do with the tracing run when @value{GDBN}
39655 disconnects from the target. A @var{value} of 1 directs the target to
39656 continue the tracing run, while 0 tells the target to stop tracing if
39657 @value{GDBN} is no longer in the picture.
39660 @cindex @samp{qTStatus} packet
39661 Ask the stub if there is a trace experiment running right now.
39663 The reply has the form:
39667 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39668 @var{running} is a single digit @code{1} if the trace is presently
39669 running, or @code{0} if not. It is followed by semicolon-separated
39670 optional fields that an agent may use to report additional status.
39674 If the trace is not running, the agent may report any of several
39675 explanations as one of the optional fields:
39680 No trace has been run yet.
39682 @item tstop[:@var{text}]:0
39683 The trace was stopped by a user-originated stop command. The optional
39684 @var{text} field is a user-supplied string supplied as part of the
39685 stop command (for instance, an explanation of why the trace was
39686 stopped manually). It is hex-encoded.
39689 The trace stopped because the trace buffer filled up.
39691 @item tdisconnected:0
39692 The trace stopped because @value{GDBN} disconnected from the target.
39694 @item tpasscount:@var{tpnum}
39695 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39697 @item terror:@var{text}:@var{tpnum}
39698 The trace stopped because tracepoint @var{tpnum} had an error. The
39699 string @var{text} is available to describe the nature of the error
39700 (for instance, a divide by zero in the condition expression); it
39704 The trace stopped for some other reason.
39708 Additional optional fields supply statistical and other information.
39709 Although not required, they are extremely useful for users monitoring
39710 the progress of a trace run. If a trace has stopped, and these
39711 numbers are reported, they must reflect the state of the just-stopped
39716 @item tframes:@var{n}
39717 The number of trace frames in the buffer.
39719 @item tcreated:@var{n}
39720 The total number of trace frames created during the run. This may
39721 be larger than the trace frame count, if the buffer is circular.
39723 @item tsize:@var{n}
39724 The total size of the trace buffer, in bytes.
39726 @item tfree:@var{n}
39727 The number of bytes still unused in the buffer.
39729 @item circular:@var{n}
39730 The value of the circular trace buffer flag. @code{1} means that the
39731 trace buffer is circular and old trace frames will be discarded if
39732 necessary to make room, @code{0} means that the trace buffer is linear
39735 @item disconn:@var{n}
39736 The value of the disconnected tracing flag. @code{1} means that
39737 tracing will continue after @value{GDBN} disconnects, @code{0} means
39738 that the trace run will stop.
39742 @item qTP:@var{tp}:@var{addr}
39743 @cindex tracepoint status, remote request
39744 @cindex @samp{qTP} packet
39745 Ask the stub for the current state of tracepoint number @var{tp} at
39746 address @var{addr}.
39750 @item V@var{hits}:@var{usage}
39751 The tracepoint has been hit @var{hits} times so far during the trace
39752 run, and accounts for @var{usage} in the trace buffer. Note that
39753 @code{while-stepping} steps are not counted as separate hits, but the
39754 steps' space consumption is added into the usage number.
39758 @item qTV:@var{var}
39759 @cindex trace state variable value, remote request
39760 @cindex @samp{qTV} packet
39761 Ask the stub for the value of the trace state variable number @var{var}.
39766 The value of the variable is @var{value}. This will be the current
39767 value of the variable if the user is examining a running target, or a
39768 saved value if the variable was collected in the trace frame that the
39769 user is looking at. Note that multiple requests may result in
39770 different reply values, such as when requesting values while the
39771 program is running.
39774 The value of the variable is unknown. This would occur, for example,
39775 if the user is examining a trace frame in which the requested variable
39780 @cindex @samp{qTfP} packet
39782 @cindex @samp{qTsP} packet
39783 These packets request data about tracepoints that are being used by
39784 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39785 of data, and multiple @code{qTsP} to get additional pieces. Replies
39786 to these packets generally take the form of the @code{QTDP} packets
39787 that define tracepoints. (FIXME add detailed syntax)
39790 @cindex @samp{qTfV} packet
39792 @cindex @samp{qTsV} packet
39793 These packets request data about trace state variables that are on the
39794 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39795 and multiple @code{qTsV} to get additional variables. Replies to
39796 these packets follow the syntax of the @code{QTDV} packets that define
39797 trace state variables.
39803 @cindex @samp{qTfSTM} packet
39804 @cindex @samp{qTsSTM} packet
39805 These packets request data about static tracepoint markers that exist
39806 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39807 first piece of data, and multiple @code{qTsSTM} to get additional
39808 pieces. Replies to these packets take the following form:
39812 @item m @var{address}:@var{id}:@var{extra}
39814 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39815 a comma-separated list of markers
39817 (lower case letter @samp{L}) denotes end of list.
39819 An error occurred. The error number @var{nn} is given as hex digits.
39821 An empty reply indicates that the request is not supported by the
39825 The @var{address} is encoded in hex;
39826 @var{id} and @var{extra} are strings encoded in hex.
39828 In response to each query, the target will reply with a list of one or
39829 more markers, separated by commas. @value{GDBN} will respond to each
39830 reply with a request for more markers (using the @samp{qs} form of the
39831 query), until the target responds with @samp{l} (lower-case ell, for
39834 @item qTSTMat:@var{address}
39836 @cindex @samp{qTSTMat} packet
39837 This packets requests data about static tracepoint markers in the
39838 target program at @var{address}. Replies to this packet follow the
39839 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39840 tracepoint markers.
39842 @item QTSave:@var{filename}
39843 @cindex @samp{QTSave} packet
39844 This packet directs the target to save trace data to the file name
39845 @var{filename} in the target's filesystem. The @var{filename} is encoded
39846 as a hex string; the interpretation of the file name (relative vs
39847 absolute, wild cards, etc) is up to the target.
39849 @item qTBuffer:@var{offset},@var{len}
39850 @cindex @samp{qTBuffer} packet
39851 Return up to @var{len} bytes of the current contents of trace buffer,
39852 starting at @var{offset}. The trace buffer is treated as if it were
39853 a contiguous collection of traceframes, as per the trace file format.
39854 The reply consists as many hex-encoded bytes as the target can deliver
39855 in a packet; it is not an error to return fewer than were asked for.
39856 A reply consisting of just @code{l} indicates that no bytes are
39859 @item QTBuffer:circular:@var{value}
39860 This packet directs the target to use a circular trace buffer if
39861 @var{value} is 1, or a linear buffer if the value is 0.
39863 @item QTBuffer:size:@var{size}
39864 @anchor{QTBuffer-size}
39865 @cindex @samp{QTBuffer size} packet
39866 This packet directs the target to make the trace buffer be of size
39867 @var{size} if possible. A value of @code{-1} tells the target to
39868 use whatever size it prefers.
39870 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39871 @cindex @samp{QTNotes} packet
39872 This packet adds optional textual notes to the trace run. Allowable
39873 types include @code{user}, @code{notes}, and @code{tstop}, the
39874 @var{text} fields are arbitrary strings, hex-encoded.
39878 @subsection Relocate instruction reply packet
39879 When installing fast tracepoints in memory, the target may need to
39880 relocate the instruction currently at the tracepoint address to a
39881 different address in memory. For most instructions, a simple copy is
39882 enough, but, for example, call instructions that implicitly push the
39883 return address on the stack, and relative branches or other
39884 PC-relative instructions require offset adjustment, so that the effect
39885 of executing the instruction at a different address is the same as if
39886 it had executed in the original location.
39888 In response to several of the tracepoint packets, the target may also
39889 respond with a number of intermediate @samp{qRelocInsn} request
39890 packets before the final result packet, to have @value{GDBN} handle
39891 this relocation operation. If a packet supports this mechanism, its
39892 documentation will explicitly say so. See for example the above
39893 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39894 format of the request is:
39897 @item qRelocInsn:@var{from};@var{to}
39899 This requests @value{GDBN} to copy instruction at address @var{from}
39900 to address @var{to}, possibly adjusted so that executing the
39901 instruction at @var{to} has the same effect as executing it at
39902 @var{from}. @value{GDBN} writes the adjusted instruction to target
39903 memory starting at @var{to}.
39908 @item qRelocInsn:@var{adjusted_size}
39909 Informs the stub the relocation is complete. The @var{adjusted_size} is
39910 the length in bytes of resulting relocated instruction sequence.
39912 A badly formed request was detected, or an error was encountered while
39913 relocating the instruction.
39916 @node Host I/O Packets
39917 @section Host I/O Packets
39918 @cindex Host I/O, remote protocol
39919 @cindex file transfer, remote protocol
39921 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39922 operations on the far side of a remote link. For example, Host I/O is
39923 used to upload and download files to a remote target with its own
39924 filesystem. Host I/O uses the same constant values and data structure
39925 layout as the target-initiated File-I/O protocol. However, the
39926 Host I/O packets are structured differently. The target-initiated
39927 protocol relies on target memory to store parameters and buffers.
39928 Host I/O requests are initiated by @value{GDBN}, and the
39929 target's memory is not involved. @xref{File-I/O Remote Protocol
39930 Extension}, for more details on the target-initiated protocol.
39932 The Host I/O request packets all encode a single operation along with
39933 its arguments. They have this format:
39937 @item vFile:@var{operation}: @var{parameter}@dots{}
39938 @var{operation} is the name of the particular request; the target
39939 should compare the entire packet name up to the second colon when checking
39940 for a supported operation. The format of @var{parameter} depends on
39941 the operation. Numbers are always passed in hexadecimal. Negative
39942 numbers have an explicit minus sign (i.e.@: two's complement is not
39943 used). Strings (e.g.@: filenames) are encoded as a series of
39944 hexadecimal bytes. The last argument to a system call may be a
39945 buffer of escaped binary data (@pxref{Binary Data}).
39949 The valid responses to Host I/O packets are:
39953 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39954 @var{result} is the integer value returned by this operation, usually
39955 non-negative for success and -1 for errors. If an error has occured,
39956 @var{errno} will be included in the result specifying a
39957 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39958 operations which return data, @var{attachment} supplies the data as a
39959 binary buffer. Binary buffers in response packets are escaped in the
39960 normal way (@pxref{Binary Data}). See the individual packet
39961 documentation for the interpretation of @var{result} and
39965 An empty response indicates that this operation is not recognized.
39969 These are the supported Host I/O operations:
39972 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39973 Open a file at @var{filename} and return a file descriptor for it, or
39974 return -1 if an error occurs. The @var{filename} is a string,
39975 @var{flags} is an integer indicating a mask of open flags
39976 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39977 of mode bits to use if the file is created (@pxref{mode_t Values}).
39978 @xref{open}, for details of the open flags and mode values.
39980 @item vFile:close: @var{fd}
39981 Close the open file corresponding to @var{fd} and return 0, or
39982 -1 if an error occurs.
39984 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39985 Read data from the open file corresponding to @var{fd}. Up to
39986 @var{count} bytes will be read from the file, starting at @var{offset}
39987 relative to the start of the file. The target may read fewer bytes;
39988 common reasons include packet size limits and an end-of-file
39989 condition. The number of bytes read is returned. Zero should only be
39990 returned for a successful read at the end of the file, or if
39991 @var{count} was zero.
39993 The data read should be returned as a binary attachment on success.
39994 If zero bytes were read, the response should include an empty binary
39995 attachment (i.e.@: a trailing semicolon). The return value is the
39996 number of target bytes read; the binary attachment may be longer if
39997 some characters were escaped.
39999 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40000 Write @var{data} (a binary buffer) to the open file corresponding
40001 to @var{fd}. Start the write at @var{offset} from the start of the
40002 file. Unlike many @code{write} system calls, there is no
40003 separate @var{count} argument; the length of @var{data} in the
40004 packet is used. @samp{vFile:write} returns the number of bytes written,
40005 which may be shorter than the length of @var{data}, or -1 if an
40008 @item vFile:fstat: @var{fd}
40009 Get information about the open file corresponding to @var{fd}.
40010 On success the information is returned as a binary attachment
40011 and the return value is the size of this attachment in bytes.
40012 If an error occurs the return value is -1. The format of the
40013 returned binary attachment is as described in @ref{struct stat}.
40015 @item vFile:unlink: @var{filename}
40016 Delete the file at @var{filename} on the target. Return 0,
40017 or -1 if an error occurs. The @var{filename} is a string.
40019 @item vFile:readlink: @var{filename}
40020 Read value of symbolic link @var{filename} on the target. Return
40021 the number of bytes read, or -1 if an error occurs.
40023 The data read should be returned as a binary attachment on success.
40024 If zero bytes were read, the response should include an empty binary
40025 attachment (i.e.@: a trailing semicolon). The return value is the
40026 number of target bytes read; the binary attachment may be longer if
40027 some characters were escaped.
40029 @item vFile:setfs: @var{pid}
40030 Select the filesystem on which @code{vFile} operations with
40031 @var{filename} arguments will operate. This is required for
40032 @value{GDBN} to be able to access files on remote targets where
40033 the remote stub does not share a common filesystem with the
40036 If @var{pid} is nonzero, select the filesystem as seen by process
40037 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40038 the remote stub. Return 0 on success, or -1 if an error occurs.
40039 If @code{vFile:setfs:} indicates success, the selected filesystem
40040 remains selected until the next successful @code{vFile:setfs:}
40046 @section Interrupts
40047 @cindex interrupts (remote protocol)
40048 @anchor{interrupting remote targets}
40050 In all-stop mode, when a program on the remote target is running,
40051 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40052 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40053 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40055 The precise meaning of @code{BREAK} is defined by the transport
40056 mechanism and may, in fact, be undefined. @value{GDBN} does not
40057 currently define a @code{BREAK} mechanism for any of the network
40058 interfaces except for TCP, in which case @value{GDBN} sends the
40059 @code{telnet} BREAK sequence.
40061 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40062 transport mechanisms. It is represented by sending the single byte
40063 @code{0x03} without any of the usual packet overhead described in
40064 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40065 transmitted as part of a packet, it is considered to be packet data
40066 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40067 (@pxref{X packet}), used for binary downloads, may include an unescaped
40068 @code{0x03} as part of its packet.
40070 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40071 When Linux kernel receives this sequence from serial port,
40072 it stops execution and connects to gdb.
40074 In non-stop mode, because packet resumptions are asynchronous
40075 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40076 command to the remote stub, even when the target is running. For that
40077 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40078 packet}) with the usual packet framing instead of the single byte
40081 Stubs are not required to recognize these interrupt mechanisms and the
40082 precise meaning associated with receipt of the interrupt is
40083 implementation defined. If the target supports debugging of multiple
40084 threads and/or processes, it should attempt to interrupt all
40085 currently-executing threads and processes.
40086 If the stub is successful at interrupting the
40087 running program, it should send one of the stop
40088 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40089 of successfully stopping the program in all-stop mode, and a stop reply
40090 for each stopped thread in non-stop mode.
40091 Interrupts received while the
40092 program is stopped are queued and the program will be interrupted when
40093 it is resumed next time.
40095 @node Notification Packets
40096 @section Notification Packets
40097 @cindex notification packets
40098 @cindex packets, notification
40100 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40101 packets that require no acknowledgment. Both the GDB and the stub
40102 may send notifications (although the only notifications defined at
40103 present are sent by the stub). Notifications carry information
40104 without incurring the round-trip latency of an acknowledgment, and so
40105 are useful for low-impact communications where occasional packet loss
40108 A notification packet has the form @samp{% @var{data} #
40109 @var{checksum}}, where @var{data} is the content of the notification,
40110 and @var{checksum} is a checksum of @var{data}, computed and formatted
40111 as for ordinary @value{GDBN} packets. A notification's @var{data}
40112 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40113 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40114 to acknowledge the notification's receipt or to report its corruption.
40116 Every notification's @var{data} begins with a name, which contains no
40117 colon characters, followed by a colon character.
40119 Recipients should silently ignore corrupted notifications and
40120 notifications they do not understand. Recipients should restart
40121 timeout periods on receipt of a well-formed notification, whether or
40122 not they understand it.
40124 Senders should only send the notifications described here when this
40125 protocol description specifies that they are permitted. In the
40126 future, we may extend the protocol to permit existing notifications in
40127 new contexts; this rule helps older senders avoid confusing newer
40130 (Older versions of @value{GDBN} ignore bytes received until they see
40131 the @samp{$} byte that begins an ordinary packet, so new stubs may
40132 transmit notifications without fear of confusing older clients. There
40133 are no notifications defined for @value{GDBN} to send at the moment, but we
40134 assume that most older stubs would ignore them, as well.)
40136 Each notification is comprised of three parts:
40138 @item @var{name}:@var{event}
40139 The notification packet is sent by the side that initiates the
40140 exchange (currently, only the stub does that), with @var{event}
40141 carrying the specific information about the notification, and
40142 @var{name} specifying the name of the notification.
40144 The acknowledge sent by the other side, usually @value{GDBN}, to
40145 acknowledge the exchange and request the event.
40148 The purpose of an asynchronous notification mechanism is to report to
40149 @value{GDBN} that something interesting happened in the remote stub.
40151 The remote stub may send notification @var{name}:@var{event}
40152 at any time, but @value{GDBN} acknowledges the notification when
40153 appropriate. The notification event is pending before @value{GDBN}
40154 acknowledges. Only one notification at a time may be pending; if
40155 additional events occur before @value{GDBN} has acknowledged the
40156 previous notification, they must be queued by the stub for later
40157 synchronous transmission in response to @var{ack} packets from
40158 @value{GDBN}. Because the notification mechanism is unreliable,
40159 the stub is permitted to resend a notification if it believes
40160 @value{GDBN} may not have received it.
40162 Specifically, notifications may appear when @value{GDBN} is not
40163 otherwise reading input from the stub, or when @value{GDBN} is
40164 expecting to read a normal synchronous response or a
40165 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40166 Notification packets are distinct from any other communication from
40167 the stub so there is no ambiguity.
40169 After receiving a notification, @value{GDBN} shall acknowledge it by
40170 sending a @var{ack} packet as a regular, synchronous request to the
40171 stub. Such acknowledgment is not required to happen immediately, as
40172 @value{GDBN} is permitted to send other, unrelated packets to the
40173 stub first, which the stub should process normally.
40175 Upon receiving a @var{ack} packet, if the stub has other queued
40176 events to report to @value{GDBN}, it shall respond by sending a
40177 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40178 packet to solicit further responses; again, it is permitted to send
40179 other, unrelated packets as well which the stub should process
40182 If the stub receives a @var{ack} packet and there are no additional
40183 @var{event} to report, the stub shall return an @samp{OK} response.
40184 At this point, @value{GDBN} has finished processing a notification
40185 and the stub has completed sending any queued events. @value{GDBN}
40186 won't accept any new notifications until the final @samp{OK} is
40187 received . If further notification events occur, the stub shall send
40188 a new notification, @value{GDBN} shall accept the notification, and
40189 the process shall be repeated.
40191 The process of asynchronous notification can be illustrated by the
40194 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40197 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40199 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40204 The following notifications are defined:
40205 @multitable @columnfractions 0.12 0.12 0.38 0.38
40214 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40215 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40216 for information on how these notifications are acknowledged by
40218 @tab Report an asynchronous stop event in non-stop mode.
40222 @node Remote Non-Stop
40223 @section Remote Protocol Support for Non-Stop Mode
40225 @value{GDBN}'s remote protocol supports non-stop debugging of
40226 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40227 supports non-stop mode, it should report that to @value{GDBN} by including
40228 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40230 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40231 establishing a new connection with the stub. Entering non-stop mode
40232 does not alter the state of any currently-running threads, but targets
40233 must stop all threads in any already-attached processes when entering
40234 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40235 probe the target state after a mode change.
40237 In non-stop mode, when an attached process encounters an event that
40238 would otherwise be reported with a stop reply, it uses the
40239 asynchronous notification mechanism (@pxref{Notification Packets}) to
40240 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40241 in all processes are stopped when a stop reply is sent, in non-stop
40242 mode only the thread reporting the stop event is stopped. That is,
40243 when reporting a @samp{S} or @samp{T} response to indicate completion
40244 of a step operation, hitting a breakpoint, or a fault, only the
40245 affected thread is stopped; any other still-running threads continue
40246 to run. When reporting a @samp{W} or @samp{X} response, all running
40247 threads belonging to other attached processes continue to run.
40249 In non-stop mode, the target shall respond to the @samp{?} packet as
40250 follows. First, any incomplete stop reply notification/@samp{vStopped}
40251 sequence in progress is abandoned. The target must begin a new
40252 sequence reporting stop events for all stopped threads, whether or not
40253 it has previously reported those events to @value{GDBN}. The first
40254 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40255 subsequent stop replies are sent as responses to @samp{vStopped} packets
40256 using the mechanism described above. The target must not send
40257 asynchronous stop reply notifications until the sequence is complete.
40258 If all threads are running when the target receives the @samp{?} packet,
40259 or if the target is not attached to any process, it shall respond
40262 If the stub supports non-stop mode, it should also support the
40263 @samp{swbreak} stop reason if software breakpoints are supported, and
40264 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40265 (@pxref{swbreak stop reason}). This is because given the asynchronous
40266 nature of non-stop mode, between the time a thread hits a breakpoint
40267 and the time the event is finally processed by @value{GDBN}, the
40268 breakpoint may have already been removed from the target. Due to
40269 this, @value{GDBN} needs to be able to tell whether a trap stop was
40270 caused by a delayed breakpoint event, which should be ignored, as
40271 opposed to a random trap signal, which should be reported to the user.
40272 Note the @samp{swbreak} feature implies that the target is responsible
40273 for adjusting the PC when a software breakpoint triggers, if
40274 necessary, such as on the x86 architecture.
40276 @node Packet Acknowledgment
40277 @section Packet Acknowledgment
40279 @cindex acknowledgment, for @value{GDBN} remote
40280 @cindex packet acknowledgment, for @value{GDBN} remote
40281 By default, when either the host or the target machine receives a packet,
40282 the first response expected is an acknowledgment: either @samp{+} (to indicate
40283 the package was received correctly) or @samp{-} (to request retransmission).
40284 This mechanism allows the @value{GDBN} remote protocol to operate over
40285 unreliable transport mechanisms, such as a serial line.
40287 In cases where the transport mechanism is itself reliable (such as a pipe or
40288 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40289 It may be desirable to disable them in that case to reduce communication
40290 overhead, or for other reasons. This can be accomplished by means of the
40291 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40293 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40294 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40295 and response format still includes the normal checksum, as described in
40296 @ref{Overview}, but the checksum may be ignored by the receiver.
40298 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40299 no-acknowledgment mode, it should report that to @value{GDBN}
40300 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40301 @pxref{qSupported}.
40302 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40303 disabled via the @code{set remote noack-packet off} command
40304 (@pxref{Remote Configuration}),
40305 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40306 Only then may the stub actually turn off packet acknowledgments.
40307 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40308 response, which can be safely ignored by the stub.
40310 Note that @code{set remote noack-packet} command only affects negotiation
40311 between @value{GDBN} and the stub when subsequent connections are made;
40312 it does not affect the protocol acknowledgment state for any current
40314 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40315 new connection is established,
40316 there is also no protocol request to re-enable the acknowledgments
40317 for the current connection, once disabled.
40322 Example sequence of a target being re-started. Notice how the restart
40323 does not get any direct output:
40328 @emph{target restarts}
40331 <- @code{T001:1234123412341234}
40335 Example sequence of a target being stepped by a single instruction:
40338 -> @code{G1445@dots{}}
40343 <- @code{T001:1234123412341234}
40347 <- @code{1455@dots{}}
40351 @node File-I/O Remote Protocol Extension
40352 @section File-I/O Remote Protocol Extension
40353 @cindex File-I/O remote protocol extension
40356 * File-I/O Overview::
40357 * Protocol Basics::
40358 * The F Request Packet::
40359 * The F Reply Packet::
40360 * The Ctrl-C Message::
40362 * List of Supported Calls::
40363 * Protocol-specific Representation of Datatypes::
40365 * File-I/O Examples::
40368 @node File-I/O Overview
40369 @subsection File-I/O Overview
40370 @cindex file-i/o overview
40372 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40373 target to use the host's file system and console I/O to perform various
40374 system calls. System calls on the target system are translated into a
40375 remote protocol packet to the host system, which then performs the needed
40376 actions and returns a response packet to the target system.
40377 This simulates file system operations even on targets that lack file systems.
40379 The protocol is defined to be independent of both the host and target systems.
40380 It uses its own internal representation of datatypes and values. Both
40381 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40382 translating the system-dependent value representations into the internal
40383 protocol representations when data is transmitted.
40385 The communication is synchronous. A system call is possible only when
40386 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40387 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40388 the target is stopped to allow deterministic access to the target's
40389 memory. Therefore File-I/O is not interruptible by target signals. On
40390 the other hand, it is possible to interrupt File-I/O by a user interrupt
40391 (@samp{Ctrl-C}) within @value{GDBN}.
40393 The target's request to perform a host system call does not finish
40394 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40395 after finishing the system call, the target returns to continuing the
40396 previous activity (continue, step). No additional continue or step
40397 request from @value{GDBN} is required.
40400 (@value{GDBP}) continue
40401 <- target requests 'system call X'
40402 target is stopped, @value{GDBN} executes system call
40403 -> @value{GDBN} returns result
40404 ... target continues, @value{GDBN} returns to wait for the target
40405 <- target hits breakpoint and sends a Txx packet
40408 The protocol only supports I/O on the console and to regular files on
40409 the host file system. Character or block special devices, pipes,
40410 named pipes, sockets or any other communication method on the host
40411 system are not supported by this protocol.
40413 File I/O is not supported in non-stop mode.
40415 @node Protocol Basics
40416 @subsection Protocol Basics
40417 @cindex protocol basics, file-i/o
40419 The File-I/O protocol uses the @code{F} packet as the request as well
40420 as reply packet. Since a File-I/O system call can only occur when
40421 @value{GDBN} is waiting for a response from the continuing or stepping target,
40422 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40423 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40424 This @code{F} packet contains all information needed to allow @value{GDBN}
40425 to call the appropriate host system call:
40429 A unique identifier for the requested system call.
40432 All parameters to the system call. Pointers are given as addresses
40433 in the target memory address space. Pointers to strings are given as
40434 pointer/length pair. Numerical values are given as they are.
40435 Numerical control flags are given in a protocol-specific representation.
40439 At this point, @value{GDBN} has to perform the following actions.
40443 If the parameters include pointer values to data needed as input to a
40444 system call, @value{GDBN} requests this data from the target with a
40445 standard @code{m} packet request. This additional communication has to be
40446 expected by the target implementation and is handled as any other @code{m}
40450 @value{GDBN} translates all value from protocol representation to host
40451 representation as needed. Datatypes are coerced into the host types.
40454 @value{GDBN} calls the system call.
40457 It then coerces datatypes back to protocol representation.
40460 If the system call is expected to return data in buffer space specified
40461 by pointer parameters to the call, the data is transmitted to the
40462 target using a @code{M} or @code{X} packet. This packet has to be expected
40463 by the target implementation and is handled as any other @code{M} or @code{X}
40468 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40469 necessary information for the target to continue. This at least contains
40476 @code{errno}, if has been changed by the system call.
40483 After having done the needed type and value coercion, the target continues
40484 the latest continue or step action.
40486 @node The F Request Packet
40487 @subsection The @code{F} Request Packet
40488 @cindex file-i/o request packet
40489 @cindex @code{F} request packet
40491 The @code{F} request packet has the following format:
40494 @item F@var{call-id},@var{parameter@dots{}}
40496 @var{call-id} is the identifier to indicate the host system call to be called.
40497 This is just the name of the function.
40499 @var{parameter@dots{}} are the parameters to the system call.
40500 Parameters are hexadecimal integer values, either the actual values in case
40501 of scalar datatypes, pointers to target buffer space in case of compound
40502 datatypes and unspecified memory areas, or pointer/length pairs in case
40503 of string parameters. These are appended to the @var{call-id} as a
40504 comma-delimited list. All values are transmitted in ASCII
40505 string representation, pointer/length pairs separated by a slash.
40511 @node The F Reply Packet
40512 @subsection The @code{F} Reply Packet
40513 @cindex file-i/o reply packet
40514 @cindex @code{F} reply packet
40516 The @code{F} reply packet has the following format:
40520 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40522 @var{retcode} is the return code of the system call as hexadecimal value.
40524 @var{errno} is the @code{errno} set by the call, in protocol-specific
40526 This parameter can be omitted if the call was successful.
40528 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40529 case, @var{errno} must be sent as well, even if the call was successful.
40530 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40537 or, if the call was interrupted before the host call has been performed:
40544 assuming 4 is the protocol-specific representation of @code{EINTR}.
40549 @node The Ctrl-C Message
40550 @subsection The @samp{Ctrl-C} Message
40551 @cindex ctrl-c message, in file-i/o protocol
40553 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40554 reply packet (@pxref{The F Reply Packet}),
40555 the target should behave as if it had
40556 gotten a break message. The meaning for the target is ``system call
40557 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40558 (as with a break message) and return to @value{GDBN} with a @code{T02}
40561 It's important for the target to know in which
40562 state the system call was interrupted. There are two possible cases:
40566 The system call hasn't been performed on the host yet.
40569 The system call on the host has been finished.
40573 These two states can be distinguished by the target by the value of the
40574 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40575 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40576 on POSIX systems. In any other case, the target may presume that the
40577 system call has been finished --- successfully or not --- and should behave
40578 as if the break message arrived right after the system call.
40580 @value{GDBN} must behave reliably. If the system call has not been called
40581 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40582 @code{errno} in the packet. If the system call on the host has been finished
40583 before the user requests a break, the full action must be finished by
40584 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40585 The @code{F} packet may only be sent when either nothing has happened
40586 or the full action has been completed.
40589 @subsection Console I/O
40590 @cindex console i/o as part of file-i/o
40592 By default and if not explicitly closed by the target system, the file
40593 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40594 on the @value{GDBN} console is handled as any other file output operation
40595 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40596 by @value{GDBN} so that after the target read request from file descriptor
40597 0 all following typing is buffered until either one of the following
40602 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40604 system call is treated as finished.
40607 The user presses @key{RET}. This is treated as end of input with a trailing
40611 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40612 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40616 If the user has typed more characters than fit in the buffer given to
40617 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40618 either another @code{read(0, @dots{})} is requested by the target, or debugging
40619 is stopped at the user's request.
40622 @node List of Supported Calls
40623 @subsection List of Supported Calls
40624 @cindex list of supported file-i/o calls
40641 @unnumberedsubsubsec open
40642 @cindex open, file-i/o system call
40647 int open(const char *pathname, int flags);
40648 int open(const char *pathname, int flags, mode_t mode);
40652 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40655 @var{flags} is the bitwise @code{OR} of the following values:
40659 If the file does not exist it will be created. The host
40660 rules apply as far as file ownership and time stamps
40664 When used with @code{O_CREAT}, if the file already exists it is
40665 an error and open() fails.
40668 If the file already exists and the open mode allows
40669 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40670 truncated to zero length.
40673 The file is opened in append mode.
40676 The file is opened for reading only.
40679 The file is opened for writing only.
40682 The file is opened for reading and writing.
40686 Other bits are silently ignored.
40690 @var{mode} is the bitwise @code{OR} of the following values:
40694 User has read permission.
40697 User has write permission.
40700 Group has read permission.
40703 Group has write permission.
40706 Others have read permission.
40709 Others have write permission.
40713 Other bits are silently ignored.
40716 @item Return value:
40717 @code{open} returns the new file descriptor or -1 if an error
40724 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40727 @var{pathname} refers to a directory.
40730 The requested access is not allowed.
40733 @var{pathname} was too long.
40736 A directory component in @var{pathname} does not exist.
40739 @var{pathname} refers to a device, pipe, named pipe or socket.
40742 @var{pathname} refers to a file on a read-only filesystem and
40743 write access was requested.
40746 @var{pathname} is an invalid pointer value.
40749 No space on device to create the file.
40752 The process already has the maximum number of files open.
40755 The limit on the total number of files open on the system
40759 The call was interrupted by the user.
40765 @unnumberedsubsubsec close
40766 @cindex close, file-i/o system call
40775 @samp{Fclose,@var{fd}}
40777 @item Return value:
40778 @code{close} returns zero on success, or -1 if an error occurred.
40784 @var{fd} isn't a valid open file descriptor.
40787 The call was interrupted by the user.
40793 @unnumberedsubsubsec read
40794 @cindex read, file-i/o system call
40799 int read(int fd, void *buf, unsigned int count);
40803 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40805 @item Return value:
40806 On success, the number of bytes read is returned.
40807 Zero indicates end of file. If count is zero, read
40808 returns zero as well. On error, -1 is returned.
40814 @var{fd} is not a valid file descriptor or is not open for
40818 @var{bufptr} is an invalid pointer value.
40821 The call was interrupted by the user.
40827 @unnumberedsubsubsec write
40828 @cindex write, file-i/o system call
40833 int write(int fd, const void *buf, unsigned int count);
40837 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40839 @item Return value:
40840 On success, the number of bytes written are returned.
40841 Zero indicates nothing was written. On error, -1
40848 @var{fd} is not a valid file descriptor or is not open for
40852 @var{bufptr} is an invalid pointer value.
40855 An attempt was made to write a file that exceeds the
40856 host-specific maximum file size allowed.
40859 No space on device to write the data.
40862 The call was interrupted by the user.
40868 @unnumberedsubsubsec lseek
40869 @cindex lseek, file-i/o system call
40874 long lseek (int fd, long offset, int flag);
40878 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40880 @var{flag} is one of:
40884 The offset is set to @var{offset} bytes.
40887 The offset is set to its current location plus @var{offset}
40891 The offset is set to the size of the file plus @var{offset}
40895 @item Return value:
40896 On success, the resulting unsigned offset in bytes from
40897 the beginning of the file is returned. Otherwise, a
40898 value of -1 is returned.
40904 @var{fd} is not a valid open file descriptor.
40907 @var{fd} is associated with the @value{GDBN} console.
40910 @var{flag} is not a proper value.
40913 The call was interrupted by the user.
40919 @unnumberedsubsubsec rename
40920 @cindex rename, file-i/o system call
40925 int rename(const char *oldpath, const char *newpath);
40929 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40931 @item Return value:
40932 On success, zero is returned. On error, -1 is returned.
40938 @var{newpath} is an existing directory, but @var{oldpath} is not a
40942 @var{newpath} is a non-empty directory.
40945 @var{oldpath} or @var{newpath} is a directory that is in use by some
40949 An attempt was made to make a directory a subdirectory
40953 A component used as a directory in @var{oldpath} or new
40954 path is not a directory. Or @var{oldpath} is a directory
40955 and @var{newpath} exists but is not a directory.
40958 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40961 No access to the file or the path of the file.
40965 @var{oldpath} or @var{newpath} was too long.
40968 A directory component in @var{oldpath} or @var{newpath} does not exist.
40971 The file is on a read-only filesystem.
40974 The device containing the file has no room for the new
40978 The call was interrupted by the user.
40984 @unnumberedsubsubsec unlink
40985 @cindex unlink, file-i/o system call
40990 int unlink(const char *pathname);
40994 @samp{Funlink,@var{pathnameptr}/@var{len}}
40996 @item Return value:
40997 On success, zero is returned. On error, -1 is returned.
41003 No access to the file or the path of the file.
41006 The system does not allow unlinking of directories.
41009 The file @var{pathname} cannot be unlinked because it's
41010 being used by another process.
41013 @var{pathnameptr} is an invalid pointer value.
41016 @var{pathname} was too long.
41019 A directory component in @var{pathname} does not exist.
41022 A component of the path is not a directory.
41025 The file is on a read-only filesystem.
41028 The call was interrupted by the user.
41034 @unnumberedsubsubsec stat/fstat
41035 @cindex fstat, file-i/o system call
41036 @cindex stat, file-i/o system call
41041 int stat(const char *pathname, struct stat *buf);
41042 int fstat(int fd, struct stat *buf);
41046 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41047 @samp{Ffstat,@var{fd},@var{bufptr}}
41049 @item Return value:
41050 On success, zero is returned. On error, -1 is returned.
41056 @var{fd} is not a valid open file.
41059 A directory component in @var{pathname} does not exist or the
41060 path is an empty string.
41063 A component of the path is not a directory.
41066 @var{pathnameptr} is an invalid pointer value.
41069 No access to the file or the path of the file.
41072 @var{pathname} was too long.
41075 The call was interrupted by the user.
41081 @unnumberedsubsubsec gettimeofday
41082 @cindex gettimeofday, file-i/o system call
41087 int gettimeofday(struct timeval *tv, void *tz);
41091 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41093 @item Return value:
41094 On success, 0 is returned, -1 otherwise.
41100 @var{tz} is a non-NULL pointer.
41103 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41109 @unnumberedsubsubsec isatty
41110 @cindex isatty, file-i/o system call
41115 int isatty(int fd);
41119 @samp{Fisatty,@var{fd}}
41121 @item Return value:
41122 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41128 The call was interrupted by the user.
41133 Note that the @code{isatty} call is treated as a special case: it returns
41134 1 to the target if the file descriptor is attached
41135 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41136 would require implementing @code{ioctl} and would be more complex than
41141 @unnumberedsubsubsec system
41142 @cindex system, file-i/o system call
41147 int system(const char *command);
41151 @samp{Fsystem,@var{commandptr}/@var{len}}
41153 @item Return value:
41154 If @var{len} is zero, the return value indicates whether a shell is
41155 available. A zero return value indicates a shell is not available.
41156 For non-zero @var{len}, the value returned is -1 on error and the
41157 return status of the command otherwise. Only the exit status of the
41158 command is returned, which is extracted from the host's @code{system}
41159 return value by calling @code{WEXITSTATUS(retval)}. In case
41160 @file{/bin/sh} could not be executed, 127 is returned.
41166 The call was interrupted by the user.
41171 @value{GDBN} takes over the full task of calling the necessary host calls
41172 to perform the @code{system} call. The return value of @code{system} on
41173 the host is simplified before it's returned
41174 to the target. Any termination signal information from the child process
41175 is discarded, and the return value consists
41176 entirely of the exit status of the called command.
41178 Due to security concerns, the @code{system} call is by default refused
41179 by @value{GDBN}. The user has to allow this call explicitly with the
41180 @code{set remote system-call-allowed 1} command.
41183 @item set remote system-call-allowed
41184 @kindex set remote system-call-allowed
41185 Control whether to allow the @code{system} calls in the File I/O
41186 protocol for the remote target. The default is zero (disabled).
41188 @item show remote system-call-allowed
41189 @kindex show remote system-call-allowed
41190 Show whether the @code{system} calls are allowed in the File I/O
41194 @node Protocol-specific Representation of Datatypes
41195 @subsection Protocol-specific Representation of Datatypes
41196 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41199 * Integral Datatypes::
41201 * Memory Transfer::
41206 @node Integral Datatypes
41207 @unnumberedsubsubsec Integral Datatypes
41208 @cindex integral datatypes, in file-i/o protocol
41210 The integral datatypes used in the system calls are @code{int},
41211 @code{unsigned int}, @code{long}, @code{unsigned long},
41212 @code{mode_t}, and @code{time_t}.
41214 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41215 implemented as 32 bit values in this protocol.
41217 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41219 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41220 in @file{limits.h}) to allow range checking on host and target.
41222 @code{time_t} datatypes are defined as seconds since the Epoch.
41224 All integral datatypes transferred as part of a memory read or write of a
41225 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41228 @node Pointer Values
41229 @unnumberedsubsubsec Pointer Values
41230 @cindex pointer values, in file-i/o protocol
41232 Pointers to target data are transmitted as they are. An exception
41233 is made for pointers to buffers for which the length isn't
41234 transmitted as part of the function call, namely strings. Strings
41235 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41242 which is a pointer to data of length 18 bytes at position 0x1aaf.
41243 The length is defined as the full string length in bytes, including
41244 the trailing null byte. For example, the string @code{"hello world"}
41245 at address 0x123456 is transmitted as
41251 @node Memory Transfer
41252 @unnumberedsubsubsec Memory Transfer
41253 @cindex memory transfer, in file-i/o protocol
41255 Structured data which is transferred using a memory read or write (for
41256 example, a @code{struct stat}) is expected to be in a protocol-specific format
41257 with all scalar multibyte datatypes being big endian. Translation to
41258 this representation needs to be done both by the target before the @code{F}
41259 packet is sent, and by @value{GDBN} before
41260 it transfers memory to the target. Transferred pointers to structured
41261 data should point to the already-coerced data at any time.
41265 @unnumberedsubsubsec struct stat
41266 @cindex struct stat, in file-i/o protocol
41268 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41269 is defined as follows:
41273 unsigned int st_dev; /* device */
41274 unsigned int st_ino; /* inode */
41275 mode_t st_mode; /* protection */
41276 unsigned int st_nlink; /* number of hard links */
41277 unsigned int st_uid; /* user ID of owner */
41278 unsigned int st_gid; /* group ID of owner */
41279 unsigned int st_rdev; /* device type (if inode device) */
41280 unsigned long st_size; /* total size, in bytes */
41281 unsigned long st_blksize; /* blocksize for filesystem I/O */
41282 unsigned long st_blocks; /* number of blocks allocated */
41283 time_t st_atime; /* time of last access */
41284 time_t st_mtime; /* time of last modification */
41285 time_t st_ctime; /* time of last change */
41289 The integral datatypes conform to the definitions given in the
41290 appropriate section (see @ref{Integral Datatypes}, for details) so this
41291 structure is of size 64 bytes.
41293 The values of several fields have a restricted meaning and/or
41299 A value of 0 represents a file, 1 the console.
41302 No valid meaning for the target. Transmitted unchanged.
41305 Valid mode bits are described in @ref{Constants}. Any other
41306 bits have currently no meaning for the target.
41311 No valid meaning for the target. Transmitted unchanged.
41316 These values have a host and file system dependent
41317 accuracy. Especially on Windows hosts, the file system may not
41318 support exact timing values.
41321 The target gets a @code{struct stat} of the above representation and is
41322 responsible for coercing it to the target representation before
41325 Note that due to size differences between the host, target, and protocol
41326 representations of @code{struct stat} members, these members could eventually
41327 get truncated on the target.
41329 @node struct timeval
41330 @unnumberedsubsubsec struct timeval
41331 @cindex struct timeval, in file-i/o protocol
41333 The buffer of type @code{struct timeval} used by the File-I/O protocol
41334 is defined as follows:
41338 time_t tv_sec; /* second */
41339 long tv_usec; /* microsecond */
41343 The integral datatypes conform to the definitions given in the
41344 appropriate section (see @ref{Integral Datatypes}, for details) so this
41345 structure is of size 8 bytes.
41348 @subsection Constants
41349 @cindex constants, in file-i/o protocol
41351 The following values are used for the constants inside of the
41352 protocol. @value{GDBN} and target are responsible for translating these
41353 values before and after the call as needed.
41364 @unnumberedsubsubsec Open Flags
41365 @cindex open flags, in file-i/o protocol
41367 All values are given in hexadecimal representation.
41379 @node mode_t Values
41380 @unnumberedsubsubsec mode_t Values
41381 @cindex mode_t values, in file-i/o protocol
41383 All values are given in octal representation.
41400 @unnumberedsubsubsec Errno Values
41401 @cindex errno values, in file-i/o protocol
41403 All values are given in decimal representation.
41428 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41429 any error value not in the list of supported error numbers.
41432 @unnumberedsubsubsec Lseek Flags
41433 @cindex lseek flags, in file-i/o protocol
41442 @unnumberedsubsubsec Limits
41443 @cindex limits, in file-i/o protocol
41445 All values are given in decimal representation.
41448 INT_MIN -2147483648
41450 UINT_MAX 4294967295
41451 LONG_MIN -9223372036854775808
41452 LONG_MAX 9223372036854775807
41453 ULONG_MAX 18446744073709551615
41456 @node File-I/O Examples
41457 @subsection File-I/O Examples
41458 @cindex file-i/o examples
41460 Example sequence of a write call, file descriptor 3, buffer is at target
41461 address 0x1234, 6 bytes should be written:
41464 <- @code{Fwrite,3,1234,6}
41465 @emph{request memory read from target}
41468 @emph{return "6 bytes written"}
41472 Example sequence of a read call, file descriptor 3, buffer is at target
41473 address 0x1234, 6 bytes should be read:
41476 <- @code{Fread,3,1234,6}
41477 @emph{request memory write to target}
41478 -> @code{X1234,6:XXXXXX}
41479 @emph{return "6 bytes read"}
41483 Example sequence of a read call, call fails on the host due to invalid
41484 file descriptor (@code{EBADF}):
41487 <- @code{Fread,3,1234,6}
41491 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41495 <- @code{Fread,3,1234,6}
41500 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41504 <- @code{Fread,3,1234,6}
41505 -> @code{X1234,6:XXXXXX}
41509 @node Library List Format
41510 @section Library List Format
41511 @cindex library list format, remote protocol
41513 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41514 same process as your application to manage libraries. In this case,
41515 @value{GDBN} can use the loader's symbol table and normal memory
41516 operations to maintain a list of shared libraries. On other
41517 platforms, the operating system manages loaded libraries.
41518 @value{GDBN} can not retrieve the list of currently loaded libraries
41519 through memory operations, so it uses the @samp{qXfer:libraries:read}
41520 packet (@pxref{qXfer library list read}) instead. The remote stub
41521 queries the target's operating system and reports which libraries
41524 The @samp{qXfer:libraries:read} packet returns an XML document which
41525 lists loaded libraries and their offsets. Each library has an
41526 associated name and one or more segment or section base addresses,
41527 which report where the library was loaded in memory.
41529 For the common case of libraries that are fully linked binaries, the
41530 library should have a list of segments. If the target supports
41531 dynamic linking of a relocatable object file, its library XML element
41532 should instead include a list of allocated sections. The segment or
41533 section bases are start addresses, not relocation offsets; they do not
41534 depend on the library's link-time base addresses.
41536 @value{GDBN} must be linked with the Expat library to support XML
41537 library lists. @xref{Expat}.
41539 A simple memory map, with one loaded library relocated by a single
41540 offset, looks like this:
41544 <library name="/lib/libc.so.6">
41545 <segment address="0x10000000"/>
41550 Another simple memory map, with one loaded library with three
41551 allocated sections (.text, .data, .bss), looks like this:
41555 <library name="sharedlib.o">
41556 <section address="0x10000000"/>
41557 <section address="0x20000000"/>
41558 <section address="0x30000000"/>
41563 The format of a library list is described by this DTD:
41566 <!-- library-list: Root element with versioning -->
41567 <!ELEMENT library-list (library)*>
41568 <!ATTLIST library-list version CDATA #FIXED "1.0">
41569 <!ELEMENT library (segment*, section*)>
41570 <!ATTLIST library name CDATA #REQUIRED>
41571 <!ELEMENT segment EMPTY>
41572 <!ATTLIST segment address CDATA #REQUIRED>
41573 <!ELEMENT section EMPTY>
41574 <!ATTLIST section address CDATA #REQUIRED>
41577 In addition, segments and section descriptors cannot be mixed within a
41578 single library element, and you must supply at least one segment or
41579 section for each library.
41581 @node Library List Format for SVR4 Targets
41582 @section Library List Format for SVR4 Targets
41583 @cindex library list format, remote protocol
41585 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41586 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41587 shared libraries. Still a special library list provided by this packet is
41588 more efficient for the @value{GDBN} remote protocol.
41590 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41591 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41592 target, the following parameters are reported:
41596 @code{name}, the absolute file name from the @code{l_name} field of
41597 @code{struct link_map}.
41599 @code{lm} with address of @code{struct link_map} used for TLS
41600 (Thread Local Storage) access.
41602 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41603 @code{struct link_map}. For prelinked libraries this is not an absolute
41604 memory address. It is a displacement of absolute memory address against
41605 address the file was prelinked to during the library load.
41607 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41610 Additionally the single @code{main-lm} attribute specifies address of
41611 @code{struct link_map} used for the main executable. This parameter is used
41612 for TLS access and its presence is optional.
41614 @value{GDBN} must be linked with the Expat library to support XML
41615 SVR4 library lists. @xref{Expat}.
41617 A simple memory map, with two loaded libraries (which do not use prelink),
41621 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41622 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41624 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41626 </library-list-svr>
41629 The format of an SVR4 library list is described by this DTD:
41632 <!-- library-list-svr4: Root element with versioning -->
41633 <!ELEMENT library-list-svr4 (library)*>
41634 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41635 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41636 <!ELEMENT library EMPTY>
41637 <!ATTLIST library name CDATA #REQUIRED>
41638 <!ATTLIST library lm CDATA #REQUIRED>
41639 <!ATTLIST library l_addr CDATA #REQUIRED>
41640 <!ATTLIST library l_ld CDATA #REQUIRED>
41643 @node Memory Map Format
41644 @section Memory Map Format
41645 @cindex memory map format
41647 To be able to write into flash memory, @value{GDBN} needs to obtain a
41648 memory map from the target. This section describes the format of the
41651 The memory map is obtained using the @samp{qXfer:memory-map:read}
41652 (@pxref{qXfer memory map read}) packet and is an XML document that
41653 lists memory regions.
41655 @value{GDBN} must be linked with the Expat library to support XML
41656 memory maps. @xref{Expat}.
41658 The top-level structure of the document is shown below:
41661 <?xml version="1.0"?>
41662 <!DOCTYPE memory-map
41663 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41664 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41670 Each region can be either:
41675 A region of RAM starting at @var{addr} and extending for @var{length}
41679 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41684 A region of read-only memory:
41687 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41692 A region of flash memory, with erasure blocks @var{blocksize}
41696 <memory type="flash" start="@var{addr}" length="@var{length}">
41697 <property name="blocksize">@var{blocksize}</property>
41703 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41704 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41705 packets to write to addresses in such ranges.
41707 The formal DTD for memory map format is given below:
41710 <!-- ................................................... -->
41711 <!-- Memory Map XML DTD ................................ -->
41712 <!-- File: memory-map.dtd .............................. -->
41713 <!-- .................................... .............. -->
41714 <!-- memory-map.dtd -->
41715 <!-- memory-map: Root element with versioning -->
41716 <!ELEMENT memory-map (memory)*>
41717 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41718 <!ELEMENT memory (property)*>
41719 <!-- memory: Specifies a memory region,
41720 and its type, or device. -->
41721 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41722 start CDATA #REQUIRED
41723 length CDATA #REQUIRED>
41724 <!-- property: Generic attribute tag -->
41725 <!ELEMENT property (#PCDATA | property)*>
41726 <!ATTLIST property name (blocksize) #REQUIRED>
41729 @node Thread List Format
41730 @section Thread List Format
41731 @cindex thread list format
41733 To efficiently update the list of threads and their attributes,
41734 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41735 (@pxref{qXfer threads read}) and obtains the XML document with
41736 the following structure:
41739 <?xml version="1.0"?>
41741 <thread id="id" core="0" name="name">
41742 ... description ...
41747 Each @samp{thread} element must have the @samp{id} attribute that
41748 identifies the thread (@pxref{thread-id syntax}). The
41749 @samp{core} attribute, if present, specifies which processor core
41750 the thread was last executing on. The @samp{name} attribute, if
41751 present, specifies the human-readable name of the thread. The content
41752 of the of @samp{thread} element is interpreted as human-readable
41753 auxiliary information. The @samp{handle} attribute, if present,
41754 is a hex encoded representation of the thread handle.
41757 @node Traceframe Info Format
41758 @section Traceframe Info Format
41759 @cindex traceframe info format
41761 To be able to know which objects in the inferior can be examined when
41762 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41763 memory ranges, registers and trace state variables that have been
41764 collected in a traceframe.
41766 This list is obtained using the @samp{qXfer:traceframe-info:read}
41767 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41769 @value{GDBN} must be linked with the Expat library to support XML
41770 traceframe info discovery. @xref{Expat}.
41772 The top-level structure of the document is shown below:
41775 <?xml version="1.0"?>
41776 <!DOCTYPE traceframe-info
41777 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41778 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41784 Each traceframe block can be either:
41789 A region of collected memory starting at @var{addr} and extending for
41790 @var{length} bytes from there:
41793 <memory start="@var{addr}" length="@var{length}"/>
41797 A block indicating trace state variable numbered @var{number} has been
41801 <tvar id="@var{number}"/>
41806 The formal DTD for the traceframe info format is given below:
41809 <!ELEMENT traceframe-info (memory | tvar)* >
41810 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41812 <!ELEMENT memory EMPTY>
41813 <!ATTLIST memory start CDATA #REQUIRED
41814 length CDATA #REQUIRED>
41816 <!ATTLIST tvar id CDATA #REQUIRED>
41819 @node Branch Trace Format
41820 @section Branch Trace Format
41821 @cindex branch trace format
41823 In order to display the branch trace of an inferior thread,
41824 @value{GDBN} needs to obtain the list of branches. This list is
41825 represented as list of sequential code blocks that are connected via
41826 branches. The code in each block has been executed sequentially.
41828 This list is obtained using the @samp{qXfer:btrace:read}
41829 (@pxref{qXfer btrace read}) packet and is an XML document.
41831 @value{GDBN} must be linked with the Expat library to support XML
41832 traceframe info discovery. @xref{Expat}.
41834 The top-level structure of the document is shown below:
41837 <?xml version="1.0"?>
41839 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41840 "http://sourceware.org/gdb/gdb-btrace.dtd">
41849 A block of sequentially executed instructions starting at @var{begin}
41850 and ending at @var{end}:
41853 <block begin="@var{begin}" end="@var{end}"/>
41858 The formal DTD for the branch trace format is given below:
41861 <!ELEMENT btrace (block* | pt) >
41862 <!ATTLIST btrace version CDATA #FIXED "1.0">
41864 <!ELEMENT block EMPTY>
41865 <!ATTLIST block begin CDATA #REQUIRED
41866 end CDATA #REQUIRED>
41868 <!ELEMENT pt (pt-config?, raw?)>
41870 <!ELEMENT pt-config (cpu?)>
41872 <!ELEMENT cpu EMPTY>
41873 <!ATTLIST cpu vendor CDATA #REQUIRED
41874 family CDATA #REQUIRED
41875 model CDATA #REQUIRED
41876 stepping CDATA #REQUIRED>
41878 <!ELEMENT raw (#PCDATA)>
41881 @node Branch Trace Configuration Format
41882 @section Branch Trace Configuration Format
41883 @cindex branch trace configuration format
41885 For each inferior thread, @value{GDBN} can obtain the branch trace
41886 configuration using the @samp{qXfer:btrace-conf:read}
41887 (@pxref{qXfer btrace-conf read}) packet.
41889 The configuration describes the branch trace format and configuration
41890 settings for that format. The following information is described:
41894 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41897 The size of the @acronym{BTS} ring buffer in bytes.
41900 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41904 The size of the @acronym{Intel PT} ring buffer in bytes.
41908 @value{GDBN} must be linked with the Expat library to support XML
41909 branch trace configuration discovery. @xref{Expat}.
41911 The formal DTD for the branch trace configuration format is given below:
41914 <!ELEMENT btrace-conf (bts?, pt?)>
41915 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41917 <!ELEMENT bts EMPTY>
41918 <!ATTLIST bts size CDATA #IMPLIED>
41920 <!ELEMENT pt EMPTY>
41921 <!ATTLIST pt size CDATA #IMPLIED>
41924 @include agentexpr.texi
41926 @node Target Descriptions
41927 @appendix Target Descriptions
41928 @cindex target descriptions
41930 One of the challenges of using @value{GDBN} to debug embedded systems
41931 is that there are so many minor variants of each processor
41932 architecture in use. It is common practice for vendors to start with
41933 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41934 and then make changes to adapt it to a particular market niche. Some
41935 architectures have hundreds of variants, available from dozens of
41936 vendors. This leads to a number of problems:
41940 With so many different customized processors, it is difficult for
41941 the @value{GDBN} maintainers to keep up with the changes.
41943 Since individual variants may have short lifetimes or limited
41944 audiences, it may not be worthwhile to carry information about every
41945 variant in the @value{GDBN} source tree.
41947 When @value{GDBN} does support the architecture of the embedded system
41948 at hand, the task of finding the correct architecture name to give the
41949 @command{set architecture} command can be error-prone.
41952 To address these problems, the @value{GDBN} remote protocol allows a
41953 target system to not only identify itself to @value{GDBN}, but to
41954 actually describe its own features. This lets @value{GDBN} support
41955 processor variants it has never seen before --- to the extent that the
41956 descriptions are accurate, and that @value{GDBN} understands them.
41958 @value{GDBN} must be linked with the Expat library to support XML
41959 target descriptions. @xref{Expat}.
41962 * Retrieving Descriptions:: How descriptions are fetched from a target.
41963 * Target Description Format:: The contents of a target description.
41964 * Predefined Target Types:: Standard types available for target
41966 * Enum Target Types:: How to define enum target types.
41967 * Standard Target Features:: Features @value{GDBN} knows about.
41970 @node Retrieving Descriptions
41971 @section Retrieving Descriptions
41973 Target descriptions can be read from the target automatically, or
41974 specified by the user manually. The default behavior is to read the
41975 description from the target. @value{GDBN} retrieves it via the remote
41976 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41977 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41978 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41979 XML document, of the form described in @ref{Target Description
41982 Alternatively, you can specify a file to read for the target description.
41983 If a file is set, the target will not be queried. The commands to
41984 specify a file are:
41987 @cindex set tdesc filename
41988 @item set tdesc filename @var{path}
41989 Read the target description from @var{path}.
41991 @cindex unset tdesc filename
41992 @item unset tdesc filename
41993 Do not read the XML target description from a file. @value{GDBN}
41994 will use the description supplied by the current target.
41996 @cindex show tdesc filename
41997 @item show tdesc filename
41998 Show the filename to read for a target description, if any.
42002 @node Target Description Format
42003 @section Target Description Format
42004 @cindex target descriptions, XML format
42006 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42007 document which complies with the Document Type Definition provided in
42008 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42009 means you can use generally available tools like @command{xmllint} to
42010 check that your feature descriptions are well-formed and valid.
42011 However, to help people unfamiliar with XML write descriptions for
42012 their targets, we also describe the grammar here.
42014 Target descriptions can identify the architecture of the remote target
42015 and (for some architectures) provide information about custom register
42016 sets. They can also identify the OS ABI of the remote target.
42017 @value{GDBN} can use this information to autoconfigure for your
42018 target, or to warn you if you connect to an unsupported target.
42020 Here is a simple target description:
42023 <target version="1.0">
42024 <architecture>i386:x86-64</architecture>
42029 This minimal description only says that the target uses
42030 the x86-64 architecture.
42032 A target description has the following overall form, with [ ] marking
42033 optional elements and @dots{} marking repeatable elements. The elements
42034 are explained further below.
42037 <?xml version="1.0"?>
42038 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42039 <target version="1.0">
42040 @r{[}@var{architecture}@r{]}
42041 @r{[}@var{osabi}@r{]}
42042 @r{[}@var{compatible}@r{]}
42043 @r{[}@var{feature}@dots{}@r{]}
42048 The description is generally insensitive to whitespace and line
42049 breaks, under the usual common-sense rules. The XML version
42050 declaration and document type declaration can generally be omitted
42051 (@value{GDBN} does not require them), but specifying them may be
42052 useful for XML validation tools. The @samp{version} attribute for
42053 @samp{<target>} may also be omitted, but we recommend
42054 including it; if future versions of @value{GDBN} use an incompatible
42055 revision of @file{gdb-target.dtd}, they will detect and report
42056 the version mismatch.
42058 @subsection Inclusion
42059 @cindex target descriptions, inclusion
42062 @cindex <xi:include>
42065 It can sometimes be valuable to split a target description up into
42066 several different annexes, either for organizational purposes, or to
42067 share files between different possible target descriptions. You can
42068 divide a description into multiple files by replacing any element of
42069 the target description with an inclusion directive of the form:
42072 <xi:include href="@var{document}"/>
42076 When @value{GDBN} encounters an element of this form, it will retrieve
42077 the named XML @var{document}, and replace the inclusion directive with
42078 the contents of that document. If the current description was read
42079 using @samp{qXfer}, then so will be the included document;
42080 @var{document} will be interpreted as the name of an annex. If the
42081 current description was read from a file, @value{GDBN} will look for
42082 @var{document} as a file in the same directory where it found the
42083 original description.
42085 @subsection Architecture
42086 @cindex <architecture>
42088 An @samp{<architecture>} element has this form:
42091 <architecture>@var{arch}</architecture>
42094 @var{arch} is one of the architectures from the set accepted by
42095 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42098 @cindex @code{<osabi>}
42100 This optional field was introduced in @value{GDBN} version 7.0.
42101 Previous versions of @value{GDBN} ignore it.
42103 An @samp{<osabi>} element has this form:
42106 <osabi>@var{abi-name}</osabi>
42109 @var{abi-name} is an OS ABI name from the same selection accepted by
42110 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42112 @subsection Compatible Architecture
42113 @cindex @code{<compatible>}
42115 This optional field was introduced in @value{GDBN} version 7.0.
42116 Previous versions of @value{GDBN} ignore it.
42118 A @samp{<compatible>} element has this form:
42121 <compatible>@var{arch}</compatible>
42124 @var{arch} is one of the architectures from the set accepted by
42125 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42127 A @samp{<compatible>} element is used to specify that the target
42128 is able to run binaries in some other than the main target architecture
42129 given by the @samp{<architecture>} element. For example, on the
42130 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42131 or @code{powerpc:common64}, but the system is able to run binaries
42132 in the @code{spu} architecture as well. The way to describe this
42133 capability with @samp{<compatible>} is as follows:
42136 <architecture>powerpc:common</architecture>
42137 <compatible>spu</compatible>
42140 @subsection Features
42143 Each @samp{<feature>} describes some logical portion of the target
42144 system. Features are currently used to describe available CPU
42145 registers and the types of their contents. A @samp{<feature>} element
42149 <feature name="@var{name}">
42150 @r{[}@var{type}@dots{}@r{]}
42156 Each feature's name should be unique within the description. The name
42157 of a feature does not matter unless @value{GDBN} has some special
42158 knowledge of the contents of that feature; if it does, the feature
42159 should have its standard name. @xref{Standard Target Features}.
42163 Any register's value is a collection of bits which @value{GDBN} must
42164 interpret. The default interpretation is a two's complement integer,
42165 but other types can be requested by name in the register description.
42166 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42167 Target Types}), and the description can define additional composite
42170 Each type element must have an @samp{id} attribute, which gives
42171 a unique (within the containing @samp{<feature>}) name to the type.
42172 Types must be defined before they are used.
42175 Some targets offer vector registers, which can be treated as arrays
42176 of scalar elements. These types are written as @samp{<vector>} elements,
42177 specifying the array element type, @var{type}, and the number of elements,
42181 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42185 If a register's value is usefully viewed in multiple ways, define it
42186 with a union type containing the useful representations. The
42187 @samp{<union>} element contains one or more @samp{<field>} elements,
42188 each of which has a @var{name} and a @var{type}:
42191 <union id="@var{id}">
42192 <field name="@var{name}" type="@var{type}"/>
42199 If a register's value is composed from several separate values, define
42200 it with either a structure type or a flags type.
42201 A flags type may only contain bitfields.
42202 A structure type may either contain only bitfields or contain no bitfields.
42203 If the value contains only bitfields, its total size in bytes must be
42206 Non-bitfield values have a @var{name} and @var{type}.
42209 <struct id="@var{id}">
42210 <field name="@var{name}" type="@var{type}"/>
42215 Both @var{name} and @var{type} values are required.
42216 No implicit padding is added.
42218 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42221 <struct id="@var{id}" size="@var{size}">
42222 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42228 <flags id="@var{id}" size="@var{size}">
42229 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42234 The @var{name} value is required.
42235 Bitfield values may be named with the empty string, @samp{""},
42236 in which case the field is ``filler'' and its value is not printed.
42237 Not all bits need to be specified, so ``filler'' fields are optional.
42239 The @var{start} and @var{end} values are required, and @var{type}
42241 The field's @var{start} must be less than or equal to its @var{end},
42242 and zero represents the least significant bit.
42244 The default value of @var{type} is @code{bool} for single bit fields,
42245 and an unsigned integer otherwise.
42247 Which to choose? Structures or flags?
42249 Registers defined with @samp{flags} have these advantages over
42250 defining them with @samp{struct}:
42254 Arithmetic may be performed on them as if they were integers.
42256 They are printed in a more readable fashion.
42259 Registers defined with @samp{struct} have one advantage over
42260 defining them with @samp{flags}:
42264 One can fetch individual fields like in @samp{C}.
42267 (gdb) print $my_struct_reg.field3
42273 @subsection Registers
42276 Each register is represented as an element with this form:
42279 <reg name="@var{name}"
42280 bitsize="@var{size}"
42281 @r{[}regnum="@var{num}"@r{]}
42282 @r{[}save-restore="@var{save-restore}"@r{]}
42283 @r{[}type="@var{type}"@r{]}
42284 @r{[}group="@var{group}"@r{]}/>
42288 The components are as follows:
42293 The register's name; it must be unique within the target description.
42296 The register's size, in bits.
42299 The register's number. If omitted, a register's number is one greater
42300 than that of the previous register (either in the current feature or in
42301 a preceding feature); the first register in the target description
42302 defaults to zero. This register number is used to read or write
42303 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42304 packets, and registers appear in the @code{g} and @code{G} packets
42305 in order of increasing register number.
42308 Whether the register should be preserved across inferior function
42309 calls; this must be either @code{yes} or @code{no}. The default is
42310 @code{yes}, which is appropriate for most registers except for
42311 some system control registers; this is not related to the target's
42315 The type of the register. It may be a predefined type, a type
42316 defined in the current feature, or one of the special types @code{int}
42317 and @code{float}. @code{int} is an integer type of the correct size
42318 for @var{bitsize}, and @code{float} is a floating point type (in the
42319 architecture's normal floating point format) of the correct size for
42320 @var{bitsize}. The default is @code{int}.
42323 The register group to which this register belongs. It can be one of the
42324 standard register groups @code{general}, @code{float}, @code{vector} or an
42325 arbitrary string. Group names should be limited to alphanumeric characters.
42326 If a group name is made up of multiple words the words may be separated by
42327 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42328 @var{group} is specified, @value{GDBN} will not display the register in
42329 @code{info registers}.
42333 @node Predefined Target Types
42334 @section Predefined Target Types
42335 @cindex target descriptions, predefined types
42337 Type definitions in the self-description can build up composite types
42338 from basic building blocks, but can not define fundamental types. Instead,
42339 standard identifiers are provided by @value{GDBN} for the fundamental
42340 types. The currently supported types are:
42345 Boolean type, occupying a single bit.
42352 Signed integer types holding the specified number of bits.
42359 Unsigned integer types holding the specified number of bits.
42363 Pointers to unspecified code and data. The program counter and
42364 any dedicated return address register may be marked as code
42365 pointers; printing a code pointer converts it into a symbolic
42366 address. The stack pointer and any dedicated address registers
42367 may be marked as data pointers.
42370 Single precision IEEE floating point.
42373 Double precision IEEE floating point.
42376 The 12-byte extended precision format used by ARM FPA registers.
42379 The 10-byte extended precision format used by x87 registers.
42382 32bit @sc{eflags} register used by x86.
42385 32bit @sc{mxcsr} register used by x86.
42389 @node Enum Target Types
42390 @section Enum Target Types
42391 @cindex target descriptions, enum types
42393 Enum target types are useful in @samp{struct} and @samp{flags}
42394 register descriptions. @xref{Target Description Format}.
42396 Enum types have a name, size and a list of name/value pairs.
42399 <enum id="@var{id}" size="@var{size}">
42400 <evalue name="@var{name}" value="@var{value}"/>
42405 Enums must be defined before they are used.
42408 <enum id="levels_type" size="4">
42409 <evalue name="low" value="0"/>
42410 <evalue name="high" value="1"/>
42412 <flags id="flags_type" size="4">
42413 <field name="X" start="0"/>
42414 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42416 <reg name="flags" bitsize="32" type="flags_type"/>
42419 Given that description, a value of 3 for the @samp{flags} register
42420 would be printed as:
42423 (gdb) info register flags
42424 flags 0x3 [ X LEVEL=high ]
42427 @node Standard Target Features
42428 @section Standard Target Features
42429 @cindex target descriptions, standard features
42431 A target description must contain either no registers or all the
42432 target's registers. If the description contains no registers, then
42433 @value{GDBN} will assume a default register layout, selected based on
42434 the architecture. If the description contains any registers, the
42435 default layout will not be used; the standard registers must be
42436 described in the target description, in such a way that @value{GDBN}
42437 can recognize them.
42439 This is accomplished by giving specific names to feature elements
42440 which contain standard registers. @value{GDBN} will look for features
42441 with those names and verify that they contain the expected registers;
42442 if any known feature is missing required registers, or if any required
42443 feature is missing, @value{GDBN} will reject the target
42444 description. You can add additional registers to any of the
42445 standard features --- @value{GDBN} will display them just as if
42446 they were added to an unrecognized feature.
42448 This section lists the known features and their expected contents.
42449 Sample XML documents for these features are included in the
42450 @value{GDBN} source tree, in the directory @file{gdb/features}.
42452 Names recognized by @value{GDBN} should include the name of the
42453 company or organization which selected the name, and the overall
42454 architecture to which the feature applies; so e.g.@: the feature
42455 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42457 The names of registers are not case sensitive for the purpose
42458 of recognizing standard features, but @value{GDBN} will only display
42459 registers using the capitalization used in the description.
42462 * AArch64 Features::
42466 * MicroBlaze Features::
42470 * Nios II Features::
42471 * OpenRISC 1000 Features::
42472 * PowerPC Features::
42473 * S/390 and System z Features::
42479 @node AArch64 Features
42480 @subsection AArch64 Features
42481 @cindex target descriptions, AArch64 features
42483 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42484 targets. It should contain registers @samp{x0} through @samp{x30},
42485 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42487 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42488 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42491 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42492 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42493 through @samp{p15}, @samp{ffr} and @samp{vg}.
42496 @subsection ARC Features
42497 @cindex target descriptions, ARC Features
42499 ARC processors are highly configurable, so even core registers and their number
42500 are not completely predetermined. In addition flags and PC registers which are
42501 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42502 that one of the core registers features is present.
42503 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42505 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42506 targets with a normal register file. It should contain registers @samp{r0}
42507 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42508 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42509 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42510 @samp{ilink} and extension core registers are not available to read/write, when
42511 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42513 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42514 ARC HS targets with a reduced register file. It should contain registers
42515 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42516 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42517 This feature may contain register @samp{ilink} and any of extension core
42518 registers @samp{r32} through @samp{r59/acch}.
42520 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42521 targets with a normal register file. It should contain registers @samp{r0}
42522 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42523 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42524 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
42525 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
42526 registers are not available when debugging GNU/Linux applications. The only
42527 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
42528 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
42529 ARC v2, but @samp{ilink2} is optional on ARCompact.
42531 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42532 targets. It should contain registers @samp{pc} and @samp{status32}.
42535 @subsection ARM Features
42536 @cindex target descriptions, ARM features
42538 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42540 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42541 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42543 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42544 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42545 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42548 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42549 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42551 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42552 it should contain at least registers @samp{wR0} through @samp{wR15} and
42553 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42554 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42556 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42557 should contain at least registers @samp{d0} through @samp{d15}. If
42558 they are present, @samp{d16} through @samp{d31} should also be included.
42559 @value{GDBN} will synthesize the single-precision registers from
42560 halves of the double-precision registers.
42562 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42563 need to contain registers; it instructs @value{GDBN} to display the
42564 VFP double-precision registers as vectors and to synthesize the
42565 quad-precision registers from pairs of double-precision registers.
42566 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42567 be present and include 32 double-precision registers.
42569 @node i386 Features
42570 @subsection i386 Features
42571 @cindex target descriptions, i386 features
42573 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42574 targets. It should describe the following registers:
42578 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42580 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42582 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42583 @samp{fs}, @samp{gs}
42585 @samp{st0} through @samp{st7}
42587 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42588 @samp{foseg}, @samp{fooff} and @samp{fop}
42591 The register sets may be different, depending on the target.
42593 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42594 describe registers:
42598 @samp{xmm0} through @samp{xmm7} for i386
42600 @samp{xmm0} through @samp{xmm15} for amd64
42605 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42606 @samp{org.gnu.gdb.i386.sse} feature. It should
42607 describe the upper 128 bits of @sc{ymm} registers:
42611 @samp{ymm0h} through @samp{ymm7h} for i386
42613 @samp{ymm0h} through @samp{ymm15h} for amd64
42616 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42617 Memory Protection Extension (MPX). It should describe the following registers:
42621 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42623 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42626 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42627 describe a single register, @samp{orig_eax}.
42629 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42630 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42632 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42633 @samp{org.gnu.gdb.i386.avx} feature. It should
42634 describe additional @sc{xmm} registers:
42638 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42641 It should describe the upper 128 bits of additional @sc{ymm} registers:
42645 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42649 describe the upper 256 bits of @sc{zmm} registers:
42653 @samp{zmm0h} through @samp{zmm7h} for i386.
42655 @samp{zmm0h} through @samp{zmm15h} for amd64.
42659 describe the additional @sc{zmm} registers:
42663 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42666 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42667 describe a single register, @samp{pkru}. It is a 32-bit register
42668 valid for i386 and amd64.
42670 @node MicroBlaze Features
42671 @subsection MicroBlaze Features
42672 @cindex target descriptions, MicroBlaze features
42674 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42675 targets. It should contain registers @samp{r0} through @samp{r31},
42676 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42677 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42678 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42680 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42681 If present, it should contain registers @samp{rshr} and @samp{rslr}
42683 @node MIPS Features
42684 @subsection @acronym{MIPS} Features
42685 @cindex target descriptions, @acronym{MIPS} features
42687 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42688 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42689 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42692 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42693 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42694 registers. They may be 32-bit or 64-bit depending on the target.
42696 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42697 it may be optional in a future version of @value{GDBN}. It should
42698 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42699 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42701 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42702 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42703 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42704 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42706 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42707 contain a single register, @samp{restart}, which is used by the
42708 Linux kernel to control restartable syscalls.
42710 @node M68K Features
42711 @subsection M68K Features
42712 @cindex target descriptions, M68K features
42715 @item @samp{org.gnu.gdb.m68k.core}
42716 @itemx @samp{org.gnu.gdb.coldfire.core}
42717 @itemx @samp{org.gnu.gdb.fido.core}
42718 One of those features must be always present.
42719 The feature that is present determines which flavor of m68k is
42720 used. The feature that is present should contain registers
42721 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42722 @samp{sp}, @samp{ps} and @samp{pc}.
42724 @item @samp{org.gnu.gdb.coldfire.fp}
42725 This feature is optional. If present, it should contain registers
42726 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42730 @node NDS32 Features
42731 @subsection NDS32 Features
42732 @cindex target descriptions, NDS32 features
42734 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42735 targets. It should contain at least registers @samp{r0} through
42736 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42739 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42740 it should contain 64-bit double-precision floating-point registers
42741 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42742 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42744 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42745 registers are overlapped with the thirty-two 32-bit single-precision
42746 floating-point registers. The 32-bit single-precision registers, if
42747 not being listed explicitly, will be synthesized from halves of the
42748 overlapping 64-bit double-precision registers. Listing 32-bit
42749 single-precision registers explicitly is deprecated, and the
42750 support to it could be totally removed some day.
42752 @node Nios II Features
42753 @subsection Nios II Features
42754 @cindex target descriptions, Nios II features
42756 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42757 targets. It should contain the 32 core registers (@samp{zero},
42758 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42759 @samp{pc}, and the 16 control registers (@samp{status} through
42762 @node OpenRISC 1000 Features
42763 @subsection Openrisc 1000 Features
42764 @cindex target descriptions, OpenRISC 1000 features
42766 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42767 targets. It should contain the 32 general purpose registers (@samp{r0}
42768 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42770 @node PowerPC Features
42771 @subsection PowerPC Features
42772 @cindex target descriptions, PowerPC features
42774 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42775 targets. It should contain registers @samp{r0} through @samp{r31},
42776 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42777 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42779 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42780 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42782 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42783 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42786 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42787 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42788 will combine these registers with the floating point registers
42789 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42790 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42791 through @samp{vs63}, the set of vector registers for POWER7.
42793 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42794 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42795 @samp{spefscr}. SPE targets should provide 32-bit registers in
42796 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42797 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42798 these to present registers @samp{ev0} through @samp{ev31} to the
42801 @node S/390 and System z Features
42802 @subsection S/390 and System z Features
42803 @cindex target descriptions, S/390 features
42804 @cindex target descriptions, System z features
42806 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42807 System z targets. It should contain the PSW and the 16 general
42808 registers. In particular, System z targets should provide the 64-bit
42809 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42810 S/390 targets should provide the 32-bit versions of these registers.
42811 A System z target that runs in 31-bit addressing mode should provide
42812 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42813 register's upper halves @samp{r0h} through @samp{r15h}, and their
42814 lower halves @samp{r0l} through @samp{r15l}.
42816 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42817 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42820 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42821 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42823 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42824 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42825 targets and 32-bit otherwise. In addition, the feature may contain
42826 the @samp{last_break} register, whose width depends on the addressing
42827 mode, as well as the @samp{system_call} register, which is always
42830 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42831 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42832 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42834 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42835 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42836 combined by @value{GDBN} with the floating point registers @samp{f0}
42837 through @samp{f15} to present the 128-bit wide vector registers
42838 @samp{v0} through @samp{v15}. In addition, this feature should
42839 contain the 128-bit wide vector registers @samp{v16} through
42842 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42843 the 64-bit wide guarded-storage-control registers @samp{gsd},
42844 @samp{gssm}, and @samp{gsepla}.
42846 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42847 the 64-bit wide guarded-storage broadcast control registers
42848 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42850 @node Sparc Features
42851 @subsection Sparc Features
42852 @cindex target descriptions, sparc32 features
42853 @cindex target descriptions, sparc64 features
42854 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42855 targets. It should describe the following registers:
42859 @samp{g0} through @samp{g7}
42861 @samp{o0} through @samp{o7}
42863 @samp{l0} through @samp{l7}
42865 @samp{i0} through @samp{i7}
42868 They may be 32-bit or 64-bit depending on the target.
42870 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42871 targets. It should describe the following registers:
42875 @samp{f0} through @samp{f31}
42877 @samp{f32} through @samp{f62} for sparc64
42880 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42881 targets. It should describe the following registers:
42885 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42886 @samp{fsr}, and @samp{csr} for sparc32
42888 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42892 @node TIC6x Features
42893 @subsection TMS320C6x Features
42894 @cindex target descriptions, TIC6x features
42895 @cindex target descriptions, TMS320C6x features
42896 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42897 targets. It should contain registers @samp{A0} through @samp{A15},
42898 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42900 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42901 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42902 through @samp{B31}.
42904 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42905 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42907 @node Operating System Information
42908 @appendix Operating System Information
42909 @cindex operating system information
42915 Users of @value{GDBN} often wish to obtain information about the state of
42916 the operating system running on the target---for example the list of
42917 processes, or the list of open files. This section describes the
42918 mechanism that makes it possible. This mechanism is similar to the
42919 target features mechanism (@pxref{Target Descriptions}), but focuses
42920 on a different aspect of target.
42922 Operating system information is retrived from the target via the
42923 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42924 read}). The object name in the request should be @samp{osdata}, and
42925 the @var{annex} identifies the data to be fetched.
42928 @appendixsection Process list
42929 @cindex operating system information, process list
42931 When requesting the process list, the @var{annex} field in the
42932 @samp{qXfer} request should be @samp{processes}. The returned data is
42933 an XML document. The formal syntax of this document is defined in
42934 @file{gdb/features/osdata.dtd}.
42936 An example document is:
42939 <?xml version="1.0"?>
42940 <!DOCTYPE target SYSTEM "osdata.dtd">
42941 <osdata type="processes">
42943 <column name="pid">1</column>
42944 <column name="user">root</column>
42945 <column name="command">/sbin/init</column>
42946 <column name="cores">1,2,3</column>
42951 Each item should include a column whose name is @samp{pid}. The value
42952 of that column should identify the process on the target. The
42953 @samp{user} and @samp{command} columns are optional, and will be
42954 displayed by @value{GDBN}. The @samp{cores} column, if present,
42955 should contain a comma-separated list of cores that this process
42956 is running on. Target may provide additional columns,
42957 which @value{GDBN} currently ignores.
42959 @node Trace File Format
42960 @appendix Trace File Format
42961 @cindex trace file format
42963 The trace file comes in three parts: a header, a textual description
42964 section, and a trace frame section with binary data.
42966 The header has the form @code{\x7fTRACE0\n}. The first byte is
42967 @code{0x7f} so as to indicate that the file contains binary data,
42968 while the @code{0} is a version number that may have different values
42971 The description section consists of multiple lines of @sc{ascii} text
42972 separated by newline characters (@code{0xa}). The lines may include a
42973 variety of optional descriptive or context-setting information, such
42974 as tracepoint definitions or register set size. @value{GDBN} will
42975 ignore any line that it does not recognize. An empty line marks the end
42980 Specifies the size of a register block in bytes. This is equal to the
42981 size of a @code{g} packet payload in the remote protocol. @var{size}
42982 is an ascii decimal number. There should be only one such line in
42983 a single trace file.
42985 @item status @var{status}
42986 Trace status. @var{status} has the same format as a @code{qTStatus}
42987 remote packet reply. There should be only one such line in a single trace
42990 @item tp @var{payload}
42991 Tracepoint definition. The @var{payload} has the same format as
42992 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42993 may take multiple lines of definition, corresponding to the multiple
42996 @item tsv @var{payload}
42997 Trace state variable definition. The @var{payload} has the same format as
42998 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42999 may take multiple lines of definition, corresponding to the multiple
43002 @item tdesc @var{payload}
43003 Target description in XML format. The @var{payload} is a single line of
43004 the XML file. All such lines should be concatenated together to get
43005 the original XML file. This file is in the same format as @code{qXfer}
43006 @code{features} payload, and corresponds to the main @code{target.xml}
43007 file. Includes are not allowed.
43011 The trace frame section consists of a number of consecutive frames.
43012 Each frame begins with a two-byte tracepoint number, followed by a
43013 four-byte size giving the amount of data in the frame. The data in
43014 the frame consists of a number of blocks, each introduced by a
43015 character indicating its type (at least register, memory, and trace
43016 state variable). The data in this section is raw binary, not a
43017 hexadecimal or other encoding; its endianness matches the target's
43020 @c FIXME bi-arch may require endianness/arch info in description section
43023 @item R @var{bytes}
43024 Register block. The number and ordering of bytes matches that of a
43025 @code{g} packet in the remote protocol. Note that these are the
43026 actual bytes, in target order, not a hexadecimal encoding.
43028 @item M @var{address} @var{length} @var{bytes}...
43029 Memory block. This is a contiguous block of memory, at the 8-byte
43030 address @var{address}, with a 2-byte length @var{length}, followed by
43031 @var{length} bytes.
43033 @item V @var{number} @var{value}
43034 Trace state variable block. This records the 8-byte signed value
43035 @var{value} of trace state variable numbered @var{number}.
43039 Future enhancements of the trace file format may include additional types
43042 @node Index Section Format
43043 @appendix @code{.gdb_index} section format
43044 @cindex .gdb_index section format
43045 @cindex index section format
43047 This section documents the index section that is created by @code{save
43048 gdb-index} (@pxref{Index Files}). The index section is
43049 DWARF-specific; some knowledge of DWARF is assumed in this
43052 The mapped index file format is designed to be directly
43053 @code{mmap}able on any architecture. In most cases, a datum is
43054 represented using a little-endian 32-bit integer value, called an
43055 @code{offset_type}. Big endian machines must byte-swap the values
43056 before using them. Exceptions to this rule are noted. The data is
43057 laid out such that alignment is always respected.
43059 A mapped index consists of several areas, laid out in order.
43063 The file header. This is a sequence of values, of @code{offset_type}
43064 unless otherwise noted:
43068 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43069 Version 4 uses a different hashing function from versions 5 and 6.
43070 Version 6 includes symbols for inlined functions, whereas versions 4
43071 and 5 do not. Version 7 adds attributes to the CU indices in the
43072 symbol table. Version 8 specifies that symbols from DWARF type units
43073 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43074 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43076 @value{GDBN} will only read version 4, 5, or 6 indices
43077 by specifying @code{set use-deprecated-index-sections on}.
43078 GDB has a workaround for potentially broken version 7 indices so it is
43079 currently not flagged as deprecated.
43082 The offset, from the start of the file, of the CU list.
43085 The offset, from the start of the file, of the types CU list. Note
43086 that this area can be empty, in which case this offset will be equal
43087 to the next offset.
43090 The offset, from the start of the file, of the address area.
43093 The offset, from the start of the file, of the symbol table.
43096 The offset, from the start of the file, of the constant pool.
43100 The CU list. This is a sequence of pairs of 64-bit little-endian
43101 values, sorted by the CU offset. The first element in each pair is
43102 the offset of a CU in the @code{.debug_info} section. The second
43103 element in each pair is the length of that CU. References to a CU
43104 elsewhere in the map are done using a CU index, which is just the
43105 0-based index into this table. Note that if there are type CUs, then
43106 conceptually CUs and type CUs form a single list for the purposes of
43110 The types CU list. This is a sequence of triplets of 64-bit
43111 little-endian values. In a triplet, the first value is the CU offset,
43112 the second value is the type offset in the CU, and the third value is
43113 the type signature. The types CU list is not sorted.
43116 The address area. The address area consists of a sequence of address
43117 entries. Each address entry has three elements:
43121 The low address. This is a 64-bit little-endian value.
43124 The high address. This is a 64-bit little-endian value. Like
43125 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43128 The CU index. This is an @code{offset_type} value.
43132 The symbol table. This is an open-addressed hash table. The size of
43133 the hash table is always a power of 2.
43135 Each slot in the hash table consists of a pair of @code{offset_type}
43136 values. The first value is the offset of the symbol's name in the
43137 constant pool. The second value is the offset of the CU vector in the
43140 If both values are 0, then this slot in the hash table is empty. This
43141 is ok because while 0 is a valid constant pool index, it cannot be a
43142 valid index for both a string and a CU vector.
43144 The hash value for a table entry is computed by applying an
43145 iterative hash function to the symbol's name. Starting with an
43146 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43147 the string is incorporated into the hash using the formula depending on the
43152 The formula is @code{r = r * 67 + c - 113}.
43154 @item Versions 5 to 7
43155 The formula is @code{r = r * 67 + tolower (c) - 113}.
43158 The terminating @samp{\0} is not incorporated into the hash.
43160 The step size used in the hash table is computed via
43161 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43162 value, and @samp{size} is the size of the hash table. The step size
43163 is used to find the next candidate slot when handling a hash
43166 The names of C@t{++} symbols in the hash table are canonicalized. We
43167 don't currently have a simple description of the canonicalization
43168 algorithm; if you intend to create new index sections, you must read
43172 The constant pool. This is simply a bunch of bytes. It is organized
43173 so that alignment is correct: CU vectors are stored first, followed by
43176 A CU vector in the constant pool is a sequence of @code{offset_type}
43177 values. The first value is the number of CU indices in the vector.
43178 Each subsequent value is the index and symbol attributes of a CU in
43179 the CU list. This element in the hash table is used to indicate which
43180 CUs define the symbol and how the symbol is used.
43181 See below for the format of each CU index+attributes entry.
43183 A string in the constant pool is zero-terminated.
43186 Attributes were added to CU index values in @code{.gdb_index} version 7.
43187 If a symbol has multiple uses within a CU then there is one
43188 CU index+attributes value for each use.
43190 The format of each CU index+attributes entry is as follows
43196 This is the index of the CU in the CU list.
43198 These bits are reserved for future purposes and must be zero.
43200 The kind of the symbol in the CU.
43204 This value is reserved and should not be used.
43205 By reserving zero the full @code{offset_type} value is backwards compatible
43206 with previous versions of the index.
43208 The symbol is a type.
43210 The symbol is a variable or an enum value.
43212 The symbol is a function.
43214 Any other kind of symbol.
43216 These values are reserved.
43220 This bit is zero if the value is global and one if it is static.
43222 The determination of whether a symbol is global or static is complicated.
43223 The authorative reference is the file @file{dwarf2read.c} in
43224 @value{GDBN} sources.
43228 This pseudo-code describes the computation of a symbol's kind and
43229 global/static attributes in the index.
43232 is_external = get_attribute (die, DW_AT_external);
43233 language = get_attribute (cu_die, DW_AT_language);
43236 case DW_TAG_typedef:
43237 case DW_TAG_base_type:
43238 case DW_TAG_subrange_type:
43242 case DW_TAG_enumerator:
43244 is_static = language != CPLUS;
43246 case DW_TAG_subprogram:
43248 is_static = ! (is_external || language == ADA);
43250 case DW_TAG_constant:
43252 is_static = ! is_external;
43254 case DW_TAG_variable:
43256 is_static = ! is_external;
43258 case DW_TAG_namespace:
43262 case DW_TAG_class_type:
43263 case DW_TAG_interface_type:
43264 case DW_TAG_structure_type:
43265 case DW_TAG_union_type:
43266 case DW_TAG_enumeration_type:
43268 is_static = language != CPLUS;
43276 @appendix Manual pages
43280 * gdb man:: The GNU Debugger man page
43281 * gdbserver man:: Remote Server for the GNU Debugger man page
43282 * gcore man:: Generate a core file of a running program
43283 * gdbinit man:: gdbinit scripts
43284 * gdb-add-index man:: Add index files to speed up GDB
43290 @c man title gdb The GNU Debugger
43292 @c man begin SYNOPSIS gdb
43293 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43294 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43295 [@option{-b}@w{ }@var{bps}]
43296 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43297 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43298 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43299 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43300 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43303 @c man begin DESCRIPTION gdb
43304 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43305 going on ``inside'' another program while it executes -- or what another
43306 program was doing at the moment it crashed.
43308 @value{GDBN} can do four main kinds of things (plus other things in support of
43309 these) to help you catch bugs in the act:
43313 Start your program, specifying anything that might affect its behavior.
43316 Make your program stop on specified conditions.
43319 Examine what has happened, when your program has stopped.
43322 Change things in your program, so you can experiment with correcting the
43323 effects of one bug and go on to learn about another.
43326 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43329 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43330 commands from the terminal until you tell it to exit with the @value{GDBN}
43331 command @code{quit}. You can get online help from @value{GDBN} itself
43332 by using the command @code{help}.
43334 You can run @code{gdb} with no arguments or options; but the most
43335 usual way to start @value{GDBN} is with one argument or two, specifying an
43336 executable program as the argument:
43342 You can also start with both an executable program and a core file specified:
43348 You can, instead, specify a process ID as a second argument, if you want
43349 to debug a running process:
43357 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43358 named @file{1234}; @value{GDBN} does check for a core file first).
43359 With option @option{-p} you can omit the @var{program} filename.
43361 Here are some of the most frequently needed @value{GDBN} commands:
43363 @c pod2man highlights the right hand side of the @item lines.
43365 @item break [@var{file}:]@var{function}
43366 Set a breakpoint at @var{function} (in @var{file}).
43368 @item run [@var{arglist}]
43369 Start your program (with @var{arglist}, if specified).
43372 Backtrace: display the program stack.
43374 @item print @var{expr}
43375 Display the value of an expression.
43378 Continue running your program (after stopping, e.g. at a breakpoint).
43381 Execute next program line (after stopping); step @emph{over} any
43382 function calls in the line.
43384 @item edit [@var{file}:]@var{function}
43385 look at the program line where it is presently stopped.
43387 @item list [@var{file}:]@var{function}
43388 type the text of the program in the vicinity of where it is presently stopped.
43391 Execute next program line (after stopping); step @emph{into} any
43392 function calls in the line.
43394 @item help [@var{name}]
43395 Show information about @value{GDBN} command @var{name}, or general information
43396 about using @value{GDBN}.
43399 Exit from @value{GDBN}.
43403 For full details on @value{GDBN},
43404 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43405 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43406 as the @code{gdb} entry in the @code{info} program.
43410 @c man begin OPTIONS gdb
43411 Any arguments other than options specify an executable
43412 file and core file (or process ID); that is, the first argument
43413 encountered with no
43414 associated option flag is equivalent to a @option{-se} option, and the second,
43415 if any, is equivalent to a @option{-c} option if it's the name of a file.
43417 both long and short forms; both are shown here. The long forms are also
43418 recognized if you truncate them, so long as enough of the option is
43419 present to be unambiguous. (If you prefer, you can flag option
43420 arguments with @option{+} rather than @option{-}, though we illustrate the
43421 more usual convention.)
43423 All the options and command line arguments you give are processed
43424 in sequential order. The order makes a difference when the @option{-x}
43430 List all options, with brief explanations.
43432 @item -symbols=@var{file}
43433 @itemx -s @var{file}
43434 Read symbol table from file @var{file}.
43437 Enable writing into executable and core files.
43439 @item -exec=@var{file}
43440 @itemx -e @var{file}
43441 Use file @var{file} as the executable file to execute when
43442 appropriate, and for examining pure data in conjunction with a core
43445 @item -se=@var{file}
43446 Read symbol table from file @var{file} and use it as the executable
43449 @item -core=@var{file}
43450 @itemx -c @var{file}
43451 Use file @var{file} as a core dump to examine.
43453 @item -command=@var{file}
43454 @itemx -x @var{file}
43455 Execute @value{GDBN} commands from file @var{file}.
43457 @item -ex @var{command}
43458 Execute given @value{GDBN} @var{command}.
43460 @item -directory=@var{directory}
43461 @itemx -d @var{directory}
43462 Add @var{directory} to the path to search for source files.
43465 Do not execute commands from @file{~/.gdbinit}.
43469 Do not execute commands from any @file{.gdbinit} initialization files.
43473 ``Quiet''. Do not print the introductory and copyright messages. These
43474 messages are also suppressed in batch mode.
43477 Run in batch mode. Exit with status @code{0} after processing all the command
43478 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43479 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43480 commands in the command files.
43482 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43483 download and run a program on another computer; in order to make this
43484 more useful, the message
43487 Program exited normally.
43491 (which is ordinarily issued whenever a program running under @value{GDBN} control
43492 terminates) is not issued when running in batch mode.
43494 @item -cd=@var{directory}
43495 Run @value{GDBN} using @var{directory} as its working directory,
43496 instead of the current directory.
43500 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43501 @value{GDBN} to output the full file name and line number in a standard,
43502 recognizable fashion each time a stack frame is displayed (which
43503 includes each time the program stops). This recognizable format looks
43504 like two @samp{\032} characters, followed by the file name, line number
43505 and character position separated by colons, and a newline. The
43506 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43507 characters as a signal to display the source code for the frame.
43510 Set the line speed (baud rate or bits per second) of any serial
43511 interface used by @value{GDBN} for remote debugging.
43513 @item -tty=@var{device}
43514 Run using @var{device} for your program's standard input and output.
43518 @c man begin SEEALSO gdb
43520 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43521 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43522 documentation are properly installed at your site, the command
43529 should give you access to the complete manual.
43531 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43532 Richard M. Stallman and Roland H. Pesch, July 1991.
43536 @node gdbserver man
43537 @heading gdbserver man
43539 @c man title gdbserver Remote Server for the GNU Debugger
43541 @c man begin SYNOPSIS gdbserver
43542 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43544 gdbserver --attach @var{comm} @var{pid}
43546 gdbserver --multi @var{comm}
43550 @c man begin DESCRIPTION gdbserver
43551 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43552 than the one which is running the program being debugged.
43555 @subheading Usage (server (target) side)
43558 Usage (server (target) side):
43561 First, you need to have a copy of the program you want to debug put onto
43562 the target system. The program can be stripped to save space if needed, as
43563 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43564 the @value{GDBN} running on the host system.
43566 To use the server, you log on to the target system, and run the @command{gdbserver}
43567 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43568 your program, and (c) its arguments. The general syntax is:
43571 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43574 For example, using a serial port, you might say:
43578 @c @file would wrap it as F</dev/com1>.
43579 target> gdbserver /dev/com1 emacs foo.txt
43582 target> gdbserver @file{/dev/com1} emacs foo.txt
43586 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43587 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43588 waits patiently for the host @value{GDBN} to communicate with it.
43590 To use a TCP connection, you could say:
43593 target> gdbserver host:2345 emacs foo.txt
43596 This says pretty much the same thing as the last example, except that we are
43597 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43598 that we are expecting to see a TCP connection from @code{host} to local TCP port
43599 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43600 want for the port number as long as it does not conflict with any existing TCP
43601 ports on the target system. This same port number must be used in the host
43602 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43603 you chose a port number that conflicts with another service, @command{gdbserver} will
43604 print an error message and exit.
43606 @command{gdbserver} can also attach to running programs.
43607 This is accomplished via the @option{--attach} argument. The syntax is:
43610 target> gdbserver --attach @var{comm} @var{pid}
43613 @var{pid} is the process ID of a currently running process. It isn't
43614 necessary to point @command{gdbserver} at a binary for the running process.
43616 To start @code{gdbserver} without supplying an initial command to run
43617 or process ID to attach, use the @option{--multi} command line option.
43618 In such case you should connect using @kbd{target extended-remote} to start
43619 the program you want to debug.
43622 target> gdbserver --multi @var{comm}
43626 @subheading Usage (host side)
43632 You need an unstripped copy of the target program on your host system, since
43633 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43634 would, with the target program as the first argument. (You may need to use the
43635 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43636 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43637 new command you need to know about is @code{target remote}
43638 (or @code{target extended-remote}). Its argument is either
43639 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43640 descriptor. For example:
43644 @c @file would wrap it as F</dev/ttyb>.
43645 (gdb) target remote /dev/ttyb
43648 (gdb) target remote @file{/dev/ttyb}
43653 communicates with the server via serial line @file{/dev/ttyb}, and:
43656 (gdb) target remote the-target:2345
43660 communicates via a TCP connection to port 2345 on host `the-target', where
43661 you previously started up @command{gdbserver} with the same port number. Note that for
43662 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43663 command, otherwise you may get an error that looks something like
43664 `Connection refused'.
43666 @command{gdbserver} can also debug multiple inferiors at once,
43669 the @value{GDBN} manual in node @code{Inferiors and Programs}
43670 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43673 @ref{Inferiors and Programs}.
43675 In such case use the @code{extended-remote} @value{GDBN} command variant:
43678 (gdb) target extended-remote the-target:2345
43681 The @command{gdbserver} option @option{--multi} may or may not be used in such
43685 @c man begin OPTIONS gdbserver
43686 There are three different modes for invoking @command{gdbserver}:
43691 Debug a specific program specified by its program name:
43694 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43697 The @var{comm} parameter specifies how should the server communicate
43698 with @value{GDBN}; it is either a device name (to use a serial line),
43699 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43700 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43701 debug in @var{prog}. Any remaining arguments will be passed to the
43702 program verbatim. When the program exits, @value{GDBN} will close the
43703 connection, and @code{gdbserver} will exit.
43706 Debug a specific program by specifying the process ID of a running
43710 gdbserver --attach @var{comm} @var{pid}
43713 The @var{comm} parameter is as described above. Supply the process ID
43714 of a running program in @var{pid}; @value{GDBN} will do everything
43715 else. Like with the previous mode, when the process @var{pid} exits,
43716 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43719 Multi-process mode -- debug more than one program/process:
43722 gdbserver --multi @var{comm}
43725 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43726 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43727 close the connection when a process being debugged exits, so you can
43728 debug several processes in the same session.
43731 In each of the modes you may specify these options:
43736 List all options, with brief explanations.
43739 This option causes @command{gdbserver} to print its version number and exit.
43742 @command{gdbserver} will attach to a running program. The syntax is:
43745 target> gdbserver --attach @var{comm} @var{pid}
43748 @var{pid} is the process ID of a currently running process. It isn't
43749 necessary to point @command{gdbserver} at a binary for the running process.
43752 To start @code{gdbserver} without supplying an initial command to run
43753 or process ID to attach, use this command line option.
43754 Then you can connect using @kbd{target extended-remote} and start
43755 the program you want to debug. The syntax is:
43758 target> gdbserver --multi @var{comm}
43762 Instruct @code{gdbserver} to display extra status information about the debugging
43764 This option is intended for @code{gdbserver} development and for bug reports to
43767 @item --remote-debug
43768 Instruct @code{gdbserver} to display remote protocol debug output.
43769 This option is intended for @code{gdbserver} development and for bug reports to
43772 @item --debug-format=option1@r{[},option2,...@r{]}
43773 Instruct @code{gdbserver} to include extra information in each line
43774 of debugging output.
43775 @xref{Other Command-Line Arguments for gdbserver}.
43778 Specify a wrapper to launch programs
43779 for debugging. The option should be followed by the name of the
43780 wrapper, then any command-line arguments to pass to the wrapper, then
43781 @kbd{--} indicating the end of the wrapper arguments.
43784 By default, @command{gdbserver} keeps the listening TCP port open, so that
43785 additional connections are possible. However, if you start @code{gdbserver}
43786 with the @option{--once} option, it will stop listening for any further
43787 connection attempts after connecting to the first @value{GDBN} session.
43789 @c --disable-packet is not documented for users.
43791 @c --disable-randomization and --no-disable-randomization are superseded by
43792 @c QDisableRandomization.
43797 @c man begin SEEALSO gdbserver
43799 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43800 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43801 documentation are properly installed at your site, the command
43807 should give you access to the complete manual.
43809 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43810 Richard M. Stallman and Roland H. Pesch, July 1991.
43817 @c man title gcore Generate a core file of a running program
43820 @c man begin SYNOPSIS gcore
43821 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
43825 @c man begin DESCRIPTION gcore
43826 Generate core dumps of one or more running programs with process IDs
43827 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
43828 is equivalent to one produced by the kernel when the process crashes
43829 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
43830 limit). However, unlike after a crash, after @command{gcore} finishes
43831 its job the program remains running without any change.
43834 @c man begin OPTIONS gcore
43837 Dump all memory mappings. The actual effect of this option depends on
43838 the Operating System. On @sc{gnu}/Linux, it will disable
43839 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43840 enable @code{dump-excluded-mappings} (@pxref{set
43841 dump-excluded-mappings}).
43843 @item -o @var{prefix}
43844 The optional argument @var{prefix} specifies the prefix to be used
43845 when composing the file names of the core dumps. The file name is
43846 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
43847 process ID of the running program being analyzed by @command{gcore}.
43848 If not specified, @var{prefix} defaults to @var{gcore}.
43852 @c man begin SEEALSO gcore
43854 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43855 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43856 documentation are properly installed at your site, the command
43863 should give you access to the complete manual.
43865 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43866 Richard M. Stallman and Roland H. Pesch, July 1991.
43873 @c man title gdbinit GDB initialization scripts
43876 @c man begin SYNOPSIS gdbinit
43877 @ifset SYSTEM_GDBINIT
43878 @value{SYSTEM_GDBINIT}
43887 @c man begin DESCRIPTION gdbinit
43888 These files contain @value{GDBN} commands to automatically execute during
43889 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43892 the @value{GDBN} manual in node @code{Sequences}
43893 -- shell command @code{info -f gdb -n Sequences}.
43899 Please read more in
43901 the @value{GDBN} manual in node @code{Startup}
43902 -- shell command @code{info -f gdb -n Startup}.
43909 @ifset SYSTEM_GDBINIT
43910 @item @value{SYSTEM_GDBINIT}
43912 @ifclear SYSTEM_GDBINIT
43913 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43915 System-wide initialization file. It is executed unless user specified
43916 @value{GDBN} option @code{-nx} or @code{-n}.
43919 the @value{GDBN} manual in node @code{System-wide configuration}
43920 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43923 @ref{System-wide configuration}.
43927 User initialization file. It is executed unless user specified
43928 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43931 Initialization file for current directory. It may need to be enabled with
43932 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43935 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43936 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43939 @ref{Init File in the Current Directory}.
43944 @c man begin SEEALSO gdbinit
43946 gdb(1), @code{info -f gdb -n Startup}
43948 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43949 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43950 documentation are properly installed at your site, the command
43956 should give you access to the complete manual.
43958 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43959 Richard M. Stallman and Roland H. Pesch, July 1991.
43963 @node gdb-add-index man
43964 @heading gdb-add-index
43965 @pindex gdb-add-index
43966 @anchor{gdb-add-index}
43968 @c man title gdb-add-index Add index files to speed up GDB
43970 @c man begin SYNOPSIS gdb-add-index
43971 gdb-add-index @var{filename}
43974 @c man begin DESCRIPTION gdb-add-index
43975 When @value{GDBN} finds a symbol file, it scans the symbols in the
43976 file in order to construct an internal symbol table. This lets most
43977 @value{GDBN} operations work quickly--at the cost of a delay early on.
43978 For large programs, this delay can be quite lengthy, so @value{GDBN}
43979 provides a way to build an index, which speeds up startup.
43981 To determine whether a file contains such an index, use the command
43982 @kbd{readelf -S filename}: the index is stored in a section named
43983 @code{.gdb_index}. The index file can only be produced on systems
43984 which use ELF binaries and DWARF debug information (i.e., sections
43985 named @code{.debug_*}).
43987 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
43988 in the @env{PATH} environment variable. If you want to use different
43989 versions of these programs, you can specify them through the
43990 @env{GDB} and @env{OBJDUMP} environment variables.
43994 the @value{GDBN} manual in node @code{Index Files}
43995 -- shell command @kbd{info -f gdb -n "Index Files"}.
44002 @c man begin SEEALSO gdb-add-index
44004 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44005 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44006 documentation are properly installed at your site, the command
44012 should give you access to the complete manual.
44014 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44015 Richard M. Stallman and Roland H. Pesch, July 1991.
44021 @node GNU Free Documentation License
44022 @appendix GNU Free Documentation License
44025 @node Concept Index
44026 @unnumbered Concept Index
44030 @node Command and Variable Index
44031 @unnumbered Command, Variable, and Function Index
44036 % I think something like @@colophon should be in texinfo. In the
44038 \long\def\colophon{\hbox to0pt{}\vfill
44039 \centerline{The body of this manual is set in}
44040 \centerline{\fontname\tenrm,}
44041 \centerline{with headings in {\bf\fontname\tenbf}}
44042 \centerline{and examples in {\tt\fontname\tentt}.}
44043 \centerline{{\it\fontname\tenit\/},}
44044 \centerline{{\bf\fontname\tenbf}, and}
44045 \centerline{{\sl\fontname\tensl\/}}
44046 \centerline{are used for emphasis.}\vfill}
44048 % Blame: doc@@cygnus.com, 1991.