1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2022 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{} 1988-2022 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 @*
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) 1988-2022 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 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share GDB
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 Many options have both long and short forms; both are shown in the
966 following list. @value{GDBN} also recognizes the long forms if you truncate
967 them, so long as enough of the option is present to be unambiguous.
968 (If you prefer, you can flag option arguments with @samp{--} rather
969 than @samp{-}, though we illustrate the more usual convention.)
971 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
972 @c way, both those who look for -foo and --foo in the index, will find
976 @item -symbols @var{file}
978 @cindex @code{--symbols}
980 Read symbol table from file @var{file}.
982 @item -exec @var{file}
984 @cindex @code{--exec}
986 Use file @var{file} as the executable file to execute when appropriate,
987 and for examining pure data in conjunction with a core dump.
991 Read symbol table from file @var{file} and use it as the executable
994 @item -core @var{file}
996 @cindex @code{--core}
998 Use file @var{file} as a core dump to examine.
1000 @item -pid @var{number}
1001 @itemx -p @var{number}
1002 @cindex @code{--pid}
1004 Connect to process ID @var{number}, as with the @code{attach} command.
1006 @item -command @var{file}
1007 @itemx -x @var{file}
1008 @cindex @code{--command}
1010 Execute commands from file @var{file}. The contents of this file is
1011 evaluated exactly as the @code{source} command would.
1012 @xref{Command Files,, Command files}.
1014 @item -eval-command @var{command}
1015 @itemx -ex @var{command}
1016 @cindex @code{--eval-command}
1018 Execute a single @value{GDBN} command.
1020 This option may be used multiple times to call multiple commands. It may
1021 also be interleaved with @samp{-command} as required.
1024 @value{GDBP} -ex 'target sim' -ex 'load' \
1025 -x setbreakpoints -ex 'run' a.out
1028 @item -init-command @var{file}
1029 @itemx -ix @var{file}
1030 @cindex @code{--init-command}
1032 Execute commands from file @var{file} before loading the inferior (but
1033 after loading gdbinit files).
1036 @item -init-eval-command @var{command}
1037 @itemx -iex @var{command}
1038 @cindex @code{--init-eval-command}
1040 Execute a single @value{GDBN} command before loading the inferior (but
1041 after loading gdbinit files).
1044 @item -early-init-command @var{file}
1045 @itemx -eix @var{file}
1046 @cindex @code{--early-init-command}
1048 Execute commands from @var{file} very early in the initialization
1049 process, before any output is produced. @xref{Startup}.
1051 @item -early-init-eval-command @var{command}
1052 @itemx -eiex @var{command}
1053 @cindex @code{--early-init-eval-command}
1054 @cindex @code{-eiex}
1055 Execute a single @value{GDBN} command very early in the initialization
1056 process, before any output is produced.
1058 @item -directory @var{directory}
1059 @itemx -d @var{directory}
1060 @cindex @code{--directory}
1062 Add @var{directory} to the path to search for source and script files.
1066 @cindex @code{--readnow}
1068 Read each symbol file's entire symbol table immediately, rather than
1069 the default, which is to read it incrementally as it is needed.
1070 This makes startup slower, but makes future operations faster.
1073 @anchor{--readnever}
1074 @cindex @code{--readnever}, command-line option
1075 Do not read each symbol file's symbolic debug information. This makes
1076 startup faster but at the expense of not being able to perform
1077 symbolic debugging. DWARF unwind information is also not read,
1078 meaning backtraces may become incomplete or inaccurate. One use of
1079 this is when a user simply wants to do the following sequence: attach,
1080 dump core, detach. Loading the debugging information in this case is
1081 an unnecessary cause of delay.
1085 @subsection Choosing Modes
1087 You can run @value{GDBN} in various alternative modes---for example, in
1088 batch mode or quiet mode.
1096 Do not execute commands found in any initialization files
1097 (@pxref{Initialization Files}).
1102 Do not execute commands found in any home directory initialization
1103 file (@pxref{Initialization Files,,Home directory initialization
1104 file}). The system wide and current directory initialization files
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1116 @kindex set startup-quietly
1117 @kindex show startup-quietly
1118 This can also be enabled using @code{set startup-quietly on}. The
1119 default is @code{off}. Use @code{show startup-quietly} to see the
1120 current setting. Place @code{set startup-quietly on} into your early
1121 initialization file (@pxref{Initialization Files,,Initialization
1122 Files}) to have future @value{GDBN} sessions startup quietly.
1125 @cindex @code{--batch}
1126 Run in batch mode. Exit with status @code{0} after processing all the
1127 command files specified with @samp{-x} (and all commands from
1128 initialization files, if not inhibited with @samp{-n}). Exit with
1129 nonzero status if an error occurs in executing the @value{GDBN} commands
1130 in the command files. Batch mode also disables pagination, sets unlimited
1131 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1132 off} were in effect (@pxref{Messages/Warnings}).
1134 Batch mode may be useful for running @value{GDBN} as a filter, for
1135 example to download and run a program on another computer; in order to
1136 make this more useful, the message
1139 Program exited normally.
1143 (which is ordinarily issued whenever a program running under
1144 @value{GDBN} control terminates) is not issued when running in batch
1148 @cindex @code{--batch-silent}
1149 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1150 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1151 unaffected). This is much quieter than @samp{-silent} and would be useless
1152 for an interactive session.
1154 This is particularly useful when using targets that give @samp{Loading section}
1155 messages, for example.
1157 Note that targets that give their output via @value{GDBN}, as opposed to
1158 writing directly to @code{stdout}, will also be made silent.
1160 @item -return-child-result
1161 @cindex @code{--return-child-result}
1162 The return code from @value{GDBN} will be the return code from the child
1163 process (the process being debugged), with the following exceptions:
1167 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1168 internal error. In this case the exit code is the same as it would have been
1169 without @samp{-return-child-result}.
1171 The user quits with an explicit value. E.g., @samp{quit 1}.
1173 The child process never runs, or is not allowed to terminate, in which case
1174 the exit code will be -1.
1177 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1178 when @value{GDBN} is being used as a remote program loader or simulator
1183 @cindex @code{--nowindows}
1185 ``No windows''. If @value{GDBN} comes with a graphical user interface
1186 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1187 interface. If no GUI is available, this option has no effect.
1191 @cindex @code{--windows}
1193 If @value{GDBN} includes a GUI, then this option requires it to be
1196 @item -cd @var{directory}
1198 Run @value{GDBN} using @var{directory} as its working directory,
1199 instead of the current directory.
1201 @item -data-directory @var{directory}
1202 @itemx -D @var{directory}
1203 @cindex @code{--data-directory}
1205 Run @value{GDBN} using @var{directory} as its data directory.
1206 The data directory is where @value{GDBN} searches for its
1207 auxiliary files. @xref{Data Files}.
1211 @cindex @code{--fullname}
1213 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1214 subprocess. It tells @value{GDBN} to output the full file name and line
1215 number in a standard, recognizable fashion each time a stack frame is
1216 displayed (which includes each time your program stops). This
1217 recognizable format looks like two @samp{\032} characters, followed by
1218 the file name, line number and character position separated by colons,
1219 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1220 @samp{\032} characters as a signal to display the source code for the
1223 @item -annotate @var{level}
1224 @cindex @code{--annotate}
1225 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1226 effect is identical to using @samp{set annotate @var{level}}
1227 (@pxref{Annotations}). The annotation @var{level} controls how much
1228 information @value{GDBN} prints together with its prompt, values of
1229 expressions, source lines, and other types of output. Level 0 is the
1230 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1231 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1232 that control @value{GDBN}, and level 2 has been deprecated.
1234 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1238 @cindex @code{--args}
1239 Change interpretation of command line so that arguments following the
1240 executable file are passed as command line arguments to the inferior.
1241 This option stops option processing.
1243 @item -baud @var{bps}
1245 @cindex @code{--baud}
1247 Set the line speed (baud rate or bits per second) of any serial
1248 interface used by @value{GDBN} for remote debugging.
1250 @item -l @var{timeout}
1252 Set the timeout (in seconds) of any communication used by @value{GDBN}
1253 for remote debugging.
1255 @item -tty @var{device}
1256 @itemx -t @var{device}
1257 @cindex @code{--tty}
1259 Run using @var{device} for your program's standard input and output.
1260 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1262 @c resolve the situation of these eventually
1264 @cindex @code{--tui}
1265 Activate the @dfn{Text User Interface} when starting. The Text User
1266 Interface manages several text windows on the terminal, showing
1267 source, assembly, registers and @value{GDBN} command outputs
1268 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1269 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1270 Using @value{GDBN} under @sc{gnu} Emacs}).
1272 @item -interpreter @var{interp}
1273 @cindex @code{--interpreter}
1274 Use the interpreter @var{interp} for interface with the controlling
1275 program or device. This option is meant to be set by programs which
1276 communicate with @value{GDBN} using it as a back end.
1277 @xref{Interpreters, , Command Interpreters}.
1279 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1280 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1281 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1282 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1283 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1284 interfaces are no longer supported.
1287 @cindex @code{--write}
1288 Open the executable and core files for both reading and writing. This
1289 is equivalent to the @samp{set write on} command inside @value{GDBN}
1293 @cindex @code{--statistics}
1294 This option causes @value{GDBN} to print statistics about time and
1295 memory usage after it completes each command and returns to the prompt.
1298 @cindex @code{--version}
1299 This option causes @value{GDBN} to print its version number and
1300 no-warranty blurb, and exit.
1302 @item -configuration
1303 @cindex @code{--configuration}
1304 This option causes @value{GDBN} to print details about its build-time
1305 configuration parameters, and then exit. These details can be
1306 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1311 @subsection What @value{GDBN} Does During Startup
1312 @cindex @value{GDBN} startup
1314 Here's the description of what @value{GDBN} does during session startup:
1319 Performs minimal setup required to initialize basic internal state.
1322 @cindex early initialization file
1323 Reads commands from the early initialization file (if any) in your
1324 home directory. Only a restricted set of commands can be placed into
1325 an early initialization file, see @ref{Initialization Files}, for
1329 Executes commands and command files specified by the @samp{-eiex} and
1330 @samp{-eix} command line options in their specified order. Only a
1331 restricted set of commands can be used with @samp{-eiex} and
1332 @samp{eix}, see @ref{Initialization Files}, for details.
1335 Sets up the command interpreter as specified by the command line
1336 (@pxref{Mode Options, interpreter}).
1340 Reads the system wide initialization file and the files from the
1341 system wide initialization directory, @pxref{System Wide Init Files}.
1344 Reads the initialization file (if any) in your home directory and
1345 executes all the commands in that file, @pxref{Home Directory Init
1348 @anchor{Option -init-eval-command}
1350 Executes commands and command files specified by the @samp{-iex} and
1351 @samp{-ix} options in their specified order. Usually you should use the
1352 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1353 settings before @value{GDBN} init files get executed and before inferior
1357 Processes command line options and operands.
1360 Reads and executes the commands from the initialization file (if any)
1361 in the current working directory as long as @samp{set auto-load
1362 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1363 Directory}). This is only done if the current directory is different
1364 from your home directory. Thus, you can have more than one init file,
1365 one generic in your home directory, and another, specific to the
1366 program you are debugging, in the directory where you invoke
1367 @value{GDBN}. @xref{Init File in the Current Directory during
1371 If the command line specified a program to debug, or a process to
1372 attach to, or a core file, @value{GDBN} loads any auto-loaded
1373 scripts provided for the program or for its loaded shared libraries.
1374 @xref{Auto-loading}.
1376 If you wish to disable the auto-loading during startup,
1377 you must do something like the following:
1380 $ gdb -iex "set auto-load python-scripts off" myprogram
1383 Option @samp{-ex} does not work because the auto-loading is then turned
1387 Executes commands and command files specified by the @samp{-ex} and
1388 @samp{-x} options in their specified order. @xref{Command Files}, for
1389 more details about @value{GDBN} command files.
1392 Reads the command history recorded in the @dfn{history file}.
1393 @xref{Command History}, for more details about the command history and the
1394 files where @value{GDBN} records it.
1397 @node Initialization Files
1398 @subsection Initialization Files
1399 @cindex init file name
1401 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1402 from several initialization files. These initialization files use the
1403 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1404 processed by @value{GDBN} in the same way.
1406 To display the list of initialization files loaded by @value{GDBN} at
1407 startup, in the order they will be loaded, you can use @kbd{gdb
1410 @cindex early initialization
1411 The @dfn{early initialization} file is loaded very early in
1412 @value{GDBN}'s initialization process, before the interpreter
1413 (@pxref{Interpreters}) has been initialized, and before the default
1414 target (@pxref{Targets}) is initialized. Only @code{set} or
1415 @code{source} commands should be placed into an early initialization
1416 file, and the only @code{set} commands that can be used are those that
1417 control how @value{GDBN} starts up.
1419 Commands that can be placed into an early initialization file will be
1420 documented as such throughout this manual. Any command that is not
1421 documented as being suitable for an early initialization file should
1422 instead be placed into a general initialization file. Command files
1423 passed to @code{--early-init-command} or @code{-eix} are also early
1424 initialization files, with the same command restrictions. Only
1425 commands that can appear in an early initialization file should be
1426 passed to @code{--early-init-eval-command} or @code{-eiex}.
1428 @cindex general initialization
1429 In contrast, the @dfn{general initialization} files are processed
1430 later, after @value{GDBN} has finished its own internal initialization
1431 process, any valid command can be used in these files.
1433 @cindex initialization file
1434 Throughout the rest of this document the term @dfn{initialization
1435 file} refers to one of the general initialization files, not the early
1436 initialization file. Any discussion of the early initialization file
1437 will specifically mention that it is the early initialization file
1440 As the system wide and home directory initialization files are
1441 processed before most command line options, changes to settings
1442 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1443 command line options and operands.
1445 The following sections describe where @value{GDBN} looks for the early
1446 initialization and initialization files, and the order that the files
1449 @subsubsection Home directory early initialization files
1451 @value{GDBN} initially looks for an early initialization file in the
1452 users home directory@footnote{On DOS/Windows systems, the home
1453 directory is the one pointed to by the @env{HOME} environment
1454 variable.}. There are a number of locations that @value{GDBN} will
1455 search in the home directory, these locations are searched in order
1456 and @value{GDBN} will load the first file that it finds, and
1457 subsequent locations will not be checked.
1459 On non-macOS hosts the locations searched are:
1462 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1463 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1465 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1466 by the environment variable @env{HOME}, if it is defined.
1468 The file @file{.gdbearlyinit} within the directory pointed to by the
1469 environment variable @env{HOME}, if it is defined.
1472 By contrast, on macOS hosts the locations searched are:
1475 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1476 directory pointed to by the environment variable @env{HOME}, if it is
1479 The file @file{.gdbearlyinit} within the directory pointed to by the
1480 environment variable @env{HOME}, if it is defined.
1483 It is possible to prevent the home directory early initialization file
1484 from being loaded using the @samp{-nx} or @samp{-nh} command line
1485 options, @pxref{Mode Options,,Choosing Modes}.
1487 @anchor{System Wide Init Files}
1488 @subsubsection System wide initialization files
1490 There are two locations that are searched for system wide
1491 initialization files. Both of these locations are always checked:
1495 @item @file{system.gdbinit}
1496 This is a single system-wide initialization file. Its location is
1497 specified with the @code{--with-system-gdbinit} configure option
1498 (@pxref{System-wide configuration}). It is loaded first when
1499 @value{GDBN} starts, before command line options have been processed.
1501 @item @file{system.gdbinit.d}
1502 This is the system-wide initialization directory. Its location is
1503 specified with the @code{--with-system-gdbinit-dir} configure option
1504 (@pxref{System-wide configuration}). Files in this directory are
1505 loaded in alphabetical order immediately after @file{system.gdbinit}
1506 (if enabled) when @value{GDBN} starts, before command line options
1507 have been processed. Files need to have a recognized scripting
1508 language extension (@file{.py}/@file{.scm}) or be named with a
1509 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1510 commands. @value{GDBN} will not recurse into any subdirectories of
1515 It is possible to prevent the system wide initialization files from
1516 being loaded using the @samp{-nx} command line option, @pxref{Mode
1517 Options,,Choosing Modes}.
1519 @anchor{Home Directory Init File}
1520 @subsubsection Home directory initialization file
1521 @cindex @file{gdbinit}
1522 @cindex @file{.gdbinit}
1523 @cindex @file{gdb.ini}
1525 After loading the system wide initialization files @value{GDBN} will
1526 look for an initialization file in the users home
1527 directory@footnote{On DOS/Windows systems, the home directory is the
1528 one pointed to by the @env{HOME} environment variable.}. There are a
1529 number of locations that @value{GDBN} will search in the home
1530 directory, these locations are searched in order and @value{GDBN} will
1531 load the first file that it finds, and subsequent locations will not
1534 On non-Apple hosts the locations searched are:
1536 @item $XDG_CONFIG_HOME/gdb/gdbinit
1537 @item $HOME/.config/gdb/gdbinit
1538 @item $HOME/.gdbinit
1541 While on Apple hosts the locations searched are:
1543 @item $HOME/Library/Preferences/gdb/gdbinit
1544 @item $HOME/.gdbinit
1547 It is possible to prevent the home directory initialization file from
1548 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1549 @pxref{Mode Options,,Choosing Modes}.
1551 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1552 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1553 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1554 uses the standard name, but if it finds a @file{gdb.ini} file in your
1555 home directory, it warns you about that and suggests to rename the
1556 file to the standard name.
1558 @anchor{Init File in the Current Directory during Startup}
1559 @subsubsection Local directory initialization file
1561 @value{GDBN} will check the current directory for a file called
1562 @file{.gdbinit}. It is loaded last, after command line options
1563 other than @samp{-x} and @samp{-ex} have been processed. The command
1564 line options @samp{-x} and @samp{-ex} are processed last, after
1565 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1568 If the file in the current directory was already loaded as the home
1569 directory initialization file then it will not be loaded a second
1572 It is possible to prevent the local directory initialization file from
1573 being loaded using the @samp{-nx} command line option, @pxref{Mode
1574 Options,,Choosing Modes}.
1577 @section Quitting @value{GDBN}
1578 @cindex exiting @value{GDBN}
1579 @cindex leaving @value{GDBN}
1582 @kindex quit @r{[}@var{expression}@r{]}
1583 @kindex exit @r{[}@var{expression}@r{]}
1584 @kindex q @r{(@code{quit})}
1585 @item quit @r{[}@var{expression}@r{]}
1586 @itemx exit @r{[}@var{expression}@r{]}
1588 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1589 @code{q}), the @code{exit} command, or type an end-of-file
1590 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1591 @value{GDBN} will terminate normally; otherwise it will terminate using
1592 the result of @var{expression} as the error code.
1596 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1597 terminates the action of any @value{GDBN} command that is in progress and
1598 returns to @value{GDBN} command level. It is safe to type the interrupt
1599 character at any time because @value{GDBN} does not allow it to take effect
1600 until a time when it is safe.
1602 If you have been using @value{GDBN} to control an attached process or
1603 device, you can release it with the @code{detach} command
1604 (@pxref{Attach, ,Debugging an Already-running Process}).
1606 @node Shell Commands
1607 @section Shell Commands
1609 If you need to execute occasional shell commands during your
1610 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1611 just use the @code{shell} command.
1616 @cindex shell escape
1617 @item shell @var{command-string}
1618 @itemx !@var{command-string}
1619 Invoke a standard shell to execute @var{command-string}.
1620 Note that no space is needed between @code{!} and @var{command-string}.
1621 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1622 exists, determines which shell to run. Otherwise @value{GDBN} uses
1623 the default shell (@file{/bin/sh} on GNU and Unix systems,
1624 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1627 The utility @code{make} is often needed in development environments.
1628 You do not have to use the @code{shell} command for this purpose in
1633 @cindex calling make
1634 @item make @var{make-args}
1635 Execute the @code{make} program with the specified
1636 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1642 @cindex send the output of a gdb command to a shell command
1644 @item pipe [@var{command}] | @var{shell_command}
1645 @itemx | [@var{command}] | @var{shell_command}
1646 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1647 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1648 Executes @var{command} and sends its output to @var{shell_command}.
1649 Note that no space is needed around @code{|}.
1650 If no @var{command} is provided, the last command executed is repeated.
1652 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1653 can be used to specify an alternate delimiter string @var{delim} that separates
1654 the @var{command} from the @var{shell_command}.
1687 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1688 this contains a PIPE char
1689 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1690 this contains a PIPE char!
1696 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1697 can be used to examine the exit status of the last shell command launched
1698 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1699 @xref{Convenience Vars,, Convenience Variables}.
1701 @node Logging Output
1702 @section Logging Output
1703 @cindex logging @value{GDBN} output
1704 @cindex save @value{GDBN} output to a file
1706 You may want to save the output of @value{GDBN} commands to a file.
1707 There are several commands to control @value{GDBN}'s logging.
1710 @kindex set logging enabled
1711 @item set logging enabled [on|off]
1712 Enable or disable logging.
1713 @cindex logging file name
1714 @item set logging file @var{file}
1715 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1716 @item set logging overwrite [on|off]
1717 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1718 you want @code{set logging enabled on} to overwrite the logfile instead.
1719 @item set logging redirect [on|off]
1720 By default, @value{GDBN} output will go to both the terminal and the logfile.
1721 Set @code{redirect} if you want output to go only to the log file.
1722 @item set logging debugredirect [on|off]
1723 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1724 Set @code{debugredirect} if you want debug output to go only to the log file.
1725 @kindex show logging
1727 Show the current values of the logging settings.
1730 You can also redirect the output of a @value{GDBN} command to a
1731 shell command. @xref{pipe}.
1733 @chapter @value{GDBN} Commands
1735 You can abbreviate a @value{GDBN} command to the first few letters of the command
1736 name, if that abbreviation is unambiguous; and you can repeat certain
1737 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1738 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1739 show you the alternatives available, if there is more than one possibility).
1742 * Command Syntax:: How to give commands to @value{GDBN}
1743 * Command Settings:: How to change default behavior of commands
1744 * Completion:: Command completion
1745 * Command Options:: Command options
1746 * Help:: How to ask @value{GDBN} for help
1749 @node Command Syntax
1750 @section Command Syntax
1752 A @value{GDBN} command is a single line of input. There is no limit on
1753 how long it can be. It starts with a command name, which is followed by
1754 arguments whose meaning depends on the command name. For example, the
1755 command @code{step} accepts an argument which is the number of times to
1756 step, as in @samp{step 5}. You can also use the @code{step} command
1757 with no arguments. Some commands do not allow any arguments.
1759 @cindex abbreviation
1760 @value{GDBN} command names may always be truncated if that abbreviation is
1761 unambiguous. Other possible command abbreviations are listed in the
1762 documentation for individual commands. In some cases, even ambiguous
1763 abbreviations are allowed; for example, @code{s} is specially defined as
1764 equivalent to @code{step} even though there are other commands whose
1765 names start with @code{s}. You can test abbreviations by using them as
1766 arguments to the @code{help} command.
1768 @cindex repeating commands
1769 @kindex RET @r{(repeat last command)}
1770 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1771 repeat the previous command. Certain commands (for example, @code{run})
1772 will not repeat this way; these are commands whose unintentional
1773 repetition might cause trouble and which you are unlikely to want to
1774 repeat. User-defined commands can disable this feature; see
1775 @ref{Define, dont-repeat}.
1777 The @code{list} and @code{x} commands, when you repeat them with
1778 @key{RET}, construct new arguments rather than repeating
1779 exactly as typed. This permits easy scanning of source or memory.
1781 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1782 output, in a way similar to the common utility @code{more}
1783 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1784 @key{RET} too many in this situation, @value{GDBN} disables command
1785 repetition after any command that generates this sort of display.
1787 @kindex # @r{(a comment)}
1789 Any text from a @kbd{#} to the end of the line is a comment; it does
1790 nothing. This is useful mainly in command files (@pxref{Command
1791 Files,,Command Files}).
1793 @cindex repeating command sequences
1794 @kindex Ctrl-o @r{(operate-and-get-next)}
1795 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1796 commands. This command accepts the current line, like @key{RET}, and
1797 then fetches the next line relative to the current line from the history
1801 @node Command Settings
1802 @section Command Settings
1803 @cindex default behavior of commands, changing
1804 @cindex default settings, changing
1806 Many commands change their behavior according to command-specific
1807 variables or settings. These settings can be changed with the
1808 @code{set} subcommands. For example, the @code{print} command
1809 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1810 settings changeable with the commands @code{set print elements
1811 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1813 You can change these settings to your preference in the gdbinit files
1814 loaded at @value{GDBN} startup. @xref{Startup}.
1816 The settings can also be changed interactively during the debugging
1817 session. For example, to change the limit of array elements to print,
1818 you can do the following:
1820 (@value{GDBN}) set print elements 10
1821 (@value{GDBN}) print some_array
1822 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1825 The above @code{set print elements 10} command changes the number of
1826 elements to print from the default of 200 to 10. If you only intend
1827 this limit of 10 to be used for printing @code{some_array}, then you
1828 must restore the limit back to 200, with @code{set print elements
1831 Some commands allow overriding settings with command options. For
1832 example, the @code{print} command supports a number of options that
1833 allow overriding relevant global print settings as set by @code{set
1834 print} subcommands. @xref{print options}. The example above could be
1837 (@value{GDBN}) print -elements 10 -- some_array
1838 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1841 Alternatively, you can use the @code{with} command to change a setting
1842 temporarily, for the duration of a command invocation.
1845 @kindex with command
1846 @kindex w @r{(@code{with})}
1848 @cindex temporarily change settings
1849 @item with @var{setting} [@var{value}] [-- @var{command}]
1850 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1851 Temporarily set @var{setting} to @var{value} for the duration of
1854 @var{setting} is any setting you can change with the @code{set}
1855 subcommands. @var{value} is the value to assign to @code{setting}
1856 while running @code{command}.
1858 If no @var{command} is provided, the last command executed is
1861 If a @var{command} is provided, it must be preceded by a double dash
1862 (@code{--}) separator. This is required because some settings accept
1863 free-form arguments, such as expressions or filenames.
1865 For example, the command
1867 (@value{GDBN}) with print array on -- print some_array
1870 is equivalent to the following 3 commands:
1872 (@value{GDBN}) set print array on
1873 (@value{GDBN}) print some_array
1874 (@value{GDBN}) set print array off
1877 The @code{with} command is particularly useful when you want to
1878 override a setting while running user-defined commands, or commands
1879 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1882 (@value{GDBN}) with print pretty on -- my_complex_command
1885 To change several settings for the same command, you can nest
1886 @code{with} commands. For example, @code{with language ada -- with
1887 print elements 10} temporarily changes the language to Ada and sets a
1888 limit of 10 elements to print for arrays and strings.
1893 @section Command Completion
1896 @cindex word completion
1897 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1898 only one possibility; it can also show you what the valid possibilities
1899 are for the next word in a command, at any time. This works for @value{GDBN}
1900 commands, @value{GDBN} subcommands, command options, and the names of symbols
1903 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1904 of a word. If there is only one possibility, @value{GDBN} fills in the
1905 word, and waits for you to finish the command (or press @key{RET} to
1906 enter it). For example, if you type
1908 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1909 @c complete accuracy in these examples; space introduced for clarity.
1910 @c If texinfo enhancements make it unnecessary, it would be nice to
1911 @c replace " @key" by "@key" in the following...
1913 (@value{GDBP}) info bre @key{TAB}
1917 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1918 the only @code{info} subcommand beginning with @samp{bre}:
1921 (@value{GDBP}) info breakpoints
1925 You can either press @key{RET} at this point, to run the @code{info
1926 breakpoints} command, or backspace and enter something else, if
1927 @samp{breakpoints} does not look like the command you expected. (If you
1928 were sure you wanted @code{info breakpoints} in the first place, you
1929 might as well just type @key{RET} immediately after @samp{info bre},
1930 to exploit command abbreviations rather than command completion).
1932 If there is more than one possibility for the next word when you press
1933 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1934 characters and try again, or just press @key{TAB} a second time;
1935 @value{GDBN} displays all the possible completions for that word. For
1936 example, you might want to set a breakpoint on a subroutine whose name
1937 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1938 just sounds the bell. Typing @key{TAB} again displays all the
1939 function names in your program that begin with those characters, for
1943 (@value{GDBP}) b make_ @key{TAB}
1944 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1945 make_a_section_from_file make_environ
1946 make_abs_section make_function_type
1947 make_blockvector make_pointer_type
1948 make_cleanup make_reference_type
1949 make_command make_symbol_completion_list
1950 (@value{GDBP}) b make_
1954 After displaying the available possibilities, @value{GDBN} copies your
1955 partial input (@samp{b make_} in the example) so you can finish the
1958 If you just want to see the list of alternatives in the first place, you
1959 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1960 means @kbd{@key{META} ?}. You can type this either by holding down a
1961 key designated as the @key{META} shift on your keyboard (if there is
1962 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1964 If the number of possible completions is large, @value{GDBN} will
1965 print as much of the list as it has collected, as well as a message
1966 indicating that the list may be truncated.
1969 (@value{GDBP}) b m@key{TAB}@key{TAB}
1971 <... the rest of the possible completions ...>
1972 *** List may be truncated, max-completions reached. ***
1977 This behavior can be controlled with the following commands:
1980 @kindex set max-completions
1981 @item set max-completions @var{limit}
1982 @itemx set max-completions unlimited
1983 Set the maximum number of completion candidates. @value{GDBN} will
1984 stop looking for more completions once it collects this many candidates.
1985 This is useful when completing on things like function names as collecting
1986 all the possible candidates can be time consuming.
1987 The default value is 200. A value of zero disables tab-completion.
1988 Note that setting either no limit or a very large limit can make
1990 @kindex show max-completions
1991 @item show max-completions
1992 Show the maximum number of candidates that @value{GDBN} will collect and show
1996 @cindex quotes in commands
1997 @cindex completion of quoted strings
1998 Sometimes the string you need, while logically a ``word'', may contain
1999 parentheses or other characters that @value{GDBN} normally excludes from
2000 its notion of a word. To permit word completion to work in this
2001 situation, you may enclose words in @code{'} (single quote marks) in
2002 @value{GDBN} commands.
2004 A likely situation where you might need this is in typing an
2005 expression that involves a C@t{++} symbol name with template
2006 parameters. This is because when completing expressions, GDB treats
2007 the @samp{<} character as word delimiter, assuming that it's the
2008 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2011 For example, when you want to call a C@t{++} template function
2012 interactively using the @code{print} or @code{call} commands, you may
2013 need to distinguish whether you mean the version of @code{name} that
2014 was specialized for @code{int}, @code{name<int>()}, or the version
2015 that was specialized for @code{float}, @code{name<float>()}. To use
2016 the word-completion facilities in this situation, type a single quote
2017 @code{'} at the beginning of the function name. This alerts
2018 @value{GDBN} that it may need to consider more information than usual
2019 when you press @key{TAB} or @kbd{M-?} to request word completion:
2022 (@value{GDBP}) p 'func< @kbd{M-?}
2023 func<int>() func<float>()
2024 (@value{GDBP}) p 'func<
2027 When setting breakpoints however (@pxref{Specify Location}), you don't
2028 usually need to type a quote before the function name, because
2029 @value{GDBN} understands that you want to set a breakpoint on a
2033 (@value{GDBP}) b func< @kbd{M-?}
2034 func<int>() func<float>()
2035 (@value{GDBP}) b func<
2038 This is true even in the case of typing the name of C@t{++} overloaded
2039 functions (multiple definitions of the same function, distinguished by
2040 argument type). For example, when you want to set a breakpoint you
2041 don't need to distinguish whether you mean the version of @code{name}
2042 that takes an @code{int} parameter, @code{name(int)}, or the version
2043 that takes a @code{float} parameter, @code{name(float)}.
2046 (@value{GDBP}) b bubble( @kbd{M-?}
2047 bubble(int) bubble(double)
2048 (@value{GDBP}) b bubble(dou @kbd{M-?}
2052 See @ref{quoting names} for a description of other scenarios that
2055 For more information about overloaded functions, see @ref{C Plus Plus
2056 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2057 overload-resolution off} to disable overload resolution;
2058 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2060 @cindex completion of structure field names
2061 @cindex structure field name completion
2062 @cindex completion of union field names
2063 @cindex union field name completion
2064 When completing in an expression which looks up a field in a
2065 structure, @value{GDBN} also tries@footnote{The completer can be
2066 confused by certain kinds of invalid expressions. Also, it only
2067 examines the static type of the expression, not the dynamic type.} to
2068 limit completions to the field names available in the type of the
2072 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2073 magic to_fputs to_rewind
2074 to_data to_isatty to_write
2075 to_delete to_put to_write_async_safe
2080 This is because the @code{gdb_stdout} is a variable of the type
2081 @code{struct ui_file} that is defined in @value{GDBN} sources as
2088 ui_file_flush_ftype *to_flush;
2089 ui_file_write_ftype *to_write;
2090 ui_file_write_async_safe_ftype *to_write_async_safe;
2091 ui_file_fputs_ftype *to_fputs;
2092 ui_file_read_ftype *to_read;
2093 ui_file_delete_ftype *to_delete;
2094 ui_file_isatty_ftype *to_isatty;
2095 ui_file_rewind_ftype *to_rewind;
2096 ui_file_put_ftype *to_put;
2101 @node Command Options
2102 @section Command options
2104 @cindex command options
2105 Some commands accept options starting with a leading dash. For
2106 example, @code{print -pretty}. Similarly to command names, you can
2107 abbreviate a @value{GDBN} option to the first few letters of the
2108 option name, if that abbreviation is unambiguous, and you can also use
2109 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2110 in an option (or to show you the alternatives available, if there is
2111 more than one possibility).
2113 @cindex command options, raw input
2114 Some commands take raw input as argument. For example, the print
2115 command processes arbitrary expressions in any of the languages
2116 supported by @value{GDBN}. With such commands, because raw input may
2117 start with a leading dash that would be confused with an option or any
2118 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2119 -pretty} or printing negative @code{p}?), if you specify any command
2120 option, then you must use a double-dash (@code{--}) delimiter to
2121 indicate the end of options.
2123 @cindex command options, boolean
2125 Some options are described as accepting an argument which can be
2126 either @code{on} or @code{off}. These are known as @dfn{boolean
2127 options}. Similarly to boolean settings commands---@code{on} and
2128 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2129 @code{enable} can also be used as ``true'' value, and any of @code{0},
2130 @code{no} and @code{disable} can also be used as ``false'' value. You
2131 can also omit a ``true'' value, as it is implied by default.
2133 For example, these are equivalent:
2136 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2137 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2140 You can discover the set of options some command accepts by completing
2141 on @code{-} after the command name. For example:
2144 (@value{GDBP}) print -@key{TAB}@key{TAB}
2145 -address -max-depth -pretty -symbol
2146 -array -memory-tag-violations -raw-values -union
2147 -array-indexes -null-stop -repeats -vtbl
2148 -elements -object -static-members
2151 Completion will in some cases guide you with a suggestion of what kind
2152 of argument an option expects. For example:
2155 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2159 Here, the option expects a number (e.g., @code{100}), not literal
2160 @code{NUMBER}. Such metasyntactical arguments are always presented in
2163 (For more on using the @code{print} command, see @ref{Data, ,Examining
2167 @section Getting Help
2168 @cindex online documentation
2171 You can always ask @value{GDBN} itself for information on its commands,
2172 using the command @code{help}.
2175 @kindex h @r{(@code{help})}
2178 You can use @code{help} (abbreviated @code{h}) with no arguments to
2179 display a short list of named classes of commands:
2183 List of classes of commands:
2185 aliases -- User-defined aliases of other commands
2186 breakpoints -- Making program stop at certain points
2187 data -- Examining data
2188 files -- Specifying and examining files
2189 internals -- Maintenance commands
2190 obscure -- Obscure features
2191 running -- Running the program
2192 stack -- Examining the stack
2193 status -- Status inquiries
2194 support -- Support facilities
2195 tracepoints -- Tracing of program execution without
2196 stopping the program
2197 user-defined -- User-defined commands
2199 Type "help" followed by a class name for a list of
2200 commands in that class.
2201 Type "help" followed by command name for full
2203 Command name abbreviations are allowed if unambiguous.
2206 @c the above line break eliminates huge line overfull...
2208 @item help @var{class}
2209 Using one of the general help classes as an argument, you can get a
2210 list of the individual commands in that class. If a command has
2211 aliases, the aliases are given after the command name, separated by
2212 commas. If an alias has default arguments, the full definition of
2213 the alias is given after the first line.
2214 For example, here is the help display for the class @code{status}:
2217 (@value{GDBP}) help status
2222 @c Line break in "show" line falsifies real output, but needed
2223 @c to fit in smallbook page size.
2224 info, inf, i -- Generic command for showing things
2225 about the program being debugged
2226 info address, iamain -- Describe where symbol SYM is stored.
2227 alias iamain = info address main
2228 info all-registers -- List of all registers and their contents,
2229 for selected stack frame.
2231 show, info set -- Generic command for showing things
2234 Type "help" followed by command name for full
2236 Command name abbreviations are allowed if unambiguous.
2240 @item help @var{command}
2241 With a command name as @code{help} argument, @value{GDBN} displays a
2242 short paragraph on how to use that command. If that command has
2243 one or more aliases, @value{GDBN} will display a first line with
2244 the command name and all its aliases separated by commas.
2245 This first line will be followed by the full definition of all aliases
2246 having default arguments.
2249 @item apropos [-v] @var{regexp}
2250 The @code{apropos} command searches through all of the @value{GDBN}
2251 commands, and their documentation, for the regular expression specified in
2252 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2253 which stands for @samp{verbose}, indicates to output the full documentation
2254 of the matching commands and highlight the parts of the documentation
2255 matching @var{regexp}. For example:
2266 alias -- Define a new command that is an alias of an existing command
2267 aliases -- User-defined aliases of other commands
2275 apropos -v cut.*thread apply
2279 results in the below output, where @samp{cut for 'thread apply}
2280 is highlighted if styling is enabled.
2284 taas -- Apply a command to all threads (ignoring errors
2287 shortcut for 'thread apply all -s COMMAND'
2289 tfaas -- Apply a command to all frames of all threads
2290 (ignoring errors and empty output).
2291 Usage: tfaas COMMAND
2292 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2297 @item complete @var{args}
2298 The @code{complete @var{args}} command lists all the possible completions
2299 for the beginning of a command. Use @var{args} to specify the beginning of the
2300 command you want completed. For example:
2306 @noindent results in:
2317 @noindent This is intended for use by @sc{gnu} Emacs.
2320 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2321 and @code{show} to inquire about the state of your program, or the state
2322 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2323 manual introduces each of them in the appropriate context. The listings
2324 under @code{info} and under @code{show} in the Command, Variable, and
2325 Function Index point to all the sub-commands. @xref{Command and Variable
2331 @kindex i @r{(@code{info})}
2333 This command (abbreviated @code{i}) is for describing the state of your
2334 program. For example, you can show the arguments passed to a function
2335 with @code{info args}, list the registers currently in use with @code{info
2336 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2337 You can get a complete list of the @code{info} sub-commands with
2338 @w{@code{help info}}.
2342 You can assign the result of an expression to an environment variable with
2343 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2344 @code{set prompt $}.
2348 In contrast to @code{info}, @code{show} is for describing the state of
2349 @value{GDBN} itself.
2350 You can change most of the things you can @code{show}, by using the
2351 related command @code{set}; for example, you can control what number
2352 system is used for displays with @code{set radix}, or simply inquire
2353 which is currently in use with @code{show radix}.
2356 To display all the settable parameters and their current
2357 values, you can use @code{show} with no arguments; you may also use
2358 @code{info set}. Both commands produce the same display.
2359 @c FIXME: "info set" violates the rule that "info" is for state of
2360 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2361 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2365 Here are several miscellaneous @code{show} subcommands, all of which are
2366 exceptional in lacking corresponding @code{set} commands:
2369 @kindex show version
2370 @cindex @value{GDBN} version number
2372 Show what version of @value{GDBN} is running. You should include this
2373 information in @value{GDBN} bug-reports. If multiple versions of
2374 @value{GDBN} are in use at your site, you may need to determine which
2375 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2376 commands are introduced, and old ones may wither away. Also, many
2377 system vendors ship variant versions of @value{GDBN}, and there are
2378 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2379 The version number is the same as the one announced when you start
2382 @kindex show copying
2383 @kindex info copying
2384 @cindex display @value{GDBN} copyright
2387 Display information about permission for copying @value{GDBN}.
2389 @kindex show warranty
2390 @kindex info warranty
2392 @itemx info warranty
2393 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2394 if your version of @value{GDBN} comes with one.
2396 @kindex show configuration
2397 @item show configuration
2398 Display detailed information about the way @value{GDBN} was configured
2399 when it was built. This displays the optional arguments passed to the
2400 @file{configure} script and also configuration parameters detected
2401 automatically by @command{configure}. When reporting a @value{GDBN}
2402 bug (@pxref{GDB Bugs}), it is important to include this information in
2408 @chapter Running Programs Under @value{GDBN}
2410 When you run a program under @value{GDBN}, you must first generate
2411 debugging information when you compile it.
2413 You may start @value{GDBN} with its arguments, if any, in an environment
2414 of your choice. If you are doing native debugging, you may redirect
2415 your program's input and output, debug an already running process, or
2416 kill a child process.
2419 * Compilation:: Compiling for debugging
2420 * Starting:: Starting your program
2421 * Arguments:: Your program's arguments
2422 * Environment:: Your program's environment
2424 * Working Directory:: Your program's working directory
2425 * Input/Output:: Your program's input and output
2426 * Attach:: Debugging an already-running process
2427 * Kill Process:: Killing the child process
2428 * Inferiors Connections and Programs:: Debugging multiple inferiors
2429 connections and programs
2430 * Threads:: Debugging programs with multiple threads
2431 * Forks:: Debugging forks
2432 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2436 @section Compiling for Debugging
2438 In order to debug a program effectively, you need to generate
2439 debugging information when you compile it. This debugging information
2440 is stored in the object file; it describes the data type of each
2441 variable or function and the correspondence between source line numbers
2442 and addresses in the executable code.
2444 To request debugging information, specify the @samp{-g} option when you run
2447 Programs that are to be shipped to your customers are compiled with
2448 optimizations, using the @samp{-O} compiler option. However, some
2449 compilers are unable to handle the @samp{-g} and @samp{-O} options
2450 together. Using those compilers, you cannot generate optimized
2451 executables containing debugging information.
2453 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2454 without @samp{-O}, making it possible to debug optimized code. We
2455 recommend that you @emph{always} use @samp{-g} whenever you compile a
2456 program. You may think your program is correct, but there is no sense
2457 in pushing your luck. For more information, see @ref{Optimized Code}.
2459 Older versions of the @sc{gnu} C compiler permitted a variant option
2460 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2461 format; if your @sc{gnu} C compiler has this option, do not use it.
2463 @value{GDBN} knows about preprocessor macros and can show you their
2464 expansion (@pxref{Macros}). Most compilers do not include information
2465 about preprocessor macros in the debugging information if you specify
2466 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2467 the @sc{gnu} C compiler, provides macro information if you are using
2468 the DWARF debugging format, and specify the option @option{-g3}.
2470 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2471 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2472 information on @value{NGCC} options affecting debug information.
2474 You will have the best debugging experience if you use the latest
2475 version of the DWARF debugging format that your compiler supports.
2476 DWARF is currently the most expressive and best supported debugging
2477 format in @value{GDBN}.
2481 @section Starting your Program
2487 @kindex r @r{(@code{run})}
2490 Use the @code{run} command to start your program under @value{GDBN}.
2491 You must first specify the program name with an argument to
2492 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2493 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2494 command (@pxref{Files, ,Commands to Specify Files}).
2498 If you are running your program in an execution environment that
2499 supports processes, @code{run} creates an inferior process and makes
2500 that process run your program. In some environments without processes,
2501 @code{run} jumps to the start of your program. Other targets,
2502 like @samp{remote}, are always running. If you get an error
2503 message like this one:
2506 The "remote" target does not support "run".
2507 Try "help target" or "continue".
2511 then use @code{continue} to run your program. You may need @code{load}
2512 first (@pxref{load}).
2514 The execution of a program is affected by certain information it
2515 receives from its superior. @value{GDBN} provides ways to specify this
2516 information, which you must do @emph{before} starting your program. (You
2517 can change it after starting your program, but such changes only affect
2518 your program the next time you start it.) This information may be
2519 divided into four categories:
2522 @item The @emph{arguments.}
2523 Specify the arguments to give your program as the arguments of the
2524 @code{run} command. If a shell is available on your target, the shell
2525 is used to pass the arguments, so that you may use normal conventions
2526 (such as wildcard expansion or variable substitution) in describing
2528 In Unix systems, you can control which shell is used with the
2529 @env{SHELL} environment variable. If you do not define @env{SHELL},
2530 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2531 use of any shell with the @code{set startup-with-shell} command (see
2534 @item The @emph{environment.}
2535 Your program normally inherits its environment from @value{GDBN}, but you can
2536 use the @value{GDBN} commands @code{set environment} and @code{unset
2537 environment} to change parts of the environment that affect
2538 your program. @xref{Environment, ,Your Program's Environment}.
2540 @item The @emph{working directory.}
2541 You can set your program's working directory with the command
2542 @kbd{set cwd}. If you do not set any working directory with this
2543 command, your program will inherit @value{GDBN}'s working directory if
2544 native debugging, or the remote server's working directory if remote
2545 debugging. @xref{Working Directory, ,Your Program's Working
2548 @item The @emph{standard input and output.}
2549 Your program normally uses the same device for standard input and
2550 standard output as @value{GDBN} is using. You can redirect input and output
2551 in the @code{run} command line, or you can use the @code{tty} command to
2552 set a different device for your program.
2553 @xref{Input/Output, ,Your Program's Input and Output}.
2556 @emph{Warning:} While input and output redirection work, you cannot use
2557 pipes to pass the output of the program you are debugging to another
2558 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2562 When you issue the @code{run} command, your program begins to execute
2563 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2564 of how to arrange for your program to stop. Once your program has
2565 stopped, you may call functions in your program, using the @code{print}
2566 or @code{call} commands. @xref{Data, ,Examining Data}.
2568 If the modification time of your symbol file has changed since the last
2569 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2570 table, and reads it again. When it does this, @value{GDBN} tries to retain
2571 your current breakpoints.
2576 @cindex run to main procedure
2577 The name of the main procedure can vary from language to language.
2578 With C or C@t{++}, the main procedure name is always @code{main}, but
2579 other languages such as Ada do not require a specific name for their
2580 main procedure. The debugger provides a convenient way to start the
2581 execution of the program and to stop at the beginning of the main
2582 procedure, depending on the language used.
2584 The @samp{start} command does the equivalent of setting a temporary
2585 breakpoint at the beginning of the main procedure and then invoking
2586 the @samp{run} command.
2588 @cindex elaboration phase
2589 Some programs contain an @dfn{elaboration} phase where some startup code is
2590 executed before the main procedure is called. This depends on the
2591 languages used to write your program. In C@t{++}, for instance,
2592 constructors for static and global objects are executed before
2593 @code{main} is called. It is therefore possible that the debugger stops
2594 before reaching the main procedure. However, the temporary breakpoint
2595 will remain to halt execution.
2597 Specify the arguments to give to your program as arguments to the
2598 @samp{start} command. These arguments will be given verbatim to the
2599 underlying @samp{run} command. Note that the same arguments will be
2600 reused if no argument is provided during subsequent calls to
2601 @samp{start} or @samp{run}.
2603 It is sometimes necessary to debug the program during elaboration. In
2604 these cases, using the @code{start} command would stop the execution
2605 of your program too late, as the program would have already completed
2606 the elaboration phase. Under these circumstances, either insert
2607 breakpoints in your elaboration code before running your program or
2608 use the @code{starti} command.
2612 @cindex run to first instruction
2613 The @samp{starti} command does the equivalent of setting a temporary
2614 breakpoint at the first instruction of a program's execution and then
2615 invoking the @samp{run} command. For programs containing an
2616 elaboration phase, the @code{starti} command will stop execution at
2617 the start of the elaboration phase.
2619 @anchor{set exec-wrapper}
2620 @kindex set exec-wrapper
2621 @item set exec-wrapper @var{wrapper}
2622 @itemx show exec-wrapper
2623 @itemx unset exec-wrapper
2624 When @samp{exec-wrapper} is set, the specified wrapper is used to
2625 launch programs for debugging. @value{GDBN} starts your program
2626 with a shell command of the form @kbd{exec @var{wrapper}
2627 @var{program}}. Quoting is added to @var{program} and its
2628 arguments, but not to @var{wrapper}, so you should add quotes if
2629 appropriate for your shell. The wrapper runs until it executes
2630 your program, and then @value{GDBN} takes control.
2632 You can use any program that eventually calls @code{execve} with
2633 its arguments as a wrapper. Several standard Unix utilities do
2634 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2635 with @code{exec "$@@"} will also work.
2637 For example, you can use @code{env} to pass an environment variable to
2638 the debugged program, without setting the variable in your shell's
2642 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2646 This command is available when debugging locally on most targets, excluding
2647 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2649 @kindex set startup-with-shell
2650 @anchor{set startup-with-shell}
2651 @item set startup-with-shell
2652 @itemx set startup-with-shell on
2653 @itemx set startup-with-shell off
2654 @itemx show startup-with-shell
2655 On Unix systems, by default, if a shell is available on your target,
2656 @value{GDBN}) uses it to start your program. Arguments of the
2657 @code{run} command are passed to the shell, which does variable
2658 substitution, expands wildcard characters and performs redirection of
2659 I/O. In some circumstances, it may be useful to disable such use of a
2660 shell, for example, when debugging the shell itself or diagnosing
2661 startup failures such as:
2665 Starting program: ./a.out
2666 During startup program terminated with signal SIGSEGV, Segmentation fault.
2670 which indicates the shell or the wrapper specified with
2671 @samp{exec-wrapper} crashed, not your program. Most often, this is
2672 caused by something odd in your shell's non-interactive mode
2673 initialization file---such as @file{.cshrc} for C-shell,
2674 $@file{.zshenv} for the Z shell, or the file specified in the
2675 @env{BASH_ENV} environment variable for BASH.
2677 @anchor{set auto-connect-native-target}
2678 @kindex set auto-connect-native-target
2679 @item set auto-connect-native-target
2680 @itemx set auto-connect-native-target on
2681 @itemx set auto-connect-native-target off
2682 @itemx show auto-connect-native-target
2684 By default, if the current inferior is not connected to any target yet
2685 (e.g., with @code{target remote}), the @code{run} command starts your
2686 program as a native process under @value{GDBN}, on your local machine.
2687 If you're sure you don't want to debug programs on your local machine,
2688 you can tell @value{GDBN} to not connect to the native target
2689 automatically with the @code{set auto-connect-native-target off}
2692 If @code{on}, which is the default, and if the current inferior is not
2693 connected to a target already, the @code{run} command automaticaly
2694 connects to the native target, if one is available.
2696 If @code{off}, and if the current inferior is not connected to a
2697 target already, the @code{run} command fails with an error:
2701 Don't know how to run. Try "help target".
2704 If the current inferior is already connected to a target, @value{GDBN}
2705 always uses it with the @code{run} command.
2707 In any case, you can explicitly connect to the native target with the
2708 @code{target native} command. For example,
2711 (@value{GDBP}) set auto-connect-native-target off
2713 Don't know how to run. Try "help target".
2714 (@value{GDBP}) target native
2716 Starting program: ./a.out
2717 [Inferior 1 (process 10421) exited normally]
2720 In case you connected explicitly to the @code{native} target,
2721 @value{GDBN} remains connected even if all inferiors exit, ready for
2722 the next @code{run} command. Use the @code{disconnect} command to
2725 Examples of other commands that likewise respect the
2726 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2727 proc}, @code{info os}.
2729 @kindex set disable-randomization
2730 @item set disable-randomization
2731 @itemx set disable-randomization on
2732 This option (enabled by default in @value{GDBN}) will turn off the native
2733 randomization of the virtual address space of the started program. This option
2734 is useful for multiple debugging sessions to make the execution better
2735 reproducible and memory addresses reusable across debugging sessions.
2737 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2738 On @sc{gnu}/Linux you can get the same behavior using
2741 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2744 @item set disable-randomization off
2745 Leave the behavior of the started executable unchanged. Some bugs rear their
2746 ugly heads only when the program is loaded at certain addresses. If your bug
2747 disappears when you run the program under @value{GDBN}, that might be because
2748 @value{GDBN} by default disables the address randomization on platforms, such
2749 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2750 disable-randomization off} to try to reproduce such elusive bugs.
2752 On targets where it is available, virtual address space randomization
2753 protects the programs against certain kinds of security attacks. In these
2754 cases the attacker needs to know the exact location of a concrete executable
2755 code. Randomizing its location makes it impossible to inject jumps misusing
2756 a code at its expected addresses.
2758 Prelinking shared libraries provides a startup performance advantage but it
2759 makes addresses in these libraries predictable for privileged processes by
2760 having just unprivileged access at the target system. Reading the shared
2761 library binary gives enough information for assembling the malicious code
2762 misusing it. Still even a prelinked shared library can get loaded at a new
2763 random address just requiring the regular relocation process during the
2764 startup. Shared libraries not already prelinked are always loaded at
2765 a randomly chosen address.
2767 Position independent executables (PIE) contain position independent code
2768 similar to the shared libraries and therefore such executables get loaded at
2769 a randomly chosen address upon startup. PIE executables always load even
2770 already prelinked shared libraries at a random address. You can build such
2771 executable using @command{gcc -fPIE -pie}.
2773 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2774 (as long as the randomization is enabled).
2776 @item show disable-randomization
2777 Show the current setting of the explicit disable of the native randomization of
2778 the virtual address space of the started program.
2783 @section Your Program's Arguments
2785 @cindex arguments (to your program)
2786 The arguments to your program can be specified by the arguments of the
2788 They are passed to a shell, which expands wildcard characters and
2789 performs redirection of I/O, and thence to your program. Your
2790 @env{SHELL} environment variable (if it exists) specifies what shell
2791 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2792 the default shell (@file{/bin/sh} on Unix).
2794 On non-Unix systems, the program is usually invoked directly by
2795 @value{GDBN}, which emulates I/O redirection via the appropriate system
2796 calls, and the wildcard characters are expanded by the startup code of
2797 the program, not by the shell.
2799 @code{run} with no arguments uses the same arguments used by the previous
2800 @code{run}, or those set by the @code{set args} command.
2805 Specify the arguments to be used the next time your program is run. If
2806 @code{set args} has no arguments, @code{run} executes your program
2807 with no arguments. Once you have run your program with arguments,
2808 using @code{set args} before the next @code{run} is the only way to run
2809 it again without arguments.
2813 Show the arguments to give your program when it is started.
2817 @section Your Program's Environment
2819 @cindex environment (of your program)
2820 The @dfn{environment} consists of a set of environment variables and
2821 their values. Environment variables conventionally record such things as
2822 your user name, your home directory, your terminal type, and your search
2823 path for programs to run. Usually you set up environment variables with
2824 the shell and they are inherited by all the other programs you run. When
2825 debugging, it can be useful to try running your program with a modified
2826 environment without having to start @value{GDBN} over again.
2830 @item path @var{directory}
2831 Add @var{directory} to the front of the @env{PATH} environment variable
2832 (the search path for executables) that will be passed to your program.
2833 The value of @env{PATH} used by @value{GDBN} does not change.
2834 You may specify several directory names, separated by whitespace or by a
2835 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2836 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2837 is moved to the front, so it is searched sooner.
2839 You can use the string @samp{$cwd} to refer to whatever is the current
2840 working directory at the time @value{GDBN} searches the path. If you
2841 use @samp{.} instead, it refers to the directory where you executed the
2842 @code{path} command. @value{GDBN} replaces @samp{.} in the
2843 @var{directory} argument (with the current path) before adding
2844 @var{directory} to the search path.
2845 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2846 @c document that, since repeating it would be a no-op.
2850 Display the list of search paths for executables (the @env{PATH}
2851 environment variable).
2853 @kindex show environment
2854 @item show environment @r{[}@var{varname}@r{]}
2855 Print the value of environment variable @var{varname} to be given to
2856 your program when it starts. If you do not supply @var{varname},
2857 print the names and values of all environment variables to be given to
2858 your program. You can abbreviate @code{environment} as @code{env}.
2860 @kindex set environment
2861 @anchor{set environment}
2862 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2863 Set environment variable @var{varname} to @var{value}. The value
2864 changes for your program (and the shell @value{GDBN} uses to launch
2865 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2866 values of environment variables are just strings, and any
2867 interpretation is supplied by your program itself. The @var{value}
2868 parameter is optional; if it is eliminated, the variable is set to a
2870 @c "any string" here does not include leading, trailing
2871 @c blanks. Gnu asks: does anyone care?
2873 For example, this command:
2880 tells the debugged program, when subsequently run, that its user is named
2881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2882 are not actually required.)
2884 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2885 which also inherits the environment set with @code{set environment}.
2886 If necessary, you can avoid that by using the @samp{env} program as a
2887 wrapper instead of using @code{set environment}. @xref{set
2888 exec-wrapper}, for an example doing just that.
2890 Environment variables that are set by the user are also transmitted to
2891 @command{gdbserver} to be used when starting the remote inferior.
2892 @pxref{QEnvironmentHexEncoded}.
2894 @kindex unset environment
2895 @anchor{unset environment}
2896 @item unset environment @var{varname}
2897 Remove variable @var{varname} from the environment to be passed to your
2898 program. This is different from @samp{set env @var{varname} =};
2899 @code{unset environment} removes the variable from the environment,
2900 rather than assigning it an empty value.
2902 Environment variables that are unset by the user are also unset on
2903 @command{gdbserver} when starting the remote inferior.
2904 @pxref{QEnvironmentUnset}.
2907 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2908 the shell indicated by your @env{SHELL} environment variable if it
2909 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2910 names a shell that runs an initialization file when started
2911 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2912 for the Z shell, or the file specified in the @env{BASH_ENV}
2913 environment variable for BASH---any variables you set in that file
2914 affect your program. You may wish to move setting of environment
2915 variables to files that are only run when you sign on, such as
2916 @file{.login} or @file{.profile}.
2918 @node Working Directory
2919 @section Your Program's Working Directory
2921 @cindex working directory (of your program)
2922 Each time you start your program with @code{run}, the inferior will be
2923 initialized with the current working directory specified by the
2924 @kbd{set cwd} command. If no directory has been specified by this
2925 command, then the inferior will inherit @value{GDBN}'s current working
2926 directory as its working directory if native debugging, or it will
2927 inherit the remote server's current working directory if remote
2932 @cindex change inferior's working directory
2933 @anchor{set cwd command}
2934 @item set cwd @r{[}@var{directory}@r{]}
2935 Set the inferior's working directory to @var{directory}, which will be
2936 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2937 argument has been specified, the command clears the setting and resets
2938 it to an empty state. This setting has no effect on @value{GDBN}'s
2939 working directory, and it only takes effect the next time you start
2940 the inferior. The @file{~} in @var{directory} is a short for the
2941 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2942 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2943 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2946 You can also change @value{GDBN}'s current working directory by using
2947 the @code{cd} command.
2951 @cindex show inferior's working directory
2953 Show the inferior's working directory. If no directory has been
2954 specified by @kbd{set cwd}, then the default inferior's working
2955 directory is the same as @value{GDBN}'s working directory.
2958 @cindex change @value{GDBN}'s working directory
2960 @item cd @r{[}@var{directory}@r{]}
2961 Set the @value{GDBN} working directory to @var{directory}. If not
2962 given, @var{directory} uses @file{'~'}.
2964 The @value{GDBN} working directory serves as a default for the
2965 commands that specify files for @value{GDBN} to operate on.
2966 @xref{Files, ,Commands to Specify Files}.
2967 @xref{set cwd command}.
2971 Print the @value{GDBN} working directory.
2974 It is generally impossible to find the current working directory of
2975 the process being debugged (since a program can change its directory
2976 during its run). If you work on a system where @value{GDBN} supports
2977 the @code{info proc} command (@pxref{Process Information}), you can
2978 use the @code{info proc} command to find out the
2979 current working directory of the debuggee.
2982 @section Your Program's Input and Output
2987 By default, the program you run under @value{GDBN} does input and output to
2988 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2989 to its own terminal modes to interact with you, but it records the terminal
2990 modes your program was using and switches back to them when you continue
2991 running your program.
2994 @kindex info terminal
2996 Displays information recorded by @value{GDBN} about the terminal modes your
3000 You can redirect your program's input and/or output using shell
3001 redirection with the @code{run} command. For example,
3008 starts your program, diverting its output to the file @file{outfile}.
3011 @cindex controlling terminal
3012 Another way to specify where your program should do input and output is
3013 with the @code{tty} command. This command accepts a file name as
3014 argument, and causes this file to be the default for future @code{run}
3015 commands. It also resets the controlling terminal for the child
3016 process, for future @code{run} commands. For example,
3023 directs that processes started with subsequent @code{run} commands
3024 default to do input and output on the terminal @file{/dev/ttyb} and have
3025 that as their controlling terminal.
3027 An explicit redirection in @code{run} overrides the @code{tty} command's
3028 effect on the input/output device, but not its effect on the controlling
3031 When you use the @code{tty} command or redirect input in the @code{run}
3032 command, only the input @emph{for your program} is affected. The input
3033 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3034 for @code{set inferior-tty}.
3036 @cindex inferior tty
3037 @cindex set inferior controlling terminal
3038 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3039 display the name of the terminal that will be used for future runs of your
3043 @item set inferior-tty [ @var{tty} ]
3044 @kindex set inferior-tty
3045 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3046 restores the default behavior, which is to use the same terminal as
3049 @item show inferior-tty
3050 @kindex show inferior-tty
3051 Show the current tty for the program being debugged.
3055 @section Debugging an Already-running Process
3060 @item attach @var{process-id}
3061 This command attaches to a running process---one that was started
3062 outside @value{GDBN}. (@code{info files} shows your active
3063 targets.) The command takes as argument a process ID. The usual way to
3064 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3065 or with the @samp{jobs -l} shell command.
3067 @code{attach} does not repeat if you press @key{RET} a second time after
3068 executing the command.
3071 To use @code{attach}, your program must be running in an environment
3072 which supports processes; for example, @code{attach} does not work for
3073 programs on bare-board targets that lack an operating system. You must
3074 also have permission to send the process a signal.
3076 When you use @code{attach}, the debugger finds the program running in
3077 the process first by looking in the current working directory, then (if
3078 the program is not found) by using the source file search path
3079 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3080 the @code{file} command to load the program. @xref{Files, ,Commands to
3083 @anchor{set exec-file-mismatch}
3084 If the debugger can determine that the executable file running in the
3085 process it is attaching to does not match the current exec-file loaded
3086 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3087 handle the mismatch. @value{GDBN} tries to compare the files by
3088 comparing their build IDs (@pxref{build ID}), if available.
3091 @kindex exec-file-mismatch
3092 @cindex set exec-file-mismatch
3093 @item set exec-file-mismatch @samp{ask|warn|off}
3095 Whether to detect mismatch between the current executable file loaded
3096 by @value{GDBN} and the executable file used to start the process. If
3097 @samp{ask}, the default, display a warning and ask the user whether to
3098 load the process executable file; if @samp{warn}, just display a
3099 warning; if @samp{off}, don't attempt to detect a mismatch.
3100 If the user confirms loading the process executable file, then its symbols
3101 will be loaded as well.
3103 @cindex show exec-file-mismatch
3104 @item show exec-file-mismatch
3105 Show the current value of @code{exec-file-mismatch}.
3109 The first thing @value{GDBN} does after arranging to debug the specified
3110 process is to stop it. You can examine and modify an attached process
3111 with all the @value{GDBN} commands that are ordinarily available when
3112 you start processes with @code{run}. You can insert breakpoints; you
3113 can step and continue; you can modify storage. If you would rather the
3114 process continue running, you may use the @code{continue} command after
3115 attaching @value{GDBN} to the process.
3120 When you have finished debugging the attached process, you can use the
3121 @code{detach} command to release it from @value{GDBN} control. Detaching
3122 the process continues its execution. After the @code{detach} command,
3123 that process and @value{GDBN} become completely independent once more, and you
3124 are ready to @code{attach} another process or start one with @code{run}.
3125 @code{detach} does not repeat if you press @key{RET} again after
3126 executing the command.
3129 If you exit @value{GDBN} while you have an attached process, you detach
3130 that process. If you use the @code{run} command, you kill that process.
3131 By default, @value{GDBN} asks for confirmation if you try to do either of these
3132 things; you can control whether or not you need to confirm by using the
3133 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3137 @section Killing the Child Process
3142 Kill the child process in which your program is running under @value{GDBN}.
3145 This command is useful if you wish to debug a core dump instead of a
3146 running process. @value{GDBN} ignores any core dump file while your program
3149 On some operating systems, a program cannot be executed outside @value{GDBN}
3150 while you have breakpoints set on it inside @value{GDBN}. You can use the
3151 @code{kill} command in this situation to permit running your program
3152 outside the debugger.
3154 The @code{kill} command is also useful if you wish to recompile and
3155 relink your program, since on many systems it is impossible to modify an
3156 executable file while it is running in a process. In this case, when you
3157 next type @code{run}, @value{GDBN} notices that the file has changed, and
3158 reads the symbol table again (while trying to preserve your current
3159 breakpoint settings).
3161 @node Inferiors Connections and Programs
3162 @section Debugging Multiple Inferiors Connections and Programs
3164 @value{GDBN} lets you run and debug multiple programs in a single
3165 session. In addition, @value{GDBN} on some systems may let you run
3166 several programs simultaneously (otherwise you have to exit from one
3167 before starting another). On some systems @value{GDBN} may even let
3168 you debug several programs simultaneously on different remote systems.
3169 In the most general case, you can have multiple threads of execution
3170 in each of multiple processes, launched from multiple executables,
3171 running on different machines.
3174 @value{GDBN} represents the state of each program execution with an
3175 object called an @dfn{inferior}. An inferior typically corresponds to
3176 a process, but is more general and applies also to targets that do not
3177 have processes. Inferiors may be created before a process runs, and
3178 may be retained after a process exits. Inferiors have unique
3179 identifiers that are different from process ids. Usually each
3180 inferior will also have its own distinct address space, although some
3181 embedded targets may have several inferiors running in different parts
3182 of a single address space. Each inferior may in turn have multiple
3183 threads running in it.
3185 To find out what inferiors exist at any moment, use @w{@code{info
3189 @kindex info inferiors [ @var{id}@dots{} ]
3190 @item info inferiors
3191 Print a list of all inferiors currently being managed by @value{GDBN}.
3192 By default all inferiors are printed, but the argument @var{id}@dots{}
3193 -- a space separated list of inferior numbers -- can be used to limit
3194 the display to just the requested inferiors.
3196 @value{GDBN} displays for each inferior (in this order):
3200 the inferior number assigned by @value{GDBN}
3203 the target system's inferior identifier
3206 the target connection the inferior is bound to, including the unique
3207 connection number assigned by @value{GDBN}, and the protocol used by
3211 the name of the executable the inferior is running.
3216 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3217 indicates the current inferior.
3221 @c end table here to get a little more width for example
3224 (@value{GDBP}) info inferiors
3225 Num Description Connection Executable
3226 * 1 process 3401 1 (native) goodbye
3227 2 process 2307 2 (extended-remote host:10000) hello
3230 To get informations about the current inferior, use @code{inferior}:
3235 Shows information about the current inferior.
3239 @c end table here to get a little more width for example
3242 (@value{GDBP}) inferior
3243 [Current inferior is 1 [process 3401] (helloworld)]
3246 To find out what open target connections exist at any moment, use
3247 @w{@code{info connections}}:
3250 @kindex info connections [ @var{id}@dots{} ]
3251 @item info connections
3252 Print a list of all open target connections currently being managed by
3253 @value{GDBN}. By default all connections are printed, but the
3254 argument @var{id}@dots{} -- a space separated list of connections
3255 numbers -- can be used to limit the display to just the requested
3258 @value{GDBN} displays for each connection (in this order):
3262 the connection number assigned by @value{GDBN}.
3265 the protocol used by the connection.
3268 a textual description of the protocol used by the connection.
3273 An asterisk @samp{*} preceding the connection number indicates the
3274 connection of the current inferior.
3278 @c end table here to get a little more width for example
3281 (@value{GDBP}) info connections
3282 Num What Description
3283 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3284 2 native Native process
3285 3 core Local core dump file
3288 To switch focus between inferiors, use the @code{inferior} command:
3291 @kindex inferior @var{infno}
3292 @item inferior @var{infno}
3293 Make inferior number @var{infno} the current inferior. The argument
3294 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3295 in the first field of the @samp{info inferiors} display.
3298 @vindex $_inferior@r{, convenience variable}
3299 The debugger convenience variable @samp{$_inferior} contains the
3300 number of the current inferior. You may find this useful in writing
3301 breakpoint conditional expressions, command scripts, and so forth.
3302 @xref{Convenience Vars,, Convenience Variables}, for general
3303 information on convenience variables.
3305 You can get multiple executables into a debugging session via the
3306 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3307 systems @value{GDBN} can add inferiors to the debug session
3308 automatically by following calls to @code{fork} and @code{exec}. To
3309 remove inferiors from the debugging session use the
3310 @w{@code{remove-inferiors}} command.
3313 @anchor{add_inferior_cli}
3314 @kindex add-inferior
3315 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3316 Adds @var{n} inferiors to be run using @var{executable} as the
3317 executable; @var{n} defaults to 1. If no executable is specified,
3318 the inferiors begins empty, with no program. You can still assign or
3319 change the program assigned to the inferior at any time by using the
3320 @code{file} command with the executable name as its argument.
3322 By default, the new inferior begins connected to the same target
3323 connection as the current inferior. For example, if the current
3324 inferior was connected to @code{gdbserver} with @code{target remote},
3325 then the new inferior will be connected to the same @code{gdbserver}
3326 instance. The @samp{-no-connection} option starts the new inferior
3327 with no connection yet. You can then for example use the @code{target
3328 remote} command to connect to some other @code{gdbserver} instance,
3329 use @code{run} to spawn a local program, etc.
3331 @kindex clone-inferior
3332 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3333 Adds @var{n} inferiors ready to execute the same program as inferior
3334 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3335 number of the current inferior. This command copies the values of the
3336 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3337 current inferior to the new one. It also propagates changes the user
3338 made to environment variables using the @w{@code{set environment}} and
3339 @w{@code{unset environment}} commands. This is a convenient command
3340 when you want to run another instance of the inferior you are debugging.
3343 (@value{GDBP}) info inferiors
3344 Num Description Connection Executable
3345 * 1 process 29964 1 (native) helloworld
3346 (@value{GDBP}) clone-inferior
3349 (@value{GDBP}) info inferiors
3350 Num Description Connection Executable
3351 * 1 process 29964 1 (native) helloworld
3352 2 <null> 1 (native) helloworld
3355 You can now simply switch focus to inferior 2 and run it.
3357 @kindex remove-inferiors
3358 @item remove-inferiors @var{infno}@dots{}
3359 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3360 possible to remove an inferior that is running with this command. For
3361 those, use the @code{kill} or @code{detach} command first.
3365 To quit debugging one of the running inferiors that is not the current
3366 inferior, you can either detach from it by using the @w{@code{detach
3367 inferior}} command (allowing it to run independently), or kill it
3368 using the @w{@code{kill inferiors}} command:
3371 @kindex detach inferiors @var{infno}@dots{}
3372 @item detach inferior @var{infno}@dots{}
3373 Detach from the inferior or inferiors identified by @value{GDBN}
3374 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3375 still stays on the list of inferiors shown by @code{info inferiors},
3376 but its Description will show @samp{<null>}.
3378 @kindex kill inferiors @var{infno}@dots{}
3379 @item kill inferiors @var{infno}@dots{}
3380 Kill the inferior or inferiors identified by @value{GDBN} inferior
3381 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3382 stays on the list of inferiors shown by @code{info inferiors}, but its
3383 Description will show @samp{<null>}.
3386 After the successful completion of a command such as @code{detach},
3387 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3388 a normal process exit, the inferior is still valid and listed with
3389 @code{info inferiors}, ready to be restarted.
3392 To be notified when inferiors are started or exit under @value{GDBN}'s
3393 control use @w{@code{set print inferior-events}}:
3396 @kindex set print inferior-events
3397 @cindex print messages on inferior start and exit
3398 @item set print inferior-events
3399 @itemx set print inferior-events on
3400 @itemx set print inferior-events off
3401 The @code{set print inferior-events} command allows you to enable or
3402 disable printing of messages when @value{GDBN} notices that new
3403 inferiors have started or that inferiors have exited or have been
3404 detached. By default, these messages will be printed.
3406 @kindex show print inferior-events
3407 @item show print inferior-events
3408 Show whether messages will be printed when @value{GDBN} detects that
3409 inferiors have started, exited or have been detached.
3412 Many commands will work the same with multiple programs as with a
3413 single program: e.g., @code{print myglobal} will simply display the
3414 value of @code{myglobal} in the current inferior.
3417 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3418 get more info about the relationship of inferiors, programs, address
3419 spaces in a debug session. You can do that with the @w{@code{maint
3420 info program-spaces}} command.
3423 @kindex maint info program-spaces
3424 @item maint info program-spaces
3425 Print a list of all program spaces currently being managed by
3428 @value{GDBN} displays for each program space (in this order):
3432 the program space number assigned by @value{GDBN}
3435 the name of the executable loaded into the program space, with e.g.,
3436 the @code{file} command.
3441 An asterisk @samp{*} preceding the @value{GDBN} program space number
3442 indicates the current program space.
3444 In addition, below each program space line, @value{GDBN} prints extra
3445 information that isn't suitable to display in tabular form. For
3446 example, the list of inferiors bound to the program space.
3449 (@value{GDBP}) maint info program-spaces
3453 Bound inferiors: ID 1 (process 21561)
3456 Here we can see that no inferior is running the program @code{hello},
3457 while @code{process 21561} is running the program @code{goodbye}. On
3458 some targets, it is possible that multiple inferiors are bound to the
3459 same program space. The most common example is that of debugging both
3460 the parent and child processes of a @code{vfork} call. For example,
3463 (@value{GDBP}) maint info program-spaces
3466 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3469 Here, both inferior 2 and inferior 1 are running in the same program
3470 space as a result of inferior 1 having executed a @code{vfork} call.
3474 @section Debugging Programs with Multiple Threads
3476 @cindex threads of execution
3477 @cindex multiple threads
3478 @cindex switching threads
3479 In some operating systems, such as GNU/Linux and Solaris, a single program
3480 may have more than one @dfn{thread} of execution. The precise semantics
3481 of threads differ from one operating system to another, but in general
3482 the threads of a single program are akin to multiple processes---except
3483 that they share one address space (that is, they can all examine and
3484 modify the same variables). On the other hand, each thread has its own
3485 registers and execution stack, and perhaps private memory.
3487 @value{GDBN} provides these facilities for debugging multi-thread
3491 @item automatic notification of new threads
3492 @item @samp{thread @var{thread-id}}, a command to switch among threads
3493 @item @samp{info threads}, a command to inquire about existing threads
3494 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3495 a command to apply a command to a list of threads
3496 @item thread-specific breakpoints
3497 @item @samp{set print thread-events}, which controls printing of
3498 messages on thread start and exit.
3499 @item @samp{set libthread-db-search-path @var{path}}, which lets
3500 the user specify which @code{libthread_db} to use if the default choice
3501 isn't compatible with the program.
3504 @cindex focus of debugging
3505 @cindex current thread
3506 The @value{GDBN} thread debugging facility allows you to observe all
3507 threads while your program runs---but whenever @value{GDBN} takes
3508 control, one thread in particular is always the focus of debugging.
3509 This thread is called the @dfn{current thread}. Debugging commands show
3510 program information from the perspective of the current thread.
3512 @cindex @code{New} @var{systag} message
3513 @cindex thread identifier (system)
3514 @c FIXME-implementors!! It would be more helpful if the [New...] message
3515 @c included GDB's numeric thread handle, so you could just go to that
3516 @c thread without first checking `info threads'.
3517 Whenever @value{GDBN} detects a new thread in your program, it displays
3518 the target system's identification for the thread with a message in the
3519 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3520 whose form varies depending on the particular system. For example, on
3521 @sc{gnu}/Linux, you might see
3524 [New Thread 0x41e02940 (LWP 25582)]
3528 when @value{GDBN} notices a new thread. In contrast, on other systems,
3529 the @var{systag} is simply something like @samp{process 368}, with no
3532 @c FIXME!! (1) Does the [New...] message appear even for the very first
3533 @c thread of a program, or does it only appear for the
3534 @c second---i.e.@: when it becomes obvious we have a multithread
3536 @c (2) *Is* there necessarily a first thread always? Or do some
3537 @c multithread systems permit starting a program with multiple
3538 @c threads ab initio?
3540 @anchor{thread numbers}
3541 @cindex thread number, per inferior
3542 @cindex thread identifier (GDB)
3543 For debugging purposes, @value{GDBN} associates its own thread number
3544 ---always a single integer---with each thread of an inferior. This
3545 number is unique between all threads of an inferior, but not unique
3546 between threads of different inferiors.
3548 @cindex qualified thread ID
3549 You can refer to a given thread in an inferior using the qualified
3550 @var{inferior-num}.@var{thread-num} syntax, also known as
3551 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3552 number and @var{thread-num} being the thread number of the given
3553 inferior. For example, thread @code{2.3} refers to thread number 3 of
3554 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3555 then @value{GDBN} infers you're referring to a thread of the current
3558 Until you create a second inferior, @value{GDBN} does not show the
3559 @var{inferior-num} part of thread IDs, even though you can always use
3560 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3561 of inferior 1, the initial inferior.
3563 @anchor{thread ID lists}
3564 @cindex thread ID lists
3565 Some commands accept a space-separated @dfn{thread ID list} as
3566 argument. A list element can be:
3570 A thread ID as shown in the first field of the @samp{info threads}
3571 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3575 A range of thread numbers, again with or without an inferior
3576 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3577 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3580 All threads of an inferior, specified with a star wildcard, with or
3581 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3582 @samp{1.*}) or @code{*}. The former refers to all threads of the
3583 given inferior, and the latter form without an inferior qualifier
3584 refers to all threads of the current inferior.
3588 For example, if the current inferior is 1, and inferior 7 has one
3589 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3590 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3591 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3592 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3596 @anchor{global thread numbers}
3597 @cindex global thread number
3598 @cindex global thread identifier (GDB)
3599 In addition to a @emph{per-inferior} number, each thread is also
3600 assigned a unique @emph{global} number, also known as @dfn{global
3601 thread ID}, a single integer. Unlike the thread number component of
3602 the thread ID, no two threads have the same global ID, even when
3603 you're debugging multiple inferiors.
3605 From @value{GDBN}'s perspective, a process always has at least one
3606 thread. In other words, @value{GDBN} assigns a thread number to the
3607 program's ``main thread'' even if the program is not multi-threaded.
3609 @vindex $_thread@r{, convenience variable}
3610 @vindex $_gthread@r{, convenience variable}
3611 The debugger convenience variables @samp{$_thread} and
3612 @samp{$_gthread} contain, respectively, the per-inferior thread number
3613 and the global thread number of the current thread. You may find this
3614 useful in writing breakpoint conditional expressions, command scripts,
3615 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3616 general information on convenience variables.
3618 If @value{GDBN} detects the program is multi-threaded, it augments the
3619 usual message about stopping at a breakpoint with the ID and name of
3620 the thread that hit the breakpoint.
3623 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3626 Likewise when the program receives a signal:
3629 Thread 1 "main" received signal SIGINT, Interrupt.
3633 @anchor{info_threads}
3634 @kindex info threads
3635 @item info threads @r{[}@var{thread-id-list}@r{]}
3637 Display information about one or more threads. With no arguments
3638 displays information about all threads. You can specify the list of
3639 threads that you want to display using the thread ID list syntax
3640 (@pxref{thread ID lists}).
3642 @value{GDBN} displays for each thread (in this order):
3646 the per-inferior thread number assigned by @value{GDBN}
3649 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3650 option was specified
3653 the target system's thread identifier (@var{systag})
3656 the thread's name, if one is known. A thread can either be named by
3657 the user (see @code{thread name}, below), or, in some cases, by the
3661 the current stack frame summary for that thread
3665 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3666 indicates the current thread.
3670 @c end table here to get a little more width for example
3673 (@value{GDBP}) info threads
3675 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3676 2 process 35 thread 23 0x34e5 in sigpause ()
3677 3 process 35 thread 27 0x34e5 in sigpause ()
3681 If you're debugging multiple inferiors, @value{GDBN} displays thread
3682 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3683 Otherwise, only @var{thread-num} is shown.
3685 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3686 indicating each thread's global thread ID:
3689 (@value{GDBP}) info threads
3690 Id GId Target Id Frame
3691 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3692 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3693 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3694 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3697 On Solaris, you can display more information about user threads with a
3698 Solaris-specific command:
3701 @item maint info sol-threads
3702 @kindex maint info sol-threads
3703 @cindex thread info (Solaris)
3704 Display info on Solaris user threads.
3708 @kindex thread @var{thread-id}
3709 @item thread @var{thread-id}
3710 Make thread ID @var{thread-id} the current thread. The command
3711 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3712 the first field of the @samp{info threads} display, with or without an
3713 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3715 @value{GDBN} responds by displaying the system identifier of the
3716 thread you selected, and its current stack frame summary:
3719 (@value{GDBP}) thread 2
3720 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3721 #0 some_function (ignore=0x0) at example.c:8
3722 8 printf ("hello\n");
3726 As with the @samp{[New @dots{}]} message, the form of the text after
3727 @samp{Switching to} depends on your system's conventions for identifying
3730 @anchor{thread apply all}
3731 @kindex thread apply
3732 @cindex apply command to several threads
3733 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3734 The @code{thread apply} command allows you to apply the named
3735 @var{command} to one or more threads. Specify the threads that you
3736 want affected using the thread ID list syntax (@pxref{thread ID
3737 lists}), or specify @code{all} to apply to all threads. To apply a
3738 command to all threads in descending order, type @kbd{thread apply all
3739 @var{command}}. To apply a command to all threads in ascending order,
3740 type @kbd{thread apply all -ascending @var{command}}.
3742 The @var{flag} arguments control what output to produce and how to handle
3743 errors raised when applying @var{command} to a thread. @var{flag}
3744 must start with a @code{-} directly followed by one letter in
3745 @code{qcs}. If several flags are provided, they must be given
3746 individually, such as @code{-c -q}.
3748 By default, @value{GDBN} displays some thread information before the
3749 output produced by @var{command}, and an error raised during the
3750 execution of a @var{command} will abort @code{thread apply}. The
3751 following flags can be used to fine-tune this behavior:
3755 The flag @code{-c}, which stands for @samp{continue}, causes any
3756 errors in @var{command} to be displayed, and the execution of
3757 @code{thread apply} then continues.
3759 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3760 or empty output produced by a @var{command} to be silently ignored.
3761 That is, the execution continues, but the thread information and errors
3764 The flag @code{-q} (@samp{quiet}) disables printing the thread
3768 Flags @code{-c} and @code{-s} cannot be used together.
3771 @cindex apply command to all threads (ignoring errors and empty output)
3772 @item taas [@var{option}]@dots{} @var{command}
3773 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3774 Applies @var{command} on all threads, ignoring errors and empty output.
3776 The @code{taas} command accepts the same options as the @code{thread
3777 apply all} command. @xref{thread apply all}.
3780 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3781 @item tfaas [@var{option}]@dots{} @var{command}
3782 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3783 Applies @var{command} on all frames of all threads, ignoring errors
3784 and empty output. Note that the flag @code{-s} is specified twice:
3785 The first @code{-s} ensures that @code{thread apply} only shows the thread
3786 information of the threads for which @code{frame apply} produces
3787 some output. The second @code{-s} is needed to ensure that @code{frame
3788 apply} shows the frame information of a frame only if the
3789 @var{command} successfully produced some output.
3791 It can for example be used to print a local variable or a function
3792 argument without knowing the thread or frame where this variable or argument
3795 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3798 The @code{tfaas} command accepts the same options as the @code{frame
3799 apply} command. @xref{Frame Apply,,frame apply}.
3802 @cindex name a thread
3803 @item thread name [@var{name}]
3804 This command assigns a name to the current thread. If no argument is
3805 given, any existing user-specified name is removed. The thread name
3806 appears in the @samp{info threads} display.
3808 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3809 determine the name of the thread as given by the OS. On these
3810 systems, a name specified with @samp{thread name} will override the
3811 system-give name, and removing the user-specified name will cause
3812 @value{GDBN} to once again display the system-specified name.
3815 @cindex search for a thread
3816 @item thread find [@var{regexp}]
3817 Search for and display thread ids whose name or @var{systag}
3818 matches the supplied regular expression.
3820 As well as being the complement to the @samp{thread name} command,
3821 this command also allows you to identify a thread by its target
3822 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3826 (@value{GDBN}) thread find 26688
3827 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3828 (@value{GDBN}) info thread 4
3830 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3833 @kindex set print thread-events
3834 @cindex print messages on thread start and exit
3835 @item set print thread-events
3836 @itemx set print thread-events on
3837 @itemx set print thread-events off
3838 The @code{set print thread-events} command allows you to enable or
3839 disable printing of messages when @value{GDBN} notices that new threads have
3840 started or that threads have exited. By default, these messages will
3841 be printed if detection of these events is supported by the target.
3842 Note that these messages cannot be disabled on all targets.
3844 @kindex show print thread-events
3845 @item show print thread-events
3846 Show whether messages will be printed when @value{GDBN} detects that threads
3847 have started and exited.
3850 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3851 more information about how @value{GDBN} behaves when you stop and start
3852 programs with multiple threads.
3854 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3855 watchpoints in programs with multiple threads.
3857 @anchor{set libthread-db-search-path}
3859 @kindex set libthread-db-search-path
3860 @cindex search path for @code{libthread_db}
3861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3862 If this variable is set, @var{path} is a colon-separated list of
3863 directories @value{GDBN} will use to search for @code{libthread_db}.
3864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3870 @code{libthread_db} library to obtain information about threads in the
3871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3872 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3873 specific thread debugging library loading is enabled
3874 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3876 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3877 refers to the default system directories that are
3878 normally searched for loading shared libraries. The @samp{$sdir} entry
3879 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3880 (@pxref{libthread_db.so.1 file}).
3882 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3883 refers to the directory from which @code{libpthread}
3884 was loaded in the inferior process.
3886 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3887 @value{GDBN} attempts to initialize it with the current inferior process.
3888 If this initialization fails (which could happen because of a version
3889 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3890 will unload @code{libthread_db}, and continue with the next directory.
3891 If none of @code{libthread_db} libraries initialize successfully,
3892 @value{GDBN} will issue a warning and thread debugging will be disabled.
3894 Setting @code{libthread-db-search-path} is currently implemented
3895 only on some platforms.
3897 @kindex show libthread-db-search-path
3898 @item show libthread-db-search-path
3899 Display current libthread_db search path.
3901 @kindex set debug libthread-db
3902 @kindex show debug libthread-db
3903 @cindex debugging @code{libthread_db}
3904 @item set debug libthread-db
3905 @itemx show debug libthread-db
3906 Turns on or off display of @code{libthread_db}-related events.
3907 Use @code{1} to enable, @code{0} to disable.
3909 @kindex set debug threads
3910 @kindex show debug threads
3911 @cindex debugging @code{threads}
3912 @item set debug threads @r{[}on@r{|}off@r{]}
3913 @itemx show debug threads
3914 When @samp{on} @value{GDBN} will print additional messages when
3915 threads are created and deleted.
3919 @section Debugging Forks
3921 @cindex fork, debugging programs which call
3922 @cindex multiple processes
3923 @cindex processes, multiple
3924 On most systems, @value{GDBN} has no special support for debugging
3925 programs which create additional processes using the @code{fork}
3926 function. When a program forks, @value{GDBN} will continue to debug the
3927 parent process and the child process will run unimpeded. If you have
3928 set a breakpoint in any code which the child then executes, the child
3929 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3930 will cause it to terminate.
3932 However, if you want to debug the child process there is a workaround
3933 which isn't too painful. Put a call to @code{sleep} in the code which
3934 the child process executes after the fork. It may be useful to sleep
3935 only if a certain environment variable is set, or a certain file exists,
3936 so that the delay need not occur when you don't want to run @value{GDBN}
3937 on the child. While the child is sleeping, use the @code{ps} program to
3938 get its process ID. Then tell @value{GDBN} (a new invocation of
3939 @value{GDBN} if you are also debugging the parent process) to attach to
3940 the child process (@pxref{Attach}). From that point on you can debug
3941 the child process just like any other process which you attached to.
3943 On some systems, @value{GDBN} provides support for debugging programs
3944 that create additional processes using the @code{fork} or @code{vfork}
3945 functions. On @sc{gnu}/Linux platforms, this feature is supported
3946 with kernel version 2.5.46 and later.
3948 The fork debugging commands are supported in native mode and when
3949 connected to @code{gdbserver} in either @code{target remote} mode or
3950 @code{target extended-remote} mode.
3952 By default, when a program forks, @value{GDBN} will continue to debug
3953 the parent process and the child process will run unimpeded.
3955 If you want to follow the child process instead of the parent process,
3956 use the command @w{@code{set follow-fork-mode}}.
3959 @kindex set follow-fork-mode
3960 @item set follow-fork-mode @var{mode}
3961 Set the debugger response to a program call of @code{fork} or
3962 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3963 process. The @var{mode} argument can be:
3967 The original process is debugged after a fork. The child process runs
3968 unimpeded. This is the default.
3971 The new process is debugged after a fork. The parent process runs
3976 @kindex show follow-fork-mode
3977 @item show follow-fork-mode
3978 Display the current debugger response to a @code{fork} or @code{vfork} call.
3981 @cindex debugging multiple processes
3982 On Linux, if you want to debug both the parent and child processes, use the
3983 command @w{@code{set detach-on-fork}}.
3986 @kindex set detach-on-fork
3987 @item set detach-on-fork @var{mode}
3988 Tells gdb whether to detach one of the processes after a fork, or
3989 retain debugger control over them both.
3993 The child process (or parent process, depending on the value of
3994 @code{follow-fork-mode}) will be detached and allowed to run
3995 independently. This is the default.
3998 Both processes will be held under the control of @value{GDBN}.
3999 One process (child or parent, depending on the value of
4000 @code{follow-fork-mode}) is debugged as usual, while the other
4005 @kindex show detach-on-fork
4006 @item show detach-on-fork
4007 Show whether detach-on-fork mode is on/off.
4010 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4011 will retain control of all forked processes (including nested forks).
4012 You can list the forked processes under the control of @value{GDBN} by
4013 using the @w{@code{info inferiors}} command, and switch from one fork
4014 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4015 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4017 To quit debugging one of the forked processes, you can either detach
4018 from it by using the @w{@code{detach inferiors}} command (allowing it
4019 to run independently), or kill it using the @w{@code{kill inferiors}}
4020 command. @xref{Inferiors Connections and Programs, ,Debugging
4021 Multiple Inferiors Connections and Programs}.
4023 If you ask to debug a child process and a @code{vfork} is followed by an
4024 @code{exec}, @value{GDBN} executes the new target up to the first
4025 breakpoint in the new target. If you have a breakpoint set on
4026 @code{main} in your original program, the breakpoint will also be set on
4027 the child process's @code{main}.
4029 On some systems, when a child process is spawned by @code{vfork}, you
4030 cannot debug the child or parent until an @code{exec} call completes.
4032 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4033 call executes, the new target restarts. To restart the parent
4034 process, use the @code{file} command with the parent executable name
4035 as its argument. By default, after an @code{exec} call executes,
4036 @value{GDBN} discards the symbols of the previous executable image.
4037 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4041 @kindex set follow-exec-mode
4042 @item set follow-exec-mode @var{mode}
4044 Set debugger response to a program call of @code{exec}. An
4045 @code{exec} call replaces the program image of a process.
4047 @code{follow-exec-mode} can be:
4051 @value{GDBN} creates a new inferior and rebinds the process to this
4052 new inferior. The program the process was running before the
4053 @code{exec} call can be restarted afterwards by restarting the
4059 (@value{GDBP}) info inferiors
4061 Id Description Executable
4064 process 12020 is executing new program: prog2
4065 Program exited normally.
4066 (@value{GDBP}) info inferiors
4067 Id Description Executable
4073 @value{GDBN} keeps the process bound to the same inferior. The new
4074 executable image replaces the previous executable loaded in the
4075 inferior. Restarting the inferior after the @code{exec} call, with
4076 e.g., the @code{run} command, restarts the executable the process was
4077 running after the @code{exec} call. This is the default mode.
4082 (@value{GDBP}) info inferiors
4083 Id Description Executable
4086 process 12020 is executing new program: prog2
4087 Program exited normally.
4088 (@value{GDBP}) info inferiors
4089 Id Description Executable
4096 @code{follow-exec-mode} is supported in native mode and
4097 @code{target extended-remote} mode.
4099 You can use the @code{catch} command to make @value{GDBN} stop whenever
4100 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4101 Catchpoints, ,Setting Catchpoints}.
4103 @node Checkpoint/Restart
4104 @section Setting a @emph{Bookmark} to Return to Later
4109 @cindex snapshot of a process
4110 @cindex rewind program state
4112 On certain operating systems@footnote{Currently, only
4113 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4114 program's state, called a @dfn{checkpoint}, and come back to it
4117 Returning to a checkpoint effectively undoes everything that has
4118 happened in the program since the @code{checkpoint} was saved. This
4119 includes changes in memory, registers, and even (within some limits)
4120 system state. Effectively, it is like going back in time to the
4121 moment when the checkpoint was saved.
4123 Thus, if you're stepping thru a program and you think you're
4124 getting close to the point where things go wrong, you can save
4125 a checkpoint. Then, if you accidentally go too far and miss
4126 the critical statement, instead of having to restart your program
4127 from the beginning, you can just go back to the checkpoint and
4128 start again from there.
4130 This can be especially useful if it takes a lot of time or
4131 steps to reach the point where you think the bug occurs.
4133 To use the @code{checkpoint}/@code{restart} method of debugging:
4138 Save a snapshot of the debugged program's current execution state.
4139 The @code{checkpoint} command takes no arguments, but each checkpoint
4140 is assigned a small integer id, similar to a breakpoint id.
4142 @kindex info checkpoints
4143 @item info checkpoints
4144 List the checkpoints that have been saved in the current debugging
4145 session. For each checkpoint, the following information will be
4152 @item Source line, or label
4155 @kindex restart @var{checkpoint-id}
4156 @item restart @var{checkpoint-id}
4157 Restore the program state that was saved as checkpoint number
4158 @var{checkpoint-id}. All program variables, registers, stack frames
4159 etc.@: will be returned to the values that they had when the checkpoint
4160 was saved. In essence, gdb will ``wind back the clock'' to the point
4161 in time when the checkpoint was saved.
4163 Note that breakpoints, @value{GDBN} variables, command history etc.
4164 are not affected by restoring a checkpoint. In general, a checkpoint
4165 only restores things that reside in the program being debugged, not in
4168 @kindex delete checkpoint @var{checkpoint-id}
4169 @item delete checkpoint @var{checkpoint-id}
4170 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4174 Returning to a previously saved checkpoint will restore the user state
4175 of the program being debugged, plus a significant subset of the system
4176 (OS) state, including file pointers. It won't ``un-write'' data from
4177 a file, but it will rewind the file pointer to the previous location,
4178 so that the previously written data can be overwritten. For files
4179 opened in read mode, the pointer will also be restored so that the
4180 previously read data can be read again.
4182 Of course, characters that have been sent to a printer (or other
4183 external device) cannot be ``snatched back'', and characters received
4184 from eg.@: a serial device can be removed from internal program buffers,
4185 but they cannot be ``pushed back'' into the serial pipeline, ready to
4186 be received again. Similarly, the actual contents of files that have
4187 been changed cannot be restored (at this time).
4189 However, within those constraints, you actually can ``rewind'' your
4190 program to a previously saved point in time, and begin debugging it
4191 again --- and you can change the course of events so as to debug a
4192 different execution path this time.
4194 @cindex checkpoints and process id
4195 Finally, there is one bit of internal program state that will be
4196 different when you return to a checkpoint --- the program's process
4197 id. Each checkpoint will have a unique process id (or @var{pid}),
4198 and each will be different from the program's original @var{pid}.
4199 If your program has saved a local copy of its process id, this could
4200 potentially pose a problem.
4202 @subsection A Non-obvious Benefit of Using Checkpoints
4204 On some systems such as @sc{gnu}/Linux, address space randomization
4205 is performed on new processes for security reasons. This makes it
4206 difficult or impossible to set a breakpoint, or watchpoint, on an
4207 absolute address if you have to restart the program, since the
4208 absolute location of a symbol will change from one execution to the
4211 A checkpoint, however, is an @emph{identical} copy of a process.
4212 Therefore if you create a checkpoint at (eg.@:) the start of main,
4213 and simply return to that checkpoint instead of restarting the
4214 process, you can avoid the effects of address randomization and
4215 your symbols will all stay in the same place.
4218 @chapter Stopping and Continuing
4220 The principal purposes of using a debugger are so that you can stop your
4221 program before it terminates; or so that, if your program runs into
4222 trouble, you can investigate and find out why.
4224 Inside @value{GDBN}, your program may stop for any of several reasons,
4225 such as a signal, a breakpoint, or reaching a new line after a
4226 @value{GDBN} command such as @code{step}. You may then examine and
4227 change variables, set new breakpoints or remove old ones, and then
4228 continue execution. Usually, the messages shown by @value{GDBN} provide
4229 ample explanation of the status of your program---but you can also
4230 explicitly request this information at any time.
4233 @kindex info program
4235 Display information about the status of your program: whether it is
4236 running or not, what process it is, and why it stopped.
4240 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4241 * Continuing and Stepping:: Resuming execution
4242 * Skipping Over Functions and Files::
4243 Skipping over functions and files
4245 * Thread Stops:: Stopping and starting multi-thread programs
4249 @section Breakpoints, Watchpoints, and Catchpoints
4252 A @dfn{breakpoint} makes your program stop whenever a certain point in
4253 the program is reached. For each breakpoint, you can add conditions to
4254 control in finer detail whether your program stops. You can set
4255 breakpoints with the @code{break} command and its variants (@pxref{Set
4256 Breaks, ,Setting Breakpoints}), to specify the place where your program
4257 should stop by line number, function name or exact address in the
4260 On some systems, you can set breakpoints in shared libraries before
4261 the executable is run.
4264 @cindex data breakpoints
4265 @cindex memory tracing
4266 @cindex breakpoint on memory address
4267 @cindex breakpoint on variable modification
4268 A @dfn{watchpoint} is a special breakpoint that stops your program
4269 when the value of an expression changes. The expression may be a value
4270 of a variable, or it could involve values of one or more variables
4271 combined by operators, such as @samp{a + b}. This is sometimes called
4272 @dfn{data breakpoints}. You must use a different command to set
4273 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4274 from that, you can manage a watchpoint like any other breakpoint: you
4275 enable, disable, and delete both breakpoints and watchpoints using the
4278 You can arrange to have values from your program displayed automatically
4279 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4283 @cindex breakpoint on events
4284 A @dfn{catchpoint} is another special breakpoint that stops your program
4285 when a certain kind of event occurs, such as the throwing of a C@t{++}
4286 exception or the loading of a library. As with watchpoints, you use a
4287 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4288 Catchpoints}), but aside from that, you can manage a catchpoint like any
4289 other breakpoint. (To stop when your program receives a signal, use the
4290 @code{handle} command; see @ref{Signals, ,Signals}.)
4292 @cindex breakpoint numbers
4293 @cindex numbers for breakpoints
4294 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4295 catchpoint when you create it; these numbers are successive integers
4296 starting with one. In many of the commands for controlling various
4297 features of breakpoints you use the breakpoint number to say which
4298 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4299 @dfn{disabled}; if disabled, it has no effect on your program until you
4302 @cindex breakpoint ranges
4303 @cindex breakpoint lists
4304 @cindex ranges of breakpoints
4305 @cindex lists of breakpoints
4306 Some @value{GDBN} commands accept a space-separated list of breakpoints
4307 on which to operate. A list element can be either a single breakpoint number,
4308 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4309 When a breakpoint list is given to a command, all breakpoints in that list
4313 * Set Breaks:: Setting breakpoints
4314 * Set Watchpoints:: Setting watchpoints
4315 * Set Catchpoints:: Setting catchpoints
4316 * Delete Breaks:: Deleting breakpoints
4317 * Disabling:: Disabling breakpoints
4318 * Conditions:: Break conditions
4319 * Break Commands:: Breakpoint command lists
4320 * Dynamic Printf:: Dynamic printf
4321 * Save Breakpoints:: How to save breakpoints in a file
4322 * Static Probe Points:: Listing static probe points
4323 * Error in Breakpoints:: ``Cannot insert breakpoints''
4324 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4328 @subsection Setting Breakpoints
4330 @c FIXME LMB what does GDB do if no code on line of breakpt?
4331 @c consider in particular declaration with/without initialization.
4333 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4336 @kindex b @r{(@code{break})}
4337 @vindex $bpnum@r{, convenience variable}
4338 @cindex latest breakpoint
4339 Breakpoints are set with the @code{break} command (abbreviated
4340 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4341 number of the breakpoint you've set most recently; see @ref{Convenience
4342 Vars,, Convenience Variables}, for a discussion of what you can do with
4343 convenience variables.
4346 @item break @var{location}
4347 Set a breakpoint at the given @var{location}, which can specify a
4348 function name, a line number, or an address of an instruction.
4349 (@xref{Specify Location}, for a list of all the possible ways to
4350 specify a @var{location}.) The breakpoint will stop your program just
4351 before it executes any of the code in the specified @var{location}.
4353 When using source languages that permit overloading of symbols, such as
4354 C@t{++}, a function name may refer to more than one possible place to break.
4355 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4358 It is also possible to insert a breakpoint that will stop the program
4359 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4360 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4363 When called without any arguments, @code{break} sets a breakpoint at
4364 the next instruction to be executed in the selected stack frame
4365 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4366 innermost, this makes your program stop as soon as control
4367 returns to that frame. This is similar to the effect of a
4368 @code{finish} command in the frame inside the selected frame---except
4369 that @code{finish} does not leave an active breakpoint. If you use
4370 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4371 the next time it reaches the current location; this may be useful
4374 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4375 least one instruction has been executed. If it did not do this, you
4376 would be unable to proceed past a breakpoint without first disabling the
4377 breakpoint. This rule applies whether or not the breakpoint already
4378 existed when your program stopped.
4380 @item break @dots{} if @var{cond}
4381 Set a breakpoint with condition @var{cond}; evaluate the expression
4382 @var{cond} each time the breakpoint is reached, and stop only if the
4383 value is nonzero---that is, if @var{cond} evaluates as true.
4384 @samp{@dots{}} stands for one of the possible arguments described
4385 above (or no argument) specifying where to break. @xref{Conditions,
4386 ,Break Conditions}, for more information on breakpoint conditions.
4388 The breakpoint may be mapped to multiple locations. If the breakpoint
4389 condition @var{cond} is invalid at some but not all of the locations,
4390 the locations for which the condition is invalid are disabled. For
4391 example, @value{GDBN} reports below that two of the three locations
4395 (@value{GDBP}) break func if a == 10
4396 warning: failed to validate condition at location 0x11ce, disabling:
4397 No symbol "a" in current context.
4398 warning: failed to validate condition at location 0x11b6, disabling:
4399 No symbol "a" in current context.
4400 Breakpoint 1 at 0x11b6: func. (3 locations)
4403 Locations that are disabled because of the condition are denoted by an
4404 uppercase @code{N} in the output of the @code{info breakpoints}
4408 (@value{GDBP}) info breakpoints
4409 Num Type Disp Enb Address What
4410 1 breakpoint keep y <MULTIPLE>
4411 stop only if a == 10
4412 1.1 N* 0x00000000000011b6 in ...
4413 1.2 y 0x00000000000011c2 in ...
4414 1.3 N* 0x00000000000011ce in ...
4415 (*): Breakpoint condition is invalid at this location.
4418 If the breakpoint condition @var{cond} is invalid in the context of
4419 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4420 define the breakpoint. For example, if variable @code{foo} is an
4424 (@value{GDBP}) break func if foo
4425 No symbol "foo" in current context.
4428 @item break @dots{} -force-condition if @var{cond}
4429 There may be cases where the condition @var{cond} is invalid at all
4430 the current locations, but the user knows that it will be valid at a
4431 future location; for example, because of a library load. In such
4432 cases, by using the @code{-force-condition} keyword before @samp{if},
4433 @value{GDBN} can be forced to define the breakpoint with the given
4434 condition expression instead of refusing it.
4437 (@value{GDBP}) break func -force-condition if foo
4438 warning: failed to validate condition at location 1, disabling:
4439 No symbol "foo" in current context.
4440 warning: failed to validate condition at location 2, disabling:
4441 No symbol "foo" in current context.
4442 warning: failed to validate condition at location 3, disabling:
4443 No symbol "foo" in current context.
4444 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4447 This causes all the present locations where the breakpoint would
4448 otherwise be inserted, to be disabled, as seen in the example above.
4449 However, if there exist locations at which the condition is valid, the
4450 @code{-force-condition} keyword has no effect.
4453 @item tbreak @var{args}
4454 Set a breakpoint enabled only for one stop. The @var{args} are the
4455 same as for the @code{break} command, and the breakpoint is set in the same
4456 way, but the breakpoint is automatically deleted after the first time your
4457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4460 @cindex hardware breakpoints
4461 @item hbreak @var{args}
4462 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4463 @code{break} command and the breakpoint is set in the same way, but the
4464 breakpoint requires hardware support and some target hardware may not
4465 have this support. The main purpose of this is EPROM/ROM code
4466 debugging, so you can set a breakpoint at an instruction without
4467 changing the instruction. This can be used with the new trap-generation
4468 provided by SPARClite DSU and most x86-based targets. These targets
4469 will generate traps when a program accesses some data or instruction
4470 address that is assigned to the debug registers. However the hardware
4471 breakpoint registers can take a limited number of breakpoints. For
4472 example, on the DSU, only two data breakpoints can be set at a time, and
4473 @value{GDBN} will reject this command if more than two are used. Delete
4474 or disable unused hardware breakpoints before setting new ones
4475 (@pxref{Disabling, ,Disabling Breakpoints}).
4476 @xref{Conditions, ,Break Conditions}.
4477 For remote targets, you can restrict the number of hardware
4478 breakpoints @value{GDBN} will use, see @ref{set remote
4479 hardware-breakpoint-limit}.
4482 @item thbreak @var{args}
4483 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4484 are the same as for the @code{hbreak} command and the breakpoint is set in
4485 the same way. However, like the @code{tbreak} command,
4486 the breakpoint is automatically deleted after the
4487 first time your program stops there. Also, like the @code{hbreak}
4488 command, the breakpoint requires hardware support and some target hardware
4489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4490 See also @ref{Conditions, ,Break Conditions}.
4493 @cindex regular expression
4494 @cindex breakpoints at functions matching a regexp
4495 @cindex set breakpoints in many functions
4496 @item rbreak @var{regex}
4497 Set breakpoints on all functions matching the regular expression
4498 @var{regex}. This command sets an unconditional breakpoint on all
4499 matches, printing a list of all breakpoints it set. Once these
4500 breakpoints are set, they are treated just like the breakpoints set with
4501 the @code{break} command. You can delete them, disable them, or make
4502 them conditional the same way as any other breakpoint.
4504 In programs using different languages, @value{GDBN} chooses the syntax
4505 to print the list of all breakpoints it sets according to the
4506 @samp{set language} value: using @samp{set language auto}
4507 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4508 language of the breakpoint's function, other values mean to use
4509 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4511 The syntax of the regular expression is the standard one used with tools
4512 like @file{grep}. Note that this is different from the syntax used by
4513 shells, so for instance @code{foo*} matches all functions that include
4514 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4515 @code{.*} leading and trailing the regular expression you supply, so to
4516 match only functions that begin with @code{foo}, use @code{^foo}.
4518 @cindex non-member C@t{++} functions, set breakpoint in
4519 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4520 breakpoints on overloaded functions that are not members of any special
4523 @cindex set breakpoints on all functions
4524 The @code{rbreak} command can be used to set breakpoints in
4525 @strong{all} the functions in a program, like this:
4528 (@value{GDBP}) rbreak .
4531 @item rbreak @var{file}:@var{regex}
4532 If @code{rbreak} is called with a filename qualification, it limits
4533 the search for functions matching the given regular expression to the
4534 specified @var{file}. This can be used, for example, to set breakpoints on
4535 every function in a given file:
4538 (@value{GDBP}) rbreak file.c:.
4541 The colon separating the filename qualifier from the regex may
4542 optionally be surrounded by spaces.
4544 @kindex info breakpoints
4545 @cindex @code{$_} and @code{info breakpoints}
4546 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4547 @itemx info break @r{[}@var{list}@dots{}@r{]}
4548 Print a table of all breakpoints, watchpoints, and catchpoints set and
4549 not deleted. Optional argument @var{n} means print information only
4550 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4551 For each breakpoint, following columns are printed:
4554 @item Breakpoint Numbers
4556 Breakpoint, watchpoint, or catchpoint.
4558 Whether the breakpoint is marked to be disabled or deleted when hit.
4559 @item Enabled or Disabled
4560 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4561 that are not enabled.
4563 Where the breakpoint is in your program, as a memory address. For a
4564 pending breakpoint whose address is not yet known, this field will
4565 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4566 library that has the symbol or line referred by breakpoint is loaded.
4567 See below for details. A breakpoint with several locations will
4568 have @samp{<MULTIPLE>} in this field---see below for details.
4570 Where the breakpoint is in the source for your program, as a file and
4571 line number. For a pending breakpoint, the original string passed to
4572 the breakpoint command will be listed as it cannot be resolved until
4573 the appropriate shared library is loaded in the future.
4577 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4578 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4579 @value{GDBN} on the host's side. If it is ``target'', then the condition
4580 is evaluated by the target. The @code{info break} command shows
4581 the condition on the line following the affected breakpoint, together with
4582 its condition evaluation mode in between parentheses.
4584 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4585 allowed to have a condition specified for it. The condition is not parsed for
4586 validity until a shared library is loaded that allows the pending
4587 breakpoint to resolve to a valid location.
4590 @code{info break} with a breakpoint
4591 number @var{n} as argument lists only that breakpoint. The
4592 convenience variable @code{$_} and the default examining-address for
4593 the @code{x} command are set to the address of the last breakpoint
4594 listed (@pxref{Memory, ,Examining Memory}).
4597 @code{info break} displays a count of the number of times the breakpoint
4598 has been hit. This is especially useful in conjunction with the
4599 @code{ignore} command. You can ignore a large number of breakpoint
4600 hits, look at the breakpoint info to see how many times the breakpoint
4601 was hit, and then run again, ignoring one less than that number. This
4602 will get you quickly to the last hit of that breakpoint.
4605 For a breakpoints with an enable count (xref) greater than 1,
4606 @code{info break} also displays that count.
4610 @value{GDBN} allows you to set any number of breakpoints at the same place in
4611 your program. There is nothing silly or meaningless about this. When
4612 the breakpoints are conditional, this is even useful
4613 (@pxref{Conditions, ,Break Conditions}).
4615 @cindex multiple locations, breakpoints
4616 @cindex breakpoints, multiple locations
4617 It is possible that a breakpoint corresponds to several locations
4618 in your program. Examples of this situation are:
4622 Multiple functions in the program may have the same name.
4625 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4626 instances of the function body, used in different cases.
4629 For a C@t{++} template function, a given line in the function can
4630 correspond to any number of instantiations.
4633 For an inlined function, a given source line can correspond to
4634 several places where that function is inlined.
4637 In all those cases, @value{GDBN} will insert a breakpoint at all
4638 the relevant locations.
4640 A breakpoint with multiple locations is displayed in the breakpoint
4641 table using several rows---one header row, followed by one row for
4642 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4643 address column. The rows for individual locations contain the actual
4644 addresses for locations, and show the functions to which those
4645 locations belong. The number column for a location is of the form
4646 @var{breakpoint-number}.@var{location-number}.
4651 Num Type Disp Enb Address What
4652 1 breakpoint keep y <MULTIPLE>
4654 breakpoint already hit 1 time
4655 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4656 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4659 You cannot delete the individual locations from a breakpoint. However,
4660 each location can be individually enabled or disabled by passing
4661 @var{breakpoint-number}.@var{location-number} as argument to the
4662 @code{enable} and @code{disable} commands. It's also possible to
4663 @code{enable} and @code{disable} a range of @var{location-number}
4664 locations using a @var{breakpoint-number} and two @var{location-number}s,
4665 in increasing order, separated by a hyphen, like
4666 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4667 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4668 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4669 all of the locations that belong to that breakpoint.
4671 @cindex pending breakpoints
4672 It's quite common to have a breakpoint inside a shared library.
4673 Shared libraries can be loaded and unloaded explicitly,
4674 and possibly repeatedly, as the program is executed. To support
4675 this use case, @value{GDBN} updates breakpoint locations whenever
4676 any shared library is loaded or unloaded. Typically, you would
4677 set a breakpoint in a shared library at the beginning of your
4678 debugging session, when the library is not loaded, and when the
4679 symbols from the library are not available. When you try to set
4680 breakpoint, @value{GDBN} will ask you if you want to set
4681 a so called @dfn{pending breakpoint}---breakpoint whose address
4682 is not yet resolved.
4684 After the program is run, whenever a new shared library is loaded,
4685 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4686 shared library contains the symbol or line referred to by some
4687 pending breakpoint, that breakpoint is resolved and becomes an
4688 ordinary breakpoint. When a library is unloaded, all breakpoints
4689 that refer to its symbols or source lines become pending again.
4691 This logic works for breakpoints with multiple locations, too. For
4692 example, if you have a breakpoint in a C@t{++} template function, and
4693 a newly loaded shared library has an instantiation of that template,
4694 a new location is added to the list of locations for the breakpoint.
4696 Except for having unresolved address, pending breakpoints do not
4697 differ from regular breakpoints. You can set conditions or commands,
4698 enable and disable them and perform other breakpoint operations.
4700 @value{GDBN} provides some additional commands for controlling what
4701 happens when the @samp{break} command cannot resolve breakpoint
4702 address specification to an address:
4704 @kindex set breakpoint pending
4705 @kindex show breakpoint pending
4707 @item set breakpoint pending auto
4708 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4709 location, it queries you whether a pending breakpoint should be created.
4711 @item set breakpoint pending on
4712 This indicates that an unrecognized breakpoint location should automatically
4713 result in a pending breakpoint being created.
4715 @item set breakpoint pending off
4716 This indicates that pending breakpoints are not to be created. Any
4717 unrecognized breakpoint location results in an error. This setting does
4718 not affect any pending breakpoints previously created.
4720 @item show breakpoint pending
4721 Show the current behavior setting for creating pending breakpoints.
4724 The settings above only affect the @code{break} command and its
4725 variants. Once breakpoint is set, it will be automatically updated
4726 as shared libraries are loaded and unloaded.
4728 @cindex automatic hardware breakpoints
4729 For some targets, @value{GDBN} can automatically decide if hardware or
4730 software breakpoints should be used, depending on whether the
4731 breakpoint address is read-only or read-write. This applies to
4732 breakpoints set with the @code{break} command as well as to internal
4733 breakpoints set by commands like @code{next} and @code{finish}. For
4734 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4737 You can control this automatic behaviour with the following commands:
4739 @kindex set breakpoint auto-hw
4740 @kindex show breakpoint auto-hw
4742 @item set breakpoint auto-hw on
4743 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4744 will try to use the target memory map to decide if software or hardware
4745 breakpoint must be used.
4747 @item set breakpoint auto-hw off
4748 This indicates @value{GDBN} should not automatically select breakpoint
4749 type. If the target provides a memory map, @value{GDBN} will warn when
4750 trying to set software breakpoint at a read-only address.
4753 @value{GDBN} normally implements breakpoints by replacing the program code
4754 at the breakpoint address with a special instruction, which, when
4755 executed, given control to the debugger. By default, the program
4756 code is so modified only when the program is resumed. As soon as
4757 the program stops, @value{GDBN} restores the original instructions. This
4758 behaviour guards against leaving breakpoints inserted in the
4759 target should gdb abrubptly disconnect. However, with slow remote
4760 targets, inserting and removing breakpoint can reduce the performance.
4761 This behavior can be controlled with the following commands::
4763 @kindex set breakpoint always-inserted
4764 @kindex show breakpoint always-inserted
4766 @item set breakpoint always-inserted off
4767 All breakpoints, including newly added by the user, are inserted in
4768 the target only when the target is resumed. All breakpoints are
4769 removed from the target when it stops. This is the default mode.
4771 @item set breakpoint always-inserted on
4772 Causes all breakpoints to be inserted in the target at all times. If
4773 the user adds a new breakpoint, or changes an existing breakpoint, the
4774 breakpoints in the target are updated immediately. A breakpoint is
4775 removed from the target only when breakpoint itself is deleted.
4778 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4779 when a breakpoint breaks. If the condition is true, then the process being
4780 debugged stops, otherwise the process is resumed.
4782 If the target supports evaluating conditions on its end, @value{GDBN} may
4783 download the breakpoint, together with its conditions, to it.
4785 This feature can be controlled via the following commands:
4787 @kindex set breakpoint condition-evaluation
4788 @kindex show breakpoint condition-evaluation
4790 @item set breakpoint condition-evaluation host
4791 This option commands @value{GDBN} to evaluate the breakpoint
4792 conditions on the host's side. Unconditional breakpoints are sent to
4793 the target which in turn receives the triggers and reports them back to GDB
4794 for condition evaluation. This is the standard evaluation mode.
4796 @item set breakpoint condition-evaluation target
4797 This option commands @value{GDBN} to download breakpoint conditions
4798 to the target at the moment of their insertion. The target
4799 is responsible for evaluating the conditional expression and reporting
4800 breakpoint stop events back to @value{GDBN} whenever the condition
4801 is true. Due to limitations of target-side evaluation, some conditions
4802 cannot be evaluated there, e.g., conditions that depend on local data
4803 that is only known to the host. Examples include
4804 conditional expressions involving convenience variables, complex types
4805 that cannot be handled by the agent expression parser and expressions
4806 that are too long to be sent over to the target, specially when the
4807 target is a remote system. In these cases, the conditions will be
4808 evaluated by @value{GDBN}.
4810 @item set breakpoint condition-evaluation auto
4811 This is the default mode. If the target supports evaluating breakpoint
4812 conditions on its end, @value{GDBN} will download breakpoint conditions to
4813 the target (limitations mentioned previously apply). If the target does
4814 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4815 to evaluating all these conditions on the host's side.
4819 @cindex negative breakpoint numbers
4820 @cindex internal @value{GDBN} breakpoints
4821 @value{GDBN} itself sometimes sets breakpoints in your program for
4822 special purposes, such as proper handling of @code{longjmp} (in C
4823 programs). These internal breakpoints are assigned negative numbers,
4824 starting with @code{-1}; @samp{info breakpoints} does not display them.
4825 You can see these breakpoints with the @value{GDBN} maintenance command
4826 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4829 @node Set Watchpoints
4830 @subsection Setting Watchpoints
4832 @cindex setting watchpoints
4833 You can use a watchpoint to stop execution whenever the value of an
4834 expression changes, without having to predict a particular place where
4835 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4836 The expression may be as simple as the value of a single variable, or
4837 as complex as many variables combined by operators. Examples include:
4841 A reference to the value of a single variable.
4844 An address cast to an appropriate data type. For example,
4845 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4846 address (assuming an @code{int} occupies 4 bytes).
4849 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4850 expression can use any operators valid in the program's native
4851 language (@pxref{Languages}).
4854 You can set a watchpoint on an expression even if the expression can
4855 not be evaluated yet. For instance, you can set a watchpoint on
4856 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4857 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4858 the expression produces a valid value. If the expression becomes
4859 valid in some other way than changing a variable (e.g.@: if the memory
4860 pointed to by @samp{*global_ptr} becomes readable as the result of a
4861 @code{malloc} call), @value{GDBN} may not stop until the next time
4862 the expression changes.
4864 @cindex software watchpoints
4865 @cindex hardware watchpoints
4866 Depending on your system, watchpoints may be implemented in software or
4867 hardware. @value{GDBN} does software watchpointing by single-stepping your
4868 program and testing the variable's value each time, which is hundreds of
4869 times slower than normal execution. (But this may still be worth it, to
4870 catch errors where you have no clue what part of your program is the
4873 On some systems, such as most PowerPC or x86-based targets,
4874 @value{GDBN} includes support for hardware watchpoints, which do not
4875 slow down the running of your program.
4879 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
4880 Set a watchpoint for an expression. @value{GDBN} will break when the
4881 expression @var{expr} is written into by the program and its value
4882 changes. The simplest (and the most popular) use of this command is
4883 to watch the value of a single variable:
4886 (@value{GDBP}) watch foo
4889 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4890 argument, @value{GDBN} breaks only when the thread identified by
4891 @var{thread-id} changes the value of @var{expr}. If any other threads
4892 change the value of @var{expr}, @value{GDBN} will not break. Note
4893 that watchpoints restricted to a single thread in this way only work
4894 with Hardware Watchpoints.
4896 Similarly, if the @code{task} argument is given, then the watchpoint
4897 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4899 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4900 (see below). The @code{-location} argument tells @value{GDBN} to
4901 instead watch the memory referred to by @var{expr}. In this case,
4902 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4903 and watch the memory at that address. The type of the result is used
4904 to determine the size of the watched memory. If the expression's
4905 result does not have an address, then @value{GDBN} will print an
4908 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4909 of masked watchpoints, if the current architecture supports this
4910 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4911 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4912 to an address to watch. The mask specifies that some bits of an address
4913 (the bits which are reset in the mask) should be ignored when matching
4914 the address accessed by the inferior against the watchpoint address.
4915 Thus, a masked watchpoint watches many addresses simultaneously---those
4916 addresses whose unmasked bits are identical to the unmasked bits in the
4917 watchpoint address. The @code{mask} argument implies @code{-location}.
4921 (@value{GDBP}) watch foo mask 0xffff00ff
4922 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4926 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4927 Set a watchpoint that will break when the value of @var{expr} is read
4931 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4932 Set a watchpoint that will break when @var{expr} is either read from
4933 or written into by the program.
4935 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4936 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4937 This command prints a list of watchpoints, using the same format as
4938 @code{info break} (@pxref{Set Breaks}).
4941 If you watch for a change in a numerically entered address you need to
4942 dereference it, as the address itself is just a constant number which will
4943 never change. @value{GDBN} refuses to create a watchpoint that watches
4944 a never-changing value:
4947 (@value{GDBP}) watch 0x600850
4948 Cannot watch constant value 0x600850.
4949 (@value{GDBP}) watch *(int *) 0x600850
4950 Watchpoint 1: *(int *) 6293584
4953 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4954 watchpoints execute very quickly, and the debugger reports a change in
4955 value at the exact instruction where the change occurs. If @value{GDBN}
4956 cannot set a hardware watchpoint, it sets a software watchpoint, which
4957 executes more slowly and reports the change in value at the next
4958 @emph{statement}, not the instruction, after the change occurs.
4960 @cindex use only software watchpoints
4961 You can force @value{GDBN} to use only software watchpoints with the
4962 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4963 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4964 the underlying system supports them. (Note that hardware-assisted
4965 watchpoints that were set @emph{before} setting
4966 @code{can-use-hw-watchpoints} to zero will still use the hardware
4967 mechanism of watching expression values.)
4970 @item set can-use-hw-watchpoints
4971 @kindex set can-use-hw-watchpoints
4972 Set whether or not to use hardware watchpoints.
4974 @item show can-use-hw-watchpoints
4975 @kindex show can-use-hw-watchpoints
4976 Show the current mode of using hardware watchpoints.
4979 For remote targets, you can restrict the number of hardware
4980 watchpoints @value{GDBN} will use, see @ref{set remote
4981 hardware-breakpoint-limit}.
4983 When you issue the @code{watch} command, @value{GDBN} reports
4986 Hardware watchpoint @var{num}: @var{expr}
4990 if it was able to set a hardware watchpoint.
4992 Currently, the @code{awatch} and @code{rwatch} commands can only set
4993 hardware watchpoints, because accesses to data that don't change the
4994 value of the watched expression cannot be detected without examining
4995 every instruction as it is being executed, and @value{GDBN} does not do
4996 that currently. If @value{GDBN} finds that it is unable to set a
4997 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4998 will print a message like this:
5001 Expression cannot be implemented with read/access watchpoint.
5004 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5005 data type of the watched expression is wider than what a hardware
5006 watchpoint on the target machine can handle. For example, some systems
5007 can only watch regions that are up to 4 bytes wide; on such systems you
5008 cannot set hardware watchpoints for an expression that yields a
5009 double-precision floating-point number (which is typically 8 bytes
5010 wide). As a work-around, it might be possible to break the large region
5011 into a series of smaller ones and watch them with separate watchpoints.
5013 If you set too many hardware watchpoints, @value{GDBN} might be unable
5014 to insert all of them when you resume the execution of your program.
5015 Since the precise number of active watchpoints is unknown until such
5016 time as the program is about to be resumed, @value{GDBN} might not be
5017 able to warn you about this when you set the watchpoints, and the
5018 warning will be printed only when the program is resumed:
5021 Hardware watchpoint @var{num}: Could not insert watchpoint
5025 If this happens, delete or disable some of the watchpoints.
5027 Watching complex expressions that reference many variables can also
5028 exhaust the resources available for hardware-assisted watchpoints.
5029 That's because @value{GDBN} needs to watch every variable in the
5030 expression with separately allocated resources.
5032 If you call a function interactively using @code{print} or @code{call},
5033 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5034 kind of breakpoint or the call completes.
5036 @value{GDBN} automatically deletes watchpoints that watch local
5037 (automatic) variables, or expressions that involve such variables, when
5038 they go out of scope, that is, when the execution leaves the block in
5039 which these variables were defined. In particular, when the program
5040 being debugged terminates, @emph{all} local variables go out of scope,
5041 and so only watchpoints that watch global variables remain set. If you
5042 rerun the program, you will need to set all such watchpoints again. One
5043 way of doing that would be to set a code breakpoint at the entry to the
5044 @code{main} function and when it breaks, set all the watchpoints.
5046 @cindex watchpoints and threads
5047 @cindex threads and watchpoints
5048 In multi-threaded programs, watchpoints will detect changes to the
5049 watched expression from every thread.
5052 @emph{Warning:} In multi-threaded programs, software watchpoints
5053 have only limited usefulness. If @value{GDBN} creates a software
5054 watchpoint, it can only watch the value of an expression @emph{in a
5055 single thread}. If you are confident that the expression can only
5056 change due to the current thread's activity (and if you are also
5057 confident that no other thread can become current), then you can use
5058 software watchpoints as usual. However, @value{GDBN} may not notice
5059 when a non-current thread's activity changes the expression. (Hardware
5060 watchpoints, in contrast, watch an expression in all threads.)
5063 @xref{set remote hardware-watchpoint-limit}.
5065 @node Set Catchpoints
5066 @subsection Setting Catchpoints
5067 @cindex catchpoints, setting
5068 @cindex exception handlers
5069 @cindex event handling
5071 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5072 kinds of program events, such as C@t{++} exceptions or the loading of a
5073 shared library. Use the @code{catch} command to set a catchpoint.
5077 @item catch @var{event}
5078 Stop when @var{event} occurs. The @var{event} can be any of the following:
5081 @item throw @r{[}@var{regexp}@r{]}
5082 @itemx rethrow @r{[}@var{regexp}@r{]}
5083 @itemx catch @r{[}@var{regexp}@r{]}
5085 @kindex catch rethrow
5087 @cindex stop on C@t{++} exceptions
5088 The throwing, re-throwing, or catching of a C@t{++} exception.
5090 If @var{regexp} is given, then only exceptions whose type matches the
5091 regular expression will be caught.
5093 @vindex $_exception@r{, convenience variable}
5094 The convenience variable @code{$_exception} is available at an
5095 exception-related catchpoint, on some systems. This holds the
5096 exception being thrown.
5098 There are currently some limitations to C@t{++} exception handling in
5103 The support for these commands is system-dependent. Currently, only
5104 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5108 The regular expression feature and the @code{$_exception} convenience
5109 variable rely on the presence of some SDT probes in @code{libstdc++}.
5110 If these probes are not present, then these features cannot be used.
5111 These probes were first available in the GCC 4.8 release, but whether
5112 or not they are available in your GCC also depends on how it was
5116 The @code{$_exception} convenience variable is only valid at the
5117 instruction at which an exception-related catchpoint is set.
5120 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5121 location in the system library which implements runtime exception
5122 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5123 (@pxref{Selection}) to get to your code.
5126 If you call a function interactively, @value{GDBN} normally returns
5127 control to you when the function has finished executing. If the call
5128 raises an exception, however, the call may bypass the mechanism that
5129 returns control to you and cause your program either to abort or to
5130 simply continue running until it hits a breakpoint, catches a signal
5131 that @value{GDBN} is listening for, or exits. This is the case even if
5132 you set a catchpoint for the exception; catchpoints on exceptions are
5133 disabled within interactive calls. @xref{Calling}, for information on
5134 controlling this with @code{set unwind-on-terminating-exception}.
5137 You cannot raise an exception interactively.
5140 You cannot install an exception handler interactively.
5143 @item exception @r{[}@var{name}@r{]}
5144 @kindex catch exception
5145 @cindex Ada exception catching
5146 @cindex catch Ada exceptions
5147 An Ada exception being raised. If an exception name is specified
5148 at the end of the command (eg @code{catch exception Program_Error}),
5149 the debugger will stop only when this specific exception is raised.
5150 Otherwise, the debugger stops execution when any Ada exception is raised.
5152 When inserting an exception catchpoint on a user-defined exception whose
5153 name is identical to one of the exceptions defined by the language, the
5154 fully qualified name must be used as the exception name. Otherwise,
5155 @value{GDBN} will assume that it should stop on the pre-defined exception
5156 rather than the user-defined one. For instance, assuming an exception
5157 called @code{Constraint_Error} is defined in package @code{Pck}, then
5158 the command to use to catch such exceptions is @kbd{catch exception
5159 Pck.Constraint_Error}.
5161 @vindex $_ada_exception@r{, convenience variable}
5162 The convenience variable @code{$_ada_exception} holds the address of
5163 the exception being thrown. This can be useful when setting a
5164 condition for such a catchpoint.
5166 @item exception unhandled
5167 @kindex catch exception unhandled
5168 An exception that was raised but is not handled by the program. The
5169 convenience variable @code{$_ada_exception} is set as for @code{catch
5172 @item handlers @r{[}@var{name}@r{]}
5173 @kindex catch handlers
5174 @cindex Ada exception handlers catching
5175 @cindex catch Ada exceptions when handled
5176 An Ada exception being handled. If an exception name is
5177 specified at the end of the command
5178 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5179 only when this specific exception is handled.
5180 Otherwise, the debugger stops execution when any Ada exception is handled.
5182 When inserting a handlers catchpoint on a user-defined
5183 exception whose name is identical to one of the exceptions
5184 defined by the language, the fully qualified name must be used
5185 as the exception name. Otherwise, @value{GDBN} will assume that it
5186 should stop on the pre-defined exception rather than the
5187 user-defined one. For instance, assuming an exception called
5188 @code{Constraint_Error} is defined in package @code{Pck}, then the
5189 command to use to catch such exceptions handling is
5190 @kbd{catch handlers Pck.Constraint_Error}.
5192 The convenience variable @code{$_ada_exception} is set as for
5193 @code{catch exception}.
5196 @kindex catch assert
5197 A failed Ada assertion. Note that the convenience variable
5198 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5202 @cindex break on fork/exec
5203 A call to @code{exec}.
5205 @anchor{catch syscall}
5207 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5208 @kindex catch syscall
5209 @cindex break on a system call.
5210 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5211 syscall is a mechanism for application programs to request a service
5212 from the operating system (OS) or one of the OS system services.
5213 @value{GDBN} can catch some or all of the syscalls issued by the
5214 debuggee, and show the related information for each syscall. If no
5215 argument is specified, calls to and returns from all system calls
5218 @var{name} can be any system call name that is valid for the
5219 underlying OS. Just what syscalls are valid depends on the OS. On
5220 GNU and Unix systems, you can find the full list of valid syscall
5221 names on @file{/usr/include/asm/unistd.h}.
5223 @c For MS-Windows, the syscall names and the corresponding numbers
5224 @c can be found, e.g., on this URL:
5225 @c http://www.metasploit.com/users/opcode/syscalls.html
5226 @c but we don't support Windows syscalls yet.
5228 Normally, @value{GDBN} knows in advance which syscalls are valid for
5229 each OS, so you can use the @value{GDBN} command-line completion
5230 facilities (@pxref{Completion,, command completion}) to list the
5233 You may also specify the system call numerically. A syscall's
5234 number is the value passed to the OS's syscall dispatcher to
5235 identify the requested service. When you specify the syscall by its
5236 name, @value{GDBN} uses its database of syscalls to convert the name
5237 into the corresponding numeric code, but using the number directly
5238 may be useful if @value{GDBN}'s database does not have the complete
5239 list of syscalls on your system (e.g., because @value{GDBN} lags
5240 behind the OS upgrades).
5242 You may specify a group of related syscalls to be caught at once using
5243 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5244 instance, on some platforms @value{GDBN} allows you to catch all
5245 network related syscalls, by passing the argument @code{group:network}
5246 to @code{catch syscall}. Note that not all syscall groups are
5247 available in every system. You can use the command completion
5248 facilities (@pxref{Completion,, command completion}) to list the
5249 syscall groups available on your environment.
5251 The example below illustrates how this command works if you don't provide
5255 (@value{GDBP}) catch syscall
5256 Catchpoint 1 (syscall)
5258 Starting program: /tmp/catch-syscall
5260 Catchpoint 1 (call to syscall 'close'), \
5261 0xffffe424 in __kernel_vsyscall ()
5265 Catchpoint 1 (returned from syscall 'close'), \
5266 0xffffe424 in __kernel_vsyscall ()
5270 Here is an example of catching a system call by name:
5273 (@value{GDBP}) catch syscall chroot
5274 Catchpoint 1 (syscall 'chroot' [61])
5276 Starting program: /tmp/catch-syscall
5278 Catchpoint 1 (call to syscall 'chroot'), \
5279 0xffffe424 in __kernel_vsyscall ()
5283 Catchpoint 1 (returned from syscall 'chroot'), \
5284 0xffffe424 in __kernel_vsyscall ()
5288 An example of specifying a system call numerically. In the case
5289 below, the syscall number has a corresponding entry in the XML
5290 file, so @value{GDBN} finds its name and prints it:
5293 (@value{GDBP}) catch syscall 252
5294 Catchpoint 1 (syscall(s) 'exit_group')
5296 Starting program: /tmp/catch-syscall
5298 Catchpoint 1 (call to syscall 'exit_group'), \
5299 0xffffe424 in __kernel_vsyscall ()
5303 Program exited normally.
5307 Here is an example of catching a syscall group:
5310 (@value{GDBP}) catch syscall group:process
5311 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5312 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5313 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5315 Starting program: /tmp/catch-syscall
5317 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5318 from /lib64/ld-linux-x86-64.so.2
5324 However, there can be situations when there is no corresponding name
5325 in XML file for that syscall number. In this case, @value{GDBN} prints
5326 a warning message saying that it was not able to find the syscall name,
5327 but the catchpoint will be set anyway. See the example below:
5330 (@value{GDBP}) catch syscall 764
5331 warning: The number '764' does not represent a known syscall.
5332 Catchpoint 2 (syscall 764)
5336 If you configure @value{GDBN} using the @samp{--without-expat} option,
5337 it will not be able to display syscall names. Also, if your
5338 architecture does not have an XML file describing its system calls,
5339 you will not be able to see the syscall names. It is important to
5340 notice that these two features are used for accessing the syscall
5341 name database. In either case, you will see a warning like this:
5344 (@value{GDBP}) catch syscall
5345 warning: Could not open "syscalls/i386-linux.xml"
5346 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5347 GDB will not be able to display syscall names.
5348 Catchpoint 1 (syscall)
5352 Of course, the file name will change depending on your architecture and system.
5354 Still using the example above, you can also try to catch a syscall by its
5355 number. In this case, you would see something like:
5358 (@value{GDBP}) catch syscall 252
5359 Catchpoint 1 (syscall(s) 252)
5362 Again, in this case @value{GDBN} would not be able to display syscall's names.
5366 A call to @code{fork}.
5370 A call to @code{vfork}.
5372 @item load @r{[}@var{regexp}@r{]}
5373 @itemx unload @r{[}@var{regexp}@r{]}
5375 @kindex catch unload
5376 The loading or unloading of a shared library. If @var{regexp} is
5377 given, then the catchpoint will stop only if the regular expression
5378 matches one of the affected libraries.
5380 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5381 @kindex catch signal
5382 The delivery of a signal.
5384 With no arguments, this catchpoint will catch any signal that is not
5385 used internally by @value{GDBN}, specifically, all signals except
5386 @samp{SIGTRAP} and @samp{SIGINT}.
5388 With the argument @samp{all}, all signals, including those used by
5389 @value{GDBN}, will be caught. This argument cannot be used with other
5392 Otherwise, the arguments are a list of signal names as given to
5393 @code{handle} (@pxref{Signals}). Only signals specified in this list
5396 One reason that @code{catch signal} can be more useful than
5397 @code{handle} is that you can attach commands and conditions to the
5400 When a signal is caught by a catchpoint, the signal's @code{stop} and
5401 @code{print} settings, as specified by @code{handle}, are ignored.
5402 However, whether the signal is still delivered to the inferior depends
5403 on the @code{pass} setting; this can be changed in the catchpoint's
5408 @item tcatch @var{event}
5410 Set a catchpoint that is enabled only for one stop. The catchpoint is
5411 automatically deleted after the first time the event is caught.
5415 Use the @code{info break} command to list the current catchpoints.
5419 @subsection Deleting Breakpoints
5421 @cindex clearing breakpoints, watchpoints, catchpoints
5422 @cindex deleting breakpoints, watchpoints, catchpoints
5423 It is often necessary to eliminate a breakpoint, watchpoint, or
5424 catchpoint once it has done its job and you no longer want your program
5425 to stop there. This is called @dfn{deleting} the breakpoint. A
5426 breakpoint that has been deleted no longer exists; it is forgotten.
5428 With the @code{clear} command you can delete breakpoints according to
5429 where they are in your program. With the @code{delete} command you can
5430 delete individual breakpoints, watchpoints, or catchpoints by specifying
5431 their breakpoint numbers.
5433 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5434 automatically ignores breakpoints on the first instruction to be executed
5435 when you continue execution without changing the execution address.
5440 Delete any breakpoints at the next instruction to be executed in the
5441 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5442 the innermost frame is selected, this is a good way to delete a
5443 breakpoint where your program just stopped.
5445 @item clear @var{location}
5446 Delete any breakpoints set at the specified @var{location}.
5447 @xref{Specify Location}, for the various forms of @var{location}; the
5448 most useful ones are listed below:
5451 @item clear @var{function}
5452 @itemx clear @var{filename}:@var{function}
5453 Delete any breakpoints set at entry to the named @var{function}.
5455 @item clear @var{linenum}
5456 @itemx clear @var{filename}:@var{linenum}
5457 Delete any breakpoints set at or within the code of the specified
5458 @var{linenum} of the specified @var{filename}.
5461 @cindex delete breakpoints
5463 @kindex d @r{(@code{delete})}
5464 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5465 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5466 list specified as argument. If no argument is specified, delete all
5467 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5468 confirm off}). You can abbreviate this command as @code{d}.
5472 @subsection Disabling Breakpoints
5474 @cindex enable/disable a breakpoint
5475 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5476 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5477 it had been deleted, but remembers the information on the breakpoint so
5478 that you can @dfn{enable} it again later.
5480 You disable and enable breakpoints, watchpoints, and catchpoints with
5481 the @code{enable} and @code{disable} commands, optionally specifying
5482 one or more breakpoint numbers as arguments. Use @code{info break} to
5483 print a list of all breakpoints, watchpoints, and catchpoints if you
5484 do not know which numbers to use.
5486 Disabling and enabling a breakpoint that has multiple locations
5487 affects all of its locations.
5489 A breakpoint, watchpoint, or catchpoint can have any of several
5490 different states of enablement:
5494 Enabled. The breakpoint stops your program. A breakpoint set
5495 with the @code{break} command starts out in this state.
5497 Disabled. The breakpoint has no effect on your program.
5499 Enabled once. The breakpoint stops your program, but then becomes
5502 Enabled for a count. The breakpoint stops your program for the next
5503 N times, then becomes disabled.
5505 Enabled for deletion. The breakpoint stops your program, but
5506 immediately after it does so it is deleted permanently. A breakpoint
5507 set with the @code{tbreak} command starts out in this state.
5510 You can use the following commands to enable or disable breakpoints,
5511 watchpoints, and catchpoints:
5515 @kindex dis @r{(@code{disable})}
5516 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5517 Disable the specified breakpoints---or all breakpoints, if none are
5518 listed. A disabled breakpoint has no effect but is not forgotten. All
5519 options such as ignore-counts, conditions and commands are remembered in
5520 case the breakpoint is enabled again later. You may abbreviate
5521 @code{disable} as @code{dis}.
5524 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5525 Enable the specified breakpoints (or all defined breakpoints). They
5526 become effective once again in stopping your program.
5528 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5529 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5530 of these breakpoints immediately after stopping your program.
5532 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5533 Enable the specified breakpoints temporarily. @value{GDBN} records
5534 @var{count} with each of the specified breakpoints, and decrements a
5535 breakpoint's count when it is hit. When any count reaches 0,
5536 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5537 count (@pxref{Conditions, ,Break Conditions}), that will be
5538 decremented to 0 before @var{count} is affected.
5540 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5541 Enable the specified breakpoints to work once, then die. @value{GDBN}
5542 deletes any of these breakpoints as soon as your program stops there.
5543 Breakpoints set by the @code{tbreak} command start out in this state.
5546 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5547 @c confusing: tbreak is also initially enabled.
5548 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5549 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5550 subsequently, they become disabled or enabled only when you use one of
5551 the commands above. (The command @code{until} can set and delete a
5552 breakpoint of its own, but it does not change the state of your other
5553 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5557 @subsection Break Conditions
5558 @cindex conditional breakpoints
5559 @cindex breakpoint conditions
5561 @c FIXME what is scope of break condition expr? Context where wanted?
5562 @c in particular for a watchpoint?
5563 The simplest sort of breakpoint breaks every time your program reaches a
5564 specified place. You can also specify a @dfn{condition} for a
5565 breakpoint. A condition is just a Boolean expression in your
5566 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5567 a condition evaluates the expression each time your program reaches it,
5568 and your program stops only if the condition is @emph{true}.
5570 This is the converse of using assertions for program validation; in that
5571 situation, you want to stop when the assertion is violated---that is,
5572 when the condition is false. In C, if you want to test an assertion expressed
5573 by the condition @var{assert}, you should set the condition
5574 @samp{! @var{assert}} on the appropriate breakpoint.
5576 Conditions are also accepted for watchpoints; you may not need them,
5577 since a watchpoint is inspecting the value of an expression anyhow---but
5578 it might be simpler, say, to just set a watchpoint on a variable name,
5579 and specify a condition that tests whether the new value is an interesting
5582 Break conditions can have side effects, and may even call functions in
5583 your program. This can be useful, for example, to activate functions
5584 that log program progress, or to use your own print functions to
5585 format special data structures. The effects are completely predictable
5586 unless there is another enabled breakpoint at the same address. (In
5587 that case, @value{GDBN} might see the other breakpoint first and stop your
5588 program without checking the condition of this one.) Note that
5589 breakpoint commands are usually more convenient and flexible than break
5591 purpose of performing side effects when a breakpoint is reached
5592 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5594 Breakpoint conditions can also be evaluated on the target's side if
5595 the target supports it. Instead of evaluating the conditions locally,
5596 @value{GDBN} encodes the expression into an agent expression
5597 (@pxref{Agent Expressions}) suitable for execution on the target,
5598 independently of @value{GDBN}. Global variables become raw memory
5599 locations, locals become stack accesses, and so forth.
5601 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5602 when its condition evaluates to true. This mechanism may provide faster
5603 response times depending on the performance characteristics of the target
5604 since it does not need to keep @value{GDBN} informed about
5605 every breakpoint trigger, even those with false conditions.
5607 Break conditions can be specified when a breakpoint is set, by using
5608 @samp{if} in the arguments to the @code{break} command. @xref{Set
5609 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5610 with the @code{condition} command.
5612 You can also use the @code{if} keyword with the @code{watch} command.
5613 The @code{catch} command does not recognize the @code{if} keyword;
5614 @code{condition} is the only way to impose a further condition on a
5619 @item condition @var{bnum} @var{expression}
5620 Specify @var{expression} as the break condition for breakpoint,
5621 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5622 breakpoint @var{bnum} stops your program only if the value of
5623 @var{expression} is true (nonzero, in C). When you use
5624 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5625 syntactic correctness, and to determine whether symbols in it have
5626 referents in the context of your breakpoint. If @var{expression} uses
5627 symbols not referenced in the context of the breakpoint, @value{GDBN}
5628 prints an error message:
5631 No symbol "foo" in current context.
5636 not actually evaluate @var{expression} at the time the @code{condition}
5637 command (or a command that sets a breakpoint with a condition, like
5638 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5640 @item condition -force @var{bnum} @var{expression}
5641 When the @code{-force} flag is used, define the condition even if
5642 @var{expression} is invalid at all the current locations of breakpoint
5643 @var{bnum}. This is similar to the @code{-force-condition} option
5644 of the @code{break} command.
5646 @item condition @var{bnum}
5647 Remove the condition from breakpoint number @var{bnum}. It becomes
5648 an ordinary unconditional breakpoint.
5651 @cindex ignore count (of breakpoint)
5652 A special case of a breakpoint condition is to stop only when the
5653 breakpoint has been reached a certain number of times. This is so
5654 useful that there is a special way to do it, using the @dfn{ignore
5655 count} of the breakpoint. Every breakpoint has an ignore count, which
5656 is an integer. Most of the time, the ignore count is zero, and
5657 therefore has no effect. But if your program reaches a breakpoint whose
5658 ignore count is positive, then instead of stopping, it just decrements
5659 the ignore count by one and continues. As a result, if the ignore count
5660 value is @var{n}, the breakpoint does not stop the next @var{n} times
5661 your program reaches it.
5665 @item ignore @var{bnum} @var{count}
5666 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5667 The next @var{count} times the breakpoint is reached, your program's
5668 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5671 To make the breakpoint stop the next time it is reached, specify
5674 When you use @code{continue} to resume execution of your program from a
5675 breakpoint, you can specify an ignore count directly as an argument to
5676 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5677 Stepping,,Continuing and Stepping}.
5679 If a breakpoint has a positive ignore count and a condition, the
5680 condition is not checked. Once the ignore count reaches zero,
5681 @value{GDBN} resumes checking the condition.
5683 You could achieve the effect of the ignore count with a condition such
5684 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5685 is decremented each time. @xref{Convenience Vars, ,Convenience
5689 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5692 @node Break Commands
5693 @subsection Breakpoint Command Lists
5695 @cindex breakpoint commands
5696 You can give any breakpoint (or watchpoint or catchpoint) a series of
5697 commands to execute when your program stops due to that breakpoint. For
5698 example, you might want to print the values of certain expressions, or
5699 enable other breakpoints.
5703 @kindex end@r{ (breakpoint commands)}
5704 @item commands @r{[}@var{list}@dots{}@r{]}
5705 @itemx @dots{} @var{command-list} @dots{}
5707 Specify a list of commands for the given breakpoints. The commands
5708 themselves appear on the following lines. Type a line containing just
5709 @code{end} to terminate the commands.
5711 To remove all commands from a breakpoint, type @code{commands} and
5712 follow it immediately with @code{end}; that is, give no commands.
5714 With no argument, @code{commands} refers to the last breakpoint,
5715 watchpoint, or catchpoint set (not to the breakpoint most recently
5716 encountered). If the most recent breakpoints were set with a single
5717 command, then the @code{commands} will apply to all the breakpoints
5718 set by that command. This applies to breakpoints set by
5719 @code{rbreak}, and also applies when a single @code{break} command
5720 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5724 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5725 disabled within a @var{command-list}.
5727 You can use breakpoint commands to start your program up again. Simply
5728 use the @code{continue} command, or @code{step}, or any other command
5729 that resumes execution.
5731 Any other commands in the command list, after a command that resumes
5732 execution, are ignored. This is because any time you resume execution
5733 (even with a simple @code{next} or @code{step}), you may encounter
5734 another breakpoint---which could have its own command list, leading to
5735 ambiguities about which list to execute.
5738 If the first command you specify in a command list is @code{silent}, the
5739 usual message about stopping at a breakpoint is not printed. This may
5740 be desirable for breakpoints that are to print a specific message and
5741 then continue. If none of the remaining commands print anything, you
5742 see no sign that the breakpoint was reached. @code{silent} is
5743 meaningful only at the beginning of a breakpoint command list.
5745 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5746 print precisely controlled output, and are often useful in silent
5747 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5749 For example, here is how you could use breakpoint commands to print the
5750 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5756 printf "x is %d\n",x
5761 One application for breakpoint commands is to compensate for one bug so
5762 you can test for another. Put a breakpoint just after the erroneous line
5763 of code, give it a condition to detect the case in which something
5764 erroneous has been done, and give it commands to assign correct values
5765 to any variables that need them. End with the @code{continue} command
5766 so that your program does not stop, and start with the @code{silent}
5767 command so that no output is produced. Here is an example:
5778 @node Dynamic Printf
5779 @subsection Dynamic Printf
5781 @cindex dynamic printf
5783 The dynamic printf command @code{dprintf} combines a breakpoint with
5784 formatted printing of your program's data to give you the effect of
5785 inserting @code{printf} calls into your program on-the-fly, without
5786 having to recompile it.
5788 In its most basic form, the output goes to the GDB console. However,
5789 you can set the variable @code{dprintf-style} for alternate handling.
5790 For instance, you can ask to format the output by calling your
5791 program's @code{printf} function. This has the advantage that the
5792 characters go to the program's output device, so they can recorded in
5793 redirects to files and so forth.
5795 If you are doing remote debugging with a stub or agent, you can also
5796 ask to have the printf handled by the remote agent. In addition to
5797 ensuring that the output goes to the remote program's device along
5798 with any other output the program might produce, you can also ask that
5799 the dprintf remain active even after disconnecting from the remote
5800 target. Using the stub/agent is also more efficient, as it can do
5801 everything without needing to communicate with @value{GDBN}.
5805 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5806 Whenever execution reaches @var{location}, print the values of one or
5807 more @var{expressions} under the control of the string @var{template}.
5808 To print several values, separate them with commas.
5810 @item set dprintf-style @var{style}
5811 Set the dprintf output to be handled in one of several different
5812 styles enumerated below. A change of style affects all existing
5813 dynamic printfs immediately. (If you need individual control over the
5814 print commands, simply define normal breakpoints with
5815 explicitly-supplied command lists.)
5819 @kindex dprintf-style gdb
5820 Handle the output using the @value{GDBN} @code{printf} command.
5823 @kindex dprintf-style call
5824 Handle the output by calling a function in your program (normally
5828 @kindex dprintf-style agent
5829 Have the remote debugging agent (such as @code{gdbserver}) handle
5830 the output itself. This style is only available for agents that
5831 support running commands on the target.
5834 @item set dprintf-function @var{function}
5835 Set the function to call if the dprintf style is @code{call}. By
5836 default its value is @code{printf}. You may set it to any expression.
5837 that @value{GDBN} can evaluate to a function, as per the @code{call}
5840 @item set dprintf-channel @var{channel}
5841 Set a ``channel'' for dprintf. If set to a non-empty value,
5842 @value{GDBN} will evaluate it as an expression and pass the result as
5843 a first argument to the @code{dprintf-function}, in the manner of
5844 @code{fprintf} and similar functions. Otherwise, the dprintf format
5845 string will be the first argument, in the manner of @code{printf}.
5847 As an example, if you wanted @code{dprintf} output to go to a logfile
5848 that is a standard I/O stream assigned to the variable @code{mylog},
5849 you could do the following:
5852 (gdb) set dprintf-style call
5853 (gdb) set dprintf-function fprintf
5854 (gdb) set dprintf-channel mylog
5855 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5856 Dprintf 1 at 0x123456: file main.c, line 25.
5858 1 dprintf keep y 0x00123456 in main at main.c:25
5859 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5864 Note that the @code{info break} displays the dynamic printf commands
5865 as normal breakpoint commands; you can thus easily see the effect of
5866 the variable settings.
5868 @item set disconnected-dprintf on
5869 @itemx set disconnected-dprintf off
5870 @kindex set disconnected-dprintf
5871 Choose whether @code{dprintf} commands should continue to run if
5872 @value{GDBN} has disconnected from the target. This only applies
5873 if the @code{dprintf-style} is @code{agent}.
5875 @item show disconnected-dprintf off
5876 @kindex show disconnected-dprintf
5877 Show the current choice for disconnected @code{dprintf}.
5881 @value{GDBN} does not check the validity of function and channel,
5882 relying on you to supply values that are meaningful for the contexts
5883 in which they are being used. For instance, the function and channel
5884 may be the values of local variables, but if that is the case, then
5885 all enabled dynamic prints must be at locations within the scope of
5886 those locals. If evaluation fails, @value{GDBN} will report an error.
5888 @node Save Breakpoints
5889 @subsection How to save breakpoints to a file
5891 To save breakpoint definitions to a file use the @w{@code{save
5892 breakpoints}} command.
5895 @kindex save breakpoints
5896 @cindex save breakpoints to a file for future sessions
5897 @item save breakpoints [@var{filename}]
5898 This command saves all current breakpoint definitions together with
5899 their commands and ignore counts, into a file @file{@var{filename}}
5900 suitable for use in a later debugging session. This includes all
5901 types of breakpoints (breakpoints, watchpoints, catchpoints,
5902 tracepoints). To read the saved breakpoint definitions, use the
5903 @code{source} command (@pxref{Command Files}). Note that watchpoints
5904 with expressions involving local variables may fail to be recreated
5905 because it may not be possible to access the context where the
5906 watchpoint is valid anymore. Because the saved breakpoint definitions
5907 are simply a sequence of @value{GDBN} commands that recreate the
5908 breakpoints, you can edit the file in your favorite editing program,
5909 and remove the breakpoint definitions you're not interested in, or
5910 that can no longer be recreated.
5913 @node Static Probe Points
5914 @subsection Static Probe Points
5916 @cindex static probe point, SystemTap
5917 @cindex static probe point, DTrace
5918 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5919 for Statically Defined Tracing, and the probes are designed to have a tiny
5920 runtime code and data footprint, and no dynamic relocations.
5922 Currently, the following types of probes are supported on
5923 ELF-compatible systems:
5927 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5928 @acronym{SDT} probes@footnote{See
5929 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5930 for more information on how to add @code{SystemTap} @acronym{SDT}
5931 probes in your applications.}. @code{SystemTap} probes are usable
5932 from assembly, C and C@t{++} languages@footnote{See
5933 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5934 for a good reference on how the @acronym{SDT} probes are implemented.}.
5936 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5937 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5941 @cindex semaphores on static probe points
5942 Some @code{SystemTap} probes have an associated semaphore variable;
5943 for instance, this happens automatically if you defined your probe
5944 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5945 @value{GDBN} will automatically enable it when you specify a
5946 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5947 breakpoint at a probe's location by some other method (e.g.,
5948 @code{break file:line}), then @value{GDBN} will not automatically set
5949 the semaphore. @code{DTrace} probes do not support semaphores.
5951 You can examine the available static static probes using @code{info
5952 probes}, with optional arguments:
5956 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5957 If given, @var{type} is either @code{stap} for listing
5958 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5959 probes. If omitted all probes are listed regardless of their types.
5961 If given, @var{provider} is a regular expression used to match against provider
5962 names when selecting which probes to list. If omitted, probes by all
5963 probes from all providers are listed.
5965 If given, @var{name} is a regular expression to match against probe names
5966 when selecting which probes to list. If omitted, probe names are not
5967 considered when deciding whether to display them.
5969 If given, @var{objfile} is a regular expression used to select which
5970 object files (executable or shared libraries) to examine. If not
5971 given, all object files are considered.
5973 @item info probes all
5974 List the available static probes, from all types.
5977 @cindex enabling and disabling probes
5978 Some probe points can be enabled and/or disabled. The effect of
5979 enabling or disabling a probe depends on the type of probe being
5980 handled. Some @code{DTrace} probes can be enabled or
5981 disabled, but @code{SystemTap} probes cannot be disabled.
5983 You can enable (or disable) one or more probes using the following
5984 commands, with optional arguments:
5987 @kindex enable probes
5988 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5989 If given, @var{provider} is a regular expression used to match against
5990 provider names when selecting which probes to enable. If omitted,
5991 all probes from all providers are enabled.
5993 If given, @var{name} is a regular expression to match against probe
5994 names when selecting which probes to enable. If omitted, probe names
5995 are not considered when deciding whether to enable them.
5997 If given, @var{objfile} is a regular expression used to select which
5998 object files (executable or shared libraries) to examine. If not
5999 given, all object files are considered.
6001 @kindex disable probes
6002 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6003 See the @code{enable probes} command above for a description of the
6004 optional arguments accepted by this command.
6007 @vindex $_probe_arg@r{, convenience variable}
6008 A probe may specify up to twelve arguments. These are available at the
6009 point at which the probe is defined---that is, when the current PC is
6010 at the probe's location. The arguments are available using the
6011 convenience variables (@pxref{Convenience Vars})
6012 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6013 probes each probe argument is an integer of the appropriate size;
6014 types are not preserved. In @code{DTrace} probes types are preserved
6015 provided that they are recognized as such by @value{GDBN}; otherwise
6016 the value of the probe argument will be a long integer. The
6017 convenience variable @code{$_probe_argc} holds the number of arguments
6018 at the current probe point.
6020 These variables are always available, but attempts to access them at
6021 any location other than a probe point will cause @value{GDBN} to give
6025 @c @ifclear BARETARGET
6026 @node Error in Breakpoints
6027 @subsection ``Cannot insert breakpoints''
6029 If you request too many active hardware-assisted breakpoints and
6030 watchpoints, you will see this error message:
6032 @c FIXME: the precise wording of this message may change; the relevant
6033 @c source change is not committed yet (Sep 3, 1999).
6035 Stopped; cannot insert breakpoints.
6036 You may have requested too many hardware breakpoints and watchpoints.
6040 This message is printed when you attempt to resume the program, since
6041 only then @value{GDBN} knows exactly how many hardware breakpoints and
6042 watchpoints it needs to insert.
6044 When this message is printed, you need to disable or remove some of the
6045 hardware-assisted breakpoints and watchpoints, and then continue.
6047 @node Breakpoint-related Warnings
6048 @subsection ``Breakpoint address adjusted...''
6049 @cindex breakpoint address adjusted
6051 Some processor architectures place constraints on the addresses at
6052 which breakpoints may be placed. For architectures thus constrained,
6053 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6054 with the constraints dictated by the architecture.
6056 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6057 a VLIW architecture in which a number of RISC-like instructions may be
6058 bundled together for parallel execution. The FR-V architecture
6059 constrains the location of a breakpoint instruction within such a
6060 bundle to the instruction with the lowest address. @value{GDBN}
6061 honors this constraint by adjusting a breakpoint's address to the
6062 first in the bundle.
6064 It is not uncommon for optimized code to have bundles which contain
6065 instructions from different source statements, thus it may happen that
6066 a breakpoint's address will be adjusted from one source statement to
6067 another. Since this adjustment may significantly alter @value{GDBN}'s
6068 breakpoint related behavior from what the user expects, a warning is
6069 printed when the breakpoint is first set and also when the breakpoint
6072 A warning like the one below is printed when setting a breakpoint
6073 that's been subject to address adjustment:
6076 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6079 Such warnings are printed both for user settable and @value{GDBN}'s
6080 internal breakpoints. If you see one of these warnings, you should
6081 verify that a breakpoint set at the adjusted address will have the
6082 desired affect. If not, the breakpoint in question may be removed and
6083 other breakpoints may be set which will have the desired behavior.
6084 E.g., it may be sufficient to place the breakpoint at a later
6085 instruction. A conditional breakpoint may also be useful in some
6086 cases to prevent the breakpoint from triggering too often.
6088 @value{GDBN} will also issue a warning when stopping at one of these
6089 adjusted breakpoints:
6092 warning: Breakpoint 1 address previously adjusted from 0x00010414
6096 When this warning is encountered, it may be too late to take remedial
6097 action except in cases where the breakpoint is hit earlier or more
6098 frequently than expected.
6100 @node Continuing and Stepping
6101 @section Continuing and Stepping
6105 @cindex resuming execution
6106 @dfn{Continuing} means resuming program execution until your program
6107 completes normally. In contrast, @dfn{stepping} means executing just
6108 one more ``step'' of your program, where ``step'' may mean either one
6109 line of source code, or one machine instruction (depending on what
6110 particular command you use). Either when continuing or when stepping,
6111 your program may stop even sooner, due to a breakpoint or a signal. (If
6112 it stops due to a signal, you may want to use @code{handle}, or use
6113 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6114 or you may step into the signal's handler (@pxref{stepping and signal
6119 @kindex c @r{(@code{continue})}
6120 @kindex fg @r{(resume foreground execution)}
6121 @item continue @r{[}@var{ignore-count}@r{]}
6122 @itemx c @r{[}@var{ignore-count}@r{]}
6123 @itemx fg @r{[}@var{ignore-count}@r{]}
6124 Resume program execution, at the address where your program last stopped;
6125 any breakpoints set at that address are bypassed. The optional argument
6126 @var{ignore-count} allows you to specify a further number of times to
6127 ignore a breakpoint at this location; its effect is like that of
6128 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6130 The argument @var{ignore-count} is meaningful only when your program
6131 stopped due to a breakpoint. At other times, the argument to
6132 @code{continue} is ignored.
6134 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6135 debugged program is deemed to be the foreground program) are provided
6136 purely for convenience, and have exactly the same behavior as
6140 To resume execution at a different place, you can use @code{return}
6141 (@pxref{Returning, ,Returning from a Function}) to go back to the
6142 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6143 Different Address}) to go to an arbitrary location in your program.
6145 A typical technique for using stepping is to set a breakpoint
6146 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6147 beginning of the function or the section of your program where a problem
6148 is believed to lie, run your program until it stops at that breakpoint,
6149 and then step through the suspect area, examining the variables that are
6150 interesting, until you see the problem happen.
6154 @kindex s @r{(@code{step})}
6156 Continue running your program until control reaches a different source
6157 line, then stop it and return control to @value{GDBN}. This command is
6158 abbreviated @code{s}.
6161 @c "without debugging information" is imprecise; actually "without line
6162 @c numbers in the debugging information". (gcc -g1 has debugging info but
6163 @c not line numbers). But it seems complex to try to make that
6164 @c distinction here.
6165 @emph{Warning:} If you use the @code{step} command while control is
6166 within a function that was compiled without debugging information,
6167 execution proceeds until control reaches a function that does have
6168 debugging information. Likewise, it will not step into a function which
6169 is compiled without debugging information. To step through functions
6170 without debugging information, use the @code{stepi} command, described
6174 The @code{step} command only stops at the first instruction of a source
6175 line. This prevents the multiple stops that could otherwise occur in
6176 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6177 to stop if a function that has debugging information is called within
6178 the line. In other words, @code{step} @emph{steps inside} any functions
6179 called within the line.
6181 Also, the @code{step} command only enters a function if there is line
6182 number information for the function. Otherwise it acts like the
6183 @code{next} command. This avoids problems when using @code{cc -gl}
6184 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6185 was any debugging information about the routine.
6187 @item step @var{count}
6188 Continue running as in @code{step}, but do so @var{count} times. If a
6189 breakpoint is reached, or a signal not related to stepping occurs before
6190 @var{count} steps, stepping stops right away.
6193 @kindex n @r{(@code{next})}
6194 @item next @r{[}@var{count}@r{]}
6195 Continue to the next source line in the current (innermost) stack frame.
6196 This is similar to @code{step}, but function calls that appear within
6197 the line of code are executed without stopping. Execution stops when
6198 control reaches a different line of code at the original stack level
6199 that was executing when you gave the @code{next} command. This command
6200 is abbreviated @code{n}.
6202 An argument @var{count} is a repeat count, as for @code{step}.
6205 @c FIX ME!! Do we delete this, or is there a way it fits in with
6206 @c the following paragraph? --- Vctoria
6208 @c @code{next} within a function that lacks debugging information acts like
6209 @c @code{step}, but any function calls appearing within the code of the
6210 @c function are executed without stopping.
6212 The @code{next} command only stops at the first instruction of a
6213 source line. This prevents multiple stops that could otherwise occur in
6214 @code{switch} statements, @code{for} loops, etc.
6216 @kindex set step-mode
6218 @cindex functions without line info, and stepping
6219 @cindex stepping into functions with no line info
6220 @itemx set step-mode on
6221 The @code{set step-mode on} command causes the @code{step} command to
6222 stop at the first instruction of a function which contains no debug line
6223 information rather than stepping over it.
6225 This is useful in cases where you may be interested in inspecting the
6226 machine instructions of a function which has no symbolic info and do not
6227 want @value{GDBN} to automatically skip over this function.
6229 @item set step-mode off
6230 Causes the @code{step} command to step over any functions which contains no
6231 debug information. This is the default.
6233 @item show step-mode
6234 Show whether @value{GDBN} will stop in or step over functions without
6235 source line debug information.
6238 @kindex fin @r{(@code{finish})}
6240 Continue running until just after function in the selected stack frame
6241 returns. Print the returned value (if any). This command can be
6242 abbreviated as @code{fin}.
6244 Contrast this with the @code{return} command (@pxref{Returning,
6245 ,Returning from a Function}).
6247 @kindex set print finish
6248 @kindex show print finish
6249 @item set print finish @r{[}on|off@r{]}
6250 @itemx show print finish
6251 By default the @code{finish} command will show the value that is
6252 returned by the function. This can be disabled using @code{set print
6253 finish off}. When disabled, the value is still entered into the value
6254 history (@pxref{Value History}), but not displayed.
6257 @kindex u @r{(@code{until})}
6258 @cindex run until specified location
6261 Continue running until a source line past the current line, in the
6262 current stack frame, is reached. This command is used to avoid single
6263 stepping through a loop more than once. It is like the @code{next}
6264 command, except that when @code{until} encounters a jump, it
6265 automatically continues execution until the program counter is greater
6266 than the address of the jump.
6268 This means that when you reach the end of a loop after single stepping
6269 though it, @code{until} makes your program continue execution until it
6270 exits the loop. In contrast, a @code{next} command at the end of a loop
6271 simply steps back to the beginning of the loop, which forces you to step
6272 through the next iteration.
6274 @code{until} always stops your program if it attempts to exit the current
6277 @code{until} may produce somewhat counterintuitive results if the order
6278 of machine code does not match the order of the source lines. For
6279 example, in the following excerpt from a debugging session, the @code{f}
6280 (@code{frame}) command shows that execution is stopped at line
6281 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6285 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6287 (@value{GDBP}) until
6288 195 for ( ; argc > 0; NEXTARG) @{
6291 This happened because, for execution efficiency, the compiler had
6292 generated code for the loop closure test at the end, rather than the
6293 start, of the loop---even though the test in a C @code{for}-loop is
6294 written before the body of the loop. The @code{until} command appeared
6295 to step back to the beginning of the loop when it advanced to this
6296 expression; however, it has not really gone to an earlier
6297 statement---not in terms of the actual machine code.
6299 @code{until} with no argument works by means of single
6300 instruction stepping, and hence is slower than @code{until} with an
6303 @item until @var{location}
6304 @itemx u @var{location}
6305 Continue running your program until either the specified @var{location} is
6306 reached, or the current stack frame returns. The location is any of
6307 the forms described in @ref{Specify Location}.
6308 This form of the command uses temporary breakpoints, and
6309 hence is quicker than @code{until} without an argument. The specified
6310 location is actually reached only if it is in the current frame. This
6311 implies that @code{until} can be used to skip over recursive function
6312 invocations. For instance in the code below, if the current location is
6313 line @code{96}, issuing @code{until 99} will execute the program up to
6314 line @code{99} in the same invocation of factorial, i.e., after the inner
6315 invocations have returned.
6318 94 int factorial (int value)
6320 96 if (value > 1) @{
6321 97 value *= factorial (value - 1);
6328 @kindex advance @var{location}
6329 @item advance @var{location}
6330 Continue running the program up to the given @var{location}. An argument is
6331 required, which should be of one of the forms described in
6332 @ref{Specify Location}.
6333 Execution will also stop upon exit from the current stack
6334 frame. This command is similar to @code{until}, but @code{advance} will
6335 not skip over recursive function calls, and the target location doesn't
6336 have to be in the same frame as the current one.
6340 @kindex si @r{(@code{stepi})}
6342 @itemx stepi @var{arg}
6344 Execute one machine instruction, then stop and return to the debugger.
6346 It is often useful to do @samp{display/i $pc} when stepping by machine
6347 instructions. This makes @value{GDBN} automatically display the next
6348 instruction to be executed, each time your program stops. @xref{Auto
6349 Display,, Automatic Display}.
6351 An argument is a repeat count, as in @code{step}.
6355 @kindex ni @r{(@code{nexti})}
6357 @itemx nexti @var{arg}
6359 Execute one machine instruction, but if it is a function call,
6360 proceed until the function returns.
6362 An argument is a repeat count, as in @code{next}.
6366 @anchor{range stepping}
6367 @cindex range stepping
6368 @cindex target-assisted range stepping
6369 By default, and if available, @value{GDBN} makes use of
6370 target-assisted @dfn{range stepping}. In other words, whenever you
6371 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6372 tells the target to step the corresponding range of instruction
6373 addresses instead of issuing multiple single-steps. This speeds up
6374 line stepping, particularly for remote targets. Ideally, there should
6375 be no reason you would want to turn range stepping off. However, it's
6376 possible that a bug in the debug info, a bug in the remote stub (for
6377 remote targets), or even a bug in @value{GDBN} could make line
6378 stepping behave incorrectly when target-assisted range stepping is
6379 enabled. You can use the following command to turn off range stepping
6383 @kindex set range-stepping
6384 @kindex show range-stepping
6385 @item set range-stepping
6386 @itemx show range-stepping
6387 Control whether range stepping is enabled.
6389 If @code{on}, and the target supports it, @value{GDBN} tells the
6390 target to step a range of addresses itself, instead of issuing
6391 multiple single-steps. If @code{off}, @value{GDBN} always issues
6392 single-steps, even if range stepping is supported by the target. The
6393 default is @code{on}.
6397 @node Skipping Over Functions and Files
6398 @section Skipping Over Functions and Files
6399 @cindex skipping over functions and files
6401 The program you are debugging may contain some functions which are
6402 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6403 skip a function, all functions in a file or a particular function in
6404 a particular file when stepping.
6406 For example, consider the following C function:
6417 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6418 are not interested in stepping through @code{boring}. If you run @code{step}
6419 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6420 step over both @code{foo} and @code{boring}!
6422 One solution is to @code{step} into @code{boring} and use the @code{finish}
6423 command to immediately exit it. But this can become tedious if @code{boring}
6424 is called from many places.
6426 A more flexible solution is to execute @kbd{skip boring}. This instructs
6427 @value{GDBN} never to step into @code{boring}. Now when you execute
6428 @code{step} at line 103, you'll step over @code{boring} and directly into
6431 Functions may be skipped by providing either a function name, linespec
6432 (@pxref{Specify Location}), regular expression that matches the function's
6433 name, file name or a @code{glob}-style pattern that matches the file name.
6435 On Posix systems the form of the regular expression is
6436 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6437 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6438 expression is whatever is provided by the @code{regcomp} function of
6439 the underlying system.
6440 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6441 description of @code{glob}-style patterns.
6445 @item skip @r{[}@var{options}@r{]}
6446 The basic form of the @code{skip} command takes zero or more options
6447 that specify what to skip.
6448 The @var{options} argument is any useful combination of the following:
6451 @item -file @var{file}
6452 @itemx -fi @var{file}
6453 Functions in @var{file} will be skipped over when stepping.
6455 @item -gfile @var{file-glob-pattern}
6456 @itemx -gfi @var{file-glob-pattern}
6457 @cindex skipping over files via glob-style patterns
6458 Functions in files matching @var{file-glob-pattern} will be skipped
6462 (gdb) skip -gfi utils/*.c
6465 @item -function @var{linespec}
6466 @itemx -fu @var{linespec}
6467 Functions named by @var{linespec} or the function containing the line
6468 named by @var{linespec} will be skipped over when stepping.
6469 @xref{Specify Location}.
6471 @item -rfunction @var{regexp}
6472 @itemx -rfu @var{regexp}
6473 @cindex skipping over functions via regular expressions
6474 Functions whose name matches @var{regexp} will be skipped over when stepping.
6476 This form is useful for complex function names.
6477 For example, there is generally no need to step into C@t{++} @code{std::string}
6478 constructors or destructors. Plus with C@t{++} templates it can be hard to
6479 write out the full name of the function, and often it doesn't matter what
6480 the template arguments are. Specifying the function to be skipped as a
6481 regular expression makes this easier.
6484 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6487 If you want to skip every templated C@t{++} constructor and destructor
6488 in the @code{std} namespace you can do:
6491 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6495 If no options are specified, the function you're currently debugging
6498 @kindex skip function
6499 @item skip function @r{[}@var{linespec}@r{]}
6500 After running this command, the function named by @var{linespec} or the
6501 function containing the line named by @var{linespec} will be skipped over when
6502 stepping. @xref{Specify Location}.
6504 If you do not specify @var{linespec}, the function you're currently debugging
6507 (If you have a function called @code{file} that you want to skip, use
6508 @kbd{skip function file}.)
6511 @item skip file @r{[}@var{filename}@r{]}
6512 After running this command, any function whose source lives in @var{filename}
6513 will be skipped over when stepping.
6516 (gdb) skip file boring.c
6517 File boring.c will be skipped when stepping.
6520 If you do not specify @var{filename}, functions whose source lives in the file
6521 you're currently debugging will be skipped.
6524 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6525 These are the commands for managing your list of skips:
6529 @item info skip @r{[}@var{range}@r{]}
6530 Print details about the specified skip(s). If @var{range} is not specified,
6531 print a table with details about all functions and files marked for skipping.
6532 @code{info skip} prints the following information about each skip:
6536 A number identifying this skip.
6537 @item Enabled or Disabled
6538 Enabled skips are marked with @samp{y}.
6539 Disabled skips are marked with @samp{n}.
6541 If the file name is a @samp{glob} pattern this is @samp{y}.
6542 Otherwise it is @samp{n}.
6544 The name or @samp{glob} pattern of the file to be skipped.
6545 If no file is specified this is @samp{<none>}.
6547 If the function name is a @samp{regular expression} this is @samp{y}.
6548 Otherwise it is @samp{n}.
6550 The name or regular expression of the function to skip.
6551 If no function is specified this is @samp{<none>}.
6555 @item skip delete @r{[}@var{range}@r{]}
6556 Delete the specified skip(s). If @var{range} is not specified, delete all
6560 @item skip enable @r{[}@var{range}@r{]}
6561 Enable the specified skip(s). If @var{range} is not specified, enable all
6564 @kindex skip disable
6565 @item skip disable @r{[}@var{range}@r{]}
6566 Disable the specified skip(s). If @var{range} is not specified, disable all
6569 @kindex set debug skip
6570 @item set debug skip @r{[}on|off@r{]}
6571 Set whether to print the debug output about skipping files and functions.
6573 @kindex show debug skip
6574 @item show debug skip
6575 Show whether the debug output about skipping files and functions is printed.
6583 A signal is an asynchronous event that can happen in a program. The
6584 operating system defines the possible kinds of signals, and gives each
6585 kind a name and a number. For example, in Unix @code{SIGINT} is the
6586 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6587 @code{SIGSEGV} is the signal a program gets from referencing a place in
6588 memory far away from all the areas in use; @code{SIGALRM} occurs when
6589 the alarm clock timer goes off (which happens only if your program has
6590 requested an alarm).
6592 @cindex fatal signals
6593 Some signals, including @code{SIGALRM}, are a normal part of the
6594 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6595 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6596 program has not specified in advance some other way to handle the signal.
6597 @code{SIGINT} does not indicate an error in your program, but it is normally
6598 fatal so it can carry out the purpose of the interrupt: to kill the program.
6600 @value{GDBN} has the ability to detect any occurrence of a signal in your
6601 program. You can tell @value{GDBN} in advance what to do for each kind of
6604 @cindex handling signals
6605 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6606 @code{SIGALRM} be silently passed to your program
6607 (so as not to interfere with their role in the program's functioning)
6608 but to stop your program immediately whenever an error signal happens.
6609 You can change these settings with the @code{handle} command.
6612 @kindex info signals
6616 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6617 handle each one. You can use this to see the signal numbers of all
6618 the defined types of signals.
6620 @item info signals @var{sig}
6621 Similar, but print information only about the specified signal number.
6623 @code{info handle} is an alias for @code{info signals}.
6625 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6626 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6627 for details about this command.
6630 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6631 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6632 can be the number of a signal or its name (with or without the
6633 @samp{SIG} at the beginning); a list of signal numbers of the form
6634 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6635 known signals. Optional arguments @var{keywords}, described below,
6636 say what change to make.
6640 The keywords allowed by the @code{handle} command can be abbreviated.
6641 Their full names are:
6645 @value{GDBN} should not stop your program when this signal happens. It may
6646 still print a message telling you that the signal has come in.
6649 @value{GDBN} should stop your program when this signal happens. This implies
6650 the @code{print} keyword as well.
6653 @value{GDBN} should print a message when this signal happens.
6656 @value{GDBN} should not mention the occurrence of the signal at all. This
6657 implies the @code{nostop} keyword as well.
6661 @value{GDBN} should allow your program to see this signal; your program
6662 can handle the signal, or else it may terminate if the signal is fatal
6663 and not handled. @code{pass} and @code{noignore} are synonyms.
6667 @value{GDBN} should not allow your program to see this signal.
6668 @code{nopass} and @code{ignore} are synonyms.
6672 When a signal stops your program, the signal is not visible to the
6674 continue. Your program sees the signal then, if @code{pass} is in
6675 effect for the signal in question @emph{at that time}. In other words,
6676 after @value{GDBN} reports a signal, you can use the @code{handle}
6677 command with @code{pass} or @code{nopass} to control whether your
6678 program sees that signal when you continue.
6680 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6681 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6682 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6685 You can also use the @code{signal} command to prevent your program from
6686 seeing a signal, or cause it to see a signal it normally would not see,
6687 or to give it any signal at any time. For example, if your program stopped
6688 due to some sort of memory reference error, you might store correct
6689 values into the erroneous variables and continue, hoping to see more
6690 execution; but your program would probably terminate immediately as
6691 a result of the fatal signal once it saw the signal. To prevent this,
6692 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6695 @cindex stepping and signal handlers
6696 @anchor{stepping and signal handlers}
6698 @value{GDBN} optimizes for stepping the mainline code. If a signal
6699 that has @code{handle nostop} and @code{handle pass} set arrives while
6700 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6701 in progress, @value{GDBN} lets the signal handler run and then resumes
6702 stepping the mainline code once the signal handler returns. In other
6703 words, @value{GDBN} steps over the signal handler. This prevents
6704 signals that you've specified as not interesting (with @code{handle
6705 nostop}) from changing the focus of debugging unexpectedly. Note that
6706 the signal handler itself may still hit a breakpoint, stop for another
6707 signal that has @code{handle stop} in effect, or for any other event
6708 that normally results in stopping the stepping command sooner. Also
6709 note that @value{GDBN} still informs you that the program received a
6710 signal if @code{handle print} is set.
6712 @anchor{stepping into signal handlers}
6714 If you set @code{handle pass} for a signal, and your program sets up a
6715 handler for it, then issuing a stepping command, such as @code{step}
6716 or @code{stepi}, when your program is stopped due to the signal will
6717 step @emph{into} the signal handler (if the target supports that).
6719 Likewise, if you use the @code{queue-signal} command to queue a signal
6720 to be delivered to the current thread when execution of the thread
6721 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6722 stepping command will step into the signal handler.
6724 Here's an example, using @code{stepi} to step to the first instruction
6725 of @code{SIGUSR1}'s handler:
6728 (@value{GDBP}) handle SIGUSR1
6729 Signal Stop Print Pass to program Description
6730 SIGUSR1 Yes Yes Yes User defined signal 1
6734 Program received signal SIGUSR1, User defined signal 1.
6735 main () sigusr1.c:28
6738 sigusr1_handler () at sigusr1.c:9
6742 The same, but using @code{queue-signal} instead of waiting for the
6743 program to receive the signal first:
6748 (@value{GDBP}) queue-signal SIGUSR1
6750 sigusr1_handler () at sigusr1.c:9
6755 @cindex extra signal information
6756 @anchor{extra signal information}
6758 On some targets, @value{GDBN} can inspect extra signal information
6759 associated with the intercepted signal, before it is actually
6760 delivered to the program being debugged. This information is exported
6761 by the convenience variable @code{$_siginfo}, and consists of data
6762 that is passed by the kernel to the signal handler at the time of the
6763 receipt of a signal. The data type of the information itself is
6764 target dependent. You can see the data type using the @code{ptype
6765 $_siginfo} command. On Unix systems, it typically corresponds to the
6766 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6769 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6770 referenced address that raised a segmentation fault.
6774 (@value{GDBP}) continue
6775 Program received signal SIGSEGV, Segmentation fault.
6776 0x0000000000400766 in main ()
6778 (@value{GDBP}) ptype $_siginfo
6785 struct @{...@} _kill;
6786 struct @{...@} _timer;
6788 struct @{...@} _sigchld;
6789 struct @{...@} _sigfault;
6790 struct @{...@} _sigpoll;
6793 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6797 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6798 $1 = (void *) 0x7ffff7ff7000
6802 Depending on target support, @code{$_siginfo} may also be writable.
6804 @cindex Intel MPX boundary violations
6805 @cindex boundary violations, Intel MPX
6806 On some targets, a @code{SIGSEGV} can be caused by a boundary
6807 violation, i.e., accessing an address outside of the allowed range.
6808 In those cases @value{GDBN} may displays additional information,
6809 depending on how @value{GDBN} has been told to handle the signal.
6810 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6811 kind: "Upper" or "Lower", the memory address accessed and the
6812 bounds, while with @code{handle nostop SIGSEGV} no additional
6813 information is displayed.
6815 The usual output of a segfault is:
6817 Program received signal SIGSEGV, Segmentation fault
6818 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6819 68 value = *(p + len);
6822 While a bound violation is presented as:
6824 Program received signal SIGSEGV, Segmentation fault
6825 Upper bound violation while accessing address 0x7fffffffc3b3
6826 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6827 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6828 68 value = *(p + len);
6832 @section Stopping and Starting Multi-thread Programs
6834 @cindex stopped threads
6835 @cindex threads, stopped
6837 @cindex continuing threads
6838 @cindex threads, continuing
6840 @value{GDBN} supports debugging programs with multiple threads
6841 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6842 are two modes of controlling execution of your program within the
6843 debugger. In the default mode, referred to as @dfn{all-stop mode},
6844 when any thread in your program stops (for example, at a breakpoint
6845 or while being stepped), all other threads in the program are also stopped by
6846 @value{GDBN}. On some targets, @value{GDBN} also supports
6847 @dfn{non-stop mode}, in which other threads can continue to run freely while
6848 you examine the stopped thread in the debugger.
6851 * All-Stop Mode:: All threads stop when GDB takes control
6852 * Non-Stop Mode:: Other threads continue to execute
6853 * Background Execution:: Running your program asynchronously
6854 * Thread-Specific Breakpoints:: Controlling breakpoints
6855 * Interrupted System Calls:: GDB may interfere with system calls
6856 * Observer Mode:: GDB does not alter program behavior
6860 @subsection All-Stop Mode
6862 @cindex all-stop mode
6864 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6865 @emph{all} threads of execution stop, not just the current thread. This
6866 allows you to examine the overall state of the program, including
6867 switching between threads, without worrying that things may change
6870 Conversely, whenever you restart the program, @emph{all} threads start
6871 executing. @emph{This is true even when single-stepping} with commands
6872 like @code{step} or @code{next}.
6874 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6875 Since thread scheduling is up to your debugging target's operating
6876 system (not controlled by @value{GDBN}), other threads may
6877 execute more than one statement while the current thread completes a
6878 single step. Moreover, in general other threads stop in the middle of a
6879 statement, rather than at a clean statement boundary, when the program
6882 You might even find your program stopped in another thread after
6883 continuing or even single-stepping. This happens whenever some other
6884 thread runs into a breakpoint, a signal, or an exception before the
6885 first thread completes whatever you requested.
6887 @cindex automatic thread selection
6888 @cindex switching threads automatically
6889 @cindex threads, automatic switching
6890 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6891 signal, it automatically selects the thread where that breakpoint or
6892 signal happened. @value{GDBN} alerts you to the context switch with a
6893 message such as @samp{[Switching to Thread @var{n}]} to identify the
6896 On some OSes, you can modify @value{GDBN}'s default behavior by
6897 locking the OS scheduler to allow only a single thread to run.
6900 @item set scheduler-locking @var{mode}
6901 @cindex scheduler locking mode
6902 @cindex lock scheduler
6903 Set the scheduler locking mode. It applies to normal execution,
6904 record mode, and replay mode. If it is @code{off}, then there is no
6905 locking and any thread may run at any time. If @code{on}, then only
6906 the current thread may run when the inferior is resumed. The
6907 @code{step} mode optimizes for single-stepping; it prevents other
6908 threads from preempting the current thread while you are stepping, so
6909 that the focus of debugging does not change unexpectedly. Other
6910 threads never get a chance to run when you step, and they are
6911 completely free to run when you use commands like @samp{continue},
6912 @samp{until}, or @samp{finish}. However, unless another thread hits a
6913 breakpoint during its timeslice, @value{GDBN} does not change the
6914 current thread away from the thread that you are debugging. The
6915 @code{replay} mode behaves like @code{off} in record mode and like
6916 @code{on} in replay mode.
6918 @item show scheduler-locking
6919 Display the current scheduler locking mode.
6922 @cindex resume threads of multiple processes simultaneously
6923 By default, when you issue one of the execution commands such as
6924 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6925 threads of the current inferior to run. For example, if @value{GDBN}
6926 is attached to two inferiors, each with two threads, the
6927 @code{continue} command resumes only the two threads of the current
6928 inferior. This is useful, for example, when you debug a program that
6929 forks and you want to hold the parent stopped (so that, for instance,
6930 it doesn't run to exit), while you debug the child. In other
6931 situations, you may not be interested in inspecting the current state
6932 of any of the processes @value{GDBN} is attached to, and you may want
6933 to resume them all until some breakpoint is hit. In the latter case,
6934 you can instruct @value{GDBN} to allow all threads of all the
6935 inferiors to run with the @w{@code{set schedule-multiple}} command.
6938 @kindex set schedule-multiple
6939 @item set schedule-multiple
6940 Set the mode for allowing threads of multiple processes to be resumed
6941 when an execution command is issued. When @code{on}, all threads of
6942 all processes are allowed to run. When @code{off}, only the threads
6943 of the current process are resumed. The default is @code{off}. The
6944 @code{scheduler-locking} mode takes precedence when set to @code{on},
6945 or while you are stepping and set to @code{step}.
6947 @item show schedule-multiple
6948 Display the current mode for resuming the execution of threads of
6953 @subsection Non-Stop Mode
6955 @cindex non-stop mode
6957 @c This section is really only a place-holder, and needs to be expanded
6958 @c with more details.
6960 For some multi-threaded targets, @value{GDBN} supports an optional
6961 mode of operation in which you can examine stopped program threads in
6962 the debugger while other threads continue to execute freely. This
6963 minimizes intrusion when debugging live systems, such as programs
6964 where some threads have real-time constraints or must continue to
6965 respond to external events. This is referred to as @dfn{non-stop} mode.
6967 In non-stop mode, when a thread stops to report a debugging event,
6968 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6969 threads as well, in contrast to the all-stop mode behavior. Additionally,
6970 execution commands such as @code{continue} and @code{step} apply by default
6971 only to the current thread in non-stop mode, rather than all threads as
6972 in all-stop mode. This allows you to control threads explicitly in
6973 ways that are not possible in all-stop mode --- for example, stepping
6974 one thread while allowing others to run freely, stepping
6975 one thread while holding all others stopped, or stepping several threads
6976 independently and simultaneously.
6978 To enter non-stop mode, use this sequence of commands before you run
6979 or attach to your program:
6982 # If using the CLI, pagination breaks non-stop.
6985 # Finally, turn it on!
6989 You can use these commands to manipulate the non-stop mode setting:
6992 @kindex set non-stop
6993 @item set non-stop on
6994 Enable selection of non-stop mode.
6995 @item set non-stop off
6996 Disable selection of non-stop mode.
6997 @kindex show non-stop
6999 Show the current non-stop enablement setting.
7002 Note these commands only reflect whether non-stop mode is enabled,
7003 not whether the currently-executing program is being run in non-stop mode.
7004 In particular, the @code{set non-stop} preference is only consulted when
7005 @value{GDBN} starts or connects to the target program, and it is generally
7006 not possible to switch modes once debugging has started. Furthermore,
7007 since not all targets support non-stop mode, even when you have enabled
7008 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7011 In non-stop mode, all execution commands apply only to the current thread
7012 by default. That is, @code{continue} only continues one thread.
7013 To continue all threads, issue @code{continue -a} or @code{c -a}.
7015 You can use @value{GDBN}'s background execution commands
7016 (@pxref{Background Execution}) to run some threads in the background
7017 while you continue to examine or step others from @value{GDBN}.
7018 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7019 always executed asynchronously in non-stop mode.
7021 Suspending execution is done with the @code{interrupt} command when
7022 running in the background, or @kbd{Ctrl-c} during foreground execution.
7023 In all-stop mode, this stops the whole process;
7024 but in non-stop mode the interrupt applies only to the current thread.
7025 To stop the whole program, use @code{interrupt -a}.
7027 Other execution commands do not currently support the @code{-a} option.
7029 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7030 that thread current, as it does in all-stop mode. This is because the
7031 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7032 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7033 changed to a different thread just as you entered a command to operate on the
7034 previously current thread.
7036 @node Background Execution
7037 @subsection Background Execution
7039 @cindex foreground execution
7040 @cindex background execution
7041 @cindex asynchronous execution
7042 @cindex execution, foreground, background and asynchronous
7044 @value{GDBN}'s execution commands have two variants: the normal
7045 foreground (synchronous) behavior, and a background
7046 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7047 the program to report that some thread has stopped before prompting for
7048 another command. In background execution, @value{GDBN} immediately gives
7049 a command prompt so that you can issue other commands while your program runs.
7051 If the target doesn't support async mode, @value{GDBN} issues an error
7052 message if you attempt to use the background execution commands.
7054 @cindex @code{&}, background execution of commands
7055 To specify background execution, add a @code{&} to the command. For example,
7056 the background form of the @code{continue} command is @code{continue&}, or
7057 just @code{c&}. The execution commands that accept background execution
7063 @xref{Starting, , Starting your Program}.
7067 @xref{Attach, , Debugging an Already-running Process}.
7071 @xref{Continuing and Stepping, step}.
7075 @xref{Continuing and Stepping, stepi}.
7079 @xref{Continuing and Stepping, next}.
7083 @xref{Continuing and Stepping, nexti}.
7087 @xref{Continuing and Stepping, continue}.
7091 @xref{Continuing and Stepping, finish}.
7095 @xref{Continuing and Stepping, until}.
7099 Background execution is especially useful in conjunction with non-stop
7100 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7101 However, you can also use these commands in the normal all-stop mode with
7102 the restriction that you cannot issue another execution command until the
7103 previous one finishes. Examples of commands that are valid in all-stop
7104 mode while the program is running include @code{help} and @code{info break}.
7106 You can interrupt your program while it is running in the background by
7107 using the @code{interrupt} command.
7114 Suspend execution of the running program. In all-stop mode,
7115 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7116 only the current thread. To stop the whole program in non-stop mode,
7117 use @code{interrupt -a}.
7120 @node Thread-Specific Breakpoints
7121 @subsection Thread-Specific Breakpoints
7123 When your program has multiple threads (@pxref{Threads,, Debugging
7124 Programs with Multiple Threads}), you can choose whether to set
7125 breakpoints on all threads, or on a particular thread.
7128 @cindex breakpoints and threads
7129 @cindex thread breakpoints
7130 @kindex break @dots{} thread @var{thread-id}
7131 @item break @var{location} thread @var{thread-id}
7132 @itemx break @var{location} thread @var{thread-id} if @dots{}
7133 @var{location} specifies source lines; there are several ways of
7134 writing them (@pxref{Specify Location}), but the effect is always to
7135 specify some source line.
7137 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7138 to specify that you only want @value{GDBN} to stop the program when a
7139 particular thread reaches this breakpoint. The @var{thread-id} specifier
7140 is one of the thread identifiers assigned by @value{GDBN}, shown
7141 in the first column of the @samp{info threads} display.
7143 If you do not specify @samp{thread @var{thread-id}} when you set a
7144 breakpoint, the breakpoint applies to @emph{all} threads of your
7147 You can use the @code{thread} qualifier on conditional breakpoints as
7148 well; in this case, place @samp{thread @var{thread-id}} before or
7149 after the breakpoint condition, like this:
7152 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7157 Thread-specific breakpoints are automatically deleted when
7158 @value{GDBN} detects the corresponding thread is no longer in the
7159 thread list. For example:
7163 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7166 There are several ways for a thread to disappear, such as a regular
7167 thread exit, but also when you detach from the process with the
7168 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7169 Process}), or if @value{GDBN} loses the remote connection
7170 (@pxref{Remote Debugging}), etc. Note that with some targets,
7171 @value{GDBN} is only able to detect a thread has exited when the user
7172 explictly asks for the thread list with the @code{info threads}
7175 @node Interrupted System Calls
7176 @subsection Interrupted System Calls
7178 @cindex thread breakpoints and system calls
7179 @cindex system calls and thread breakpoints
7180 @cindex premature return from system calls
7181 There is an unfortunate side effect when using @value{GDBN} to debug
7182 multi-threaded programs. If one thread stops for a
7183 breakpoint, or for some other reason, and another thread is blocked in a
7184 system call, then the system call may return prematurely. This is a
7185 consequence of the interaction between multiple threads and the signals
7186 that @value{GDBN} uses to implement breakpoints and other events that
7189 To handle this problem, your program should check the return value of
7190 each system call and react appropriately. This is good programming
7193 For example, do not write code like this:
7199 The call to @code{sleep} will return early if a different thread stops
7200 at a breakpoint or for some other reason.
7202 Instead, write this:
7207 unslept = sleep (unslept);
7210 A system call is allowed to return early, so the system is still
7211 conforming to its specification. But @value{GDBN} does cause your
7212 multi-threaded program to behave differently than it would without
7215 Also, @value{GDBN} uses internal breakpoints in the thread library to
7216 monitor certain events such as thread creation and thread destruction.
7217 When such an event happens, a system call in another thread may return
7218 prematurely, even though your program does not appear to stop.
7221 @subsection Observer Mode
7223 If you want to build on non-stop mode and observe program behavior
7224 without any chance of disruption by @value{GDBN}, you can set
7225 variables to disable all of the debugger's attempts to modify state,
7226 whether by writing memory, inserting breakpoints, etc. These operate
7227 at a low level, intercepting operations from all commands.
7229 When all of these are set to @code{off}, then @value{GDBN} is said to
7230 be @dfn{observer mode}. As a convenience, the variable
7231 @code{observer} can be set to disable these, plus enable non-stop
7234 Note that @value{GDBN} will not prevent you from making nonsensical
7235 combinations of these settings. For instance, if you have enabled
7236 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7237 then breakpoints that work by writing trap instructions into the code
7238 stream will still not be able to be placed.
7243 @item set observer on
7244 @itemx set observer off
7245 When set to @code{on}, this disables all the permission variables
7246 below (except for @code{insert-fast-tracepoints}), plus enables
7247 non-stop debugging. Setting this to @code{off} switches back to
7248 normal debugging, though remaining in non-stop mode.
7251 Show whether observer mode is on or off.
7253 @kindex may-write-registers
7254 @item set may-write-registers on
7255 @itemx set may-write-registers off
7256 This controls whether @value{GDBN} will attempt to alter the values of
7257 registers, such as with assignment expressions in @code{print}, or the
7258 @code{jump} command. It defaults to @code{on}.
7260 @item show may-write-registers
7261 Show the current permission to write registers.
7263 @kindex may-write-memory
7264 @item set may-write-memory on
7265 @itemx set may-write-memory off
7266 This controls whether @value{GDBN} will attempt to alter the contents
7267 of memory, such as with assignment expressions in @code{print}. It
7268 defaults to @code{on}.
7270 @item show may-write-memory
7271 Show the current permission to write memory.
7273 @kindex may-insert-breakpoints
7274 @item set may-insert-breakpoints on
7275 @itemx set may-insert-breakpoints off
7276 This controls whether @value{GDBN} will attempt to insert breakpoints.
7277 This affects all breakpoints, including internal breakpoints defined
7278 by @value{GDBN}. It defaults to @code{on}.
7280 @item show may-insert-breakpoints
7281 Show the current permission to insert breakpoints.
7283 @kindex may-insert-tracepoints
7284 @item set may-insert-tracepoints on
7285 @itemx set may-insert-tracepoints off
7286 This controls whether @value{GDBN} will attempt to insert (regular)
7287 tracepoints at the beginning of a tracing experiment. It affects only
7288 non-fast tracepoints, fast tracepoints being under the control of
7289 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7291 @item show may-insert-tracepoints
7292 Show the current permission to insert tracepoints.
7294 @kindex may-insert-fast-tracepoints
7295 @item set may-insert-fast-tracepoints on
7296 @itemx set may-insert-fast-tracepoints off
7297 This controls whether @value{GDBN} will attempt to insert fast
7298 tracepoints at the beginning of a tracing experiment. It affects only
7299 fast tracepoints, regular (non-fast) tracepoints being under the
7300 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7302 @item show may-insert-fast-tracepoints
7303 Show the current permission to insert fast tracepoints.
7305 @kindex may-interrupt
7306 @item set may-interrupt on
7307 @itemx set may-interrupt off
7308 This controls whether @value{GDBN} will attempt to interrupt or stop
7309 program execution. When this variable is @code{off}, the
7310 @code{interrupt} command will have no effect, nor will
7311 @kbd{Ctrl-c}. It defaults to @code{on}.
7313 @item show may-interrupt
7314 Show the current permission to interrupt or stop the program.
7318 @node Reverse Execution
7319 @chapter Running programs backward
7320 @cindex reverse execution
7321 @cindex running programs backward
7323 When you are debugging a program, it is not unusual to realize that
7324 you have gone too far, and some event of interest has already happened.
7325 If the target environment supports it, @value{GDBN} can allow you to
7326 ``rewind'' the program by running it backward.
7328 A target environment that supports reverse execution should be able
7329 to ``undo'' the changes in machine state that have taken place as the
7330 program was executing normally. Variables, registers etc.@: should
7331 revert to their previous values. Obviously this requires a great
7332 deal of sophistication on the part of the target environment; not
7333 all target environments can support reverse execution.
7335 When a program is executed in reverse, the instructions that
7336 have most recently been executed are ``un-executed'', in reverse
7337 order. The program counter runs backward, following the previous
7338 thread of execution in reverse. As each instruction is ``un-executed'',
7339 the values of memory and/or registers that were changed by that
7340 instruction are reverted to their previous states. After executing
7341 a piece of source code in reverse, all side effects of that code
7342 should be ``undone'', and all variables should be returned to their
7343 prior values@footnote{
7344 Note that some side effects are easier to undo than others. For instance,
7345 memory and registers are relatively easy, but device I/O is hard. Some
7346 targets may be able undo things like device I/O, and some may not.
7348 The contract between @value{GDBN} and the reverse executing target
7349 requires only that the target do something reasonable when
7350 @value{GDBN} tells it to execute backwards, and then report the
7351 results back to @value{GDBN}. Whatever the target reports back to
7352 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7353 assumes that the memory and registers that the target reports are in a
7354 consistent state, but @value{GDBN} accepts whatever it is given.
7357 On some platforms, @value{GDBN} has built-in support for reverse
7358 execution, activated with the @code{record} or @code{record btrace}
7359 commands. @xref{Process Record and Replay}. Some remote targets,
7360 typically full system emulators, support reverse execution directly
7361 without requiring any special command.
7363 If you are debugging in a target environment that supports
7364 reverse execution, @value{GDBN} provides the following commands.
7367 @kindex reverse-continue
7368 @kindex rc @r{(@code{reverse-continue})}
7369 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7370 @itemx rc @r{[}@var{ignore-count}@r{]}
7371 Beginning at the point where your program last stopped, start executing
7372 in reverse. Reverse execution will stop for breakpoints and synchronous
7373 exceptions (signals), just like normal execution. Behavior of
7374 asynchronous signals depends on the target environment.
7376 @kindex reverse-step
7377 @kindex rs @r{(@code{step})}
7378 @item reverse-step @r{[}@var{count}@r{]}
7379 Run the program backward until control reaches the start of a
7380 different source line; then stop it, and return control to @value{GDBN}.
7382 Like the @code{step} command, @code{reverse-step} will only stop
7383 at the beginning of a source line. It ``un-executes'' the previously
7384 executed source line. If the previous source line included calls to
7385 debuggable functions, @code{reverse-step} will step (backward) into
7386 the called function, stopping at the beginning of the @emph{last}
7387 statement in the called function (typically a return statement).
7389 Also, as with the @code{step} command, if non-debuggable functions are
7390 called, @code{reverse-step} will run thru them backward without stopping.
7392 @kindex reverse-stepi
7393 @kindex rsi @r{(@code{reverse-stepi})}
7394 @item reverse-stepi @r{[}@var{count}@r{]}
7395 Reverse-execute one machine instruction. Note that the instruction
7396 to be reverse-executed is @emph{not} the one pointed to by the program
7397 counter, but the instruction executed prior to that one. For instance,
7398 if the last instruction was a jump, @code{reverse-stepi} will take you
7399 back from the destination of the jump to the jump instruction itself.
7401 @kindex reverse-next
7402 @kindex rn @r{(@code{reverse-next})}
7403 @item reverse-next @r{[}@var{count}@r{]}
7404 Run backward to the beginning of the previous line executed in
7405 the current (innermost) stack frame. If the line contains function
7406 calls, they will be ``un-executed'' without stopping. Starting from
7407 the first line of a function, @code{reverse-next} will take you back
7408 to the caller of that function, @emph{before} the function was called,
7409 just as the normal @code{next} command would take you from the last
7410 line of a function back to its return to its caller
7411 @footnote{Unless the code is too heavily optimized.}.
7413 @kindex reverse-nexti
7414 @kindex rni @r{(@code{reverse-nexti})}
7415 @item reverse-nexti @r{[}@var{count}@r{]}
7416 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7417 in reverse, except that called functions are ``un-executed'' atomically.
7418 That is, if the previously executed instruction was a return from
7419 another function, @code{reverse-nexti} will continue to execute
7420 in reverse until the call to that function (from the current stack
7423 @kindex reverse-finish
7424 @item reverse-finish
7425 Just as the @code{finish} command takes you to the point where the
7426 current function returns, @code{reverse-finish} takes you to the point
7427 where it was called. Instead of ending up at the end of the current
7428 function invocation, you end up at the beginning.
7430 @kindex set exec-direction
7431 @item set exec-direction
7432 Set the direction of target execution.
7433 @item set exec-direction reverse
7434 @cindex execute forward or backward in time
7435 @value{GDBN} will perform all execution commands in reverse, until the
7436 exec-direction mode is changed to ``forward''. Affected commands include
7437 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7438 command cannot be used in reverse mode.
7439 @item set exec-direction forward
7440 @value{GDBN} will perform all execution commands in the normal fashion.
7441 This is the default.
7445 @node Process Record and Replay
7446 @chapter Recording Inferior's Execution and Replaying It
7447 @cindex process record and replay
7448 @cindex recording inferior's execution and replaying it
7450 On some platforms, @value{GDBN} provides a special @dfn{process record
7451 and replay} target that can record a log of the process execution, and
7452 replay it later with both forward and reverse execution commands.
7455 When this target is in use, if the execution log includes the record
7456 for the next instruction, @value{GDBN} will debug in @dfn{replay
7457 mode}. In the replay mode, the inferior does not really execute code
7458 instructions. Instead, all the events that normally happen during
7459 code execution are taken from the execution log. While code is not
7460 really executed in replay mode, the values of registers (including the
7461 program counter register) and the memory of the inferior are still
7462 changed as they normally would. Their contents are taken from the
7466 If the record for the next instruction is not in the execution log,
7467 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7468 inferior executes normally, and @value{GDBN} records the execution log
7471 The process record and replay target supports reverse execution
7472 (@pxref{Reverse Execution}), even if the platform on which the
7473 inferior runs does not. However, the reverse execution is limited in
7474 this case by the range of the instructions recorded in the execution
7475 log. In other words, reverse execution on platforms that don't
7476 support it directly can only be done in the replay mode.
7478 When debugging in the reverse direction, @value{GDBN} will work in
7479 replay mode as long as the execution log includes the record for the
7480 previous instruction; otherwise, it will work in record mode, if the
7481 platform supports reverse execution, or stop if not.
7483 Currently, process record and replay is supported on ARM, Aarch64,
7484 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7485 GNU/Linux. Process record and replay can be used both when native
7486 debugging, and when remote debugging via @code{gdbserver}.
7488 For architecture environments that support process record and replay,
7489 @value{GDBN} provides the following commands:
7492 @kindex target record
7493 @kindex target record-full
7494 @kindex target record-btrace
7497 @kindex record btrace
7498 @kindex record btrace bts
7499 @kindex record btrace pt
7505 @kindex rec btrace bts
7506 @kindex rec btrace pt
7509 @item record @var{method}
7510 This command starts the process record and replay target. The
7511 recording method can be specified as parameter. Without a parameter
7512 the command uses the @code{full} recording method. The following
7513 recording methods are available:
7517 Full record/replay recording using @value{GDBN}'s software record and
7518 replay implementation. This method allows replaying and reverse
7521 @item btrace @var{format}
7522 Hardware-supported instruction recording, supported on Intel
7523 processors. This method does not record data. Further, the data is
7524 collected in a ring buffer so old data will be overwritten when the
7525 buffer is full. It allows limited reverse execution. Variables and
7526 registers are not available during reverse execution. In remote
7527 debugging, recording continues on disconnect. Recorded data can be
7528 inspected after reconnecting. The recording may be stopped using
7531 The recording format can be specified as parameter. Without a parameter
7532 the command chooses the recording format. The following recording
7533 formats are available:
7537 @cindex branch trace store
7538 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7539 this format, the processor stores a from/to record for each executed
7540 branch in the btrace ring buffer.
7543 @cindex Intel Processor Trace
7544 Use the @dfn{Intel Processor Trace} recording format. In this
7545 format, the processor stores the execution trace in a compressed form
7546 that is afterwards decoded by @value{GDBN}.
7548 The trace can be recorded with very low overhead. The compressed
7549 trace format also allows small trace buffers to already contain a big
7550 number of instructions compared to @acronym{BTS}.
7552 Decoding the recorded execution trace, on the other hand, is more
7553 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7554 increased number of instructions to process. You should increase the
7555 buffer-size with care.
7558 Not all recording formats may be available on all processors.
7561 The process record and replay target can only debug a process that is
7562 already running. Therefore, you need first to start the process with
7563 the @kbd{run} or @kbd{start} commands, and then start the recording
7564 with the @kbd{record @var{method}} command.
7566 @cindex displaced stepping, and process record and replay
7567 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7568 will be automatically disabled when process record and replay target
7569 is started. That's because the process record and replay target
7570 doesn't support displaced stepping.
7572 @cindex non-stop mode, and process record and replay
7573 @cindex asynchronous execution, and process record and replay
7574 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7575 the asynchronous execution mode (@pxref{Background Execution}), not
7576 all recording methods are available. The @code{full} recording method
7577 does not support these two modes.
7582 Stop the process record and replay target. When process record and
7583 replay target stops, the entire execution log will be deleted and the
7584 inferior will either be terminated, or will remain in its final state.
7586 When you stop the process record and replay target in record mode (at
7587 the end of the execution log), the inferior will be stopped at the
7588 next instruction that would have been recorded. In other words, if
7589 you record for a while and then stop recording, the inferior process
7590 will be left in the same state as if the recording never happened.
7592 On the other hand, if the process record and replay target is stopped
7593 while in replay mode (that is, not at the end of the execution log,
7594 but at some earlier point), the inferior process will become ``live''
7595 at that earlier state, and it will then be possible to continue the
7596 usual ``live'' debugging of the process from that state.
7598 When the inferior process exits, or @value{GDBN} detaches from it,
7599 process record and replay target will automatically stop itself.
7603 Go to a specific location in the execution log. There are several
7604 ways to specify the location to go to:
7607 @item record goto begin
7608 @itemx record goto start
7609 Go to the beginning of the execution log.
7611 @item record goto end
7612 Go to the end of the execution log.
7614 @item record goto @var{n}
7615 Go to instruction number @var{n} in the execution log.
7619 @item record save @var{filename}
7620 Save the execution log to a file @file{@var{filename}}.
7621 Default filename is @file{gdb_record.@var{process_id}}, where
7622 @var{process_id} is the process ID of the inferior.
7624 This command may not be available for all recording methods.
7626 @kindex record restore
7627 @item record restore @var{filename}
7628 Restore the execution log from a file @file{@var{filename}}.
7629 File must have been created with @code{record save}.
7631 @kindex set record full
7632 @item set record full insn-number-max @var{limit}
7633 @itemx set record full insn-number-max unlimited
7634 Set the limit of instructions to be recorded for the @code{full}
7635 recording method. Default value is 200000.
7637 If @var{limit} is a positive number, then @value{GDBN} will start
7638 deleting instructions from the log once the number of the record
7639 instructions becomes greater than @var{limit}. For every new recorded
7640 instruction, @value{GDBN} will delete the earliest recorded
7641 instruction to keep the number of recorded instructions at the limit.
7642 (Since deleting recorded instructions loses information, @value{GDBN}
7643 lets you control what happens when the limit is reached, by means of
7644 the @code{stop-at-limit} option, described below.)
7646 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7647 delete recorded instructions from the execution log. The number of
7648 recorded instructions is limited only by the available memory.
7650 @kindex show record full
7651 @item show record full insn-number-max
7652 Show the limit of instructions to be recorded with the @code{full}
7655 @item set record full stop-at-limit
7656 Control the behavior of the @code{full} recording method when the
7657 number of recorded instructions reaches the limit. If ON (the
7658 default), @value{GDBN} will stop when the limit is reached for the
7659 first time and ask you whether you want to stop the inferior or
7660 continue running it and recording the execution log. If you decide
7661 to continue recording, each new recorded instruction will cause the
7662 oldest one to be deleted.
7664 If this option is OFF, @value{GDBN} will automatically delete the
7665 oldest record to make room for each new one, without asking.
7667 @item show record full stop-at-limit
7668 Show the current setting of @code{stop-at-limit}.
7670 @item set record full memory-query
7671 Control the behavior when @value{GDBN} is unable to record memory
7672 changes caused by an instruction for the @code{full} recording method.
7673 If ON, @value{GDBN} will query whether to stop the inferior in that
7676 If this option is OFF (the default), @value{GDBN} will automatically
7677 ignore the effect of such instructions on memory. Later, when
7678 @value{GDBN} replays this execution log, it will mark the log of this
7679 instruction as not accessible, and it will not affect the replay
7682 @item show record full memory-query
7683 Show the current setting of @code{memory-query}.
7685 @kindex set record btrace
7686 The @code{btrace} record target does not trace data. As a
7687 convenience, when replaying, @value{GDBN} reads read-only memory off
7688 the live program directly, assuming that the addresses of the
7689 read-only areas don't change. This for example makes it possible to
7690 disassemble code while replaying, but not to print variables.
7691 In some cases, being able to inspect variables might be useful.
7692 You can use the following command for that:
7694 @item set record btrace replay-memory-access
7695 Control the behavior of the @code{btrace} recording method when
7696 accessing memory during replay. If @code{read-only} (the default),
7697 @value{GDBN} will only allow accesses to read-only memory.
7698 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7699 and to read-write memory. Beware that the accessed memory corresponds
7700 to the live target and not necessarily to the current replay
7703 @item set record btrace cpu @var{identifier}
7704 Set the processor to be used for enabling workarounds for processor
7705 errata when decoding the trace.
7707 Processor errata are defects in processor operation, caused by its
7708 design or manufacture. They can cause a trace not to match the
7709 specification. This, in turn, may cause trace decode to fail.
7710 @value{GDBN} can detect erroneous trace packets and correct them, thus
7711 avoiding the decoding failures. These corrections are known as
7712 @dfn{errata workarounds}, and are enabled based on the processor on
7713 which the trace was recorded.
7715 By default, @value{GDBN} attempts to detect the processor
7716 automatically, and apply the necessary workarounds for it. However,
7717 you may need to specify the processor if @value{GDBN} does not yet
7718 support it. This command allows you to do that, and also allows to
7719 disable the workarounds.
7721 The argument @var{identifier} identifies the @sc{cpu} and is of the
7722 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7723 there are two special identifiers, @code{none} and @code{auto}
7726 The following vendor identifiers and corresponding processor
7727 identifiers are currently supported:
7729 @multitable @columnfractions .1 .9
7732 @tab @var{family}/@var{model}[/@var{stepping}]
7736 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7737 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7739 If @var{identifier} is @code{auto}, enable errata workarounds for the
7740 processor on which the trace was recorded. If @var{identifier} is
7741 @code{none}, errata workarounds are disabled.
7743 For example, when using an old @value{GDBN} on a new system, decode
7744 may fail because @value{GDBN} does not support the new processor. It
7745 often suffices to specify an older processor that @value{GDBN}
7750 Active record target: record-btrace
7751 Recording format: Intel Processor Trace.
7753 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7754 (gdb) set record btrace cpu intel:6/158
7756 Active record target: record-btrace
7757 Recording format: Intel Processor Trace.
7759 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7762 @kindex show record btrace
7763 @item show record btrace replay-memory-access
7764 Show the current setting of @code{replay-memory-access}.
7766 @item show record btrace cpu
7767 Show the processor to be used for enabling trace decode errata
7770 @kindex set record btrace bts
7771 @item set record btrace bts buffer-size @var{size}
7772 @itemx set record btrace bts buffer-size unlimited
7773 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7774 format. Default is 64KB.
7776 If @var{size} is a positive number, then @value{GDBN} will try to
7777 allocate a buffer of at least @var{size} bytes for each new thread
7778 that uses the btrace recording method and the @acronym{BTS} format.
7779 The actually obtained buffer size may differ from the requested
7780 @var{size}. Use the @code{info record} command to see the actual
7781 buffer size for each thread that uses the btrace recording method and
7782 the @acronym{BTS} format.
7784 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7785 allocate a buffer of 4MB.
7787 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7788 also need longer to process the branch trace data before it can be used.
7790 @item show record btrace bts buffer-size @var{size}
7791 Show the current setting of the requested ring buffer size for branch
7792 tracing in @acronym{BTS} format.
7794 @kindex set record btrace pt
7795 @item set record btrace pt buffer-size @var{size}
7796 @itemx set record btrace pt buffer-size unlimited
7797 Set the requested ring buffer size for branch tracing in Intel
7798 Processor Trace format. Default is 16KB.
7800 If @var{size} is a positive number, then @value{GDBN} will try to
7801 allocate a buffer of at least @var{size} bytes for each new thread
7802 that uses the btrace recording method and the Intel Processor Trace
7803 format. The actually obtained buffer size may differ from the
7804 requested @var{size}. Use the @code{info record} command to see the
7805 actual buffer size for each thread.
7807 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7808 allocate a buffer of 4MB.
7810 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7811 also need longer to process the branch trace data before it can be used.
7813 @item show record btrace pt buffer-size @var{size}
7814 Show the current setting of the requested ring buffer size for branch
7815 tracing in Intel Processor Trace format.
7819 Show various statistics about the recording depending on the recording
7824 For the @code{full} recording method, it shows the state of process
7825 record and its in-memory execution log buffer, including:
7829 Whether in record mode or replay mode.
7831 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7833 Highest recorded instruction number.
7835 Current instruction about to be replayed (if in replay mode).
7837 Number of instructions contained in the execution log.
7839 Maximum number of instructions that may be contained in the execution log.
7843 For the @code{btrace} recording method, it shows:
7849 Number of instructions that have been recorded.
7851 Number of blocks of sequential control-flow formed by the recorded
7854 Whether in record mode or replay mode.
7857 For the @code{bts} recording format, it also shows:
7860 Size of the perf ring buffer.
7863 For the @code{pt} recording format, it also shows:
7866 Size of the perf ring buffer.
7870 @kindex record delete
7873 When record target runs in replay mode (``in the past''), delete the
7874 subsequent execution log and begin to record a new execution log starting
7875 from the current address. This means you will abandon the previously
7876 recorded ``future'' and begin recording a new ``future''.
7878 @kindex record instruction-history
7879 @kindex rec instruction-history
7880 @item record instruction-history
7881 Disassembles instructions from the recorded execution log. By
7882 default, ten instructions are disassembled. This can be changed using
7883 the @code{set record instruction-history-size} command. Instructions
7884 are printed in execution order.
7886 It can also print mixed source+disassembly if you specify the the
7887 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7888 as well as in symbolic form by specifying the @code{/r} modifier.
7890 The current position marker is printed for the instruction at the
7891 current program counter value. This instruction can appear multiple
7892 times in the trace and the current position marker will be printed
7893 every time. To omit the current position marker, specify the
7896 To better align the printed instructions when the trace contains
7897 instructions from more than one function, the function name may be
7898 omitted by specifying the @code{/f} modifier.
7900 Speculatively executed instructions are prefixed with @samp{?}. This
7901 feature is not available for all recording formats.
7903 There are several ways to specify what part of the execution log to
7907 @item record instruction-history @var{insn}
7908 Disassembles ten instructions starting from instruction number
7911 @item record instruction-history @var{insn}, +/-@var{n}
7912 Disassembles @var{n} instructions around instruction number
7913 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7914 @var{n} instructions after instruction number @var{insn}. If
7915 @var{n} is preceded with @code{-}, disassembles @var{n}
7916 instructions before instruction number @var{insn}.
7918 @item record instruction-history
7919 Disassembles ten more instructions after the last disassembly.
7921 @item record instruction-history -
7922 Disassembles ten more instructions before the last disassembly.
7924 @item record instruction-history @var{begin}, @var{end}
7925 Disassembles instructions beginning with instruction number
7926 @var{begin} until instruction number @var{end}. The instruction
7927 number @var{end} is included.
7930 This command may not be available for all recording methods.
7933 @item set record instruction-history-size @var{size}
7934 @itemx set record instruction-history-size unlimited
7935 Define how many instructions to disassemble in the @code{record
7936 instruction-history} command. The default value is 10.
7937 A @var{size} of @code{unlimited} means unlimited instructions.
7940 @item show record instruction-history-size
7941 Show how many instructions to disassemble in the @code{record
7942 instruction-history} command.
7944 @kindex record function-call-history
7945 @kindex rec function-call-history
7946 @item record function-call-history
7947 Prints the execution history at function granularity. For each sequence
7948 of instructions that belong to the same function, it prints the name of
7949 that function, the source lines for this instruction sequence (if the
7950 @code{/l} modifier is specified), and the instructions numbers that form
7951 the sequence (if the @code{/i} modifier is specified). The function names
7952 are indented to reflect the call stack depth if the @code{/c} modifier is
7953 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7957 (@value{GDBP}) @b{list 1, 10}
7968 (@value{GDBP}) @b{record function-call-history /ilc}
7969 1 bar inst 1,4 at foo.c:6,8
7970 2 foo inst 5,10 at foo.c:2,3
7971 3 bar inst 11,13 at foo.c:9,10
7974 By default, ten functions are printed. This can be changed using the
7975 @code{set record function-call-history-size} command. Functions are
7976 printed in execution order. There are several ways to specify what
7980 @item record function-call-history @var{func}
7981 Prints ten functions starting from function number @var{func}.
7983 @item record function-call-history @var{func}, +/-@var{n}
7984 Prints @var{n} functions around function number @var{func}. If
7985 @var{n} is preceded with @code{+}, prints @var{n} functions after
7986 function number @var{func}. If @var{n} is preceded with @code{-},
7987 prints @var{n} functions before function number @var{func}.
7989 @item record function-call-history
7990 Prints ten more functions after the last ten-function print.
7992 @item record function-call-history -
7993 Prints ten more functions before the last ten-function print.
7995 @item record function-call-history @var{begin}, @var{end}
7996 Prints functions beginning with function number @var{begin} until
7997 function number @var{end}. The function number @var{end} is included.
8000 This command may not be available for all recording methods.
8002 @item set record function-call-history-size @var{size}
8003 @itemx set record function-call-history-size unlimited
8004 Define how many functions to print in the
8005 @code{record function-call-history} command. The default value is 10.
8006 A size of @code{unlimited} means unlimited functions.
8008 @item show record function-call-history-size
8009 Show how many functions to print in the
8010 @code{record function-call-history} command.
8015 @chapter Examining the Stack
8017 When your program has stopped, the first thing you need to know is where it
8018 stopped and how it got there.
8021 Each time your program performs a function call, information about the call
8023 That information includes the location of the call in your program,
8024 the arguments of the call,
8025 and the local variables of the function being called.
8026 The information is saved in a block of data called a @dfn{stack frame}.
8027 The stack frames are allocated in a region of memory called the @dfn{call
8030 When your program stops, the @value{GDBN} commands for examining the
8031 stack allow you to see all of this information.
8033 @cindex selected frame
8034 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8035 @value{GDBN} commands refer implicitly to the selected frame. In
8036 particular, whenever you ask @value{GDBN} for the value of a variable in
8037 your program, the value is found in the selected frame. There are
8038 special @value{GDBN} commands to select whichever frame you are
8039 interested in. @xref{Selection, ,Selecting a Frame}.
8041 When your program stops, @value{GDBN} automatically selects the
8042 currently executing frame and describes it briefly, similar to the
8043 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8046 * Frames:: Stack frames
8047 * Backtrace:: Backtraces
8048 * Selection:: Selecting a frame
8049 * Frame Info:: Information on a frame
8050 * Frame Apply:: Applying a command to several frames
8051 * Frame Filter Management:: Managing frame filters
8056 @section Stack Frames
8058 @cindex frame, definition
8060 The call stack is divided up into contiguous pieces called @dfn{stack
8061 frames}, or @dfn{frames} for short; each frame is the data associated
8062 with one call to one function. The frame contains the arguments given
8063 to the function, the function's local variables, and the address at
8064 which the function is executing.
8066 @cindex initial frame
8067 @cindex outermost frame
8068 @cindex innermost frame
8069 When your program is started, the stack has only one frame, that of the
8070 function @code{main}. This is called the @dfn{initial} frame or the
8071 @dfn{outermost} frame. Each time a function is called, a new frame is
8072 made. Each time a function returns, the frame for that function invocation
8073 is eliminated. If a function is recursive, there can be many frames for
8074 the same function. The frame for the function in which execution is
8075 actually occurring is called the @dfn{innermost} frame. This is the most
8076 recently created of all the stack frames that still exist.
8078 @cindex frame pointer
8079 Inside your program, stack frames are identified by their addresses. A
8080 stack frame consists of many bytes, each of which has its own address; each
8081 kind of computer has a convention for choosing one byte whose
8082 address serves as the address of the frame. Usually this address is kept
8083 in a register called the @dfn{frame pointer register}
8084 (@pxref{Registers, $fp}) while execution is going on in that frame.
8087 @cindex frame number
8088 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8089 number that is zero for the innermost frame, one for the frame that
8090 called it, and so on upward. These level numbers give you a way of
8091 designating stack frames in @value{GDBN} commands. The terms
8092 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8093 describe this number.
8095 @c The -fomit-frame-pointer below perennially causes hbox overflow
8096 @c underflow problems.
8097 @cindex frameless execution
8098 Some compilers provide a way to compile functions so that they operate
8099 without stack frames. (For example, the @value{NGCC} option
8101 @samp{-fomit-frame-pointer}
8103 generates functions without a frame.)
8104 This is occasionally done with heavily used library functions to save
8105 the frame setup time. @value{GDBN} has limited facilities for dealing
8106 with these function invocations. If the innermost function invocation
8107 has no stack frame, @value{GDBN} nevertheless regards it as though
8108 it had a separate frame, which is numbered zero as usual, allowing
8109 correct tracing of the function call chain. However, @value{GDBN} has
8110 no provision for frameless functions elsewhere in the stack.
8116 @cindex call stack traces
8117 A backtrace is a summary of how your program got where it is. It shows one
8118 line per frame, for many frames, starting with the currently executing
8119 frame (frame zero), followed by its caller (frame one), and on up the
8122 @anchor{backtrace-command}
8124 @kindex bt @r{(@code{backtrace})}
8125 To print a backtrace of the entire stack, use the @code{backtrace}
8126 command, or its alias @code{bt}. This command will print one line per
8127 frame for frames in the stack. By default, all stack frames are
8128 printed. You can stop the backtrace at any time by typing the system
8129 interrupt character, normally @kbd{Ctrl-c}.
8132 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8133 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8134 Print the backtrace of the entire stack.
8136 The optional @var{count} can be one of the following:
8141 Print only the innermost @var{n} frames, where @var{n} is a positive
8146 Print only the outermost @var{n} frames, where @var{n} is a positive
8154 Print the values of the local variables also. This can be combined
8155 with the optional @var{count} to limit the number of frames shown.
8158 Do not run Python frame filters on this backtrace. @xref{Frame
8159 Filter API}, for more information. Additionally use @ref{disable
8160 frame-filter all} to turn off all frame filters. This is only
8161 relevant when @value{GDBN} has been configured with @code{Python}
8165 A Python frame filter might decide to ``elide'' some frames. Normally
8166 such elided frames are still printed, but they are indented relative
8167 to the filtered frames that cause them to be elided. The @code{-hide}
8168 option causes elided frames to not be printed at all.
8171 The @code{backtrace} command also supports a number of options that
8172 allow overriding relevant global print settings as set by @code{set
8173 backtrace} and @code{set print} subcommands:
8176 @item -past-main [@code{on}|@code{off}]
8177 Set whether backtraces should continue past @code{main}. Related setting:
8178 @ref{set backtrace past-main}.
8180 @item -past-entry [@code{on}|@code{off}]
8181 Set whether backtraces should continue past the entry point of a program.
8182 Related setting: @ref{set backtrace past-entry}.
8184 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8185 Set printing of function arguments at function entry.
8186 Related setting: @ref{set print entry-values}.
8188 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8189 Set printing of non-scalar frame arguments.
8190 Related setting: @ref{set print frame-arguments}.
8192 @item -raw-frame-arguments [@code{on}|@code{off}]
8193 Set whether to print frame arguments in raw form.
8194 Related setting: @ref{set print raw-frame-arguments}.
8196 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8197 Set printing of frame information.
8198 Related setting: @ref{set print frame-info}.
8201 The optional @var{qualifier} is maintained for backward compatibility.
8202 It can be one of the following:
8206 Equivalent to the @code{-full} option.
8209 Equivalent to the @code{-no-filters} option.
8212 Equivalent to the @code{-hide} option.
8219 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8220 are additional aliases for @code{backtrace}.
8222 @cindex multiple threads, backtrace
8223 In a multi-threaded program, @value{GDBN} by default shows the
8224 backtrace only for the current thread. To display the backtrace for
8225 several or all of the threads, use the command @code{thread apply}
8226 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8227 apply all backtrace}, @value{GDBN} will display the backtrace for all
8228 the threads; this is handy when you debug a core dump of a
8229 multi-threaded program.
8231 Each line in the backtrace shows the frame number and the function name.
8232 The program counter value is also shown---unless you use @code{set
8233 print address off}. The backtrace also shows the source file name and
8234 line number, as well as the arguments to the function. The program
8235 counter value is omitted if it is at the beginning of the code for that
8238 Here is an example of a backtrace. It was made with the command
8239 @samp{bt 3}, so it shows the innermost three frames.
8243 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8245 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8246 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8248 (More stack frames follow...)
8253 The display for frame zero does not begin with a program counter
8254 value, indicating that your program has stopped at the beginning of the
8255 code for line @code{993} of @code{builtin.c}.
8258 The value of parameter @code{data} in frame 1 has been replaced by
8259 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8260 only if it is a scalar (integer, pointer, enumeration, etc). See command
8261 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8262 on how to configure the way function parameter values are printed.
8263 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8264 what frame information is printed.
8266 @cindex optimized out, in backtrace
8267 @cindex function call arguments, optimized out
8268 If your program was compiled with optimizations, some compilers will
8269 optimize away arguments passed to functions if those arguments are
8270 never used after the call. Such optimizations generate code that
8271 passes arguments through registers, but doesn't store those arguments
8272 in the stack frame. @value{GDBN} has no way of displaying such
8273 arguments in stack frames other than the innermost one. Here's what
8274 such a backtrace might look like:
8278 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8280 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8281 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8283 (More stack frames follow...)
8288 The values of arguments that were not saved in their stack frames are
8289 shown as @samp{<optimized out>}.
8291 If you need to display the values of such optimized-out arguments,
8292 either deduce that from other variables whose values depend on the one
8293 you are interested in, or recompile without optimizations.
8295 @cindex backtrace beyond @code{main} function
8296 @cindex program entry point
8297 @cindex startup code, and backtrace
8298 Most programs have a standard user entry point---a place where system
8299 libraries and startup code transition into user code. For C this is
8300 @code{main}@footnote{
8301 Note that embedded programs (the so-called ``free-standing''
8302 environment) are not required to have a @code{main} function as the
8303 entry point. They could even have multiple entry points.}.
8304 When @value{GDBN} finds the entry function in a backtrace
8305 it will terminate the backtrace, to avoid tracing into highly
8306 system-specific (and generally uninteresting) code.
8308 If you need to examine the startup code, or limit the number of levels
8309 in a backtrace, you can change this behavior:
8312 @item set backtrace past-main
8313 @itemx set backtrace past-main on
8314 @anchor{set backtrace past-main}
8315 @kindex set backtrace
8316 Backtraces will continue past the user entry point.
8318 @item set backtrace past-main off
8319 Backtraces will stop when they encounter the user entry point. This is the
8322 @item show backtrace past-main
8323 @kindex show backtrace
8324 Display the current user entry point backtrace policy.
8326 @item set backtrace past-entry
8327 @itemx set backtrace past-entry on
8328 @anchor{set backtrace past-entry}
8329 Backtraces will continue past the internal entry point of an application.
8330 This entry point is encoded by the linker when the application is built,
8331 and is likely before the user entry point @code{main} (or equivalent) is called.
8333 @item set backtrace past-entry off
8334 Backtraces will stop when they encounter the internal entry point of an
8335 application. This is the default.
8337 @item show backtrace past-entry
8338 Display the current internal entry point backtrace policy.
8340 @item set backtrace limit @var{n}
8341 @itemx set backtrace limit 0
8342 @itemx set backtrace limit unlimited
8343 @anchor{set backtrace limit}
8344 @cindex backtrace limit
8345 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8346 or zero means unlimited levels.
8348 @item show backtrace limit
8349 Display the current limit on backtrace levels.
8352 You can control how file names are displayed.
8355 @item set filename-display
8356 @itemx set filename-display relative
8357 @cindex filename-display
8358 Display file names relative to the compilation directory. This is the default.
8360 @item set filename-display basename
8361 Display only basename of a filename.
8363 @item set filename-display absolute
8364 Display an absolute filename.
8366 @item show filename-display
8367 Show the current way to display filenames.
8371 @section Selecting a Frame
8373 Most commands for examining the stack and other data in your program work on
8374 whichever stack frame is selected at the moment. Here are the commands for
8375 selecting a stack frame; all of them finish by printing a brief description
8376 of the stack frame just selected.
8379 @kindex frame@r{, selecting}
8380 @kindex f @r{(@code{frame})}
8381 @item frame @r{[} @var{frame-selection-spec} @r{]}
8382 @item f @r{[} @var{frame-selection-spec} @r{]}
8383 The @command{frame} command allows different stack frames to be
8384 selected. The @var{frame-selection-spec} can be any of the following:
8389 @item level @var{num}
8390 Select frame level @var{num}. Recall that frame zero is the innermost
8391 (currently executing) frame, frame one is the frame that called the
8392 innermost one, and so on. The highest level frame is usually the one
8395 As this is the most common method of navigating the frame stack, the
8396 string @command{level} can be omitted. For example, the following two
8397 commands are equivalent:
8400 (@value{GDBP}) frame 3
8401 (@value{GDBP}) frame level 3
8404 @kindex frame address
8405 @item address @var{stack-address}
8406 Select the frame with stack address @var{stack-address}. The
8407 @var{stack-address} for a frame can be seen in the output of
8408 @command{info frame}, for example:
8412 Stack level 1, frame at 0x7fffffffda30:
8413 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8414 tail call frame, caller of frame at 0x7fffffffda30
8415 source language c++.
8416 Arglist at unknown address.
8417 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8420 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8421 indicated by the line:
8424 Stack level 1, frame at 0x7fffffffda30:
8427 @kindex frame function
8428 @item function @var{function-name}
8429 Select the stack frame for function @var{function-name}. If there are
8430 multiple stack frames for function @var{function-name} then the inner
8431 most stack frame is selected.
8434 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8435 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8436 viewed has stack address @var{stack-addr}, and optionally, a program
8437 counter address of @var{pc-addr}.
8439 This is useful mainly if the chaining of stack frames has been
8440 damaged by a bug, making it impossible for @value{GDBN} to assign
8441 numbers properly to all frames. In addition, this can be useful
8442 when your program has multiple stacks and switches between them.
8444 When viewing a frame outside the current backtrace using
8445 @command{frame view} then you can always return to the original
8446 stack using one of the previous stack frame selection instructions,
8447 for example @command{frame level 0}.
8453 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8454 numbers @var{n}, this advances toward the outermost frame, to higher
8455 frame numbers, to frames that have existed longer.
8458 @kindex do @r{(@code{down})}
8460 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8461 positive numbers @var{n}, this advances toward the innermost frame, to
8462 lower frame numbers, to frames that were created more recently.
8463 You may abbreviate @code{down} as @code{do}.
8466 All of these commands end by printing two lines of output describing the
8467 frame. The first line shows the frame number, the function name, the
8468 arguments, and the source file and line number of execution in that
8469 frame. The second line shows the text of that source line.
8477 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8479 10 read_input_file (argv[i]);
8483 After such a printout, the @code{list} command with no arguments
8484 prints ten lines centered on the point of execution in the frame.
8485 You can also edit the program at the point of execution with your favorite
8486 editing program by typing @code{edit}.
8487 @xref{List, ,Printing Source Lines},
8491 @kindex select-frame
8492 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8493 The @code{select-frame} command is a variant of @code{frame} that does
8494 not display the new frame after selecting it. This command is
8495 intended primarily for use in @value{GDBN} command scripts, where the
8496 output might be unnecessary and distracting. The
8497 @var{frame-selection-spec} is as for the @command{frame} command
8498 described in @ref{Selection, ,Selecting a Frame}.
8500 @kindex down-silently
8502 @item up-silently @var{n}
8503 @itemx down-silently @var{n}
8504 These two commands are variants of @code{up} and @code{down},
8505 respectively; they differ in that they do their work silently, without
8506 causing display of the new frame. They are intended primarily for use
8507 in @value{GDBN} command scripts, where the output might be unnecessary and
8512 @section Information About a Frame
8514 There are several other commands to print information about the selected
8520 When used without any argument, this command does not change which
8521 frame is selected, but prints a brief description of the currently
8522 selected stack frame. It can be abbreviated @code{f}. With an
8523 argument, this command is used to select a stack frame.
8524 @xref{Selection, ,Selecting a Frame}.
8527 @kindex info f @r{(@code{info frame})}
8530 This command prints a verbose description of the selected stack frame,
8535 the address of the frame
8537 the address of the next frame down (called by this frame)
8539 the address of the next frame up (caller of this frame)
8541 the language in which the source code corresponding to this frame is written
8543 the address of the frame's arguments
8545 the address of the frame's local variables
8547 the program counter saved in it (the address of execution in the caller frame)
8549 which registers were saved in the frame
8552 @noindent The verbose description is useful when
8553 something has gone wrong that has made the stack format fail to fit
8554 the usual conventions.
8556 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8557 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8558 Print a verbose description of the frame selected by
8559 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8560 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8561 a Frame}). The selected frame remains unchanged by this command.
8564 @item info args [-q]
8565 Print the arguments of the selected frame, each on a separate line.
8567 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8568 printing header information and messages explaining why no argument
8571 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8572 Like @kbd{info args}, but only print the arguments selected
8573 with the provided regexp(s).
8575 If @var{regexp} is provided, print only the arguments whose names
8576 match the regular expression @var{regexp}.
8578 If @var{type_regexp} is provided, print only the arguments whose
8579 types, as printed by the @code{whatis} command, match
8580 the regular expression @var{type_regexp}.
8581 If @var{type_regexp} contains space(s), it should be enclosed in
8582 quote characters. If needed, use backslash to escape the meaning
8583 of special characters or quotes.
8585 If both @var{regexp} and @var{type_regexp} are provided, an argument
8586 is printed only if its name matches @var{regexp} and its type matches
8589 @item info locals [-q]
8591 Print the local variables of the selected frame, each on a separate
8592 line. These are all variables (declared either static or automatic)
8593 accessible at the point of execution of the selected frame.
8595 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8596 printing header information and messages explaining why no local variables
8599 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8600 Like @kbd{info locals}, but only print the local variables selected
8601 with the provided regexp(s).
8603 If @var{regexp} is provided, print only the local variables whose names
8604 match the regular expression @var{regexp}.
8606 If @var{type_regexp} is provided, print only the local variables whose
8607 types, as printed by the @code{whatis} command, match
8608 the regular expression @var{type_regexp}.
8609 If @var{type_regexp} contains space(s), it should be enclosed in
8610 quote characters. If needed, use backslash to escape the meaning
8611 of special characters or quotes.
8613 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8614 is printed only if its name matches @var{regexp} and its type matches
8617 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8618 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8619 For example, your program might use Resource Acquisition Is
8620 Initialization types (RAII) such as @code{lock_something_t}: each
8621 local variable of type @code{lock_something_t} automatically places a
8622 lock that is destroyed when the variable goes out of scope. You can
8623 then list all acquired locks in your program by doing
8625 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8628 or the equivalent shorter form
8630 tfaas i lo -q -t lock_something_t
8636 @section Applying a Command to Several Frames.
8638 @cindex apply command to several frames
8640 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8641 The @code{frame apply} command allows you to apply the named
8642 @var{command} to one or more frames.
8646 Specify @code{all} to apply @var{command} to all frames.
8649 Use @var{count} to apply @var{command} to the innermost @var{count}
8650 frames, where @var{count} is a positive number.
8653 Use @var{-count} to apply @var{command} to the outermost @var{count}
8654 frames, where @var{count} is a positive number.
8657 Use @code{level} to apply @var{command} to the set of frames identified
8658 by the @var{level} list. @var{level} is a frame level or a range of frame
8659 levels as @var{level1}-@var{level2}. The frame level is the number shown
8660 in the first field of the @samp{backtrace} command output.
8661 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8662 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8666 Note that the frames on which @code{frame apply} applies a command are
8667 also influenced by the @code{set backtrace} settings such as @code{set
8668 backtrace past-main} and @code{set backtrace limit N}.
8669 @xref{Backtrace,,Backtraces}.
8671 The @code{frame apply} command also supports a number of options that
8672 allow overriding relevant @code{set backtrace} settings:
8675 @item -past-main [@code{on}|@code{off}]
8676 Whether backtraces should continue past @code{main}.
8677 Related setting: @ref{set backtrace past-main}.
8679 @item -past-entry [@code{on}|@code{off}]
8680 Whether backtraces should continue past the entry point of a program.
8681 Related setting: @ref{set backtrace past-entry}.
8684 By default, @value{GDBN} displays some frame information before the
8685 output produced by @var{command}, and an error raised during the
8686 execution of a @var{command} will abort @code{frame apply}. The
8687 following options can be used to fine-tune these behaviors:
8691 The flag @code{-c}, which stands for @samp{continue}, causes any
8692 errors in @var{command} to be displayed, and the execution of
8693 @code{frame apply} then continues.
8695 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8696 or empty output produced by a @var{command} to be silently ignored.
8697 That is, the execution continues, but the frame information and errors
8700 The flag @code{-q} (@samp{quiet}) disables printing the frame
8704 The following example shows how the flags @code{-c} and @code{-s} are
8705 working when applying the command @code{p j} to all frames, where
8706 variable @code{j} can only be successfully printed in the outermost
8707 @code{#1 main} frame.
8711 (gdb) frame apply all p j
8712 #0 some_function (i=5) at fun.c:4
8713 No symbol "j" in current context.
8714 (gdb) frame apply all -c p j
8715 #0 some_function (i=5) at fun.c:4
8716 No symbol "j" in current context.
8717 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8719 (gdb) frame apply all -s p j
8720 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8726 By default, @samp{frame apply}, prints the frame location
8727 information before the command output:
8731 (gdb) frame apply all p $sp
8732 #0 some_function (i=5) at fun.c:4
8733 $4 = (void *) 0xffffd1e0
8734 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8735 $5 = (void *) 0xffffd1f0
8740 If the flag @code{-q} is given, no frame information is printed:
8743 (gdb) frame apply all -q p $sp
8744 $12 = (void *) 0xffffd1e0
8745 $13 = (void *) 0xffffd1f0
8755 @cindex apply a command to all frames (ignoring errors and empty output)
8756 @item faas @var{command}
8757 Shortcut for @code{frame apply all -s @var{command}}.
8758 Applies @var{command} on all frames, ignoring errors and empty output.
8760 It can for example be used to print a local variable or a function
8761 argument without knowing the frame where this variable or argument
8764 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8767 The @code{faas} command accepts the same options as the @code{frame
8768 apply} command. @xref{Frame Apply,,frame apply}.
8770 Note that the command @code{tfaas @var{command}} applies @var{command}
8771 on all frames of all threads. See @xref{Threads,,Threads}.
8775 @node Frame Filter Management
8776 @section Management of Frame Filters.
8777 @cindex managing frame filters
8779 Frame filters are Python based utilities to manage and decorate the
8780 output of frames. @xref{Frame Filter API}, for further information.
8782 Managing frame filters is performed by several commands available
8783 within @value{GDBN}, detailed here.
8786 @kindex info frame-filter
8787 @item info frame-filter
8788 Print a list of installed frame filters from all dictionaries, showing
8789 their name, priority and enabled status.
8791 @kindex disable frame-filter
8792 @anchor{disable frame-filter all}
8793 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8794 Disable a frame filter in the dictionary matching
8795 @var{filter-dictionary} and @var{filter-name}. The
8796 @var{filter-dictionary} may be @code{all}, @code{global},
8797 @code{progspace}, or the name of the object file where the frame filter
8798 dictionary resides. When @code{all} is specified, all frame filters
8799 across all dictionaries are disabled. The @var{filter-name} is the name
8800 of the frame filter and is used when @code{all} is not the option for
8801 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8802 may be enabled again later.
8804 @kindex enable frame-filter
8805 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8806 Enable a frame filter in the dictionary matching
8807 @var{filter-dictionary} and @var{filter-name}. The
8808 @var{filter-dictionary} may be @code{all}, @code{global},
8809 @code{progspace} or the name of the object file where the frame filter
8810 dictionary resides. When @code{all} is specified, all frame filters across
8811 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8812 filter and is used when @code{all} is not the option for
8813 @var{filter-dictionary}.
8818 (gdb) info frame-filter
8820 global frame-filters:
8821 Priority Enabled Name
8822 1000 No PrimaryFunctionFilter
8825 progspace /build/test frame-filters:
8826 Priority Enabled Name
8827 100 Yes ProgspaceFilter
8829 objfile /build/test frame-filters:
8830 Priority Enabled Name
8831 999 Yes BuildProgramFilter
8833 (gdb) disable frame-filter /build/test BuildProgramFilter
8834 (gdb) info frame-filter
8836 global frame-filters:
8837 Priority Enabled Name
8838 1000 No PrimaryFunctionFilter
8841 progspace /build/test frame-filters:
8842 Priority Enabled Name
8843 100 Yes ProgspaceFilter
8845 objfile /build/test frame-filters:
8846 Priority Enabled Name
8847 999 No BuildProgramFilter
8849 (gdb) enable frame-filter global PrimaryFunctionFilter
8850 (gdb) info frame-filter
8852 global frame-filters:
8853 Priority Enabled Name
8854 1000 Yes PrimaryFunctionFilter
8857 progspace /build/test frame-filters:
8858 Priority Enabled Name
8859 100 Yes ProgspaceFilter
8861 objfile /build/test frame-filters:
8862 Priority Enabled Name
8863 999 No BuildProgramFilter
8866 @kindex set frame-filter priority
8867 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8868 Set the @var{priority} of a frame filter in the dictionary matching
8869 @var{filter-dictionary}, and the frame filter name matching
8870 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8871 @code{progspace} or the name of the object file where the frame filter
8872 dictionary resides. The @var{priority} is an integer.
8874 @kindex show frame-filter priority
8875 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8876 Show the @var{priority} of a frame filter in the dictionary matching
8877 @var{filter-dictionary}, and the frame filter name matching
8878 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8879 @code{progspace} or the name of the object file where the frame filter
8885 (gdb) info frame-filter
8887 global frame-filters:
8888 Priority Enabled Name
8889 1000 Yes PrimaryFunctionFilter
8892 progspace /build/test frame-filters:
8893 Priority Enabled Name
8894 100 Yes ProgspaceFilter
8896 objfile /build/test frame-filters:
8897 Priority Enabled Name
8898 999 No BuildProgramFilter
8900 (gdb) set frame-filter priority global Reverse 50
8901 (gdb) info frame-filter
8903 global frame-filters:
8904 Priority Enabled Name
8905 1000 Yes PrimaryFunctionFilter
8908 progspace /build/test frame-filters:
8909 Priority Enabled Name
8910 100 Yes ProgspaceFilter
8912 objfile /build/test frame-filters:
8913 Priority Enabled Name
8914 999 No BuildProgramFilter
8919 @chapter Examining Source Files
8921 @value{GDBN} can print parts of your program's source, since the debugging
8922 information recorded in the program tells @value{GDBN} what source files were
8923 used to build it. When your program stops, @value{GDBN} spontaneously prints
8924 the line where it stopped. Likewise, when you select a stack frame
8925 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8926 execution in that frame has stopped. You can print other portions of
8927 source files by explicit command.
8929 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8930 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8931 @value{GDBN} under @sc{gnu} Emacs}.
8934 * List:: Printing source lines
8935 * Specify Location:: How to specify code locations
8936 * Edit:: Editing source files
8937 * Search:: Searching source files
8938 * Source Path:: Specifying source directories
8939 * Machine Code:: Source and machine code
8940 * Disable Reading Source:: Disable Reading Source Code
8944 @section Printing Source Lines
8947 @kindex l @r{(@code{list})}
8948 To print lines from a source file, use the @code{list} command
8949 (abbreviated @code{l}). By default, ten lines are printed.
8950 There are several ways to specify what part of the file you want to
8951 print; see @ref{Specify Location}, for the full list.
8953 Here are the forms of the @code{list} command most commonly used:
8956 @item list @var{linenum}
8957 Print lines centered around line number @var{linenum} in the
8958 current source file.
8960 @item list @var{function}
8961 Print lines centered around the beginning of function
8965 Print more lines. If the last lines printed were printed with a
8966 @code{list} command, this prints lines following the last lines
8967 printed; however, if the last line printed was a solitary line printed
8968 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8969 Stack}), this prints lines centered around that line.
8972 Print lines just before the lines last printed.
8975 @cindex @code{list}, how many lines to display
8976 By default, @value{GDBN} prints ten source lines with any of these forms of
8977 the @code{list} command. You can change this using @code{set listsize}:
8980 @kindex set listsize
8981 @item set listsize @var{count}
8982 @itemx set listsize unlimited
8983 Make the @code{list} command display @var{count} source lines (unless
8984 the @code{list} argument explicitly specifies some other number).
8985 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8987 @kindex show listsize
8989 Display the number of lines that @code{list} prints.
8992 Repeating a @code{list} command with @key{RET} discards the argument,
8993 so it is equivalent to typing just @code{list}. This is more useful
8994 than listing the same lines again. An exception is made for an
8995 argument of @samp{-}; that argument is preserved in repetition so that
8996 each repetition moves up in the source file.
8998 In general, the @code{list} command expects you to supply zero, one or two
8999 @dfn{locations}. Locations specify source lines; there are several ways
9000 of writing them (@pxref{Specify Location}), but the effect is always
9001 to specify some source line.
9003 Here is a complete description of the possible arguments for @code{list}:
9006 @item list @var{location}
9007 Print lines centered around the line specified by @var{location}.
9009 @item list @var{first},@var{last}
9010 Print lines from @var{first} to @var{last}. Both arguments are
9011 locations. When a @code{list} command has two locations, and the
9012 source file of the second location is omitted, this refers to
9013 the same source file as the first location.
9015 @item list ,@var{last}
9016 Print lines ending with @var{last}.
9018 @item list @var{first},
9019 Print lines starting with @var{first}.
9022 Print lines just after the lines last printed.
9025 Print lines just before the lines last printed.
9028 As described in the preceding table.
9031 @node Specify Location
9032 @section Specifying a Location
9033 @cindex specifying location
9035 @cindex source location
9037 Several @value{GDBN} commands accept arguments that specify a location
9038 of your program's code. Since @value{GDBN} is a source-level
9039 debugger, a location usually specifies some line in the source code.
9040 Locations may be specified using three different formats:
9041 linespec locations, explicit locations, or address locations.
9044 * Linespec Locations:: Linespec locations
9045 * Explicit Locations:: Explicit locations
9046 * Address Locations:: Address locations
9049 @node Linespec Locations
9050 @subsection Linespec Locations
9051 @cindex linespec locations
9053 A @dfn{linespec} is a colon-separated list of source location parameters such
9054 as file name, function name, etc. Here are all the different ways of
9055 specifying a linespec:
9059 Specifies the line number @var{linenum} of the current source file.
9062 @itemx +@var{offset}
9063 Specifies the line @var{offset} lines before or after the @dfn{current
9064 line}. For the @code{list} command, the current line is the last one
9065 printed; for the breakpoint commands, this is the line at which
9066 execution stopped in the currently selected @dfn{stack frame}
9067 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9068 used as the second of the two linespecs in a @code{list} command,
9069 this specifies the line @var{offset} lines up or down from the first
9072 @item @var{filename}:@var{linenum}
9073 Specifies the line @var{linenum} in the source file @var{filename}.
9074 If @var{filename} is a relative file name, then it will match any
9075 source file name with the same trailing components. For example, if
9076 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9077 name of @file{/build/trunk/gcc/expr.c}, but not
9078 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9080 @item @var{function}
9081 Specifies the line that begins the body of the function @var{function}.
9082 For example, in C, this is the line with the open brace.
9084 By default, in C@t{++} and Ada, @var{function} is interpreted as
9085 specifying all functions named @var{function} in all scopes. For
9086 C@t{++}, this means in all namespaces and classes. For Ada, this
9087 means in all packages.
9089 For example, assuming a program with C@t{++} symbols named
9090 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9091 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9093 Commands that accept a linespec let you override this with the
9094 @code{-qualified} option. For example, @w{@kbd{break -qualified
9095 func}} sets a breakpoint on a free-function named @code{func} ignoring
9096 any C@t{++} class methods and namespace functions called @code{func}.
9098 @xref{Explicit Locations}.
9100 @item @var{function}:@var{label}
9101 Specifies the line where @var{label} appears in @var{function}.
9103 @item @var{filename}:@var{function}
9104 Specifies the line that begins the body of the function @var{function}
9105 in the file @var{filename}. You only need the file name with a
9106 function name to avoid ambiguity when there are identically named
9107 functions in different source files.
9110 Specifies the line at which the label named @var{label} appears
9111 in the function corresponding to the currently selected stack frame.
9112 If there is no current selected stack frame (for instance, if the inferior
9113 is not running), then @value{GDBN} will not search for a label.
9115 @cindex breakpoint at static probe point
9116 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9117 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9118 applications to embed static probes. @xref{Static Probe Points}, for more
9119 information on finding and using static probes. This form of linespec
9120 specifies the location of such a static probe.
9122 If @var{objfile} is given, only probes coming from that shared library
9123 or executable matching @var{objfile} as a regular expression are considered.
9124 If @var{provider} is given, then only probes from that provider are considered.
9125 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9126 each one of those probes.
9129 @node Explicit Locations
9130 @subsection Explicit Locations
9131 @cindex explicit locations
9133 @dfn{Explicit locations} allow the user to directly specify the source
9134 location's parameters using option-value pairs.
9136 Explicit locations are useful when several functions, labels, or
9137 file names have the same name (base name for files) in the program's
9138 sources. In these cases, explicit locations point to the source
9139 line you meant more accurately and unambiguously. Also, using
9140 explicit locations might be faster in large programs.
9142 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9143 defined in the file named @file{foo} or the label @code{bar} in a function
9144 named @code{foo}. @value{GDBN} must search either the file system or
9145 the symbol table to know.
9147 The list of valid explicit location options is summarized in the
9151 @item -source @var{filename}
9152 The value specifies the source file name. To differentiate between
9153 files with the same base name, prepend as many directories as is necessary
9154 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9155 @value{GDBN} will use the first file it finds with the given base
9156 name. This option requires the use of either @code{-function} or @code{-line}.
9158 @item -function @var{function}
9159 The value specifies the name of a function. Operations
9160 on function locations unmodified by other options (such as @code{-label}
9161 or @code{-line}) refer to the line that begins the body of the function.
9162 In C, for example, this is the line with the open brace.
9164 By default, in C@t{++} and Ada, @var{function} is interpreted as
9165 specifying all functions named @var{function} in all scopes. For
9166 C@t{++}, this means in all namespaces and classes. For Ada, this
9167 means in all packages.
9169 For example, assuming a program with C@t{++} symbols named
9170 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9171 -function func}} and @w{@kbd{break -function B::func}} set a
9172 breakpoint on both symbols.
9174 You can use the @kbd{-qualified} flag to override this (see below).
9178 This flag makes @value{GDBN} interpret a function name specified with
9179 @kbd{-function} as a complete fully-qualified name.
9181 For example, assuming a C@t{++} program with symbols named
9182 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9183 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9185 (Note: the @kbd{-qualified} option can precede a linespec as well
9186 (@pxref{Linespec Locations}), so the particular example above could be
9187 simplified as @w{@kbd{break -qualified B::func}}.)
9189 @item -label @var{label}
9190 The value specifies the name of a label. When the function
9191 name is not specified, the label is searched in the function of the currently
9192 selected stack frame.
9194 @item -line @var{number}
9195 The value specifies a line offset for the location. The offset may either
9196 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9197 the command. When specified without any other options, the line offset is
9198 relative to the current line.
9201 Explicit location options may be abbreviated by omitting any non-unique
9202 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9204 @node Address Locations
9205 @subsection Address Locations
9206 @cindex address locations
9208 @dfn{Address locations} indicate a specific program address. They have
9209 the generalized form *@var{address}.
9211 For line-oriented commands, such as @code{list} and @code{edit}, this
9212 specifies a source line that contains @var{address}. For @code{break} and
9213 other breakpoint-oriented commands, this can be used to set breakpoints in
9214 parts of your program which do not have debugging information or
9217 Here @var{address} may be any expression valid in the current working
9218 language (@pxref{Languages, working language}) that specifies a code
9219 address. In addition, as a convenience, @value{GDBN} extends the
9220 semantics of expressions used in locations to cover several situations
9221 that frequently occur during debugging. Here are the various forms
9225 @item @var{expression}
9226 Any expression valid in the current working language.
9228 @item @var{funcaddr}
9229 An address of a function or procedure derived from its name. In C,
9230 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9231 simply the function's name @var{function} (and actually a special case
9232 of a valid expression). In Pascal and Modula-2, this is
9233 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9234 (although the Pascal form also works).
9236 This form specifies the address of the function's first instruction,
9237 before the stack frame and arguments have been set up.
9239 @item '@var{filename}':@var{funcaddr}
9240 Like @var{funcaddr} above, but also specifies the name of the source
9241 file explicitly. This is useful if the name of the function does not
9242 specify the function unambiguously, e.g., if there are several
9243 functions with identical names in different source files.
9247 @section Editing Source Files
9248 @cindex editing source files
9251 @kindex e @r{(@code{edit})}
9252 To edit the lines in a source file, use the @code{edit} command.
9253 The editing program of your choice
9254 is invoked with the current line set to
9255 the active line in the program.
9256 Alternatively, there are several ways to specify what part of the file you
9257 want to print if you want to see other parts of the program:
9260 @item edit @var{location}
9261 Edit the source file specified by @code{location}. Editing starts at
9262 that @var{location}, e.g., at the specified source line of the
9263 specified file. @xref{Specify Location}, for all the possible forms
9264 of the @var{location} argument; here are the forms of the @code{edit}
9265 command most commonly used:
9268 @item edit @var{number}
9269 Edit the current source file with @var{number} as the active line number.
9271 @item edit @var{function}
9272 Edit the file containing @var{function} at the beginning of its definition.
9277 @subsection Choosing your Editor
9278 You can customize @value{GDBN} to use any editor you want
9280 The only restriction is that your editor (say @code{ex}), recognizes the
9281 following command-line syntax:
9283 ex +@var{number} file
9285 The optional numeric value +@var{number} specifies the number of the line in
9286 the file where to start editing.}.
9287 By default, it is @file{@value{EDITOR}}, but you can change this
9288 by setting the environment variable @env{EDITOR} before using
9289 @value{GDBN}. For example, to configure @value{GDBN} to use the
9290 @code{vi} editor, you could use these commands with the @code{sh} shell:
9296 or in the @code{csh} shell,
9298 setenv EDITOR /usr/bin/vi
9303 @section Searching Source Files
9304 @cindex searching source files
9306 There are two commands for searching through the current source file for a
9311 @kindex forward-search
9312 @kindex fo @r{(@code{forward-search})}
9313 @item forward-search @var{regexp}
9314 @itemx search @var{regexp}
9315 The command @samp{forward-search @var{regexp}} checks each line,
9316 starting with the one following the last line listed, for a match for
9317 @var{regexp}. It lists the line that is found. You can use the
9318 synonym @samp{search @var{regexp}} or abbreviate the command name as
9321 @kindex reverse-search
9322 @item reverse-search @var{regexp}
9323 The command @samp{reverse-search @var{regexp}} checks each line, starting
9324 with the one before the last line listed and going backward, for a match
9325 for @var{regexp}. It lists the line that is found. You can abbreviate
9326 this command as @code{rev}.
9330 @section Specifying Source Directories
9333 @cindex directories for source files
9334 Executable programs sometimes do not record the directories of the source
9335 files from which they were compiled, just the names. Even when they do,
9336 the directories could be moved between the compilation and your debugging
9337 session. @value{GDBN} has a list of directories to search for source files;
9338 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9339 it tries all the directories in the list, in the order they are present
9340 in the list, until it finds a file with the desired name.
9342 For example, suppose an executable references the file
9343 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9344 directory, and the @dfn{source path} is @file{/mnt/cross}.
9345 @value{GDBN} would look for the source file in the following
9350 @item @file{/usr/src/foo-1.0/lib/foo.c}
9351 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9352 @item @file{/mnt/cross/foo.c}
9356 If the source file is not present at any of the above locations then
9357 an error is printed. @value{GDBN} does not look up the parts of the
9358 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9359 Likewise, the subdirectories of the source path are not searched: if
9360 the source path is @file{/mnt/cross}, and the binary refers to
9361 @file{foo.c}, @value{GDBN} would not find it under
9362 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9364 Plain file names, relative file names with leading directories, file
9365 names containing dots, etc.@: are all treated as described above,
9366 except that non-absolute file names are not looked up literally. If
9367 the @dfn{source path} is @file{/mnt/cross}, the source file is
9368 recorded as @file{../lib/foo.c}, and no compilation directory is
9369 recorded, then @value{GDBN} will search in the following locations:
9373 @item @file{/mnt/cross/../lib/foo.c}
9374 @item @file{/mnt/cross/foo.c}
9380 @vindex $cdir@r{, convenience variable}
9381 @vindex $cwd@r{, convenience variable}
9382 @cindex compilation directory
9383 @cindex current directory
9384 @cindex working directory
9385 @cindex directory, current
9386 @cindex directory, compilation
9387 The @dfn{source path} will always include two special entries
9388 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9389 (if one is recorded) and the current working directory respectively.
9391 @samp{$cdir} causes @value{GDBN} to search within the compilation
9392 directory, if one is recorded in the debug information. If no
9393 compilation directory is recorded in the debug information then
9394 @samp{$cdir} is ignored.
9396 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9397 current working directory as it changes during your @value{GDBN}
9398 session, while the latter is immediately expanded to the current
9399 directory at the time you add an entry to the source path.
9401 If a compilation directory is recorded in the debug information, and
9402 @value{GDBN} has not found the source file after the first search
9403 using @dfn{source path}, then @value{GDBN} will combine the
9404 compilation directory and the filename, and then search for the source
9405 file again using the @dfn{source path}.
9407 For example, if the executable records the source file as
9408 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9409 recorded as @file{/project/build}, and the @dfn{source path} is
9410 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9411 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9412 search for the source file in the following locations:
9416 @item @file{/usr/src/foo-1.0/lib/foo.c}
9417 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9418 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9419 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9420 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9421 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9422 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9423 @item @file{/mnt/cross/foo.c}
9424 @item @file{/project/build/foo.c}
9425 @item @file{/home/user/foo.c}
9429 If the file name in the previous example had been recorded in the
9430 executable as a relative path rather than an absolute path, then the
9431 first look up would not have occurred, but all of the remaining steps
9434 When searching for source files on MS-DOS and MS-Windows, where
9435 absolute paths start with a drive letter (e.g.@:
9436 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9437 from the file name before appending it to a search directory from
9438 @dfn{source path}; for instance if the executable references the
9439 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9440 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9441 locations for the source file:
9445 @item @file{C:/project/foo.c}
9446 @item @file{D:/mnt/cross/project/foo.c}
9447 @item @file{D:/mnt/cross/foo.c}
9451 Note that the executable search path is @emph{not} used to locate the
9454 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9455 any information it has cached about where source files are found and where
9456 each line is in the file.
9460 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9461 and @samp{$cwd}, in that order.
9462 To add other directories, use the @code{directory} command.
9464 The search path is used to find both program source files and @value{GDBN}
9465 script files (read using the @samp{-command} option and @samp{source} command).
9467 In addition to the source path, @value{GDBN} provides a set of commands
9468 that manage a list of source path substitution rules. A @dfn{substitution
9469 rule} specifies how to rewrite source directories stored in the program's
9470 debug information in case the sources were moved to a different
9471 directory between compilation and debugging. A rule is made of
9472 two strings, the first specifying what needs to be rewritten in
9473 the path, and the second specifying how it should be rewritten.
9474 In @ref{set substitute-path}, we name these two parts @var{from} and
9475 @var{to} respectively. @value{GDBN} does a simple string replacement
9476 of @var{from} with @var{to} at the start of the directory part of the
9477 source file name, and uses that result instead of the original file
9478 name to look up the sources.
9480 Using the previous example, suppose the @file{foo-1.0} tree has been
9481 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9482 @value{GDBN} to replace @file{/usr/src} in all source path names with
9483 @file{/mnt/cross}. The first lookup will then be
9484 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9485 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9486 substitution rule, use the @code{set substitute-path} command
9487 (@pxref{set substitute-path}).
9489 To avoid unexpected substitution results, a rule is applied only if the
9490 @var{from} part of the directory name ends at a directory separator.
9491 For instance, a rule substituting @file{/usr/source} into
9492 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9493 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9494 is applied only at the beginning of the directory name, this rule will
9495 not be applied to @file{/root/usr/source/baz.c} either.
9497 In many cases, you can achieve the same result using the @code{directory}
9498 command. However, @code{set substitute-path} can be more efficient in
9499 the case where the sources are organized in a complex tree with multiple
9500 subdirectories. With the @code{directory} command, you need to add each
9501 subdirectory of your project. If you moved the entire tree while
9502 preserving its internal organization, then @code{set substitute-path}
9503 allows you to direct the debugger to all the sources with one single
9506 @code{set substitute-path} is also more than just a shortcut command.
9507 The source path is only used if the file at the original location no
9508 longer exists. On the other hand, @code{set substitute-path} modifies
9509 the debugger behavior to look at the rewritten location instead. So, if
9510 for any reason a source file that is not relevant to your executable is
9511 located at the original location, a substitution rule is the only
9512 method available to point @value{GDBN} at the new location.
9514 @cindex @samp{--with-relocated-sources}
9515 @cindex default source path substitution
9516 You can configure a default source path substitution rule by
9517 configuring @value{GDBN} with the
9518 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9519 should be the name of a directory under @value{GDBN}'s configured
9520 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9521 directory names in debug information under @var{dir} will be adjusted
9522 automatically if the installed @value{GDBN} is moved to a new
9523 location. This is useful if @value{GDBN}, libraries or executables
9524 with debug information and corresponding source code are being moved
9528 @item directory @var{dirname} @dots{}
9529 @item dir @var{dirname} @dots{}
9530 Add directory @var{dirname} to the front of the source path. Several
9531 directory names may be given to this command, separated by @samp{:}
9532 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9533 part of absolute file names) or
9534 whitespace. You may specify a directory that is already in the source
9535 path; this moves it forward, so @value{GDBN} searches it sooner.
9537 The special strings @samp{$cdir} (to refer to the compilation
9538 directory, if one is recorded), and @samp{$cwd} (to refer to the
9539 current working directory) can also be included in the list of
9540 directories @var{dirname}. Though these will already be in the source
9541 path they will be moved forward in the list so @value{GDBN} searches
9545 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9547 @c RET-repeat for @code{directory} is explicitly disabled, but since
9548 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9550 @item set directories @var{path-list}
9551 @kindex set directories
9552 Set the source path to @var{path-list}.
9553 @samp{$cdir:$cwd} are added if missing.
9555 @item show directories
9556 @kindex show directories
9557 Print the source path: show which directories it contains.
9559 @anchor{set substitute-path}
9560 @item set substitute-path @var{from} @var{to}
9561 @kindex set substitute-path
9562 Define a source path substitution rule, and add it at the end of the
9563 current list of existing substitution rules. If a rule with the same
9564 @var{from} was already defined, then the old rule is also deleted.
9566 For example, if the file @file{/foo/bar/baz.c} was moved to
9567 @file{/mnt/cross/baz.c}, then the command
9570 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9574 will tell @value{GDBN} to replace @samp{/foo/bar} with
9575 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9576 @file{baz.c} even though it was moved.
9578 In the case when more than one substitution rule have been defined,
9579 the rules are evaluated one by one in the order where they have been
9580 defined. The first one matching, if any, is selected to perform
9583 For instance, if we had entered the following commands:
9586 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9587 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9591 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9592 @file{/mnt/include/defs.h} by using the first rule. However, it would
9593 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9594 @file{/mnt/src/lib/foo.c}.
9597 @item unset substitute-path [path]
9598 @kindex unset substitute-path
9599 If a path is specified, search the current list of substitution rules
9600 for a rule that would rewrite that path. Delete that rule if found.
9601 A warning is emitted by the debugger if no rule could be found.
9603 If no path is specified, then all substitution rules are deleted.
9605 @item show substitute-path [path]
9606 @kindex show substitute-path
9607 If a path is specified, then print the source path substitution rule
9608 which would rewrite that path, if any.
9610 If no path is specified, then print all existing source path substitution
9615 If your source path is cluttered with directories that are no longer of
9616 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9617 versions of source. You can correct the situation as follows:
9621 Use @code{directory} with no argument to reset the source path to its default value.
9624 Use @code{directory} with suitable arguments to reinstall the
9625 directories you want in the source path. You can add all the
9626 directories in one command.
9630 @section Source and Machine Code
9631 @cindex source line and its code address
9633 You can use the command @code{info line} to map source lines to program
9634 addresses (and vice versa), and the command @code{disassemble} to display
9635 a range of addresses as machine instructions. You can use the command
9636 @code{set disassemble-next-line} to set whether to disassemble next
9637 source line when execution stops. When run under @sc{gnu} Emacs
9638 mode, the @code{info line} command causes the arrow to point to the
9639 line specified. Also, @code{info line} prints addresses in symbolic form as
9645 @itemx info line @var{location}
9646 Print the starting and ending addresses of the compiled code for
9647 source line @var{location}. You can specify source lines in any of
9648 the ways documented in @ref{Specify Location}. With no @var{location}
9649 information about the current source line is printed.
9652 For example, we can use @code{info line} to discover the location of
9653 the object code for the first line of function
9654 @code{m4_changequote}:
9657 (@value{GDBP}) info line m4_changequote
9658 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9659 ends at 0x6350 <m4_changequote+4>.
9663 @cindex code address and its source line
9664 We can also inquire (using @code{*@var{addr}} as the form for
9665 @var{location}) what source line covers a particular address:
9667 (@value{GDBP}) info line *0x63ff
9668 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9669 ends at 0x6404 <m4_changequote+184>.
9672 @cindex @code{$_} and @code{info line}
9673 @cindex @code{x} command, default address
9674 @kindex x@r{(examine), and} info line
9675 After @code{info line}, the default address for the @code{x} command
9676 is changed to the starting address of the line, so that @samp{x/i} is
9677 sufficient to begin examining the machine code (@pxref{Memory,
9678 ,Examining Memory}). Also, this address is saved as the value of the
9679 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9682 @cindex info line, repeated calls
9683 After @code{info line}, using @code{info line} again without
9684 specifying a location will display information about the next source
9689 @cindex assembly instructions
9690 @cindex instructions, assembly
9691 @cindex machine instructions
9692 @cindex listing machine instructions
9694 @itemx disassemble /m
9695 @itemx disassemble /s
9696 @itemx disassemble /r
9697 This specialized command dumps a range of memory as machine
9698 instructions. It can also print mixed source+disassembly by specifying
9699 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9700 as well as in symbolic form by specifying the @code{/r} modifier.
9701 The default memory range is the function surrounding the
9702 program counter of the selected frame. A single argument to this
9703 command is a program counter value; @value{GDBN} dumps the function
9704 surrounding this value. When two arguments are given, they should
9705 be separated by a comma, possibly surrounded by whitespace. The
9706 arguments specify a range of addresses to dump, in one of two forms:
9709 @item @var{start},@var{end}
9710 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9711 @item @var{start},+@var{length}
9712 the addresses from @var{start} (inclusive) to
9713 @code{@var{start}+@var{length}} (exclusive).
9717 When 2 arguments are specified, the name of the function is also
9718 printed (since there could be several functions in the given range).
9720 The argument(s) can be any expression yielding a numeric value, such as
9721 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9723 If the range of memory being disassembled contains current program counter,
9724 the instruction at that location is shown with a @code{=>} marker.
9727 The following example shows the disassembly of a range of addresses of
9728 HP PA-RISC 2.0 code:
9731 (@value{GDBP}) disas 0x32c4, 0x32e4
9732 Dump of assembler code from 0x32c4 to 0x32e4:
9733 0x32c4 <main+204>: addil 0,dp
9734 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9735 0x32cc <main+212>: ldil 0x3000,r31
9736 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9737 0x32d4 <main+220>: ldo 0(r31),rp
9738 0x32d8 <main+224>: addil -0x800,dp
9739 0x32dc <main+228>: ldo 0x588(r1),r26
9740 0x32e0 <main+232>: ldil 0x3000,r31
9741 End of assembler dump.
9744 Here is an example showing mixed source+assembly for Intel x86
9745 with @code{/m} or @code{/s}, when the program is stopped just after
9746 function prologue in a non-optimized function with no inline code.
9749 (@value{GDBP}) disas /m main
9750 Dump of assembler code for function main:
9752 0x08048330 <+0>: push %ebp
9753 0x08048331 <+1>: mov %esp,%ebp
9754 0x08048333 <+3>: sub $0x8,%esp
9755 0x08048336 <+6>: and $0xfffffff0,%esp
9756 0x08048339 <+9>: sub $0x10,%esp
9758 6 printf ("Hello.\n");
9759 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9760 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9764 0x08048348 <+24>: mov $0x0,%eax
9765 0x0804834d <+29>: leave
9766 0x0804834e <+30>: ret
9768 End of assembler dump.
9771 The @code{/m} option is deprecated as its output is not useful when
9772 there is either inlined code or re-ordered code.
9773 The @code{/s} option is the preferred choice.
9774 Here is an example for AMD x86-64 showing the difference between
9775 @code{/m} output and @code{/s} output.
9776 This example has one inline function defined in a header file,
9777 and the code is compiled with @samp{-O2} optimization.
9778 Note how the @code{/m} output is missing the disassembly of
9779 several instructions that are present in the @code{/s} output.
9809 (@value{GDBP}) disas /m main
9810 Dump of assembler code for function main:
9814 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9815 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9819 0x000000000040041d <+29>: xor %eax,%eax
9820 0x000000000040041f <+31>: retq
9821 0x0000000000400420 <+32>: add %eax,%eax
9822 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9824 End of assembler dump.
9825 (@value{GDBP}) disas /s main
9826 Dump of assembler code for function main:
9830 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9834 0x0000000000400406 <+6>: test %eax,%eax
9835 0x0000000000400408 <+8>: js 0x400420 <main+32>
9840 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9841 0x000000000040040d <+13>: test %eax,%eax
9842 0x000000000040040f <+15>: mov $0x1,%eax
9843 0x0000000000400414 <+20>: cmovne %edx,%eax
9847 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9851 0x000000000040041d <+29>: xor %eax,%eax
9852 0x000000000040041f <+31>: retq
9856 0x0000000000400420 <+32>: add %eax,%eax
9857 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9858 End of assembler dump.
9861 Here is another example showing raw instructions in hex for AMD x86-64,
9864 (gdb) disas /r 0x400281,+10
9865 Dump of assembler code from 0x400281 to 0x40028b:
9866 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9867 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9868 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9869 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9870 End of assembler dump.
9873 Addresses cannot be specified as a location (@pxref{Specify Location}).
9874 So, for example, if you want to disassemble function @code{bar}
9875 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9876 and not @samp{disassemble foo.c:bar}.
9878 Some architectures have more than one commonly-used set of instruction
9879 mnemonics or other syntax.
9881 For programs that were dynamically linked and use shared libraries,
9882 instructions that call functions or branch to locations in the shared
9883 libraries might show a seemingly bogus location---it's actually a
9884 location of the relocation table. On some architectures, @value{GDBN}
9885 might be able to resolve these to actual function names.
9888 @kindex set disassembler-options
9889 @cindex disassembler options
9890 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9891 This command controls the passing of target specific information to
9892 the disassembler. For a list of valid options, please refer to the
9893 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9894 manual and/or the output of @kbd{objdump --help}
9895 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9896 The default value is the empty string.
9898 If it is necessary to specify more than one disassembler option, then
9899 multiple options can be placed together into a comma separated list.
9900 Currently this command is only supported on targets ARC, ARM, MIPS,
9903 @kindex show disassembler-options
9904 @item show disassembler-options
9905 Show the current setting of the disassembler options.
9909 @kindex set disassembly-flavor
9910 @cindex Intel disassembly flavor
9911 @cindex AT&T disassembly flavor
9912 @item set disassembly-flavor @var{instruction-set}
9913 Select the instruction set to use when disassembling the
9914 program via the @code{disassemble} or @code{x/i} commands.
9916 Currently this command is only defined for the Intel x86 family. You
9917 can set @var{instruction-set} to either @code{intel} or @code{att}.
9918 The default is @code{att}, the AT&T flavor used by default by Unix
9919 assemblers for x86-based targets.
9921 @kindex show disassembly-flavor
9922 @item show disassembly-flavor
9923 Show the current setting of the disassembly flavor.
9927 @kindex set disassemble-next-line
9928 @kindex show disassemble-next-line
9929 @item set disassemble-next-line
9930 @itemx show disassemble-next-line
9931 Control whether or not @value{GDBN} will disassemble the next source
9932 line or instruction when execution stops. If ON, @value{GDBN} will
9933 display disassembly of the next source line when execution of the
9934 program being debugged stops. This is @emph{in addition} to
9935 displaying the source line itself, which @value{GDBN} always does if
9936 possible. If the next source line cannot be displayed for some reason
9937 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9938 info in the debug info), @value{GDBN} will display disassembly of the
9939 next @emph{instruction} instead of showing the next source line. If
9940 AUTO, @value{GDBN} will display disassembly of next instruction only
9941 if the source line cannot be displayed. This setting causes
9942 @value{GDBN} to display some feedback when you step through a function
9943 with no line info or whose source file is unavailable. The default is
9944 OFF, which means never display the disassembly of the next line or
9948 @node Disable Reading Source
9949 @section Disable Reading Source Code
9950 @cindex source code, disable access
9952 In some cases it can be desirable to prevent @value{GDBN} from
9953 accessing source code files. One case where this might be desirable
9954 is if the source code files are located over a slow network
9957 The following command can be used to control whether @value{GDBN}
9958 should access source code files or not:
9961 @kindex set source open
9962 @kindex show source open
9963 @item set source open @r{[}on@r{|}off@r{]}
9964 @itemx show source open
9965 When this option is @code{on}, which is the default, @value{GDBN} will
9966 access source code files when needed, for example to print source
9967 lines when @value{GDBN} stops, or in response to the @code{list}
9970 When this option is @code{off}, @value{GDBN} will not access source
9975 @chapter Examining Data
9977 @cindex printing data
9978 @cindex examining data
9981 The usual way to examine data in your program is with the @code{print}
9982 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9983 evaluates and prints the value of an expression of the language your
9984 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9985 Different Languages}). It may also print the expression using a
9986 Python-based pretty-printer (@pxref{Pretty Printing}).
9989 @item print [[@var{options}] --] @var{expr}
9990 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9991 @var{expr} is an expression (in the source language). By default the
9992 value of @var{expr} is printed in a format appropriate to its data type;
9993 you can choose a different format by specifying @samp{/@var{f}}, where
9994 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9997 @anchor{print options}
9998 The @code{print} command supports a number of options that allow
9999 overriding relevant global print settings as set by @code{set print}
10003 @item -address [@code{on}|@code{off}]
10004 Set printing of addresses.
10005 Related setting: @ref{set print address}.
10007 @item -array [@code{on}|@code{off}]
10008 Pretty formatting of arrays.
10009 Related setting: @ref{set print array}.
10011 @item -array-indexes [@code{on}|@code{off}]
10012 Set printing of array indexes.
10013 Related setting: @ref{set print array-indexes}.
10015 @item -elements @var{number-of-elements}|@code{unlimited}
10016 Set limit on string chars or array elements to print. The value
10017 @code{unlimited} causes there to be no limit. Related setting:
10018 @ref{set print elements}.
10020 @item -max-depth @var{depth}|@code{unlimited}
10021 Set the threshold after which nested structures are replaced with
10022 ellipsis. Related setting: @ref{set print max-depth}.
10024 @item -memory-tag-violations [@code{on}|@code{off}]
10025 Set printing of additional information about memory tag violations.
10026 @xref{set print memory-tag-violations}.
10028 @item -null-stop [@code{on}|@code{off}]
10029 Set printing of char arrays to stop at first null char. Related
10030 setting: @ref{set print null-stop}.
10032 @item -object [@code{on}|@code{off}]
10033 Set printing C@t{++} virtual function tables. Related setting:
10034 @ref{set print object}.
10036 @item -pretty [@code{on}|@code{off}]
10037 Set pretty formatting of structures. Related setting: @ref{set print
10040 @item -raw-values [@code{on}|@code{off}]
10041 Set whether to print values in raw form, bypassing any
10042 pretty-printers for that value. Related setting: @ref{set print
10045 @item -repeats @var{number-of-repeats}|@code{unlimited}
10046 Set threshold for repeated print elements. @code{unlimited} causes
10047 all elements to be individually printed. Related setting: @ref{set
10050 @item -static-members [@code{on}|@code{off}]
10051 Set printing C@t{++} static members. Related setting: @ref{set print
10054 @item -symbol [@code{on}|@code{off}]
10055 Set printing of symbol names when printing pointers. Related setting:
10056 @ref{set print symbol}.
10058 @item -union [@code{on}|@code{off}]
10059 Set printing of unions interior to structures. Related setting:
10060 @ref{set print union}.
10062 @item -vtbl [@code{on}|@code{off}]
10063 Set printing of C++ virtual function tables. Related setting:
10064 @ref{set print vtbl}.
10067 Because the @code{print} command accepts arbitrary expressions which
10068 may look like options (including abbreviations), if you specify any
10069 command option, then you must use a double dash (@code{--}) to mark
10070 the end of option processing.
10072 For example, this prints the value of the @code{-p} expression:
10075 (@value{GDBP}) print -p
10078 While this repeats the last value in the value history (see below)
10079 with the @code{-pretty} option in effect:
10082 (@value{GDBP}) print -p --
10085 Here is an example including both on option and an expression:
10089 (@value{GDBP}) print -pretty -- *myptr
10101 @item print [@var{options}]
10102 @itemx print [@var{options}] /@var{f}
10103 @cindex reprint the last value
10104 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10105 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10106 conveniently inspect the same value in an alternative format.
10109 If the architecture supports memory tagging, the @code{print} command will
10110 display pointer/memory tag mismatches if what is being printed is a pointer
10111 or reference type. @xref{Memory Tagging}.
10113 A more low-level way of examining data is with the @code{x} command.
10114 It examines data in memory at a specified address and prints it in a
10115 specified format. @xref{Memory, ,Examining Memory}.
10117 If you are interested in information about types, or about how the
10118 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
10119 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10122 @cindex exploring hierarchical data structures
10124 Another way of examining values of expressions and type information is
10125 through the Python extension command @code{explore} (available only if
10126 the @value{GDBN} build is configured with @code{--with-python}). It
10127 offers an interactive way to start at the highest level (or, the most
10128 abstract level) of the data type of an expression (or, the data type
10129 itself) and explore all the way down to leaf scalar values/fields
10130 embedded in the higher level data types.
10133 @item explore @var{arg}
10134 @var{arg} is either an expression (in the source language), or a type
10135 visible in the current context of the program being debugged.
10138 The working of the @code{explore} command can be illustrated with an
10139 example. If a data type @code{struct ComplexStruct} is defined in your
10143 struct SimpleStruct
10149 struct ComplexStruct
10151 struct SimpleStruct *ss_p;
10157 followed by variable declarations as
10160 struct SimpleStruct ss = @{ 10, 1.11 @};
10161 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10165 then, the value of the variable @code{cs} can be explored using the
10166 @code{explore} command as follows.
10170 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10171 the following fields:
10173 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10174 arr = <Enter 1 to explore this field of type `int [10]'>
10176 Enter the field number of choice:
10180 Since the fields of @code{cs} are not scalar values, you are being
10181 prompted to chose the field you want to explore. Let's say you choose
10182 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10183 pointer, you will be asked if it is pointing to a single value. From
10184 the declaration of @code{cs} above, it is indeed pointing to a single
10185 value, hence you enter @code{y}. If you enter @code{n}, then you will
10186 be asked if it were pointing to an array of values, in which case this
10187 field will be explored as if it were an array.
10190 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10191 Continue exploring it as a pointer to a single value [y/n]: y
10192 The value of `*(cs.ss_p)' is a struct/class of type `struct
10193 SimpleStruct' with the following fields:
10195 i = 10 .. (Value of type `int')
10196 d = 1.1100000000000001 .. (Value of type `double')
10198 Press enter to return to parent value:
10202 If the field @code{arr} of @code{cs} was chosen for exploration by
10203 entering @code{1} earlier, then since it is as array, you will be
10204 prompted to enter the index of the element in the array that you want
10208 `cs.arr' is an array of `int'.
10209 Enter the index of the element you want to explore in `cs.arr': 5
10211 `(cs.arr)[5]' is a scalar value of type `int'.
10215 Press enter to return to parent value:
10218 In general, at any stage of exploration, you can go deeper towards the
10219 leaf values by responding to the prompts appropriately, or hit the
10220 return key to return to the enclosing data structure (the @i{higher}
10221 level data structure).
10223 Similar to exploring values, you can use the @code{explore} command to
10224 explore types. Instead of specifying a value (which is typically a
10225 variable name or an expression valid in the current context of the
10226 program being debugged), you specify a type name. If you consider the
10227 same example as above, your can explore the type
10228 @code{struct ComplexStruct} by passing the argument
10229 @code{struct ComplexStruct} to the @code{explore} command.
10232 (gdb) explore struct ComplexStruct
10236 By responding to the prompts appropriately in the subsequent interactive
10237 session, you can explore the type @code{struct ComplexStruct} in a
10238 manner similar to how the value @code{cs} was explored in the above
10241 The @code{explore} command also has two sub-commands,
10242 @code{explore value} and @code{explore type}. The former sub-command is
10243 a way to explicitly specify that value exploration of the argument is
10244 being invoked, while the latter is a way to explicitly specify that type
10245 exploration of the argument is being invoked.
10248 @item explore value @var{expr}
10249 @cindex explore value
10250 This sub-command of @code{explore} explores the value of the
10251 expression @var{expr} (if @var{expr} is an expression valid in the
10252 current context of the program being debugged). The behavior of this
10253 command is identical to that of the behavior of the @code{explore}
10254 command being passed the argument @var{expr}.
10256 @item explore type @var{arg}
10257 @cindex explore type
10258 This sub-command of @code{explore} explores the type of @var{arg} (if
10259 @var{arg} is a type visible in the current context of program being
10260 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10261 is an expression valid in the current context of the program being
10262 debugged). If @var{arg} is a type, then the behavior of this command is
10263 identical to that of the @code{explore} command being passed the
10264 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10265 this command will be identical to that of the @code{explore} command
10266 being passed the type of @var{arg} as the argument.
10270 * Expressions:: Expressions
10271 * Ambiguous Expressions:: Ambiguous Expressions
10272 * Variables:: Program variables
10273 * Arrays:: Artificial arrays
10274 * Output Formats:: Output formats
10275 * Memory:: Examining memory
10276 * Memory Tagging:: Memory Tagging
10277 * Auto Display:: Automatic display
10278 * Print Settings:: Print settings
10279 * Pretty Printing:: Python pretty printing
10280 * Value History:: Value history
10281 * Convenience Vars:: Convenience variables
10282 * Convenience Funs:: Convenience functions
10283 * Registers:: Registers
10284 * Floating Point Hardware:: Floating point hardware
10285 * Vector Unit:: Vector Unit
10286 * OS Information:: Auxiliary data provided by operating system
10287 * Memory Region Attributes:: Memory region attributes
10288 * Dump/Restore Files:: Copy between memory and a file
10289 * Core File Generation:: Cause a program dump its core
10290 * Character Sets:: Debugging programs that use a different
10291 character set than GDB does
10292 * Caching Target Data:: Data caching for targets
10293 * Searching Memory:: Searching memory for a sequence of bytes
10294 * Value Sizes:: Managing memory allocated for values
10298 @section Expressions
10300 @cindex expressions
10301 @code{print} and many other @value{GDBN} commands accept an expression and
10302 compute its value. Any kind of constant, variable or operator defined
10303 by the programming language you are using is valid in an expression in
10304 @value{GDBN}. This includes conditional expressions, function calls,
10305 casts, and string constants. It also includes preprocessor macros, if
10306 you compiled your program to include this information; see
10309 @cindex arrays in expressions
10310 @value{GDBN} supports array constants in expressions input by
10311 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10312 you can use the command @code{print @{1, 2, 3@}} to create an array
10313 of three integers. If you pass an array to a function or assign it
10314 to a program variable, @value{GDBN} copies the array to memory that
10315 is @code{malloc}ed in the target program.
10317 Because C is so widespread, most of the expressions shown in examples in
10318 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10319 Languages}, for information on how to use expressions in other
10322 In this section, we discuss operators that you can use in @value{GDBN}
10323 expressions regardless of your programming language.
10325 @cindex casts, in expressions
10326 Casts are supported in all languages, not just in C, because it is so
10327 useful to cast a number into a pointer in order to examine a structure
10328 at that address in memory.
10329 @c FIXME: casts supported---Mod2 true?
10331 @value{GDBN} supports these operators, in addition to those common
10332 to programming languages:
10336 @samp{@@} is a binary operator for treating parts of memory as arrays.
10337 @xref{Arrays, ,Artificial Arrays}, for more information.
10340 @samp{::} allows you to specify a variable in terms of the file or
10341 function where it is defined. @xref{Variables, ,Program Variables}.
10343 @cindex @{@var{type}@}
10344 @cindex type casting memory
10345 @cindex memory, viewing as typed object
10346 @cindex casts, to view memory
10347 @item @{@var{type}@} @var{addr}
10348 Refers to an object of type @var{type} stored at address @var{addr} in
10349 memory. The address @var{addr} may be any expression whose value is
10350 an integer or pointer (but parentheses are required around binary
10351 operators, just as in a cast). This construct is allowed regardless
10352 of what kind of data is normally supposed to reside at @var{addr}.
10355 @node Ambiguous Expressions
10356 @section Ambiguous Expressions
10357 @cindex ambiguous expressions
10359 Expressions can sometimes contain some ambiguous elements. For instance,
10360 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10361 a single function name to be defined several times, for application in
10362 different contexts. This is called @dfn{overloading}. Another example
10363 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10364 templates and is typically instantiated several times, resulting in
10365 the same function name being defined in different contexts.
10367 In some cases and depending on the language, it is possible to adjust
10368 the expression to remove the ambiguity. For instance in C@t{++}, you
10369 can specify the signature of the function you want to break on, as in
10370 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10371 qualified name of your function often makes the expression unambiguous
10374 When an ambiguity that needs to be resolved is detected, the debugger
10375 has the capability to display a menu of numbered choices for each
10376 possibility, and then waits for the selection with the prompt @samp{>}.
10377 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10378 aborts the current command. If the command in which the expression was
10379 used allows more than one choice to be selected, the next option in the
10380 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10383 For example, the following session excerpt shows an attempt to set a
10384 breakpoint at the overloaded symbol @code{String::after}.
10385 We choose three particular definitions of that function name:
10387 @c FIXME! This is likely to change to show arg type lists, at least
10390 (@value{GDBP}) b String::after
10393 [2] file:String.cc; line number:867
10394 [3] file:String.cc; line number:860
10395 [4] file:String.cc; line number:875
10396 [5] file:String.cc; line number:853
10397 [6] file:String.cc; line number:846
10398 [7] file:String.cc; line number:735
10400 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10401 Breakpoint 2 at 0xb344: file String.cc, line 875.
10402 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10403 Multiple breakpoints were set.
10404 Use the "delete" command to delete unwanted
10411 @kindex set multiple-symbols
10412 @item set multiple-symbols @var{mode}
10413 @cindex multiple-symbols menu
10415 This option allows you to adjust the debugger behavior when an expression
10418 By default, @var{mode} is set to @code{all}. If the command with which
10419 the expression is used allows more than one choice, then @value{GDBN}
10420 automatically selects all possible choices. For instance, inserting
10421 a breakpoint on a function using an ambiguous name results in a breakpoint
10422 inserted on each possible match. However, if a unique choice must be made,
10423 then @value{GDBN} uses the menu to help you disambiguate the expression.
10424 For instance, printing the address of an overloaded function will result
10425 in the use of the menu.
10427 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10428 when an ambiguity is detected.
10430 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10431 an error due to the ambiguity and the command is aborted.
10433 @kindex show multiple-symbols
10434 @item show multiple-symbols
10435 Show the current value of the @code{multiple-symbols} setting.
10439 @section Program Variables
10441 The most common kind of expression to use is the name of a variable
10444 Variables in expressions are understood in the selected stack frame
10445 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10449 global (or file-static)
10456 visible according to the scope rules of the
10457 programming language from the point of execution in that frame
10460 @noindent This means that in the function
10475 you can examine and use the variable @code{a} whenever your program is
10476 executing within the function @code{foo}, but you can only use or
10477 examine the variable @code{b} while your program is executing inside
10478 the block where @code{b} is declared.
10480 @cindex variable name conflict
10481 There is an exception: you can refer to a variable or function whose
10482 scope is a single source file even if the current execution point is not
10483 in this file. But it is possible to have more than one such variable or
10484 function with the same name (in different source files). If that
10485 happens, referring to that name has unpredictable effects. If you wish,
10486 you can specify a static variable in a particular function or file by
10487 using the colon-colon (@code{::}) notation:
10489 @cindex colon-colon, context for variables/functions
10491 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10492 @cindex @code{::}, context for variables/functions
10495 @var{file}::@var{variable}
10496 @var{function}::@var{variable}
10500 Here @var{file} or @var{function} is the name of the context for the
10501 static @var{variable}. In the case of file names, you can use quotes to
10502 make sure @value{GDBN} parses the file name as a single word---for example,
10503 to print a global value of @code{x} defined in @file{f2.c}:
10506 (@value{GDBP}) p 'f2.c'::x
10509 The @code{::} notation is normally used for referring to
10510 static variables, since you typically disambiguate uses of local variables
10511 in functions by selecting the appropriate frame and using the
10512 simple name of the variable. However, you may also use this notation
10513 to refer to local variables in frames enclosing the selected frame:
10522 process (a); /* Stop here */
10533 For example, if there is a breakpoint at the commented line,
10534 here is what you might see
10535 when the program stops after executing the call @code{bar(0)}:
10540 (@value{GDBP}) p bar::a
10542 (@value{GDBP}) up 2
10543 #2 0x080483d0 in foo (a=5) at foobar.c:12
10546 (@value{GDBP}) p bar::a
10550 @cindex C@t{++} scope resolution
10551 These uses of @samp{::} are very rarely in conflict with the very
10552 similar use of the same notation in C@t{++}. When they are in
10553 conflict, the C@t{++} meaning takes precedence; however, this can be
10554 overridden by quoting the file or function name with single quotes.
10556 For example, suppose the program is stopped in a method of a class
10557 that has a field named @code{includefile}, and there is also an
10558 include file named @file{includefile} that defines a variable,
10559 @code{some_global}.
10562 (@value{GDBP}) p includefile
10564 (@value{GDBP}) p includefile::some_global
10565 A syntax error in expression, near `'.
10566 (@value{GDBP}) p 'includefile'::some_global
10570 @cindex wrong values
10571 @cindex variable values, wrong
10572 @cindex function entry/exit, wrong values of variables
10573 @cindex optimized code, wrong values of variables
10575 @emph{Warning:} Occasionally, a local variable may appear to have the
10576 wrong value at certain points in a function---just after entry to a new
10577 scope, and just before exit.
10579 You may see this problem when you are stepping by machine instructions.
10580 This is because, on most machines, it takes more than one instruction to
10581 set up a stack frame (including local variable definitions); if you are
10582 stepping by machine instructions, variables may appear to have the wrong
10583 values until the stack frame is completely built. On exit, it usually
10584 also takes more than one machine instruction to destroy a stack frame;
10585 after you begin stepping through that group of instructions, local
10586 variable definitions may be gone.
10588 This may also happen when the compiler does significant optimizations.
10589 To be sure of always seeing accurate values, turn off all optimization
10592 @cindex ``No symbol "foo" in current context''
10593 Another possible effect of compiler optimizations is to optimize
10594 unused variables out of existence, or assign variables to registers (as
10595 opposed to memory addresses). Depending on the support for such cases
10596 offered by the debug info format used by the compiler, @value{GDBN}
10597 might not be able to display values for such local variables. If that
10598 happens, @value{GDBN} will print a message like this:
10601 No symbol "foo" in current context.
10604 To solve such problems, either recompile without optimizations, or use a
10605 different debug info format, if the compiler supports several such
10606 formats. @xref{Compilation}, for more information on choosing compiler
10607 options. @xref{C, ,C and C@t{++}}, for more information about debug
10608 info formats that are best suited to C@t{++} programs.
10610 If you ask to print an object whose contents are unknown to
10611 @value{GDBN}, e.g., because its data type is not completely specified
10612 by the debug information, @value{GDBN} will say @samp{<incomplete
10613 type>}. @xref{Symbols, incomplete type}, for more about this.
10615 @cindex no debug info variables
10616 If you try to examine or use the value of a (global) variable for
10617 which @value{GDBN} has no type information, e.g., because the program
10618 includes no debug information, @value{GDBN} displays an error message.
10619 @xref{Symbols, unknown type}, for more about unknown types. If you
10620 cast the variable to its declared type, @value{GDBN} gets the
10621 variable's value using the cast-to type as the variable's type. For
10622 example, in a C program:
10625 (@value{GDBP}) p var
10626 'var' has unknown type; cast it to its declared type
10627 (@value{GDBP}) p (float) var
10631 If you append @kbd{@@entry} string to a function parameter name you get its
10632 value at the time the function got called. If the value is not available an
10633 error message is printed. Entry values are available only with some compilers.
10634 Entry values are normally also printed at the function parameter list according
10635 to @ref{set print entry-values}.
10638 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10644 (gdb) print i@@entry
10648 Strings are identified as arrays of @code{char} values without specified
10649 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10650 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10651 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10652 defines literal string type @code{"char"} as @code{char} without a sign.
10657 signed char var1[] = "A";
10660 You get during debugging
10665 $2 = @{65 'A', 0 '\0'@}
10669 @section Artificial Arrays
10671 @cindex artificial array
10673 @kindex @@@r{, referencing memory as an array}
10674 It is often useful to print out several successive objects of the
10675 same type in memory; a section of an array, or an array of
10676 dynamically determined size for which only a pointer exists in the
10679 You can do this by referring to a contiguous span of memory as an
10680 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10681 operand of @samp{@@} should be the first element of the desired array
10682 and be an individual object. The right operand should be the desired length
10683 of the array. The result is an array value whose elements are all of
10684 the type of the left argument. The first element is actually the left
10685 argument; the second element comes from bytes of memory immediately
10686 following those that hold the first element, and so on. Here is an
10687 example. If a program says
10690 int *array = (int *) malloc (len * sizeof (int));
10694 you can print the contents of @code{array} with
10700 The left operand of @samp{@@} must reside in memory. Array values made
10701 with @samp{@@} in this way behave just like other arrays in terms of
10702 subscripting, and are coerced to pointers when used in expressions.
10703 Artificial arrays most often appear in expressions via the value history
10704 (@pxref{Value History, ,Value History}), after printing one out.
10706 Another way to create an artificial array is to use a cast.
10707 This re-interprets a value as if it were an array.
10708 The value need not be in memory:
10710 (@value{GDBP}) p/x (short[2])0x12345678
10711 $1 = @{0x1234, 0x5678@}
10714 As a convenience, if you leave the array length out (as in
10715 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10716 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10718 (@value{GDBP}) p/x (short[])0x12345678
10719 $2 = @{0x1234, 0x5678@}
10722 Sometimes the artificial array mechanism is not quite enough; in
10723 moderately complex data structures, the elements of interest may not
10724 actually be adjacent---for example, if you are interested in the values
10725 of pointers in an array. One useful work-around in this situation is
10726 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10727 Variables}) as a counter in an expression that prints the first
10728 interesting value, and then repeat that expression via @key{RET}. For
10729 instance, suppose you have an array @code{dtab} of pointers to
10730 structures, and you are interested in the values of a field @code{fv}
10731 in each structure. Here is an example of what you might type:
10741 @node Output Formats
10742 @section Output Formats
10744 @cindex formatted output
10745 @cindex output formats
10746 By default, @value{GDBN} prints a value according to its data type. Sometimes
10747 this is not what you want. For example, you might want to print a number
10748 in hex, or a pointer in decimal. Or you might want to view data in memory
10749 at a certain address as a character string or as an instruction. To do
10750 these things, specify an @dfn{output format} when you print a value.
10752 The simplest use of output formats is to say how to print a value
10753 already computed. This is done by starting the arguments of the
10754 @code{print} command with a slash and a format letter. The format
10755 letters supported are:
10759 Print the binary representation of the value in hexadecimal.
10762 Print the binary representation of the value in decimal.
10765 Print the binary representation of the value as an decimal, as if it
10769 Print the binary representation of the value in octal.
10772 Print the binary representation of the value in binary. The letter
10773 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
10774 because these format letters are also used with the @code{x} command,
10775 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
10779 @cindex unknown address, locating
10780 @cindex locate address
10781 Print as an address, both absolute in hexadecimal and as an offset from
10782 the nearest preceding symbol. You can use this format used to discover
10783 where (in what function) an unknown address is located:
10786 (@value{GDBP}) p/a 0x54320
10787 $3 = 0x54320 <_initialize_vx+396>
10791 The command @code{info symbol 0x54320} yields similar results.
10792 @xref{Symbols, info symbol}.
10795 Cast the value to an integer (unlike other formats, this does not just
10796 reinterpret the underlying bits) and print it as a character constant.
10797 This prints both the numerical value and its character representation.
10798 The character representation is replaced with the octal escape
10799 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
10801 Without this format, @value{GDBN} displays @code{char},
10802 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10803 constants. Single-byte members of vectors are displayed as integer
10807 Regard the bits of the value as a floating point number and print
10808 using typical floating point syntax.
10811 @cindex printing strings
10812 @cindex printing byte arrays
10813 Regard as a string, if possible. With this format, pointers to single-byte
10814 data are displayed as null-terminated strings and arrays of single-byte data
10815 are displayed as fixed-length strings. Other values are displayed in their
10818 Without this format, @value{GDBN} displays pointers to and arrays of
10819 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10820 strings. Single-byte members of a vector are displayed as an integer
10824 Like @samp{x} formatting, the value is treated as an integer and
10825 printed as hexadecimal, but leading zeros are printed to pad the value
10826 to the size of the integer type.
10829 @cindex raw printing
10830 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10831 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10832 Printing}). This typically results in a higher-level display of the
10833 value's contents. The @samp{r} format bypasses any Python
10834 pretty-printer which might exist.
10837 For example, to print the program counter in hex (@pxref{Registers}), type
10844 Note that no space is required before the slash; this is because command
10845 names in @value{GDBN} cannot contain a slash.
10847 To reprint the last value in the value history with a different format,
10848 you can use the @code{print} command with just a format and no
10849 expression. For example, @samp{p/x} reprints the last value in hex.
10852 @section Examining Memory
10854 You can use the command @code{x} (for ``examine'') to examine memory in
10855 any of several formats, independently of your program's data types.
10857 @cindex examining memory
10859 @kindex x @r{(examine memory)}
10860 @item x/@var{nfu} @var{addr}
10861 @itemx x @var{addr}
10863 Use the @code{x} command to examine memory.
10866 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10867 much memory to display and how to format it; @var{addr} is an
10868 expression giving the address where you want to start displaying memory.
10869 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10870 Several commands set convenient defaults for @var{addr}.
10873 @item @var{n}, the repeat count
10874 The repeat count is a decimal integer; the default is 1. It specifies
10875 how much memory (counting by units @var{u}) to display. If a negative
10876 number is specified, memory is examined backward from @var{addr}.
10877 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10880 @item @var{f}, the display format
10881 The display format is one of the formats used by @code{print}
10882 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10883 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
10884 @samp{m} (for displaying memory tags).
10885 The default is @samp{x} (hexadecimal) initially. The default changes
10886 each time you use either @code{x} or @code{print}.
10888 @item @var{u}, the unit size
10889 The unit size is any of
10895 Halfwords (two bytes).
10897 Words (four bytes). This is the initial default.
10899 Giant words (eight bytes).
10902 Each time you specify a unit size with @code{x}, that size becomes the
10903 default unit the next time you use @code{x}. For the @samp{i} format,
10904 the unit size is ignored and is normally not written. For the @samp{s} format,
10905 the unit size defaults to @samp{b}, unless it is explicitly given.
10906 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10907 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10908 Note that the results depend on the programming language of the
10909 current compilation unit. If the language is C, the @samp{s}
10910 modifier will use the UTF-16 encoding while @samp{w} will use
10911 UTF-32. The encoding is set by the programming language and cannot
10914 @item @var{addr}, starting display address
10915 @var{addr} is the address where you want @value{GDBN} to begin displaying
10916 memory. The expression need not have a pointer value (though it may);
10917 it is always interpreted as an integer address of a byte of memory.
10918 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10919 @var{addr} is usually just after the last address examined---but several
10920 other commands also set the default address: @code{info breakpoints} (to
10921 the address of the last breakpoint listed), @code{info line} (to the
10922 starting address of a line), and @code{print} (if you use it to display
10923 a value from memory).
10926 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10927 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10928 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10929 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10930 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10932 You can also specify a negative repeat count to examine memory backward
10933 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10934 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
10936 Since the letters indicating unit sizes are all distinct from the
10937 letters specifying output formats, you do not have to remember whether
10938 unit size or format comes first; either order works. The output
10939 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10940 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10942 Even though the unit size @var{u} is ignored for the formats @samp{s}
10943 and @samp{i}, you might still want to use a count @var{n}; for example,
10944 @samp{3i} specifies that you want to see three machine instructions,
10945 including any operands. For convenience, especially when used with
10946 the @code{display} command, the @samp{i} format also prints branch delay
10947 slot instructions, if any, beyond the count specified, which immediately
10948 follow the last instruction that is within the count. The command
10949 @code{disassemble} gives an alternative way of inspecting machine
10950 instructions; see @ref{Machine Code,,Source and Machine Code}.
10952 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10953 the command displays null-terminated strings or instructions before the given
10954 address as many as the absolute value of the given number. For the @samp{i}
10955 format, we use line number information in the debug info to accurately locate
10956 instruction boundaries while disassembling backward. If line info is not
10957 available, the command stops examining memory with an error message.
10959 All the defaults for the arguments to @code{x} are designed to make it
10960 easy to continue scanning memory with minimal specifications each time
10961 you use @code{x}. For example, after you have inspected three machine
10962 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10963 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10964 the repeat count @var{n} is used again; the other arguments default as
10965 for successive uses of @code{x}.
10967 When examining machine instructions, the instruction at current program
10968 counter is shown with a @code{=>} marker. For example:
10971 (@value{GDBP}) x/5i $pc-6
10972 0x804837f <main+11>: mov %esp,%ebp
10973 0x8048381 <main+13>: push %ecx
10974 0x8048382 <main+14>: sub $0x4,%esp
10975 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10976 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10979 If the architecture supports memory tagging, the tags can be displayed by
10980 using @samp{m}. @xref{Memory Tagging}.
10982 The information will be displayed once per granule size
10983 (the amount of bytes a particular memory tag covers). For example, AArch64
10984 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
10986 Due to the way @value{GDBN} prints information with the @code{x} command (not
10987 aligned to a particular boundary), the tag information will refer to the
10988 initial address displayed on a particular line. If a memory tag boundary
10989 is crossed in the middle of a line displayed by the @code{x} command, it
10990 will be displayed on the next line.
10992 The @samp{m} format doesn't affect any other specified formats that were
10993 passed to the @code{x} command.
10995 @cindex @code{$_}, @code{$__}, and value history
10996 The addresses and contents printed by the @code{x} command are not saved
10997 in the value history because there is often too much of them and they
10998 would get in the way. Instead, @value{GDBN} makes these values available for
10999 subsequent use in expressions as values of the convenience variables
11000 @code{$_} and @code{$__}. After an @code{x} command, the last address
11001 examined is available for use in expressions in the convenience variable
11002 @code{$_}. The contents of that address, as examined, are available in
11003 the convenience variable @code{$__}.
11005 If the @code{x} command has a repeat count, the address and contents saved
11006 are from the last memory unit printed; this is not the same as the last
11007 address printed if several units were printed on the last line of output.
11009 @anchor{addressable memory unit}
11010 @cindex addressable memory unit
11011 Most targets have an addressable memory unit size of 8 bits. This means
11012 that to each memory address are associated 8 bits of data. Some
11013 targets, however, have other addressable memory unit sizes.
11014 Within @value{GDBN} and this document, the term
11015 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11016 when explicitly referring to a chunk of data of that size. The word
11017 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11018 the addressable memory unit size of the target. For most systems,
11019 addressable memory unit is a synonym of byte.
11021 @cindex remote memory comparison
11022 @cindex target memory comparison
11023 @cindex verify remote memory image
11024 @cindex verify target memory image
11025 When you are debugging a program running on a remote target machine
11026 (@pxref{Remote Debugging}), you may wish to verify the program's image
11027 in the remote machine's memory against the executable file you
11028 downloaded to the target. Or, on any target, you may want to check
11029 whether the program has corrupted its own read-only sections. The
11030 @code{compare-sections} command is provided for such situations.
11033 @kindex compare-sections
11034 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11035 Compare the data of a loadable section @var{section-name} in the
11036 executable file of the program being debugged with the same section in
11037 the target machine's memory, and report any mismatches. With no
11038 arguments, compares all loadable sections. With an argument of
11039 @code{-r}, compares all loadable read-only sections.
11041 Note: for remote targets, this command can be accelerated if the
11042 target supports computing the CRC checksum of a block of memory
11043 (@pxref{qCRC packet}).
11046 @node Memory Tagging
11047 @section Memory Tagging
11049 Memory tagging is a memory protection technology that uses a pair of tags to
11050 validate memory accesses through pointers. The tags are integer values
11051 usually comprised of a few bits, depending on the architecture.
11053 There are two types of tags that are used in this setup: logical and
11054 allocation. A logical tag is stored in the pointers themselves, usually at the
11055 higher bits of the pointers. An allocation tag is the tag associated
11056 with particular ranges of memory in the physical address space, against which
11057 the logical tags from pointers are compared.
11059 The pointer tag (logical tag) must match the memory tag (allocation tag)
11060 for the memory access to be valid. If the logical tag does not match the
11061 allocation tag, that will raise a memory violation.
11063 Allocation tags cover multiple contiguous bytes of physical memory. This
11064 range of bytes is called a memory tag granule and is architecture-specific.
11065 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11066 tag spans 16 bytes of memory.
11068 If the underlying architecture supports memory tagging, like AArch64 MTE
11069 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11070 against memory allocation tags.
11072 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11073 display tag information when appropriate, and a command prefix of
11074 @code{memory-tag} gives access to the various memory tagging commands.
11076 The @code{memory-tag} commands are the following:
11079 @kindex memory-tag print-logical-tag
11080 @item memory-tag print-logical-tag @var{pointer_expression}
11081 Print the logical tag stored in @var{pointer_expression}.
11082 @kindex memory-tag with-logical-tag
11083 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11084 Print the pointer given by @var{pointer_expression}, augmented with a logical
11085 tag of @var{tag_bytes}.
11086 @kindex memory-tag print-allocation-tag
11087 @item memory-tag print-allocation-tag @var{address_expression}
11088 Print the allocation tag associated with the memory address given by
11089 @var{address_expression}.
11090 @kindex memory-tag setatag
11091 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11092 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11093 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11094 @kindex memory-tag check
11095 @item memory-tag check @var{pointer_expression}
11096 Check if the logical tag in the pointer given by @var{pointer_expression}
11097 matches the allocation tag for the memory referenced by the pointer.
11099 This essentially emulates the hardware validation that is done when tagged
11100 memory is accessed through a pointer, but does not cause a memory fault as
11101 it would during hardware validation.
11103 It can be used to inspect potential memory tagging violations in the running
11104 process, before any faults get triggered.
11108 @section Automatic Display
11109 @cindex automatic display
11110 @cindex display of expressions
11112 If you find that you want to print the value of an expression frequently
11113 (to see how it changes), you might want to add it to the @dfn{automatic
11114 display list} so that @value{GDBN} prints its value each time your program stops.
11115 Each expression added to the list is given a number to identify it;
11116 to remove an expression from the list, you specify that number.
11117 The automatic display looks like this:
11121 3: bar[5] = (struct hack *) 0x3804
11125 This display shows item numbers, expressions and their current values. As with
11126 displays you request manually using @code{x} or @code{print}, you can
11127 specify the output format you prefer; in fact, @code{display} decides
11128 whether to use @code{print} or @code{x} depending your format
11129 specification---it uses @code{x} if you specify either the @samp{i}
11130 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11134 @item display @var{expr}
11135 Add the expression @var{expr} to the list of expressions to display
11136 each time your program stops. @xref{Expressions, ,Expressions}.
11138 @code{display} does not repeat if you press @key{RET} again after using it.
11140 @item display/@var{fmt} @var{expr}
11141 For @var{fmt} specifying only a display format and not a size or
11142 count, add the expression @var{expr} to the auto-display list but
11143 arrange to display it each time in the specified format @var{fmt}.
11144 @xref{Output Formats,,Output Formats}.
11146 @item display/@var{fmt} @var{addr}
11147 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11148 number of units, add the expression @var{addr} as a memory address to
11149 be examined each time your program stops. Examining means in effect
11150 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11153 For example, @samp{display/i $pc} can be helpful, to see the machine
11154 instruction about to be executed each time execution stops (@samp{$pc}
11155 is a common name for the program counter; @pxref{Registers, ,Registers}).
11158 @kindex delete display
11160 @item undisplay @var{dnums}@dots{}
11161 @itemx delete display @var{dnums}@dots{}
11162 Remove items from the list of expressions to display. Specify the
11163 numbers of the displays that you want affected with the command
11164 argument @var{dnums}. It can be a single display number, one of the
11165 numbers shown in the first field of the @samp{info display} display;
11166 or it could be a range of display numbers, as in @code{2-4}.
11168 @code{undisplay} does not repeat if you press @key{RET} after using it.
11169 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11171 @kindex disable display
11172 @item disable display @var{dnums}@dots{}
11173 Disable the display of item numbers @var{dnums}. A disabled display
11174 item is not printed automatically, but is not forgotten. It may be
11175 enabled again later. Specify the numbers of the displays that you
11176 want affected with the command argument @var{dnums}. It can be a
11177 single display number, one of the numbers shown in the first field of
11178 the @samp{info display} display; or it could be a range of display
11179 numbers, as in @code{2-4}.
11181 @kindex enable display
11182 @item enable display @var{dnums}@dots{}
11183 Enable display of item numbers @var{dnums}. It becomes effective once
11184 again in auto display of its expression, until you specify otherwise.
11185 Specify the numbers of the displays that you want affected with the
11186 command argument @var{dnums}. It can be a single display number, one
11187 of the numbers shown in the first field of the @samp{info display}
11188 display; or it could be a range of display numbers, as in @code{2-4}.
11191 Display the current values of the expressions on the list, just as is
11192 done when your program stops.
11194 @kindex info display
11196 Print the list of expressions previously set up to display
11197 automatically, each one with its item number, but without showing the
11198 values. This includes disabled expressions, which are marked as such.
11199 It also includes expressions which would not be displayed right now
11200 because they refer to automatic variables not currently available.
11203 @cindex display disabled out of scope
11204 If a display expression refers to local variables, then it does not make
11205 sense outside the lexical context for which it was set up. Such an
11206 expression is disabled when execution enters a context where one of its
11207 variables is not defined. For example, if you give the command
11208 @code{display last_char} while inside a function with an argument
11209 @code{last_char}, @value{GDBN} displays this argument while your program
11210 continues to stop inside that function. When it stops elsewhere---where
11211 there is no variable @code{last_char}---the display is disabled
11212 automatically. The next time your program stops where @code{last_char}
11213 is meaningful, you can enable the display expression once again.
11215 @node Print Settings
11216 @section Print Settings
11218 @cindex format options
11219 @cindex print settings
11220 @value{GDBN} provides the following ways to control how arrays, structures,
11221 and symbols are printed.
11224 These settings are useful for debugging programs in any language:
11228 @anchor{set print address}
11229 @item set print address
11230 @itemx set print address on
11231 @cindex print/don't print memory addresses
11232 @value{GDBN} prints memory addresses showing the location of stack
11233 traces, structure values, pointer values, breakpoints, and so forth,
11234 even when it also displays the contents of those addresses. The default
11235 is @code{on}. For example, this is what a stack frame display looks like with
11236 @code{set print address on}:
11241 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11243 530 if (lquote != def_lquote)
11247 @item set print address off
11248 Do not print addresses when displaying their contents. For example,
11249 this is the same stack frame displayed with @code{set print address off}:
11253 (@value{GDBP}) set print addr off
11255 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11256 530 if (lquote != def_lquote)
11260 You can use @samp{set print address off} to eliminate all machine
11261 dependent displays from the @value{GDBN} interface. For example, with
11262 @code{print address off}, you should get the same text for backtraces on
11263 all machines---whether or not they involve pointer arguments.
11266 @item show print address
11267 Show whether or not addresses are to be printed.
11270 When @value{GDBN} prints a symbolic address, it normally prints the
11271 closest earlier symbol plus an offset. If that symbol does not uniquely
11272 identify the address (for example, it is a name whose scope is a single
11273 source file), you may need to clarify. One way to do this is with
11274 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11275 you can set @value{GDBN} to print the source file and line number when
11276 it prints a symbolic address:
11279 @item set print symbol-filename on
11280 @cindex source file and line of a symbol
11281 @cindex symbol, source file and line
11282 Tell @value{GDBN} to print the source file name and line number of a
11283 symbol in the symbolic form of an address.
11285 @item set print symbol-filename off
11286 Do not print source file name and line number of a symbol. This is the
11289 @item show print symbol-filename
11290 Show whether or not @value{GDBN} will print the source file name and
11291 line number of a symbol in the symbolic form of an address.
11294 Another situation where it is helpful to show symbol filenames and line
11295 numbers is when disassembling code; @value{GDBN} shows you the line
11296 number and source file that corresponds to each instruction.
11298 Also, you may wish to see the symbolic form only if the address being
11299 printed is reasonably close to the closest earlier symbol:
11302 @item set print max-symbolic-offset @var{max-offset}
11303 @itemx set print max-symbolic-offset unlimited
11304 @cindex maximum value for offset of closest symbol
11305 Tell @value{GDBN} to only display the symbolic form of an address if the
11306 offset between the closest earlier symbol and the address is less than
11307 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11308 to always print the symbolic form of an address if any symbol precedes
11309 it. Zero is equivalent to @code{unlimited}.
11311 @item show print max-symbolic-offset
11312 Ask how large the maximum offset is that @value{GDBN} prints in a
11316 @cindex wild pointer, interpreting
11317 @cindex pointer, finding referent
11318 If you have a pointer and you are not sure where it points, try
11319 @samp{set print symbol-filename on}. Then you can determine the name
11320 and source file location of the variable where it points, using
11321 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11322 For example, here @value{GDBN} shows that a variable @code{ptt} points
11323 at another variable @code{t}, defined in @file{hi2.c}:
11326 (@value{GDBP}) set print symbol-filename on
11327 (@value{GDBP}) p/a ptt
11328 $4 = 0xe008 <t in hi2.c>
11332 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11333 does not show the symbol name and filename of the referent, even with
11334 the appropriate @code{set print} options turned on.
11337 You can also enable @samp{/a}-like formatting all the time using
11338 @samp{set print symbol on}:
11340 @anchor{set print symbol}
11342 @item set print symbol on
11343 Tell @value{GDBN} to print the symbol corresponding to an address, if
11346 @item set print symbol off
11347 Tell @value{GDBN} not to print the symbol corresponding to an
11348 address. In this mode, @value{GDBN} will still print the symbol
11349 corresponding to pointers to functions. This is the default.
11351 @item show print symbol
11352 Show whether @value{GDBN} will display the symbol corresponding to an
11356 Other settings control how different kinds of objects are printed:
11359 @anchor{set print array}
11360 @item set print array
11361 @itemx set print array on
11362 @cindex pretty print arrays
11363 Pretty print arrays. This format is more convenient to read,
11364 but uses more space. The default is off.
11366 @item set print array off
11367 Return to compressed format for arrays.
11369 @item show print array
11370 Show whether compressed or pretty format is selected for displaying
11373 @cindex print array indexes
11374 @anchor{set print array-indexes}
11375 @item set print array-indexes
11376 @itemx set print array-indexes on
11377 Print the index of each element when displaying arrays. May be more
11378 convenient to locate a given element in the array or quickly find the
11379 index of a given element in that printed array. The default is off.
11381 @item set print array-indexes off
11382 Stop printing element indexes when displaying arrays.
11384 @item show print array-indexes
11385 Show whether the index of each element is printed when displaying
11388 @anchor{set print elements}
11389 @item set print elements @var{number-of-elements}
11390 @itemx set print elements unlimited
11391 @cindex number of array elements to print
11392 @cindex limit on number of printed array elements
11393 Set a limit on how many elements of an array @value{GDBN} will print.
11394 If @value{GDBN} is printing a large array, it stops printing after it has
11395 printed the number of elements set by the @code{set print elements} command.
11396 This limit also applies to the display of strings.
11397 When @value{GDBN} starts, this limit is set to 200.
11398 Setting @var{number-of-elements} to @code{unlimited} or zero means
11399 that the number of elements to print is unlimited.
11401 @item show print elements
11402 Display the number of elements of a large array that @value{GDBN} will print.
11404 @anchor{set print frame-arguments}
11405 @item set print frame-arguments @var{value}
11406 @kindex set print frame-arguments
11407 @cindex printing frame argument values
11408 @cindex print all frame argument values
11409 @cindex print frame argument values for scalars only
11410 @cindex do not print frame arguments
11411 This command allows to control how the values of arguments are printed
11412 when the debugger prints a frame (@pxref{Frames}). The possible
11417 The values of all arguments are printed.
11420 Print the value of an argument only if it is a scalar. The value of more
11421 complex arguments such as arrays, structures, unions, etc, is replaced
11422 by @code{@dots{}}. This is the default. Here is an example where
11423 only scalar arguments are shown:
11426 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11431 None of the argument values are printed. Instead, the value of each argument
11432 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11435 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11440 Only the presence of arguments is indicated by @code{@dots{}}.
11441 The @code{@dots{}} are not printed for function without any arguments.
11442 None of the argument names and values are printed.
11443 In this case, the example above now becomes:
11446 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11451 By default, only scalar arguments are printed. This command can be used
11452 to configure the debugger to print the value of all arguments, regardless
11453 of their type. However, it is often advantageous to not print the value
11454 of more complex parameters. For instance, it reduces the amount of
11455 information printed in each frame, making the backtrace more readable.
11456 Also, it improves performance when displaying Ada frames, because
11457 the computation of large arguments can sometimes be CPU-intensive,
11458 especially in large applications. Setting @code{print frame-arguments}
11459 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11460 this computation, thus speeding up the display of each Ada frame.
11462 @item show print frame-arguments
11463 Show how the value of arguments should be displayed when printing a frame.
11465 @anchor{set print raw-frame-arguments}
11466 @item set print raw-frame-arguments on
11467 Print frame arguments in raw, non pretty-printed, form.
11469 @item set print raw-frame-arguments off
11470 Print frame arguments in pretty-printed form, if there is a pretty-printer
11471 for the value (@pxref{Pretty Printing}),
11472 otherwise print the value in raw form.
11473 This is the default.
11475 @item show print raw-frame-arguments
11476 Show whether to print frame arguments in raw form.
11478 @anchor{set print entry-values}
11479 @item set print entry-values @var{value}
11480 @kindex set print entry-values
11481 Set printing of frame argument values at function entry. In some cases
11482 @value{GDBN} can determine the value of function argument which was passed by
11483 the function caller, even if the value was modified inside the called function
11484 and therefore is different. With optimized code, the current value could be
11485 unavailable, but the entry value may still be known.
11487 The default value is @code{default} (see below for its description). Older
11488 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11489 this feature will behave in the @code{default} setting the same way as with the
11492 This functionality is currently supported only by DWARF 2 debugging format and
11493 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11494 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11497 The @var{value} parameter can be one of the following:
11501 Print only actual parameter values, never print values from function entry
11505 #0 different (val=6)
11506 #0 lost (val=<optimized out>)
11508 #0 invalid (val=<optimized out>)
11512 Print only parameter values from function entry point. The actual parameter
11513 values are never printed.
11515 #0 equal (val@@entry=5)
11516 #0 different (val@@entry=5)
11517 #0 lost (val@@entry=5)
11518 #0 born (val@@entry=<optimized out>)
11519 #0 invalid (val@@entry=<optimized out>)
11523 Print only parameter values from function entry point. If value from function
11524 entry point is not known while the actual value is known, print the actual
11525 value for such parameter.
11527 #0 equal (val@@entry=5)
11528 #0 different (val@@entry=5)
11529 #0 lost (val@@entry=5)
11531 #0 invalid (val@@entry=<optimized out>)
11535 Print actual parameter values. If actual parameter value is not known while
11536 value from function entry point is known, print the entry point value for such
11540 #0 different (val=6)
11541 #0 lost (val@@entry=5)
11543 #0 invalid (val=<optimized out>)
11547 Always print both the actual parameter value and its value from function entry
11548 point, even if values of one or both are not available due to compiler
11551 #0 equal (val=5, val@@entry=5)
11552 #0 different (val=6, val@@entry=5)
11553 #0 lost (val=<optimized out>, val@@entry=5)
11554 #0 born (val=10, val@@entry=<optimized out>)
11555 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11559 Print the actual parameter value if it is known and also its value from
11560 function entry point if it is known. If neither is known, print for the actual
11561 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11562 values are known and identical, print the shortened
11563 @code{param=param@@entry=VALUE} notation.
11565 #0 equal (val=val@@entry=5)
11566 #0 different (val=6, val@@entry=5)
11567 #0 lost (val@@entry=5)
11569 #0 invalid (val=<optimized out>)
11573 Always print the actual parameter value. Print also its value from function
11574 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11575 if both values are known and identical, print the shortened
11576 @code{param=param@@entry=VALUE} notation.
11578 #0 equal (val=val@@entry=5)
11579 #0 different (val=6, val@@entry=5)
11580 #0 lost (val=<optimized out>, val@@entry=5)
11582 #0 invalid (val=<optimized out>)
11586 For analysis messages on possible failures of frame argument values at function
11587 entry resolution see @ref{set debug entry-values}.
11589 @item show print entry-values
11590 Show the method being used for printing of frame argument values at function
11593 @anchor{set print frame-info}
11594 @item set print frame-info @var{value}
11595 @kindex set print frame-info
11596 @cindex printing frame information
11597 @cindex frame information, printing
11598 This command allows to control the information printed when
11599 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11600 for a general explanation about frames and frame information.
11601 Note that some other settings (such as @code{set print frame-arguments}
11602 and @code{set print address}) are also influencing if and how some frame
11603 information is displayed. In particular, the frame program counter is never
11604 printed if @code{set print address} is off.
11606 The possible values for @code{set print frame-info} are:
11608 @item short-location
11609 Print the frame level, the program counter (if not at the
11610 beginning of the location source line), the function, the function
11613 Same as @code{short-location} but also print the source file and source line
11615 @item location-and-address
11616 Same as @code{location} but print the program counter even if located at the
11617 beginning of the location source line.
11619 Print the program counter (if not at the beginning of the location
11620 source line), the line number and the source line.
11621 @item source-and-location
11622 Print what @code{location} and @code{source-line} are printing.
11624 The information printed for a frame is decided automatically
11625 by the @value{GDBN} command that prints a frame.
11626 For example, @code{frame} prints the information printed by
11627 @code{source-and-location} while @code{stepi} will switch between
11628 @code{source-line} and @code{source-and-location} depending on the program
11630 The default value is @code{auto}.
11633 @anchor{set print repeats}
11634 @item set print repeats @var{number-of-repeats}
11635 @itemx set print repeats unlimited
11636 @cindex repeated array elements
11637 Set the threshold for suppressing display of repeated array
11638 elements. When the number of consecutive identical elements of an
11639 array exceeds the threshold, @value{GDBN} prints the string
11640 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11641 identical repetitions, instead of displaying the identical elements
11642 themselves. Setting the threshold to @code{unlimited} or zero will
11643 cause all elements to be individually printed. The default threshold
11646 @item show print repeats
11647 Display the current threshold for printing repeated identical
11650 @anchor{set print max-depth}
11651 @item set print max-depth @var{depth}
11652 @item set print max-depth unlimited
11653 @cindex printing nested structures
11654 Set the threshold after which nested structures are replaced with
11655 ellipsis, this can make visualising deeply nested structures easier.
11657 For example, given this C code
11660 typedef struct s1 @{ int a; @} s1;
11661 typedef struct s2 @{ s1 b; @} s2;
11662 typedef struct s3 @{ s2 c; @} s3;
11663 typedef struct s4 @{ s3 d; @} s4;
11665 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11668 The following table shows how different values of @var{depth} will
11669 effect how @code{var} is printed by @value{GDBN}:
11671 @multitable @columnfractions .3 .7
11672 @headitem @var{depth} setting @tab Result of @samp{p var}
11674 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11676 @tab @code{$1 = @{...@}}
11678 @tab @code{$1 = @{d = @{...@}@}}
11680 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11682 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11684 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11687 To see the contents of structures that have been hidden the user can
11688 either increase the print max-depth, or they can print the elements of
11689 the structure that are visible, for example
11692 (gdb) set print max-depth 2
11694 $1 = @{d = @{c = @{...@}@}@}
11696 $2 = @{c = @{b = @{...@}@}@}
11698 $3 = @{b = @{a = 3@}@}
11701 The pattern used to replace nested structures varies based on
11702 language, for most languages @code{@{...@}} is used, but Fortran uses
11705 @item show print max-depth
11706 Display the current threshold after which nested structures are
11707 replaces with ellipsis.
11709 @anchor{set print memory-tag-violations}
11710 @cindex printing memory tag violation information
11711 @item set print memory-tag-violations
11712 @itemx set print memory-tag-violations on
11713 Cause @value{GDBN} to display additional information about memory tag violations
11714 when printing pointers and addresses.
11716 @item set print memory-tag-violations off
11717 Stop printing memory tag violation information.
11719 @item show print memory-tag-violations
11720 Show whether memory tag violation information is displayed when printing
11721 pointers and addresses.
11723 @anchor{set print null-stop}
11724 @item set print null-stop
11725 @cindex @sc{null} elements in arrays
11726 Cause @value{GDBN} to stop printing the characters of an array when the first
11727 @sc{null} is encountered. This is useful when large arrays actually
11728 contain only short strings.
11729 The default is off.
11731 @item show print null-stop
11732 Show whether @value{GDBN} stops printing an array on the first
11733 @sc{null} character.
11735 @anchor{set print pretty}
11736 @item set print pretty on
11737 @cindex print structures in indented form
11738 @cindex indentation in structure display
11739 Cause @value{GDBN} to print structures in an indented format with one member
11740 per line, like this:
11755 @item set print pretty off
11756 Cause @value{GDBN} to print structures in a compact format, like this:
11760 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11761 meat = 0x54 "Pork"@}
11766 This is the default format.
11768 @item show print pretty
11769 Show which format @value{GDBN} is using to print structures.
11771 @anchor{set print raw-values}
11772 @item set print raw-values on
11773 Print values in raw form, without applying the pretty
11774 printers for the value.
11776 @item set print raw-values off
11777 Print values in pretty-printed form, if there is a pretty-printer
11778 for the value (@pxref{Pretty Printing}),
11779 otherwise print the value in raw form.
11781 The default setting is ``off''.
11783 @item show print raw-values
11784 Show whether to print values in raw form.
11786 @item set print sevenbit-strings on
11787 @cindex eight-bit characters in strings
11788 @cindex octal escapes in strings
11789 Print using only seven-bit characters; if this option is set,
11790 @value{GDBN} displays any eight-bit characters (in strings or
11791 character values) using the notation @code{\}@var{nnn}. This setting is
11792 best if you are working in English (@sc{ascii}) and you use the
11793 high-order bit of characters as a marker or ``meta'' bit.
11795 @item set print sevenbit-strings off
11796 Print full eight-bit characters. This allows the use of more
11797 international character sets, and is the default.
11799 @item show print sevenbit-strings
11800 Show whether or not @value{GDBN} is printing only seven-bit characters.
11802 @anchor{set print union}
11803 @item set print union on
11804 @cindex unions in structures, printing
11805 Tell @value{GDBN} to print unions which are contained in structures
11806 and other unions. This is the default setting.
11808 @item set print union off
11809 Tell @value{GDBN} not to print unions which are contained in
11810 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11813 @item show print union
11814 Ask @value{GDBN} whether or not it will print unions which are contained in
11815 structures and other unions.
11817 For example, given the declarations
11820 typedef enum @{Tree, Bug@} Species;
11821 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11822 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11833 struct thing foo = @{Tree, @{Acorn@}@};
11837 with @code{set print union on} in effect @samp{p foo} would print
11840 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11844 and with @code{set print union off} in effect it would print
11847 $1 = @{it = Tree, form = @{...@}@}
11851 @code{set print union} affects programs written in C-like languages
11857 These settings are of interest when debugging C@t{++} programs:
11860 @cindex demangling C@t{++} names
11861 @item set print demangle
11862 @itemx set print demangle on
11863 Print C@t{++} names in their source form rather than in the encoded
11864 (``mangled'') form passed to the assembler and linker for type-safe
11865 linkage. The default is on.
11867 @item show print demangle
11868 Show whether C@t{++} names are printed in mangled or demangled form.
11870 @item set print asm-demangle
11871 @itemx set print asm-demangle on
11872 Print C@t{++} names in their source form rather than their mangled form, even
11873 in assembler code printouts such as instruction disassemblies.
11874 The default is off.
11876 @item show print asm-demangle
11877 Show whether C@t{++} names in assembly listings are printed in mangled
11880 @cindex C@t{++} symbol decoding style
11881 @cindex symbol decoding style, C@t{++}
11882 @kindex set demangle-style
11883 @item set demangle-style @var{style}
11884 Choose among several encoding schemes used by different compilers to represent
11885 C@t{++} names. If you omit @var{style}, you will see a list of possible
11886 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11887 decoding style by inspecting your program.
11889 @item show demangle-style
11890 Display the encoding style currently in use for decoding C@t{++} symbols.
11892 @anchor{set print object}
11893 @item set print object
11894 @itemx set print object on
11895 @cindex derived type of an object, printing
11896 @cindex display derived types
11897 When displaying a pointer to an object, identify the @emph{actual}
11898 (derived) type of the object rather than the @emph{declared} type, using
11899 the virtual function table. Note that the virtual function table is
11900 required---this feature can only work for objects that have run-time
11901 type identification; a single virtual method in the object's declared
11902 type is sufficient. Note that this setting is also taken into account when
11903 working with variable objects via MI (@pxref{GDB/MI}).
11905 @item set print object off
11906 Display only the declared type of objects, without reference to the
11907 virtual function table. This is the default setting.
11909 @item show print object
11910 Show whether actual, or declared, object types are displayed.
11912 @anchor{set print static-members}
11913 @item set print static-members
11914 @itemx set print static-members on
11915 @cindex static members of C@t{++} objects
11916 Print static members when displaying a C@t{++} object. The default is on.
11918 @item set print static-members off
11919 Do not print static members when displaying a C@t{++} object.
11921 @item show print static-members
11922 Show whether C@t{++} static members are printed or not.
11924 @item set print pascal_static-members
11925 @itemx set print pascal_static-members on
11926 @cindex static members of Pascal objects
11927 @cindex Pascal objects, static members display
11928 Print static members when displaying a Pascal object. The default is on.
11930 @item set print pascal_static-members off
11931 Do not print static members when displaying a Pascal object.
11933 @item show print pascal_static-members
11934 Show whether Pascal static members are printed or not.
11936 @c These don't work with HP ANSI C++ yet.
11937 @anchor{set print vtbl}
11938 @item set print vtbl
11939 @itemx set print vtbl on
11940 @cindex pretty print C@t{++} virtual function tables
11941 @cindex virtual functions (C@t{++}) display
11942 @cindex VTBL display
11943 Pretty print C@t{++} virtual function tables. The default is off.
11944 (The @code{vtbl} commands do not work on programs compiled with the HP
11945 ANSI C@t{++} compiler (@code{aCC}).)
11947 @item set print vtbl off
11948 Do not pretty print C@t{++} virtual function tables.
11950 @item show print vtbl
11951 Show whether C@t{++} virtual function tables are pretty printed, or not.
11954 @node Pretty Printing
11955 @section Pretty Printing
11957 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11958 Python code. It greatly simplifies the display of complex objects. This
11959 mechanism works for both MI and the CLI.
11962 * Pretty-Printer Introduction:: Introduction to pretty-printers
11963 * Pretty-Printer Example:: An example pretty-printer
11964 * Pretty-Printer Commands:: Pretty-printer commands
11967 @node Pretty-Printer Introduction
11968 @subsection Pretty-Printer Introduction
11970 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11971 registered for the value. If there is then @value{GDBN} invokes the
11972 pretty-printer to print the value. Otherwise the value is printed normally.
11974 Pretty-printers are normally named. This makes them easy to manage.
11975 The @samp{info pretty-printer} command will list all the installed
11976 pretty-printers with their names.
11977 If a pretty-printer can handle multiple data types, then its
11978 @dfn{subprinters} are the printers for the individual data types.
11979 Each such subprinter has its own name.
11980 The format of the name is @var{printer-name};@var{subprinter-name}.
11982 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11983 Typically they are automatically loaded and registered when the corresponding
11984 debug information is loaded, thus making them available without having to
11985 do anything special.
11987 There are three places where a pretty-printer can be registered.
11991 Pretty-printers registered globally are available when debugging
11995 Pretty-printers registered with a program space are available only
11996 when debugging that program.
11997 @xref{Progspaces In Python}, for more details on program spaces in Python.
12000 Pretty-printers registered with an objfile are loaded and unloaded
12001 with the corresponding objfile (e.g., shared library).
12002 @xref{Objfiles In Python}, for more details on objfiles in Python.
12005 @xref{Selecting Pretty-Printers}, for further information on how
12006 pretty-printers are selected,
12008 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12011 @node Pretty-Printer Example
12012 @subsection Pretty-Printer Example
12014 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12017 (@value{GDBP}) print s
12019 static npos = 4294967295,
12021 <std::allocator<char>> = @{
12022 <__gnu_cxx::new_allocator<char>> = @{
12023 <No data fields>@}, <No data fields>
12025 members of std::basic_string<char, std::char_traits<char>,
12026 std::allocator<char> >::_Alloc_hider:
12027 _M_p = 0x804a014 "abcd"
12032 With a pretty-printer for @code{std::string} only the contents are printed:
12035 (@value{GDBP}) print s
12039 @node Pretty-Printer Commands
12040 @subsection Pretty-Printer Commands
12041 @cindex pretty-printer commands
12044 @kindex info pretty-printer
12045 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12046 Print the list of installed pretty-printers.
12047 This includes disabled pretty-printers, which are marked as such.
12049 @var{object-regexp} is a regular expression matching the objects
12050 whose pretty-printers to list.
12051 Objects can be @code{global}, the program space's file
12052 (@pxref{Progspaces In Python}),
12053 and the object files within that program space (@pxref{Objfiles In Python}).
12054 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12055 looks up a printer from these three objects.
12057 @var{name-regexp} is a regular expression matching the name of the printers
12060 @kindex disable pretty-printer
12061 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12062 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12063 A disabled pretty-printer is not forgotten, it may be enabled again later.
12065 @kindex enable pretty-printer
12066 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12067 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12072 Suppose we have three pretty-printers installed: one from library1.so
12073 named @code{foo} that prints objects of type @code{foo}, and
12074 another from library2.so named @code{bar} that prints two types of objects,
12075 @code{bar1} and @code{bar2}.
12078 (gdb) info pretty-printer
12085 (gdb) info pretty-printer library2
12090 (gdb) disable pretty-printer library1
12092 2 of 3 printers enabled
12093 (gdb) info pretty-printer
12100 (gdb) disable pretty-printer library2 bar;bar1
12102 1 of 3 printers enabled
12103 (gdb) info pretty-printer library2
12110 (gdb) disable pretty-printer library2 bar
12112 0 of 3 printers enabled
12113 (gdb) info pretty-printer library2
12122 Note that for @code{bar} the entire printer can be disabled,
12123 as can each individual subprinter.
12125 Printing values and frame arguments is done by default using
12126 the enabled pretty printers.
12128 The print option @code{-raw-values} and @value{GDBN} setting
12129 @code{set print raw-values} (@pxref{set print raw-values}) can be
12130 used to print values without applying the enabled pretty printers.
12132 Similarly, the backtrace option @code{-raw-frame-arguments} and
12133 @value{GDBN} setting @code{set print raw-frame-arguments}
12134 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12135 enabled pretty printers when printing frame argument values.
12137 @node Value History
12138 @section Value History
12140 @cindex value history
12141 @cindex history of values printed by @value{GDBN}
12142 Values printed by the @code{print} command are saved in the @value{GDBN}
12143 @dfn{value history}. This allows you to refer to them in other expressions.
12144 Values are kept until the symbol table is re-read or discarded
12145 (for example with the @code{file} or @code{symbol-file} commands).
12146 When the symbol table changes, the value history is discarded,
12147 since the values may contain pointers back to the types defined in the
12152 @cindex history number
12153 The values printed are given @dfn{history numbers} by which you can
12154 refer to them. These are successive integers starting with one.
12155 @code{print} shows you the history number assigned to a value by
12156 printing @samp{$@var{num} = } before the value; here @var{num} is the
12159 To refer to any previous value, use @samp{$} followed by the value's
12160 history number. The way @code{print} labels its output is designed to
12161 remind you of this. Just @code{$} refers to the most recent value in
12162 the history, and @code{$$} refers to the value before that.
12163 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12164 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12165 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12167 For example, suppose you have just printed a pointer to a structure and
12168 want to see the contents of the structure. It suffices to type
12174 If you have a chain of structures where the component @code{next} points
12175 to the next one, you can print the contents of the next one with this:
12182 You can print successive links in the chain by repeating this
12183 command---which you can do by just typing @key{RET}.
12185 Note that the history records values, not expressions. If the value of
12186 @code{x} is 4 and you type these commands:
12194 then the value recorded in the value history by the @code{print} command
12195 remains 4 even though the value of @code{x} has changed.
12198 @kindex show values
12200 Print the last ten values in the value history, with their item numbers.
12201 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12202 values} does not change the history.
12204 @item show values @var{n}
12205 Print ten history values centered on history item number @var{n}.
12207 @item show values +
12208 Print ten history values just after the values last printed. If no more
12209 values are available, @code{show values +} produces no display.
12212 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12213 same effect as @samp{show values +}.
12215 @node Convenience Vars
12216 @section Convenience Variables
12218 @cindex convenience variables
12219 @cindex user-defined variables
12220 @value{GDBN} provides @dfn{convenience variables} that you can use within
12221 @value{GDBN} to hold on to a value and refer to it later. These variables
12222 exist entirely within @value{GDBN}; they are not part of your program, and
12223 setting a convenience variable has no direct effect on further execution
12224 of your program. That is why you can use them freely.
12226 Convenience variables are prefixed with @samp{$}. Any name preceded by
12227 @samp{$} can be used for a convenience variable, unless it is one of
12228 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12229 (Value history references, in contrast, are @emph{numbers} preceded
12230 by @samp{$}. @xref{Value History, ,Value History}.)
12232 You can save a value in a convenience variable with an assignment
12233 expression, just as you would set a variable in your program.
12237 set $foo = *object_ptr
12241 would save in @code{$foo} the value contained in the object pointed to by
12244 Using a convenience variable for the first time creates it, but its
12245 value is @code{void} until you assign a new value. You can alter the
12246 value with another assignment at any time.
12248 Convenience variables have no fixed types. You can assign a convenience
12249 variable any type of value, including structures and arrays, even if
12250 that variable already has a value of a different type. The convenience
12251 variable, when used as an expression, has the type of its current value.
12254 @kindex show convenience
12255 @cindex show all user variables and functions
12256 @item show convenience
12257 Print a list of convenience variables used so far, and their values,
12258 as well as a list of the convenience functions.
12259 Abbreviated @code{show conv}.
12261 @kindex init-if-undefined
12262 @cindex convenience variables, initializing
12263 @item init-if-undefined $@var{variable} = @var{expression}
12264 Set a convenience variable if it has not already been set. This is useful
12265 for user-defined commands that keep some state. It is similar, in concept,
12266 to using local static variables with initializers in C (except that
12267 convenience variables are global). It can also be used to allow users to
12268 override default values used in a command script.
12270 If the variable is already defined then the expression is not evaluated so
12271 any side-effects do not occur.
12274 One of the ways to use a convenience variable is as a counter to be
12275 incremented or a pointer to be advanced. For example, to print
12276 a field from successive elements of an array of structures:
12280 print bar[$i++]->contents
12284 Repeat that command by typing @key{RET}.
12286 Some convenience variables are created automatically by @value{GDBN} and given
12287 values likely to be useful.
12290 @vindex $_@r{, convenience variable}
12292 The variable @code{$_} is automatically set by the @code{x} command to
12293 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12294 commands which provide a default address for @code{x} to examine also
12295 set @code{$_} to that address; these commands include @code{info line}
12296 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12297 except when set by the @code{x} command, in which case it is a pointer
12298 to the type of @code{$__}.
12300 @vindex $__@r{, convenience variable}
12302 The variable @code{$__} is automatically set by the @code{x} command
12303 to the value found in the last address examined. Its type is chosen
12304 to match the format in which the data was printed.
12307 @vindex $_exitcode@r{, convenience variable}
12308 When the program being debugged terminates normally, @value{GDBN}
12309 automatically sets this variable to the exit code of the program, and
12310 resets @code{$_exitsignal} to @code{void}.
12313 @vindex $_exitsignal@r{, convenience variable}
12314 When the program being debugged dies due to an uncaught signal,
12315 @value{GDBN} automatically sets this variable to that signal's number,
12316 and resets @code{$_exitcode} to @code{void}.
12318 To distinguish between whether the program being debugged has exited
12319 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12320 @code{$_exitsignal} is not @code{void}), the convenience function
12321 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12322 Functions}). For example, considering the following source code:
12325 #include <signal.h>
12328 main (int argc, char *argv[])
12335 A valid way of telling whether the program being debugged has exited
12336 or signalled would be:
12339 (@value{GDBP}) define has_exited_or_signalled
12340 Type commands for definition of ``has_exited_or_signalled''.
12341 End with a line saying just ``end''.
12342 >if $_isvoid ($_exitsignal)
12343 >echo The program has exited\n
12345 >echo The program has signalled\n
12351 Program terminated with signal SIGALRM, Alarm clock.
12352 The program no longer exists.
12353 (@value{GDBP}) has_exited_or_signalled
12354 The program has signalled
12357 As can be seen, @value{GDBN} correctly informs that the program being
12358 debugged has signalled, since it calls @code{raise} and raises a
12359 @code{SIGALRM} signal. If the program being debugged had not called
12360 @code{raise}, then @value{GDBN} would report a normal exit:
12363 (@value{GDBP}) has_exited_or_signalled
12364 The program has exited
12368 The variable @code{$_exception} is set to the exception object being
12369 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12371 @item $_ada_exception
12372 The variable @code{$_ada_exception} is set to the address of the
12373 exception being caught or thrown at an Ada exception-related
12374 catchpoint. @xref{Set Catchpoints}.
12377 @itemx $_probe_arg0@dots{}$_probe_arg11
12378 Arguments to a static probe. @xref{Static Probe Points}.
12381 @vindex $_sdata@r{, inspect, convenience variable}
12382 The variable @code{$_sdata} contains extra collected static tracepoint
12383 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12384 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12385 if extra static tracepoint data has not been collected.
12388 @vindex $_siginfo@r{, convenience variable}
12389 The variable @code{$_siginfo} contains extra signal information
12390 (@pxref{extra signal information}). Note that @code{$_siginfo}
12391 could be empty, if the application has not yet received any signals.
12392 For example, it will be empty before you execute the @code{run} command.
12395 @vindex $_tlb@r{, convenience variable}
12396 The variable @code{$_tlb} is automatically set when debugging
12397 applications running on MS-Windows in native mode or connected to
12398 gdbserver that supports the @code{qGetTIBAddr} request.
12399 @xref{General Query Packets}.
12400 This variable contains the address of the thread information block.
12403 The number of the current inferior. @xref{Inferiors Connections and
12404 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12407 The thread number of the current thread. @xref{thread numbers}.
12410 The global number of the current thread. @xref{global thread numbers}.
12414 @vindex $_gdb_major@r{, convenience variable}
12415 @vindex $_gdb_minor@r{, convenience variable}
12416 The major and minor version numbers of the running @value{GDBN}.
12417 Development snapshots and pretest versions have their minor version
12418 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12419 the value 12 for @code{$_gdb_minor}. These variables allow you to
12420 write scripts that work with different versions of @value{GDBN}
12421 without errors caused by features unavailable in some of those
12424 @item $_shell_exitcode
12425 @itemx $_shell_exitsignal
12426 @vindex $_shell_exitcode@r{, convenience variable}
12427 @vindex $_shell_exitsignal@r{, convenience variable}
12428 @cindex shell command, exit code
12429 @cindex shell command, exit signal
12430 @cindex exit status of shell commands
12431 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12432 shell commands. When a launched command terminates, @value{GDBN}
12433 automatically maintains the variables @code{$_shell_exitcode}
12434 and @code{$_shell_exitsignal} according to the exit status of the last
12435 launched command. These variables are set and used similarly to
12436 the variables @code{$_exitcode} and @code{$_exitsignal}.
12440 @node Convenience Funs
12441 @section Convenience Functions
12443 @cindex convenience functions
12444 @value{GDBN} also supplies some @dfn{convenience functions}. These
12445 have a syntax similar to convenience variables. A convenience
12446 function can be used in an expression just like an ordinary function;
12447 however, a convenience function is implemented internally to
12450 These functions do not require @value{GDBN} to be configured with
12451 @code{Python} support, which means that they are always available.
12455 @item $_isvoid (@var{expr})
12456 @findex $_isvoid@r{, convenience function}
12457 Return one if the expression @var{expr} is @code{void}. Otherwise it
12460 A @code{void} expression is an expression where the type of the result
12461 is @code{void}. For example, you can examine a convenience variable
12462 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12466 (@value{GDBP}) print $_exitcode
12468 (@value{GDBP}) print $_isvoid ($_exitcode)
12471 Starting program: ./a.out
12472 [Inferior 1 (process 29572) exited normally]
12473 (@value{GDBP}) print $_exitcode
12475 (@value{GDBP}) print $_isvoid ($_exitcode)
12479 In the example above, we used @code{$_isvoid} to check whether
12480 @code{$_exitcode} is @code{void} before and after the execution of the
12481 program being debugged. Before the execution there is no exit code to
12482 be examined, therefore @code{$_exitcode} is @code{void}. After the
12483 execution the program being debugged returned zero, therefore
12484 @code{$_exitcode} is zero, which means that it is not @code{void}
12487 The @code{void} expression can also be a call of a function from the
12488 program being debugged. For example, given the following function:
12497 The result of calling it inside @value{GDBN} is @code{void}:
12500 (@value{GDBP}) print foo ()
12502 (@value{GDBP}) print $_isvoid (foo ())
12504 (@value{GDBP}) set $v = foo ()
12505 (@value{GDBP}) print $v
12507 (@value{GDBP}) print $_isvoid ($v)
12511 @item $_gdb_setting_str (@var{setting})
12512 @findex $_gdb_setting_str@r{, convenience function}
12513 Return the value of the @value{GDBN} @var{setting} as a string.
12514 @var{setting} is any setting that can be used in a @code{set} or
12515 @code{show} command (@pxref{Controlling GDB}).
12518 (@value{GDBP}) show print frame-arguments
12519 Printing of non-scalar frame arguments is "scalars".
12520 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12522 (@value{GDBP}) p $_gdb_setting_str("height")
12527 @item $_gdb_setting (@var{setting})
12528 @findex $_gdb_setting@r{, convenience function}
12529 Return the value of the @value{GDBN} @var{setting}.
12530 The type of the returned value depends on the setting.
12532 The value type for boolean and auto boolean settings is @code{int}.
12533 The boolean values @code{off} and @code{on} are converted to
12534 the integer values @code{0} and @code{1}. The value @code{auto} is
12535 converted to the value @code{-1}.
12537 The value type for integer settings is either @code{unsigned int}
12538 or @code{int}, depending on the setting.
12540 Some integer settings accept an @code{unlimited} value.
12541 Depending on the setting, the @code{set} command also accepts
12542 the value @code{0} or the value @code{@minus{}1} as a synonym for
12544 For example, @code{set height unlimited} is equivalent to
12545 @code{set height 0}.
12547 Some other settings that accept the @code{unlimited} value
12548 use the value @code{0} to literally mean zero.
12549 For example, @code{set history size 0} indicates to not
12550 record any @value{GDBN} commands in the command history.
12551 For such settings, @code{@minus{}1} is the synonym
12552 for @code{unlimited}.
12554 See the documentation of the corresponding @code{set} command for
12555 the numerical value equivalent to @code{unlimited}.
12557 The @code{$_gdb_setting} function converts the unlimited value
12558 to a @code{0} or a @code{@minus{}1} value according to what the
12559 @code{set} command uses.
12563 (@value{GDBP}) p $_gdb_setting_str("height")
12565 (@value{GDBP}) p $_gdb_setting("height")
12567 (@value{GDBP}) set height unlimited
12568 (@value{GDBP}) p $_gdb_setting_str("height")
12570 (@value{GDBP}) p $_gdb_setting("height")
12574 (@value{GDBP}) p $_gdb_setting_str("history size")
12576 (@value{GDBP}) p $_gdb_setting("history size")
12578 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12580 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12586 Other setting types (enum, filename, optional filename, string, string noescape)
12587 are returned as string values.
12590 @item $_gdb_maint_setting_str (@var{setting})
12591 @findex $_gdb_maint_setting_str@r{, convenience function}
12592 Like the @code{$_gdb_setting_str} function, but works with
12593 @code{maintenance set} variables.
12595 @item $_gdb_maint_setting (@var{setting})
12596 @findex $_gdb_maint_setting@r{, convenience function}
12597 Like the @code{$_gdb_setting} function, but works with
12598 @code{maintenance set} variables.
12602 The following functions require @value{GDBN} to be configured with
12603 @code{Python} support.
12607 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12608 @findex $_memeq@r{, convenience function}
12609 Returns one if the @var{length} bytes at the addresses given by
12610 @var{buf1} and @var{buf2} are equal.
12611 Otherwise it returns zero.
12613 @item $_regex(@var{str}, @var{regex})
12614 @findex $_regex@r{, convenience function}
12615 Returns one if the string @var{str} matches the regular expression
12616 @var{regex}. Otherwise it returns zero.
12617 The syntax of the regular expression is that specified by @code{Python}'s
12618 regular expression support.
12620 @item $_streq(@var{str1}, @var{str2})
12621 @findex $_streq@r{, convenience function}
12622 Returns one if the strings @var{str1} and @var{str2} are equal.
12623 Otherwise it returns zero.
12625 @item $_strlen(@var{str})
12626 @findex $_strlen@r{, convenience function}
12627 Returns the length of string @var{str}.
12629 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12630 @findex $_caller_is@r{, convenience function}
12631 Returns one if the calling function's name is equal to @var{name}.
12632 Otherwise it returns zero.
12634 If the optional argument @var{number_of_frames} is provided,
12635 it is the number of frames up in the stack to look.
12643 at testsuite/gdb.python/py-caller-is.c:21
12644 #1 0x00000000004005a0 in middle_func ()
12645 at testsuite/gdb.python/py-caller-is.c:27
12646 #2 0x00000000004005ab in top_func ()
12647 at testsuite/gdb.python/py-caller-is.c:33
12648 #3 0x00000000004005b6 in main ()
12649 at testsuite/gdb.python/py-caller-is.c:39
12650 (gdb) print $_caller_is ("middle_func")
12652 (gdb) print $_caller_is ("top_func", 2)
12656 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12657 @findex $_caller_matches@r{, convenience function}
12658 Returns one if the calling function's name matches the regular expression
12659 @var{regexp}. Otherwise it returns zero.
12661 If the optional argument @var{number_of_frames} is provided,
12662 it is the number of frames up in the stack to look.
12665 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12666 @findex $_any_caller_is@r{, convenience function}
12667 Returns one if any calling function's name is equal to @var{name}.
12668 Otherwise it returns zero.
12670 If the optional argument @var{number_of_frames} is provided,
12671 it is the number of frames up in the stack to look.
12674 This function differs from @code{$_caller_is} in that this function
12675 checks all stack frames from the immediate caller to the frame specified
12676 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12677 frame specified by @var{number_of_frames}.
12679 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12680 @findex $_any_caller_matches@r{, convenience function}
12681 Returns one if any calling function's name matches the regular expression
12682 @var{regexp}. Otherwise it returns zero.
12684 If the optional argument @var{number_of_frames} is provided,
12685 it is the number of frames up in the stack to look.
12688 This function differs from @code{$_caller_matches} in that this function
12689 checks all stack frames from the immediate caller to the frame specified
12690 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12691 frame specified by @var{number_of_frames}.
12693 @item $_as_string(@var{value})
12694 @findex $_as_string@r{, convenience function}
12695 Return the string representation of @var{value}.
12697 This function is useful to obtain the textual label (enumerator) of an
12698 enumeration value. For example, assuming the variable @var{node} is of
12699 an enumerated type:
12702 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12703 Visiting node of type NODE_INTEGER
12706 @item $_cimag(@var{value})
12707 @itemx $_creal(@var{value})
12708 @findex $_cimag@r{, convenience function}
12709 @findex $_creal@r{, convenience function}
12710 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12711 the complex number @var{value}.
12713 The type of the imaginary or real part depends on the type of the
12714 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12715 will return an imaginary part of type @code{float}.
12719 @value{GDBN} provides the ability to list and get help on
12720 convenience functions.
12723 @item help function
12724 @kindex help function
12725 @cindex show all convenience functions
12726 Print a list of all convenience functions.
12733 You can refer to machine register contents, in expressions, as variables
12734 with names starting with @samp{$}. The names of registers are different
12735 for each machine; use @code{info registers} to see the names used on
12739 @kindex info registers
12740 @item info registers
12741 Print the names and values of all registers except floating-point
12742 and vector registers (in the selected stack frame).
12744 @kindex info all-registers
12745 @cindex floating point registers
12746 @item info all-registers
12747 Print the names and values of all registers, including floating-point
12748 and vector registers (in the selected stack frame).
12750 @anchor{info_registers_reggroup}
12751 @item info registers @var{reggroup} @dots{}
12752 Print the name and value of the registers in each of the specified
12753 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12754 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12756 @item info registers @var{regname} @dots{}
12757 Print the @dfn{relativized} value of each specified register @var{regname}.
12758 As discussed in detail below, register values are normally relative to
12759 the selected stack frame. The @var{regname} may be any register name valid on
12760 the machine you are using, with or without the initial @samp{$}.
12763 @anchor{standard registers}
12764 @cindex stack pointer register
12765 @cindex program counter register
12766 @cindex process status register
12767 @cindex frame pointer register
12768 @cindex standard registers
12769 @value{GDBN} has four ``standard'' register names that are available (in
12770 expressions) on most machines---whenever they do not conflict with an
12771 architecture's canonical mnemonics for registers. The register names
12772 @code{$pc} and @code{$sp} are used for the program counter register and
12773 the stack pointer. @code{$fp} is used for a register that contains a
12774 pointer to the current stack frame, and @code{$ps} is used for a
12775 register that contains the processor status. For example,
12776 you could print the program counter in hex with
12783 or print the instruction to be executed next with
12790 or add four to the stack pointer@footnote{This is a way of removing
12791 one word from the stack, on machines where stacks grow downward in
12792 memory (most machines, nowadays). This assumes that the innermost
12793 stack frame is selected; setting @code{$sp} is not allowed when other
12794 stack frames are selected. To pop entire frames off the stack,
12795 regardless of machine architecture, use @code{return};
12796 see @ref{Returning, ,Returning from a Function}.} with
12802 Whenever possible, these four standard register names are available on
12803 your machine even though the machine has different canonical mnemonics,
12804 so long as there is no conflict. The @code{info registers} command
12805 shows the canonical names. For example, on the SPARC, @code{info
12806 registers} displays the processor status register as @code{$psr} but you
12807 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12808 is an alias for the @sc{eflags} register.
12810 @value{GDBN} always considers the contents of an ordinary register as an
12811 integer when the register is examined in this way. Some machines have
12812 special registers which can hold nothing but floating point; these
12813 registers are considered to have floating point values. There is no way
12814 to refer to the contents of an ordinary register as floating point value
12815 (although you can @emph{print} it as a floating point value with
12816 @samp{print/f $@var{regname}}).
12818 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12819 means that the data format in which the register contents are saved by
12820 the operating system is not the same one that your program normally
12821 sees. For example, the registers of the 68881 floating point
12822 coprocessor are always saved in ``extended'' (raw) format, but all C
12823 programs expect to work with ``double'' (virtual) format. In such
12824 cases, @value{GDBN} normally works with the virtual format only (the format
12825 that makes sense for your program), but the @code{info registers} command
12826 prints the data in both formats.
12828 @cindex SSE registers (x86)
12829 @cindex MMX registers (x86)
12830 Some machines have special registers whose contents can be interpreted
12831 in several different ways. For example, modern x86-based machines
12832 have SSE and MMX registers that can hold several values packed
12833 together in several different formats. @value{GDBN} refers to such
12834 registers in @code{struct} notation:
12837 (@value{GDBP}) print $xmm1
12839 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12840 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12841 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12842 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12843 v4_int32 = @{0, 20657912, 11, 13@},
12844 v2_int64 = @{88725056443645952, 55834574859@},
12845 uint128 = 0x0000000d0000000b013b36f800000000
12850 To set values of such registers, you need to tell @value{GDBN} which
12851 view of the register you wish to change, as if you were assigning
12852 value to a @code{struct} member:
12855 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12858 Normally, register values are relative to the selected stack frame
12859 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12860 value that the register would contain if all stack frames farther in
12861 were exited and their saved registers restored. In order to see the
12862 true contents of hardware registers, you must select the innermost
12863 frame (with @samp{frame 0}).
12865 @cindex caller-saved registers
12866 @cindex call-clobbered registers
12867 @cindex volatile registers
12868 @cindex <not saved> values
12869 Usually ABIs reserve some registers as not needed to be saved by the
12870 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12871 registers). It may therefore not be possible for @value{GDBN} to know
12872 the value a register had before the call (in other words, in the outer
12873 frame), if the register value has since been changed by the callee.
12874 @value{GDBN} tries to deduce where the inner frame saved
12875 (``callee-saved'') registers, from the debug info, unwind info, or the
12876 machine code generated by your compiler. If some register is not
12877 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12878 its own knowledge of the ABI, or because the debug/unwind info
12879 explicitly says the register's value is undefined), @value{GDBN}
12880 displays @w{@samp{<not saved>}} as the register's value. With targets
12881 that @value{GDBN} has no knowledge of the register saving convention,
12882 if a register was not saved by the callee, then its value and location
12883 in the outer frame are assumed to be the same of the inner frame.
12884 This is usually harmless, because if the register is call-clobbered,
12885 the caller either does not care what is in the register after the
12886 call, or has code to restore the value that it does care about. Note,
12887 however, that if you change such a register in the outer frame, you
12888 may also be affecting the inner frame. Also, the more ``outer'' the
12889 frame is you're looking at, the more likely a call-clobbered
12890 register's value is to be wrong, in the sense that it doesn't actually
12891 represent the value the register had just before the call.
12893 @node Floating Point Hardware
12894 @section Floating Point Hardware
12895 @cindex floating point
12897 Depending on the configuration, @value{GDBN} may be able to give
12898 you more information about the status of the floating point hardware.
12903 Display hardware-dependent information about the floating
12904 point unit. The exact contents and layout vary depending on the
12905 floating point chip. Currently, @samp{info float} is supported on
12906 the ARM and x86 machines.
12910 @section Vector Unit
12911 @cindex vector unit
12913 Depending on the configuration, @value{GDBN} may be able to give you
12914 more information about the status of the vector unit.
12917 @kindex info vector
12919 Display information about the vector unit. The exact contents and
12920 layout vary depending on the hardware.
12923 @node OS Information
12924 @section Operating System Auxiliary Information
12925 @cindex OS information
12927 @value{GDBN} provides interfaces to useful OS facilities that can help
12928 you debug your program.
12930 @cindex auxiliary vector
12931 @cindex vector, auxiliary
12932 Some operating systems supply an @dfn{auxiliary vector} to programs at
12933 startup. This is akin to the arguments and environment that you
12934 specify for a program, but contains a system-dependent variety of
12935 binary values that tell system libraries important details about the
12936 hardware, operating system, and process. Each value's purpose is
12937 identified by an integer tag; the meanings are well-known but system-specific.
12938 Depending on the configuration and operating system facilities,
12939 @value{GDBN} may be able to show you this information. For remote
12940 targets, this functionality may further depend on the remote stub's
12941 support of the @samp{qXfer:auxv:read} packet, see
12942 @ref{qXfer auxiliary vector read}.
12947 Display the auxiliary vector of the inferior, which can be either a
12948 live process or a core dump file. @value{GDBN} prints each tag value
12949 numerically, and also shows names and text descriptions for recognized
12950 tags. Some values in the vector are numbers, some bit masks, and some
12951 pointers to strings or other data. @value{GDBN} displays each value in the
12952 most appropriate form for a recognized tag, and in hexadecimal for
12953 an unrecognized tag.
12956 On some targets, @value{GDBN} can access operating system-specific
12957 information and show it to you. The types of information available
12958 will differ depending on the type of operating system running on the
12959 target. The mechanism used to fetch the data is described in
12960 @ref{Operating System Information}. For remote targets, this
12961 functionality depends on the remote stub's support of the
12962 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12966 @item info os @var{infotype}
12968 Display OS information of the requested type.
12970 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12972 @anchor{linux info os infotypes}
12974 @kindex info os cpus
12976 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12977 the available fields from /proc/cpuinfo. For each supported architecture
12978 different fields are available. Two common entries are processor which gives
12979 CPU number and bogomips; a system constant that is calculated during
12980 kernel initialization.
12982 @kindex info os files
12984 Display the list of open file descriptors on the target. For each
12985 file descriptor, @value{GDBN} prints the identifier of the process
12986 owning the descriptor, the command of the owning process, the value
12987 of the descriptor, and the target of the descriptor.
12989 @kindex info os modules
12991 Display the list of all loaded kernel modules on the target. For each
12992 module, @value{GDBN} prints the module name, the size of the module in
12993 bytes, the number of times the module is used, the dependencies of the
12994 module, the status of the module, and the address of the loaded module
12997 @kindex info os msg
12999 Display the list of all System V message queues on the target. For each
13000 message queue, @value{GDBN} prints the message queue key, the message
13001 queue identifier, the access permissions, the current number of bytes
13002 on the queue, the current number of messages on the queue, the processes
13003 that last sent and received a message on the queue, the user and group
13004 of the owner and creator of the message queue, the times at which a
13005 message was last sent and received on the queue, and the time at which
13006 the message queue was last changed.
13008 @kindex info os processes
13010 Display the list of processes on the target. For each process,
13011 @value{GDBN} prints the process identifier, the name of the user, the
13012 command corresponding to the process, and the list of processor cores
13013 that the process is currently running on. (To understand what these
13014 properties mean, for this and the following info types, please consult
13015 the general @sc{gnu}/Linux documentation.)
13017 @kindex info os procgroups
13019 Display the list of process groups on the target. For each process,
13020 @value{GDBN} prints the identifier of the process group that it belongs
13021 to, the command corresponding to the process group leader, the process
13022 identifier, and the command line of the process. The list is sorted
13023 first by the process group identifier, then by the process identifier,
13024 so that processes belonging to the same process group are grouped together
13025 and the process group leader is listed first.
13027 @kindex info os semaphores
13029 Display the list of all System V semaphore sets on the target. For each
13030 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13031 set identifier, the access permissions, the number of semaphores in the
13032 set, the user and group of the owner and creator of the semaphore set,
13033 and the times at which the semaphore set was operated upon and changed.
13035 @kindex info os shm
13037 Display the list of all System V shared-memory regions on the target.
13038 For each shared-memory region, @value{GDBN} prints the region key,
13039 the shared-memory identifier, the access permissions, the size of the
13040 region, the process that created the region, the process that last
13041 attached to or detached from the region, the current number of live
13042 attaches to the region, and the times at which the region was last
13043 attached to, detach from, and changed.
13045 @kindex info os sockets
13047 Display the list of Internet-domain sockets on the target. For each
13048 socket, @value{GDBN} prints the address and port of the local and
13049 remote endpoints, the current state of the connection, the creator of
13050 the socket, the IP address family of the socket, and the type of the
13053 @kindex info os threads
13055 Display the list of threads running on the target. For each thread,
13056 @value{GDBN} prints the identifier of the process that the thread
13057 belongs to, the command of the process, the thread identifier, and the
13058 processor core that it is currently running on. The main thread of a
13059 process is not listed.
13063 If @var{infotype} is omitted, then list the possible values for
13064 @var{infotype} and the kind of OS information available for each
13065 @var{infotype}. If the target does not return a list of possible
13066 types, this command will report an error.
13069 @node Memory Region Attributes
13070 @section Memory Region Attributes
13071 @cindex memory region attributes
13073 @dfn{Memory region attributes} allow you to describe special handling
13074 required by regions of your target's memory. @value{GDBN} uses
13075 attributes to determine whether to allow certain types of memory
13076 accesses; whether to use specific width accesses; and whether to cache
13077 target memory. By default the description of memory regions is
13078 fetched from the target (if the current target supports this), but the
13079 user can override the fetched regions.
13081 Defined memory regions can be individually enabled and disabled. When a
13082 memory region is disabled, @value{GDBN} uses the default attributes when
13083 accessing memory in that region. Similarly, if no memory regions have
13084 been defined, @value{GDBN} uses the default attributes when accessing
13087 When a memory region is defined, it is given a number to identify it;
13088 to enable, disable, or remove a memory region, you specify that number.
13092 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13093 Define a memory region bounded by @var{lower} and @var{upper} with
13094 attributes @var{attributes}@dots{}, and add it to the list of regions
13095 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13096 case: it is treated as the target's maximum memory address.
13097 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13100 Discard any user changes to the memory regions and use target-supplied
13101 regions, if available, or no regions if the target does not support.
13104 @item delete mem @var{nums}@dots{}
13105 Remove memory regions @var{nums}@dots{} from the list of regions
13106 monitored by @value{GDBN}.
13108 @kindex disable mem
13109 @item disable mem @var{nums}@dots{}
13110 Disable monitoring of memory regions @var{nums}@dots{}.
13111 A disabled memory region is not forgotten.
13112 It may be enabled again later.
13115 @item enable mem @var{nums}@dots{}
13116 Enable monitoring of memory regions @var{nums}@dots{}.
13120 Print a table of all defined memory regions, with the following columns
13124 @item Memory Region Number
13125 @item Enabled or Disabled.
13126 Enabled memory regions are marked with @samp{y}.
13127 Disabled memory regions are marked with @samp{n}.
13130 The address defining the inclusive lower bound of the memory region.
13133 The address defining the exclusive upper bound of the memory region.
13136 The list of attributes set for this memory region.
13141 @subsection Attributes
13143 @subsubsection Memory Access Mode
13144 The access mode attributes set whether @value{GDBN} may make read or
13145 write accesses to a memory region.
13147 While these attributes prevent @value{GDBN} from performing invalid
13148 memory accesses, they do nothing to prevent the target system, I/O DMA,
13149 etc.@: from accessing memory.
13153 Memory is read only.
13155 Memory is write only.
13157 Memory is read/write. This is the default.
13160 @subsubsection Memory Access Size
13161 The access size attribute tells @value{GDBN} to use specific sized
13162 accesses in the memory region. Often memory mapped device registers
13163 require specific sized accesses. If no access size attribute is
13164 specified, @value{GDBN} may use accesses of any size.
13168 Use 8 bit memory accesses.
13170 Use 16 bit memory accesses.
13172 Use 32 bit memory accesses.
13174 Use 64 bit memory accesses.
13177 @c @subsubsection Hardware/Software Breakpoints
13178 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13179 @c will use hardware or software breakpoints for the internal breakpoints
13180 @c used by the step, next, finish, until, etc. commands.
13184 @c Always use hardware breakpoints
13185 @c @item swbreak (default)
13188 @subsubsection Data Cache
13189 The data cache attributes set whether @value{GDBN} will cache target
13190 memory. While this generally improves performance by reducing debug
13191 protocol overhead, it can lead to incorrect results because @value{GDBN}
13192 does not know about volatile variables or memory mapped device
13197 Enable @value{GDBN} to cache target memory.
13199 Disable @value{GDBN} from caching target memory. This is the default.
13202 @subsection Memory Access Checking
13203 @value{GDBN} can be instructed to refuse accesses to memory that is
13204 not explicitly described. This can be useful if accessing such
13205 regions has undesired effects for a specific target, or to provide
13206 better error checking. The following commands control this behaviour.
13209 @kindex set mem inaccessible-by-default
13210 @item set mem inaccessible-by-default [on|off]
13211 If @code{on} is specified, make @value{GDBN} treat memory not
13212 explicitly described by the memory ranges as non-existent and refuse accesses
13213 to such memory. The checks are only performed if there's at least one
13214 memory range defined. If @code{off} is specified, make @value{GDBN}
13215 treat the memory not explicitly described by the memory ranges as RAM.
13216 The default value is @code{on}.
13217 @kindex show mem inaccessible-by-default
13218 @item show mem inaccessible-by-default
13219 Show the current handling of accesses to unknown memory.
13223 @c @subsubsection Memory Write Verification
13224 @c The memory write verification attributes set whether @value{GDBN}
13225 @c will re-reads data after each write to verify the write was successful.
13229 @c @item noverify (default)
13232 @node Dump/Restore Files
13233 @section Copy Between Memory and a File
13234 @cindex dump/restore files
13235 @cindex append data to a file
13236 @cindex dump data to a file
13237 @cindex restore data from a file
13239 You can use the commands @code{dump}, @code{append}, and
13240 @code{restore} to copy data between target memory and a file. The
13241 @code{dump} and @code{append} commands write data to a file, and the
13242 @code{restore} command reads data from a file back into the inferior's
13243 memory. Files may be in binary, Motorola S-record, Intel hex,
13244 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13245 append to binary files, and cannot read from Verilog Hex files.
13250 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13251 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13252 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13253 or the value of @var{expr}, to @var{filename} in the given format.
13255 The @var{format} parameter may be any one of:
13262 Motorola S-record format.
13264 Tektronix Hex format.
13266 Verilog Hex format.
13269 @value{GDBN} uses the same definitions of these formats as the
13270 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13271 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13275 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13276 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13277 Append the contents of memory from @var{start_addr} to @var{end_addr},
13278 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13279 (@value{GDBN} can only append data to files in raw binary form.)
13282 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13283 Restore the contents of file @var{filename} into memory. The
13284 @code{restore} command can automatically recognize any known @sc{bfd}
13285 file format, except for raw binary. To restore a raw binary file you
13286 must specify the optional keyword @code{binary} after the filename.
13288 If @var{bias} is non-zero, its value will be added to the addresses
13289 contained in the file. Binary files always start at address zero, so
13290 they will be restored at address @var{bias}. Other bfd files have
13291 a built-in location; they will be restored at offset @var{bias}
13292 from that location.
13294 If @var{start} and/or @var{end} are non-zero, then only data between
13295 file offset @var{start} and file offset @var{end} will be restored.
13296 These offsets are relative to the addresses in the file, before
13297 the @var{bias} argument is applied.
13301 @node Core File Generation
13302 @section How to Produce a Core File from Your Program
13303 @cindex dump core from inferior
13305 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13306 image of a running process and its process status (register values
13307 etc.). Its primary use is post-mortem debugging of a program that
13308 crashed while it ran outside a debugger. A program that crashes
13309 automatically produces a core file, unless this feature is disabled by
13310 the user. @xref{Files}, for information on invoking @value{GDBN} in
13311 the post-mortem debugging mode.
13313 Occasionally, you may wish to produce a core file of the program you
13314 are debugging in order to preserve a snapshot of its state.
13315 @value{GDBN} has a special command for that.
13319 @kindex generate-core-file
13320 @item generate-core-file [@var{file}]
13321 @itemx gcore [@var{file}]
13322 Produce a core dump of the inferior process. The optional argument
13323 @var{file} specifies the file name where to put the core dump. If not
13324 specified, the file name defaults to @file{core.@var{pid}}, where
13325 @var{pid} is the inferior process ID.
13327 Note that this command is implemented only for some systems (as of
13328 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13330 On @sc{gnu}/Linux, this command can take into account the value of the
13331 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13332 dump (@pxref{set use-coredump-filter}), and by default honors the
13333 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13334 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13336 @kindex set use-coredump-filter
13337 @anchor{set use-coredump-filter}
13338 @item set use-coredump-filter on
13339 @itemx set use-coredump-filter off
13340 Enable or disable the use of the file
13341 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13342 files. This file is used by the Linux kernel to decide what types of
13343 memory mappings will be dumped or ignored when generating a core dump
13344 file. @var{pid} is the process ID of a currently running process.
13346 To make use of this feature, you have to write in the
13347 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13348 which is a bit mask representing the memory mapping types. If a bit
13349 is set in the bit mask, then the memory mappings of the corresponding
13350 types will be dumped; otherwise, they will be ignored. This
13351 configuration is inherited by child processes. For more information
13352 about the bits that can be set in the
13353 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13354 manpage of @code{core(5)}.
13356 By default, this option is @code{on}. If this option is turned
13357 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13358 and instead uses the same default value as the Linux kernel in order
13359 to decide which pages will be dumped in the core dump file. This
13360 value is currently @code{0x33}, which means that bits @code{0}
13361 (anonymous private mappings), @code{1} (anonymous shared mappings),
13362 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13363 This will cause these memory mappings to be dumped automatically.
13365 @kindex set dump-excluded-mappings
13366 @anchor{set dump-excluded-mappings}
13367 @item set dump-excluded-mappings on
13368 @itemx set dump-excluded-mappings off
13369 If @code{on} is specified, @value{GDBN} will dump memory mappings
13370 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13371 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13373 The default value is @code{off}.
13376 @node Character Sets
13377 @section Character Sets
13378 @cindex character sets
13380 @cindex translating between character sets
13381 @cindex host character set
13382 @cindex target character set
13384 If the program you are debugging uses a different character set to
13385 represent characters and strings than the one @value{GDBN} uses itself,
13386 @value{GDBN} can automatically translate between the character sets for
13387 you. The character set @value{GDBN} uses we call the @dfn{host
13388 character set}; the one the inferior program uses we call the
13389 @dfn{target character set}.
13391 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13392 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13393 remote protocol (@pxref{Remote Debugging}) to debug a program
13394 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13395 then the host character set is Latin-1, and the target character set is
13396 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13397 target-charset EBCDIC-US}, then @value{GDBN} translates between
13398 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13399 character and string literals in expressions.
13401 @value{GDBN} has no way to automatically recognize which character set
13402 the inferior program uses; you must tell it, using the @code{set
13403 target-charset} command, described below.
13405 Here are the commands for controlling @value{GDBN}'s character set
13409 @item set target-charset @var{charset}
13410 @kindex set target-charset
13411 Set the current target character set to @var{charset}. To display the
13412 list of supported target character sets, type
13413 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13415 @item set host-charset @var{charset}
13416 @kindex set host-charset
13417 Set the current host character set to @var{charset}.
13419 By default, @value{GDBN} uses a host character set appropriate to the
13420 system it is running on; you can override that default using the
13421 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13422 automatically determine the appropriate host character set. In this
13423 case, @value{GDBN} uses @samp{UTF-8}.
13425 @value{GDBN} can only use certain character sets as its host character
13426 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13427 @value{GDBN} will list the host character sets it supports.
13429 @item set charset @var{charset}
13430 @kindex set charset
13431 Set the current host and target character sets to @var{charset}. As
13432 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13433 @value{GDBN} will list the names of the character sets that can be used
13434 for both host and target.
13437 @kindex show charset
13438 Show the names of the current host and target character sets.
13440 @item show host-charset
13441 @kindex show host-charset
13442 Show the name of the current host character set.
13444 @item show target-charset
13445 @kindex show target-charset
13446 Show the name of the current target character set.
13448 @item set target-wide-charset @var{charset}
13449 @kindex set target-wide-charset
13450 Set the current target's wide character set to @var{charset}. This is
13451 the character set used by the target's @code{wchar_t} type. To
13452 display the list of supported wide character sets, type
13453 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13455 @item show target-wide-charset
13456 @kindex show target-wide-charset
13457 Show the name of the current target's wide character set.
13460 Here is an example of @value{GDBN}'s character set support in action.
13461 Assume that the following source code has been placed in the file
13462 @file{charset-test.c}:
13468 = @{72, 101, 108, 108, 111, 44, 32, 119,
13469 111, 114, 108, 100, 33, 10, 0@};
13470 char ibm1047_hello[]
13471 = @{200, 133, 147, 147, 150, 107, 64, 166,
13472 150, 153, 147, 132, 90, 37, 0@};
13476 printf ("Hello, world!\n");
13480 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13481 containing the string @samp{Hello, world!} followed by a newline,
13482 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13484 We compile the program, and invoke the debugger on it:
13487 $ gcc -g charset-test.c -o charset-test
13488 $ gdb -nw charset-test
13489 GNU gdb 2001-12-19-cvs
13490 Copyright 2001 Free Software Foundation, Inc.
13495 We can use the @code{show charset} command to see what character sets
13496 @value{GDBN} is currently using to interpret and display characters and
13500 (@value{GDBP}) show charset
13501 The current host and target character set is `ISO-8859-1'.
13505 For the sake of printing this manual, let's use @sc{ascii} as our
13506 initial character set:
13508 (@value{GDBP}) set charset ASCII
13509 (@value{GDBP}) show charset
13510 The current host and target character set is `ASCII'.
13514 Let's assume that @sc{ascii} is indeed the correct character set for our
13515 host system --- in other words, let's assume that if @value{GDBN} prints
13516 characters using the @sc{ascii} character set, our terminal will display
13517 them properly. Since our current target character set is also
13518 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13521 (@value{GDBP}) print ascii_hello
13522 $1 = 0x401698 "Hello, world!\n"
13523 (@value{GDBP}) print ascii_hello[0]
13528 @value{GDBN} uses the target character set for character and string
13529 literals you use in expressions:
13532 (@value{GDBP}) print '+'
13537 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13540 @value{GDBN} relies on the user to tell it which character set the
13541 target program uses. If we print @code{ibm1047_hello} while our target
13542 character set is still @sc{ascii}, we get jibberish:
13545 (@value{GDBP}) print ibm1047_hello
13546 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13547 (@value{GDBP}) print ibm1047_hello[0]
13552 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13553 @value{GDBN} tells us the character sets it supports:
13556 (@value{GDBP}) set target-charset
13557 ASCII EBCDIC-US IBM1047 ISO-8859-1
13558 (@value{GDBP}) set target-charset
13561 We can select @sc{ibm1047} as our target character set, and examine the
13562 program's strings again. Now the @sc{ascii} string is wrong, but
13563 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13564 target character set, @sc{ibm1047}, to the host character set,
13565 @sc{ascii}, and they display correctly:
13568 (@value{GDBP}) set target-charset IBM1047
13569 (@value{GDBP}) show charset
13570 The current host character set is `ASCII'.
13571 The current target character set is `IBM1047'.
13572 (@value{GDBP}) print ascii_hello
13573 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13574 (@value{GDBP}) print ascii_hello[0]
13576 (@value{GDBP}) print ibm1047_hello
13577 $8 = 0x4016a8 "Hello, world!\n"
13578 (@value{GDBP}) print ibm1047_hello[0]
13583 As above, @value{GDBN} uses the target character set for character and
13584 string literals you use in expressions:
13587 (@value{GDBP}) print '+'
13592 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13595 @node Caching Target Data
13596 @section Caching Data of Targets
13597 @cindex caching data of targets
13599 @value{GDBN} caches data exchanged between the debugger and a target.
13600 Each cache is associated with the address space of the inferior.
13601 @xref{Inferiors Connections and Programs}, about inferior and address space.
13602 Such caching generally improves performance in remote debugging
13603 (@pxref{Remote Debugging}), because it reduces the overhead of the
13604 remote protocol by bundling memory reads and writes into large chunks.
13605 Unfortunately, simply caching everything would lead to incorrect results,
13606 since @value{GDBN} does not necessarily know anything about volatile
13607 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13608 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13610 Therefore, by default, @value{GDBN} only caches data
13611 known to be on the stack@footnote{In non-stop mode, it is moderately
13612 rare for a running thread to modify the stack of a stopped thread
13613 in a way that would interfere with a backtrace, and caching of
13614 stack reads provides a significant speed up of remote backtraces.} or
13615 in the code segment.
13616 Other regions of memory can be explicitly marked as
13617 cacheable; @pxref{Memory Region Attributes}.
13620 @kindex set remotecache
13621 @item set remotecache on
13622 @itemx set remotecache off
13623 This option no longer does anything; it exists for compatibility
13626 @kindex show remotecache
13627 @item show remotecache
13628 Show the current state of the obsolete remotecache flag.
13630 @kindex set stack-cache
13631 @item set stack-cache on
13632 @itemx set stack-cache off
13633 Enable or disable caching of stack accesses. When @code{on}, use
13634 caching. By default, this option is @code{on}.
13636 @kindex show stack-cache
13637 @item show stack-cache
13638 Show the current state of data caching for memory accesses.
13640 @kindex set code-cache
13641 @item set code-cache on
13642 @itemx set code-cache off
13643 Enable or disable caching of code segment accesses. When @code{on},
13644 use caching. By default, this option is @code{on}. This improves
13645 performance of disassembly in remote debugging.
13647 @kindex show code-cache
13648 @item show code-cache
13649 Show the current state of target memory cache for code segment
13652 @kindex info dcache
13653 @item info dcache @r{[}line@r{]}
13654 Print the information about the performance of data cache of the
13655 current inferior's address space. The information displayed
13656 includes the dcache width and depth, and for each cache line, its
13657 number, address, and how many times it was referenced. This
13658 command is useful for debugging the data cache operation.
13660 If a line number is specified, the contents of that line will be
13663 @item set dcache size @var{size}
13664 @cindex dcache size
13665 @kindex set dcache size
13666 Set maximum number of entries in dcache (dcache depth above).
13668 @item set dcache line-size @var{line-size}
13669 @cindex dcache line-size
13670 @kindex set dcache line-size
13671 Set number of bytes each dcache entry caches (dcache width above).
13672 Must be a power of 2.
13674 @item show dcache size
13675 @kindex show dcache size
13676 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13678 @item show dcache line-size
13679 @kindex show dcache line-size
13680 Show default size of dcache lines.
13682 @item maint flush dcache
13683 @cindex dcache, flushing
13684 @kindex maint flush dcache
13685 Flush the contents (if any) of the dcache. This maintainer command is
13686 useful when debugging the dcache implementation.
13690 @node Searching Memory
13691 @section Search Memory
13692 @cindex searching memory
13694 Memory can be searched for a particular sequence of bytes with the
13695 @code{find} command.
13699 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13700 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13701 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13702 etc. The search begins at address @var{start_addr} and continues for either
13703 @var{len} bytes or through to @var{end_addr} inclusive.
13706 @var{s} and @var{n} are optional parameters.
13707 They may be specified in either order, apart or together.
13710 @item @var{s}, search query size
13711 The size of each search query value.
13717 halfwords (two bytes)
13721 giant words (eight bytes)
13724 All values are interpreted in the current language.
13725 This means, for example, that if the current source language is C/C@t{++}
13726 then searching for the string ``hello'' includes the trailing '\0'.
13727 The null terminator can be removed from searching by using casts,
13728 e.g.: @samp{@{char[5]@}"hello"}.
13730 If the value size is not specified, it is taken from the
13731 value's type in the current language.
13732 This is useful when one wants to specify the search
13733 pattern as a mixture of types.
13734 Note that this means, for example, that in the case of C-like languages
13735 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13736 which is typically four bytes.
13738 @item @var{n}, maximum number of finds
13739 The maximum number of matches to print. The default is to print all finds.
13742 You can use strings as search values. Quote them with double-quotes
13744 The string value is copied into the search pattern byte by byte,
13745 regardless of the endianness of the target and the size specification.
13747 The address of each match found is printed as well as a count of the
13748 number of matches found.
13750 The address of the last value found is stored in convenience variable
13752 A count of the number of matches is stored in @samp{$numfound}.
13754 For example, if stopped at the @code{printf} in this function:
13760 static char hello[] = "hello-hello";
13761 static struct @{ char c; short s; int i; @}
13762 __attribute__ ((packed)) mixed
13763 = @{ 'c', 0x1234, 0x87654321 @};
13764 printf ("%s\n", hello);
13769 you get during debugging:
13772 (gdb) find &hello[0], +sizeof(hello), "hello"
13773 0x804956d <hello.1620+6>
13775 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13776 0x8049567 <hello.1620>
13777 0x804956d <hello.1620+6>
13779 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13780 0x8049567 <hello.1620>
13781 0x804956d <hello.1620+6>
13783 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13784 0x8049567 <hello.1620>
13786 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13787 0x8049560 <mixed.1625>
13789 (gdb) print $numfound
13792 $2 = (void *) 0x8049560
13796 @section Value Sizes
13798 Whenever @value{GDBN} prints a value memory will be allocated within
13799 @value{GDBN} to hold the contents of the value. It is possible in
13800 some languages with dynamic typing systems, that an invalid program
13801 may indicate a value that is incorrectly large, this in turn may cause
13802 @value{GDBN} to try and allocate an overly large amount of memory.
13805 @kindex set max-value-size
13806 @item set max-value-size @var{bytes}
13807 @itemx set max-value-size unlimited
13808 Set the maximum size of memory that @value{GDBN} will allocate for the
13809 contents of a value to @var{bytes}, trying to display a value that
13810 requires more memory than that will result in an error.
13812 Setting this variable does not effect values that have already been
13813 allocated within @value{GDBN}, only future allocations.
13815 There's a minimum size that @code{max-value-size} can be set to in
13816 order that @value{GDBN} can still operate correctly, this minimum is
13817 currently 16 bytes.
13819 The limit applies to the results of some subexpressions as well as to
13820 complete expressions. For example, an expression denoting a simple
13821 integer component, such as @code{x.y.z}, may fail if the size of
13822 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13823 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13824 @var{A} is an array variable with non-constant size, will generally
13825 succeed regardless of the bounds on @var{A}, as long as the component
13826 size is less than @var{bytes}.
13828 The default value of @code{max-value-size} is currently 64k.
13830 @kindex show max-value-size
13831 @item show max-value-size
13832 Show the maximum size of memory, in bytes, that @value{GDBN} will
13833 allocate for the contents of a value.
13836 @node Optimized Code
13837 @chapter Debugging Optimized Code
13838 @cindex optimized code, debugging
13839 @cindex debugging optimized code
13841 Almost all compilers support optimization. With optimization
13842 disabled, the compiler generates assembly code that corresponds
13843 directly to your source code, in a simplistic way. As the compiler
13844 applies more powerful optimizations, the generated assembly code
13845 diverges from your original source code. With help from debugging
13846 information generated by the compiler, @value{GDBN} can map from
13847 the running program back to constructs from your original source.
13849 @value{GDBN} is more accurate with optimization disabled. If you
13850 can recompile without optimization, it is easier to follow the
13851 progress of your program during debugging. But, there are many cases
13852 where you may need to debug an optimized version.
13854 When you debug a program compiled with @samp{-g -O}, remember that the
13855 optimizer has rearranged your code; the debugger shows you what is
13856 really there. Do not be too surprised when the execution path does not
13857 exactly match your source file! An extreme example: if you define a
13858 variable, but never use it, @value{GDBN} never sees that
13859 variable---because the compiler optimizes it out of existence.
13861 Some things do not work as well with @samp{-g -O} as with just
13862 @samp{-g}, particularly on machines with instruction scheduling. If in
13863 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13864 please report it to us as a bug (including a test case!).
13865 @xref{Variables}, for more information about debugging optimized code.
13868 * Inline Functions:: How @value{GDBN} presents inlining
13869 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13872 @node Inline Functions
13873 @section Inline Functions
13874 @cindex inline functions, debugging
13876 @dfn{Inlining} is an optimization that inserts a copy of the function
13877 body directly at each call site, instead of jumping to a shared
13878 routine. @value{GDBN} displays inlined functions just like
13879 non-inlined functions. They appear in backtraces. You can view their
13880 arguments and local variables, step into them with @code{step}, skip
13881 them with @code{next}, and escape from them with @code{finish}.
13882 You can check whether a function was inlined by using the
13883 @code{info frame} command.
13885 For @value{GDBN} to support inlined functions, the compiler must
13886 record information about inlining in the debug information ---
13887 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13888 other compilers do also. @value{GDBN} only supports inlined functions
13889 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13890 do not emit two required attributes (@samp{DW_AT_call_file} and
13891 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13892 function calls with earlier versions of @value{NGCC}. It instead
13893 displays the arguments and local variables of inlined functions as
13894 local variables in the caller.
13896 The body of an inlined function is directly included at its call site;
13897 unlike a non-inlined function, there are no instructions devoted to
13898 the call. @value{GDBN} still pretends that the call site and the
13899 start of the inlined function are different instructions. Stepping to
13900 the call site shows the call site, and then stepping again shows
13901 the first line of the inlined function, even though no additional
13902 instructions are executed.
13904 This makes source-level debugging much clearer; you can see both the
13905 context of the call and then the effect of the call. Only stepping by
13906 a single instruction using @code{stepi} or @code{nexti} does not do
13907 this; single instruction steps always show the inlined body.
13909 There are some ways that @value{GDBN} does not pretend that inlined
13910 function calls are the same as normal calls:
13914 Setting breakpoints at the call site of an inlined function may not
13915 work, because the call site does not contain any code. @value{GDBN}
13916 may incorrectly move the breakpoint to the next line of the enclosing
13917 function, after the call. This limitation will be removed in a future
13918 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13919 or inside the inlined function instead.
13922 @value{GDBN} cannot locate the return value of inlined calls after
13923 using the @code{finish} command. This is a limitation of compiler-generated
13924 debugging information; after @code{finish}, you can step to the next line
13925 and print a variable where your program stored the return value.
13929 @node Tail Call Frames
13930 @section Tail Call Frames
13931 @cindex tail call frames, debugging
13933 Function @code{B} can call function @code{C} in its very last statement. In
13934 unoptimized compilation the call of @code{C} is immediately followed by return
13935 instruction at the end of @code{B} code. Optimizing compiler may replace the
13936 call and return in function @code{B} into one jump to function @code{C}
13937 instead. Such use of a jump instruction is called @dfn{tail call}.
13939 During execution of function @code{C}, there will be no indication in the
13940 function call stack frames that it was tail-called from @code{B}. If function
13941 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13942 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13943 some cases @value{GDBN} can determine that @code{C} was tail-called from
13944 @code{B}, and it will then create fictitious call frame for that, with the
13945 return address set up as if @code{B} called @code{C} normally.
13947 This functionality is currently supported only by DWARF 2 debugging format and
13948 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13949 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13952 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13953 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13957 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13959 Stack level 1, frame at 0x7fffffffda30:
13960 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13961 tail call frame, caller of frame at 0x7fffffffda30
13962 source language c++.
13963 Arglist at unknown address.
13964 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13967 The detection of all the possible code path executions can find them ambiguous.
13968 There is no execution history stored (possible @ref{Reverse Execution} is never
13969 used for this purpose) and the last known caller could have reached the known
13970 callee by multiple different jump sequences. In such case @value{GDBN} still
13971 tries to show at least all the unambiguous top tail callers and all the
13972 unambiguous bottom tail calees, if any.
13975 @anchor{set debug entry-values}
13976 @item set debug entry-values
13977 @kindex set debug entry-values
13978 When set to on, enables printing of analysis messages for both frame argument
13979 values at function entry and tail calls. It will show all the possible valid
13980 tail calls code paths it has considered. It will also print the intersection
13981 of them with the final unambiguous (possibly partial or even empty) code path
13984 @item show debug entry-values
13985 @kindex show debug entry-values
13986 Show the current state of analysis messages printing for both frame argument
13987 values at function entry and tail calls.
13990 The analysis messages for tail calls can for example show why the virtual tail
13991 call frame for function @code{c} has not been recognized (due to the indirect
13992 reference by variable @code{x}):
13995 static void __attribute__((noinline, noclone)) c (void);
13996 void (*x) (void) = c;
13997 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13998 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13999 int main (void) @{ x (); return 0; @}
14001 Breakpoint 1, DW_OP_entry_value resolving cannot find
14002 DW_TAG_call_site 0x40039a in main
14004 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14007 #1 0x000000000040039a in main () at t.c:5
14010 Another possibility is an ambiguous virtual tail call frames resolution:
14014 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14015 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14016 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14017 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14018 static void __attribute__((noinline, noclone)) b (void)
14019 @{ if (i) c (); else e (); @}
14020 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14021 int main (void) @{ a (); return 0; @}
14023 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14024 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14025 tailcall: reduced: 0x4004d2(a) |
14028 #1 0x00000000004004d2 in a () at t.c:8
14029 #2 0x0000000000400395 in main () at t.c:9
14032 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14033 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14035 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14036 @ifset HAVE_MAKEINFO_CLICK
14037 @set ARROW @click{}
14038 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14039 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14041 @ifclear HAVE_MAKEINFO_CLICK
14043 @set CALLSEQ1B @value{CALLSEQ1A}
14044 @set CALLSEQ2B @value{CALLSEQ2A}
14047 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14048 The code can have possible execution paths @value{CALLSEQ1B} or
14049 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14051 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14052 has found. It then finds another possible calling sequence - that one is
14053 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14054 printed as the @code{reduced:} calling sequence. That one could have many
14055 further @code{compare:} and @code{reduced:} statements as long as there remain
14056 any non-ambiguous sequence entries.
14058 For the frame of function @code{b} in both cases there are different possible
14059 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14060 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14061 therefore this one is displayed to the user while the ambiguous frames are
14064 There can be also reasons why printing of frame argument values at function
14069 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14070 static void __attribute__((noinline, noclone)) a (int i);
14071 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14072 static void __attribute__((noinline, noclone)) a (int i)
14073 @{ if (i) b (i - 1); else c (0); @}
14074 int main (void) @{ a (5); return 0; @}
14077 #0 c (i=i@@entry=0) at t.c:2
14078 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14079 function "a" at 0x400420 can call itself via tail calls
14080 i=<optimized out>) at t.c:6
14081 #2 0x000000000040036e in main () at t.c:7
14084 @value{GDBN} cannot find out from the inferior state if and how many times did
14085 function @code{a} call itself (via function @code{b}) as these calls would be
14086 tail calls. Such tail calls would modify the @code{i} variable, therefore
14087 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14088 prints @code{<optimized out>} instead.
14091 @chapter C Preprocessor Macros
14093 Some languages, such as C and C@t{++}, provide a way to define and invoke
14094 ``preprocessor macros'' which expand into strings of tokens.
14095 @value{GDBN} can evaluate expressions containing macro invocations, show
14096 the result of macro expansion, and show a macro's definition, including
14097 where it was defined.
14099 You may need to compile your program specially to provide @value{GDBN}
14100 with information about preprocessor macros. Most compilers do not
14101 include macros in their debugging information, even when you compile
14102 with the @option{-g} flag. @xref{Compilation}.
14104 A program may define a macro at one point, remove that definition later,
14105 and then provide a different definition after that. Thus, at different
14106 points in the program, a macro may have different definitions, or have
14107 no definition at all. If there is a current stack frame, @value{GDBN}
14108 uses the macros in scope at that frame's source code line. Otherwise,
14109 @value{GDBN} uses the macros in scope at the current listing location;
14112 Whenever @value{GDBN} evaluates an expression, it always expands any
14113 macro invocations present in the expression. @value{GDBN} also provides
14114 the following commands for working with macros explicitly.
14118 @kindex macro expand
14119 @cindex macro expansion, showing the results of preprocessor
14120 @cindex preprocessor macro expansion, showing the results of
14121 @cindex expanding preprocessor macros
14122 @item macro expand @var{expression}
14123 @itemx macro exp @var{expression}
14124 Show the results of expanding all preprocessor macro invocations in
14125 @var{expression}. Since @value{GDBN} simply expands macros, but does
14126 not parse the result, @var{expression} need not be a valid expression;
14127 it can be any string of tokens.
14130 @item macro expand-once @var{expression}
14131 @itemx macro exp1 @var{expression}
14132 @cindex expand macro once
14133 @i{(This command is not yet implemented.)} Show the results of
14134 expanding those preprocessor macro invocations that appear explicitly in
14135 @var{expression}. Macro invocations appearing in that expansion are
14136 left unchanged. This command allows you to see the effect of a
14137 particular macro more clearly, without being confused by further
14138 expansions. Since @value{GDBN} simply expands macros, but does not
14139 parse the result, @var{expression} need not be a valid expression; it
14140 can be any string of tokens.
14143 @cindex macro definition, showing
14144 @cindex definition of a macro, showing
14145 @cindex macros, from debug info
14146 @item info macro [-a|-all] [--] @var{macro}
14147 Show the current definition or all definitions of the named @var{macro},
14148 and describe the source location or compiler command-line where that
14149 definition was established. The optional double dash is to signify the end of
14150 argument processing and the beginning of @var{macro} for non C-like macros where
14151 the macro may begin with a hyphen.
14153 @kindex info macros
14154 @item info macros @var{location}
14155 Show all macro definitions that are in effect at the location specified
14156 by @var{location}, and describe the source location or compiler
14157 command-line where those definitions were established.
14159 @kindex macro define
14160 @cindex user-defined macros
14161 @cindex defining macros interactively
14162 @cindex macros, user-defined
14163 @item macro define @var{macro} @var{replacement-list}
14164 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14165 Introduce a definition for a preprocessor macro named @var{macro},
14166 invocations of which are replaced by the tokens given in
14167 @var{replacement-list}. The first form of this command defines an
14168 ``object-like'' macro, which takes no arguments; the second form
14169 defines a ``function-like'' macro, which takes the arguments given in
14172 A definition introduced by this command is in scope in every
14173 expression evaluated in @value{GDBN}, until it is removed with the
14174 @code{macro undef} command, described below. The definition overrides
14175 all definitions for @var{macro} present in the program being debugged,
14176 as well as any previous user-supplied definition.
14178 @kindex macro undef
14179 @item macro undef @var{macro}
14180 Remove any user-supplied definition for the macro named @var{macro}.
14181 This command only affects definitions provided with the @code{macro
14182 define} command, described above; it cannot remove definitions present
14183 in the program being debugged.
14187 List all the macros defined using the @code{macro define} command.
14190 @cindex macros, example of debugging with
14191 Here is a transcript showing the above commands in action. First, we
14192 show our source files:
14197 #include "sample.h"
14200 #define ADD(x) (M + x)
14205 printf ("Hello, world!\n");
14207 printf ("We're so creative.\n");
14209 printf ("Goodbye, world!\n");
14216 Now, we compile the program using the @sc{gnu} C compiler,
14217 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14218 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14219 and @option{-gdwarf-4}; we recommend always choosing the most recent
14220 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14221 includes information about preprocessor macros in the debugging
14225 $ gcc -gdwarf-2 -g3 sample.c -o sample
14229 Now, we start @value{GDBN} on our sample program:
14233 GNU gdb 2002-05-06-cvs
14234 Copyright 2002 Free Software Foundation, Inc.
14235 GDB is free software, @dots{}
14239 We can expand macros and examine their definitions, even when the
14240 program is not running. @value{GDBN} uses the current listing position
14241 to decide which macro definitions are in scope:
14244 (@value{GDBP}) list main
14247 5 #define ADD(x) (M + x)
14252 10 printf ("Hello, world!\n");
14254 12 printf ("We're so creative.\n");
14255 (@value{GDBP}) info macro ADD
14256 Defined at /home/jimb/gdb/macros/play/sample.c:5
14257 #define ADD(x) (M + x)
14258 (@value{GDBP}) info macro Q
14259 Defined at /home/jimb/gdb/macros/play/sample.h:1
14260 included at /home/jimb/gdb/macros/play/sample.c:2
14262 (@value{GDBP}) macro expand ADD(1)
14263 expands to: (42 + 1)
14264 (@value{GDBP}) macro expand-once ADD(1)
14265 expands to: once (M + 1)
14269 In the example above, note that @code{macro expand-once} expands only
14270 the macro invocation explicit in the original text --- the invocation of
14271 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14272 which was introduced by @code{ADD}.
14274 Once the program is running, @value{GDBN} uses the macro definitions in
14275 force at the source line of the current stack frame:
14278 (@value{GDBP}) break main
14279 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14281 Starting program: /home/jimb/gdb/macros/play/sample
14283 Breakpoint 1, main () at sample.c:10
14284 10 printf ("Hello, world!\n");
14288 At line 10, the definition of the macro @code{N} at line 9 is in force:
14291 (@value{GDBP}) info macro N
14292 Defined at /home/jimb/gdb/macros/play/sample.c:9
14294 (@value{GDBP}) macro expand N Q M
14295 expands to: 28 < 42
14296 (@value{GDBP}) print N Q M
14301 As we step over directives that remove @code{N}'s definition, and then
14302 give it a new definition, @value{GDBN} finds the definition (or lack
14303 thereof) in force at each point:
14306 (@value{GDBP}) next
14308 12 printf ("We're so creative.\n");
14309 (@value{GDBP}) info macro N
14310 The symbol `N' has no definition as a C/C++ preprocessor macro
14311 at /home/jimb/gdb/macros/play/sample.c:12
14312 (@value{GDBP}) next
14314 14 printf ("Goodbye, world!\n");
14315 (@value{GDBP}) info macro N
14316 Defined at /home/jimb/gdb/macros/play/sample.c:13
14318 (@value{GDBP}) macro expand N Q M
14319 expands to: 1729 < 42
14320 (@value{GDBP}) print N Q M
14325 In addition to source files, macros can be defined on the compilation command
14326 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14327 such a way, @value{GDBN} displays the location of their definition as line zero
14328 of the source file submitted to the compiler.
14331 (@value{GDBP}) info macro __STDC__
14332 Defined at /home/jimb/gdb/macros/play/sample.c:0
14339 @chapter Tracepoints
14340 @c This chapter is based on the documentation written by Michael
14341 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14343 @cindex tracepoints
14344 In some applications, it is not feasible for the debugger to interrupt
14345 the program's execution long enough for the developer to learn
14346 anything helpful about its behavior. If the program's correctness
14347 depends on its real-time behavior, delays introduced by a debugger
14348 might cause the program to change its behavior drastically, or perhaps
14349 fail, even when the code itself is correct. It is useful to be able
14350 to observe the program's behavior without interrupting it.
14352 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14353 specify locations in the program, called @dfn{tracepoints}, and
14354 arbitrary expressions to evaluate when those tracepoints are reached.
14355 Later, using the @code{tfind} command, you can examine the values
14356 those expressions had when the program hit the tracepoints. The
14357 expressions may also denote objects in memory---structures or arrays,
14358 for example---whose values @value{GDBN} should record; while visiting
14359 a particular tracepoint, you may inspect those objects as if they were
14360 in memory at that moment. However, because @value{GDBN} records these
14361 values without interacting with you, it can do so quickly and
14362 unobtrusively, hopefully not disturbing the program's behavior.
14364 The tracepoint facility is currently available only for remote
14365 targets. @xref{Targets}. In addition, your remote target must know
14366 how to collect trace data. This functionality is implemented in the
14367 remote stub; however, none of the stubs distributed with @value{GDBN}
14368 support tracepoints as of this writing. The format of the remote
14369 packets used to implement tracepoints are described in @ref{Tracepoint
14372 It is also possible to get trace data from a file, in a manner reminiscent
14373 of corefiles; you specify the filename, and use @code{tfind} to search
14374 through the file. @xref{Trace Files}, for more details.
14376 This chapter describes the tracepoint commands and features.
14379 * Set Tracepoints::
14380 * Analyze Collected Data::
14381 * Tracepoint Variables::
14385 @node Set Tracepoints
14386 @section Commands to Set Tracepoints
14388 Before running such a @dfn{trace experiment}, an arbitrary number of
14389 tracepoints can be set. A tracepoint is actually a special type of
14390 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14391 standard breakpoint commands. For instance, as with breakpoints,
14392 tracepoint numbers are successive integers starting from one, and many
14393 of the commands associated with tracepoints take the tracepoint number
14394 as their argument, to identify which tracepoint to work on.
14396 For each tracepoint, you can specify, in advance, some arbitrary set
14397 of data that you want the target to collect in the trace buffer when
14398 it hits that tracepoint. The collected data can include registers,
14399 local variables, or global data. Later, you can use @value{GDBN}
14400 commands to examine the values these data had at the time the
14401 tracepoint was hit.
14403 Tracepoints do not support every breakpoint feature. Ignore counts on
14404 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14405 commands when they are hit. Tracepoints may not be thread-specific
14408 @cindex fast tracepoints
14409 Some targets may support @dfn{fast tracepoints}, which are inserted in
14410 a different way (such as with a jump instead of a trap), that is
14411 faster but possibly restricted in where they may be installed.
14413 @cindex static tracepoints
14414 @cindex markers, static tracepoints
14415 @cindex probing markers, static tracepoints
14416 Regular and fast tracepoints are dynamic tracing facilities, meaning
14417 that they can be used to insert tracepoints at (almost) any location
14418 in the target. Some targets may also support controlling @dfn{static
14419 tracepoints} from @value{GDBN}. With static tracing, a set of
14420 instrumentation points, also known as @dfn{markers}, are embedded in
14421 the target program, and can be activated or deactivated by name or
14422 address. These are usually placed at locations which facilitate
14423 investigating what the target is actually doing. @value{GDBN}'s
14424 support for static tracing includes being able to list instrumentation
14425 points, and attach them with @value{GDBN} defined high level
14426 tracepoints that expose the whole range of convenience of
14427 @value{GDBN}'s tracepoints support. Namely, support for collecting
14428 registers values and values of global or local (to the instrumentation
14429 point) variables; tracepoint conditions and trace state variables.
14430 The act of installing a @value{GDBN} static tracepoint on an
14431 instrumentation point, or marker, is referred to as @dfn{probing} a
14432 static tracepoint marker.
14434 @code{gdbserver} supports tracepoints on some target systems.
14435 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14437 This section describes commands to set tracepoints and associated
14438 conditions and actions.
14441 * Create and Delete Tracepoints::
14442 * Enable and Disable Tracepoints::
14443 * Tracepoint Passcounts::
14444 * Tracepoint Conditions::
14445 * Trace State Variables::
14446 * Tracepoint Actions::
14447 * Listing Tracepoints::
14448 * Listing Static Tracepoint Markers::
14449 * Starting and Stopping Trace Experiments::
14450 * Tracepoint Restrictions::
14453 @node Create and Delete Tracepoints
14454 @subsection Create and Delete Tracepoints
14457 @cindex set tracepoint
14459 @item trace @var{location}
14460 The @code{trace} command is very similar to the @code{break} command.
14461 Its argument @var{location} can be any valid location.
14462 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14463 which is a point in the target program where the debugger will briefly stop,
14464 collect some data, and then allow the program to continue. Setting a tracepoint
14465 or changing its actions takes effect immediately if the remote stub
14466 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14468 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14469 these changes don't take effect until the next @code{tstart}
14470 command, and once a trace experiment is running, further changes will
14471 not have any effect until the next trace experiment starts. In addition,
14472 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14473 address is not yet resolved. (This is similar to pending breakpoints.)
14474 Pending tracepoints are not downloaded to the target and not installed
14475 until they are resolved. The resolution of pending tracepoints requires
14476 @value{GDBN} support---when debugging with the remote target, and
14477 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14478 tracing}), pending tracepoints can not be resolved (and downloaded to
14479 the remote stub) while @value{GDBN} is disconnected.
14481 Here are some examples of using the @code{trace} command:
14484 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14486 (@value{GDBP}) @b{trace +2} // 2 lines forward
14488 (@value{GDBP}) @b{trace my_function} // first source line of function
14490 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14492 (@value{GDBP}) @b{trace *0x2117c4} // an address
14496 You can abbreviate @code{trace} as @code{tr}.
14498 @item trace @var{location} if @var{cond}
14499 Set a tracepoint with condition @var{cond}; evaluate the expression
14500 @var{cond} each time the tracepoint is reached, and collect data only
14501 if the value is nonzero---that is, if @var{cond} evaluates as true.
14502 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14503 information on tracepoint conditions.
14505 @item ftrace @var{location} [ if @var{cond} ]
14506 @cindex set fast tracepoint
14507 @cindex fast tracepoints, setting
14509 The @code{ftrace} command sets a fast tracepoint. For targets that
14510 support them, fast tracepoints will use a more efficient but possibly
14511 less general technique to trigger data collection, such as a jump
14512 instruction instead of a trap, or some sort of hardware support. It
14513 may not be possible to create a fast tracepoint at the desired
14514 location, in which case the command will exit with an explanatory
14517 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14520 On 32-bit x86-architecture systems, fast tracepoints normally need to
14521 be placed at an instruction that is 5 bytes or longer, but can be
14522 placed at 4-byte instructions if the low 64K of memory of the target
14523 program is available to install trampolines. Some Unix-type systems,
14524 such as @sc{gnu}/Linux, exclude low addresses from the program's
14525 address space; but for instance with the Linux kernel it is possible
14526 to let @value{GDBN} use this area by doing a @command{sysctl} command
14527 to set the @code{mmap_min_addr} kernel parameter, as in
14530 sudo sysctl -w vm.mmap_min_addr=32768
14534 which sets the low address to 32K, which leaves plenty of room for
14535 trampolines. The minimum address should be set to a page boundary.
14537 @item strace @var{location} [ if @var{cond} ]
14538 @cindex set static tracepoint
14539 @cindex static tracepoints, setting
14540 @cindex probe static tracepoint marker
14542 The @code{strace} command sets a static tracepoint. For targets that
14543 support it, setting a static tracepoint probes a static
14544 instrumentation point, or marker, found at @var{location}. It may not
14545 be possible to set a static tracepoint at the desired location, in
14546 which case the command will exit with an explanatory message.
14548 @value{GDBN} handles arguments to @code{strace} exactly as for
14549 @code{trace}, with the addition that the user can also specify
14550 @code{-m @var{marker}} as @var{location}. This probes the marker
14551 identified by the @var{marker} string identifier. This identifier
14552 depends on the static tracepoint backend library your program is
14553 using. You can find all the marker identifiers in the @samp{ID} field
14554 of the @code{info static-tracepoint-markers} command output.
14555 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14556 Markers}. For example, in the following small program using the UST
14562 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14567 the marker id is composed of joining the first two arguments to the
14568 @code{trace_mark} call with a slash, which translates to:
14571 (@value{GDBP}) info static-tracepoint-markers
14572 Cnt Enb ID Address What
14573 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14579 so you may probe the marker above with:
14582 (@value{GDBP}) strace -m ust/bar33
14585 Static tracepoints accept an extra collect action --- @code{collect
14586 $_sdata}. This collects arbitrary user data passed in the probe point
14587 call to the tracing library. In the UST example above, you'll see
14588 that the third argument to @code{trace_mark} is a printf-like format
14589 string. The user data is then the result of running that formatting
14590 string against the following arguments. Note that @code{info
14591 static-tracepoint-markers} command output lists that format string in
14592 the @samp{Data:} field.
14594 You can inspect this data when analyzing the trace buffer, by printing
14595 the $_sdata variable like any other variable available to
14596 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14599 @cindex last tracepoint number
14600 @cindex recent tracepoint number
14601 @cindex tracepoint number
14602 The convenience variable @code{$tpnum} records the tracepoint number
14603 of the most recently set tracepoint.
14605 @kindex delete tracepoint
14606 @cindex tracepoint deletion
14607 @item delete tracepoint @r{[}@var{num}@r{]}
14608 Permanently delete one or more tracepoints. With no argument, the
14609 default is to delete all tracepoints. Note that the regular
14610 @code{delete} command can remove tracepoints also.
14615 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14617 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14621 You can abbreviate this command as @code{del tr}.
14624 @node Enable and Disable Tracepoints
14625 @subsection Enable and Disable Tracepoints
14627 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14630 @kindex disable tracepoint
14631 @item disable tracepoint @r{[}@var{num}@r{]}
14632 Disable tracepoint @var{num}, or all tracepoints if no argument
14633 @var{num} is given. A disabled tracepoint will have no effect during
14634 a trace experiment, but it is not forgotten. You can re-enable
14635 a disabled tracepoint using the @code{enable tracepoint} command.
14636 If the command is issued during a trace experiment and the debug target
14637 has support for disabling tracepoints during a trace experiment, then the
14638 change will be effective immediately. Otherwise, it will be applied to the
14639 next trace experiment.
14641 @kindex enable tracepoint
14642 @item enable tracepoint @r{[}@var{num}@r{]}
14643 Enable tracepoint @var{num}, or all tracepoints. If this command is
14644 issued during a trace experiment and the debug target supports enabling
14645 tracepoints during a trace experiment, then the enabled tracepoints will
14646 become effective immediately. Otherwise, they will become effective the
14647 next time a trace experiment is run.
14650 @node Tracepoint Passcounts
14651 @subsection Tracepoint Passcounts
14655 @cindex tracepoint pass count
14656 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14657 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14658 automatically stop a trace experiment. If a tracepoint's passcount is
14659 @var{n}, then the trace experiment will be automatically stopped on
14660 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14661 @var{num} is not specified, the @code{passcount} command sets the
14662 passcount of the most recently defined tracepoint. If no passcount is
14663 given, the trace experiment will run until stopped explicitly by the
14669 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14670 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14672 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14673 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14674 (@value{GDBP}) @b{trace foo}
14675 (@value{GDBP}) @b{pass 3}
14676 (@value{GDBP}) @b{trace bar}
14677 (@value{GDBP}) @b{pass 2}
14678 (@value{GDBP}) @b{trace baz}
14679 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14680 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14681 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14682 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14686 @node Tracepoint Conditions
14687 @subsection Tracepoint Conditions
14688 @cindex conditional tracepoints
14689 @cindex tracepoint conditions
14691 The simplest sort of tracepoint collects data every time your program
14692 reaches a specified place. You can also specify a @dfn{condition} for
14693 a tracepoint. A condition is just a Boolean expression in your
14694 programming language (@pxref{Expressions, ,Expressions}). A
14695 tracepoint with a condition evaluates the expression each time your
14696 program reaches it, and data collection happens only if the condition
14699 Tracepoint conditions can be specified when a tracepoint is set, by
14700 using @samp{if} in the arguments to the @code{trace} command.
14701 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14702 also be set or changed at any time with the @code{condition} command,
14703 just as with breakpoints.
14705 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14706 the conditional expression itself. Instead, @value{GDBN} encodes the
14707 expression into an agent expression (@pxref{Agent Expressions})
14708 suitable for execution on the target, independently of @value{GDBN}.
14709 Global variables become raw memory locations, locals become stack
14710 accesses, and so forth.
14712 For instance, suppose you have a function that is usually called
14713 frequently, but should not be called after an error has occurred. You
14714 could use the following tracepoint command to collect data about calls
14715 of that function that happen while the error code is propagating
14716 through the program; an unconditional tracepoint could end up
14717 collecting thousands of useless trace frames that you would have to
14721 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14724 @node Trace State Variables
14725 @subsection Trace State Variables
14726 @cindex trace state variables
14728 A @dfn{trace state variable} is a special type of variable that is
14729 created and managed by target-side code. The syntax is the same as
14730 that for GDB's convenience variables (a string prefixed with ``$''),
14731 but they are stored on the target. They must be created explicitly,
14732 using a @code{tvariable} command. They are always 64-bit signed
14735 Trace state variables are remembered by @value{GDBN}, and downloaded
14736 to the target along with tracepoint information when the trace
14737 experiment starts. There are no intrinsic limits on the number of
14738 trace state variables, beyond memory limitations of the target.
14740 @cindex convenience variables, and trace state variables
14741 Although trace state variables are managed by the target, you can use
14742 them in print commands and expressions as if they were convenience
14743 variables; @value{GDBN} will get the current value from the target
14744 while the trace experiment is running. Trace state variables share
14745 the same namespace as other ``$'' variables, which means that you
14746 cannot have trace state variables with names like @code{$23} or
14747 @code{$pc}, nor can you have a trace state variable and a convenience
14748 variable with the same name.
14752 @item tvariable $@var{name} [ = @var{expression} ]
14754 The @code{tvariable} command creates a new trace state variable named
14755 @code{$@var{name}}, and optionally gives it an initial value of
14756 @var{expression}. The @var{expression} is evaluated when this command is
14757 entered; the result will be converted to an integer if possible,
14758 otherwise @value{GDBN} will report an error. A subsequent
14759 @code{tvariable} command specifying the same name does not create a
14760 variable, but instead assigns the supplied initial value to the
14761 existing variable of that name, overwriting any previous initial
14762 value. The default initial value is 0.
14764 @item info tvariables
14765 @kindex info tvariables
14766 List all the trace state variables along with their initial values.
14767 Their current values may also be displayed, if the trace experiment is
14770 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14771 @kindex delete tvariable
14772 Delete the given trace state variables, or all of them if no arguments
14777 @node Tracepoint Actions
14778 @subsection Tracepoint Action Lists
14782 @cindex tracepoint actions
14783 @item actions @r{[}@var{num}@r{]}
14784 This command will prompt for a list of actions to be taken when the
14785 tracepoint is hit. If the tracepoint number @var{num} is not
14786 specified, this command sets the actions for the one that was most
14787 recently defined (so that you can define a tracepoint and then say
14788 @code{actions} without bothering about its number). You specify the
14789 actions themselves on the following lines, one action at a time, and
14790 terminate the actions list with a line containing just @code{end}. So
14791 far, the only defined actions are @code{collect}, @code{teval}, and
14792 @code{while-stepping}.
14794 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14795 Commands, ,Breakpoint Command Lists}), except that only the defined
14796 actions are allowed; any other @value{GDBN} command is rejected.
14798 @cindex remove actions from a tracepoint
14799 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14800 and follow it immediately with @samp{end}.
14803 (@value{GDBP}) @b{collect @var{data}} // collect some data
14805 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14807 (@value{GDBP}) @b{end} // signals the end of actions.
14810 In the following example, the action list begins with @code{collect}
14811 commands indicating the things to be collected when the tracepoint is
14812 hit. Then, in order to single-step and collect additional data
14813 following the tracepoint, a @code{while-stepping} command is used,
14814 followed by the list of things to be collected after each step in a
14815 sequence of single steps. The @code{while-stepping} command is
14816 terminated by its own separate @code{end} command. Lastly, the action
14817 list is terminated by an @code{end} command.
14820 (@value{GDBP}) @b{trace foo}
14821 (@value{GDBP}) @b{actions}
14822 Enter actions for tracepoint 1, one per line:
14825 > while-stepping 12
14826 > collect $pc, arr[i]
14831 @kindex collect @r{(tracepoints)}
14832 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14833 Collect values of the given expressions when the tracepoint is hit.
14834 This command accepts a comma-separated list of any valid expressions.
14835 In addition to global, static, or local variables, the following
14836 special arguments are supported:
14840 Collect all registers.
14843 Collect all function arguments.
14846 Collect all local variables.
14849 Collect the return address. This is helpful if you want to see more
14852 @emph{Note:} The return address location can not always be reliably
14853 determined up front, and the wrong address / registers may end up
14854 collected instead. On some architectures the reliability is higher
14855 for tracepoints at function entry, while on others it's the opposite.
14856 When this happens, backtracing will stop because the return address is
14857 found unavailable (unless another collect rule happened to match it).
14860 Collects the number of arguments from the static probe at which the
14861 tracepoint is located.
14862 @xref{Static Probe Points}.
14864 @item $_probe_arg@var{n}
14865 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14866 from the static probe at which the tracepoint is located.
14867 @xref{Static Probe Points}.
14870 @vindex $_sdata@r{, collect}
14871 Collect static tracepoint marker specific data. Only available for
14872 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14873 Lists}. On the UST static tracepoints library backend, an
14874 instrumentation point resembles a @code{printf} function call. The
14875 tracing library is able to collect user specified data formatted to a
14876 character string using the format provided by the programmer that
14877 instrumented the program. Other backends have similar mechanisms.
14878 Here's an example of a UST marker call:
14881 const char master_name[] = "$your_name";
14882 trace_mark(channel1, marker1, "hello %s", master_name)
14885 In this case, collecting @code{$_sdata} collects the string
14886 @samp{hello $yourname}. When analyzing the trace buffer, you can
14887 inspect @samp{$_sdata} like any other variable available to
14891 You can give several consecutive @code{collect} commands, each one
14892 with a single argument, or one @code{collect} command with several
14893 arguments separated by commas; the effect is the same.
14895 The optional @var{mods} changes the usual handling of the arguments.
14896 @code{s} requests that pointers to chars be handled as strings, in
14897 particular collecting the contents of the memory being pointed at, up
14898 to the first zero. The upper bound is by default the value of the
14899 @code{print elements} variable; if @code{s} is followed by a decimal
14900 number, that is the upper bound instead. So for instance
14901 @samp{collect/s25 mystr} collects as many as 25 characters at
14904 The command @code{info scope} (@pxref{Symbols, info scope}) is
14905 particularly useful for figuring out what data to collect.
14907 @kindex teval @r{(tracepoints)}
14908 @item teval @var{expr1}, @var{expr2}, @dots{}
14909 Evaluate the given expressions when the tracepoint is hit. This
14910 command accepts a comma-separated list of expressions. The results
14911 are discarded, so this is mainly useful for assigning values to trace
14912 state variables (@pxref{Trace State Variables}) without adding those
14913 values to the trace buffer, as would be the case if the @code{collect}
14916 @kindex while-stepping @r{(tracepoints)}
14917 @item while-stepping @var{n}
14918 Perform @var{n} single-step instruction traces after the tracepoint,
14919 collecting new data after each step. The @code{while-stepping}
14920 command is followed by the list of what to collect while stepping
14921 (followed by its own @code{end} command):
14924 > while-stepping 12
14925 > collect $regs, myglobal
14931 Note that @code{$pc} is not automatically collected by
14932 @code{while-stepping}; you need to explicitly collect that register if
14933 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14936 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14937 @kindex set default-collect
14938 @cindex default collection action
14939 This variable is a list of expressions to collect at each tracepoint
14940 hit. It is effectively an additional @code{collect} action prepended
14941 to every tracepoint action list. The expressions are parsed
14942 individually for each tracepoint, so for instance a variable named
14943 @code{xyz} may be interpreted as a global for one tracepoint, and a
14944 local for another, as appropriate to the tracepoint's location.
14946 @item show default-collect
14947 @kindex show default-collect
14948 Show the list of expressions that are collected by default at each
14953 @node Listing Tracepoints
14954 @subsection Listing Tracepoints
14957 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14958 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14959 @cindex information about tracepoints
14960 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14961 Display information about the tracepoint @var{num}. If you don't
14962 specify a tracepoint number, displays information about all the
14963 tracepoints defined so far. The format is similar to that used for
14964 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14965 command, simply restricting itself to tracepoints.
14967 A tracepoint's listing may include additional information specific to
14972 its passcount as given by the @code{passcount @var{n}} command
14975 the state about installed on target of each location
14979 (@value{GDBP}) @b{info trace}
14980 Num Type Disp Enb Address What
14981 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14983 collect globfoo, $regs
14988 2 tracepoint keep y <MULTIPLE>
14990 2.1 y 0x0804859c in func4 at change-loc.h:35
14991 installed on target
14992 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14993 installed on target
14994 2.3 y <PENDING> set_tracepoint
14995 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14996 not installed on target
15001 This command can be abbreviated @code{info tp}.
15004 @node Listing Static Tracepoint Markers
15005 @subsection Listing Static Tracepoint Markers
15008 @kindex info static-tracepoint-markers
15009 @cindex information about static tracepoint markers
15010 @item info static-tracepoint-markers
15011 Display information about all static tracepoint markers defined in the
15014 For each marker, the following columns are printed:
15018 An incrementing counter, output to help readability. This is not a
15021 The marker ID, as reported by the target.
15022 @item Enabled or Disabled
15023 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15024 that are not enabled.
15026 Where the marker is in your program, as a memory address.
15028 Where the marker is in the source for your program, as a file and line
15029 number. If the debug information included in the program does not
15030 allow @value{GDBN} to locate the source of the marker, this column
15031 will be left blank.
15035 In addition, the following information may be printed for each marker:
15039 User data passed to the tracing library by the marker call. In the
15040 UST backend, this is the format string passed as argument to the
15042 @item Static tracepoints probing the marker
15043 The list of static tracepoints attached to the marker.
15047 (@value{GDBP}) info static-tracepoint-markers
15048 Cnt ID Enb Address What
15049 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15050 Data: number1 %d number2 %d
15051 Probed by static tracepoints: #2
15052 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15058 @node Starting and Stopping Trace Experiments
15059 @subsection Starting and Stopping Trace Experiments
15062 @kindex tstart [ @var{notes} ]
15063 @cindex start a new trace experiment
15064 @cindex collected data discarded
15066 This command starts the trace experiment, and begins collecting data.
15067 It has the side effect of discarding all the data collected in the
15068 trace buffer during the previous trace experiment. If any arguments
15069 are supplied, they are taken as a note and stored with the trace
15070 experiment's state. The notes may be arbitrary text, and are
15071 especially useful with disconnected tracing in a multi-user context;
15072 the notes can explain what the trace is doing, supply user contact
15073 information, and so forth.
15075 @kindex tstop [ @var{notes} ]
15076 @cindex stop a running trace experiment
15078 This command stops the trace experiment. If any arguments are
15079 supplied, they are recorded with the experiment as a note. This is
15080 useful if you are stopping a trace started by someone else, for
15081 instance if the trace is interfering with the system's behavior and
15082 needs to be stopped quickly.
15084 @strong{Note}: a trace experiment and data collection may stop
15085 automatically if any tracepoint's passcount is reached
15086 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15089 @cindex status of trace data collection
15090 @cindex trace experiment, status of
15092 This command displays the status of the current trace data
15096 Here is an example of the commands we described so far:
15099 (@value{GDBP}) @b{trace gdb_c_test}
15100 (@value{GDBP}) @b{actions}
15101 Enter actions for tracepoint #1, one per line.
15102 > collect $regs,$locals,$args
15103 > while-stepping 11
15107 (@value{GDBP}) @b{tstart}
15108 [time passes @dots{}]
15109 (@value{GDBP}) @b{tstop}
15112 @anchor{disconnected tracing}
15113 @cindex disconnected tracing
15114 You can choose to continue running the trace experiment even if
15115 @value{GDBN} disconnects from the target, voluntarily or
15116 involuntarily. For commands such as @code{detach}, the debugger will
15117 ask what you want to do with the trace. But for unexpected
15118 terminations (@value{GDBN} crash, network outage), it would be
15119 unfortunate to lose hard-won trace data, so the variable
15120 @code{disconnected-tracing} lets you decide whether the trace should
15121 continue running without @value{GDBN}.
15124 @item set disconnected-tracing on
15125 @itemx set disconnected-tracing off
15126 @kindex set disconnected-tracing
15127 Choose whether a tracing run should continue to run if @value{GDBN}
15128 has disconnected from the target. Note that @code{detach} or
15129 @code{quit} will ask you directly what to do about a running trace no
15130 matter what this variable's setting, so the variable is mainly useful
15131 for handling unexpected situations, such as loss of the network.
15133 @item show disconnected-tracing
15134 @kindex show disconnected-tracing
15135 Show the current choice for disconnected tracing.
15139 When you reconnect to the target, the trace experiment may or may not
15140 still be running; it might have filled the trace buffer in the
15141 meantime, or stopped for one of the other reasons. If it is running,
15142 it will continue after reconnection.
15144 Upon reconnection, the target will upload information about the
15145 tracepoints in effect. @value{GDBN} will then compare that
15146 information to the set of tracepoints currently defined, and attempt
15147 to match them up, allowing for the possibility that the numbers may
15148 have changed due to creation and deletion in the meantime. If one of
15149 the target's tracepoints does not match any in @value{GDBN}, the
15150 debugger will create a new tracepoint, so that you have a number with
15151 which to specify that tracepoint. This matching-up process is
15152 necessarily heuristic, and it may result in useless tracepoints being
15153 created; you may simply delete them if they are of no use.
15155 @cindex circular trace buffer
15156 If your target agent supports a @dfn{circular trace buffer}, then you
15157 can run a trace experiment indefinitely without filling the trace
15158 buffer; when space runs out, the agent deletes already-collected trace
15159 frames, oldest first, until there is enough room to continue
15160 collecting. This is especially useful if your tracepoints are being
15161 hit too often, and your trace gets terminated prematurely because the
15162 buffer is full. To ask for a circular trace buffer, simply set
15163 @samp{circular-trace-buffer} to on. You can set this at any time,
15164 including during tracing; if the agent can do it, it will change
15165 buffer handling on the fly, otherwise it will not take effect until
15169 @item set circular-trace-buffer on
15170 @itemx set circular-trace-buffer off
15171 @kindex set circular-trace-buffer
15172 Choose whether a tracing run should use a linear or circular buffer
15173 for trace data. A linear buffer will not lose any trace data, but may
15174 fill up prematurely, while a circular buffer will discard old trace
15175 data, but it will have always room for the latest tracepoint hits.
15177 @item show circular-trace-buffer
15178 @kindex show circular-trace-buffer
15179 Show the current choice for the trace buffer. Note that this may not
15180 match the agent's current buffer handling, nor is it guaranteed to
15181 match the setting that might have been in effect during a past run,
15182 for instance if you are looking at frames from a trace file.
15187 @item set trace-buffer-size @var{n}
15188 @itemx set trace-buffer-size unlimited
15189 @kindex set trace-buffer-size
15190 Request that the target use a trace buffer of @var{n} bytes. Not all
15191 targets will honor the request; they may have a compiled-in size for
15192 the trace buffer, or some other limitation. Set to a value of
15193 @code{unlimited} or @code{-1} to let the target use whatever size it
15194 likes. This is also the default.
15196 @item show trace-buffer-size
15197 @kindex show trace-buffer-size
15198 Show the current requested size for the trace buffer. Note that this
15199 will only match the actual size if the target supports size-setting,
15200 and was able to handle the requested size. For instance, if the
15201 target can only change buffer size between runs, this variable will
15202 not reflect the change until the next run starts. Use @code{tstatus}
15203 to get a report of the actual buffer size.
15207 @item set trace-user @var{text}
15208 @kindex set trace-user
15210 @item show trace-user
15211 @kindex show trace-user
15213 @item set trace-notes @var{text}
15214 @kindex set trace-notes
15215 Set the trace run's notes.
15217 @item show trace-notes
15218 @kindex show trace-notes
15219 Show the trace run's notes.
15221 @item set trace-stop-notes @var{text}
15222 @kindex set trace-stop-notes
15223 Set the trace run's stop notes. The handling of the note is as for
15224 @code{tstop} arguments; the set command is convenient way to fix a
15225 stop note that is mistaken or incomplete.
15227 @item show trace-stop-notes
15228 @kindex show trace-stop-notes
15229 Show the trace run's stop notes.
15233 @node Tracepoint Restrictions
15234 @subsection Tracepoint Restrictions
15236 @cindex tracepoint restrictions
15237 There are a number of restrictions on the use of tracepoints. As
15238 described above, tracepoint data gathering occurs on the target
15239 without interaction from @value{GDBN}. Thus the full capabilities of
15240 the debugger are not available during data gathering, and then at data
15241 examination time, you will be limited by only having what was
15242 collected. The following items describe some common problems, but it
15243 is not exhaustive, and you may run into additional difficulties not
15249 Tracepoint expressions are intended to gather objects (lvalues). Thus
15250 the full flexibility of GDB's expression evaluator is not available.
15251 You cannot call functions, cast objects to aggregate types, access
15252 convenience variables or modify values (except by assignment to trace
15253 state variables). Some language features may implicitly call
15254 functions (for instance Objective-C fields with accessors), and therefore
15255 cannot be collected either.
15258 Collection of local variables, either individually or in bulk with
15259 @code{$locals} or @code{$args}, during @code{while-stepping} may
15260 behave erratically. The stepping action may enter a new scope (for
15261 instance by stepping into a function), or the location of the variable
15262 may change (for instance it is loaded into a register). The
15263 tracepoint data recorded uses the location information for the
15264 variables that is correct for the tracepoint location. When the
15265 tracepoint is created, it is not possible, in general, to determine
15266 where the steps of a @code{while-stepping} sequence will advance the
15267 program---particularly if a conditional branch is stepped.
15270 Collection of an incompletely-initialized or partially-destroyed object
15271 may result in something that @value{GDBN} cannot display, or displays
15272 in a misleading way.
15275 When @value{GDBN} displays a pointer to character it automatically
15276 dereferences the pointer to also display characters of the string
15277 being pointed to. However, collecting the pointer during tracing does
15278 not automatically collect the string. You need to explicitly
15279 dereference the pointer and provide size information if you want to
15280 collect not only the pointer, but the memory pointed to. For example,
15281 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15285 It is not possible to collect a complete stack backtrace at a
15286 tracepoint. Instead, you may collect the registers and a few hundred
15287 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15288 (adjust to use the name of the actual stack pointer register on your
15289 target architecture, and the amount of stack you wish to capture).
15290 Then the @code{backtrace} command will show a partial backtrace when
15291 using a trace frame. The number of stack frames that can be examined
15292 depends on the sizes of the frames in the collected stack. Note that
15293 if you ask for a block so large that it goes past the bottom of the
15294 stack, the target agent may report an error trying to read from an
15298 If you do not collect registers at a tracepoint, @value{GDBN} can
15299 infer that the value of @code{$pc} must be the same as the address of
15300 the tracepoint and use that when you are looking at a trace frame
15301 for that tracepoint. However, this cannot work if the tracepoint has
15302 multiple locations (for instance if it was set in a function that was
15303 inlined), or if it has a @code{while-stepping} loop. In those cases
15304 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15309 @node Analyze Collected Data
15310 @section Using the Collected Data
15312 After the tracepoint experiment ends, you use @value{GDBN} commands
15313 for examining the trace data. The basic idea is that each tracepoint
15314 collects a trace @dfn{snapshot} every time it is hit and another
15315 snapshot every time it single-steps. All these snapshots are
15316 consecutively numbered from zero and go into a buffer, and you can
15317 examine them later. The way you examine them is to @dfn{focus} on a
15318 specific trace snapshot. When the remote stub is focused on a trace
15319 snapshot, it will respond to all @value{GDBN} requests for memory and
15320 registers by reading from the buffer which belongs to that snapshot,
15321 rather than from @emph{real} memory or registers of the program being
15322 debugged. This means that @strong{all} @value{GDBN} commands
15323 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15324 behave as if we were currently debugging the program state as it was
15325 when the tracepoint occurred. Any requests for data that are not in
15326 the buffer will fail.
15329 * tfind:: How to select a trace snapshot
15330 * tdump:: How to display all data for a snapshot
15331 * save tracepoints:: How to save tracepoints for a future run
15335 @subsection @code{tfind @var{n}}
15338 @cindex select trace snapshot
15339 @cindex find trace snapshot
15340 The basic command for selecting a trace snapshot from the buffer is
15341 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15342 counting from zero. If no argument @var{n} is given, the next
15343 snapshot is selected.
15345 Here are the various forms of using the @code{tfind} command.
15349 Find the first snapshot in the buffer. This is a synonym for
15350 @code{tfind 0} (since 0 is the number of the first snapshot).
15353 Stop debugging trace snapshots, resume @emph{live} debugging.
15356 Same as @samp{tfind none}.
15359 No argument means find the next trace snapshot or find the first
15360 one if no trace snapshot is selected.
15363 Find the previous trace snapshot before the current one. This permits
15364 retracing earlier steps.
15366 @item tfind tracepoint @var{num}
15367 Find the next snapshot associated with tracepoint @var{num}. Search
15368 proceeds forward from the last examined trace snapshot. If no
15369 argument @var{num} is given, it means find the next snapshot collected
15370 for the same tracepoint as the current snapshot.
15372 @item tfind pc @var{addr}
15373 Find the next snapshot associated with the value @var{addr} of the
15374 program counter. Search proceeds forward from the last examined trace
15375 snapshot. If no argument @var{addr} is given, it means find the next
15376 snapshot with the same value of PC as the current snapshot.
15378 @item tfind outside @var{addr1}, @var{addr2}
15379 Find the next snapshot whose PC is outside the given range of
15380 addresses (exclusive).
15382 @item tfind range @var{addr1}, @var{addr2}
15383 Find the next snapshot whose PC is between @var{addr1} and
15384 @var{addr2} (inclusive).
15386 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15387 Find the next snapshot associated with the source line @var{n}. If
15388 the optional argument @var{file} is given, refer to line @var{n} in
15389 that source file. Search proceeds forward from the last examined
15390 trace snapshot. If no argument @var{n} is given, it means find the
15391 next line other than the one currently being examined; thus saying
15392 @code{tfind line} repeatedly can appear to have the same effect as
15393 stepping from line to line in a @emph{live} debugging session.
15396 The default arguments for the @code{tfind} commands are specifically
15397 designed to make it easy to scan through the trace buffer. For
15398 instance, @code{tfind} with no argument selects the next trace
15399 snapshot, and @code{tfind -} with no argument selects the previous
15400 trace snapshot. So, by giving one @code{tfind} command, and then
15401 simply hitting @key{RET} repeatedly you can examine all the trace
15402 snapshots in order. Or, by saying @code{tfind -} and then hitting
15403 @key{RET} repeatedly you can examine the snapshots in reverse order.
15404 The @code{tfind line} command with no argument selects the snapshot
15405 for the next source line executed. The @code{tfind pc} command with
15406 no argument selects the next snapshot with the same program counter
15407 (PC) as the current frame. The @code{tfind tracepoint} command with
15408 no argument selects the next trace snapshot collected by the same
15409 tracepoint as the current one.
15411 In addition to letting you scan through the trace buffer manually,
15412 these commands make it easy to construct @value{GDBN} scripts that
15413 scan through the trace buffer and print out whatever collected data
15414 you are interested in. Thus, if we want to examine the PC, FP, and SP
15415 registers from each trace frame in the buffer, we can say this:
15418 (@value{GDBP}) @b{tfind start}
15419 (@value{GDBP}) @b{while ($trace_frame != -1)}
15420 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15421 $trace_frame, $pc, $sp, $fp
15425 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15426 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15427 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15428 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15429 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15430 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15431 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15432 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15433 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15434 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15435 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15438 Or, if we want to examine the variable @code{X} at each source line in
15442 (@value{GDBP}) @b{tfind start}
15443 (@value{GDBP}) @b{while ($trace_frame != -1)}
15444 > printf "Frame %d, X == %d\n", $trace_frame, X
15454 @subsection @code{tdump}
15456 @cindex dump all data collected at tracepoint
15457 @cindex tracepoint data, display
15459 This command takes no arguments. It prints all the data collected at
15460 the current trace snapshot.
15463 (@value{GDBP}) @b{trace 444}
15464 (@value{GDBP}) @b{actions}
15465 Enter actions for tracepoint #2, one per line:
15466 > collect $regs, $locals, $args, gdb_long_test
15469 (@value{GDBP}) @b{tstart}
15471 (@value{GDBP}) @b{tfind line 444}
15472 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15474 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15476 (@value{GDBP}) @b{tdump}
15477 Data collected at tracepoint 2, trace frame 1:
15478 d0 0xc4aa0085 -995491707
15482 d4 0x71aea3d 119204413
15485 d7 0x380035 3670069
15486 a0 0x19e24a 1696330
15487 a1 0x3000668 50333288
15489 a3 0x322000 3284992
15490 a4 0x3000698 50333336
15491 a5 0x1ad3cc 1758156
15492 fp 0x30bf3c 0x30bf3c
15493 sp 0x30bf34 0x30bf34
15495 pc 0x20b2c8 0x20b2c8
15499 p = 0x20e5b4 "gdb-test"
15506 gdb_long_test = 17 '\021'
15511 @code{tdump} works by scanning the tracepoint's current collection
15512 actions and printing the value of each expression listed. So
15513 @code{tdump} can fail, if after a run, you change the tracepoint's
15514 actions to mention variables that were not collected during the run.
15516 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15517 uses the collected value of @code{$pc} to distinguish between trace
15518 frames that were collected at the tracepoint hit, and frames that were
15519 collected while stepping. This allows it to correctly choose whether
15520 to display the basic list of collections, or the collections from the
15521 body of the while-stepping loop. However, if @code{$pc} was not collected,
15522 then @code{tdump} will always attempt to dump using the basic collection
15523 list, and may fail if a while-stepping frame does not include all the
15524 same data that is collected at the tracepoint hit.
15525 @c This is getting pretty arcane, example would be good.
15527 @node save tracepoints
15528 @subsection @code{save tracepoints @var{filename}}
15529 @kindex save tracepoints
15530 @kindex save-tracepoints
15531 @cindex save tracepoints for future sessions
15533 This command saves all current tracepoint definitions together with
15534 their actions and passcounts, into a file @file{@var{filename}}
15535 suitable for use in a later debugging session. To read the saved
15536 tracepoint definitions, use the @code{source} command (@pxref{Command
15537 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15538 alias for @w{@code{save tracepoints}}
15540 @node Tracepoint Variables
15541 @section Convenience Variables for Tracepoints
15542 @cindex tracepoint variables
15543 @cindex convenience variables for tracepoints
15546 @vindex $trace_frame
15547 @item (int) $trace_frame
15548 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15549 snapshot is selected.
15551 @vindex $tracepoint
15552 @item (int) $tracepoint
15553 The tracepoint for the current trace snapshot.
15555 @vindex $trace_line
15556 @item (int) $trace_line
15557 The line number for the current trace snapshot.
15559 @vindex $trace_file
15560 @item (char []) $trace_file
15561 The source file for the current trace snapshot.
15563 @vindex $trace_func
15564 @item (char []) $trace_func
15565 The name of the function containing @code{$tracepoint}.
15568 Note: @code{$trace_file} is not suitable for use in @code{printf},
15569 use @code{output} instead.
15571 Here's a simple example of using these convenience variables for
15572 stepping through all the trace snapshots and printing some of their
15573 data. Note that these are not the same as trace state variables,
15574 which are managed by the target.
15577 (@value{GDBP}) @b{tfind start}
15579 (@value{GDBP}) @b{while $trace_frame != -1}
15580 > output $trace_file
15581 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15587 @section Using Trace Files
15588 @cindex trace files
15590 In some situations, the target running a trace experiment may no
15591 longer be available; perhaps it crashed, or the hardware was needed
15592 for a different activity. To handle these cases, you can arrange to
15593 dump the trace data into a file, and later use that file as a source
15594 of trace data, via the @code{target tfile} command.
15599 @item tsave [ -r ] @var{filename}
15600 @itemx tsave [-ctf] @var{dirname}
15601 Save the trace data to @var{filename}. By default, this command
15602 assumes that @var{filename} refers to the host filesystem, so if
15603 necessary @value{GDBN} will copy raw trace data up from the target and
15604 then save it. If the target supports it, you can also supply the
15605 optional argument @code{-r} (``remote'') to direct the target to save
15606 the data directly into @var{filename} in its own filesystem, which may be
15607 more efficient if the trace buffer is very large. (Note, however, that
15608 @code{target tfile} can only read from files accessible to the host.)
15609 By default, this command will save trace frame in tfile format.
15610 You can supply the optional argument @code{-ctf} to save data in CTF
15611 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15612 that can be shared by multiple debugging and tracing tools. Please go to
15613 @indicateurl{http://www.efficios.com/ctf} to get more information.
15615 @kindex target tfile
15619 @item target tfile @var{filename}
15620 @itemx target ctf @var{dirname}
15621 Use the file named @var{filename} or directory named @var{dirname} as
15622 a source of trace data. Commands that examine data work as they do with
15623 a live target, but it is not possible to run any new trace experiments.
15624 @code{tstatus} will report the state of the trace run at the moment
15625 the data was saved, as well as the current trace frame you are examining.
15626 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15630 (@value{GDBP}) target ctf ctf.ctf
15631 (@value{GDBP}) tfind
15632 Found trace frame 0, tracepoint 2
15633 39 ++a; /* set tracepoint 1 here */
15634 (@value{GDBP}) tdump
15635 Data collected at tracepoint 2, trace frame 0:
15639 c = @{"123", "456", "789", "123", "456", "789"@}
15640 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15648 @chapter Debugging Programs That Use Overlays
15651 If your program is too large to fit completely in your target system's
15652 memory, you can sometimes use @dfn{overlays} to work around this
15653 problem. @value{GDBN} provides some support for debugging programs that
15657 * How Overlays Work:: A general explanation of overlays.
15658 * Overlay Commands:: Managing overlays in @value{GDBN}.
15659 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15660 mapped by asking the inferior.
15661 * Overlay Sample Program:: A sample program using overlays.
15664 @node How Overlays Work
15665 @section How Overlays Work
15666 @cindex mapped overlays
15667 @cindex unmapped overlays
15668 @cindex load address, overlay's
15669 @cindex mapped address
15670 @cindex overlay area
15672 Suppose you have a computer whose instruction address space is only 64
15673 kilobytes long, but which has much more memory which can be accessed by
15674 other means: special instructions, segment registers, or memory
15675 management hardware, for example. Suppose further that you want to
15676 adapt a program which is larger than 64 kilobytes to run on this system.
15678 One solution is to identify modules of your program which are relatively
15679 independent, and need not call each other directly; call these modules
15680 @dfn{overlays}. Separate the overlays from the main program, and place
15681 their machine code in the larger memory. Place your main program in
15682 instruction memory, but leave at least enough space there to hold the
15683 largest overlay as well.
15685 Now, to call a function located in an overlay, you must first copy that
15686 overlay's machine code from the large memory into the space set aside
15687 for it in the instruction memory, and then jump to its entry point
15690 @c NB: In the below the mapped area's size is greater or equal to the
15691 @c size of all overlays. This is intentional to remind the developer
15692 @c that overlays don't necessarily need to be the same size.
15696 Data Instruction Larger
15697 Address Space Address Space Address Space
15698 +-----------+ +-----------+ +-----------+
15700 +-----------+ +-----------+ +-----------+<-- overlay 1
15701 | program | | main | .----| overlay 1 | load address
15702 | variables | | program | | +-----------+
15703 | and heap | | | | | |
15704 +-----------+ | | | +-----------+<-- overlay 2
15705 | | +-----------+ | | | load address
15706 +-----------+ | | | .-| overlay 2 |
15708 mapped --->+-----------+ | | +-----------+
15709 address | | | | | |
15710 | overlay | <-' | | |
15711 | area | <---' +-----------+<-- overlay 3
15712 | | <---. | | load address
15713 +-----------+ `--| overlay 3 |
15720 @anchor{A code overlay}A code overlay
15724 The diagram (@pxref{A code overlay}) shows a system with separate data
15725 and instruction address spaces. To map an overlay, the program copies
15726 its code from the larger address space to the instruction address space.
15727 Since the overlays shown here all use the same mapped address, only one
15728 may be mapped at a time. For a system with a single address space for
15729 data and instructions, the diagram would be similar, except that the
15730 program variables and heap would share an address space with the main
15731 program and the overlay area.
15733 An overlay loaded into instruction memory and ready for use is called a
15734 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15735 instruction memory. An overlay not present (or only partially present)
15736 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15737 is its address in the larger memory. The mapped address is also called
15738 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15739 called the @dfn{load memory address}, or @dfn{LMA}.
15741 Unfortunately, overlays are not a completely transparent way to adapt a
15742 program to limited instruction memory. They introduce a new set of
15743 global constraints you must keep in mind as you design your program:
15748 Before calling or returning to a function in an overlay, your program
15749 must make sure that overlay is actually mapped. Otherwise, the call or
15750 return will transfer control to the right address, but in the wrong
15751 overlay, and your program will probably crash.
15754 If the process of mapping an overlay is expensive on your system, you
15755 will need to choose your overlays carefully to minimize their effect on
15756 your program's performance.
15759 The executable file you load onto your system must contain each
15760 overlay's instructions, appearing at the overlay's load address, not its
15761 mapped address. However, each overlay's instructions must be relocated
15762 and its symbols defined as if the overlay were at its mapped address.
15763 You can use GNU linker scripts to specify different load and relocation
15764 addresses for pieces of your program; see @ref{Overlay Description,,,
15765 ld.info, Using ld: the GNU linker}.
15768 The procedure for loading executable files onto your system must be able
15769 to load their contents into the larger address space as well as the
15770 instruction and data spaces.
15774 The overlay system described above is rather simple, and could be
15775 improved in many ways:
15780 If your system has suitable bank switch registers or memory management
15781 hardware, you could use those facilities to make an overlay's load area
15782 contents simply appear at their mapped address in instruction space.
15783 This would probably be faster than copying the overlay to its mapped
15784 area in the usual way.
15787 If your overlays are small enough, you could set aside more than one
15788 overlay area, and have more than one overlay mapped at a time.
15791 You can use overlays to manage data, as well as instructions. In
15792 general, data overlays are even less transparent to your design than
15793 code overlays: whereas code overlays only require care when you call or
15794 return to functions, data overlays require care every time you access
15795 the data. Also, if you change the contents of a data overlay, you
15796 must copy its contents back out to its load address before you can copy a
15797 different data overlay into the same mapped area.
15802 @node Overlay Commands
15803 @section Overlay Commands
15805 To use @value{GDBN}'s overlay support, each overlay in your program must
15806 correspond to a separate section of the executable file. The section's
15807 virtual memory address and load memory address must be the overlay's
15808 mapped and load addresses. Identifying overlays with sections allows
15809 @value{GDBN} to determine the appropriate address of a function or
15810 variable, depending on whether the overlay is mapped or not.
15812 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15813 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15818 Disable @value{GDBN}'s overlay support. When overlay support is
15819 disabled, @value{GDBN} assumes that all functions and variables are
15820 always present at their mapped addresses. By default, @value{GDBN}'s
15821 overlay support is disabled.
15823 @item overlay manual
15824 @cindex manual overlay debugging
15825 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15826 relies on you to tell it which overlays are mapped, and which are not,
15827 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15828 commands described below.
15830 @item overlay map-overlay @var{overlay}
15831 @itemx overlay map @var{overlay}
15832 @cindex map an overlay
15833 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15834 be the name of the object file section containing the overlay. When an
15835 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15836 functions and variables at their mapped addresses. @value{GDBN} assumes
15837 that any other overlays whose mapped ranges overlap that of
15838 @var{overlay} are now unmapped.
15840 @item overlay unmap-overlay @var{overlay}
15841 @itemx overlay unmap @var{overlay}
15842 @cindex unmap an overlay
15843 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15844 must be the name of the object file section containing the overlay.
15845 When an overlay is unmapped, @value{GDBN} assumes it can find the
15846 overlay's functions and variables at their load addresses.
15849 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15850 consults a data structure the overlay manager maintains in the inferior
15851 to see which overlays are mapped. For details, see @ref{Automatic
15852 Overlay Debugging}.
15854 @item overlay load-target
15855 @itemx overlay load
15856 @cindex reloading the overlay table
15857 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15858 re-reads the table @value{GDBN} automatically each time the inferior
15859 stops, so this command should only be necessary if you have changed the
15860 overlay mapping yourself using @value{GDBN}. This command is only
15861 useful when using automatic overlay debugging.
15863 @item overlay list-overlays
15864 @itemx overlay list
15865 @cindex listing mapped overlays
15866 Display a list of the overlays currently mapped, along with their mapped
15867 addresses, load addresses, and sizes.
15871 Normally, when @value{GDBN} prints a code address, it includes the name
15872 of the function the address falls in:
15875 (@value{GDBP}) print main
15876 $3 = @{int ()@} 0x11a0 <main>
15879 When overlay debugging is enabled, @value{GDBN} recognizes code in
15880 unmapped overlays, and prints the names of unmapped functions with
15881 asterisks around them. For example, if @code{foo} is a function in an
15882 unmapped overlay, @value{GDBN} prints it this way:
15885 (@value{GDBP}) overlay list
15886 No sections are mapped.
15887 (@value{GDBP}) print foo
15888 $5 = @{int (int)@} 0x100000 <*foo*>
15891 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15895 (@value{GDBP}) overlay list
15896 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15897 mapped at 0x1016 - 0x104a
15898 (@value{GDBP}) print foo
15899 $6 = @{int (int)@} 0x1016 <foo>
15902 When overlay debugging is enabled, @value{GDBN} can find the correct
15903 address for functions and variables in an overlay, whether or not the
15904 overlay is mapped. This allows most @value{GDBN} commands, like
15905 @code{break} and @code{disassemble}, to work normally, even on unmapped
15906 code. However, @value{GDBN}'s breakpoint support has some limitations:
15910 @cindex breakpoints in overlays
15911 @cindex overlays, setting breakpoints in
15912 You can set breakpoints in functions in unmapped overlays, as long as
15913 @value{GDBN} can write to the overlay at its load address.
15915 @value{GDBN} can not set hardware or simulator-based breakpoints in
15916 unmapped overlays. However, if you set a breakpoint at the end of your
15917 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15918 you are using manual overlay management), @value{GDBN} will re-set its
15919 breakpoints properly.
15923 @node Automatic Overlay Debugging
15924 @section Automatic Overlay Debugging
15925 @cindex automatic overlay debugging
15927 @value{GDBN} can automatically track which overlays are mapped and which
15928 are not, given some simple co-operation from the overlay manager in the
15929 inferior. If you enable automatic overlay debugging with the
15930 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15931 looks in the inferior's memory for certain variables describing the
15932 current state of the overlays.
15934 Here are the variables your overlay manager must define to support
15935 @value{GDBN}'s automatic overlay debugging:
15939 @item @code{_ovly_table}:
15940 This variable must be an array of the following structures:
15945 /* The overlay's mapped address. */
15948 /* The size of the overlay, in bytes. */
15949 unsigned long size;
15951 /* The overlay's load address. */
15954 /* Non-zero if the overlay is currently mapped;
15956 unsigned long mapped;
15960 @item @code{_novlys}:
15961 This variable must be a four-byte signed integer, holding the total
15962 number of elements in @code{_ovly_table}.
15966 To decide whether a particular overlay is mapped or not, @value{GDBN}
15967 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15968 @code{lma} members equal the VMA and LMA of the overlay's section in the
15969 executable file. When @value{GDBN} finds a matching entry, it consults
15970 the entry's @code{mapped} member to determine whether the overlay is
15973 In addition, your overlay manager may define a function called
15974 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15975 will silently set a breakpoint there. If the overlay manager then
15976 calls this function whenever it has changed the overlay table, this
15977 will enable @value{GDBN} to accurately keep track of which overlays
15978 are in program memory, and update any breakpoints that may be set
15979 in overlays. This will allow breakpoints to work even if the
15980 overlays are kept in ROM or other non-writable memory while they
15981 are not being executed.
15983 @node Overlay Sample Program
15984 @section Overlay Sample Program
15985 @cindex overlay example program
15987 When linking a program which uses overlays, you must place the overlays
15988 at their load addresses, while relocating them to run at their mapped
15989 addresses. To do this, you must write a linker script (@pxref{Overlay
15990 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15991 since linker scripts are specific to a particular host system, target
15992 architecture, and target memory layout, this manual cannot provide
15993 portable sample code demonstrating @value{GDBN}'s overlay support.
15995 However, the @value{GDBN} source distribution does contain an overlaid
15996 program, with linker scripts for a few systems, as part of its test
15997 suite. The program consists of the following files from
15998 @file{gdb/testsuite/gdb.base}:
16002 The main program file.
16004 A simple overlay manager, used by @file{overlays.c}.
16009 Overlay modules, loaded and used by @file{overlays.c}.
16012 Linker scripts for linking the test program on the @code{d10v-elf}
16013 and @code{m32r-elf} targets.
16016 You can build the test program using the @code{d10v-elf} GCC
16017 cross-compiler like this:
16020 $ d10v-elf-gcc -g -c overlays.c
16021 $ d10v-elf-gcc -g -c ovlymgr.c
16022 $ d10v-elf-gcc -g -c foo.c
16023 $ d10v-elf-gcc -g -c bar.c
16024 $ d10v-elf-gcc -g -c baz.c
16025 $ d10v-elf-gcc -g -c grbx.c
16026 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16027 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16030 The build process is identical for any other architecture, except that
16031 you must substitute the appropriate compiler and linker script for the
16032 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16036 @chapter Using @value{GDBN} with Different Languages
16039 Although programming languages generally have common aspects, they are
16040 rarely expressed in the same manner. For instance, in ANSI C,
16041 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16042 Modula-2, it is accomplished by @code{p^}. Values can also be
16043 represented (and displayed) differently. Hex numbers in C appear as
16044 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16046 @cindex working language
16047 Language-specific information is built into @value{GDBN} for some languages,
16048 allowing you to express operations like the above in your program's
16049 native language, and allowing @value{GDBN} to output values in a manner
16050 consistent with the syntax of your program's native language. The
16051 language you use to build expressions is called the @dfn{working
16055 * Setting:: Switching between source languages
16056 * Show:: Displaying the language
16057 * Checks:: Type and range checks
16058 * Supported Languages:: Supported languages
16059 * Unsupported Languages:: Unsupported languages
16063 @section Switching Between Source Languages
16065 There are two ways to control the working language---either have @value{GDBN}
16066 set it automatically, or select it manually yourself. You can use the
16067 @code{set language} command for either purpose. On startup, @value{GDBN}
16068 defaults to setting the language automatically. The working language is
16069 used to determine how expressions you type are interpreted, how values
16072 In addition to the working language, every source file that
16073 @value{GDBN} knows about has its own working language. For some object
16074 file formats, the compiler might indicate which language a particular
16075 source file is in. However, most of the time @value{GDBN} infers the
16076 language from the name of the file. The language of a source file
16077 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16078 show each frame appropriately for its own language. There is no way to
16079 set the language of a source file from within @value{GDBN}, but you can
16080 set the language associated with a filename extension. @xref{Show, ,
16081 Displaying the Language}.
16083 This is most commonly a problem when you use a program, such
16084 as @code{cfront} or @code{f2c}, that generates C but is written in
16085 another language. In that case, make the
16086 program use @code{#line} directives in its C output; that way
16087 @value{GDBN} will know the correct language of the source code of the original
16088 program, and will display that source code, not the generated C code.
16091 * Filenames:: Filename extensions and languages.
16092 * Manually:: Setting the working language manually
16093 * Automatically:: Having @value{GDBN} infer the source language
16097 @subsection List of Filename Extensions and Languages
16099 If a source file name ends in one of the following extensions, then
16100 @value{GDBN} infers that its language is the one indicated.
16118 C@t{++} source file
16124 Objective-C source file
16128 Fortran source file
16131 Modula-2 source file
16135 Assembler source file. This actually behaves almost like C, but
16136 @value{GDBN} does not skip over function prologues when stepping.
16139 In addition, you may set the language associated with a filename
16140 extension. @xref{Show, , Displaying the Language}.
16143 @subsection Setting the Working Language
16145 If you allow @value{GDBN} to set the language automatically,
16146 expressions are interpreted the same way in your debugging session and
16149 @kindex set language
16150 If you wish, you may set the language manually. To do this, issue the
16151 command @samp{set language @var{lang}}, where @var{lang} is the name of
16152 a language, such as
16153 @code{c} or @code{modula-2}.
16154 For a list of the supported languages, type @samp{set language}.
16156 Setting the language manually prevents @value{GDBN} from updating the working
16157 language automatically. This can lead to confusion if you try
16158 to debug a program when the working language is not the same as the
16159 source language, when an expression is acceptable to both
16160 languages---but means different things. For instance, if the current
16161 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16169 might not have the effect you intended. In C, this means to add
16170 @code{b} and @code{c} and place the result in @code{a}. The result
16171 printed would be the value of @code{a}. In Modula-2, this means to compare
16172 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16174 @node Automatically
16175 @subsection Having @value{GDBN} Infer the Source Language
16177 To have @value{GDBN} set the working language automatically, use
16178 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16179 then infers the working language. That is, when your program stops in a
16180 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16181 working language to the language recorded for the function in that
16182 frame. If the language for a frame is unknown (that is, if the function
16183 or block corresponding to the frame was defined in a source file that
16184 does not have a recognized extension), the current working language is
16185 not changed, and @value{GDBN} issues a warning.
16187 This may not seem necessary for most programs, which are written
16188 entirely in one source language. However, program modules and libraries
16189 written in one source language can be used by a main program written in
16190 a different source language. Using @samp{set language auto} in this
16191 case frees you from having to set the working language manually.
16194 @section Displaying the Language
16196 The following commands help you find out which language is the
16197 working language, and also what language source files were written in.
16200 @item show language
16201 @anchor{show language}
16202 @kindex show language
16203 Display the current working language. This is the
16204 language you can use with commands such as @code{print} to
16205 build and compute expressions that may involve variables in your program.
16208 @kindex info frame@r{, show the source language}
16209 Display the source language for this frame. This language becomes the
16210 working language if you use an identifier from this frame.
16211 @xref{Frame Info, ,Information about a Frame}, to identify the other
16212 information listed here.
16215 @kindex info source@r{, show the source language}
16216 Display the source language of this source file.
16217 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16218 information listed here.
16221 In unusual circumstances, you may have source files with extensions
16222 not in the standard list. You can then set the extension associated
16223 with a language explicitly:
16226 @item set extension-language @var{ext} @var{language}
16227 @kindex set extension-language
16228 Tell @value{GDBN} that source files with extension @var{ext} are to be
16229 assumed as written in the source language @var{language}.
16231 @item info extensions
16232 @kindex info extensions
16233 List all the filename extensions and the associated languages.
16237 @section Type and Range Checking
16239 Some languages are designed to guard you against making seemingly common
16240 errors through a series of compile- and run-time checks. These include
16241 checking the type of arguments to functions and operators and making
16242 sure mathematical overflows are caught at run time. Checks such as
16243 these help to ensure a program's correctness once it has been compiled
16244 by eliminating type mismatches and providing active checks for range
16245 errors when your program is running.
16247 By default @value{GDBN} checks for these errors according to the
16248 rules of the current source language. Although @value{GDBN} does not check
16249 the statements in your program, it can check expressions entered directly
16250 into @value{GDBN} for evaluation via the @code{print} command, for example.
16253 * Type Checking:: An overview of type checking
16254 * Range Checking:: An overview of range checking
16257 @cindex type checking
16258 @cindex checks, type
16259 @node Type Checking
16260 @subsection An Overview of Type Checking
16262 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16263 arguments to operators and functions have to be of the correct type,
16264 otherwise an error occurs. These checks prevent type mismatch
16265 errors from ever causing any run-time problems. For example,
16268 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16270 (@value{GDBP}) print obj.my_method (0)
16273 (@value{GDBP}) print obj.my_method (0x1234)
16274 Cannot resolve method klass::my_method to any overloaded instance
16277 The second example fails because in C@t{++} the integer constant
16278 @samp{0x1234} is not type-compatible with the pointer parameter type.
16280 For the expressions you use in @value{GDBN} commands, you can tell
16281 @value{GDBN} to not enforce strict type checking or
16282 to treat any mismatches as errors and abandon the expression;
16283 When type checking is disabled, @value{GDBN} successfully evaluates
16284 expressions like the second example above.
16286 Even if type checking is off, there may be other reasons
16287 related to type that prevent @value{GDBN} from evaluating an expression.
16288 For instance, @value{GDBN} does not know how to add an @code{int} and
16289 a @code{struct foo}. These particular type errors have nothing to do
16290 with the language in use and usually arise from expressions which make
16291 little sense to evaluate anyway.
16293 @value{GDBN} provides some additional commands for controlling type checking:
16295 @kindex set check type
16296 @kindex show check type
16298 @item set check type on
16299 @itemx set check type off
16300 Set strict type checking on or off. If any type mismatches occur in
16301 evaluating an expression while type checking is on, @value{GDBN} prints a
16302 message and aborts evaluation of the expression.
16304 @item show check type
16305 Show the current setting of type checking and whether @value{GDBN}
16306 is enforcing strict type checking rules.
16309 @cindex range checking
16310 @cindex checks, range
16311 @node Range Checking
16312 @subsection An Overview of Range Checking
16314 In some languages (such as Modula-2), it is an error to exceed the
16315 bounds of a type; this is enforced with run-time checks. Such range
16316 checking is meant to ensure program correctness by making sure
16317 computations do not overflow, or indices on an array element access do
16318 not exceed the bounds of the array.
16320 For expressions you use in @value{GDBN} commands, you can tell
16321 @value{GDBN} to treat range errors in one of three ways: ignore them,
16322 always treat them as errors and abandon the expression, or issue
16323 warnings but evaluate the expression anyway.
16325 A range error can result from numerical overflow, from exceeding an
16326 array index bound, or when you type a constant that is not a member
16327 of any type. Some languages, however, do not treat overflows as an
16328 error. In many implementations of C, mathematical overflow causes the
16329 result to ``wrap around'' to lower values---for example, if @var{m} is
16330 the largest integer value, and @var{s} is the smallest, then
16333 @var{m} + 1 @result{} @var{s}
16336 This, too, is specific to individual languages, and in some cases
16337 specific to individual compilers or machines. @xref{Supported Languages, ,
16338 Supported Languages}, for further details on specific languages.
16340 @value{GDBN} provides some additional commands for controlling the range checker:
16342 @kindex set check range
16343 @kindex show check range
16345 @item set check range auto
16346 Set range checking on or off based on the current working language.
16347 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16350 @item set check range on
16351 @itemx set check range off
16352 Set range checking on or off, overriding the default setting for the
16353 current working language. A warning is issued if the setting does not
16354 match the language default. If a range error occurs and range checking is on,
16355 then a message is printed and evaluation of the expression is aborted.
16357 @item set check range warn
16358 Output messages when the @value{GDBN} range checker detects a range error,
16359 but attempt to evaluate the expression anyway. Evaluating the
16360 expression may still be impossible for other reasons, such as accessing
16361 memory that the process does not own (a typical example from many Unix
16364 @item show check range
16365 Show the current setting of the range checker, and whether or not it is
16366 being set automatically by @value{GDBN}.
16369 @node Supported Languages
16370 @section Supported Languages
16372 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16373 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16374 @c This is false ...
16375 Some @value{GDBN} features may be used in expressions regardless of the
16376 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16377 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16378 ,Expressions}) can be used with the constructs of any supported
16381 The following sections detail to what degree each source language is
16382 supported by @value{GDBN}. These sections are not meant to be language
16383 tutorials or references, but serve only as a reference guide to what the
16384 @value{GDBN} expression parser accepts, and what input and output
16385 formats should look like for different languages. There are many good
16386 books written on each of these languages; please look to these for a
16387 language reference or tutorial.
16390 * C:: C and C@t{++}
16393 * Objective-C:: Objective-C
16394 * OpenCL C:: OpenCL C
16395 * Fortran:: Fortran
16398 * Modula-2:: Modula-2
16403 @subsection C and C@t{++}
16405 @cindex C and C@t{++}
16406 @cindex expressions in C or C@t{++}
16408 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16409 to both languages. Whenever this is the case, we discuss those languages
16413 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16414 @cindex @sc{gnu} C@t{++}
16415 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16416 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16417 effectively, you must compile your C@t{++} programs with a supported
16418 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16419 compiler (@code{aCC}).
16422 * C Operators:: C and C@t{++} operators
16423 * C Constants:: C and C@t{++} constants
16424 * C Plus Plus Expressions:: C@t{++} expressions
16425 * C Defaults:: Default settings for C and C@t{++}
16426 * C Checks:: C and C@t{++} type and range checks
16427 * Debugging C:: @value{GDBN} and C
16428 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16429 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16433 @subsubsection C and C@t{++} Operators
16435 @cindex C and C@t{++} operators
16437 Operators must be defined on values of specific types. For instance,
16438 @code{+} is defined on numbers, but not on structures. Operators are
16439 often defined on groups of types.
16441 For the purposes of C and C@t{++}, the following definitions hold:
16446 @emph{Integral types} include @code{int} with any of its storage-class
16447 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16450 @emph{Floating-point types} include @code{float}, @code{double}, and
16451 @code{long double} (if supported by the target platform).
16454 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16457 @emph{Scalar types} include all of the above.
16462 The following operators are supported. They are listed here
16463 in order of increasing precedence:
16467 The comma or sequencing operator. Expressions in a comma-separated list
16468 are evaluated from left to right, with the result of the entire
16469 expression being the last expression evaluated.
16472 Assignment. The value of an assignment expression is the value
16473 assigned. Defined on scalar types.
16476 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16477 and translated to @w{@code{@var{a} = @var{a op b}}}.
16478 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16479 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16480 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16483 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16484 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16485 should be of an integral type.
16488 Logical @sc{or}. Defined on integral types.
16491 Logical @sc{and}. Defined on integral types.
16494 Bitwise @sc{or}. Defined on integral types.
16497 Bitwise exclusive-@sc{or}. Defined on integral types.
16500 Bitwise @sc{and}. Defined on integral types.
16503 Equality and inequality. Defined on scalar types. The value of these
16504 expressions is 0 for false and non-zero for true.
16506 @item <@r{, }>@r{, }<=@r{, }>=
16507 Less than, greater than, less than or equal, greater than or equal.
16508 Defined on scalar types. The value of these expressions is 0 for false
16509 and non-zero for true.
16512 left shift, and right shift. Defined on integral types.
16515 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16518 Addition and subtraction. Defined on integral types, floating-point types and
16521 @item *@r{, }/@r{, }%
16522 Multiplication, division, and modulus. Multiplication and division are
16523 defined on integral and floating-point types. Modulus is defined on
16527 Increment and decrement. When appearing before a variable, the
16528 operation is performed before the variable is used in an expression;
16529 when appearing after it, the variable's value is used before the
16530 operation takes place.
16533 Pointer dereferencing. Defined on pointer types. Same precedence as
16537 Address operator. Defined on variables. Same precedence as @code{++}.
16539 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16540 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16541 to examine the address
16542 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16546 Negative. Defined on integral and floating-point types. Same
16547 precedence as @code{++}.
16550 Logical negation. Defined on integral types. Same precedence as
16554 Bitwise complement operator. Defined on integral types. Same precedence as
16559 Structure member, and pointer-to-structure member. For convenience,
16560 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16561 pointer based on the stored type information.
16562 Defined on @code{struct} and @code{union} data.
16565 Dereferences of pointers to members.
16568 Array indexing. @code{@var{a}[@var{i}]} is defined as
16569 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16572 Function parameter list. Same precedence as @code{->}.
16575 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16576 and @code{class} types.
16579 Doubled colons also represent the @value{GDBN} scope operator
16580 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16584 If an operator is redefined in the user code, @value{GDBN} usually
16585 attempts to invoke the redefined version instead of using the operator's
16586 predefined meaning.
16589 @subsubsection C and C@t{++} Constants
16591 @cindex C and C@t{++} constants
16593 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16598 Integer constants are a sequence of digits. Octal constants are
16599 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16600 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16601 @samp{l}, specifying that the constant should be treated as a
16605 Floating point constants are a sequence of digits, followed by a decimal
16606 point, followed by a sequence of digits, and optionally followed by an
16607 exponent. An exponent is of the form:
16608 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16609 sequence of digits. The @samp{+} is optional for positive exponents.
16610 A floating-point constant may also end with a letter @samp{f} or
16611 @samp{F}, specifying that the constant should be treated as being of
16612 the @code{float} (as opposed to the default @code{double}) type; or with
16613 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16617 Enumerated constants consist of enumerated identifiers, or their
16618 integral equivalents.
16621 Character constants are a single character surrounded by single quotes
16622 (@code{'}), or a number---the ordinal value of the corresponding character
16623 (usually its @sc{ascii} value). Within quotes, the single character may
16624 be represented by a letter or by @dfn{escape sequences}, which are of
16625 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16626 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16627 @samp{@var{x}} is a predefined special character---for example,
16628 @samp{\n} for newline.
16630 Wide character constants can be written by prefixing a character
16631 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16632 form of @samp{x}. The target wide character set is used when
16633 computing the value of this constant (@pxref{Character Sets}).
16636 String constants are a sequence of character constants surrounded by
16637 double quotes (@code{"}). Any valid character constant (as described
16638 above) may appear. Double quotes within the string must be preceded by
16639 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16642 Wide string constants can be written by prefixing a string constant
16643 with @samp{L}, as in C. The target wide character set is used when
16644 computing the value of this constant (@pxref{Character Sets}).
16647 Pointer constants are an integral value. You can also write pointers
16648 to constants using the C operator @samp{&}.
16651 Array constants are comma-separated lists surrounded by braces @samp{@{}
16652 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16653 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16654 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16657 @node C Plus Plus Expressions
16658 @subsubsection C@t{++} Expressions
16660 @cindex expressions in C@t{++}
16661 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16663 @cindex debugging C@t{++} programs
16664 @cindex C@t{++} compilers
16665 @cindex debug formats and C@t{++}
16666 @cindex @value{NGCC} and C@t{++}
16668 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16669 the proper compiler and the proper debug format. Currently,
16670 @value{GDBN} works best when debugging C@t{++} code that is compiled
16671 with the most recent version of @value{NGCC} possible. The DWARF
16672 debugging format is preferred; @value{NGCC} defaults to this on most
16673 popular platforms. Other compilers and/or debug formats are likely to
16674 work badly or not at all when using @value{GDBN} to debug C@t{++}
16675 code. @xref{Compilation}.
16680 @cindex member functions
16682 Member function calls are allowed; you can use expressions like
16685 count = aml->GetOriginal(x, y)
16688 @vindex this@r{, inside C@t{++} member functions}
16689 @cindex namespace in C@t{++}
16691 While a member function is active (in the selected stack frame), your
16692 expressions have the same namespace available as the member function;
16693 that is, @value{GDBN} allows implicit references to the class instance
16694 pointer @code{this} following the same rules as C@t{++}. @code{using}
16695 declarations in the current scope are also respected by @value{GDBN}.
16697 @cindex call overloaded functions
16698 @cindex overloaded functions, calling
16699 @cindex type conversions in C@t{++}
16701 You can call overloaded functions; @value{GDBN} resolves the function
16702 call to the right definition, with some restrictions. @value{GDBN} does not
16703 perform overload resolution involving user-defined type conversions,
16704 calls to constructors, or instantiations of templates that do not exist
16705 in the program. It also cannot handle ellipsis argument lists or
16708 It does perform integral conversions and promotions, floating-point
16709 promotions, arithmetic conversions, pointer conversions, conversions of
16710 class objects to base classes, and standard conversions such as those of
16711 functions or arrays to pointers; it requires an exact match on the
16712 number of function arguments.
16714 Overload resolution is always performed, unless you have specified
16715 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16716 ,@value{GDBN} Features for C@t{++}}.
16718 You must specify @code{set overload-resolution off} in order to use an
16719 explicit function signature to call an overloaded function, as in
16721 p 'foo(char,int)'('x', 13)
16724 The @value{GDBN} command-completion facility can simplify this;
16725 see @ref{Completion, ,Command Completion}.
16727 @cindex reference declarations
16729 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16730 references; you can use them in expressions just as you do in C@t{++}
16731 source---they are automatically dereferenced.
16733 In the parameter list shown when @value{GDBN} displays a frame, the values of
16734 reference variables are not displayed (unlike other variables); this
16735 avoids clutter, since references are often used for large structures.
16736 The @emph{address} of a reference variable is always shown, unless
16737 you have specified @samp{set print address off}.
16740 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16741 expressions can use it just as expressions in your program do. Since
16742 one scope may be defined in another, you can use @code{::} repeatedly if
16743 necessary, for example in an expression like
16744 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16745 resolving name scope by reference to source files, in both C and C@t{++}
16746 debugging (@pxref{Variables, ,Program Variables}).
16749 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16754 @subsubsection C and C@t{++} Defaults
16756 @cindex C and C@t{++} defaults
16758 If you allow @value{GDBN} to set range checking automatically, it
16759 defaults to @code{off} whenever the working language changes to
16760 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16761 selects the working language.
16763 If you allow @value{GDBN} to set the language automatically, it
16764 recognizes source files whose names end with @file{.c}, @file{.C}, or
16765 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16766 these files, it sets the working language to C or C@t{++}.
16767 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16768 for further details.
16771 @subsubsection C and C@t{++} Type and Range Checks
16773 @cindex C and C@t{++} checks
16775 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16776 checking is used. However, if you turn type checking off, @value{GDBN}
16777 will allow certain non-standard conversions, such as promoting integer
16778 constants to pointers.
16780 Range checking, if turned on, is done on mathematical operations. Array
16781 indices are not checked, since they are often used to index a pointer
16782 that is not itself an array.
16785 @subsubsection @value{GDBN} and C
16787 The @code{set print union} and @code{show print union} commands apply to
16788 the @code{union} type. When set to @samp{on}, any @code{union} that is
16789 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16790 appears as @samp{@{...@}}.
16792 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16793 with pointers and a memory allocation function. @xref{Expressions,
16796 @node Debugging C Plus Plus
16797 @subsubsection @value{GDBN} Features for C@t{++}
16799 @cindex commands for C@t{++}
16801 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16802 designed specifically for use with C@t{++}. Here is a summary:
16805 @cindex break in overloaded functions
16806 @item @r{breakpoint menus}
16807 When you want a breakpoint in a function whose name is overloaded,
16808 @value{GDBN} has the capability to display a menu of possible breakpoint
16809 locations to help you specify which function definition you want.
16810 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16812 @cindex overloading in C@t{++}
16813 @item rbreak @var{regex}
16814 Setting breakpoints using regular expressions is helpful for setting
16815 breakpoints on overloaded functions that are not members of any special
16817 @xref{Set Breaks, ,Setting Breakpoints}.
16819 @cindex C@t{++} exception handling
16821 @itemx catch rethrow
16823 Debug C@t{++} exception handling using these commands. @xref{Set
16824 Catchpoints, , Setting Catchpoints}.
16826 @cindex inheritance
16827 @item ptype @var{typename}
16828 Print inheritance relationships as well as other information for type
16830 @xref{Symbols, ,Examining the Symbol Table}.
16832 @item info vtbl @var{expression}.
16833 The @code{info vtbl} command can be used to display the virtual
16834 method tables of the object computed by @var{expression}. This shows
16835 one entry per virtual table; there may be multiple virtual tables when
16836 multiple inheritance is in use.
16838 @cindex C@t{++} demangling
16839 @item demangle @var{name}
16840 Demangle @var{name}.
16841 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16843 @cindex C@t{++} symbol display
16844 @item set print demangle
16845 @itemx show print demangle
16846 @itemx set print asm-demangle
16847 @itemx show print asm-demangle
16848 Control whether C@t{++} symbols display in their source form, both when
16849 displaying code as C@t{++} source and when displaying disassemblies.
16850 @xref{Print Settings, ,Print Settings}.
16852 @item set print object
16853 @itemx show print object
16854 Choose whether to print derived (actual) or declared types of objects.
16855 @xref{Print Settings, ,Print Settings}.
16857 @item set print vtbl
16858 @itemx show print vtbl
16859 Control the format for printing virtual function tables.
16860 @xref{Print Settings, ,Print Settings}.
16861 (The @code{vtbl} commands do not work on programs compiled with the HP
16862 ANSI C@t{++} compiler (@code{aCC}).)
16864 @kindex set overload-resolution
16865 @cindex overloaded functions, overload resolution
16866 @item set overload-resolution on
16867 Enable overload resolution for C@t{++} expression evaluation. The default
16868 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16869 and searches for a function whose signature matches the argument types,
16870 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16871 Expressions, ,C@t{++} Expressions}, for details).
16872 If it cannot find a match, it emits a message.
16874 @item set overload-resolution off
16875 Disable overload resolution for C@t{++} expression evaluation. For
16876 overloaded functions that are not class member functions, @value{GDBN}
16877 chooses the first function of the specified name that it finds in the
16878 symbol table, whether or not its arguments are of the correct type. For
16879 overloaded functions that are class member functions, @value{GDBN}
16880 searches for a function whose signature @emph{exactly} matches the
16883 @kindex show overload-resolution
16884 @item show overload-resolution
16885 Show the current setting of overload resolution.
16887 @item @r{Overloaded symbol names}
16888 You can specify a particular definition of an overloaded symbol, using
16889 the same notation that is used to declare such symbols in C@t{++}: type
16890 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16891 also use the @value{GDBN} command-line word completion facilities to list the
16892 available choices, or to finish the type list for you.
16893 @xref{Completion,, Command Completion}, for details on how to do this.
16895 @item @r{Breakpoints in template functions}
16897 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
16898 template parameter lists when it encounters a symbol which includes a
16899 C@t{++} template. This permits setting breakpoints on families of template functions
16900 or functions whose parameters include template types.
16902 The @kbd{-qualified} flag may be used to override this behavior, causing
16903 @value{GDBN} to search for a specific function or type.
16905 The @value{GDBN} command-line word completion facility also understands
16906 template parameters and may be used to list available choices or finish
16907 template parameter lists for you. @xref{Completion,, Command Completion}, for
16908 details on how to do this.
16910 @item @r{Breakpoints in functions with ABI tags}
16912 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16913 correspond to changes in the ABI of a type, function, or variable that
16914 would not otherwise be reflected in a mangled name. See
16915 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16918 The ABI tags are visible in C@t{++} demangled names. For example, a
16919 function that returns a std::string:
16922 std::string function(int);
16926 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16927 tag, and @value{GDBN} displays the symbol like this:
16930 function[abi:cxx11](int)
16933 You can set a breakpoint on such functions simply as if they had no
16937 (gdb) b function(int)
16938 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16939 (gdb) info breakpoints
16940 Num Type Disp Enb Address What
16941 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16945 On the rare occasion you need to disambiguate between different ABI
16946 tags, you can do so by simply including the ABI tag in the function
16950 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16954 @node Decimal Floating Point
16955 @subsubsection Decimal Floating Point format
16956 @cindex decimal floating point format
16958 @value{GDBN} can examine, set and perform computations with numbers in
16959 decimal floating point format, which in the C language correspond to the
16960 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16961 specified by the extension to support decimal floating-point arithmetic.
16963 There are two encodings in use, depending on the architecture: BID (Binary
16964 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16965 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16968 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16969 to manipulate decimal floating point numbers, it is not possible to convert
16970 (using a cast, for example) integers wider than 32-bit to decimal float.
16972 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16973 point computations, error checking in decimal float operations ignores
16974 underflow, overflow and divide by zero exceptions.
16976 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16977 to inspect @code{_Decimal128} values stored in floating point registers.
16978 See @ref{PowerPC,,PowerPC} for more details.
16984 @value{GDBN} can be used to debug programs written in D and compiled with
16985 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16986 specific feature --- dynamic arrays.
16991 @cindex Go (programming language)
16992 @value{GDBN} can be used to debug programs written in Go and compiled with
16993 @file{gccgo} or @file{6g} compilers.
16995 Here is a summary of the Go-specific features and restrictions:
16998 @cindex current Go package
16999 @item The current Go package
17000 The name of the current package does not need to be specified when
17001 specifying global variables and functions.
17003 For example, given the program:
17007 var myglob = "Shall we?"
17013 When stopped inside @code{main} either of these work:
17017 (gdb) p main.myglob
17020 @cindex builtin Go types
17021 @item Builtin Go types
17022 The @code{string} type is recognized by @value{GDBN} and is printed
17025 @cindex builtin Go functions
17026 @item Builtin Go functions
17027 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17028 function and handles it internally.
17030 @cindex restrictions on Go expressions
17031 @item Restrictions on Go expressions
17032 All Go operators are supported except @code{&^}.
17033 The Go @code{_} ``blank identifier'' is not supported.
17034 Automatic dereferencing of pointers is not supported.
17038 @subsection Objective-C
17040 @cindex Objective-C
17041 This section provides information about some commands and command
17042 options that are useful for debugging Objective-C code. See also
17043 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17044 few more commands specific to Objective-C support.
17047 * Method Names in Commands::
17048 * The Print Command with Objective-C::
17051 @node Method Names in Commands
17052 @subsubsection Method Names in Commands
17054 The following commands have been extended to accept Objective-C method
17055 names as line specifications:
17057 @kindex clear@r{, and Objective-C}
17058 @kindex break@r{, and Objective-C}
17059 @kindex info line@r{, and Objective-C}
17060 @kindex jump@r{, and Objective-C}
17061 @kindex list@r{, and Objective-C}
17065 @item @code{info line}
17070 A fully qualified Objective-C method name is specified as
17073 -[@var{Class} @var{methodName}]
17076 where the minus sign is used to indicate an instance method and a
17077 plus sign (not shown) is used to indicate a class method. The class
17078 name @var{Class} and method name @var{methodName} are enclosed in
17079 brackets, similar to the way messages are specified in Objective-C
17080 source code. For example, to set a breakpoint at the @code{create}
17081 instance method of class @code{Fruit} in the program currently being
17085 break -[Fruit create]
17088 To list ten program lines around the @code{initialize} class method,
17092 list +[NSText initialize]
17095 In the current version of @value{GDBN}, the plus or minus sign is
17096 required. In future versions of @value{GDBN}, the plus or minus
17097 sign will be optional, but you can use it to narrow the search. It
17098 is also possible to specify just a method name:
17104 You must specify the complete method name, including any colons. If
17105 your program's source files contain more than one @code{create} method,
17106 you'll be presented with a numbered list of classes that implement that
17107 method. Indicate your choice by number, or type @samp{0} to exit if
17110 As another example, to clear a breakpoint established at the
17111 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17114 clear -[NSWindow makeKeyAndOrderFront:]
17117 @node The Print Command with Objective-C
17118 @subsubsection The Print Command With Objective-C
17119 @cindex Objective-C, print objects
17120 @kindex print-object
17121 @kindex po @r{(@code{print-object})}
17123 The print command has also been extended to accept methods. For example:
17126 print -[@var{object} hash]
17129 @cindex print an Objective-C object description
17130 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17132 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17133 and print the result. Also, an additional command has been added,
17134 @code{print-object} or @code{po} for short, which is meant to print
17135 the description of an object. However, this command may only work
17136 with certain Objective-C libraries that have a particular hook
17137 function, @code{_NSPrintForDebugger}, defined.
17140 @subsection OpenCL C
17143 This section provides information about @value{GDBN}s OpenCL C support.
17146 * OpenCL C Datatypes::
17147 * OpenCL C Expressions::
17148 * OpenCL C Operators::
17151 @node OpenCL C Datatypes
17152 @subsubsection OpenCL C Datatypes
17154 @cindex OpenCL C Datatypes
17155 @value{GDBN} supports the builtin scalar and vector datatypes specified
17156 by OpenCL 1.1. In addition the half- and double-precision floating point
17157 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17158 extensions are also known to @value{GDBN}.
17160 @node OpenCL C Expressions
17161 @subsubsection OpenCL C Expressions
17163 @cindex OpenCL C Expressions
17164 @value{GDBN} supports accesses to vector components including the access as
17165 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17166 supported by @value{GDBN} can be used as well.
17168 @node OpenCL C Operators
17169 @subsubsection OpenCL C Operators
17171 @cindex OpenCL C Operators
17172 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17176 @subsection Fortran
17177 @cindex Fortran-specific support in @value{GDBN}
17179 @value{GDBN} can be used to debug programs written in Fortran, but it
17180 currently supports only the features of Fortran 77 language.
17182 @cindex trailing underscore, in Fortran symbols
17183 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17184 among them) append an underscore to the names of variables and
17185 functions. When you debug programs compiled by those compilers, you
17186 will need to refer to variables and functions with a trailing
17190 * Fortran Operators:: Fortran operators and expressions
17191 * Fortran Defaults:: Default settings for Fortran
17192 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17195 @node Fortran Operators
17196 @subsubsection Fortran Operators and Expressions
17198 @cindex Fortran operators and expressions
17200 Operators must be defined on values of specific types. For instance,
17201 @code{+} is defined on numbers, but not on characters or other non-
17202 arithmetic types. Operators are often defined on groups of types.
17206 The exponentiation operator. It raises the first operand to the power
17210 The range operator. Normally used in the form of array(low:high) to
17211 represent a section of array.
17214 The access component operator. Normally used to access elements in derived
17215 types. Also suitable for unions. As unions aren't part of regular Fortran,
17216 this can only happen when accessing a register that uses a gdbarch-defined
17219 The scope operator. Normally used to access variables in modules or
17220 to set breakpoints on subroutines nested in modules or in other
17221 subroutines (internal subroutines).
17224 @node Fortran Defaults
17225 @subsubsection Fortran Defaults
17227 @cindex Fortran Defaults
17229 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17230 default uses case-insensitive matches for Fortran symbols. You can
17231 change that with the @samp{set case-insensitive} command, see
17232 @ref{Symbols}, for the details.
17234 @node Special Fortran Commands
17235 @subsubsection Special Fortran Commands
17237 @cindex Special Fortran commands
17239 @value{GDBN} has some commands to support Fortran-specific features,
17240 such as displaying common blocks.
17243 @cindex @code{COMMON} blocks, Fortran
17244 @kindex info common
17245 @item info common @r{[}@var{common-name}@r{]}
17246 This command prints the values contained in the Fortran @code{COMMON}
17247 block whose name is @var{common-name}. With no argument, the names of
17248 all @code{COMMON} blocks visible at the current program location are
17250 @cindex arrays slices (Fortran)
17251 @kindex set fortran repack-array-slices
17252 @kindex show fortran repack-array-slices
17253 @item set fortran repack-array-slices [on|off]
17254 @item show fortran repack-array-slices
17255 When taking a slice from an array, a Fortran compiler can choose to
17256 either produce an array descriptor that describes the slice in place,
17257 or it may repack the slice, copying the elements of the slice into a
17258 new region of memory.
17260 When this setting is on, then @value{GDBN} will also repack array
17261 slices in some situations. When this setting is off, then
17262 @value{GDBN} will create array descriptors for slices that reference
17263 the original data in place.
17265 @value{GDBN} will never repack an array slice if the data for the
17266 slice is contiguous within the original array.
17268 @value{GDBN} will always repack string slices if the data for the
17269 slice is non-contiguous within the original string as @value{GDBN}
17270 does not support printing non-contiguous strings.
17272 The default for this setting is @code{off}.
17278 @cindex Pascal support in @value{GDBN}, limitations
17279 Debugging Pascal programs which use sets, subranges, file variables, or
17280 nested functions does not currently work. @value{GDBN} does not support
17281 entering expressions, printing values, or similar features using Pascal
17284 The Pascal-specific command @code{set print pascal_static-members}
17285 controls whether static members of Pascal objects are displayed.
17286 @xref{Print Settings, pascal_static-members}.
17291 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17292 Programming Language}. Type- and value-printing, and expression
17293 parsing, are reasonably complete. However, there are a few
17294 peculiarities and holes to be aware of.
17298 Linespecs (@pxref{Specify Location}) are never relative to the current
17299 crate. Instead, they act as if there were a global namespace of
17300 crates, somewhat similar to the way @code{extern crate} behaves.
17302 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17303 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17304 to set a breakpoint in a function named @samp{f} in a crate named
17307 As a consequence of this approach, linespecs also cannot refer to
17308 items using @samp{self::} or @samp{super::}.
17311 Because @value{GDBN} implements Rust name-lookup semantics in
17312 expressions, it will sometimes prepend the current crate to a name.
17313 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17314 @samp{K}, then @code{print ::x::y} will try to find the symbol
17317 However, since it is useful to be able to refer to other crates when
17318 debugging, @value{GDBN} provides the @code{extern} extension to
17319 circumvent this. To use the extension, just put @code{extern} before
17320 a path expression to refer to the otherwise unavailable ``global''
17323 In the above example, if you wanted to refer to the symbol @samp{y} in
17324 the crate @samp{x}, you would use @code{print extern x::y}.
17327 The Rust expression evaluator does not support ``statement-like''
17328 expressions such as @code{if} or @code{match}, or lambda expressions.
17331 Tuple expressions are not implemented.
17334 The Rust expression evaluator does not currently implement the
17335 @code{Drop} trait. Objects that may be created by the evaluator will
17336 never be destroyed.
17339 @value{GDBN} does not implement type inference for generics. In order
17340 to call generic functions or otherwise refer to generic items, you
17341 will have to specify the type parameters manually.
17344 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17345 cases this does not cause any problems. However, in an expression
17346 context, completing a generic function name will give syntactically
17347 invalid results. This happens because Rust requires the @samp{::}
17348 operator between the function name and its generic arguments. For
17349 example, @value{GDBN} might provide a completion like
17350 @code{crate::f<u32>}, where the parser would require
17351 @code{crate::f::<u32>}.
17354 As of this writing, the Rust compiler (version 1.8) has a few holes in
17355 the debugging information it generates. These holes prevent certain
17356 features from being implemented by @value{GDBN}:
17360 Method calls cannot be made via traits.
17363 Operator overloading is not implemented.
17366 When debugging in a monomorphized function, you cannot use the generic
17370 The type @code{Self} is not available.
17373 @code{use} statements are not available, so some names may not be
17374 available in the crate.
17379 @subsection Modula-2
17381 @cindex Modula-2, @value{GDBN} support
17383 The extensions made to @value{GDBN} to support Modula-2 only support
17384 output from the @sc{gnu} Modula-2 compiler (which is currently being
17385 developed). Other Modula-2 compilers are not currently supported, and
17386 attempting to debug executables produced by them is most likely
17387 to give an error as @value{GDBN} reads in the executable's symbol
17390 @cindex expressions in Modula-2
17392 * M2 Operators:: Built-in operators
17393 * Built-In Func/Proc:: Built-in functions and procedures
17394 * M2 Constants:: Modula-2 constants
17395 * M2 Types:: Modula-2 types
17396 * M2 Defaults:: Default settings for Modula-2
17397 * Deviations:: Deviations from standard Modula-2
17398 * M2 Checks:: Modula-2 type and range checks
17399 * M2 Scope:: The scope operators @code{::} and @code{.}
17400 * GDB/M2:: @value{GDBN} and Modula-2
17404 @subsubsection Operators
17405 @cindex Modula-2 operators
17407 Operators must be defined on values of specific types. For instance,
17408 @code{+} is defined on numbers, but not on structures. Operators are
17409 often defined on groups of types. For the purposes of Modula-2, the
17410 following definitions hold:
17415 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17419 @emph{Character types} consist of @code{CHAR} and its subranges.
17422 @emph{Floating-point types} consist of @code{REAL}.
17425 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17429 @emph{Scalar types} consist of all of the above.
17432 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17435 @emph{Boolean types} consist of @code{BOOLEAN}.
17439 The following operators are supported, and appear in order of
17440 increasing precedence:
17444 Function argument or array index separator.
17447 Assignment. The value of @var{var} @code{:=} @var{value} is
17451 Less than, greater than on integral, floating-point, or enumerated
17455 Less than or equal to, greater than or equal to
17456 on integral, floating-point and enumerated types, or set inclusion on
17457 set types. Same precedence as @code{<}.
17459 @item =@r{, }<>@r{, }#
17460 Equality and two ways of expressing inequality, valid on scalar types.
17461 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17462 available for inequality, since @code{#} conflicts with the script
17466 Set membership. Defined on set types and the types of their members.
17467 Same precedence as @code{<}.
17470 Boolean disjunction. Defined on boolean types.
17473 Boolean conjunction. Defined on boolean types.
17476 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17479 Addition and subtraction on integral and floating-point types, or union
17480 and difference on set types.
17483 Multiplication on integral and floating-point types, or set intersection
17487 Division on floating-point types, or symmetric set difference on set
17488 types. Same precedence as @code{*}.
17491 Integer division and remainder. Defined on integral types. Same
17492 precedence as @code{*}.
17495 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17498 Pointer dereferencing. Defined on pointer types.
17501 Boolean negation. Defined on boolean types. Same precedence as
17505 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17506 precedence as @code{^}.
17509 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17512 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17516 @value{GDBN} and Modula-2 scope operators.
17520 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17521 treats the use of the operator @code{IN}, or the use of operators
17522 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17523 @code{<=}, and @code{>=} on sets as an error.
17527 @node Built-In Func/Proc
17528 @subsubsection Built-in Functions and Procedures
17529 @cindex Modula-2 built-ins
17531 Modula-2 also makes available several built-in procedures and functions.
17532 In describing these, the following metavariables are used:
17537 represents an @code{ARRAY} variable.
17540 represents a @code{CHAR} constant or variable.
17543 represents a variable or constant of integral type.
17546 represents an identifier that belongs to a set. Generally used in the
17547 same function with the metavariable @var{s}. The type of @var{s} should
17548 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17551 represents a variable or constant of integral or floating-point type.
17554 represents a variable or constant of floating-point type.
17560 represents a variable.
17563 represents a variable or constant of one of many types. See the
17564 explanation of the function for details.
17567 All Modula-2 built-in procedures also return a result, described below.
17571 Returns the absolute value of @var{n}.
17574 If @var{c} is a lower case letter, it returns its upper case
17575 equivalent, otherwise it returns its argument.
17578 Returns the character whose ordinal value is @var{i}.
17581 Decrements the value in the variable @var{v} by one. Returns the new value.
17583 @item DEC(@var{v},@var{i})
17584 Decrements the value in the variable @var{v} by @var{i}. Returns the
17587 @item EXCL(@var{m},@var{s})
17588 Removes the element @var{m} from the set @var{s}. Returns the new
17591 @item FLOAT(@var{i})
17592 Returns the floating point equivalent of the integer @var{i}.
17594 @item HIGH(@var{a})
17595 Returns the index of the last member of @var{a}.
17598 Increments the value in the variable @var{v} by one. Returns the new value.
17600 @item INC(@var{v},@var{i})
17601 Increments the value in the variable @var{v} by @var{i}. Returns the
17604 @item INCL(@var{m},@var{s})
17605 Adds the element @var{m} to the set @var{s} if it is not already
17606 there. Returns the new set.
17609 Returns the maximum value of the type @var{t}.
17612 Returns the minimum value of the type @var{t}.
17615 Returns boolean TRUE if @var{i} is an odd number.
17618 Returns the ordinal value of its argument. For example, the ordinal
17619 value of a character is its @sc{ascii} value (on machines supporting
17620 the @sc{ascii} character set). The argument @var{x} must be of an
17621 ordered type, which include integral, character and enumerated types.
17623 @item SIZE(@var{x})
17624 Returns the size of its argument. The argument @var{x} can be a
17625 variable or a type.
17627 @item TRUNC(@var{r})
17628 Returns the integral part of @var{r}.
17630 @item TSIZE(@var{x})
17631 Returns the size of its argument. The argument @var{x} can be a
17632 variable or a type.
17634 @item VAL(@var{t},@var{i})
17635 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17639 @emph{Warning:} Sets and their operations are not yet supported, so
17640 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17644 @cindex Modula-2 constants
17646 @subsubsection Constants
17648 @value{GDBN} allows you to express the constants of Modula-2 in the following
17654 Integer constants are simply a sequence of digits. When used in an
17655 expression, a constant is interpreted to be type-compatible with the
17656 rest of the expression. Hexadecimal integers are specified by a
17657 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17660 Floating point constants appear as a sequence of digits, followed by a
17661 decimal point and another sequence of digits. An optional exponent can
17662 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17663 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17664 digits of the floating point constant must be valid decimal (base 10)
17668 Character constants consist of a single character enclosed by a pair of
17669 like quotes, either single (@code{'}) or double (@code{"}). They may
17670 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17671 followed by a @samp{C}.
17674 String constants consist of a sequence of characters enclosed by a
17675 pair of like quotes, either single (@code{'}) or double (@code{"}).
17676 Escape sequences in the style of C are also allowed. @xref{C
17677 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17681 Enumerated constants consist of an enumerated identifier.
17684 Boolean constants consist of the identifiers @code{TRUE} and
17688 Pointer constants consist of integral values only.
17691 Set constants are not yet supported.
17695 @subsubsection Modula-2 Types
17696 @cindex Modula-2 types
17698 Currently @value{GDBN} can print the following data types in Modula-2
17699 syntax: array types, record types, set types, pointer types, procedure
17700 types, enumerated types, subrange types and base types. You can also
17701 print the contents of variables declared using these type.
17702 This section gives a number of simple source code examples together with
17703 sample @value{GDBN} sessions.
17705 The first example contains the following section of code:
17714 and you can request @value{GDBN} to interrogate the type and value of
17715 @code{r} and @code{s}.
17718 (@value{GDBP}) print s
17720 (@value{GDBP}) ptype s
17722 (@value{GDBP}) print r
17724 (@value{GDBP}) ptype r
17729 Likewise if your source code declares @code{s} as:
17733 s: SET ['A'..'Z'] ;
17737 then you may query the type of @code{s} by:
17740 (@value{GDBP}) ptype s
17741 type = SET ['A'..'Z']
17745 Note that at present you cannot interactively manipulate set
17746 expressions using the debugger.
17748 The following example shows how you might declare an array in Modula-2
17749 and how you can interact with @value{GDBN} to print its type and contents:
17753 s: ARRAY [-10..10] OF CHAR ;
17757 (@value{GDBP}) ptype s
17758 ARRAY [-10..10] OF CHAR
17761 Note that the array handling is not yet complete and although the type
17762 is printed correctly, expression handling still assumes that all
17763 arrays have a lower bound of zero and not @code{-10} as in the example
17766 Here are some more type related Modula-2 examples:
17770 colour = (blue, red, yellow, green) ;
17771 t = [blue..yellow] ;
17779 The @value{GDBN} interaction shows how you can query the data type
17780 and value of a variable.
17783 (@value{GDBP}) print s
17785 (@value{GDBP}) ptype t
17786 type = [blue..yellow]
17790 In this example a Modula-2 array is declared and its contents
17791 displayed. Observe that the contents are written in the same way as
17792 their @code{C} counterparts.
17796 s: ARRAY [1..5] OF CARDINAL ;
17802 (@value{GDBP}) print s
17803 $1 = @{1, 0, 0, 0, 0@}
17804 (@value{GDBP}) ptype s
17805 type = ARRAY [1..5] OF CARDINAL
17808 The Modula-2 language interface to @value{GDBN} also understands
17809 pointer types as shown in this example:
17813 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17820 and you can request that @value{GDBN} describes the type of @code{s}.
17823 (@value{GDBP}) ptype s
17824 type = POINTER TO ARRAY [1..5] OF CARDINAL
17827 @value{GDBN} handles compound types as we can see in this example.
17828 Here we combine array types, record types, pointer types and subrange
17839 myarray = ARRAY myrange OF CARDINAL ;
17840 myrange = [-2..2] ;
17842 s: POINTER TO ARRAY myrange OF foo ;
17846 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17850 (@value{GDBP}) ptype s
17851 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17854 f3 : ARRAY [-2..2] OF CARDINAL;
17859 @subsubsection Modula-2 Defaults
17860 @cindex Modula-2 defaults
17862 If type and range checking are set automatically by @value{GDBN}, they
17863 both default to @code{on} whenever the working language changes to
17864 Modula-2. This happens regardless of whether you or @value{GDBN}
17865 selected the working language.
17867 If you allow @value{GDBN} to set the language automatically, then entering
17868 code compiled from a file whose name ends with @file{.mod} sets the
17869 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17870 Infer the Source Language}, for further details.
17873 @subsubsection Deviations from Standard Modula-2
17874 @cindex Modula-2, deviations from
17876 A few changes have been made to make Modula-2 programs easier to debug.
17877 This is done primarily via loosening its type strictness:
17881 Unlike in standard Modula-2, pointer constants can be formed by
17882 integers. This allows you to modify pointer variables during
17883 debugging. (In standard Modula-2, the actual address contained in a
17884 pointer variable is hidden from you; it can only be modified
17885 through direct assignment to another pointer variable or expression that
17886 returned a pointer.)
17889 C escape sequences can be used in strings and characters to represent
17890 non-printable characters. @value{GDBN} prints out strings with these
17891 escape sequences embedded. Single non-printable characters are
17892 printed using the @samp{CHR(@var{nnn})} format.
17895 The assignment operator (@code{:=}) returns the value of its right-hand
17899 All built-in procedures both modify @emph{and} return their argument.
17903 @subsubsection Modula-2 Type and Range Checks
17904 @cindex Modula-2 checks
17907 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17910 @c FIXME remove warning when type/range checks added
17912 @value{GDBN} considers two Modula-2 variables type equivalent if:
17916 They are of types that have been declared equivalent via a @code{TYPE
17917 @var{t1} = @var{t2}} statement
17920 They have been declared on the same line. (Note: This is true of the
17921 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17924 As long as type checking is enabled, any attempt to combine variables
17925 whose types are not equivalent is an error.
17927 Range checking is done on all mathematical operations, assignment, array
17928 index bounds, and all built-in functions and procedures.
17931 @subsubsection The Scope Operators @code{::} and @code{.}
17933 @cindex @code{.}, Modula-2 scope operator
17934 @cindex colon, doubled as scope operator
17936 @vindex colon-colon@r{, in Modula-2}
17937 @c Info cannot handle :: but TeX can.
17940 @vindex ::@r{, in Modula-2}
17943 There are a few subtle differences between the Modula-2 scope operator
17944 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17949 @var{module} . @var{id}
17950 @var{scope} :: @var{id}
17954 where @var{scope} is the name of a module or a procedure,
17955 @var{module} the name of a module, and @var{id} is any declared
17956 identifier within your program, except another module.
17958 Using the @code{::} operator makes @value{GDBN} search the scope
17959 specified by @var{scope} for the identifier @var{id}. If it is not
17960 found in the specified scope, then @value{GDBN} searches all scopes
17961 enclosing the one specified by @var{scope}.
17963 Using the @code{.} operator makes @value{GDBN} search the current scope for
17964 the identifier specified by @var{id} that was imported from the
17965 definition module specified by @var{module}. With this operator, it is
17966 an error if the identifier @var{id} was not imported from definition
17967 module @var{module}, or if @var{id} is not an identifier in
17971 @subsubsection @value{GDBN} and Modula-2
17973 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17974 Five subcommands of @code{set print} and @code{show print} apply
17975 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17976 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17977 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17978 analogue in Modula-2.
17980 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17981 with any language, is not useful with Modula-2. Its
17982 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17983 created in Modula-2 as they can in C or C@t{++}. However, because an
17984 address can be specified by an integral constant, the construct
17985 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17987 @cindex @code{#} in Modula-2
17988 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17989 interpreted as the beginning of a comment. Use @code{<>} instead.
17995 The extensions made to @value{GDBN} for Ada only support
17996 output from the @sc{gnu} Ada (GNAT) compiler.
17997 Other Ada compilers are not currently supported, and
17998 attempting to debug executables produced by them is most likely
18002 @cindex expressions in Ada
18004 * Ada Mode Intro:: General remarks on the Ada syntax
18005 and semantics supported by Ada mode
18007 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18008 * Additions to Ada:: Extensions of the Ada expression syntax.
18009 * Overloading support for Ada:: Support for expressions involving overloaded
18011 * Stopping Before Main Program:: Debugging the program during elaboration.
18012 * Ada Exceptions:: Ada Exceptions
18013 * Ada Tasks:: Listing and setting breakpoints in tasks.
18014 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18015 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18017 * Ada Settings:: New settable GDB parameters for Ada.
18018 * Ada Source Character Set:: Character set of Ada source files.
18019 * Ada Glitches:: Known peculiarities of Ada mode.
18022 @node Ada Mode Intro
18023 @subsubsection Introduction
18024 @cindex Ada mode, general
18026 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18027 syntax, with some extensions.
18028 The philosophy behind the design of this subset is
18032 That @value{GDBN} should provide basic literals and access to operations for
18033 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18034 leaving more sophisticated computations to subprograms written into the
18035 program (which therefore may be called from @value{GDBN}).
18038 That type safety and strict adherence to Ada language restrictions
18039 are not particularly important to the @value{GDBN} user.
18042 That brevity is important to the @value{GDBN} user.
18045 Thus, for brevity, the debugger acts as if all names declared in
18046 user-written packages are directly visible, even if they are not visible
18047 according to Ada rules, thus making it unnecessary to fully qualify most
18048 names with their packages, regardless of context. Where this causes
18049 ambiguity, @value{GDBN} asks the user's intent.
18051 The debugger will start in Ada mode if it detects an Ada main program.
18052 As for other languages, it will enter Ada mode when stopped in a program that
18053 was translated from an Ada source file.
18055 While in Ada mode, you may use `@t{--}' for comments. This is useful
18056 mostly for documenting command files. The standard @value{GDBN} comment
18057 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18058 middle (to allow based literals).
18060 @node Omissions from Ada
18061 @subsubsection Omissions from Ada
18062 @cindex Ada, omissions from
18064 Here are the notable omissions from the subset:
18068 Only a subset of the attributes are supported:
18072 @t{'First}, @t{'Last}, and @t{'Length}
18073 on array objects (not on types and subtypes).
18076 @t{'Min} and @t{'Max}.
18079 @t{'Pos} and @t{'Val}.
18085 @t{'Range} on array objects (not subtypes), but only as the right
18086 operand of the membership (@code{in}) operator.
18089 @t{'Access}, @t{'Unchecked_Access}, and
18090 @t{'Unrestricted_Access} (a GNAT extension).
18097 The names in @code{Characters.Latin_1} are not available.
18100 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18101 equality of representations. They will generally work correctly
18102 for strings and arrays whose elements have integer or enumeration types.
18103 They may not work correctly for arrays whose element
18104 types have user-defined equality, for arrays of real values
18105 (in particular, IEEE-conformant floating point, because of negative
18106 zeroes and NaNs), and for arrays whose elements contain unused bits with
18107 indeterminate values.
18110 The other component-by-component array operations (@code{and}, @code{or},
18111 @code{xor}, @code{not}, and relational tests other than equality)
18112 are not implemented.
18115 @cindex array aggregates (Ada)
18116 @cindex record aggregates (Ada)
18117 @cindex aggregates (Ada)
18118 There is limited support for array and record aggregates. They are
18119 permitted only on the right sides of assignments, as in these examples:
18122 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18123 (@value{GDBP}) set An_Array := (1, others => 0)
18124 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18125 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18126 (@value{GDBP}) set A_Record := (1, "Peter", True);
18127 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18131 discriminant's value by assigning an aggregate has an
18132 undefined effect if that discriminant is used within the record.
18133 However, you can first modify discriminants by directly assigning to
18134 them (which normally would not be allowed in Ada), and then performing an
18135 aggregate assignment. For example, given a variable @code{A_Rec}
18136 declared to have a type such as:
18139 type Rec (Len : Small_Integer := 0) is record
18141 Vals : IntArray (1 .. Len);
18145 you can assign a value with a different size of @code{Vals} with two
18149 (@value{GDBP}) set A_Rec.Len := 4
18150 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18153 As this example also illustrates, @value{GDBN} is very loose about the usual
18154 rules concerning aggregates. You may leave out some of the
18155 components of an array or record aggregate (such as the @code{Len}
18156 component in the assignment to @code{A_Rec} above); they will retain their
18157 original values upon assignment. You may freely use dynamic values as
18158 indices in component associations. You may even use overlapping or
18159 redundant component associations, although which component values are
18160 assigned in such cases is not defined.
18163 Calls to dispatching subprograms are not implemented.
18166 The overloading algorithm is much more limited (i.e., less selective)
18167 than that of real Ada. It makes only limited use of the context in
18168 which a subexpression appears to resolve its meaning, and it is much
18169 looser in its rules for allowing type matches. As a result, some
18170 function calls will be ambiguous, and the user will be asked to choose
18171 the proper resolution.
18174 The @code{new} operator is not implemented.
18177 Entry calls are not implemented.
18180 Aside from printing, arithmetic operations on the native VAX floating-point
18181 formats are not supported.
18184 It is not possible to slice a packed array.
18187 The names @code{True} and @code{False}, when not part of a qualified name,
18188 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18190 Should your program
18191 redefine these names in a package or procedure (at best a dubious practice),
18192 you will have to use fully qualified names to access their new definitions.
18195 Based real literals are not implemented.
18198 @node Additions to Ada
18199 @subsubsection Additions to Ada
18200 @cindex Ada, deviations from
18202 As it does for other languages, @value{GDBN} makes certain generic
18203 extensions to Ada (@pxref{Expressions}):
18207 If the expression @var{E} is a variable residing in memory (typically
18208 a local variable or array element) and @var{N} is a positive integer,
18209 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18210 @var{N}-1 adjacent variables following it in memory as an array. In
18211 Ada, this operator is generally not necessary, since its prime use is
18212 in displaying parts of an array, and slicing will usually do this in
18213 Ada. However, there are occasional uses when debugging programs in
18214 which certain debugging information has been optimized away.
18217 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18218 appears in function or file @var{B}.'' When @var{B} is a file name,
18219 you must typically surround it in single quotes.
18222 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18223 @var{type} that appears at address @var{addr}.''
18226 A name starting with @samp{$} is a convenience variable
18227 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18230 In addition, @value{GDBN} provides a few other shortcuts and outright
18231 additions specific to Ada:
18235 The assignment statement is allowed as an expression, returning
18236 its right-hand operand as its value. Thus, you may enter
18239 (@value{GDBP}) set x := y + 3
18240 (@value{GDBP}) print A(tmp := y + 1)
18244 The semicolon is allowed as an ``operator,'' returning as its value
18245 the value of its right-hand operand.
18246 This allows, for example,
18247 complex conditional breaks:
18250 (@value{GDBP}) break f
18251 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18255 An extension to based literals can be used to specify the exact byte
18256 contents of a floating-point literal. After the base, you can use
18257 from zero to two @samp{l} characters, followed by an @samp{f}. The
18258 number of @samp{l} characters controls the width of the resulting real
18259 constant: zero means @code{Float} is used, one means
18260 @code{Long_Float}, and two means @code{Long_Long_Float}.
18263 (@value{GDBP}) print 16f#41b80000#
18268 Rather than use catenation and symbolic character names to introduce special
18269 characters into strings, one may instead use a special bracket notation,
18270 which is also used to print strings. A sequence of characters of the form
18271 @samp{["@var{XX}"]} within a string or character literal denotes the
18272 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18273 sequence of characters @samp{["""]} also denotes a single quotation mark
18274 in strings. For example,
18276 "One line.["0a"]Next line.["0a"]"
18279 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18283 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18284 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18288 (@value{GDBP}) print 'max(x, y)
18292 When printing arrays, @value{GDBN} uses positional notation when the
18293 array has a lower bound of 1, and uses a modified named notation otherwise.
18294 For example, a one-dimensional array of three integers with a lower bound
18295 of 3 might print as
18302 That is, in contrast to valid Ada, only the first component has a @code{=>}
18306 You may abbreviate attributes in expressions with any unique,
18307 multi-character subsequence of
18308 their names (an exact match gets preference).
18309 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18310 in place of @t{a'length}.
18313 @cindex quoting Ada internal identifiers
18314 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18315 to lower case. The GNAT compiler uses upper-case characters for
18316 some of its internal identifiers, which are normally of no interest to users.
18317 For the rare occasions when you actually have to look at them,
18318 enclose them in angle brackets to avoid the lower-case mapping.
18321 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18325 Printing an object of class-wide type or dereferencing an
18326 access-to-class-wide value will display all the components of the object's
18327 specific type (as indicated by its run-time tag). Likewise, component
18328 selection on such a value will operate on the specific type of the
18333 @node Overloading support for Ada
18334 @subsubsection Overloading support for Ada
18335 @cindex overloading, Ada
18337 The debugger supports limited overloading. Given a subprogram call in which
18338 the function symbol has multiple definitions, it will use the number of
18339 actual parameters and some information about their types to attempt to narrow
18340 the set of definitions. It also makes very limited use of context, preferring
18341 procedures to functions in the context of the @code{call} command, and
18342 functions to procedures elsewhere.
18344 If, after narrowing, the set of matching definitions still contains more than
18345 one definition, @value{GDBN} will display a menu to query which one it should
18349 (@value{GDBP}) print f(1)
18350 Multiple matches for f
18352 [1] foo.f (integer) return boolean at foo.adb:23
18353 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18357 In this case, just select one menu entry either to cancel expression evaluation
18358 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18359 instance (type the corresponding number and press @key{RET}).
18361 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18366 @kindex set ada print-signatures
18367 @item set ada print-signatures
18368 Control whether parameter types and return types are displayed in overloads
18369 selection menus. It is @code{on} by default.
18370 @xref{Overloading support for Ada}.
18372 @kindex show ada print-signatures
18373 @item show ada print-signatures
18374 Show the current setting for displaying parameter types and return types in
18375 overloads selection menu.
18376 @xref{Overloading support for Ada}.
18380 @node Stopping Before Main Program
18381 @subsubsection Stopping at the Very Beginning
18383 @cindex breakpointing Ada elaboration code
18384 It is sometimes necessary to debug the program during elaboration, and
18385 before reaching the main procedure.
18386 As defined in the Ada Reference
18387 Manual, the elaboration code is invoked from a procedure called
18388 @code{adainit}. To run your program up to the beginning of
18389 elaboration, simply use the following two commands:
18390 @code{tbreak adainit} and @code{run}.
18392 @node Ada Exceptions
18393 @subsubsection Ada Exceptions
18395 A command is provided to list all Ada exceptions:
18398 @kindex info exceptions
18399 @item info exceptions
18400 @itemx info exceptions @var{regexp}
18401 The @code{info exceptions} command allows you to list all Ada exceptions
18402 defined within the program being debugged, as well as their addresses.
18403 With a regular expression, @var{regexp}, as argument, only those exceptions
18404 whose names match @var{regexp} are listed.
18407 Below is a small example, showing how the command can be used, first
18408 without argument, and next with a regular expression passed as an
18412 (@value{GDBP}) info exceptions
18413 All defined Ada exceptions:
18414 constraint_error: 0x613da0
18415 program_error: 0x613d20
18416 storage_error: 0x613ce0
18417 tasking_error: 0x613ca0
18418 const.aint_global_e: 0x613b00
18419 (@value{GDBP}) info exceptions const.aint
18420 All Ada exceptions matching regular expression "const.aint":
18421 constraint_error: 0x613da0
18422 const.aint_global_e: 0x613b00
18425 It is also possible to ask @value{GDBN} to stop your program's execution
18426 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18429 @subsubsection Extensions for Ada Tasks
18430 @cindex Ada, tasking
18432 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18433 @value{GDBN} provides the following task-related commands:
18438 This command shows a list of current Ada tasks, as in the following example:
18445 (@value{GDBP}) info tasks
18446 ID TID P-ID Pri State Name
18447 1 8088000 0 15 Child Activation Wait main_task
18448 2 80a4000 1 15 Accept Statement b
18449 3 809a800 1 15 Child Activation Wait a
18450 * 4 80ae800 3 15 Runnable c
18455 In this listing, the asterisk before the last task indicates it to be the
18456 task currently being inspected.
18460 Represents @value{GDBN}'s internal task number.
18466 The parent's task ID (@value{GDBN}'s internal task number).
18469 The base priority of the task.
18472 Current state of the task.
18476 The task has been created but has not been activated. It cannot be
18480 The task is not blocked for any reason known to Ada. (It may be waiting
18481 for a mutex, though.) It is conceptually "executing" in normal mode.
18484 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18485 that were waiting on terminate alternatives have been awakened and have
18486 terminated themselves.
18488 @item Child Activation Wait
18489 The task is waiting for created tasks to complete activation.
18491 @item Accept Statement
18492 The task is waiting on an accept or selective wait statement.
18494 @item Waiting on entry call
18495 The task is waiting on an entry call.
18497 @item Async Select Wait
18498 The task is waiting to start the abortable part of an asynchronous
18502 The task is waiting on a select statement with only a delay
18505 @item Child Termination Wait
18506 The task is sleeping having completed a master within itself, and is
18507 waiting for the tasks dependent on that master to become terminated or
18508 waiting on a terminate Phase.
18510 @item Wait Child in Term Alt
18511 The task is sleeping waiting for tasks on terminate alternatives to
18512 finish terminating.
18514 @item Accepting RV with @var{taskno}
18515 The task is accepting a rendez-vous with the task @var{taskno}.
18519 Name of the task in the program.
18523 @kindex info task @var{taskno}
18524 @item info task @var{taskno}
18525 This command shows detailed informations on the specified task, as in
18526 the following example:
18531 (@value{GDBP}) info tasks
18532 ID TID P-ID Pri State Name
18533 1 8077880 0 15 Child Activation Wait main_task
18534 * 2 807c468 1 15 Runnable task_1
18535 (@value{GDBP}) info task 2
18536 Ada Task: 0x807c468
18540 Parent: 1 ("main_task")
18546 @kindex task@r{ (Ada)}
18547 @cindex current Ada task ID
18548 This command prints the ID and name of the current task.
18554 (@value{GDBP}) info tasks
18555 ID TID P-ID Pri State Name
18556 1 8077870 0 15 Child Activation Wait main_task
18557 * 2 807c458 1 15 Runnable some_task
18558 (@value{GDBP}) task
18559 [Current task is 2 "some_task"]
18562 @item task @var{taskno}
18563 @cindex Ada task switching
18564 This command is like the @code{thread @var{thread-id}}
18565 command (@pxref{Threads}). It switches the context of debugging
18566 from the current task to the given task.
18572 (@value{GDBP}) info tasks
18573 ID TID P-ID Pri State Name
18574 1 8077870 0 15 Child Activation Wait main_task
18575 * 2 807c458 1 15 Runnable some_task
18576 (@value{GDBP}) task 1
18577 [Switching to task 1 "main_task"]
18578 #0 0x8067726 in pthread_cond_wait ()
18580 #0 0x8067726 in pthread_cond_wait ()
18581 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18582 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18583 #3 0x806153e in system.tasking.stages.activate_tasks ()
18584 #4 0x804aacc in un () at un.adb:5
18587 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18588 The @code{task apply} command is the Ada tasking analogue of
18589 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18590 named @var{command} to one or more tasks. Specify the tasks that you
18591 want affected using a list of task IDs, or specify @code{all} to apply
18594 The @var{flag} arguments control what output to produce and how to
18595 handle errors raised when applying @var{command} to a task.
18596 @var{flag} must start with a @code{-} directly followed by one letter
18597 in @code{qcs}. If several flags are provided, they must be given
18598 individually, such as @code{-c -q}.
18600 By default, @value{GDBN} displays some task information before the
18601 output produced by @var{command}, and an error raised during the
18602 execution of a @var{command} will abort @code{task apply}. The
18603 following flags can be used to fine-tune this behavior:
18607 The flag @code{-c}, which stands for @samp{continue}, causes any
18608 errors in @var{command} to be displayed, and the execution of
18609 @code{task apply} then continues.
18611 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18612 or empty output produced by a @var{command} to be silently ignored.
18613 That is, the execution continues, but the task information and errors
18616 The flag @code{-q} (@samp{quiet}) disables printing the task
18620 Flags @code{-c} and @code{-s} cannot be used together.
18622 @item break @var{location} task @var{taskno}
18623 @itemx break @var{location} task @var{taskno} if @dots{}
18624 @cindex breakpoints and tasks, in Ada
18625 @cindex task breakpoints, in Ada
18626 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18627 These commands are like the @code{break @dots{} thread @dots{}}
18628 command (@pxref{Thread Stops}). The
18629 @var{location} argument specifies source lines, as described
18630 in @ref{Specify Location}.
18632 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18633 to specify that you only want @value{GDBN} to stop the program when a
18634 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18635 numeric task identifiers assigned by @value{GDBN}, shown in the first
18636 column of the @samp{info tasks} display.
18638 If you do not specify @samp{task @var{taskno}} when you set a
18639 breakpoint, the breakpoint applies to @emph{all} tasks of your
18642 You can use the @code{task} qualifier on conditional breakpoints as
18643 well; in this case, place @samp{task @var{taskno}} before the
18644 breakpoint condition (before the @code{if}).
18652 (@value{GDBP}) info tasks
18653 ID TID P-ID Pri State Name
18654 1 140022020 0 15 Child Activation Wait main_task
18655 2 140045060 1 15 Accept/Select Wait t2
18656 3 140044840 1 15 Runnable t1
18657 * 4 140056040 1 15 Runnable t3
18658 (@value{GDBP}) b 15 task 2
18659 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18660 (@value{GDBP}) cont
18665 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18667 (@value{GDBP}) info tasks
18668 ID TID P-ID Pri State Name
18669 1 140022020 0 15 Child Activation Wait main_task
18670 * 2 140045060 1 15 Runnable t2
18671 3 140044840 1 15 Runnable t1
18672 4 140056040 1 15 Delay Sleep t3
18676 @node Ada Tasks and Core Files
18677 @subsubsection Tasking Support when Debugging Core Files
18678 @cindex Ada tasking and core file debugging
18680 When inspecting a core file, as opposed to debugging a live program,
18681 tasking support may be limited or even unavailable, depending on
18682 the platform being used.
18683 For instance, on x86-linux, the list of tasks is available, but task
18684 switching is not supported.
18686 On certain platforms, the debugger needs to perform some
18687 memory writes in order to provide Ada tasking support. When inspecting
18688 a core file, this means that the core file must be opened with read-write
18689 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18690 Under these circumstances, you should make a backup copy of the core
18691 file before inspecting it with @value{GDBN}.
18693 @node Ravenscar Profile
18694 @subsubsection Tasking Support when using the Ravenscar Profile
18695 @cindex Ravenscar Profile
18697 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18698 specifically designed for systems with safety-critical real-time
18702 @kindex set ravenscar task-switching on
18703 @cindex task switching with program using Ravenscar Profile
18704 @item set ravenscar task-switching on
18705 Allows task switching when debugging a program that uses the Ravenscar
18706 Profile. This is the default.
18708 @kindex set ravenscar task-switching off
18709 @item set ravenscar task-switching off
18710 Turn off task switching when debugging a program that uses the Ravenscar
18711 Profile. This is mostly intended to disable the code that adds support
18712 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18713 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18714 To be effective, this command should be run before the program is started.
18716 @kindex show ravenscar task-switching
18717 @item show ravenscar task-switching
18718 Show whether it is possible to switch from task to task in a program
18719 using the Ravenscar Profile.
18723 @cindex Ravenscar thread
18724 When Ravenscar task-switching is enabled, Ravenscar tasks are
18725 announced by @value{GDBN} as if they were threads:
18729 [New Ravenscar Thread 0x2b8f0]
18732 Both Ravenscar tasks and the underlying CPU threads will show up in
18733 the output of @code{info threads}:
18738 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18739 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18740 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18741 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18742 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18743 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18746 One known limitation of the Ravenscar support in @value{GDBN} is that
18747 it isn't currently possible to single-step through the runtime
18748 initialization sequence. If you need to debug this code, you should
18749 use @code{set ravenscar task-switching off}.
18752 @subsubsection Ada Settings
18753 @cindex Ada settings
18756 @kindex set varsize-limit
18757 @item set varsize-limit @var{size}
18758 Prevent @value{GDBN} from attempting to evaluate objects whose size
18759 is above the given limit (@var{size}) when those sizes are computed
18760 from run-time quantities. This is typically the case when the object
18761 has a variable size, such as an array whose bounds are not known at
18762 compile time for example. Setting @var{size} to @code{unlimited}
18763 removes the size limitation. By default, the limit is about 65KB.
18765 The purpose of having such a limit is to prevent @value{GDBN} from
18766 trying to grab enormous chunks of virtual memory when asked to evaluate
18767 a quantity whose bounds have been corrupted or have not yet been fully
18768 initialized. The limit applies to the results of some subexpressions
18769 as well as to complete expressions. For example, an expression denoting
18770 a simple integer component, such as @code{x.y.z}, may fail if the size of
18771 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18772 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18773 @code{A} is an array variable with non-constant size, will generally
18774 succeed regardless of the bounds on @code{A}, as long as the component
18775 size is less than @var{size}.
18777 @kindex show varsize-limit
18778 @item show varsize-limit
18779 Show the limit on types whose size is determined by run-time quantities.
18782 @node Ada Source Character Set
18783 @subsubsection Ada Source Character Set
18784 @cindex Ada, source character set
18786 The GNAT compiler supports a number of character sets for source
18787 files. @xref{Character Set Control, , Character Set Control,
18788 gnat_ugn}. @value{GDBN} includes support for this as well.
18791 @item set ada source-charset @var{charset}
18792 @kindex set ada source-charset
18793 Set the source character set for Ada. The character set must be
18794 supported by GNAT. Because this setting affects the decoding of
18795 symbols coming from the debug information in your program, the setting
18796 should be set as early as possible. The default is @code{ISO-8859-1},
18797 because that is also GNAT's default.
18799 @item show ada source-charset
18800 @kindex show ada source-charset
18801 Show the current source character set for Ada.
18805 @subsubsection Known Peculiarities of Ada Mode
18806 @cindex Ada, problems
18808 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18809 we know of several problems with and limitations of Ada mode in
18811 some of which will be fixed with planned future releases of the debugger
18812 and the GNU Ada compiler.
18816 Static constants that the compiler chooses not to materialize as objects in
18817 storage are invisible to the debugger.
18820 Named parameter associations in function argument lists are ignored (the
18821 argument lists are treated as positional).
18824 Many useful library packages are currently invisible to the debugger.
18827 Fixed-point arithmetic, conversions, input, and output is carried out using
18828 floating-point arithmetic, and may give results that only approximate those on
18832 The GNAT compiler never generates the prefix @code{Standard} for any of
18833 the standard symbols defined by the Ada language. @value{GDBN} knows about
18834 this: it will strip the prefix from names when you use it, and will never
18835 look for a name you have so qualified among local symbols, nor match against
18836 symbols in other packages or subprograms. If you have
18837 defined entities anywhere in your program other than parameters and
18838 local variables whose simple names match names in @code{Standard},
18839 GNAT's lack of qualification here can cause confusion. When this happens,
18840 you can usually resolve the confusion
18841 by qualifying the problematic names with package
18842 @code{Standard} explicitly.
18845 Older versions of the compiler sometimes generate erroneous debugging
18846 information, resulting in the debugger incorrectly printing the value
18847 of affected entities. In some cases, the debugger is able to work
18848 around an issue automatically. In other cases, the debugger is able
18849 to work around the issue, but the work-around has to be specifically
18852 @kindex set ada trust-PAD-over-XVS
18853 @kindex show ada trust-PAD-over-XVS
18856 @item set ada trust-PAD-over-XVS on
18857 Configure GDB to strictly follow the GNAT encoding when computing the
18858 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18859 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18860 a complete description of the encoding used by the GNAT compiler).
18861 This is the default.
18863 @item set ada trust-PAD-over-XVS off
18864 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18865 sometimes prints the wrong value for certain entities, changing @code{ada
18866 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18867 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18868 @code{off}, but this incurs a slight performance penalty, so it is
18869 recommended to leave this setting to @code{on} unless necessary.
18873 @cindex GNAT descriptive types
18874 @cindex GNAT encoding
18875 Internally, the debugger also relies on the compiler following a number
18876 of conventions known as the @samp{GNAT Encoding}, all documented in
18877 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18878 how the debugging information should be generated for certain types.
18879 In particular, this convention makes use of @dfn{descriptive types},
18880 which are artificial types generated purely to help the debugger.
18882 These encodings were defined at a time when the debugging information
18883 format used was not powerful enough to describe some of the more complex
18884 types available in Ada. Since DWARF allows us to express nearly all
18885 Ada features, the long-term goal is to slowly replace these descriptive
18886 types by their pure DWARF equivalent. To facilitate that transition,
18887 a new maintenance option is available to force the debugger to ignore
18888 those descriptive types. It allows the user to quickly evaluate how
18889 well @value{GDBN} works without them.
18893 @kindex maint ada set ignore-descriptive-types
18894 @item maintenance ada set ignore-descriptive-types [on|off]
18895 Control whether the debugger should ignore descriptive types.
18896 The default is not to ignore descriptives types (@code{off}).
18898 @kindex maint ada show ignore-descriptive-types
18899 @item maintenance ada show ignore-descriptive-types
18900 Show if descriptive types are ignored by @value{GDBN}.
18904 @node Unsupported Languages
18905 @section Unsupported Languages
18907 @cindex unsupported languages
18908 @cindex minimal language
18909 In addition to the other fully-supported programming languages,
18910 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18911 It does not represent a real programming language, but provides a set
18912 of capabilities close to what the C or assembly languages provide.
18913 This should allow most simple operations to be performed while debugging
18914 an application that uses a language currently not supported by @value{GDBN}.
18916 If the language is set to @code{auto}, @value{GDBN} will automatically
18917 select this language if the current frame corresponds to an unsupported
18921 @chapter Examining the Symbol Table
18923 The commands described in this chapter allow you to inquire about the
18924 symbols (names of variables, functions and types) defined in your
18925 program. This information is inherent in the text of your program and
18926 does not change as your program executes. @value{GDBN} finds it in your
18927 program's symbol table, in the file indicated when you started @value{GDBN}
18928 (@pxref{File Options, ,Choosing Files}), or by one of the
18929 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18931 @cindex symbol names
18932 @cindex names of symbols
18933 @cindex quoting names
18934 @anchor{quoting names}
18935 Occasionally, you may need to refer to symbols that contain unusual
18936 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18937 most frequent case is in referring to static variables in other
18938 source files (@pxref{Variables,,Program Variables}). File names
18939 are recorded in object files as debugging symbols, but @value{GDBN} would
18940 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18941 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18942 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18949 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18952 @cindex case-insensitive symbol names
18953 @cindex case sensitivity in symbol names
18954 @kindex set case-sensitive
18955 @item set case-sensitive on
18956 @itemx set case-sensitive off
18957 @itemx set case-sensitive auto
18958 Normally, when @value{GDBN} looks up symbols, it matches their names
18959 with case sensitivity determined by the current source language.
18960 Occasionally, you may wish to control that. The command @code{set
18961 case-sensitive} lets you do that by specifying @code{on} for
18962 case-sensitive matches or @code{off} for case-insensitive ones. If
18963 you specify @code{auto}, case sensitivity is reset to the default
18964 suitable for the source language. The default is case-sensitive
18965 matches for all languages except for Fortran, for which the default is
18966 case-insensitive matches.
18968 @kindex show case-sensitive
18969 @item show case-sensitive
18970 This command shows the current setting of case sensitivity for symbols
18973 @kindex set print type methods
18974 @item set print type methods
18975 @itemx set print type methods on
18976 @itemx set print type methods off
18977 Normally, when @value{GDBN} prints a class, it displays any methods
18978 declared in that class. You can control this behavior either by
18979 passing the appropriate flag to @code{ptype}, or using @command{set
18980 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18981 display the methods; this is the default. Specifying @code{off} will
18982 cause @value{GDBN} to omit the methods.
18984 @kindex show print type methods
18985 @item show print type methods
18986 This command shows the current setting of method display when printing
18989 @kindex set print type nested-type-limit
18990 @item set print type nested-type-limit @var{limit}
18991 @itemx set print type nested-type-limit unlimited
18992 Set the limit of displayed nested types that the type printer will
18993 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18994 nested definitions. By default, the type printer will not show any nested
18995 types defined in classes.
18997 @kindex show print type nested-type-limit
18998 @item show print type nested-type-limit
18999 This command shows the current display limit of nested types when
19002 @kindex set print type typedefs
19003 @item set print type typedefs
19004 @itemx set print type typedefs on
19005 @itemx set print type typedefs off
19007 Normally, when @value{GDBN} prints a class, it displays any typedefs
19008 defined in that class. You can control this behavior either by
19009 passing the appropriate flag to @code{ptype}, or using @command{set
19010 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19011 display the typedef definitions; this is the default. Specifying
19012 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19013 Note that this controls whether the typedef definition itself is
19014 printed, not whether typedef names are substituted when printing other
19017 @kindex show print type typedefs
19018 @item show print type typedefs
19019 This command shows the current setting of typedef display when
19022 @kindex set print type hex
19023 @item set print type hex
19024 @itemx set print type hex on
19025 @itemx set print type hex off
19027 When @value{GDBN} prints sizes and offsets of struct members, it can use
19028 either the decimal or hexadecimal notation. You can select one or the
19029 other either by passing the appropriate flag to @code{ptype}, or by using
19030 the @command{set print type hex} command.
19032 @kindex show print type hex
19033 @item show print type hex
19034 This command shows whether the sizes and offsets of struct members are
19035 printed in decimal or hexadecimal notation.
19037 @kindex info address
19038 @cindex address of a symbol
19039 @item info address @var{symbol}
19040 Describe where the data for @var{symbol} is stored. For a register
19041 variable, this says which register it is kept in. For a non-register
19042 local variable, this prints the stack-frame offset at which the variable
19045 Note the contrast with @samp{print &@var{symbol}}, which does not work
19046 at all for a register variable, and for a stack local variable prints
19047 the exact address of the current instantiation of the variable.
19049 @kindex info symbol
19050 @cindex symbol from address
19051 @cindex closest symbol and offset for an address
19052 @item info symbol @var{addr}
19053 Print the name of a symbol which is stored at the address @var{addr}.
19054 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19055 nearest symbol and an offset from it:
19058 (@value{GDBP}) info symbol 0x54320
19059 _initialize_vx + 396 in section .text
19063 This is the opposite of the @code{info address} command. You can use
19064 it to find out the name of a variable or a function given its address.
19066 For dynamically linked executables, the name of executable or shared
19067 library containing the symbol is also printed:
19070 (@value{GDBP}) info symbol 0x400225
19071 _start + 5 in section .text of /tmp/a.out
19072 (@value{GDBP}) info symbol 0x2aaaac2811cf
19073 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19078 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19079 Demangle @var{name}.
19080 If @var{language} is provided it is the name of the language to demangle
19081 @var{name} in. Otherwise @var{name} is demangled in the current language.
19083 The @samp{--} option specifies the end of options,
19084 and is useful when @var{name} begins with a dash.
19086 The parameter @code{demangle-style} specifies how to interpret the kind
19087 of mangling used. @xref{Print Settings}.
19090 @item whatis[/@var{flags}] [@var{arg}]
19091 Print the data type of @var{arg}, which can be either an expression
19092 or a name of a data type. With no argument, print the data type of
19093 @code{$}, the last value in the value history.
19095 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19096 is not actually evaluated, and any side-effecting operations (such as
19097 assignments or function calls) inside it do not take place.
19099 If @var{arg} is a variable or an expression, @code{whatis} prints its
19100 literal type as it is used in the source code. If the type was
19101 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19102 the data type underlying the @code{typedef}. If the type of the
19103 variable or the expression is a compound data type, such as
19104 @code{struct} or @code{class}, @code{whatis} never prints their
19105 fields or methods. It just prints the @code{struct}/@code{class}
19106 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19107 such a compound data type, use @code{ptype}.
19109 If @var{arg} is a type name that was defined using @code{typedef},
19110 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19111 Unrolling means that @code{whatis} will show the underlying type used
19112 in the @code{typedef} declaration of @var{arg}. However, if that
19113 underlying type is also a @code{typedef}, @code{whatis} will not
19116 For C code, the type names may also have the form @samp{class
19117 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19118 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19120 @var{flags} can be used to modify how the type is displayed.
19121 Available flags are:
19125 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19126 parameters and typedefs defined in a class when printing the class'
19127 members. The @code{/r} flag disables this.
19130 Do not print methods defined in the class.
19133 Print methods defined in the class. This is the default, but the flag
19134 exists in case you change the default with @command{set print type methods}.
19137 Do not print typedefs defined in the class. Note that this controls
19138 whether the typedef definition itself is printed, not whether typedef
19139 names are substituted when printing other types.
19142 Print typedefs defined in the class. This is the default, but the flag
19143 exists in case you change the default with @command{set print type typedefs}.
19146 Print the offsets and sizes of fields in a struct, similar to what the
19147 @command{pahole} tool does. This option implies the @code{/tm} flags.
19150 Use hexadecimal notation when printing offsets and sizes of fields in a
19154 Use decimal notation when printing offsets and sizes of fields in a
19157 For example, given the following declarations:
19193 Issuing a @kbd{ptype /o struct tuv} command would print:
19196 (@value{GDBP}) ptype /o struct tuv
19197 /* offset | size */ type = struct tuv @{
19198 /* 0 | 4 */ int a1;
19199 /* XXX 4-byte hole */
19200 /* 8 | 8 */ char *a2;
19201 /* 16 | 4 */ int a3;
19203 /* total size (bytes): 24 */
19207 Notice the format of the first column of comments. There, you can
19208 find two parts separated by the @samp{|} character: the @emph{offset},
19209 which indicates where the field is located inside the struct, in
19210 bytes, and the @emph{size} of the field. Another interesting line is
19211 the marker of a @emph{hole} in the struct, indicating that it may be
19212 possible to pack the struct and make it use less space by reorganizing
19215 It is also possible to print offsets inside an union:
19218 (@value{GDBP}) ptype /o union qwe
19219 /* offset | size */ type = union qwe @{
19220 /* 24 */ struct tuv @{
19221 /* 0 | 4 */ int a1;
19222 /* XXX 4-byte hole */
19223 /* 8 | 8 */ char *a2;
19224 /* 16 | 4 */ int a3;
19226 /* total size (bytes): 24 */
19228 /* 40 */ struct xyz @{
19229 /* 0 | 4 */ int f1;
19230 /* 4 | 1 */ char f2;
19231 /* XXX 3-byte hole */
19232 /* 8 | 8 */ void *f3;
19233 /* 16 | 24 */ struct tuv @{
19234 /* 16 | 4 */ int a1;
19235 /* XXX 4-byte hole */
19236 /* 24 | 8 */ char *a2;
19237 /* 32 | 4 */ int a3;
19239 /* total size (bytes): 24 */
19242 /* total size (bytes): 40 */
19245 /* total size (bytes): 40 */
19249 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19250 same space (because we are dealing with an union), the offset is not
19251 printed for them. However, you can still examine the offset of each
19252 of these structures' fields.
19254 Another useful scenario is printing the offsets of a struct containing
19258 (@value{GDBP}) ptype /o struct tyu
19259 /* offset | size */ type = struct tyu @{
19260 /* 0:31 | 4 */ int a1 : 1;
19261 /* 0:28 | 4 */ int a2 : 3;
19262 /* 0: 5 | 4 */ int a3 : 23;
19263 /* 3: 3 | 1 */ signed char a4 : 2;
19264 /* XXX 3-bit hole */
19265 /* XXX 4-byte hole */
19266 /* 8 | 8 */ int64_t a5;
19267 /* 16: 0 | 4 */ int a6 : 5;
19268 /* 16: 5 | 8 */ int64_t a7 : 3;
19269 /* XXX 7-byte padding */
19271 /* total size (bytes): 24 */
19275 Note how the offset information is now extended to also include the
19276 first bit of the bitfield.
19280 @item ptype[/@var{flags}] [@var{arg}]
19281 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19282 detailed description of the type, instead of just the name of the type.
19283 @xref{Expressions, ,Expressions}.
19285 Contrary to @code{whatis}, @code{ptype} always unrolls any
19286 @code{typedef}s in its argument declaration, whether the argument is
19287 a variable, expression, or a data type. This means that @code{ptype}
19288 of a variable or an expression will not print literally its type as
19289 present in the source code---use @code{whatis} for that. @code{typedef}s at
19290 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19291 fields, methods and inner @code{class typedef}s of @code{struct}s,
19292 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19294 For example, for this variable declaration:
19297 typedef double real_t;
19298 struct complex @{ real_t real; double imag; @};
19299 typedef struct complex complex_t;
19301 real_t *real_pointer_var;
19305 the two commands give this output:
19309 (@value{GDBP}) whatis var
19311 (@value{GDBP}) ptype var
19312 type = struct complex @{
19316 (@value{GDBP}) whatis complex_t
19317 type = struct complex
19318 (@value{GDBP}) whatis struct complex
19319 type = struct complex
19320 (@value{GDBP}) ptype struct complex
19321 type = struct complex @{
19325 (@value{GDBP}) whatis real_pointer_var
19327 (@value{GDBP}) ptype real_pointer_var
19333 As with @code{whatis}, using @code{ptype} without an argument refers to
19334 the type of @code{$}, the last value in the value history.
19336 @cindex incomplete type
19337 Sometimes, programs use opaque data types or incomplete specifications
19338 of complex data structure. If the debug information included in the
19339 program does not allow @value{GDBN} to display a full declaration of
19340 the data type, it will say @samp{<incomplete type>}. For example,
19341 given these declarations:
19345 struct foo *fooptr;
19349 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19352 (@value{GDBP}) ptype foo
19353 $1 = <incomplete type>
19357 ``Incomplete type'' is C terminology for data types that are not
19358 completely specified.
19360 @cindex unknown type
19361 Othertimes, information about a variable's type is completely absent
19362 from the debug information included in the program. This most often
19363 happens when the program or library where the variable is defined
19364 includes no debug information at all. @value{GDBN} knows the variable
19365 exists from inspecting the linker/loader symbol table (e.g., the ELF
19366 dynamic symbol table), but such symbols do not contain type
19367 information. Inspecting the type of a (global) variable for which
19368 @value{GDBN} has no type information shows:
19371 (@value{GDBP}) ptype var
19372 type = <data variable, no debug info>
19375 @xref{Variables, no debug info variables}, for how to print the values
19379 @item info types [-q] [@var{regexp}]
19380 Print a brief description of all types whose names match the regular
19381 expression @var{regexp} (or all types in your program, if you supply
19382 no argument). Each complete typename is matched as though it were a
19383 complete line; thus, @samp{i type value} gives information on all
19384 types in your program whose names include the string @code{value}, but
19385 @samp{i type ^value$} gives information only on types whose complete
19386 name is @code{value}.
19388 In programs using different languages, @value{GDBN} chooses the syntax
19389 to print the type description according to the
19390 @samp{set language} value: using @samp{set language auto}
19391 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19392 language of the type, other values mean to use
19393 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19395 This command differs from @code{ptype} in two ways: first, like
19396 @code{whatis}, it does not print a detailed description; second, it
19397 lists all source files and line numbers where a type is defined.
19399 The output from @samp{into types} is proceeded with a header line
19400 describing what types are being listed. The optional flag @samp{-q},
19401 which stands for @samp{quiet}, disables printing this header
19404 @kindex info type-printers
19405 @item info type-printers
19406 Versions of @value{GDBN} that ship with Python scripting enabled may
19407 have ``type printers'' available. When using @command{ptype} or
19408 @command{whatis}, these printers are consulted when the name of a type
19409 is needed. @xref{Type Printing API}, for more information on writing
19412 @code{info type-printers} displays all the available type printers.
19414 @kindex enable type-printer
19415 @kindex disable type-printer
19416 @item enable type-printer @var{name}@dots{}
19417 @item disable type-printer @var{name}@dots{}
19418 These commands can be used to enable or disable type printers.
19421 @cindex local variables
19422 @item info scope @var{location}
19423 List all the variables local to a particular scope. This command
19424 accepts a @var{location} argument---a function name, a source line, or
19425 an address preceded by a @samp{*}, and prints all the variables local
19426 to the scope defined by that location. (@xref{Specify Location}, for
19427 details about supported forms of @var{location}.) For example:
19430 (@value{GDBP}) @b{info scope command_line_handler}
19431 Scope for command_line_handler:
19432 Symbol rl is an argument at stack/frame offset 8, length 4.
19433 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19434 Symbol linelength is in static storage at address 0x150a1c, length 4.
19435 Symbol p is a local variable in register $esi, length 4.
19436 Symbol p1 is a local variable in register $ebx, length 4.
19437 Symbol nline is a local variable in register $edx, length 4.
19438 Symbol repeat is a local variable at frame offset -8, length 4.
19442 This command is especially useful for determining what data to collect
19443 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19446 @kindex info source
19448 Show information about the current source file---that is, the source file for
19449 the function containing the current point of execution:
19452 the name of the source file, and the directory containing it,
19454 the directory it was compiled in,
19456 its length, in lines,
19458 which programming language it is written in,
19460 if the debug information provides it, the program that compiled the file
19461 (which may include, e.g., the compiler version and command line arguments),
19463 whether the executable includes debugging information for that file, and
19464 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19466 whether the debugging information includes information about
19467 preprocessor macros.
19471 @kindex info sources
19472 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19475 With no options @samp{info sources} prints the names of all source
19476 files in your program for which there is debugging information. The
19477 source files are presented based on a list of object files
19478 (executables and libraries) currently loaded into @value{GDBN}. For
19479 each object file all of the associated source files are listed.
19481 Each source file will only be printed once for each object file, but a
19482 single source file can be repeated in the output if it is part of
19483 multiple object files.
19485 If the optional @var{regexp} is provided, then only source files that
19486 match the regular expression will be printed. The matching is
19487 case-sensitive, except on operating systems that have case-insensitive
19488 filesystem (e.g., MS-Windows). @samp{--} can be used before
19489 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19490 command option (e.g. if @var{regexp} starts with @samp{-}).
19492 By default, the @var{regexp} is used to match anywhere in the
19493 filename. If @code{-dirname}, only files having a dirname matching
19494 @var{regexp} are shown. If @code{-basename}, only files having a
19495 basename matching @var{regexp} are shown.
19497 It is possible that an object file may be printed in the list with no
19498 associated source files. This can happen when either no source files
19499 match @var{regexp}, or, the object file was compiled without debug
19500 information and so @value{GDBN} is unable to find any source file
19503 @kindex info functions
19504 @item info functions [-q] [-n]
19505 Print the names and data types of all defined functions.
19506 Similarly to @samp{info types}, this command groups its output by source
19507 files and annotates each function definition with its source line
19510 In programs using different languages, @value{GDBN} chooses the syntax
19511 to print the function name and type according to the
19512 @samp{set language} value: using @samp{set language auto}
19513 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19514 language of the function, other values mean to use
19515 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19517 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19518 results. A non-debugging symbol is a symbol that comes from the
19519 executable's symbol table, not from the debug information (for
19520 example, DWARF) associated with the executable.
19522 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19523 printing header information and messages explaining why no functions
19526 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19527 Like @samp{info functions}, but only print the names and data types
19528 of the functions selected with the provided regexp(s).
19530 If @var{regexp} is provided, print only the functions whose names
19531 match the regular expression @var{regexp}.
19532 Thus, @samp{info fun step} finds all functions whose
19533 names include @code{step}; @samp{info fun ^step} finds those whose names
19534 start with @code{step}. If a function name contains characters that
19535 conflict with the regular expression language (e.g.@:
19536 @samp{operator*()}), they may be quoted with a backslash.
19538 If @var{type_regexp} is provided, print only the functions whose
19539 types, as printed by the @code{whatis} command, match
19540 the regular expression @var{type_regexp}.
19541 If @var{type_regexp} contains space(s), it should be enclosed in
19542 quote characters. If needed, use backslash to escape the meaning
19543 of special characters or quotes.
19544 Thus, @samp{info fun -t '^int ('} finds the functions that return
19545 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19546 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19547 finds the functions whose names start with @code{step} and that return
19550 If both @var{regexp} and @var{type_regexp} are provided, a function
19551 is printed only if its name matches @var{regexp} and its type matches
19555 @kindex info variables
19556 @item info variables [-q] [-n]
19557 Print the names and data types of all variables that are defined
19558 outside of functions (i.e.@: excluding local variables).
19559 The printed variables are grouped by source files and annotated with
19560 their respective source line numbers.
19562 In programs using different languages, @value{GDBN} chooses the syntax
19563 to print the variable name and type according to the
19564 @samp{set language} value: using @samp{set language auto}
19565 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19566 language of the variable, other values mean to use
19567 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19569 The @samp{-n} flag excludes non-debugging symbols from the results.
19571 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19572 printing header information and messages explaining why no variables
19575 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19576 Like @kbd{info variables}, but only print the variables selected
19577 with the provided regexp(s).
19579 If @var{regexp} is provided, print only the variables whose names
19580 match the regular expression @var{regexp}.
19582 If @var{type_regexp} is provided, print only the variables whose
19583 types, as printed by the @code{whatis} command, match
19584 the regular expression @var{type_regexp}.
19585 If @var{type_regexp} contains space(s), it should be enclosed in
19586 quote characters. If needed, use backslash to escape the meaning
19587 of special characters or quotes.
19589 If both @var{regexp} and @var{type_regexp} are provided, an argument
19590 is printed only if its name matches @var{regexp} and its type matches
19593 @kindex info modules
19595 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19596 List all Fortran modules in the program, or all modules matching the
19597 optional regular expression @var{regexp}.
19599 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19600 printing header information and messages explaining why no modules
19603 @kindex info module
19604 @cindex Fortran modules, information about
19605 @cindex functions and variables by Fortran module
19606 @cindex module functions and variables
19607 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19608 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19609 List all functions or variables within all Fortran modules. The set
19610 of functions or variables listed can be limited by providing some or
19611 all of the optional regular expressions. If @var{module-regexp} is
19612 provided, then only Fortran modules matching @var{module-regexp} will
19613 be searched. Only functions or variables whose type matches the
19614 optional regular expression @var{type-regexp} will be listed. And
19615 only functions or variables whose name matches the optional regular
19616 expression @var{regexp} will be listed.
19618 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19619 printing header information and messages explaining why no functions
19620 or variables have been printed.
19622 @kindex info classes
19623 @cindex Objective-C, classes and selectors
19625 @itemx info classes @var{regexp}
19626 Display all Objective-C classes in your program, or
19627 (with the @var{regexp} argument) all those matching a particular regular
19630 @kindex info selectors
19631 @item info selectors
19632 @itemx info selectors @var{regexp}
19633 Display all Objective-C selectors in your program, or
19634 (with the @var{regexp} argument) all those matching a particular regular
19638 This was never implemented.
19639 @kindex info methods
19641 @itemx info methods @var{regexp}
19642 The @code{info methods} command permits the user to examine all defined
19643 methods within C@t{++} program, or (with the @var{regexp} argument) a
19644 specific set of methods found in the various C@t{++} classes. Many
19645 C@t{++} classes provide a large number of methods. Thus, the output
19646 from the @code{ptype} command can be overwhelming and hard to use. The
19647 @code{info-methods} command filters the methods, printing only those
19648 which match the regular-expression @var{regexp}.
19651 @cindex opaque data types
19652 @kindex set opaque-type-resolution
19653 @item set opaque-type-resolution on
19654 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19655 declared as a pointer to a @code{struct}, @code{class}, or
19656 @code{union}---for example, @code{struct MyType *}---that is used in one
19657 source file although the full declaration of @code{struct MyType} is in
19658 another source file. The default is on.
19660 A change in the setting of this subcommand will not take effect until
19661 the next time symbols for a file are loaded.
19663 @item set opaque-type-resolution off
19664 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19665 is printed as follows:
19667 @{<no data fields>@}
19670 @kindex show opaque-type-resolution
19671 @item show opaque-type-resolution
19672 Show whether opaque types are resolved or not.
19674 @kindex set print symbol-loading
19675 @cindex print messages when symbols are loaded
19676 @item set print symbol-loading
19677 @itemx set print symbol-loading full
19678 @itemx set print symbol-loading brief
19679 @itemx set print symbol-loading off
19680 The @code{set print symbol-loading} command allows you to control the
19681 printing of messages when @value{GDBN} loads symbol information.
19682 By default a message is printed for the executable and one for each
19683 shared library, and normally this is what you want. However, when
19684 debugging apps with large numbers of shared libraries these messages
19686 When set to @code{brief} a message is printed for each executable,
19687 and when @value{GDBN} loads a collection of shared libraries at once
19688 it will only print one message regardless of the number of shared
19689 libraries. When set to @code{off} no messages are printed.
19691 @kindex show print symbol-loading
19692 @item show print symbol-loading
19693 Show whether messages will be printed when a @value{GDBN} command
19694 entered from the keyboard causes symbol information to be loaded.
19696 @kindex maint print symbols
19697 @cindex symbol dump
19698 @kindex maint print psymbols
19699 @cindex partial symbol dump
19700 @kindex maint print msymbols
19701 @cindex minimal symbol dump
19702 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19703 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19704 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19705 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19706 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19707 Write a dump of debugging symbol data into the file @var{filename} or
19708 the terminal if @var{filename} is unspecified.
19709 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19711 If @code{-pc @var{address}} is specified, only dump symbols for the file
19712 with code at that address. Note that @var{address} may be a symbol like
19714 If @code{-source @var{source}} is specified, only dump symbols for that
19717 These commands are used to debug the @value{GDBN} symbol-reading code.
19718 These commands do not modify internal @value{GDBN} state, therefore
19719 @samp{maint print symbols} will only print symbols for already expanded symbol
19721 You can use the command @code{info sources} to find out which files these are.
19722 If you use @samp{maint print psymbols} instead, the dump shows information
19723 about symbols that @value{GDBN} only knows partially---that is, symbols
19724 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19725 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19728 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19729 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19731 @kindex maint info symtabs
19732 @kindex maint info psymtabs
19733 @cindex listing @value{GDBN}'s internal symbol tables
19734 @cindex symbol tables, listing @value{GDBN}'s internal
19735 @cindex full symbol tables, listing @value{GDBN}'s internal
19736 @cindex partial symbol tables, listing @value{GDBN}'s internal
19737 @item maint info symtabs @r{[} @var{regexp} @r{]}
19738 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19740 List the @code{struct symtab} or @code{struct partial_symtab}
19741 structures whose names match @var{regexp}. If @var{regexp} is not
19742 given, list them all. The output includes expressions which you can
19743 copy into a @value{GDBN} debugging this one to examine a particular
19744 structure in more detail. For example:
19747 (@value{GDBP}) maint info psymtabs dwarf2read
19748 @{ objfile /home/gnu/build/gdb/gdb
19749 ((struct objfile *) 0x82e69d0)
19750 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19751 ((struct partial_symtab *) 0x8474b10)
19754 text addresses 0x814d3c8 -- 0x8158074
19755 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19756 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19757 dependencies (none)
19760 (@value{GDBP}) maint info symtabs
19764 We see that there is one partial symbol table whose filename contains
19765 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19766 and we see that @value{GDBN} has not read in any symtabs yet at all.
19767 If we set a breakpoint on a function, that will cause @value{GDBN} to
19768 read the symtab for the compilation unit containing that function:
19771 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19772 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19774 (@value{GDBP}) maint info symtabs
19775 @{ objfile /home/gnu/build/gdb/gdb
19776 ((struct objfile *) 0x82e69d0)
19777 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19778 ((struct symtab *) 0x86c1f38)
19781 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19782 linetable ((struct linetable *) 0x8370fa0)
19783 debugformat DWARF 2
19789 @kindex maint info line-table
19790 @cindex listing @value{GDBN}'s internal line tables
19791 @cindex line tables, listing @value{GDBN}'s internal
19792 @item maint info line-table @r{[} @var{regexp} @r{]}
19794 List the @code{struct linetable} from all @code{struct symtab}
19795 instances whose name matches @var{regexp}. If @var{regexp} is not
19796 given, list the @code{struct linetable} from all @code{struct symtab}.
19798 @kindex maint set symbol-cache-size
19799 @cindex symbol cache size
19800 @item maint set symbol-cache-size @var{size}
19801 Set the size of the symbol cache to @var{size}.
19802 The default size is intended to be good enough for debugging
19803 most applications. This option exists to allow for experimenting
19804 with different sizes.
19806 @kindex maint show symbol-cache-size
19807 @item maint show symbol-cache-size
19808 Show the size of the symbol cache.
19810 @kindex maint print symbol-cache
19811 @cindex symbol cache, printing its contents
19812 @item maint print symbol-cache
19813 Print the contents of the symbol cache.
19814 This is useful when debugging symbol cache issues.
19816 @kindex maint print symbol-cache-statistics
19817 @cindex symbol cache, printing usage statistics
19818 @item maint print symbol-cache-statistics
19819 Print symbol cache usage statistics.
19820 This helps determine how well the cache is being utilized.
19822 @kindex maint flush symbol-cache
19823 @kindex maint flush-symbol-cache
19824 @cindex symbol cache, flushing
19825 @item maint flush symbol-cache
19826 @itemx maint flush-symbol-cache
19827 Flush the contents of the symbol cache, all entries are removed. This
19828 command is useful when debugging the symbol cache. It is also useful
19829 when collecting performance data. The command @code{maint
19830 flush-symbol-cache} is deprecated in favor of @code{maint flush
19836 @chapter Altering Execution
19838 Once you think you have found an error in your program, you might want to
19839 find out for certain whether correcting the apparent error would lead to
19840 correct results in the rest of the run. You can find the answer by
19841 experiment, using the @value{GDBN} features for altering execution of the
19844 For example, you can store new values into variables or memory
19845 locations, give your program a signal, restart it at a different
19846 address, or even return prematurely from a function.
19849 * Assignment:: Assignment to variables
19850 * Jumping:: Continuing at a different address
19851 * Signaling:: Giving your program a signal
19852 * Returning:: Returning from a function
19853 * Calling:: Calling your program's functions
19854 * Patching:: Patching your program
19855 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19859 @section Assignment to Variables
19862 @cindex setting variables
19863 To alter the value of a variable, evaluate an assignment expression.
19864 @xref{Expressions, ,Expressions}. For example,
19871 stores the value 4 into the variable @code{x}, and then prints the
19872 value of the assignment expression (which is 4).
19873 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19874 information on operators in supported languages.
19876 @kindex set variable
19877 @cindex variables, setting
19878 If you are not interested in seeing the value of the assignment, use the
19879 @code{set} command instead of the @code{print} command. @code{set} is
19880 really the same as @code{print} except that the expression's value is
19881 not printed and is not put in the value history (@pxref{Value History,
19882 ,Value History}). The expression is evaluated only for its effects.
19884 If the beginning of the argument string of the @code{set} command
19885 appears identical to a @code{set} subcommand, use the @code{set
19886 variable} command instead of just @code{set}. This command is identical
19887 to @code{set} except for its lack of subcommands. For example, if your
19888 program has a variable @code{width}, you get an error if you try to set
19889 a new value with just @samp{set width=13}, because @value{GDBN} has the
19890 command @code{set width}:
19893 (@value{GDBP}) whatis width
19895 (@value{GDBP}) p width
19897 (@value{GDBP}) set width=47
19898 Invalid syntax in expression.
19902 The invalid expression, of course, is @samp{=47}. In
19903 order to actually set the program's variable @code{width}, use
19906 (@value{GDBP}) set var width=47
19909 Because the @code{set} command has many subcommands that can conflict
19910 with the names of program variables, it is a good idea to use the
19911 @code{set variable} command instead of just @code{set}. For example, if
19912 your program has a variable @code{g}, you run into problems if you try
19913 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19914 the command @code{set gnutarget}, abbreviated @code{set g}:
19918 (@value{GDBP}) whatis g
19922 (@value{GDBP}) set g=4
19926 The program being debugged has been started already.
19927 Start it from the beginning? (y or n) y
19928 Starting program: /home/smith/cc_progs/a.out
19929 "/home/smith/cc_progs/a.out": can't open to read symbols:
19930 Invalid bfd target.
19931 (@value{GDBP}) show g
19932 The current BFD target is "=4".
19937 The program variable @code{g} did not change, and you silently set the
19938 @code{gnutarget} to an invalid value. In order to set the variable
19942 (@value{GDBP}) set var g=4
19945 @value{GDBN} allows more implicit conversions in assignments than C; you can
19946 freely store an integer value into a pointer variable or vice versa,
19947 and you can convert any structure to any other structure that is the
19948 same length or shorter.
19949 @comment FIXME: how do structs align/pad in these conversions?
19950 @comment /doc@cygnus.com 18dec1990
19952 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19953 construct to generate a value of specified type at a specified address
19954 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19955 to memory location @code{0x83040} as an integer (which implies a certain size
19956 and representation in memory), and
19959 set @{int@}0x83040 = 4
19963 stores the value 4 into that memory location.
19966 @section Continuing at a Different Address
19968 Ordinarily, when you continue your program, you do so at the place where
19969 it stopped, with the @code{continue} command. You can instead continue at
19970 an address of your own choosing, with the following commands:
19974 @kindex j @r{(@code{jump})}
19975 @item jump @var{location}
19976 @itemx j @var{location}
19977 Resume execution at @var{location}. Execution stops again immediately
19978 if there is a breakpoint there. @xref{Specify Location}, for a description
19979 of the different forms of @var{location}. It is common
19980 practice to use the @code{tbreak} command in conjunction with
19981 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19983 The @code{jump} command does not change the current stack frame, or
19984 the stack pointer, or the contents of any memory location or any
19985 register other than the program counter. If @var{location} is in
19986 a different function from the one currently executing, the results may
19987 be bizarre if the two functions expect different patterns of arguments or
19988 of local variables. For this reason, the @code{jump} command requests
19989 confirmation if the specified line is not in the function currently
19990 executing. However, even bizarre results are predictable if you are
19991 well acquainted with the machine-language code of your program.
19994 On many systems, you can get much the same effect as the @code{jump}
19995 command by storing a new value into the register @code{$pc}. The
19996 difference is that this does not start your program running; it only
19997 changes the address of where it @emph{will} run when you continue. For
20005 makes the next @code{continue} command or stepping command execute at
20006 address @code{0x485}, rather than at the address where your program stopped.
20007 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20009 The most common occasion to use the @code{jump} command is to back
20010 up---perhaps with more breakpoints set---over a portion of a program
20011 that has already executed, in order to examine its execution in more
20016 @section Giving your Program a Signal
20017 @cindex deliver a signal to a program
20021 @item signal @var{signal}
20022 Resume execution where your program is stopped, but immediately give it the
20023 signal @var{signal}. The @var{signal} can be the name or the number of a
20024 signal. For example, on many systems @code{signal 2} and @code{signal
20025 SIGINT} are both ways of sending an interrupt signal.
20027 Alternatively, if @var{signal} is zero, continue execution without
20028 giving a signal. This is useful when your program stopped on account of
20029 a signal and would ordinarily see the signal when resumed with the
20030 @code{continue} command; @samp{signal 0} causes it to resume without a
20033 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20034 delivered to the currently selected thread, not the thread that last
20035 reported a stop. This includes the situation where a thread was
20036 stopped due to a signal. So if you want to continue execution
20037 suppressing the signal that stopped a thread, you should select that
20038 same thread before issuing the @samp{signal 0} command. If you issue
20039 the @samp{signal 0} command with another thread as the selected one,
20040 @value{GDBN} detects that and asks for confirmation.
20042 Invoking the @code{signal} command is not the same as invoking the
20043 @code{kill} utility from the shell. Sending a signal with @code{kill}
20044 causes @value{GDBN} to decide what to do with the signal depending on
20045 the signal handling tables (@pxref{Signals}). The @code{signal} command
20046 passes the signal directly to your program.
20048 @code{signal} does not repeat when you press @key{RET} a second time
20049 after executing the command.
20051 @kindex queue-signal
20052 @item queue-signal @var{signal}
20053 Queue @var{signal} to be delivered immediately to the current thread
20054 when execution of the thread resumes. The @var{signal} can be the name or
20055 the number of a signal. For example, on many systems @code{signal 2} and
20056 @code{signal SIGINT} are both ways of sending an interrupt signal.
20057 The handling of the signal must be set to pass the signal to the program,
20058 otherwise @value{GDBN} will report an error.
20059 You can control the handling of signals from @value{GDBN} with the
20060 @code{handle} command (@pxref{Signals}).
20062 Alternatively, if @var{signal} is zero, any currently queued signal
20063 for the current thread is discarded and when execution resumes no signal
20064 will be delivered. This is useful when your program stopped on account
20065 of a signal and would ordinarily see the signal when resumed with the
20066 @code{continue} command.
20068 This command differs from the @code{signal} command in that the signal
20069 is just queued, execution is not resumed. And @code{queue-signal} cannot
20070 be used to pass a signal whose handling state has been set to @code{nopass}
20075 @xref{stepping into signal handlers}, for information on how stepping
20076 commands behave when the thread has a signal queued.
20079 @section Returning from a Function
20082 @cindex returning from a function
20085 @itemx return @var{expression}
20086 You can cancel execution of a function call with the @code{return}
20087 command. If you give an
20088 @var{expression} argument, its value is used as the function's return
20092 When you use @code{return}, @value{GDBN} discards the selected stack frame
20093 (and all frames within it). You can think of this as making the
20094 discarded frame return prematurely. If you wish to specify a value to
20095 be returned, give that value as the argument to @code{return}.
20097 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20098 Frame}), and any other frames inside of it, leaving its caller as the
20099 innermost remaining frame. That frame becomes selected. The
20100 specified value is stored in the registers used for returning values
20103 The @code{return} command does not resume execution; it leaves the
20104 program stopped in the state that would exist if the function had just
20105 returned. In contrast, the @code{finish} command (@pxref{Continuing
20106 and Stepping, ,Continuing and Stepping}) resumes execution until the
20107 selected stack frame returns naturally.
20109 @value{GDBN} needs to know how the @var{expression} argument should be set for
20110 the inferior. The concrete registers assignment depends on the OS ABI and the
20111 type being returned by the selected stack frame. For example it is common for
20112 OS ABI to return floating point values in FPU registers while integer values in
20113 CPU registers. Still some ABIs return even floating point values in CPU
20114 registers. Larger integer widths (such as @code{long long int}) also have
20115 specific placement rules. @value{GDBN} already knows the OS ABI from its
20116 current target so it needs to find out also the type being returned to make the
20117 assignment into the right register(s).
20119 Normally, the selected stack frame has debug info. @value{GDBN} will always
20120 use the debug info instead of the implicit type of @var{expression} when the
20121 debug info is available. For example, if you type @kbd{return -1}, and the
20122 function in the current stack frame is declared to return a @code{long long
20123 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20124 into a @code{long long int}:
20127 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20129 (@value{GDBP}) return -1
20130 Make func return now? (y or n) y
20131 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20132 43 printf ("result=%lld\n", func ());
20136 However, if the selected stack frame does not have a debug info, e.g., if the
20137 function was compiled without debug info, @value{GDBN} has to find out the type
20138 to return from user. Specifying a different type by mistake may set the value
20139 in different inferior registers than the caller code expects. For example,
20140 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20141 of a @code{long long int} result for a debug info less function (on 32-bit
20142 architectures). Therefore the user is required to specify the return type by
20143 an appropriate cast explicitly:
20146 Breakpoint 2, 0x0040050b in func ()
20147 (@value{GDBP}) return -1
20148 Return value type not available for selected stack frame.
20149 Please use an explicit cast of the value to return.
20150 (@value{GDBP}) return (long long int) -1
20151 Make selected stack frame return now? (y or n) y
20152 #0 0x00400526 in main ()
20157 @section Calling Program Functions
20160 @cindex calling functions
20161 @cindex inferior functions, calling
20162 @item print @var{expr}
20163 Evaluate the expression @var{expr} and display the resulting value.
20164 The expression may include calls to functions in the program being
20168 @item call @var{expr}
20169 Evaluate the expression @var{expr} without displaying @code{void}
20172 You can use this variant of the @code{print} command if you want to
20173 execute a function from your program that does not return anything
20174 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20175 with @code{void} returned values that @value{GDBN} will otherwise
20176 print. If the result is not void, it is printed and saved in the
20180 It is possible for the function you call via the @code{print} or
20181 @code{call} command to generate a signal (e.g., if there's a bug in
20182 the function, or if you passed it incorrect arguments). What happens
20183 in that case is controlled by the @code{set unwindonsignal} command.
20185 Similarly, with a C@t{++} program it is possible for the function you
20186 call via the @code{print} or @code{call} command to generate an
20187 exception that is not handled due to the constraints of the dummy
20188 frame. In this case, any exception that is raised in the frame, but has
20189 an out-of-frame exception handler will not be found. GDB builds a
20190 dummy-frame for the inferior function call, and the unwinder cannot
20191 seek for exception handlers outside of this dummy-frame. What happens
20192 in that case is controlled by the
20193 @code{set unwind-on-terminating-exception} command.
20196 @item set unwindonsignal
20197 @kindex set unwindonsignal
20198 @cindex unwind stack in called functions
20199 @cindex call dummy stack unwinding
20200 Set unwinding of the stack if a signal is received while in a function
20201 that @value{GDBN} called in the program being debugged. If set to on,
20202 @value{GDBN} unwinds the stack it created for the call and restores
20203 the context to what it was before the call. If set to off (the
20204 default), @value{GDBN} stops in the frame where the signal was
20207 @item show unwindonsignal
20208 @kindex show unwindonsignal
20209 Show the current setting of stack unwinding in the functions called by
20212 @item set unwind-on-terminating-exception
20213 @kindex set unwind-on-terminating-exception
20214 @cindex unwind stack in called functions with unhandled exceptions
20215 @cindex call dummy stack unwinding on unhandled exception.
20216 Set unwinding of the stack if a C@t{++} exception is raised, but left
20217 unhandled while in a function that @value{GDBN} called in the program being
20218 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20219 it created for the call and restores the context to what it was before
20220 the call. If set to off, @value{GDBN} the exception is delivered to
20221 the default C@t{++} exception handler and the inferior terminated.
20223 @item show unwind-on-terminating-exception
20224 @kindex show unwind-on-terminating-exception
20225 Show the current setting of stack unwinding in the functions called by
20228 @item set may-call-functions
20229 @kindex set may-call-functions
20230 @cindex disabling calling functions in the program
20231 @cindex calling functions in the program, disabling
20232 Set permission to call functions in the program.
20233 This controls whether @value{GDBN} will attempt to call functions in
20234 the program, such as with expressions in the @code{print} command. It
20235 defaults to @code{on}.
20237 To call a function in the program, @value{GDBN} has to temporarily
20238 modify the state of the inferior. This has potentially undesired side
20239 effects. Also, having @value{GDBN} call nested functions is likely to
20240 be erroneous and may even crash the program being debugged. You can
20241 avoid such hazards by forbidding @value{GDBN} from calling functions
20242 in the program being debugged. If calling functions in the program
20243 is forbidden, GDB will throw an error when a command (such as printing
20244 an expression) starts a function call in the program.
20246 @item show may-call-functions
20247 @kindex show may-call-functions
20248 Show permission to call functions in the program.
20252 @subsection Calling functions with no debug info
20254 @cindex no debug info functions
20255 Sometimes, a function you wish to call is missing debug information.
20256 In such case, @value{GDBN} does not know the type of the function,
20257 including the types of the function's parameters. To avoid calling
20258 the inferior function incorrectly, which could result in the called
20259 function functioning erroneously and even crash, @value{GDBN} refuses
20260 to call the function unless you tell it the type of the function.
20262 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20263 to do that. The simplest is to cast the call to the function's
20264 declared return type. For example:
20267 (@value{GDBP}) p getenv ("PATH")
20268 'getenv' has unknown return type; cast the call to its declared return type
20269 (@value{GDBP}) p (char *) getenv ("PATH")
20270 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20273 Casting the return type of a no-debug function is equivalent to
20274 casting the function to a pointer to a prototyped function that has a
20275 prototype that matches the types of the passed-in arguments, and
20276 calling that. I.e., the call above is equivalent to:
20279 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20283 and given this prototyped C or C++ function with float parameters:
20286 float multiply (float v1, float v2) @{ return v1 * v2; @}
20290 these calls are equivalent:
20293 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20294 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20297 If the function you wish to call is declared as unprototyped (i.e.@:
20298 old K&R style), you must use the cast-to-function-pointer syntax, so
20299 that @value{GDBN} knows that it needs to apply default argument
20300 promotions (promote float arguments to double). @xref{ABI, float
20301 promotion}. For example, given this unprototyped C function with
20302 float parameters, and no debug info:
20306 multiply_noproto (v1, v2)
20314 you call it like this:
20317 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20321 @section Patching Programs
20323 @cindex patching binaries
20324 @cindex writing into executables
20325 @cindex writing into corefiles
20327 By default, @value{GDBN} opens the file containing your program's
20328 executable code (or the corefile) read-only. This prevents accidental
20329 alterations to machine code; but it also prevents you from intentionally
20330 patching your program's binary.
20332 If you'd like to be able to patch the binary, you can specify that
20333 explicitly with the @code{set write} command. For example, you might
20334 want to turn on internal debugging flags, or even to make emergency
20340 @itemx set write off
20341 If you specify @samp{set write on}, @value{GDBN} opens executable and
20342 core files for both reading and writing; if you specify @kbd{set write
20343 off} (the default), @value{GDBN} opens them read-only.
20345 If you have already loaded a file, you must load it again (using the
20346 @code{exec-file} or @code{core-file} command) after changing @code{set
20347 write}, for your new setting to take effect.
20351 Display whether executable files and core files are opened for writing
20352 as well as reading.
20355 @node Compiling and Injecting Code
20356 @section Compiling and injecting code in @value{GDBN}
20357 @cindex injecting code
20358 @cindex writing into executables
20359 @cindex compiling code
20361 @value{GDBN} supports on-demand compilation and code injection into
20362 programs running under @value{GDBN}. GCC 5.0 or higher built with
20363 @file{libcc1.so} must be installed for this functionality to be enabled.
20364 This functionality is implemented with the following commands.
20367 @kindex compile code
20368 @item compile code @var{source-code}
20369 @itemx compile code -raw @var{--} @var{source-code}
20370 Compile @var{source-code} with the compiler language found as the current
20371 language in @value{GDBN} (@pxref{Languages}). If compilation and
20372 injection is not supported with the current language specified in
20373 @value{GDBN}, or the compiler does not support this feature, an error
20374 message will be printed. If @var{source-code} compiles and links
20375 successfully, @value{GDBN} will load the object-code emitted,
20376 and execute it within the context of the currently selected inferior.
20377 It is important to note that the compiled code is executed immediately.
20378 After execution, the compiled code is removed from @value{GDBN} and any
20379 new types or variables you have defined will be deleted.
20381 The command allows you to specify @var{source-code} in two ways.
20382 The simplest method is to provide a single line of code to the command.
20386 compile code printf ("hello world\n");
20389 If you specify options on the command line as well as source code, they
20390 may conflict. The @samp{--} delimiter can be used to separate options
20391 from actual source code. E.g.:
20394 compile code -r -- printf ("hello world\n");
20397 Alternatively you can enter source code as multiple lines of text. To
20398 enter this mode, invoke the @samp{compile code} command without any text
20399 following the command. This will start the multiple-line editor and
20400 allow you to type as many lines of source code as required. When you
20401 have completed typing, enter @samp{end} on its own line to exit the
20406 >printf ("hello\n");
20407 >printf ("world\n");
20411 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20412 provided @var{source-code} in a callable scope. In this case, you must
20413 specify the entry point of the code by defining a function named
20414 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20415 inferior. Using @samp{-raw} option may be needed for example when
20416 @var{source-code} requires @samp{#include} lines which may conflict with
20417 inferior symbols otherwise.
20419 @kindex compile file
20420 @item compile file @var{filename}
20421 @itemx compile file -raw @var{filename}
20422 Like @code{compile code}, but take the source code from @var{filename}.
20425 compile file /home/user/example.c
20430 @item compile print [[@var{options}] --] @var{expr}
20431 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20432 Compile and execute @var{expr} with the compiler language found as the
20433 current language in @value{GDBN} (@pxref{Languages}). By default the
20434 value of @var{expr} is printed in a format appropriate to its data type;
20435 you can choose a different format by specifying @samp{/@var{f}}, where
20436 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20437 Formats}. The @code{compile print} command accepts the same options
20438 as the @code{print} command; see @ref{print options}.
20440 @item compile print [[@var{options}] --]
20441 @itemx compile print [[@var{options}] --] /@var{f}
20442 @cindex reprint the last value
20443 Alternatively you can enter the expression (source code producing it) as
20444 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20445 command without any text following the command. This will start the
20446 multiple-line editor.
20450 The process of compiling and injecting the code can be inspected using:
20453 @anchor{set debug compile}
20454 @item set debug compile
20455 @cindex compile command debugging info
20456 Turns on or off display of @value{GDBN} process of compiling and
20457 injecting the code. The default is off.
20459 @item show debug compile
20460 Displays the current state of displaying @value{GDBN} process of
20461 compiling and injecting the code.
20463 @anchor{set debug compile-cplus-types}
20464 @item set debug compile-cplus-types
20465 @cindex compile C@t{++} type conversion
20466 Turns on or off the display of C@t{++} type conversion debugging information.
20467 The default is off.
20469 @item show debug compile-cplus-types
20470 Displays the current state of displaying debugging information for
20471 C@t{++} type conversion.
20474 @subsection Compilation options for the @code{compile} command
20476 @value{GDBN} needs to specify the right compilation options for the code
20477 to be injected, in part to make its ABI compatible with the inferior
20478 and in part to make the injected code compatible with @value{GDBN}'s
20482 The options used, in increasing precedence:
20485 @item target architecture and OS options (@code{gdbarch})
20486 These options depend on target processor type and target operating
20487 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20488 (@code{-m64}) compilation option.
20490 @item compilation options recorded in the target
20491 @value{NGCC} (since version 4.7) stores the options used for compilation
20492 into @code{DW_AT_producer} part of DWARF debugging information according
20493 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20494 explicitly specify @code{-g} during inferior compilation otherwise
20495 @value{NGCC} produces no DWARF. This feature is only relevant for
20496 platforms where @code{-g} produces DWARF by default, otherwise one may
20497 try to enforce DWARF by using @code{-gdwarf-4}.
20499 @item compilation options set by @code{set compile-args}
20503 You can override compilation options using the following command:
20506 @item set compile-args
20507 @cindex compile command options override
20508 Set compilation options used for compiling and injecting code with the
20509 @code{compile} commands. These options override any conflicting ones
20510 from the target architecture and/or options stored during inferior
20513 @item show compile-args
20514 Displays the current state of compilation options override.
20515 This does not show all the options actually used during compilation,
20516 use @ref{set debug compile} for that.
20519 @subsection Caveats when using the @code{compile} command
20521 There are a few caveats to keep in mind when using the @code{compile}
20522 command. As the caveats are different per language, the table below
20523 highlights specific issues on a per language basis.
20526 @item C code examples and caveats
20527 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20528 attempt to compile the source code with a @samp{C} compiler. The source
20529 code provided to the @code{compile} command will have much the same
20530 access to variables and types as it normally would if it were part of
20531 the program currently being debugged in @value{GDBN}.
20533 Below is a sample program that forms the basis of the examples that
20534 follow. This program has been compiled and loaded into @value{GDBN},
20535 much like any other normal debugging session.
20538 void function1 (void)
20541 printf ("function 1\n");
20544 void function2 (void)
20559 For the purposes of the examples in this section, the program above has
20560 been compiled, loaded into @value{GDBN}, stopped at the function
20561 @code{main}, and @value{GDBN} is awaiting input from the user.
20563 To access variables and types for any program in @value{GDBN}, the
20564 program must be compiled and packaged with debug information. The
20565 @code{compile} command is not an exception to this rule. Without debug
20566 information, you can still use the @code{compile} command, but you will
20567 be very limited in what variables and types you can access.
20569 So with that in mind, the example above has been compiled with debug
20570 information enabled. The @code{compile} command will have access to
20571 all variables and types (except those that may have been optimized
20572 out). Currently, as @value{GDBN} has stopped the program in the
20573 @code{main} function, the @code{compile} command would have access to
20574 the variable @code{k}. You could invoke the @code{compile} command
20575 and type some source code to set the value of @code{k}. You can also
20576 read it, or do anything with that variable you would normally do in
20577 @code{C}. Be aware that changes to inferior variables in the
20578 @code{compile} command are persistent. In the following example:
20581 compile code k = 3;
20585 the variable @code{k} is now 3. It will retain that value until
20586 something else in the example program changes it, or another
20587 @code{compile} command changes it.
20589 Normal scope and access rules apply to source code compiled and
20590 injected by the @code{compile} command. In the example, the variables
20591 @code{j} and @code{k} are not accessible yet, because the program is
20592 currently stopped in the @code{main} function, where these variables
20593 are not in scope. Therefore, the following command
20596 compile code j = 3;
20600 will result in a compilation error message.
20602 Once the program is continued, execution will bring these variables in
20603 scope, and they will become accessible; then the code you specify via
20604 the @code{compile} command will be able to access them.
20606 You can create variables and types with the @code{compile} command as
20607 part of your source code. Variables and types that are created as part
20608 of the @code{compile} command are not visible to the rest of the program for
20609 the duration of its run. This example is valid:
20612 compile code int ff = 5; printf ("ff is %d\n", ff);
20615 However, if you were to type the following into @value{GDBN} after that
20616 command has completed:
20619 compile code printf ("ff is %d\n'', ff);
20623 a compiler error would be raised as the variable @code{ff} no longer
20624 exists. Object code generated and injected by the @code{compile}
20625 command is removed when its execution ends. Caution is advised
20626 when assigning to program variables values of variables created by the
20627 code submitted to the @code{compile} command. This example is valid:
20630 compile code int ff = 5; k = ff;
20633 The value of the variable @code{ff} is assigned to @code{k}. The variable
20634 @code{k} does not require the existence of @code{ff} to maintain the value
20635 it has been assigned. However, pointers require particular care in
20636 assignment. If the source code compiled with the @code{compile} command
20637 changed the address of a pointer in the example program, perhaps to a
20638 variable created in the @code{compile} command, that pointer would point
20639 to an invalid location when the command exits. The following example
20640 would likely cause issues with your debugged program:
20643 compile code int ff = 5; p = &ff;
20646 In this example, @code{p} would point to @code{ff} when the
20647 @code{compile} command is executing the source code provided to it.
20648 However, as variables in the (example) program persist with their
20649 assigned values, the variable @code{p} would point to an invalid
20650 location when the command exists. A general rule should be followed
20651 in that you should either assign @code{NULL} to any assigned pointers,
20652 or restore a valid location to the pointer before the command exits.
20654 Similar caution must be exercised with any structs, unions, and typedefs
20655 defined in @code{compile} command. Types defined in the @code{compile}
20656 command will no longer be available in the next @code{compile} command.
20657 Therefore, if you cast a variable to a type defined in the
20658 @code{compile} command, care must be taken to ensure that any future
20659 need to resolve the type can be achieved.
20662 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20663 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20664 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20665 Compilation failed.
20666 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20670 Variables that have been optimized away by the compiler are not
20671 accessible to the code submitted to the @code{compile} command.
20672 Access to those variables will generate a compiler error which @value{GDBN}
20673 will print to the console.
20676 @subsection Compiler search for the @code{compile} command
20678 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20679 which may not be obvious for remote targets of different architecture
20680 than where @value{GDBN} is running. Environment variable @env{PATH} on
20681 @value{GDBN} host is searched for @value{NGCC} binary matching the
20682 target architecture and operating system. This search can be overriden
20683 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
20684 taken from shell that executed @value{GDBN}, it is not the value set by
20685 @value{GDBN} command @code{set environment}). @xref{Environment}.
20688 Specifically @env{PATH} is searched for binaries matching regular expression
20689 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20690 debugged. @var{arch} is processor name --- multiarch is supported, so for
20691 example both @code{i386} and @code{x86_64} targets look for pattern
20692 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20693 for pattern @code{s390x?}. @var{os} is currently supported only for
20694 pattern @code{linux(-gnu)?}.
20696 On Posix hosts the compiler driver @value{GDBN} needs to find also
20697 shared library @file{libcc1.so} from the compiler. It is searched in
20698 default shared library search path (overridable with usual environment
20699 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
20700 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20701 according to the installation of the found compiler --- as possibly
20702 specified by the @code{set compile-gcc} command.
20705 @item set compile-gcc
20706 @cindex compile command driver filename override
20707 Set compilation command used for compiling and injecting code with the
20708 @code{compile} commands. If this option is not set (it is set to
20709 an empty string), the search described above will occur --- that is the
20712 @item show compile-gcc
20713 Displays the current compile command @value{NGCC} driver filename.
20714 If set, it is the main command @command{gcc}, found usually for example
20715 under name @file{x86_64-linux-gnu-gcc}.
20719 @chapter @value{GDBN} Files
20721 @value{GDBN} needs to know the file name of the program to be debugged,
20722 both in order to read its symbol table and in order to start your
20723 program. To debug a core dump of a previous run, you must also tell
20724 @value{GDBN} the name of the core dump file.
20727 * Files:: Commands to specify files
20728 * File Caching:: Information about @value{GDBN}'s file caching
20729 * Separate Debug Files:: Debugging information in separate files
20730 * MiniDebugInfo:: Debugging information in a special section
20731 * Index Files:: Index files speed up GDB
20732 * Symbol Errors:: Errors reading symbol files
20733 * Data Files:: GDB data files
20737 @section Commands to Specify Files
20739 @cindex symbol table
20740 @cindex core dump file
20742 You may want to specify executable and core dump file names. The usual
20743 way to do this is at start-up time, using the arguments to
20744 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20745 Out of @value{GDBN}}).
20747 Occasionally it is necessary to change to a different file during a
20748 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20749 specify a file you want to use. Or you are debugging a remote target
20750 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20751 Program}). In these situations the @value{GDBN} commands to specify
20752 new files are useful.
20755 @cindex executable file
20757 @item file @var{filename}
20758 Use @var{filename} as the program to be debugged. It is read for its
20759 symbols and for the contents of pure memory. It is also the program
20760 executed when you use the @code{run} command. If you do not specify a
20761 directory and the file is not found in the @value{GDBN} working directory,
20762 @value{GDBN} uses the environment variable @env{PATH} as a list of
20763 directories to search, just as the shell does when looking for a program
20764 to run. You can change the value of this variable, for both @value{GDBN}
20765 and your program, using the @code{path} command.
20767 @cindex unlinked object files
20768 @cindex patching object files
20769 You can load unlinked object @file{.o} files into @value{GDBN} using
20770 the @code{file} command. You will not be able to ``run'' an object
20771 file, but you can disassemble functions and inspect variables. Also,
20772 if the underlying BFD functionality supports it, you could use
20773 @kbd{gdb -write} to patch object files using this technique. Note
20774 that @value{GDBN} can neither interpret nor modify relocations in this
20775 case, so branches and some initialized variables will appear to go to
20776 the wrong place. But this feature is still handy from time to time.
20779 @code{file} with no argument makes @value{GDBN} discard any information it
20780 has on both executable file and the symbol table.
20783 @item exec-file @r{[} @var{filename} @r{]}
20784 Specify that the program to be run (but not the symbol table) is found
20785 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
20786 if necessary to locate your program. Omitting @var{filename} means to
20787 discard information on the executable file.
20789 @kindex symbol-file
20790 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20791 Read symbol table information from file @var{filename}. @env{PATH} is
20792 searched when necessary. Use the @code{file} command to get both symbol
20793 table and program to run from the same file.
20795 If an optional @var{offset} is specified, it is added to the start
20796 address of each section in the symbol file. This is useful if the
20797 program is relocated at runtime, such as the Linux kernel with kASLR
20800 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20801 program's symbol table.
20803 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20804 some breakpoints and auto-display expressions. This is because they may
20805 contain pointers to the internal data recording symbols and data types,
20806 which are part of the old symbol table data being discarded inside
20809 @code{symbol-file} does not repeat if you press @key{RET} again after
20812 When @value{GDBN} is configured for a particular environment, it
20813 understands debugging information in whatever format is the standard
20814 generated for that environment; you may use either a @sc{gnu} compiler, or
20815 other compilers that adhere to the local conventions.
20816 Best results are usually obtained from @sc{gnu} compilers; for example,
20817 using @code{@value{NGCC}} you can generate debugging information for
20820 For most kinds of object files, with the exception of old SVR3 systems
20821 using COFF, the @code{symbol-file} command does not normally read the
20822 symbol table in full right away. Instead, it scans the symbol table
20823 quickly to find which source files and which symbols are present. The
20824 details are read later, one source file at a time, as they are needed.
20826 The purpose of this two-stage reading strategy is to make @value{GDBN}
20827 start up faster. For the most part, it is invisible except for
20828 occasional pauses while the symbol table details for a particular source
20829 file are being read. (The @code{set verbose} command can turn these
20830 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20831 Warnings and Messages}.)
20833 We have not implemented the two-stage strategy for COFF yet. When the
20834 symbol table is stored in COFF format, @code{symbol-file} reads the
20835 symbol table data in full right away. Note that ``stabs-in-COFF''
20836 still does the two-stage strategy, since the debug info is actually
20840 @cindex reading symbols immediately
20841 @cindex symbols, reading immediately
20842 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20843 @itemx file @r{[} -readnow @r{]} @var{filename}
20844 You can override the @value{GDBN} two-stage strategy for reading symbol
20845 tables by using the @samp{-readnow} option with any of the commands that
20846 load symbol table information, if you want to be sure @value{GDBN} has the
20847 entire symbol table available.
20849 @cindex @code{-readnever}, option for symbol-file command
20850 @cindex never read symbols
20851 @cindex symbols, never read
20852 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20853 @itemx file @r{[} -readnever @r{]} @var{filename}
20854 You can instruct @value{GDBN} to never read the symbolic information
20855 contained in @var{filename} by using the @samp{-readnever} option.
20856 @xref{--readnever}.
20858 @c FIXME: for now no mention of directories, since this seems to be in
20859 @c flux. 13mar1992 status is that in theory GDB would look either in
20860 @c current dir or in same dir as myprog; but issues like competing
20861 @c GDB's, or clutter in system dirs, mean that in practice right now
20862 @c only current dir is used. FFish says maybe a special GDB hierarchy
20863 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20867 @item core-file @r{[}@var{filename}@r{]}
20869 Specify the whereabouts of a core dump file to be used as the ``contents
20870 of memory''. Traditionally, core files contain only some parts of the
20871 address space of the process that generated them; @value{GDBN} can access the
20872 executable file itself for other parts.
20874 @code{core-file} with no argument specifies that no core file is
20877 Note that the core file is ignored when your program is actually running
20878 under @value{GDBN}. So, if you have been running your program and you
20879 wish to debug a core file instead, you must kill the subprocess in which
20880 the program is running. To do this, use the @code{kill} command
20881 (@pxref{Kill Process, ,Killing the Child Process}).
20883 @kindex add-symbol-file
20884 @cindex dynamic linking
20885 @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{]}
20886 The @code{add-symbol-file} command reads additional symbol table
20887 information from the file @var{filename}. You would use this command
20888 when @var{filename} has been dynamically loaded (by some other means)
20889 into the program that is running. The @var{textaddress} parameter gives
20890 the memory address at which the file's text section has been loaded.
20891 You can additionally specify the base address of other sections using
20892 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20893 If a section is omitted, @value{GDBN} will use its default addresses
20894 as found in @var{filename}. Any @var{address} or @var{textaddress}
20895 can be given as an expression.
20897 If an optional @var{offset} is specified, it is added to the start
20898 address of each section, except those for which the address was
20899 specified explicitly.
20901 The symbol table of the file @var{filename} is added to the symbol table
20902 originally read with the @code{symbol-file} command. You can use the
20903 @code{add-symbol-file} command any number of times; the new symbol data
20904 thus read is kept in addition to the old.
20906 Changes can be reverted using the command @code{remove-symbol-file}.
20908 @cindex relocatable object files, reading symbols from
20909 @cindex object files, relocatable, reading symbols from
20910 @cindex reading symbols from relocatable object files
20911 @cindex symbols, reading from relocatable object files
20912 @cindex @file{.o} files, reading symbols from
20913 Although @var{filename} is typically a shared library file, an
20914 executable file, or some other object file which has been fully
20915 relocated for loading into a process, you can also load symbolic
20916 information from relocatable @file{.o} files, as long as:
20920 the file's symbolic information refers only to linker symbols defined in
20921 that file, not to symbols defined by other object files,
20923 every section the file's symbolic information refers to has actually
20924 been loaded into the inferior, as it appears in the file, and
20926 you can determine the address at which every section was loaded, and
20927 provide these to the @code{add-symbol-file} command.
20931 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20932 relocatable files into an already running program; such systems
20933 typically make the requirements above easy to meet. However, it's
20934 important to recognize that many native systems use complex link
20935 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20936 assembly, for example) that make the requirements difficult to meet. In
20937 general, one cannot assume that using @code{add-symbol-file} to read a
20938 relocatable object file's symbolic information will have the same effect
20939 as linking the relocatable object file into the program in the normal
20942 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20944 @kindex remove-symbol-file
20945 @item remove-symbol-file @var{filename}
20946 @item remove-symbol-file -a @var{address}
20947 Remove a symbol file added via the @code{add-symbol-file} command. The
20948 file to remove can be identified by its @var{filename} or by an @var{address}
20949 that lies within the boundaries of this symbol file in memory. Example:
20952 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20953 add symbol table from file "/home/user/gdb/mylib.so" at
20954 .text_addr = 0x7ffff7ff9480
20956 Reading symbols from /home/user/gdb/mylib.so...
20957 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20958 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20963 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20965 @kindex add-symbol-file-from-memory
20966 @cindex @code{syscall DSO}
20967 @cindex load symbols from memory
20968 @item add-symbol-file-from-memory @var{address}
20969 Load symbols from the given @var{address} in a dynamically loaded
20970 object file whose image is mapped directly into the inferior's memory.
20971 For example, the Linux kernel maps a @code{syscall DSO} into each
20972 process's address space; this DSO provides kernel-specific code for
20973 some system calls. The argument can be any expression whose
20974 evaluation yields the address of the file's shared object file header.
20975 For this command to work, you must have used @code{symbol-file} or
20976 @code{exec-file} commands in advance.
20979 @item section @var{section} @var{addr}
20980 The @code{section} command changes the base address of the named
20981 @var{section} of the exec file to @var{addr}. This can be used if the
20982 exec file does not contain section addresses, (such as in the
20983 @code{a.out} format), or when the addresses specified in the file
20984 itself are wrong. Each section must be changed separately. The
20985 @code{info files} command, described below, lists all the sections and
20989 @kindex info target
20992 @code{info files} and @code{info target} are synonymous; both print the
20993 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20994 including the names of the executable and core dump files currently in
20995 use by @value{GDBN}, and the files from which symbols were loaded. The
20996 command @code{help target} lists all possible targets rather than
20999 @kindex maint info sections
21000 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21001 Another command that can give you extra information about program sections
21002 is @code{maint info sections}. In addition to the section information
21003 displayed by @code{info files}, this command displays the flags and file
21004 offset of each section in the executable and core dump files.
21006 When @samp{-all-objects} is passed then sections from all loaded object
21007 files, including shared libraries, are printed.
21009 The optional @var{filter-list} is a space separated list of filter
21010 keywords. Sections that match any one of the filter criteria will be
21011 printed. There are two types of filter:
21014 @item @var{section-name}
21015 Display information about any section named @var{section-name}.
21016 @item @var{section-flag}
21017 Display information for any section with @var{section-flag}. The
21018 section flags that @value{GDBN} currently knows about are:
21021 Section will have space allocated in the process when loaded.
21022 Set for all sections except those containing debug information.
21024 Section will be loaded from the file into the child process memory.
21025 Set for pre-initialized code and data, clear for @code{.bss} sections.
21027 Section needs to be relocated before loading.
21029 Section cannot be modified by the child process.
21031 Section contains executable code only.
21033 Section contains data only (no executable code).
21035 Section will reside in ROM.
21037 Section contains data for constructor/destructor lists.
21039 Section is not empty.
21041 An instruction to the linker to not output the section.
21042 @item COFF_SHARED_LIBRARY
21043 A notification to the linker that the section contains
21044 COFF shared library information.
21046 Section contains common symbols.
21050 @kindex maint info target-sections
21051 @item maint info target-sections
21052 This command prints @value{GDBN}'s internal section table. For each
21053 target @value{GDBN} maintains a table containing the allocatable
21054 sections from all currently mapped objects, along with information
21055 about where the section is mapped.
21057 @kindex set trust-readonly-sections
21058 @cindex read-only sections
21059 @item set trust-readonly-sections on
21060 Tell @value{GDBN} that readonly sections in your object file
21061 really are read-only (i.e.@: that their contents will not change).
21062 In that case, @value{GDBN} can fetch values from these sections
21063 out of the object file, rather than from the target program.
21064 For some targets (notably embedded ones), this can be a significant
21065 enhancement to debugging performance.
21067 The default is off.
21069 @item set trust-readonly-sections off
21070 Tell @value{GDBN} not to trust readonly sections. This means that
21071 the contents of the section might change while the program is running,
21072 and must therefore be fetched from the target when needed.
21074 @item show trust-readonly-sections
21075 Show the current setting of trusting readonly sections.
21078 All file-specifying commands allow both absolute and relative file names
21079 as arguments. @value{GDBN} always converts the file name to an absolute file
21080 name and remembers it that way.
21082 @cindex shared libraries
21083 @anchor{Shared Libraries}
21084 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21085 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21086 DSBT (TIC6X) shared libraries.
21088 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21089 shared libraries. @xref{Expat}.
21091 @value{GDBN} automatically loads symbol definitions from shared libraries
21092 when you use the @code{run} command, or when you examine a core file.
21093 (Before you issue the @code{run} command, @value{GDBN} does not understand
21094 references to a function in a shared library, however---unless you are
21095 debugging a core file).
21097 @c FIXME: some @value{GDBN} release may permit some refs to undef
21098 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21099 @c FIXME...lib; check this from time to time when updating manual
21101 There are times, however, when you may wish to not automatically load
21102 symbol definitions from shared libraries, such as when they are
21103 particularly large or there are many of them.
21105 To control the automatic loading of shared library symbols, use the
21109 @kindex set auto-solib-add
21110 @item set auto-solib-add @var{mode}
21111 If @var{mode} is @code{on}, symbols from all shared object libraries
21112 will be loaded automatically when the inferior begins execution, you
21113 attach to an independently started inferior, or when the dynamic linker
21114 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21115 is @code{off}, symbols must be loaded manually, using the
21116 @code{sharedlibrary} command. The default value is @code{on}.
21118 @cindex memory used for symbol tables
21119 If your program uses lots of shared libraries with debug info that
21120 takes large amounts of memory, you can decrease the @value{GDBN}
21121 memory footprint by preventing it from automatically loading the
21122 symbols from shared libraries. To that end, type @kbd{set
21123 auto-solib-add off} before running the inferior, then load each
21124 library whose debug symbols you do need with @kbd{sharedlibrary
21125 @var{regexp}}, where @var{regexp} is a regular expression that matches
21126 the libraries whose symbols you want to be loaded.
21128 @kindex show auto-solib-add
21129 @item show auto-solib-add
21130 Display the current autoloading mode.
21133 @cindex load shared library
21134 To explicitly load shared library symbols, use the @code{sharedlibrary}
21138 @kindex info sharedlibrary
21140 @item info share @var{regex}
21141 @itemx info sharedlibrary @var{regex}
21142 Print the names of the shared libraries which are currently loaded
21143 that match @var{regex}. If @var{regex} is omitted then print
21144 all shared libraries that are loaded.
21147 @item info dll @var{regex}
21148 This is an alias of @code{info sharedlibrary}.
21150 @kindex sharedlibrary
21152 @item sharedlibrary @var{regex}
21153 @itemx share @var{regex}
21154 Load shared object library symbols for files matching a
21155 Unix regular expression.
21156 As with files loaded automatically, it only loads shared libraries
21157 required by your program for a core file or after typing @code{run}. If
21158 @var{regex} is omitted all shared libraries required by your program are
21161 @item nosharedlibrary
21162 @kindex nosharedlibrary
21163 @cindex unload symbols from shared libraries
21164 Unload all shared object library symbols. This discards all symbols
21165 that have been loaded from all shared libraries. Symbols from shared
21166 libraries that were loaded by explicit user requests are not
21170 Sometimes you may wish that @value{GDBN} stops and gives you control
21171 when any of shared library events happen. The best way to do this is
21172 to use @code{catch load} and @code{catch unload} (@pxref{Set
21175 @value{GDBN} also supports the @code{set stop-on-solib-events}
21176 command for this. This command exists for historical reasons. It is
21177 less useful than setting a catchpoint, because it does not allow for
21178 conditions or commands as a catchpoint does.
21181 @item set stop-on-solib-events
21182 @kindex set stop-on-solib-events
21183 This command controls whether @value{GDBN} should give you control
21184 when the dynamic linker notifies it about some shared library event.
21185 The most common event of interest is loading or unloading of a new
21188 @item show stop-on-solib-events
21189 @kindex show stop-on-solib-events
21190 Show whether @value{GDBN} stops and gives you control when shared
21191 library events happen.
21194 Shared libraries are also supported in many cross or remote debugging
21195 configurations. @value{GDBN} needs to have access to the target's libraries;
21196 this can be accomplished either by providing copies of the libraries
21197 on the host system, or by asking @value{GDBN} to automatically retrieve the
21198 libraries from the target. If copies of the target libraries are
21199 provided, they need to be the same as the target libraries, although the
21200 copies on the target can be stripped as long as the copies on the host are
21203 @cindex where to look for shared libraries
21204 For remote debugging, you need to tell @value{GDBN} where the target
21205 libraries are, so that it can load the correct copies---otherwise, it
21206 may try to load the host's libraries. @value{GDBN} has two variables
21207 to specify the search directories for target libraries.
21210 @cindex prefix for executable and shared library file names
21211 @cindex system root, alternate
21212 @kindex set solib-absolute-prefix
21213 @kindex set sysroot
21214 @item set sysroot @var{path}
21215 Use @var{path} as the system root for the program being debugged. Any
21216 absolute shared library paths will be prefixed with @var{path}; many
21217 runtime loaders store the absolute paths to the shared library in the
21218 target program's memory. When starting processes remotely, and when
21219 attaching to already-running processes (local or remote), their
21220 executable filenames will be prefixed with @var{path} if reported to
21221 @value{GDBN} as absolute by the operating system. If you use
21222 @code{set sysroot} to find executables and shared libraries, they need
21223 to be laid out in the same way that they are on the target, with
21224 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21227 If @var{path} starts with the sequence @file{target:} and the target
21228 system is remote then @value{GDBN} will retrieve the target binaries
21229 from the remote system. This is only supported when using a remote
21230 target that supports the @code{remote get} command (@pxref{File
21231 Transfer,,Sending files to a remote system}). The part of @var{path}
21232 following the initial @file{target:} (if present) is used as system
21233 root prefix on the remote file system. If @var{path} starts with the
21234 sequence @file{remote:} this is converted to the sequence
21235 @file{target:} by @code{set sysroot}@footnote{Historically the
21236 functionality to retrieve binaries from the remote system was
21237 provided by prefixing @var{path} with @file{remote:}}. If you want
21238 to specify a local system root using a directory that happens to be
21239 named @file{target:} or @file{remote:}, you need to use some
21240 equivalent variant of the name like @file{./target:}.
21242 For targets with an MS-DOS based filesystem, such as MS-Windows,
21243 @value{GDBN} tries prefixing a few variants of the target
21244 absolute file name with @var{path}. But first, on Unix hosts,
21245 @value{GDBN} converts all backslash directory separators into forward
21246 slashes, because the backslash is not a directory separator on Unix:
21249 c:\foo\bar.dll @result{} c:/foo/bar.dll
21252 Then, @value{GDBN} attempts prefixing the target file name with
21253 @var{path}, and looks for the resulting file name in the host file
21257 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21260 If that does not find the binary, @value{GDBN} tries removing
21261 the @samp{:} character from the drive spec, both for convenience, and,
21262 for the case of the host file system not supporting file names with
21266 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21269 This makes it possible to have a system root that mirrors a target
21270 with more than one drive. E.g., you may want to setup your local
21271 copies of the target system shared libraries like so (note @samp{c} vs
21275 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21276 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21277 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21281 and point the system root at @file{/path/to/sysroot}, so that
21282 @value{GDBN} can find the correct copies of both
21283 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21285 If that still does not find the binary, @value{GDBN} tries
21286 removing the whole drive spec from the target file name:
21289 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21292 This last lookup makes it possible to not care about the drive name,
21293 if you don't want or need to.
21295 The @code{set solib-absolute-prefix} command is an alias for @code{set
21298 @cindex default system root
21299 @cindex @samp{--with-sysroot}
21300 You can set the default system root by using the configure-time
21301 @samp{--with-sysroot} option. If the system root is inside
21302 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21303 @samp{--exec-prefix}), then the default system root will be updated
21304 automatically if the installed @value{GDBN} is moved to a new
21307 @kindex show sysroot
21309 Display the current executable and shared library prefix.
21311 @kindex set solib-search-path
21312 @item set solib-search-path @var{path}
21313 If this variable is set, @var{path} is a colon-separated list of
21314 directories to search for shared libraries. @samp{solib-search-path}
21315 is used after @samp{sysroot} fails to locate the library, or if the
21316 path to the library is relative instead of absolute. If you want to
21317 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21318 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21319 finding your host's libraries. @samp{sysroot} is preferred; setting
21320 it to a nonexistent directory may interfere with automatic loading
21321 of shared library symbols.
21323 @kindex show solib-search-path
21324 @item show solib-search-path
21325 Display the current shared library search path.
21327 @cindex DOS file-name semantics of file names.
21328 @kindex set target-file-system-kind (unix|dos-based|auto)
21329 @kindex show target-file-system-kind
21330 @item set target-file-system-kind @var{kind}
21331 Set assumed file system kind for target reported file names.
21333 Shared library file names as reported by the target system may not
21334 make sense as is on the system @value{GDBN} is running on. For
21335 example, when remote debugging a target that has MS-DOS based file
21336 system semantics, from a Unix host, the target may be reporting to
21337 @value{GDBN} a list of loaded shared libraries with file names such as
21338 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21339 drive letters, so the @samp{c:\} prefix is not normally understood as
21340 indicating an absolute file name, and neither is the backslash
21341 normally considered a directory separator character. In that case,
21342 the native file system would interpret this whole absolute file name
21343 as a relative file name with no directory components. This would make
21344 it impossible to point @value{GDBN} at a copy of the remote target's
21345 shared libraries on the host using @code{set sysroot}, and impractical
21346 with @code{set solib-search-path}. Setting
21347 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21348 to interpret such file names similarly to how the target would, and to
21349 map them to file names valid on @value{GDBN}'s native file system
21350 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21351 to one of the supported file system kinds. In that case, @value{GDBN}
21352 tries to determine the appropriate file system variant based on the
21353 current target's operating system (@pxref{ABI, ,Configuring the
21354 Current ABI}). The supported file system settings are:
21358 Instruct @value{GDBN} to assume the target file system is of Unix
21359 kind. Only file names starting the forward slash (@samp{/}) character
21360 are considered absolute, and the directory separator character is also
21364 Instruct @value{GDBN} to assume the target file system is DOS based.
21365 File names starting with either a forward slash, or a drive letter
21366 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21367 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21368 considered directory separators.
21371 Instruct @value{GDBN} to use the file system kind associated with the
21372 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21373 This is the default.
21377 @cindex file name canonicalization
21378 @cindex base name differences
21379 When processing file names provided by the user, @value{GDBN}
21380 frequently needs to compare them to the file names recorded in the
21381 program's debug info. Normally, @value{GDBN} compares just the
21382 @dfn{base names} of the files as strings, which is reasonably fast
21383 even for very large programs. (The base name of a file is the last
21384 portion of its name, after stripping all the leading directories.)
21385 This shortcut in comparison is based upon the assumption that files
21386 cannot have more than one base name. This is usually true, but
21387 references to files that use symlinks or similar filesystem
21388 facilities violate that assumption. If your program records files
21389 using such facilities, or if you provide file names to @value{GDBN}
21390 using symlinks etc., you can set @code{basenames-may-differ} to
21391 @code{true} to instruct @value{GDBN} to completely canonicalize each
21392 pair of file names it needs to compare. This will make file-name
21393 comparisons accurate, but at a price of a significant slowdown.
21396 @item set basenames-may-differ
21397 @kindex set basenames-may-differ
21398 Set whether a source file may have multiple base names.
21400 @item show basenames-may-differ
21401 @kindex show basenames-may-differ
21402 Show whether a source file may have multiple base names.
21406 @section File Caching
21407 @cindex caching of opened files
21408 @cindex caching of bfd objects
21410 To speed up file loading, and reduce memory usage, @value{GDBN} will
21411 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21412 BFD, bfd, The Binary File Descriptor Library}. The following commands
21413 allow visibility and control of the caching behavior.
21416 @kindex maint info bfds
21417 @item maint info bfds
21418 This prints information about each @code{bfd} object that is known to
21421 @kindex maint set bfd-sharing
21422 @kindex maint show bfd-sharing
21423 @kindex bfd caching
21424 @item maint set bfd-sharing
21425 @item maint show bfd-sharing
21426 Control whether @code{bfd} objects can be shared. When sharing is
21427 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21428 than reopening the same file. Turning sharing off does not cause
21429 already shared @code{bfd} objects to be unshared, but all future files
21430 that are opened will create a new @code{bfd} object. Similarly,
21431 re-enabling sharing does not cause multiple existing @code{bfd}
21432 objects to be collapsed into a single shared @code{bfd} object.
21434 @kindex set debug bfd-cache @var{level}
21435 @kindex bfd caching
21436 @item set debug bfd-cache @var{level}
21437 Turns on debugging of the bfd cache, setting the level to @var{level}.
21439 @kindex show debug bfd-cache
21440 @kindex bfd caching
21441 @item show debug bfd-cache
21442 Show the current debugging level of the bfd cache.
21445 @node Separate Debug Files
21446 @section Debugging Information in Separate Files
21447 @cindex separate debugging information files
21448 @cindex debugging information in separate files
21449 @cindex @file{.debug} subdirectories
21450 @cindex debugging information directory, global
21451 @cindex global debugging information directories
21452 @cindex build ID, and separate debugging files
21453 @cindex @file{.build-id} directory
21455 @value{GDBN} allows you to put a program's debugging information in a
21456 file separate from the executable itself, in a way that allows
21457 @value{GDBN} to find and load the debugging information automatically.
21458 Since debugging information can be very large---sometimes larger
21459 than the executable code itself---some systems distribute debugging
21460 information for their executables in separate files, which users can
21461 install only when they need to debug a problem.
21463 @value{GDBN} supports two ways of specifying the separate debug info
21468 The executable contains a @dfn{debug link} that specifies the name of
21469 the separate debug info file. The separate debug file's name is
21470 usually @file{@var{executable}.debug}, where @var{executable} is the
21471 name of the corresponding executable file without leading directories
21472 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21473 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21474 checksum for the debug file, which @value{GDBN} uses to validate that
21475 the executable and the debug file came from the same build.
21479 The executable contains a @dfn{build ID}, a unique bit string that is
21480 also present in the corresponding debug info file. (This is supported
21481 only on some operating systems, when using the ELF or PE file formats
21482 for binary files and the @sc{gnu} Binutils.) For more details about
21483 this feature, see the description of the @option{--build-id}
21484 command-line option in @ref{Options, , Command Line Options, ld,
21485 The GNU Linker}. The debug info file's name is not specified
21486 explicitly by the build ID, but can be computed from the build ID, see
21490 Depending on the way the debug info file is specified, @value{GDBN}
21491 uses two different methods of looking for the debug file:
21495 For the ``debug link'' method, @value{GDBN} looks up the named file in
21496 the directory of the executable file, then in a subdirectory of that
21497 directory named @file{.debug}, and finally under each one of the
21498 global debug directories, in a subdirectory whose name is identical to
21499 the leading directories of the executable's absolute file name. (On
21500 MS-Windows/MS-DOS, the drive letter of the executable's leading
21501 directories is converted to a one-letter subdirectory, i.e.@:
21502 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21503 filesystems disallow colons in file names.)
21506 For the ``build ID'' method, @value{GDBN} looks in the
21507 @file{.build-id} subdirectory of each one of the global debug directories for
21508 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21509 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21510 are the rest of the bit string. (Real build ID strings are 32 or more
21511 hex characters, not 10.) @value{GDBN} can automatically query
21512 @code{debuginfod} servers using build IDs in order to download separate debug
21513 files that cannot be found locally. For more information see @ref{Debuginfod}.
21516 So, for example, suppose you ask @value{GDBN} to debug
21517 @file{/usr/bin/ls}, which has a debug link that specifies the
21518 file @file{ls.debug}, and a build ID whose value in hex is
21519 @code{abcdef1234}. If the list of the global debug directories includes
21520 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21521 debug information files, in the indicated order:
21525 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21527 @file{/usr/bin/ls.debug}
21529 @file{/usr/bin/.debug/ls.debug}
21531 @file{/usr/lib/debug/usr/bin/ls.debug}.
21534 If the debug file still has not been found and @code{debuginfod}
21535 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21536 file from @code{debuginfod} servers.
21538 @anchor{debug-file-directory}
21539 Global debugging info directories default to what is set by @value{GDBN}
21540 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21541 you can also set the global debugging info directories, and view the list
21542 @value{GDBN} is currently using.
21546 @kindex set debug-file-directory
21547 @item set debug-file-directory @var{directories}
21548 Set the directories which @value{GDBN} searches for separate debugging
21549 information files to @var{directory}. Multiple path components can be set
21550 concatenating them by a path separator.
21552 @kindex show debug-file-directory
21553 @item show debug-file-directory
21554 Show the directories @value{GDBN} searches for separate debugging
21559 @cindex @code{.gnu_debuglink} sections
21560 @cindex debug link sections
21561 A debug link is a special section of the executable file named
21562 @code{.gnu_debuglink}. The section must contain:
21566 A filename, with any leading directory components removed, followed by
21569 zero to three bytes of padding, as needed to reach the next four-byte
21570 boundary within the section, and
21572 a four-byte CRC checksum, stored in the same endianness used for the
21573 executable file itself. The checksum is computed on the debugging
21574 information file's full contents by the function given below, passing
21575 zero as the @var{crc} argument.
21578 Any executable file format can carry a debug link, as long as it can
21579 contain a section named @code{.gnu_debuglink} with the contents
21582 @cindex @code{.note.gnu.build-id} sections
21583 @cindex build ID sections
21584 The build ID is a special section in the executable file (and in other
21585 ELF binary files that @value{GDBN} may consider). This section is
21586 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21587 It contains unique identification for the built files---the ID remains
21588 the same across multiple builds of the same build tree. The default
21589 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21590 content for the build ID string. The same section with an identical
21591 value is present in the original built binary with symbols, in its
21592 stripped variant, and in the separate debugging information file.
21594 The debugging information file itself should be an ordinary
21595 executable, containing a full set of linker symbols, sections, and
21596 debugging information. The sections of the debugging information file
21597 should have the same names, addresses, and sizes as the original file,
21598 but they need not contain any data---much like a @code{.bss} section
21599 in an ordinary executable.
21601 The @sc{gnu} binary utilities (Binutils) package includes the
21602 @samp{objcopy} utility that can produce
21603 the separated executable / debugging information file pairs using the
21604 following commands:
21607 @kbd{objcopy --only-keep-debug foo foo.debug}
21612 These commands remove the debugging
21613 information from the executable file @file{foo} and place it in the file
21614 @file{foo.debug}. You can use the first, second or both methods to link the
21619 The debug link method needs the following additional command to also leave
21620 behind a debug link in @file{foo}:
21623 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21626 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21627 a version of the @code{strip} command such that the command @kbd{strip foo -f
21628 foo.debug} has the same functionality as the two @code{objcopy} commands and
21629 the @code{ln -s} command above, together.
21632 Build ID gets embedded into the main executable using @code{ld --build-id} or
21633 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21634 compatibility fixes for debug files separation are present in @sc{gnu} binary
21635 utilities (Binutils) package since version 2.18.
21640 @cindex CRC algorithm definition
21641 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21642 IEEE 802.3 using the polynomial:
21644 @c TexInfo requires naked braces for multi-digit exponents for Tex
21645 @c output, but this causes HTML output to barf. HTML has to be set using
21646 @c raw commands. So we end up having to specify this equation in 2
21651 <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>
21652 + <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
21658 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21659 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21663 The function is computed byte at a time, taking the least
21664 significant bit of each byte first. The initial pattern
21665 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21666 the final result is inverted to ensure trailing zeros also affect the
21669 @emph{Note:} This is the same CRC polynomial as used in handling the
21670 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21671 However in the case of the Remote Serial Protocol, the CRC is computed
21672 @emph{most} significant bit first, and the result is not inverted, so
21673 trailing zeros have no effect on the CRC value.
21675 To complete the description, we show below the code of the function
21676 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21677 initially supplied @code{crc} argument means that an initial call to
21678 this function passing in zero will start computing the CRC using
21681 @kindex gnu_debuglink_crc32
21684 gnu_debuglink_crc32 (unsigned long crc,
21685 unsigned char *buf, size_t len)
21687 static const unsigned long crc32_table[256] =
21689 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21690 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21691 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21692 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21693 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21694 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21695 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21696 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21697 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21698 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21699 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21700 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21701 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21702 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21703 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21704 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21705 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21706 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21707 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21708 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21709 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21710 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21711 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21712 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21713 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21714 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21715 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21716 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21717 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21718 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21719 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21720 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21721 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21722 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21723 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21724 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21725 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21726 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21727 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21728 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21729 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21730 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21731 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21732 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21733 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21734 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21735 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21736 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21737 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21738 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21739 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21742 unsigned char *end;
21744 crc = ~crc & 0xffffffff;
21745 for (end = buf + len; buf < end; ++buf)
21746 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21747 return ~crc & 0xffffffff;
21752 This computation does not apply to the ``build ID'' method.
21754 @node MiniDebugInfo
21755 @section Debugging information in a special section
21756 @cindex separate debug sections
21757 @cindex @samp{.gnu_debugdata} section
21759 Some systems ship pre-built executables and libraries that have a
21760 special @samp{.gnu_debugdata} section. This feature is called
21761 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21762 is used to supply extra symbols for backtraces.
21764 The intent of this section is to provide extra minimal debugging
21765 information for use in simple backtraces. It is not intended to be a
21766 replacement for full separate debugging information (@pxref{Separate
21767 Debug Files}). The example below shows the intended use; however,
21768 @value{GDBN} does not currently put restrictions on what sort of
21769 debugging information might be included in the section.
21771 @value{GDBN} has support for this extension. If the section exists,
21772 then it is used provided that no other source of debugging information
21773 can be found, and that @value{GDBN} was configured with LZMA support.
21775 This section can be easily created using @command{objcopy} and other
21776 standard utilities:
21779 # Extract the dynamic symbols from the main binary, there is no need
21780 # to also have these in the normal symbol table.
21781 nm -D @var{binary} --format=posix --defined-only \
21782 | awk '@{ print $1 @}' | sort > dynsyms
21784 # Extract all the text (i.e. function) symbols from the debuginfo.
21785 # (Note that we actually also accept "D" symbols, for the benefit
21786 # of platforms like PowerPC64 that use function descriptors.)
21787 nm @var{binary} --format=posix --defined-only \
21788 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21791 # Keep all the function symbols not already in the dynamic symbol
21793 comm -13 dynsyms funcsyms > keep_symbols
21795 # Separate full debug info into debug binary.
21796 objcopy --only-keep-debug @var{binary} debug
21798 # Copy the full debuginfo, keeping only a minimal set of symbols and
21799 # removing some unnecessary sections.
21800 objcopy -S --remove-section .gdb_index --remove-section .comment \
21801 --keep-symbols=keep_symbols debug mini_debuginfo
21803 # Drop the full debug info from the original binary.
21804 strip --strip-all -R .comment @var{binary}
21806 # Inject the compressed data into the .gnu_debugdata section of the
21809 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21813 @section Index Files Speed Up @value{GDBN}
21814 @cindex index files
21815 @cindex @samp{.gdb_index} section
21817 When @value{GDBN} finds a symbol file, it scans the symbols in the
21818 file in order to construct an internal symbol table. This lets most
21819 @value{GDBN} operations work quickly---at the cost of a delay early
21820 on. For large programs, this delay can be quite lengthy, so
21821 @value{GDBN} provides a way to build an index, which speeds up
21824 For convenience, @value{GDBN} comes with a program,
21825 @command{gdb-add-index}, which can be used to add the index to a
21826 symbol file. It takes the symbol file as its only argument:
21829 $ gdb-add-index symfile
21832 @xref{gdb-add-index}.
21834 It is also possible to do the work manually. Here is what
21835 @command{gdb-add-index} does behind the curtains.
21837 The index is stored as a section in the symbol file. @value{GDBN} can
21838 write the index to a file, then you can put it into the symbol file
21839 using @command{objcopy}.
21841 To create an index file, use the @code{save gdb-index} command:
21844 @item save gdb-index [-dwarf-5] @var{directory}
21845 @kindex save gdb-index
21846 Create index files for all symbol files currently known by
21847 @value{GDBN}. For each known @var{symbol-file}, this command by
21848 default creates it produces a single file
21849 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21850 the @option{-dwarf-5} option, it produces 2 files:
21851 @file{@var{symbol-file}.debug_names} and
21852 @file{@var{symbol-file}.debug_str}. The files are created in the
21853 given @var{directory}.
21856 Once you have created an index file you can merge it into your symbol
21857 file, here named @file{symfile}, using @command{objcopy}:
21860 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21861 --set-section-flags .gdb_index=readonly symfile symfile
21864 Or for @code{-dwarf-5}:
21867 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21868 $ cat symfile.debug_str >>symfile.debug_str.new
21869 $ objcopy --add-section .debug_names=symfile.gdb-index \
21870 --set-section-flags .debug_names=readonly \
21871 --update-section .debug_str=symfile.debug_str.new symfile symfile
21874 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21875 sections that have been deprecated. Usually they are deprecated because
21876 they are missing a new feature or have performance issues.
21877 To tell @value{GDBN} to use a deprecated index section anyway
21878 specify @code{set use-deprecated-index-sections on}.
21879 The default is @code{off}.
21880 This can speed up startup, but may result in some functionality being lost.
21881 @xref{Index Section Format}.
21883 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21884 must be done before gdb reads the file. The following will not work:
21887 $ gdb -ex "set use-deprecated-index-sections on" <program>
21890 Instead you must do, for example,
21893 $ gdb -iex "set use-deprecated-index-sections on" <program>
21896 Indices only work when using DWARF debugging information, not stabs.
21898 @subsection Automatic symbol index cache
21900 @cindex automatic symbol index cache
21901 It is possible for @value{GDBN} to automatically save a copy of this index in a
21902 cache on disk and retrieve it from there when loading the same binary in the
21903 future. This feature can be turned on with @kbd{set index-cache enabled on}.
21904 The following commands can be used to tweak the behavior of the index cache.
21908 @kindex set index-cache
21909 @item set index-cache enabled on
21910 @itemx set index-cache enabled off
21911 Enable or disable the use of the symbol index cache.
21913 @item set index-cache directory @var{directory}
21914 @kindex show index-cache
21915 @itemx show index-cache directory
21916 Set/show the directory where index files will be saved.
21918 The default value for this directory depends on the host platform. On
21919 most systems, the index is cached in the @file{gdb} subdirectory of
21920 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21921 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21922 of your home directory. However, on some systems, the default may
21923 differ according to local convention.
21925 There is no limit on the disk space used by index cache. It is perfectly safe
21926 to delete the content of that directory to free up disk space.
21928 @item show index-cache stats
21929 Print the number of cache hits and misses since the launch of @value{GDBN}.
21933 @node Symbol Errors
21934 @section Errors Reading Symbol Files
21936 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21937 such as symbol types it does not recognize, or known bugs in compiler
21938 output. By default, @value{GDBN} does not notify you of such problems, since
21939 they are relatively common and primarily of interest to people
21940 debugging compilers. If you are interested in seeing information
21941 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21942 only one message about each such type of problem, no matter how many
21943 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21944 to see how many times the problems occur, with the @code{set
21945 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21948 The messages currently printed, and their meanings, include:
21951 @item inner block not inside outer block in @var{symbol}
21953 The symbol information shows where symbol scopes begin and end
21954 (such as at the start of a function or a block of statements). This
21955 error indicates that an inner scope block is not fully contained
21956 in its outer scope blocks.
21958 @value{GDBN} circumvents the problem by treating the inner block as if it had
21959 the same scope as the outer block. In the error message, @var{symbol}
21960 may be shown as ``@code{(don't know)}'' if the outer block is not a
21963 @item block at @var{address} out of order
21965 The symbol information for symbol scope blocks should occur in
21966 order of increasing addresses. This error indicates that it does not
21969 @value{GDBN} does not circumvent this problem, and has trouble
21970 locating symbols in the source file whose symbols it is reading. (You
21971 can often determine what source file is affected by specifying
21972 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21975 @item bad block start address patched
21977 The symbol information for a symbol scope block has a start address
21978 smaller than the address of the preceding source line. This is known
21979 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21981 @value{GDBN} circumvents the problem by treating the symbol scope block as
21982 starting on the previous source line.
21984 @item bad string table offset in symbol @var{n}
21987 Symbol number @var{n} contains a pointer into the string table which is
21988 larger than the size of the string table.
21990 @value{GDBN} circumvents the problem by considering the symbol to have the
21991 name @code{foo}, which may cause other problems if many symbols end up
21994 @item unknown symbol type @code{0x@var{nn}}
21996 The symbol information contains new data types that @value{GDBN} does
21997 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21998 uncomprehended information, in hexadecimal.
22000 @value{GDBN} circumvents the error by ignoring this symbol information.
22001 This usually allows you to debug your program, though certain symbols
22002 are not accessible. If you encounter such a problem and feel like
22003 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22004 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22005 and examine @code{*bufp} to see the symbol.
22007 @item stub type has NULL name
22009 @value{GDBN} could not find the full definition for a struct or class.
22011 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22012 The symbol information for a C@t{++} member function is missing some
22013 information that recent versions of the compiler should have output for
22016 @item info mismatch between compiler and debugger
22018 @value{GDBN} could not parse a type specification output by the compiler.
22023 @section GDB Data Files
22025 @cindex prefix for data files
22026 @value{GDBN} will sometimes read an auxiliary data file. These files
22027 are kept in a directory known as the @dfn{data directory}.
22029 You can set the data directory's name, and view the name @value{GDBN}
22030 is currently using.
22033 @kindex set data-directory
22034 @item set data-directory @var{directory}
22035 Set the directory which @value{GDBN} searches for auxiliary data files
22036 to @var{directory}.
22038 @kindex show data-directory
22039 @item show data-directory
22040 Show the directory @value{GDBN} searches for auxiliary data files.
22043 @cindex default data directory
22044 @cindex @samp{--with-gdb-datadir}
22045 You can set the default data directory by using the configure-time
22046 @samp{--with-gdb-datadir} option. If the data directory is inside
22047 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22048 @samp{--exec-prefix}), then the default data directory will be updated
22049 automatically if the installed @value{GDBN} is moved to a new
22052 The data directory may also be specified with the
22053 @code{--data-directory} command line option.
22054 @xref{Mode Options}.
22057 @chapter Specifying a Debugging Target
22059 @cindex debugging target
22060 A @dfn{target} is the execution environment occupied by your program.
22062 Often, @value{GDBN} runs in the same host environment as your program;
22063 in that case, the debugging target is specified as a side effect when
22064 you use the @code{file} or @code{core} commands. When you need more
22065 flexibility---for example, running @value{GDBN} on a physically separate
22066 host, or controlling a standalone system over a serial port or a
22067 realtime system over a TCP/IP connection---you can use the @code{target}
22068 command to specify one of the target types configured for @value{GDBN}
22069 (@pxref{Target Commands, ,Commands for Managing Targets}).
22071 @cindex target architecture
22072 It is possible to build @value{GDBN} for several different @dfn{target
22073 architectures}. When @value{GDBN} is built like that, you can choose
22074 one of the available architectures with the @kbd{set architecture}
22078 @kindex set architecture
22079 @kindex show architecture
22080 @item set architecture @var{arch}
22081 This command sets the current target architecture to @var{arch}. The
22082 value of @var{arch} can be @code{"auto"}, in addition to one of the
22083 supported architectures.
22085 @item show architecture
22086 Show the current target architecture.
22088 @item set processor
22090 @kindex set processor
22091 @kindex show processor
22092 These are alias commands for, respectively, @code{set architecture}
22093 and @code{show architecture}.
22097 * Active Targets:: Active targets
22098 * Target Commands:: Commands for managing targets
22099 * Byte Order:: Choosing target byte order
22102 @node Active Targets
22103 @section Active Targets
22105 @cindex stacking targets
22106 @cindex active targets
22107 @cindex multiple targets
22109 There are multiple classes of targets such as: processes, executable files or
22110 recording sessions. Core files belong to the process class, making core file
22111 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22112 on multiple active targets, one in each class. This allows you to (for
22113 example) start a process and inspect its activity, while still having access to
22114 the executable file after the process finishes. Or if you start process
22115 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22116 presented a virtual layer of the recording target, while the process target
22117 remains stopped at the chronologically last point of the process execution.
22119 Use the @code{core-file} and @code{exec-file} commands to select a new core
22120 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22121 specify as a target a process that is already running, use the @code{attach}
22122 command (@pxref{Attach, ,Debugging an Already-running Process}).
22124 @node Target Commands
22125 @section Commands for Managing Targets
22128 @item target @var{type} @var{parameters}
22129 Connects the @value{GDBN} host environment to a target machine or
22130 process. A target is typically a protocol for talking to debugging
22131 facilities. You use the argument @var{type} to specify the type or
22132 protocol of the target machine.
22134 Further @var{parameters} are interpreted by the target protocol, but
22135 typically include things like device names or host names to connect
22136 with, process numbers, and baud rates.
22138 The @code{target} command does not repeat if you press @key{RET} again
22139 after executing the command.
22141 @kindex help target
22143 Displays the names of all targets available. To display targets
22144 currently selected, use either @code{info target} or @code{info files}
22145 (@pxref{Files, ,Commands to Specify Files}).
22147 @item help target @var{name}
22148 Describe a particular target, including any parameters necessary to
22151 @kindex set gnutarget
22152 @item set gnutarget @var{args}
22153 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22154 knows whether it is reading an @dfn{executable},
22155 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22156 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22157 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22160 @emph{Warning:} To specify a file format with @code{set gnutarget},
22161 you must know the actual BFD name.
22165 @xref{Files, , Commands to Specify Files}.
22167 @kindex show gnutarget
22168 @item show gnutarget
22169 Use the @code{show gnutarget} command to display what file format
22170 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22171 @value{GDBN} will determine the file format for each file automatically,
22172 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22175 @cindex common targets
22176 Here are some common targets (available, or not, depending on the GDB
22181 @item target exec @var{program}
22182 @cindex executable file target
22183 An executable file. @samp{target exec @var{program}} is the same as
22184 @samp{exec-file @var{program}}.
22186 @item target core @var{filename}
22187 @cindex core dump file target
22188 A core dump file. @samp{target core @var{filename}} is the same as
22189 @samp{core-file @var{filename}}.
22191 @item target remote @var{medium}
22192 @cindex remote target
22193 A remote system connected to @value{GDBN} via a serial line or network
22194 connection. This command tells @value{GDBN} to use its own remote
22195 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22197 For example, if you have a board connected to @file{/dev/ttya} on the
22198 machine running @value{GDBN}, you could say:
22201 target remote /dev/ttya
22204 @code{target remote} supports the @code{load} command. This is only
22205 useful if you have some other way of getting the stub to the target
22206 system, and you can put it somewhere in memory where it won't get
22207 clobbered by the download.
22209 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22210 @cindex built-in simulator target
22211 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22219 works; however, you cannot assume that a specific memory map, device
22220 drivers, or even basic I/O is available, although some simulators do
22221 provide these. For info about any processor-specific simulator details,
22222 see the appropriate section in @ref{Embedded Processors, ,Embedded
22225 @item target native
22226 @cindex native target
22227 Setup for local/native process debugging. Useful to make the
22228 @code{run} command spawn native processes (likewise @code{attach},
22229 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22230 (@pxref{set auto-connect-native-target}).
22234 Different targets are available on different configurations of @value{GDBN};
22235 your configuration may have more or fewer targets.
22237 Many remote targets require you to download the executable's code once
22238 you've successfully established a connection. You may wish to control
22239 various aspects of this process.
22244 @kindex set hash@r{, for remote monitors}
22245 @cindex hash mark while downloading
22246 This command controls whether a hash mark @samp{#} is displayed while
22247 downloading a file to the remote monitor. If on, a hash mark is
22248 displayed after each S-record is successfully downloaded to the
22252 @kindex show hash@r{, for remote monitors}
22253 Show the current status of displaying the hash mark.
22255 @item set debug monitor
22256 @kindex set debug monitor
22257 @cindex display remote monitor communications
22258 Enable or disable display of communications messages between
22259 @value{GDBN} and the remote monitor.
22261 @item show debug monitor
22262 @kindex show debug monitor
22263 Show the current status of displaying communications between
22264 @value{GDBN} and the remote monitor.
22269 @kindex load @var{filename} @var{offset}
22270 @item load @var{filename} @var{offset}
22272 Depending on what remote debugging facilities are configured into
22273 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22274 is meant to make @var{filename} (an executable) available for debugging
22275 on the remote system---by downloading, or dynamic linking, for example.
22276 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22277 the @code{add-symbol-file} command.
22279 If your @value{GDBN} does not have a @code{load} command, attempting to
22280 execute it gets the error message ``@code{You can't do that when your
22281 target is @dots{}}''
22283 The file is loaded at whatever address is specified in the executable.
22284 For some object file formats, you can specify the load address when you
22285 link the program; for other formats, like a.out, the object file format
22286 specifies a fixed address.
22287 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22289 It is also possible to tell @value{GDBN} to load the executable file at a
22290 specific offset described by the optional argument @var{offset}. When
22291 @var{offset} is provided, @var{filename} must also be provided.
22293 Depending on the remote side capabilities, @value{GDBN} may be able to
22294 load programs into flash memory.
22296 @code{load} does not repeat if you press @key{RET} again after using it.
22301 @kindex flash-erase
22303 @anchor{flash-erase}
22305 Erases all known flash memory regions on the target.
22310 @section Choosing Target Byte Order
22312 @cindex choosing target byte order
22313 @cindex target byte order
22315 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22316 offer the ability to run either big-endian or little-endian byte
22317 orders. Usually the executable or symbol will include a bit to
22318 designate the endian-ness, and you will not need to worry about
22319 which to use. However, you may still find it useful to adjust
22320 @value{GDBN}'s idea of processor endian-ness manually.
22324 @item set endian big
22325 Instruct @value{GDBN} to assume the target is big-endian.
22327 @item set endian little
22328 Instruct @value{GDBN} to assume the target is little-endian.
22330 @item set endian auto
22331 Instruct @value{GDBN} to use the byte order associated with the
22335 Display @value{GDBN}'s current idea of the target byte order.
22339 If the @code{set endian auto} mode is in effect and no executable has
22340 been selected, then the endianness used is the last one chosen either
22341 by one of the @code{set endian big} and @code{set endian little}
22342 commands or by inferring from the last executable used. If no
22343 endianness has been previously chosen, then the default for this mode
22344 is inferred from the target @value{GDBN} has been built for, and is
22345 @code{little} if the name of the target CPU has an @code{el} suffix
22346 and @code{big} otherwise.
22348 Note that these commands merely adjust interpretation of symbolic
22349 data on the host, and that they have absolutely no effect on the
22353 @node Remote Debugging
22354 @chapter Debugging Remote Programs
22355 @cindex remote debugging
22357 If you are trying to debug a program running on a machine that cannot run
22358 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22359 For example, you might use remote debugging on an operating system kernel,
22360 or on a small system which does not have a general purpose operating system
22361 powerful enough to run a full-featured debugger.
22363 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22364 to make this work with particular debugging targets. In addition,
22365 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22366 but not specific to any particular target system) which you can use if you
22367 write the remote stubs---the code that runs on the remote system to
22368 communicate with @value{GDBN}.
22370 Other remote targets may be available in your
22371 configuration of @value{GDBN}; use @code{help target} to list them.
22374 * Connecting:: Connecting to a remote target
22375 * File Transfer:: Sending files to a remote system
22376 * Server:: Using the gdbserver program
22377 * Remote Configuration:: Remote configuration
22378 * Remote Stub:: Implementing a remote stub
22382 @section Connecting to a Remote Target
22383 @cindex remote debugging, connecting
22384 @cindex @code{gdbserver}, connecting
22385 @cindex remote debugging, types of connections
22386 @cindex @code{gdbserver}, types of connections
22387 @cindex @code{gdbserver}, @code{target remote} mode
22388 @cindex @code{gdbserver}, @code{target extended-remote} mode
22390 This section describes how to connect to a remote target, including the
22391 types of connections and their differences, how to set up executable and
22392 symbol files on the host and target, and the commands used for
22393 connecting to and disconnecting from the remote target.
22395 @subsection Types of Remote Connections
22397 @value{GDBN} supports two types of remote connections, @code{target remote}
22398 mode and @code{target extended-remote} mode. Note that many remote targets
22399 support only @code{target remote} mode. There are several major
22400 differences between the two types of connections, enumerated here:
22404 @cindex remote debugging, detach and program exit
22405 @item Result of detach or program exit
22406 @strong{With target remote mode:} When the debugged program exits or you
22407 detach from it, @value{GDBN} disconnects from the target. When using
22408 @code{gdbserver}, @code{gdbserver} will exit.
22410 @strong{With target extended-remote mode:} When the debugged program exits or
22411 you detach from it, @value{GDBN} remains connected to the target, even
22412 though no program is running. You can rerun the program, attach to a
22413 running program, or use @code{monitor} commands specific to the target.
22415 When using @code{gdbserver} in this case, it does not exit unless it was
22416 invoked using the @option{--once} option. If the @option{--once} option
22417 was not used, you can ask @code{gdbserver} to exit using the
22418 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22420 @item Specifying the program to debug
22421 For both connection types you use the @code{file} command to specify the
22422 program on the host system. If you are using @code{gdbserver} there are
22423 some differences in how to specify the location of the program on the
22426 @strong{With target remote mode:} You must either specify the program to debug
22427 on the @code{gdbserver} command line or use the @option{--attach} option
22428 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22430 @cindex @option{--multi}, @code{gdbserver} option
22431 @strong{With target extended-remote mode:} You may specify the program to debug
22432 on the @code{gdbserver} command line, or you can load the program or attach
22433 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22435 @anchor{--multi Option in Types of Remote Connnections}
22436 You can start @code{gdbserver} without supplying an initial command to run
22437 or process ID to attach. To do this, use the @option{--multi} command line
22438 option. Then you can connect using @code{target extended-remote} and start
22439 the program you want to debug (see below for details on using the
22440 @code{run} command in this scenario). Note that the conditions under which
22441 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22442 (@code{target remote} or @code{target extended-remote}). The
22443 @option{--multi} option to @code{gdbserver} has no influence on that.
22445 @item The @code{run} command
22446 @strong{With target remote mode:} The @code{run} command is not
22447 supported. Once a connection has been established, you can use all
22448 the usual @value{GDBN} commands to examine and change data. The
22449 remote program is already running, so you can use commands like
22450 @kbd{step} and @kbd{continue}.
22452 @strong{With target extended-remote mode:} The @code{run} command is
22453 supported. The @code{run} command uses the value set by
22454 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22455 the program to run. Command line arguments are supported, except for
22456 wildcard expansion and I/O redirection (@pxref{Arguments}).
22458 If you specify the program to debug on the command line, then the
22459 @code{run} command is not required to start execution, and you can
22460 resume using commands like @kbd{step} and @kbd{continue} as with
22461 @code{target remote} mode.
22463 @anchor{Attaching in Types of Remote Connections}
22465 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22466 not supported. To attach to a running program using @code{gdbserver}, you
22467 must use the @option{--attach} option (@pxref{Running gdbserver}).
22469 @strong{With target extended-remote mode:} To attach to a running program,
22470 you may use the @code{attach} command after the connection has been
22471 established. If you are using @code{gdbserver}, you may also invoke
22472 @code{gdbserver} using the @option{--attach} option
22473 (@pxref{Running gdbserver}).
22475 Some remote targets allow @value{GDBN} to determine the executable file running
22476 in the process the debugger is attaching to. In such a case, @value{GDBN}
22477 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22478 between the executable file name running in the process and the name of the
22479 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22483 @anchor{Host and target files}
22484 @subsection Host and Target Files
22485 @cindex remote debugging, symbol files
22486 @cindex symbol files, remote debugging
22488 @value{GDBN}, running on the host, needs access to symbol and debugging
22489 information for your program running on the target. This requires
22490 access to an unstripped copy of your program, and possibly any associated
22491 symbol files. Note that this section applies equally to both @code{target
22492 remote} mode and @code{target extended-remote} mode.
22494 Some remote targets (@pxref{qXfer executable filename read}, and
22495 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22496 the same connection used to communicate with @value{GDBN}. With such a
22497 target, if the remote program is unstripped, the only command you need is
22498 @code{target remote} (or @code{target extended-remote}).
22500 If the remote program is stripped, or the target does not support remote
22501 program file access, start up @value{GDBN} using the name of the local
22502 unstripped copy of your program as the first argument, or use the
22503 @code{file} command. Use @code{set sysroot} to specify the location (on
22504 the host) of target libraries (unless your @value{GDBN} was compiled with
22505 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22506 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22509 The symbol file and target libraries must exactly match the executable
22510 and libraries on the target, with one exception: the files on the host
22511 system should not be stripped, even if the files on the target system
22512 are. Mismatched or missing files will lead to confusing results
22513 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22514 files may also prevent @code{gdbserver} from debugging multi-threaded
22517 @subsection Remote Connection Commands
22518 @cindex remote connection commands
22519 @value{GDBN} can communicate with the target over a serial line, a
22520 local Unix domain socket, or
22521 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22522 each case, @value{GDBN} uses the same protocol for debugging your
22523 program; only the medium carrying the debugging packets varies. The
22524 @code{target remote} and @code{target extended-remote} commands
22525 establish a connection to the target. Both commands accept the same
22526 arguments, which indicate the medium to use:
22530 @item target remote @var{serial-device}
22531 @itemx target extended-remote @var{serial-device}
22532 @cindex serial line, @code{target remote}
22533 Use @var{serial-device} to communicate with the target. For example,
22534 to use a serial line connected to the device named @file{/dev/ttyb}:
22537 target remote /dev/ttyb
22540 If you're using a serial line, you may want to give @value{GDBN} the
22541 @samp{--baud} option, or use the @code{set serial baud} command
22542 (@pxref{Remote Configuration, set serial baud}) before the
22543 @code{target} command.
22545 @item target remote @var{local-socket}
22546 @itemx target extended-remote @var{local-socket}
22547 @cindex local socket, @code{target remote}
22548 @cindex Unix domain socket
22549 Use @var{local-socket} to communicate with the target. For example,
22550 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22553 target remote /tmp/gdb-socket0
22556 Note that this command has the same form as the command to connect
22557 to a serial line. @value{GDBN} will automatically determine which
22558 kind of file you have specified and will make the appropriate kind
22560 This feature is not available if the host system does not support
22561 Unix domain sockets.
22563 @item target remote @code{@var{host}:@var{port}}
22564 @itemx target remote @code{[@var{host}]:@var{port}}
22565 @itemx target remote @code{tcp:@var{host}:@var{port}}
22566 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22567 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22568 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22569 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22570 @itemx target extended-remote @code{@var{host}:@var{port}}
22571 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22572 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22573 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22574 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22575 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22576 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22577 @cindex @acronym{TCP} port, @code{target remote}
22578 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22579 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22580 address, or a numeric @acronym{IPv6} address (with or without the
22581 square brackets to separate the address from the port); @var{port}
22582 must be a decimal number. The @var{host} could be the target machine
22583 itself, if it is directly connected to the net, or it might be a
22584 terminal server which in turn has a serial line to the target.
22586 For example, to connect to port 2828 on a terminal server named
22590 target remote manyfarms:2828
22593 To connect to port 2828 on a terminal server whose address is
22594 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22595 square bracket syntax:
22598 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22602 or explicitly specify the @acronym{IPv6} protocol:
22605 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22608 This last example may be confusing to the reader, because there is no
22609 visible separation between the hostname and the port number.
22610 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22611 using square brackets for clarity. However, it is important to
22612 mention that for @value{GDBN} there is no ambiguity: the number after
22613 the last colon is considered to be the port number.
22615 If your remote target is actually running on the same machine as your
22616 debugger session (e.g.@: a simulator for your target running on the
22617 same host), you can omit the hostname. For example, to connect to
22618 port 1234 on your local machine:
22621 target remote :1234
22625 Note that the colon is still required here.
22627 @item target remote @code{udp:@var{host}:@var{port}}
22628 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22629 @itemx target remote @code{udp4:@var{host}:@var{port}}
22630 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22631 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22632 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22633 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22634 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22635 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22636 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22637 @cindex @acronym{UDP} port, @code{target remote}
22638 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22639 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22642 target remote udp:manyfarms:2828
22645 When using a @acronym{UDP} connection for remote debugging, you should
22646 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22647 can silently drop packets on busy or unreliable networks, which will
22648 cause havoc with your debugging session.
22650 @item target remote | @var{command}
22651 @itemx target extended-remote | @var{command}
22652 @cindex pipe, @code{target remote} to
22653 Run @var{command} in the background and communicate with it using a
22654 pipe. The @var{command} is a shell command, to be parsed and expanded
22655 by the system's command shell, @code{/bin/sh}; it should expect remote
22656 protocol packets on its standard input, and send replies on its
22657 standard output. You could use this to run a stand-alone simulator
22658 that speaks the remote debugging protocol, to make net connections
22659 using programs like @code{ssh}, or for other similar tricks.
22661 If @var{command} closes its standard output (perhaps by exiting),
22662 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22663 program has already exited, this will have no effect.)
22667 @cindex interrupting remote programs
22668 @cindex remote programs, interrupting
22669 Whenever @value{GDBN} is waiting for the remote program, if you type the
22670 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22671 program. This may or may not succeed, depending in part on the hardware
22672 and the serial drivers the remote system uses. If you type the
22673 interrupt character once again, @value{GDBN} displays this prompt:
22676 Interrupted while waiting for the program.
22677 Give up (and stop debugging it)? (y or n)
22680 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22681 the remote debugging session. (If you decide you want to try again later,
22682 you can use @kbd{target remote} again to connect once more.) If you type
22683 @kbd{n}, @value{GDBN} goes back to waiting.
22685 In @code{target extended-remote} mode, typing @kbd{n} will leave
22686 @value{GDBN} connected to the target.
22689 @kindex detach (remote)
22691 When you have finished debugging the remote program, you can use the
22692 @code{detach} command to release it from @value{GDBN} control.
22693 Detaching from the target normally resumes its execution, but the results
22694 will depend on your particular remote stub. After the @code{detach}
22695 command in @code{target remote} mode, @value{GDBN} is free to connect to
22696 another target. In @code{target extended-remote} mode, @value{GDBN} is
22697 still connected to the target.
22701 The @code{disconnect} command closes the connection to the target, and
22702 the target is generally not resumed. It will wait for @value{GDBN}
22703 (this instance or another one) to connect and continue debugging. After
22704 the @code{disconnect} command, @value{GDBN} is again free to connect to
22707 @cindex send command to remote monitor
22708 @cindex extend @value{GDBN} for remote targets
22709 @cindex add new commands for external monitor
22711 @item monitor @var{cmd}
22712 This command allows you to send arbitrary commands directly to the
22713 remote monitor. Since @value{GDBN} doesn't care about the commands it
22714 sends like this, this command is the way to extend @value{GDBN}---you
22715 can add new commands that only the external monitor will understand
22719 @node File Transfer
22720 @section Sending files to a remote system
22721 @cindex remote target, file transfer
22722 @cindex file transfer
22723 @cindex sending files to remote systems
22725 Some remote targets offer the ability to transfer files over the same
22726 connection used to communicate with @value{GDBN}. This is convenient
22727 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22728 running @code{gdbserver} over a network interface. For other targets,
22729 e.g.@: embedded devices with only a single serial port, this may be
22730 the only way to upload or download files.
22732 Not all remote targets support these commands.
22736 @item remote put @var{hostfile} @var{targetfile}
22737 Copy file @var{hostfile} from the host system (the machine running
22738 @value{GDBN}) to @var{targetfile} on the target system.
22741 @item remote get @var{targetfile} @var{hostfile}
22742 Copy file @var{targetfile} from the target system to @var{hostfile}
22743 on the host system.
22745 @kindex remote delete
22746 @item remote delete @var{targetfile}
22747 Delete @var{targetfile} from the target system.
22752 @section Using the @code{gdbserver} Program
22755 @cindex remote connection without stubs
22756 @code{gdbserver} is a control program for Unix-like systems, which
22757 allows you to connect your program with a remote @value{GDBN} via
22758 @code{target remote} or @code{target extended-remote}---but without
22759 linking in the usual debugging stub.
22761 @code{gdbserver} is not a complete replacement for the debugging stubs,
22762 because it requires essentially the same operating-system facilities
22763 that @value{GDBN} itself does. In fact, a system that can run
22764 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22765 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22766 because it is a much smaller program than @value{GDBN} itself. It is
22767 also easier to port than all of @value{GDBN}, so you may be able to get
22768 started more quickly on a new system by using @code{gdbserver}.
22769 Finally, if you develop code for real-time systems, you may find that
22770 the tradeoffs involved in real-time operation make it more convenient to
22771 do as much development work as possible on another system, for example
22772 by cross-compiling. You can use @code{gdbserver} to make a similar
22773 choice for debugging.
22775 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22776 or a TCP connection, using the standard @value{GDBN} remote serial
22780 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22781 Do not run @code{gdbserver} connected to any public network; a
22782 @value{GDBN} connection to @code{gdbserver} provides access to the
22783 target system with the same privileges as the user running
22787 @anchor{Running gdbserver}
22788 @subsection Running @code{gdbserver}
22789 @cindex arguments, to @code{gdbserver}
22790 @cindex @code{gdbserver}, command-line arguments
22792 Run @code{gdbserver} on the target system. You need a copy of the
22793 program you want to debug, including any libraries it requires.
22794 @code{gdbserver} does not need your program's symbol table, so you can
22795 strip the program if necessary to save space. @value{GDBN} on the host
22796 system does all the symbol handling.
22798 To use the server, you must tell it how to communicate with @value{GDBN};
22799 the name of your program; and the arguments for your program. The usual
22803 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22806 @var{comm} is either a device name (to use a serial line), or a TCP
22807 hostname and portnumber, or @code{-} or @code{stdio} to use
22808 stdin/stdout of @code{gdbserver}.
22809 For example, to debug Emacs with the argument
22810 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22814 target> gdbserver /dev/com1 emacs foo.txt
22817 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22820 To use a TCP connection instead of a serial line:
22823 target> gdbserver host:2345 emacs foo.txt
22826 The only difference from the previous example is the first argument,
22827 specifying that you are communicating with the host @value{GDBN} via
22828 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22829 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22830 (Currently, the @samp{host} part is ignored.) You can choose any number
22831 you want for the port number as long as it does not conflict with any
22832 TCP ports already in use on the target system (for example, @code{23} is
22833 reserved for @code{telnet}).@footnote{If you choose a port number that
22834 conflicts with another service, @code{gdbserver} prints an error message
22835 and exits.} You must use the same port number with the host @value{GDBN}
22836 @code{target remote} command.
22838 The @code{stdio} connection is useful when starting @code{gdbserver}
22842 (gdb) target remote | ssh -T hostname gdbserver - hello
22845 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22846 and we don't want escape-character handling. Ssh does this by default when
22847 a command is provided, the flag is provided to make it explicit.
22848 You could elide it if you want to.
22850 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22851 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22852 display through a pipe connected to gdbserver.
22853 Both @code{stdout} and @code{stderr} use the same pipe.
22855 @anchor{Attaching to a program}
22856 @subsubsection Attaching to a Running Program
22857 @cindex attach to a program, @code{gdbserver}
22858 @cindex @option{--attach}, @code{gdbserver} option
22860 On some targets, @code{gdbserver} can also attach to running programs.
22861 This is accomplished via the @code{--attach} argument. The syntax is:
22864 target> gdbserver --attach @var{comm} @var{pid}
22867 @var{pid} is the process ID of a currently running process. It isn't
22868 necessary to point @code{gdbserver} at a binary for the running process.
22870 In @code{target extended-remote} mode, you can also attach using the
22871 @value{GDBN} attach command
22872 (@pxref{Attaching in Types of Remote Connections}).
22875 You can debug processes by name instead of process ID if your target has the
22876 @code{pidof} utility:
22879 target> gdbserver --attach @var{comm} `pidof @var{program}`
22882 In case more than one copy of @var{program} is running, or @var{program}
22883 has multiple threads, most versions of @code{pidof} support the
22884 @code{-s} option to only return the first process ID.
22886 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22888 This section applies only when @code{gdbserver} is run to listen on a TCP
22891 @code{gdbserver} normally terminates after all of its debugged processes have
22892 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22893 extended-remote}, @code{gdbserver} stays running even with no processes left.
22894 @value{GDBN} normally terminates the spawned debugged process on its exit,
22895 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22896 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22897 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22898 stays running even in the @kbd{target remote} mode.
22900 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22901 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22902 completeness, at most one @value{GDBN} can be connected at a time.
22904 @cindex @option{--once}, @code{gdbserver} option
22905 By default, @code{gdbserver} keeps the listening TCP port open, so that
22906 subsequent connections are possible. However, if you start @code{gdbserver}
22907 with the @option{--once} option, it will stop listening for any further
22908 connection attempts after connecting to the first @value{GDBN} session. This
22909 means no further connections to @code{gdbserver} will be possible after the
22910 first one. It also means @code{gdbserver} will terminate after the first
22911 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22912 connections and even in the @kbd{target extended-remote} mode. The
22913 @option{--once} option allows reusing the same port number for connecting to
22914 multiple instances of @code{gdbserver} running on the same host, since each
22915 instance closes its port after the first connection.
22917 @anchor{Other Command-Line Arguments for gdbserver}
22918 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22920 You can use the @option{--multi} option to start @code{gdbserver} without
22921 specifying a program to debug or a process to attach to. Then you can
22922 attach in @code{target extended-remote} mode and run or attach to a
22923 program. For more information,
22924 @pxref{--multi Option in Types of Remote Connnections}.
22926 @cindex @option{--debug}, @code{gdbserver} option
22927 The @option{--debug} option tells @code{gdbserver} to display extra
22928 status information about the debugging process.
22929 @cindex @option{--remote-debug}, @code{gdbserver} option
22930 The @option{--remote-debug} option tells @code{gdbserver} to display
22931 remote protocol debug output.
22932 @cindex @option{--debug-file}, @code{gdbserver} option
22933 @cindex @code{gdbserver}, send all debug output to a single file
22934 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22935 write any debug output to the given @var{filename}. These options are intended
22936 for @code{gdbserver} development and for bug reports to the developers.
22938 @cindex @option{--debug-format}, @code{gdbserver} option
22939 The @option{--debug-format=option1[,option2,...]} option tells
22940 @code{gdbserver} to include additional information in each output.
22941 Possible options are:
22945 Turn off all extra information in debugging output.
22947 Turn on all extra information in debugging output.
22949 Include a timestamp in each line of debugging output.
22952 Options are processed in order. Thus, for example, if @option{none}
22953 appears last then no additional information is added to debugging output.
22955 @cindex @option{--wrapper}, @code{gdbserver} option
22956 The @option{--wrapper} option specifies a wrapper to launch programs
22957 for debugging. The option should be followed by the name of the
22958 wrapper, then any command-line arguments to pass to the wrapper, then
22959 @kbd{--} indicating the end of the wrapper arguments.
22961 @code{gdbserver} runs the specified wrapper program with a combined
22962 command line including the wrapper arguments, then the name of the
22963 program to debug, then any arguments to the program. The wrapper
22964 runs until it executes your program, and then @value{GDBN} gains control.
22966 You can use any program that eventually calls @code{execve} with
22967 its arguments as a wrapper. Several standard Unix utilities do
22968 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22969 with @code{exec "$@@"} will also work.
22971 For example, you can use @code{env} to pass an environment variable to
22972 the debugged program, without setting the variable in @code{gdbserver}'s
22976 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22979 @cindex @option{--selftest}
22980 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22983 $ gdbserver --selftest
22984 Ran 2 unit tests, 0 failed
22987 These tests are disabled in release.
22988 @subsection Connecting to @code{gdbserver}
22990 The basic procedure for connecting to the remote target is:
22994 Run @value{GDBN} on the host system.
22997 Make sure you have the necessary symbol files
22998 (@pxref{Host and target files}).
22999 Load symbols for your application using the @code{file} command before you
23000 connect. Use @code{set sysroot} to locate target libraries (unless your
23001 @value{GDBN} was compiled with the correct sysroot using
23002 @code{--with-sysroot}).
23005 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23006 For TCP connections, you must start up @code{gdbserver} prior to using
23007 the @code{target} command. Otherwise you may get an error whose
23008 text depends on the host system, but which usually looks something like
23009 @samp{Connection refused}. Don't use the @code{load}
23010 command in @value{GDBN} when using @code{target remote} mode, since the
23011 program is already on the target.
23015 @anchor{Monitor Commands for gdbserver}
23016 @subsection Monitor Commands for @code{gdbserver}
23017 @cindex monitor commands, for @code{gdbserver}
23019 During a @value{GDBN} session using @code{gdbserver}, you can use the
23020 @code{monitor} command to send special requests to @code{gdbserver}.
23021 Here are the available commands.
23025 List the available monitor commands.
23027 @item monitor set debug 0
23028 @itemx monitor set debug 1
23029 Disable or enable general debugging messages.
23031 @item monitor set remote-debug 0
23032 @itemx monitor set remote-debug 1
23033 Disable or enable specific debugging messages associated with the remote
23034 protocol (@pxref{Remote Protocol}).
23036 @item monitor set debug-file filename
23037 @itemx monitor set debug-file
23038 Send any debug output to the given file, or to stderr.
23040 @item monitor set debug-format option1@r{[},option2,...@r{]}
23041 Specify additional text to add to debugging messages.
23042 Possible options are:
23046 Turn off all extra information in debugging output.
23048 Turn on all extra information in debugging output.
23050 Include a timestamp in each line of debugging output.
23053 Options are processed in order. Thus, for example, if @option{none}
23054 appears last then no additional information is added to debugging output.
23056 @item monitor set libthread-db-search-path [PATH]
23057 @cindex gdbserver, search path for @code{libthread_db}
23058 When this command is issued, @var{path} is a colon-separated list of
23059 directories to search for @code{libthread_db} (@pxref{Threads,,set
23060 libthread-db-search-path}). If you omit @var{path},
23061 @samp{libthread-db-search-path} will be reset to its default value.
23063 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23064 not supported in @code{gdbserver}.
23067 Tell gdbserver to exit immediately. This command should be followed by
23068 @code{disconnect} to close the debugging session. @code{gdbserver} will
23069 detach from any attached processes and kill any processes it created.
23070 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23071 of a multi-process mode debug session.
23075 @subsection Tracepoints support in @code{gdbserver}
23076 @cindex tracepoints support in @code{gdbserver}
23078 On some targets, @code{gdbserver} supports tracepoints, fast
23079 tracepoints and static tracepoints.
23081 For fast or static tracepoints to work, a special library called the
23082 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23083 This library is built and distributed as an integral part of
23084 @code{gdbserver}. In addition, support for static tracepoints
23085 requires building the in-process agent library with static tracepoints
23086 support. At present, the UST (LTTng Userspace Tracer,
23087 @url{http://lttng.org/ust}) tracing engine is supported. This support
23088 is automatically available if UST development headers are found in the
23089 standard include path when @code{gdbserver} is built, or if
23090 @code{gdbserver} was explicitly configured using @option{--with-ust}
23091 to point at such headers. You can explicitly disable the support
23092 using @option{--with-ust=no}.
23094 There are several ways to load the in-process agent in your program:
23097 @item Specifying it as dependency at link time
23099 You can link your program dynamically with the in-process agent
23100 library. On most systems, this is accomplished by adding
23101 @code{-linproctrace} to the link command.
23103 @item Using the system's preloading mechanisms
23105 You can force loading the in-process agent at startup time by using
23106 your system's support for preloading shared libraries. Many Unixes
23107 support the concept of preloading user defined libraries. In most
23108 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23109 in the environment. See also the description of @code{gdbserver}'s
23110 @option{--wrapper} command line option.
23112 @item Using @value{GDBN} to force loading the agent at run time
23114 On some systems, you can force the inferior to load a shared library,
23115 by calling a dynamic loader function in the inferior that takes care
23116 of dynamically looking up and loading a shared library. On most Unix
23117 systems, the function is @code{dlopen}. You'll use the @code{call}
23118 command for that. For example:
23121 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23124 Note that on most Unix systems, for the @code{dlopen} function to be
23125 available, the program needs to be linked with @code{-ldl}.
23128 On systems that have a userspace dynamic loader, like most Unix
23129 systems, when you connect to @code{gdbserver} using @code{target
23130 remote}, you'll find that the program is stopped at the dynamic
23131 loader's entry point, and no shared library has been loaded in the
23132 program's address space yet, including the in-process agent. In that
23133 case, before being able to use any of the fast or static tracepoints
23134 features, you need to let the loader run and load the shared
23135 libraries. The simplest way to do that is to run the program to the
23136 main procedure. E.g., if debugging a C or C@t{++} program, start
23137 @code{gdbserver} like so:
23140 $ gdbserver :9999 myprogram
23143 Start GDB and connect to @code{gdbserver} like so, and run to main:
23147 (@value{GDBP}) target remote myhost:9999
23148 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23149 (@value{GDBP}) b main
23150 (@value{GDBP}) continue
23153 The in-process tracing agent library should now be loaded into the
23154 process; you can confirm it with the @code{info sharedlibrary}
23155 command, which will list @file{libinproctrace.so} as loaded in the
23156 process. You are now ready to install fast tracepoints, list static
23157 tracepoint markers, probe static tracepoints markers, and start
23160 @node Remote Configuration
23161 @section Remote Configuration
23164 @kindex show remote
23165 This section documents the configuration options available when
23166 debugging remote programs. For the options related to the File I/O
23167 extensions of the remote protocol, see @ref{system,
23168 system-call-allowed}.
23171 @item set remoteaddresssize @var{bits}
23172 @cindex address size for remote targets
23173 @cindex bits in remote address
23174 Set the maximum size of address in a memory packet to the specified
23175 number of bits. @value{GDBN} will mask off the address bits above
23176 that number, when it passes addresses to the remote target. The
23177 default value is the number of bits in the target's address.
23179 @item show remoteaddresssize
23180 Show the current value of remote address size in bits.
23182 @item set serial baud @var{n}
23183 @cindex baud rate for remote targets
23184 Set the baud rate for the remote serial I/O to @var{n} baud. The
23185 value is used to set the speed of the serial port used for debugging
23188 @item show serial baud
23189 Show the current speed of the remote connection.
23191 @item set serial parity @var{parity}
23192 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23193 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23195 @item show serial parity
23196 Show the current parity of the serial port.
23198 @item set remotebreak
23199 @cindex interrupt remote programs
23200 @cindex BREAK signal instead of Ctrl-C
23201 @anchor{set remotebreak}
23202 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23203 when you type @kbd{Ctrl-c} to interrupt the program running
23204 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23205 character instead. The default is off, since most remote systems
23206 expect to see @samp{Ctrl-C} as the interrupt signal.
23208 @item show remotebreak
23209 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23210 interrupt the remote program.
23212 @item set remoteflow on
23213 @itemx set remoteflow off
23214 @kindex set remoteflow
23215 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23216 on the serial port used to communicate to the remote target.
23218 @item show remoteflow
23219 @kindex show remoteflow
23220 Show the current setting of hardware flow control.
23222 @item set remotelogbase @var{base}
23223 Set the base (a.k.a.@: radix) of logging serial protocol
23224 communications to @var{base}. Supported values of @var{base} are:
23225 @code{ascii}, @code{octal}, and @code{hex}. The default is
23228 @item show remotelogbase
23229 Show the current setting of the radix for logging remote serial
23232 @item set remotelogfile @var{file}
23233 @cindex record serial communications on file
23234 Record remote serial communications on the named @var{file}. The
23235 default is not to record at all.
23237 @item show remotelogfile
23238 Show the current setting of the file name on which to record the
23239 serial communications.
23241 @item set remotetimeout @var{num}
23242 @cindex timeout for serial communications
23243 @cindex remote timeout
23244 Set the timeout limit to wait for the remote target to respond to
23245 @var{num} seconds. The default is 2 seconds.
23247 @item show remotetimeout
23248 Show the current number of seconds to wait for the remote target
23251 @cindex limit hardware breakpoints and watchpoints
23252 @cindex remote target, limit break- and watchpoints
23253 @anchor{set remote hardware-watchpoint-limit}
23254 @anchor{set remote hardware-breakpoint-limit}
23255 @item set remote hardware-watchpoint-limit @var{limit}
23256 @itemx set remote hardware-breakpoint-limit @var{limit}
23257 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23258 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23259 watchpoints or breakpoints, and @code{unlimited} for unlimited
23260 watchpoints or breakpoints.
23262 @item show remote hardware-watchpoint-limit
23263 @itemx show remote hardware-breakpoint-limit
23264 Show the current limit for the number of hardware watchpoints or
23265 breakpoints that @value{GDBN} can use.
23267 @cindex limit hardware watchpoints length
23268 @cindex remote target, limit watchpoints length
23269 @anchor{set remote hardware-watchpoint-length-limit}
23270 @item set remote hardware-watchpoint-length-limit @var{limit}
23271 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23272 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23273 hardware watchpoints and @code{unlimited} allows watchpoints of any
23276 @item show remote hardware-watchpoint-length-limit
23277 Show the current limit (in bytes) of the maximum length of
23278 a remote hardware watchpoint.
23280 @item set remote exec-file @var{filename}
23281 @itemx show remote exec-file
23282 @anchor{set remote exec-file}
23283 @cindex executable file, for remote target
23284 Select the file used for @code{run} with @code{target
23285 extended-remote}. This should be set to a filename valid on the
23286 target system. If it is not set, the target will use a default
23287 filename (e.g.@: the last program run).
23289 @item set remote interrupt-sequence
23290 @cindex interrupt remote programs
23291 @cindex select Ctrl-C, BREAK or BREAK-g
23292 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23293 @samp{BREAK-g} as the
23294 sequence to the remote target in order to interrupt the execution.
23295 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23296 is high level of serial line for some certain time.
23297 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23298 It is @code{BREAK} signal followed by character @code{g}.
23300 @item show remote interrupt-sequence
23301 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23302 is sent by @value{GDBN} to interrupt the remote program.
23303 @code{BREAK-g} is BREAK signal followed by @code{g} and
23304 also known as Magic SysRq g.
23306 @item set remote interrupt-on-connect
23307 @cindex send interrupt-sequence on start
23308 Specify whether interrupt-sequence is sent to remote target when
23309 @value{GDBN} connects to it. This is mostly needed when you debug
23310 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23311 which is known as Magic SysRq g in order to connect @value{GDBN}.
23313 @item show remote interrupt-on-connect
23314 Show whether interrupt-sequence is sent
23315 to remote target when @value{GDBN} connects to it.
23319 @item set tcp auto-retry on
23320 @cindex auto-retry, for remote TCP target
23321 Enable auto-retry for remote TCP connections. This is useful if the remote
23322 debugging agent is launched in parallel with @value{GDBN}; there is a race
23323 condition because the agent may not become ready to accept the connection
23324 before @value{GDBN} attempts to connect. When auto-retry is
23325 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23326 to establish the connection using the timeout specified by
23327 @code{set tcp connect-timeout}.
23329 @item set tcp auto-retry off
23330 Do not auto-retry failed TCP connections.
23332 @item show tcp auto-retry
23333 Show the current auto-retry setting.
23335 @item set tcp connect-timeout @var{seconds}
23336 @itemx set tcp connect-timeout unlimited
23337 @cindex connection timeout, for remote TCP target
23338 @cindex timeout, for remote target connection
23339 Set the timeout for establishing a TCP connection to the remote target to
23340 @var{seconds}. The timeout affects both polling to retry failed connections
23341 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23342 that are merely slow to complete, and represents an approximate cumulative
23343 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23344 @value{GDBN} will keep attempting to establish a connection forever,
23345 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23347 @item show tcp connect-timeout
23348 Show the current connection timeout setting.
23351 @cindex remote packets, enabling and disabling
23352 The @value{GDBN} remote protocol autodetects the packets supported by
23353 your debugging stub. If you need to override the autodetection, you
23354 can use these commands to enable or disable individual packets. Each
23355 packet can be set to @samp{on} (the remote target supports this
23356 packet), @samp{off} (the remote target does not support this packet),
23357 or @samp{auto} (detect remote target support for this packet). They
23358 all default to @samp{auto}. For more information about each packet,
23359 see @ref{Remote Protocol}.
23361 During normal use, you should not have to use any of these commands.
23362 If you do, that may be a bug in your remote debugging stub, or a bug
23363 in @value{GDBN}. You may want to report the problem to the
23364 @value{GDBN} developers.
23366 For each packet @var{name}, the command to enable or disable the
23367 packet is @code{set remote @var{name}-packet}. The available settings
23370 @multitable @columnfractions 0.28 0.32 0.25
23373 @tab Related Features
23375 @item @code{fetch-register}
23377 @tab @code{info registers}
23379 @item @code{set-register}
23383 @item @code{binary-download}
23385 @tab @code{load}, @code{set}
23387 @item @code{read-aux-vector}
23388 @tab @code{qXfer:auxv:read}
23389 @tab @code{info auxv}
23391 @item @code{symbol-lookup}
23392 @tab @code{qSymbol}
23393 @tab Detecting multiple threads
23395 @item @code{attach}
23396 @tab @code{vAttach}
23399 @item @code{verbose-resume}
23401 @tab Stepping or resuming multiple threads
23407 @item @code{software-breakpoint}
23411 @item @code{hardware-breakpoint}
23415 @item @code{write-watchpoint}
23419 @item @code{read-watchpoint}
23423 @item @code{access-watchpoint}
23427 @item @code{pid-to-exec-file}
23428 @tab @code{qXfer:exec-file:read}
23429 @tab @code{attach}, @code{run}
23431 @item @code{target-features}
23432 @tab @code{qXfer:features:read}
23433 @tab @code{set architecture}
23435 @item @code{library-info}
23436 @tab @code{qXfer:libraries:read}
23437 @tab @code{info sharedlibrary}
23439 @item @code{memory-map}
23440 @tab @code{qXfer:memory-map:read}
23441 @tab @code{info mem}
23443 @item @code{read-sdata-object}
23444 @tab @code{qXfer:sdata:read}
23445 @tab @code{print $_sdata}
23447 @item @code{read-siginfo-object}
23448 @tab @code{qXfer:siginfo:read}
23449 @tab @code{print $_siginfo}
23451 @item @code{write-siginfo-object}
23452 @tab @code{qXfer:siginfo:write}
23453 @tab @code{set $_siginfo}
23455 @item @code{threads}
23456 @tab @code{qXfer:threads:read}
23457 @tab @code{info threads}
23459 @item @code{get-thread-local-@*storage-address}
23460 @tab @code{qGetTLSAddr}
23461 @tab Displaying @code{__thread} variables
23463 @item @code{get-thread-information-block-address}
23464 @tab @code{qGetTIBAddr}
23465 @tab Display MS-Windows Thread Information Block.
23467 @item @code{search-memory}
23468 @tab @code{qSearch:memory}
23471 @item @code{supported-packets}
23472 @tab @code{qSupported}
23473 @tab Remote communications parameters
23475 @item @code{catch-syscalls}
23476 @tab @code{QCatchSyscalls}
23477 @tab @code{catch syscall}
23479 @item @code{pass-signals}
23480 @tab @code{QPassSignals}
23481 @tab @code{handle @var{signal}}
23483 @item @code{program-signals}
23484 @tab @code{QProgramSignals}
23485 @tab @code{handle @var{signal}}
23487 @item @code{hostio-close-packet}
23488 @tab @code{vFile:close}
23489 @tab @code{remote get}, @code{remote put}
23491 @item @code{hostio-open-packet}
23492 @tab @code{vFile:open}
23493 @tab @code{remote get}, @code{remote put}
23495 @item @code{hostio-pread-packet}
23496 @tab @code{vFile:pread}
23497 @tab @code{remote get}, @code{remote put}
23499 @item @code{hostio-pwrite-packet}
23500 @tab @code{vFile:pwrite}
23501 @tab @code{remote get}, @code{remote put}
23503 @item @code{hostio-unlink-packet}
23504 @tab @code{vFile:unlink}
23505 @tab @code{remote delete}
23507 @item @code{hostio-readlink-packet}
23508 @tab @code{vFile:readlink}
23511 @item @code{hostio-fstat-packet}
23512 @tab @code{vFile:fstat}
23515 @item @code{hostio-setfs-packet}
23516 @tab @code{vFile:setfs}
23519 @item @code{noack-packet}
23520 @tab @code{QStartNoAckMode}
23521 @tab Packet acknowledgment
23523 @item @code{osdata}
23524 @tab @code{qXfer:osdata:read}
23525 @tab @code{info os}
23527 @item @code{query-attached}
23528 @tab @code{qAttached}
23529 @tab Querying remote process attach state.
23531 @item @code{trace-buffer-size}
23532 @tab @code{QTBuffer:size}
23533 @tab @code{set trace-buffer-size}
23535 @item @code{trace-status}
23536 @tab @code{qTStatus}
23537 @tab @code{tstatus}
23539 @item @code{traceframe-info}
23540 @tab @code{qXfer:traceframe-info:read}
23541 @tab Traceframe info
23543 @item @code{install-in-trace}
23544 @tab @code{InstallInTrace}
23545 @tab Install tracepoint in tracing
23547 @item @code{disable-randomization}
23548 @tab @code{QDisableRandomization}
23549 @tab @code{set disable-randomization}
23551 @item @code{startup-with-shell}
23552 @tab @code{QStartupWithShell}
23553 @tab @code{set startup-with-shell}
23555 @item @code{environment-hex-encoded}
23556 @tab @code{QEnvironmentHexEncoded}
23557 @tab @code{set environment}
23559 @item @code{environment-unset}
23560 @tab @code{QEnvironmentUnset}
23561 @tab @code{unset environment}
23563 @item @code{environment-reset}
23564 @tab @code{QEnvironmentReset}
23565 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23567 @item @code{set-working-dir}
23568 @tab @code{QSetWorkingDir}
23569 @tab @code{set cwd}
23571 @item @code{conditional-breakpoints-packet}
23572 @tab @code{Z0 and Z1}
23573 @tab @code{Support for target-side breakpoint condition evaluation}
23575 @item @code{multiprocess-extensions}
23576 @tab @code{multiprocess extensions}
23577 @tab Debug multiple processes and remote process PID awareness
23579 @item @code{swbreak-feature}
23580 @tab @code{swbreak stop reason}
23583 @item @code{hwbreak-feature}
23584 @tab @code{hwbreak stop reason}
23587 @item @code{fork-event-feature}
23588 @tab @code{fork stop reason}
23591 @item @code{vfork-event-feature}
23592 @tab @code{vfork stop reason}
23595 @item @code{exec-event-feature}
23596 @tab @code{exec stop reason}
23599 @item @code{thread-events}
23600 @tab @code{QThreadEvents}
23601 @tab Tracking thread lifetime.
23603 @item @code{no-resumed-stop-reply}
23604 @tab @code{no resumed thread left stop reply}
23605 @tab Tracking thread lifetime.
23610 @section Implementing a Remote Stub
23612 @cindex debugging stub, example
23613 @cindex remote stub, example
23614 @cindex stub example, remote debugging
23615 The stub files provided with @value{GDBN} implement the target side of the
23616 communication protocol, and the @value{GDBN} side is implemented in the
23617 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23618 these subroutines to communicate, and ignore the details. (If you're
23619 implementing your own stub file, you can still ignore the details: start
23620 with one of the existing stub files. @file{sparc-stub.c} is the best
23621 organized, and therefore the easiest to read.)
23623 @cindex remote serial debugging, overview
23624 To debug a program running on another machine (the debugging
23625 @dfn{target} machine), you must first arrange for all the usual
23626 prerequisites for the program to run by itself. For example, for a C
23631 A startup routine to set up the C runtime environment; these usually
23632 have a name like @file{crt0}. The startup routine may be supplied by
23633 your hardware supplier, or you may have to write your own.
23636 A C subroutine library to support your program's
23637 subroutine calls, notably managing input and output.
23640 A way of getting your program to the other machine---for example, a
23641 download program. These are often supplied by the hardware
23642 manufacturer, but you may have to write your own from hardware
23646 The next step is to arrange for your program to use a serial port to
23647 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23648 machine). In general terms, the scheme looks like this:
23652 @value{GDBN} already understands how to use this protocol; when everything
23653 else is set up, you can simply use the @samp{target remote} command
23654 (@pxref{Targets,,Specifying a Debugging Target}).
23656 @item On the target,
23657 you must link with your program a few special-purpose subroutines that
23658 implement the @value{GDBN} remote serial protocol. The file containing these
23659 subroutines is called a @dfn{debugging stub}.
23661 On certain remote targets, you can use an auxiliary program
23662 @code{gdbserver} instead of linking a stub into your program.
23663 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23666 The debugging stub is specific to the architecture of the remote
23667 machine; for example, use @file{sparc-stub.c} to debug programs on
23670 @cindex remote serial stub list
23671 These working remote stubs are distributed with @value{GDBN}:
23676 @cindex @file{i386-stub.c}
23679 For Intel 386 and compatible architectures.
23682 @cindex @file{m68k-stub.c}
23683 @cindex Motorola 680x0
23685 For Motorola 680x0 architectures.
23688 @cindex @file{sh-stub.c}
23691 For Renesas SH architectures.
23694 @cindex @file{sparc-stub.c}
23696 For @sc{sparc} architectures.
23698 @item sparcl-stub.c
23699 @cindex @file{sparcl-stub.c}
23702 For Fujitsu @sc{sparclite} architectures.
23706 The @file{README} file in the @value{GDBN} distribution may list other
23707 recently added stubs.
23710 * Stub Contents:: What the stub can do for you
23711 * Bootstrapping:: What you must do for the stub
23712 * Debug Session:: Putting it all together
23715 @node Stub Contents
23716 @subsection What the Stub Can Do for You
23718 @cindex remote serial stub
23719 The debugging stub for your architecture supplies these three
23723 @item set_debug_traps
23724 @findex set_debug_traps
23725 @cindex remote serial stub, initialization
23726 This routine arranges for @code{handle_exception} to run when your
23727 program stops. You must call this subroutine explicitly in your
23728 program's startup code.
23730 @item handle_exception
23731 @findex handle_exception
23732 @cindex remote serial stub, main routine
23733 This is the central workhorse, but your program never calls it
23734 explicitly---the setup code arranges for @code{handle_exception} to
23735 run when a trap is triggered.
23737 @code{handle_exception} takes control when your program stops during
23738 execution (for example, on a breakpoint), and mediates communications
23739 with @value{GDBN} on the host machine. This is where the communications
23740 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23741 representative on the target machine. It begins by sending summary
23742 information on the state of your program, then continues to execute,
23743 retrieving and transmitting any information @value{GDBN} needs, until you
23744 execute a @value{GDBN} command that makes your program resume; at that point,
23745 @code{handle_exception} returns control to your own code on the target
23749 @cindex @code{breakpoint} subroutine, remote
23750 Use this auxiliary subroutine to make your program contain a
23751 breakpoint. Depending on the particular situation, this may be the only
23752 way for @value{GDBN} to get control. For instance, if your target
23753 machine has some sort of interrupt button, you won't need to call this;
23754 pressing the interrupt button transfers control to
23755 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23756 simply receiving characters on the serial port may also trigger a trap;
23757 again, in that situation, you don't need to call @code{breakpoint} from
23758 your own program---simply running @samp{target remote} from the host
23759 @value{GDBN} session gets control.
23761 Call @code{breakpoint} if none of these is true, or if you simply want
23762 to make certain your program stops at a predetermined point for the
23763 start of your debugging session.
23766 @node Bootstrapping
23767 @subsection What You Must Do for the Stub
23769 @cindex remote stub, support routines
23770 The debugging stubs that come with @value{GDBN} are set up for a particular
23771 chip architecture, but they have no information about the rest of your
23772 debugging target machine.
23774 First of all you need to tell the stub how to communicate with the
23778 @item int getDebugChar()
23779 @findex getDebugChar
23780 Write this subroutine to read a single character from the serial port.
23781 It may be identical to @code{getchar} for your target system; a
23782 different name is used to allow you to distinguish the two if you wish.
23784 @item void putDebugChar(int)
23785 @findex putDebugChar
23786 Write this subroutine to write a single character to the serial port.
23787 It may be identical to @code{putchar} for your target system; a
23788 different name is used to allow you to distinguish the two if you wish.
23791 @cindex control C, and remote debugging
23792 @cindex interrupting remote targets
23793 If you want @value{GDBN} to be able to stop your program while it is
23794 running, you need to use an interrupt-driven serial driver, and arrange
23795 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23796 character). That is the character which @value{GDBN} uses to tell the
23797 remote system to stop.
23799 Getting the debugging target to return the proper status to @value{GDBN}
23800 probably requires changes to the standard stub; one quick and dirty way
23801 is to just execute a breakpoint instruction (the ``dirty'' part is that
23802 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23804 Other routines you need to supply are:
23807 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23808 @findex exceptionHandler
23809 Write this function to install @var{exception_address} in the exception
23810 handling tables. You need to do this because the stub does not have any
23811 way of knowing what the exception handling tables on your target system
23812 are like (for example, the processor's table might be in @sc{rom},
23813 containing entries which point to a table in @sc{ram}).
23814 The @var{exception_number} specifies the exception which should be changed;
23815 its meaning is architecture-dependent (for example, different numbers
23816 might represent divide by zero, misaligned access, etc). When this
23817 exception occurs, control should be transferred directly to
23818 @var{exception_address}, and the processor state (stack, registers,
23819 and so on) should be just as it is when a processor exception occurs. So if
23820 you want to use a jump instruction to reach @var{exception_address}, it
23821 should be a simple jump, not a jump to subroutine.
23823 For the 386, @var{exception_address} should be installed as an interrupt
23824 gate so that interrupts are masked while the handler runs. The gate
23825 should be at privilege level 0 (the most privileged level). The
23826 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23827 help from @code{exceptionHandler}.
23829 @item void flush_i_cache()
23830 @findex flush_i_cache
23831 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23832 instruction cache, if any, on your target machine. If there is no
23833 instruction cache, this subroutine may be a no-op.
23835 On target machines that have instruction caches, @value{GDBN} requires this
23836 function to make certain that the state of your program is stable.
23840 You must also make sure this library routine is available:
23843 @item void *memset(void *, int, int)
23845 This is the standard library function @code{memset} that sets an area of
23846 memory to a known value. If you have one of the free versions of
23847 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23848 either obtain it from your hardware manufacturer, or write your own.
23851 If you do not use the GNU C compiler, you may need other standard
23852 library subroutines as well; this varies from one stub to another,
23853 but in general the stubs are likely to use any of the common library
23854 subroutines which @code{@value{NGCC}} generates as inline code.
23857 @node Debug Session
23858 @subsection Putting it All Together
23860 @cindex remote serial debugging summary
23861 In summary, when your program is ready to debug, you must follow these
23866 Make sure you have defined the supporting low-level routines
23867 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23869 @code{getDebugChar}, @code{putDebugChar},
23870 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23874 Insert these lines in your program's startup code, before the main
23875 procedure is called:
23882 On some machines, when a breakpoint trap is raised, the hardware
23883 automatically makes the PC point to the instruction after the
23884 breakpoint. If your machine doesn't do that, you may need to adjust
23885 @code{handle_exception} to arrange for it to return to the instruction
23886 after the breakpoint on this first invocation, so that your program
23887 doesn't keep hitting the initial breakpoint instead of making
23891 For the 680x0 stub only, you need to provide a variable called
23892 @code{exceptionHook}. Normally you just use:
23895 void (*exceptionHook)() = 0;
23899 but if before calling @code{set_debug_traps}, you set it to point to a
23900 function in your program, that function is called when
23901 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23902 error). The function indicated by @code{exceptionHook} is called with
23903 one parameter: an @code{int} which is the exception number.
23906 Compile and link together: your program, the @value{GDBN} debugging stub for
23907 your target architecture, and the supporting subroutines.
23910 Make sure you have a serial connection between your target machine and
23911 the @value{GDBN} host, and identify the serial port on the host.
23914 @c The "remote" target now provides a `load' command, so we should
23915 @c document that. FIXME.
23916 Download your program to your target machine (or get it there by
23917 whatever means the manufacturer provides), and start it.
23920 Start @value{GDBN} on the host, and connect to the target
23921 (@pxref{Connecting,,Connecting to a Remote Target}).
23925 @node Configurations
23926 @chapter Configuration-Specific Information
23928 While nearly all @value{GDBN} commands are available for all native and
23929 cross versions of the debugger, there are some exceptions. This chapter
23930 describes things that are only available in certain configurations.
23932 There are three major categories of configurations: native
23933 configurations, where the host and target are the same, embedded
23934 operating system configurations, which are usually the same for several
23935 different processor architectures, and bare embedded processors, which
23936 are quite different from each other.
23941 * Embedded Processors::
23948 This section describes details specific to particular native
23952 * BSD libkvm Interface:: Debugging BSD kernel memory images
23953 * Process Information:: Process information
23954 * DJGPP Native:: Features specific to the DJGPP port
23955 * Cygwin Native:: Features specific to the Cygwin port
23956 * Hurd Native:: Features specific to @sc{gnu} Hurd
23957 * Darwin:: Features specific to Darwin
23958 * FreeBSD:: Features specific to FreeBSD
23961 @node BSD libkvm Interface
23962 @subsection BSD libkvm Interface
23965 @cindex kernel memory image
23966 @cindex kernel crash dump
23968 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23969 interface that provides a uniform interface for accessing kernel virtual
23970 memory images, including live systems and crash dumps. @value{GDBN}
23971 uses this interface to allow you to debug live kernels and kernel crash
23972 dumps on many native BSD configurations. This is implemented as a
23973 special @code{kvm} debugging target. For debugging a live system, load
23974 the currently running kernel into @value{GDBN} and connect to the
23978 (@value{GDBP}) @b{target kvm}
23981 For debugging crash dumps, provide the file name of the crash dump as an
23985 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23988 Once connected to the @code{kvm} target, the following commands are
23994 Set current context from the @dfn{Process Control Block} (PCB) address.
23997 Set current context from proc address. This command isn't available on
23998 modern FreeBSD systems.
24001 @node Process Information
24002 @subsection Process Information
24004 @cindex examine process image
24005 @cindex process info via @file{/proc}
24007 Some operating systems provide interfaces to fetch additional
24008 information about running processes beyond memory and per-thread
24009 register state. If @value{GDBN} is configured for an operating system
24010 with a supported interface, the command @code{info proc} is available
24011 to report information about the process running your program, or about
24012 any process running on your system.
24014 One supported interface is a facility called @samp{/proc} that can be
24015 used to examine the image of a running process using file-system
24016 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24019 On FreeBSD and NetBSD systems, system control nodes are used to query
24020 process information.
24022 In addition, some systems may provide additional process information
24023 in core files. Note that a core file may include a subset of the
24024 information available from a live process. Process information is
24025 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24032 @itemx info proc @var{process-id}
24033 Summarize available information about a process. If a
24034 process ID is specified by @var{process-id}, display information about
24035 that process; otherwise display information about the program being
24036 debugged. The summary includes the debugged process ID, the command
24037 line used to invoke it, its current working directory, and its
24038 executable file's absolute file name.
24040 On some systems, @var{process-id} can be of the form
24041 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24042 within a process. If the optional @var{pid} part is missing, it means
24043 a thread from the process being debugged (the leading @samp{/} still
24044 needs to be present, or else @value{GDBN} will interpret the number as
24045 a process ID rather than a thread ID).
24047 @item info proc cmdline
24048 @cindex info proc cmdline
24049 Show the original command line of the process. This command is
24050 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24052 @item info proc cwd
24053 @cindex info proc cwd
24054 Show the current working directory of the process. This command is
24055 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24057 @item info proc exe
24058 @cindex info proc exe
24059 Show the name of executable of the process. This command is supported
24060 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24062 @item info proc files
24063 @cindex info proc files
24064 Show the file descriptors open by the process. For each open file
24065 descriptor, @value{GDBN} shows its number, type (file, directory,
24066 character device, socket), file pointer offset, and the name of the
24067 resource open on the descriptor. The resource name can be a file name
24068 (for files, directories, and devices) or a protocol followed by socket
24069 address (for network connections). This command is supported on
24072 This example shows the open file descriptors for a process using a
24073 tty for standard input and output as well as two network sockets:
24076 (gdb) info proc files 22136
24080 FD Type Offset Flags Name
24081 text file - r-------- /usr/bin/ssh
24082 ctty chr - rw------- /dev/pts/20
24083 cwd dir - r-------- /usr/home/john
24084 root dir - r-------- /
24085 0 chr 0x32933a4 rw------- /dev/pts/20
24086 1 chr 0x32933a4 rw------- /dev/pts/20
24087 2 chr 0x32933a4 rw------- /dev/pts/20
24088 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24089 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24092 @item info proc mappings
24093 @cindex memory address space mappings
24094 Report the memory address space ranges accessible in a process. On
24095 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24096 on whether the process has read, write, or execute access rights to each
24097 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24098 includes the object file which is mapped to that range.
24100 @item info proc stat
24101 @itemx info proc status
24102 @cindex process detailed status information
24103 Show additional process-related information, including the user ID and
24104 group ID; virtual memory usage; the signals that are pending, blocked,
24105 and ignored; its TTY; its consumption of system and user time; its
24106 stack size; its @samp{nice} value; etc. These commands are supported
24107 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24109 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24110 information (type @kbd{man 5 proc} from your shell prompt).
24112 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24113 @code{info proc status}.
24115 @item info proc all
24116 Show all the information about the process described under all of the
24117 above @code{info proc} subcommands.
24120 @comment These sub-options of 'info proc' were not included when
24121 @comment procfs.c was re-written. Keep their descriptions around
24122 @comment against the day when someone finds the time to put them back in.
24123 @kindex info proc times
24124 @item info proc times
24125 Starting time, user CPU time, and system CPU time for your program and
24128 @kindex info proc id
24130 Report on the process IDs related to your program: its own process ID,
24131 the ID of its parent, the process group ID, and the session ID.
24134 @item set procfs-trace
24135 @kindex set procfs-trace
24136 @cindex @code{procfs} API calls
24137 This command enables and disables tracing of @code{procfs} API calls.
24139 @item show procfs-trace
24140 @kindex show procfs-trace
24141 Show the current state of @code{procfs} API call tracing.
24143 @item set procfs-file @var{file}
24144 @kindex set procfs-file
24145 Tell @value{GDBN} to write @code{procfs} API trace to the named
24146 @var{file}. @value{GDBN} appends the trace info to the previous
24147 contents of the file. The default is to display the trace on the
24150 @item show procfs-file
24151 @kindex show procfs-file
24152 Show the file to which @code{procfs} API trace is written.
24154 @item proc-trace-entry
24155 @itemx proc-trace-exit
24156 @itemx proc-untrace-entry
24157 @itemx proc-untrace-exit
24158 @kindex proc-trace-entry
24159 @kindex proc-trace-exit
24160 @kindex proc-untrace-entry
24161 @kindex proc-untrace-exit
24162 These commands enable and disable tracing of entries into and exits
24163 from the @code{syscall} interface.
24166 @kindex info pidlist
24167 @cindex process list, QNX Neutrino
24168 For QNX Neutrino only, this command displays the list of all the
24169 processes and all the threads within each process.
24172 @kindex info meminfo
24173 @cindex mapinfo list, QNX Neutrino
24174 For QNX Neutrino only, this command displays the list of all mapinfos.
24178 @subsection Features for Debugging @sc{djgpp} Programs
24179 @cindex @sc{djgpp} debugging
24180 @cindex native @sc{djgpp} debugging
24181 @cindex MS-DOS-specific commands
24184 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24185 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24186 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24187 top of real-mode DOS systems and their emulations.
24189 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24190 defines a few commands specific to the @sc{djgpp} port. This
24191 subsection describes those commands.
24196 This is a prefix of @sc{djgpp}-specific commands which print
24197 information about the target system and important OS structures.
24200 @cindex MS-DOS system info
24201 @cindex free memory information (MS-DOS)
24202 @item info dos sysinfo
24203 This command displays assorted information about the underlying
24204 platform: the CPU type and features, the OS version and flavor, the
24205 DPMI version, and the available conventional and DPMI memory.
24210 @cindex segment descriptor tables
24211 @cindex descriptor tables display
24213 @itemx info dos ldt
24214 @itemx info dos idt
24215 These 3 commands display entries from, respectively, Global, Local,
24216 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24217 tables are data structures which store a descriptor for each segment
24218 that is currently in use. The segment's selector is an index into a
24219 descriptor table; the table entry for that index holds the
24220 descriptor's base address and limit, and its attributes and access
24223 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24224 segment (used for both data and the stack), and a DOS segment (which
24225 allows access to DOS/BIOS data structures and absolute addresses in
24226 conventional memory). However, the DPMI host will usually define
24227 additional segments in order to support the DPMI environment.
24229 @cindex garbled pointers
24230 These commands allow to display entries from the descriptor tables.
24231 Without an argument, all entries from the specified table are
24232 displayed. An argument, which should be an integer expression, means
24233 display a single entry whose index is given by the argument. For
24234 example, here's a convenient way to display information about the
24235 debugged program's data segment:
24238 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24239 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24243 This comes in handy when you want to see whether a pointer is outside
24244 the data segment's limit (i.e.@: @dfn{garbled}).
24246 @cindex page tables display (MS-DOS)
24248 @itemx info dos pte
24249 These two commands display entries from, respectively, the Page
24250 Directory and the Page Tables. Page Directories and Page Tables are
24251 data structures which control how virtual memory addresses are mapped
24252 into physical addresses. A Page Table includes an entry for every
24253 page of memory that is mapped into the program's address space; there
24254 may be several Page Tables, each one holding up to 4096 entries. A
24255 Page Directory has up to 4096 entries, one each for every Page Table
24256 that is currently in use.
24258 Without an argument, @kbd{info dos pde} displays the entire Page
24259 Directory, and @kbd{info dos pte} displays all the entries in all of
24260 the Page Tables. An argument, an integer expression, given to the
24261 @kbd{info dos pde} command means display only that entry from the Page
24262 Directory table. An argument given to the @kbd{info dos pte} command
24263 means display entries from a single Page Table, the one pointed to by
24264 the specified entry in the Page Directory.
24266 @cindex direct memory access (DMA) on MS-DOS
24267 These commands are useful when your program uses @dfn{DMA} (Direct
24268 Memory Access), which needs physical addresses to program the DMA
24271 These commands are supported only with some DPMI servers.
24273 @cindex physical address from linear address
24274 @item info dos address-pte @var{addr}
24275 This command displays the Page Table entry for a specified linear
24276 address. The argument @var{addr} is a linear address which should
24277 already have the appropriate segment's base address added to it,
24278 because this command accepts addresses which may belong to @emph{any}
24279 segment. For example, here's how to display the Page Table entry for
24280 the page where a variable @code{i} is stored:
24283 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24284 @exdent @code{Page Table entry for address 0x11a00d30:}
24285 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24289 This says that @code{i} is stored at offset @code{0xd30} from the page
24290 whose physical base address is @code{0x02698000}, and shows all the
24291 attributes of that page.
24293 Note that you must cast the addresses of variables to a @code{char *},
24294 since otherwise the value of @code{__djgpp_base_address}, the base
24295 address of all variables and functions in a @sc{djgpp} program, will
24296 be added using the rules of C pointer arithmetics: if @code{i} is
24297 declared an @code{int}, @value{GDBN} will add 4 times the value of
24298 @code{__djgpp_base_address} to the address of @code{i}.
24300 Here's another example, it displays the Page Table entry for the
24304 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24305 @exdent @code{Page Table entry for address 0x29110:}
24306 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24310 (The @code{+ 3} offset is because the transfer buffer's address is the
24311 3rd member of the @code{_go32_info_block} structure.) The output
24312 clearly shows that this DPMI server maps the addresses in conventional
24313 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24314 linear (@code{0x29110}) addresses are identical.
24316 This command is supported only with some DPMI servers.
24319 @cindex DOS serial data link, remote debugging
24320 In addition to native debugging, the DJGPP port supports remote
24321 debugging via a serial data link. The following commands are specific
24322 to remote serial debugging in the DJGPP port of @value{GDBN}.
24325 @kindex set com1base
24326 @kindex set com1irq
24327 @kindex set com2base
24328 @kindex set com2irq
24329 @kindex set com3base
24330 @kindex set com3irq
24331 @kindex set com4base
24332 @kindex set com4irq
24333 @item set com1base @var{addr}
24334 This command sets the base I/O port address of the @file{COM1} serial
24337 @item set com1irq @var{irq}
24338 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24339 for the @file{COM1} serial port.
24341 There are similar commands @samp{set com2base}, @samp{set com3irq},
24342 etc.@: for setting the port address and the @code{IRQ} lines for the
24345 @kindex show com1base
24346 @kindex show com1irq
24347 @kindex show com2base
24348 @kindex show com2irq
24349 @kindex show com3base
24350 @kindex show com3irq
24351 @kindex show com4base
24352 @kindex show com4irq
24353 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24354 display the current settings of the base address and the @code{IRQ}
24355 lines used by the COM ports.
24358 @kindex info serial
24359 @cindex DOS serial port status
24360 This command prints the status of the 4 DOS serial ports. For each
24361 port, it prints whether it's active or not, its I/O base address and
24362 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24363 counts of various errors encountered so far.
24367 @node Cygwin Native
24368 @subsection Features for Debugging MS Windows PE Executables
24369 @cindex MS Windows debugging
24370 @cindex native Cygwin debugging
24371 @cindex Cygwin-specific commands
24373 @value{GDBN} supports native debugging of MS Windows programs, including
24374 DLLs with and without symbolic debugging information.
24376 @cindex Ctrl-BREAK, MS-Windows
24377 @cindex interrupt debuggee on MS-Windows
24378 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24379 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24380 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24381 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24382 sequence, which can be used to interrupt the debuggee even if it
24385 There are various additional Cygwin-specific commands, described in
24386 this section. Working with DLLs that have no debugging symbols is
24387 described in @ref{Non-debug DLL Symbols}.
24392 This is a prefix of MS Windows-specific commands which print
24393 information about the target system and important OS structures.
24395 @item info w32 selector
24396 This command displays information returned by
24397 the Win32 API @code{GetThreadSelectorEntry} function.
24398 It takes an optional argument that is evaluated to
24399 a long value to give the information about this given selector.
24400 Without argument, this command displays information
24401 about the six segment registers.
24403 @item info w32 thread-information-block
24404 This command displays thread specific information stored in the
24405 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24406 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24408 @kindex signal-event
24409 @item signal-event @var{id}
24410 This command signals an event with user-provided @var{id}. Used to resume
24411 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24413 To use it, create or edit the following keys in
24414 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24415 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24416 (for x86_64 versions):
24420 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24421 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24422 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24424 The first @code{%ld} will be replaced by the process ID of the
24425 crashing process, the second @code{%ld} will be replaced by the ID of
24426 the event that blocks the crashing process, waiting for @value{GDBN}
24430 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24431 make the system run debugger specified by the Debugger key
24432 automatically, @code{0} will cause a dialog box with ``OK'' and
24433 ``Cancel'' buttons to appear, which allows the user to either
24434 terminate the crashing process (OK) or debug it (Cancel).
24437 @kindex set cygwin-exceptions
24438 @cindex debugging the Cygwin DLL
24439 @cindex Cygwin DLL, debugging
24440 @item set cygwin-exceptions @var{mode}
24441 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24442 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24443 @value{GDBN} will delay recognition of exceptions, and may ignore some
24444 exceptions which seem to be caused by internal Cygwin DLL
24445 ``bookkeeping''. This option is meant primarily for debugging the
24446 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24447 @value{GDBN} users with false @code{SIGSEGV} signals.
24449 @kindex show cygwin-exceptions
24450 @item show cygwin-exceptions
24451 Displays whether @value{GDBN} will break on exceptions that happen
24452 inside the Cygwin DLL itself.
24454 @kindex set new-console
24455 @item set new-console @var{mode}
24456 If @var{mode} is @code{on} the debuggee will
24457 be started in a new console on next start.
24458 If @var{mode} is @code{off}, the debuggee will
24459 be started in the same console as the debugger.
24461 @kindex show new-console
24462 @item show new-console
24463 Displays whether a new console is used
24464 when the debuggee is started.
24466 @kindex set new-group
24467 @item set new-group @var{mode}
24468 This boolean value controls whether the debuggee should
24469 start a new group or stay in the same group as the debugger.
24470 This affects the way the Windows OS handles
24473 @kindex show new-group
24474 @item show new-group
24475 Displays current value of new-group boolean.
24477 @kindex set debugevents
24478 @item set debugevents
24479 This boolean value adds debug output concerning kernel events related
24480 to the debuggee seen by the debugger. This includes events that
24481 signal thread and process creation and exit, DLL loading and
24482 unloading, console interrupts, and debugging messages produced by the
24483 Windows @code{OutputDebugString} API call.
24485 @kindex set debugexec
24486 @item set debugexec
24487 This boolean value adds debug output concerning execute events
24488 (such as resume thread) seen by the debugger.
24490 @kindex set debugexceptions
24491 @item set debugexceptions
24492 This boolean value adds debug output concerning exceptions in the
24493 debuggee seen by the debugger.
24495 @kindex set debugmemory
24496 @item set debugmemory
24497 This boolean value adds debug output concerning debuggee memory reads
24498 and writes by the debugger.
24502 This boolean values specifies whether the debuggee is called
24503 via a shell or directly (default value is on).
24507 Displays if the debuggee will be started with a shell.
24512 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24515 @node Non-debug DLL Symbols
24516 @subsubsection Support for DLLs without Debugging Symbols
24517 @cindex DLLs with no debugging symbols
24518 @cindex Minimal symbols and DLLs
24520 Very often on windows, some of the DLLs that your program relies on do
24521 not include symbolic debugging information (for example,
24522 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24523 symbols in a DLL, it relies on the minimal amount of symbolic
24524 information contained in the DLL's export table. This section
24525 describes working with such symbols, known internally to @value{GDBN} as
24526 ``minimal symbols''.
24528 Note that before the debugged program has started execution, no DLLs
24529 will have been loaded. The easiest way around this problem is simply to
24530 start the program --- either by setting a breakpoint or letting the
24531 program run once to completion.
24533 @subsubsection DLL Name Prefixes
24535 In keeping with the naming conventions used by the Microsoft debugging
24536 tools, DLL export symbols are made available with a prefix based on the
24537 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24538 also entered into the symbol table, so @code{CreateFileA} is often
24539 sufficient. In some cases there will be name clashes within a program
24540 (particularly if the executable itself includes full debugging symbols)
24541 necessitating the use of the fully qualified name when referring to the
24542 contents of the DLL. Use single-quotes around the name to avoid the
24543 exclamation mark (``!'') being interpreted as a language operator.
24545 Note that the internal name of the DLL may be all upper-case, even
24546 though the file name of the DLL is lower-case, or vice-versa. Since
24547 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24548 some confusion. If in doubt, try the @code{info functions} and
24549 @code{info variables} commands or even @code{maint print msymbols}
24550 (@pxref{Symbols}). Here's an example:
24553 (@value{GDBP}) info function CreateFileA
24554 All functions matching regular expression "CreateFileA":
24556 Non-debugging symbols:
24557 0x77e885f4 CreateFileA
24558 0x77e885f4 KERNEL32!CreateFileA
24562 (@value{GDBP}) info function !
24563 All functions matching regular expression "!":
24565 Non-debugging symbols:
24566 0x6100114c cygwin1!__assert
24567 0x61004034 cygwin1!_dll_crt0@@0
24568 0x61004240 cygwin1!dll_crt0(per_process *)
24572 @subsubsection Working with Minimal Symbols
24574 Symbols extracted from a DLL's export table do not contain very much
24575 type information. All that @value{GDBN} can do is guess whether a symbol
24576 refers to a function or variable depending on the linker section that
24577 contains the symbol. Also note that the actual contents of the memory
24578 contained in a DLL are not available unless the program is running. This
24579 means that you cannot examine the contents of a variable or disassemble
24580 a function within a DLL without a running program.
24582 Variables are generally treated as pointers and dereferenced
24583 automatically. For this reason, it is often necessary to prefix a
24584 variable name with the address-of operator (``&'') and provide explicit
24585 type information in the command. Here's an example of the type of
24589 (@value{GDBP}) print 'cygwin1!__argv'
24590 'cygwin1!__argv' has unknown type; cast it to its declared type
24594 (@value{GDBP}) x 'cygwin1!__argv'
24595 'cygwin1!__argv' has unknown type; cast it to its declared type
24598 And two possible solutions:
24601 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24602 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24606 (@value{GDBP}) x/2x &'cygwin1!__argv'
24607 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24608 (@value{GDBP}) x/x 0x10021608
24609 0x10021608: 0x0022fd98
24610 (@value{GDBP}) x/s 0x0022fd98
24611 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24614 Setting a break point within a DLL is possible even before the program
24615 starts execution. However, under these circumstances, @value{GDBN} can't
24616 examine the initial instructions of the function in order to skip the
24617 function's frame set-up code. You can work around this by using ``*&''
24618 to set the breakpoint at a raw memory address:
24621 (@value{GDBP}) break *&'python22!PyOS_Readline'
24622 Breakpoint 1 at 0x1e04eff0
24625 The author of these extensions is not entirely convinced that setting a
24626 break point within a shared DLL like @file{kernel32.dll} is completely
24630 @subsection Commands Specific to @sc{gnu} Hurd Systems
24631 @cindex @sc{gnu} Hurd debugging
24633 This subsection describes @value{GDBN} commands specific to the
24634 @sc{gnu} Hurd native debugging.
24639 @kindex set signals@r{, Hurd command}
24640 @kindex set sigs@r{, Hurd command}
24641 This command toggles the state of inferior signal interception by
24642 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24643 affected by this command. @code{sigs} is a shorthand alias for
24648 @kindex show signals@r{, Hurd command}
24649 @kindex show sigs@r{, Hurd command}
24650 Show the current state of intercepting inferior's signals.
24652 @item set signal-thread
24653 @itemx set sigthread
24654 @kindex set signal-thread
24655 @kindex set sigthread
24656 This command tells @value{GDBN} which thread is the @code{libc} signal
24657 thread. That thread is run when a signal is delivered to a running
24658 process. @code{set sigthread} is the shorthand alias of @code{set
24661 @item show signal-thread
24662 @itemx show sigthread
24663 @kindex show signal-thread
24664 @kindex show sigthread
24665 These two commands show which thread will run when the inferior is
24666 delivered a signal.
24669 @kindex set stopped@r{, Hurd command}
24670 This commands tells @value{GDBN} that the inferior process is stopped,
24671 as with the @code{SIGSTOP} signal. The stopped process can be
24672 continued by delivering a signal to it.
24675 @kindex show stopped@r{, Hurd command}
24676 This command shows whether @value{GDBN} thinks the debuggee is
24679 @item set exceptions
24680 @kindex set exceptions@r{, Hurd command}
24681 Use this command to turn off trapping of exceptions in the inferior.
24682 When exception trapping is off, neither breakpoints nor
24683 single-stepping will work. To restore the default, set exception
24686 @item show exceptions
24687 @kindex show exceptions@r{, Hurd command}
24688 Show the current state of trapping exceptions in the inferior.
24690 @item set task pause
24691 @kindex set task@r{, Hurd commands}
24692 @cindex task attributes (@sc{gnu} Hurd)
24693 @cindex pause current task (@sc{gnu} Hurd)
24694 This command toggles task suspension when @value{GDBN} has control.
24695 Setting it to on takes effect immediately, and the task is suspended
24696 whenever @value{GDBN} gets control. Setting it to off will take
24697 effect the next time the inferior is continued. If this option is set
24698 to off, you can use @code{set thread default pause on} or @code{set
24699 thread pause on} (see below) to pause individual threads.
24701 @item show task pause
24702 @kindex show task@r{, Hurd commands}
24703 Show the current state of task suspension.
24705 @item set task detach-suspend-count
24706 @cindex task suspend count
24707 @cindex detach from task, @sc{gnu} Hurd
24708 This command sets the suspend count the task will be left with when
24709 @value{GDBN} detaches from it.
24711 @item show task detach-suspend-count
24712 Show the suspend count the task will be left with when detaching.
24714 @item set task exception-port
24715 @itemx set task excp
24716 @cindex task exception port, @sc{gnu} Hurd
24717 This command sets the task exception port to which @value{GDBN} will
24718 forward exceptions. The argument should be the value of the @dfn{send
24719 rights} of the task. @code{set task excp} is a shorthand alias.
24721 @item set noninvasive
24722 @cindex noninvasive task options
24723 This command switches @value{GDBN} to a mode that is the least
24724 invasive as far as interfering with the inferior is concerned. This
24725 is the same as using @code{set task pause}, @code{set exceptions}, and
24726 @code{set signals} to values opposite to the defaults.
24728 @item info send-rights
24729 @itemx info receive-rights
24730 @itemx info port-rights
24731 @itemx info port-sets
24732 @itemx info dead-names
24735 @cindex send rights, @sc{gnu} Hurd
24736 @cindex receive rights, @sc{gnu} Hurd
24737 @cindex port rights, @sc{gnu} Hurd
24738 @cindex port sets, @sc{gnu} Hurd
24739 @cindex dead names, @sc{gnu} Hurd
24740 These commands display information about, respectively, send rights,
24741 receive rights, port rights, port sets, and dead names of a task.
24742 There are also shorthand aliases: @code{info ports} for @code{info
24743 port-rights} and @code{info psets} for @code{info port-sets}.
24745 @item set thread pause
24746 @kindex set thread@r{, Hurd command}
24747 @cindex thread properties, @sc{gnu} Hurd
24748 @cindex pause current thread (@sc{gnu} Hurd)
24749 This command toggles current thread suspension when @value{GDBN} has
24750 control. Setting it to on takes effect immediately, and the current
24751 thread is suspended whenever @value{GDBN} gets control. Setting it to
24752 off will take effect the next time the inferior is continued.
24753 Normally, this command has no effect, since when @value{GDBN} has
24754 control, the whole task is suspended. However, if you used @code{set
24755 task pause off} (see above), this command comes in handy to suspend
24756 only the current thread.
24758 @item show thread pause
24759 @kindex show thread@r{, Hurd command}
24760 This command shows the state of current thread suspension.
24762 @item set thread run
24763 This command sets whether the current thread is allowed to run.
24765 @item show thread run
24766 Show whether the current thread is allowed to run.
24768 @item set thread detach-suspend-count
24769 @cindex thread suspend count, @sc{gnu} Hurd
24770 @cindex detach from thread, @sc{gnu} Hurd
24771 This command sets the suspend count @value{GDBN} will leave on a
24772 thread when detaching. This number is relative to the suspend count
24773 found by @value{GDBN} when it notices the thread; use @code{set thread
24774 takeover-suspend-count} to force it to an absolute value.
24776 @item show thread detach-suspend-count
24777 Show the suspend count @value{GDBN} will leave on the thread when
24780 @item set thread exception-port
24781 @itemx set thread excp
24782 Set the thread exception port to which to forward exceptions. This
24783 overrides the port set by @code{set task exception-port} (see above).
24784 @code{set thread excp} is the shorthand alias.
24786 @item set thread takeover-suspend-count
24787 Normally, @value{GDBN}'s thread suspend counts are relative to the
24788 value @value{GDBN} finds when it notices each thread. This command
24789 changes the suspend counts to be absolute instead.
24791 @item set thread default
24792 @itemx show thread default
24793 @cindex thread default settings, @sc{gnu} Hurd
24794 Each of the above @code{set thread} commands has a @code{set thread
24795 default} counterpart (e.g., @code{set thread default pause}, @code{set
24796 thread default exception-port}, etc.). The @code{thread default}
24797 variety of commands sets the default thread properties for all
24798 threads; you can then change the properties of individual threads with
24799 the non-default commands.
24806 @value{GDBN} provides the following commands specific to the Darwin target:
24809 @item set debug darwin @var{num}
24810 @kindex set debug darwin
24811 When set to a non zero value, enables debugging messages specific to
24812 the Darwin support. Higher values produce more verbose output.
24814 @item show debug darwin
24815 @kindex show debug darwin
24816 Show the current state of Darwin messages.
24818 @item set debug mach-o @var{num}
24819 @kindex set debug mach-o
24820 When set to a non zero value, enables debugging messages while
24821 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24822 file format used on Darwin for object and executable files.) Higher
24823 values produce more verbose output. This is a command to diagnose
24824 problems internal to @value{GDBN} and should not be needed in normal
24827 @item show debug mach-o
24828 @kindex show debug mach-o
24829 Show the current state of Mach-O file messages.
24831 @item set mach-exceptions on
24832 @itemx set mach-exceptions off
24833 @kindex set mach-exceptions
24834 On Darwin, faults are first reported as a Mach exception and are then
24835 mapped to a Posix signal. Use this command to turn on trapping of
24836 Mach exceptions in the inferior. This might be sometimes useful to
24837 better understand the cause of a fault. The default is off.
24839 @item show mach-exceptions
24840 @kindex show mach-exceptions
24841 Show the current state of exceptions trapping.
24845 @subsection FreeBSD
24848 When the ABI of a system call is changed in the FreeBSD kernel, this
24849 is implemented by leaving a compatibility system call using the old
24850 ABI at the existing number and allocating a new system call number for
24851 the version using the new ABI. As a convenience, when a system call
24852 is caught by name (@pxref{catch syscall}), compatibility system calls
24855 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24856 system call and catching the @code{kevent} system call by name catches
24860 (@value{GDBP}) catch syscall kevent
24861 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24867 @section Embedded Operating Systems
24869 This section describes configurations involving the debugging of
24870 embedded operating systems that are available for several different
24873 @value{GDBN} includes the ability to debug programs running on
24874 various real-time operating systems.
24876 @node Embedded Processors
24877 @section Embedded Processors
24879 This section goes into details specific to particular embedded
24882 @cindex send command to simulator
24883 Whenever a specific embedded processor has a simulator, @value{GDBN}
24884 allows to send an arbitrary command to the simulator.
24887 @item sim @var{command}
24888 @kindex sim@r{, a command}
24889 Send an arbitrary @var{command} string to the simulator. Consult the
24890 documentation for the specific simulator in use for information about
24891 acceptable commands.
24896 * ARC:: Synopsys ARC
24899 * M68K:: Motorola M68K
24900 * MicroBlaze:: Xilinx MicroBlaze
24901 * MIPS Embedded:: MIPS Embedded
24902 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24903 * PowerPC Embedded:: PowerPC Embedded
24906 * Super-H:: Renesas Super-H
24910 @subsection Synopsys ARC
24911 @cindex Synopsys ARC
24912 @cindex ARC specific commands
24918 @value{GDBN} provides the following ARC-specific commands:
24921 @item set debug arc
24922 @kindex set debug arc
24923 Control the level of ARC specific debug messages. Use 0 for no messages (the
24924 default), 1 for debug messages, and 2 for even more debug messages.
24926 @item show debug arc
24927 @kindex show debug arc
24928 Show the level of ARC specific debugging in operation.
24930 @item maint print arc arc-instruction @var{address}
24931 @kindex maint print arc arc-instruction
24932 Print internal disassembler information about instruction at a given address.
24939 @value{GDBN} provides the following ARM-specific commands:
24942 @item set arm disassembler
24944 This commands selects from a list of disassembly styles. The
24945 @code{"std"} style is the standard style.
24947 @item show arm disassembler
24949 Show the current disassembly style.
24951 @item set arm apcs32
24952 @cindex ARM 32-bit mode
24953 This command toggles ARM operation mode between 32-bit and 26-bit.
24955 @item show arm apcs32
24956 Display the current usage of the ARM 32-bit mode.
24958 @item set arm fpu @var{fputype}
24959 This command sets the ARM floating-point unit (FPU) type. The
24960 argument @var{fputype} can be one of these:
24964 Determine the FPU type by querying the OS ABI.
24966 Software FPU, with mixed-endian doubles on little-endian ARM
24969 GCC-compiled FPA co-processor.
24971 Software FPU with pure-endian doubles.
24977 Show the current type of the FPU.
24980 This command forces @value{GDBN} to use the specified ABI.
24983 Show the currently used ABI.
24985 @item set arm fallback-mode (arm|thumb|auto)
24986 @value{GDBN} uses the symbol table, when available, to determine
24987 whether instructions are ARM or Thumb. This command controls
24988 @value{GDBN}'s default behavior when the symbol table is not
24989 available. The default is @samp{auto}, which causes @value{GDBN} to
24990 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24993 @item show arm fallback-mode
24994 Show the current fallback instruction mode.
24996 @item set arm force-mode (arm|thumb|auto)
24997 This command overrides use of the symbol table to determine whether
24998 instructions are ARM or Thumb. The default is @samp{auto}, which
24999 causes @value{GDBN} to use the symbol table and then the setting
25000 of @samp{set arm fallback-mode}.
25002 @item show arm force-mode
25003 Show the current forced instruction mode.
25005 @item set debug arm
25006 Toggle whether to display ARM-specific debugging messages from the ARM
25007 target support subsystem.
25009 @item show debug arm
25010 Show whether ARM-specific debugging messages are enabled.
25014 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25015 The @value{GDBN} ARM simulator accepts the following optional arguments.
25018 @item --swi-support=@var{type}
25019 Tell the simulator which SWI interfaces to support. The argument
25020 @var{type} may be a comma separated list of the following values.
25021 The default value is @code{all}.
25037 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25038 The @value{GDBN} BPF simulator accepts the following optional arguments.
25041 @item --skb-data-offset=@var{offset}
25042 Tell the simulator the offset, measured in bytes, of the
25043 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25044 This offset is used by some BPF specific-purpose load/store
25045 instructions. Defaults to 0.
25052 The Motorola m68k configuration includes ColdFire support.
25055 @subsection MicroBlaze
25056 @cindex Xilinx MicroBlaze
25057 @cindex XMD, Xilinx Microprocessor Debugger
25059 The MicroBlaze is a soft-core processor supported on various Xilinx
25060 FPGAs, such as Spartan or Virtex series. Boards with these processors
25061 usually have JTAG ports which connect to a host system running the Xilinx
25062 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25063 This host system is used to download the configuration bitstream to
25064 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25065 communicates with the target board using the JTAG interface and
25066 presents a @code{gdbserver} interface to the board. By default
25067 @code{xmd} uses port @code{1234}. (While it is possible to change
25068 this default port, it requires the use of undocumented @code{xmd}
25069 commands. Contact Xilinx support if you need to do this.)
25071 Use these GDB commands to connect to the MicroBlaze target processor.
25074 @item target remote :1234
25075 Use this command to connect to the target if you are running @value{GDBN}
25076 on the same system as @code{xmd}.
25078 @item target remote @var{xmd-host}:1234
25079 Use this command to connect to the target if it is connected to @code{xmd}
25080 running on a different system named @var{xmd-host}.
25083 Use this command to download a program to the MicroBlaze target.
25085 @item set debug microblaze @var{n}
25086 Enable MicroBlaze-specific debugging messages if non-zero.
25088 @item show debug microblaze @var{n}
25089 Show MicroBlaze-specific debugging level.
25092 @node MIPS Embedded
25093 @subsection @acronym{MIPS} Embedded
25096 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25099 @item set mipsfpu double
25100 @itemx set mipsfpu single
25101 @itemx set mipsfpu none
25102 @itemx set mipsfpu auto
25103 @itemx show mipsfpu
25104 @kindex set mipsfpu
25105 @kindex show mipsfpu
25106 @cindex @acronym{MIPS} remote floating point
25107 @cindex floating point, @acronym{MIPS} remote
25108 If your target board does not support the @acronym{MIPS} floating point
25109 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25110 need this, you may wish to put the command in your @value{GDBN} init
25111 file). This tells @value{GDBN} how to find the return value of
25112 functions which return floating point values. It also allows
25113 @value{GDBN} to avoid saving the floating point registers when calling
25114 functions on the board. If you are using a floating point coprocessor
25115 with only single precision floating point support, as on the @sc{r4650}
25116 processor, use the command @samp{set mipsfpu single}. The default
25117 double precision floating point coprocessor may be selected using
25118 @samp{set mipsfpu double}.
25120 In previous versions the only choices were double precision or no
25121 floating point, so @samp{set mipsfpu on} will select double precision
25122 and @samp{set mipsfpu off} will select no floating point.
25124 As usual, you can inquire about the @code{mipsfpu} variable with
25125 @samp{show mipsfpu}.
25128 @node OpenRISC 1000
25129 @subsection OpenRISC 1000
25130 @cindex OpenRISC 1000
25133 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25134 mainly provided as a soft-core which can run on Xilinx, Altera and other
25137 @value{GDBN} for OpenRISC supports the below commands when connecting to
25145 Runs the builtin CPU simulator which can run very basic
25146 programs but does not support most hardware functions like MMU.
25147 For more complex use cases the user is advised to run an external
25148 target, and connect using @samp{target remote}.
25150 Example: @code{target sim}
25152 @item set debug or1k
25153 Toggle whether to display OpenRISC-specific debugging messages from the
25154 OpenRISC target support subsystem.
25156 @item show debug or1k
25157 Show whether OpenRISC-specific debugging messages are enabled.
25160 @node PowerPC Embedded
25161 @subsection PowerPC Embedded
25163 @cindex DVC register
25164 @value{GDBN} supports using the DVC (Data Value Compare) register to
25165 implement in hardware simple hardware watchpoint conditions of the form:
25168 (@value{GDBP}) watch @var{address|variable} \
25169 if @var{address|variable} == @var{constant expression}
25172 The DVC register will be automatically used when @value{GDBN} detects
25173 such pattern in a condition expression, and the created watchpoint uses one
25174 debug register (either the @code{exact-watchpoints} option is on and the
25175 variable is scalar, or the variable has a length of one byte). This feature
25176 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25179 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25180 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25181 in which case watchpoints using only one debug register are created when
25182 watching variables of scalar types.
25184 You can create an artificial array to watch an arbitrary memory
25185 region using one of the following commands (@pxref{Expressions}):
25188 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25189 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25192 PowerPC embedded processors support masked watchpoints. See the discussion
25193 about the @code{mask} argument in @ref{Set Watchpoints}.
25195 @cindex ranged breakpoint
25196 PowerPC embedded processors support hardware accelerated
25197 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25198 the inferior whenever it executes an instruction at any address within
25199 the range it specifies. To set a ranged breakpoint in @value{GDBN},
25200 use the @code{break-range} command.
25202 @value{GDBN} provides the following PowerPC-specific commands:
25205 @kindex break-range
25206 @item break-range @var{start-location}, @var{end-location}
25207 Set a breakpoint for an address range given by
25208 @var{start-location} and @var{end-location}, which can specify a function name,
25209 a line number, an offset of lines from the current line or from the start
25210 location, or an address of an instruction (see @ref{Specify Location},
25211 for a list of all the possible ways to specify a @var{location}.)
25212 The breakpoint will stop execution of the inferior whenever it
25213 executes an instruction at any address within the specified range,
25214 (including @var{start-location} and @var{end-location}.)
25216 @kindex set powerpc
25217 @item set powerpc soft-float
25218 @itemx show powerpc soft-float
25219 Force @value{GDBN} to use (or not use) a software floating point calling
25220 convention. By default, @value{GDBN} selects the calling convention based
25221 on the selected architecture and the provided executable file.
25223 @item set powerpc vector-abi
25224 @itemx show powerpc vector-abi
25225 Force @value{GDBN} to use the specified calling convention for vector
25226 arguments and return values. The valid options are @samp{auto};
25227 @samp{generic}, to avoid vector registers even if they are present;
25228 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25229 registers. By default, @value{GDBN} selects the calling convention
25230 based on the selected architecture and the provided executable file.
25232 @item set powerpc exact-watchpoints
25233 @itemx show powerpc exact-watchpoints
25234 Allow @value{GDBN} to use only one debug register when watching a variable
25235 of scalar type, thus assuming that the variable is accessed through the
25236 address of its first byte.
25241 @subsection Atmel AVR
25244 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25245 following AVR-specific commands:
25248 @item info io_registers
25249 @kindex info io_registers@r{, AVR}
25250 @cindex I/O registers (Atmel AVR)
25251 This command displays information about the AVR I/O registers. For
25252 each register, @value{GDBN} prints its number and value.
25259 When configured for debugging CRIS, @value{GDBN} provides the
25260 following CRIS-specific commands:
25263 @item set cris-version @var{ver}
25264 @cindex CRIS version
25265 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25266 The CRIS version affects register names and sizes. This command is useful in
25267 case autodetection of the CRIS version fails.
25269 @item show cris-version
25270 Show the current CRIS version.
25272 @item set cris-dwarf2-cfi
25273 @cindex DWARF-2 CFI and CRIS
25274 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25275 Change to @samp{off} when using @code{gcc-cris} whose version is below
25278 @item show cris-dwarf2-cfi
25279 Show the current state of using DWARF-2 CFI.
25281 @item set cris-mode @var{mode}
25283 Set the current CRIS mode to @var{mode}. It should only be changed when
25284 debugging in guru mode, in which case it should be set to
25285 @samp{guru} (the default is @samp{normal}).
25287 @item show cris-mode
25288 Show the current CRIS mode.
25292 @subsection Renesas Super-H
25295 For the Renesas Super-H processor, @value{GDBN} provides these
25299 @item set sh calling-convention @var{convention}
25300 @kindex set sh calling-convention
25301 Set the calling-convention used when calling functions from @value{GDBN}.
25302 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25303 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25304 convention. If the DWARF-2 information of the called function specifies
25305 that the function follows the Renesas calling convention, the function
25306 is called using the Renesas calling convention. If the calling convention
25307 is set to @samp{renesas}, the Renesas calling convention is always used,
25308 regardless of the DWARF-2 information. This can be used to override the
25309 default of @samp{gcc} if debug information is missing, or the compiler
25310 does not emit the DWARF-2 calling convention entry for a function.
25312 @item show sh calling-convention
25313 @kindex show sh calling-convention
25314 Show the current calling convention setting.
25319 @node Architectures
25320 @section Architectures
25322 This section describes characteristics of architectures that affect
25323 all uses of @value{GDBN} with the architecture, both native and cross.
25330 * HPPA:: HP PA architecture
25338 @subsection AArch64
25339 @cindex AArch64 support
25341 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25342 following special commands:
25345 @item set debug aarch64
25346 @kindex set debug aarch64
25347 This command determines whether AArch64 architecture-specific debugging
25348 messages are to be displayed.
25350 @item show debug aarch64
25351 Show whether AArch64 debugging messages are displayed.
25355 @subsubsection AArch64 SVE.
25356 @cindex AArch64 SVE.
25358 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25359 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25360 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25361 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25362 @code{$vg} will be provided. This is the vector granule for the current thread
25363 and represents the number of 64-bit chunks in an SVE @code{z} register.
25365 If the vector length changes, then the @code{$vg} register will be updated,
25366 but the lengths of the @code{z} and @code{p} registers will not change. This
25367 is a known limitation of @value{GDBN} and does not affect the execution of the
25370 @subsubsection AArch64 Pointer Authentication.
25371 @cindex AArch64 Pointer Authentication.
25373 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25374 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25375 register @code{$lr} is pointing to an PAC function its value will be masked.
25376 When GDB prints a backtrace, any addresses that required unmasking will be
25377 postfixed with the marker [PAC]. When using the MI, this is printed as part
25378 of the @code{addr_flags} field.
25380 @subsubsection AArch64 Memory Tagging Extension.
25381 @cindex AArch64 Memory Tagging Extension.
25383 When @value{GDBN} is debugging the AArch64 architecture, the program is
25384 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25385 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25386 available for inspection and editing of logical and allocation tags.
25387 @xref{Memory Tagging}.
25389 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25390 signals are generated as a result of memory tag failures.
25392 If the tag violation is synchronous, the following will be shown:
25395 Program received signal SIGSEGV, Segmentation fault
25396 Memory tag violation while accessing address 0x0500fffff7ff8000
25401 If the tag violation is asynchronous, the fault address is not available.
25402 In this case @value{GDBN} will show the following:
25405 Program received signal SIGSEGV, Segmentation fault
25406 Memory tag violation
25407 Fault address unavailable.
25410 A special register, @code{tag_ctl}, is made available through the
25411 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25412 options that can be controlled at runtime and emulates the @code{prctl}
25413 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25414 documentation in the Linux kernel.
25417 @subsection x86 Architecture-specific Issues
25420 @item set struct-convention @var{mode}
25421 @kindex set struct-convention
25422 @cindex struct return convention
25423 @cindex struct/union returned in registers
25424 Set the convention used by the inferior to return @code{struct}s and
25425 @code{union}s from functions to @var{mode}. Possible values of
25426 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25427 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25428 are returned on the stack, while @code{"reg"} means that a
25429 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25430 be returned in a register.
25432 @item show struct-convention
25433 @kindex show struct-convention
25434 Show the current setting of the convention to return @code{struct}s
25439 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25440 @cindex Intel Memory Protection Extensions (MPX).
25442 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25443 @footnote{The register named with capital letters represent the architecture
25444 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25445 which are the lower bound and upper bound. Bounds are effective addresses or
25446 memory locations. The upper bounds are architecturally represented in 1's
25447 complement form. A bound having lower bound = 0, and upper bound = 0
25448 (1's complement of all bits set) will allow access to the entire address space.
25450 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25451 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25452 display the upper bound performing the complement of one operation on the
25453 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25454 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25455 can also be noted that the upper bounds are inclusive.
25457 As an example, assume that the register BND0 holds bounds for a pointer having
25458 access allowed for the range between 0x32 and 0x71. The values present on
25459 bnd0raw and bnd registers are presented as follows:
25462 bnd0raw = @{0x32, 0xffffffff8e@}
25463 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25466 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25467 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25468 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25469 Python, the display includes the memory size, in bits, accessible to
25472 Bounds can also be stored in bounds tables, which are stored in
25473 application memory. These tables store bounds for pointers by specifying
25474 the bounds pointer's value along with its bounds. Evaluating and changing
25475 bounds located in bound tables is therefore interesting while investigating
25476 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25479 @item show mpx bound @var{pointer}
25480 @kindex show mpx bound
25481 Display bounds of the given @var{pointer}.
25483 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25484 @kindex set mpx bound
25485 Set the bounds of a pointer in the bound table.
25486 This command takes three parameters: @var{pointer} is the pointers
25487 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25488 for lower and upper bounds respectively.
25491 When you call an inferior function on an Intel MPX enabled program,
25492 GDB sets the inferior's bound registers to the init (disabled) state
25493 before calling the function. As a consequence, bounds checks for the
25494 pointer arguments passed to the function will always pass.
25496 This is necessary because when you call an inferior function, the
25497 program is usually in the middle of the execution of other function.
25498 Since at that point bound registers are in an arbitrary state, not
25499 clearing them would lead to random bound violations in the called
25502 You can still examine the influence of the bound registers on the
25503 execution of the called function by stopping the execution of the
25504 called function at its prologue, setting bound registers, and
25505 continuing the execution. For example:
25509 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25510 $ print upper (a, b, c, d, 1)
25511 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25513 @{lbound = 0x0, ubound = ffffffff@} : size -1
25516 At this last step the value of bnd0 can be changed for investigation of bound
25517 violations caused along the execution of the call. In order to know how to
25518 set the bound registers or bound table for the call consult the ABI.
25523 See the following section.
25526 @subsection @acronym{MIPS}
25528 @cindex stack on Alpha
25529 @cindex stack on @acronym{MIPS}
25530 @cindex Alpha stack
25531 @cindex @acronym{MIPS} stack
25532 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25533 sometimes requires @value{GDBN} to search backward in the object code to
25534 find the beginning of a function.
25536 @cindex response time, @acronym{MIPS} debugging
25537 To improve response time (especially for embedded applications, where
25538 @value{GDBN} may be restricted to a slow serial line for this search)
25539 you may want to limit the size of this search, using one of these
25543 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25544 @item set heuristic-fence-post @var{limit}
25545 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25546 search for the beginning of a function. A value of @var{0} (the
25547 default) means there is no limit. However, except for @var{0}, the
25548 larger the limit the more bytes @code{heuristic-fence-post} must search
25549 and therefore the longer it takes to run. You should only need to use
25550 this command when debugging a stripped executable.
25552 @item show heuristic-fence-post
25553 Display the current limit.
25557 These commands are available @emph{only} when @value{GDBN} is configured
25558 for debugging programs on Alpha or @acronym{MIPS} processors.
25560 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25564 @item set mips abi @var{arg}
25565 @kindex set mips abi
25566 @cindex set ABI for @acronym{MIPS}
25567 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25568 values of @var{arg} are:
25572 The default ABI associated with the current binary (this is the
25582 @item show mips abi
25583 @kindex show mips abi
25584 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25586 @item set mips compression @var{arg}
25587 @kindex set mips compression
25588 @cindex code compression, @acronym{MIPS}
25589 Tell @value{GDBN} which @acronym{MIPS} compressed
25590 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25591 inferior. @value{GDBN} uses this for code disassembly and other
25592 internal interpretation purposes. This setting is only referred to
25593 when no executable has been associated with the debugging session or
25594 the executable does not provide information about the encoding it uses.
25595 Otherwise this setting is automatically updated from information
25596 provided by the executable.
25598 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25599 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25600 executables containing @acronym{MIPS16} code frequently are not
25601 identified as such.
25603 This setting is ``sticky''; that is, it retains its value across
25604 debugging sessions until reset either explicitly with this command or
25605 implicitly from an executable.
25607 The compiler and/or assembler typically add symbol table annotations to
25608 identify functions compiled for the @acronym{MIPS16} or
25609 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25610 are present, @value{GDBN} uses them in preference to the global
25611 compressed @acronym{ISA} encoding setting.
25613 @item show mips compression
25614 @kindex show mips compression
25615 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25616 @value{GDBN} to debug the inferior.
25619 @itemx show mipsfpu
25620 @xref{MIPS Embedded, set mipsfpu}.
25622 @item set mips mask-address @var{arg}
25623 @kindex set mips mask-address
25624 @cindex @acronym{MIPS} addresses, masking
25625 This command determines whether the most-significant 32 bits of 64-bit
25626 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25627 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25628 setting, which lets @value{GDBN} determine the correct value.
25630 @item show mips mask-address
25631 @kindex show mips mask-address
25632 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25635 @item set remote-mips64-transfers-32bit-regs
25636 @kindex set remote-mips64-transfers-32bit-regs
25637 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25638 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25639 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25640 and 64 bits for other registers, set this option to @samp{on}.
25642 @item show remote-mips64-transfers-32bit-regs
25643 @kindex show remote-mips64-transfers-32bit-regs
25644 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25646 @item set debug mips
25647 @kindex set debug mips
25648 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25649 target code in @value{GDBN}.
25651 @item show debug mips
25652 @kindex show debug mips
25653 Show the current setting of @acronym{MIPS} debugging messages.
25659 @cindex HPPA support
25661 When @value{GDBN} is debugging the HP PA architecture, it provides the
25662 following special commands:
25665 @item set debug hppa
25666 @kindex set debug hppa
25667 This command determines whether HPPA architecture-specific debugging
25668 messages are to be displayed.
25670 @item show debug hppa
25671 Show whether HPPA debugging messages are displayed.
25673 @item maint print unwind @var{address}
25674 @kindex maint print unwind@r{, HPPA}
25675 This command displays the contents of the unwind table entry at the
25676 given @var{address}.
25682 @subsection PowerPC
25683 @cindex PowerPC architecture
25685 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25686 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25687 numbers stored in the floating point registers. These values must be stored
25688 in two consecutive registers, always starting at an even register like
25689 @code{f0} or @code{f2}.
25691 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25692 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25693 @code{f2} and @code{f3} for @code{$dl1} and so on.
25695 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25696 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25699 @subsection Nios II
25700 @cindex Nios II architecture
25702 When @value{GDBN} is debugging the Nios II architecture,
25703 it provides the following special commands:
25707 @item set debug nios2
25708 @kindex set debug nios2
25709 This command turns on and off debugging messages for the Nios II
25710 target code in @value{GDBN}.
25712 @item show debug nios2
25713 @kindex show debug nios2
25714 Show the current setting of Nios II debugging messages.
25718 @subsection Sparc64
25719 @cindex Sparc64 support
25720 @cindex Application Data Integrity
25721 @subsubsection ADI Support
25723 The M7 processor supports an Application Data Integrity (ADI) feature that
25724 detects invalid data accesses. When software allocates memory and enables
25725 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25726 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25727 the 4-bit version in every cacheline of that data. Hardware saves the latter
25728 in spare bits in the cache and memory hierarchy. On each load and store,
25729 the processor compares the upper 4 VA (virtual address) bits to the
25730 cacheline's version. If there is a mismatch, the processor generates a
25731 version mismatch trap which can be either precise or disrupting. The trap
25732 is an error condition which the kernel delivers to the process as a SIGSEGV
25735 Note that only 64-bit applications can use ADI and need to be built with
25738 Values of the ADI version tags, which are in granularity of a
25739 cacheline (64 bytes), can be viewed or modified.
25743 @kindex adi examine
25744 @item adi (examine | x) [ / @var{n} ] @var{addr}
25746 The @code{adi examine} command displays the value of one ADI version tag per
25749 @var{n} is a decimal integer specifying the number in bytes; the default
25750 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25751 block size, to display.
25753 @var{addr} is the address in user address space where you want @value{GDBN}
25754 to begin displaying the ADI version tags.
25756 Below is an example of displaying ADI versions of variable "shmaddr".
25759 (@value{GDBP}) adi x/100 shmaddr
25760 0xfff800010002c000: 0 0
25764 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25766 The @code{adi assign} command is used to assign new ADI version tag
25769 @var{n} is a decimal integer specifying the number in bytes;
25770 the default is 1. It specifies how much ADI version information, at the
25771 ratio of 1:ADI block size, to modify.
25773 @var{addr} is the address in user address space where you want @value{GDBN}
25774 to begin modifying the ADI version tags.
25776 @var{tag} is the new ADI version tag.
25778 For example, do the following to modify then verify ADI versions of
25779 variable "shmaddr":
25782 (@value{GDBP}) adi a/100 shmaddr = 7
25783 (@value{GDBP}) adi x/100 shmaddr
25784 0xfff800010002c000: 7 7
25791 @cindex S12Z support
25793 When @value{GDBN} is debugging the S12Z architecture,
25794 it provides the following special command:
25797 @item maint info bdccsr
25798 @kindex maint info bdccsr@r{, S12Z}
25799 This command displays the current value of the microprocessor's
25804 @node Controlling GDB
25805 @chapter Controlling @value{GDBN}
25807 You can alter the way @value{GDBN} interacts with you by using the
25808 @code{set} command. For commands controlling how @value{GDBN} displays
25809 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25814 * Editing:: Command editing
25815 * Command History:: Command history
25816 * Screen Size:: Screen size
25817 * Output Styling:: Output styling
25818 * Numbers:: Numbers
25819 * ABI:: Configuring the current ABI
25820 * Auto-loading:: Automatically loading associated files
25821 * Messages/Warnings:: Optional warnings and messages
25822 * Debugging Output:: Optional messages about internal happenings
25823 * Other Misc Settings:: Other Miscellaneous Settings
25831 @value{GDBN} indicates its readiness to read a command by printing a string
25832 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25833 can change the prompt string with the @code{set prompt} command. For
25834 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25835 the prompt in one of the @value{GDBN} sessions so that you can always tell
25836 which one you are talking to.
25838 @emph{Note:} @code{set prompt} does not add a space for you after the
25839 prompt you set. This allows you to set a prompt which ends in a space
25840 or a prompt that does not.
25844 @item set prompt @var{newprompt}
25845 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25847 @kindex show prompt
25849 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25852 Versions of @value{GDBN} that ship with Python scripting enabled have
25853 prompt extensions. The commands for interacting with these extensions
25857 @kindex set extended-prompt
25858 @item set extended-prompt @var{prompt}
25859 Set an extended prompt that allows for substitutions.
25860 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25861 substitution. Any escape sequences specified as part of the prompt
25862 string are replaced with the corresponding strings each time the prompt
25868 set extended-prompt Current working directory: \w (gdb)
25871 Note that when an extended-prompt is set, it takes control of the
25872 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25874 @kindex show extended-prompt
25875 @item show extended-prompt
25876 Prints the extended prompt. Any escape sequences specified as part of
25877 the prompt string with @code{set extended-prompt}, are replaced with the
25878 corresponding strings each time the prompt is displayed.
25882 @section Command Editing
25884 @cindex command line editing
25886 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25887 @sc{gnu} library provides consistent behavior for programs which provide a
25888 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25889 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25890 substitution, and a storage and recall of command history across
25891 debugging sessions.
25893 You may control the behavior of command line editing in @value{GDBN} with the
25894 command @code{set}.
25897 @kindex set editing
25900 @itemx set editing on
25901 Enable command line editing (enabled by default).
25903 @item set editing off
25904 Disable command line editing.
25906 @kindex show editing
25908 Show whether command line editing is enabled.
25911 @ifset SYSTEM_READLINE
25912 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25914 @ifclear SYSTEM_READLINE
25915 @xref{Command Line Editing},
25917 for more details about the Readline
25918 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25919 encouraged to read that chapter.
25921 @cindex Readline application name
25922 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25923 is useful for conditions in @file{.inputrc}.
25925 @cindex operate-and-get-next
25926 @value{GDBN} defines a bindable Readline command,
25927 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25928 This command accepts the current line for execution and fetches the
25929 next line relative to the current line from the history for editing.
25930 Any argument is ignored.
25932 @node Command History
25933 @section Command History
25934 @cindex command history
25936 @value{GDBN} can keep track of the commands you type during your
25937 debugging sessions, so that you can be certain of precisely what
25938 happened. Use these commands to manage the @value{GDBN} command
25941 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25942 package, to provide the history facility.
25943 @ifset SYSTEM_READLINE
25944 @xref{Using History Interactively, , , history, GNU History Library},
25946 @ifclear SYSTEM_READLINE
25947 @xref{Using History Interactively},
25949 for the detailed description of the History library.
25951 To issue a command to @value{GDBN} without affecting certain aspects of
25952 the state which is seen by users, prefix it with @samp{server }
25953 (@pxref{Server Prefix}). This
25954 means that this command will not affect the command history, nor will it
25955 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25956 pressed on a line by itself.
25958 @cindex @code{server}, command prefix
25959 The server prefix does not affect the recording of values into the value
25960 history; to print a value without recording it into the value history,
25961 use the @code{output} command instead of the @code{print} command.
25963 Here is the description of @value{GDBN} commands related to command
25967 @cindex history substitution
25968 @cindex history file
25969 @kindex set history filename
25970 @cindex @env{GDBHISTFILE}, environment variable
25971 @item set history filename @r{[}@var{fname}@r{]}
25972 Set the name of the @value{GDBN} command history file to @var{fname}.
25973 This is the file where @value{GDBN} reads an initial command history
25974 list, and where it writes the command history from this session when it
25975 exits. You can access this list through history expansion or through
25976 the history command editing characters listed below. This file defaults
25977 to the value of the environment variable @env{GDBHISTFILE}, or to
25978 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25981 The @env{GDBHISTFILE} environment variable is read after processing
25982 any @value{GDBN} initialization files (@pxref{Startup}) and after
25983 processing any commands passed using command line options (for
25984 example, @code{-ex}).
25986 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
25987 is the empty string then @value{GDBN} will neither try to load an
25988 existing history file, nor will it try to save the history on exit.
25990 @cindex save command history
25991 @kindex set history save
25992 @item set history save
25993 @itemx set history save on
25994 Record command history in a file, whose name may be specified with the
25995 @code{set history filename} command. By default, this option is
25996 disabled. The command history will be recorded when @value{GDBN}
25997 exits. If @code{set history filename} is set to the empty string then
25998 history saving is disabled, even when @code{set history save} is
26001 @item set history save off
26002 Don't record the command history into the file specified by @code{set
26003 history filename} when @value{GDBN} exits.
26005 @cindex history size
26006 @kindex set history size
26007 @cindex @env{GDBHISTSIZE}, environment variable
26008 @item set history size @var{size}
26009 @itemx set history size unlimited
26010 Set the number of commands which @value{GDBN} keeps in its history list.
26011 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26012 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26013 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26014 either a negative number or the empty string, then the number of commands
26015 @value{GDBN} keeps in the history list is unlimited.
26017 The @env{GDBHISTSIZE} environment variable is read after processing
26018 any @value{GDBN} initialization files (@pxref{Startup}) and after
26019 processing any commands passed using command line options (for
26020 example, @code{-ex}).
26022 @cindex remove duplicate history
26023 @kindex set history remove-duplicates
26024 @item set history remove-duplicates @var{count}
26025 @itemx set history remove-duplicates unlimited
26026 Control the removal of duplicate history entries in the command history list.
26027 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26028 history entries and remove the first entry that is a duplicate of the current
26029 entry being added to the command history list. If @var{count} is
26030 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26031 removal of duplicate history entries is disabled.
26033 Only history entries added during the current session are considered for
26034 removal. This option is set to 0 by default.
26038 History expansion assigns special meaning to the character @kbd{!}.
26039 @ifset SYSTEM_READLINE
26040 @xref{Event Designators, , , history, GNU History Library},
26042 @ifclear SYSTEM_READLINE
26043 @xref{Event Designators},
26047 @cindex history expansion, turn on/off
26048 Since @kbd{!} is also the logical not operator in C, history expansion
26049 is off by default. If you decide to enable history expansion with the
26050 @code{set history expansion on} command, you may sometimes need to
26051 follow @kbd{!} (when it is used as logical not, in an expression) with
26052 a space or a tab to prevent it from being expanded. The readline
26053 history facilities do not attempt substitution on the strings
26054 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26056 The commands to control history expansion are:
26059 @item set history expansion on
26060 @itemx set history expansion
26061 @kindex set history expansion
26062 Enable history expansion. History expansion is off by default.
26064 @item set history expansion off
26065 Disable history expansion.
26068 @kindex show history
26070 @itemx show history filename
26071 @itemx show history save
26072 @itemx show history size
26073 @itemx show history expansion
26074 These commands display the state of the @value{GDBN} history parameters.
26075 @code{show history} by itself displays all four states.
26080 @kindex show commands
26081 @cindex show last commands
26082 @cindex display command history
26083 @item show commands
26084 Display the last ten commands in the command history.
26086 @item show commands @var{n}
26087 Print ten commands centered on command number @var{n}.
26089 @item show commands +
26090 Print ten commands just after the commands last printed.
26094 @section Screen Size
26095 @cindex size of screen
26096 @cindex screen size
26099 @cindex pauses in output
26101 Certain commands to @value{GDBN} may produce large amounts of
26102 information output to the screen. To help you read all of it,
26103 @value{GDBN} pauses and asks you for input at the end of each page of
26104 output. Type @key{RET} when you want to see one more page of output,
26105 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26106 without paging for the rest of the current command. Also, the screen
26107 width setting determines when to wrap lines of output. Depending on
26108 what is being printed, @value{GDBN} tries to break the line at a
26109 readable place, rather than simply letting it overflow onto the
26112 Normally @value{GDBN} knows the size of the screen from the terminal
26113 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26114 together with the value of the @env{TERM} environment variable and the
26115 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26116 you can override it with the @code{set height} and @code{set
26123 @kindex show height
26124 @item set height @var{lpp}
26125 @itemx set height unlimited
26127 @itemx set width @var{cpl}
26128 @itemx set width unlimited
26130 These @code{set} commands specify a screen height of @var{lpp} lines and
26131 a screen width of @var{cpl} characters. The associated @code{show}
26132 commands display the current settings.
26134 If you specify a height of either @code{unlimited} or zero lines,
26135 @value{GDBN} does not pause during output no matter how long the
26136 output is. This is useful if output is to a file or to an editor
26139 Likewise, you can specify @samp{set width unlimited} or @samp{set
26140 width 0} to prevent @value{GDBN} from wrapping its output.
26142 @item set pagination on
26143 @itemx set pagination off
26144 @kindex set pagination
26145 Turn the output pagination on or off; the default is on. Turning
26146 pagination off is the alternative to @code{set height unlimited}. Note that
26147 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26148 Options, -batch}) also automatically disables pagination.
26150 @item show pagination
26151 @kindex show pagination
26152 Show the current pagination mode.
26155 @node Output Styling
26156 @section Output Styling
26162 @value{GDBN} can style its output on a capable terminal. This is
26163 enabled by default on most systems, but disabled by default when in
26164 batch mode (@pxref{Mode Options}). Various style settings are available;
26165 and styles can also be disabled entirely.
26168 @item set style enabled @samp{on|off}
26169 Enable or disable all styling. The default is host-dependent, with
26170 most hosts defaulting to @samp{on}.
26172 @item show style enabled
26173 Show the current state of styling.
26175 @item set style sources @samp{on|off}
26176 Enable or disable source code styling. This affects whether source
26177 code, such as the output of the @code{list} command, is styled. The
26178 default is @samp{on}. Note that source styling only works if styling
26179 in general is enabled, and if a source highlighting library is
26180 available to @value{GDBN}.
26182 There are two ways that highlighting can be done. First, if
26183 @value{GDBN} was linked with the GNU Source Highlight library, then it
26184 is used. Otherwise, if @value{GDBN} was configured with Python
26185 scripting support, and if the Python Pygments package is available,
26186 then it will be used.
26188 @item show style sources
26189 Show the current state of source code styling.
26191 @item set style disassembler enabled @samp{on|off}
26192 Enable or disable disassembler styling. This affects whether
26193 disassembler output, such as the output of the @code{disassemble}
26194 command, is styled. Disassembler styling only works if styling in
26195 general is enabled (with @code{set style enabled on}), and if a source
26196 highlighting library is available to @value{GDBN}.
26198 To highlight disassembler output, @value{GDBN} must be compiled with
26199 Python support, and the Python Pygments package must be available. If
26200 these requirements are not met then @value{GDBN} will not highlight
26201 disassembler output, even when this option is @samp{on}.
26203 @item show style disassembler enabled
26204 Show the current state of disassembler styling.
26207 Subcommands of @code{set style} control specific forms of styling.
26208 These subcommands all follow the same pattern: each style-able object
26209 can be styled with a foreground color, a background color, and an
26212 For example, the style of file names can be controlled using the
26213 @code{set style filename} group of commands:
26216 @item set style filename background @var{color}
26217 Set the background to @var{color}. Valid colors are @samp{none}
26218 (meaning the terminal's default color), @samp{black}, @samp{red},
26219 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26222 @item set style filename foreground @var{color}
26223 Set the foreground to @var{color}. Valid colors are @samp{none}
26224 (meaning the terminal's default color), @samp{black}, @samp{red},
26225 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26228 @item set style filename intensity @var{value}
26229 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26230 (the default), @samp{bold}, and @samp{dim}.
26233 The @code{show style} command and its subcommands are styling
26234 a style name in their output using its own style.
26235 So, use @command{show style} to see the complete list of styles,
26236 their characteristics and the visual aspect of each style.
26238 The style-able objects are:
26241 Control the styling of file names and URLs. By default, this style's
26242 foreground color is green.
26245 Control the styling of function names. These are managed with the
26246 @code{set style function} family of commands. By default, this
26247 style's foreground color is yellow.
26250 Control the styling of variable names. These are managed with the
26251 @code{set style variable} family of commands. By default, this style's
26252 foreground color is cyan.
26255 Control the styling of addresses. These are managed with the
26256 @code{set style address} family of commands. By default, this style's
26257 foreground color is blue.
26260 Control the styling of @value{GDBN}'s version number text. By
26261 default, this style's foreground color is magenta and it has bold
26262 intensity. The version number is displayed in two places, the output
26263 of @command{show version}, and when @value{GDBN} starts up.
26265 In order to control how @value{GDBN} styles the version number at
26266 startup, add the @code{set style version} family of commands to the
26267 early initialization command file (@pxref{Initialization
26271 Control the styling of titles. These are managed with the
26272 @code{set style title} family of commands. By default, this style's
26273 intensity is bold. Commands are using the title style to improve
26274 the readability of large output. For example, the commands
26275 @command{apropos} and @command{help} are using the title style
26276 for the command names.
26279 Control the styling of highlightings. These are managed with the
26280 @code{set style highlight} family of commands. By default, this style's
26281 foreground color is red. Commands are using the highlight style to draw
26282 the user attention to some specific parts of their output. For example,
26283 the command @command{apropos -v REGEXP} uses the highlight style to
26284 mark the documentation parts matching @var{regexp}.
26287 Control the styling of the TUI border. Note that, unlike other
26288 styling options, only the color of the border can be controlled via
26289 @code{set style}. This was done for compatibility reasons, as TUI
26290 controls to set the border's intensity predated the addition of
26291 general styling to @value{GDBN}. @xref{TUI Configuration}.
26293 @item tui-active-border
26294 Control the styling of the active TUI border; that is, the TUI window
26295 that has the focus.
26301 @cindex number representation
26302 @cindex entering numbers
26304 You can always enter numbers in octal, decimal, or hexadecimal in
26305 @value{GDBN} by the usual conventions: octal numbers begin with
26306 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26307 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26308 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26309 10; likewise, the default display for numbers---when no particular
26310 format is specified---is base 10. You can change the default base for
26311 both input and output with the commands described below.
26314 @kindex set input-radix
26315 @item set input-radix @var{base}
26316 Set the default base for numeric input. Supported choices
26317 for @var{base} are decimal 8, 10, or 16. The base must itself be
26318 specified either unambiguously or using the current input radix; for
26322 set input-radix 012
26323 set input-radix 10.
26324 set input-radix 0xa
26328 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26329 leaves the input radix unchanged, no matter what it was, since
26330 @samp{10}, being without any leading or trailing signs of its base, is
26331 interpreted in the current radix. Thus, if the current radix is 16,
26332 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26335 @kindex set output-radix
26336 @item set output-radix @var{base}
26337 Set the default base for numeric display. Supported choices
26338 for @var{base} are decimal 8, 10, or 16. The base must itself be
26339 specified either unambiguously or using the current input radix.
26341 @kindex show input-radix
26342 @item show input-radix
26343 Display the current default base for numeric input.
26345 @kindex show output-radix
26346 @item show output-radix
26347 Display the current default base for numeric display.
26349 @item set radix @r{[}@var{base}@r{]}
26353 These commands set and show the default base for both input and output
26354 of numbers. @code{set radix} sets the radix of input and output to
26355 the same base; without an argument, it resets the radix back to its
26356 default value of 10.
26361 @section Configuring the Current ABI
26363 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26364 application automatically. However, sometimes you need to override its
26365 conclusions. Use these commands to manage @value{GDBN}'s view of the
26371 @cindex Newlib OS ABI and its influence on the longjmp handling
26373 One @value{GDBN} configuration can debug binaries for multiple operating
26374 system targets, either via remote debugging or native emulation.
26375 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26376 but you can override its conclusion using the @code{set osabi} command.
26377 One example where this is useful is in debugging of binaries which use
26378 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26379 not have the same identifying marks that the standard C library for your
26382 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26383 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26384 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26385 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26389 Show the OS ABI currently in use.
26392 With no argument, show the list of registered available OS ABI's.
26394 @item set osabi @var{abi}
26395 Set the current OS ABI to @var{abi}.
26398 @cindex float promotion
26400 Generally, the way that an argument of type @code{float} is passed to a
26401 function depends on whether the function is prototyped. For a prototyped
26402 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26403 according to the architecture's convention for @code{float}. For unprototyped
26404 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26405 @code{double} and then passed.
26407 Unfortunately, some forms of debug information do not reliably indicate whether
26408 a function is prototyped. If @value{GDBN} calls a function that is not marked
26409 as prototyped, it consults @kbd{set coerce-float-to-double}.
26412 @kindex set coerce-float-to-double
26413 @item set coerce-float-to-double
26414 @itemx set coerce-float-to-double on
26415 Arguments of type @code{float} will be promoted to @code{double} when passed
26416 to an unprototyped function. This is the default setting.
26418 @item set coerce-float-to-double off
26419 Arguments of type @code{float} will be passed directly to unprototyped
26422 @kindex show coerce-float-to-double
26423 @item show coerce-float-to-double
26424 Show the current setting of promoting @code{float} to @code{double}.
26428 @kindex show cp-abi
26429 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26430 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26431 used to build your application. @value{GDBN} only fully supports
26432 programs with a single C@t{++} ABI; if your program contains code using
26433 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26434 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26435 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26436 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26437 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26438 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26443 Show the C@t{++} ABI currently in use.
26446 With no argument, show the list of supported C@t{++} ABI's.
26448 @item set cp-abi @var{abi}
26449 @itemx set cp-abi auto
26450 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26454 @section Automatically loading associated files
26455 @cindex auto-loading
26457 @value{GDBN} sometimes reads files with commands and settings automatically,
26458 without being explicitly told so by the user. We call this feature
26459 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26460 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26461 results or introduce security risks (e.g., if the file comes from untrusted
26464 There are various kinds of files @value{GDBN} can automatically load.
26465 In addition to these files, @value{GDBN} supports auto-loading code written
26466 in various extension languages. @xref{Auto-loading extensions}.
26468 Note that loading of these associated files (including the local @file{.gdbinit}
26469 file) requires accordingly configured @code{auto-load safe-path}
26470 (@pxref{Auto-loading safe path}).
26472 For these reasons, @value{GDBN} includes commands and options to let you
26473 control when to auto-load files and which files should be auto-loaded.
26476 @anchor{set auto-load off}
26477 @kindex set auto-load off
26478 @item set auto-load off
26479 Globally disable loading of all auto-loaded files.
26480 You may want to use this command with the @samp{-iex} option
26481 (@pxref{Option -init-eval-command}) such as:
26483 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26486 Be aware that system init file (@pxref{System-wide configuration})
26487 and init files from your home directory (@pxref{Home Directory Init File})
26488 still get read (as they come from generally trusted directories).
26489 To prevent @value{GDBN} from auto-loading even those init files, use the
26490 @option{-nx} option (@pxref{Mode Options}), in addition to
26491 @code{set auto-load no}.
26493 @anchor{show auto-load}
26494 @kindex show auto-load
26495 @item show auto-load
26496 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26500 (gdb) show auto-load
26501 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26502 libthread-db: Auto-loading of inferior specific libthread_db is on.
26503 local-gdbinit: Auto-loading of .gdbinit script from current directory
26505 python-scripts: Auto-loading of Python scripts is on.
26506 safe-path: List of directories from which it is safe to auto-load files
26507 is $debugdir:$datadir/auto-load.
26508 scripts-directory: List of directories from which to load auto-loaded scripts
26509 is $debugdir:$datadir/auto-load.
26512 @anchor{info auto-load}
26513 @kindex info auto-load
26514 @item info auto-load
26515 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26519 (gdb) info auto-load
26522 Yes /home/user/gdb/gdb-gdb.gdb
26523 libthread-db: No auto-loaded libthread-db.
26524 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26528 Yes /home/user/gdb/gdb-gdb.py
26532 These are @value{GDBN} control commands for the auto-loading:
26534 @multitable @columnfractions .5 .5
26535 @item @xref{set auto-load off}.
26536 @tab Disable auto-loading globally.
26537 @item @xref{show auto-load}.
26538 @tab Show setting of all kinds of files.
26539 @item @xref{info auto-load}.
26540 @tab Show state of all kinds of files.
26541 @item @xref{set auto-load gdb-scripts}.
26542 @tab Control for @value{GDBN} command scripts.
26543 @item @xref{show auto-load gdb-scripts}.
26544 @tab Show setting of @value{GDBN} command scripts.
26545 @item @xref{info auto-load gdb-scripts}.
26546 @tab Show state of @value{GDBN} command scripts.
26547 @item @xref{set auto-load python-scripts}.
26548 @tab Control for @value{GDBN} Python scripts.
26549 @item @xref{show auto-load python-scripts}.
26550 @tab Show setting of @value{GDBN} Python scripts.
26551 @item @xref{info auto-load python-scripts}.
26552 @tab Show state of @value{GDBN} Python scripts.
26553 @item @xref{set auto-load guile-scripts}.
26554 @tab Control for @value{GDBN} Guile scripts.
26555 @item @xref{show auto-load guile-scripts}.
26556 @tab Show setting of @value{GDBN} Guile scripts.
26557 @item @xref{info auto-load guile-scripts}.
26558 @tab Show state of @value{GDBN} Guile scripts.
26559 @item @xref{set auto-load scripts-directory}.
26560 @tab Control for @value{GDBN} auto-loaded scripts location.
26561 @item @xref{show auto-load scripts-directory}.
26562 @tab Show @value{GDBN} auto-loaded scripts location.
26563 @item @xref{add-auto-load-scripts-directory}.
26564 @tab Add directory for auto-loaded scripts location list.
26565 @item @xref{set auto-load local-gdbinit}.
26566 @tab Control for init file in the current directory.
26567 @item @xref{show auto-load local-gdbinit}.
26568 @tab Show setting of init file in the current directory.
26569 @item @xref{info auto-load local-gdbinit}.
26570 @tab Show state of init file in the current directory.
26571 @item @xref{set auto-load libthread-db}.
26572 @tab Control for thread debugging library.
26573 @item @xref{show auto-load libthread-db}.
26574 @tab Show setting of thread debugging library.
26575 @item @xref{info auto-load libthread-db}.
26576 @tab Show state of thread debugging library.
26577 @item @xref{set auto-load safe-path}.
26578 @tab Control directories trusted for automatic loading.
26579 @item @xref{show auto-load safe-path}.
26580 @tab Show directories trusted for automatic loading.
26581 @item @xref{add-auto-load-safe-path}.
26582 @tab Add directory trusted for automatic loading.
26586 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26587 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26589 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26590 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26593 @node Init File in the Current Directory
26594 @subsection Automatically loading init file in the current directory
26595 @cindex auto-loading init file in the current directory
26597 By default, @value{GDBN} reads and executes the canned sequences of commands
26598 from init file (if any) in the current working directory,
26599 see @ref{Init File in the Current Directory during Startup}.
26601 Note that loading of this local @file{.gdbinit} file also requires accordingly
26602 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26605 @anchor{set auto-load local-gdbinit}
26606 @kindex set auto-load local-gdbinit
26607 @item set auto-load local-gdbinit [on|off]
26608 Enable or disable the auto-loading of canned sequences of commands
26609 (@pxref{Sequences}) found in init file in the current directory.
26611 @anchor{show auto-load local-gdbinit}
26612 @kindex show auto-load local-gdbinit
26613 @item show auto-load local-gdbinit
26614 Show whether auto-loading of canned sequences of commands from init file in the
26615 current directory is enabled or disabled.
26617 @anchor{info auto-load local-gdbinit}
26618 @kindex info auto-load local-gdbinit
26619 @item info auto-load local-gdbinit
26620 Print whether canned sequences of commands from init file in the
26621 current directory have been auto-loaded.
26624 @node libthread_db.so.1 file
26625 @subsection Automatically loading thread debugging library
26626 @cindex auto-loading libthread_db.so.1
26628 This feature is currently present only on @sc{gnu}/Linux native hosts.
26630 @value{GDBN} reads in some cases thread debugging library from places specific
26631 to the inferior (@pxref{set libthread-db-search-path}).
26633 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26634 without checking this @samp{set auto-load libthread-db} switch as system
26635 libraries have to be trusted in general. In all other cases of
26636 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26637 auto-load libthread-db} is enabled before trying to open such thread debugging
26640 Note that loading of this debugging library also requires accordingly configured
26641 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26644 @anchor{set auto-load libthread-db}
26645 @kindex set auto-load libthread-db
26646 @item set auto-load libthread-db [on|off]
26647 Enable or disable the auto-loading of inferior specific thread debugging library.
26649 @anchor{show auto-load libthread-db}
26650 @kindex show auto-load libthread-db
26651 @item show auto-load libthread-db
26652 Show whether auto-loading of inferior specific thread debugging library is
26653 enabled or disabled.
26655 @anchor{info auto-load libthread-db}
26656 @kindex info auto-load libthread-db
26657 @item info auto-load libthread-db
26658 Print the list of all loaded inferior specific thread debugging libraries and
26659 for each such library print list of inferior @var{pid}s using it.
26662 @node Auto-loading safe path
26663 @subsection Security restriction for auto-loading
26664 @cindex auto-loading safe-path
26666 As the files of inferior can come from untrusted source (such as submitted by
26667 an application user) @value{GDBN} does not always load any files automatically.
26668 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26669 directories trusted for loading files not explicitly requested by user.
26670 Each directory can also be a shell wildcard pattern.
26672 If the path is not set properly you will see a warning and the file will not
26677 Reading symbols from /home/user/gdb/gdb...
26678 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26679 declined by your `auto-load safe-path' set
26680 to "$debugdir:$datadir/auto-load".
26681 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26682 declined by your `auto-load safe-path' set
26683 to "$debugdir:$datadir/auto-load".
26687 To instruct @value{GDBN} to go ahead and use the init files anyway,
26688 invoke @value{GDBN} like this:
26691 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26694 The list of trusted directories is controlled by the following commands:
26697 @anchor{set auto-load safe-path}
26698 @kindex set auto-load safe-path
26699 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26700 Set the list of directories (and their subdirectories) trusted for automatic
26701 loading and execution of scripts. You can also enter a specific trusted file.
26702 Each directory can also be a shell wildcard pattern; wildcards do not match
26703 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26704 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26705 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26706 its default value as specified during @value{GDBN} compilation.
26708 The list of directories uses path separator (@samp{:} on GNU and Unix
26709 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26710 to the @env{PATH} environment variable.
26712 @anchor{show auto-load safe-path}
26713 @kindex show auto-load safe-path
26714 @item show auto-load safe-path
26715 Show the list of directories trusted for automatic loading and execution of
26718 @anchor{add-auto-load-safe-path}
26719 @kindex add-auto-load-safe-path
26720 @item add-auto-load-safe-path
26721 Add an entry (or list of entries) to the list of directories trusted for
26722 automatic loading and execution of scripts. Multiple entries may be delimited
26723 by the host platform path separator in use.
26726 This variable defaults to what @code{--with-auto-load-dir} has been configured
26727 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26728 substitution applies the same as for @ref{set auto-load scripts-directory}.
26729 The default @code{set auto-load safe-path} value can be also overriden by
26730 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26732 Setting this variable to @file{/} disables this security protection,
26733 corresponding @value{GDBN} configuration option is
26734 @option{--without-auto-load-safe-path}.
26735 This variable is supposed to be set to the system directories writable by the
26736 system superuser only. Users can add their source directories in init files in
26737 their home directories (@pxref{Home Directory Init File}). See also deprecated
26738 init file in the current directory
26739 (@pxref{Init File in the Current Directory during Startup}).
26741 To force @value{GDBN} to load the files it declined to load in the previous
26742 example, you could use one of the following ways:
26745 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26746 Specify this trusted directory (or a file) as additional component of the list.
26747 You have to specify also any existing directories displayed by
26748 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26750 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26751 Specify this directory as in the previous case but just for a single
26752 @value{GDBN} session.
26754 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26755 Disable auto-loading safety for a single @value{GDBN} session.
26756 This assumes all the files you debug during this @value{GDBN} session will come
26757 from trusted sources.
26759 @item @kbd{./configure --without-auto-load-safe-path}
26760 During compilation of @value{GDBN} you may disable any auto-loading safety.
26761 This assumes all the files you will ever debug with this @value{GDBN} come from
26765 On the other hand you can also explicitly forbid automatic files loading which
26766 also suppresses any such warning messages:
26769 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26770 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26772 @item @file{~/.gdbinit}: @samp{set auto-load no}
26773 Disable auto-loading globally for the user
26774 (@pxref{Home Directory Init File}). While it is improbable, you could also
26775 use system init file instead (@pxref{System-wide configuration}).
26778 This setting applies to the file names as entered by user. If no entry matches
26779 @value{GDBN} tries as a last resort to also resolve all the file names into
26780 their canonical form (typically resolving symbolic links) and compare the
26781 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26782 own before starting the comparison so a canonical form of directories is
26783 recommended to be entered.
26785 @node Auto-loading verbose mode
26786 @subsection Displaying files tried for auto-load
26787 @cindex auto-loading verbose mode
26789 For better visibility of all the file locations where you can place scripts to
26790 be auto-loaded with inferior --- or to protect yourself against accidental
26791 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26792 all the files attempted to be loaded. Both existing and non-existing files may
26795 For example the list of directories from which it is safe to auto-load files
26796 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26797 may not be too obvious while setting it up.
26800 (gdb) set debug auto-load on
26801 (gdb) file ~/src/t/true
26802 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26803 for objfile "/tmp/true".
26804 auto-load: Updating directories of "/usr:/opt".
26805 auto-load: Using directory "/usr".
26806 auto-load: Using directory "/opt".
26807 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26808 by your `auto-load safe-path' set to "/usr:/opt".
26812 @anchor{set debug auto-load}
26813 @kindex set debug auto-load
26814 @item set debug auto-load [on|off]
26815 Set whether to print the filenames attempted to be auto-loaded.
26817 @anchor{show debug auto-load}
26818 @kindex show debug auto-load
26819 @item show debug auto-load
26820 Show whether printing of the filenames attempted to be auto-loaded is turned
26824 @node Messages/Warnings
26825 @section Optional Warnings and Messages
26827 @cindex verbose operation
26828 @cindex optional warnings
26829 By default, @value{GDBN} is silent about its inner workings. If you are
26830 running on a slow machine, you may want to use the @code{set verbose}
26831 command. This makes @value{GDBN} tell you when it does a lengthy
26832 internal operation, so you will not think it has crashed.
26834 Currently, the messages controlled by @code{set verbose} are those
26835 which announce that the symbol table for a source file is being read;
26836 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26839 @kindex set verbose
26840 @item set verbose on
26841 Enables @value{GDBN} output of certain informational messages.
26843 @item set verbose off
26844 Disables @value{GDBN} output of certain informational messages.
26846 @kindex show verbose
26848 Displays whether @code{set verbose} is on or off.
26851 By default, if @value{GDBN} encounters bugs in the symbol table of an
26852 object file, it is silent; but if you are debugging a compiler, you may
26853 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26858 @kindex set complaints
26859 @item set complaints @var{limit}
26860 Permits @value{GDBN} to output @var{limit} complaints about each type of
26861 unusual symbols before becoming silent about the problem. Set
26862 @var{limit} to zero to suppress all complaints; set it to a large number
26863 to prevent complaints from being suppressed.
26865 @kindex show complaints
26866 @item show complaints
26867 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26871 @anchor{confirmation requests}
26872 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26873 lot of stupid questions to confirm certain commands. For example, if
26874 you try to run a program which is already running:
26878 The program being debugged has been started already.
26879 Start it from the beginning? (y or n)
26882 If you are willing to unflinchingly face the consequences of your own
26883 commands, you can disable this ``feature'':
26887 @kindex set confirm
26889 @cindex confirmation
26890 @cindex stupid questions
26891 @item set confirm off
26892 Disables confirmation requests. Note that running @value{GDBN} with
26893 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26894 automatically disables confirmation requests.
26896 @item set confirm on
26897 Enables confirmation requests (the default).
26899 @kindex show confirm
26901 Displays state of confirmation requests.
26905 @cindex command tracing
26906 If you need to debug user-defined commands or sourced files you may find it
26907 useful to enable @dfn{command tracing}. In this mode each command will be
26908 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26909 quantity denoting the call depth of each command.
26912 @kindex set trace-commands
26913 @cindex command scripts, debugging
26914 @item set trace-commands on
26915 Enable command tracing.
26916 @item set trace-commands off
26917 Disable command tracing.
26918 @item show trace-commands
26919 Display the current state of command tracing.
26922 @node Debugging Output
26923 @section Optional Messages about Internal Happenings
26924 @cindex optional debugging messages
26926 @value{GDBN} has commands that enable optional debugging messages from
26927 various @value{GDBN} subsystems; normally these commands are of
26928 interest to @value{GDBN} maintainers, or when reporting a bug. This
26929 section documents those commands.
26932 @kindex set exec-done-display
26933 @item set exec-done-display
26934 Turns on or off the notification of asynchronous commands'
26935 completion. When on, @value{GDBN} will print a message when an
26936 asynchronous command finishes its execution. The default is off.
26937 @kindex show exec-done-display
26938 @item show exec-done-display
26939 Displays the current setting of asynchronous command completion
26943 @cindex ARM AArch64
26944 @item set debug aarch64
26945 Turns on or off display of debugging messages related to ARM AArch64.
26946 The default is off.
26948 @item show debug aarch64
26949 Displays the current state of displaying debugging messages related to
26952 @cindex gdbarch debugging info
26953 @cindex architecture debugging info
26954 @item set debug arch
26955 Turns on or off display of gdbarch debugging info. The default is off
26956 @item show debug arch
26957 Displays the current state of displaying gdbarch debugging info.
26959 @item set debug aix-solib
26960 @cindex AIX shared library debugging
26961 Control display of debugging messages from the AIX shared library
26962 support module. The default is off.
26963 @item show debug aix-solib
26964 Show the current state of displaying AIX shared library debugging messages.
26966 @item set debug aix-thread
26967 @cindex AIX threads
26968 Display debugging messages about inner workings of the AIX thread
26970 @item show debug aix-thread
26971 Show the current state of AIX thread debugging info display.
26973 @item set debug check-physname
26975 Check the results of the ``physname'' computation. When reading DWARF
26976 debugging information for C@t{++}, @value{GDBN} attempts to compute
26977 each entity's name. @value{GDBN} can do this computation in two
26978 different ways, depending on exactly what information is present.
26979 When enabled, this setting causes @value{GDBN} to compute the names
26980 both ways and display any discrepancies.
26981 @item show debug check-physname
26982 Show the current state of ``physname'' checking.
26984 @item set debug coff-pe-read
26985 @cindex COFF/PE exported symbols
26986 Control display of debugging messages related to reading of COFF/PE
26987 exported symbols. The default is off.
26988 @item show debug coff-pe-read
26989 Displays the current state of displaying debugging messages related to
26990 reading of COFF/PE exported symbols.
26992 @item set debug dwarf-die
26994 Dump DWARF DIEs after they are read in.
26995 The value is the number of nesting levels to print.
26996 A value of zero turns off the display.
26997 @item show debug dwarf-die
26998 Show the current state of DWARF DIE debugging.
27000 @item set debug dwarf-line
27001 @cindex DWARF Line Tables
27002 Turns on or off display of debugging messages related to reading
27003 DWARF line tables. The default is 0 (off).
27004 A value of 1 provides basic information.
27005 A value greater than 1 provides more verbose information.
27006 @item show debug dwarf-line
27007 Show the current state of DWARF line table debugging.
27009 @item set debug dwarf-read
27010 @cindex DWARF Reading
27011 Turns on or off display of debugging messages related to reading
27012 DWARF debug info. The default is 0 (off).
27013 A value of 1 provides basic information.
27014 A value greater than 1 provides more verbose information.
27015 @item show debug dwarf-read
27016 Show the current state of DWARF reader debugging.
27018 @item set debug displaced
27019 @cindex displaced stepping debugging info
27020 Turns on or off display of @value{GDBN} debugging info for the
27021 displaced stepping support. The default is off.
27022 @item show debug displaced
27023 Displays the current state of displaying @value{GDBN} debugging info
27024 related to displaced stepping.
27026 @item set debug event
27027 @cindex event debugging info
27028 Turns on or off display of @value{GDBN} event debugging info. The
27030 @item show debug event
27031 Displays the current state of displaying @value{GDBN} event debugging
27034 @item set debug event-loop
27035 @cindex event-loop debugging
27036 Controls output of debugging info about the event loop. The possible
27037 values are @samp{off}, @samp{all} (shows all debugging info) and
27038 @samp{all-except-ui} (shows all debugging info except those about
27039 UI-related events).
27040 @item show debug event-loop
27041 Shows the current state of displaying debugging info about the event
27044 @item set debug expression
27045 @cindex expression debugging info
27046 Turns on or off display of debugging info about @value{GDBN}
27047 expression parsing. The default is off.
27048 @item show debug expression
27049 Displays the current state of displaying debugging info about
27050 @value{GDBN} expression parsing.
27052 @item set debug fbsd-lwp
27053 @cindex FreeBSD LWP debug messages
27054 Turns on or off debugging messages from the FreeBSD LWP debug support.
27055 @item show debug fbsd-lwp
27056 Show the current state of FreeBSD LWP debugging messages.
27058 @item set debug fbsd-nat
27059 @cindex FreeBSD native target debug messages
27060 Turns on or off debugging messages from the FreeBSD native target.
27061 @item show debug fbsd-nat
27062 Show the current state of FreeBSD native target debugging messages.
27064 @item set debug fortran-array-slicing
27065 @cindex fortran array slicing debugging info
27066 Turns on or off display of @value{GDBN} Fortran array slicing
27067 debugging info. The default is off.
27069 @item show debug fortran-array-slicing
27070 Displays the current state of displaying @value{GDBN} Fortran array
27071 slicing debugging info.
27073 @item set debug frame
27074 @cindex frame debugging info
27075 Turns on or off display of @value{GDBN} frame debugging info. The
27077 @item show debug frame
27078 Displays the current state of displaying @value{GDBN} frame debugging
27081 @item set debug gnu-nat
27082 @cindex @sc{gnu}/Hurd debug messages
27083 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27084 @item show debug gnu-nat
27085 Show the current state of @sc{gnu}/Hurd debugging messages.
27087 @item set debug infrun
27088 @cindex inferior debugging info
27089 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27090 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27091 for implementing operations such as single-stepping the inferior.
27092 @item show debug infrun
27093 Displays the current state of @value{GDBN} inferior debugging.
27095 @item set debug jit
27096 @cindex just-in-time compilation, debugging messages
27097 Turn on or off debugging messages from JIT debug support.
27098 @item show debug jit
27099 Displays the current state of @value{GDBN} JIT debugging.
27101 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27102 @cindex @sc{gnu}/Linux native target debug messages
27103 @cindex Linux native targets
27104 Turn on or off debugging messages from the Linux native target debug support.
27105 @item show debug linux-nat
27106 Show the current state of Linux native target debugging messages.
27108 @item set debug linux-namespaces
27109 @cindex @sc{gnu}/Linux namespaces debug messages
27110 Turn on or off debugging messages from the Linux namespaces debug support.
27111 @item show debug linux-namespaces
27112 Show the current state of Linux namespaces debugging messages.
27114 @item set debug mach-o
27115 @cindex Mach-O symbols processing
27116 Control display of debugging messages related to Mach-O symbols
27117 processing. The default is off.
27118 @item show debug mach-o
27119 Displays the current state of displaying debugging messages related to
27120 reading of COFF/PE exported symbols.
27122 @item set debug notification
27123 @cindex remote async notification debugging info
27124 Turn on or off debugging messages about remote async notification.
27125 The default is off.
27126 @item show debug notification
27127 Displays the current state of remote async notification debugging messages.
27129 @item set debug observer
27130 @cindex observer debugging info
27131 Turns on or off display of @value{GDBN} observer debugging. This
27132 includes info such as the notification of observable events.
27133 @item show debug observer
27134 Displays the current state of observer debugging.
27136 @item set debug overload
27137 @cindex C@t{++} overload debugging info
27138 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27139 info. This includes info such as ranking of functions, etc. The default
27141 @item show debug overload
27142 Displays the current state of displaying @value{GDBN} C@t{++} overload
27145 @cindex expression parser, debugging info
27146 @cindex debug expression parser
27147 @item set debug parser
27148 Turns on or off the display of expression parser debugging output.
27149 Internally, this sets the @code{yydebug} variable in the expression
27150 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27151 details. The default is off.
27152 @item show debug parser
27153 Show the current state of expression parser debugging.
27155 @cindex packets, reporting on stdout
27156 @cindex serial connections, debugging
27157 @cindex debug remote protocol
27158 @cindex remote protocol debugging
27159 @cindex display remote packets
27160 @item set debug remote
27161 Turns on or off display of reports on all packets sent back and forth across
27162 the serial line to the remote machine. The info is printed on the
27163 @value{GDBN} standard output stream. The default is off.
27164 @item show debug remote
27165 Displays the state of display of remote packets.
27167 @item set debug remote-packet-max-chars
27168 Sets the maximum number of characters to display for each remote packet when
27169 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27170 displaying lengthy remote packets and polluting the console.
27172 The default value is @code{512}, which means @value{GDBN} will truncate each
27173 remote packet after 512 bytes.
27175 Setting this option to @code{unlimited} will disable truncation and will output
27176 the full length of the remote packets.
27177 @item show debug remote-packet-max-chars
27178 Displays the number of bytes to output for remote packet debugging.
27180 @item set debug separate-debug-file
27181 Turns on or off display of debug output about separate debug file search.
27182 @item show debug separate-debug-file
27183 Displays the state of separate debug file search debug output.
27185 @item set debug serial
27186 Turns on or off display of @value{GDBN} serial debugging info. The
27188 @item show debug serial
27189 Displays the current state of displaying @value{GDBN} serial debugging
27192 @item set debug solib-frv
27193 @cindex FR-V shared-library debugging
27194 Turn on or off debugging messages for FR-V shared-library code.
27195 @item show debug solib-frv
27196 Display the current state of FR-V shared-library code debugging
27199 @item set debug symbol-lookup
27200 @cindex symbol lookup
27201 Turns on or off display of debugging messages related to symbol lookup.
27202 The default is 0 (off).
27203 A value of 1 provides basic information.
27204 A value greater than 1 provides more verbose information.
27205 @item show debug symbol-lookup
27206 Show the current state of symbol lookup debugging messages.
27208 @item set debug symfile
27209 @cindex symbol file functions
27210 Turns on or off display of debugging messages related to symbol file functions.
27211 The default is off. @xref{Files}.
27212 @item show debug symfile
27213 Show the current state of symbol file debugging messages.
27215 @item set debug symtab-create
27216 @cindex symbol table creation
27217 Turns on or off display of debugging messages related to symbol table creation.
27218 The default is 0 (off).
27219 A value of 1 provides basic information.
27220 A value greater than 1 provides more verbose information.
27221 @item show debug symtab-create
27222 Show the current state of symbol table creation debugging.
27224 @item set debug target
27225 @cindex target debugging info
27226 Turns on or off display of @value{GDBN} target debugging info. This info
27227 includes what is going on at the target level of GDB, as it happens. The
27228 default is 0. Set it to 1 to track events, and to 2 to also track the
27229 value of large memory transfers.
27230 @item show debug target
27231 Displays the current state of displaying @value{GDBN} target debugging
27234 @item set debug timestamp
27235 @cindex timestamping debugging info
27236 Turns on or off display of timestamps with @value{GDBN} debugging info.
27237 When enabled, seconds and microseconds are displayed before each debugging
27239 @item show debug timestamp
27240 Displays the current state of displaying timestamps with @value{GDBN}
27243 @item set debug varobj
27244 @cindex variable object debugging info
27245 Turns on or off display of @value{GDBN} variable object debugging
27246 info. The default is off.
27247 @item show debug varobj
27248 Displays the current state of displaying @value{GDBN} variable object
27251 @item set debug xml
27252 @cindex XML parser debugging
27253 Turn on or off debugging messages for built-in XML parsers.
27254 @item show debug xml
27255 Displays the current state of XML debugging messages.
27258 @node Other Misc Settings
27259 @section Other Miscellaneous Settings
27260 @cindex miscellaneous settings
27263 @kindex set interactive-mode
27264 @item set interactive-mode
27265 If @code{on}, forces @value{GDBN} to assume that GDB was started
27266 in a terminal. In practice, this means that @value{GDBN} should wait
27267 for the user to answer queries generated by commands entered at
27268 the command prompt. If @code{off}, forces @value{GDBN} to operate
27269 in the opposite mode, and it uses the default answers to all queries.
27270 If @code{auto} (the default), @value{GDBN} tries to determine whether
27271 its standard input is a terminal, and works in interactive-mode if it
27272 is, non-interactively otherwise.
27274 In the vast majority of cases, the debugger should be able to guess
27275 correctly which mode should be used. But this setting can be useful
27276 in certain specific cases, such as running a MinGW @value{GDBN}
27277 inside a cygwin window.
27279 @kindex show interactive-mode
27280 @item show interactive-mode
27281 Displays whether the debugger is operating in interactive mode or not.
27285 @kindex set suppress-cli-notifications
27286 @item set suppress-cli-notifications
27287 If @code{on}, command-line-interface (CLI) notifications that are
27288 printed by @value{GDBN} are suppressed. If @code{off}, the
27289 notifications are printed as usual. The default value is @code{off}.
27290 CLI notifications occur when you change the selected context or when
27291 the program being debugged stops, as detailed below.
27294 @item User-selected context changes:
27295 When you change the selected context (i.e.@: the current inferior,
27296 thread and/or the frame), @value{GDBN} prints information about the
27297 new context. For example, the default behavior is below:
27301 [Switching to inferior 1 [process 634] (/tmp/test)]
27302 [Switching to thread 1 (process 634)]
27303 #0 main () at test.c:3
27308 When the notifications are suppressed, the new context is not printed:
27311 (gdb) set suppress-cli-notifications on
27316 @item The program being debugged stops:
27317 When the program you are debugging stops (e.g.@: because of hitting a
27318 breakpoint, completing source-stepping, an interrupt, etc.),
27319 @value{GDBN} prints information about the stop event. For example,
27320 below is a breakpoint hit:
27323 (gdb) break test.c:3
27324 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27328 Breakpoint 2, main () at test.c:3
27333 When the notifications are suppressed, the output becomes:
27336 (gdb) break test.c:3
27337 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27338 (gdb) set suppress-cli-notifications on
27344 Suppressing CLI notifications may be useful in scripts to obtain a
27345 reduced output from a list of commands.
27348 @kindex show suppress-cli-notifications
27349 @item show suppress-cli-notifications
27350 Displays whether printing CLI notifications is suppressed or not.
27353 @node Extending GDB
27354 @chapter Extending @value{GDBN}
27355 @cindex extending GDB
27357 @value{GDBN} provides several mechanisms for extension.
27358 @value{GDBN} also provides the ability to automatically load
27359 extensions when it reads a file for debugging. This allows the
27360 user to automatically customize @value{GDBN} for the program
27363 To facilitate the use of extension languages, @value{GDBN} is capable
27364 of evaluating the contents of a file. When doing so, @value{GDBN}
27365 can recognize which extension language is being used by looking at
27366 the filename extension. Files with an unrecognized filename extension
27367 are always treated as a @value{GDBN} Command Files.
27368 @xref{Command Files,, Command files}.
27370 You can control how @value{GDBN} evaluates these files with the following
27374 @kindex set script-extension
27375 @kindex show script-extension
27376 @item set script-extension off
27377 All scripts are always evaluated as @value{GDBN} Command Files.
27379 @item set script-extension soft
27380 The debugger determines the scripting language based on filename
27381 extension. If this scripting language is supported, @value{GDBN}
27382 evaluates the script using that language. Otherwise, it evaluates
27383 the file as a @value{GDBN} Command File.
27385 @item set script-extension strict
27386 The debugger determines the scripting language based on filename
27387 extension, and evaluates the script using that language. If the
27388 language is not supported, then the evaluation fails.
27390 @item show script-extension
27391 Display the current value of the @code{script-extension} option.
27395 @ifset SYSTEM_GDBINIT_DIR
27396 This setting is not used for files in the system-wide gdbinit directory.
27397 Files in that directory must have an extension matching their language,
27398 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27399 commands. @xref{Startup}.
27403 * Sequences:: Canned Sequences of @value{GDBN} Commands
27404 * Aliases:: Command Aliases
27405 * Python:: Extending @value{GDBN} using Python
27406 * Guile:: Extending @value{GDBN} using Guile
27407 * Auto-loading extensions:: Automatically loading extensions
27408 * Multiple Extension Languages:: Working with multiple extension languages
27412 @section Canned Sequences of Commands
27414 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27415 Command Lists}), @value{GDBN} provides two ways to store sequences of
27416 commands for execution as a unit: user-defined commands and command
27420 * Define:: How to define your own commands
27421 * Hooks:: Hooks for user-defined commands
27422 * Command Files:: How to write scripts of commands to be stored in a file
27423 * Output:: Commands for controlled output
27424 * Auto-loading sequences:: Controlling auto-loaded command files
27428 @subsection User-defined Commands
27430 @cindex user-defined command
27431 @cindex arguments, to user-defined commands
27432 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27433 which you assign a new name as a command. This is done with the
27434 @code{define} command. User commands may accept an unlimited number of arguments
27435 separated by whitespace. Arguments are accessed within the user command
27436 via @code{$arg0@dots{}$argN}. A trivial example:
27440 print $arg0 + $arg1 + $arg2
27445 To execute the command use:
27452 This defines the command @code{adder}, which prints the sum of
27453 its three arguments. Note the arguments are text substitutions, so they may
27454 reference variables, use complex expressions, or even perform inferior
27457 @cindex argument count in user-defined commands
27458 @cindex how many arguments (user-defined commands)
27459 In addition, @code{$argc} may be used to find out how many arguments have
27465 print $arg0 + $arg1
27468 print $arg0 + $arg1 + $arg2
27473 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27474 to process a variable number of arguments:
27481 eval "set $sum = $sum + $arg%d", $i
27491 @item define @var{commandname}
27492 Define a command named @var{commandname}. If there is already a command
27493 by that name, you are asked to confirm that you want to redefine it.
27494 The argument @var{commandname} may be a bare command name consisting of letters,
27495 numbers, dashes, dots, and underscores. It may also start with any
27496 predefined or user-defined prefix command.
27497 For example, @samp{define target my-target} creates
27498 a user-defined @samp{target my-target} command.
27500 The definition of the command is made up of other @value{GDBN} command lines,
27501 which are given following the @code{define} command. The end of these
27502 commands is marked by a line containing @code{end}.
27505 @kindex end@r{ (user-defined commands)}
27506 @item document @var{commandname}
27507 Document the user-defined command @var{commandname}, so that it can be
27508 accessed by @code{help}. The command @var{commandname} must already be
27509 defined. This command reads lines of documentation just as @code{define}
27510 reads the lines of the command definition, ending with @code{end}.
27511 After the @code{document} command is finished, @code{help} on command
27512 @var{commandname} displays the documentation you have written.
27514 You may use the @code{document} command again to change the
27515 documentation of a command. Redefining the command with @code{define}
27516 does not change the documentation.
27518 @kindex define-prefix
27519 @item define-prefix @var{commandname}
27520 Define or mark the command @var{commandname} as a user-defined prefix
27521 command. Once marked, @var{commandname} can be used as prefix command
27522 by the @code{define} command.
27523 Note that @code{define-prefix} can be used with a not yet defined
27524 @var{commandname}. In such a case, @var{commandname} is defined as
27525 an empty user-defined command.
27526 In case you redefine a command that was marked as a user-defined
27527 prefix command, the subcommands of the redefined command are kept
27528 (and @value{GDBN} indicates so to the user).
27532 (gdb) define-prefix abc
27533 (gdb) define-prefix abc def
27534 (gdb) define abc def
27535 Type commands for definition of "abc def".
27536 End with a line saying just "end".
27537 >echo command initial def\n
27539 (gdb) define abc def ghi
27540 Type commands for definition of "abc def ghi".
27541 End with a line saying just "end".
27542 >echo command ghi\n
27544 (gdb) define abc def
27545 Keeping subcommands of prefix command "def".
27546 Redefine command "def"? (y or n) y
27547 Type commands for definition of "abc def".
27548 End with a line saying just "end".
27549 >echo command def\n
27558 @kindex dont-repeat
27559 @cindex don't repeat command
27561 Used inside a user-defined command, this tells @value{GDBN} that this
27562 command should not be repeated when the user hits @key{RET}
27563 (@pxref{Command Syntax, repeat last command}).
27565 @kindex help user-defined
27566 @item help user-defined
27567 List all user-defined commands and all python commands defined in class
27568 COMMAND_USER. The first line of the documentation or docstring is
27573 @itemx show user @var{commandname}
27574 Display the @value{GDBN} commands used to define @var{commandname} (but
27575 not its documentation). If no @var{commandname} is given, display the
27576 definitions for all user-defined commands.
27577 This does not work for user-defined python commands.
27579 @cindex infinite recursion in user-defined commands
27580 @kindex show max-user-call-depth
27581 @kindex set max-user-call-depth
27582 @item show max-user-call-depth
27583 @itemx set max-user-call-depth
27584 The value of @code{max-user-call-depth} controls how many recursion
27585 levels are allowed in user-defined commands before @value{GDBN} suspects an
27586 infinite recursion and aborts the command.
27587 This does not apply to user-defined python commands.
27590 In addition to the above commands, user-defined commands frequently
27591 use control flow commands, described in @ref{Command Files}.
27593 When user-defined commands are executed, the
27594 commands of the definition are not printed. An error in any command
27595 stops execution of the user-defined command.
27597 If used interactively, commands that would ask for confirmation proceed
27598 without asking when used inside a user-defined command. Many @value{GDBN}
27599 commands that normally print messages to say what they are doing omit the
27600 messages when used in a user-defined command.
27603 @subsection User-defined Command Hooks
27604 @cindex command hooks
27605 @cindex hooks, for commands
27606 @cindex hooks, pre-command
27609 You may define @dfn{hooks}, which are a special kind of user-defined
27610 command. Whenever you run the command @samp{foo}, if the user-defined
27611 command @samp{hook-foo} exists, it is executed (with no arguments)
27612 before that command.
27614 @cindex hooks, post-command
27616 A hook may also be defined which is run after the command you executed.
27617 Whenever you run the command @samp{foo}, if the user-defined command
27618 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27619 that command. Post-execution hooks may exist simultaneously with
27620 pre-execution hooks, for the same command.
27622 It is valid for a hook to call the command which it hooks. If this
27623 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27625 @c It would be nice if hookpost could be passed a parameter indicating
27626 @c if the command it hooks executed properly or not. FIXME!
27628 @kindex stop@r{, a pseudo-command}
27629 In addition, a pseudo-command, @samp{stop} exists. Defining
27630 (@samp{hook-stop}) makes the associated commands execute every time
27631 execution stops in your program: before breakpoint commands are run,
27632 displays are printed, or the stack frame is printed.
27634 For example, to ignore @code{SIGALRM} signals while
27635 single-stepping, but treat them normally during normal execution,
27640 handle SIGALRM nopass
27644 handle SIGALRM pass
27647 define hook-continue
27648 handle SIGALRM pass
27652 As a further example, to hook at the beginning and end of the @code{echo}
27653 command, and to add extra text to the beginning and end of the message,
27661 define hookpost-echo
27665 (@value{GDBP}) echo Hello World
27666 <<<---Hello World--->>>
27671 You can define a hook for any single-word command in @value{GDBN}, but
27672 not for command aliases; you should define a hook for the basic command
27673 name, e.g.@: @code{backtrace} rather than @code{bt}.
27674 @c FIXME! So how does Joe User discover whether a command is an alias
27676 You can hook a multi-word command by adding @code{hook-} or
27677 @code{hookpost-} to the last word of the command, e.g.@:
27678 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27680 If an error occurs during the execution of your hook, execution of
27681 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27682 (before the command that you actually typed had a chance to run).
27684 If you try to define a hook which does not match any known command, you
27685 get a warning from the @code{define} command.
27687 @node Command Files
27688 @subsection Command Files
27690 @cindex command files
27691 @cindex scripting commands
27692 A command file for @value{GDBN} is a text file made of lines that are
27693 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27694 also be included. An empty line in a command file does nothing; it
27695 does not mean to repeat the last command, as it would from the
27698 You can request the execution of a command file with the @code{source}
27699 command. Note that the @code{source} command is also used to evaluate
27700 scripts that are not Command Files. The exact behavior can be configured
27701 using the @code{script-extension} setting.
27702 @xref{Extending GDB,, Extending GDB}.
27706 @cindex execute commands from a file
27707 @item source [-s] [-v] @var{filename}
27708 Execute the command file @var{filename}.
27711 The lines in a command file are generally executed sequentially,
27712 unless the order of execution is changed by one of the
27713 @emph{flow-control commands} described below. The commands are not
27714 printed as they are executed. An error in any command terminates
27715 execution of the command file and control is returned to the console.
27717 @value{GDBN} first searches for @var{filename} in the current directory.
27718 If the file is not found there, and @var{filename} does not specify a
27719 directory, then @value{GDBN} also looks for the file on the source search path
27720 (specified with the @samp{directory} command);
27721 except that @file{$cdir} is not searched because the compilation directory
27722 is not relevant to scripts.
27724 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27725 on the search path even if @var{filename} specifies a directory.
27726 The search is done by appending @var{filename} to each element of the
27727 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27728 and the search path contains @file{/home/user} then @value{GDBN} will
27729 look for the script @file{/home/user/mylib/myscript}.
27730 The search is also done if @var{filename} is an absolute path.
27731 For example, if @var{filename} is @file{/tmp/myscript} and
27732 the search path contains @file{/home/user} then @value{GDBN} will
27733 look for the script @file{/home/user/tmp/myscript}.
27734 For DOS-like systems, if @var{filename} contains a drive specification,
27735 it is stripped before concatenation. For example, if @var{filename} is
27736 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27737 will look for the script @file{c:/tmp/myscript}.
27739 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27740 each command as it is executed. The option must be given before
27741 @var{filename}, and is interpreted as part of the filename anywhere else.
27743 Commands that would ask for confirmation if used interactively proceed
27744 without asking when used in a command file. Many @value{GDBN} commands that
27745 normally print messages to say what they are doing omit the messages
27746 when called from command files.
27748 @value{GDBN} also accepts command input from standard input. In this
27749 mode, normal output goes to standard output and error output goes to
27750 standard error. Errors in a command file supplied on standard input do
27751 not terminate execution of the command file---execution continues with
27755 gdb < cmds > log 2>&1
27758 (The syntax above will vary depending on the shell used.) This example
27759 will execute commands from the file @file{cmds}. All output and errors
27760 would be directed to @file{log}.
27762 Since commands stored on command files tend to be more general than
27763 commands typed interactively, they frequently need to deal with
27764 complicated situations, such as different or unexpected values of
27765 variables and symbols, changes in how the program being debugged is
27766 built, etc. @value{GDBN} provides a set of flow-control commands to
27767 deal with these complexities. Using these commands, you can write
27768 complex scripts that loop over data structures, execute commands
27769 conditionally, etc.
27776 This command allows to include in your script conditionally executed
27777 commands. The @code{if} command takes a single argument, which is an
27778 expression to evaluate. It is followed by a series of commands that
27779 are executed only if the expression is true (its value is nonzero).
27780 There can then optionally be an @code{else} line, followed by a series
27781 of commands that are only executed if the expression was false. The
27782 end of the list is marked by a line containing @code{end}.
27786 This command allows to write loops. Its syntax is similar to
27787 @code{if}: the command takes a single argument, which is an expression
27788 to evaluate, and must be followed by the commands to execute, one per
27789 line, terminated by an @code{end}. These commands are called the
27790 @dfn{body} of the loop. The commands in the body of @code{while} are
27791 executed repeatedly as long as the expression evaluates to true.
27795 This command exits the @code{while} loop in whose body it is included.
27796 Execution of the script continues after that @code{while}s @code{end}
27799 @kindex loop_continue
27800 @item loop_continue
27801 This command skips the execution of the rest of the body of commands
27802 in the @code{while} loop in whose body it is included. Execution
27803 branches to the beginning of the @code{while} loop, where it evaluates
27804 the controlling expression.
27806 @kindex end@r{ (if/else/while commands)}
27808 Terminate the block of commands that are the body of @code{if},
27809 @code{else}, or @code{while} flow-control commands.
27814 @subsection Commands for Controlled Output
27816 During the execution of a command file or a user-defined command, normal
27817 @value{GDBN} output is suppressed; the only output that appears is what is
27818 explicitly printed by the commands in the definition. This section
27819 describes three commands useful for generating exactly the output you
27824 @item echo @var{text}
27825 @c I do not consider backslash-space a standard C escape sequence
27826 @c because it is not in ANSI.
27827 Print @var{text}. Nonprinting characters can be included in
27828 @var{text} using C escape sequences, such as @samp{\n} to print a
27829 newline. @strong{No newline is printed unless you specify one.}
27830 In addition to the standard C escape sequences, a backslash followed
27831 by a space stands for a space. This is useful for displaying a
27832 string with spaces at the beginning or the end, since leading and
27833 trailing spaces are otherwise trimmed from all arguments.
27834 To print @samp{@w{ }and foo =@w{ }}, use the command
27835 @samp{echo \@w{ }and foo = \@w{ }}.
27837 A backslash at the end of @var{text} can be used, as in C, to continue
27838 the command onto subsequent lines. For example,
27841 echo This is some text\n\
27842 which is continued\n\
27843 onto several lines.\n
27846 produces the same output as
27849 echo This is some text\n
27850 echo which is continued\n
27851 echo onto several lines.\n
27855 @item output @var{expression}
27856 Print the value of @var{expression} and nothing but that value: no
27857 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27858 value history either. @xref{Expressions, ,Expressions}, for more information
27861 @item output/@var{fmt} @var{expression}
27862 Print the value of @var{expression} in format @var{fmt}. You can use
27863 the same formats as for @code{print}. @xref{Output Formats,,Output
27864 Formats}, for more information.
27867 @item printf @var{template}, @var{expressions}@dots{}
27868 Print the values of one or more @var{expressions} under the control of
27869 the string @var{template}. To print several values, make
27870 @var{expressions} be a comma-separated list of individual expressions,
27871 which may be either numbers or pointers. Their values are printed as
27872 specified by @var{template}, exactly as a C program would do by
27873 executing the code below:
27876 printf (@var{template}, @var{expressions}@dots{});
27879 As in @code{C} @code{printf}, ordinary characters in @var{template}
27880 are printed verbatim, while @dfn{conversion specification} introduced
27881 by the @samp{%} character cause subsequent @var{expressions} to be
27882 evaluated, their values converted and formatted according to type and
27883 style information encoded in the conversion specifications, and then
27886 For example, you can print two values in hex like this:
27889 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27892 @code{printf} supports all the standard @code{C} conversion
27893 specifications, including the flags and modifiers between the @samp{%}
27894 character and the conversion letter, with the following exceptions:
27898 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27901 The modifier @samp{*} is not supported for specifying precision or
27905 The @samp{'} flag (for separation of digits into groups according to
27906 @code{LC_NUMERIC'}) is not supported.
27909 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27913 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27916 The conversion letters @samp{a} and @samp{A} are not supported.
27920 Note that the @samp{ll} type modifier is supported only if the
27921 underlying @code{C} implementation used to build @value{GDBN} supports
27922 the @code{long long int} type, and the @samp{L} type modifier is
27923 supported only if @code{long double} type is available.
27925 As in @code{C}, @code{printf} supports simple backslash-escape
27926 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27927 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27928 single character. Octal and hexadecimal escape sequences are not
27931 Additionally, @code{printf} supports conversion specifications for DFP
27932 (@dfn{Decimal Floating Point}) types using the following length modifiers
27933 together with a floating point specifier.
27938 @samp{H} for printing @code{Decimal32} types.
27941 @samp{D} for printing @code{Decimal64} types.
27944 @samp{DD} for printing @code{Decimal128} types.
27947 If the underlying @code{C} implementation used to build @value{GDBN} has
27948 support for the three length modifiers for DFP types, other modifiers
27949 such as width and precision will also be available for @value{GDBN} to use.
27951 In case there is no such @code{C} support, no additional modifiers will be
27952 available and the value will be printed in the standard way.
27954 Here's an example of printing DFP types using the above conversion letters:
27956 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27961 @item eval @var{template}, @var{expressions}@dots{}
27962 Convert the values of one or more @var{expressions} under the control of
27963 the string @var{template} to a command line, and call it.
27967 @node Auto-loading sequences
27968 @subsection Controlling auto-loading native @value{GDBN} scripts
27969 @cindex native script auto-loading
27971 When a new object file is read (for example, due to the @code{file}
27972 command, or because the inferior has loaded a shared library),
27973 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27974 @xref{Auto-loading extensions}.
27976 Auto-loading can be enabled or disabled,
27977 and the list of auto-loaded scripts can be printed.
27980 @anchor{set auto-load gdb-scripts}
27981 @kindex set auto-load gdb-scripts
27982 @item set auto-load gdb-scripts [on|off]
27983 Enable or disable the auto-loading of canned sequences of commands scripts.
27985 @anchor{show auto-load gdb-scripts}
27986 @kindex show auto-load gdb-scripts
27987 @item show auto-load gdb-scripts
27988 Show whether auto-loading of canned sequences of commands scripts is enabled or
27991 @anchor{info auto-load gdb-scripts}
27992 @kindex info auto-load gdb-scripts
27993 @cindex print list of auto-loaded canned sequences of commands scripts
27994 @item info auto-load gdb-scripts [@var{regexp}]
27995 Print the list of all canned sequences of commands scripts that @value{GDBN}
27999 If @var{regexp} is supplied only canned sequences of commands scripts with
28000 matching names are printed.
28003 @section Command Aliases
28004 @cindex aliases for commands
28006 Aliases allow you to define alternate spellings for existing commands.
28007 For example, if a new @value{GDBN} command defined in Python
28008 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28009 version of it that involves less typing.
28011 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28012 of the @samp{step} command even though it is otherwise an ambiguous
28013 abbreviation of other commands like @samp{set} and @samp{show}.
28015 Aliases are also used to provide shortened or more common versions
28016 of multi-word commands. For example, @value{GDBN} provides the
28017 @samp{tty} alias of the @samp{set inferior-tty} command.
28019 You can define a new alias with the @samp{alias} command.
28024 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28028 @var{alias} specifies the name of the new alias. Each word of
28029 @var{alias} must consist of letters, numbers, dashes and underscores.
28031 @var{command} specifies the name of an existing command
28032 that is being aliased.
28034 @var{command} can also be the name of an existing alias. In this
28035 case, @var{command} cannot be an alias that has default arguments.
28037 The @samp{-a} option specifies that the new alias is an abbreviation
28038 of the command. Abbreviations are not used in command completion.
28040 The @samp{--} option specifies the end of options,
28041 and is useful when @var{alias} begins with a dash.
28043 You can specify @var{default-args} for your alias. These
28044 @var{default-args} will be automatically added before the alias
28045 arguments typed explicitly on the command line.
28047 For example, the below defines an alias @code{btfullall} that shows all local
28048 variables and all frame arguments:
28050 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28053 For more information about @var{default-args}, see @ref{Command
28054 aliases default args, ,Default Arguments}.
28056 Here is a simple example showing how to make an abbreviation of a
28057 command so that there is less to type. Suppose you were tired of
28058 typing @samp{disas}, the current shortest unambiguous abbreviation of
28059 the @samp{disassemble} command and you wanted an even shorter version
28060 named @samp{di}. The following will accomplish this.
28063 (gdb) alias -a di = disas
28066 Note that aliases are different from user-defined commands. With a
28067 user-defined command, you also need to write documentation for it with
28068 the @samp{document} command. An alias automatically picks up the
28069 documentation of the existing command.
28071 Here is an example where we make @samp{elms} an abbreviation of
28072 @samp{elements} in the @samp{set print elements} command.
28073 This is to show that you can make an abbreviation of any part
28077 (gdb) alias -a set print elms = set print elements
28078 (gdb) alias -a show print elms = show print elements
28079 (gdb) set p elms 200
28081 Limit on string chars or array elements to print is 200.
28084 Note that if you are defining an alias of a @samp{set} command,
28085 and you want to have an alias for the corresponding @samp{show}
28086 command, then you need to define the latter separately.
28088 Unambiguously abbreviated commands are allowed in @var{command} and
28089 @var{alias}, just as they are normally.
28092 (gdb) alias -a set pr elms = set p ele
28095 Finally, here is an example showing the creation of a one word
28096 alias for a more complex command.
28097 This creates alias @samp{spe} of the command @samp{set print elements}.
28100 (gdb) alias spe = set print elements
28105 * Command aliases default args:: Default arguments for aliases
28108 @node Command aliases default args
28109 @subsection Default Arguments
28110 @cindex aliases for commands, default arguments
28112 You can tell @value{GDBN} to always prepend some default arguments to
28113 the list of arguments provided explicitly by the user when using a
28114 user-defined alias.
28116 If you repeatedly use the same arguments or options for a command, you
28117 can define an alias for this command and tell @value{GDBN} to
28118 automatically prepend these arguments or options to the list of
28119 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28120 could easily accept default arguments for pre-defined commands and aliases,
28121 but it was deemed this would be confusing, and so is not allowed.}.
28123 For example, if you often use the command @code{thread apply all}
28124 specifying to work on the threads in ascending order and to continue in case it
28125 encounters an error, you can tell @value{GDBN} to automatically preprend
28126 the @code{-ascending} and @code{-c} options by using:
28129 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28132 Once you have defined this alias with its default args, any time you type
28133 the @code{thread apply asc-all} followed by @code{some arguments},
28134 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28136 To have even less to type, you can also define a one word alias:
28138 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28141 As usual, unambiguous abbreviations can be used for @var{alias}
28142 and @var{default-args}.
28144 The different aliases of a command do not share their default args.
28145 For example, you define a new alias @code{bt_ALL} showing all possible
28146 information and another alias @code{bt_SMALL} showing very limited information
28149 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28150 -past-main -past-entry -full
28151 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28152 -past-main off -past-entry off
28155 (For more on using the @code{alias} command, see @ref{Aliases}.)
28157 Default args are not limited to the arguments and options of @var{command},
28158 but can specify nested commands if @var{command} accepts such a nested command
28160 For example, the below defines @code{faalocalsoftype} that lists the
28161 frames having locals of a certain type, together with the matching
28164 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28165 (@value{GDBP}) faalocalsoftype int
28166 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28171 This is also very useful to define an alias for a set of nested @code{with}
28172 commands to have a particular combination of temporary settings. For example,
28173 the below defines the alias @code{pp10} that pretty prints an expression
28174 argument, with a maximum of 10 elements if the expression is a string or
28177 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28179 This defines the alias @code{pp10} as being a sequence of 3 commands.
28180 The first part @code{with print pretty --} temporarily activates the setting
28181 @code{set print pretty}, then launches the command that follows the separator
28183 The command following the first part is also a @code{with} command that
28184 temporarily changes the setting @code{set print elements} to 10, then
28185 launches the command that follows the second separator @code{--}.
28186 The third part @code{print} is the command the @code{pp10} alias will launch,
28187 using the temporary values of the settings and the arguments explicitly given
28189 For more information about the @code{with} command usage,
28190 see @ref{Command Settings}.
28192 @c Python docs live in a separate file.
28193 @include python.texi
28195 @c Guile docs live in a separate file.
28196 @include guile.texi
28198 @node Auto-loading extensions
28199 @section Auto-loading extensions
28200 @cindex auto-loading extensions
28202 @value{GDBN} provides two mechanisms for automatically loading
28203 extensions when a new object file is read (for example, due to the
28204 @code{file} command, or because the inferior has loaded a shared
28205 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28206 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28207 @code{.debug_gdb_scripts} section of modern file formats like ELF
28208 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28209 section}). For a discussion of the differences between these two
28210 approaches see @ref{Which flavor to choose?}.
28212 The auto-loading feature is useful for supplying application-specific
28213 debugging commands and features.
28215 Auto-loading can be enabled or disabled,
28216 and the list of auto-loaded scripts can be printed.
28217 See the @samp{auto-loading} section of each extension language
28218 for more information.
28219 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28220 For Python files see @ref{Python Auto-loading}.
28222 Note that loading of this script file also requires accordingly configured
28223 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28226 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28227 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28228 * Which flavor to choose?:: Choosing between these approaches
28231 @node objfile-gdbdotext file
28232 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28233 @cindex @file{@var{objfile}-gdb.gdb}
28234 @cindex @file{@var{objfile}-gdb.py}
28235 @cindex @file{@var{objfile}-gdb.scm}
28237 When a new object file is read, @value{GDBN} looks for a file named
28238 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28239 where @var{objfile} is the object file's name and
28240 where @var{ext} is the file extension for the extension language:
28243 @item @file{@var{objfile}-gdb.gdb}
28244 GDB's own command language
28245 @item @file{@var{objfile}-gdb.py}
28247 @item @file{@var{objfile}-gdb.scm}
28251 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28252 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28253 components, and appending the @file{-gdb.@var{ext}} suffix.
28254 If this file exists and is readable, @value{GDBN} will evaluate it as a
28255 script in the specified extension language.
28257 If this file does not exist, then @value{GDBN} will look for
28258 @var{script-name} file in all of the directories as specified below.
28259 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28260 directories is converted to a one-letter subdirectory, i.e.@:
28261 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28262 filesystems disallow colons in file names.)
28264 Note that loading of these files requires an accordingly configured
28265 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28267 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28268 scripts normally according to its @file{.exe} filename. But if no scripts are
28269 found @value{GDBN} also tries script filenames matching the object file without
28270 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28271 is attempted on any platform. This makes the script filenames compatible
28272 between Unix and MS-Windows hosts.
28275 @anchor{set auto-load scripts-directory}
28276 @kindex set auto-load scripts-directory
28277 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28278 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28279 may be delimited by the host platform path separator in use
28280 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28282 Each entry here needs to be covered also by the security setting
28283 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28285 @anchor{with-auto-load-dir}
28286 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28287 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28288 configuration option @option{--with-auto-load-dir}.
28290 Any reference to @file{$debugdir} will get replaced by
28291 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28292 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28293 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28294 @file{$datadir} must be placed as a directory component --- either alone or
28295 delimited by @file{/} or @file{\} directory separators, depending on the host
28298 The list of directories uses path separator (@samp{:} on GNU and Unix
28299 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28300 to the @env{PATH} environment variable.
28302 @anchor{show auto-load scripts-directory}
28303 @kindex show auto-load scripts-directory
28304 @item show auto-load scripts-directory
28305 Show @value{GDBN} auto-loaded scripts location.
28307 @anchor{add-auto-load-scripts-directory}
28308 @kindex add-auto-load-scripts-directory
28309 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28310 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28311 Multiple entries may be delimited by the host platform path separator in use.
28314 @value{GDBN} does not track which files it has already auto-loaded this way.
28315 @value{GDBN} will load the associated script every time the corresponding
28316 @var{objfile} is opened.
28317 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28318 is evaluated more than once.
28320 @node dotdebug_gdb_scripts section
28321 @subsection The @code{.debug_gdb_scripts} section
28322 @cindex @code{.debug_gdb_scripts} section
28324 For systems using file formats like ELF and COFF,
28325 when @value{GDBN} loads a new object file
28326 it will look for a special section named @code{.debug_gdb_scripts}.
28327 If this section exists, its contents is a list of null-terminated entries
28328 specifying scripts to load. Each entry begins with a non-null prefix byte that
28329 specifies the kind of entry, typically the extension language and whether the
28330 script is in a file or inlined in @code{.debug_gdb_scripts}.
28332 The following entries are supported:
28335 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28336 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28337 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28338 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28341 @subsubsection Script File Entries
28343 If the entry specifies a file, @value{GDBN} will look for the file first
28344 in the current directory and then along the source search path
28345 (@pxref{Source Path, ,Specifying Source Directories}),
28346 except that @file{$cdir} is not searched, since the compilation
28347 directory is not relevant to scripts.
28349 File entries can be placed in section @code{.debug_gdb_scripts} with,
28350 for example, this GCC macro for Python scripts.
28353 /* Note: The "MS" section flags are to remove duplicates. */
28354 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28356 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28357 .byte 1 /* Python */\n\
28358 .asciz \"" script_name "\"\n\
28364 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28365 Then one can reference the macro in a header or source file like this:
28368 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28371 The script name may include directories if desired.
28373 Note that loading of this script file also requires accordingly configured
28374 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28376 If the macro invocation is put in a header, any application or library
28377 using this header will get a reference to the specified script,
28378 and with the use of @code{"MS"} attributes on the section, the linker
28379 will remove duplicates.
28381 @subsubsection Script Text Entries
28383 Script text entries allow to put the executable script in the entry
28384 itself instead of loading it from a file.
28385 The first line of the entry, everything after the prefix byte and up to
28386 the first newline (@code{0xa}) character, is the script name, and must not
28387 contain any kind of space character, e.g., spaces or tabs.
28388 The rest of the entry, up to the trailing null byte, is the script to
28389 execute in the specified language. The name needs to be unique among
28390 all script names, as @value{GDBN} executes each script only once based
28393 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28397 #include "symcat.h"
28398 #include "gdb/section-scripts.h"
28400 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28401 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28402 ".ascii \"gdb.inlined-script\\n\"\n"
28403 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28404 ".ascii \" def __init__ (self):\\n\"\n"
28405 ".ascii \" super (test_cmd, self).__init__ ("
28406 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28407 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28408 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28409 ".ascii \"test_cmd ()\\n\"\n"
28415 Loading of inlined scripts requires a properly configured
28416 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28417 The path to specify in @code{auto-load safe-path} is the path of the file
28418 containing the @code{.debug_gdb_scripts} section.
28420 @node Which flavor to choose?
28421 @subsection Which flavor to choose?
28423 Given the multiple ways of auto-loading extensions, it might not always
28424 be clear which one to choose. This section provides some guidance.
28427 Benefits of the @file{-gdb.@var{ext}} way:
28431 Can be used with file formats that don't support multiple sections.
28434 Ease of finding scripts for public libraries.
28436 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28437 in the source search path.
28438 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28439 isn't a source directory in which to find the script.
28442 Doesn't require source code additions.
28446 Benefits of the @code{.debug_gdb_scripts} way:
28450 Works with static linking.
28452 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28453 trigger their loading. When an application is statically linked the only
28454 objfile available is the executable, and it is cumbersome to attach all the
28455 scripts from all the input libraries to the executable's
28456 @file{-gdb.@var{ext}} script.
28459 Works with classes that are entirely inlined.
28461 Some classes can be entirely inlined, and thus there may not be an associated
28462 shared library to attach a @file{-gdb.@var{ext}} script to.
28465 Scripts needn't be copied out of the source tree.
28467 In some circumstances, apps can be built out of large collections of internal
28468 libraries, and the build infrastructure necessary to install the
28469 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28470 cumbersome. It may be easier to specify the scripts in the
28471 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28472 top of the source tree to the source search path.
28475 @node Multiple Extension Languages
28476 @section Multiple Extension Languages
28478 The Guile and Python extension languages do not share any state,
28479 and generally do not interfere with each other.
28480 There are some things to be aware of, however.
28482 @subsection Python comes first
28484 Python was @value{GDBN}'s first extension language, and to avoid breaking
28485 existing behaviour Python comes first. This is generally solved by the
28486 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28487 extension languages, and when it makes a call to an extension language,
28488 (say to pretty-print a value), it tries each in turn until an extension
28489 language indicates it has performed the request (e.g., has returned the
28490 pretty-printed form of a value).
28491 This extends to errors while performing such requests: If an error happens
28492 while, for example, trying to pretty-print an object then the error is
28493 reported and any following extension languages are not tried.
28496 @chapter Command Interpreters
28497 @cindex command interpreters
28499 @value{GDBN} supports multiple command interpreters, and some command
28500 infrastructure to allow users or user interface writers to switch
28501 between interpreters or run commands in other interpreters.
28503 @value{GDBN} currently supports two command interpreters, the console
28504 interpreter (sometimes called the command-line interpreter or @sc{cli})
28505 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28506 describes both of these interfaces in great detail.
28508 By default, @value{GDBN} will start with the console interpreter.
28509 However, the user may choose to start @value{GDBN} with another
28510 interpreter by specifying the @option{-i} or @option{--interpreter}
28511 startup options. Defined interpreters include:
28515 @cindex console interpreter
28516 The traditional console or command-line interpreter. This is the most often
28517 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28518 @value{GDBN} will use this interpreter.
28521 @cindex mi interpreter
28522 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28523 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28524 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28528 @cindex mi3 interpreter
28529 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28532 @cindex mi2 interpreter
28533 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28536 @cindex mi1 interpreter
28537 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28541 @cindex invoke another interpreter
28543 @kindex interpreter-exec
28544 You may execute commands in any interpreter from the current
28545 interpreter using the appropriate command. If you are running the
28546 console interpreter, simply use the @code{interpreter-exec} command:
28549 interpreter-exec mi "-data-list-register-names"
28552 @sc{gdb/mi} has a similar command, although it is only available in versions of
28553 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28555 Note that @code{interpreter-exec} only changes the interpreter for the
28556 duration of the specified command. It does not change the interpreter
28559 @cindex start a new independent interpreter
28561 Although you may only choose a single interpreter at startup, it is
28562 possible to run an independent interpreter on a specified input/output
28563 device (usually a tty).
28565 For example, consider a debugger GUI or IDE that wants to provide a
28566 @value{GDBN} console view. It may do so by embedding a terminal
28567 emulator widget in its GUI, starting @value{GDBN} in the traditional
28568 command-line mode with stdin/stdout/stderr redirected to that
28569 terminal, and then creating an MI interpreter running on a specified
28570 input/output device. The console interpreter created by @value{GDBN}
28571 at startup handles commands the user types in the terminal widget,
28572 while the GUI controls and synchronizes state with @value{GDBN} using
28573 the separate MI interpreter.
28575 To start a new secondary @dfn{user interface} running MI, use the
28576 @code{new-ui} command:
28579 @cindex new user interface
28581 new-ui @var{interpreter} @var{tty}
28584 The @var{interpreter} parameter specifies the interpreter to run.
28585 This accepts the same values as the @code{interpreter-exec} command.
28586 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28587 @var{tty} parameter specifies the name of the bidirectional file the
28588 interpreter uses for input/output, usually the name of a
28589 pseudoterminal slave on Unix systems. For example:
28592 (@value{GDBP}) new-ui mi /dev/pts/9
28596 runs an MI interpreter on @file{/dev/pts/9}.
28599 @chapter @value{GDBN} Text User Interface
28601 @cindex Text User Interface
28603 The @value{GDBN} Text User Interface (TUI) is a terminal
28604 interface which uses the @code{curses} library to show the source
28605 file, the assembly output, the program registers and @value{GDBN}
28606 commands in separate text windows. The TUI mode is supported only
28607 on platforms where a suitable version of the @code{curses} library
28610 The TUI mode is enabled by default when you invoke @value{GDBN} as
28611 @samp{@value{GDBP} -tui}.
28612 You can also switch in and out of TUI mode while @value{GDBN} runs by
28613 using various TUI commands and key bindings, such as @command{tui
28614 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28615 @ref{TUI Keys, ,TUI Key Bindings}.
28618 * TUI Overview:: TUI overview
28619 * TUI Keys:: TUI key bindings
28620 * TUI Single Key Mode:: TUI single key mode
28621 * TUI Mouse Support:: TUI mouse support
28622 * TUI Commands:: TUI-specific commands
28623 * TUI Configuration:: TUI configuration variables
28627 @section TUI Overview
28629 In TUI mode, @value{GDBN} can display several text windows:
28633 This window is the @value{GDBN} command window with the @value{GDBN}
28634 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28635 managed using readline.
28638 The source window shows the source file of the program. The current
28639 line and active breakpoints are displayed in this window.
28642 The assembly window shows the disassembly output of the program.
28645 This window shows the processor registers. Registers are highlighted
28646 when their values change.
28649 The source and assembly windows show the current program position
28650 by highlighting the current line and marking it with a @samp{>} marker.
28651 Breakpoints are indicated with two markers. The first marker
28652 indicates the breakpoint type:
28656 Breakpoint which was hit at least once.
28659 Breakpoint which was never hit.
28662 Hardware breakpoint which was hit at least once.
28665 Hardware breakpoint which was never hit.
28668 The second marker indicates whether the breakpoint is enabled or not:
28672 Breakpoint is enabled.
28675 Breakpoint is disabled.
28678 The source, assembly and register windows are updated when the current
28679 thread changes, when the frame changes, or when the program counter
28682 These windows are not all visible at the same time. The command
28683 window is always visible. The others can be arranged in several
28694 source and assembly,
28697 source and registers, or
28700 assembly and registers.
28703 These are the standard layouts, but other layouts can be defined.
28705 A status line above the command window shows the following information:
28709 Indicates the current @value{GDBN} target.
28710 (@pxref{Targets, ,Specifying a Debugging Target}).
28713 Gives the current process or thread number.
28714 When no process is being debugged, this field is set to @code{No process}.
28717 Gives the current function name for the selected frame.
28718 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28719 When there is no symbol corresponding to the current program counter,
28720 the string @code{??} is displayed.
28723 Indicates the current line number for the selected frame.
28724 When the current line number is not known, the string @code{??} is displayed.
28727 Indicates the current program counter address.
28731 @section TUI Key Bindings
28732 @cindex TUI key bindings
28734 The TUI installs several key bindings in the readline keymaps
28735 @ifset SYSTEM_READLINE
28736 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28738 @ifclear SYSTEM_READLINE
28739 (@pxref{Command Line Editing}).
28741 The following key bindings are installed for both TUI mode and the
28742 @value{GDBN} standard mode.
28751 Enter or leave the TUI mode. When leaving the TUI mode,
28752 the curses window management stops and @value{GDBN} operates using
28753 its standard mode, writing on the terminal directly. When reentering
28754 the TUI mode, control is given back to the curses windows.
28755 The screen is then refreshed.
28757 This key binding uses the bindable Readline function
28758 @code{tui-switch-mode}.
28762 Use a TUI layout with only one window. The layout will
28763 either be @samp{source} or @samp{assembly}. When the TUI mode
28764 is not active, it will switch to the TUI mode.
28766 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28768 This key binding uses the bindable Readline function
28769 @code{tui-delete-other-windows}.
28773 Use a TUI layout with at least two windows. When the current
28774 layout already has two windows, the next layout with two windows is used.
28775 When a new layout is chosen, one window will always be common to the
28776 previous layout and the new one.
28778 Think of it as the Emacs @kbd{C-x 2} binding.
28780 This key binding uses the bindable Readline function
28781 @code{tui-change-windows}.
28785 Change the active window. The TUI associates several key bindings
28786 (like scrolling and arrow keys) with the active window. This command
28787 gives the focus to the next TUI window.
28789 Think of it as the Emacs @kbd{C-x o} binding.
28791 This key binding uses the bindable Readline function
28792 @code{tui-other-window}.
28796 Switch in and out of the TUI SingleKey mode that binds single
28797 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28799 This key binding uses the bindable Readline function
28800 @code{next-keymap}.
28803 The following key bindings only work in the TUI mode:
28808 Scroll the active window one page up.
28812 Scroll the active window one page down.
28816 Scroll the active window one line up.
28820 Scroll the active window one line down.
28824 Scroll the active window one column left.
28828 Scroll the active window one column right.
28832 Refresh the screen.
28835 Because the arrow keys scroll the active window in the TUI mode, they
28836 are not available for their normal use by readline unless the command
28837 window has the focus. When another window is active, you must use
28838 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28839 and @kbd{C-f} to control the command window.
28841 @node TUI Single Key Mode
28842 @section TUI Single Key Mode
28843 @cindex TUI single key mode
28845 The TUI also provides a @dfn{SingleKey} mode, which binds several
28846 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28847 switch into this mode, where the following key bindings are used:
28850 @kindex c @r{(SingleKey TUI key)}
28854 @kindex d @r{(SingleKey TUI key)}
28858 @kindex f @r{(SingleKey TUI key)}
28862 @kindex n @r{(SingleKey TUI key)}
28866 @kindex o @r{(SingleKey TUI key)}
28868 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28870 @kindex q @r{(SingleKey TUI key)}
28872 exit the SingleKey mode.
28874 @kindex r @r{(SingleKey TUI key)}
28878 @kindex s @r{(SingleKey TUI key)}
28882 @kindex i @r{(SingleKey TUI key)}
28884 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28886 @kindex u @r{(SingleKey TUI key)}
28890 @kindex v @r{(SingleKey TUI key)}
28894 @kindex w @r{(SingleKey TUI key)}
28899 Other keys temporarily switch to the @value{GDBN} command prompt.
28900 The key that was pressed is inserted in the editing buffer so that
28901 it is possible to type most @value{GDBN} commands without interaction
28902 with the TUI SingleKey mode. Once the command is entered the TUI
28903 SingleKey mode is restored. The only way to permanently leave
28904 this mode is by typing @kbd{q} or @kbd{C-x s}.
28906 @cindex SingleKey keymap name
28907 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28908 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28909 @file{.inputrc} to add additional bindings to this keymap.
28911 @node TUI Mouse Support
28912 @section TUI Mouse Support
28913 @cindex TUI mouse support
28915 If the curses library supports the mouse, the TUI supports mouse
28918 The mouse wheel scrolls the appropriate window under the mouse cursor.
28920 The TUI itself does not directly support copying/pasting with the
28921 mouse. However, on Unix terminals, you can typically press and hold
28922 the @key{SHIFT} key on your keyboard to temporarily bypass
28923 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
28924 functionality (commonly, click-drag-release or double-click to select
28925 text, middle-click to paste). This copy/paste works with the
28926 terminal's selection buffer, as opposed to the TUI's buffer.
28929 @section TUI-specific Commands
28930 @cindex TUI commands
28932 The TUI has specific commands to control the text windows.
28933 These commands are always available, even when @value{GDBN} is not in
28934 the TUI mode. When @value{GDBN} is in the standard mode, most
28935 of these commands will automatically switch to the TUI mode.
28937 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28938 terminal, or @value{GDBN} has been started with the machine interface
28939 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28940 these commands will fail with an error, because it would not be
28941 possible or desirable to enable curses window management.
28946 Activate TUI mode. The last active TUI window layout will be used if
28947 TUI mode has previously been used in the current debugging session,
28948 otherwise a default layout is used.
28951 @kindex tui disable
28952 Disable TUI mode, returning to the console interpreter.
28954 @anchor{info_win_command}
28957 List the names and sizes of all currently displayed windows.
28959 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28960 @kindex tui new-layout
28961 Create a new TUI layout. The new layout will be named @var{name}, and
28962 can be accessed using the @code{layout} command (see below).
28964 Each @var{window} parameter is either the name of a window to display,
28965 or a window description. The windows will be displayed from top to
28966 bottom in the order listed.
28968 The names of the windows are the same as the ones given to the
28969 @code{focus} command (see below); additional, the @code{status}
28970 window can be specified. Note that, because it is of fixed height,
28971 the weight assigned to the status window is of no importance. It is
28972 conventional to use @samp{0} here.
28974 A window description looks a bit like an invocation of @code{tui
28975 new-layout}, and is of the form
28976 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28978 This specifies a sub-layout. If @code{-horizontal} is given, the
28979 windows in this description will be arranged side-by-side, rather than
28982 Each @var{weight} is an integer. It is the weight of this window
28983 relative to all the other windows in the layout. These numbers are
28984 used to calculate how much of the screen is given to each window.
28989 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28992 Here, the new layout is called @samp{example}. It shows the source
28993 and register windows, followed by the status window, and then finally
28994 the command window. The non-status windows all have the same weight,
28995 so the terminal will be split into three roughly equal sections.
28997 Here is a more complex example, showing a horizontal layout:
29000 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29003 This will result in side-by-side source and assembly windows; with the
29004 status and command window being beneath these, filling the entire
29005 width of the terminal. Because they have weight 2, the source and
29006 assembly windows will be twice the height of the command window.
29010 @item tui layout @var{name}
29011 @itemx layout @var{name}
29012 Changes which TUI windows are displayed. The @var{name} parameter
29013 controls which layout is shown. It can be either one of the built-in
29014 layout names, or the name of a layout defined by the user using
29015 @code{tui new-layout}.
29017 The built-in layouts are as follows:
29021 Display the next layout.
29024 Display the previous layout.
29027 Display the source and command windows.
29030 Display the assembly and command windows.
29033 Display the source, assembly, and command windows.
29036 When in @code{src} layout display the register, source, and command
29037 windows. When in @code{asm} or @code{split} layout display the
29038 register, assembler, and command windows.
29042 @item tui focus @var{name}
29043 @itemx focus @var{name}
29044 Changes which TUI window is currently active for scrolling. The
29045 @var{name} parameter can be any of the following:
29049 Make the next window active for scrolling.
29052 Make the previous window active for scrolling.
29055 Make the source window active for scrolling.
29058 Make the assembly window active for scrolling.
29061 Make the register window active for scrolling.
29064 Make the command window active for scrolling.
29067 @kindex tui refresh
29071 Refresh the screen. This is similar to typing @kbd{C-L}.
29073 @item tui reg @var{group}
29075 Changes the register group displayed in the tui register window to
29076 @var{group}. If the register window is not currently displayed this
29077 command will cause the register window to be displayed. The list of
29078 register groups, as well as their order is target specific. The
29079 following groups are available on most targets:
29082 Repeatedly selecting this group will cause the display to cycle
29083 through all of the available register groups.
29086 Repeatedly selecting this group will cause the display to cycle
29087 through all of the available register groups in the reverse order to
29091 Display the general registers.
29093 Display the floating point registers.
29095 Display the system registers.
29097 Display the vector registers.
29099 Display all registers.
29104 Update the source window and the current execution point.
29106 @kindex tui window height
29108 @item tui window height @var{name} +@var{count}
29109 @itemx tui window height @var{name} -@var{count}
29110 @itemx winheight @var{name} +@var{count}
29111 @itemx winheight @var{name} -@var{count}
29112 Change the height of the window @var{name} by @var{count} lines.
29113 Positive counts increase the height, while negative counts decrease
29114 it. The @var{name} parameter can be the name of any currently visible
29115 window. The names of the currently visible windows can be discovered
29116 using @kbd{info win} (@pxref{info_win_command,,info win}).
29118 The set of currently visible windows must always fill the terminal,
29119 and so, it is only possible to resize on window if there are other
29120 visible windows that can either give or receive the extra terminal
29123 @kindex tui window width
29125 @item tui window width @var{name} +@var{count}
29126 @itemx tui window width @var{name} -@var{count}
29127 @itemx winwidth @var{name} +@var{count}
29128 @itemx winwidth @var{name} -@var{count}
29129 Change the width of the window @var{name} by @var{count} columns.
29130 Positive counts increase the width, while negative counts decrease it.
29131 The @var{name} parameter can be the name of any currently visible
29132 window. The names of the currently visible windows can be discovered
29133 using @code{info win} (@pxref{info_win_command,,info win}).
29135 The set of currently visible windows must always fill the terminal,
29136 and so, it is only possible to resize on window if there are other
29137 visible windows that can either give or receive the extra terminal
29141 @node TUI Configuration
29142 @section TUI Configuration Variables
29143 @cindex TUI configuration variables
29145 Several configuration variables control the appearance of TUI windows.
29148 @item set tui border-kind @var{kind}
29149 @kindex set tui border-kind
29150 Select the border appearance for the source, assembly and register windows.
29151 The possible values are the following:
29154 Use a space character to draw the border.
29157 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29160 Use the Alternate Character Set to draw the border. The border is
29161 drawn using character line graphics if the terminal supports them.
29164 @item set tui border-mode @var{mode}
29165 @kindex set tui border-mode
29166 @itemx set tui active-border-mode @var{mode}
29167 @kindex set tui active-border-mode
29168 Select the display attributes for the borders of the inactive windows
29169 or the active window. The @var{mode} can be one of the following:
29172 Use normal attributes to display the border.
29178 Use reverse video mode.
29181 Use half bright mode.
29183 @item half-standout
29184 Use half bright and standout mode.
29187 Use extra bright or bold mode.
29189 @item bold-standout
29190 Use extra bright or bold and standout mode.
29193 @item set tui tab-width @var{nchars}
29194 @kindex set tui tab-width
29196 Set the width of tab stops to be @var{nchars} characters. This
29197 setting affects the display of TAB characters in the source and
29200 @item set tui compact-source @r{[}on@r{|}off@r{]}
29201 @kindex set tui compact-source
29202 Set whether the TUI source window is displayed in ``compact'' form.
29203 The default display uses more space for line numbers and starts the
29204 source text at the next tab stop; the compact display uses only as
29205 much space as is needed for the line numbers in the current file, and
29206 only a single space to separate the line numbers from the source.
29208 @kindex set debug tui
29209 @item set debug tui @r{[}on|off@r{]}
29210 Turn on or off display of @value{GDBN} internal debug messages relating
29213 @kindex show debug tui
29214 @item show debug tui
29215 Show the current status of displaying @value{GDBN} internal debug
29216 messages relating to the TUI.
29220 Note that the colors of the TUI borders can be controlled using the
29221 appropriate @code{set style} commands. @xref{Output Styling}.
29224 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29227 @cindex @sc{gnu} Emacs
29228 A special interface allows you to use @sc{gnu} Emacs to view (and
29229 edit) the source files for the program you are debugging with
29232 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29233 executable file you want to debug as an argument. This command starts
29234 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29235 created Emacs buffer.
29236 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29238 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29243 All ``terminal'' input and output goes through an Emacs buffer, called
29246 This applies both to @value{GDBN} commands and their output, and to the input
29247 and output done by the program you are debugging.
29249 This is useful because it means that you can copy the text of previous
29250 commands and input them again; you can even use parts of the output
29253 All the facilities of Emacs' Shell mode are available for interacting
29254 with your program. In particular, you can send signals the usual
29255 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29259 @value{GDBN} displays source code through Emacs.
29261 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29262 source file for that frame and puts an arrow (@samp{=>}) at the
29263 left margin of the current line. Emacs uses a separate buffer for
29264 source display, and splits the screen to show both your @value{GDBN} session
29267 Explicit @value{GDBN} @code{list} or search commands still produce output as
29268 usual, but you probably have no reason to use them from Emacs.
29271 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29272 a graphical mode, enabled by default, which provides further buffers
29273 that can control the execution and describe the state of your program.
29274 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29276 If you specify an absolute file name when prompted for the @kbd{M-x
29277 gdb} argument, then Emacs sets your current working directory to where
29278 your program resides. If you only specify the file name, then Emacs
29279 sets your current working directory to the directory associated
29280 with the previous buffer. In this case, @value{GDBN} may find your
29281 program by searching your environment's @env{PATH} variable, but on
29282 some operating systems it might not find the source. So, although the
29283 @value{GDBN} input and output session proceeds normally, the auxiliary
29284 buffer does not display the current source and line of execution.
29286 The initial working directory of @value{GDBN} is printed on the top
29287 line of the GUD buffer and this serves as a default for the commands
29288 that specify files for @value{GDBN} to operate on. @xref{Files,
29289 ,Commands to Specify Files}.
29291 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29292 need to call @value{GDBN} by a different name (for example, if you
29293 keep several configurations around, with different names) you can
29294 customize the Emacs variable @code{gud-gdb-command-name} to run the
29297 In the GUD buffer, you can use these special Emacs commands in
29298 addition to the standard Shell mode commands:
29302 Describe the features of Emacs' GUD Mode.
29305 Execute to another source line, like the @value{GDBN} @code{step} command; also
29306 update the display window to show the current file and location.
29309 Execute to next source line in this function, skipping all function
29310 calls, like the @value{GDBN} @code{next} command. Then update the display window
29311 to show the current file and location.
29314 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29315 display window accordingly.
29318 Execute until exit from the selected stack frame, like the @value{GDBN}
29319 @code{finish} command.
29322 Continue execution of your program, like the @value{GDBN} @code{continue}
29326 Go up the number of frames indicated by the numeric argument
29327 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29328 like the @value{GDBN} @code{up} command.
29331 Go down the number of frames indicated by the numeric argument, like the
29332 @value{GDBN} @code{down} command.
29335 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29336 tells @value{GDBN} to set a breakpoint on the source line point is on.
29338 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29339 separate frame which shows a backtrace when the GUD buffer is current.
29340 Move point to any frame in the stack and type @key{RET} to make it
29341 become the current frame and display the associated source in the
29342 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29343 selected frame become the current one. In graphical mode, the
29344 speedbar displays watch expressions.
29346 If you accidentally delete the source-display buffer, an easy way to get
29347 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29348 request a frame display; when you run under Emacs, this recreates
29349 the source buffer if necessary to show you the context of the current
29352 The source files displayed in Emacs are in ordinary Emacs buffers
29353 which are visiting the source files in the usual way. You can edit
29354 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29355 communicates with Emacs in terms of line numbers. If you add or
29356 delete lines from the text, the line numbers that @value{GDBN} knows cease
29357 to correspond properly with the code.
29359 A more detailed description of Emacs' interaction with @value{GDBN} is
29360 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29364 @chapter The @sc{gdb/mi} Interface
29366 @unnumberedsec Function and Purpose
29368 @cindex @sc{gdb/mi}, its purpose
29369 @sc{gdb/mi} is a line based machine oriented text interface to
29370 @value{GDBN} and is activated by specifying using the
29371 @option{--interpreter} command line option (@pxref{Mode Options}). It
29372 is specifically intended to support the development of systems which
29373 use the debugger as just one small component of a larger system.
29375 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29376 in the form of a reference manual.
29378 Note that @sc{gdb/mi} is still under construction, so some of the
29379 features described below are incomplete and subject to change
29380 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29382 @unnumberedsec Notation and Terminology
29384 @cindex notational conventions, for @sc{gdb/mi}
29385 This chapter uses the following notation:
29389 @code{|} separates two alternatives.
29392 @code{[ @var{something} ]} indicates that @var{something} is optional:
29393 it may or may not be given.
29396 @code{( @var{group} )*} means that @var{group} inside the parentheses
29397 may repeat zero or more times.
29400 @code{( @var{group} )+} means that @var{group} inside the parentheses
29401 may repeat one or more times.
29404 @code{"@var{string}"} means a literal @var{string}.
29408 @heading Dependencies
29412 * GDB/MI General Design::
29413 * GDB/MI Command Syntax::
29414 * GDB/MI Compatibility with CLI::
29415 * GDB/MI Development and Front Ends::
29416 * GDB/MI Output Records::
29417 * GDB/MI Simple Examples::
29418 * GDB/MI Command Description Format::
29419 * GDB/MI Breakpoint Commands::
29420 * GDB/MI Catchpoint Commands::
29421 * GDB/MI Program Context::
29422 * GDB/MI Thread Commands::
29423 * GDB/MI Ada Tasking Commands::
29424 * GDB/MI Program Execution::
29425 * GDB/MI Stack Manipulation::
29426 * GDB/MI Variable Objects::
29427 * GDB/MI Data Manipulation::
29428 * GDB/MI Tracepoint Commands::
29429 * GDB/MI Symbol Query::
29430 * GDB/MI File Commands::
29432 * GDB/MI Kod Commands::
29433 * GDB/MI Memory Overlay Commands::
29434 * GDB/MI Signal Handling Commands::
29436 * GDB/MI Target Manipulation::
29437 * GDB/MI File Transfer Commands::
29438 * GDB/MI Ada Exceptions Commands::
29439 * GDB/MI Support Commands::
29440 * GDB/MI Miscellaneous Commands::
29443 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29444 @node GDB/MI General Design
29445 @section @sc{gdb/mi} General Design
29446 @cindex GDB/MI General Design
29448 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29449 parts---commands sent to @value{GDBN}, responses to those commands
29450 and notifications. Each command results in exactly one response,
29451 indicating either successful completion of the command, or an error.
29452 For the commands that do not resume the target, the response contains the
29453 requested information. For the commands that resume the target, the
29454 response only indicates whether the target was successfully resumed.
29455 Notifications is the mechanism for reporting changes in the state of the
29456 target, or in @value{GDBN} state, that cannot conveniently be associated with
29457 a command and reported as part of that command response.
29459 The important examples of notifications are:
29463 Exec notifications. These are used to report changes in
29464 target state---when a target is resumed, or stopped. It would not
29465 be feasible to include this information in response of resuming
29466 commands, because one resume commands can result in multiple events in
29467 different threads. Also, quite some time may pass before any event
29468 happens in the target, while a frontend needs to know whether the resuming
29469 command itself was successfully executed.
29472 Console output, and status notifications. Console output
29473 notifications are used to report output of CLI commands, as well as
29474 diagnostics for other commands. Status notifications are used to
29475 report the progress of a long-running operation. Naturally, including
29476 this information in command response would mean no output is produced
29477 until the command is finished, which is undesirable.
29480 General notifications. Commands may have various side effects on
29481 the @value{GDBN} or target state beyond their official purpose. For example,
29482 a command may change the selected thread. Although such changes can
29483 be included in command response, using notification allows for more
29484 orthogonal frontend design.
29488 There's no guarantee that whenever an MI command reports an error,
29489 @value{GDBN} or the target are in any specific state, and especially,
29490 the state is not reverted to the state before the MI command was
29491 processed. Therefore, whenever an MI command results in an error,
29492 we recommend that the frontend refreshes all the information shown in
29493 the user interface.
29497 * Context management::
29498 * Asynchronous and non-stop modes::
29502 @node Context management
29503 @subsection Context management
29505 @subsubsection Threads and Frames
29507 In most cases when @value{GDBN} accesses the target, this access is
29508 done in context of a specific thread and frame (@pxref{Frames}).
29509 Often, even when accessing global data, the target requires that a thread
29510 be specified. The CLI interface maintains the selected thread and frame,
29511 and supplies them to target on each command. This is convenient,
29512 because a command line user would not want to specify that information
29513 explicitly on each command, and because user interacts with
29514 @value{GDBN} via a single terminal, so no confusion is possible as
29515 to what thread and frame are the current ones.
29517 In the case of MI, the concept of selected thread and frame is less
29518 useful. First, a frontend can easily remember this information
29519 itself. Second, a graphical frontend can have more than one window,
29520 each one used for debugging a different thread, and the frontend might
29521 want to access additional threads for internal purposes. This
29522 increases the risk that by relying on implicitly selected thread, the
29523 frontend may be operating on a wrong one. Therefore, each MI command
29524 should explicitly specify which thread and frame to operate on. To
29525 make it possible, each MI command accepts the @samp{--thread} and
29526 @samp{--frame} options, the value to each is @value{GDBN} global
29527 identifier for thread and frame to operate on.
29529 Usually, each top-level window in a frontend allows the user to select
29530 a thread and a frame, and remembers the user selection for further
29531 operations. However, in some cases @value{GDBN} may suggest that the
29532 current thread or frame be changed. For example, when stopping on a
29533 breakpoint it is reasonable to switch to the thread where breakpoint is
29534 hit. For another example, if the user issues the CLI @samp{thread} or
29535 @samp{frame} commands via the frontend, it is desirable to change the
29536 frontend's selection to the one specified by user. @value{GDBN}
29537 communicates the suggestion to change current thread and frame using the
29538 @samp{=thread-selected} notification.
29540 Note that historically, MI shares the selected thread with CLI, so
29541 frontends used the @code{-thread-select} to execute commands in the
29542 right context. However, getting this to work right is cumbersome. The
29543 simplest way is for frontend to emit @code{-thread-select} command
29544 before every command. This doubles the number of commands that need
29545 to be sent. The alternative approach is to suppress @code{-thread-select}
29546 if the selected thread in @value{GDBN} is supposed to be identical to the
29547 thread the frontend wants to operate on. However, getting this
29548 optimization right can be tricky. In particular, if the frontend
29549 sends several commands to @value{GDBN}, and one of the commands changes the
29550 selected thread, then the behaviour of subsequent commands will
29551 change. So, a frontend should either wait for response from such
29552 problematic commands, or explicitly add @code{-thread-select} for
29553 all subsequent commands. No frontend is known to do this exactly
29554 right, so it is suggested to just always pass the @samp{--thread} and
29555 @samp{--frame} options.
29557 @subsubsection Language
29559 The execution of several commands depends on which language is selected.
29560 By default, the current language (@pxref{show language}) is used.
29561 But for commands known to be language-sensitive, it is recommended
29562 to use the @samp{--language} option. This option takes one argument,
29563 which is the name of the language to use while executing the command.
29567 -data-evaluate-expression --language c "sizeof (void*)"
29572 The valid language names are the same names accepted by the
29573 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29574 @samp{local} or @samp{unknown}.
29576 @node Asynchronous and non-stop modes
29577 @subsection Asynchronous command execution and non-stop mode
29579 On some targets, @value{GDBN} is capable of processing MI commands
29580 even while the target is running. This is called @dfn{asynchronous
29581 command execution} (@pxref{Background Execution}). The frontend may
29582 specify a preference for asynchronous execution using the
29583 @code{-gdb-set mi-async 1} command, which should be emitted before
29584 either running the executable or attaching to the target. After the
29585 frontend has started the executable or attached to the target, it can
29586 find if asynchronous execution is enabled using the
29587 @code{-list-target-features} command.
29590 @cindex foreground execution
29591 @cindex background execution
29592 @cindex asynchronous execution
29593 @cindex execution, foreground, background and asynchronous
29594 @kindex set mi-async
29595 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
29596 Set whether MI is in asynchronous mode.
29598 When @code{off}, which is the default, MI execution commands (e.g.,
29599 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29600 for the program to stop before processing further commands.
29602 When @code{on}, MI execution commands are background execution
29603 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29604 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29605 MI commands even while the target is running.
29607 @kindex show mi-async
29608 @item -gdb-show mi-async
29609 Show whether MI asynchronous mode is enabled.
29612 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29613 @code{target-async} instead of @code{mi-async}, and it had the effect
29614 of both putting MI in asynchronous mode and making CLI background
29615 commands possible. CLI background commands are now always possible
29616 ``out of the box'' if the target supports them. The old spelling is
29617 kept as a deprecated alias for backwards compatibility.
29619 Even if @value{GDBN} can accept a command while target is running,
29620 many commands that access the target do not work when the target is
29621 running. Therefore, asynchronous command execution is most useful
29622 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29623 it is possible to examine the state of one thread, while other threads
29626 When a given thread is running, MI commands that try to access the
29627 target in the context of that thread may not work, or may work only on
29628 some targets. In particular, commands that try to operate on thread's
29629 stack will not work, on any target. Commands that read memory, or
29630 modify breakpoints, may work or not work, depending on the target. Note
29631 that even commands that operate on global state, such as @code{print},
29632 @code{set}, and breakpoint commands, still access the target in the
29633 context of a specific thread, so frontend should try to find a
29634 stopped thread and perform the operation on that thread (using the
29635 @samp{--thread} option).
29637 Which commands will work in the context of a running thread is
29638 highly target dependent. However, the two commands
29639 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29640 to find the state of a thread, will always work.
29642 @node Thread groups
29643 @subsection Thread groups
29644 @value{GDBN} may be used to debug several processes at the same time.
29645 On some platforms, @value{GDBN} may support debugging of several
29646 hardware systems, each one having several cores with several different
29647 processes running on each core. This section describes the MI
29648 mechanism to support such debugging scenarios.
29650 The key observation is that regardless of the structure of the
29651 target, MI can have a global list of threads, because most commands that
29652 accept the @samp{--thread} option do not need to know what process that
29653 thread belongs to. Therefore, it is not necessary to introduce
29654 neither additional @samp{--process} option, nor an notion of the
29655 current process in the MI interface. The only strictly new feature
29656 that is required is the ability to find how the threads are grouped
29659 To allow the user to discover such grouping, and to support arbitrary
29660 hierarchy of machines/cores/processes, MI introduces the concept of a
29661 @dfn{thread group}. Thread group is a collection of threads and other
29662 thread groups. A thread group always has a string identifier, a type,
29663 and may have additional attributes specific to the type. A new
29664 command, @code{-list-thread-groups}, returns the list of top-level
29665 thread groups, which correspond to processes that @value{GDBN} is
29666 debugging at the moment. By passing an identifier of a thread group
29667 to the @code{-list-thread-groups} command, it is possible to obtain
29668 the members of specific thread group.
29670 To allow the user to easily discover processes, and other objects, he
29671 wishes to debug, a concept of @dfn{available thread group} is
29672 introduced. Available thread group is an thread group that
29673 @value{GDBN} is not debugging, but that can be attached to, using the
29674 @code{-target-attach} command. The list of available top-level thread
29675 groups can be obtained using @samp{-list-thread-groups --available}.
29676 In general, the content of a thread group may be only retrieved only
29677 after attaching to that thread group.
29679 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29680 Programs}). Each inferior corresponds to a thread group of a special
29681 type @samp{process}, and some additional operations are permitted on
29682 such thread groups.
29684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29685 @node GDB/MI Command Syntax
29686 @section @sc{gdb/mi} Command Syntax
29689 * GDB/MI Input Syntax::
29690 * GDB/MI Output Syntax::
29693 @node GDB/MI Input Syntax
29694 @subsection @sc{gdb/mi} Input Syntax
29696 @cindex input syntax for @sc{gdb/mi}
29697 @cindex @sc{gdb/mi}, input syntax
29699 @item @var{command} @expansion{}
29700 @code{@var{cli-command} | @var{mi-command}}
29702 @item @var{cli-command} @expansion{}
29703 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29704 @var{cli-command} is any existing @value{GDBN} CLI command.
29706 @item @var{mi-command} @expansion{}
29707 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29708 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29710 @item @var{token} @expansion{}
29711 "any sequence of digits"
29713 @item @var{option} @expansion{}
29714 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29716 @item @var{parameter} @expansion{}
29717 @code{@var{non-blank-sequence} | @var{c-string}}
29719 @item @var{operation} @expansion{}
29720 @emph{any of the operations described in this chapter}
29722 @item @var{non-blank-sequence} @expansion{}
29723 @emph{anything, provided it doesn't contain special characters such as
29724 "-", @var{nl}, """ and of course " "}
29726 @item @var{c-string} @expansion{}
29727 @code{""" @var{seven-bit-iso-c-string-content} """}
29729 @item @var{nl} @expansion{}
29738 The CLI commands are still handled by the @sc{mi} interpreter; their
29739 output is described below.
29742 The @code{@var{token}}, when present, is passed back when the command
29746 Some @sc{mi} commands accept optional arguments as part of the parameter
29747 list. Each option is identified by a leading @samp{-} (dash) and may be
29748 followed by an optional argument parameter. Options occur first in the
29749 parameter list and can be delimited from normal parameters using
29750 @samp{--} (this is useful when some parameters begin with a dash).
29757 We want easy access to the existing CLI syntax (for debugging).
29760 We want it to be easy to spot a @sc{mi} operation.
29763 @node GDB/MI Output Syntax
29764 @subsection @sc{gdb/mi} Output Syntax
29766 @cindex output syntax of @sc{gdb/mi}
29767 @cindex @sc{gdb/mi}, output syntax
29768 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29769 followed, optionally, by a single result record. This result record
29770 is for the most recent command. The sequence of output records is
29771 terminated by @samp{(gdb)}.
29773 If an input command was prefixed with a @code{@var{token}} then the
29774 corresponding output for that command will also be prefixed by that same
29778 @item @var{output} @expansion{}
29779 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29781 @item @var{result-record} @expansion{}
29782 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29784 @item @var{out-of-band-record} @expansion{}
29785 @code{@var{async-record} | @var{stream-record}}
29787 @item @var{async-record} @expansion{}
29788 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29790 @item @var{exec-async-output} @expansion{}
29791 @code{[ @var{token} ] "*" @var{async-output nl}}
29793 @item @var{status-async-output} @expansion{}
29794 @code{[ @var{token} ] "+" @var{async-output nl}}
29796 @item @var{notify-async-output} @expansion{}
29797 @code{[ @var{token} ] "=" @var{async-output nl}}
29799 @item @var{async-output} @expansion{}
29800 @code{@var{async-class} ( "," @var{result} )*}
29802 @item @var{result-class} @expansion{}
29803 @code{"done" | "running" | "connected" | "error" | "exit"}
29805 @item @var{async-class} @expansion{}
29806 @code{"stopped" | @var{others}} (where @var{others} will be added
29807 depending on the needs---this is still in development).
29809 @item @var{result} @expansion{}
29810 @code{ @var{variable} "=" @var{value}}
29812 @item @var{variable} @expansion{}
29813 @code{ @var{string} }
29815 @item @var{value} @expansion{}
29816 @code{ @var{const} | @var{tuple} | @var{list} }
29818 @item @var{const} @expansion{}
29819 @code{@var{c-string}}
29821 @item @var{tuple} @expansion{}
29822 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29824 @item @var{list} @expansion{}
29825 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29826 @var{result} ( "," @var{result} )* "]" }
29828 @item @var{stream-record} @expansion{}
29829 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29831 @item @var{console-stream-output} @expansion{}
29832 @code{"~" @var{c-string nl}}
29834 @item @var{target-stream-output} @expansion{}
29835 @code{"@@" @var{c-string nl}}
29837 @item @var{log-stream-output} @expansion{}
29838 @code{"&" @var{c-string nl}}
29840 @item @var{nl} @expansion{}
29843 @item @var{token} @expansion{}
29844 @emph{any sequence of digits}.
29852 All output sequences end in a single line containing a period.
29855 The @code{@var{token}} is from the corresponding request. Note that
29856 for all async output, while the token is allowed by the grammar and
29857 may be output by future versions of @value{GDBN} for select async
29858 output messages, it is generally omitted. Frontends should treat
29859 all async output as reporting general changes in the state of the
29860 target and there should be no need to associate async output to any
29864 @cindex status output in @sc{gdb/mi}
29865 @var{status-async-output} contains on-going status information about the
29866 progress of a slow operation. It can be discarded. All status output is
29867 prefixed by @samp{+}.
29870 @cindex async output in @sc{gdb/mi}
29871 @var{exec-async-output} contains asynchronous state change on the target
29872 (stopped, started, disappeared). All async output is prefixed by
29876 @cindex notify output in @sc{gdb/mi}
29877 @var{notify-async-output} contains supplementary information that the
29878 client should handle (e.g., a new breakpoint information). All notify
29879 output is prefixed by @samp{=}.
29882 @cindex console output in @sc{gdb/mi}
29883 @var{console-stream-output} is output that should be displayed as is in the
29884 console. It is the textual response to a CLI command. All the console
29885 output is prefixed by @samp{~}.
29888 @cindex target output in @sc{gdb/mi}
29889 @var{target-stream-output} is the output produced by the target program.
29890 All the target output is prefixed by @samp{@@}.
29893 @cindex log output in @sc{gdb/mi}
29894 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29895 instance messages that should be displayed as part of an error log. All
29896 the log output is prefixed by @samp{&}.
29899 @cindex list output in @sc{gdb/mi}
29900 New @sc{gdb/mi} commands should only output @var{lists} containing
29906 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29907 details about the various output records.
29909 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29910 @node GDB/MI Compatibility with CLI
29911 @section @sc{gdb/mi} Compatibility with CLI
29913 @cindex compatibility, @sc{gdb/mi} and CLI
29914 @cindex @sc{gdb/mi}, compatibility with CLI
29916 For the developers convenience CLI commands can be entered directly,
29917 but there may be some unexpected behaviour. For example, commands
29918 that query the user will behave as if the user replied yes, breakpoint
29919 command lists are not executed and some CLI commands, such as
29920 @code{if}, @code{when} and @code{define}, prompt for further input with
29921 @samp{>}, which is not valid MI output.
29923 This feature may be removed at some stage in the future and it is
29924 recommended that front ends use the @code{-interpreter-exec} command
29925 (@pxref{-interpreter-exec}).
29927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29928 @node GDB/MI Development and Front Ends
29929 @section @sc{gdb/mi} Development and Front Ends
29930 @cindex @sc{gdb/mi} development
29932 The application which takes the MI output and presents the state of the
29933 program being debugged to the user is called a @dfn{front end}.
29935 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29936 to the MI interface may break existing usage. This section describes how the
29937 protocol changes and how to request previous version of the protocol when it
29940 Some changes in MI need not break a carefully designed front end, and
29941 for these the MI version will remain unchanged. The following is a
29942 list of changes that may occur within one level, so front ends should
29943 parse MI output in a way that can handle them:
29947 New MI commands may be added.
29950 New fields may be added to the output of any MI command.
29953 The range of values for fields with specified values, e.g.,
29954 @code{in_scope} (@pxref{-var-update}) may be extended.
29956 @c The format of field's content e.g type prefix, may change so parse it
29957 @c at your own risk. Yes, in general?
29959 @c The order of fields may change? Shouldn't really matter but it might
29960 @c resolve inconsistencies.
29963 If the changes are likely to break front ends, the MI version level
29964 will be increased by one. The new versions of the MI protocol are not compatible
29965 with the old versions. Old versions of MI remain available, allowing front ends
29966 to keep using them until they are modified to use the latest MI version.
29968 Since @code{--interpreter=mi} always points to the latest MI version, it is
29969 recommended that front ends request a specific version of MI when launching
29970 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
29971 interpreter with the MI version they expect.
29973 The following table gives a summary of the released versions of the MI
29974 interface: the version number, the version of GDB in which it first appeared
29975 and the breaking changes compared to the previous version.
29977 @multitable @columnfractions .05 .05 .9
29978 @headitem MI version @tab GDB version @tab Breaking changes
29995 The @code{-environment-pwd}, @code{-environment-directory} and
29996 @code{-environment-path} commands now returns values using the MI output
29997 syntax, rather than CLI output syntax.
30000 @code{-var-list-children}'s @code{children} result field is now a list, rather
30004 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30016 The output of information about multi-location breakpoints has changed in the
30017 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30018 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30019 The multiple locations are now placed in a @code{locations} field, whose value
30025 If your front end cannot yet migrate to a more recent version of the
30026 MI protocol, you can nevertheless selectively enable specific features
30027 available in those recent MI versions, using the following commands:
30031 @item -fix-multi-location-breakpoint-output
30032 Use the output for multi-location breakpoints which was introduced by
30033 MI 3, even when using MI versions 2 or 1. This command has no
30034 effect when using MI version 3 or later.
30038 The best way to avoid unexpected changes in MI that might break your front
30039 end is to make your project known to @value{GDBN} developers and
30040 follow development on @email{gdb@@sourceware.org} and
30041 @email{gdb-patches@@sourceware.org}.
30042 @cindex mailing lists
30044 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30045 @node GDB/MI Output Records
30046 @section @sc{gdb/mi} Output Records
30049 * GDB/MI Result Records::
30050 * GDB/MI Stream Records::
30051 * GDB/MI Async Records::
30052 * GDB/MI Breakpoint Information::
30053 * GDB/MI Frame Information::
30054 * GDB/MI Thread Information::
30055 * GDB/MI Ada Exception Information::
30058 @node GDB/MI Result Records
30059 @subsection @sc{gdb/mi} Result Records
30061 @cindex result records in @sc{gdb/mi}
30062 @cindex @sc{gdb/mi}, result records
30063 In addition to a number of out-of-band notifications, the response to a
30064 @sc{gdb/mi} command includes one of the following result indications:
30068 @item "^done" [ "," @var{results} ]
30069 The synchronous operation was successful, @code{@var{results}} are the return
30074 This result record is equivalent to @samp{^done}. Historically, it
30075 was output instead of @samp{^done} if the command has resumed the
30076 target. This behaviour is maintained for backward compatibility, but
30077 all frontends should treat @samp{^done} and @samp{^running}
30078 identically and rely on the @samp{*running} output record to determine
30079 which threads are resumed.
30083 @value{GDBN} has connected to a remote target.
30085 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30087 The operation failed. The @code{msg=@var{c-string}} variable contains
30088 the corresponding error message.
30090 If present, the @code{code=@var{c-string}} variable provides an error
30091 code on which consumers can rely on to detect the corresponding
30092 error condition. At present, only one error code is defined:
30095 @item "undefined-command"
30096 Indicates that the command causing the error does not exist.
30101 @value{GDBN} has terminated.
30105 @node GDB/MI Stream Records
30106 @subsection @sc{gdb/mi} Stream Records
30108 @cindex @sc{gdb/mi}, stream records
30109 @cindex stream records in @sc{gdb/mi}
30110 @value{GDBN} internally maintains a number of output streams: the console, the
30111 target, and the log. The output intended for each of these streams is
30112 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30114 Each stream record begins with a unique @dfn{prefix character} which
30115 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30116 Syntax}). In addition to the prefix, each stream record contains a
30117 @code{@var{string-output}}. This is either raw text (with an implicit new
30118 line) or a quoted C string (which does not contain an implicit newline).
30121 @item "~" @var{string-output}
30122 The console output stream contains text that should be displayed in the
30123 CLI console window. It contains the textual responses to CLI commands.
30125 @item "@@" @var{string-output}
30126 The target output stream contains any textual output from the running
30127 target. This is only present when GDB's event loop is truly
30128 asynchronous, which is currently only the case for remote targets.
30130 @item "&" @var{string-output}
30131 The log stream contains debugging messages being produced by @value{GDBN}'s
30135 @node GDB/MI Async Records
30136 @subsection @sc{gdb/mi} Async Records
30138 @cindex async records in @sc{gdb/mi}
30139 @cindex @sc{gdb/mi}, async records
30140 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30141 additional changes that have occurred. Those changes can either be a
30142 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30143 target activity (e.g., target stopped).
30145 The following is the list of possible async records:
30149 @item *running,thread-id="@var{thread}"
30150 The target is now running. The @var{thread} field can be the global
30151 thread ID of the thread that is now running, and it can be
30152 @samp{all} if all threads are running. The frontend should assume
30153 that no interaction with a running thread is possible after this
30154 notification is produced. The frontend should not assume that this
30155 notification is output only once for any command. @value{GDBN} may
30156 emit this notification several times, either for different threads,
30157 because it cannot resume all threads together, or even for a single
30158 thread, if the thread must be stepped though some code before letting
30161 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30162 The target has stopped. The @var{reason} field can have one of the
30166 @item breakpoint-hit
30167 A breakpoint was reached.
30168 @item watchpoint-trigger
30169 A watchpoint was triggered.
30170 @item read-watchpoint-trigger
30171 A read watchpoint was triggered.
30172 @item access-watchpoint-trigger
30173 An access watchpoint was triggered.
30174 @item function-finished
30175 An -exec-finish or similar CLI command was accomplished.
30176 @item location-reached
30177 An -exec-until or similar CLI command was accomplished.
30178 @item watchpoint-scope
30179 A watchpoint has gone out of scope.
30180 @item end-stepping-range
30181 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30182 similar CLI command was accomplished.
30183 @item exited-signalled
30184 The inferior exited because of a signal.
30186 The inferior exited.
30187 @item exited-normally
30188 The inferior exited normally.
30189 @item signal-received
30190 A signal was received by the inferior.
30192 The inferior has stopped due to a library being loaded or unloaded.
30193 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30194 set or when a @code{catch load} or @code{catch unload} catchpoint is
30195 in use (@pxref{Set Catchpoints}).
30197 The inferior has forked. This is reported when @code{catch fork}
30198 (@pxref{Set Catchpoints}) has been used.
30200 The inferior has vforked. This is reported in when @code{catch vfork}
30201 (@pxref{Set Catchpoints}) has been used.
30202 @item syscall-entry
30203 The inferior entered a system call. This is reported when @code{catch
30204 syscall} (@pxref{Set Catchpoints}) has been used.
30205 @item syscall-return
30206 The inferior returned from a system call. This is reported when
30207 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30209 The inferior called @code{exec}. This is reported when @code{catch exec}
30210 (@pxref{Set Catchpoints}) has been used.
30213 The @var{id} field identifies the global thread ID of the thread
30214 that directly caused the stop -- for example by hitting a breakpoint.
30215 Depending on whether all-stop
30216 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30217 stop all threads, or only the thread that directly triggered the stop.
30218 If all threads are stopped, the @var{stopped} field will have the
30219 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30220 field will be a list of thread identifiers. Presently, this list will
30221 always include a single thread, but frontend should be prepared to see
30222 several threads in the list. The @var{core} field reports the
30223 processor core on which the stop event has happened. This field may be absent
30224 if such information is not available.
30226 @item =thread-group-added,id="@var{id}"
30227 @itemx =thread-group-removed,id="@var{id}"
30228 A thread group was either added or removed. The @var{id} field
30229 contains the @value{GDBN} identifier of the thread group. When a thread
30230 group is added, it generally might not be associated with a running
30231 process. When a thread group is removed, its id becomes invalid and
30232 cannot be used in any way.
30234 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30235 A thread group became associated with a running program,
30236 either because the program was just started or the thread group
30237 was attached to a program. The @var{id} field contains the
30238 @value{GDBN} identifier of the thread group. The @var{pid} field
30239 contains process identifier, specific to the operating system.
30241 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30242 A thread group is no longer associated with a running program,
30243 either because the program has exited, or because it was detached
30244 from. The @var{id} field contains the @value{GDBN} identifier of the
30245 thread group. The @var{code} field is the exit code of the inferior; it exists
30246 only when the inferior exited with some code.
30248 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30249 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30250 A thread either was created, or has exited. The @var{id} field
30251 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30252 field identifies the thread group this thread belongs to.
30254 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30255 Informs that the selected thread or frame were changed. This notification
30256 is not emitted as result of the @code{-thread-select} or
30257 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30258 that is not documented to change the selected thread and frame actually
30259 changes them. In particular, invoking, directly or indirectly
30260 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30261 will generate this notification. Changing the thread or frame from another
30262 user interface (see @ref{Interpreters}) will also generate this notification.
30264 The @var{frame} field is only present if the newly selected thread is
30265 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30267 We suggest that in response to this notification, front ends
30268 highlight the selected thread and cause subsequent commands to apply to
30271 @item =library-loaded,...
30272 Reports that a new library file was loaded by the program. This
30273 notification has 5 fields---@var{id}, @var{target-name},
30274 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30275 opaque identifier of the library. For remote debugging case,
30276 @var{target-name} and @var{host-name} fields give the name of the
30277 library file on the target, and on the host respectively. For native
30278 debugging, both those fields have the same value. The
30279 @var{symbols-loaded} field is emitted only for backward compatibility
30280 and should not be relied on to convey any useful information. The
30281 @var{thread-group} field, if present, specifies the id of the thread
30282 group in whose context the library was loaded. If the field is
30283 absent, it means the library was loaded in the context of all present
30284 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30287 @item =library-unloaded,...
30288 Reports that a library was unloaded by the program. This notification
30289 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30290 the same meaning as for the @code{=library-loaded} notification.
30291 The @var{thread-group} field, if present, specifies the id of the
30292 thread group in whose context the library was unloaded. If the field is
30293 absent, it means the library was unloaded in the context of all present
30296 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30297 @itemx =traceframe-changed,end
30298 Reports that the trace frame was changed and its new number is
30299 @var{tfnum}. The number of the tracepoint associated with this trace
30300 frame is @var{tpnum}.
30302 @item =tsv-created,name=@var{name},initial=@var{initial}
30303 Reports that the new trace state variable @var{name} is created with
30304 initial value @var{initial}.
30306 @item =tsv-deleted,name=@var{name}
30307 @itemx =tsv-deleted
30308 Reports that the trace state variable @var{name} is deleted or all
30309 trace state variables are deleted.
30311 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30312 Reports that the trace state variable @var{name} is modified with
30313 the initial value @var{initial}. The current value @var{current} of
30314 trace state variable is optional and is reported if the current
30315 value of trace state variable is known.
30317 @item =breakpoint-created,bkpt=@{...@}
30318 @itemx =breakpoint-modified,bkpt=@{...@}
30319 @itemx =breakpoint-deleted,id=@var{number}
30320 Reports that a breakpoint was created, modified, or deleted,
30321 respectively. Only user-visible breakpoints are reported to the MI
30324 The @var{bkpt} argument is of the same form as returned by the various
30325 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30326 @var{number} is the ordinal number of the breakpoint.
30328 Note that if a breakpoint is emitted in the result record of a
30329 command, then it will not also be emitted in an async record.
30331 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30332 @itemx =record-stopped,thread-group="@var{id}"
30333 Execution log recording was either started or stopped on an
30334 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30335 group corresponding to the affected inferior.
30337 The @var{method} field indicates the method used to record execution. If the
30338 method in use supports multiple recording formats, @var{format} will be present
30339 and contain the currently used format. @xref{Process Record and Replay},
30340 for existing method and format values.
30342 @item =cmd-param-changed,param=@var{param},value=@var{value}
30343 Reports that a parameter of the command @code{set @var{param}} is
30344 changed to @var{value}. In the multi-word @code{set} command,
30345 the @var{param} is the whole parameter list to @code{set} command.
30346 For example, In command @code{set check type on}, @var{param}
30347 is @code{check type} and @var{value} is @code{on}.
30349 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30350 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30351 written in an inferior. The @var{id} is the identifier of the
30352 thread group corresponding to the affected inferior. The optional
30353 @code{type="code"} part is reported if the memory written to holds
30357 @node GDB/MI Breakpoint Information
30358 @subsection @sc{gdb/mi} Breakpoint Information
30360 When @value{GDBN} reports information about a breakpoint, a
30361 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30366 The breakpoint number.
30369 The type of the breakpoint. For ordinary breakpoints this will be
30370 @samp{breakpoint}, but many values are possible.
30373 If the type of the breakpoint is @samp{catchpoint}, then this
30374 indicates the exact type of catchpoint.
30377 This is the breakpoint disposition---either @samp{del}, meaning that
30378 the breakpoint will be deleted at the next stop, or @samp{keep},
30379 meaning that the breakpoint will not be deleted.
30382 This indicates whether the breakpoint is enabled, in which case the
30383 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30384 Note that this is not the same as the field @code{enable}.
30387 The address of the breakpoint. This may be a hexidecimal number,
30388 giving the address; or the string @samp{<PENDING>}, for a pending
30389 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30390 multiple locations. This field will not be present if no address can
30391 be determined. For example, a watchpoint does not have an address.
30394 Optional field containing any flags related to the address. These flags are
30395 architecture-dependent; see @ref{Architectures} for their meaning for a
30399 If known, the function in which the breakpoint appears.
30400 If not known, this field is not present.
30403 The name of the source file which contains this function, if known.
30404 If not known, this field is not present.
30407 The full file name of the source file which contains this function, if
30408 known. If not known, this field is not present.
30411 The line number at which this breakpoint appears, if known.
30412 If not known, this field is not present.
30415 If the source file is not known, this field may be provided. If
30416 provided, this holds the address of the breakpoint, possibly followed
30420 If this breakpoint is pending, this field is present and holds the
30421 text used to set the breakpoint, as entered by the user.
30424 Where this breakpoint's condition is evaluated, either @samp{host} or
30428 If this is a thread-specific breakpoint, then this identifies the
30429 thread in which the breakpoint can trigger.
30432 If this breakpoint is restricted to a particular Ada task, then this
30433 field will hold the task identifier.
30436 If the breakpoint is conditional, this is the condition expression.
30439 The ignore count of the breakpoint.
30442 The enable count of the breakpoint.
30444 @item traceframe-usage
30447 @item static-tracepoint-marker-string-id
30448 For a static tracepoint, the name of the static tracepoint marker.
30451 For a masked watchpoint, this is the mask.
30454 A tracepoint's pass count.
30456 @item original-location
30457 The location of the breakpoint as originally specified by the user.
30458 This field is optional.
30461 The number of times the breakpoint has been hit.
30464 This field is only given for tracepoints. This is either @samp{y},
30465 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30469 Some extra data, the exact contents of which are type-dependent.
30472 This field is present if the breakpoint has multiple locations. It is also
30473 exceptionally present if the breakpoint is enabled and has a single, disabled
30476 The value is a list of locations. The format of a location is described below.
30480 A location in a multi-location breakpoint is represented as a tuple with the
30486 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30487 number of the parent breakpoint. The second digit is the number of the
30488 location within that breakpoint.
30491 There are three possible values, with the following meanings:
30494 The location is enabled.
30496 The location is disabled by the user.
30498 The location is disabled because the breakpoint condition is invalid
30503 The address of this location as an hexidecimal number.
30506 Optional field containing any flags related to the address. These flags are
30507 architecture-dependent; see @ref{Architectures} for their meaning for a
30511 If known, the function in which the location appears.
30512 If not known, this field is not present.
30515 The name of the source file which contains this location, if known.
30516 If not known, this field is not present.
30519 The full file name of the source file which contains this location, if
30520 known. If not known, this field is not present.
30523 The line number at which this location appears, if known.
30524 If not known, this field is not present.
30526 @item thread-groups
30527 The thread groups this location is in.
30531 For example, here is what the output of @code{-break-insert}
30532 (@pxref{GDB/MI Breakpoint Commands}) might be:
30535 -> -break-insert main
30536 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30537 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30538 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30543 @node GDB/MI Frame Information
30544 @subsection @sc{gdb/mi} Frame Information
30546 Response from many MI commands includes an information about stack
30547 frame. This information is a tuple that may have the following
30552 The level of the stack frame. The innermost frame has the level of
30553 zero. This field is always present.
30556 The name of the function corresponding to the frame. This field may
30557 be absent if @value{GDBN} is unable to determine the function name.
30560 The code address for the frame. This field is always present.
30563 Optional field containing any flags related to the address. These flags are
30564 architecture-dependent; see @ref{Architectures} for their meaning for a
30568 The name of the source files that correspond to the frame's code
30569 address. This field may be absent.
30572 The source line corresponding to the frames' code address. This field
30576 The name of the binary file (either executable or shared library) the
30577 corresponds to the frame's code address. This field may be absent.
30581 @node GDB/MI Thread Information
30582 @subsection @sc{gdb/mi} Thread Information
30584 Whenever @value{GDBN} has to report an information about a thread, it
30585 uses a tuple with the following fields. The fields are always present unless
30590 The global numeric id assigned to the thread by @value{GDBN}.
30593 The target-specific string identifying the thread.
30596 Additional information about the thread provided by the target.
30597 It is supposed to be human-readable and not interpreted by the
30598 frontend. This field is optional.
30601 The name of the thread. If the user specified a name using the
30602 @code{thread name} command, then this name is given. Otherwise, if
30603 @value{GDBN} can extract the thread name from the target, then that
30604 name is given. If @value{GDBN} cannot find the thread name, then this
30608 The execution state of the thread, either @samp{stopped} or @samp{running},
30609 depending on whether the thread is presently running.
30612 The stack frame currently executing in the thread. This field is only present
30613 if the thread is stopped. Its format is documented in
30614 @ref{GDB/MI Frame Information}.
30617 The value of this field is an integer number of the processor core the
30618 thread was last seen on. This field is optional.
30621 @node GDB/MI Ada Exception Information
30622 @subsection @sc{gdb/mi} Ada Exception Information
30624 Whenever a @code{*stopped} record is emitted because the program
30625 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30626 @value{GDBN} provides the name of the exception that was raised via
30627 the @code{exception-name} field. Also, for exceptions that were raised
30628 with an exception message, @value{GDBN} provides that message via
30629 the @code{exception-message} field.
30631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30632 @node GDB/MI Simple Examples
30633 @section Simple Examples of @sc{gdb/mi} Interaction
30634 @cindex @sc{gdb/mi}, simple examples
30636 This subsection presents several simple examples of interaction using
30637 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30638 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30639 the output received from @sc{gdb/mi}.
30641 Note the line breaks shown in the examples are here only for
30642 readability, they don't appear in the real output.
30644 @subheading Setting a Breakpoint
30646 Setting a breakpoint generates synchronous output which contains detailed
30647 information of the breakpoint.
30650 -> -break-insert main
30651 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30652 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30653 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30658 @subheading Program Execution
30660 Program execution generates asynchronous records and MI gives the
30661 reason that execution stopped.
30667 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30668 frame=@{addr="0x08048564",func="main",
30669 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30670 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30671 arch="i386:x86_64"@}
30676 <- *stopped,reason="exited-normally"
30680 @subheading Quitting @value{GDBN}
30682 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30690 Please note that @samp{^exit} is printed immediately, but it might
30691 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30692 performs necessary cleanups, including killing programs being debugged
30693 or disconnecting from debug hardware, so the frontend should wait till
30694 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30695 fails to exit in reasonable time.
30697 @subheading A Bad Command
30699 Here's what happens if you pass a non-existent command:
30703 <- ^error,msg="Undefined MI command: rubbish"
30708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30709 @node GDB/MI Command Description Format
30710 @section @sc{gdb/mi} Command Description Format
30712 The remaining sections describe blocks of commands. Each block of
30713 commands is laid out in a fashion similar to this section.
30715 @subheading Motivation
30717 The motivation for this collection of commands.
30719 @subheading Introduction
30721 A brief introduction to this collection of commands as a whole.
30723 @subheading Commands
30725 For each command in the block, the following is described:
30727 @subsubheading Synopsis
30730 -command @var{args}@dots{}
30733 @subsubheading Result
30735 @subsubheading @value{GDBN} Command
30737 The corresponding @value{GDBN} CLI command(s), if any.
30739 @subsubheading Example
30741 Example(s) formatted for readability. Some of the described commands have
30742 not been implemented yet and these are labeled N.A.@: (not available).
30745 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30746 @node GDB/MI Breakpoint Commands
30747 @section @sc{gdb/mi} Breakpoint Commands
30749 @cindex breakpoint commands for @sc{gdb/mi}
30750 @cindex @sc{gdb/mi}, breakpoint commands
30751 This section documents @sc{gdb/mi} commands for manipulating
30754 @subheading The @code{-break-after} Command
30755 @findex -break-after
30757 @subsubheading Synopsis
30760 -break-after @var{number} @var{count}
30763 The breakpoint number @var{number} is not in effect until it has been
30764 hit @var{count} times. To see how this is reflected in the output of
30765 the @samp{-break-list} command, see the description of the
30766 @samp{-break-list} command below.
30768 @subsubheading @value{GDBN} Command
30770 The corresponding @value{GDBN} command is @samp{ignore}.
30772 @subsubheading Example
30777 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30778 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30779 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30787 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30788 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30789 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30790 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30791 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30792 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30793 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30794 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30795 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30796 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30801 @subheading The @code{-break-catch} Command
30802 @findex -break-catch
30805 @subheading The @code{-break-commands} Command
30806 @findex -break-commands
30808 @subsubheading Synopsis
30811 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30814 Specifies the CLI commands that should be executed when breakpoint
30815 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30816 are the commands. If no command is specified, any previously-set
30817 commands are cleared. @xref{Break Commands}. Typical use of this
30818 functionality is tracing a program, that is, printing of values of
30819 some variables whenever breakpoint is hit and then continuing.
30821 @subsubheading @value{GDBN} Command
30823 The corresponding @value{GDBN} command is @samp{commands}.
30825 @subsubheading Example
30830 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30831 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30832 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30835 -break-commands 1 "print v" "continue"
30840 @subheading The @code{-break-condition} Command
30841 @findex -break-condition
30843 @subsubheading Synopsis
30846 -break-condition [ --force ] @var{number} [ @var{expr} ]
30849 Breakpoint @var{number} will stop the program only if the condition in
30850 @var{expr} is true. The condition becomes part of the
30851 @samp{-break-list} output (see the description of the @samp{-break-list}
30852 command below). If the @samp{--force} flag is passed, the condition
30853 is forcibly defined even when it is invalid for all locations of
30854 breakpoint @var{number}. If the @var{expr} argument is omitted,
30855 breakpoint @var{number} becomes unconditional.
30857 @subsubheading @value{GDBN} Command
30859 The corresponding @value{GDBN} command is @samp{condition}.
30861 @subsubheading Example
30865 -break-condition 1 1
30869 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30870 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30871 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30872 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30873 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30874 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30875 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30876 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30877 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30878 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30882 @subheading The @code{-break-delete} Command
30883 @findex -break-delete
30885 @subsubheading Synopsis
30888 -break-delete ( @var{breakpoint} )+
30891 Delete the breakpoint(s) whose number(s) are specified in the argument
30892 list. This is obviously reflected in the breakpoint list.
30894 @subsubheading @value{GDBN} Command
30896 The corresponding @value{GDBN} command is @samp{delete}.
30898 @subsubheading Example
30906 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30907 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30908 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30909 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30910 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30911 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30912 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30917 @subheading The @code{-break-disable} Command
30918 @findex -break-disable
30920 @subsubheading Synopsis
30923 -break-disable ( @var{breakpoint} )+
30926 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30927 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30929 @subsubheading @value{GDBN} Command
30931 The corresponding @value{GDBN} command is @samp{disable}.
30933 @subsubheading Example
30941 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30942 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30943 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30944 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30945 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30946 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30947 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30948 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30949 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30950 line="5",thread-groups=["i1"],times="0"@}]@}
30954 @subheading The @code{-break-enable} Command
30955 @findex -break-enable
30957 @subsubheading Synopsis
30960 -break-enable ( @var{breakpoint} )+
30963 Enable (previously disabled) @var{breakpoint}(s).
30965 @subsubheading @value{GDBN} Command
30967 The corresponding @value{GDBN} command is @samp{enable}.
30969 @subsubheading Example
30977 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30978 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30979 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30980 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30981 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30982 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30983 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30984 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30985 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30986 line="5",thread-groups=["i1"],times="0"@}]@}
30990 @subheading The @code{-break-info} Command
30991 @findex -break-info
30993 @subsubheading Synopsis
30996 -break-info @var{breakpoint}
31000 Get information about a single breakpoint.
31002 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31003 Information}, for details on the format of each breakpoint in the
31006 @subsubheading @value{GDBN} Command
31008 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31010 @subsubheading Example
31013 @subheading The @code{-break-insert} Command
31014 @findex -break-insert
31015 @anchor{-break-insert}
31017 @subsubheading Synopsis
31020 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31021 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31022 [ -p @var{thread-id} ] [ @var{location} ]
31026 If specified, @var{location}, can be one of:
31029 @item linespec location
31030 A linespec location. @xref{Linespec Locations}.
31032 @item explicit location
31033 An explicit location. @sc{gdb/mi} explicit locations are
31034 analogous to the CLI's explicit locations using the option names
31035 listed below. @xref{Explicit Locations}.
31038 @item --source @var{filename}
31039 The source file name of the location. This option requires the use
31040 of either @samp{--function} or @samp{--line}.
31042 @item --function @var{function}
31043 The name of a function or method.
31045 @item --label @var{label}
31046 The name of a label.
31048 @item --line @var{lineoffset}
31049 An absolute or relative line offset from the start of the location.
31052 @item address location
31053 An address location, *@var{address}. @xref{Address Locations}.
31057 The possible optional parameters of this command are:
31061 Insert a temporary breakpoint.
31063 Insert a hardware breakpoint.
31065 If @var{location} cannot be parsed (for example if it
31066 refers to unknown files or functions), create a pending
31067 breakpoint. Without this flag, @value{GDBN} will report
31068 an error, and won't create a breakpoint, if @var{location}
31071 Create a disabled breakpoint.
31073 Create a tracepoint. @xref{Tracepoints}. When this parameter
31074 is used together with @samp{-h}, a fast tracepoint is created.
31075 @item -c @var{condition}
31076 Make the breakpoint conditional on @var{condition}.
31077 @item --force-condition
31078 Forcibly define the breakpoint even if the condition is invalid at
31079 all of the breakpoint locations.
31080 @item -i @var{ignore-count}
31081 Initialize the @var{ignore-count}.
31082 @item -p @var{thread-id}
31083 Restrict the breakpoint to the thread with the specified global
31086 This option makes @value{GDBN} interpret a function name specified as
31087 a complete fully-qualified name.
31090 @subsubheading Result
31092 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31093 resulting breakpoint.
31095 Note: this format is open to change.
31096 @c An out-of-band breakpoint instead of part of the result?
31098 @subsubheading @value{GDBN} Command
31100 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31101 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31103 @subsubheading Example
31108 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31109 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31112 -break-insert -t foo
31113 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31114 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31118 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31119 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31120 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31121 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31122 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31123 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31124 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31125 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31126 addr="0x0001072c", func="main",file="recursive2.c",
31127 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31129 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31130 addr="0x00010774",func="foo",file="recursive2.c",
31131 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31134 @c -break-insert -r foo.*
31135 @c ~int foo(int, int);
31136 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
31137 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31142 @subheading The @code{-dprintf-insert} Command
31143 @findex -dprintf-insert
31145 @subsubheading Synopsis
31148 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31149 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31150 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
31155 If supplied, @var{location} and @code{--qualified} may be specified
31156 the same way as for the @code{-break-insert} command.
31157 @xref{-break-insert}.
31159 The possible optional parameters of this command are:
31163 Insert a temporary breakpoint.
31165 If @var{location} cannot be parsed (for example, if it
31166 refers to unknown files or functions), create a pending
31167 breakpoint. Without this flag, @value{GDBN} will report
31168 an error, and won't create a breakpoint, if @var{location}
31171 Create a disabled breakpoint.
31172 @item -c @var{condition}
31173 Make the breakpoint conditional on @var{condition}.
31174 @item --force-condition
31175 Forcibly define the breakpoint even if the condition is invalid at
31176 all of the breakpoint locations.
31177 @item -i @var{ignore-count}
31178 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31179 to @var{ignore-count}.
31180 @item -p @var{thread-id}
31181 Restrict the breakpoint to the thread with the specified global
31185 @subsubheading Result
31187 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31188 resulting breakpoint.
31190 @c An out-of-band breakpoint instead of part of the result?
31192 @subsubheading @value{GDBN} Command
31194 The corresponding @value{GDBN} command is @samp{dprintf}.
31196 @subsubheading Example
31200 4-dprintf-insert foo "At foo entry\n"
31201 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31202 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31203 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31204 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31205 original-location="foo"@}
31207 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31208 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31209 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31210 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31211 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31212 original-location="mi-dprintf.c:26"@}
31216 @subheading The @code{-break-list} Command
31217 @findex -break-list
31219 @subsubheading Synopsis
31225 Displays the list of inserted breakpoints, showing the following fields:
31229 number of the breakpoint
31231 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31233 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31236 is the breakpoint enabled or no: @samp{y} or @samp{n}
31238 memory location at which the breakpoint is set
31240 logical location of the breakpoint, expressed by function name, file
31242 @item Thread-groups
31243 list of thread groups to which this breakpoint applies
31245 number of times the breakpoint has been hit
31248 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31249 @code{body} field is an empty list.
31251 @subsubheading @value{GDBN} Command
31253 The corresponding @value{GDBN} command is @samp{info break}.
31255 @subsubheading Example
31260 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31261 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31262 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31263 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31264 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31265 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31266 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31267 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31268 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31270 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31271 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31272 line="13",thread-groups=["i1"],times="0"@}]@}
31276 Here's an example of the result when there are no breakpoints:
31281 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31282 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31283 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31284 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31285 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31286 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31287 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31292 @subheading The @code{-break-passcount} Command
31293 @findex -break-passcount
31295 @subsubheading Synopsis
31298 -break-passcount @var{tracepoint-number} @var{passcount}
31301 Set the passcount for tracepoint @var{tracepoint-number} to
31302 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31303 is not a tracepoint, error is emitted. This corresponds to CLI
31304 command @samp{passcount}.
31306 @subheading The @code{-break-watch} Command
31307 @findex -break-watch
31309 @subsubheading Synopsis
31312 -break-watch [ -a | -r ]
31315 Create a watchpoint. With the @samp{-a} option it will create an
31316 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31317 read from or on a write to the memory location. With the @samp{-r}
31318 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31319 trigger only when the memory location is accessed for reading. Without
31320 either of the options, the watchpoint created is a regular watchpoint,
31321 i.e., it will trigger when the memory location is accessed for writing.
31322 @xref{Set Watchpoints, , Setting Watchpoints}.
31324 Note that @samp{-break-list} will report a single list of watchpoints and
31325 breakpoints inserted.
31327 @subsubheading @value{GDBN} Command
31329 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31332 @subsubheading Example
31334 Setting a watchpoint on a variable in the @code{main} function:
31339 ^done,wpt=@{number="2",exp="x"@}
31344 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31345 value=@{old="-268439212",new="55"@},
31346 frame=@{func="main",args=[],file="recursive2.c",
31347 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31351 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31352 the program execution twice: first for the variable changing value, then
31353 for the watchpoint going out of scope.
31358 ^done,wpt=@{number="5",exp="C"@}
31363 *stopped,reason="watchpoint-trigger",
31364 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31365 frame=@{func="callee4",args=[],
31366 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31367 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31368 arch="i386:x86_64"@}
31373 *stopped,reason="watchpoint-scope",wpnum="5",
31374 frame=@{func="callee3",args=[@{name="strarg",
31375 value="0x11940 \"A string argument.\""@}],
31376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31377 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31378 arch="i386:x86_64"@}
31382 Listing breakpoints and watchpoints, at different points in the program
31383 execution. Note that once the watchpoint goes out of scope, it is
31389 ^done,wpt=@{number="2",exp="C"@}
31392 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31393 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31394 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31395 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31396 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31397 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31398 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31399 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31400 addr="0x00010734",func="callee4",
31401 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31402 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31404 bkpt=@{number="2",type="watchpoint",disp="keep",
31405 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31410 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31411 value=@{old="-276895068",new="3"@},
31412 frame=@{func="callee4",args=[],
31413 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31414 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31415 arch="i386:x86_64"@}
31418 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31419 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31420 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31421 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31422 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31423 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31424 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31425 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31426 addr="0x00010734",func="callee4",
31427 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31428 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31430 bkpt=@{number="2",type="watchpoint",disp="keep",
31431 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31435 ^done,reason="watchpoint-scope",wpnum="2",
31436 frame=@{func="callee3",args=[@{name="strarg",
31437 value="0x11940 \"A string argument.\""@}],
31438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31439 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31440 arch="i386:x86_64"@}
31443 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31444 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31445 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31446 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31447 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31448 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31449 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31450 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31451 addr="0x00010734",func="callee4",
31452 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31453 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31454 thread-groups=["i1"],times="1"@}]@}
31459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31460 @node GDB/MI Catchpoint Commands
31461 @section @sc{gdb/mi} Catchpoint Commands
31463 This section documents @sc{gdb/mi} commands for manipulating
31467 * Shared Library GDB/MI Catchpoint Commands::
31468 * Ada Exception GDB/MI Catchpoint Commands::
31469 * C++ Exception GDB/MI Catchpoint Commands::
31472 @node Shared Library GDB/MI Catchpoint Commands
31473 @subsection Shared Library @sc{gdb/mi} Catchpoints
31475 @subheading The @code{-catch-load} Command
31476 @findex -catch-load
31478 @subsubheading Synopsis
31481 -catch-load [ -t ] [ -d ] @var{regexp}
31484 Add a catchpoint for library load events. If the @samp{-t} option is used,
31485 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31486 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31487 in a disabled state. The @samp{regexp} argument is a regular
31488 expression used to match the name of the loaded library.
31491 @subsubheading @value{GDBN} Command
31493 The corresponding @value{GDBN} command is @samp{catch load}.
31495 @subsubheading Example
31498 -catch-load -t foo.so
31499 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31500 what="load of library matching foo.so",catch-type="load",times="0"@}
31505 @subheading The @code{-catch-unload} Command
31506 @findex -catch-unload
31508 @subsubheading Synopsis
31511 -catch-unload [ -t ] [ -d ] @var{regexp}
31514 Add a catchpoint for library unload events. If the @samp{-t} option is
31515 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31516 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31517 created in a disabled state. The @samp{regexp} argument is a regular
31518 expression used to match the name of the unloaded library.
31520 @subsubheading @value{GDBN} Command
31522 The corresponding @value{GDBN} command is @samp{catch unload}.
31524 @subsubheading Example
31527 -catch-unload -d bar.so
31528 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31529 what="load of library matching bar.so",catch-type="unload",times="0"@}
31533 @node Ada Exception GDB/MI Catchpoint Commands
31534 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31536 The following @sc{gdb/mi} commands can be used to create catchpoints
31537 that stop the execution when Ada exceptions are being raised.
31539 @subheading The @code{-catch-assert} Command
31540 @findex -catch-assert
31542 @subsubheading Synopsis
31545 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31548 Add a catchpoint for failed Ada assertions.
31550 The possible optional parameters for this command are:
31553 @item -c @var{condition}
31554 Make the catchpoint conditional on @var{condition}.
31556 Create a disabled catchpoint.
31558 Create a temporary catchpoint.
31561 @subsubheading @value{GDBN} Command
31563 The corresponding @value{GDBN} command is @samp{catch assert}.
31565 @subsubheading Example
31569 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31570 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31571 thread-groups=["i1"],times="0",
31572 original-location="__gnat_debug_raise_assert_failure"@}
31576 @subheading The @code{-catch-exception} Command
31577 @findex -catch-exception
31579 @subsubheading Synopsis
31582 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31586 Add a catchpoint stopping when Ada exceptions are raised.
31587 By default, the command stops the program when any Ada exception
31588 gets raised. But it is also possible, by using some of the
31589 optional parameters described below, to create more selective
31592 The possible optional parameters for this command are:
31595 @item -c @var{condition}
31596 Make the catchpoint conditional on @var{condition}.
31598 Create a disabled catchpoint.
31599 @item -e @var{exception-name}
31600 Only stop when @var{exception-name} is raised. This option cannot
31601 be used combined with @samp{-u}.
31603 Create a temporary catchpoint.
31605 Stop only when an unhandled exception gets raised. This option
31606 cannot be used combined with @samp{-e}.
31609 @subsubheading @value{GDBN} Command
31611 The corresponding @value{GDBN} commands are @samp{catch exception}
31612 and @samp{catch exception unhandled}.
31614 @subsubheading Example
31617 -catch-exception -e Program_Error
31618 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31619 enabled="y",addr="0x0000000000404874",
31620 what="`Program_Error' Ada exception", thread-groups=["i1"],
31621 times="0",original-location="__gnat_debug_raise_exception"@}
31625 @subheading The @code{-catch-handlers} Command
31626 @findex -catch-handlers
31628 @subsubheading Synopsis
31631 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31635 Add a catchpoint stopping when Ada exceptions are handled.
31636 By default, the command stops the program when any Ada exception
31637 gets handled. But it is also possible, by using some of the
31638 optional parameters described below, to create more selective
31641 The possible optional parameters for this command are:
31644 @item -c @var{condition}
31645 Make the catchpoint conditional on @var{condition}.
31647 Create a disabled catchpoint.
31648 @item -e @var{exception-name}
31649 Only stop when @var{exception-name} is handled.
31651 Create a temporary catchpoint.
31654 @subsubheading @value{GDBN} Command
31656 The corresponding @value{GDBN} command is @samp{catch handlers}.
31658 @subsubheading Example
31661 -catch-handlers -e Constraint_Error
31662 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31663 enabled="y",addr="0x0000000000402f68",
31664 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31665 times="0",original-location="__gnat_begin_handler"@}
31669 @node C++ Exception GDB/MI Catchpoint Commands
31670 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31672 The following @sc{gdb/mi} commands can be used to create catchpoints
31673 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31676 @subheading The @code{-catch-throw} Command
31677 @findex -catch-throw
31679 @subsubheading Synopsis
31682 -catch-throw [ -t ] [ -r @var{regexp}]
31685 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31686 given, then only exceptions whose type matches the regular expression
31689 If @samp{-t} is given, then the catchpoint is enabled only for one
31690 stop, the catchpoint is automatically deleted after stopping once for
31693 @subsubheading @value{GDBN} Command
31695 The corresponding @value{GDBN} commands are @samp{catch throw}
31696 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31698 @subsubheading Example
31701 -catch-throw -r exception_type
31702 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31703 what="exception throw",catch-type="throw",
31704 thread-groups=["i1"],
31705 regexp="exception_type",times="0"@}
31711 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31712 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31713 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31714 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31715 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31716 thread-id="1",stopped-threads="all",core="6"
31720 @subheading The @code{-catch-rethrow} Command
31721 @findex -catch-rethrow
31723 @subsubheading Synopsis
31726 -catch-rethrow [ -t ] [ -r @var{regexp}]
31729 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31730 then only exceptions whose type matches the regular expression will be
31733 If @samp{-t} is given, then the catchpoint is enabled only for one
31734 stop, the catchpoint is automatically deleted after the first event is
31737 @subsubheading @value{GDBN} Command
31739 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31740 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31742 @subsubheading Example
31745 -catch-rethrow -r exception_type
31746 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31747 what="exception rethrow",catch-type="rethrow",
31748 thread-groups=["i1"],
31749 regexp="exception_type",times="0"@}
31755 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31756 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31757 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31758 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31759 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31760 thread-id="1",stopped-threads="all",core="6"
31764 @subheading The @code{-catch-catch} Command
31765 @findex -catch-catch
31767 @subsubheading Synopsis
31770 -catch-catch [ -t ] [ -r @var{regexp}]
31773 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31774 is given, then only exceptions whose type matches the regular
31775 expression will be caught.
31777 If @samp{-t} is given, then the catchpoint is enabled only for one
31778 stop, the catchpoint is automatically deleted after the first event is
31781 @subsubheading @value{GDBN} Command
31783 The corresponding @value{GDBN} commands are @samp{catch catch}
31784 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31786 @subsubheading Example
31789 -catch-catch -r exception_type
31790 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31791 what="exception catch",catch-type="catch",
31792 thread-groups=["i1"],
31793 regexp="exception_type",times="0"@}
31799 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31800 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31801 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31802 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31803 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31804 thread-id="1",stopped-threads="all",core="6"
31808 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31809 @node GDB/MI Program Context
31810 @section @sc{gdb/mi} Program Context
31812 @subheading The @code{-exec-arguments} Command
31813 @findex -exec-arguments
31816 @subsubheading Synopsis
31819 -exec-arguments @var{args}
31822 Set the inferior program arguments, to be used in the next
31825 @subsubheading @value{GDBN} Command
31827 The corresponding @value{GDBN} command is @samp{set args}.
31829 @subsubheading Example
31833 -exec-arguments -v word
31840 @subheading The @code{-exec-show-arguments} Command
31841 @findex -exec-show-arguments
31843 @subsubheading Synopsis
31846 -exec-show-arguments
31849 Print the arguments of the program.
31851 @subsubheading @value{GDBN} Command
31853 The corresponding @value{GDBN} command is @samp{show args}.
31855 @subsubheading Example
31860 @subheading The @code{-environment-cd} Command
31861 @findex -environment-cd
31863 @subsubheading Synopsis
31866 -environment-cd @var{pathdir}
31869 Set @value{GDBN}'s working directory.
31871 @subsubheading @value{GDBN} Command
31873 The corresponding @value{GDBN} command is @samp{cd}.
31875 @subsubheading Example
31879 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31885 @subheading The @code{-environment-directory} Command
31886 @findex -environment-directory
31888 @subsubheading Synopsis
31891 -environment-directory [ -r ] [ @var{pathdir} ]+
31894 Add directories @var{pathdir} to beginning of search path for source files.
31895 If the @samp{-r} option is used, the search path is reset to the default
31896 search path. If directories @var{pathdir} are supplied in addition to the
31897 @samp{-r} option, the search path is first reset and then addition
31899 Multiple directories may be specified, separated by blanks. Specifying
31900 multiple directories in a single command
31901 results in the directories added to the beginning of the
31902 search path in the same order they were presented in the command.
31903 If blanks are needed as
31904 part of a directory name, double-quotes should be used around
31905 the name. In the command output, the path will show up separated
31906 by the system directory-separator character. The directory-separator
31907 character must not be used
31908 in any directory name.
31909 If no directories are specified, the current search path is displayed.
31911 @subsubheading @value{GDBN} Command
31913 The corresponding @value{GDBN} command is @samp{dir}.
31915 @subsubheading Example
31919 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31920 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31922 -environment-directory ""
31923 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31925 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31926 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31928 -environment-directory -r
31929 ^done,source-path="$cdir:$cwd"
31934 @subheading The @code{-environment-path} Command
31935 @findex -environment-path
31937 @subsubheading Synopsis
31940 -environment-path [ -r ] [ @var{pathdir} ]+
31943 Add directories @var{pathdir} to beginning of search path for object files.
31944 If the @samp{-r} option is used, the search path is reset to the original
31945 search path that existed at gdb start-up. If directories @var{pathdir} are
31946 supplied in addition to the
31947 @samp{-r} option, the search path is first reset and then addition
31949 Multiple directories may be specified, separated by blanks. Specifying
31950 multiple directories in a single command
31951 results in the directories added to the beginning of the
31952 search path in the same order they were presented in the command.
31953 If blanks are needed as
31954 part of a directory name, double-quotes should be used around
31955 the name. In the command output, the path will show up separated
31956 by the system directory-separator character. The directory-separator
31957 character must not be used
31958 in any directory name.
31959 If no directories are specified, the current path is displayed.
31962 @subsubheading @value{GDBN} Command
31964 The corresponding @value{GDBN} command is @samp{path}.
31966 @subsubheading Example
31971 ^done,path="/usr/bin"
31973 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31974 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31976 -environment-path -r /usr/local/bin
31977 ^done,path="/usr/local/bin:/usr/bin"
31982 @subheading The @code{-environment-pwd} Command
31983 @findex -environment-pwd
31985 @subsubheading Synopsis
31991 Show the current working directory.
31993 @subsubheading @value{GDBN} Command
31995 The corresponding @value{GDBN} command is @samp{pwd}.
31997 @subsubheading Example
32002 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32007 @node GDB/MI Thread Commands
32008 @section @sc{gdb/mi} Thread Commands
32011 @subheading The @code{-thread-info} Command
32012 @findex -thread-info
32014 @subsubheading Synopsis
32017 -thread-info [ @var{thread-id} ]
32020 Reports information about either a specific thread, if the
32021 @var{thread-id} parameter is present, or about all threads.
32022 @var{thread-id} is the thread's global thread ID. When printing
32023 information about all threads, also reports the global ID of the
32026 @subsubheading @value{GDBN} Command
32028 The @samp{info thread} command prints the same information
32031 @subsubheading Result
32033 The result contains the following attributes:
32037 A list of threads. The format of the elements of the list is described in
32038 @ref{GDB/MI Thread Information}.
32040 @item current-thread-id
32041 The global id of the currently selected thread. This field is omitted if there
32042 is no selected thread (for example, when the selected inferior is not running,
32043 and therefore has no threads) or if a @var{thread-id} argument was passed to
32048 @subsubheading Example
32053 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32054 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32055 args=[]@},state="running"@},
32056 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32057 frame=@{level="0",addr="0x0804891f",func="foo",
32058 args=[@{name="i",value="10"@}],
32059 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32060 state="running"@}],
32061 current-thread-id="1"
32065 @subheading The @code{-thread-list-ids} Command
32066 @findex -thread-list-ids
32068 @subsubheading Synopsis
32074 Produces a list of the currently known global @value{GDBN} thread ids.
32075 At the end of the list it also prints the total number of such
32078 This command is retained for historical reasons, the
32079 @code{-thread-info} command should be used instead.
32081 @subsubheading @value{GDBN} Command
32083 Part of @samp{info threads} supplies the same information.
32085 @subsubheading Example
32090 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32091 current-thread-id="1",number-of-threads="3"
32096 @subheading The @code{-thread-select} Command
32097 @findex -thread-select
32099 @subsubheading Synopsis
32102 -thread-select @var{thread-id}
32105 Make thread with global thread number @var{thread-id} the current
32106 thread. It prints the number of the new current thread, and the
32107 topmost frame for that thread.
32109 This command is deprecated in favor of explicitly using the
32110 @samp{--thread} option to each command.
32112 @subsubheading @value{GDBN} Command
32114 The corresponding @value{GDBN} command is @samp{thread}.
32116 @subsubheading Example
32123 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32124 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32128 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32129 number-of-threads="3"
32132 ^done,new-thread-id="3",
32133 frame=@{level="0",func="vprintf",
32134 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32135 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32139 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32140 @node GDB/MI Ada Tasking Commands
32141 @section @sc{gdb/mi} Ada Tasking Commands
32143 @subheading The @code{-ada-task-info} Command
32144 @findex -ada-task-info
32146 @subsubheading Synopsis
32149 -ada-task-info [ @var{task-id} ]
32152 Reports information about either a specific Ada task, if the
32153 @var{task-id} parameter is present, or about all Ada tasks.
32155 @subsubheading @value{GDBN} Command
32157 The @samp{info tasks} command prints the same information
32158 about all Ada tasks (@pxref{Ada Tasks}).
32160 @subsubheading Result
32162 The result is a table of Ada tasks. The following columns are
32163 defined for each Ada task:
32167 This field exists only for the current thread. It has the value @samp{*}.
32170 The identifier that @value{GDBN} uses to refer to the Ada task.
32173 The identifier that the target uses to refer to the Ada task.
32176 The global thread identifier of the thread corresponding to the Ada
32179 This field should always exist, as Ada tasks are always implemented
32180 on top of a thread. But if @value{GDBN} cannot find this corresponding
32181 thread for any reason, the field is omitted.
32184 This field exists only when the task was created by another task.
32185 In this case, it provides the ID of the parent task.
32188 The base priority of the task.
32191 The current state of the task. For a detailed description of the
32192 possible states, see @ref{Ada Tasks}.
32195 The name of the task.
32199 @subsubheading Example
32203 ^done,tasks=@{nr_rows="3",nr_cols="8",
32204 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32205 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32206 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32207 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32208 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32209 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32210 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32211 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32212 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32213 state="Child Termination Wait",name="main_task"@}]@}
32217 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32218 @node GDB/MI Program Execution
32219 @section @sc{gdb/mi} Program Execution
32221 These are the asynchronous commands which generate the out-of-band
32222 record @samp{*stopped}. Currently @value{GDBN} only really executes
32223 asynchronously with remote targets and this interaction is mimicked in
32226 @subheading The @code{-exec-continue} Command
32227 @findex -exec-continue
32229 @subsubheading Synopsis
32232 -exec-continue [--reverse] [--all|--thread-group N]
32235 Resumes the execution of the inferior program, which will continue
32236 to execute until it reaches a debugger stop event. If the
32237 @samp{--reverse} option is specified, execution resumes in reverse until
32238 it reaches a stop event. Stop events may include
32241 breakpoints or watchpoints
32243 signals or exceptions
32245 the end of the process (or its beginning under @samp{--reverse})
32247 the end or beginning of a replay log if one is being used.
32249 In all-stop mode (@pxref{All-Stop
32250 Mode}), may resume only one thread, or all threads, depending on the
32251 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32252 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32253 ignored in all-stop mode. If the @samp{--thread-group} options is
32254 specified, then all threads in that thread group are resumed.
32256 @subsubheading @value{GDBN} Command
32258 The corresponding @value{GDBN} corresponding is @samp{continue}.
32260 @subsubheading Example
32267 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32268 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32269 line="13",arch="i386:x86_64"@}
32274 @subheading The @code{-exec-finish} Command
32275 @findex -exec-finish
32277 @subsubheading Synopsis
32280 -exec-finish [--reverse]
32283 Resumes the execution of the inferior program until the current
32284 function is exited. Displays the results returned by the function.
32285 If the @samp{--reverse} option is specified, resumes the reverse
32286 execution of the inferior program until the point where current
32287 function was called.
32289 @subsubheading @value{GDBN} Command
32291 The corresponding @value{GDBN} command is @samp{finish}.
32293 @subsubheading Example
32295 Function returning @code{void}.
32302 *stopped,reason="function-finished",frame=@{func="main",args=[],
32303 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32307 Function returning other than @code{void}. The name of the internal
32308 @value{GDBN} variable storing the result is printed, together with the
32315 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32316 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32317 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32318 arch="i386:x86_64"@},
32319 gdb-result-var="$1",return-value="0"
32324 @subheading The @code{-exec-interrupt} Command
32325 @findex -exec-interrupt
32327 @subsubheading Synopsis
32330 -exec-interrupt [--all|--thread-group N]
32333 Interrupts the background execution of the target. Note how the token
32334 associated with the stop message is the one for the execution command
32335 that has been interrupted. The token for the interrupt itself only
32336 appears in the @samp{^done} output. If the user is trying to
32337 interrupt a non-running program, an error message will be printed.
32339 Note that when asynchronous execution is enabled, this command is
32340 asynchronous just like other execution commands. That is, first the
32341 @samp{^done} response will be printed, and the target stop will be
32342 reported after that using the @samp{*stopped} notification.
32344 In non-stop mode, only the context thread is interrupted by default.
32345 All threads (in all inferiors) will be interrupted if the
32346 @samp{--all} option is specified. If the @samp{--thread-group}
32347 option is specified, all threads in that group will be interrupted.
32349 @subsubheading @value{GDBN} Command
32351 The corresponding @value{GDBN} command is @samp{interrupt}.
32353 @subsubheading Example
32364 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32365 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32366 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32371 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32375 @subheading The @code{-exec-jump} Command
32378 @subsubheading Synopsis
32381 -exec-jump @var{location}
32384 Resumes execution of the inferior program at the location specified by
32385 parameter. @xref{Specify Location}, for a description of the
32386 different forms of @var{location}.
32388 @subsubheading @value{GDBN} Command
32390 The corresponding @value{GDBN} command is @samp{jump}.
32392 @subsubheading Example
32395 -exec-jump foo.c:10
32396 *running,thread-id="all"
32401 @subheading The @code{-exec-next} Command
32404 @subsubheading Synopsis
32407 -exec-next [--reverse]
32410 Resumes execution of the inferior program, stopping when the beginning
32411 of the next source line is reached.
32413 If the @samp{--reverse} option is specified, resumes reverse execution
32414 of the inferior program, stopping at the beginning of the previous
32415 source line. If you issue this command on the first line of a
32416 function, it will take you back to the caller of that function, to the
32417 source line where the function was called.
32420 @subsubheading @value{GDBN} Command
32422 The corresponding @value{GDBN} command is @samp{next}.
32424 @subsubheading Example
32430 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32435 @subheading The @code{-exec-next-instruction} Command
32436 @findex -exec-next-instruction
32438 @subsubheading Synopsis
32441 -exec-next-instruction [--reverse]
32444 Executes one machine instruction. If the instruction is a function
32445 call, continues until the function returns. If the program stops at an
32446 instruction in the middle of a source line, the address will be
32449 If the @samp{--reverse} option is specified, resumes reverse execution
32450 of the inferior program, stopping at the previous instruction. If the
32451 previously executed instruction was a return from another function,
32452 it will continue to execute in reverse until the call to that function
32453 (from the current stack frame) is reached.
32455 @subsubheading @value{GDBN} Command
32457 The corresponding @value{GDBN} command is @samp{nexti}.
32459 @subsubheading Example
32463 -exec-next-instruction
32467 *stopped,reason="end-stepping-range",
32468 addr="0x000100d4",line="5",file="hello.c"
32473 @subheading The @code{-exec-return} Command
32474 @findex -exec-return
32476 @subsubheading Synopsis
32482 Makes current function return immediately. Doesn't execute the inferior.
32483 Displays the new current frame.
32485 @subsubheading @value{GDBN} Command
32487 The corresponding @value{GDBN} command is @samp{return}.
32489 @subsubheading Example
32493 200-break-insert callee4
32494 200^done,bkpt=@{number="1",addr="0x00010734",
32495 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32500 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32501 frame=@{func="callee4",args=[],
32502 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32503 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32504 arch="i386:x86_64"@}
32510 111^done,frame=@{level="0",func="callee3",
32511 args=[@{name="strarg",
32512 value="0x11940 \"A string argument.\""@}],
32513 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32514 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32515 arch="i386:x86_64"@}
32520 @subheading The @code{-exec-run} Command
32523 @subsubheading Synopsis
32526 -exec-run [ --all | --thread-group N ] [ --start ]
32529 Starts execution of the inferior from the beginning. The inferior
32530 executes until either a breakpoint is encountered or the program
32531 exits. In the latter case the output will include an exit code, if
32532 the program has exited exceptionally.
32534 When neither the @samp{--all} nor the @samp{--thread-group} option
32535 is specified, the current inferior is started. If the
32536 @samp{--thread-group} option is specified, it should refer to a thread
32537 group of type @samp{process}, and that thread group will be started.
32538 If the @samp{--all} option is specified, then all inferiors will be started.
32540 Using the @samp{--start} option instructs the debugger to stop
32541 the execution at the start of the inferior's main subprogram,
32542 following the same behavior as the @code{start} command
32543 (@pxref{Starting}).
32545 @subsubheading @value{GDBN} Command
32547 The corresponding @value{GDBN} command is @samp{run}.
32549 @subsubheading Examples
32554 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32559 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32560 frame=@{func="main",args=[],file="recursive2.c",
32561 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32566 Program exited normally:
32574 *stopped,reason="exited-normally"
32579 Program exited exceptionally:
32587 *stopped,reason="exited",exit-code="01"
32591 Another way the program can terminate is if it receives a signal such as
32592 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32596 *stopped,reason="exited-signalled",signal-name="SIGINT",
32597 signal-meaning="Interrupt"
32601 @c @subheading -exec-signal
32604 @subheading The @code{-exec-step} Command
32607 @subsubheading Synopsis
32610 -exec-step [--reverse]
32613 Resumes execution of the inferior program, stopping when the beginning
32614 of the next source line is reached, if the next source line is not a
32615 function call. If it is, stop at the first instruction of the called
32616 function. If the @samp{--reverse} option is specified, resumes reverse
32617 execution of the inferior program, stopping at the beginning of the
32618 previously executed source line.
32620 @subsubheading @value{GDBN} Command
32622 The corresponding @value{GDBN} command is @samp{step}.
32624 @subsubheading Example
32626 Stepping into a function:
32632 *stopped,reason="end-stepping-range",
32633 frame=@{func="foo",args=[@{name="a",value="10"@},
32634 @{name="b",value="0"@}],file="recursive2.c",
32635 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32645 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32650 @subheading The @code{-exec-step-instruction} Command
32651 @findex -exec-step-instruction
32653 @subsubheading Synopsis
32656 -exec-step-instruction [--reverse]
32659 Resumes the inferior which executes one machine instruction. If the
32660 @samp{--reverse} option is specified, resumes reverse execution of the
32661 inferior program, stopping at the previously executed instruction.
32662 The output, once @value{GDBN} has stopped, will vary depending on
32663 whether we have stopped in the middle of a source line or not. In the
32664 former case, the address at which the program stopped will be printed
32667 @subsubheading @value{GDBN} Command
32669 The corresponding @value{GDBN} command is @samp{stepi}.
32671 @subsubheading Example
32675 -exec-step-instruction
32679 *stopped,reason="end-stepping-range",
32680 frame=@{func="foo",args=[],file="try.c",
32681 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32683 -exec-step-instruction
32687 *stopped,reason="end-stepping-range",
32688 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32689 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32694 @subheading The @code{-exec-until} Command
32695 @findex -exec-until
32697 @subsubheading Synopsis
32700 -exec-until [ @var{location} ]
32703 Executes the inferior until the @var{location} specified in the
32704 argument is reached. If there is no argument, the inferior executes
32705 until a source line greater than the current one is reached. The
32706 reason for stopping in this case will be @samp{location-reached}.
32708 @subsubheading @value{GDBN} Command
32710 The corresponding @value{GDBN} command is @samp{until}.
32712 @subsubheading Example
32716 -exec-until recursive2.c:6
32720 *stopped,reason="location-reached",frame=@{func="main",args=[],
32721 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32722 arch="i386:x86_64"@}
32727 @subheading -file-clear
32728 Is this going away????
32731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32732 @node GDB/MI Stack Manipulation
32733 @section @sc{gdb/mi} Stack Manipulation Commands
32735 @subheading The @code{-enable-frame-filters} Command
32736 @findex -enable-frame-filters
32739 -enable-frame-filters
32742 @value{GDBN} allows Python-based frame filters to affect the output of
32743 the MI commands relating to stack traces. As there is no way to
32744 implement this in a fully backward-compatible way, a front end must
32745 request that this functionality be enabled.
32747 Once enabled, this feature cannot be disabled.
32749 Note that if Python support has not been compiled into @value{GDBN},
32750 this command will still succeed (and do nothing).
32752 @subheading The @code{-stack-info-frame} Command
32753 @findex -stack-info-frame
32755 @subsubheading Synopsis
32761 Get info on the selected frame.
32763 @subsubheading @value{GDBN} Command
32765 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32766 (without arguments).
32768 @subsubheading Example
32773 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32774 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32775 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32776 arch="i386:x86_64"@}
32780 @subheading The @code{-stack-info-depth} Command
32781 @findex -stack-info-depth
32783 @subsubheading Synopsis
32786 -stack-info-depth [ @var{max-depth} ]
32789 Return the depth of the stack. If the integer argument @var{max-depth}
32790 is specified, do not count beyond @var{max-depth} frames.
32792 @subsubheading @value{GDBN} Command
32794 There's no equivalent @value{GDBN} command.
32796 @subsubheading Example
32798 For a stack with frame levels 0 through 11:
32805 -stack-info-depth 4
32808 -stack-info-depth 12
32811 -stack-info-depth 11
32814 -stack-info-depth 13
32819 @anchor{-stack-list-arguments}
32820 @subheading The @code{-stack-list-arguments} Command
32821 @findex -stack-list-arguments
32823 @subsubheading Synopsis
32826 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32827 [ @var{low-frame} @var{high-frame} ]
32830 Display a list of the arguments for the frames between @var{low-frame}
32831 and @var{high-frame} (inclusive). If @var{low-frame} and
32832 @var{high-frame} are not provided, list the arguments for the whole
32833 call stack. If the two arguments are equal, show the single frame
32834 at the corresponding level. It is an error if @var{low-frame} is
32835 larger than the actual number of frames. On the other hand,
32836 @var{high-frame} may be larger than the actual number of frames, in
32837 which case only existing frames will be returned.
32839 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32840 the variables; if it is 1 or @code{--all-values}, print also their
32841 values; and if it is 2 or @code{--simple-values}, print the name,
32842 type and value for simple data types, and the name and type for arrays,
32843 structures and unions. If the option @code{--no-frame-filters} is
32844 supplied, then Python frame filters will not be executed.
32846 If the @code{--skip-unavailable} option is specified, arguments that
32847 are not available are not listed. Partially available arguments
32848 are still displayed, however.
32850 Use of this command to obtain arguments in a single frame is
32851 deprecated in favor of the @samp{-stack-list-variables} command.
32853 @subsubheading @value{GDBN} Command
32855 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32856 @samp{gdb_get_args} command which partially overlaps with the
32857 functionality of @samp{-stack-list-arguments}.
32859 @subsubheading Example
32866 frame=@{level="0",addr="0x00010734",func="callee4",
32867 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32868 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32869 arch="i386:x86_64"@},
32870 frame=@{level="1",addr="0x0001076c",func="callee3",
32871 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32872 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32873 arch="i386:x86_64"@},
32874 frame=@{level="2",addr="0x0001078c",func="callee2",
32875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32876 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32877 arch="i386:x86_64"@},
32878 frame=@{level="3",addr="0x000107b4",func="callee1",
32879 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32880 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32881 arch="i386:x86_64"@},
32882 frame=@{level="4",addr="0x000107e0",func="main",
32883 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32884 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32885 arch="i386:x86_64"@}]
32887 -stack-list-arguments 0
32890 frame=@{level="0",args=[]@},
32891 frame=@{level="1",args=[name="strarg"]@},
32892 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32893 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32894 frame=@{level="4",args=[]@}]
32896 -stack-list-arguments 1
32899 frame=@{level="0",args=[]@},
32901 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32902 frame=@{level="2",args=[
32903 @{name="intarg",value="2"@},
32904 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32905 @{frame=@{level="3",args=[
32906 @{name="intarg",value="2"@},
32907 @{name="strarg",value="0x11940 \"A string argument.\""@},
32908 @{name="fltarg",value="3.5"@}]@},
32909 frame=@{level="4",args=[]@}]
32911 -stack-list-arguments 0 2 2
32912 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32914 -stack-list-arguments 1 2 2
32915 ^done,stack-args=[frame=@{level="2",
32916 args=[@{name="intarg",value="2"@},
32917 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32921 @c @subheading -stack-list-exception-handlers
32924 @anchor{-stack-list-frames}
32925 @subheading The @code{-stack-list-frames} Command
32926 @findex -stack-list-frames
32928 @subsubheading Synopsis
32931 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32934 List the frames currently on the stack. For each frame it displays the
32939 The frame number, 0 being the topmost frame, i.e., the innermost function.
32941 The @code{$pc} value for that frame.
32945 File name of the source file where the function lives.
32946 @item @var{fullname}
32947 The full file name of the source file where the function lives.
32949 Line number corresponding to the @code{$pc}.
32951 The shared library where this function is defined. This is only given
32952 if the frame's function is not known.
32954 Frame's architecture.
32957 If invoked without arguments, this command prints a backtrace for the
32958 whole stack. If given two integer arguments, it shows the frames whose
32959 levels are between the two arguments (inclusive). If the two arguments
32960 are equal, it shows the single frame at the corresponding level. It is
32961 an error if @var{low-frame} is larger than the actual number of
32962 frames. On the other hand, @var{high-frame} may be larger than the
32963 actual number of frames, in which case only existing frames will be
32964 returned. If the option @code{--no-frame-filters} is supplied, then
32965 Python frame filters will not be executed.
32967 @subsubheading @value{GDBN} Command
32969 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32971 @subsubheading Example
32973 Full stack backtrace:
32979 [frame=@{level="0",addr="0x0001076c",func="foo",
32980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32981 arch="i386:x86_64"@},
32982 frame=@{level="1",addr="0x000107a4",func="foo",
32983 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32984 arch="i386:x86_64"@},
32985 frame=@{level="2",addr="0x000107a4",func="foo",
32986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32987 arch="i386:x86_64"@},
32988 frame=@{level="3",addr="0x000107a4",func="foo",
32989 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32990 arch="i386:x86_64"@},
32991 frame=@{level="4",addr="0x000107a4",func="foo",
32992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32993 arch="i386:x86_64"@},
32994 frame=@{level="5",addr="0x000107a4",func="foo",
32995 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32996 arch="i386:x86_64"@},
32997 frame=@{level="6",addr="0x000107a4",func="foo",
32998 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32999 arch="i386:x86_64"@},
33000 frame=@{level="7",addr="0x000107a4",func="foo",
33001 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33002 arch="i386:x86_64"@},
33003 frame=@{level="8",addr="0x000107a4",func="foo",
33004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33005 arch="i386:x86_64"@},
33006 frame=@{level="9",addr="0x000107a4",func="foo",
33007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33008 arch="i386:x86_64"@},
33009 frame=@{level="10",addr="0x000107a4",func="foo",
33010 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33011 arch="i386:x86_64"@},
33012 frame=@{level="11",addr="0x00010738",func="main",
33013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33014 arch="i386:x86_64"@}]
33018 Show frames between @var{low_frame} and @var{high_frame}:
33022 -stack-list-frames 3 5
33024 [frame=@{level="3",addr="0x000107a4",func="foo",
33025 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33026 arch="i386:x86_64"@},
33027 frame=@{level="4",addr="0x000107a4",func="foo",
33028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33029 arch="i386:x86_64"@},
33030 frame=@{level="5",addr="0x000107a4",func="foo",
33031 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33032 arch="i386:x86_64"@}]
33036 Show a single frame:
33040 -stack-list-frames 3 3
33042 [frame=@{level="3",addr="0x000107a4",func="foo",
33043 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33044 arch="i386:x86_64"@}]
33049 @subheading The @code{-stack-list-locals} Command
33050 @findex -stack-list-locals
33051 @anchor{-stack-list-locals}
33053 @subsubheading Synopsis
33056 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33059 Display the local variable names for the selected frame. If
33060 @var{print-values} is 0 or @code{--no-values}, print only the names of
33061 the variables; if it is 1 or @code{--all-values}, print also their
33062 values; and if it is 2 or @code{--simple-values}, print the name,
33063 type and value for simple data types, and the name and type for arrays,
33064 structures and unions. In this last case, a frontend can immediately
33065 display the value of simple data types and create variable objects for
33066 other data types when the user wishes to explore their values in
33067 more detail. If the option @code{--no-frame-filters} is supplied, then
33068 Python frame filters will not be executed.
33070 If the @code{--skip-unavailable} option is specified, local variables
33071 that are not available are not listed. Partially available local
33072 variables are still displayed, however.
33074 This command is deprecated in favor of the
33075 @samp{-stack-list-variables} command.
33077 @subsubheading @value{GDBN} Command
33079 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33081 @subsubheading Example
33085 -stack-list-locals 0
33086 ^done,locals=[name="A",name="B",name="C"]
33088 -stack-list-locals --all-values
33089 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33090 @{name="C",value="@{1, 2, 3@}"@}]
33091 -stack-list-locals --simple-values
33092 ^done,locals=[@{name="A",type="int",value="1"@},
33093 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33097 @anchor{-stack-list-variables}
33098 @subheading The @code{-stack-list-variables} Command
33099 @findex -stack-list-variables
33101 @subsubheading Synopsis
33104 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33107 Display the names of local variables and function arguments for the selected frame. If
33108 @var{print-values} is 0 or @code{--no-values}, print only the names of
33109 the variables; if it is 1 or @code{--all-values}, print also their
33110 values; and if it is 2 or @code{--simple-values}, print the name,
33111 type and value for simple data types, and the name and type for arrays,
33112 structures and unions. If the option @code{--no-frame-filters} is
33113 supplied, then Python frame filters will not be executed.
33115 If the @code{--skip-unavailable} option is specified, local variables
33116 and arguments that are not available are not listed. Partially
33117 available arguments and local variables are still displayed, however.
33119 @subsubheading Example
33123 -stack-list-variables --thread 1 --frame 0 --all-values
33124 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33129 @subheading The @code{-stack-select-frame} Command
33130 @findex -stack-select-frame
33132 @subsubheading Synopsis
33135 -stack-select-frame @var{framenum}
33138 Change the selected frame. Select a different frame @var{framenum} on
33141 This command in deprecated in favor of passing the @samp{--frame}
33142 option to every command.
33144 @subsubheading @value{GDBN} Command
33146 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33147 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33149 @subsubheading Example
33153 -stack-select-frame 2
33158 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33159 @node GDB/MI Variable Objects
33160 @section @sc{gdb/mi} Variable Objects
33164 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33166 For the implementation of a variable debugger window (locals, watched
33167 expressions, etc.), we are proposing the adaptation of the existing code
33168 used by @code{Insight}.
33170 The two main reasons for that are:
33174 It has been proven in practice (it is already on its second generation).
33177 It will shorten development time (needless to say how important it is
33181 The original interface was designed to be used by Tcl code, so it was
33182 slightly changed so it could be used through @sc{gdb/mi}. This section
33183 describes the @sc{gdb/mi} operations that will be available and gives some
33184 hints about their use.
33186 @emph{Note}: In addition to the set of operations described here, we
33187 expect the @sc{gui} implementation of a variable window to require, at
33188 least, the following operations:
33191 @item @code{-gdb-show} @code{output-radix}
33192 @item @code{-stack-list-arguments}
33193 @item @code{-stack-list-locals}
33194 @item @code{-stack-select-frame}
33199 @subheading Introduction to Variable Objects
33201 @cindex variable objects in @sc{gdb/mi}
33203 Variable objects are "object-oriented" MI interface for examining and
33204 changing values of expressions. Unlike some other MI interfaces that
33205 work with expressions, variable objects are specifically designed for
33206 simple and efficient presentation in the frontend. A variable object
33207 is identified by string name. When a variable object is created, the
33208 frontend specifies the expression for that variable object. The
33209 expression can be a simple variable, or it can be an arbitrary complex
33210 expression, and can even involve CPU registers. After creating a
33211 variable object, the frontend can invoke other variable object
33212 operations---for example to obtain or change the value of a variable
33213 object, or to change display format.
33215 Variable objects have hierarchical tree structure. Any variable object
33216 that corresponds to a composite type, such as structure in C, has
33217 a number of child variable objects, for example corresponding to each
33218 element of a structure. A child variable object can itself have
33219 children, recursively. Recursion ends when we reach
33220 leaf variable objects, which always have built-in types. Child variable
33221 objects are created only by explicit request, so if a frontend
33222 is not interested in the children of a particular variable object, no
33223 child will be created.
33225 For a leaf variable object it is possible to obtain its value as a
33226 string, or set the value from a string. String value can be also
33227 obtained for a non-leaf variable object, but it's generally a string
33228 that only indicates the type of the object, and does not list its
33229 contents. Assignment to a non-leaf variable object is not allowed.
33231 A frontend does not need to read the values of all variable objects each time
33232 the program stops. Instead, MI provides an update command that lists all
33233 variable objects whose values has changed since the last update
33234 operation. This considerably reduces the amount of data that must
33235 be transferred to the frontend. As noted above, children variable
33236 objects are created on demand, and only leaf variable objects have a
33237 real value. As result, gdb will read target memory only for leaf
33238 variables that frontend has created.
33240 The automatic update is not always desirable. For example, a frontend
33241 might want to keep a value of some expression for future reference,
33242 and never update it. For another example, fetching memory is
33243 relatively slow for embedded targets, so a frontend might want
33244 to disable automatic update for the variables that are either not
33245 visible on the screen, or ``closed''. This is possible using so
33246 called ``frozen variable objects''. Such variable objects are never
33247 implicitly updated.
33249 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33250 fixed variable object, the expression is parsed when the variable
33251 object is created, including associating identifiers to specific
33252 variables. The meaning of expression never changes. For a floating
33253 variable object the values of variables whose names appear in the
33254 expressions are re-evaluated every time in the context of the current
33255 frame. Consider this example:
33260 struct work_state state;
33267 If a fixed variable object for the @code{state} variable is created in
33268 this function, and we enter the recursive call, the variable
33269 object will report the value of @code{state} in the top-level
33270 @code{do_work} invocation. On the other hand, a floating variable
33271 object will report the value of @code{state} in the current frame.
33273 If an expression specified when creating a fixed variable object
33274 refers to a local variable, the variable object becomes bound to the
33275 thread and frame in which the variable object is created. When such
33276 variable object is updated, @value{GDBN} makes sure that the
33277 thread/frame combination the variable object is bound to still exists,
33278 and re-evaluates the variable object in context of that thread/frame.
33280 The following is the complete set of @sc{gdb/mi} operations defined to
33281 access this functionality:
33283 @multitable @columnfractions .4 .6
33284 @item @strong{Operation}
33285 @tab @strong{Description}
33287 @item @code{-enable-pretty-printing}
33288 @tab enable Python-based pretty-printing
33289 @item @code{-var-create}
33290 @tab create a variable object
33291 @item @code{-var-delete}
33292 @tab delete the variable object and/or its children
33293 @item @code{-var-set-format}
33294 @tab set the display format of this variable
33295 @item @code{-var-show-format}
33296 @tab show the display format of this variable
33297 @item @code{-var-info-num-children}
33298 @tab tells how many children this object has
33299 @item @code{-var-list-children}
33300 @tab return a list of the object's children
33301 @item @code{-var-info-type}
33302 @tab show the type of this variable object
33303 @item @code{-var-info-expression}
33304 @tab print parent-relative expression that this variable object represents
33305 @item @code{-var-info-path-expression}
33306 @tab print full expression that this variable object represents
33307 @item @code{-var-show-attributes}
33308 @tab is this variable editable? does it exist here?
33309 @item @code{-var-evaluate-expression}
33310 @tab get the value of this variable
33311 @item @code{-var-assign}
33312 @tab set the value of this variable
33313 @item @code{-var-update}
33314 @tab update the variable and its children
33315 @item @code{-var-set-frozen}
33316 @tab set frozenness attribute
33317 @item @code{-var-set-update-range}
33318 @tab set range of children to display on update
33321 In the next subsection we describe each operation in detail and suggest
33322 how it can be used.
33324 @subheading Description And Use of Operations on Variable Objects
33326 @subheading The @code{-enable-pretty-printing} Command
33327 @findex -enable-pretty-printing
33330 -enable-pretty-printing
33333 @value{GDBN} allows Python-based visualizers to affect the output of the
33334 MI variable object commands. However, because there was no way to
33335 implement this in a fully backward-compatible way, a front end must
33336 request that this functionality be enabled.
33338 Once enabled, this feature cannot be disabled.
33340 Note that if Python support has not been compiled into @value{GDBN},
33341 this command will still succeed (and do nothing).
33343 This feature is currently (as of @value{GDBN} 7.0) experimental, and
33344 may work differently in future versions of @value{GDBN}.
33346 @subheading The @code{-var-create} Command
33347 @findex -var-create
33349 @subsubheading Synopsis
33352 -var-create @{@var{name} | "-"@}
33353 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33356 This operation creates a variable object, which allows the monitoring of
33357 a variable, the result of an expression, a memory cell or a CPU
33360 The @var{name} parameter is the string by which the object can be
33361 referenced. It must be unique. If @samp{-} is specified, the varobj
33362 system will generate a string ``varNNNNNN'' automatically. It will be
33363 unique provided that one does not specify @var{name} of that format.
33364 The command fails if a duplicate name is found.
33366 The frame under which the expression should be evaluated can be
33367 specified by @var{frame-addr}. A @samp{*} indicates that the current
33368 frame should be used. A @samp{@@} indicates that a floating variable
33369 object must be created.
33371 @var{expression} is any expression valid on the current language set (must not
33372 begin with a @samp{*}), or one of the following:
33376 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33379 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33382 @samp{$@var{regname}} --- a CPU register name
33385 @cindex dynamic varobj
33386 A varobj's contents may be provided by a Python-based pretty-printer. In this
33387 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33388 have slightly different semantics in some cases. If the
33389 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33390 will never create a dynamic varobj. This ensures backward
33391 compatibility for existing clients.
33393 @subsubheading Result
33395 This operation returns attributes of the newly-created varobj. These
33400 The name of the varobj.
33403 The number of children of the varobj. This number is not necessarily
33404 reliable for a dynamic varobj. Instead, you must examine the
33405 @samp{has_more} attribute.
33408 The varobj's scalar value. For a varobj whose type is some sort of
33409 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33410 will not be interesting.
33413 The varobj's type. This is a string representation of the type, as
33414 would be printed by the @value{GDBN} CLI. If @samp{print object}
33415 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33416 @emph{actual} (derived) type of the object is shown rather than the
33417 @emph{declared} one.
33420 If a variable object is bound to a specific thread, then this is the
33421 thread's global identifier.
33424 For a dynamic varobj, this indicates whether there appear to be any
33425 children available. For a non-dynamic varobj, this will be 0.
33428 This attribute will be present and have the value @samp{1} if the
33429 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33430 then this attribute will not be present.
33433 A dynamic varobj can supply a display hint to the front end. The
33434 value comes directly from the Python pretty-printer object's
33435 @code{display_hint} method. @xref{Pretty Printing API}.
33438 Typical output will look like this:
33441 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33442 has_more="@var{has_more}"
33446 @subheading The @code{-var-delete} Command
33447 @findex -var-delete
33449 @subsubheading Synopsis
33452 -var-delete [ -c ] @var{name}
33455 Deletes a previously created variable object and all of its children.
33456 With the @samp{-c} option, just deletes the children.
33458 Returns an error if the object @var{name} is not found.
33461 @subheading The @code{-var-set-format} Command
33462 @findex -var-set-format
33464 @subsubheading Synopsis
33467 -var-set-format @var{name} @var{format-spec}
33470 Sets the output format for the value of the object @var{name} to be
33473 @anchor{-var-set-format}
33474 The syntax for the @var{format-spec} is as follows:
33477 @var{format-spec} @expansion{}
33478 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33481 The natural format is the default format choosen automatically
33482 based on the variable type (like decimal for an @code{int}, hex
33483 for pointers, etc.).
33485 The zero-hexadecimal format has a representation similar to hexadecimal
33486 but with padding zeroes to the left of the value. For example, a 32-bit
33487 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33488 zero-hexadecimal format.
33490 For a variable with children, the format is set only on the
33491 variable itself, and the children are not affected.
33493 @subheading The @code{-var-show-format} Command
33494 @findex -var-show-format
33496 @subsubheading Synopsis
33499 -var-show-format @var{name}
33502 Returns the format used to display the value of the object @var{name}.
33505 @var{format} @expansion{}
33510 @subheading The @code{-var-info-num-children} Command
33511 @findex -var-info-num-children
33513 @subsubheading Synopsis
33516 -var-info-num-children @var{name}
33519 Returns the number of children of a variable object @var{name}:
33525 Note that this number is not completely reliable for a dynamic varobj.
33526 It will return the current number of children, but more children may
33530 @subheading The @code{-var-list-children} Command
33531 @findex -var-list-children
33533 @subsubheading Synopsis
33536 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33538 @anchor{-var-list-children}
33540 Return a list of the children of the specified variable object and
33541 create variable objects for them, if they do not already exist. With
33542 a single argument or if @var{print-values} has a value of 0 or
33543 @code{--no-values}, print only the names of the variables; if
33544 @var{print-values} is 1 or @code{--all-values}, also print their
33545 values; and if it is 2 or @code{--simple-values} print the name and
33546 value for simple data types and just the name for arrays, structures
33549 @var{from} and @var{to}, if specified, indicate the range of children
33550 to report. If @var{from} or @var{to} is less than zero, the range is
33551 reset and all children will be reported. Otherwise, children starting
33552 at @var{from} (zero-based) and up to and excluding @var{to} will be
33555 If a child range is requested, it will only affect the current call to
33556 @code{-var-list-children}, but not future calls to @code{-var-update}.
33557 For this, you must instead use @code{-var-set-update-range}. The
33558 intent of this approach is to enable a front end to implement any
33559 update approach it likes; for example, scrolling a view may cause the
33560 front end to request more children with @code{-var-list-children}, and
33561 then the front end could call @code{-var-set-update-range} with a
33562 different range to ensure that future updates are restricted to just
33565 For each child the following results are returned:
33570 Name of the variable object created for this child.
33573 The expression to be shown to the user by the front end to designate this child.
33574 For example this may be the name of a structure member.
33576 For a dynamic varobj, this value cannot be used to form an
33577 expression. There is no way to do this at all with a dynamic varobj.
33579 For C/C@t{++} structures there are several pseudo children returned to
33580 designate access qualifiers. For these pseudo children @var{exp} is
33581 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33582 type and value are not present.
33584 A dynamic varobj will not report the access qualifying
33585 pseudo-children, regardless of the language. This information is not
33586 available at all with a dynamic varobj.
33589 Number of children this child has. For a dynamic varobj, this will be
33593 The type of the child. If @samp{print object}
33594 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33595 @emph{actual} (derived) type of the object is shown rather than the
33596 @emph{declared} one.
33599 If values were requested, this is the value.
33602 If this variable object is associated with a thread, this is the
33603 thread's global thread id. Otherwise this result is not present.
33606 If the variable object is frozen, this variable will be present with a value of 1.
33609 A dynamic varobj can supply a display hint to the front end. The
33610 value comes directly from the Python pretty-printer object's
33611 @code{display_hint} method. @xref{Pretty Printing API}.
33614 This attribute will be present and have the value @samp{1} if the
33615 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33616 then this attribute will not be present.
33620 The result may have its own attributes:
33624 A dynamic varobj can supply a display hint to the front end. The
33625 value comes directly from the Python pretty-printer object's
33626 @code{display_hint} method. @xref{Pretty Printing API}.
33629 This is an integer attribute which is nonzero if there are children
33630 remaining after the end of the selected range.
33633 @subsubheading Example
33637 -var-list-children n
33638 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33639 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33641 -var-list-children --all-values n
33642 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33643 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33647 @subheading The @code{-var-info-type} Command
33648 @findex -var-info-type
33650 @subsubheading Synopsis
33653 -var-info-type @var{name}
33656 Returns the type of the specified variable @var{name}. The type is
33657 returned as a string in the same format as it is output by the
33661 type=@var{typename}
33665 @subheading The @code{-var-info-expression} Command
33666 @findex -var-info-expression
33668 @subsubheading Synopsis
33671 -var-info-expression @var{name}
33674 Returns a string that is suitable for presenting this
33675 variable object in user interface. The string is generally
33676 not valid expression in the current language, and cannot be evaluated.
33678 For example, if @code{a} is an array, and variable object
33679 @code{A} was created for @code{a}, then we'll get this output:
33682 (gdb) -var-info-expression A.1
33683 ^done,lang="C",exp="1"
33687 Here, the value of @code{lang} is the language name, which can be
33688 found in @ref{Supported Languages}.
33690 Note that the output of the @code{-var-list-children} command also
33691 includes those expressions, so the @code{-var-info-expression} command
33694 @subheading The @code{-var-info-path-expression} Command
33695 @findex -var-info-path-expression
33697 @subsubheading Synopsis
33700 -var-info-path-expression @var{name}
33703 Returns an expression that can be evaluated in the current
33704 context and will yield the same value that a variable object has.
33705 Compare this with the @code{-var-info-expression} command, which
33706 result can be used only for UI presentation. Typical use of
33707 the @code{-var-info-path-expression} command is creating a
33708 watchpoint from a variable object.
33710 This command is currently not valid for children of a dynamic varobj,
33711 and will give an error when invoked on one.
33713 For example, suppose @code{C} is a C@t{++} class, derived from class
33714 @code{Base}, and that the @code{Base} class has a member called
33715 @code{m_size}. Assume a variable @code{c} is has the type of
33716 @code{C} and a variable object @code{C} was created for variable
33717 @code{c}. Then, we'll get this output:
33719 (gdb) -var-info-path-expression C.Base.public.m_size
33720 ^done,path_expr=((Base)c).m_size)
33723 @subheading The @code{-var-show-attributes} Command
33724 @findex -var-show-attributes
33726 @subsubheading Synopsis
33729 -var-show-attributes @var{name}
33732 List attributes of the specified variable object @var{name}:
33735 status=@var{attr} [ ( ,@var{attr} )* ]
33739 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33741 @subheading The @code{-var-evaluate-expression} Command
33742 @findex -var-evaluate-expression
33744 @subsubheading Synopsis
33747 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33750 Evaluates the expression that is represented by the specified variable
33751 object and returns its value as a string. The format of the string
33752 can be specified with the @samp{-f} option. The possible values of
33753 this option are the same as for @code{-var-set-format}
33754 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33755 the current display format will be used. The current display format
33756 can be changed using the @code{-var-set-format} command.
33762 Note that one must invoke @code{-var-list-children} for a variable
33763 before the value of a child variable can be evaluated.
33765 @subheading The @code{-var-assign} Command
33766 @findex -var-assign
33768 @subsubheading Synopsis
33771 -var-assign @var{name} @var{expression}
33774 Assigns the value of @var{expression} to the variable object specified
33775 by @var{name}. The object must be @samp{editable}. If the variable's
33776 value is altered by the assign, the variable will show up in any
33777 subsequent @code{-var-update} list.
33779 @subsubheading Example
33787 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33791 @subheading The @code{-var-update} Command
33792 @findex -var-update
33794 @subsubheading Synopsis
33797 -var-update [@var{print-values}] @{@var{name} | "*"@}
33800 Reevaluate the expressions corresponding to the variable object
33801 @var{name} and all its direct and indirect children, and return the
33802 list of variable objects whose values have changed; @var{name} must
33803 be a root variable object. Here, ``changed'' means that the result of
33804 @code{-var-evaluate-expression} before and after the
33805 @code{-var-update} is different. If @samp{*} is used as the variable
33806 object names, all existing variable objects are updated, except
33807 for frozen ones (@pxref{-var-set-frozen}). The option
33808 @var{print-values} determines whether both names and values, or just
33809 names are printed. The possible values of this option are the same
33810 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33811 recommended to use the @samp{--all-values} option, to reduce the
33812 number of MI commands needed on each program stop.
33814 With the @samp{*} parameter, if a variable object is bound to a
33815 currently running thread, it will not be updated, without any
33818 If @code{-var-set-update-range} was previously used on a varobj, then
33819 only the selected range of children will be reported.
33821 @code{-var-update} reports all the changed varobjs in a tuple named
33824 Each item in the change list is itself a tuple holding:
33828 The name of the varobj.
33831 If values were requested for this update, then this field will be
33832 present and will hold the value of the varobj.
33835 @anchor{-var-update}
33836 This field is a string which may take one of three values:
33840 The variable object's current value is valid.
33843 The variable object does not currently hold a valid value but it may
33844 hold one in the future if its associated expression comes back into
33848 The variable object no longer holds a valid value.
33849 This can occur when the executable file being debugged has changed,
33850 either through recompilation or by using the @value{GDBN} @code{file}
33851 command. The front end should normally choose to delete these variable
33855 In the future new values may be added to this list so the front should
33856 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33859 This is only present if the varobj is still valid. If the type
33860 changed, then this will be the string @samp{true}; otherwise it will
33863 When a varobj's type changes, its children are also likely to have
33864 become incorrect. Therefore, the varobj's children are automatically
33865 deleted when this attribute is @samp{true}. Also, the varobj's update
33866 range, when set using the @code{-var-set-update-range} command, is
33870 If the varobj's type changed, then this field will be present and will
33873 @item new_num_children
33874 For a dynamic varobj, if the number of children changed, or if the
33875 type changed, this will be the new number of children.
33877 The @samp{numchild} field in other varobj responses is generally not
33878 valid for a dynamic varobj -- it will show the number of children that
33879 @value{GDBN} knows about, but because dynamic varobjs lazily
33880 instantiate their children, this will not reflect the number of
33881 children which may be available.
33883 The @samp{new_num_children} attribute only reports changes to the
33884 number of children known by @value{GDBN}. This is the only way to
33885 detect whether an update has removed children (which necessarily can
33886 only happen at the end of the update range).
33889 The display hint, if any.
33892 This is an integer value, which will be 1 if there are more children
33893 available outside the varobj's update range.
33896 This attribute will be present and have the value @samp{1} if the
33897 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33898 then this attribute will not be present.
33901 If new children were added to a dynamic varobj within the selected
33902 update range (as set by @code{-var-set-update-range}), then they will
33903 be listed in this attribute.
33906 @subsubheading Example
33913 -var-update --all-values var1
33914 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33915 type_changed="false"@}]
33919 @subheading The @code{-var-set-frozen} Command
33920 @findex -var-set-frozen
33921 @anchor{-var-set-frozen}
33923 @subsubheading Synopsis
33926 -var-set-frozen @var{name} @var{flag}
33929 Set the frozenness flag on the variable object @var{name}. The
33930 @var{flag} parameter should be either @samp{1} to make the variable
33931 frozen or @samp{0} to make it unfrozen. If a variable object is
33932 frozen, then neither itself, nor any of its children, are
33933 implicitly updated by @code{-var-update} of
33934 a parent variable or by @code{-var-update *}. Only
33935 @code{-var-update} of the variable itself will update its value and
33936 values of its children. After a variable object is unfrozen, it is
33937 implicitly updated by all subsequent @code{-var-update} operations.
33938 Unfreezing a variable does not update it, only subsequent
33939 @code{-var-update} does.
33941 @subsubheading Example
33945 -var-set-frozen V 1
33950 @subheading The @code{-var-set-update-range} command
33951 @findex -var-set-update-range
33952 @anchor{-var-set-update-range}
33954 @subsubheading Synopsis
33957 -var-set-update-range @var{name} @var{from} @var{to}
33960 Set the range of children to be returned by future invocations of
33961 @code{-var-update}.
33963 @var{from} and @var{to} indicate the range of children to report. If
33964 @var{from} or @var{to} is less than zero, the range is reset and all
33965 children will be reported. Otherwise, children starting at @var{from}
33966 (zero-based) and up to and excluding @var{to} will be reported.
33968 @subsubheading Example
33972 -var-set-update-range V 1 2
33976 @subheading The @code{-var-set-visualizer} command
33977 @findex -var-set-visualizer
33978 @anchor{-var-set-visualizer}
33980 @subsubheading Synopsis
33983 -var-set-visualizer @var{name} @var{visualizer}
33986 Set a visualizer for the variable object @var{name}.
33988 @var{visualizer} is the visualizer to use. The special value
33989 @samp{None} means to disable any visualizer in use.
33991 If not @samp{None}, @var{visualizer} must be a Python expression.
33992 This expression must evaluate to a callable object which accepts a
33993 single argument. @value{GDBN} will call this object with the value of
33994 the varobj @var{name} as an argument (this is done so that the same
33995 Python pretty-printing code can be used for both the CLI and MI).
33996 When called, this object must return an object which conforms to the
33997 pretty-printing interface (@pxref{Pretty Printing API}).
33999 The pre-defined function @code{gdb.default_visualizer} may be used to
34000 select a visualizer by following the built-in process
34001 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34002 a varobj is created, and so ordinarily is not needed.
34004 This feature is only available if Python support is enabled. The MI
34005 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34006 can be used to check this.
34008 @subsubheading Example
34010 Resetting the visualizer:
34014 -var-set-visualizer V None
34018 Reselecting the default (type-based) visualizer:
34022 -var-set-visualizer V gdb.default_visualizer
34026 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34027 can be used to instantiate this class for a varobj:
34031 -var-set-visualizer V "lambda val: SomeClass()"
34035 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34036 @node GDB/MI Data Manipulation
34037 @section @sc{gdb/mi} Data Manipulation
34039 @cindex data manipulation, in @sc{gdb/mi}
34040 @cindex @sc{gdb/mi}, data manipulation
34041 This section describes the @sc{gdb/mi} commands that manipulate data:
34042 examine memory and registers, evaluate expressions, etc.
34044 For details about what an addressable memory unit is,
34045 @pxref{addressable memory unit}.
34047 @c REMOVED FROM THE INTERFACE.
34048 @c @subheading -data-assign
34049 @c Change the value of a program variable. Plenty of side effects.
34050 @c @subsubheading GDB Command
34052 @c @subsubheading Example
34055 @subheading The @code{-data-disassemble} Command
34056 @findex -data-disassemble
34058 @subsubheading Synopsis
34062 [ -s @var{start-addr} -e @var{end-addr} ]
34063 | [ -a @var{addr} ]
34064 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34072 @item @var{start-addr}
34073 is the beginning address (or @code{$pc})
34074 @item @var{end-addr}
34077 is an address anywhere within (or the name of) the function to
34078 disassemble. If an address is specified, the whole function
34079 surrounding that address will be disassembled. If a name is
34080 specified, the whole function with that name will be disassembled.
34081 @item @var{filename}
34082 is the name of the file to disassemble
34083 @item @var{linenum}
34084 is the line number to disassemble around
34086 is the number of disassembly lines to be produced. If it is -1,
34087 the whole function will be disassembled, in case no @var{end-addr} is
34088 specified. If @var{end-addr} is specified as a non-zero value, and
34089 @var{lines} is lower than the number of disassembly lines between
34090 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34091 displayed; if @var{lines} is higher than the number of lines between
34092 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34097 @item 0 disassembly only
34098 @item 1 mixed source and disassembly (deprecated)
34099 @item 2 disassembly with raw opcodes
34100 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34101 @item 4 mixed source and disassembly
34102 @item 5 mixed source and disassembly with raw opcodes
34105 Modes 1 and 3 are deprecated. The output is ``source centric''
34106 which hasn't proved useful in practice.
34107 @xref{Machine Code}, for a discussion of the difference between
34108 @code{/m} and @code{/s} output of the @code{disassemble} command.
34111 @subsubheading Result
34113 The result of the @code{-data-disassemble} command will be a list named
34114 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34115 used with the @code{-data-disassemble} command.
34117 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34122 The address at which this instruction was disassembled.
34125 The name of the function this instruction is within.
34128 The decimal offset in bytes from the start of @samp{func-name}.
34131 The text disassembly for this @samp{address}.
34134 This field is only present for modes 2, 3 and 5. This contains the raw opcode
34135 bytes for the @samp{inst} field.
34139 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34140 @samp{src_and_asm_line}, each of which has the following fields:
34144 The line number within @samp{file}.
34147 The file name from the compilation unit. This might be an absolute
34148 file name or a relative file name depending on the compile command
34152 Absolute file name of @samp{file}. It is converted to a canonical form
34153 using the source file search path
34154 (@pxref{Source Path, ,Specifying Source Directories})
34155 and after resolving all the symbolic links.
34157 If the source file is not found this field will contain the path as
34158 present in the debug information.
34160 @item line_asm_insn
34161 This is a list of tuples containing the disassembly for @samp{line} in
34162 @samp{file}. The fields of each tuple are the same as for
34163 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34164 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34169 Note that whatever included in the @samp{inst} field, is not
34170 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34173 @subsubheading @value{GDBN} Command
34175 The corresponding @value{GDBN} command is @samp{disassemble}.
34177 @subsubheading Example
34179 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34183 -data-disassemble -s $pc -e "$pc + 20" -- 0
34186 @{address="0x000107c0",func-name="main",offset="4",
34187 inst="mov 2, %o0"@},
34188 @{address="0x000107c4",func-name="main",offset="8",
34189 inst="sethi %hi(0x11800), %o2"@},
34190 @{address="0x000107c8",func-name="main",offset="12",
34191 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34192 @{address="0x000107cc",func-name="main",offset="16",
34193 inst="sethi %hi(0x11800), %o2"@},
34194 @{address="0x000107d0",func-name="main",offset="20",
34195 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34199 Disassemble the whole @code{main} function. Line 32 is part of
34203 -data-disassemble -f basics.c -l 32 -- 0
34205 @{address="0x000107bc",func-name="main",offset="0",
34206 inst="save %sp, -112, %sp"@},
34207 @{address="0x000107c0",func-name="main",offset="4",
34208 inst="mov 2, %o0"@},
34209 @{address="0x000107c4",func-name="main",offset="8",
34210 inst="sethi %hi(0x11800), %o2"@},
34212 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34213 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34217 Disassemble 3 instructions from the start of @code{main}:
34221 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34223 @{address="0x000107bc",func-name="main",offset="0",
34224 inst="save %sp, -112, %sp"@},
34225 @{address="0x000107c0",func-name="main",offset="4",
34226 inst="mov 2, %o0"@},
34227 @{address="0x000107c4",func-name="main",offset="8",
34228 inst="sethi %hi(0x11800), %o2"@}]
34232 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34236 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34238 src_and_asm_line=@{line="31",
34239 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34240 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34241 line_asm_insn=[@{address="0x000107bc",
34242 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34243 src_and_asm_line=@{line="32",
34244 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34245 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34246 line_asm_insn=[@{address="0x000107c0",
34247 func-name="main",offset="4",inst="mov 2, %o0"@},
34248 @{address="0x000107c4",func-name="main",offset="8",
34249 inst="sethi %hi(0x11800), %o2"@}]@}]
34254 @subheading The @code{-data-evaluate-expression} Command
34255 @findex -data-evaluate-expression
34257 @subsubheading Synopsis
34260 -data-evaluate-expression @var{expr}
34263 Evaluate @var{expr} as an expression. The expression could contain an
34264 inferior function call. The function call will execute synchronously.
34265 If the expression contains spaces, it must be enclosed in double quotes.
34267 @subsubheading @value{GDBN} Command
34269 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34270 @samp{call}. In @code{gdbtk} only, there's a corresponding
34271 @samp{gdb_eval} command.
34273 @subsubheading Example
34275 In the following example, the numbers that precede the commands are the
34276 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34277 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34281 211-data-evaluate-expression A
34284 311-data-evaluate-expression &A
34285 311^done,value="0xefffeb7c"
34287 411-data-evaluate-expression A+3
34290 511-data-evaluate-expression "A + 3"
34296 @subheading The @code{-data-list-changed-registers} Command
34297 @findex -data-list-changed-registers
34299 @subsubheading Synopsis
34302 -data-list-changed-registers
34305 Display a list of the registers that have changed.
34307 @subsubheading @value{GDBN} Command
34309 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34310 has the corresponding command @samp{gdb_changed_register_list}.
34312 @subsubheading Example
34314 On a PPC MBX board:
34322 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34323 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34324 line="5",arch="powerpc"@}
34326 -data-list-changed-registers
34327 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34328 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34329 "24","25","26","27","28","30","31","64","65","66","67","69"]
34334 @subheading The @code{-data-list-register-names} Command
34335 @findex -data-list-register-names
34337 @subsubheading Synopsis
34340 -data-list-register-names [ ( @var{regno} )+ ]
34343 Show a list of register names for the current target. If no arguments
34344 are given, it shows a list of the names of all the registers. If
34345 integer numbers are given as arguments, it will print a list of the
34346 names of the registers corresponding to the arguments. To ensure
34347 consistency between a register name and its number, the output list may
34348 include empty register names.
34350 @subsubheading @value{GDBN} Command
34352 @value{GDBN} does not have a command which corresponds to
34353 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34354 corresponding command @samp{gdb_regnames}.
34356 @subsubheading Example
34358 For the PPC MBX board:
34361 -data-list-register-names
34362 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34363 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34364 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34365 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34366 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34367 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34368 "", "pc","ps","cr","lr","ctr","xer"]
34370 -data-list-register-names 1 2 3
34371 ^done,register-names=["r1","r2","r3"]
34375 @subheading The @code{-data-list-register-values} Command
34376 @findex -data-list-register-values
34378 @subsubheading Synopsis
34381 -data-list-register-values
34382 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34385 Display the registers' contents. The format according to which the
34386 registers' contents are to be returned is given by @var{fmt}, followed
34387 by an optional list of numbers specifying the registers to display. A
34388 missing list of numbers indicates that the contents of all the
34389 registers must be returned. The @code{--skip-unavailable} option
34390 indicates that only the available registers are to be returned.
34392 Allowed formats for @var{fmt} are:
34409 @subsubheading @value{GDBN} Command
34411 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34412 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34414 @subsubheading Example
34416 For a PPC MBX board (note: line breaks are for readability only, they
34417 don't appear in the actual output):
34421 -data-list-register-values r 64 65
34422 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34423 @{number="65",value="0x00029002"@}]
34425 -data-list-register-values x
34426 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34427 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34428 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34429 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34430 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34431 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34432 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34433 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34434 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34435 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34436 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34437 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34438 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34439 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34440 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34441 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34442 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34443 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34444 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34445 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34446 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34447 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34448 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34449 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34450 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34451 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34452 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34453 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34454 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34455 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34456 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34457 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34458 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34459 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34460 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34461 @{number="69",value="0x20002b03"@}]
34466 @subheading The @code{-data-read-memory} Command
34467 @findex -data-read-memory
34469 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34471 @subsubheading Synopsis
34474 -data-read-memory [ -o @var{byte-offset} ]
34475 @var{address} @var{word-format} @var{word-size}
34476 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34483 @item @var{address}
34484 An expression specifying the address of the first memory word to be
34485 read. Complex expressions containing embedded white space should be
34486 quoted using the C convention.
34488 @item @var{word-format}
34489 The format to be used to print the memory words. The notation is the
34490 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34493 @item @var{word-size}
34494 The size of each memory word in bytes.
34496 @item @var{nr-rows}
34497 The number of rows in the output table.
34499 @item @var{nr-cols}
34500 The number of columns in the output table.
34503 If present, indicates that each row should include an @sc{ascii} dump. The
34504 value of @var{aschar} is used as a padding character when a byte is not a
34505 member of the printable @sc{ascii} character set (printable @sc{ascii}
34506 characters are those whose code is between 32 and 126, inclusively).
34508 @item @var{byte-offset}
34509 An offset to add to the @var{address} before fetching memory.
34512 This command displays memory contents as a table of @var{nr-rows} by
34513 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34514 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34515 (returned as @samp{total-bytes}). Should less than the requested number
34516 of bytes be returned by the target, the missing words are identified
34517 using @samp{N/A}. The number of bytes read from the target is returned
34518 in @samp{nr-bytes} and the starting address used to read memory in
34521 The address of the next/previous row or page is available in
34522 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34525 @subsubheading @value{GDBN} Command
34527 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34528 @samp{gdb_get_mem} memory read command.
34530 @subsubheading Example
34532 Read six bytes of memory starting at @code{bytes+6} but then offset by
34533 @code{-6} bytes. Format as three rows of two columns. One byte per
34534 word. Display each word in hex.
34538 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34539 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34540 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34541 prev-page="0x0000138a",memory=[
34542 @{addr="0x00001390",data=["0x00","0x01"]@},
34543 @{addr="0x00001392",data=["0x02","0x03"]@},
34544 @{addr="0x00001394",data=["0x04","0x05"]@}]
34548 Read two bytes of memory starting at address @code{shorts + 64} and
34549 display as a single word formatted in decimal.
34553 5-data-read-memory shorts+64 d 2 1 1
34554 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34555 next-row="0x00001512",prev-row="0x0000150e",
34556 next-page="0x00001512",prev-page="0x0000150e",memory=[
34557 @{addr="0x00001510",data=["128"]@}]
34561 Read thirty two bytes of memory starting at @code{bytes+16} and format
34562 as eight rows of four columns. Include a string encoding with @samp{x}
34563 used as the non-printable character.
34567 4-data-read-memory bytes+16 x 1 8 4 x
34568 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34569 next-row="0x000013c0",prev-row="0x0000139c",
34570 next-page="0x000013c0",prev-page="0x00001380",memory=[
34571 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34572 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34573 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34574 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34575 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34576 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34577 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34578 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34582 @subheading The @code{-data-read-memory-bytes} Command
34583 @findex -data-read-memory-bytes
34585 @subsubheading Synopsis
34588 -data-read-memory-bytes [ -o @var{offset} ]
34589 @var{address} @var{count}
34596 @item @var{address}
34597 An expression specifying the address of the first addressable memory unit
34598 to be read. Complex expressions containing embedded white space should be
34599 quoted using the C convention.
34602 The number of addressable memory units to read. This should be an integer
34606 The offset relative to @var{address} at which to start reading. This
34607 should be an integer literal. This option is provided so that a frontend
34608 is not required to first evaluate address and then perform address
34609 arithmetics itself.
34613 This command attempts to read all accessible memory regions in the
34614 specified range. First, all regions marked as unreadable in the memory
34615 map (if one is defined) will be skipped. @xref{Memory Region
34616 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34617 regions. For each one, if reading full region results in an errors,
34618 @value{GDBN} will try to read a subset of the region.
34620 In general, every single memory unit in the region may be readable or not,
34621 and the only way to read every readable unit is to try a read at
34622 every address, which is not practical. Therefore, @value{GDBN} will
34623 attempt to read all accessible memory units at either beginning or the end
34624 of the region, using a binary division scheme. This heuristic works
34625 well for reading across a memory map boundary. Note that if a region
34626 has a readable range that is neither at the beginning or the end,
34627 @value{GDBN} will not read it.
34629 The result record (@pxref{GDB/MI Result Records}) that is output of
34630 the command includes a field named @samp{memory} whose content is a
34631 list of tuples. Each tuple represent a successfully read memory block
34632 and has the following fields:
34636 The start address of the memory block, as hexadecimal literal.
34639 The end address of the memory block, as hexadecimal literal.
34642 The offset of the memory block, as hexadecimal literal, relative to
34643 the start address passed to @code{-data-read-memory-bytes}.
34646 The contents of the memory block, in hex.
34652 @subsubheading @value{GDBN} Command
34654 The corresponding @value{GDBN} command is @samp{x}.
34656 @subsubheading Example
34660 -data-read-memory-bytes &a 10
34661 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34663 contents="01000000020000000300"@}]
34668 @subheading The @code{-data-write-memory-bytes} Command
34669 @findex -data-write-memory-bytes
34671 @subsubheading Synopsis
34674 -data-write-memory-bytes @var{address} @var{contents}
34675 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34682 @item @var{address}
34683 An expression specifying the address of the first addressable memory unit
34684 to be written. Complex expressions containing embedded white space should
34685 be quoted using the C convention.
34687 @item @var{contents}
34688 The hex-encoded data to write. It is an error if @var{contents} does
34689 not represent an integral number of addressable memory units.
34692 Optional argument indicating the number of addressable memory units to be
34693 written. If @var{count} is greater than @var{contents}' length,
34694 @value{GDBN} will repeatedly write @var{contents} until it fills
34695 @var{count} memory units.
34699 @subsubheading @value{GDBN} Command
34701 There's no corresponding @value{GDBN} command.
34703 @subsubheading Example
34707 -data-write-memory-bytes &a "aabbccdd"
34714 -data-write-memory-bytes &a "aabbccdd" 16e
34719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34720 @node GDB/MI Tracepoint Commands
34721 @section @sc{gdb/mi} Tracepoint Commands
34723 The commands defined in this section implement MI support for
34724 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34726 @subheading The @code{-trace-find} Command
34727 @findex -trace-find
34729 @subsubheading Synopsis
34732 -trace-find @var{mode} [@var{parameters}@dots{}]
34735 Find a trace frame using criteria defined by @var{mode} and
34736 @var{parameters}. The following table lists permissible
34737 modes and their parameters. For details of operation, see @ref{tfind}.
34742 No parameters are required. Stops examining trace frames.
34745 An integer is required as parameter. Selects tracepoint frame with
34748 @item tracepoint-number
34749 An integer is required as parameter. Finds next
34750 trace frame that corresponds to tracepoint with the specified number.
34753 An address is required as parameter. Finds
34754 next trace frame that corresponds to any tracepoint at the specified
34757 @item pc-inside-range
34758 Two addresses are required as parameters. Finds next trace
34759 frame that corresponds to a tracepoint at an address inside the
34760 specified range. Both bounds are considered to be inside the range.
34762 @item pc-outside-range
34763 Two addresses are required as parameters. Finds
34764 next trace frame that corresponds to a tracepoint at an address outside
34765 the specified range. Both bounds are considered to be inside the range.
34768 Line specification is required as parameter. @xref{Specify Location}.
34769 Finds next trace frame that corresponds to a tracepoint at
34770 the specified location.
34774 If @samp{none} was passed as @var{mode}, the response does not
34775 have fields. Otherwise, the response may have the following fields:
34779 This field has either @samp{0} or @samp{1} as the value, depending
34780 on whether a matching tracepoint was found.
34783 The index of the found traceframe. This field is present iff
34784 the @samp{found} field has value of @samp{1}.
34787 The index of the found tracepoint. This field is present iff
34788 the @samp{found} field has value of @samp{1}.
34791 The information about the frame corresponding to the found trace
34792 frame. This field is present only if a trace frame was found.
34793 @xref{GDB/MI Frame Information}, for description of this field.
34797 @subsubheading @value{GDBN} Command
34799 The corresponding @value{GDBN} command is @samp{tfind}.
34801 @subheading -trace-define-variable
34802 @findex -trace-define-variable
34804 @subsubheading Synopsis
34807 -trace-define-variable @var{name} [ @var{value} ]
34810 Create trace variable @var{name} if it does not exist. If
34811 @var{value} is specified, sets the initial value of the specified
34812 trace variable to that value. Note that the @var{name} should start
34813 with the @samp{$} character.
34815 @subsubheading @value{GDBN} Command
34817 The corresponding @value{GDBN} command is @samp{tvariable}.
34819 @subheading The @code{-trace-frame-collected} Command
34820 @findex -trace-frame-collected
34822 @subsubheading Synopsis
34825 -trace-frame-collected
34826 [--var-print-values @var{var_pval}]
34827 [--comp-print-values @var{comp_pval}]
34828 [--registers-format @var{regformat}]
34829 [--memory-contents]
34832 This command returns the set of collected objects, register names,
34833 trace state variable names, memory ranges and computed expressions
34834 that have been collected at a particular trace frame. The optional
34835 parameters to the command affect the output format in different ways.
34836 See the output description table below for more details.
34838 The reported names can be used in the normal manner to create
34839 varobjs and inspect the objects themselves. The items returned by
34840 this command are categorized so that it is clear which is a variable,
34841 which is a register, which is a trace state variable, which is a
34842 memory range and which is a computed expression.
34844 For instance, if the actions were
34846 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34847 collect *(int*)0xaf02bef0@@40
34851 the object collected in its entirety would be @code{myVar}. The
34852 object @code{myArray} would be partially collected, because only the
34853 element at index @code{myIndex} would be collected. The remaining
34854 objects would be computed expressions.
34856 An example output would be:
34860 -trace-frame-collected
34862 explicit-variables=[@{name="myVar",value="1"@}],
34863 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34864 @{name="myObj.field",value="0"@},
34865 @{name="myPtr->field",value="1"@},
34866 @{name="myCount + 2",value="3"@},
34867 @{name="$tvar1 + 1",value="43970027"@}],
34868 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34869 @{number="1",value="0x0"@},
34870 @{number="2",value="0x4"@},
34872 @{number="125",value="0x0"@}],
34873 tvars=[@{name="$tvar1",current="43970026"@}],
34874 memory=[@{address="0x0000000000602264",length="4"@},
34875 @{address="0x0000000000615bc0",length="4"@}]
34882 @item explicit-variables
34883 The set of objects that have been collected in their entirety (as
34884 opposed to collecting just a few elements of an array or a few struct
34885 members). For each object, its name and value are printed.
34886 The @code{--var-print-values} option affects how or whether the value
34887 field is output. If @var{var_pval} is 0, then print only the names;
34888 if it is 1, print also their values; and if it is 2, print the name,
34889 type and value for simple data types, and the name and type for
34890 arrays, structures and unions.
34892 @item computed-expressions
34893 The set of computed expressions that have been collected at the
34894 current trace frame. The @code{--comp-print-values} option affects
34895 this set like the @code{--var-print-values} option affects the
34896 @code{explicit-variables} set. See above.
34899 The registers that have been collected at the current trace frame.
34900 For each register collected, the name and current value are returned.
34901 The value is formatted according to the @code{--registers-format}
34902 option. See the @command{-data-list-register-values} command for a
34903 list of the allowed formats. The default is @samp{x}.
34906 The trace state variables that have been collected at the current
34907 trace frame. For each trace state variable collected, the name and
34908 current value are returned.
34911 The set of memory ranges that have been collected at the current trace
34912 frame. Its content is a list of tuples. Each tuple represents a
34913 collected memory range and has the following fields:
34917 The start address of the memory range, as hexadecimal literal.
34920 The length of the memory range, as decimal literal.
34923 The contents of the memory block, in hex. This field is only present
34924 if the @code{--memory-contents} option is specified.
34930 @subsubheading @value{GDBN} Command
34932 There is no corresponding @value{GDBN} command.
34934 @subsubheading Example
34936 @subheading -trace-list-variables
34937 @findex -trace-list-variables
34939 @subsubheading Synopsis
34942 -trace-list-variables
34945 Return a table of all defined trace variables. Each element of the
34946 table has the following fields:
34950 The name of the trace variable. This field is always present.
34953 The initial value. This is a 64-bit signed integer. This
34954 field is always present.
34957 The value the trace variable has at the moment. This is a 64-bit
34958 signed integer. This field is absent iff current value is
34959 not defined, for example if the trace was never run, or is
34964 @subsubheading @value{GDBN} Command
34966 The corresponding @value{GDBN} command is @samp{tvariables}.
34968 @subsubheading Example
34972 -trace-list-variables
34973 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34974 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34975 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34976 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34977 body=[variable=@{name="$trace_timestamp",initial="0"@}
34978 variable=@{name="$foo",initial="10",current="15"@}]@}
34982 @subheading -trace-save
34983 @findex -trace-save
34985 @subsubheading Synopsis
34988 -trace-save [ -r ] [ -ctf ] @var{filename}
34991 Saves the collected trace data to @var{filename}. Without the
34992 @samp{-r} option, the data is downloaded from the target and saved
34993 in a local file. With the @samp{-r} option the target is asked
34994 to perform the save.
34996 By default, this command will save the trace in the tfile format. You can
34997 supply the optional @samp{-ctf} argument to save it the CTF format. See
34998 @ref{Trace Files} for more information about CTF.
35000 @subsubheading @value{GDBN} Command
35002 The corresponding @value{GDBN} command is @samp{tsave}.
35005 @subheading -trace-start
35006 @findex -trace-start
35008 @subsubheading Synopsis
35014 Starts a tracing experiment. The result of this command does not
35017 @subsubheading @value{GDBN} Command
35019 The corresponding @value{GDBN} command is @samp{tstart}.
35021 @subheading -trace-status
35022 @findex -trace-status
35024 @subsubheading Synopsis
35030 Obtains the status of a tracing experiment. The result may include
35031 the following fields:
35036 May have a value of either @samp{0}, when no tracing operations are
35037 supported, @samp{1}, when all tracing operations are supported, or
35038 @samp{file} when examining trace file. In the latter case, examining
35039 of trace frame is possible but new tracing experiement cannot be
35040 started. This field is always present.
35043 May have a value of either @samp{0} or @samp{1} depending on whether
35044 tracing experiement is in progress on target. This field is present
35045 if @samp{supported} field is not @samp{0}.
35048 Report the reason why the tracing was stopped last time. This field
35049 may be absent iff tracing was never stopped on target yet. The
35050 value of @samp{request} means the tracing was stopped as result of
35051 the @code{-trace-stop} command. The value of @samp{overflow} means
35052 the tracing buffer is full. The value of @samp{disconnection} means
35053 tracing was automatically stopped when @value{GDBN} has disconnected.
35054 The value of @samp{passcount} means tracing was stopped when a
35055 tracepoint was passed a maximal number of times for that tracepoint.
35056 This field is present if @samp{supported} field is not @samp{0}.
35058 @item stopping-tracepoint
35059 The number of tracepoint whose passcount as exceeded. This field is
35060 present iff the @samp{stop-reason} field has the value of
35064 @itemx frames-created
35065 The @samp{frames} field is a count of the total number of trace frames
35066 in the trace buffer, while @samp{frames-created} is the total created
35067 during the run, including ones that were discarded, such as when a
35068 circular trace buffer filled up. Both fields are optional.
35072 These fields tell the current size of the tracing buffer and the
35073 remaining space. These fields are optional.
35076 The value of the circular trace buffer flag. @code{1} means that the
35077 trace buffer is circular and old trace frames will be discarded if
35078 necessary to make room, @code{0} means that the trace buffer is linear
35082 The value of the disconnected tracing flag. @code{1} means that
35083 tracing will continue after @value{GDBN} disconnects, @code{0} means
35084 that the trace run will stop.
35087 The filename of the trace file being examined. This field is
35088 optional, and only present when examining a trace file.
35092 @subsubheading @value{GDBN} Command
35094 The corresponding @value{GDBN} command is @samp{tstatus}.
35096 @subheading -trace-stop
35097 @findex -trace-stop
35099 @subsubheading Synopsis
35105 Stops a tracing experiment. The result of this command has the same
35106 fields as @code{-trace-status}, except that the @samp{supported} and
35107 @samp{running} fields are not output.
35109 @subsubheading @value{GDBN} Command
35111 The corresponding @value{GDBN} command is @samp{tstop}.
35114 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35115 @node GDB/MI Symbol Query
35116 @section @sc{gdb/mi} Symbol Query Commands
35120 @subheading The @code{-symbol-info-address} Command
35121 @findex -symbol-info-address
35123 @subsubheading Synopsis
35126 -symbol-info-address @var{symbol}
35129 Describe where @var{symbol} is stored.
35131 @subsubheading @value{GDBN} Command
35133 The corresponding @value{GDBN} command is @samp{info address}.
35135 @subsubheading Example
35139 @subheading The @code{-symbol-info-file} Command
35140 @findex -symbol-info-file
35142 @subsubheading Synopsis
35148 Show the file for the symbol.
35150 @subsubheading @value{GDBN} Command
35152 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35153 @samp{gdb_find_file}.
35155 @subsubheading Example
35159 @subheading The @code{-symbol-info-functions} Command
35160 @findex -symbol-info-functions
35161 @anchor{-symbol-info-functions}
35163 @subsubheading Synopsis
35166 -symbol-info-functions [--include-nondebug]
35167 [--type @var{type_regexp}]
35168 [--name @var{name_regexp}]
35169 [--max-results @var{limit}]
35173 Return a list containing the names and types for all global functions
35174 taken from the debug information. The functions are grouped by source
35175 file, and shown with the line number on which each function is
35178 The @code{--include-nondebug} option causes the output to include
35179 code symbols from the symbol table.
35181 The options @code{--type} and @code{--name} allow the symbols returned
35182 to be filtered based on either the name of the function, or the type
35183 signature of the function.
35185 The option @code{--max-results} restricts the command to return no
35186 more than @var{limit} results. If exactly @var{limit} results are
35187 returned then there might be additional results available if a higher
35190 @subsubheading @value{GDBN} Command
35192 The corresponding @value{GDBN} command is @samp{info functions}.
35194 @subsubheading Example
35198 -symbol-info-functions
35201 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35202 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35203 symbols=[@{line="36", name="f4", type="void (int *)",
35204 description="void f4(int *);"@},
35205 @{line="42", name="main", type="int ()",
35206 description="int main();"@},
35207 @{line="30", name="f1", type="my_int_t (int, int)",
35208 description="static my_int_t f1(int, int);"@}]@},
35209 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35210 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35211 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35212 description="float f2(another_float_t);"@},
35213 @{line="39", name="f3", type="int (another_int_t)",
35214 description="int f3(another_int_t);"@},
35215 @{line="27", name="f1", type="another_float_t (int)",
35216 description="static another_float_t f1(int);"@}]@}]@}
35220 -symbol-info-functions --name f1
35223 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35224 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35225 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35226 description="static my_int_t f1(int, int);"@}]@},
35227 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35228 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35229 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35230 description="static another_float_t f1(int);"@}]@}]@}
35234 -symbol-info-functions --type void
35237 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35238 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35239 symbols=[@{line="36", name="f4", type="void (int *)",
35240 description="void f4(int *);"@}]@}]@}
35244 -symbol-info-functions --include-nondebug
35247 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35248 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35249 symbols=[@{line="36", name="f4", type="void (int *)",
35250 description="void f4(int *);"@},
35251 @{line="42", name="main", type="int ()",
35252 description="int main();"@},
35253 @{line="30", name="f1", type="my_int_t (int, int)",
35254 description="static my_int_t f1(int, int);"@}]@},
35255 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35256 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35257 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35258 description="float f2(another_float_t);"@},
35259 @{line="39", name="f3", type="int (another_int_t)",
35260 description="int f3(another_int_t);"@},
35261 @{line="27", name="f1", type="another_float_t (int)",
35262 description="static another_float_t f1(int);"@}]@}],
35264 [@{address="0x0000000000400398",name="_init"@},
35265 @{address="0x00000000004003b0",name="_start"@},
35271 @subheading The @code{-symbol-info-module-functions} Command
35272 @findex -symbol-info-module-functions
35273 @anchor{-symbol-info-module-functions}
35275 @subsubheading Synopsis
35278 -symbol-info-module-functions [--module @var{module_regexp}]
35279 [--name @var{name_regexp}]
35280 [--type @var{type_regexp}]
35284 Return a list containing the names of all known functions within all
35285 know Fortran modules. The functions are grouped by source file and
35286 containing module, and shown with the line number on which each
35287 function is defined.
35289 The option @code{--module} only returns results for modules matching
35290 @var{module_regexp}. The option @code{--name} only returns functions
35291 whose name matches @var{name_regexp}, and @code{--type} only returns
35292 functions whose type matches @var{type_regexp}.
35294 @subsubheading @value{GDBN} Command
35296 The corresponding @value{GDBN} command is @samp{info module functions}.
35298 @subsubheading Example
35303 -symbol-info-module-functions
35306 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35307 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35308 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35309 description="void mod1::check_all(void);"@}]@}]@},
35311 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35312 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35313 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35314 description="void mod2::check_var_i(void);"@}]@}]@},
35316 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35317 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35318 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35319 description="void mod3::check_all(void);"@},
35320 @{line="27",name="mod3::check_mod2",type="void (void)",
35321 description="void mod3::check_mod2(void);"@}]@}]@},
35322 @{module="modmany",
35323 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35324 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35325 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35326 description="void modmany::check_some(void);"@}]@}]@},
35328 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35329 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35330 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35331 description="void moduse::check_all(void);"@},
35332 @{line="49",name="moduse::check_var_x",type="void (void)",
35333 description="void moduse::check_var_x(void);"@}]@}]@}]
35337 @subheading The @code{-symbol-info-module-variables} Command
35338 @findex -symbol-info-module-variables
35339 @anchor{-symbol-info-module-variables}
35341 @subsubheading Synopsis
35344 -symbol-info-module-variables [--module @var{module_regexp}]
35345 [--name @var{name_regexp}]
35346 [--type @var{type_regexp}]
35350 Return a list containing the names of all known variables within all
35351 know Fortran modules. The variables are grouped by source file and
35352 containing module, and shown with the line number on which each
35353 variable is defined.
35355 The option @code{--module} only returns results for modules matching
35356 @var{module_regexp}. The option @code{--name} only returns variables
35357 whose name matches @var{name_regexp}, and @code{--type} only returns
35358 variables whose type matches @var{type_regexp}.
35360 @subsubheading @value{GDBN} Command
35362 The corresponding @value{GDBN} command is @samp{info module variables}.
35364 @subsubheading Example
35369 -symbol-info-module-variables
35372 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35373 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35374 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35375 description="integer(kind=4) mod1::var_const;"@},
35376 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35377 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35379 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35380 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35381 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35382 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35384 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35385 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35386 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35387 description="integer(kind=4) mod3::mod1;"@},
35388 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35389 description="integer(kind=4) mod3::mod2;"@},
35390 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35391 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35392 @{module="modmany",
35393 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35394 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35395 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35396 description="integer(kind=4) modmany::var_a;"@},
35397 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35398 description="integer(kind=4) modmany::var_b;"@},
35399 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35400 description="integer(kind=4) modmany::var_c;"@},
35401 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35402 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35404 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35405 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35406 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35407 description="integer(kind=4) moduse::var_x;"@},
35408 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35409 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35413 @subheading The @code{-symbol-info-modules} Command
35414 @findex -symbol-info-modules
35415 @anchor{-symbol-info-modules}
35417 @subsubheading Synopsis
35420 -symbol-info-modules [--name @var{name_regexp}]
35421 [--max-results @var{limit}]
35426 Return a list containing the names of all known Fortran modules. The
35427 modules are grouped by source file, and shown with the line number on
35428 which each modules is defined.
35430 The option @code{--name} allows the modules returned to be filtered
35431 based the name of the module.
35433 The option @code{--max-results} restricts the command to return no
35434 more than @var{limit} results. If exactly @var{limit} results are
35435 returned then there might be additional results available if a higher
35438 @subsubheading @value{GDBN} Command
35440 The corresponding @value{GDBN} command is @samp{info modules}.
35442 @subsubheading Example
35446 -symbol-info-modules
35449 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35450 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35451 symbols=[@{line="16",name="mod1"@},
35452 @{line="22",name="mod2"@}]@},
35453 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35454 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35455 symbols=[@{line="16",name="mod3"@},
35456 @{line="22",name="modmany"@},
35457 @{line="26",name="moduse"@}]@}]@}
35461 -symbol-info-modules --name mod[123]
35464 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35465 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35466 symbols=[@{line="16",name="mod1"@},
35467 @{line="22",name="mod2"@}]@},
35468 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35469 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35470 symbols=[@{line="16",name="mod3"@}]@}]@}
35474 @subheading The @code{-symbol-info-types} Command
35475 @findex -symbol-info-types
35476 @anchor{-symbol-info-types}
35478 @subsubheading Synopsis
35481 -symbol-info-types [--name @var{name_regexp}]
35482 [--max-results @var{limit}]
35487 Return a list of all defined types. The types are grouped by source
35488 file, and shown with the line number on which each user defined type
35489 is defined. Some base types are not defined in the source code but
35490 are added to the debug information by the compiler, for example
35491 @code{int}, @code{float}, etc.; these types do not have an associated
35494 The option @code{--name} allows the list of types returned to be
35497 The option @code{--max-results} restricts the command to return no
35498 more than @var{limit} results. If exactly @var{limit} results are
35499 returned then there might be additional results available if a higher
35502 @subsubheading @value{GDBN} Command
35504 The corresponding @value{GDBN} command is @samp{info types}.
35506 @subsubheading Example
35513 [@{filename="gdb.mi/mi-sym-info-1.c",
35514 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35515 symbols=[@{name="float"@},
35517 @{line="27",name="typedef int my_int_t;"@}]@},
35518 @{filename="gdb.mi/mi-sym-info-2.c",
35519 fullname="/project/gdb.mi/mi-sym-info-2.c",
35520 symbols=[@{line="24",name="typedef float another_float_t;"@},
35521 @{line="23",name="typedef int another_int_t;"@},
35523 @{name="int"@}]@}]@}
35527 -symbol-info-types --name _int_
35530 [@{filename="gdb.mi/mi-sym-info-1.c",
35531 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35532 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35533 @{filename="gdb.mi/mi-sym-info-2.c",
35534 fullname="/project/gdb.mi/mi-sym-info-2.c",
35535 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35539 @subheading The @code{-symbol-info-variables} Command
35540 @findex -symbol-info-variables
35541 @anchor{-symbol-info-variables}
35543 @subsubheading Synopsis
35546 -symbol-info-variables [--include-nondebug]
35547 [--type @var{type_regexp}]
35548 [--name @var{name_regexp}]
35549 [--max-results @var{limit}]
35554 Return a list containing the names and types for all global variables
35555 taken from the debug information. The variables are grouped by source
35556 file, and shown with the line number on which each variable is
35559 The @code{--include-nondebug} option causes the output to include
35560 data symbols from the symbol table.
35562 The options @code{--type} and @code{--name} allow the symbols returned
35563 to be filtered based on either the name of the variable, or the type
35566 The option @code{--max-results} restricts the command to return no
35567 more than @var{limit} results. If exactly @var{limit} results are
35568 returned then there might be additional results available if a higher
35571 @subsubheading @value{GDBN} Command
35573 The corresponding @value{GDBN} command is @samp{info variables}.
35575 @subsubheading Example
35579 -symbol-info-variables
35582 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35583 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35584 symbols=[@{line="25",name="global_f1",type="float",
35585 description="static float global_f1;"@},
35586 @{line="24",name="global_i1",type="int",
35587 description="static int global_i1;"@}]@},
35588 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35589 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35590 symbols=[@{line="21",name="global_f2",type="int",
35591 description="int global_f2;"@},
35592 @{line="20",name="global_i2",type="int",
35593 description="int global_i2;"@},
35594 @{line="19",name="global_f1",type="float",
35595 description="static float global_f1;"@},
35596 @{line="18",name="global_i1",type="int",
35597 description="static int global_i1;"@}]@}]@}
35601 -symbol-info-variables --name f1
35604 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35605 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35606 symbols=[@{line="25",name="global_f1",type="float",
35607 description="static float global_f1;"@}]@},
35608 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35609 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35610 symbols=[@{line="19",name="global_f1",type="float",
35611 description="static float global_f1;"@}]@}]@}
35615 -symbol-info-variables --type float
35618 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35619 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35620 symbols=[@{line="25",name="global_f1",type="float",
35621 description="static float global_f1;"@}]@},
35622 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35623 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35624 symbols=[@{line="19",name="global_f1",type="float",
35625 description="static float global_f1;"@}]@}]@}
35629 -symbol-info-variables --include-nondebug
35632 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35633 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35634 symbols=[@{line="25",name="global_f1",type="float",
35635 description="static float global_f1;"@},
35636 @{line="24",name="global_i1",type="int",
35637 description="static int global_i1;"@}]@},
35638 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35639 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35640 symbols=[@{line="21",name="global_f2",type="int",
35641 description="int global_f2;"@},
35642 @{line="20",name="global_i2",type="int",
35643 description="int global_i2;"@},
35644 @{line="19",name="global_f1",type="float",
35645 description="static float global_f1;"@},
35646 @{line="18",name="global_i1",type="int",
35647 description="static int global_i1;"@}]@}],
35649 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35650 @{address="0x00000000004005d8",name="__dso_handle"@}
35657 @subheading The @code{-symbol-info-line} Command
35658 @findex -symbol-info-line
35660 @subsubheading Synopsis
35666 Show the core addresses of the code for a source line.
35668 @subsubheading @value{GDBN} Command
35670 The corresponding @value{GDBN} command is @samp{info line}.
35671 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35673 @subsubheading Example
35677 @subheading The @code{-symbol-info-symbol} Command
35678 @findex -symbol-info-symbol
35680 @subsubheading Synopsis
35683 -symbol-info-symbol @var{addr}
35686 Describe what symbol is at location @var{addr}.
35688 @subsubheading @value{GDBN} Command
35690 The corresponding @value{GDBN} command is @samp{info symbol}.
35692 @subsubheading Example
35696 @subheading The @code{-symbol-list-functions} Command
35697 @findex -symbol-list-functions
35699 @subsubheading Synopsis
35702 -symbol-list-functions
35705 List the functions in the executable.
35707 @subsubheading @value{GDBN} Command
35709 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35710 @samp{gdb_search} in @code{gdbtk}.
35712 @subsubheading Example
35717 @subheading The @code{-symbol-list-lines} Command
35718 @findex -symbol-list-lines
35720 @subsubheading Synopsis
35723 -symbol-list-lines @var{filename}
35726 Print the list of lines that contain code and their associated program
35727 addresses for the given source filename. The entries are sorted in
35728 ascending PC order.
35730 @subsubheading @value{GDBN} Command
35732 There is no corresponding @value{GDBN} command.
35734 @subsubheading Example
35737 -symbol-list-lines basics.c
35738 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35744 @subheading The @code{-symbol-list-types} Command
35745 @findex -symbol-list-types
35747 @subsubheading Synopsis
35753 List all the type names.
35755 @subsubheading @value{GDBN} Command
35757 The corresponding commands are @samp{info types} in @value{GDBN},
35758 @samp{gdb_search} in @code{gdbtk}.
35760 @subsubheading Example
35764 @subheading The @code{-symbol-list-variables} Command
35765 @findex -symbol-list-variables
35767 @subsubheading Synopsis
35770 -symbol-list-variables
35773 List all the global and static variable names.
35775 @subsubheading @value{GDBN} Command
35777 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35779 @subsubheading Example
35783 @subheading The @code{-symbol-locate} Command
35784 @findex -symbol-locate
35786 @subsubheading Synopsis
35792 @subsubheading @value{GDBN} Command
35794 @samp{gdb_loc} in @code{gdbtk}.
35796 @subsubheading Example
35800 @subheading The @code{-symbol-type} Command
35801 @findex -symbol-type
35803 @subsubheading Synopsis
35806 -symbol-type @var{variable}
35809 Show type of @var{variable}.
35811 @subsubheading @value{GDBN} Command
35813 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35814 @samp{gdb_obj_variable}.
35816 @subsubheading Example
35821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35822 @node GDB/MI File Commands
35823 @section @sc{gdb/mi} File Commands
35825 This section describes the GDB/MI commands to specify executable file names
35826 and to read in and obtain symbol table information.
35828 @subheading The @code{-file-exec-and-symbols} Command
35829 @findex -file-exec-and-symbols
35831 @subsubheading Synopsis
35834 -file-exec-and-symbols @var{file}
35837 Specify the executable file to be debugged. This file is the one from
35838 which the symbol table is also read. If no file is specified, the
35839 command clears the executable and symbol information. If breakpoints
35840 are set when using this command with no arguments, @value{GDBN} will produce
35841 error messages. Otherwise, no output is produced, except a completion
35844 @subsubheading @value{GDBN} Command
35846 The corresponding @value{GDBN} command is @samp{file}.
35848 @subsubheading Example
35852 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35858 @subheading The @code{-file-exec-file} Command
35859 @findex -file-exec-file
35861 @subsubheading Synopsis
35864 -file-exec-file @var{file}
35867 Specify the executable file to be debugged. Unlike
35868 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35869 from this file. If used without argument, @value{GDBN} clears the information
35870 about the executable file. No output is produced, except a completion
35873 @subsubheading @value{GDBN} Command
35875 The corresponding @value{GDBN} command is @samp{exec-file}.
35877 @subsubheading Example
35881 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35888 @subheading The @code{-file-list-exec-sections} Command
35889 @findex -file-list-exec-sections
35891 @subsubheading Synopsis
35894 -file-list-exec-sections
35897 List the sections of the current executable file.
35899 @subsubheading @value{GDBN} Command
35901 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35902 information as this command. @code{gdbtk} has a corresponding command
35903 @samp{gdb_load_info}.
35905 @subsubheading Example
35910 @subheading The @code{-file-list-exec-source-file} Command
35911 @findex -file-list-exec-source-file
35913 @subsubheading Synopsis
35916 -file-list-exec-source-file
35919 List the line number, the current source file, and the absolute path
35920 to the current source file for the current executable. The macro
35921 information field has a value of @samp{1} or @samp{0} depending on
35922 whether or not the file includes preprocessor macro information.
35924 @subsubheading @value{GDBN} Command
35926 The @value{GDBN} equivalent is @samp{info source}
35928 @subsubheading Example
35932 123-file-list-exec-source-file
35933 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35938 @subheading The @code{-file-list-exec-source-files} Command
35939 @kindex info sources
35940 @findex -file-list-exec-source-files
35942 @subsubheading Synopsis
35945 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
35946 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
35948 @r{[} @var{regexp} @r{]}
35951 This command returns information about the source files @value{GDBN}
35952 knows about, it will output both the filename and fullname (absolute
35953 file name) of a source file, though the fullname can be elided if this
35954 information is not known to @value{GDBN}.
35956 With no arguments this command returns a list of source files. Each
35957 source file is represented by a tuple with the fields; @var{file},
35958 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
35959 display name for the file, while @var{fullname} is the absolute name
35960 of the file. The @var{fullname} field can be elided if the absolute
35961 name of the source file can't be computed. The field
35962 @var{debug-fully-read} will be a string, either @code{true} or
35963 @code{false}. When @code{true}, this indicates the full debug
35964 information for the compilation unit describing this file has been
35965 read in. When @code{false}, the full debug information has not yet
35966 been read in. While reading in the full debug information it is
35967 possible that @value{GDBN} could become aware of additional source
35970 The optional @var{regexp} can be used to filter the list of source
35971 files returned. The @var{regexp} will be matched against the full
35972 source file name. The matching is case-sensitive, except on operating
35973 systems that have case-insensitive filesystem (e.g.,
35974 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
35975 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
35976 @var{regexp} starts with @samp{-}).
35978 If @code{--dirname} is provided, then @var{regexp} is matched only
35979 against the directory name of each source file. If @code{--basename}
35980 is provided, then @var{regexp} is matched against the basename of each
35981 source file. Only one of @code{--dirname} or @code{--basename} may be
35982 given, and if either is given then @var{regexp} is required.
35984 If @code{--group-by-objfile} is used then the format of the results is
35985 changed. The results will now be a list of tuples, with each tuple
35986 representing an object file (executable or shared library) loaded into
35987 @value{GDBN}. The fields of these tuples are; @var{filename},
35988 @var{debug-info}, and @var{sources}. The @var{filename} is the
35989 absolute name of the object file, @var{debug-info} is a string with
35990 one of the following values:
35994 This object file has no debug information.
35995 @item partially-read
35996 This object file has debug information, but it is not fully read in
35997 yet. When it is read in later, GDB might become aware of additional
36000 This object file has debug information, and this information is fully
36001 read into GDB. The list of source files is complete.
36004 The @var{sources} is a list or tuples, with each tuple describing a
36005 single source file with the same fields as described previously. The
36006 @var{sources} list can be empty for object files that have no debug
36009 @subsubheading @value{GDBN} Command
36011 The @value{GDBN} equivalent is @samp{info sources}.
36012 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36014 @subsubheading Example
36017 -file-list-exec-source-files
36018 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36019 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36020 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36022 -file-list-exec-source-files
36023 ^done,files=[@{file="test.c",
36024 fullname="/tmp/info-sources/test.c",
36025 debug-fully-read="true"@},
36026 @{file="/usr/include/stdc-predef.h",
36027 fullname="/usr/include/stdc-predef.h",
36028 debug-fully-read="true"@},
36030 fullname="/tmp/info-sources/header.h",
36031 debug-fully-read="true"@},
36033 fullname="/tmp/info-sources/helper.c",
36034 debug-fully-read="true"@}]
36036 -file-list-exec-source-files -- \\.c
36037 ^done,files=[@{file="test.c",
36038 fullname="/tmp/info-sources/test.c",
36039 debug-fully-read="true"@},
36041 fullname="/tmp/info-sources/helper.c",
36042 debug-fully-read="true"@}]
36044 -file-list-exec-source-files --group-by-objfile
36045 ^done,files=[@{filename="/tmp/info-sources/test.x",
36046 debug-info="fully-read",
36047 sources=[@{file="test.c",
36048 fullname="/tmp/info-sources/test.c",
36049 debug-fully-read="true"@},
36050 @{file="/usr/include/stdc-predef.h",
36051 fullname="/usr/include/stdc-predef.h",
36052 debug-fully-read="true"@},
36054 fullname="/tmp/info-sources/header.h",
36055 debug-fully-read="true"@}]@},
36056 @{filename="/lib64/ld-linux-x86-64.so.2",
36059 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36062 @{filename="/tmp/info-sources/libhelper.so",
36063 debug-info="fully-read",
36064 sources=[@{file="helper.c",
36065 fullname="/tmp/info-sources/helper.c",
36066 debug-fully-read="true"@},
36067 @{file="/usr/include/stdc-predef.h",
36068 fullname="/usr/include/stdc-predef.h",
36069 debug-fully-read="true"@},
36071 fullname="/tmp/info-sources/header.h",
36072 debug-fully-read="true"@}]@},
36073 @{filename="/lib64/libc.so.6",
36078 @subheading The @code{-file-list-shared-libraries} Command
36079 @findex -file-list-shared-libraries
36081 @subsubheading Synopsis
36084 -file-list-shared-libraries [ @var{regexp} ]
36087 List the shared libraries in the program.
36088 With a regular expression @var{regexp}, only those libraries whose
36089 names match @var{regexp} are listed.
36091 @subsubheading @value{GDBN} Command
36093 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36094 have a similar meaning to the @code{=library-loaded} notification.
36095 The @code{ranges} field specifies the multiple segments belonging to this
36096 library. Each range has the following fields:
36100 The address defining the inclusive lower bound of the segment.
36102 The address defining the exclusive upper bound of the segment.
36105 @subsubheading Example
36108 -file-list-exec-source-files
36109 ^done,shared-libraries=[
36110 @{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"@}]@},
36111 @{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"@}]@}]
36117 @subheading The @code{-file-list-symbol-files} Command
36118 @findex -file-list-symbol-files
36120 @subsubheading Synopsis
36123 -file-list-symbol-files
36128 @subsubheading @value{GDBN} Command
36130 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36132 @subsubheading Example
36137 @subheading The @code{-file-symbol-file} Command
36138 @findex -file-symbol-file
36140 @subsubheading Synopsis
36143 -file-symbol-file @var{file}
36146 Read symbol table info from the specified @var{file} argument. When
36147 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36148 produced, except for a completion notification.
36150 @subsubheading @value{GDBN} Command
36152 The corresponding @value{GDBN} command is @samp{symbol-file}.
36154 @subsubheading Example
36158 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36164 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36165 @node GDB/MI Memory Overlay Commands
36166 @section @sc{gdb/mi} Memory Overlay Commands
36168 The memory overlay commands are not implemented.
36170 @c @subheading -overlay-auto
36172 @c @subheading -overlay-list-mapping-state
36174 @c @subheading -overlay-list-overlays
36176 @c @subheading -overlay-map
36178 @c @subheading -overlay-off
36180 @c @subheading -overlay-on
36182 @c @subheading -overlay-unmap
36184 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36185 @node GDB/MI Signal Handling Commands
36186 @section @sc{gdb/mi} Signal Handling Commands
36188 Signal handling commands are not implemented.
36190 @c @subheading -signal-handle
36192 @c @subheading -signal-list-handle-actions
36194 @c @subheading -signal-list-signal-types
36198 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36199 @node GDB/MI Target Manipulation
36200 @section @sc{gdb/mi} Target Manipulation Commands
36203 @subheading The @code{-target-attach} Command
36204 @findex -target-attach
36206 @subsubheading Synopsis
36209 -target-attach @var{pid} | @var{gid} | @var{file}
36212 Attach to a process @var{pid} or a file @var{file} outside of
36213 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36214 group, the id previously returned by
36215 @samp{-list-thread-groups --available} must be used.
36217 @subsubheading @value{GDBN} Command
36219 The corresponding @value{GDBN} command is @samp{attach}.
36221 @subsubheading Example
36225 =thread-created,id="1"
36226 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36232 @subheading The @code{-target-compare-sections} Command
36233 @findex -target-compare-sections
36235 @subsubheading Synopsis
36238 -target-compare-sections [ @var{section} ]
36241 Compare data of section @var{section} on target to the exec file.
36242 Without the argument, all sections are compared.
36244 @subsubheading @value{GDBN} Command
36246 The @value{GDBN} equivalent is @samp{compare-sections}.
36248 @subsubheading Example
36253 @subheading The @code{-target-detach} Command
36254 @findex -target-detach
36256 @subsubheading Synopsis
36259 -target-detach [ @var{pid} | @var{gid} ]
36262 Detach from the remote target which normally resumes its execution.
36263 If either @var{pid} or @var{gid} is specified, detaches from either
36264 the specified process, or specified thread group. There's no output.
36266 @subsubheading @value{GDBN} Command
36268 The corresponding @value{GDBN} command is @samp{detach}.
36270 @subsubheading Example
36280 @subheading The @code{-target-disconnect} Command
36281 @findex -target-disconnect
36283 @subsubheading Synopsis
36289 Disconnect from the remote target. There's no output and the target is
36290 generally not resumed.
36292 @subsubheading @value{GDBN} Command
36294 The corresponding @value{GDBN} command is @samp{disconnect}.
36296 @subsubheading Example
36306 @subheading The @code{-target-download} Command
36307 @findex -target-download
36309 @subsubheading Synopsis
36315 Loads the executable onto the remote target.
36316 It prints out an update message every half second, which includes the fields:
36320 The name of the section.
36322 The size of what has been sent so far for that section.
36324 The size of the section.
36326 The total size of what was sent so far (the current and the previous sections).
36328 The size of the overall executable to download.
36332 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36333 @sc{gdb/mi} Output Syntax}).
36335 In addition, it prints the name and size of the sections, as they are
36336 downloaded. These messages include the following fields:
36340 The name of the section.
36342 The size of the section.
36344 The size of the overall executable to download.
36348 At the end, a summary is printed.
36350 @subsubheading @value{GDBN} Command
36352 The corresponding @value{GDBN} command is @samp{load}.
36354 @subsubheading Example
36356 Note: each status message appears on a single line. Here the messages
36357 have been broken down so that they can fit onto a page.
36362 +download,@{section=".text",section-size="6668",total-size="9880"@}
36363 +download,@{section=".text",section-sent="512",section-size="6668",
36364 total-sent="512",total-size="9880"@}
36365 +download,@{section=".text",section-sent="1024",section-size="6668",
36366 total-sent="1024",total-size="9880"@}
36367 +download,@{section=".text",section-sent="1536",section-size="6668",
36368 total-sent="1536",total-size="9880"@}
36369 +download,@{section=".text",section-sent="2048",section-size="6668",
36370 total-sent="2048",total-size="9880"@}
36371 +download,@{section=".text",section-sent="2560",section-size="6668",
36372 total-sent="2560",total-size="9880"@}
36373 +download,@{section=".text",section-sent="3072",section-size="6668",
36374 total-sent="3072",total-size="9880"@}
36375 +download,@{section=".text",section-sent="3584",section-size="6668",
36376 total-sent="3584",total-size="9880"@}
36377 +download,@{section=".text",section-sent="4096",section-size="6668",
36378 total-sent="4096",total-size="9880"@}
36379 +download,@{section=".text",section-sent="4608",section-size="6668",
36380 total-sent="4608",total-size="9880"@}
36381 +download,@{section=".text",section-sent="5120",section-size="6668",
36382 total-sent="5120",total-size="9880"@}
36383 +download,@{section=".text",section-sent="5632",section-size="6668",
36384 total-sent="5632",total-size="9880"@}
36385 +download,@{section=".text",section-sent="6144",section-size="6668",
36386 total-sent="6144",total-size="9880"@}
36387 +download,@{section=".text",section-sent="6656",section-size="6668",
36388 total-sent="6656",total-size="9880"@}
36389 +download,@{section=".init",section-size="28",total-size="9880"@}
36390 +download,@{section=".fini",section-size="28",total-size="9880"@}
36391 +download,@{section=".data",section-size="3156",total-size="9880"@}
36392 +download,@{section=".data",section-sent="512",section-size="3156",
36393 total-sent="7236",total-size="9880"@}
36394 +download,@{section=".data",section-sent="1024",section-size="3156",
36395 total-sent="7748",total-size="9880"@}
36396 +download,@{section=".data",section-sent="1536",section-size="3156",
36397 total-sent="8260",total-size="9880"@}
36398 +download,@{section=".data",section-sent="2048",section-size="3156",
36399 total-sent="8772",total-size="9880"@}
36400 +download,@{section=".data",section-sent="2560",section-size="3156",
36401 total-sent="9284",total-size="9880"@}
36402 +download,@{section=".data",section-sent="3072",section-size="3156",
36403 total-sent="9796",total-size="9880"@}
36404 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36411 @subheading The @code{-target-exec-status} Command
36412 @findex -target-exec-status
36414 @subsubheading Synopsis
36417 -target-exec-status
36420 Provide information on the state of the target (whether it is running or
36421 not, for instance).
36423 @subsubheading @value{GDBN} Command
36425 There's no equivalent @value{GDBN} command.
36427 @subsubheading Example
36431 @subheading The @code{-target-list-available-targets} Command
36432 @findex -target-list-available-targets
36434 @subsubheading Synopsis
36437 -target-list-available-targets
36440 List the possible targets to connect to.
36442 @subsubheading @value{GDBN} Command
36444 The corresponding @value{GDBN} command is @samp{help target}.
36446 @subsubheading Example
36450 @subheading The @code{-target-list-current-targets} Command
36451 @findex -target-list-current-targets
36453 @subsubheading Synopsis
36456 -target-list-current-targets
36459 Describe the current target.
36461 @subsubheading @value{GDBN} Command
36463 The corresponding information is printed by @samp{info file} (among
36466 @subsubheading Example
36470 @subheading The @code{-target-list-parameters} Command
36471 @findex -target-list-parameters
36473 @subsubheading Synopsis
36476 -target-list-parameters
36482 @subsubheading @value{GDBN} Command
36486 @subsubheading Example
36489 @subheading The @code{-target-flash-erase} Command
36490 @findex -target-flash-erase
36492 @subsubheading Synopsis
36495 -target-flash-erase
36498 Erases all known flash memory regions on the target.
36500 The corresponding @value{GDBN} command is @samp{flash-erase}.
36502 The output is a list of flash regions that have been erased, with starting
36503 addresses and memory region sizes.
36507 -target-flash-erase
36508 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36512 @subheading The @code{-target-select} Command
36513 @findex -target-select
36515 @subsubheading Synopsis
36518 -target-select @var{type} @var{parameters @dots{}}
36521 Connect @value{GDBN} to the remote target. This command takes two args:
36525 The type of target, for instance @samp{remote}, etc.
36526 @item @var{parameters}
36527 Device names, host names and the like. @xref{Target Commands, ,
36528 Commands for Managing Targets}, for more details.
36531 The output is a connection notification, followed by the address at
36532 which the target program is, in the following form:
36535 ^connected,addr="@var{address}",func="@var{function name}",
36536 args=[@var{arg list}]
36539 @subsubheading @value{GDBN} Command
36541 The corresponding @value{GDBN} command is @samp{target}.
36543 @subsubheading Example
36547 -target-select remote /dev/ttya
36548 ^connected,addr="0xfe00a300",func="??",args=[]
36552 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36553 @node GDB/MI File Transfer Commands
36554 @section @sc{gdb/mi} File Transfer Commands
36557 @subheading The @code{-target-file-put} Command
36558 @findex -target-file-put
36560 @subsubheading Synopsis
36563 -target-file-put @var{hostfile} @var{targetfile}
36566 Copy file @var{hostfile} from the host system (the machine running
36567 @value{GDBN}) to @var{targetfile} on the target system.
36569 @subsubheading @value{GDBN} Command
36571 The corresponding @value{GDBN} command is @samp{remote put}.
36573 @subsubheading Example
36577 -target-file-put localfile remotefile
36583 @subheading The @code{-target-file-get} Command
36584 @findex -target-file-get
36586 @subsubheading Synopsis
36589 -target-file-get @var{targetfile} @var{hostfile}
36592 Copy file @var{targetfile} from the target system to @var{hostfile}
36593 on the host system.
36595 @subsubheading @value{GDBN} Command
36597 The corresponding @value{GDBN} command is @samp{remote get}.
36599 @subsubheading Example
36603 -target-file-get remotefile localfile
36609 @subheading The @code{-target-file-delete} Command
36610 @findex -target-file-delete
36612 @subsubheading Synopsis
36615 -target-file-delete @var{targetfile}
36618 Delete @var{targetfile} from the target system.
36620 @subsubheading @value{GDBN} Command
36622 The corresponding @value{GDBN} command is @samp{remote delete}.
36624 @subsubheading Example
36628 -target-file-delete remotefile
36634 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36635 @node GDB/MI Ada Exceptions Commands
36636 @section Ada Exceptions @sc{gdb/mi} Commands
36638 @subheading The @code{-info-ada-exceptions} Command
36639 @findex -info-ada-exceptions
36641 @subsubheading Synopsis
36644 -info-ada-exceptions [ @var{regexp}]
36647 List all Ada exceptions defined within the program being debugged.
36648 With a regular expression @var{regexp}, only those exceptions whose
36649 names match @var{regexp} are listed.
36651 @subsubheading @value{GDBN} Command
36653 The corresponding @value{GDBN} command is @samp{info exceptions}.
36655 @subsubheading Result
36657 The result is a table of Ada exceptions. The following columns are
36658 defined for each exception:
36662 The name of the exception.
36665 The address of the exception.
36669 @subsubheading Example
36672 -info-ada-exceptions aint
36673 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
36674 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
36675 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
36676 body=[@{name="constraint_error",address="0x0000000000613da0"@},
36677 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
36680 @subheading Catching Ada Exceptions
36682 The commands describing how to ask @value{GDBN} to stop when a program
36683 raises an exception are described at @ref{Ada Exception GDB/MI
36684 Catchpoint Commands}.
36687 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36688 @node GDB/MI Support Commands
36689 @section @sc{gdb/mi} Support Commands
36691 Since new commands and features get regularly added to @sc{gdb/mi},
36692 some commands are available to help front-ends query the debugger
36693 about support for these capabilities. Similarly, it is also possible
36694 to query @value{GDBN} about target support of certain features.
36696 @subheading The @code{-info-gdb-mi-command} Command
36697 @cindex @code{-info-gdb-mi-command}
36698 @findex -info-gdb-mi-command
36700 @subsubheading Synopsis
36703 -info-gdb-mi-command @var{cmd_name}
36706 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
36708 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
36709 is technically not part of the command name (@pxref{GDB/MI Input
36710 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36711 for ease of use, this command also accepts the form with the leading
36714 @subsubheading @value{GDBN} Command
36716 There is no corresponding @value{GDBN} command.
36718 @subsubheading Result
36720 The result is a tuple. There is currently only one field:
36724 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36725 @code{"false"} otherwise.
36729 @subsubheading Example
36731 Here is an example where the @sc{gdb/mi} command does not exist:
36734 -info-gdb-mi-command unsupported-command
36735 ^done,command=@{exists="false"@}
36739 And here is an example where the @sc{gdb/mi} command is known
36743 -info-gdb-mi-command symbol-list-lines
36744 ^done,command=@{exists="true"@}
36747 @subheading The @code{-list-features} Command
36748 @findex -list-features
36749 @cindex supported @sc{gdb/mi} features, list
36751 Returns a list of particular features of the MI protocol that
36752 this version of gdb implements. A feature can be a command,
36753 or a new field in an output of some command, or even an
36754 important bugfix. While a frontend can sometimes detect presence
36755 of a feature at runtime, it is easier to perform detection at debugger
36758 The command returns a list of strings, with each string naming an
36759 available feature. Each returned string is just a name, it does not
36760 have any internal structure. The list of possible feature names
36766 (gdb) -list-features
36767 ^done,result=["feature1","feature2"]
36770 The current list of features is:
36773 @item frozen-varobjs
36774 Indicates support for the @code{-var-set-frozen} command, as well
36775 as possible presence of the @code{frozen} field in the output
36776 of @code{-varobj-create}.
36777 @item pending-breakpoints
36778 Indicates support for the @option{-f} option to the @code{-break-insert}
36781 Indicates Python scripting support, Python-based
36782 pretty-printing commands, and possible presence of the
36783 @samp{display_hint} field in the output of @code{-var-list-children}
36785 Indicates support for the @code{-thread-info} command.
36786 @item data-read-memory-bytes
36787 Indicates support for the @code{-data-read-memory-bytes} and the
36788 @code{-data-write-memory-bytes} commands.
36789 @item breakpoint-notifications
36790 Indicates that changes to breakpoints and breakpoints created via the
36791 CLI will be announced via async records.
36792 @item ada-task-info
36793 Indicates support for the @code{-ada-task-info} command.
36794 @item language-option
36795 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36796 option (@pxref{Context management}).
36797 @item info-gdb-mi-command
36798 Indicates support for the @code{-info-gdb-mi-command} command.
36799 @item undefined-command-error-code
36800 Indicates support for the "undefined-command" error code in error result
36801 records, produced when trying to execute an undefined @sc{gdb/mi} command
36802 (@pxref{GDB/MI Result Records}).
36803 @item exec-run-start-option
36804 Indicates that the @code{-exec-run} command supports the @option{--start}
36805 option (@pxref{GDB/MI Program Execution}).
36806 @item data-disassemble-a-option
36807 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36808 option (@pxref{GDB/MI Data Manipulation}).
36811 @subheading The @code{-list-target-features} Command
36812 @findex -list-target-features
36814 Returns a list of particular features that are supported by the
36815 target. Those features affect the permitted MI commands, but
36816 unlike the features reported by the @code{-list-features} command, the
36817 features depend on which target GDB is using at the moment. Whenever
36818 a target can change, due to commands such as @code{-target-select},
36819 @code{-target-attach} or @code{-exec-run}, the list of target features
36820 may change, and the frontend should obtain it again.
36824 (gdb) -list-target-features
36825 ^done,result=["async"]
36828 The current list of features is:
36832 Indicates that the target is capable of asynchronous command
36833 execution, which means that @value{GDBN} will accept further commands
36834 while the target is running.
36837 Indicates that the target is capable of reverse execution.
36838 @xref{Reverse Execution}, for more information.
36842 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36843 @node GDB/MI Miscellaneous Commands
36844 @section Miscellaneous @sc{gdb/mi} Commands
36846 @c @subheading -gdb-complete
36848 @subheading The @code{-gdb-exit} Command
36851 @subsubheading Synopsis
36857 Exit @value{GDBN} immediately.
36859 @subsubheading @value{GDBN} Command
36861 Approximately corresponds to @samp{quit}.
36863 @subsubheading Example
36873 @subheading The @code{-exec-abort} Command
36874 @findex -exec-abort
36876 @subsubheading Synopsis
36882 Kill the inferior running program.
36884 @subsubheading @value{GDBN} Command
36886 The corresponding @value{GDBN} command is @samp{kill}.
36888 @subsubheading Example
36893 @subheading The @code{-gdb-set} Command
36896 @subsubheading Synopsis
36902 Set an internal @value{GDBN} variable.
36903 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
36905 @subsubheading @value{GDBN} Command
36907 The corresponding @value{GDBN} command is @samp{set}.
36909 @subsubheading Example
36919 @subheading The @code{-gdb-show} Command
36922 @subsubheading Synopsis
36928 Show the current value of a @value{GDBN} variable.
36930 @subsubheading @value{GDBN} Command
36932 The corresponding @value{GDBN} command is @samp{show}.
36934 @subsubheading Example
36943 @c @subheading -gdb-source
36946 @subheading The @code{-gdb-version} Command
36947 @findex -gdb-version
36949 @subsubheading Synopsis
36955 Show version information for @value{GDBN}. Used mostly in testing.
36957 @subsubheading @value{GDBN} Command
36959 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36960 default shows this information when you start an interactive session.
36962 @subsubheading Example
36964 @c This example modifies the actual output from GDB to avoid overfull
36970 ~Copyright 2000 Free Software Foundation, Inc.
36971 ~GDB is free software, covered by the GNU General Public License, and
36972 ~you are welcome to change it and/or distribute copies of it under
36973 ~ certain conditions.
36974 ~Type "show copying" to see the conditions.
36975 ~There is absolutely no warranty for GDB. Type "show warranty" for
36977 ~This GDB was configured as
36978 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36983 @subheading The @code{-list-thread-groups} Command
36984 @findex -list-thread-groups
36986 @subheading Synopsis
36989 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36992 Lists thread groups (@pxref{Thread groups}). When a single thread
36993 group is passed as the argument, lists the children of that group.
36994 When several thread group are passed, lists information about those
36995 thread groups. Without any parameters, lists information about all
36996 top-level thread groups.
36998 Normally, thread groups that are being debugged are reported.
36999 With the @samp{--available} option, @value{GDBN} reports thread groups
37000 available on the target.
37002 The output of this command may have either a @samp{threads} result or
37003 a @samp{groups} result. The @samp{thread} result has a list of tuples
37004 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37005 Information}). The @samp{groups} result has a list of tuples as value,
37006 each tuple describing a thread group. If top-level groups are
37007 requested (that is, no parameter is passed), or when several groups
37008 are passed, the output always has a @samp{groups} result. The format
37009 of the @samp{group} result is described below.
37011 To reduce the number of roundtrips it's possible to list thread groups
37012 together with their children, by passing the @samp{--recurse} option
37013 and the recursion depth. Presently, only recursion depth of 1 is
37014 permitted. If this option is present, then every reported thread group
37015 will also include its children, either as @samp{group} or
37016 @samp{threads} field.
37018 In general, any combination of option and parameters is permitted, with
37019 the following caveats:
37023 When a single thread group is passed, the output will typically
37024 be the @samp{threads} result. Because threads may not contain
37025 anything, the @samp{recurse} option will be ignored.
37028 When the @samp{--available} option is passed, limited information may
37029 be available. In particular, the list of threads of a process might
37030 be inaccessible. Further, specifying specific thread groups might
37031 not give any performance advantage over listing all thread groups.
37032 The frontend should assume that @samp{-list-thread-groups --available}
37033 is always an expensive operation and cache the results.
37037 The @samp{groups} result is a list of tuples, where each tuple may
37038 have the following fields:
37042 Identifier of the thread group. This field is always present.
37043 The identifier is an opaque string; frontends should not try to
37044 convert it to an integer, even though it might look like one.
37047 The type of the thread group. At present, only @samp{process} is a
37051 The target-specific process identifier. This field is only present
37052 for thread groups of type @samp{process} and only if the process exists.
37055 The exit code of this group's last exited thread, formatted in octal.
37056 This field is only present for thread groups of type @samp{process} and
37057 only if the process is not running.
37060 The number of children this thread group has. This field may be
37061 absent for an available thread group.
37064 This field has a list of tuples as value, each tuple describing a
37065 thread. It may be present if the @samp{--recurse} option is
37066 specified, and it's actually possible to obtain the threads.
37069 This field is a list of integers, each identifying a core that one
37070 thread of the group is running on. This field may be absent if
37071 such information is not available.
37074 The name of the executable file that corresponds to this thread group.
37075 The field is only present for thread groups of type @samp{process},
37076 and only if there is a corresponding executable file.
37080 @subheading Example
37084 -list-thread-groups
37085 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37086 -list-thread-groups 17
37087 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37088 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37089 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37090 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37091 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37092 -list-thread-groups --available
37093 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37094 -list-thread-groups --available --recurse 1
37095 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37096 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37097 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37098 -list-thread-groups --available --recurse 1 17 18
37099 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37100 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37101 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37104 @subheading The @code{-info-os} Command
37107 @subsubheading Synopsis
37110 -info-os [ @var{type} ]
37113 If no argument is supplied, the command returns a table of available
37114 operating-system-specific information types. If one of these types is
37115 supplied as an argument @var{type}, then the command returns a table
37116 of data of that type.
37118 The types of information available depend on the target operating
37121 @subsubheading @value{GDBN} Command
37123 The corresponding @value{GDBN} command is @samp{info os}.
37125 @subsubheading Example
37127 When run on a @sc{gnu}/Linux system, the output will look something
37133 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37134 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37135 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37136 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37137 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37139 item=@{col0="files",col1="Listing of all file descriptors",
37140 col2="File descriptors"@},
37141 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37142 col2="Kernel modules"@},
37143 item=@{col0="msg",col1="Listing of all message queues",
37144 col2="Message queues"@},
37145 item=@{col0="processes",col1="Listing of all processes",
37146 col2="Processes"@},
37147 item=@{col0="procgroups",col1="Listing of all process groups",
37148 col2="Process groups"@},
37149 item=@{col0="semaphores",col1="Listing of all semaphores",
37150 col2="Semaphores"@},
37151 item=@{col0="shm",col1="Listing of all shared-memory regions",
37152 col2="Shared-memory regions"@},
37153 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37155 item=@{col0="threads",col1="Listing of all threads",
37159 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37160 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37161 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37162 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37163 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37164 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37165 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37166 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37168 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37169 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37173 (Note that the MI output here includes a @code{"Title"} column that
37174 does not appear in command-line @code{info os}; this column is useful
37175 for MI clients that want to enumerate the types of data, such as in a
37176 popup menu, but is needless clutter on the command line, and
37177 @code{info os} omits it.)
37179 @subheading The @code{-add-inferior} Command
37180 @findex -add-inferior
37182 @subheading Synopsis
37185 -add-inferior [ --no-connection ]
37188 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37189 inferior is not associated with any executable. Such association may
37190 be established with the @samp{-file-exec-and-symbols} command
37191 (@pxref{GDB/MI File Commands}).
37193 By default, the new inferior begins connected to the same target
37194 connection as the current inferior. For example, if the current
37195 inferior was connected to @code{gdbserver} with @code{target remote},
37196 then the new inferior will be connected to the same @code{gdbserver}
37197 instance. The @samp{--no-connection} option starts the new inferior
37198 with no connection yet. You can then for example use the
37199 @code{-target-select remote} command to connect to some other
37200 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37203 The command response always has a field, @var{inferior}, whose value
37204 is the identifier of the thread group corresponding to the new
37207 An additional section field, @var{connection}, is optional. This
37208 field will only exist if the new inferior has a target connection. If
37209 this field exists, then its value will be a tuple containing the
37214 The number of the connection used for the new inferior.
37217 The name of the connection type used for the new inferior.
37220 @subheading @value{GDBN} Command
37222 The corresponding @value{GDBN} command is @samp{add-inferior}
37223 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37225 @subheading Example
37230 ^done,inferior="i3"
37233 @subheading The @code{-interpreter-exec} Command
37234 @findex -interpreter-exec
37236 @subheading Synopsis
37239 -interpreter-exec @var{interpreter} @var{command}
37241 @anchor{-interpreter-exec}
37243 Execute the specified @var{command} in the given @var{interpreter}.
37245 @subheading @value{GDBN} Command
37247 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37249 @subheading Example
37253 -interpreter-exec console "break main"
37254 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37255 &"During symbol reading, bad structure-type format.\n"
37256 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37261 @subheading The @code{-inferior-tty-set} Command
37262 @findex -inferior-tty-set
37264 @subheading Synopsis
37267 -inferior-tty-set /dev/pts/1
37270 Set terminal for future runs of the program being debugged.
37272 @subheading @value{GDBN} Command
37274 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37276 @subheading Example
37280 -inferior-tty-set /dev/pts/1
37285 @subheading The @code{-inferior-tty-show} Command
37286 @findex -inferior-tty-show
37288 @subheading Synopsis
37294 Show terminal for future runs of program being debugged.
37296 @subheading @value{GDBN} Command
37298 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37300 @subheading Example
37304 -inferior-tty-set /dev/pts/1
37308 ^done,inferior_tty_terminal="/dev/pts/1"
37312 @subheading The @code{-enable-timings} Command
37313 @findex -enable-timings
37315 @subheading Synopsis
37318 -enable-timings [yes | no]
37321 Toggle the printing of the wallclock, user and system times for an MI
37322 command as a field in its output. This command is to help frontend
37323 developers optimize the performance of their code. No argument is
37324 equivalent to @samp{yes}.
37326 @subheading @value{GDBN} Command
37330 @subheading Example
37338 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37339 addr="0x080484ed",func="main",file="myprog.c",
37340 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37342 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37350 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37351 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37352 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37353 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37357 @subheading The @code{-complete} Command
37360 @subheading Synopsis
37363 -complete @var{command}
37366 Show a list of completions for partially typed CLI @var{command}.
37368 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37369 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37370 because @value{GDBN} is used remotely via a SSH connection.
37374 The result consists of two or three fields:
37378 This field contains the completed @var{command}. If @var{command}
37379 has no known completions, this field is omitted.
37382 This field contains a (possibly empty) array of matches. It is always present.
37384 @item max_completions_reached
37385 This field contains @code{1} if number of known completions is above
37386 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37387 @code{0}. It is always present.
37391 @subheading @value{GDBN} Command
37393 The corresponding @value{GDBN} command is @samp{complete}.
37395 @subheading Example
37400 ^done,completion="break",
37401 matches=["break","break-range"],
37402 max_completions_reached="0"
37405 ^done,completion="b ma",
37406 matches=["b madvise","b main"],max_completions_reached="0"
37408 -complete "b push_b"
37409 ^done,completion="b push_back(",
37411 "b A::push_back(void*)",
37412 "b std::string::push_back(char)",
37413 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37414 max_completions_reached="0"
37416 -complete "nonexist"
37417 ^done,matches=[],max_completions_reached="0"
37423 @chapter @value{GDBN} Annotations
37425 This chapter describes annotations in @value{GDBN}. Annotations were
37426 designed to interface @value{GDBN} to graphical user interfaces or other
37427 similar programs which want to interact with @value{GDBN} at a
37428 relatively high level.
37430 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37434 This is Edition @value{EDITION}, @value{DATE}.
37438 * Annotations Overview:: What annotations are; the general syntax.
37439 * Server Prefix:: Issuing a command without affecting user state.
37440 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37441 * Errors:: Annotations for error messages.
37442 * Invalidation:: Some annotations describe things now invalid.
37443 * Annotations for Running::
37444 Whether the program is running, how it stopped, etc.
37445 * Source Annotations:: Annotations describing source code.
37448 @node Annotations Overview
37449 @section What is an Annotation?
37450 @cindex annotations
37452 Annotations start with a newline character, two @samp{control-z}
37453 characters, and the name of the annotation. If there is no additional
37454 information associated with this annotation, the name of the annotation
37455 is followed immediately by a newline. If there is additional
37456 information, the name of the annotation is followed by a space, the
37457 additional information, and a newline. The additional information
37458 cannot contain newline characters.
37460 Any output not beginning with a newline and two @samp{control-z}
37461 characters denotes literal output from @value{GDBN}. Currently there is
37462 no need for @value{GDBN} to output a newline followed by two
37463 @samp{control-z} characters, but if there was such a need, the
37464 annotations could be extended with an @samp{escape} annotation which
37465 means those three characters as output.
37467 The annotation @var{level}, which is specified using the
37468 @option{--annotate} command line option (@pxref{Mode Options}), controls
37469 how much information @value{GDBN} prints together with its prompt,
37470 values of expressions, source lines, and other types of output. Level 0
37471 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37472 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37473 for programs that control @value{GDBN}, and level 2 annotations have
37474 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37475 Interface, annotate, GDB's Obsolete Annotations}).
37478 @kindex set annotate
37479 @item set annotate @var{level}
37480 The @value{GDBN} command @code{set annotate} sets the level of
37481 annotations to the specified @var{level}.
37483 @item show annotate
37484 @kindex show annotate
37485 Show the current annotation level.
37488 This chapter describes level 3 annotations.
37490 A simple example of starting up @value{GDBN} with annotations is:
37493 $ @kbd{gdb --annotate=3}
37495 Copyright 2003 Free Software Foundation, Inc.
37496 GDB is free software, covered by the GNU General Public License,
37497 and you are welcome to change it and/or distribute copies of it
37498 under certain conditions.
37499 Type "show copying" to see the conditions.
37500 There is absolutely no warranty for GDB. Type "show warranty"
37502 This GDB was configured as "i386-pc-linux-gnu"
37513 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37514 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37515 denotes a @samp{control-z} character) are annotations; the rest is
37516 output from @value{GDBN}.
37518 @node Server Prefix
37519 @section The Server Prefix
37520 @cindex server prefix
37522 If you prefix a command with @samp{server } then it will not affect
37523 the command history, nor will it affect @value{GDBN}'s notion of which
37524 command to repeat if @key{RET} is pressed on a line by itself. This
37525 means that commands can be run behind a user's back by a front-end in
37526 a transparent manner.
37528 The @code{server } prefix does not affect the recording of values into
37529 the value history; to print a value without recording it into the
37530 value history, use the @code{output} command instead of the
37531 @code{print} command.
37533 Using this prefix also disables confirmation requests
37534 (@pxref{confirmation requests}).
37537 @section Annotation for @value{GDBN} Input
37539 @cindex annotations for prompts
37540 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37541 to know when to send output, when the output from a given command is
37544 Different kinds of input each have a different @dfn{input type}. Each
37545 input type has three annotations: a @code{pre-} annotation, which
37546 denotes the beginning of any prompt which is being output, a plain
37547 annotation, which denotes the end of the prompt, and then a @code{post-}
37548 annotation which denotes the end of any echo which may (or may not) be
37549 associated with the input. For example, the @code{prompt} input type
37550 features the following annotations:
37558 The input types are
37561 @findex pre-prompt annotation
37562 @findex prompt annotation
37563 @findex post-prompt annotation
37565 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37567 @findex pre-commands annotation
37568 @findex commands annotation
37569 @findex post-commands annotation
37571 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37572 command. The annotations are repeated for each command which is input.
37574 @findex pre-overload-choice annotation
37575 @findex overload-choice annotation
37576 @findex post-overload-choice annotation
37577 @item overload-choice
37578 When @value{GDBN} wants the user to select between various overloaded functions.
37580 @findex pre-query annotation
37581 @findex query annotation
37582 @findex post-query annotation
37584 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37586 @findex pre-prompt-for-continue annotation
37587 @findex prompt-for-continue annotation
37588 @findex post-prompt-for-continue annotation
37589 @item prompt-for-continue
37590 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37591 expect this to work well; instead use @code{set height 0} to disable
37592 prompting. This is because the counting of lines is buggy in the
37593 presence of annotations.
37598 @cindex annotations for errors, warnings and interrupts
37600 @findex quit annotation
37605 This annotation occurs right before @value{GDBN} responds to an interrupt.
37607 @findex error annotation
37612 This annotation occurs right before @value{GDBN} responds to an error.
37614 Quit and error annotations indicate that any annotations which @value{GDBN} was
37615 in the middle of may end abruptly. For example, if a
37616 @code{value-history-begin} annotation is followed by a @code{error}, one
37617 cannot expect to receive the matching @code{value-history-end}. One
37618 cannot expect not to receive it either, however; an error annotation
37619 does not necessarily mean that @value{GDBN} is immediately returning all the way
37622 @findex error-begin annotation
37623 A quit or error annotation may be preceded by
37629 Any output between that and the quit or error annotation is the error
37632 Warning messages are not yet annotated.
37633 @c If we want to change that, need to fix warning(), type_error(),
37634 @c range_error(), and possibly other places.
37637 @section Invalidation Notices
37639 @cindex annotations for invalidation messages
37640 The following annotations say that certain pieces of state may have
37644 @findex frames-invalid annotation
37645 @item ^Z^Zframes-invalid
37647 The frames (for example, output from the @code{backtrace} command) may
37650 @findex breakpoints-invalid annotation
37651 @item ^Z^Zbreakpoints-invalid
37653 The breakpoints may have changed. For example, the user just added or
37654 deleted a breakpoint.
37657 @node Annotations for Running
37658 @section Running the Program
37659 @cindex annotations for running programs
37661 @findex starting annotation
37662 @findex stopping annotation
37663 When the program starts executing due to a @value{GDBN} command such as
37664 @code{step} or @code{continue},
37670 is output. When the program stops,
37676 is output. Before the @code{stopped} annotation, a variety of
37677 annotations describe how the program stopped.
37680 @findex exited annotation
37681 @item ^Z^Zexited @var{exit-status}
37682 The program exited, and @var{exit-status} is the exit status (zero for
37683 successful exit, otherwise nonzero).
37685 @findex signalled annotation
37686 @findex signal-name annotation
37687 @findex signal-name-end annotation
37688 @findex signal-string annotation
37689 @findex signal-string-end annotation
37690 @item ^Z^Zsignalled
37691 The program exited with a signal. After the @code{^Z^Zsignalled}, the
37692 annotation continues:
37698 ^Z^Zsignal-name-end
37702 ^Z^Zsignal-string-end
37707 where @var{name} is the name of the signal, such as @code{SIGILL} or
37708 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
37709 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
37710 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
37711 user's benefit and have no particular format.
37713 @findex signal annotation
37715 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
37716 just saying that the program received the signal, not that it was
37717 terminated with it.
37719 @findex breakpoint annotation
37720 @item ^Z^Zbreakpoint @var{number}
37721 The program hit breakpoint number @var{number}.
37723 @findex watchpoint annotation
37724 @item ^Z^Zwatchpoint @var{number}
37725 The program hit watchpoint number @var{number}.
37728 @node Source Annotations
37729 @section Displaying Source
37730 @cindex annotations for source display
37732 @findex source annotation
37733 The following annotation is used instead of displaying source code:
37736 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
37739 where @var{filename} is an absolute file name indicating which source
37740 file, @var{line} is the line number within that file (where 1 is the
37741 first line in the file), @var{character} is the character position
37742 within the file (where 0 is the first character in the file) (for most
37743 debug formats this will necessarily point to the beginning of a line),
37744 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37745 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37746 @var{addr} is the address in the target program associated with the
37747 source which is being displayed. The @var{addr} is in the form @samp{0x}
37748 followed by one or more lowercase hex digits (note that this does not
37749 depend on the language).
37751 @node JIT Interface
37752 @chapter JIT Compilation Interface
37753 @cindex just-in-time compilation
37754 @cindex JIT compilation interface
37756 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37757 interface. A JIT compiler is a program or library that generates native
37758 executable code at runtime and executes it, usually in order to achieve good
37759 performance while maintaining platform independence.
37761 Programs that use JIT compilation are normally difficult to debug because
37762 portions of their code are generated at runtime, instead of being loaded from
37763 object files, which is where @value{GDBN} normally finds the program's symbols
37764 and debug information. In order to debug programs that use JIT compilation,
37765 @value{GDBN} has an interface that allows the program to register in-memory
37766 symbol files with @value{GDBN} at runtime.
37768 If you are using @value{GDBN} to debug a program that uses this interface, then
37769 it should work transparently so long as you have not stripped the binary. If
37770 you are developing a JIT compiler, then the interface is documented in the rest
37771 of this chapter. At this time, the only known client of this interface is the
37774 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37775 JIT compiler communicates with @value{GDBN} by writing data into a global
37776 variable and calling a function at a well-known symbol. When @value{GDBN}
37777 attaches, it reads a linked list of symbol files from the global variable to
37778 find existing code, and puts a breakpoint in the function so that it can find
37779 out about additional code.
37782 * Declarations:: Relevant C struct declarations
37783 * Registering Code:: Steps to register code
37784 * Unregistering Code:: Steps to unregister code
37785 * Custom Debug Info:: Emit debug information in a custom format
37789 @section JIT Declarations
37791 These are the relevant struct declarations that a C program should include to
37792 implement the interface:
37802 struct jit_code_entry
37804 struct jit_code_entry *next_entry;
37805 struct jit_code_entry *prev_entry;
37806 const char *symfile_addr;
37807 uint64_t symfile_size;
37810 struct jit_descriptor
37813 /* This type should be jit_actions_t, but we use uint32_t
37814 to be explicit about the bitwidth. */
37815 uint32_t action_flag;
37816 struct jit_code_entry *relevant_entry;
37817 struct jit_code_entry *first_entry;
37820 /* GDB puts a breakpoint in this function. */
37821 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37823 /* Make sure to specify the version statically, because the
37824 debugger may check the version before we can set it. */
37825 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37828 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37829 modifications to this global data properly, which can easily be done by putting
37830 a global mutex around modifications to these structures.
37832 @node Registering Code
37833 @section Registering Code
37835 To register code with @value{GDBN}, the JIT should follow this protocol:
37839 Generate an object file in memory with symbols and other desired debug
37840 information. The file must include the virtual addresses of the sections.
37843 Create a code entry for the file, which gives the start and size of the symbol
37847 Add it to the linked list in the JIT descriptor.
37850 Point the relevant_entry field of the descriptor at the entry.
37853 Set @code{action_flag} to @code{JIT_REGISTER} and call
37854 @code{__jit_debug_register_code}.
37857 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37858 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37859 new code. However, the linked list must still be maintained in order to allow
37860 @value{GDBN} to attach to a running process and still find the symbol files.
37862 @node Unregistering Code
37863 @section Unregistering Code
37865 If code is freed, then the JIT should use the following protocol:
37869 Remove the code entry corresponding to the code from the linked list.
37872 Point the @code{relevant_entry} field of the descriptor at the code entry.
37875 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
37876 @code{__jit_debug_register_code}.
37879 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
37880 and the JIT will leak the memory used for the associated symbol files.
37882 @node Custom Debug Info
37883 @section Custom Debug Info
37884 @cindex custom JIT debug info
37885 @cindex JIT debug info reader
37887 Generating debug information in platform-native file formats (like ELF
37888 or COFF) may be an overkill for JIT compilers; especially if all the
37889 debug info is used for is displaying a meaningful backtrace. The
37890 issue can be resolved by having the JIT writers decide on a debug info
37891 format and also provide a reader that parses the debug info generated
37892 by the JIT compiler. This section gives a brief overview on writing
37893 such a parser. More specific details can be found in the source file
37894 @file{gdb/jit-reader.in}, which is also installed as a header at
37895 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
37897 The reader is implemented as a shared object (so this functionality is
37898 not available on platforms which don't allow loading shared objects at
37899 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
37900 @code{jit-reader-unload} are provided, to be used to load and unload
37901 the readers from a preconfigured directory. Once loaded, the shared
37902 object is used the parse the debug information emitted by the JIT
37906 * Using JIT Debug Info Readers:: How to use supplied readers correctly
37907 * Writing JIT Debug Info Readers:: Creating a debug-info reader
37910 @node Using JIT Debug Info Readers
37911 @subsection Using JIT Debug Info Readers
37912 @kindex jit-reader-load
37913 @kindex jit-reader-unload
37915 Readers can be loaded and unloaded using the @code{jit-reader-load}
37916 and @code{jit-reader-unload} commands.
37919 @item jit-reader-load @var{reader}
37920 Load the JIT reader named @var{reader}, which is a shared
37921 object specified as either an absolute or a relative file name. In
37922 the latter case, @value{GDBN} will try to load the reader from a
37923 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
37924 system (here @var{libdir} is the system library directory, often
37925 @file{/usr/local/lib}).
37927 Only one reader can be active at a time; trying to load a second
37928 reader when one is already loaded will result in @value{GDBN}
37929 reporting an error. A new JIT reader can be loaded by first unloading
37930 the current one using @code{jit-reader-unload} and then invoking
37931 @code{jit-reader-load}.
37933 @item jit-reader-unload
37934 Unload the currently loaded JIT reader.
37938 @node Writing JIT Debug Info Readers
37939 @subsection Writing JIT Debug Info Readers
37940 @cindex writing JIT debug info readers
37942 As mentioned, a reader is essentially a shared object conforming to a
37943 certain ABI. This ABI is described in @file{jit-reader.h}.
37945 @file{jit-reader.h} defines the structures, macros and functions
37946 required to write a reader. It is installed (along with
37947 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
37948 the system include directory.
37950 Readers need to be released under a GPL compatible license. A reader
37951 can be declared as released under such a license by placing the macro
37952 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37954 The entry point for readers is the symbol @code{gdb_init_reader},
37955 which is expected to be a function with the prototype
37957 @findex gdb_init_reader
37959 extern struct gdb_reader_funcs *gdb_init_reader (void);
37962 @cindex @code{struct gdb_reader_funcs}
37964 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37965 functions. These functions are executed to read the debug info
37966 generated by the JIT compiler (@code{read}), to unwind stack frames
37967 (@code{unwind}) and to create canonical frame IDs
37968 (@code{get_frame_id}). It also has a callback that is called when the
37969 reader is being unloaded (@code{destroy}). The struct looks like this
37972 struct gdb_reader_funcs
37974 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37975 int reader_version;
37977 /* For use by the reader. */
37980 gdb_read_debug_info *read;
37981 gdb_unwind_frame *unwind;
37982 gdb_get_frame_id *get_frame_id;
37983 gdb_destroy_reader *destroy;
37987 @cindex @code{struct gdb_symbol_callbacks}
37988 @cindex @code{struct gdb_unwind_callbacks}
37990 The callbacks are provided with another set of callbacks by
37991 @value{GDBN} to do their job. For @code{read}, these callbacks are
37992 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37993 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37994 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37995 files and new symbol tables inside those object files. @code{struct
37996 gdb_unwind_callbacks} has callbacks to read registers off the current
37997 frame and to write out the values of the registers in the previous
37998 frame. Both have a callback (@code{target_read}) to read bytes off the
37999 target's address space.
38001 @node In-Process Agent
38002 @chapter In-Process Agent
38003 @cindex debugging agent
38004 The traditional debugging model is conceptually low-speed, but works fine,
38005 because most bugs can be reproduced in debugging-mode execution. However,
38006 as multi-core or many-core processors are becoming mainstream, and
38007 multi-threaded programs become more and more popular, there should be more
38008 and more bugs that only manifest themselves at normal-mode execution, for
38009 example, thread races, because debugger's interference with the program's
38010 timing may conceal the bugs. On the other hand, in some applications,
38011 it is not feasible for the debugger to interrupt the program's execution
38012 long enough for the developer to learn anything helpful about its behavior.
38013 If the program's correctness depends on its real-time behavior, delays
38014 introduced by a debugger might cause the program to fail, even when the
38015 code itself is correct. It is useful to be able to observe the program's
38016 behavior without interrupting it.
38018 Therefore, traditional debugging model is too intrusive to reproduce
38019 some bugs. In order to reduce the interference with the program, we can
38020 reduce the number of operations performed by debugger. The
38021 @dfn{In-Process Agent}, a shared library, is running within the same
38022 process with inferior, and is able to perform some debugging operations
38023 itself. As a result, debugger is only involved when necessary, and
38024 performance of debugging can be improved accordingly. Note that
38025 interference with program can be reduced but can't be removed completely,
38026 because the in-process agent will still stop or slow down the program.
38028 The in-process agent can interpret and execute Agent Expressions
38029 (@pxref{Agent Expressions}) during performing debugging operations. The
38030 agent expressions can be used for different purposes, such as collecting
38031 data in tracepoints, and condition evaluation in breakpoints.
38033 @anchor{Control Agent}
38034 You can control whether the in-process agent is used as an aid for
38035 debugging with the following commands:
38038 @kindex set agent on
38040 Causes the in-process agent to perform some operations on behalf of the
38041 debugger. Just which operations requested by the user will be done
38042 by the in-process agent depends on the its capabilities. For example,
38043 if you request to evaluate breakpoint conditions in the in-process agent,
38044 and the in-process agent has such capability as well, then breakpoint
38045 conditions will be evaluated in the in-process agent.
38047 @kindex set agent off
38048 @item set agent off
38049 Disables execution of debugging operations by the in-process agent. All
38050 of the operations will be performed by @value{GDBN}.
38054 Display the current setting of execution of debugging operations by
38055 the in-process agent.
38059 * In-Process Agent Protocol::
38062 @node In-Process Agent Protocol
38063 @section In-Process Agent Protocol
38064 @cindex in-process agent protocol
38066 The in-process agent is able to communicate with both @value{GDBN} and
38067 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38068 used for communications between @value{GDBN} or GDBserver and the IPA.
38069 In general, @value{GDBN} or GDBserver sends commands
38070 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38071 in-process agent replies back with the return result of the command, or
38072 some other information. The data sent to in-process agent is composed
38073 of primitive data types, such as 4-byte or 8-byte type, and composite
38074 types, which are called objects (@pxref{IPA Protocol Objects}).
38077 * IPA Protocol Objects::
38078 * IPA Protocol Commands::
38081 @node IPA Protocol Objects
38082 @subsection IPA Protocol Objects
38083 @cindex ipa protocol objects
38085 The commands sent to and results received from agent may contain some
38086 complex data types called @dfn{objects}.
38088 The in-process agent is running on the same machine with @value{GDBN}
38089 or GDBserver, so it doesn't have to handle as much differences between
38090 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38091 However, there are still some differences of two ends in two processes:
38095 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38096 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38098 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38099 GDBserver is compiled with one, and in-process agent is compiled with
38103 Here are the IPA Protocol Objects:
38107 agent expression object. It represents an agent expression
38108 (@pxref{Agent Expressions}).
38109 @anchor{agent expression object}
38111 tracepoint action object. It represents a tracepoint action
38112 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38113 memory, static trace data and to evaluate expression.
38114 @anchor{tracepoint action object}
38116 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38117 @anchor{tracepoint object}
38121 The following table describes important attributes of each IPA protocol
38124 @multitable @columnfractions .30 .20 .50
38125 @headitem Name @tab Size @tab Description
38126 @item @emph{agent expression object} @tab @tab
38127 @item length @tab 4 @tab length of bytes code
38128 @item byte code @tab @var{length} @tab contents of byte code
38129 @item @emph{tracepoint action for collecting memory} @tab @tab
38130 @item 'M' @tab 1 @tab type of tracepoint action
38131 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38132 address of the lowest byte to collect, otherwise @var{addr} is the offset
38133 of @var{basereg} for memory collecting.
38134 @item len @tab 8 @tab length of memory for collecting
38135 @item basereg @tab 4 @tab the register number containing the starting
38136 memory address for collecting.
38137 @item @emph{tracepoint action for collecting registers} @tab @tab
38138 @item 'R' @tab 1 @tab type of tracepoint action
38139 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38140 @item 'L' @tab 1 @tab type of tracepoint action
38141 @item @emph{tracepoint action for expression evaluation} @tab @tab
38142 @item 'X' @tab 1 @tab type of tracepoint action
38143 @item agent expression @tab length of @tab @ref{agent expression object}
38144 @item @emph{tracepoint object} @tab @tab
38145 @item number @tab 4 @tab number of tracepoint
38146 @item address @tab 8 @tab address of tracepoint inserted on
38147 @item type @tab 4 @tab type of tracepoint
38148 @item enabled @tab 1 @tab enable or disable of tracepoint
38149 @item step_count @tab 8 @tab step
38150 @item pass_count @tab 8 @tab pass
38151 @item numactions @tab 4 @tab number of tracepoint actions
38152 @item hit count @tab 8 @tab hit count
38153 @item trace frame usage @tab 8 @tab trace frame usage
38154 @item compiled_cond @tab 8 @tab compiled condition
38155 @item orig_size @tab 8 @tab orig size
38156 @item condition @tab 4 if condition is NULL otherwise length of
38157 @ref{agent expression object}
38158 @tab zero if condition is NULL, otherwise is
38159 @ref{agent expression object}
38160 @item actions @tab variable
38161 @tab numactions number of @ref{tracepoint action object}
38164 @node IPA Protocol Commands
38165 @subsection IPA Protocol Commands
38166 @cindex ipa protocol commands
38168 The spaces in each command are delimiters to ease reading this commands
38169 specification. They don't exist in real commands.
38173 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38174 Installs a new fast tracepoint described by @var{tracepoint_object}
38175 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38176 head of @dfn{jumppad}, which is used to jump to data collection routine
38181 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38182 @var{target_address} is address of tracepoint in the inferior.
38183 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38184 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38185 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38186 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38193 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38194 is about to kill inferiors.
38202 @item probe_marker_at:@var{address}
38203 Asks in-process agent to probe the marker at @var{address}.
38210 @item unprobe_marker_at:@var{address}
38211 Asks in-process agent to unprobe the marker at @var{address}.
38215 @chapter Reporting Bugs in @value{GDBN}
38216 @cindex bugs in @value{GDBN}
38217 @cindex reporting bugs in @value{GDBN}
38219 Your bug reports play an essential role in making @value{GDBN} reliable.
38221 Reporting a bug may help you by bringing a solution to your problem, or it
38222 may not. But in any case the principal function of a bug report is to help
38223 the entire community by making the next version of @value{GDBN} work better. Bug
38224 reports are your contribution to the maintenance of @value{GDBN}.
38226 In order for a bug report to serve its purpose, you must include the
38227 information that enables us to fix the bug.
38230 * Bug Criteria:: Have you found a bug?
38231 * Bug Reporting:: How to report bugs
38235 @section Have You Found a Bug?
38236 @cindex bug criteria
38238 If you are not sure whether you have found a bug, here are some guidelines:
38241 @cindex fatal signal
38242 @cindex debugger crash
38243 @cindex crash of debugger
38245 If the debugger gets a fatal signal, for any input whatever, that is a
38246 @value{GDBN} bug. Reliable debuggers never crash.
38248 @cindex error on valid input
38250 If @value{GDBN} produces an error message for valid input, that is a
38251 bug. (Note that if you're cross debugging, the problem may also be
38252 somewhere in the connection to the target.)
38254 @cindex invalid input
38256 If @value{GDBN} does not produce an error message for invalid input,
38257 that is a bug. However, you should note that your idea of
38258 ``invalid input'' might be our idea of ``an extension'' or ``support
38259 for traditional practice''.
38262 If you are an experienced user of debugging tools, your suggestions
38263 for improvement of @value{GDBN} are welcome in any case.
38266 @node Bug Reporting
38267 @section How to Report Bugs
38268 @cindex bug reports
38269 @cindex @value{GDBN} bugs, reporting
38271 A number of companies and individuals offer support for @sc{gnu} products.
38272 If you obtained @value{GDBN} from a support organization, we recommend you
38273 contact that organization first.
38275 You can find contact information for many support companies and
38276 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38278 @c should add a web page ref...
38281 @ifset BUGURL_DEFAULT
38282 In any event, we also recommend that you submit bug reports for
38283 @value{GDBN}. The preferred method is to submit them directly using
38284 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38285 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38288 @strong{Do not send bug reports to @samp{info-gdb}, or to
38289 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38290 not want to receive bug reports. Those that do have arranged to receive
38293 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38294 serves as a repeater. The mailing list and the newsgroup carry exactly
38295 the same messages. Often people think of posting bug reports to the
38296 newsgroup instead of mailing them. This appears to work, but it has one
38297 problem which can be crucial: a newsgroup posting often lacks a mail
38298 path back to the sender. Thus, if we need to ask for more information,
38299 we may be unable to reach you. For this reason, it is better to send
38300 bug reports to the mailing list.
38302 @ifclear BUGURL_DEFAULT
38303 In any event, we also recommend that you submit bug reports for
38304 @value{GDBN} to @value{BUGURL}.
38308 The fundamental principle of reporting bugs usefully is this:
38309 @strong{report all the facts}. If you are not sure whether to state a
38310 fact or leave it out, state it!
38312 Often people omit facts because they think they know what causes the
38313 problem and assume that some details do not matter. Thus, you might
38314 assume that the name of the variable you use in an example does not matter.
38315 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38316 stray memory reference which happens to fetch from the location where that
38317 name is stored in memory; perhaps, if the name were different, the contents
38318 of that location would fool the debugger into doing the right thing despite
38319 the bug. Play it safe and give a specific, complete example. That is the
38320 easiest thing for you to do, and the most helpful.
38322 Keep in mind that the purpose of a bug report is to enable us to fix the
38323 bug. It may be that the bug has been reported previously, but neither
38324 you nor we can know that unless your bug report is complete and
38327 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38328 bell?'' Those bug reports are useless, and we urge everyone to
38329 @emph{refuse to respond to them} except to chide the sender to report
38332 To enable us to fix the bug, you should include all these things:
38336 The version of @value{GDBN}. @value{GDBN} announces it if you start
38337 with no arguments; you can also print it at any time using @code{show
38340 Without this, we will not know whether there is any point in looking for
38341 the bug in the current version of @value{GDBN}.
38344 The type of machine you are using, and the operating system name and
38348 The details of the @value{GDBN} build-time configuration.
38349 @value{GDBN} shows these details if you invoke it with the
38350 @option{--configuration} command-line option, or if you type
38351 @code{show configuration} at @value{GDBN}'s prompt.
38354 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38355 ``@value{GCC}--2.8.1''.
38358 What compiler (and its version) was used to compile the program you are
38359 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38360 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38361 to get this information; for other compilers, see the documentation for
38365 The command arguments you gave the compiler to compile your example and
38366 observe the bug. For example, did you use @samp{-O}? To guarantee
38367 you will not omit something important, list them all. A copy of the
38368 Makefile (or the output from make) is sufficient.
38370 If we were to try to guess the arguments, we would probably guess wrong
38371 and then we might not encounter the bug.
38374 A complete input script, and all necessary source files, that will
38378 A description of what behavior you observe that you believe is
38379 incorrect. For example, ``It gets a fatal signal.''
38381 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38382 will certainly notice it. But if the bug is incorrect output, we might
38383 not notice unless it is glaringly wrong. You might as well not give us
38384 a chance to make a mistake.
38386 Even if the problem you experience is a fatal signal, you should still
38387 say so explicitly. Suppose something strange is going on, such as, your
38388 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38389 the C library on your system. (This has happened!) Your copy might
38390 crash and ours would not. If you told us to expect a crash, then when
38391 ours fails to crash, we would know that the bug was not happening for
38392 us. If you had not told us to expect a crash, then we would not be able
38393 to draw any conclusion from our observations.
38396 @cindex recording a session script
38397 To collect all this information, you can use a session recording program
38398 such as @command{script}, which is available on many Unix systems.
38399 Just run your @value{GDBN} session inside @command{script} and then
38400 include the @file{typescript} file with your bug report.
38402 Another way to record a @value{GDBN} session is to run @value{GDBN}
38403 inside Emacs and then save the entire buffer to a file.
38406 If you wish to suggest changes to the @value{GDBN} source, send us context
38407 diffs. If you even discuss something in the @value{GDBN} source, refer to
38408 it by context, not by line number.
38410 The line numbers in our development sources will not match those in your
38411 sources. Your line numbers would convey no useful information to us.
38415 Here are some things that are not necessary:
38419 A description of the envelope of the bug.
38421 Often people who encounter a bug spend a lot of time investigating
38422 which changes to the input file will make the bug go away and which
38423 changes will not affect it.
38425 This is often time consuming and not very useful, because the way we
38426 will find the bug is by running a single example under the debugger
38427 with breakpoints, not by pure deduction from a series of examples.
38428 We recommend that you save your time for something else.
38430 Of course, if you can find a simpler example to report @emph{instead}
38431 of the original one, that is a convenience for us. Errors in the
38432 output will be easier to spot, running under the debugger will take
38433 less time, and so on.
38435 However, simplification is not vital; if you do not want to do this,
38436 report the bug anyway and send us the entire test case you used.
38439 A patch for the bug.
38441 A patch for the bug does help us if it is a good one. But do not omit
38442 the necessary information, such as the test case, on the assumption that
38443 a patch is all we need. We might see problems with your patch and decide
38444 to fix the problem another way, or we might not understand it at all.
38446 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38447 construct an example that will make the program follow a certain path
38448 through the code. If you do not send us the example, we will not be able
38449 to construct one, so we will not be able to verify that the bug is fixed.
38451 And if we cannot understand what bug you are trying to fix, or why your
38452 patch should be an improvement, we will not install it. A test case will
38453 help us to understand.
38456 A guess about what the bug is or what it depends on.
38458 Such guesses are usually wrong. Even we cannot guess right about such
38459 things without first using the debugger to find the facts.
38462 @c The readline documentation is distributed with the readline code
38463 @c and consists of the two following files:
38466 @c Use -I with makeinfo to point to the appropriate directory,
38467 @c environment var TEXINPUTS with TeX.
38468 @ifclear SYSTEM_READLINE
38469 @include rluser.texi
38470 @include hsuser.texi
38474 @appendix In Memoriam
38476 The @value{GDBN} project mourns the loss of the following long-time
38481 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38482 to Free Software in general. Outside of @value{GDBN}, he was known in
38483 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38485 @item Michael Snyder
38486 Michael was one of the Global Maintainers of the @value{GDBN} project,
38487 with contributions recorded as early as 1996, until 2011. In addition
38488 to his day to day participation, he was a large driving force behind
38489 adding Reverse Debugging to @value{GDBN}.
38492 Beyond their technical contributions to the project, they were also
38493 enjoyable members of the Free Software Community. We will miss them.
38495 @node Formatting Documentation
38496 @appendix Formatting Documentation
38498 @cindex @value{GDBN} reference card
38499 @cindex reference card
38500 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38501 for printing with PostScript or Ghostscript, in the @file{gdb}
38502 subdirectory of the main source directory@footnote{In
38503 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38504 release.}. If you can use PostScript or Ghostscript with your printer,
38505 you can print the reference card immediately with @file{refcard.ps}.
38507 The release also includes the source for the reference card. You
38508 can format it, using @TeX{}, by typing:
38514 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38515 mode on US ``letter'' size paper;
38516 that is, on a sheet 11 inches wide by 8.5 inches
38517 high. You will need to specify this form of printing as an option to
38518 your @sc{dvi} output program.
38520 @cindex documentation
38522 All the documentation for @value{GDBN} comes as part of the machine-readable
38523 distribution. The documentation is written in Texinfo format, which is
38524 a documentation system that uses a single source file to produce both
38525 on-line information and a printed manual. You can use one of the Info
38526 formatting commands to create the on-line version of the documentation
38527 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38529 @value{GDBN} includes an already formatted copy of the on-line Info
38530 version of this manual in the @file{gdb} subdirectory. The main Info
38531 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38532 subordinate files matching @samp{gdb.info*} in the same directory. If
38533 necessary, you can print out these files, or read them with any editor;
38534 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38535 Emacs or the standalone @code{info} program, available as part of the
38536 @sc{gnu} Texinfo distribution.
38538 If you want to format these Info files yourself, you need one of the
38539 Info formatting programs, such as @code{texinfo-format-buffer} or
38542 If you have @code{makeinfo} installed, and are in the top level
38543 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38544 version @value{GDBVN}), you can make the Info file by typing:
38551 If you want to typeset and print copies of this manual, you need @TeX{},
38552 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38553 Texinfo definitions file.
38555 @TeX{} is a typesetting program; it does not print files directly, but
38556 produces output files called @sc{dvi} files. To print a typeset
38557 document, you need a program to print @sc{dvi} files. If your system
38558 has @TeX{} installed, chances are it has such a program. The precise
38559 command to use depends on your system; @kbd{lpr -d} is common; another
38560 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38561 require a file name without any extension or a @samp{.dvi} extension.
38563 @TeX{} also requires a macro definitions file called
38564 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38565 written in Texinfo format. On its own, @TeX{} cannot either read or
38566 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38567 and is located in the @file{gdb-@var{version-number}/texinfo}
38570 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38571 typeset and print this manual. First switch to the @file{gdb}
38572 subdirectory of the main source directory (for example, to
38573 @file{gdb-@value{GDBVN}/gdb}) and type:
38579 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38581 @node Installing GDB
38582 @appendix Installing @value{GDBN}
38583 @cindex installation
38586 * Requirements:: Requirements for building @value{GDBN}
38587 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38588 * Separate Objdir:: Compiling @value{GDBN} in another directory
38589 * Config Names:: Specifying names for hosts and targets
38590 * Configure Options:: Summary of options for configure
38591 * System-wide configuration:: Having a system-wide init file
38595 @section Requirements for Building @value{GDBN}
38596 @cindex building @value{GDBN}, requirements for
38598 Building @value{GDBN} requires various tools and packages to be available.
38599 Other packages will be used only if they are found.
38601 @heading Tools/Packages Necessary for Building @value{GDBN}
38603 @item C@t{++}11 compiler
38604 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38605 recent C@t{++}11 compiler, e.g.@: GCC.
38608 @value{GDBN}'s build system relies on features only found in the GNU
38609 make program. Other variants of @code{make} will not work.
38611 @item GMP (The GNU Multiple Precision Arithmetic Library)
38612 @value{GDBN} now uses GMP to perform some of its arithmetics.
38613 This library may be included with your operating system distribution;
38614 if it is not, you can get the latest version from
38615 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38616 you can use the @option{--with-libgmp-prefix} option to specify
38621 @heading Tools/Packages Optional for Building @value{GDBN}
38625 @value{GDBN} can use the Expat XML parsing library. This library may be
38626 included with your operating system distribution; if it is not, you
38627 can get the latest version from @url{http://expat.sourceforge.net}.
38628 The @file{configure} script will search for this library in several
38629 standard locations; if it is installed in an unusual path, you can
38630 use the @option{--with-libexpat-prefix} option to specify its location.
38636 Remote protocol memory maps (@pxref{Memory Map Format})
38638 Target descriptions (@pxref{Target Descriptions})
38640 Remote shared library lists (@xref{Library List Format},
38641 or alternatively @pxref{Library List Format for SVR4 Targets})
38643 MS-Windows shared libraries (@pxref{Shared Libraries})
38645 Traceframe info (@pxref{Traceframe Info Format})
38647 Branch trace (@pxref{Branch Trace Format},
38648 @pxref{Branch Trace Configuration Format})
38652 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38653 default, @value{GDBN} will be compiled if the Guile libraries are
38654 installed and are found by @file{configure}. You can use the
38655 @code{--with-guile} option to request Guile, and pass either the Guile
38656 version number or the file name of the relevant @code{pkg-config}
38657 program to choose a particular version of Guile.
38660 @value{GDBN}'s features related to character sets (@pxref{Character
38661 Sets}) require a functioning @code{iconv} implementation. If you are
38662 on a GNU system, then this is provided by the GNU C Library. Some
38663 other systems also provide a working @code{iconv}.
38665 If @value{GDBN} is using the @code{iconv} program which is installed
38666 in a non-standard place, you will need to tell @value{GDBN} where to
38667 find it. This is done with @option{--with-iconv-bin} which specifies
38668 the directory that contains the @code{iconv} program. This program is
38669 run in order to make a list of the available character sets.
38671 On systems without @code{iconv}, you can install GNU Libiconv. If
38672 Libiconv is installed in a standard place, @value{GDBN} will
38673 automatically use it if it is needed. If you have previously
38674 installed Libiconv in a non-standard place, you can use the
38675 @option{--with-libiconv-prefix} option to @file{configure}.
38677 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
38678 arrange to build Libiconv if a directory named @file{libiconv} appears
38679 in the top-most source directory. If Libiconv is built this way, and
38680 if the operating system does not provide a suitable @code{iconv}
38681 implementation, then the just-built library will automatically be used
38682 by @value{GDBN}. One easy way to set this up is to download GNU
38683 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
38684 source tree, and then rename the directory holding the Libiconv source
38685 code to @samp{libiconv}.
38688 @value{GDBN} can support debugging sections that are compressed with
38689 the LZMA library. @xref{MiniDebugInfo}. If this library is not
38690 included with your operating system, you can find it in the xz package
38691 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
38692 the usual place, then the @file{configure} script will use it
38693 automatically. If it is installed in an unusual path, you can use the
38694 @option{--with-liblzma-prefix} option to specify its location.
38698 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
38699 library. This library may be included with your operating system
38700 distribution; if it is not, you can get the latest version from
38701 @url{http://www.mpfr.org}. The @file{configure} script will search
38702 for this library in several standard locations; if it is installed
38703 in an unusual path, you can use the @option{--with-libmpfr-prefix}
38704 option to specify its location.
38706 GNU MPFR is used to emulate target floating-point arithmetic during
38707 expression evaluation when the target uses different floating-point
38708 formats than the host. If GNU MPFR it is not available, @value{GDBN}
38709 will fall back to using host floating-point arithmetic.
38712 @value{GDBN} can be scripted using Python language. @xref{Python}.
38713 By default, @value{GDBN} will be compiled if the Python libraries are
38714 installed and are found by @file{configure}. You can use the
38715 @code{--with-python} option to request Python, and pass either the
38716 file name of the relevant @code{python} executable, or the name of the
38717 directory in which Python is installed, to choose a particular
38718 installation of Python.
38721 @cindex compressed debug sections
38722 @value{GDBN} will use the @samp{zlib} library, if available, to read
38723 compressed debug sections. Some linkers, such as GNU gold, are capable
38724 of producing binaries with compressed debug sections. If @value{GDBN}
38725 is compiled with @samp{zlib}, it will be able to read the debug
38726 information in such binaries.
38728 The @samp{zlib} library is likely included with your operating system
38729 distribution; if it is not, you can get the latest version from
38730 @url{http://zlib.net}.
38733 @node Running Configure
38734 @section Invoking the @value{GDBN} @file{configure} Script
38735 @cindex configuring @value{GDBN}
38736 @value{GDBN} comes with a @file{configure} script that automates the process
38737 of preparing @value{GDBN} for installation; you can then use @code{make} to
38738 build the @code{gdb} program.
38740 @c irrelevant in info file; it's as current as the code it lives with.
38741 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38742 look at the @file{README} file in the sources; we may have improved the
38743 installation procedures since publishing this manual.}
38746 The @value{GDBN} distribution includes all the source code you need for
38747 @value{GDBN} in a single directory, whose name is usually composed by
38748 appending the version number to @samp{gdb}.
38750 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38751 @file{gdb-@value{GDBVN}} directory. That directory contains:
38754 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38755 script for configuring @value{GDBN} and all its supporting libraries
38757 @item gdb-@value{GDBVN}/gdb
38758 the source specific to @value{GDBN} itself
38760 @item gdb-@value{GDBVN}/bfd
38761 source for the Binary File Descriptor library
38763 @item gdb-@value{GDBVN}/include
38764 @sc{gnu} include files
38766 @item gdb-@value{GDBVN}/libiberty
38767 source for the @samp{-liberty} free software library
38769 @item gdb-@value{GDBVN}/opcodes
38770 source for the library of opcode tables and disassemblers
38772 @item gdb-@value{GDBVN}/readline
38773 source for the @sc{gnu} command-line interface
38776 There may be other subdirectories as well.
38778 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38779 from the @file{gdb-@var{version-number}} source directory, which in
38780 this example is the @file{gdb-@value{GDBVN}} directory.
38782 First switch to the @file{gdb-@var{version-number}} source directory
38783 if you are not already in it; then run @file{configure}. Pass the
38784 identifier for the platform on which @value{GDBN} will run as an
38790 cd gdb-@value{GDBVN}
38795 Running @samp{configure} and then running @code{make} builds the
38796 included supporting libraries, then @code{gdb} itself. The configured
38797 source files, and the binaries, are left in the corresponding source
38801 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38802 system does not recognize this automatically when you run a different
38803 shell, you may need to run @code{sh} on it explicitly:
38809 You should run the @file{configure} script from the top directory in the
38810 source tree, the @file{gdb-@var{version-number}} directory. If you run
38811 @file{configure} from one of the subdirectories, you will configure only
38812 that subdirectory. That is usually not what you want. In particular,
38813 if you run the first @file{configure} from the @file{gdb} subdirectory
38814 of the @file{gdb-@var{version-number}} directory, you will omit the
38815 configuration of @file{bfd}, @file{readline}, and other sibling
38816 directories of the @file{gdb} subdirectory. This leads to build errors
38817 about missing include files such as @file{bfd/bfd.h}.
38819 You can install @code{@value{GDBN}} anywhere. The best way to do this
38820 is to pass the @code{--prefix} option to @code{configure}, and then
38821 install it with @code{make install}.
38823 @node Separate Objdir
38824 @section Compiling @value{GDBN} in Another Directory
38826 If you want to run @value{GDBN} versions for several host or target machines,
38827 you need a different @code{gdb} compiled for each combination of
38828 host and target. @file{configure} is designed to make this easy by
38829 allowing you to generate each configuration in a separate subdirectory,
38830 rather than in the source directory. If your @code{make} program
38831 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38832 @code{make} in each of these directories builds the @code{gdb}
38833 program specified there.
38835 To build @code{gdb} in a separate directory, run @file{configure}
38836 with the @samp{--srcdir} option to specify where to find the source.
38837 (You also need to specify a path to find @file{configure}
38838 itself from your working directory. If the path to @file{configure}
38839 would be the same as the argument to @samp{--srcdir}, you can leave out
38840 the @samp{--srcdir} option; it is assumed.)
38842 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38843 separate directory for a Sun 4 like this:
38847 cd gdb-@value{GDBVN}
38850 ../gdb-@value{GDBVN}/configure
38855 When @file{configure} builds a configuration using a remote source
38856 directory, it creates a tree for the binaries with the same structure
38857 (and using the same names) as the tree under the source directory. In
38858 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38859 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38860 @file{gdb-sun4/gdb}.
38862 Make sure that your path to the @file{configure} script has just one
38863 instance of @file{gdb} in it. If your path to @file{configure} looks
38864 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38865 one subdirectory of @value{GDBN}, not the whole package. This leads to
38866 build errors about missing include files such as @file{bfd/bfd.h}.
38868 One popular reason to build several @value{GDBN} configurations in separate
38869 directories is to configure @value{GDBN} for cross-compiling (where
38870 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
38871 programs that run on another machine---the @dfn{target}).
38872 You specify a cross-debugging target by
38873 giving the @samp{--target=@var{target}} option to @file{configure}.
38875 When you run @code{make} to build a program or library, you must run
38876 it in a configured directory---whatever directory you were in when you
38877 called @file{configure} (or one of its subdirectories).
38879 The @code{Makefile} that @file{configure} generates in each source
38880 directory also runs recursively. If you type @code{make} in a source
38881 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
38882 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
38883 will build all the required libraries, and then build GDB.
38885 When you have multiple hosts or targets configured in separate
38886 directories, you can run @code{make} on them in parallel (for example,
38887 if they are NFS-mounted on each of the hosts); they will not interfere
38891 @section Specifying Names for Hosts and Targets
38893 The specifications used for hosts and targets in the @file{configure}
38894 script are based on a three-part naming scheme, but some short predefined
38895 aliases are also supported. The full naming scheme encodes three pieces
38896 of information in the following pattern:
38899 @var{architecture}-@var{vendor}-@var{os}
38902 For example, you can use the alias @code{sun4} as a @var{host} argument,
38903 or as the value for @var{target} in a @code{--target=@var{target}}
38904 option. The equivalent full name is @samp{sparc-sun-sunos4}.
38906 The @file{configure} script accompanying @value{GDBN} does not provide
38907 any query facility to list all supported host and target names or
38908 aliases. @file{configure} calls the Bourne shell script
38909 @code{config.sub} to map abbreviations to full names; you can read the
38910 script, if you wish, or you can use it to test your guesses on
38911 abbreviations---for example:
38914 % sh config.sub i386-linux
38916 % sh config.sub alpha-linux
38917 alpha-unknown-linux-gnu
38918 % sh config.sub hp9k700
38920 % sh config.sub sun4
38921 sparc-sun-sunos4.1.1
38922 % sh config.sub sun3
38923 m68k-sun-sunos4.1.1
38924 % sh config.sub i986v
38925 Invalid configuration `i986v': machine `i986v' not recognized
38929 @code{config.sub} is also distributed in the @value{GDBN} source
38930 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
38932 @node Configure Options
38933 @section @file{configure} Options
38935 Here is a summary of the @file{configure} options and arguments that
38936 are most often useful for building @value{GDBN}. @file{configure}
38937 also has several other options not listed here. @xref{Running
38938 configure Scripts,,,autoconf}, for a full
38939 explanation of @file{configure}.
38942 configure @r{[}--help@r{]}
38943 @r{[}--prefix=@var{dir}@r{]}
38944 @r{[}--exec-prefix=@var{dir}@r{]}
38945 @r{[}--srcdir=@var{dirname}@r{]}
38946 @r{[}--target=@var{target}@r{]}
38950 You may introduce options with a single @samp{-} rather than
38951 @samp{--} if you prefer; but you may abbreviate option names if you use
38956 Display a quick summary of how to invoke @file{configure}.
38958 @item --prefix=@var{dir}
38959 Configure the source to install programs and files under directory
38962 @item --exec-prefix=@var{dir}
38963 Configure the source to install programs under directory
38966 @c avoid splitting the warning from the explanation:
38968 @item --srcdir=@var{dirname}
38969 Use this option to make configurations in directories separate from the
38970 @value{GDBN} source directories. Among other things, you can use this to
38971 build (or maintain) several configurations simultaneously, in separate
38972 directories. @file{configure} writes configuration-specific files in
38973 the current directory, but arranges for them to use the source in the
38974 directory @var{dirname}. @file{configure} creates directories under
38975 the working directory in parallel to the source directories below
38978 @item --target=@var{target}
38979 Configure @value{GDBN} for cross-debugging programs running on the specified
38980 @var{target}. Without this option, @value{GDBN} is configured to debug
38981 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38983 There is no convenient way to generate a list of all available
38984 targets. Also see the @code{--enable-targets} option, below.
38987 There are many other options that are specific to @value{GDBN}. This
38988 lists just the most common ones; there are some very specialized
38989 options not described here.
38992 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38993 @itemx --enable-targets=all
38994 Configure @value{GDBN} for cross-debugging programs running on the
38995 specified list of targets. The special value @samp{all} configures
38996 @value{GDBN} for debugging programs running on any target it supports.
38998 @item --with-gdb-datadir=@var{path}
38999 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39000 here for certain supporting files or scripts. This defaults to the
39001 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39004 @item --with-relocated-sources=@var{dir}
39005 Sets up the default source path substitution rule so that directory
39006 names recorded in debug information will be automatically adjusted for
39007 any directory under @var{dir}. @var{dir} should be a subdirectory of
39008 @value{GDBN}'s configured prefix, the one mentioned in the
39009 @code{--prefix} or @code{--exec-prefix} options to configure. This
39010 option is useful if GDB is supposed to be moved to a different place
39013 @item --enable-64-bit-bfd
39014 Enable 64-bit support in BFD on 32-bit hosts.
39016 @item --disable-gdbmi
39017 Build @value{GDBN} without the GDB/MI machine interface
39021 Build @value{GDBN} with the text-mode full-screen user interface
39022 (TUI). Requires a curses library (ncurses and cursesX are also
39025 @item --with-curses
39026 Use the curses library instead of the termcap library, for text-mode
39027 terminal operations.
39029 @item --with-debuginfod
39030 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39031 library. Used to automatically fetch ELF, DWARF and source files from
39032 @code{debuginfod} servers using build IDs associated with any missing
39033 files. Enabled by default if @file{libdebuginfod} is installed and found
39034 at configure time. For more information regarding @code{debuginfod} see
39037 @item --with-libunwind-ia64
39038 Use the libunwind library for unwinding function call stack on ia64
39039 target platforms. See http://www.nongnu.org/libunwind/index.html for
39042 @item --with-system-readline
39043 Use the readline library installed on the host, rather than the
39044 library supplied as part of @value{GDBN}. Readline 7 or newer is
39045 required; this is enforced by the build system.
39047 @item --with-system-zlib
39048 Use the zlib library installed on the host, rather than the library
39049 supplied as part of @value{GDBN}.
39052 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39053 default if libexpat is installed and found at configure time.) This
39054 library is used to read XML files supplied with @value{GDBN}. If it
39055 is unavailable, some features, such as remote protocol memory maps,
39056 target descriptions, and shared library lists, that are based on XML
39057 files, will not be available in @value{GDBN}. If your host does not
39058 have libexpat installed, you can get the latest version from
39059 `http://expat.sourceforge.net'.
39061 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39063 Build @value{GDBN} with GNU libiconv, a character set encoding
39064 conversion library. This is not done by default, as on GNU systems
39065 the @code{iconv} that is built in to the C library is sufficient. If
39066 your host does not have a working @code{iconv}, you can get the latest
39067 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39069 @value{GDBN}'s build system also supports building GNU libiconv as
39070 part of the overall build. @xref{Requirements}.
39073 Build @value{GDBN} with LZMA, a compression library. (Done by default
39074 if liblzma is installed and found at configure time.) LZMA is used by
39075 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39076 platforms using the ELF object file format. If your host does not
39077 have liblzma installed, you can get the latest version from
39078 `https://tukaani.org/xz/'.
39081 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39082 floating-point computation with correct rounding. (Done by default if
39083 GNU MPFR is installed and found at configure time.) This library is
39084 used to emulate target floating-point arithmetic during expression
39085 evaluation when the target uses different floating-point formats than
39086 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39087 to using host floating-point arithmetic. If your host does not have
39088 GNU MPFR installed, you can get the latest version from
39089 `http://www.mpfr.org'.
39091 @item --with-python@r{[}=@var{python}@r{]}
39092 Build @value{GDBN} with Python scripting support. (Done by default if
39093 libpython is present and found at configure time.) Python makes
39094 @value{GDBN} scripting much more powerful than the restricted CLI
39095 scripting language. If your host does not have Python installed, you
39096 can find it on `http://www.python.org/download/'. The oldest version
39097 of Python supported by GDB is 2.6. The optional argument @var{python}
39098 is used to find the Python headers and libraries. It can be either
39099 the name of a Python executable, or the name of the directory in which
39100 Python is installed.
39102 @item --with-guile[=GUILE]'
39103 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39104 if libguile is present and found at configure time.) If your host
39105 does not have Guile installed, you can find it at
39106 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39107 can be a version number, which will cause @code{configure} to try to
39108 use that version of Guile; or the file name of a @code{pkg-config}
39109 executable, which will be queried to find the information needed to
39110 compile and link against Guile.
39112 @item --without-included-regex
39113 Don't use the regex library included with @value{GDBN} (as part of the
39114 libiberty library). This is the default on hosts with version 2 of
39117 @item --with-sysroot=@var{dir}
39118 Use @var{dir} as the default system root directory for libraries whose
39119 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39120 @var{dir} can be modified at run time by using the @command{set
39121 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39122 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39123 default system root will be automatically adjusted if and when
39124 @value{GDBN} is moved to a different location.
39126 @item --with-system-gdbinit=@var{file}
39127 Configure @value{GDBN} to automatically load a system-wide init file.
39128 @var{file} should be an absolute file name. If @var{file} is in a
39129 directory under the configured prefix, and @value{GDBN} is moved to
39130 another location after being built, the location of the system-wide
39131 init file will be adjusted accordingly.
39133 @item --with-system-gdbinit-dir=@var{directory}
39134 Configure @value{GDBN} to automatically load init files from a
39135 system-wide directory. @var{directory} should be an absolute directory
39136 name. If @var{directory} is in a directory under the configured
39137 prefix, and @value{GDBN} is moved to another location after being
39138 built, the location of the system-wide init directory will be
39139 adjusted accordingly.
39141 @item --enable-build-warnings
39142 When building the @value{GDBN} sources, ask the compiler to warn about
39143 any code which looks even vaguely suspicious. It passes many
39144 different warning flags, depending on the exact version of the
39145 compiler you are using.
39147 @item --enable-werror
39148 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39149 to the compiler, which will fail the compilation if the compiler
39150 outputs any warning messages.
39152 @item --enable-ubsan
39153 Enable the GCC undefined behavior sanitizer. This is disabled by
39154 default, but passing @code{--enable-ubsan=yes} or
39155 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39156 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39157 It has a performance cost, so if you are looking at @value{GDBN}'s
39158 performance, you should disable it. The undefined behavior sanitizer
39159 was first introduced in GCC 4.9.
39162 @node System-wide configuration
39163 @section System-wide configuration and settings
39164 @cindex system-wide init file
39166 @value{GDBN} can be configured to have a system-wide init file and a
39167 system-wide init file directory; this file and files in that directory
39168 (if they have a recognized file extension) will be read and executed at
39169 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39171 Here are the corresponding configure options:
39174 @item --with-system-gdbinit=@var{file}
39175 Specify that the default location of the system-wide init file is
39177 @item --with-system-gdbinit-dir=@var{directory}
39178 Specify that the default location of the system-wide init file directory
39179 is @var{directory}.
39182 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39183 they may be subject to relocation. Two possible cases:
39187 If the default location of this init file/directory contains @file{$prefix},
39188 it will be subject to relocation. Suppose that the configure options
39189 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39190 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39191 init file is looked for as @file{$install/etc/gdbinit} instead of
39192 @file{$prefix/etc/gdbinit}.
39195 By contrast, if the default location does not contain the prefix,
39196 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39197 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39198 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39199 wherever @value{GDBN} is installed.
39202 If the configured location of the system-wide init file (as given by the
39203 @option{--with-system-gdbinit} option at configure time) is in the
39204 data-directory (as specified by @option{--with-gdb-datadir} at configure
39205 time) or in one of its subdirectories, then @value{GDBN} will look for the
39206 system-wide init file in the directory specified by the
39207 @option{--data-directory} command-line option.
39208 Note that the system-wide init file is only read once, during @value{GDBN}
39209 initialization. If the data-directory is changed after @value{GDBN} has
39210 started with the @code{set data-directory} command, the file will not be
39213 This applies similarly to the system-wide directory specified in
39214 @option{--with-system-gdbinit-dir}.
39216 Any supported scripting language can be used for these init files, as long
39217 as the file extension matches the scripting language. To be interpreted
39218 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39222 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39225 @node System-wide Configuration Scripts
39226 @subsection Installed System-wide Configuration Scripts
39227 @cindex system-wide configuration scripts
39229 The @file{system-gdbinit} directory, located inside the data-directory
39230 (as specified by @option{--with-gdb-datadir} at configure time) contains
39231 a number of scripts which can be used as system-wide init files. To
39232 automatically source those scripts at startup, @value{GDBN} should be
39233 configured with @option{--with-system-gdbinit}. Otherwise, any user
39234 should be able to source them by hand as needed.
39236 The following scripts are currently available:
39239 @item @file{elinos.py}
39241 @cindex ELinOS system-wide configuration script
39242 This script is useful when debugging a program on an ELinOS target.
39243 It takes advantage of the environment variables defined in a standard
39244 ELinOS environment in order to determine the location of the system
39245 shared libraries, and then sets the @samp{solib-absolute-prefix}
39246 and @samp{solib-search-path} variables appropriately.
39248 @item @file{wrs-linux.py}
39249 @pindex wrs-linux.py
39250 @cindex Wind River Linux system-wide configuration script
39251 This script is useful when debugging a program on a target running
39252 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39253 the host-side sysroot used by the target system.
39257 @node Maintenance Commands
39258 @appendix Maintenance Commands
39259 @cindex maintenance commands
39260 @cindex internal commands
39262 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39263 includes a number of commands intended for @value{GDBN} developers,
39264 that are not documented elsewhere in this manual. These commands are
39265 provided here for reference. (For commands that turn on debugging
39266 messages, see @ref{Debugging Output}.)
39269 @kindex maint agent
39270 @kindex maint agent-eval
39271 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39272 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39273 Translate the given @var{expression} into remote agent bytecodes.
39274 This command is useful for debugging the Agent Expression mechanism
39275 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39276 expression useful for data collection, such as by tracepoints, while
39277 @samp{maint agent-eval} produces an expression that evaluates directly
39278 to a result. For instance, a collection expression for @code{globa +
39279 globb} will include bytecodes to record four bytes of memory at each
39280 of the addresses of @code{globa} and @code{globb}, while discarding
39281 the result of the addition, while an evaluation expression will do the
39282 addition and return the sum.
39283 If @code{-at} is given, generate remote agent bytecode for @var{location}.
39284 If not, generate remote agent bytecode for current frame PC address.
39286 @kindex maint agent-printf
39287 @item maint agent-printf @var{format},@var{expr},...
39288 Translate the given format string and list of argument expressions
39289 into remote agent bytecodes and display them as a disassembled list.
39290 This command is useful for debugging the agent version of dynamic
39291 printf (@pxref{Dynamic Printf}).
39293 @kindex maint info breakpoints
39294 @item @anchor{maint info breakpoints}maint info breakpoints
39295 Using the same format as @samp{info breakpoints}, display both the
39296 breakpoints you've set explicitly, and those @value{GDBN} is using for
39297 internal purposes. Internal breakpoints are shown with negative
39298 breakpoint numbers. The type column identifies what kind of breakpoint
39303 Normal, explicitly set breakpoint.
39306 Normal, explicitly set watchpoint.
39309 Internal breakpoint, used to handle correctly stepping through
39310 @code{longjmp} calls.
39312 @item longjmp resume
39313 Internal breakpoint at the target of a @code{longjmp}.
39316 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39319 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39322 Shared library events.
39326 @kindex maint info btrace
39327 @item maint info btrace
39328 Pint information about raw branch tracing data.
39330 @kindex maint btrace packet-history
39331 @item maint btrace packet-history
39332 Print the raw branch trace packets that are used to compute the
39333 execution history for the @samp{record btrace} command. Both the
39334 information and the format in which it is printed depend on the btrace
39339 For the BTS recording format, print a list of blocks of sequential
39340 code. For each block, the following information is printed:
39344 Newer blocks have higher numbers. The oldest block has number zero.
39345 @item Lowest @samp{PC}
39346 @item Highest @samp{PC}
39350 For the Intel Processor Trace recording format, print a list of
39351 Intel Processor Trace packets. For each packet, the following
39352 information is printed:
39355 @item Packet number
39356 Newer packets have higher numbers. The oldest packet has number zero.
39358 The packet's offset in the trace stream.
39359 @item Packet opcode and payload
39363 @kindex maint btrace clear-packet-history
39364 @item maint btrace clear-packet-history
39365 Discards the cached packet history printed by the @samp{maint btrace
39366 packet-history} command. The history will be computed again when
39369 @kindex maint btrace clear
39370 @item maint btrace clear
39371 Discard the branch trace data. The data will be fetched anew and the
39372 branch trace will be recomputed when needed.
39374 This implicitly truncates the branch trace to a single branch trace
39375 buffer. When updating branch trace incrementally, the branch trace
39376 available to @value{GDBN} may be bigger than a single branch trace
39379 @kindex maint set btrace pt skip-pad
39380 @item maint set btrace pt skip-pad
39381 @kindex maint show btrace pt skip-pad
39382 @item maint show btrace pt skip-pad
39383 Control whether @value{GDBN} will skip PAD packets when computing the
39386 @kindex maint info jit
39387 @item maint info jit
39388 Print information about JIT code objects loaded in the current inferior.
39390 @kindex set displaced-stepping
39391 @kindex show displaced-stepping
39392 @cindex displaced stepping support
39393 @cindex out-of-line single-stepping
39394 @item set displaced-stepping
39395 @itemx show displaced-stepping
39396 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39397 if the target supports it. Displaced stepping is a way to single-step
39398 over breakpoints without removing them from the inferior, by executing
39399 an out-of-line copy of the instruction that was originally at the
39400 breakpoint location. It is also known as out-of-line single-stepping.
39403 @item set displaced-stepping on
39404 If the target architecture supports it, @value{GDBN} will use
39405 displaced stepping to step over breakpoints.
39407 @item set displaced-stepping off
39408 @value{GDBN} will not use displaced stepping to step over breakpoints,
39409 even if such is supported by the target architecture.
39411 @cindex non-stop mode, and @samp{set displaced-stepping}
39412 @item set displaced-stepping auto
39413 This is the default mode. @value{GDBN} will use displaced stepping
39414 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39415 architecture supports displaced stepping.
39418 @kindex maint check-psymtabs
39419 @item maint check-psymtabs
39420 Check the consistency of currently expanded psymtabs versus symtabs.
39421 Use this to check, for example, whether a symbol is in one but not the other.
39423 @kindex maint check-symtabs
39424 @item maint check-symtabs
39425 Check the consistency of currently expanded symtabs.
39427 @kindex maint expand-symtabs
39428 @item maint expand-symtabs [@var{regexp}]
39429 Expand symbol tables.
39430 If @var{regexp} is specified, only expand symbol tables for file
39431 names matching @var{regexp}.
39433 @kindex maint set catch-demangler-crashes
39434 @kindex maint show catch-demangler-crashes
39435 @cindex demangler crashes
39436 @item maint set catch-demangler-crashes [on|off]
39437 @itemx maint show catch-demangler-crashes
39438 Control whether @value{GDBN} should attempt to catch crashes in the
39439 symbol name demangler. The default is to attempt to catch crashes.
39440 If enabled, the first time a crash is caught, a core file is created,
39441 the offending symbol is displayed and the user is presented with the
39442 option to terminate the current session.
39444 @kindex maint cplus first_component
39445 @item maint cplus first_component @var{name}
39446 Print the first C@t{++} class/namespace component of @var{name}.
39448 @kindex maint cplus namespace
39449 @item maint cplus namespace
39450 Print the list of possible C@t{++} namespaces.
39452 @kindex maint deprecate
39453 @kindex maint undeprecate
39454 @cindex deprecated commands
39455 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39456 @itemx maint undeprecate @var{command}
39457 Deprecate or undeprecate the named @var{command}. Deprecated commands
39458 cause @value{GDBN} to issue a warning when you use them. The optional
39459 argument @var{replacement} says which newer command should be used in
39460 favor of the deprecated one; if it is given, @value{GDBN} will mention
39461 the replacement as part of the warning.
39463 @kindex maint dump-me
39464 @item maint dump-me
39465 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39466 Cause a fatal signal in the debugger and force it to dump its core.
39467 This is supported only on systems which support aborting a program
39468 with the @code{SIGQUIT} signal.
39470 @kindex maint internal-error
39471 @kindex maint internal-warning
39472 @kindex maint demangler-warning
39473 @cindex demangler crashes
39474 @item maint internal-error @r{[}@var{message-text}@r{]}
39475 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39476 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39478 Cause @value{GDBN} to call the internal function @code{internal_error},
39479 @code{internal_warning} or @code{demangler_warning} and hence behave
39480 as though an internal problem has been detected. In addition to
39481 reporting the internal problem, these functions give the user the
39482 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39483 and @code{internal_warning}) create a core file of the current
39484 @value{GDBN} session.
39486 These commands take an optional parameter @var{message-text} that is
39487 used as the text of the error or warning message.
39489 Here's an example of using @code{internal-error}:
39492 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39493 @dots{}/maint.c:121: internal-error: testing, 1, 2
39494 A problem internal to GDB has been detected. Further
39495 debugging may prove unreliable.
39496 Quit this debugging session? (y or n) @kbd{n}
39497 Create a core file? (y or n) @kbd{n}
39501 @cindex @value{GDBN} internal error
39502 @cindex internal errors, control of @value{GDBN} behavior
39503 @cindex demangler crashes
39505 @kindex maint set internal-error
39506 @kindex maint show internal-error
39507 @kindex maint set internal-warning
39508 @kindex maint show internal-warning
39509 @kindex maint set demangler-warning
39510 @kindex maint show demangler-warning
39511 @item maint set internal-error @var{action} [ask|yes|no]
39512 @itemx maint show internal-error @var{action}
39513 @itemx maint set internal-warning @var{action} [ask|yes|no]
39514 @itemx maint show internal-warning @var{action}
39515 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39516 @itemx maint show demangler-warning @var{action}
39517 When @value{GDBN} reports an internal problem (error or warning) it
39518 gives the user the opportunity to both quit @value{GDBN} and create a
39519 core file of the current @value{GDBN} session. These commands let you
39520 override the default behaviour for each particular @var{action},
39521 described in the table below.
39525 You can specify that @value{GDBN} should always (yes) or never (no)
39526 quit. The default is to ask the user what to do.
39529 You can specify that @value{GDBN} should always (yes) or never (no)
39530 create a core file. The default is to ask the user what to do. Note
39531 that there is no @code{corefile} option for @code{demangler-warning}:
39532 demangler warnings always create a core file and this cannot be
39536 @kindex maint set internal-error
39537 @kindex maint show internal-error
39538 @kindex maint set internal-warning
39539 @kindex maint show internal-warning
39540 @item maint set internal-error backtrace @r{[}on|off@r{]}
39541 @itemx maint show internal-error backtrace
39542 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
39543 @itemx maint show internal-warning backtrace
39544 When @value{GDBN} reports an internal problem (error or warning) it is
39545 possible to have a backtrace of @value{GDBN} printed to the standard
39546 error stream. This is @samp{on} by default for @code{internal-error}
39547 and @samp{off} by default for @code{internal-warning}.
39549 @anchor{maint packet}
39550 @kindex maint packet
39551 @item maint packet @var{text}
39552 If @value{GDBN} is talking to an inferior via the serial protocol,
39553 then this command sends the string @var{text} to the inferior, and
39554 displays the response packet. @value{GDBN} supplies the initial
39555 @samp{$} character, the terminating @samp{#} character, and the
39558 Any non-printable characters in the reply are printed as escaped hex,
39559 e.g. @samp{\x00}, @samp{\x01}, etc.
39561 @kindex maint print architecture
39562 @item maint print architecture @r{[}@var{file}@r{]}
39563 Print the entire architecture configuration. The optional argument
39564 @var{file} names the file where the output goes.
39566 @kindex maint print c-tdesc
39567 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39568 Print the target description (@pxref{Target Descriptions}) as
39569 a C source file. By default, the target description is for the current
39570 target, but if the optional argument @var{file} is provided, that file
39571 is used to produce the description. The @var{file} should be an XML
39572 document, of the form described in @ref{Target Description Format}.
39573 The created source file is built into @value{GDBN} when @value{GDBN} is
39574 built again. This command is used by developers after they add or
39575 modify XML target descriptions.
39577 When the optional flag @samp{-single-feature} is provided then the
39578 target description being processed (either the default, or from
39579 @var{file}) must only contain a single feature. The source file
39580 produced is different in this case.
39582 @kindex maint print xml-tdesc
39583 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39584 Print the target description (@pxref{Target Descriptions}) as an XML
39585 file. By default print the target description for the current target,
39586 but if the optional argument @var{file} is provided, then that file is
39587 read in by GDB and then used to produce the description. The
39588 @var{file} should be an XML document, of the form described in
39589 @ref{Target Description Format}.
39591 @kindex maint check xml-descriptions
39592 @item maint check xml-descriptions @var{dir}
39593 Check that the target descriptions dynamically created by @value{GDBN}
39594 equal the descriptions created from XML files found in @var{dir}.
39596 @anchor{maint check libthread-db}
39597 @kindex maint check libthread-db
39598 @item maint check libthread-db
39599 Run integrity checks on the current inferior's thread debugging
39600 library. This exercises all @code{libthread_db} functionality used by
39601 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39602 @code{proc_service} functions provided by @value{GDBN} that
39603 @code{libthread_db} uses. Note that parts of the test may be skipped
39604 on some platforms when debugging core files.
39606 @kindex maint print core-file-backed-mappings
39607 @cindex memory address space mappings
39608 @item maint print core-file-backed-mappings
39609 Print the file-backed mappings which were loaded from a core file note.
39610 This output represents state internal to @value{GDBN} and should be
39611 similar to the mappings displayed by the @code{info proc mappings}
39614 @kindex maint print dummy-frames
39615 @item maint print dummy-frames
39616 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
39619 (@value{GDBP}) @kbd{b add}
39621 (@value{GDBP}) @kbd{print add(2,3)}
39622 Breakpoint 2, add (a=2, b=3) at @dots{}
39624 The program being debugged stopped while in a function called from GDB.
39626 (@value{GDBP}) @kbd{maint print dummy-frames}
39627 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
39631 Takes an optional file parameter.
39633 @kindex maint print registers
39634 @kindex maint print raw-registers
39635 @kindex maint print cooked-registers
39636 @kindex maint print register-groups
39637 @kindex maint print remote-registers
39638 @item maint print registers @r{[}@var{file}@r{]}
39639 @itemx maint print raw-registers @r{[}@var{file}@r{]}
39640 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
39641 @itemx maint print register-groups @r{[}@var{file}@r{]}
39642 @itemx maint print remote-registers @r{[}@var{file}@r{]}
39643 Print @value{GDBN}'s internal register data structures.
39645 The command @code{maint print raw-registers} includes the contents of
39646 the raw register cache; the command @code{maint print
39647 cooked-registers} includes the (cooked) value of all registers,
39648 including registers which aren't available on the target nor visible
39649 to user; the command @code{maint print register-groups} includes the
39650 groups that each register is a member of; and the command @code{maint
39651 print remote-registers} includes the remote target's register numbers
39652 and offsets in the `G' packets.
39654 These commands take an optional parameter, a file name to which to
39655 write the information.
39657 @kindex maint print reggroups
39658 @item maint print reggroups @r{[}@var{file}@r{]}
39659 Print @value{GDBN}'s internal register group data structures. The
39660 optional argument @var{file} tells to what file to write the
39663 The register groups info looks like this:
39666 (@value{GDBP}) @kbd{maint print reggroups}
39677 @kindex maint flush register-cache
39679 @cindex register cache, flushing
39680 @item maint flush register-cache
39682 Flush the contents of the register cache and as a consequence the
39683 frame cache. This command is useful when debugging issues related to
39684 register fetching, or frame unwinding. The command @code{flushregs}
39685 is deprecated in favor of @code{maint flush register-cache}.
39687 @kindex maint flush source-cache
39688 @cindex source code, caching
39689 @item maint flush source-cache
39690 Flush @value{GDBN}'s cache of source code file contents. After
39691 @value{GDBN} reads a source file, and optionally applies styling
39692 (@pxref{Output Styling}), the file contents are cached. This command
39693 clears that cache. The next time @value{GDBN} wants to show lines
39694 from a source file, the content will be re-read.
39696 This command is useful when debugging issues related to source code
39697 styling. After flushing the cache any source code displayed by
39698 @value{GDBN} will be re-read and re-styled.
39700 @kindex maint print objfiles
39701 @cindex info for known object files
39702 @item maint print objfiles @r{[}@var{regexp}@r{]}
39703 Print a dump of all known object files.
39704 If @var{regexp} is specified, only print object files whose names
39705 match @var{regexp}. For each object file, this command prints its name,
39706 address in memory, and all of its psymtabs and symtabs.
39708 @kindex maint print user-registers
39709 @cindex user registers
39710 @item maint print user-registers
39711 List all currently available @dfn{user registers}. User registers
39712 typically provide alternate names for actual hardware registers. They
39713 include the four ``standard'' registers @code{$fp}, @code{$pc},
39714 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
39715 registers can be used in expressions in the same way as the canonical
39716 register names, but only the latter are listed by the @code{info
39717 registers} and @code{maint print registers} commands.
39719 @kindex maint print section-scripts
39720 @cindex info for known .debug_gdb_scripts-loaded scripts
39721 @item maint print section-scripts [@var{regexp}]
39722 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
39723 If @var{regexp} is specified, only print scripts loaded by object files
39724 matching @var{regexp}.
39725 For each script, this command prints its name as specified in the objfile,
39726 and the full path if known.
39727 @xref{dotdebug_gdb_scripts section}.
39729 @kindex maint print statistics
39730 @cindex bcache statistics
39731 @item maint print statistics
39732 This command prints, for each object file in the program, various data
39733 about that object file followed by the byte cache (@dfn{bcache})
39734 statistics for the object file. The objfile data includes the number
39735 of minimal, partial, full, and stabs symbols, the number of types
39736 defined by the objfile, the number of as yet unexpanded psym tables,
39737 the number of line tables and string tables, and the amount of memory
39738 used by the various tables. The bcache statistics include the counts,
39739 sizes, and counts of duplicates of all and unique objects, max,
39740 average, and median entry size, total memory used and its overhead and
39741 savings, and various measures of the hash table size and chain
39744 @kindex maint print target-stack
39745 @cindex target stack description
39746 @item maint print target-stack
39747 A @dfn{target} is an interface between the debugger and a particular
39748 kind of file or process. Targets can be stacked in @dfn{strata},
39749 so that more than one target can potentially respond to a request.
39750 In particular, memory accesses will walk down the stack of targets
39751 until they find a target that is interested in handling that particular
39754 This command prints a short description of each layer that was pushed on
39755 the @dfn{target stack}, starting from the top layer down to the bottom one.
39757 @kindex maint print type
39758 @cindex type chain of a data type
39759 @item maint print type @var{expr}
39760 Print the type chain for a type specified by @var{expr}. The argument
39761 can be either a type name or a symbol. If it is a symbol, the type of
39762 that symbol is described. The type chain produced by this command is
39763 a recursive definition of the data type as stored in @value{GDBN}'s
39764 data structures, including its flags and contained types.
39766 @kindex maint selftest
39768 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
39769 Run any self tests that were compiled in to @value{GDBN}. This will
39770 print a message showing how many tests were run, and how many failed.
39771 If a @var{filter} is passed, only the tests with @var{filter} in their
39772 name will be ran. If @code{-verbose} is passed, the self tests can be
39775 @kindex maint set selftest verbose
39776 @kindex maint show selftest verbose
39778 @item maint set selftest verbose
39779 @item maint show selftest verbose
39780 Control whether self tests are run verbosely or not.
39782 @kindex maint info selftests
39784 @item maint info selftests
39785 List the selftests compiled in to @value{GDBN}.
39787 @kindex maint set dwarf always-disassemble
39788 @kindex maint show dwarf always-disassemble
39789 @item maint set dwarf always-disassemble
39790 @item maint show dwarf always-disassemble
39791 Control the behavior of @code{info address} when using DWARF debugging
39794 The default is @code{off}, which means that @value{GDBN} should try to
39795 describe a variable's location in an easily readable format. When
39796 @code{on}, @value{GDBN} will instead display the DWARF location
39797 expression in an assembly-like format. Note that some locations are
39798 too complex for @value{GDBN} to describe simply; in this case you will
39799 always see the disassembly form.
39801 Here is an example of the resulting disassembly:
39804 (gdb) info addr argc
39805 Symbol "argc" is a complex DWARF expression:
39809 For more information on these expressions, see
39810 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39812 @kindex maint set dwarf max-cache-age
39813 @kindex maint show dwarf max-cache-age
39814 @item maint set dwarf max-cache-age
39815 @itemx maint show dwarf max-cache-age
39816 Control the DWARF compilation unit cache.
39818 @cindex DWARF compilation units cache
39819 In object files with inter-compilation-unit references, such as those
39820 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39821 reader needs to frequently refer to previously read compilation units.
39822 This setting controls how long a compilation unit will remain in the
39823 cache if it is not referenced. A higher limit means that cached
39824 compilation units will be stored in memory longer, and more total
39825 memory will be used. Setting it to zero disables caching, which will
39826 slow down @value{GDBN} startup, but reduce memory consumption.
39828 @kindex maint set dwarf unwinders
39829 @kindex maint show dwarf unwinders
39830 @item maint set dwarf unwinders
39831 @itemx maint show dwarf unwinders
39832 Control use of the DWARF frame unwinders.
39834 @cindex DWARF frame unwinders
39835 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39836 frame unwinders to build the backtrace. Many of these targets will
39837 also have a second mechanism for building the backtrace for use in
39838 cases where DWARF information is not available, this second mechanism
39839 is often an analysis of a function's prologue.
39841 In order to extend testing coverage of the second level stack
39842 unwinding mechanisms it is helpful to be able to disable the DWARF
39843 stack unwinders, this can be done with this switch.
39845 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39846 advisable, there are cases that are better handled through DWARF than
39847 prologue analysis, and the debug experience is likely to be better
39848 with the DWARF frame unwinders enabled.
39850 If DWARF frame unwinders are not supported for a particular target
39851 architecture, then enabling this flag does not cause them to be used.
39853 @kindex maint set worker-threads
39854 @kindex maint show worker-threads
39855 @item maint set worker-threads
39856 @item maint show worker-threads
39857 Control the number of worker threads that may be used by @value{GDBN}.
39858 On capable hosts, @value{GDBN} may use multiple threads to speed up
39859 certain CPU-intensive operations, such as demangling symbol names.
39860 While the number of threads used by @value{GDBN} may vary, this
39861 command can be used to set an upper bound on this number. The default
39862 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39863 number. Note that this only controls worker threads started by
39864 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39867 @kindex maint set profile
39868 @kindex maint show profile
39869 @cindex profiling GDB
39870 @item maint set profile
39871 @itemx maint show profile
39872 Control profiling of @value{GDBN}.
39874 Profiling will be disabled until you use the @samp{maint set profile}
39875 command to enable it. When you enable profiling, the system will begin
39876 collecting timing and execution count data; when you disable profiling or
39877 exit @value{GDBN}, the results will be written to a log file. Remember that
39878 if you use profiling, @value{GDBN} will overwrite the profiling log file
39879 (often called @file{gmon.out}). If you have a record of important profiling
39880 data in a @file{gmon.out} file, be sure to move it to a safe location.
39882 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
39883 compiled with the @samp{-pg} compiler option.
39885 @kindex maint set show-debug-regs
39886 @kindex maint show show-debug-regs
39887 @cindex hardware debug registers
39888 @item maint set show-debug-regs
39889 @itemx maint show show-debug-regs
39890 Control whether to show variables that mirror the hardware debug
39891 registers. Use @code{on} to enable, @code{off} to disable. If
39892 enabled, the debug registers values are shown when @value{GDBN} inserts or
39893 removes a hardware breakpoint or watchpoint, and when the inferior
39894 triggers a hardware-assisted breakpoint or watchpoint.
39896 @kindex maint set show-all-tib
39897 @kindex maint show show-all-tib
39898 @item maint set show-all-tib
39899 @itemx maint show show-all-tib
39900 Control whether to show all non zero areas within a 1k block starting
39901 at thread local base, when using the @samp{info w32 thread-information-block}
39904 @kindex maint set target-async
39905 @kindex maint show target-async
39906 @item maint set target-async
39907 @itemx maint show target-async
39908 This controls whether @value{GDBN} targets operate in synchronous or
39909 asynchronous mode (@pxref{Background Execution}). Normally the
39910 default is asynchronous, if it is available; but this can be changed
39911 to more easily debug problems occurring only in synchronous mode.
39913 @kindex maint set target-non-stop @var{mode} [on|off|auto]
39914 @kindex maint show target-non-stop
39915 @item maint set target-non-stop
39916 @itemx maint show target-non-stop
39918 This controls whether @value{GDBN} targets always operate in non-stop
39919 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
39920 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
39921 if supported by the target.
39924 @item maint set target-non-stop auto
39925 This is the default mode. @value{GDBN} controls the target in
39926 non-stop mode if the target supports it.
39928 @item maint set target-non-stop on
39929 @value{GDBN} controls the target in non-stop mode even if the target
39930 does not indicate support.
39932 @item maint set target-non-stop off
39933 @value{GDBN} does not control the target in non-stop mode even if the
39934 target supports it.
39937 @kindex maint set tui-resize-message
39938 @kindex maint show tui-resize-message
39939 @item maint set tui-resize-message
39940 @item maint show tui-resize-message
39941 Control whether @value{GDBN} displays a message each time the terminal
39942 is resized when in TUI mode. The default is @code{off}, which means
39943 that @value{GDBN} is silent during resizes. When @code{on},
39944 @value{GDBN} will display a message after a resize is completed; the
39945 message will include a number indicating how many times the terminal
39946 has been resized. This setting is intended for use by the test suite,
39947 where it would otherwise be difficult to determine when a resize and
39948 refresh has been completed.
39950 @kindex maint set per-command
39951 @kindex maint show per-command
39952 @item maint set per-command
39953 @itemx maint show per-command
39954 @cindex resources used by commands
39956 @value{GDBN} can display the resources used by each command.
39957 This is useful in debugging performance problems.
39960 @item maint set per-command space [on|off]
39961 @itemx maint show per-command space
39962 Enable or disable the printing of the memory used by GDB for each command.
39963 If enabled, @value{GDBN} will display how much memory each command
39964 took, following the command's own output.
39965 This can also be requested by invoking @value{GDBN} with the
39966 @option{--statistics} command-line switch (@pxref{Mode Options}).
39968 @item maint set per-command time [on|off]
39969 @itemx maint show per-command time
39970 Enable or disable the printing of the execution time of @value{GDBN}
39972 If enabled, @value{GDBN} will display how much time it
39973 took to execute each command, following the command's own output.
39974 Both CPU time and wallclock time are printed.
39975 Printing both is useful when trying to determine whether the cost is
39976 CPU or, e.g., disk/network latency.
39977 Note that the CPU time printed is for @value{GDBN} only, it does not include
39978 the execution time of the inferior because there's no mechanism currently
39979 to compute how much time was spent by @value{GDBN} and how much time was
39980 spent by the program been debugged.
39981 This can also be requested by invoking @value{GDBN} with the
39982 @option{--statistics} command-line switch (@pxref{Mode Options}).
39984 @item maint set per-command symtab [on|off]
39985 @itemx maint show per-command symtab
39986 Enable or disable the printing of basic symbol table statistics
39988 If enabled, @value{GDBN} will display the following information:
39992 number of symbol tables
39994 number of primary symbol tables
39996 number of blocks in the blockvector
40000 @kindex maint set check-libthread-db
40001 @kindex maint show check-libthread-db
40002 @item maint set check-libthread-db [on|off]
40003 @itemx maint show check-libthread-db
40004 Control whether @value{GDBN} should run integrity checks on inferior
40005 specific thread debugging libraries as they are loaded. The default
40006 is not to perform such checks. If any check fails @value{GDBN} will
40007 unload the library and continue searching for a suitable candidate as
40008 described in @ref{set libthread-db-search-path}. For more information
40009 about the tests, see @ref{maint check libthread-db}.
40011 @kindex maint set gnu-source-highlight enabled
40012 @kindex maint show gnu-source-highlight enabled
40013 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40014 @itemx maint show gnu-source-highlight enabled
40015 Control whether @value{GDBN} should use the GNU Source Highlight
40016 library for applying styling to source code (@pxref{Output Styling}).
40017 This will be @samp{on} by default if the GNU Source Highlight library
40018 is available. If the GNU Source Highlight library is not available,
40019 then this will be @samp{off} by default, and attempting to change this
40020 value to @samp{on} will give an error.
40022 If the GNU Source Highlight library is not being used, then
40023 @value{GDBN} will use the Python Pygments package for source code
40024 styling, if it is available.
40026 This option is useful for debugging @value{GDBN}'s use of the Pygments
40027 library when @value{GDBN} is linked against the GNU Source Highlight
40030 @kindex maint space
40031 @cindex memory used by commands
40032 @item maint space @var{value}
40033 An alias for @code{maint set per-command space}.
40034 A non-zero value enables it, zero disables it.
40037 @cindex time of command execution
40038 @item maint time @var{value}
40039 An alias for @code{maint set per-command time}.
40040 A non-zero value enables it, zero disables it.
40042 @kindex maint translate-address
40043 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40044 Find the symbol stored at the location specified by the address
40045 @var{addr} and an optional section name @var{section}. If found,
40046 @value{GDBN} prints the name of the closest symbol and an offset from
40047 the symbol's location to the specified address. This is similar to
40048 the @code{info address} command (@pxref{Symbols}), except that this
40049 command also allows to find symbols in other sections.
40051 If section was not specified, the section in which the symbol was found
40052 is also printed. For dynamically linked executables, the name of
40053 executable or shared library containing the symbol is printed as well.
40055 @kindex maint test-options
40056 @item maint test-options require-delimiter
40057 @itemx maint test-options unknown-is-error
40058 @itemx maint test-options unknown-is-operand
40059 These commands are used by the testsuite to validate the command
40060 options framework. The @code{require-delimiter} variant requires a
40061 double-dash delimiter to indicate end of options. The
40062 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40063 @code{unknown-is-error} variant throws an error on unknown option,
40064 while @code{unknown-is-operand} treats unknown options as the start of
40065 the command's operands. When run, the commands output the result of
40066 the processed options. When completed, the commands store the
40067 internal result of completion in a variable exposed by the @code{maint
40068 show test-options-completion-result} command.
40070 @kindex maint show test-options-completion-result
40071 @item maint show test-options-completion-result
40072 Shows the result of completing the @code{maint test-options}
40073 subcommands. This is used by the testsuite to validate completion
40074 support in the command options framework.
40076 @kindex maint set test-settings
40077 @kindex maint show test-settings
40078 @item maint set test-settings @var{kind}
40079 @itemx maint show test-settings @var{kind}
40080 These are representative commands for each @var{kind} of setting type
40081 @value{GDBN} supports. They are used by the testsuite for exercising
40082 the settings infrastructure.
40084 @kindex maint set backtrace-on-fatal-signal
40085 @kindex maint show backtrace-on-fatal-signal
40086 @item maint set backtrace-on-fatal-signal [on|off]
40087 @itemx maint show backtrace-on-fatal-signal
40088 When this setting is @code{on}, if @value{GDBN} itself terminates with
40089 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40090 printed to the standard error stream. This backtrace can be used to
40091 help diagnose crashes within @value{GDBN} in situations where a user
40092 is unable to share a corefile with the @value{GDBN} developers.
40094 If the functionality to provide this backtrace is not available for
40095 the platform on which GDB is running then this feature will be
40096 @code{off} by default, and attempting to turn this feature on will
40099 For platforms that do support creating the backtrace this feature is
40100 @code{on} by default.
40103 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40104 Like the @code{with} command, but works with @code{maintenance set}
40105 variables. This is used by the testsuite to exercise the @code{with}
40106 command's infrastructure.
40110 The following command is useful for non-interactive invocations of
40111 @value{GDBN}, such as in the test suite.
40114 @item set watchdog @var{nsec}
40115 @kindex set watchdog
40116 @cindex watchdog timer
40117 @cindex timeout for commands
40118 Set the maximum number of seconds @value{GDBN} will wait for the
40119 target operation to finish. If this time expires, @value{GDBN}
40120 reports and error and the command is aborted.
40122 @item show watchdog
40123 Show the current setting of the target wait timeout.
40126 @node Remote Protocol
40127 @appendix @value{GDBN} Remote Serial Protocol
40132 * Stop Reply Packets::
40133 * General Query Packets::
40134 * Architecture-Specific Protocol Details::
40135 * Tracepoint Packets::
40136 * Host I/O Packets::
40138 * Notification Packets::
40139 * Remote Non-Stop::
40140 * Packet Acknowledgment::
40142 * File-I/O Remote Protocol Extension::
40143 * Library List Format::
40144 * Library List Format for SVR4 Targets::
40145 * Memory Map Format::
40146 * Thread List Format::
40147 * Traceframe Info Format::
40148 * Branch Trace Format::
40149 * Branch Trace Configuration Format::
40155 There may be occasions when you need to know something about the
40156 protocol---for example, if there is only one serial port to your target
40157 machine, you might want your program to do something special if it
40158 recognizes a packet meant for @value{GDBN}.
40160 In the examples below, @samp{->} and @samp{<-} are used to indicate
40161 transmitted and received data, respectively.
40163 @cindex protocol, @value{GDBN} remote serial
40164 @cindex serial protocol, @value{GDBN} remote
40165 @cindex remote serial protocol
40166 All @value{GDBN} commands and responses (other than acknowledgments
40167 and notifications, see @ref{Notification Packets}) are sent as a
40168 @var{packet}. A @var{packet} is introduced with the character
40169 @samp{$}, the actual @var{packet-data}, and the terminating character
40170 @samp{#} followed by a two-digit @var{checksum}:
40173 @code{$}@var{packet-data}@code{#}@var{checksum}
40177 @cindex checksum, for @value{GDBN} remote
40179 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40180 characters between the leading @samp{$} and the trailing @samp{#} (an
40181 eight bit unsigned checksum).
40183 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40184 specification also included an optional two-digit @var{sequence-id}:
40187 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40190 @cindex sequence-id, for @value{GDBN} remote
40192 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40193 has never output @var{sequence-id}s. Stubs that handle packets added
40194 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40196 When either the host or the target machine receives a packet, the first
40197 response expected is an acknowledgment: either @samp{+} (to indicate
40198 the package was received correctly) or @samp{-} (to request
40202 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40207 The @samp{+}/@samp{-} acknowledgments can be disabled
40208 once a connection is established.
40209 @xref{Packet Acknowledgment}, for details.
40211 The host (@value{GDBN}) sends @var{command}s, and the target (the
40212 debugging stub incorporated in your program) sends a @var{response}. In
40213 the case of step and continue @var{command}s, the response is only sent
40214 when the operation has completed, and the target has again stopped all
40215 threads in all attached processes. This is the default all-stop mode
40216 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40217 execution mode; see @ref{Remote Non-Stop}, for details.
40219 @var{packet-data} consists of a sequence of characters with the
40220 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40223 @cindex remote protocol, field separator
40224 Fields within the packet should be separated using @samp{,} @samp{;} or
40225 @samp{:}. Except where otherwise noted all numbers are represented in
40226 @sc{hex} with leading zeros suppressed.
40228 Implementors should note that prior to @value{GDBN} 5.0, the character
40229 @samp{:} could not appear as the third character in a packet (as it
40230 would potentially conflict with the @var{sequence-id}).
40232 @cindex remote protocol, binary data
40233 @anchor{Binary Data}
40234 Binary data in most packets is encoded either as two hexadecimal
40235 digits per byte of binary data. This allowed the traditional remote
40236 protocol to work over connections which were only seven-bit clean.
40237 Some packets designed more recently assume an eight-bit clean
40238 connection, and use a more efficient encoding to send and receive
40241 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40242 as an escape character. Any escaped byte is transmitted as the escape
40243 character followed by the original character XORed with @code{0x20}.
40244 For example, the byte @code{0x7d} would be transmitted as the two
40245 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40246 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40247 @samp{@}}) must always be escaped. Responses sent by the stub
40248 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40249 is not interpreted as the start of a run-length encoded sequence
40252 Response @var{data} can be run-length encoded to save space.
40253 Run-length encoding replaces runs of identical characters with one
40254 instance of the repeated character, followed by a @samp{*} and a
40255 repeat count. The repeat count is itself sent encoded, to avoid
40256 binary characters in @var{data}: a value of @var{n} is sent as
40257 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40258 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40259 code 32) for a repeat count of 3. (This is because run-length
40260 encoding starts to win for counts 3 or more.) Thus, for example,
40261 @samp{0* } is a run-length encoding of ``0000'': the space character
40262 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40265 The printable characters @samp{#} and @samp{$} or with a numeric value
40266 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40267 seven repeats (@samp{$}) can be expanded using a repeat count of only
40268 five (@samp{"}). For example, @samp{00000000} can be encoded as
40271 The error response returned for some packets includes a two character
40272 error number. That number is not well defined.
40274 @cindex empty response, for unsupported packets
40275 For any @var{command} not supported by the stub, an empty response
40276 (@samp{$#00}) should be returned. That way it is possible to extend the
40277 protocol. A newer @value{GDBN} can tell if a packet is supported based
40280 At a minimum, a stub is required to support the @samp{?} command to
40281 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40282 commands for register access, and the @samp{m} and @samp{M} commands
40283 for memory access. Stubs that only control single-threaded targets
40284 can implement run control with the @samp{c} (continue) command, and if
40285 the target architecture supports hardware-assisted single-stepping,
40286 the @samp{s} (step) command. Stubs that support multi-threading
40287 targets should support the @samp{vCont} command. All other commands
40293 The following table provides a complete list of all currently defined
40294 @var{command}s and their corresponding response @var{data}.
40295 @xref{File-I/O Remote Protocol Extension}, for details about the File
40296 I/O extension of the remote protocol.
40298 Each packet's description has a template showing the packet's overall
40299 syntax, followed by an explanation of the packet's meaning. We
40300 include spaces in some of the templates for clarity; these are not
40301 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40302 separate its components. For example, a template like @samp{foo
40303 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40304 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40305 @var{baz}. @value{GDBN} does not transmit a space character between the
40306 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40309 @cindex @var{thread-id}, in remote protocol
40310 @anchor{thread-id syntax}
40311 Several packets and replies include a @var{thread-id} field to identify
40312 a thread. Normally these are positive numbers with a target-specific
40313 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40314 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40317 In addition, the remote protocol supports a multiprocess feature in
40318 which the @var{thread-id} syntax is extended to optionally include both
40319 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40320 The @var{pid} (process) and @var{tid} (thread) components each have the
40321 format described above: a positive number with target-specific
40322 interpretation formatted as a big-endian hex string, literal @samp{-1}
40323 to indicate all processes or threads (respectively), or @samp{0} to
40324 indicate an arbitrary process or thread. Specifying just a process, as
40325 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40326 error to specify all processes but a specific thread, such as
40327 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40328 for those packets and replies explicitly documented to include a process
40329 ID, rather than a @var{thread-id}.
40331 The multiprocess @var{thread-id} syntax extensions are only used if both
40332 @value{GDBN} and the stub report support for the @samp{multiprocess}
40333 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40336 Note that all packet forms beginning with an upper- or lower-case
40337 letter, other than those described here, are reserved for future use.
40339 Here are the packet descriptions.
40344 @cindex @samp{!} packet
40345 @anchor{extended mode}
40346 Enable extended mode. In extended mode, the remote server is made
40347 persistent. The @samp{R} packet is used to restart the program being
40353 The remote target both supports and has enabled extended mode.
40357 @cindex @samp{?} packet
40359 This is sent when connection is first established to query the reason
40360 the target halted. The reply is the same as for step and continue.
40361 This packet has a special interpretation when the target is in
40362 non-stop mode; see @ref{Remote Non-Stop}.
40365 @xref{Stop Reply Packets}, for the reply specifications.
40367 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40368 @cindex @samp{A} packet
40369 Initialized @code{argv[]} array passed into program. @var{arglen}
40370 specifies the number of bytes in the hex encoded byte stream
40371 @var{arg}. See @code{gdbserver} for more details.
40376 The arguments were set.
40382 @cindex @samp{b} packet
40383 (Don't use this packet; its behavior is not well-defined.)
40384 Change the serial line speed to @var{baud}.
40386 JTC: @emph{When does the transport layer state change? When it's
40387 received, or after the ACK is transmitted. In either case, there are
40388 problems if the command or the acknowledgment packet is dropped.}
40390 Stan: @emph{If people really wanted to add something like this, and get
40391 it working for the first time, they ought to modify ser-unix.c to send
40392 some kind of out-of-band message to a specially-setup stub and have the
40393 switch happen "in between" packets, so that from remote protocol's point
40394 of view, nothing actually happened.}
40396 @item B @var{addr},@var{mode}
40397 @cindex @samp{B} packet
40398 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40399 breakpoint at @var{addr}.
40401 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40402 (@pxref{insert breakpoint or watchpoint packet}).
40404 @cindex @samp{bc} packet
40407 Backward continue. Execute the target system in reverse. No parameter.
40408 @xref{Reverse Execution}, for more information.
40411 @xref{Stop Reply Packets}, for the reply specifications.
40413 @cindex @samp{bs} packet
40416 Backward single step. Execute one instruction in reverse. No parameter.
40417 @xref{Reverse Execution}, for more information.
40420 @xref{Stop Reply Packets}, for the reply specifications.
40422 @item c @r{[}@var{addr}@r{]}
40423 @cindex @samp{c} packet
40424 Continue at @var{addr}, which is the address to resume. If @var{addr}
40425 is omitted, resume at current address.
40427 This packet is deprecated for multi-threading support. @xref{vCont
40431 @xref{Stop Reply Packets}, for the reply specifications.
40433 @item C @var{sig}@r{[};@var{addr}@r{]}
40434 @cindex @samp{C} packet
40435 Continue with signal @var{sig} (hex signal number). If
40436 @samp{;@var{addr}} is omitted, resume at same address.
40438 This packet is deprecated for multi-threading support. @xref{vCont
40442 @xref{Stop Reply Packets}, for the reply specifications.
40445 @cindex @samp{d} packet
40448 Don't use this packet; instead, define a general set packet
40449 (@pxref{General Query Packets}).
40453 @cindex @samp{D} packet
40454 The first form of the packet is used to detach @value{GDBN} from the
40455 remote system. It is sent to the remote target
40456 before @value{GDBN} disconnects via the @code{detach} command.
40458 The second form, including a process ID, is used when multiprocess
40459 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40460 detach only a specific process. The @var{pid} is specified as a
40461 big-endian hex string.
40471 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40472 @cindex @samp{F} packet
40473 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40474 This is part of the File-I/O protocol extension. @xref{File-I/O
40475 Remote Protocol Extension}, for the specification.
40478 @anchor{read registers packet}
40479 @cindex @samp{g} packet
40480 Read general registers.
40484 @item @var{XX@dots{}}
40485 Each byte of register data is described by two hex digits. The bytes
40486 with the register are transmitted in target byte order. The size of
40487 each register and their position within the @samp{g} packet are
40488 determined by the @value{GDBN} internal gdbarch functions
40489 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40491 When reading registers from a trace frame (@pxref{Analyze Collected
40492 Data,,Using the Collected Data}), the stub may also return a string of
40493 literal @samp{x}'s in place of the register data digits, to indicate
40494 that the corresponding register has not been collected, thus its value
40495 is unavailable. For example, for an architecture with 4 registers of
40496 4 bytes each, the following reply indicates to @value{GDBN} that
40497 registers 0 and 2 have not been collected, while registers 1 and 3
40498 have been collected, and both have zero value:
40502 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40509 @item G @var{XX@dots{}}
40510 @cindex @samp{G} packet
40511 Write general registers. @xref{read registers packet}, for a
40512 description of the @var{XX@dots{}} data.
40522 @item H @var{op} @var{thread-id}
40523 @cindex @samp{H} packet
40524 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40525 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40526 should be @samp{c} for step and continue operations (note that this
40527 is deprecated, supporting the @samp{vCont} command is a better
40528 option), and @samp{g} for other operations. The thread designator
40529 @var{thread-id} has the format and interpretation described in
40530 @ref{thread-id syntax}.
40541 @c 'H': How restrictive (or permissive) is the thread model. If a
40542 @c thread is selected and stopped, are other threads allowed
40543 @c to continue to execute? As I mentioned above, I think the
40544 @c semantics of each command when a thread is selected must be
40545 @c described. For example:
40547 @c 'g': If the stub supports threads and a specific thread is
40548 @c selected, returns the register block from that thread;
40549 @c otherwise returns current registers.
40551 @c 'G' If the stub supports threads and a specific thread is
40552 @c selected, sets the registers of the register block of
40553 @c that thread; otherwise sets current registers.
40555 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40556 @anchor{cycle step packet}
40557 @cindex @samp{i} packet
40558 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40559 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40560 step starting at that address.
40563 @cindex @samp{I} packet
40564 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40568 @cindex @samp{k} packet
40571 The exact effect of this packet is not specified.
40573 For a bare-metal target, it may power cycle or reset the target
40574 system. For that reason, the @samp{k} packet has no reply.
40576 For a single-process target, it may kill that process if possible.
40578 A multiple-process target may choose to kill just one process, or all
40579 that are under @value{GDBN}'s control. For more precise control, use
40580 the vKill packet (@pxref{vKill packet}).
40582 If the target system immediately closes the connection in response to
40583 @samp{k}, @value{GDBN} does not consider the lack of packet
40584 acknowledgment to be an error, and assumes the kill was successful.
40586 If connected using @kbd{target extended-remote}, and the target does
40587 not close the connection in response to a kill request, @value{GDBN}
40588 probes the target state as if a new connection was opened
40589 (@pxref{? packet}).
40591 @item m @var{addr},@var{length}
40592 @cindex @samp{m} packet
40593 Read @var{length} addressable memory units starting at address @var{addr}
40594 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40595 any particular boundary.
40597 The stub need not use any particular size or alignment when gathering
40598 data from memory for the response; even if @var{addr} is word-aligned
40599 and @var{length} is a multiple of the word size, the stub is free to
40600 use byte accesses, or not. For this reason, this packet may not be
40601 suitable for accessing memory-mapped I/O devices.
40602 @cindex alignment of remote memory accesses
40603 @cindex size of remote memory accesses
40604 @cindex memory, alignment and size of remote accesses
40608 @item @var{XX@dots{}}
40609 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40610 The reply may contain fewer addressable memory units than requested if the
40611 server was able to read only part of the region of memory.
40616 @item M @var{addr},@var{length}:@var{XX@dots{}}
40617 @cindex @samp{M} packet
40618 Write @var{length} addressable memory units starting at address @var{addr}
40619 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
40620 byte is transmitted as a two-digit hexadecimal number.
40627 for an error (this includes the case where only part of the data was
40632 @cindex @samp{p} packet
40633 Read the value of register @var{n}; @var{n} is in hex.
40634 @xref{read registers packet}, for a description of how the returned
40635 register value is encoded.
40639 @item @var{XX@dots{}}
40640 the register's value
40644 Indicating an unrecognized @var{query}.
40647 @item P @var{n@dots{}}=@var{r@dots{}}
40648 @anchor{write register packet}
40649 @cindex @samp{P} packet
40650 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
40651 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
40652 digits for each byte in the register (target byte order).
40662 @item q @var{name} @var{params}@dots{}
40663 @itemx Q @var{name} @var{params}@dots{}
40664 @cindex @samp{q} packet
40665 @cindex @samp{Q} packet
40666 General query (@samp{q}) and set (@samp{Q}). These packets are
40667 described fully in @ref{General Query Packets}.
40670 @cindex @samp{r} packet
40671 Reset the entire system.
40673 Don't use this packet; use the @samp{R} packet instead.
40676 @cindex @samp{R} packet
40677 Restart the program being debugged. The @var{XX}, while needed, is ignored.
40678 This packet is only available in extended mode (@pxref{extended mode}).
40680 The @samp{R} packet has no reply.
40682 @item s @r{[}@var{addr}@r{]}
40683 @cindex @samp{s} packet
40684 Single step, resuming at @var{addr}. If
40685 @var{addr} is omitted, resume at same address.
40687 This packet is deprecated for multi-threading support. @xref{vCont
40691 @xref{Stop Reply Packets}, for the reply specifications.
40693 @item S @var{sig}@r{[};@var{addr}@r{]}
40694 @anchor{step with signal packet}
40695 @cindex @samp{S} packet
40696 Step with signal. This is analogous to the @samp{C} packet, but
40697 requests a single-step, rather than a normal resumption of execution.
40699 This packet is deprecated for multi-threading support. @xref{vCont
40703 @xref{Stop Reply Packets}, for the reply specifications.
40705 @item t @var{addr}:@var{PP},@var{MM}
40706 @cindex @samp{t} packet
40707 Search backwards starting at address @var{addr} for a match with pattern
40708 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
40709 There must be at least 3 digits in @var{addr}.
40711 @item T @var{thread-id}
40712 @cindex @samp{T} packet
40713 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
40718 thread is still alive
40724 Packets starting with @samp{v} are identified by a multi-letter name,
40725 up to the first @samp{;} or @samp{?} (or the end of the packet).
40727 @item vAttach;@var{pid}
40728 @cindex @samp{vAttach} packet
40729 Attach to a new process with the specified process ID @var{pid}.
40730 The process ID is a
40731 hexadecimal integer identifying the process. In all-stop mode, all
40732 threads in the attached process are stopped; in non-stop mode, it may be
40733 attached without being stopped if that is supported by the target.
40735 @c In non-stop mode, on a successful vAttach, the stub should set the
40736 @c current thread to a thread of the newly-attached process. After
40737 @c attaching, GDB queries for the attached process's thread ID with qC.
40738 @c Also note that, from a user perspective, whether or not the
40739 @c target is stopped on attach in non-stop mode depends on whether you
40740 @c use the foreground or background version of the attach command, not
40741 @c on what vAttach does; GDB does the right thing with respect to either
40742 @c stopping or restarting threads.
40744 This packet is only available in extended mode (@pxref{extended mode}).
40750 @item @r{Any stop packet}
40751 for success in all-stop mode (@pxref{Stop Reply Packets})
40753 for success in non-stop mode (@pxref{Remote Non-Stop})
40756 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
40757 @cindex @samp{vCont} packet
40758 @anchor{vCont packet}
40759 Resume the inferior, specifying different actions for each thread.
40761 For each inferior thread, the leftmost action with a matching
40762 @var{thread-id} is applied. Threads that don't match any action
40763 remain in their current state. Thread IDs are specified using the
40764 syntax described in @ref{thread-id syntax}. If multiprocess
40765 extensions (@pxref{multiprocess extensions}) are supported, actions
40766 can be specified to match all threads in a process by using the
40767 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
40768 @var{thread-id} matches all threads. Specifying no actions is an
40771 Currently supported actions are:
40777 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
40781 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
40784 @item r @var{start},@var{end}
40785 Step once, and then keep stepping as long as the thread stops at
40786 addresses between @var{start} (inclusive) and @var{end} (exclusive).
40787 The remote stub reports a stop reply when either the thread goes out
40788 of the range or is stopped due to an unrelated reason, such as hitting
40789 a breakpoint. @xref{range stepping}.
40791 If the range is empty (@var{start} == @var{end}), then the action
40792 becomes equivalent to the @samp{s} action. In other words,
40793 single-step once, and report the stop (even if the stepped instruction
40794 jumps to @var{start}).
40796 (A stop reply may be sent at any point even if the PC is still within
40797 the stepping range; for example, it is valid to implement this packet
40798 in a degenerate way as a single instruction step operation.)
40802 The optional argument @var{addr} normally associated with the
40803 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
40804 not supported in @samp{vCont}.
40806 The @samp{t} action is only relevant in non-stop mode
40807 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
40808 A stop reply should be generated for any affected thread not already stopped.
40809 When a thread is stopped by means of a @samp{t} action,
40810 the corresponding stop reply should indicate that the thread has stopped with
40811 signal @samp{0}, regardless of whether the target uses some other signal
40812 as an implementation detail.
40814 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
40815 @samp{r} actions for threads that are already running. Conversely,
40816 the server must ignore @samp{t} actions for threads that are already
40819 @emph{Note:} In non-stop mode, a thread is considered running until
40820 @value{GDBN} acknowledges an asynchronous stop notification for it with
40821 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40823 The stub must support @samp{vCont} if it reports support for
40824 multiprocess extensions (@pxref{multiprocess extensions}).
40827 @xref{Stop Reply Packets}, for the reply specifications.
40830 @cindex @samp{vCont?} packet
40831 Request a list of actions supported by the @samp{vCont} packet.
40835 @item vCont@r{[};@var{action}@dots{}@r{]}
40836 The @samp{vCont} packet is supported. Each @var{action} is a supported
40837 command in the @samp{vCont} packet.
40839 The @samp{vCont} packet is not supported.
40842 @anchor{vCtrlC packet}
40844 @cindex @samp{vCtrlC} packet
40845 Interrupt remote target as if a control-C was pressed on the remote
40846 terminal. This is the equivalent to reacting to the @code{^C}
40847 (@samp{\003}, the control-C character) character in all-stop mode
40848 while the target is running, except this works in non-stop mode.
40849 @xref{interrupting remote targets}, for more info on the all-stop
40860 @item vFile:@var{operation}:@var{parameter}@dots{}
40861 @cindex @samp{vFile} packet
40862 Perform a file operation on the target system. For details,
40863 see @ref{Host I/O Packets}.
40865 @item vFlashErase:@var{addr},@var{length}
40866 @cindex @samp{vFlashErase} packet
40867 Direct the stub to erase @var{length} bytes of flash starting at
40868 @var{addr}. The region may enclose any number of flash blocks, but
40869 its start and end must fall on block boundaries, as indicated by the
40870 flash block size appearing in the memory map (@pxref{Memory Map
40871 Format}). @value{GDBN} groups flash memory programming operations
40872 together, and sends a @samp{vFlashDone} request after each group; the
40873 stub is allowed to delay erase operation until the @samp{vFlashDone}
40874 packet is received.
40884 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
40885 @cindex @samp{vFlashWrite} packet
40886 Direct the stub to write data to flash address @var{addr}. The data
40887 is passed in binary form using the same encoding as for the @samp{X}
40888 packet (@pxref{Binary Data}). The memory ranges specified by
40889 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
40890 not overlap, and must appear in order of increasing addresses
40891 (although @samp{vFlashErase} packets for higher addresses may already
40892 have been received; the ordering is guaranteed only between
40893 @samp{vFlashWrite} packets). If a packet writes to an address that was
40894 neither erased by a preceding @samp{vFlashErase} packet nor by some other
40895 target-specific method, the results are unpredictable.
40903 for vFlashWrite addressing non-flash memory
40909 @cindex @samp{vFlashDone} packet
40910 Indicate to the stub that flash programming operation is finished.
40911 The stub is permitted to delay or batch the effects of a group of
40912 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
40913 @samp{vFlashDone} packet is received. The contents of the affected
40914 regions of flash memory are unpredictable until the @samp{vFlashDone}
40915 request is completed.
40917 @item vKill;@var{pid}
40918 @cindex @samp{vKill} packet
40919 @anchor{vKill packet}
40920 Kill the process with the specified process ID @var{pid}, which is a
40921 hexadecimal integer identifying the process. This packet is used in
40922 preference to @samp{k} when multiprocess protocol extensions are
40923 supported; see @ref{multiprocess extensions}.
40933 @item vMustReplyEmpty
40934 @cindex @samp{vMustReplyEmpty} packet
40935 The correct reply to an unknown @samp{v} packet is to return the empty
40936 string, however, some older versions of @command{gdbserver} would
40937 incorrectly return @samp{OK} for unknown @samp{v} packets.
40939 The @samp{vMustReplyEmpty} is used as a feature test to check how
40940 @command{gdbserver} handles unknown packets, it is important that this
40941 packet be handled in the same way as other unknown @samp{v} packets.
40942 If this packet is handled differently to other unknown @samp{v}
40943 packets then it is possible that @value{GDBN} may run into problems in
40944 other areas, specifically around use of @samp{vFile:setfs:}.
40946 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
40947 @cindex @samp{vRun} packet
40948 Run the program @var{filename}, passing it each @var{argument} on its
40949 command line. The file and arguments are hex-encoded strings. If
40950 @var{filename} is an empty string, the stub may use a default program
40951 (e.g.@: the last program run). The program is created in the stopped
40954 @c FIXME: What about non-stop mode?
40956 This packet is only available in extended mode (@pxref{extended mode}).
40962 @item @r{Any stop packet}
40963 for success (@pxref{Stop Reply Packets})
40967 @cindex @samp{vStopped} packet
40968 @xref{Notification Packets}.
40970 @item X @var{addr},@var{length}:@var{XX@dots{}}
40972 @cindex @samp{X} packet
40973 Write data to memory, where the data is transmitted in binary.
40974 Memory is specified by its address @var{addr} and number of addressable memory
40975 units @var{length} (@pxref{addressable memory unit});
40976 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
40986 @item z @var{type},@var{addr},@var{kind}
40987 @itemx Z @var{type},@var{addr},@var{kind}
40988 @anchor{insert breakpoint or watchpoint packet}
40989 @cindex @samp{z} packet
40990 @cindex @samp{Z} packets
40991 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
40992 watchpoint starting at address @var{address} of kind @var{kind}.
40994 Each breakpoint and watchpoint packet @var{type} is documented
40997 @emph{Implementation notes: A remote target shall return an empty string
40998 for an unrecognized breakpoint or watchpoint packet @var{type}. A
40999 remote target shall support either both or neither of a given
41000 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41001 avoid potential problems with duplicate packets, the operations should
41002 be implemented in an idempotent way.}
41004 @item z0,@var{addr},@var{kind}
41005 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41006 @cindex @samp{z0} packet
41007 @cindex @samp{Z0} packet
41008 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41009 @var{addr} of type @var{kind}.
41011 A software breakpoint is implemented by replacing the instruction at
41012 @var{addr} with a software breakpoint or trap instruction. The
41013 @var{kind} is target-specific and typically indicates the size of the
41014 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41015 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41016 architectures have additional meanings for @var{kind}
41017 (@pxref{Architecture-Specific Protocol Details}); if no
41018 architecture-specific value is being used, it should be @samp{0}.
41019 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41020 conditional expressions in bytecode form that should be evaluated on
41021 the target's side. These are the conditions that should be taken into
41022 consideration when deciding if the breakpoint trigger should be
41023 reported back to @value{GDBN}.
41025 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41026 for how to best report a software breakpoint event to @value{GDBN}.
41028 The @var{cond_list} parameter is comprised of a series of expressions,
41029 concatenated without separators. Each expression has the following form:
41033 @item X @var{len},@var{expr}
41034 @var{len} is the length of the bytecode expression and @var{expr} is the
41035 actual conditional expression in bytecode form.
41039 The optional @var{cmd_list} parameter introduces commands that may be
41040 run on the target, rather than being reported back to @value{GDBN}.
41041 The parameter starts with a numeric flag @var{persist}; if the flag is
41042 nonzero, then the breakpoint may remain active and the commands
41043 continue to be run even when @value{GDBN} disconnects from the target.
41044 Following this flag is a series of expressions concatenated with no
41045 separators. Each expression has the following form:
41049 @item X @var{len},@var{expr}
41050 @var{len} is the length of the bytecode expression and @var{expr} is the
41051 actual commands expression in bytecode form.
41055 @emph{Implementation note: It is possible for a target to copy or move
41056 code that contains software breakpoints (e.g., when implementing
41057 overlays). The behavior of this packet, in the presence of such a
41058 target, is not defined.}
41070 @item z1,@var{addr},@var{kind}
41071 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41072 @cindex @samp{z1} packet
41073 @cindex @samp{Z1} packet
41074 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41075 address @var{addr}.
41077 A hardware breakpoint is implemented using a mechanism that is not
41078 dependent on being able to modify the target's memory. The
41079 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41080 same meaning as in @samp{Z0} packets.
41082 @emph{Implementation note: A hardware breakpoint is not affected by code
41095 @item z2,@var{addr},@var{kind}
41096 @itemx Z2,@var{addr},@var{kind}
41097 @cindex @samp{z2} packet
41098 @cindex @samp{Z2} packet
41099 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41100 The number of bytes to watch is specified by @var{kind}.
41112 @item z3,@var{addr},@var{kind}
41113 @itemx Z3,@var{addr},@var{kind}
41114 @cindex @samp{z3} packet
41115 @cindex @samp{Z3} packet
41116 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41117 The number of bytes to watch is specified by @var{kind}.
41129 @item z4,@var{addr},@var{kind}
41130 @itemx Z4,@var{addr},@var{kind}
41131 @cindex @samp{z4} packet
41132 @cindex @samp{Z4} packet
41133 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41134 The number of bytes to watch is specified by @var{kind}.
41148 @node Stop Reply Packets
41149 @section Stop Reply Packets
41150 @cindex stop reply packets
41152 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41153 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41154 receive any of the below as a reply. Except for @samp{?}
41155 and @samp{vStopped}, that reply is only returned
41156 when the target halts. In the below the exact meaning of @dfn{signal
41157 number} is defined by the header @file{include/gdb/signals.h} in the
41158 @value{GDBN} source code.
41160 In non-stop mode, the server will simply reply @samp{OK} to commands
41161 such as @samp{vCont}; any stop will be the subject of a future
41162 notification. @xref{Remote Non-Stop}.
41164 As in the description of request packets, we include spaces in the
41165 reply templates for clarity; these are not part of the reply packet's
41166 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41172 The program received signal number @var{AA} (a two-digit hexadecimal
41173 number). This is equivalent to a @samp{T} response with no
41174 @var{n}:@var{r} pairs.
41176 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41177 @cindex @samp{T} packet reply
41178 The program received signal number @var{AA} (a two-digit hexadecimal
41179 number). This is equivalent to an @samp{S} response, except that the
41180 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41181 and other information directly in the stop reply packet, reducing
41182 round-trip latency. Single-step and breakpoint traps are reported
41183 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41187 If @var{n} is a hexadecimal number, it is a register number, and the
41188 corresponding @var{r} gives that register's value. The data @var{r} is a
41189 series of bytes in target byte order, with each byte given by a
41190 two-digit hex number.
41193 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
41194 the stopped thread, as specified in @ref{thread-id syntax}.
41197 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41198 the core on which the stop event was detected.
41201 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41202 specific event that stopped the target. The currently defined stop
41203 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41204 signal. At most one stop reason should be present.
41207 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41208 and go on to the next; this allows us to extend the protocol in the
41212 The currently defined stop reasons are:
41218 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41221 @item syscall_entry
41222 @itemx syscall_return
41223 The packet indicates a syscall entry or return, and @var{r} is the
41224 syscall number, in hex.
41226 @cindex shared library events, remote reply
41228 The packet indicates that the loaded libraries have changed.
41229 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41230 list of loaded libraries. The @var{r} part is ignored.
41232 @cindex replay log events, remote reply
41234 The packet indicates that the target cannot continue replaying
41235 logged execution events, because it has reached the end (or the
41236 beginning when executing backward) of the log. The value of @var{r}
41237 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41238 for more information.
41241 @anchor{swbreak stop reason}
41242 The packet indicates a software breakpoint instruction was executed,
41243 irrespective of whether it was @value{GDBN} that planted the
41244 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41245 part must be left empty.
41247 On some architectures, such as x86, at the architecture level, when a
41248 breakpoint instruction executes the program counter points at the
41249 breakpoint address plus an offset. On such targets, the stub is
41250 responsible for adjusting the PC to point back at the breakpoint
41253 This packet should not be sent by default; older @value{GDBN} versions
41254 did not support it. @value{GDBN} requests it, by supplying an
41255 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41256 remote stub must also supply the appropriate @samp{qSupported} feature
41257 indicating support.
41259 This packet is required for correct non-stop mode operation.
41262 The packet indicates the target stopped for a hardware breakpoint.
41263 The @var{r} part must be left empty.
41265 The same remarks about @samp{qSupported} and non-stop mode above
41268 @cindex fork events, remote reply
41270 The packet indicates that @code{fork} was called, and @var{r}
41271 is the thread ID of the new child process. Refer to
41272 @ref{thread-id syntax} for the format of the @var{thread-id}
41273 field. This packet is only applicable to targets that support
41276 This packet should not be sent by default; older @value{GDBN} versions
41277 did not support it. @value{GDBN} requests it, by supplying an
41278 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41279 remote stub must also supply the appropriate @samp{qSupported} feature
41280 indicating support.
41282 @cindex vfork events, remote reply
41284 The packet indicates that @code{vfork} was called, and @var{r}
41285 is the thread ID of the new child process. Refer to
41286 @ref{thread-id syntax} for the format of the @var{thread-id}
41287 field. This packet is only applicable to targets that support
41290 This packet should not be sent by default; older @value{GDBN} versions
41291 did not support it. @value{GDBN} requests it, by supplying an
41292 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41293 remote stub must also supply the appropriate @samp{qSupported} feature
41294 indicating support.
41296 @cindex vforkdone events, remote reply
41298 The packet indicates that a child process created by a vfork
41299 has either called @code{exec} or terminated, so that the
41300 address spaces of the parent and child process are no longer
41301 shared. The @var{r} part is ignored. This packet is only
41302 applicable to targets that support vforkdone events.
41304 This packet should not be sent by default; older @value{GDBN} versions
41305 did not support it. @value{GDBN} requests it, by supplying an
41306 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41307 remote stub must also supply the appropriate @samp{qSupported} feature
41308 indicating support.
41310 @cindex exec events, remote reply
41312 The packet indicates that @code{execve} was called, and @var{r}
41313 is the absolute pathname of the file that was executed, in hex.
41314 This packet is only applicable to targets that support exec events.
41316 This packet should not be sent by default; older @value{GDBN} versions
41317 did not support it. @value{GDBN} requests it, by supplying an
41318 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41319 remote stub must also supply the appropriate @samp{qSupported} feature
41320 indicating support.
41322 @cindex thread create event, remote reply
41323 @anchor{thread create event}
41325 The packet indicates that the thread was just created. The new thread
41326 is stopped until @value{GDBN} sets it running with a resumption packet
41327 (@pxref{vCont packet}). This packet should not be sent by default;
41328 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41329 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41330 @var{r} part is ignored.
41335 @itemx W @var{AA} ; process:@var{pid}
41336 The process exited, and @var{AA} is the exit status. This is only
41337 applicable to certain targets.
41339 The second form of the response, including the process ID of the
41340 exited process, can be used only when @value{GDBN} has reported
41341 support for multiprocess protocol extensions; see @ref{multiprocess
41342 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41346 @itemx X @var{AA} ; process:@var{pid}
41347 The process terminated with signal @var{AA}.
41349 The second form of the response, including the process ID of the
41350 terminated process, can be used only when @value{GDBN} has reported
41351 support for multiprocess protocol extensions; see @ref{multiprocess
41352 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41355 @anchor{thread exit event}
41356 @cindex thread exit event, remote reply
41357 @item w @var{AA} ; @var{tid}
41359 The thread exited, and @var{AA} is the exit status. This response
41360 should not be sent by default; @value{GDBN} requests it with the
41361 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41362 @var{AA} is formatted as a big-endian hex string.
41365 There are no resumed threads left in the target. In other words, even
41366 though the process is alive, the last resumed thread has exited. For
41367 example, say the target process has two threads: thread 1 and thread
41368 2. The client leaves thread 1 stopped, and resumes thread 2, which
41369 subsequently exits. At this point, even though the process is still
41370 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41371 executing either. The @samp{N} stop reply thus informs the client
41372 that it can stop waiting for stop replies. This packet should not be
41373 sent by default; older @value{GDBN} versions did not support it.
41374 @value{GDBN} requests it, by supplying an appropriate
41375 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41376 also supply the appropriate @samp{qSupported} feature indicating
41379 @item O @var{XX}@dots{}
41380 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41381 written as the program's console output. This can happen at any time
41382 while the program is running and the debugger should continue to wait
41383 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41385 @item F @var{call-id},@var{parameter}@dots{}
41386 @var{call-id} is the identifier which says which host system call should
41387 be called. This is just the name of the function. Translation into the
41388 correct system call is only applicable as it's defined in @value{GDBN}.
41389 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41392 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41393 this very system call.
41395 The target replies with this packet when it expects @value{GDBN} to
41396 call a host system call on behalf of the target. @value{GDBN} replies
41397 with an appropriate @samp{F} packet and keeps up waiting for the next
41398 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41399 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41400 Protocol Extension}, for more details.
41404 @node General Query Packets
41405 @section General Query Packets
41406 @cindex remote query requests
41408 Packets starting with @samp{q} are @dfn{general query packets};
41409 packets starting with @samp{Q} are @dfn{general set packets}. General
41410 query and set packets are a semi-unified form for retrieving and
41411 sending information to and from the stub.
41413 The initial letter of a query or set packet is followed by a name
41414 indicating what sort of thing the packet applies to. For example,
41415 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41416 definitions with the stub. These packet names follow some
41421 The name must not contain commas, colons or semicolons.
41423 Most @value{GDBN} query and set packets have a leading upper case
41426 The names of custom vendor packets should use a company prefix, in
41427 lower case, followed by a period. For example, packets designed at
41428 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41429 foos) or @samp{Qacme.bar} (for setting bars).
41432 The name of a query or set packet should be separated from any
41433 parameters by a @samp{:}; the parameters themselves should be
41434 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41435 full packet name, and check for a separator or the end of the packet,
41436 in case two packet names share a common prefix. New packets should not begin
41437 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41438 packets predate these conventions, and have arguments without any terminator
41439 for the packet name; we suspect they are in widespread use in places that
41440 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41441 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41444 Like the descriptions of the other packets, each description here
41445 has a template showing the packet's overall syntax, followed by an
41446 explanation of the packet's meaning. We include spaces in some of the
41447 templates for clarity; these are not part of the packet's syntax. No
41448 @value{GDBN} packet uses spaces to separate its components.
41450 Here are the currently defined query and set packets:
41456 Turn on or off the agent as a helper to perform some debugging operations
41457 delegated from @value{GDBN} (@pxref{Control Agent}).
41459 @item QAllow:@var{op}:@var{val}@dots{}
41460 @cindex @samp{QAllow} packet
41461 Specify which operations @value{GDBN} expects to request of the
41462 target, as a semicolon-separated list of operation name and value
41463 pairs. Possible values for @var{op} include @samp{WriteReg},
41464 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41465 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41466 indicating that @value{GDBN} will not request the operation, or 1,
41467 indicating that it may. (The target can then use this to set up its
41468 own internals optimally, for instance if the debugger never expects to
41469 insert breakpoints, it may not need to install its own trap handler.)
41472 @cindex current thread, remote request
41473 @cindex @samp{qC} packet
41474 Return the current thread ID.
41478 @item QC @var{thread-id}
41479 Where @var{thread-id} is a thread ID as documented in
41480 @ref{thread-id syntax}.
41481 @item @r{(anything else)}
41482 Any other reply implies the old thread ID.
41485 @item qCRC:@var{addr},@var{length}
41486 @cindex CRC of memory block, remote request
41487 @cindex @samp{qCRC} packet
41488 @anchor{qCRC packet}
41489 Compute the CRC checksum of a block of memory using CRC-32 defined in
41490 IEEE 802.3. The CRC is computed byte at a time, taking the most
41491 significant bit of each byte first. The initial pattern code
41492 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41494 @emph{Note:} This is the same CRC used in validating separate debug
41495 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41496 Files}). However the algorithm is slightly different. When validating
41497 separate debug files, the CRC is computed taking the @emph{least}
41498 significant bit of each byte first, and the final result is inverted to
41499 detect trailing zeros.
41504 An error (such as memory fault)
41505 @item C @var{crc32}
41506 The specified memory region's checksum is @var{crc32}.
41509 @item QDisableRandomization:@var{value}
41510 @cindex disable address space randomization, remote request
41511 @cindex @samp{QDisableRandomization} packet
41512 Some target operating systems will randomize the virtual address space
41513 of the inferior process as a security feature, but provide a feature
41514 to disable such randomization, e.g.@: to allow for a more deterministic
41515 debugging experience. On such systems, this packet with a @var{value}
41516 of 1 directs the target to disable address space randomization for
41517 processes subsequently started via @samp{vRun} packets, while a packet
41518 with a @var{value} of 0 tells the target to enable address space
41521 This packet is only available in extended mode (@pxref{extended mode}).
41526 The request succeeded.
41529 An error occurred. The error number @var{nn} is given as hex digits.
41532 An empty reply indicates that @samp{QDisableRandomization} is not supported
41536 This packet is not probed by default; the remote stub must request it,
41537 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41538 This should only be done on targets that actually support disabling
41539 address space randomization.
41541 @item QStartupWithShell:@var{value}
41542 @cindex startup with shell, remote request
41543 @cindex @samp{QStartupWithShell} packet
41544 On UNIX-like targets, it is possible to start the inferior using a
41545 shell program. This is the default behavior on both @value{GDBN} and
41546 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41547 used to inform @command{gdbserver} whether it should start the
41548 inferior using a shell or not.
41550 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41551 to start the inferior. If @var{value} is @samp{1},
41552 @command{gdbserver} will use a shell to start the inferior. All other
41553 values are considered an error.
41555 This packet is only available in extended mode (@pxref{extended
41561 The request succeeded.
41564 An error occurred. The error number @var{nn} is given as hex digits.
41567 This packet is not probed by default; the remote stub must request it,
41568 by supplying an appropriate @samp{qSupported} response
41569 (@pxref{qSupported}). This should only be done on targets that
41570 actually support starting the inferior using a shell.
41572 Use of this packet is controlled by the @code{set startup-with-shell}
41573 command; @pxref{set startup-with-shell}.
41575 @item QEnvironmentHexEncoded:@var{hex-value}
41576 @anchor{QEnvironmentHexEncoded}
41577 @cindex set environment variable, remote request
41578 @cindex @samp{QEnvironmentHexEncoded} packet
41579 On UNIX-like targets, it is possible to set environment variables that
41580 will be passed to the inferior during the startup process. This
41581 packet is used to inform @command{gdbserver} of an environment
41582 variable that has been defined by the user on @value{GDBN} (@pxref{set
41585 The packet is composed by @var{hex-value}, an hex encoded
41586 representation of the @var{name=value} format representing an
41587 environment variable. The name of the environment variable is
41588 represented by @var{name}, and the value to be assigned to the
41589 environment variable is represented by @var{value}. If the variable
41590 has no value (i.e., the value is @code{null}), then @var{value} will
41593 This packet is only available in extended mode (@pxref{extended
41599 The request succeeded.
41602 This packet is not probed by default; the remote stub must request it,
41603 by supplying an appropriate @samp{qSupported} response
41604 (@pxref{qSupported}). This should only be done on targets that
41605 actually support passing environment variables to the starting
41608 This packet is related to the @code{set environment} command;
41609 @pxref{set environment}.
41611 @item QEnvironmentUnset:@var{hex-value}
41612 @anchor{QEnvironmentUnset}
41613 @cindex unset environment variable, remote request
41614 @cindex @samp{QEnvironmentUnset} packet
41615 On UNIX-like targets, it is possible to unset environment variables
41616 before starting the inferior in the remote target. This packet is
41617 used to inform @command{gdbserver} of an environment variable that has
41618 been unset by the user on @value{GDBN} (@pxref{unset environment}).
41620 The packet is composed by @var{hex-value}, an hex encoded
41621 representation of the name of the environment variable to be unset.
41623 This packet is only available in extended mode (@pxref{extended
41629 The request succeeded.
41632 This packet is not probed by default; the remote stub must request it,
41633 by supplying an appropriate @samp{qSupported} response
41634 (@pxref{qSupported}). This should only be done on targets that
41635 actually support passing environment variables to the starting
41638 This packet is related to the @code{unset environment} command;
41639 @pxref{unset environment}.
41641 @item QEnvironmentReset
41642 @anchor{QEnvironmentReset}
41643 @cindex reset environment, remote request
41644 @cindex @samp{QEnvironmentReset} packet
41645 On UNIX-like targets, this packet is used to reset the state of
41646 environment variables in the remote target before starting the
41647 inferior. In this context, reset means unsetting all environment
41648 variables that were previously set by the user (i.e., were not
41649 initially present in the environment). It is sent to
41650 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
41651 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
41652 (@pxref{QEnvironmentUnset}) packets.
41654 This packet is only available in extended mode (@pxref{extended
41660 The request succeeded.
41663 This packet is not probed by default; the remote stub must request it,
41664 by supplying an appropriate @samp{qSupported} response
41665 (@pxref{qSupported}). This should only be done on targets that
41666 actually support passing environment variables to the starting
41669 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
41670 @anchor{QSetWorkingDir packet}
41671 @cindex set working directory, remote request
41672 @cindex @samp{QSetWorkingDir} packet
41673 This packet is used to inform the remote server of the intended
41674 current working directory for programs that are going to be executed.
41676 The packet is composed by @var{directory}, an hex encoded
41677 representation of the directory that the remote inferior will use as
41678 its current working directory. If @var{directory} is an empty string,
41679 the remote server should reset the inferior's current working
41680 directory to its original, empty value.
41682 This packet is only available in extended mode (@pxref{extended
41688 The request succeeded.
41692 @itemx qsThreadInfo
41693 @cindex list active threads, remote request
41694 @cindex @samp{qfThreadInfo} packet
41695 @cindex @samp{qsThreadInfo} packet
41696 Obtain a list of all active thread IDs from the target (OS). Since there
41697 may be too many active threads to fit into one reply packet, this query
41698 works iteratively: it may require more than one query/reply sequence to
41699 obtain the entire list of threads. The first query of the sequence will
41700 be the @samp{qfThreadInfo} query; subsequent queries in the
41701 sequence will be the @samp{qsThreadInfo} query.
41703 NOTE: This packet replaces the @samp{qL} query (see below).
41707 @item m @var{thread-id}
41709 @item m @var{thread-id},@var{thread-id}@dots{}
41710 a comma-separated list of thread IDs
41712 (lower case letter @samp{L}) denotes end of list.
41715 In response to each query, the target will reply with a list of one or
41716 more thread IDs, separated by commas.
41717 @value{GDBN} will respond to each reply with a request for more thread
41718 ids (using the @samp{qs} form of the query), until the target responds
41719 with @samp{l} (lower-case ell, for @dfn{last}).
41720 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
41723 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
41724 initial connection with the remote target, and the very first thread ID
41725 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
41726 message. Therefore, the stub should ensure that the first thread ID in
41727 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
41729 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
41730 @cindex get thread-local storage address, remote request
41731 @cindex @samp{qGetTLSAddr} packet
41732 Fetch the address associated with thread local storage specified
41733 by @var{thread-id}, @var{offset}, and @var{lm}.
41735 @var{thread-id} is the thread ID associated with the
41736 thread for which to fetch the TLS address. @xref{thread-id syntax}.
41738 @var{offset} is the (big endian, hex encoded) offset associated with the
41739 thread local variable. (This offset is obtained from the debug
41740 information associated with the variable.)
41742 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
41743 load module associated with the thread local storage. For example,
41744 a @sc{gnu}/Linux system will pass the link map address of the shared
41745 object associated with the thread local storage under consideration.
41746 Other operating environments may choose to represent the load module
41747 differently, so the precise meaning of this parameter will vary.
41751 @item @var{XX}@dots{}
41752 Hex encoded (big endian) bytes representing the address of the thread
41753 local storage requested.
41756 An error occurred. The error number @var{nn} is given as hex digits.
41759 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
41762 @item qGetTIBAddr:@var{thread-id}
41763 @cindex get thread information block address
41764 @cindex @samp{qGetTIBAddr} packet
41765 Fetch address of the Windows OS specific Thread Information Block.
41767 @var{thread-id} is the thread ID associated with the thread.
41771 @item @var{XX}@dots{}
41772 Hex encoded (big endian) bytes representing the linear address of the
41773 thread information block.
41776 An error occured. This means that either the thread was not found, or the
41777 address could not be retrieved.
41780 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
41783 @item qL @var{startflag} @var{threadcount} @var{nextthread}
41784 Obtain thread information from RTOS. Where: @var{startflag} (one hex
41785 digit) is one to indicate the first query and zero to indicate a
41786 subsequent query; @var{threadcount} (two hex digits) is the maximum
41787 number of threads the response packet can contain; and @var{nextthread}
41788 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
41789 returned in the response as @var{argthread}.
41791 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
41795 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
41796 Where: @var{count} (two hex digits) is the number of threads being
41797 returned; @var{done} (one hex digit) is zero to indicate more threads
41798 and one indicates no further threads; @var{argthreadid} (eight hex
41799 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
41800 is a sequence of thread IDs, @var{threadid} (eight hex
41801 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
41804 @item qMemTags:@var{start address},@var{length}:@var{type}
41806 @cindex fetch memory tags
41807 @cindex @samp{qMemTags} packet
41808 Fetch memory tags of type @var{type} from the address range
41809 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41810 target is responsible for calculating how many tags will be returned, as this
41811 is architecture-specific.
41813 @var{start address} is the starting address of the memory range.
41815 @var{length} is the length, in bytes, of the memory range.
41817 @var{type} is the type of tag the request wants to fetch. The type is a signed
41822 @item @var{mxx}@dots{}
41823 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
41824 tags found in the requested memory range.
41827 An error occured. This means that fetching of memory tags failed for some
41831 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
41832 although this should not happen given @value{GDBN} will only send this packet
41833 if the stub has advertised support for memory tagging via @samp{qSupported}.
41836 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
41838 @cindex store memory tags
41839 @cindex @samp{QMemTags} packet
41840 Store memory tags of type @var{type} to the address range
41841 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41842 target is responsible for interpreting the type, the tag bytes and modifying
41843 the memory tag granules accordingly, given this is architecture-specific.
41845 The interpretation of how many tags (@var{nt}) should be written to how many
41846 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
41847 implementation-specific, but the following is suggested.
41849 If the number of memory tags, @var{nt}, is greater than or equal to the
41850 number of memory tag granules, @var{ng}, only @var{ng} tags will be
41853 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
41854 and the tag bytes will be used as a pattern that will get repeated until
41855 @var{ng} tags are stored.
41857 @var{start address} is the starting address of the memory range. The address
41858 does not have any restriction on alignment or size.
41860 @var{length} is the length, in bytes, of the memory range.
41862 @var{type} is the type of tag the request wants to fetch. The type is a signed
41865 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
41866 interpreted by the target. Each pair of hex digits is interpreted as a
41872 The request was successful and the memory tag granules were modified
41876 An error occured. This means that modifying the memory tag granules failed
41880 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
41881 although this should not happen given @value{GDBN} will only send this packet
41882 if the stub has advertised support for memory tagging via @samp{qSupported}.
41886 @cindex section offsets, remote request
41887 @cindex @samp{qOffsets} packet
41888 Get section offsets that the target used when relocating the downloaded
41893 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
41894 Relocate the @code{Text} section by @var{xxx} from its original address.
41895 Relocate the @code{Data} section by @var{yyy} from its original address.
41896 If the object file format provides segment information (e.g.@: @sc{elf}
41897 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
41898 segments by the supplied offsets.
41900 @emph{Note: while a @code{Bss} offset may be included in the response,
41901 @value{GDBN} ignores this and instead applies the @code{Data} offset
41902 to the @code{Bss} section.}
41904 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
41905 Relocate the first segment of the object file, which conventionally
41906 contains program code, to a starting address of @var{xxx}. If
41907 @samp{DataSeg} is specified, relocate the second segment, which
41908 conventionally contains modifiable data, to a starting address of
41909 @var{yyy}. @value{GDBN} will report an error if the object file
41910 does not contain segment information, or does not contain at least
41911 as many segments as mentioned in the reply. Extra segments are
41912 kept at fixed offsets relative to the last relocated segment.
41915 @item qP @var{mode} @var{thread-id}
41916 @cindex thread information, remote request
41917 @cindex @samp{qP} packet
41918 Returns information on @var{thread-id}. Where: @var{mode} is a hex
41919 encoded 32 bit mode; @var{thread-id} is a thread ID
41920 (@pxref{thread-id syntax}).
41922 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
41925 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
41929 @cindex non-stop mode, remote request
41930 @cindex @samp{QNonStop} packet
41932 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
41933 @xref{Remote Non-Stop}, for more information.
41938 The request succeeded.
41941 An error occurred. The error number @var{nn} is given as hex digits.
41944 An empty reply indicates that @samp{QNonStop} is not supported by
41948 This packet is not probed by default; the remote stub must request it,
41949 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41950 Use of this packet is controlled by the @code{set non-stop} command;
41951 @pxref{Non-Stop Mode}.
41953 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
41954 @itemx QCatchSyscalls:0
41955 @cindex catch syscalls from inferior, remote request
41956 @cindex @samp{QCatchSyscalls} packet
41957 @anchor{QCatchSyscalls}
41958 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
41959 catching syscalls from the inferior process.
41961 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
41962 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
41963 is listed, every system call should be reported.
41965 Note that if a syscall not in the list is reported, @value{GDBN} will
41966 still filter the event according to its own list from all corresponding
41967 @code{catch syscall} commands. However, it is more efficient to only
41968 report the requested syscalls.
41970 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
41971 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
41973 If the inferior process execs, the state of @samp{QCatchSyscalls} is
41974 kept for the new process too. On targets where exec may affect syscall
41975 numbers, for example with exec between 32 and 64-bit processes, the
41976 client should send a new packet with the new syscall list.
41981 The request succeeded.
41984 An error occurred. @var{nn} are hex digits.
41987 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
41991 Use of this packet is controlled by the @code{set remote catch-syscalls}
41992 command (@pxref{Remote Configuration, set remote catch-syscalls}).
41993 This packet is not probed by default; the remote stub must request it,
41994 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41996 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41997 @cindex pass signals to inferior, remote request
41998 @cindex @samp{QPassSignals} packet
41999 @anchor{QPassSignals}
42000 Each listed @var{signal} should be passed directly to the inferior process.
42001 Signals are numbered identically to continue packets and stop replies
42002 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42003 strictly greater than the previous item. These signals do not need to stop
42004 the inferior, or be reported to @value{GDBN}. All other signals should be
42005 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42006 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42007 new list. This packet improves performance when using @samp{handle
42008 @var{signal} nostop noprint pass}.
42013 The request succeeded.
42016 An error occurred. The error number @var{nn} is given as hex digits.
42019 An empty reply indicates that @samp{QPassSignals} is not supported by
42023 Use of this packet is controlled by the @code{set remote pass-signals}
42024 command (@pxref{Remote Configuration, set remote pass-signals}).
42025 This packet is not probed by default; the remote stub must request it,
42026 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42028 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42029 @cindex signals the inferior may see, remote request
42030 @cindex @samp{QProgramSignals} packet
42031 @anchor{QProgramSignals}
42032 Each listed @var{signal} may be delivered to the inferior process.
42033 Others should be silently discarded.
42035 In some cases, the remote stub may need to decide whether to deliver a
42036 signal to the program or not without @value{GDBN} involvement. One
42037 example of that is while detaching --- the program's threads may have
42038 stopped for signals that haven't yet had a chance of being reported to
42039 @value{GDBN}, and so the remote stub can use the signal list specified
42040 by this packet to know whether to deliver or ignore those pending
42043 This does not influence whether to deliver a signal as requested by a
42044 resumption packet (@pxref{vCont packet}).
42046 Signals are numbered identically to continue packets and stop replies
42047 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42048 strictly greater than the previous item. Multiple
42049 @samp{QProgramSignals} packets do not combine; any earlier
42050 @samp{QProgramSignals} list is completely replaced by the new list.
42055 The request succeeded.
42058 An error occurred. The error number @var{nn} is given as hex digits.
42061 An empty reply indicates that @samp{QProgramSignals} is not supported
42065 Use of this packet is controlled by the @code{set remote program-signals}
42066 command (@pxref{Remote Configuration, set remote program-signals}).
42067 This packet is not probed by default; the remote stub must request it,
42068 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42070 @anchor{QThreadEvents}
42071 @item QThreadEvents:1
42072 @itemx QThreadEvents:0
42073 @cindex thread create/exit events, remote request
42074 @cindex @samp{QThreadEvents} packet
42076 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42077 reporting of thread create and exit events. @xref{thread create
42078 event}, for the reply specifications. For example, this is used in
42079 non-stop mode when @value{GDBN} stops a set of threads and
42080 synchronously waits for the their corresponding stop replies. Without
42081 exit events, if one of the threads exits, @value{GDBN} would hang
42082 forever not knowing that it should no longer expect a stop for that
42083 same thread. @value{GDBN} does not enable this feature unless the
42084 stub reports that it supports it by including @samp{QThreadEvents+} in
42085 its @samp{qSupported} reply.
42090 The request succeeded.
42093 An error occurred. The error number @var{nn} is given as hex digits.
42096 An empty reply indicates that @samp{QThreadEvents} is not supported by
42100 Use of this packet is controlled by the @code{set remote thread-events}
42101 command (@pxref{Remote Configuration, set remote thread-events}).
42103 @item qRcmd,@var{command}
42104 @cindex execute remote command, remote request
42105 @cindex @samp{qRcmd} packet
42106 @var{command} (hex encoded) is passed to the local interpreter for
42107 execution. Invalid commands should be reported using the output
42108 string. Before the final result packet, the target may also respond
42109 with a number of intermediate @samp{O@var{output}} console output
42110 packets. @emph{Implementors should note that providing access to a
42111 stubs's interpreter may have security implications}.
42116 A command response with no output.
42118 A command response with the hex encoded output string @var{OUTPUT}.
42120 Indicate a badly formed request.
42122 An empty reply indicates that @samp{qRcmd} is not recognized.
42125 (Note that the @code{qRcmd} packet's name is separated from the
42126 command by a @samp{,}, not a @samp{:}, contrary to the naming
42127 conventions above. Please don't use this packet as a model for new
42130 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42131 @cindex searching memory, in remote debugging
42133 @cindex @samp{qSearch:memory} packet
42135 @cindex @samp{qSearch memory} packet
42136 @anchor{qSearch memory}
42137 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42138 Both @var{address} and @var{length} are encoded in hex;
42139 @var{search-pattern} is a sequence of bytes, also hex encoded.
42144 The pattern was not found.
42146 The pattern was found at @var{address}.
42148 A badly formed request or an error was encountered while searching memory.
42150 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42153 @item QStartNoAckMode
42154 @cindex @samp{QStartNoAckMode} packet
42155 @anchor{QStartNoAckMode}
42156 Request that the remote stub disable the normal @samp{+}/@samp{-}
42157 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42162 The stub has switched to no-acknowledgment mode.
42163 @value{GDBN} acknowledges this response,
42164 but neither the stub nor @value{GDBN} shall send or expect further
42165 @samp{+}/@samp{-} acknowledgments in the current connection.
42167 An empty reply indicates that the stub does not support no-acknowledgment mode.
42170 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42171 @cindex supported packets, remote query
42172 @cindex features of the remote protocol
42173 @cindex @samp{qSupported} packet
42174 @anchor{qSupported}
42175 Tell the remote stub about features supported by @value{GDBN}, and
42176 query the stub for features it supports. This packet allows
42177 @value{GDBN} and the remote stub to take advantage of each others'
42178 features. @samp{qSupported} also consolidates multiple feature probes
42179 at startup, to improve @value{GDBN} performance---a single larger
42180 packet performs better than multiple smaller probe packets on
42181 high-latency links. Some features may enable behavior which must not
42182 be on by default, e.g.@: because it would confuse older clients or
42183 stubs. Other features may describe packets which could be
42184 automatically probed for, but are not. These features must be
42185 reported before @value{GDBN} will use them. This ``default
42186 unsupported'' behavior is not appropriate for all packets, but it
42187 helps to keep the initial connection time under control with new
42188 versions of @value{GDBN} which support increasing numbers of packets.
42192 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42193 The stub supports or does not support each returned @var{stubfeature},
42194 depending on the form of each @var{stubfeature} (see below for the
42197 An empty reply indicates that @samp{qSupported} is not recognized,
42198 or that no features needed to be reported to @value{GDBN}.
42201 The allowed forms for each feature (either a @var{gdbfeature} in the
42202 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42206 @item @var{name}=@var{value}
42207 The remote protocol feature @var{name} is supported, and associated
42208 with the specified @var{value}. The format of @var{value} depends
42209 on the feature, but it must not include a semicolon.
42211 The remote protocol feature @var{name} is supported, and does not
42212 need an associated value.
42214 The remote protocol feature @var{name} is not supported.
42216 The remote protocol feature @var{name} may be supported, and
42217 @value{GDBN} should auto-detect support in some other way when it is
42218 needed. This form will not be used for @var{gdbfeature} notifications,
42219 but may be used for @var{stubfeature} responses.
42222 Whenever the stub receives a @samp{qSupported} request, the
42223 supplied set of @value{GDBN} features should override any previous
42224 request. This allows @value{GDBN} to put the stub in a known
42225 state, even if the stub had previously been communicating with
42226 a different version of @value{GDBN}.
42228 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42233 This feature indicates whether @value{GDBN} supports multiprocess
42234 extensions to the remote protocol. @value{GDBN} does not use such
42235 extensions unless the stub also reports that it supports them by
42236 including @samp{multiprocess+} in its @samp{qSupported} reply.
42237 @xref{multiprocess extensions}, for details.
42240 This feature indicates that @value{GDBN} supports the XML target
42241 description. If the stub sees @samp{xmlRegisters=} with target
42242 specific strings separated by a comma, it will report register
42246 This feature indicates whether @value{GDBN} supports the
42247 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42248 instruction reply packet}).
42251 This feature indicates whether @value{GDBN} supports the swbreak stop
42252 reason in stop replies. @xref{swbreak stop reason}, for details.
42255 This feature indicates whether @value{GDBN} supports the hwbreak stop
42256 reason in stop replies. @xref{swbreak stop reason}, for details.
42259 This feature indicates whether @value{GDBN} supports fork event
42260 extensions to the remote protocol. @value{GDBN} does not use such
42261 extensions unless the stub also reports that it supports them by
42262 including @samp{fork-events+} in its @samp{qSupported} reply.
42265 This feature indicates whether @value{GDBN} supports vfork event
42266 extensions to the remote protocol. @value{GDBN} does not use such
42267 extensions unless the stub also reports that it supports them by
42268 including @samp{vfork-events+} in its @samp{qSupported} reply.
42271 This feature indicates whether @value{GDBN} supports exec event
42272 extensions to the remote protocol. @value{GDBN} does not use such
42273 extensions unless the stub also reports that it supports them by
42274 including @samp{exec-events+} in its @samp{qSupported} reply.
42276 @item vContSupported
42277 This feature indicates whether @value{GDBN} wants to know the
42278 supported actions in the reply to @samp{vCont?} packet.
42281 Stubs should ignore any unknown values for
42282 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42283 packet supports receiving packets of unlimited length (earlier
42284 versions of @value{GDBN} may reject overly long responses). Additional values
42285 for @var{gdbfeature} may be defined in the future to let the stub take
42286 advantage of new features in @value{GDBN}, e.g.@: incompatible
42287 improvements in the remote protocol---the @samp{multiprocess} feature is
42288 an example of such a feature. The stub's reply should be independent
42289 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42290 describes all the features it supports, and then the stub replies with
42291 all the features it supports.
42293 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42294 responses, as long as each response uses one of the standard forms.
42296 Some features are flags. A stub which supports a flag feature
42297 should respond with a @samp{+} form response. Other features
42298 require values, and the stub should respond with an @samp{=}
42301 Each feature has a default value, which @value{GDBN} will use if
42302 @samp{qSupported} is not available or if the feature is not mentioned
42303 in the @samp{qSupported} response. The default values are fixed; a
42304 stub is free to omit any feature responses that match the defaults.
42306 Not all features can be probed, but for those which can, the probing
42307 mechanism is useful: in some cases, a stub's internal
42308 architecture may not allow the protocol layer to know some information
42309 about the underlying target in advance. This is especially common in
42310 stubs which may be configured for multiple targets.
42312 These are the currently defined stub features and their properties:
42314 @multitable @columnfractions 0.35 0.2 0.12 0.2
42315 @c NOTE: The first row should be @headitem, but we do not yet require
42316 @c a new enough version of Texinfo (4.7) to use @headitem.
42318 @tab Value Required
42322 @item @samp{PacketSize}
42327 @item @samp{qXfer:auxv:read}
42332 @item @samp{qXfer:btrace:read}
42337 @item @samp{qXfer:btrace-conf:read}
42342 @item @samp{qXfer:exec-file:read}
42347 @item @samp{qXfer:features:read}
42352 @item @samp{qXfer:libraries:read}
42357 @item @samp{qXfer:libraries-svr4:read}
42362 @item @samp{augmented-libraries-svr4-read}
42367 @item @samp{qXfer:memory-map:read}
42372 @item @samp{qXfer:sdata:read}
42377 @item @samp{qXfer:siginfo:read}
42382 @item @samp{qXfer:siginfo:write}
42387 @item @samp{qXfer:threads:read}
42392 @item @samp{qXfer:traceframe-info:read}
42397 @item @samp{qXfer:uib:read}
42402 @item @samp{qXfer:fdpic:read}
42407 @item @samp{Qbtrace:off}
42412 @item @samp{Qbtrace:bts}
42417 @item @samp{Qbtrace:pt}
42422 @item @samp{Qbtrace-conf:bts:size}
42427 @item @samp{Qbtrace-conf:pt:size}
42432 @item @samp{QNonStop}
42437 @item @samp{QCatchSyscalls}
42442 @item @samp{QPassSignals}
42447 @item @samp{QStartNoAckMode}
42452 @item @samp{multiprocess}
42457 @item @samp{ConditionalBreakpoints}
42462 @item @samp{ConditionalTracepoints}
42467 @item @samp{ReverseContinue}
42472 @item @samp{ReverseStep}
42477 @item @samp{TracepointSource}
42482 @item @samp{QAgent}
42487 @item @samp{QAllow}
42492 @item @samp{QDisableRandomization}
42497 @item @samp{EnableDisableTracepoints}
42502 @item @samp{QTBuffer:size}
42507 @item @samp{tracenz}
42512 @item @samp{BreakpointCommands}
42517 @item @samp{swbreak}
42522 @item @samp{hwbreak}
42527 @item @samp{fork-events}
42532 @item @samp{vfork-events}
42537 @item @samp{exec-events}
42542 @item @samp{QThreadEvents}
42547 @item @samp{no-resumed}
42552 @item @samp{memory-tagging}
42559 These are the currently defined stub features, in more detail:
42562 @cindex packet size, remote protocol
42563 @item PacketSize=@var{bytes}
42564 The remote stub can accept packets up to at least @var{bytes} in
42565 length. @value{GDBN} will send packets up to this size for bulk
42566 transfers, and will never send larger packets. This is a limit on the
42567 data characters in the packet, including the frame and checksum.
42568 There is no trailing NUL byte in a remote protocol packet; if the stub
42569 stores packets in a NUL-terminated format, it should allow an extra
42570 byte in its buffer for the NUL. If this stub feature is not supported,
42571 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42573 @item qXfer:auxv:read
42574 The remote stub understands the @samp{qXfer:auxv:read} packet
42575 (@pxref{qXfer auxiliary vector read}).
42577 @item qXfer:btrace:read
42578 The remote stub understands the @samp{qXfer:btrace:read}
42579 packet (@pxref{qXfer btrace read}).
42581 @item qXfer:btrace-conf:read
42582 The remote stub understands the @samp{qXfer:btrace-conf:read}
42583 packet (@pxref{qXfer btrace-conf read}).
42585 @item qXfer:exec-file:read
42586 The remote stub understands the @samp{qXfer:exec-file:read} packet
42587 (@pxref{qXfer executable filename read}).
42589 @item qXfer:features:read
42590 The remote stub understands the @samp{qXfer:features:read} packet
42591 (@pxref{qXfer target description read}).
42593 @item qXfer:libraries:read
42594 The remote stub understands the @samp{qXfer:libraries:read} packet
42595 (@pxref{qXfer library list read}).
42597 @item qXfer:libraries-svr4:read
42598 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42599 (@pxref{qXfer svr4 library list read}).
42601 @item augmented-libraries-svr4-read
42602 The remote stub understands the augmented form of the
42603 @samp{qXfer:libraries-svr4:read} packet
42604 (@pxref{qXfer svr4 library list read}).
42606 @item qXfer:memory-map:read
42607 The remote stub understands the @samp{qXfer:memory-map:read} packet
42608 (@pxref{qXfer memory map read}).
42610 @item qXfer:sdata:read
42611 The remote stub understands the @samp{qXfer:sdata:read} packet
42612 (@pxref{qXfer sdata read}).
42614 @item qXfer:siginfo:read
42615 The remote stub understands the @samp{qXfer:siginfo:read} packet
42616 (@pxref{qXfer siginfo read}).
42618 @item qXfer:siginfo:write
42619 The remote stub understands the @samp{qXfer:siginfo:write} packet
42620 (@pxref{qXfer siginfo write}).
42622 @item qXfer:threads:read
42623 The remote stub understands the @samp{qXfer:threads:read} packet
42624 (@pxref{qXfer threads read}).
42626 @item qXfer:traceframe-info:read
42627 The remote stub understands the @samp{qXfer:traceframe-info:read}
42628 packet (@pxref{qXfer traceframe info read}).
42630 @item qXfer:uib:read
42631 The remote stub understands the @samp{qXfer:uib:read}
42632 packet (@pxref{qXfer unwind info block}).
42634 @item qXfer:fdpic:read
42635 The remote stub understands the @samp{qXfer:fdpic:read}
42636 packet (@pxref{qXfer fdpic loadmap read}).
42639 The remote stub understands the @samp{QNonStop} packet
42640 (@pxref{QNonStop}).
42642 @item QCatchSyscalls
42643 The remote stub understands the @samp{QCatchSyscalls} packet
42644 (@pxref{QCatchSyscalls}).
42647 The remote stub understands the @samp{QPassSignals} packet
42648 (@pxref{QPassSignals}).
42650 @item QStartNoAckMode
42651 The remote stub understands the @samp{QStartNoAckMode} packet and
42652 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
42655 @anchor{multiprocess extensions}
42656 @cindex multiprocess extensions, in remote protocol
42657 The remote stub understands the multiprocess extensions to the remote
42658 protocol syntax. The multiprocess extensions affect the syntax of
42659 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
42660 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
42661 replies. Note that reporting this feature indicates support for the
42662 syntactic extensions only, not that the stub necessarily supports
42663 debugging of more than one process at a time. The stub must not use
42664 multiprocess extensions in packet replies unless @value{GDBN} has also
42665 indicated it supports them in its @samp{qSupported} request.
42667 @item qXfer:osdata:read
42668 The remote stub understands the @samp{qXfer:osdata:read} packet
42669 ((@pxref{qXfer osdata read}).
42671 @item ConditionalBreakpoints
42672 The target accepts and implements evaluation of conditional expressions
42673 defined for breakpoints. The target will only report breakpoint triggers
42674 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
42676 @item ConditionalTracepoints
42677 The remote stub accepts and implements conditional expressions defined
42678 for tracepoints (@pxref{Tracepoint Conditions}).
42680 @item ReverseContinue
42681 The remote stub accepts and implements the reverse continue packet
42685 The remote stub accepts and implements the reverse step packet
42688 @item TracepointSource
42689 The remote stub understands the @samp{QTDPsrc} packet that supplies
42690 the source form of tracepoint definitions.
42693 The remote stub understands the @samp{QAgent} packet.
42696 The remote stub understands the @samp{QAllow} packet.
42698 @item QDisableRandomization
42699 The remote stub understands the @samp{QDisableRandomization} packet.
42701 @item StaticTracepoint
42702 @cindex static tracepoints, in remote protocol
42703 The remote stub supports static tracepoints.
42705 @item InstallInTrace
42706 @anchor{install tracepoint in tracing}
42707 The remote stub supports installing tracepoint in tracing.
42709 @item EnableDisableTracepoints
42710 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
42711 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
42712 to be enabled and disabled while a trace experiment is running.
42714 @item QTBuffer:size
42715 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
42716 packet that allows to change the size of the trace buffer.
42719 @cindex string tracing, in remote protocol
42720 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
42721 See @ref{Bytecode Descriptions} for details about the bytecode.
42723 @item BreakpointCommands
42724 @cindex breakpoint commands, in remote protocol
42725 The remote stub supports running a breakpoint's command list itself,
42726 rather than reporting the hit to @value{GDBN}.
42729 The remote stub understands the @samp{Qbtrace:off} packet.
42732 The remote stub understands the @samp{Qbtrace:bts} packet.
42735 The remote stub understands the @samp{Qbtrace:pt} packet.
42737 @item Qbtrace-conf:bts:size
42738 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
42740 @item Qbtrace-conf:pt:size
42741 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
42744 The remote stub reports the @samp{swbreak} stop reason for memory
42748 The remote stub reports the @samp{hwbreak} stop reason for hardware
42752 The remote stub reports the @samp{fork} stop reason for fork events.
42755 The remote stub reports the @samp{vfork} stop reason for vfork events
42756 and vforkdone events.
42759 The remote stub reports the @samp{exec} stop reason for exec events.
42761 @item vContSupported
42762 The remote stub reports the supported actions in the reply to
42763 @samp{vCont?} packet.
42765 @item QThreadEvents
42766 The remote stub understands the @samp{QThreadEvents} packet.
42769 The remote stub reports the @samp{N} stop reply.
42772 @item memory-tagging
42773 The remote stub supports and implements the required memory tagging
42774 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
42775 @samp{QMemTags} (@pxref{QMemTags}) packets.
42777 For AArch64 GNU/Linux systems, this feature also requires access to the
42778 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
42779 This is done via the @samp{vFile} requests.
42784 @cindex symbol lookup, remote request
42785 @cindex @samp{qSymbol} packet
42786 Notify the target that @value{GDBN} is prepared to serve symbol lookup
42787 requests. Accept requests from the target for the values of symbols.
42792 The target does not need to look up any (more) symbols.
42793 @item qSymbol:@var{sym_name}
42794 The target requests the value of symbol @var{sym_name} (hex encoded).
42795 @value{GDBN} may provide the value by using the
42796 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
42800 @item qSymbol:@var{sym_value}:@var{sym_name}
42801 Set the value of @var{sym_name} to @var{sym_value}.
42803 @var{sym_name} (hex encoded) is the name of a symbol whose value the
42804 target has previously requested.
42806 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
42807 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
42813 The target does not need to look up any (more) symbols.
42814 @item qSymbol:@var{sym_name}
42815 The target requests the value of a new symbol @var{sym_name} (hex
42816 encoded). @value{GDBN} will continue to supply the values of symbols
42817 (if available), until the target ceases to request them.
42822 @itemx QTDisconnected
42829 @itemx qTMinFTPILen
42831 @xref{Tracepoint Packets}.
42833 @anchor{qThreadExtraInfo}
42834 @item qThreadExtraInfo,@var{thread-id}
42835 @cindex thread attributes info, remote request
42836 @cindex @samp{qThreadExtraInfo} packet
42837 Obtain from the target OS a printable string description of thread
42838 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
42839 for the forms of @var{thread-id}. This
42840 string may contain anything that the target OS thinks is interesting
42841 for @value{GDBN} to tell the user about the thread. The string is
42842 displayed in @value{GDBN}'s @code{info threads} display. Some
42843 examples of possible thread extra info strings are @samp{Runnable}, or
42844 @samp{Blocked on Mutex}.
42848 @item @var{XX}@dots{}
42849 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
42850 comprising the printable string containing the extra information about
42851 the thread's attributes.
42854 (Note that the @code{qThreadExtraInfo} packet's name is separated from
42855 the command by a @samp{,}, not a @samp{:}, contrary to the naming
42856 conventions above. Please don't use this packet as a model for new
42875 @xref{Tracepoint Packets}.
42877 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
42878 @cindex read special object, remote request
42879 @cindex @samp{qXfer} packet
42880 @anchor{qXfer read}
42881 Read uninterpreted bytes from the target's special data area
42882 identified by the keyword @var{object}. Request @var{length} bytes
42883 starting at @var{offset} bytes into the data. The content and
42884 encoding of @var{annex} is specific to @var{object}; it can supply
42885 additional details about what data to access.
42890 Data @var{data} (@pxref{Binary Data}) has been read from the
42891 target. There may be more data at a higher address (although
42892 it is permitted to return @samp{m} even for the last valid
42893 block of data, as long as at least one byte of data was read).
42894 It is possible for @var{data} to have fewer bytes than the @var{length} in the
42898 Data @var{data} (@pxref{Binary Data}) has been read from the target.
42899 There is no more data to be read. It is possible for @var{data} to
42900 have fewer bytes than the @var{length} in the request.
42903 The @var{offset} in the request is at the end of the data.
42904 There is no more data to be read.
42907 The request was malformed, or @var{annex} was invalid.
42910 The offset was invalid, or there was an error encountered reading the data.
42911 The @var{nn} part is a hex-encoded @code{errno} value.
42914 An empty reply indicates the @var{object} string was not recognized by
42915 the stub, or that the object does not support reading.
42918 Here are the specific requests of this form defined so far. All the
42919 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
42920 formats, listed above.
42923 @item qXfer:auxv:read::@var{offset},@var{length}
42924 @anchor{qXfer auxiliary vector read}
42925 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
42926 auxiliary vector}. Note @var{annex} must be empty.
42928 This packet is not probed by default; the remote stub must request it,
42929 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42931 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
42932 @anchor{qXfer btrace read}
42934 Return a description of the current branch trace.
42935 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
42936 packet may have one of the following values:
42940 Returns all available branch trace.
42943 Returns all available branch trace if the branch trace changed since
42944 the last read request.
42947 Returns the new branch trace since the last read request. Adds a new
42948 block to the end of the trace that begins at zero and ends at the source
42949 location of the first branch in the trace buffer. This extra block is
42950 used to stitch traces together.
42952 If the trace buffer overflowed, returns an error indicating the overflow.
42955 This packet is not probed by default; the remote stub must request it
42956 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42958 @item qXfer:btrace-conf:read::@var{offset},@var{length}
42959 @anchor{qXfer btrace-conf read}
42961 Return a description of the current branch trace configuration.
42962 @xref{Branch Trace Configuration Format}.
42964 This packet is not probed by default; the remote stub must request it
42965 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42967 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
42968 @anchor{qXfer executable filename read}
42969 Return the full absolute name of the file that was executed to create
42970 a process running on the remote system. The annex specifies the
42971 numeric process ID of the process to query, encoded as a hexadecimal
42972 number. If the annex part is empty the remote stub should return the
42973 filename corresponding to the currently executing process.
42975 This packet is not probed by default; the remote stub must request it,
42976 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42978 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
42979 @anchor{qXfer target description read}
42980 Access the @dfn{target description}. @xref{Target Descriptions}. The
42981 annex specifies which XML document to access. The main description is
42982 always loaded from the @samp{target.xml} annex.
42984 This packet is not probed by default; the remote stub must request it,
42985 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42987 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
42988 @anchor{qXfer library list read}
42989 Access the target's list of loaded libraries. @xref{Library List Format}.
42990 The annex part of the generic @samp{qXfer} packet must be empty
42991 (@pxref{qXfer read}).
42993 Targets which maintain a list of libraries in the program's memory do
42994 not need to implement this packet; it is designed for platforms where
42995 the operating system manages the list of loaded libraries.
42997 This packet is not probed by default; the remote stub must request it,
42998 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43000 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43001 @anchor{qXfer svr4 library list read}
43002 Access the target's list of loaded libraries when the target is an SVR4
43003 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43004 of the generic @samp{qXfer} packet must be empty unless the remote
43005 stub indicated it supports the augmented form of this packet
43006 by supplying an appropriate @samp{qSupported} response
43007 (@pxref{qXfer read}, @ref{qSupported}).
43009 This packet is optional for better performance on SVR4 targets.
43010 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43012 This packet is not probed by default; the remote stub must request it,
43013 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43015 If the remote stub indicates it supports the augmented form of this
43016 packet then the annex part of the generic @samp{qXfer} packet may
43017 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43018 arguments. The currently supported arguments are:
43021 @item start=@var{address}
43022 A hexadecimal number specifying the address of the @samp{struct
43023 link_map} to start reading the library list from. If unset or zero
43024 then the first @samp{struct link_map} in the library list will be
43025 chosen as the starting point.
43027 @item prev=@var{address}
43028 A hexadecimal number specifying the address of the @samp{struct
43029 link_map} immediately preceding the @samp{struct link_map}
43030 specified by the @samp{start} argument. If unset or zero then
43031 the remote stub will expect that no @samp{struct link_map}
43032 exists prior to the starting point.
43036 Arguments that are not understood by the remote stub will be silently
43039 @item qXfer:memory-map:read::@var{offset},@var{length}
43040 @anchor{qXfer memory map read}
43041 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43042 annex part of the generic @samp{qXfer} packet must be empty
43043 (@pxref{qXfer read}).
43045 This packet is not probed by default; the remote stub must request it,
43046 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43048 @item qXfer:sdata:read::@var{offset},@var{length}
43049 @anchor{qXfer sdata read}
43051 Read contents of the extra collected static tracepoint marker
43052 information. The annex part of the generic @samp{qXfer} packet must
43053 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43056 This packet is not probed by default; the remote stub must request it,
43057 by supplying an appropriate @samp{qSupported} response
43058 (@pxref{qSupported}).
43060 @item qXfer:siginfo:read::@var{offset},@var{length}
43061 @anchor{qXfer siginfo read}
43062 Read contents of the extra signal information on the target
43063 system. The annex part of the generic @samp{qXfer} packet must be
43064 empty (@pxref{qXfer read}).
43066 This packet is not probed by default; the remote stub must request it,
43067 by supplying an appropriate @samp{qSupported} response
43068 (@pxref{qSupported}).
43070 @item qXfer:threads:read::@var{offset},@var{length}
43071 @anchor{qXfer threads read}
43072 Access the list of threads on target. @xref{Thread List Format}. The
43073 annex part of the generic @samp{qXfer} packet must be empty
43074 (@pxref{qXfer read}).
43076 This packet is not probed by default; the remote stub must request it,
43077 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43079 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43080 @anchor{qXfer traceframe info read}
43082 Return a description of the current traceframe's contents.
43083 @xref{Traceframe Info Format}. The annex part of the generic
43084 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43086 This packet is not probed by default; the remote stub must request it,
43087 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43089 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43090 @anchor{qXfer unwind info block}
43092 Return the unwind information block for @var{pc}. This packet is used
43093 on OpenVMS/ia64 to ask the kernel unwind information.
43095 This packet is not probed by default.
43097 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43098 @anchor{qXfer fdpic loadmap read}
43099 Read contents of @code{loadmap}s on the target system. The
43100 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43101 executable @code{loadmap} or interpreter @code{loadmap} to read.
43103 This packet is not probed by default; the remote stub must request it,
43104 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43106 @item qXfer:osdata:read::@var{offset},@var{length}
43107 @anchor{qXfer osdata read}
43108 Access the target's @dfn{operating system information}.
43109 @xref{Operating System Information}.
43113 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43114 @cindex write data into object, remote request
43115 @anchor{qXfer write}
43116 Write uninterpreted bytes into the target's special data area
43117 identified by the keyword @var{object}, starting at @var{offset} bytes
43118 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43119 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43120 is specific to @var{object}; it can supply additional details about what data
43126 @var{nn} (hex encoded) is the number of bytes written.
43127 This may be fewer bytes than supplied in the request.
43130 The request was malformed, or @var{annex} was invalid.
43133 The offset was invalid, or there was an error encountered writing the data.
43134 The @var{nn} part is a hex-encoded @code{errno} value.
43137 An empty reply indicates the @var{object} string was not
43138 recognized by the stub, or that the object does not support writing.
43141 Here are the specific requests of this form defined so far. All the
43142 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43143 formats, listed above.
43146 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43147 @anchor{qXfer siginfo write}
43148 Write @var{data} to the extra signal information on the target system.
43149 The annex part of the generic @samp{qXfer} packet must be
43150 empty (@pxref{qXfer write}).
43152 This packet is not probed by default; the remote stub must request it,
43153 by supplying an appropriate @samp{qSupported} response
43154 (@pxref{qSupported}).
43157 @item qXfer:@var{object}:@var{operation}:@dots{}
43158 Requests of this form may be added in the future. When a stub does
43159 not recognize the @var{object} keyword, or its support for
43160 @var{object} does not recognize the @var{operation} keyword, the stub
43161 must respond with an empty packet.
43163 @item qAttached:@var{pid}
43164 @cindex query attached, remote request
43165 @cindex @samp{qAttached} packet
43166 Return an indication of whether the remote server attached to an
43167 existing process or created a new process. When the multiprocess
43168 protocol extensions are supported (@pxref{multiprocess extensions}),
43169 @var{pid} is an integer in hexadecimal format identifying the target
43170 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43171 the query packet will be simplified as @samp{qAttached}.
43173 This query is used, for example, to know whether the remote process
43174 should be detached or killed when a @value{GDBN} session is ended with
43175 the @code{quit} command.
43180 The remote server attached to an existing process.
43182 The remote server created a new process.
43184 A badly formed request or an error was encountered.
43188 Enable branch tracing for the current thread using Branch Trace Store.
43193 Branch tracing has been enabled.
43195 A badly formed request or an error was encountered.
43199 Enable branch tracing for the current thread using Intel Processor Trace.
43204 Branch tracing has been enabled.
43206 A badly formed request or an error was encountered.
43210 Disable branch tracing for the current thread.
43215 Branch tracing has been disabled.
43217 A badly formed request or an error was encountered.
43220 @item Qbtrace-conf:bts:size=@var{value}
43221 Set the requested ring buffer size for new threads that use the
43222 btrace recording method in bts format.
43227 The ring buffer size has been set.
43229 A badly formed request or an error was encountered.
43232 @item Qbtrace-conf:pt:size=@var{value}
43233 Set the requested ring buffer size for new threads that use the
43234 btrace recording method in pt format.
43239 The ring buffer size has been set.
43241 A badly formed request or an error was encountered.
43246 @node Architecture-Specific Protocol Details
43247 @section Architecture-Specific Protocol Details
43249 This section describes how the remote protocol is applied to specific
43250 target architectures. Also see @ref{Standard Target Features}, for
43251 details of XML target descriptions for each architecture.
43254 * ARM-Specific Protocol Details::
43255 * MIPS-Specific Protocol Details::
43258 @node ARM-Specific Protocol Details
43259 @subsection @acronym{ARM}-specific Protocol Details
43262 * ARM Breakpoint Kinds::
43263 * ARM Memory Tag Types::
43266 @node ARM Breakpoint Kinds
43267 @subsubsection @acronym{ARM} Breakpoint Kinds
43268 @cindex breakpoint kinds, @acronym{ARM}
43270 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43275 16-bit Thumb mode breakpoint.
43278 32-bit Thumb mode (Thumb-2) breakpoint.
43281 32-bit @acronym{ARM} mode breakpoint.
43285 @node ARM Memory Tag Types
43286 @subsubsection @acronym{ARM} Memory Tag Types
43287 @cindex memory tag types, @acronym{ARM}
43289 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43302 @node MIPS-Specific Protocol Details
43303 @subsection @acronym{MIPS}-specific Protocol Details
43306 * MIPS Register packet Format::
43307 * MIPS Breakpoint Kinds::
43310 @node MIPS Register packet Format
43311 @subsubsection @acronym{MIPS} Register Packet Format
43312 @cindex register packet format, @acronym{MIPS}
43314 The following @code{g}/@code{G} packets have previously been defined.
43315 In the below, some thirty-two bit registers are transferred as
43316 sixty-four bits. Those registers should be zero/sign extended (which?)
43317 to fill the space allocated. Register bytes are transferred in target
43318 byte order. The two nibbles within a register byte are transferred
43319 most-significant -- least-significant.
43324 All registers are transferred as thirty-two bit quantities in the order:
43325 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43326 registers; fsr; fir; fp.
43329 All registers are transferred as sixty-four bit quantities (including
43330 thirty-two bit registers such as @code{sr}). The ordering is the same
43335 @node MIPS Breakpoint Kinds
43336 @subsubsection @acronym{MIPS} Breakpoint Kinds
43337 @cindex breakpoint kinds, @acronym{MIPS}
43339 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43344 16-bit @acronym{MIPS16} mode breakpoint.
43347 16-bit @acronym{microMIPS} mode breakpoint.
43350 32-bit standard @acronym{MIPS} mode breakpoint.
43353 32-bit @acronym{microMIPS} mode breakpoint.
43357 @node Tracepoint Packets
43358 @section Tracepoint Packets
43359 @cindex tracepoint packets
43360 @cindex packets, tracepoint
43362 Here we describe the packets @value{GDBN} uses to implement
43363 tracepoints (@pxref{Tracepoints}).
43367 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43368 @cindex @samp{QTDP} packet
43369 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43370 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43371 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43372 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43373 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43374 the number of bytes that the target should copy elsewhere to make room
43375 for the tracepoint. If an @samp{X} is present, it introduces a
43376 tracepoint condition, which consists of a hexadecimal length, followed
43377 by a comma and hex-encoded bytes, in a manner similar to action
43378 encodings as described below. If the trailing @samp{-} is present,
43379 further @samp{QTDP} packets will follow to specify this tracepoint's
43385 The packet was understood and carried out.
43387 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43389 The packet was not recognized.
43392 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43393 Define actions to be taken when a tracepoint is hit. The @var{n} and
43394 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43395 this tracepoint. This packet may only be sent immediately after
43396 another @samp{QTDP} packet that ended with a @samp{-}. If the
43397 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43398 specifying more actions for this tracepoint.
43400 In the series of action packets for a given tracepoint, at most one
43401 can have an @samp{S} before its first @var{action}. If such a packet
43402 is sent, it and the following packets define ``while-stepping''
43403 actions. Any prior packets define ordinary actions --- that is, those
43404 taken when the tracepoint is first hit. If no action packet has an
43405 @samp{S}, then all the packets in the series specify ordinary
43406 tracepoint actions.
43408 The @samp{@var{action}@dots{}} portion of the packet is a series of
43409 actions, concatenated without separators. Each action has one of the
43415 Collect the registers whose bits are set in @var{mask},
43416 a hexadecimal number whose @var{i}'th bit is set if register number
43417 @var{i} should be collected. (The least significant bit is numbered
43418 zero.) Note that @var{mask} may be any number of digits long; it may
43419 not fit in a 32-bit word.
43421 @item M @var{basereg},@var{offset},@var{len}
43422 Collect @var{len} bytes of memory starting at the address in register
43423 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43424 @samp{-1}, then the range has a fixed address: @var{offset} is the
43425 address of the lowest byte to collect. The @var{basereg},
43426 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43427 values (the @samp{-1} value for @var{basereg} is a special case).
43429 @item X @var{len},@var{expr}
43430 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43431 it directs. The agent expression @var{expr} is as described in
43432 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43433 two-digit hex number in the packet; @var{len} is the number of bytes
43434 in the expression (and thus one-half the number of hex digits in the
43439 Any number of actions may be packed together in a single @samp{QTDP}
43440 packet, as long as the packet does not exceed the maximum packet
43441 length (400 bytes, for many stubs). There may be only one @samp{R}
43442 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43443 actions. Any registers referred to by @samp{M} and @samp{X} actions
43444 must be collected by a preceding @samp{R} action. (The
43445 ``while-stepping'' actions are treated as if they were attached to a
43446 separate tracepoint, as far as these restrictions are concerned.)
43451 The packet was understood and carried out.
43453 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43455 The packet was not recognized.
43458 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43459 @cindex @samp{QTDPsrc} packet
43460 Specify a source string of tracepoint @var{n} at address @var{addr}.
43461 This is useful to get accurate reproduction of the tracepoints
43462 originally downloaded at the beginning of the trace run. The @var{type}
43463 is the name of the tracepoint part, such as @samp{cond} for the
43464 tracepoint's conditional expression (see below for a list of types), while
43465 @var{bytes} is the string, encoded in hexadecimal.
43467 @var{start} is the offset of the @var{bytes} within the overall source
43468 string, while @var{slen} is the total length of the source string.
43469 This is intended for handling source strings that are longer than will
43470 fit in a single packet.
43471 @c Add detailed example when this info is moved into a dedicated
43472 @c tracepoint descriptions section.
43474 The available string types are @samp{at} for the location,
43475 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43476 @value{GDBN} sends a separate packet for each command in the action
43477 list, in the same order in which the commands are stored in the list.
43479 The target does not need to do anything with source strings except
43480 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43483 Although this packet is optional, and @value{GDBN} will only send it
43484 if the target replies with @samp{TracepointSource} @xref{General
43485 Query Packets}, it makes both disconnected tracing and trace files
43486 much easier to use. Otherwise the user must be careful that the
43487 tracepoints in effect while looking at trace frames are identical to
43488 the ones in effect during the trace run; even a small discrepancy
43489 could cause @samp{tdump} not to work, or a particular trace frame not
43492 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43493 @cindex define trace state variable, remote request
43494 @cindex @samp{QTDV} packet
43495 Create a new trace state variable, number @var{n}, with an initial
43496 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43497 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43498 the option of not using this packet for initial values of zero; the
43499 target should simply create the trace state variables as they are
43500 mentioned in expressions. The value @var{builtin} should be 1 (one)
43501 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43502 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43503 @samp{qTsV} packet had it set. The contents of @var{name} is the
43504 hex-encoded name (without the leading @samp{$}) of the trace state
43507 @item QTFrame:@var{n}
43508 @cindex @samp{QTFrame} packet
43509 Select the @var{n}'th tracepoint frame from the buffer, and use the
43510 register and memory contents recorded there to answer subsequent
43511 request packets from @value{GDBN}.
43513 A successful reply from the stub indicates that the stub has found the
43514 requested frame. The response is a series of parts, concatenated
43515 without separators, describing the frame we selected. Each part has
43516 one of the following forms:
43520 The selected frame is number @var{n} in the trace frame buffer;
43521 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43522 was no frame matching the criteria in the request packet.
43525 The selected trace frame records a hit of tracepoint number @var{t};
43526 @var{t} is a hexadecimal number.
43530 @item QTFrame:pc:@var{addr}
43531 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43532 currently selected frame whose PC is @var{addr};
43533 @var{addr} is a hexadecimal number.
43535 @item QTFrame:tdp:@var{t}
43536 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43537 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43538 is a hexadecimal number.
43540 @item QTFrame:range:@var{start}:@var{end}
43541 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43542 currently selected frame whose PC is between @var{start} (inclusive)
43543 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43546 @item QTFrame:outside:@var{start}:@var{end}
43547 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43548 frame @emph{outside} the given range of addresses (exclusive).
43551 @cindex @samp{qTMinFTPILen} packet
43552 This packet requests the minimum length of instruction at which a fast
43553 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43554 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43555 it depends on the target system being able to create trampolines in
43556 the first 64K of memory, which might or might not be possible for that
43557 system. So the reply to this packet will be 4 if it is able to
43564 The minimum instruction length is currently unknown.
43566 The minimum instruction length is @var{length}, where @var{length}
43567 is a hexadecimal number greater or equal to 1. A reply
43568 of 1 means that a fast tracepoint may be placed on any instruction
43569 regardless of size.
43571 An error has occurred.
43573 An empty reply indicates that the request is not supported by the stub.
43577 @cindex @samp{QTStart} packet
43578 Begin the tracepoint experiment. Begin collecting data from
43579 tracepoint hits in the trace frame buffer. This packet supports the
43580 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43581 instruction reply packet}).
43584 @cindex @samp{QTStop} packet
43585 End the tracepoint experiment. Stop collecting trace frames.
43587 @item QTEnable:@var{n}:@var{addr}
43589 @cindex @samp{QTEnable} packet
43590 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43591 experiment. If the tracepoint was previously disabled, then collection
43592 of data from it will resume.
43594 @item QTDisable:@var{n}:@var{addr}
43596 @cindex @samp{QTDisable} packet
43597 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43598 experiment. No more data will be collected from the tracepoint unless
43599 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43602 @cindex @samp{QTinit} packet
43603 Clear the table of tracepoints, and empty the trace frame buffer.
43605 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43606 @cindex @samp{QTro} packet
43607 Establish the given ranges of memory as ``transparent''. The stub
43608 will answer requests for these ranges from memory's current contents,
43609 if they were not collected as part of the tracepoint hit.
43611 @value{GDBN} uses this to mark read-only regions of memory, like those
43612 containing program code. Since these areas never change, they should
43613 still have the same contents they did when the tracepoint was hit, so
43614 there's no reason for the stub to refuse to provide their contents.
43616 @item QTDisconnected:@var{value}
43617 @cindex @samp{QTDisconnected} packet
43618 Set the choice to what to do with the tracing run when @value{GDBN}
43619 disconnects from the target. A @var{value} of 1 directs the target to
43620 continue the tracing run, while 0 tells the target to stop tracing if
43621 @value{GDBN} is no longer in the picture.
43624 @cindex @samp{qTStatus} packet
43625 Ask the stub if there is a trace experiment running right now.
43627 The reply has the form:
43631 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
43632 @var{running} is a single digit @code{1} if the trace is presently
43633 running, or @code{0} if not. It is followed by semicolon-separated
43634 optional fields that an agent may use to report additional status.
43638 If the trace is not running, the agent may report any of several
43639 explanations as one of the optional fields:
43644 No trace has been run yet.
43646 @item tstop[:@var{text}]:0
43647 The trace was stopped by a user-originated stop command. The optional
43648 @var{text} field is a user-supplied string supplied as part of the
43649 stop command (for instance, an explanation of why the trace was
43650 stopped manually). It is hex-encoded.
43653 The trace stopped because the trace buffer filled up.
43655 @item tdisconnected:0
43656 The trace stopped because @value{GDBN} disconnected from the target.
43658 @item tpasscount:@var{tpnum}
43659 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
43661 @item terror:@var{text}:@var{tpnum}
43662 The trace stopped because tracepoint @var{tpnum} had an error. The
43663 string @var{text} is available to describe the nature of the error
43664 (for instance, a divide by zero in the condition expression); it
43668 The trace stopped for some other reason.
43672 Additional optional fields supply statistical and other information.
43673 Although not required, they are extremely useful for users monitoring
43674 the progress of a trace run. If a trace has stopped, and these
43675 numbers are reported, they must reflect the state of the just-stopped
43680 @item tframes:@var{n}
43681 The number of trace frames in the buffer.
43683 @item tcreated:@var{n}
43684 The total number of trace frames created during the run. This may
43685 be larger than the trace frame count, if the buffer is circular.
43687 @item tsize:@var{n}
43688 The total size of the trace buffer, in bytes.
43690 @item tfree:@var{n}
43691 The number of bytes still unused in the buffer.
43693 @item circular:@var{n}
43694 The value of the circular trace buffer flag. @code{1} means that the
43695 trace buffer is circular and old trace frames will be discarded if
43696 necessary to make room, @code{0} means that the trace buffer is linear
43699 @item disconn:@var{n}
43700 The value of the disconnected tracing flag. @code{1} means that
43701 tracing will continue after @value{GDBN} disconnects, @code{0} means
43702 that the trace run will stop.
43706 @item qTP:@var{tp}:@var{addr}
43707 @cindex tracepoint status, remote request
43708 @cindex @samp{qTP} packet
43709 Ask the stub for the current state of tracepoint number @var{tp} at
43710 address @var{addr}.
43714 @item V@var{hits}:@var{usage}
43715 The tracepoint has been hit @var{hits} times so far during the trace
43716 run, and accounts for @var{usage} in the trace buffer. Note that
43717 @code{while-stepping} steps are not counted as separate hits, but the
43718 steps' space consumption is added into the usage number.
43722 @item qTV:@var{var}
43723 @cindex trace state variable value, remote request
43724 @cindex @samp{qTV} packet
43725 Ask the stub for the value of the trace state variable number @var{var}.
43730 The value of the variable is @var{value}. This will be the current
43731 value of the variable if the user is examining a running target, or a
43732 saved value if the variable was collected in the trace frame that the
43733 user is looking at. Note that multiple requests may result in
43734 different reply values, such as when requesting values while the
43735 program is running.
43738 The value of the variable is unknown. This would occur, for example,
43739 if the user is examining a trace frame in which the requested variable
43744 @cindex @samp{qTfP} packet
43746 @cindex @samp{qTsP} packet
43747 These packets request data about tracepoints that are being used by
43748 the target. @value{GDBN} sends @code{qTfP} to get the first piece
43749 of data, and multiple @code{qTsP} to get additional pieces. Replies
43750 to these packets generally take the form of the @code{QTDP} packets
43751 that define tracepoints. (FIXME add detailed syntax)
43754 @cindex @samp{qTfV} packet
43756 @cindex @samp{qTsV} packet
43757 These packets request data about trace state variables that are on the
43758 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
43759 and multiple @code{qTsV} to get additional variables. Replies to
43760 these packets follow the syntax of the @code{QTDV} packets that define
43761 trace state variables.
43767 @cindex @samp{qTfSTM} packet
43768 @cindex @samp{qTsSTM} packet
43769 These packets request data about static tracepoint markers that exist
43770 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
43771 first piece of data, and multiple @code{qTsSTM} to get additional
43772 pieces. Replies to these packets take the following form:
43776 @item m @var{address}:@var{id}:@var{extra}
43778 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
43779 a comma-separated list of markers
43781 (lower case letter @samp{L}) denotes end of list.
43783 An error occurred. The error number @var{nn} is given as hex digits.
43785 An empty reply indicates that the request is not supported by the
43789 The @var{address} is encoded in hex;
43790 @var{id} and @var{extra} are strings encoded in hex.
43792 In response to each query, the target will reply with a list of one or
43793 more markers, separated by commas. @value{GDBN} will respond to each
43794 reply with a request for more markers (using the @samp{qs} form of the
43795 query), until the target responds with @samp{l} (lower-case ell, for
43798 @item qTSTMat:@var{address}
43800 @cindex @samp{qTSTMat} packet
43801 This packets requests data about static tracepoint markers in the
43802 target program at @var{address}. Replies to this packet follow the
43803 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
43804 tracepoint markers.
43806 @item QTSave:@var{filename}
43807 @cindex @samp{QTSave} packet
43808 This packet directs the target to save trace data to the file name
43809 @var{filename} in the target's filesystem. The @var{filename} is encoded
43810 as a hex string; the interpretation of the file name (relative vs
43811 absolute, wild cards, etc) is up to the target.
43813 @item qTBuffer:@var{offset},@var{len}
43814 @cindex @samp{qTBuffer} packet
43815 Return up to @var{len} bytes of the current contents of trace buffer,
43816 starting at @var{offset}. The trace buffer is treated as if it were
43817 a contiguous collection of traceframes, as per the trace file format.
43818 The reply consists as many hex-encoded bytes as the target can deliver
43819 in a packet; it is not an error to return fewer than were asked for.
43820 A reply consisting of just @code{l} indicates that no bytes are
43823 @item QTBuffer:circular:@var{value}
43824 This packet directs the target to use a circular trace buffer if
43825 @var{value} is 1, or a linear buffer if the value is 0.
43827 @item QTBuffer:size:@var{size}
43828 @anchor{QTBuffer-size}
43829 @cindex @samp{QTBuffer size} packet
43830 This packet directs the target to make the trace buffer be of size
43831 @var{size} if possible. A value of @code{-1} tells the target to
43832 use whatever size it prefers.
43834 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
43835 @cindex @samp{QTNotes} packet
43836 This packet adds optional textual notes to the trace run. Allowable
43837 types include @code{user}, @code{notes}, and @code{tstop}, the
43838 @var{text} fields are arbitrary strings, hex-encoded.
43842 @subsection Relocate instruction reply packet
43843 When installing fast tracepoints in memory, the target may need to
43844 relocate the instruction currently at the tracepoint address to a
43845 different address in memory. For most instructions, a simple copy is
43846 enough, but, for example, call instructions that implicitly push the
43847 return address on the stack, and relative branches or other
43848 PC-relative instructions require offset adjustment, so that the effect
43849 of executing the instruction at a different address is the same as if
43850 it had executed in the original location.
43852 In response to several of the tracepoint packets, the target may also
43853 respond with a number of intermediate @samp{qRelocInsn} request
43854 packets before the final result packet, to have @value{GDBN} handle
43855 this relocation operation. If a packet supports this mechanism, its
43856 documentation will explicitly say so. See for example the above
43857 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
43858 format of the request is:
43861 @item qRelocInsn:@var{from};@var{to}
43863 This requests @value{GDBN} to copy instruction at address @var{from}
43864 to address @var{to}, possibly adjusted so that executing the
43865 instruction at @var{to} has the same effect as executing it at
43866 @var{from}. @value{GDBN} writes the adjusted instruction to target
43867 memory starting at @var{to}.
43872 @item qRelocInsn:@var{adjusted_size}
43873 Informs the stub the relocation is complete. The @var{adjusted_size} is
43874 the length in bytes of resulting relocated instruction sequence.
43876 A badly formed request was detected, or an error was encountered while
43877 relocating the instruction.
43880 @node Host I/O Packets
43881 @section Host I/O Packets
43882 @cindex Host I/O, remote protocol
43883 @cindex file transfer, remote protocol
43885 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
43886 operations on the far side of a remote link. For example, Host I/O is
43887 used to upload and download files to a remote target with its own
43888 filesystem. Host I/O uses the same constant values and data structure
43889 layout as the target-initiated File-I/O protocol. However, the
43890 Host I/O packets are structured differently. The target-initiated
43891 protocol relies on target memory to store parameters and buffers.
43892 Host I/O requests are initiated by @value{GDBN}, and the
43893 target's memory is not involved. @xref{File-I/O Remote Protocol
43894 Extension}, for more details on the target-initiated protocol.
43896 The Host I/O request packets all encode a single operation along with
43897 its arguments. They have this format:
43901 @item vFile:@var{operation}: @var{parameter}@dots{}
43902 @var{operation} is the name of the particular request; the target
43903 should compare the entire packet name up to the second colon when checking
43904 for a supported operation. The format of @var{parameter} depends on
43905 the operation. Numbers are always passed in hexadecimal. Negative
43906 numbers have an explicit minus sign (i.e.@: two's complement is not
43907 used). Strings (e.g.@: filenames) are encoded as a series of
43908 hexadecimal bytes. The last argument to a system call may be a
43909 buffer of escaped binary data (@pxref{Binary Data}).
43913 The valid responses to Host I/O packets are:
43917 @item F @var{result} [, @var{errno}] [; @var{attachment}]
43918 @var{result} is the integer value returned by this operation, usually
43919 non-negative for success and -1 for errors. If an error has occured,
43920 @var{errno} will be included in the result specifying a
43921 value defined by the File-I/O protocol (@pxref{Errno Values}). For
43922 operations which return data, @var{attachment} supplies the data as a
43923 binary buffer. Binary buffers in response packets are escaped in the
43924 normal way (@pxref{Binary Data}). See the individual packet
43925 documentation for the interpretation of @var{result} and
43929 An empty response indicates that this operation is not recognized.
43933 These are the supported Host I/O operations:
43936 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
43937 Open a file at @var{filename} and return a file descriptor for it, or
43938 return -1 if an error occurs. The @var{filename} is a string,
43939 @var{flags} is an integer indicating a mask of open flags
43940 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
43941 of mode bits to use if the file is created (@pxref{mode_t Values}).
43942 @xref{open}, for details of the open flags and mode values.
43944 @item vFile:close: @var{fd}
43945 Close the open file corresponding to @var{fd} and return 0, or
43946 -1 if an error occurs.
43948 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
43949 Read data from the open file corresponding to @var{fd}. Up to
43950 @var{count} bytes will be read from the file, starting at @var{offset}
43951 relative to the start of the file. The target may read fewer bytes;
43952 common reasons include packet size limits and an end-of-file
43953 condition. The number of bytes read is returned. Zero should only be
43954 returned for a successful read at the end of the file, or if
43955 @var{count} was zero.
43957 The data read should be returned as a binary attachment on success.
43958 If zero bytes were read, the response should include an empty binary
43959 attachment (i.e.@: a trailing semicolon). The return value is the
43960 number of target bytes read; the binary attachment may be longer if
43961 some characters were escaped.
43963 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
43964 Write @var{data} (a binary buffer) to the open file corresponding
43965 to @var{fd}. Start the write at @var{offset} from the start of the
43966 file. Unlike many @code{write} system calls, there is no
43967 separate @var{count} argument; the length of @var{data} in the
43968 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
43969 which may be shorter than the length of @var{data}, or -1 if an
43972 @item vFile:fstat: @var{fd}
43973 Get information about the open file corresponding to @var{fd}.
43974 On success the information is returned as a binary attachment
43975 and the return value is the size of this attachment in bytes.
43976 If an error occurs the return value is -1. The format of the
43977 returned binary attachment is as described in @ref{struct stat}.
43979 @item vFile:unlink: @var{filename}
43980 Delete the file at @var{filename} on the target. Return 0,
43981 or -1 if an error occurs. The @var{filename} is a string.
43983 @item vFile:readlink: @var{filename}
43984 Read value of symbolic link @var{filename} on the target. Return
43985 the number of bytes read, or -1 if an error occurs.
43987 The data read should be returned as a binary attachment on success.
43988 If zero bytes were read, the response should include an empty binary
43989 attachment (i.e.@: a trailing semicolon). The return value is the
43990 number of target bytes read; the binary attachment may be longer if
43991 some characters were escaped.
43993 @item vFile:setfs: @var{pid}
43994 Select the filesystem on which @code{vFile} operations with
43995 @var{filename} arguments will operate. This is required for
43996 @value{GDBN} to be able to access files on remote targets where
43997 the remote stub does not share a common filesystem with the
44000 If @var{pid} is nonzero, select the filesystem as seen by process
44001 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44002 the remote stub. Return 0 on success, or -1 if an error occurs.
44003 If @code{vFile:setfs:} indicates success, the selected filesystem
44004 remains selected until the next successful @code{vFile:setfs:}
44010 @section Interrupts
44011 @cindex interrupts (remote protocol)
44012 @anchor{interrupting remote targets}
44014 In all-stop mode, when a program on the remote target is running,
44015 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44016 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44017 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44019 The precise meaning of @code{BREAK} is defined by the transport
44020 mechanism and may, in fact, be undefined. @value{GDBN} does not
44021 currently define a @code{BREAK} mechanism for any of the network
44022 interfaces except for TCP, in which case @value{GDBN} sends the
44023 @code{telnet} BREAK sequence.
44025 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44026 transport mechanisms. It is represented by sending the single byte
44027 @code{0x03} without any of the usual packet overhead described in
44028 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44029 transmitted as part of a packet, it is considered to be packet data
44030 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44031 (@pxref{X packet}), used for binary downloads, may include an unescaped
44032 @code{0x03} as part of its packet.
44034 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44035 When Linux kernel receives this sequence from serial port,
44036 it stops execution and connects to gdb.
44038 In non-stop mode, because packet resumptions are asynchronous
44039 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44040 command to the remote stub, even when the target is running. For that
44041 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44042 packet}) with the usual packet framing instead of the single byte
44045 Stubs are not required to recognize these interrupt mechanisms and the
44046 precise meaning associated with receipt of the interrupt is
44047 implementation defined. If the target supports debugging of multiple
44048 threads and/or processes, it should attempt to interrupt all
44049 currently-executing threads and processes.
44050 If the stub is successful at interrupting the
44051 running program, it should send one of the stop
44052 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44053 of successfully stopping the program in all-stop mode, and a stop reply
44054 for each stopped thread in non-stop mode.
44055 Interrupts received while the
44056 program is stopped are queued and the program will be interrupted when
44057 it is resumed next time.
44059 @node Notification Packets
44060 @section Notification Packets
44061 @cindex notification packets
44062 @cindex packets, notification
44064 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44065 packets that require no acknowledgment. Both the GDB and the stub
44066 may send notifications (although the only notifications defined at
44067 present are sent by the stub). Notifications carry information
44068 without incurring the round-trip latency of an acknowledgment, and so
44069 are useful for low-impact communications where occasional packet loss
44072 A notification packet has the form @samp{% @var{data} #
44073 @var{checksum}}, where @var{data} is the content of the notification,
44074 and @var{checksum} is a checksum of @var{data}, computed and formatted
44075 as for ordinary @value{GDBN} packets. A notification's @var{data}
44076 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44077 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44078 to acknowledge the notification's receipt or to report its corruption.
44080 Every notification's @var{data} begins with a name, which contains no
44081 colon characters, followed by a colon character.
44083 Recipients should silently ignore corrupted notifications and
44084 notifications they do not understand. Recipients should restart
44085 timeout periods on receipt of a well-formed notification, whether or
44086 not they understand it.
44088 Senders should only send the notifications described here when this
44089 protocol description specifies that they are permitted. In the
44090 future, we may extend the protocol to permit existing notifications in
44091 new contexts; this rule helps older senders avoid confusing newer
44094 (Older versions of @value{GDBN} ignore bytes received until they see
44095 the @samp{$} byte that begins an ordinary packet, so new stubs may
44096 transmit notifications without fear of confusing older clients. There
44097 are no notifications defined for @value{GDBN} to send at the moment, but we
44098 assume that most older stubs would ignore them, as well.)
44100 Each notification is comprised of three parts:
44102 @item @var{name}:@var{event}
44103 The notification packet is sent by the side that initiates the
44104 exchange (currently, only the stub does that), with @var{event}
44105 carrying the specific information about the notification, and
44106 @var{name} specifying the name of the notification.
44108 The acknowledge sent by the other side, usually @value{GDBN}, to
44109 acknowledge the exchange and request the event.
44112 The purpose of an asynchronous notification mechanism is to report to
44113 @value{GDBN} that something interesting happened in the remote stub.
44115 The remote stub may send notification @var{name}:@var{event}
44116 at any time, but @value{GDBN} acknowledges the notification when
44117 appropriate. The notification event is pending before @value{GDBN}
44118 acknowledges. Only one notification at a time may be pending; if
44119 additional events occur before @value{GDBN} has acknowledged the
44120 previous notification, they must be queued by the stub for later
44121 synchronous transmission in response to @var{ack} packets from
44122 @value{GDBN}. Because the notification mechanism is unreliable,
44123 the stub is permitted to resend a notification if it believes
44124 @value{GDBN} may not have received it.
44126 Specifically, notifications may appear when @value{GDBN} is not
44127 otherwise reading input from the stub, or when @value{GDBN} is
44128 expecting to read a normal synchronous response or a
44129 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44130 Notification packets are distinct from any other communication from
44131 the stub so there is no ambiguity.
44133 After receiving a notification, @value{GDBN} shall acknowledge it by
44134 sending a @var{ack} packet as a regular, synchronous request to the
44135 stub. Such acknowledgment is not required to happen immediately, as
44136 @value{GDBN} is permitted to send other, unrelated packets to the
44137 stub first, which the stub should process normally.
44139 Upon receiving a @var{ack} packet, if the stub has other queued
44140 events to report to @value{GDBN}, it shall respond by sending a
44141 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44142 packet to solicit further responses; again, it is permitted to send
44143 other, unrelated packets as well which the stub should process
44146 If the stub receives a @var{ack} packet and there are no additional
44147 @var{event} to report, the stub shall return an @samp{OK} response.
44148 At this point, @value{GDBN} has finished processing a notification
44149 and the stub has completed sending any queued events. @value{GDBN}
44150 won't accept any new notifications until the final @samp{OK} is
44151 received . If further notification events occur, the stub shall send
44152 a new notification, @value{GDBN} shall accept the notification, and
44153 the process shall be repeated.
44155 The process of asynchronous notification can be illustrated by the
44158 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44161 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44163 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44168 The following notifications are defined:
44169 @multitable @columnfractions 0.12 0.12 0.38 0.38
44178 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44179 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44180 for information on how these notifications are acknowledged by
44182 @tab Report an asynchronous stop event in non-stop mode.
44186 @node Remote Non-Stop
44187 @section Remote Protocol Support for Non-Stop Mode
44189 @value{GDBN}'s remote protocol supports non-stop debugging of
44190 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44191 supports non-stop mode, it should report that to @value{GDBN} by including
44192 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44194 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44195 establishing a new connection with the stub. Entering non-stop mode
44196 does not alter the state of any currently-running threads, but targets
44197 must stop all threads in any already-attached processes when entering
44198 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44199 probe the target state after a mode change.
44201 In non-stop mode, when an attached process encounters an event that
44202 would otherwise be reported with a stop reply, it uses the
44203 asynchronous notification mechanism (@pxref{Notification Packets}) to
44204 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44205 in all processes are stopped when a stop reply is sent, in non-stop
44206 mode only the thread reporting the stop event is stopped. That is,
44207 when reporting a @samp{S} or @samp{T} response to indicate completion
44208 of a step operation, hitting a breakpoint, or a fault, only the
44209 affected thread is stopped; any other still-running threads continue
44210 to run. When reporting a @samp{W} or @samp{X} response, all running
44211 threads belonging to other attached processes continue to run.
44213 In non-stop mode, the target shall respond to the @samp{?} packet as
44214 follows. First, any incomplete stop reply notification/@samp{vStopped}
44215 sequence in progress is abandoned. The target must begin a new
44216 sequence reporting stop events for all stopped threads, whether or not
44217 it has previously reported those events to @value{GDBN}. The first
44218 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44219 subsequent stop replies are sent as responses to @samp{vStopped} packets
44220 using the mechanism described above. The target must not send
44221 asynchronous stop reply notifications until the sequence is complete.
44222 If all threads are running when the target receives the @samp{?} packet,
44223 or if the target is not attached to any process, it shall respond
44226 If the stub supports non-stop mode, it should also support the
44227 @samp{swbreak} stop reason if software breakpoints are supported, and
44228 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44229 (@pxref{swbreak stop reason}). This is because given the asynchronous
44230 nature of non-stop mode, between the time a thread hits a breakpoint
44231 and the time the event is finally processed by @value{GDBN}, the
44232 breakpoint may have already been removed from the target. Due to
44233 this, @value{GDBN} needs to be able to tell whether a trap stop was
44234 caused by a delayed breakpoint event, which should be ignored, as
44235 opposed to a random trap signal, which should be reported to the user.
44236 Note the @samp{swbreak} feature implies that the target is responsible
44237 for adjusting the PC when a software breakpoint triggers, if
44238 necessary, such as on the x86 architecture.
44240 @node Packet Acknowledgment
44241 @section Packet Acknowledgment
44243 @cindex acknowledgment, for @value{GDBN} remote
44244 @cindex packet acknowledgment, for @value{GDBN} remote
44245 By default, when either the host or the target machine receives a packet,
44246 the first response expected is an acknowledgment: either @samp{+} (to indicate
44247 the package was received correctly) or @samp{-} (to request retransmission).
44248 This mechanism allows the @value{GDBN} remote protocol to operate over
44249 unreliable transport mechanisms, such as a serial line.
44251 In cases where the transport mechanism is itself reliable (such as a pipe or
44252 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44253 It may be desirable to disable them in that case to reduce communication
44254 overhead, or for other reasons. This can be accomplished by means of the
44255 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44257 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44258 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44259 and response format still includes the normal checksum, as described in
44260 @ref{Overview}, but the checksum may be ignored by the receiver.
44262 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44263 no-acknowledgment mode, it should report that to @value{GDBN}
44264 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44265 @pxref{qSupported}.
44266 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44267 disabled via the @code{set remote noack-packet off} command
44268 (@pxref{Remote Configuration}),
44269 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44270 Only then may the stub actually turn off packet acknowledgments.
44271 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44272 response, which can be safely ignored by the stub.
44274 Note that @code{set remote noack-packet} command only affects negotiation
44275 between @value{GDBN} and the stub when subsequent connections are made;
44276 it does not affect the protocol acknowledgment state for any current
44278 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44279 new connection is established,
44280 there is also no protocol request to re-enable the acknowledgments
44281 for the current connection, once disabled.
44286 Example sequence of a target being re-started. Notice how the restart
44287 does not get any direct output:
44292 @emph{target restarts}
44295 <- @code{T001:1234123412341234}
44299 Example sequence of a target being stepped by a single instruction:
44302 -> @code{G1445@dots{}}
44307 <- @code{T001:1234123412341234}
44311 <- @code{1455@dots{}}
44315 @node File-I/O Remote Protocol Extension
44316 @section File-I/O Remote Protocol Extension
44317 @cindex File-I/O remote protocol extension
44320 * File-I/O Overview::
44321 * Protocol Basics::
44322 * The F Request Packet::
44323 * The F Reply Packet::
44324 * The Ctrl-C Message::
44326 * List of Supported Calls::
44327 * Protocol-specific Representation of Datatypes::
44329 * File-I/O Examples::
44332 @node File-I/O Overview
44333 @subsection File-I/O Overview
44334 @cindex file-i/o overview
44336 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44337 target to use the host's file system and console I/O to perform various
44338 system calls. System calls on the target system are translated into a
44339 remote protocol packet to the host system, which then performs the needed
44340 actions and returns a response packet to the target system.
44341 This simulates file system operations even on targets that lack file systems.
44343 The protocol is defined to be independent of both the host and target systems.
44344 It uses its own internal representation of datatypes and values. Both
44345 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44346 translating the system-dependent value representations into the internal
44347 protocol representations when data is transmitted.
44349 The communication is synchronous. A system call is possible only when
44350 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44351 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44352 the target is stopped to allow deterministic access to the target's
44353 memory. Therefore File-I/O is not interruptible by target signals. On
44354 the other hand, it is possible to interrupt File-I/O by a user interrupt
44355 (@samp{Ctrl-C}) within @value{GDBN}.
44357 The target's request to perform a host system call does not finish
44358 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44359 after finishing the system call, the target returns to continuing the
44360 previous activity (continue, step). No additional continue or step
44361 request from @value{GDBN} is required.
44364 (@value{GDBP}) continue
44365 <- target requests 'system call X'
44366 target is stopped, @value{GDBN} executes system call
44367 -> @value{GDBN} returns result
44368 ... target continues, @value{GDBN} returns to wait for the target
44369 <- target hits breakpoint and sends a Txx packet
44372 The protocol only supports I/O on the console and to regular files on
44373 the host file system. Character or block special devices, pipes,
44374 named pipes, sockets or any other communication method on the host
44375 system are not supported by this protocol.
44377 File I/O is not supported in non-stop mode.
44379 @node Protocol Basics
44380 @subsection Protocol Basics
44381 @cindex protocol basics, file-i/o
44383 The File-I/O protocol uses the @code{F} packet as the request as well
44384 as reply packet. Since a File-I/O system call can only occur when
44385 @value{GDBN} is waiting for a response from the continuing or stepping target,
44386 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44387 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44388 This @code{F} packet contains all information needed to allow @value{GDBN}
44389 to call the appropriate host system call:
44393 A unique identifier for the requested system call.
44396 All parameters to the system call. Pointers are given as addresses
44397 in the target memory address space. Pointers to strings are given as
44398 pointer/length pair. Numerical values are given as they are.
44399 Numerical control flags are given in a protocol-specific representation.
44403 At this point, @value{GDBN} has to perform the following actions.
44407 If the parameters include pointer values to data needed as input to a
44408 system call, @value{GDBN} requests this data from the target with a
44409 standard @code{m} packet request. This additional communication has to be
44410 expected by the target implementation and is handled as any other @code{m}
44414 @value{GDBN} translates all value from protocol representation to host
44415 representation as needed. Datatypes are coerced into the host types.
44418 @value{GDBN} calls the system call.
44421 It then coerces datatypes back to protocol representation.
44424 If the system call is expected to return data in buffer space specified
44425 by pointer parameters to the call, the data is transmitted to the
44426 target using a @code{M} or @code{X} packet. This packet has to be expected
44427 by the target implementation and is handled as any other @code{M} or @code{X}
44432 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44433 necessary information for the target to continue. This at least contains
44440 @code{errno}, if has been changed by the system call.
44447 After having done the needed type and value coercion, the target continues
44448 the latest continue or step action.
44450 @node The F Request Packet
44451 @subsection The @code{F} Request Packet
44452 @cindex file-i/o request packet
44453 @cindex @code{F} request packet
44455 The @code{F} request packet has the following format:
44458 @item F@var{call-id},@var{parameter@dots{}}
44460 @var{call-id} is the identifier to indicate the host system call to be called.
44461 This is just the name of the function.
44463 @var{parameter@dots{}} are the parameters to the system call.
44464 Parameters are hexadecimal integer values, either the actual values in case
44465 of scalar datatypes, pointers to target buffer space in case of compound
44466 datatypes and unspecified memory areas, or pointer/length pairs in case
44467 of string parameters. These are appended to the @var{call-id} as a
44468 comma-delimited list. All values are transmitted in ASCII
44469 string representation, pointer/length pairs separated by a slash.
44475 @node The F Reply Packet
44476 @subsection The @code{F} Reply Packet
44477 @cindex file-i/o reply packet
44478 @cindex @code{F} reply packet
44480 The @code{F} reply packet has the following format:
44484 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44486 @var{retcode} is the return code of the system call as hexadecimal value.
44488 @var{errno} is the @code{errno} set by the call, in protocol-specific
44490 This parameter can be omitted if the call was successful.
44492 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44493 case, @var{errno} must be sent as well, even if the call was successful.
44494 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44501 or, if the call was interrupted before the host call has been performed:
44508 assuming 4 is the protocol-specific representation of @code{EINTR}.
44513 @node The Ctrl-C Message
44514 @subsection The @samp{Ctrl-C} Message
44515 @cindex ctrl-c message, in file-i/o protocol
44517 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44518 reply packet (@pxref{The F Reply Packet}),
44519 the target should behave as if it had
44520 gotten a break message. The meaning for the target is ``system call
44521 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44522 (as with a break message) and return to @value{GDBN} with a @code{T02}
44525 It's important for the target to know in which
44526 state the system call was interrupted. There are two possible cases:
44530 The system call hasn't been performed on the host yet.
44533 The system call on the host has been finished.
44537 These two states can be distinguished by the target by the value of the
44538 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44539 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44540 on POSIX systems. In any other case, the target may presume that the
44541 system call has been finished --- successfully or not --- and should behave
44542 as if the break message arrived right after the system call.
44544 @value{GDBN} must behave reliably. If the system call has not been called
44545 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44546 @code{errno} in the packet. If the system call on the host has been finished
44547 before the user requests a break, the full action must be finished by
44548 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44549 The @code{F} packet may only be sent when either nothing has happened
44550 or the full action has been completed.
44553 @subsection Console I/O
44554 @cindex console i/o as part of file-i/o
44556 By default and if not explicitly closed by the target system, the file
44557 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44558 on the @value{GDBN} console is handled as any other file output operation
44559 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44560 by @value{GDBN} so that after the target read request from file descriptor
44561 0 all following typing is buffered until either one of the following
44566 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44568 system call is treated as finished.
44571 The user presses @key{RET}. This is treated as end of input with a trailing
44575 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44576 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44580 If the user has typed more characters than fit in the buffer given to
44581 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44582 either another @code{read(0, @dots{})} is requested by the target, or debugging
44583 is stopped at the user's request.
44586 @node List of Supported Calls
44587 @subsection List of Supported Calls
44588 @cindex list of supported file-i/o calls
44605 @unnumberedsubsubsec open
44606 @cindex open, file-i/o system call
44611 int open(const char *pathname, int flags);
44612 int open(const char *pathname, int flags, mode_t mode);
44616 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
44619 @var{flags} is the bitwise @code{OR} of the following values:
44623 If the file does not exist it will be created. The host
44624 rules apply as far as file ownership and time stamps
44628 When used with @code{O_CREAT}, if the file already exists it is
44629 an error and open() fails.
44632 If the file already exists and the open mode allows
44633 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
44634 truncated to zero length.
44637 The file is opened in append mode.
44640 The file is opened for reading only.
44643 The file is opened for writing only.
44646 The file is opened for reading and writing.
44650 Other bits are silently ignored.
44654 @var{mode} is the bitwise @code{OR} of the following values:
44658 User has read permission.
44661 User has write permission.
44664 Group has read permission.
44667 Group has write permission.
44670 Others have read permission.
44673 Others have write permission.
44677 Other bits are silently ignored.
44680 @item Return value:
44681 @code{open} returns the new file descriptor or -1 if an error
44688 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
44691 @var{pathname} refers to a directory.
44694 The requested access is not allowed.
44697 @var{pathname} was too long.
44700 A directory component in @var{pathname} does not exist.
44703 @var{pathname} refers to a device, pipe, named pipe or socket.
44706 @var{pathname} refers to a file on a read-only filesystem and
44707 write access was requested.
44710 @var{pathname} is an invalid pointer value.
44713 No space on device to create the file.
44716 The process already has the maximum number of files open.
44719 The limit on the total number of files open on the system
44723 The call was interrupted by the user.
44729 @unnumberedsubsubsec close
44730 @cindex close, file-i/o system call
44739 @samp{Fclose,@var{fd}}
44741 @item Return value:
44742 @code{close} returns zero on success, or -1 if an error occurred.
44748 @var{fd} isn't a valid open file descriptor.
44751 The call was interrupted by the user.
44757 @unnumberedsubsubsec read
44758 @cindex read, file-i/o system call
44763 int read(int fd, void *buf, unsigned int count);
44767 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
44769 @item Return value:
44770 On success, the number of bytes read is returned.
44771 Zero indicates end of file. If count is zero, read
44772 returns zero as well. On error, -1 is returned.
44778 @var{fd} is not a valid file descriptor or is not open for
44782 @var{bufptr} is an invalid pointer value.
44785 The call was interrupted by the user.
44791 @unnumberedsubsubsec write
44792 @cindex write, file-i/o system call
44797 int write(int fd, const void *buf, unsigned int count);
44801 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
44803 @item Return value:
44804 On success, the number of bytes written are returned.
44805 Zero indicates nothing was written. On error, -1
44812 @var{fd} is not a valid file descriptor or is not open for
44816 @var{bufptr} is an invalid pointer value.
44819 An attempt was made to write a file that exceeds the
44820 host-specific maximum file size allowed.
44823 No space on device to write the data.
44826 The call was interrupted by the user.
44832 @unnumberedsubsubsec lseek
44833 @cindex lseek, file-i/o system call
44838 long lseek (int fd, long offset, int flag);
44842 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
44844 @var{flag} is one of:
44848 The offset is set to @var{offset} bytes.
44851 The offset is set to its current location plus @var{offset}
44855 The offset is set to the size of the file plus @var{offset}
44859 @item Return value:
44860 On success, the resulting unsigned offset in bytes from
44861 the beginning of the file is returned. Otherwise, a
44862 value of -1 is returned.
44868 @var{fd} is not a valid open file descriptor.
44871 @var{fd} is associated with the @value{GDBN} console.
44874 @var{flag} is not a proper value.
44877 The call was interrupted by the user.
44883 @unnumberedsubsubsec rename
44884 @cindex rename, file-i/o system call
44889 int rename(const char *oldpath, const char *newpath);
44893 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
44895 @item Return value:
44896 On success, zero is returned. On error, -1 is returned.
44902 @var{newpath} is an existing directory, but @var{oldpath} is not a
44906 @var{newpath} is a non-empty directory.
44909 @var{oldpath} or @var{newpath} is a directory that is in use by some
44913 An attempt was made to make a directory a subdirectory
44917 A component used as a directory in @var{oldpath} or new
44918 path is not a directory. Or @var{oldpath} is a directory
44919 and @var{newpath} exists but is not a directory.
44922 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
44925 No access to the file or the path of the file.
44929 @var{oldpath} or @var{newpath} was too long.
44932 A directory component in @var{oldpath} or @var{newpath} does not exist.
44935 The file is on a read-only filesystem.
44938 The device containing the file has no room for the new
44942 The call was interrupted by the user.
44948 @unnumberedsubsubsec unlink
44949 @cindex unlink, file-i/o system call
44954 int unlink(const char *pathname);
44958 @samp{Funlink,@var{pathnameptr}/@var{len}}
44960 @item Return value:
44961 On success, zero is returned. On error, -1 is returned.
44967 No access to the file or the path of the file.
44970 The system does not allow unlinking of directories.
44973 The file @var{pathname} cannot be unlinked because it's
44974 being used by another process.
44977 @var{pathnameptr} is an invalid pointer value.
44980 @var{pathname} was too long.
44983 A directory component in @var{pathname} does not exist.
44986 A component of the path is not a directory.
44989 The file is on a read-only filesystem.
44992 The call was interrupted by the user.
44998 @unnumberedsubsubsec stat/fstat
44999 @cindex fstat, file-i/o system call
45000 @cindex stat, file-i/o system call
45005 int stat(const char *pathname, struct stat *buf);
45006 int fstat(int fd, struct stat *buf);
45010 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45011 @samp{Ffstat,@var{fd},@var{bufptr}}
45013 @item Return value:
45014 On success, zero is returned. On error, -1 is returned.
45020 @var{fd} is not a valid open file.
45023 A directory component in @var{pathname} does not exist or the
45024 path is an empty string.
45027 A component of the path is not a directory.
45030 @var{pathnameptr} is an invalid pointer value.
45033 No access to the file or the path of the file.
45036 @var{pathname} was too long.
45039 The call was interrupted by the user.
45045 @unnumberedsubsubsec gettimeofday
45046 @cindex gettimeofday, file-i/o system call
45051 int gettimeofday(struct timeval *tv, void *tz);
45055 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45057 @item Return value:
45058 On success, 0 is returned, -1 otherwise.
45064 @var{tz} is a non-NULL pointer.
45067 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45073 @unnumberedsubsubsec isatty
45074 @cindex isatty, file-i/o system call
45079 int isatty(int fd);
45083 @samp{Fisatty,@var{fd}}
45085 @item Return value:
45086 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45092 The call was interrupted by the user.
45097 Note that the @code{isatty} call is treated as a special case: it returns
45098 1 to the target if the file descriptor is attached
45099 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45100 would require implementing @code{ioctl} and would be more complex than
45105 @unnumberedsubsubsec system
45106 @cindex system, file-i/o system call
45111 int system(const char *command);
45115 @samp{Fsystem,@var{commandptr}/@var{len}}
45117 @item Return value:
45118 If @var{len} is zero, the return value indicates whether a shell is
45119 available. A zero return value indicates a shell is not available.
45120 For non-zero @var{len}, the value returned is -1 on error and the
45121 return status of the command otherwise. Only the exit status of the
45122 command is returned, which is extracted from the host's @code{system}
45123 return value by calling @code{WEXITSTATUS(retval)}. In case
45124 @file{/bin/sh} could not be executed, 127 is returned.
45130 The call was interrupted by the user.
45135 @value{GDBN} takes over the full task of calling the necessary host calls
45136 to perform the @code{system} call. The return value of @code{system} on
45137 the host is simplified before it's returned
45138 to the target. Any termination signal information from the child process
45139 is discarded, and the return value consists
45140 entirely of the exit status of the called command.
45142 Due to security concerns, the @code{system} call is by default refused
45143 by @value{GDBN}. The user has to allow this call explicitly with the
45144 @code{set remote system-call-allowed 1} command.
45147 @item set remote system-call-allowed
45148 @kindex set remote system-call-allowed
45149 Control whether to allow the @code{system} calls in the File I/O
45150 protocol for the remote target. The default is zero (disabled).
45152 @item show remote system-call-allowed
45153 @kindex show remote system-call-allowed
45154 Show whether the @code{system} calls are allowed in the File I/O
45158 @node Protocol-specific Representation of Datatypes
45159 @subsection Protocol-specific Representation of Datatypes
45160 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45163 * Integral Datatypes::
45165 * Memory Transfer::
45170 @node Integral Datatypes
45171 @unnumberedsubsubsec Integral Datatypes
45172 @cindex integral datatypes, in file-i/o protocol
45174 The integral datatypes used in the system calls are @code{int},
45175 @code{unsigned int}, @code{long}, @code{unsigned long},
45176 @code{mode_t}, and @code{time_t}.
45178 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45179 implemented as 32 bit values in this protocol.
45181 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45183 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45184 in @file{limits.h}) to allow range checking on host and target.
45186 @code{time_t} datatypes are defined as seconds since the Epoch.
45188 All integral datatypes transferred as part of a memory read or write of a
45189 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45192 @node Pointer Values
45193 @unnumberedsubsubsec Pointer Values
45194 @cindex pointer values, in file-i/o protocol
45196 Pointers to target data are transmitted as they are. An exception
45197 is made for pointers to buffers for which the length isn't
45198 transmitted as part of the function call, namely strings. Strings
45199 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45206 which is a pointer to data of length 18 bytes at position 0x1aaf.
45207 The length is defined as the full string length in bytes, including
45208 the trailing null byte. For example, the string @code{"hello world"}
45209 at address 0x123456 is transmitted as
45215 @node Memory Transfer
45216 @unnumberedsubsubsec Memory Transfer
45217 @cindex memory transfer, in file-i/o protocol
45219 Structured data which is transferred using a memory read or write (for
45220 example, a @code{struct stat}) is expected to be in a protocol-specific format
45221 with all scalar multibyte datatypes being big endian. Translation to
45222 this representation needs to be done both by the target before the @code{F}
45223 packet is sent, and by @value{GDBN} before
45224 it transfers memory to the target. Transferred pointers to structured
45225 data should point to the already-coerced data at any time.
45229 @unnumberedsubsubsec struct stat
45230 @cindex struct stat, in file-i/o protocol
45232 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45233 is defined as follows:
45237 unsigned int st_dev; /* device */
45238 unsigned int st_ino; /* inode */
45239 mode_t st_mode; /* protection */
45240 unsigned int st_nlink; /* number of hard links */
45241 unsigned int st_uid; /* user ID of owner */
45242 unsigned int st_gid; /* group ID of owner */
45243 unsigned int st_rdev; /* device type (if inode device) */
45244 unsigned long st_size; /* total size, in bytes */
45245 unsigned long st_blksize; /* blocksize for filesystem I/O */
45246 unsigned long st_blocks; /* number of blocks allocated */
45247 time_t st_atime; /* time of last access */
45248 time_t st_mtime; /* time of last modification */
45249 time_t st_ctime; /* time of last change */
45253 The integral datatypes conform to the definitions given in the
45254 appropriate section (see @ref{Integral Datatypes}, for details) so this
45255 structure is of size 64 bytes.
45257 The values of several fields have a restricted meaning and/or
45263 A value of 0 represents a file, 1 the console.
45266 No valid meaning for the target. Transmitted unchanged.
45269 Valid mode bits are described in @ref{Constants}. Any other
45270 bits have currently no meaning for the target.
45275 No valid meaning for the target. Transmitted unchanged.
45280 These values have a host and file system dependent
45281 accuracy. Especially on Windows hosts, the file system may not
45282 support exact timing values.
45285 The target gets a @code{struct stat} of the above representation and is
45286 responsible for coercing it to the target representation before
45289 Note that due to size differences between the host, target, and protocol
45290 representations of @code{struct stat} members, these members could eventually
45291 get truncated on the target.
45293 @node struct timeval
45294 @unnumberedsubsubsec struct timeval
45295 @cindex struct timeval, in file-i/o protocol
45297 The buffer of type @code{struct timeval} used by the File-I/O protocol
45298 is defined as follows:
45302 time_t tv_sec; /* second */
45303 long tv_usec; /* microsecond */
45307 The integral datatypes conform to the definitions given in the
45308 appropriate section (see @ref{Integral Datatypes}, for details) so this
45309 structure is of size 8 bytes.
45312 @subsection Constants
45313 @cindex constants, in file-i/o protocol
45315 The following values are used for the constants inside of the
45316 protocol. @value{GDBN} and target are responsible for translating these
45317 values before and after the call as needed.
45328 @unnumberedsubsubsec Open Flags
45329 @cindex open flags, in file-i/o protocol
45331 All values are given in hexadecimal representation.
45343 @node mode_t Values
45344 @unnumberedsubsubsec mode_t Values
45345 @cindex mode_t values, in file-i/o protocol
45347 All values are given in octal representation.
45364 @unnumberedsubsubsec Errno Values
45365 @cindex errno values, in file-i/o protocol
45367 All values are given in decimal representation.
45392 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45393 any error value not in the list of supported error numbers.
45396 @unnumberedsubsubsec Lseek Flags
45397 @cindex lseek flags, in file-i/o protocol
45406 @unnumberedsubsubsec Limits
45407 @cindex limits, in file-i/o protocol
45409 All values are given in decimal representation.
45412 INT_MIN -2147483648
45414 UINT_MAX 4294967295
45415 LONG_MIN -9223372036854775808
45416 LONG_MAX 9223372036854775807
45417 ULONG_MAX 18446744073709551615
45420 @node File-I/O Examples
45421 @subsection File-I/O Examples
45422 @cindex file-i/o examples
45424 Example sequence of a write call, file descriptor 3, buffer is at target
45425 address 0x1234, 6 bytes should be written:
45428 <- @code{Fwrite,3,1234,6}
45429 @emph{request memory read from target}
45432 @emph{return "6 bytes written"}
45436 Example sequence of a read call, file descriptor 3, buffer is at target
45437 address 0x1234, 6 bytes should be read:
45440 <- @code{Fread,3,1234,6}
45441 @emph{request memory write to target}
45442 -> @code{X1234,6:XXXXXX}
45443 @emph{return "6 bytes read"}
45447 Example sequence of a read call, call fails on the host due to invalid
45448 file descriptor (@code{EBADF}):
45451 <- @code{Fread,3,1234,6}
45455 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45459 <- @code{Fread,3,1234,6}
45464 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45468 <- @code{Fread,3,1234,6}
45469 -> @code{X1234,6:XXXXXX}
45473 @node Library List Format
45474 @section Library List Format
45475 @cindex library list format, remote protocol
45477 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45478 same process as your application to manage libraries. In this case,
45479 @value{GDBN} can use the loader's symbol table and normal memory
45480 operations to maintain a list of shared libraries. On other
45481 platforms, the operating system manages loaded libraries.
45482 @value{GDBN} can not retrieve the list of currently loaded libraries
45483 through memory operations, so it uses the @samp{qXfer:libraries:read}
45484 packet (@pxref{qXfer library list read}) instead. The remote stub
45485 queries the target's operating system and reports which libraries
45488 The @samp{qXfer:libraries:read} packet returns an XML document which
45489 lists loaded libraries and their offsets. Each library has an
45490 associated name and one or more segment or section base addresses,
45491 which report where the library was loaded in memory.
45493 For the common case of libraries that are fully linked binaries, the
45494 library should have a list of segments. If the target supports
45495 dynamic linking of a relocatable object file, its library XML element
45496 should instead include a list of allocated sections. The segment or
45497 section bases are start addresses, not relocation offsets; they do not
45498 depend on the library's link-time base addresses.
45500 @value{GDBN} must be linked with the Expat library to support XML
45501 library lists. @xref{Expat}.
45503 A simple memory map, with one loaded library relocated by a single
45504 offset, looks like this:
45508 <library name="/lib/libc.so.6">
45509 <segment address="0x10000000"/>
45514 Another simple memory map, with one loaded library with three
45515 allocated sections (.text, .data, .bss), looks like this:
45519 <library name="sharedlib.o">
45520 <section address="0x10000000"/>
45521 <section address="0x20000000"/>
45522 <section address="0x30000000"/>
45527 The format of a library list is described by this DTD:
45530 <!-- library-list: Root element with versioning -->
45531 <!ELEMENT library-list (library)*>
45532 <!ATTLIST library-list version CDATA #FIXED "1.0">
45533 <!ELEMENT library (segment*, section*)>
45534 <!ATTLIST library name CDATA #REQUIRED>
45535 <!ELEMENT segment EMPTY>
45536 <!ATTLIST segment address CDATA #REQUIRED>
45537 <!ELEMENT section EMPTY>
45538 <!ATTLIST section address CDATA #REQUIRED>
45541 In addition, segments and section descriptors cannot be mixed within a
45542 single library element, and you must supply at least one segment or
45543 section for each library.
45545 @node Library List Format for SVR4 Targets
45546 @section Library List Format for SVR4 Targets
45547 @cindex library list format, remote protocol
45549 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45550 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45551 shared libraries. Still a special library list provided by this packet is
45552 more efficient for the @value{GDBN} remote protocol.
45554 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45555 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45556 target, the following parameters are reported:
45560 @code{name}, the absolute file name from the @code{l_name} field of
45561 @code{struct link_map}.
45563 @code{lm} with address of @code{struct link_map} used for TLS
45564 (Thread Local Storage) access.
45566 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45567 @code{struct link_map}. For prelinked libraries this is not an absolute
45568 memory address. It is a displacement of absolute memory address against
45569 address the file was prelinked to during the library load.
45571 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45574 Additionally the single @code{main-lm} attribute specifies address of
45575 @code{struct link_map} used for the main executable. This parameter is used
45576 for TLS access and its presence is optional.
45578 @value{GDBN} must be linked with the Expat library to support XML
45579 SVR4 library lists. @xref{Expat}.
45581 A simple memory map, with two loaded libraries (which do not use prelink),
45585 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45586 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45588 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45590 </library-list-svr>
45593 The format of an SVR4 library list is described by this DTD:
45596 <!-- library-list-svr4: Root element with versioning -->
45597 <!ELEMENT library-list-svr4 (library)*>
45598 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45599 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45600 <!ELEMENT library EMPTY>
45601 <!ATTLIST library name CDATA #REQUIRED>
45602 <!ATTLIST library lm CDATA #REQUIRED>
45603 <!ATTLIST library l_addr CDATA #REQUIRED>
45604 <!ATTLIST library l_ld CDATA #REQUIRED>
45607 @node Memory Map Format
45608 @section Memory Map Format
45609 @cindex memory map format
45611 To be able to write into flash memory, @value{GDBN} needs to obtain a
45612 memory map from the target. This section describes the format of the
45615 The memory map is obtained using the @samp{qXfer:memory-map:read}
45616 (@pxref{qXfer memory map read}) packet and is an XML document that
45617 lists memory regions.
45619 @value{GDBN} must be linked with the Expat library to support XML
45620 memory maps. @xref{Expat}.
45622 The top-level structure of the document is shown below:
45625 <?xml version="1.0"?>
45626 <!DOCTYPE memory-map
45627 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45628 "http://sourceware.org/gdb/gdb-memory-map.dtd">
45634 Each region can be either:
45639 A region of RAM starting at @var{addr} and extending for @var{length}
45643 <memory type="ram" start="@var{addr}" length="@var{length}"/>
45648 A region of read-only memory:
45651 <memory type="rom" start="@var{addr}" length="@var{length}"/>
45656 A region of flash memory, with erasure blocks @var{blocksize}
45660 <memory type="flash" start="@var{addr}" length="@var{length}">
45661 <property name="blocksize">@var{blocksize}</property>
45667 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
45668 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
45669 packets to write to addresses in such ranges.
45671 The formal DTD for memory map format is given below:
45674 <!-- ................................................... -->
45675 <!-- Memory Map XML DTD ................................ -->
45676 <!-- File: memory-map.dtd .............................. -->
45677 <!-- .................................... .............. -->
45678 <!-- memory-map.dtd -->
45679 <!-- memory-map: Root element with versioning -->
45680 <!ELEMENT memory-map (memory)*>
45681 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
45682 <!ELEMENT memory (property)*>
45683 <!-- memory: Specifies a memory region,
45684 and its type, or device. -->
45685 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
45686 start CDATA #REQUIRED
45687 length CDATA #REQUIRED>
45688 <!-- property: Generic attribute tag -->
45689 <!ELEMENT property (#PCDATA | property)*>
45690 <!ATTLIST property name (blocksize) #REQUIRED>
45693 @node Thread List Format
45694 @section Thread List Format
45695 @cindex thread list format
45697 To efficiently update the list of threads and their attributes,
45698 @value{GDBN} issues the @samp{qXfer:threads:read} packet
45699 (@pxref{qXfer threads read}) and obtains the XML document with
45700 the following structure:
45703 <?xml version="1.0"?>
45705 <thread id="id" core="0" name="name">
45706 ... description ...
45711 Each @samp{thread} element must have the @samp{id} attribute that
45712 identifies the thread (@pxref{thread-id syntax}). The
45713 @samp{core} attribute, if present, specifies which processor core
45714 the thread was last executing on. The @samp{name} attribute, if
45715 present, specifies the human-readable name of the thread. The content
45716 of the of @samp{thread} element is interpreted as human-readable
45717 auxiliary information. The @samp{handle} attribute, if present,
45718 is a hex encoded representation of the thread handle.
45721 @node Traceframe Info Format
45722 @section Traceframe Info Format
45723 @cindex traceframe info format
45725 To be able to know which objects in the inferior can be examined when
45726 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
45727 memory ranges, registers and trace state variables that have been
45728 collected in a traceframe.
45730 This list is obtained using the @samp{qXfer:traceframe-info:read}
45731 (@pxref{qXfer traceframe info read}) packet and is an XML document.
45733 @value{GDBN} must be linked with the Expat library to support XML
45734 traceframe info discovery. @xref{Expat}.
45736 The top-level structure of the document is shown below:
45739 <?xml version="1.0"?>
45740 <!DOCTYPE traceframe-info
45741 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45742 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
45748 Each traceframe block can be either:
45753 A region of collected memory starting at @var{addr} and extending for
45754 @var{length} bytes from there:
45757 <memory start="@var{addr}" length="@var{length}"/>
45761 A block indicating trace state variable numbered @var{number} has been
45765 <tvar id="@var{number}"/>
45770 The formal DTD for the traceframe info format is given below:
45773 <!ELEMENT traceframe-info (memory | tvar)* >
45774 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
45776 <!ELEMENT memory EMPTY>
45777 <!ATTLIST memory start CDATA #REQUIRED
45778 length CDATA #REQUIRED>
45780 <!ATTLIST tvar id CDATA #REQUIRED>
45783 @node Branch Trace Format
45784 @section Branch Trace Format
45785 @cindex branch trace format
45787 In order to display the branch trace of an inferior thread,
45788 @value{GDBN} needs to obtain the list of branches. This list is
45789 represented as list of sequential code blocks that are connected via
45790 branches. The code in each block has been executed sequentially.
45792 This list is obtained using the @samp{qXfer:btrace:read}
45793 (@pxref{qXfer btrace read}) packet and is an XML document.
45795 @value{GDBN} must be linked with the Expat library to support XML
45796 traceframe info discovery. @xref{Expat}.
45798 The top-level structure of the document is shown below:
45801 <?xml version="1.0"?>
45803 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
45804 "http://sourceware.org/gdb/gdb-btrace.dtd">
45813 A block of sequentially executed instructions starting at @var{begin}
45814 and ending at @var{end}:
45817 <block begin="@var{begin}" end="@var{end}"/>
45822 The formal DTD for the branch trace format is given below:
45825 <!ELEMENT btrace (block* | pt) >
45826 <!ATTLIST btrace version CDATA #FIXED "1.0">
45828 <!ELEMENT block EMPTY>
45829 <!ATTLIST block begin CDATA #REQUIRED
45830 end CDATA #REQUIRED>
45832 <!ELEMENT pt (pt-config?, raw?)>
45834 <!ELEMENT pt-config (cpu?)>
45836 <!ELEMENT cpu EMPTY>
45837 <!ATTLIST cpu vendor CDATA #REQUIRED
45838 family CDATA #REQUIRED
45839 model CDATA #REQUIRED
45840 stepping CDATA #REQUIRED>
45842 <!ELEMENT raw (#PCDATA)>
45845 @node Branch Trace Configuration Format
45846 @section Branch Trace Configuration Format
45847 @cindex branch trace configuration format
45849 For each inferior thread, @value{GDBN} can obtain the branch trace
45850 configuration using the @samp{qXfer:btrace-conf:read}
45851 (@pxref{qXfer btrace-conf read}) packet.
45853 The configuration describes the branch trace format and configuration
45854 settings for that format. The following information is described:
45858 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
45861 The size of the @acronym{BTS} ring buffer in bytes.
45864 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
45868 The size of the @acronym{Intel PT} ring buffer in bytes.
45872 @value{GDBN} must be linked with the Expat library to support XML
45873 branch trace configuration discovery. @xref{Expat}.
45875 The formal DTD for the branch trace configuration format is given below:
45878 <!ELEMENT btrace-conf (bts?, pt?)>
45879 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
45881 <!ELEMENT bts EMPTY>
45882 <!ATTLIST bts size CDATA #IMPLIED>
45884 <!ELEMENT pt EMPTY>
45885 <!ATTLIST pt size CDATA #IMPLIED>
45888 @include agentexpr.texi
45890 @node Target Descriptions
45891 @appendix Target Descriptions
45892 @cindex target descriptions
45894 One of the challenges of using @value{GDBN} to debug embedded systems
45895 is that there are so many minor variants of each processor
45896 architecture in use. It is common practice for vendors to start with
45897 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
45898 and then make changes to adapt it to a particular market niche. Some
45899 architectures have hundreds of variants, available from dozens of
45900 vendors. This leads to a number of problems:
45904 With so many different customized processors, it is difficult for
45905 the @value{GDBN} maintainers to keep up with the changes.
45907 Since individual variants may have short lifetimes or limited
45908 audiences, it may not be worthwhile to carry information about every
45909 variant in the @value{GDBN} source tree.
45911 When @value{GDBN} does support the architecture of the embedded system
45912 at hand, the task of finding the correct architecture name to give the
45913 @command{set architecture} command can be error-prone.
45916 To address these problems, the @value{GDBN} remote protocol allows a
45917 target system to not only identify itself to @value{GDBN}, but to
45918 actually describe its own features. This lets @value{GDBN} support
45919 processor variants it has never seen before --- to the extent that the
45920 descriptions are accurate, and that @value{GDBN} understands them.
45922 @value{GDBN} must be linked with the Expat library to support XML
45923 target descriptions. @xref{Expat}.
45926 * Retrieving Descriptions:: How descriptions are fetched from a target.
45927 * Target Description Format:: The contents of a target description.
45928 * Predefined Target Types:: Standard types available for target
45930 * Enum Target Types:: How to define enum target types.
45931 * Standard Target Features:: Features @value{GDBN} knows about.
45934 @node Retrieving Descriptions
45935 @section Retrieving Descriptions
45937 Target descriptions can be read from the target automatically, or
45938 specified by the user manually. The default behavior is to read the
45939 description from the target. @value{GDBN} retrieves it via the remote
45940 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
45941 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
45942 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
45943 XML document, of the form described in @ref{Target Description
45946 Alternatively, you can specify a file to read for the target description.
45947 If a file is set, the target will not be queried. The commands to
45948 specify a file are:
45951 @cindex set tdesc filename
45952 @item set tdesc filename @var{path}
45953 Read the target description from @var{path}.
45955 @cindex unset tdesc filename
45956 @item unset tdesc filename
45957 Do not read the XML target description from a file. @value{GDBN}
45958 will use the description supplied by the current target.
45960 @cindex show tdesc filename
45961 @item show tdesc filename
45962 Show the filename to read for a target description, if any.
45966 @node Target Description Format
45967 @section Target Description Format
45968 @cindex target descriptions, XML format
45970 A target description annex is an @uref{http://www.w3.org/XML/, XML}
45971 document which complies with the Document Type Definition provided in
45972 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
45973 means you can use generally available tools like @command{xmllint} to
45974 check that your feature descriptions are well-formed and valid.
45975 However, to help people unfamiliar with XML write descriptions for
45976 their targets, we also describe the grammar here.
45978 Target descriptions can identify the architecture of the remote target
45979 and (for some architectures) provide information about custom register
45980 sets. They can also identify the OS ABI of the remote target.
45981 @value{GDBN} can use this information to autoconfigure for your
45982 target, or to warn you if you connect to an unsupported target.
45984 Here is a simple target description:
45987 <target version="1.0">
45988 <architecture>i386:x86-64</architecture>
45993 This minimal description only says that the target uses
45994 the x86-64 architecture.
45996 A target description has the following overall form, with [ ] marking
45997 optional elements and @dots{} marking repeatable elements. The elements
45998 are explained further below.
46001 <?xml version="1.0"?>
46002 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46003 <target version="1.0">
46004 @r{[}@var{architecture}@r{]}
46005 @r{[}@var{osabi}@r{]}
46006 @r{[}@var{compatible}@r{]}
46007 @r{[}@var{feature}@dots{}@r{]}
46012 The description is generally insensitive to whitespace and line
46013 breaks, under the usual common-sense rules. The XML version
46014 declaration and document type declaration can generally be omitted
46015 (@value{GDBN} does not require them), but specifying them may be
46016 useful for XML validation tools. The @samp{version} attribute for
46017 @samp{<target>} may also be omitted, but we recommend
46018 including it; if future versions of @value{GDBN} use an incompatible
46019 revision of @file{gdb-target.dtd}, they will detect and report
46020 the version mismatch.
46022 @subsection Inclusion
46023 @cindex target descriptions, inclusion
46026 @cindex <xi:include>
46029 It can sometimes be valuable to split a target description up into
46030 several different annexes, either for organizational purposes, or to
46031 share files between different possible target descriptions. You can
46032 divide a description into multiple files by replacing any element of
46033 the target description with an inclusion directive of the form:
46036 <xi:include href="@var{document}"/>
46040 When @value{GDBN} encounters an element of this form, it will retrieve
46041 the named XML @var{document}, and replace the inclusion directive with
46042 the contents of that document. If the current description was read
46043 using @samp{qXfer}, then so will be the included document;
46044 @var{document} will be interpreted as the name of an annex. If the
46045 current description was read from a file, @value{GDBN} will look for
46046 @var{document} as a file in the same directory where it found the
46047 original description.
46049 @subsection Architecture
46050 @cindex <architecture>
46052 An @samp{<architecture>} element has this form:
46055 <architecture>@var{arch}</architecture>
46058 @var{arch} is one of the architectures from the set accepted by
46059 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46062 @cindex @code{<osabi>}
46064 This optional field was introduced in @value{GDBN} version 7.0.
46065 Previous versions of @value{GDBN} ignore it.
46067 An @samp{<osabi>} element has this form:
46070 <osabi>@var{abi-name}</osabi>
46073 @var{abi-name} is an OS ABI name from the same selection accepted by
46074 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46076 @subsection Compatible Architecture
46077 @cindex @code{<compatible>}
46079 This optional field was introduced in @value{GDBN} version 7.0.
46080 Previous versions of @value{GDBN} ignore it.
46082 A @samp{<compatible>} element has this form:
46085 <compatible>@var{arch}</compatible>
46088 @var{arch} is one of the architectures from the set accepted by
46089 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46091 A @samp{<compatible>} element is used to specify that the target
46092 is able to run binaries in some other than the main target architecture
46093 given by the @samp{<architecture>} element. For example, on the
46094 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46095 or @code{powerpc:common64}, but the system is able to run binaries
46096 in the @code{spu} architecture as well. The way to describe this
46097 capability with @samp{<compatible>} is as follows:
46100 <architecture>powerpc:common</architecture>
46101 <compatible>spu</compatible>
46104 @subsection Features
46107 Each @samp{<feature>} describes some logical portion of the target
46108 system. Features are currently used to describe available CPU
46109 registers and the types of their contents. A @samp{<feature>} element
46113 <feature name="@var{name}">
46114 @r{[}@var{type}@dots{}@r{]}
46120 Each feature's name should be unique within the description. The name
46121 of a feature does not matter unless @value{GDBN} has some special
46122 knowledge of the contents of that feature; if it does, the feature
46123 should have its standard name. @xref{Standard Target Features}.
46127 Any register's value is a collection of bits which @value{GDBN} must
46128 interpret. The default interpretation is a two's complement integer,
46129 but other types can be requested by name in the register description.
46130 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46131 Target Types}), and the description can define additional composite
46134 Each type element must have an @samp{id} attribute, which gives
46135 a unique (within the containing @samp{<feature>}) name to the type.
46136 Types must be defined before they are used.
46139 Some targets offer vector registers, which can be treated as arrays
46140 of scalar elements. These types are written as @samp{<vector>} elements,
46141 specifying the array element type, @var{type}, and the number of elements,
46145 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46149 If a register's value is usefully viewed in multiple ways, define it
46150 with a union type containing the useful representations. The
46151 @samp{<union>} element contains one or more @samp{<field>} elements,
46152 each of which has a @var{name} and a @var{type}:
46155 <union id="@var{id}">
46156 <field name="@var{name}" type="@var{type}"/>
46163 If a register's value is composed from several separate values, define
46164 it with either a structure type or a flags type.
46165 A flags type may only contain bitfields.
46166 A structure type may either contain only bitfields or contain no bitfields.
46167 If the value contains only bitfields, its total size in bytes must be
46170 Non-bitfield values have a @var{name} and @var{type}.
46173 <struct id="@var{id}">
46174 <field name="@var{name}" type="@var{type}"/>
46179 Both @var{name} and @var{type} values are required.
46180 No implicit padding is added.
46182 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46185 <struct id="@var{id}" size="@var{size}">
46186 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46192 <flags id="@var{id}" size="@var{size}">
46193 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46198 The @var{name} value is required.
46199 Bitfield values may be named with the empty string, @samp{""},
46200 in which case the field is ``filler'' and its value is not printed.
46201 Not all bits need to be specified, so ``filler'' fields are optional.
46203 The @var{start} and @var{end} values are required, and @var{type}
46205 The field's @var{start} must be less than or equal to its @var{end},
46206 and zero represents the least significant bit.
46208 The default value of @var{type} is @code{bool} for single bit fields,
46209 and an unsigned integer otherwise.
46211 Which to choose? Structures or flags?
46213 Registers defined with @samp{flags} have these advantages over
46214 defining them with @samp{struct}:
46218 Arithmetic may be performed on them as if they were integers.
46220 They are printed in a more readable fashion.
46223 Registers defined with @samp{struct} have one advantage over
46224 defining them with @samp{flags}:
46228 One can fetch individual fields like in @samp{C}.
46231 (gdb) print $my_struct_reg.field3
46237 @subsection Registers
46240 Each register is represented as an element with this form:
46243 <reg name="@var{name}"
46244 bitsize="@var{size}"
46245 @r{[}regnum="@var{num}"@r{]}
46246 @r{[}save-restore="@var{save-restore}"@r{]}
46247 @r{[}type="@var{type}"@r{]}
46248 @r{[}group="@var{group}"@r{]}/>
46252 The components are as follows:
46257 The register's name; it must be unique within the target description.
46260 The register's size, in bits.
46263 The register's number. If omitted, a register's number is one greater
46264 than that of the previous register (either in the current feature or in
46265 a preceding feature); the first register in the target description
46266 defaults to zero. This register number is used to read or write
46267 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46268 packets, and registers appear in the @code{g} and @code{G} packets
46269 in order of increasing register number.
46272 Whether the register should be preserved across inferior function
46273 calls; this must be either @code{yes} or @code{no}. The default is
46274 @code{yes}, which is appropriate for most registers except for
46275 some system control registers; this is not related to the target's
46279 The type of the register. It may be a predefined type, a type
46280 defined in the current feature, or one of the special types @code{int}
46281 and @code{float}. @code{int} is an integer type of the correct size
46282 for @var{bitsize}, and @code{float} is a floating point type (in the
46283 architecture's normal floating point format) of the correct size for
46284 @var{bitsize}. The default is @code{int}.
46287 The register group to which this register belongs. It can be one of the
46288 standard register groups @code{general}, @code{float}, @code{vector} or an
46289 arbitrary string. Group names should be limited to alphanumeric characters.
46290 If a group name is made up of multiple words the words may be separated by
46291 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46292 @var{group} is specified, @value{GDBN} will not display the register in
46293 @code{info registers}.
46297 @node Predefined Target Types
46298 @section Predefined Target Types
46299 @cindex target descriptions, predefined types
46301 Type definitions in the self-description can build up composite types
46302 from basic building blocks, but can not define fundamental types. Instead,
46303 standard identifiers are provided by @value{GDBN} for the fundamental
46304 types. The currently supported types are:
46309 Boolean type, occupying a single bit.
46317 Signed integer types holding the specified number of bits.
46325 Unsigned integer types holding the specified number of bits.
46329 Pointers to unspecified code and data. The program counter and
46330 any dedicated return address register may be marked as code
46331 pointers; printing a code pointer converts it into a symbolic
46332 address. The stack pointer and any dedicated address registers
46333 may be marked as data pointers.
46336 Half precision IEEE floating point.
46339 Single precision IEEE floating point.
46342 Double precision IEEE floating point.
46345 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46348 The 12-byte extended precision format used by ARM FPA registers.
46351 The 10-byte extended precision format used by x87 registers.
46354 32bit @sc{eflags} register used by x86.
46357 32bit @sc{mxcsr} register used by x86.
46361 @node Enum Target Types
46362 @section Enum Target Types
46363 @cindex target descriptions, enum types
46365 Enum target types are useful in @samp{struct} and @samp{flags}
46366 register descriptions. @xref{Target Description Format}.
46368 Enum types have a name, size and a list of name/value pairs.
46371 <enum id="@var{id}" size="@var{size}">
46372 <evalue name="@var{name}" value="@var{value}"/>
46377 Enums must be defined before they are used.
46380 <enum id="levels_type" size="4">
46381 <evalue name="low" value="0"/>
46382 <evalue name="high" value="1"/>
46384 <flags id="flags_type" size="4">
46385 <field name="X" start="0"/>
46386 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46388 <reg name="flags" bitsize="32" type="flags_type"/>
46391 Given that description, a value of 3 for the @samp{flags} register
46392 would be printed as:
46395 (gdb) info register flags
46396 flags 0x3 [ X LEVEL=high ]
46399 @node Standard Target Features
46400 @section Standard Target Features
46401 @cindex target descriptions, standard features
46403 A target description must contain either no registers or all the
46404 target's registers. If the description contains no registers, then
46405 @value{GDBN} will assume a default register layout, selected based on
46406 the architecture. If the description contains any registers, the
46407 default layout will not be used; the standard registers must be
46408 described in the target description, in such a way that @value{GDBN}
46409 can recognize them.
46411 This is accomplished by giving specific names to feature elements
46412 which contain standard registers. @value{GDBN} will look for features
46413 with those names and verify that they contain the expected registers;
46414 if any known feature is missing required registers, or if any required
46415 feature is missing, @value{GDBN} will reject the target
46416 description. You can add additional registers to any of the
46417 standard features --- @value{GDBN} will display them just as if
46418 they were added to an unrecognized feature.
46420 This section lists the known features and their expected contents.
46421 Sample XML documents for these features are included in the
46422 @value{GDBN} source tree, in the directory @file{gdb/features}.
46424 Names recognized by @value{GDBN} should include the name of the
46425 company or organization which selected the name, and the overall
46426 architecture to which the feature applies; so e.g.@: the feature
46427 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46429 The names of registers are not case sensitive for the purpose
46430 of recognizing standard features, but @value{GDBN} will only display
46431 registers using the capitalization used in the description.
46434 * AArch64 Features::
46438 * LoongArch Features::
46439 * MicroBlaze Features::
46443 * Nios II Features::
46444 * OpenRISC 1000 Features::
46445 * PowerPC Features::
46446 * RISC-V Features::
46448 * S/390 and System z Features::
46454 @node AArch64 Features
46455 @subsection AArch64 Features
46456 @cindex target descriptions, AArch64 features
46458 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46459 targets. It should contain registers @samp{x0} through @samp{x30},
46460 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46462 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46463 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46466 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46467 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46468 through @samp{p15}, @samp{ffr} and @samp{vg}.
46470 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46471 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46474 @subsection ARC Features
46475 @cindex target descriptions, ARC Features
46477 ARC processors are so configurable that even core registers and their numbers
46478 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46479 registers, which are important to @value{GDBN}, are not ``core'' registers in
46480 ARC. Therefore, there are two features that their presence is mandatory:
46481 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46483 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46488 @samp{r0} through @samp{r25} for normal register file targets.
46490 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46491 register file targets.
46493 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46494 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46497 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46498 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46499 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46500 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46501 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46502 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46503 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46504 because of their inaccessibility during user space debugging sessions.
46506 Extension core registers @samp{r32} through @samp{r59} are optional and their
46507 existence depends on the configuration. When debugging GNU/Linux applications,
46508 i.e.@: user space debugging, these core registers are not available.
46510 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46511 is the list of registers pertinent to this feature:
46515 mandatory: @samp{pc} and @samp{status32}.
46517 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46521 @subsection ARM Features
46522 @cindex target descriptions, ARM features
46524 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46526 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46527 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46529 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46530 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46531 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46534 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46535 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46537 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
46538 must contain register @samp{vpr}.
46540 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
46541 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
46543 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
46544 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
46545 synthesize the @samp{q} pseudo registers from @samp{d} register
46548 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46549 it should contain at least registers @samp{wR0} through @samp{wR15} and
46550 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46551 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46553 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46554 should contain at least registers @samp{d0} through @samp{d15}. If
46555 they are present, @samp{d16} through @samp{d31} should also be included.
46556 @value{GDBN} will synthesize the single-precision registers from
46557 halves of the double-precision registers.
46559 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46560 need to contain registers; it instructs @value{GDBN} to display the
46561 VFP double-precision registers as vectors and to synthesize the
46562 quad-precision registers from pairs of double-precision registers.
46563 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46564 be present and include 32 double-precision registers.
46566 @node i386 Features
46567 @subsection i386 Features
46568 @cindex target descriptions, i386 features
46570 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46571 targets. It should describe the following registers:
46575 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46577 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46579 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46580 @samp{fs}, @samp{gs}
46582 @samp{st0} through @samp{st7}
46584 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46585 @samp{foseg}, @samp{fooff} and @samp{fop}
46588 The register sets may be different, depending on the target.
46590 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46591 describe registers:
46595 @samp{xmm0} through @samp{xmm7} for i386
46597 @samp{xmm0} through @samp{xmm15} for amd64
46602 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46603 @samp{org.gnu.gdb.i386.sse} feature. It should
46604 describe the upper 128 bits of @sc{ymm} registers:
46608 @samp{ymm0h} through @samp{ymm7h} for i386
46610 @samp{ymm0h} through @samp{ymm15h} for amd64
46613 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
46614 Memory Protection Extension (MPX). It should describe the following registers:
46618 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
46620 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
46623 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
46624 describe a single register, @samp{orig_eax}.
46626 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
46627 describe two system registers: @samp{fs_base} and @samp{gs_base}.
46629 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
46630 @samp{org.gnu.gdb.i386.avx} feature. It should
46631 describe additional @sc{xmm} registers:
46635 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
46638 It should describe the upper 128 bits of additional @sc{ymm} registers:
46642 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
46646 describe the upper 256 bits of @sc{zmm} registers:
46650 @samp{zmm0h} through @samp{zmm7h} for i386.
46652 @samp{zmm0h} through @samp{zmm15h} for amd64.
46656 describe the additional @sc{zmm} registers:
46660 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
46663 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
46664 describe a single register, @samp{pkru}. It is a 32-bit register
46665 valid for i386 and amd64.
46667 @node LoongArch Features
46668 @subsection LoongArch Features
46669 @cindex target descriptions, LoongArch Features
46671 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
46672 targets. It should contain the registers @samp{r0} through @samp{r31},
46673 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
46674 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
46676 @node MicroBlaze Features
46677 @subsection MicroBlaze Features
46678 @cindex target descriptions, MicroBlaze features
46680 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
46681 targets. It should contain registers @samp{r0} through @samp{r31},
46682 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
46683 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
46684 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
46686 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
46687 If present, it should contain registers @samp{rshr} and @samp{rslr}
46689 @node MIPS Features
46690 @subsection @acronym{MIPS} Features
46691 @cindex target descriptions, @acronym{MIPS} features
46693 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
46694 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
46695 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
46698 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
46699 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
46700 registers. They may be 32-bit or 64-bit depending on the target.
46702 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
46703 it may be optional in a future version of @value{GDBN}. It should
46704 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
46705 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
46707 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
46708 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
46709 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
46710 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
46712 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
46713 contain a single register, @samp{restart}, which is used by the
46714 Linux kernel to control restartable syscalls.
46716 @node M68K Features
46717 @subsection M68K Features
46718 @cindex target descriptions, M68K features
46721 @item @samp{org.gnu.gdb.m68k.core}
46722 @itemx @samp{org.gnu.gdb.coldfire.core}
46723 @itemx @samp{org.gnu.gdb.fido.core}
46724 One of those features must be always present.
46725 The feature that is present determines which flavor of m68k is
46726 used. The feature that is present should contain registers
46727 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
46728 @samp{sp}, @samp{ps} and @samp{pc}.
46730 @item @samp{org.gnu.gdb.coldfire.fp}
46731 This feature is optional. If present, it should contain registers
46732 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
46735 Note that, despite the fact that this feature's name says
46736 @samp{coldfire}, it is used to describe any floating point registers.
46737 The size of the registers must match the main m68k flavor; so, for
46738 example, if the primary feature is reported as @samp{coldfire}, then
46739 64-bit floating point registers are required.
46742 @node NDS32 Features
46743 @subsection NDS32 Features
46744 @cindex target descriptions, NDS32 features
46746 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
46747 targets. It should contain at least registers @samp{r0} through
46748 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
46751 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
46752 it should contain 64-bit double-precision floating-point registers
46753 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
46754 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
46756 @emph{Note:} The first sixteen 64-bit double-precision floating-point
46757 registers are overlapped with the thirty-two 32-bit single-precision
46758 floating-point registers. The 32-bit single-precision registers, if
46759 not being listed explicitly, will be synthesized from halves of the
46760 overlapping 64-bit double-precision registers. Listing 32-bit
46761 single-precision registers explicitly is deprecated, and the
46762 support to it could be totally removed some day.
46764 @node Nios II Features
46765 @subsection Nios II Features
46766 @cindex target descriptions, Nios II features
46768 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
46769 targets. It should contain the 32 core registers (@samp{zero},
46770 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
46771 @samp{pc}, and the 16 control registers (@samp{status} through
46774 @node OpenRISC 1000 Features
46775 @subsection Openrisc 1000 Features
46776 @cindex target descriptions, OpenRISC 1000 features
46778 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
46779 targets. It should contain the 32 general purpose registers (@samp{r0}
46780 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
46782 @node PowerPC Features
46783 @subsection PowerPC Features
46784 @cindex target descriptions, PowerPC features
46786 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
46787 targets. It should contain registers @samp{r0} through @samp{r31},
46788 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
46789 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
46791 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
46792 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
46794 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
46795 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
46796 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
46797 through @samp{v31} as aliases for the corresponding @samp{vrX}
46800 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
46801 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
46802 combine these registers with the floating point registers (@samp{f0}
46803 through @samp{f31}) and the altivec registers (@samp{vr0} through
46804 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
46805 @samp{vs63}, the set of vector-scalar registers for POWER7.
46806 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
46807 @samp{org.gnu.gdb.power.altivec}.
46809 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
46810 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
46811 @samp{spefscr}. SPE targets should provide 32-bit registers in
46812 @samp{org.gnu.gdb.power.core} and provide the upper halves in
46813 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
46814 these to present registers @samp{ev0} through @samp{ev31} to the
46817 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
46818 contain the 64-bit register @samp{ppr}.
46820 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
46821 contain the 64-bit register @samp{dscr}.
46823 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
46824 contain the 64-bit register @samp{tar}.
46826 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
46827 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
46830 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
46831 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
46832 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
46833 server PMU registers provided by @sc{gnu}/Linux.
46835 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
46836 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
46839 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
46840 contain the checkpointed general-purpose registers @samp{cr0} through
46841 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
46842 @samp{cctr}. These registers may all be either 32-bit or 64-bit
46843 depending on the target. It should also contain the checkpointed
46844 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
46847 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
46848 contain the checkpointed 64-bit floating-point registers @samp{cf0}
46849 through @samp{cf31}, as well as the checkpointed 64-bit register
46852 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
46853 should contain the checkpointed altivec registers @samp{cvr0} through
46854 @samp{cvr31}, all 128-bit wide. It should also contain the
46855 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
46858 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
46859 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
46860 will combine these registers with the checkpointed floating point
46861 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
46862 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
46863 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
46864 @samp{cvs63}. Therefore, this feature requires both
46865 @samp{org.gnu.gdb.power.htm.altivec} and
46866 @samp{org.gnu.gdb.power.htm.fpu}.
46868 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
46869 contain the 64-bit checkpointed register @samp{cppr}.
46871 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
46872 contain the 64-bit checkpointed register @samp{cdscr}.
46874 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
46875 contain the 64-bit checkpointed register @samp{ctar}.
46878 @node RISC-V Features
46879 @subsection RISC-V Features
46880 @cindex target descriptions, RISC-V Features
46882 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
46883 targets. It should contain the registers @samp{x0} through
46884 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
46885 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
46888 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
46889 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
46890 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
46891 architectural register names, or the ABI names can be used.
46893 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
46894 it should contain registers that are not backed by real registers on
46895 the target, but are instead virtual, where the register value is
46896 derived from other target state. In many ways these are like
46897 @value{GDBN}s pseudo-registers, except implemented by the target.
46898 Currently the only register expected in this set is the one byte
46899 @samp{priv} register that contains the target's privilege level in the
46900 least significant two bits.
46902 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
46903 should contain all of the target's standard CSRs. Standard CSRs are
46904 those defined in the RISC-V specification documents. There is some
46905 overlap between this feature and the fpu feature; the @samp{fflags},
46906 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
46907 expectation is that these registers will be in the fpu feature if the
46908 target has floating point hardware, but can be moved into the csr
46909 feature if the target has the floating point control registers, but no
46910 other floating point hardware.
46912 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
46913 it should contain registers @samp{v0} through @samp{v31}, all of which
46914 must be the same size. These requirements are based on the v0.10
46915 draft vector extension, as the vector extension is not yet final. In
46916 the event that the register set of the vector extension changes for
46917 the final specification, the requirements given here could change for
46918 future releases of @value{GDBN}.
46921 @subsection RX Features
46922 @cindex target descriptions, RX Features
46924 The @samp{org.gnu.gdb.rx.core} feature is required for RX
46925 targets. It should contain the registers @samp{r0} through
46926 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
46927 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
46929 @node S/390 and System z Features
46930 @subsection S/390 and System z Features
46931 @cindex target descriptions, S/390 features
46932 @cindex target descriptions, System z features
46934 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
46935 System z targets. It should contain the PSW and the 16 general
46936 registers. In particular, System z targets should provide the 64-bit
46937 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
46938 S/390 targets should provide the 32-bit versions of these registers.
46939 A System z target that runs in 31-bit addressing mode should provide
46940 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
46941 register's upper halves @samp{r0h} through @samp{r15h}, and their
46942 lower halves @samp{r0l} through @samp{r15l}.
46944 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
46945 contain the 64-bit registers @samp{f0} through @samp{f15}, and
46948 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
46949 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
46951 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
46952 contain the register @samp{orig_r2}, which is 64-bit wide on System z
46953 targets and 32-bit otherwise. In addition, the feature may contain
46954 the @samp{last_break} register, whose width depends on the addressing
46955 mode, as well as the @samp{system_call} register, which is always
46958 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
46959 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
46960 @samp{atia}, and @samp{tr0} through @samp{tr15}.
46962 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
46963 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
46964 combined by @value{GDBN} with the floating point registers @samp{f0}
46965 through @samp{f15} to present the 128-bit wide vector registers
46966 @samp{v0} through @samp{v15}. In addition, this feature should
46967 contain the 128-bit wide vector registers @samp{v16} through
46970 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
46971 the 64-bit wide guarded-storage-control registers @samp{gsd},
46972 @samp{gssm}, and @samp{gsepla}.
46974 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
46975 the 64-bit wide guarded-storage broadcast control registers
46976 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
46978 @node Sparc Features
46979 @subsection Sparc Features
46980 @cindex target descriptions, sparc32 features
46981 @cindex target descriptions, sparc64 features
46982 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
46983 targets. It should describe the following registers:
46987 @samp{g0} through @samp{g7}
46989 @samp{o0} through @samp{o7}
46991 @samp{l0} through @samp{l7}
46993 @samp{i0} through @samp{i7}
46996 They may be 32-bit or 64-bit depending on the target.
46998 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
46999 targets. It should describe the following registers:
47003 @samp{f0} through @samp{f31}
47005 @samp{f32} through @samp{f62} for sparc64
47008 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47009 targets. It should describe the following registers:
47013 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47014 @samp{fsr}, and @samp{csr} for sparc32
47016 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47020 @node TIC6x Features
47021 @subsection TMS320C6x Features
47022 @cindex target descriptions, TIC6x features
47023 @cindex target descriptions, TMS320C6x features
47024 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47025 targets. It should contain registers @samp{A0} through @samp{A15},
47026 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47028 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47029 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47030 through @samp{B31}.
47032 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47033 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47035 @node Operating System Information
47036 @appendix Operating System Information
47037 @cindex operating system information
47039 Users of @value{GDBN} often wish to obtain information about the state of
47040 the operating system running on the target---for example the list of
47041 processes, or the list of open files. This section describes the
47042 mechanism that makes it possible. This mechanism is similar to the
47043 target features mechanism (@pxref{Target Descriptions}), but focuses
47044 on a different aspect of target.
47046 Operating system information is retrieved from the target via the
47047 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47048 read}). The object name in the request should be @samp{osdata}, and
47049 the @var{annex} identifies the data to be fetched.
47056 @appendixsection Process list
47057 @cindex operating system information, process list
47059 When requesting the process list, the @var{annex} field in the
47060 @samp{qXfer} request should be @samp{processes}. The returned data is
47061 an XML document. The formal syntax of this document is defined in
47062 @file{gdb/features/osdata.dtd}.
47064 An example document is:
47067 <?xml version="1.0"?>
47068 <!DOCTYPE target SYSTEM "osdata.dtd">
47069 <osdata type="processes">
47071 <column name="pid">1</column>
47072 <column name="user">root</column>
47073 <column name="command">/sbin/init</column>
47074 <column name="cores">1,2,3</column>
47079 Each item should include a column whose name is @samp{pid}. The value
47080 of that column should identify the process on the target. The
47081 @samp{user} and @samp{command} columns are optional, and will be
47082 displayed by @value{GDBN}. The @samp{cores} column, if present,
47083 should contain a comma-separated list of cores that this process
47084 is running on. Target may provide additional columns,
47085 which @value{GDBN} currently ignores.
47087 @node Trace File Format
47088 @appendix Trace File Format
47089 @cindex trace file format
47091 The trace file comes in three parts: a header, a textual description
47092 section, and a trace frame section with binary data.
47094 The header has the form @code{\x7fTRACE0\n}. The first byte is
47095 @code{0x7f} so as to indicate that the file contains binary data,
47096 while the @code{0} is a version number that may have different values
47099 The description section consists of multiple lines of @sc{ascii} text
47100 separated by newline characters (@code{0xa}). The lines may include a
47101 variety of optional descriptive or context-setting information, such
47102 as tracepoint definitions or register set size. @value{GDBN} will
47103 ignore any line that it does not recognize. An empty line marks the end
47108 Specifies the size of a register block in bytes. This is equal to the
47109 size of a @code{g} packet payload in the remote protocol. @var{size}
47110 is an ascii decimal number. There should be only one such line in
47111 a single trace file.
47113 @item status @var{status}
47114 Trace status. @var{status} has the same format as a @code{qTStatus}
47115 remote packet reply. There should be only one such line in a single trace
47118 @item tp @var{payload}
47119 Tracepoint definition. The @var{payload} has the same format as
47120 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47121 may take multiple lines of definition, corresponding to the multiple
47124 @item tsv @var{payload}
47125 Trace state variable definition. The @var{payload} has the same format as
47126 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47127 may take multiple lines of definition, corresponding to the multiple
47130 @item tdesc @var{payload}
47131 Target description in XML format. The @var{payload} is a single line of
47132 the XML file. All such lines should be concatenated together to get
47133 the original XML file. This file is in the same format as @code{qXfer}
47134 @code{features} payload, and corresponds to the main @code{target.xml}
47135 file. Includes are not allowed.
47139 The trace frame section consists of a number of consecutive frames.
47140 Each frame begins with a two-byte tracepoint number, followed by a
47141 four-byte size giving the amount of data in the frame. The data in
47142 the frame consists of a number of blocks, each introduced by a
47143 character indicating its type (at least register, memory, and trace
47144 state variable). The data in this section is raw binary, not a
47145 hexadecimal or other encoding; its endianness matches the target's
47148 @c FIXME bi-arch may require endianness/arch info in description section
47151 @item R @var{bytes}
47152 Register block. The number and ordering of bytes matches that of a
47153 @code{g} packet in the remote protocol. Note that these are the
47154 actual bytes, in target order, not a hexadecimal encoding.
47156 @item M @var{address} @var{length} @var{bytes}...
47157 Memory block. This is a contiguous block of memory, at the 8-byte
47158 address @var{address}, with a 2-byte length @var{length}, followed by
47159 @var{length} bytes.
47161 @item V @var{number} @var{value}
47162 Trace state variable block. This records the 8-byte signed value
47163 @var{value} of trace state variable numbered @var{number}.
47167 Future enhancements of the trace file format may include additional types
47170 @node Index Section Format
47171 @appendix @code{.gdb_index} section format
47172 @cindex .gdb_index section format
47173 @cindex index section format
47175 This section documents the index section that is created by @code{save
47176 gdb-index} (@pxref{Index Files}). The index section is
47177 DWARF-specific; some knowledge of DWARF is assumed in this
47180 The mapped index file format is designed to be directly
47181 @code{mmap}able on any architecture. In most cases, a datum is
47182 represented using a little-endian 32-bit integer value, called an
47183 @code{offset_type}. Big endian machines must byte-swap the values
47184 before using them. Exceptions to this rule are noted. The data is
47185 laid out such that alignment is always respected.
47187 A mapped index consists of several areas, laid out in order.
47191 The file header. This is a sequence of values, of @code{offset_type}
47192 unless otherwise noted:
47196 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47197 Version 4 uses a different hashing function from versions 5 and 6.
47198 Version 6 includes symbols for inlined functions, whereas versions 4
47199 and 5 do not. Version 7 adds attributes to the CU indices in the
47200 symbol table. Version 8 specifies that symbols from DWARF type units
47201 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47202 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47204 @value{GDBN} will only read version 4, 5, or 6 indices
47205 by specifying @code{set use-deprecated-index-sections on}.
47206 GDB has a workaround for potentially broken version 7 indices so it is
47207 currently not flagged as deprecated.
47210 The offset, from the start of the file, of the CU list.
47213 The offset, from the start of the file, of the types CU list. Note
47214 that this area can be empty, in which case this offset will be equal
47215 to the next offset.
47218 The offset, from the start of the file, of the address area.
47221 The offset, from the start of the file, of the symbol table.
47224 The offset, from the start of the file, of the constant pool.
47228 The CU list. This is a sequence of pairs of 64-bit little-endian
47229 values, sorted by the CU offset. The first element in each pair is
47230 the offset of a CU in the @code{.debug_info} section. The second
47231 element in each pair is the length of that CU. References to a CU
47232 elsewhere in the map are done using a CU index, which is just the
47233 0-based index into this table. Note that if there are type CUs, then
47234 conceptually CUs and type CUs form a single list for the purposes of
47238 The types CU list. This is a sequence of triplets of 64-bit
47239 little-endian values. In a triplet, the first value is the CU offset,
47240 the second value is the type offset in the CU, and the third value is
47241 the type signature. The types CU list is not sorted.
47244 The address area. The address area consists of a sequence of address
47245 entries. Each address entry has three elements:
47249 The low address. This is a 64-bit little-endian value.
47252 The high address. This is a 64-bit little-endian value. Like
47253 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47256 The CU index. This is an @code{offset_type} value.
47260 The symbol table. This is an open-addressed hash table. The size of
47261 the hash table is always a power of 2.
47263 Each slot in the hash table consists of a pair of @code{offset_type}
47264 values. The first value is the offset of the symbol's name in the
47265 constant pool. The second value is the offset of the CU vector in the
47268 If both values are 0, then this slot in the hash table is empty. This
47269 is ok because while 0 is a valid constant pool index, it cannot be a
47270 valid index for both a string and a CU vector.
47272 The hash value for a table entry is computed by applying an
47273 iterative hash function to the symbol's name. Starting with an
47274 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47275 the string is incorporated into the hash using the formula depending on the
47280 The formula is @code{r = r * 67 + c - 113}.
47282 @item Versions 5 to 7
47283 The formula is @code{r = r * 67 + tolower (c) - 113}.
47286 The terminating @samp{\0} is not incorporated into the hash.
47288 The step size used in the hash table is computed via
47289 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47290 value, and @samp{size} is the size of the hash table. The step size
47291 is used to find the next candidate slot when handling a hash
47294 The names of C@t{++} symbols in the hash table are canonicalized. We
47295 don't currently have a simple description of the canonicalization
47296 algorithm; if you intend to create new index sections, you must read
47300 The constant pool. This is simply a bunch of bytes. It is organized
47301 so that alignment is correct: CU vectors are stored first, followed by
47304 A CU vector in the constant pool is a sequence of @code{offset_type}
47305 values. The first value is the number of CU indices in the vector.
47306 Each subsequent value is the index and symbol attributes of a CU in
47307 the CU list. This element in the hash table is used to indicate which
47308 CUs define the symbol and how the symbol is used.
47309 See below for the format of each CU index+attributes entry.
47311 A string in the constant pool is zero-terminated.
47314 Attributes were added to CU index values in @code{.gdb_index} version 7.
47315 If a symbol has multiple uses within a CU then there is one
47316 CU index+attributes value for each use.
47318 The format of each CU index+attributes entry is as follows
47324 This is the index of the CU in the CU list.
47326 These bits are reserved for future purposes and must be zero.
47328 The kind of the symbol in the CU.
47332 This value is reserved and should not be used.
47333 By reserving zero the full @code{offset_type} value is backwards compatible
47334 with previous versions of the index.
47336 The symbol is a type.
47338 The symbol is a variable or an enum value.
47340 The symbol is a function.
47342 Any other kind of symbol.
47344 These values are reserved.
47348 This bit is zero if the value is global and one if it is static.
47350 The determination of whether a symbol is global or static is complicated.
47351 The authorative reference is the file @file{dwarf2read.c} in
47352 @value{GDBN} sources.
47356 This pseudo-code describes the computation of a symbol's kind and
47357 global/static attributes in the index.
47360 is_external = get_attribute (die, DW_AT_external);
47361 language = get_attribute (cu_die, DW_AT_language);
47364 case DW_TAG_typedef:
47365 case DW_TAG_base_type:
47366 case DW_TAG_subrange_type:
47370 case DW_TAG_enumerator:
47372 is_static = language != CPLUS;
47374 case DW_TAG_subprogram:
47376 is_static = ! (is_external || language == ADA);
47378 case DW_TAG_constant:
47380 is_static = ! is_external;
47382 case DW_TAG_variable:
47384 is_static = ! is_external;
47386 case DW_TAG_namespace:
47390 case DW_TAG_class_type:
47391 case DW_TAG_interface_type:
47392 case DW_TAG_structure_type:
47393 case DW_TAG_union_type:
47394 case DW_TAG_enumeration_type:
47396 is_static = language != CPLUS;
47404 @appendix Download debugging resources with Debuginfod
47407 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47410 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47411 can query servers using the build IDs associated with missing debug info,
47412 executables and source files in order to download them on demand.
47414 For instructions on building @value{GDBN} with @file{libdebuginfod},
47415 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47416 with @code{elfutils}, starting with version 0.178. See
47417 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47418 regarding @code{debuginfod}.
47421 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47424 @node Debuginfod Settings
47425 @section Debuginfod Settings
47427 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47430 @kindex set debuginfod enabled
47431 @anchor{set debuginfod enabled}
47432 @item set debuginfod enabled
47433 @itemx set debuginfod enabled on
47434 @cindex enable debuginfod
47435 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47436 info or source files.
47438 @item set debuginfod enabled off
47439 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47440 debug info or source files. By default, @code{debuginfod enabled} is set to
47441 @code{off} for non-interactive sessions.
47443 @item set debuginfod enabled ask
47444 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47445 attempting to perform the next query. By default, @code{debuginfod enabled}
47446 is set to @code{ask} for interactive sessions.
47448 @kindex show debuginfod enabled
47449 @item show debuginfod enabled
47450 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47453 @kindex set debuginfod urls
47454 @cindex configure debuginfod URLs
47455 @item set debuginfod urls
47456 @itemx set debuginfod urls @var{urls}
47457 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47458 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47459 should be used. The default value of @code{debuginfod urls} is copied from
47460 the @var{DEBUGINFOD_URLS} environment variable.
47462 @kindex show debuginfod urls
47463 @item show debuginfod urls
47464 Display the list of URLs that @code{debuginfod} will attempt to query.
47466 @kindex set debuginfod verbose
47467 @cindex debuginfod verbosity
47468 @item set debuginfod verbose
47469 @itemx set debuginfod verbose @var{n}
47470 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47471 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47474 @kindex show debuginfod verbose
47475 @item show debuginfod verbose
47476 Show the current verbosity setting.
47481 @appendix Manual pages
47485 * gdb man:: The GNU Debugger man page
47486 * gdbserver man:: Remote Server for the GNU Debugger man page
47487 * gcore man:: Generate a core file of a running program
47488 * gdbinit man:: gdbinit scripts
47489 * gdb-add-index man:: Add index files to speed up GDB
47495 @c man title gdb The GNU Debugger
47497 @c man begin SYNOPSIS gdb
47498 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
47501 @c man begin DESCRIPTION gdb
47502 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
47503 going on ``inside'' another program while it executes -- or what another
47504 program was doing at the moment it crashed.
47506 @value{GDBN} can do four main kinds of things (plus other things in support of
47507 these) to help you catch bugs in the act:
47511 Start your program, specifying anything that might affect its behavior.
47514 Make your program stop on specified conditions.
47517 Examine what has happened, when your program has stopped.
47520 Change things in your program, so you can experiment with correcting the
47521 effects of one bug and go on to learn about another.
47524 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47527 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47528 commands from the terminal until you tell it to exit with the @value{GDBN}
47529 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
47530 by using the command @code{help}.
47532 You can run @code{gdb} with no arguments or options; but the most
47533 usual way to start @value{GDBN} is with one argument or two, specifying an
47534 executable program as the argument:
47540 You can also start with both an executable program and a core file specified:
47546 You can, instead, specify a process ID as a second argument or use option
47547 @code{-p}, if you want to debug a running process:
47555 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47556 can omit the @var{program} filename.
47558 Here are some of the most frequently needed @value{GDBN} commands:
47560 @c pod2man highlights the right hand side of the @item lines.
47562 @item break [@var{file}:][@var{function}|@var{line}]
47563 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
47565 @item run [@var{arglist}]
47566 Start your program (with @var{arglist}, if specified).
47569 Backtrace: display the program stack.
47571 @item print @var{expr}
47572 Display the value of an expression.
47575 Continue running your program (after stopping, e.g.@: at a breakpoint).
47578 Execute next program line (after stopping); step @emph{over} any
47579 function calls in the line.
47581 @item edit [@var{file}:]@var{function}
47582 look at the program line where it is presently stopped.
47584 @item list [@var{file}:]@var{function}
47585 type the text of the program in the vicinity of where it is presently stopped.
47588 Execute next program line (after stopping); step @emph{into} any
47589 function calls in the line.
47591 @item help [@var{name}]
47592 Show information about @value{GDBN} command @var{name}, or general information
47593 about using @value{GDBN}.
47597 Exit from @value{GDBN}.
47601 For full details on @value{GDBN},
47602 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47603 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47604 as the @code{gdb} entry in the @code{info} program.
47608 @c man begin OPTIONS gdb
47609 Any arguments other than options specify an executable
47610 file and core file (or process ID); that is, the first argument
47611 encountered with no
47612 associated option flag is equivalent to a @option{--se} option, and the second,
47613 if any, is equivalent to a @option{-c} option if it's the name of a file.
47615 both long and abbreviated forms; both are shown here. The long forms are also
47616 recognized if you truncate them, so long as enough of the option is
47617 present to be unambiguous.
47619 The abbreviated forms are shown here with @samp{-} and long forms are shown
47620 with @samp{--} to reflect how they are shown in @option{--help}. However,
47621 @value{GDBN} recognizes all of the following conventions for most options:
47624 @item --option=@var{value}
47625 @item --option @var{value}
47626 @item -option=@var{value}
47627 @item -option @var{value}
47628 @item --o=@var{value}
47629 @item --o @var{value}
47630 @item -o=@var{value}
47631 @item -o @var{value}
47634 All the options and command line arguments you give are processed
47635 in sequential order. The order makes a difference when the @option{-x}
47641 List all options, with brief explanations.
47643 @item --symbols=@var{file}
47644 @itemx -s @var{file}
47645 Read symbol table from @var{file}.
47648 Enable writing into executable and core files.
47650 @item --exec=@var{file}
47651 @itemx -e @var{file}
47652 Use @var{file} as the executable file to execute when
47653 appropriate, and for examining pure data in conjunction with a core
47656 @item --se=@var{file}
47657 Read symbol table from @var{file} and use it as the executable
47660 @item --core=@var{file}
47661 @itemx -c @var{file}
47662 Use @var{file} as a core dump to examine.
47664 @item --command=@var{file}
47665 @itemx -x @var{file}
47666 Execute @value{GDBN} commands from @var{file}.
47668 @item --eval-command=@var{command}
47669 @item -ex @var{command}
47670 Execute given @value{GDBN} @var{command}.
47672 @item --init-eval-command=@var{command}
47674 Execute @value{GDBN} @var{command} before loading the inferior.
47676 @item --directory=@var{directory}
47677 @itemx -d @var{directory}
47678 Add @var{directory} to the path to search for source files.
47681 Do not execute commands from @file{~/.config/gdb/gdbinit},
47682 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
47683 @file{~/.gdbearlyinit}
47687 Do not execute commands from any @file{.gdbinit} or
47688 @file{.gdbearlyinit} initialization files.
47693 ``Quiet''. Do not print the introductory and copyright messages. These
47694 messages are also suppressed in batch mode.
47697 Run in batch mode. Exit with status @code{0} after processing all the command
47698 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
47699 Exit with nonzero status if an error occurs in executing the @value{GDBN}
47700 commands in the command files.
47702 Batch mode may be useful for running @value{GDBN} as a filter, for example to
47703 download and run a program on another computer; in order to make this
47704 more useful, the message
47707 Program exited normally.
47711 (which is ordinarily issued whenever a program running under @value{GDBN} control
47712 terminates) is not issued when running in batch mode.
47714 @item --batch-silent
47715 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
47716 output is supressed (stderr is unaffected). This is much quieter than
47717 @option{--silent} and would be useless for an interactive session.
47719 This is particularly useful when using targets that give @samp{Loading section}
47720 messages, for example.
47722 Note that targets that give their output via @value{GDBN}, as opposed to writing
47723 directly to @code{stdout}, will also be made silent.
47725 @item --args @var{prog} [@var{arglist}]
47726 Change interpretation of command line so that arguments following this
47727 option are passed as arguments to the inferior. As an example, take
47728 the following command:
47735 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
47736 the other hand, using:
47739 gdb --args ./a.out -q
47743 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
47745 @item --pid=@var{pid}
47746 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
47749 Open the terminal user interface.
47752 Read all symbols from the given symfile on the first access.
47755 Do not read symbol files.
47757 @item --return-child-result
47758 @value{GDBN}'s exit code will be the same as the child's exit code.
47760 @item --configuration
47761 Print details about GDB configuration and then exit.
47764 Print version information and then exit.
47766 @item --cd=@var{directory}
47767 Run @value{GDBN} using @var{directory} as its working directory,
47768 instead of the current directory.
47770 @item --data-directory=@var{directory}
47772 Run @value{GDBN} using @var{directory} as its data directory. The data
47773 directory is where @value{GDBN} searches for its auxiliary files.
47777 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
47778 @value{GDBN} to output the full file name and line number in a standard,
47779 recognizable fashion each time a stack frame is displayed (which
47780 includes each time the program stops). This recognizable format looks
47781 like two @samp{\032} characters, followed by the file name, line number
47782 and character position separated by colons, and a newline. The
47783 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
47784 characters as a signal to display the source code for the frame.
47786 @item -b @var{baudrate}
47787 Set the line speed (baud rate or bits per second) of any serial
47788 interface used by @value{GDBN} for remote debugging.
47790 @item -l @var{timeout}
47791 Set timeout, in seconds, for remote debugging.
47793 @item --tty=@var{device}
47794 Run using @var{device} for your program's standard input and output.
47798 @c man begin SEEALSO gdb
47800 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47801 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47802 documentation are properly installed at your site, the command
47809 should give you access to the complete manual.
47811 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47812 Richard M. Stallman and Roland H. Pesch, July 1991.
47816 @node gdbserver man
47817 @heading gdbserver man
47819 @c man title gdbserver Remote Server for the GNU Debugger
47821 @c man begin SYNOPSIS gdbserver
47822 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47824 gdbserver --attach @var{comm} @var{pid}
47826 gdbserver --multi @var{comm}
47830 @c man begin DESCRIPTION gdbserver
47831 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
47832 than the one which is running the program being debugged.
47835 @subheading Usage (server (target) side)
47838 Usage (server (target) side):
47841 First, you need to have a copy of the program you want to debug put onto
47842 the target system. The program can be stripped to save space if needed, as
47843 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
47844 the @value{GDBN} running on the host system.
47846 To use the server, you log on to the target system, and run the @command{gdbserver}
47847 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
47848 your program, and (c) its arguments. The general syntax is:
47851 target> gdbserver @var{comm} @var{program} [@var{args} ...]
47854 For example, using a serial port, you might say:
47858 @c @file would wrap it as F</dev/com1>.
47859 target> gdbserver /dev/com1 emacs foo.txt
47862 target> gdbserver @file{/dev/com1} emacs foo.txt
47866 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
47867 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
47868 waits patiently for the host @value{GDBN} to communicate with it.
47870 To use a TCP connection, you could say:
47873 target> gdbserver host:2345 emacs foo.txt
47876 This says pretty much the same thing as the last example, except that we are
47877 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
47878 that we are expecting to see a TCP connection from @code{host} to local TCP port
47879 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
47880 want for the port number as long as it does not conflict with any existing TCP
47881 ports on the target system. This same port number must be used in the host
47882 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
47883 you chose a port number that conflicts with another service, @command{gdbserver} will
47884 print an error message and exit.
47886 @command{gdbserver} can also attach to running programs.
47887 This is accomplished via the @option{--attach} argument. The syntax is:
47890 target> gdbserver --attach @var{comm} @var{pid}
47893 @var{pid} is the process ID of a currently running process. It isn't
47894 necessary to point @command{gdbserver} at a binary for the running process.
47896 To start @code{gdbserver} without supplying an initial command to run
47897 or process ID to attach, use the @option{--multi} command line option.
47898 In such case you should connect using @kbd{target extended-remote} to start
47899 the program you want to debug.
47902 target> gdbserver --multi @var{comm}
47906 @subheading Usage (host side)
47912 You need an unstripped copy of the target program on your host system, since
47913 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
47914 would, with the target program as the first argument. (You may need to use the
47915 @option{--baud} option if the serial line is running at anything except 9600 baud.)
47916 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
47917 new command you need to know about is @code{target remote}
47918 (or @code{target extended-remote}). Its argument is either
47919 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
47920 descriptor. For example:
47924 @c @file would wrap it as F</dev/ttyb>.
47925 (gdb) target remote /dev/ttyb
47928 (gdb) target remote @file{/dev/ttyb}
47933 communicates with the server via serial line @file{/dev/ttyb}, and:
47936 (gdb) target remote the-target:2345
47940 communicates via a TCP connection to port 2345 on host `the-target', where
47941 you previously started up @command{gdbserver} with the same port number. Note that for
47942 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
47943 command, otherwise you may get an error that looks something like
47944 `Connection refused'.
47946 @command{gdbserver} can also debug multiple inferiors at once,
47949 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
47950 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
47953 @ref{Inferiors Connections and Programs}.
47955 In such case use the @code{extended-remote} @value{GDBN} command variant:
47958 (gdb) target extended-remote the-target:2345
47961 The @command{gdbserver} option @option{--multi} may or may not be used in such
47965 @c man begin OPTIONS gdbserver
47966 There are three different modes for invoking @command{gdbserver}:
47971 Debug a specific program specified by its program name:
47974 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47977 The @var{comm} parameter specifies how should the server communicate
47978 with @value{GDBN}; it is either a device name (to use a serial line),
47979 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
47980 stdin/stdout of @code{gdbserver}. Specify the name of the program to
47981 debug in @var{prog}. Any remaining arguments will be passed to the
47982 program verbatim. When the program exits, @value{GDBN} will close the
47983 connection, and @code{gdbserver} will exit.
47986 Debug a specific program by specifying the process ID of a running
47990 gdbserver --attach @var{comm} @var{pid}
47993 The @var{comm} parameter is as described above. Supply the process ID
47994 of a running program in @var{pid}; @value{GDBN} will do everything
47995 else. Like with the previous mode, when the process @var{pid} exits,
47996 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
47999 Multi-process mode -- debug more than one program/process:
48002 gdbserver --multi @var{comm}
48005 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48006 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48007 close the connection when a process being debugged exits, so you can
48008 debug several processes in the same session.
48011 In each of the modes you may specify these options:
48016 List all options, with brief explanations.
48019 This option causes @command{gdbserver} to print its version number and exit.
48022 @command{gdbserver} will attach to a running program. The syntax is:
48025 target> gdbserver --attach @var{comm} @var{pid}
48028 @var{pid} is the process ID of a currently running process. It isn't
48029 necessary to point @command{gdbserver} at a binary for the running process.
48032 To start @code{gdbserver} without supplying an initial command to run
48033 or process ID to attach, use this command line option.
48034 Then you can connect using @kbd{target extended-remote} and start
48035 the program you want to debug. The syntax is:
48038 target> gdbserver --multi @var{comm}
48042 Instruct @code{gdbserver} to display extra status information about the debugging
48044 This option is intended for @code{gdbserver} development and for bug reports to
48047 @item --remote-debug
48048 Instruct @code{gdbserver} to display remote protocol debug output.
48049 This option is intended for @code{gdbserver} development and for bug reports to
48052 @item --debug-file=@var{filename}
48053 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48054 This option is intended for @code{gdbserver} development and for bug reports to
48057 @item --debug-format=option1@r{[},option2,...@r{]}
48058 Instruct @code{gdbserver} to include extra information in each line
48059 of debugging output.
48060 @xref{Other Command-Line Arguments for gdbserver}.
48063 Specify a wrapper to launch programs
48064 for debugging. The option should be followed by the name of the
48065 wrapper, then any command-line arguments to pass to the wrapper, then
48066 @kbd{--} indicating the end of the wrapper arguments.
48069 By default, @command{gdbserver} keeps the listening TCP port open, so that
48070 additional connections are possible. However, if you start @code{gdbserver}
48071 with the @option{--once} option, it will stop listening for any further
48072 connection attempts after connecting to the first @value{GDBN} session.
48074 @c --disable-packet is not documented for users.
48076 @c --disable-randomization and --no-disable-randomization are superseded by
48077 @c QDisableRandomization.
48082 @c man begin SEEALSO gdbserver
48084 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48085 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48086 documentation are properly installed at your site, the command
48092 should give you access to the complete manual.
48094 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48095 Richard M. Stallman and Roland H. Pesch, July 1991.
48102 @c man title gcore Generate a core file of a running program
48105 @c man begin SYNOPSIS gcore
48106 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48110 @c man begin DESCRIPTION gcore
48111 Generate core dumps of one or more running programs with process IDs
48112 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48113 is equivalent to one produced by the kernel when the process crashes
48114 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48115 limit). However, unlike after a crash, after @command{gcore} finishes
48116 its job the program remains running without any change.
48119 @c man begin OPTIONS gcore
48122 Dump all memory mappings. The actual effect of this option depends on
48123 the Operating System. On @sc{gnu}/Linux, it will disable
48124 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48125 enable @code{dump-excluded-mappings} (@pxref{set
48126 dump-excluded-mappings}).
48128 @item -o @var{prefix}
48129 The optional argument @var{prefix} specifies the prefix to be used
48130 when composing the file names of the core dumps. The file name is
48131 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48132 process ID of the running program being analyzed by @command{gcore}.
48133 If not specified, @var{prefix} defaults to @var{gcore}.
48137 @c man begin SEEALSO gcore
48139 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48140 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48141 documentation are properly installed at your site, the command
48148 should give you access to the complete manual.
48150 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48151 Richard M. Stallman and Roland H. Pesch, July 1991.
48158 @c man title gdbinit GDB initialization scripts
48161 @c man begin SYNOPSIS gdbinit
48162 @ifset SYSTEM_GDBINIT
48163 @value{SYSTEM_GDBINIT}
48166 @ifset SYSTEM_GDBINIT_DIR
48167 @value{SYSTEM_GDBINIT_DIR}/*
48170 ~/.config/gdb/gdbinit
48178 @c man begin DESCRIPTION gdbinit
48179 These files contain @value{GDBN} commands to automatically execute during
48180 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48183 the @value{GDBN} manual in node @code{Sequences}
48184 -- shell command @code{info -f gdb -n Sequences}.
48190 Please read more in
48192 the @value{GDBN} manual in node @code{Startup}
48193 -- shell command @code{info -f gdb -n Startup}.
48200 @ifset SYSTEM_GDBINIT
48201 @item @value{SYSTEM_GDBINIT}
48203 @ifclear SYSTEM_GDBINIT
48204 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48206 System-wide initialization file. It is executed unless user specified
48207 @value{GDBN} option @code{-nx} or @code{-n}.
48210 the @value{GDBN} manual in node @code{System-wide configuration}
48211 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48213 @ifset SYSTEM_GDBINIT_DIR
48214 @item @value{SYSTEM_GDBINIT_DIR}
48216 @ifclear SYSTEM_GDBINIT_DIR
48217 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48219 System-wide initialization directory. All files in this directory are
48220 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48221 @code{-n}, as long as they have a recognized file extension.
48224 the @value{GDBN} manual in node @code{System-wide configuration}
48225 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48228 @ref{System-wide configuration}.
48231 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48232 User initialization file. It is executed unless user specified
48233 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48235 @item @file{.gdbinit}
48236 Initialization file for current directory. It may need to be enabled with
48237 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48240 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48241 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48244 @ref{Init File in the Current Directory}.
48249 @c man begin SEEALSO gdbinit
48251 gdb(1), @code{info -f gdb -n Startup}
48253 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48254 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48255 documentation are properly installed at your site, the command
48261 should give you access to the complete manual.
48263 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48264 Richard M. Stallman and Roland H. Pesch, July 1991.
48268 @node gdb-add-index man
48269 @heading gdb-add-index
48270 @pindex gdb-add-index
48271 @anchor{gdb-add-index}
48273 @c man title gdb-add-index Add index files to speed up GDB
48275 @c man begin SYNOPSIS gdb-add-index
48276 gdb-add-index @var{filename}
48279 @c man begin DESCRIPTION gdb-add-index
48280 When @value{GDBN} finds a symbol file, it scans the symbols in the
48281 file in order to construct an internal symbol table. This lets most
48282 @value{GDBN} operations work quickly--at the cost of a delay early on.
48283 For large programs, this delay can be quite lengthy, so @value{GDBN}
48284 provides a way to build an index, which speeds up startup.
48286 To determine whether a file contains such an index, use the command
48287 @kbd{readelf -S filename}: the index is stored in a section named
48288 @code{.gdb_index}. The index file can only be produced on systems
48289 which use ELF binaries and DWARF debug information (i.e., sections
48290 named @code{.debug_*}).
48292 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48293 in the @env{PATH} environment variable. If you want to use different
48294 versions of these programs, you can specify them through the
48295 @env{GDB} and @env{OBJDUMP} environment variables.
48299 the @value{GDBN} manual in node @code{Index Files}
48300 -- shell command @kbd{info -f gdb -n "Index Files"}.
48307 @c man begin SEEALSO gdb-add-index
48309 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48310 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48311 documentation are properly installed at your site, the command
48317 should give you access to the complete manual.
48319 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48320 Richard M. Stallman and Roland H. Pesch, July 1991.
48326 @node GNU Free Documentation License
48327 @appendix GNU Free Documentation License
48330 @node Concept Index
48331 @unnumbered Concept Index
48335 @node Command and Variable Index
48336 @unnumbered Command, Variable, and Function Index
48341 % I think something like @@colophon should be in texinfo. In the
48343 \long\def\colophon{\hbox to0pt{}\vfill
48344 \centerline{The body of this manual is set in}
48345 \centerline{\fontname\tenrm,}
48346 \centerline{with headings in {\bf\fontname\tenbf}}
48347 \centerline{and examples in {\tt\fontname\tentt}.}
48348 \centerline{{\it\fontname\tenit\/},}
48349 \centerline{{\bf\fontname\tenbf}, and}
48350 \centerline{{\sl\fontname\tensl\/}}
48351 \centerline{are used for emphasis.}\vfill}
48353 % Blame: doc@@cygnus.com, 1991.